SOIL FERTILITY AND PERMANENT AGRICULTURE | jniversity of Southern Library F H! CYRIL G.HOPKINS UNIVERSITY OF CALIFORNIA AT LOS ANGELES Fon COUNTRY LIFE EDUCATION SERIES Edited by Charles William Burkett, recently Director of Experiment Station, Kansas State Agricultural College ; Editor of American Agriculturist TYPES AND BREEDS OF FARM ANIMALS By Charles S. Plumb, Ohio State University PRINCIPLES OF BREEDING By Eugene Davenport, University of Illinois FUNGOUS DISEASES OF PLANTS By Benjamin Minge Duggar, Cornell University SOIL FERTILITY AND PERMANENT AGRICULTURE By Cyril George Hopkins, University of Illinois PRINCIPLES AND PRACTICE OF POULTRY CULTURE By John Henry Robinson, Editor of Farm-Poultry GARDEN FARMING By Lee Cleveland Corbett, United States Depart- ment of Agriculture Other volumes in preparation SOIL FERTILITY AND PERMANENT AGRICULTURE BY CYRIL G. HOPKINS, PH.D. PROFESSOR OF AGRONOMY IN THE UNIVERSITY OF ILLINOIS, CHIEF IN AGRONOMY AND CHEMISTRY AND VICE DIRECTOR OF THE ILLINOIS AGRICULTURAL EXPERIMENT STATION GINN AND COMPANY BOSTON • NEW YORK • CHICAGO • LONDON PREFACE Liebig said, "Agriculture is, of all industrial pursuits, the rich- est in facts and the poorest in their comprehension." To a large degree this statement is still true, and the chief purpose of this volume is to bring together in convenient form the world's most essential facts gathered from the field and laboratory, and to develop from them some foundation principles of permanent agriculture ; for, as Liebig also truly said, " Facts are like grains of sand which are moved by the wind, but principles are these same grains cemented into rocks." While one dare not believe that error has been completely avoided, the facts presented have been checked with all reasonable care, and they may be accepted with the confidence that they are accurately reproduced from the original data. Unsolved problems still remain, and some conclusions which seem to be indicated by the data thus far reported may be modi- fied later when more complete information is afforded. The author will always receive with deep appreciation suggested ad- ditions, modifications, or corrections. It is, perhaps, unnecessary to say to the reader that his general knowledge of farm practice is presupposed, and no attempt has been made to include herein a thousand details with which every man experienced in the art of agriculture already is familiar. For the sake of himself and children it must be said to the practical farmer that he should encourage the teaching of the science of agriculture in the school, even though he may know much more than the teacher concerning the art of agriculture. viii PREFACE To encourage the teacher, let me say that much of the science of agriculture can be successfully taught without a field or a gar- den, and even without complete knowledge of the art. Thus, you may teach why clover should be grown and when it contains the most nitrogen, but leave the farmer to determine for himself when to plow it under, if he is the better judge of seasonal conditions and of their probable influence upon his own soil and crop. CYRIL G. HOPKINS NOTE. Opportunity has been taken to insert in this edition the later data from some of the most important long-continued field investigations. In addi- tion, a list of questions relating to the most important facts in every chapter has been prepared for the convenience of the teacher in helping the student to acquire a thorough knowledge of the most essential facts and principles of soil fertility, with economy of time and with conservation of mental energy. These questions are supplied in pamphlet form by the publishers. — C. G. H. CONTENTS PAGE INTRODUCTION xvii PART I. SCIENCE AND SOIL CHAPTER I. FOUNDATION FACTS AND PRINCIPLES i II. THE MORE IMPORTANT ELEMENTS AND COMPOUNDS . . .12 III. PLANT FOOD AND PLANT GROWTH 26 IV. THE EARTH'S CRUST 46 V. SOIL FORMATIONS AND CLASSIFICATIONS 54 VI. SOIL COMPOSITION . . . 58 VII. AVAILABLE PLANT FOOD 107 VIII. SOIL SURVEYS BY THE UNITED STATES BUREAU OF SOILS . .114 IX. SOIL ANALYSES BY THE UNITED STATES BUREAU OF SOILS . 136 » X. CROP REQUIREMENTS FOR NITROGEN, PHOSPHORUS, AND PO- TASSIUM 153 XI. SOURCES OF PLANT FOOD 156 PART II. SYSTEMS OF PERMANENT AGRICULTURE XII. LIMESTONE 160 XIII. PHOSPHORUS 183 XIV. ORGANIC MATTER AND NITROGEN 194 . XV. ROTATION SYSTEMS FOR GRAIN FARMING 226 XVI. LIVE-STOCK FARMING 231 XVII. THE USE OF PHOSPHORUS IN DIFFERENT FORMS . . . ^236 XVIII. THEORIES CONCERNING SOIL FERTILITY 300 PART III. SOIL INVESTIGATIONS BY CULTURE EXPERIMENTS XIX. THE ROTHAMSTED EXPERIMENTS 344 XX. PENNSYLVANIA FIELD EXPERIMENTS 420 XXI. OHIO FIELD EXPERIMENTS 441 XXII. ILLINOIS FIELD EXPERIMENTS 453 XXIII. FIELD EXPERIMENTS IN THE SOUTH, INCLUDING SOUTHERN ILLINOIS 476 ix CONTENTS CHAPTER PAGE XXIV, MINNESOTA SOIL INVESTIGATIONS ...... 499 XXV. CANADIAN FIELD EXPERIMENTS 505 XXVI. SHORT-TIME POT-CULTURE AND WATER-CULTURE EXPERIMENTS IN COMPARISON WITH FIELD RESULTS 513 PART IV. VARIOUS FERTILITY FACTORS XXVII. XXVIII. XXIX. XXX. XXXI. XXXII. XXXIII. XXXIV. XXXV. XXXVI. XXXVII. XXXVIII. XXXIX. MANUFACTURED COMMERCIAL FERTILIZERS .... CROP STIMULANTS AND PROTECTIVE AGENTS CRITICAL PERIODS IN PLANT LIKE FARM MANURE LOSSES OF PLANT FOOD FROM PLANTS .... LOSSES OF PLANT FOOD FROM SOILS FIXATION OF PLANT FOOD BY SOILS ANALYZING AND TESTING SOILS RELATION OF FERTILITY TO APPEARANCE OF SOILS OR CROPS FACTORS IN CROP PRODUCTION ESSENTIAL FACTORS OF SUCCESS IN FARMING THE VALUE OF LAND Two PERIODS IN AGRICULTURAL HISTORY . APPENDIX SECTION 1. THE PRODUCTION OF PHOSPHATE ROCK . . . . ' . II. MODEL FERTILIZER LAW III. COMPOSITION OF ANIMAL AND PLANT PRODUCTS IV. STATISTICS OF AGRICULTURAL PRODUCTS V. METHODS OF SOIL ANALYSIS VI. COMPOSITION OF SOME EUROPEAN SOILS VII. AGRICULTURAL COLLEGES AND EXPERIMENT STATIONS IN THE UNITED STATES AND CANADA 5'7 533 538 S4i 549 556 562 565 572 575 584 586 590 595 599 602 605 626 634 643 INDEX 647 LIST OF TABLES TABLE PAGE 1. Elements, Symbols, and Atomic Weights 10 2. The More Important Elements : Occurrence 13 3. Composition of Silicates 48 4. Composition of Rock 49 5. Composition of Fresh Limestone and Residual Clay . . 51 6. Soils: General Groups . . . . . . . . -55 7. Recognized Soil Types 56 8. Relative " Supply and Demand " of Seven Elements ... 59 9. Composition of Productive and Nonproductive Soils ... 63 10. Composition of Adobe and Coral Limestone Soils . 65 1 1 . Composition of Loess Deposits ....... 69 12. Composition of Ten Residual Soils ...... 73 13. Mineral Plant Food in Wheat, Corn, Oats, and Clover ... 75 14. Composition of New York Soils 75 15. Fertility in Illinois Soils : Surface 82 16. Fertility in Illinois Soils : Subsurface 84 17. Fertility in Illinois Soils: Subsoil ....... 86 18. Composition of Southern Indiana Surface Soils .... 88 18.1. Plant Food in Surface Soils of Iowa ...... 91 19. Composition of Surface Soils of Tennessee ..... 93 19.1. Composition of Georgia Soil ....... 94 19.2. Average Composition of Some Texas Soils 95 19.3. Composition of Some Louisiana Soils 96 20. Composition of Some Michigan Soils 98 10. i. Composition of Canadian Soils 103 20. 2. Certain Plant-food Elements in Illinois Surface Soils . . . 105 21. Annually Available Fertility in Illinois Soils . . . . .110 22. Composition of Various Extensive Soil Types of the United States 138 23. Fertility in Farm Produce . . . . . . . .154 24. Fertility in Manure, Rough Feeds, and Fertilizers . . . . 157 25. Pennsylvania Experiments with Lime . . . ... .165 25.1. Maryland Experiments with Lime . . . . . .167 26. Experiments with Magnesium Carbonate . . . • 171 27. Losses of Calcium Carbonate from Broadbalk Field . . . 174 28. Losses of Calcium Carbonate from Hoos Field .... 175 29. Digestibility of Common Food Stuffs 199 xii LIST OF TABLES TABLE PAGE 30. Plant Food recovered from Food Consumed (Illinois) . . .201 31. Plant Food recovered from Food Consumed (Pennsylvania) . . 202 32. Plant Food recovered from Six Months' Feeding (Ohio) . . 204 33. Fixation of Nitrogen by Alfalfa 214 34. Nitrogen in Sweet Clover 220 35. Composition of Crimson Clover 221 36. Composition of Legumes and Other Plants . . . . 222 37. 38, 39, and 39^. Comparison of Raw Phosphate and Acid Phosphate 247-253 40. Ohio Experiments with Manure, Phosphate, Kainit, Gypsum, and Complete Fertilizers . . 256 41. Balance Sheet for Nitrogen and Phosphorus in Manure-phosphate Experiments . . 257 42. Maryland Experiments with Different Phosphates ... . . 262 43. Pennsylvania Experiments with Different Phosphates . '. . 264 44. 45, 44C, and 45^. Rhode Island Experiments with Nine Phosphates 268-274 46 and 47. Maine Experiments with Different Phosphates . . 276, 277 48 and 49. Massachusetts Experiments with Different Phosphates 279, 282 50. Illinois Experiments with Raw Rock Phosphate . . . 285 51. Steamed Bone Meal and Raw Rock Phosphate .... 287 52-58. Rotation Crops on Agdell Field 346-352 59. Summary of Crop Yields and Values, Agdell Field . . . . 360 6oand6i. Wheat Yields, Broadbalk Field, Averages . . . 364,365 62. Wheat Yields at Rothamsted, Comparisons .... 372, 373 63. Wheat Yields, Broadbalk Field, Nitrogen Increments . . . 374' 64. Wheat Yields at Rothamsted, Summaries 375 65. Rothamsted Records, Rainfall and Drainage ..... 377 66 and 67. Barley Yields on Hoos Field 380, 381 68. Potato Yields on Hoos Field 386, 387 69. Residual Effect of Fertilizers on Hoos Field . . . . . 390 70. Hay Yields on The Park at Rothamsted 393 71. Root Crops on Barn Field 399,400 72. Rothamsted Fields abandoned to Nature 404 73. Plant Food in Soil of Broadbalk Plots .411 74. Composition of Drainage Waters from Broadbalk Field . . . 413 75. Nitrogen in Soil of Agdell Plots . . . . . . . 416 76. Composition of Crops grown on Agdell Field 417 77. Composition of Hay from The Park, Rothamsted . . . .418 78. Pennsylvania Crop Yields in Field Experiments . . '. . 423 79 and 80. Pennsylvania Experiments by Twelve-year Periods . 428, 429 81. Pennsylvania Experiments : Financial Summary .... 431 8iP. Pennsylvania Experiments : Twenty-five-year Average . . . 434 LIST OF TABLES xiii 82. Ohio Experiments : Five-year Rotation . . 442 83. Ohio Experiments : Potatoes, Wheat, Clover .... 448 84. Experiments at Strongsville, Ohio 452 85. Illinois Experiment Plots, Urbana 457 86. Comparable Corn Yields, Illinois Experiments .... 459 87. Crop Yields on Sibley Field, Illinois 462 88. Crop Yields on Bloomington Field, Illinois ..... 464 89. Crop Yields on Antioch Field, Illinois 467 90. Crop Yields on Sand Land, Illinois ...... 468 91. Corn Yields on Deep Peat Soil, Illinois . ... . . 471 92 and 93. Corn Yields on Peaty Alkali Soil, Illinois . . . 473, 475 94. Crop Yields in Southern Illinois, Odin Field .... 478 95. Crop Yields in Southern Illinois, Du Bois Field . . . .481 96 and 97. Crop Yields on Worn Hill Land, Vienna, Illinois . 483, 485 98 and 98.1. Pot-culture Experiments with Worn Hill Soil . . 486, 487 99. Southern Iowa Field Experiments ...... 488 loo. Georgia Fertilizer Experiments with Corn ..... 490 lor. Rainfall Records at Experiment, Georgia ..... 491 102 and 103. Georgia Fertilizer Experiments with Cotton . . 492, 493 104. Alabama Field Experiments with Cotton ..... 495 104.1. Louisiana Field Experiments ....... 496 105. Minnesota Soil Investigations 499 1 06 and 107. Canadian Field Experiments 508,511 108 and 109. Comparison of Pot Cultures and Field Experiments. 513, 514 no. Composition of Farm Manures 543 nr. Composition of Pulverized Dried Manures 545 112. Composition of Manure before and after Exposure . . . 547 113. Composition of Bean Crop at Different Periods of Growth . . 550 114. Composition of Barley at Different Periods of Growth . . . 552 115. Plant Food removed from Plants by Leaching .... 555 116. Nitrogen in Rothamsted Drainage Waters ..... 557 117. Soluble Nitrogen in Cropped Soils, Rothamsted .... 558 1 1 8. Ammonia Fixation and Nitrification 563 119. Effect of Soil Preparation, Cultivation, Irrigation, and Fertilization on the Yield of Corn .578 1 20. Value of Land, measured by Crop Yields 587 121. Composition of Animal and Plant Products 602 ILLUSTRATIONS PAGE GLACIAL MAP OF NORTH AMERICA 68 GENERAL SURVEY SOIL MAP OF ILLINOIS 76 A MAN OF SCIENCE: EUGENE WOLDEMAR HILGARD 102 MAP OF UNITED STATES SOIL PROVINCES 116 NITROGEN FIXATION BY CLOVER 218 TOPOGRAPHIC MAP OF OHIO EXPERIMENT FIELD 252 DIRECTOR CHARLES E. THORNE 254 SIR JOHN BENNET LAWES 342 SIR JOSEPH HENRY GILBERT 344 TURNIPS ON AGDELL FIELD, 1908 362 DIRECTOR A. D. HALL 408 DIRECTOR EDWARD B. VOORHEES 517 RAINFALL CHART OF NORTH PLATTE, NEBRASKA ...... 580 RAINFALL MAP OF THE UNITED STATES 582 .?.>•>! ,;.-.'-. 5H;:.' ~-'\ *j •:/-.!/ .lAf.',!^ V/ :-'..-;-:;••>:•{ :>;-vy;( \-_ •<,, >;.;' •'- INTRODUCTION IT is the first business of every farmer to reduce the fertility of the soil, by removing the largest crops of which the soil is capable; but ultimate failure results for the landowner unless provision is made for restoring and maintaining productiveness. Every landowner should adopt for his land a system of farming that is permanent, — a system under which the land becomes better rather than poorer. If the independent farmer is to adopt and maintain permanent systems of profitable agriculture, he cannot accept " parrot " instruction ; he must know the why and wherefore, the reason for doing things, and the ultimate effect of his agricultural practice upon the productive power of the land. Every farm is an inde- pendent enterprise in which the farmer himself is the superin- tendent and general manager, and he must be able to direct the business, even though he may be the only man to execute his own plans. The agriculture of a state cannot be managed from a central office. The landowner must think for the land. The author is familiar with the often expressed idea that what the farmer wants is a simple statement of facts, but he is even more familiar with the absolute truth that what the farmer de- mands is the most positive proof of the correctness of such state- ment before he is willing to make any change from a practice based upon long experience. In the preparation of this book free use has been made of such technical terms as are necessary to the discussion of fundamental principles with scientific correctness. No apology is offered for this. Farmers and agricultural students have at least as good intellects as other classes of people; and if when they leave the farm they can learn to understand and manage successfully such lines of business as banking, contracting, building, operating railroads, factories, and other commercial establishments, — xvii xviii INTRODUCTION which they are doing everywhere, — they can also understand their own business, if they will, when they remain on the farm or in control of land. Technical books are to be studied; they are not written for en- tertainment. They furnish definite facts, accurate data, and necessary information, relating to underlying principles upon which permanent successful practice must be based. The most important material problem of the United States is to maintain the fertility of the soil, and no extensive agricultural country has ever solved this problem. The frequent periods of famine and starvation in the great agricultural countries of China, India, and Russia, and the depleted lands and abandoned farms of our own eastern United States are facts that serve as a constant proof that the common practice of agriculture reduces the produc- tive power of land. I The rule is almost universal that old land is less productive than new land. This simple and well-recognized fact points inevitably toward future poverty, not only for the individual or the family, but likewise for the commonwealth and for the nation. We may ignore this if we choose in America for a few more years, but with the decreasing productive power of our lands and with a rapidly increasing 'population the truth must strike us in the face in the near future. / We cannot afford to let ignorance, prejudice, or bigotry blind us in this matter, neither in ourselves nor in others. Even the confi- dent assurance, by those who live in continued plenty, that the people of earth are not destined to suffer hunger, does not remove the positive fact that thousands, and sometimes millions, of people actually die of starvation within a single yearlin some of the old agricultural countries. An early recognition of these world-wide conditions and tend- encies is of paramount importance to the people controlling the more productive lands of the United States, not only for their own sake, but also for the sake of others who are dependent upon those lands for their present and future support, whether engaged directly in agricultural pursuits or in other industrial or professional lines, which cannot exist and prosper without agriculture. If the art of agriculture has ruined land, the science of agricul- INTRODUCTION xix ture must restore it; and the restoration must begin while some farmers are still prosperous, for poverty-stricken people are at once helpless and soon ignorant. Outside help will always be required to redeem impoverished soils, for poverty makes no in- vestments, and some initial investment is always required for soil improvement. It is the purpose of this book to teach the science of soil fertility and permanent agriculture, chiefly by reporting facts rather than by offering theories; and any one of common sense who reads the English language, and who can understand the common school arithmetic, can understand this book if he will study it. (The fact may well be recognized that some who have ample time for study, though physically industrious, are mentally lazy.1) The author suggests, however, that the busy farmer, who wishes to familiarize himself as quickly as possible with the most essential practical facts pertaining to the economical and perma- nent improvement of common or normal soils, and who is willing to pass over temporarily the discussion of foundation principles, may well begin the study of this book with " Systems of Perma- nent Agriculture," Part II, after first making the following facts a part of his ever ready knowledge: (1) Phosphorus and decaying organic matter are the two sub- stances which constitute the key to profitable systems of permanent agriculture on most of the normal soils of America ; although, when soils become sour, or acid, ground natural limestone should also be regularly applied, at the rate of about two tons per acre every four to six years. (2) There are six essential positive factors in crop production: the seed, a home for the plant, the food of which the plant is made (and this factor is just as important for plants as it is for animals) , moisture, heat, and light. Of these six factors, the least appre- ciated and the most neglected is that of plant food, and yet this is a factor which the farmer can very largely control, whereas the others (except the seed) are largely beyond his control. (An important negative factor is protection from weeds, insects, and disease.) 1 " Many poor farmers have a lazy faith in the Lord ; they think or hope that He will somehow make up for whatever they fail to do." — HOARD. XX INTRODUCTION (3) Of the ten different chemical elements absolutely required for the growth of every agricultural plant, three come directly from air and water in practically unlimited amounts, and these three (carbon and oxygen from air and hydrogen from water) constitute about 95 per cent of the common mature crops. Nevertheless, each one of the seven elements obtained from the soil, though aggre- gating only 5 per cent, is absolutely necessary to the life and full development of the plant. Indeed, if any one of these elements be entirely lacking, the soil would be infertile and barren. So important are these plant-food elements, that soils are found so deficient in some essential plant food that the addition of a single element will more than double the crop yield. (4) The five elements, potassium, magnesium, calcium, iron, and sulfur, are contained in most normal soils in such large amounts, compared to the requirements of crops, that the supply rarely becomes depleted. Thus, in most cases, the problem is narrowed to the two elements, nitrogen and phosphorus, although, for various reasons, potassium also has come to have a recognized money value in commercial fertilizers. (5) Nitrogen is contained in the air in inexhaustible amount, but the legumes (clover, alfalfa, peas, beans, etc.) are the only agricultural plants which have power to utilize the free nitrogen of the air. Nitrogen in limited amount is contained in the soil in the organic matter, the principal material which gives a good soil its dark color. If the supply of organic matter is maintained, by plowing under farm manure, clover, cowpeas, or other green manures, then the supply of nitrogen will also be maintained. (6) The plowed soil of an acre (2 million pounds, for a depth of 6| inches) of rich, well-balanced normal land in the Corn Belt contains about 8000 pounds of nitrogen, 2000 pounds of phosphorus, 35,000 pounds of potassium, and 15 tons of calcium carbonate (limestone) . (7) The surface soils of the United States vary in composition: (a) in nitrogen content, from 1000- pounds to 35,000 pounds; (6) in phosphorus content, from 160 pounds to 15,000 pounds; (c) in potassium content from 3000 pounds to 60,000 pounds, per acre; and many soils not only contain no lime, but are markedly acid and thus require heavy applications of lime, while some pro- INTRODUCTION xxi ductive soils contain as much as 20 per cent of calcium carbonate, corresponding to 200 tons of limestone per acre. (8) A zoo-bushel crop of corn takes from the soil about 100 pounds of nitrogen, 17 pounds of phosphorus, and 19 pounds of potassium, in the grain, and about 48, 6, and 52 pounds of these respective elements in the stalks or stover. (9) One ton of average fresh farm manure contains about 10 pounds of nitrogen, 2 pounds of phosphorus, and 8 pounds of potassium; and 100 pounds of the most common " complete " commercial fertilizer contains about 2 pounds of nitrogen, 4 pounds of phosphorus, and 2 pounds of potassium. (10) One ton of clover hay contains about 40 pounds of nitro- gen, 5 pounds of phosphorus, and 30 pounds of potassium. When grown on soil of fair productive capacity, the roots and stubble of the clover plant contain no more nitrogen than the soil has furnished to the plant; but for each ton of clover plowed under, the soil is enriched by about 40 pounds of nitrogen. (u) Roughly estimated, the plant food liberated from an aver- age soil during an average season with average farming is equiva- lent to about 2 per cent of the nitrogen, i per cent of the phos- phorus, and ^ of i per cent of the potassium, contained in the surface stratum (about 6f acre inches, or 2 million pounds of average soil). (12) As an average in live-stock farming, the animals retain about one fourth of the nitrogen and phosphorus and destroy two thirds of the organic matter of the food consumed, and large loss is likely to occur in the manure produced, especially in nitrogen and or- ganic matter, a loss of one half of these constituents being easily possible during three or four months, in part from fermentation, which may occur even under cover, and in part from leaching where the manure is exposed to the weather or where too little absorbent bedding is used. (13) It is less difficult to maintain or increase the organic matter of the soil by means of legume crops and crop residues in a good rotation for grain farming than in any system of live-stock farming which does not include the purchase of feed. (14) Some satisfactory rotation plans for grain farmers are wheat, corn, oats, and clover ; or wheat, corn, and cowpeas ; or xxn INTRODUCTION cotton, corn, and oats and cowpeas. The first of these is a four- year rotation which should include a catch crop of clover seeded the first year and plowed under for corn as late as practicable in the spring of the second year. The other two are three-year rotations, and they should also include legume catch crops wherever practicable. In each rotation for grain farming, all products are to be returned to the soil excepting the grain, or seed, and the cotton lint. Either the whole cotton seed or the hulls and meal should also be returned for fertilizer. (15) In live-stock farming the feeding should be done on the fields so far as practicable, and manure produced in the barn should be hauled and spread in the fresh condition so far as possible. Sufficient bedding should be used to absorb all of the liquid excre- ment, which is as valuable, ton for ton, as the solid excrement. (16) To insure the maintenance of the phosphorus content of the soil where large crops are produced, about 20 pounds of phos- phorus per acre for each year in the rotation should be applied in grain farming and about 10 pounds per acre in live-stock farming (aside from that returned in the manure). To enrich the soil in phosphorus, heavier applications should be made for a time. (17) The average investment required for 25 pounds of phos- phorus is about 75 cents in 200 pounds of fine-ground natural rock phosphate of good grade, about $2.50 in 200 pounds of good steamed bone meal, about $3.00 in 400 pounds of good acid phos- phate, about $6.00 in 600 pounds of the average " complete " commercial fertilizer, and about $80 in manure made from corn costing 40 cents a bushel. The natural phosphate, if ground to pass through a sieve with 10,000 meshes to the square inch, gives satisfactory results when applied in liberal amounts (as 1000 pounds per acre every three or four years), if used in connection with decaying organic matter in sufficient amount to maintain the nitrogen. (18) Potassium salts are used with very great profit on soils positively deficient in that element, as on most well-drained ex- tensive peaty swamp lands; and soluble salts, such as kainit, may produce some profit for a time if used in connection with phosphorus on soils deficient in decaying organic matter, even where the total supply of potassium in the soil is very large. INTRODUCTION xxili (19) Commercial nitrogen can usually be used with profit in market gardening, in cotton growing, and sometimes in the pro- duction of timothy hay near large cities; or, as a rule, wherever the gross returns from an acre of produce exceeds $50 or $75. (20) As a rule, commercial nitrogen cannot be used with profit for the production of the staple grain crops, such as corn and wheat, although under some conditions small applications of nitrogen alone or with other elements, as in the ordinary so-called " com- plete " fertilizer, may stimulate the plants sufficiently to enable them to draw more heavily upon the soil, and thus return apparent temporary profit in a system of ultimate land ruin. And other seed fell on good ground, and sprang up, and bare fruit an hundred fold. — JESUS. I applied mine heart to know, and to search, and to seek out wisdom, and the reason of things. — SOLOMON. Every man shall receive his own reward according to his own labor ; for we are laborers together with God. — PAUL. SOIL FERTILITY AND PERMANENT AGRICULTURE PART I , , SCIENCE AND SOIL 2-S ' CHAPTER I FOUNDATION FACTS AND PRINCIPLES Science. Science means knowledge, nothing more and nothing less. It does not mean theory unsupported by fact. To plow the land and plant the seed and cultivate the crop is art, or prac- tice. To know what the soil and air contain and what the crop requires is science. If 10 cents are taken from 70 cents, only 60 cents remain. This is science, knowledge, fact, and not mere opinion. In the study of soil fertility we must make large use of two well-established exact sciences, mathematics and chemistry. Several other sciences furnish much exact data, but in some branches the data thus far secured are not sufficient to fully reveal the controlling facts and principles. Chemistry. Chemistry is the science which deals with the com- position of matter. All material things are composed of about eighty primary substances, called elements, which may exist sepa- rately or in various combinations, called compounds. About forty of the elements are more or less common, the others being rare elements. Air and soil and plants and animals contain less than twenty elements that are of interest to agriculture; while only ten different elements are known to be essential for the making of agricultural plants. (One other element, chlorin, may be essen- tial, but, if so, only in minute quantity.) 2 SCIENCE AND SOIL Chemical elements. An element is a substance which cannot be divided into two or more different substances. Sulfur (S) is a solid, nonmetallic element, easily melted to the liquid form. A piece of sulfur may be divided into two parts, but each part is sulfur, and if nothing else is added to sulfur, nothing but sulfur can be obtained from it. Carbon (C) is the principal element con- tained in coal. Iron is a well-known metallic element. Oxygen (O) is an element contained in the air in the gas form. Chemical compounds. A[ compound is a substance which con- tains two or more different elements and which possesses some properties or characteristics not possessed by either element alone. Thus, if carbon and sulfur be mixed together at the ordi- nary temperature, the product is only a mixture in which each element retains its own properties; but, at a higher temperature and under proper conditions, one combining weight of black carbon will unite with two combining weights of yellow sulfur and form the compound called carbon disulfid (CS2), which is neither black nor yellow nor solid, but a colorless liquid somewhat resembling water, but which, when pure, contains absolutely noth- ing but the two elements, carbon and sulfur. Carbon, in charcoal for example, may be eaten in considerable quantity without harm, and sulfur is not dangerous in large doses; but the compound, carbon disulfid, is a deadly poison, and is fre- quently used as an insecticide and for the extermination of gophers and other burrowing animals. Thus the properties of the com- pound may differ in many respects from those of either element contained in it. On the other hand, when carbon is burned, by uniting with the oxygen of the air, the compound, carbon dioxid (CO2), is formed, and when sulfur is likewise burned, the compound, sulfur dioxid (SO2), is formed; while if carbon disulfid is burned, by uniting with the oxygen of the air, the products of combustion are exactly the same as though the carbon and sulfur were burned separately with oxygen, carbon dioxid and sulfur dioxid being formed. Sodium (Na, natrium in Latin) is a soft metallic element which takes fire when thrown into water, and the element chlorin (Cl) is a greenish colored poisonous gas, but when united these two elements form the compound called sodium chlorid (NaCl), salt. FOUNDATION FACTS AND PRINCIPLES 3 Chemical action. Chemical reaction is the union of two or more elements into a compound, or the separation of a compound into its elements, or the formation of new compounds from other com- pounds. In the most common chemical reactions heat is evolved. Place some coal in the stove, raise the temperature to the kin- dling point, and 32 pounds of the element oxygen entering the vent of the stove in gas form will unite with 12 pounds of the element car- bon in the coal and 44 pounds of the compound carbon dioxid (CO2) will form and pass off as a gas througn the chimney. After this chemical reaction is completed, the stove is found to contain only a few ounces of ashes, which represent the impurities in the coal. From this compound, carbon dioxid (CO2) , which is always pres- ent in the air in small amount, all agricultural plants obtain their supply of carbon and oxygen, which together constitute about 90 per cent of the total dry matter contained in plants. Combining weights. Combining weights of elements are the relative proportions in which those elements combine to form compounds. The combining weight of the element hydrogen is smaller than that of any other element, and for this reason all other combining weights are referred to that of hydrogen as the stand- ard, or unit, of weight. The combining weight of hydrogen is i. One part of hydrogen will unite with 35.5 parts of chlorin to form the compound hydrogen chlorid (HC1), which is also properly called hydrochloric acid, and sometimes incorrectly called " mu- riatic " acid. Thus, the combining weight of chlorin is 35.5. We may take i pound of hydrogen and let it unite with 35.5 pounds of chlorin to form 36.5 pounds of the compound HC1; or we may use i ounce of hydrogen and 35.5 ounces of chlorin, or i gram of hydrogen and 35.5 grams of chlorin, or i milligram of hydrogen and 35.5 milligrams of chlorin. All that is necessary is, that we maintain these proportions. This is one of the absolute mathematical laws of chemistry and is fundamental to the prin- ciples of soil fertility and plant growth. If we try to combine 3 parts of hydrogen with 35.5 parts of chlorin, 36.5 parts of the com- pound HC1 would be formed and 2 parts of hydrogen would be left in its original form. Atoms. An atom is the smallest particle of an element. It is not known how small the atom is, but it is known that the weight of 4 SCIENCE AND SOIL an atom of carbon is 12 times, of oxygen is 16 times, of sulfur is 32 times, and of chlorin is 35.5 times, as great as the weight of an atom of hydrogen. Thus the atomic weights of all other elements are referred to the weight of the hydrogen atom as the chemical unit. Molecules. A molecule is the smallest enduring particle of an element or compound. The atom, if set free, instantly unites with another atom (either of the same element or of a different element) to form a molecule, and the molecule may endure permanently. One atom of hydrogen and one atom of chlorin unite to form one molecule of hydrochloric acid, HC1. The molecular weight of this compound 1536.5, which is the sum of the atomic weights, the weight of the hydrogen atom always being i. It is true that this is an arbitrary standard, but so is every common standard of weight or measure, such as the ounce or the inch or the dollar. The inch is an arbitrary standard of length to which we may refer other lengths or distances, and likewise the weight of the hydrogen atom is an arbitrary standard to which we may with equal accuracy refer the weights of the atoms of all other elements, and also the weights of all molecules of either compounds or elements. Atomic bonds. Atomic bonds are the links of union between atoms. This bond between atoms may be likened to the hand clasp between persons, except that under normal conditions the hand of one atom always grasps the hand of another atom. If the bond is broken, the freed hands immediately grasp other hands, breaking the bonds between other atoms if necessary to secure union. At the instant a bond is broken, when free hands exist, the atoms are called nascent, and in that condition they have unusual power to attack the molecules of other elements or compounds. Free hydrogen means hydrogen not combined with some other element. Thus we have nascent hydrogen (H), ordinary free hydrogen (H^), and combined hydrogen, as in water (HjO). Of course, nascent hydrogen is also free hydrogen, but in an extraordinary form; namely, as a free atom, which as such can exist but an instant until it unites with another atom of hydrogen (or of -some other element) to form a molecule. Valence. Valence refers to the number of bonds, or hands, pos- sessed by an atom. The hydrogen atom has but one hand (H — ), while the oxygen atom has two hands ( — O — ), and the carbon FOUNDATION FACTS AND PRINCIPLES 5 atom has four hands (=C=). In hydrogen molecules the atoms are always in pairs (H — H or Hj). Thus the weight of the hydro- gen molecule is two, because it contains two of the unit atoms. The atom of oxygen weighs sixteen times as much as the hydrogen atom, consequently 16 is the atomic weight, or the combining weight, of the element oxygen. The molecule of ordinary oxygen contains two atoms (O =O or Og) , but there is a form of oxygen, called ozone, which contains three atoms in the molecule (O O or Og). The molecular weight of ordinary oxygen is 32, while the molecule of ozone weighs 48 times as much as one hydrogen atom. One oxygen atom has power to hold two hydrogen atoms (H — O — H or H2O). This is a compound which might be called dihydrogen oxid, but which is commonly called water. The molecular weight of water is 18, the sum of the atomic weights. Separately, hydrogen and oxygen are both gases under ordinary conditions, but the compound H2O possesses different properties, being a liquid at ordinary temperatures, although water becomes a gas at high temperature and a solid at low temperature. While it is common knowledge that this compound exists in three forms, solid, liquid, and vapor, and that it is easily changed from solid ice to liquid water and from liquid to vapor (steam), it is not so generally known that most elements and most com- pounds may exist in each of these three forms under proper condi- tions of temperature and pressure. One atom of carbon may combine with four atoms of hydrogen, /Hv /H x forming the gas compound I XY or CH4 ) called methane or VH/ \H marsh gas, a constituent of illuminating gas, and sometimes formed in stagnant marshes. This hydrocarbon has a molecular weight of 1 6 and is the lowest in a very large series of compounds contain- ing only hydrogen and carbon. One atom of carbon with its four bonds may unite with two atoms of oxygen, forming carbon dioxid (O = C = O or CO2) , a chemical reaction which occurs in the com- bustion of coal or other substances containing carbon, as already explained. Monovalent atoms have one bond, or one hand (mono means 6 SCIENCE AND SOIL one, as in monotone) ; bivalent atoms have two bonds (bi or di means two); trivalent atoms have three bonds; tetravalent, four bonds; pentavalent, five bonds; hexavalent, six bonds; hepta- valent atoms have seven bonds; and octovalent atoms have eight bonds, with power to hold four of the bivalent atoms of oxygen. There are a few cases in which the atom does not make common use of all the bonds it possesses. Thus the nitrogen atom has five bonds, or hands, but in some compounds only three bonds are used to hold other atoms. It might be conceived in this case that the other two hands are clasped together, and this conception might even be extended to cover a molecule composed of a single biva- lent atom (such as mercury and, possibly, argon). One atom of nitrogen and three atoms of hydrogen form the compound called ammonia (NHg). This compound is frequently sold in fertilizers, but the hydrogen has no money value because water (I^O) con- tains hydrogen. The molecular weight of ammonia is 17, of which the nitrogen atom is 14 and the hydrogen atoms are 3. If a fer- tilizer is guaranteed to contain 17 per cent of ammonia, it should contain 14 per cent of the element nitrogen; while 8| per cent of ammonia is equivalent to only 7 per cent of nitrogen. Ammonia itself contains ^, or 82 per cent, of the element nitrogen. In the compound called ammonium chlorid (NH4C1), the atom of nitrogen is pentavalent; that is, it has and uses five bonds: K H N-C1. The molecular weight of this compound is 53.5 (14 + 4 + 35-5), and it contains -^-, or 26 per cent, of nitrogen. 53-5 Phosphorus is another element which sometimes uses only three /H bonds, as in hydrogen phosphid, P^-H, and in phosphorus trichlorid, XH /Cl P^-C1, and sometimes five bonds, as in phosphorus pentachlorid, XC1 CL JC\ ^P^-C1. Thus, the hydrogen phosphid contains f^, or 91 per CK XC1 FOUNDATION FACTS AND PRINCIPLES 7 cent, of phosphorus (the atomic weight of phosphorus being 31), while the phosphorus pentachlorid contains less than 15 per cent of phosphorus. Nitrogen and phosphorus are in some respects very much alike, and in other respects they are very unlike. They are the two most precious elements of plant food, and they deserve from the author and from the reader all of the consideration they are to receive in this book. The gas law. This law is that equal volumes of gases under like conditions of temperature and pressure contain the same number of molecules. In other words, in the gas form, every molecule occupies, or controls, the same amount of space. Thus, the hydro- gen molecule, with a weight of 2, occupies as much space as the oxygen molecule, which weighs 32, or the molecule of carbon dioxid, weighing 44, or of sulfur dioxid with a molecular weight of 64. (The atomic weight of sulfur is 32.) If a 6-gallon bottle holds 2 grams of hydrogen (H2), it will hold 32 grams of oxygen (O2), 28 grams of nitrogen (N2), 16 grams of methane (CH4), 17 grams of ammonia gas (NHg), 44 grams of carbon dioxid (CO^ , 64 grams of sulfur dioxid (SOg) ,and a gram- molecule (the molecular weight in grams) of any other gas. This law does not apply to liquids or solids, but only to gases. Chemical symbols. A symbol is used to represent one atom of an element. H stands not only for the element hydrogen, but also for one atom of hydrogen with a combining weight of i. Likewise S stands for sulfur and for one atom of sulfur, and represents a weight of .32. Chemical formulas. A formula is used to represent a molecule and shows the kind and the number of atoms contained in the molecule. The formula H2O represents one molecule of water, containing two atoms of hydrogen, each having a combining weight of i, and one atom of oxygen, with a weight of 16. Thus, the molecular weight of water is 18. The formula Cag(PO4)2 (read: Ca three, PO four, twice) represents one molecule of tricalcium phosphate, the valuable phosphorus compound contained in bones and in natural phosphate rock. The metallic element calcium (Ca) is also contained in limestone, which is calcium car- bonate (CaCOs) , and in quicklime, or burned lime, which is calcium 8 SCIENCE AND SOIL oxid (CaO). The atomic weight of calcium is 40. The subscript figures used in a chemical formula always refer to the preceding element, or to the inclosed group of elements if parentheses are used. In the calcium phosphate, Ca3(PO4)2, the subscript 3 shows that three atoms of calcium are contained in the molecule. The parentheses are used to inclose a group of atoms (one atom of phosphorus and four atoms of oxygen) which occurs in many other compounds, as in H3PO4 (phosphoric acid), FePO4 (iron phosphate), etc. (Fe is fromferrum, the Latin word for iron, and I is the symbol used for the element iodin.) The subscript 2 follow- ing the parenthesis in Ca3(PO4)2 means that the molecule contains the PO4 group twice, and for this reason Ca3(PO4)2 is a better for- mula than Ca3P2O8, which may also be correctly used. A mole- cule of tricalcium phosphate contains three atoms of calcium (3 X 40 = 120), two atoms of phosphorus (2 x 31 = 62), and eight atoms of oxygen (2 X 4 X 16 = 128), and the molecular weight is 310 (120 + 62 + 128), of which the phosphorus represents only 62. Thus, tricalcium phosphate contains -/^$, or 20 per cent, of the element phosphorus. In other words, one fifth of pure tricalcium phosphate is phosphorus, while the remaining four fifths consist of calcium and oxygen in nearly equal parts. The law of constant proportions. This law is that in every chemi- cal combination the constituents occur in definite and constant proportions by weight. The percentage of phosphorus in pure tricalcium phosphate is absolutely constant. It matters not whether the compound is made in the United States, in Germany, or in Japan, nor whether it is obtained from bones or from phos- phate rock, the percentage of phosphorus it contains is always the same, if the compound is pure. This percentage is exactly 20, according to the most accurate accepted determinations. The atomic weights are determined by several different methods, but, even with the finest and most accurate balances and other instru- ments and means, absolute exactness may not be achieved, be- cause of the human error. No man can measure a mile with absolute exactness, because two different measurements made by one man may vary by an inch, a tenth of an inch, or, at least, by a hundredth or a thousandth of an inch. According to the chemical law, the proportion of the different FOUNDATION FACTS AND PRINCIPLES 9 elements in any pure compound is absolutely definite and constant, in strict accordance with the chemical law, and the proportion can be determined with ten times the degree of accuracy required for all practical purposes ; nevertheless, the determination may not be absolutely exact. While all atomic weights are essentially referred to hydrogen as unity, the mathematical basis is exactly 16 for the atomic weight of oxygen, because the element oxygen constitutes in quantity one half of the earth's crust (including the air, the ocean, and the solid crust to a depth of ten miles), and forms compounds with nearly all other elements, thus affording closer comparisons than hydrogen. The known chemical elements. In the accompanying table is the complete list of 80 known elements. For convenience the more common elements, that every one should know, are given in one group, arid the rare elements, that few people have ever seen, are grouped by themselves. The symbols used for the chemical elements are essentially the same in all languages. In a few cases where the modern name varies in different languages, the nations have agreed upon a symbol derived from the Latin name of the element; as, for example, Fe for iron (ferrum in Latin), K for potassium (kalium), and Na for sodium (natrium). Some of the atomic weights of the rare elements have not yet been determined with a sufficient degree of accuracy to justify assigning a more specific value than the nearest whole number. Further investigation must determine whether such whole numbers are correct. It is a noteworthy fact that the chemists of the world are agreed that, of these forty more common elements, sixteen have atomic weights that differ from whole numbers by less than .05, and' twelve others differ only by about .1, thus showing twenty-eight of the best-established atomic weights apparently grouped with relation to the unit, with only twelve scattering ; and some of these (as nickel) are doubtful, while others are high atomic weights with consequent possibilities of error, the accepted atomic weights of gold and platinum both having been changed by .5 within recent years. These data and the recognized periodic law, that the properties of the elements are periodic functions of their 10 SCIENCE AND SOIL TABLE i. ELEMENTS, SYMBOLS, AND INTERNATIONAL ATOMIC WEIGHTS FOR 1909. (Decimals, including ciphers, indicate supposed accuracy.) THE MORE COMMON ELEMENTS THE RARER ELEMENTS Name Symbol Atomic Weight Name Symbol Atomic Weight Aluminum .... Antimony (Stibium) . Argon Al Sb A As Ba Bi B Br Cd Ca C Cl Cr Co Cu F Au H I Fe Pb Li Mg Mn Hg Mo Ni N O P Pt K Si Ag Na Sr S Sn Ti Zn 27.1 1 20. 2 39-9 75-o 137-4 208.0 II. 0 79-9 112.4 40.1 I2.O 35-5 52-1 59-o 63.6 19.0 197.2 1.008 126.9 55-9 207.1 7.0 24-3 54-9 2OO.O 96.0 58.7 14.0 IO.OOO 3I.O 195.0 39-i 28.3 107.9 23.0 87.6 32.1 119.0 48.1 65-7 Caesium .... Cerium Columbium . . . Dysprosium . . . Erbiym .... Cs Ce Cb Dy Er Eu Gd Ga Ge Gl He In Ir Kr La Nd Ne Os Pd Pr Ra Rh Rb Ru Sa Sc Se Ta Te Tb Tl Th Tm W U V Xe Yb Y Zr 132.8 140.3 93-5 162.5 167.4 152 157-3 69.9 72-5 9.1 4.0 114.8 J93-1 81.8 139.0 144-3 20 190.9 106.7 140.6 226.4 102.9 85-5 101.7 150.4 44.1 79-2 181 127-5 159-2 204.0 232.4 168.5 184.0 238-5 5i-2 128 172.0 89.0 90.6 Arsenic Barium .... Bismuth Europium .... Gadolinium . . . Gallium .... Germanium Glucinum .... Helium Boron Bromin ..... Cadmium .... Calcium Carbon Chlorin Indium Chromium .... Cobalt Iridium .... Krypton .... Lanthanum . . . Neodymium . . . Neon Copper (Cuprum) Fluorin Gold (Aurum) . . . Hydrogen .... lodin Osmium .... Palladium .... Praseodymium . . Radium .... Rhodium .... Rubidium .... Ruthenium . . . Samarium .... Scandium .... Selenium .... Tantalum .... Tellurium .... Terbium .... Thallium .... Thorium .... Thulium ... Tungsten (Wolfram) Uranium .... Vanadium .... Xenon Iron (Ferrum) . . . Lead (Plumbum) . . Lithium .... Magnesium . . . Manganese . . . Mercury (Hydrar- gyrum) .... Molybdenum . . . Nickel Nitrogen .... Oxvgren . Phosphorus . . . Platinum .... Potassium (Kalium) . Silicon Silver (Argentum) Sodium (Natrium) . Strontium .... Sulfur Tin (Stannum) . . Titanium .... Zinc Ytterbium .... Yttrium .... Zirconium .... FOUNDATION FACTS AND PRINCIPLES n atomic weights,1 together with the recently discovered radium and radio activity, and the evidences 2 of accomplished transformation of one element into another, strongly indicate a common origin for different elements, and lend to the subject a present-day in- terest as intense as ever moved the alchemist to try to turn the baser metals into gold. 1 It is worth while to note some relations that exist between the monovalent elements fluorin, chlorin, bromin, iodin; between the bivalent elements oxygen, sulfur, selenium, molybdenum; between the trivalent (or pentavalent) nitrogen, phosphorus, arsenic, antimony; and also between the tetravalent carbon, silicon, titanium, and germanium: Fluorin Chlorin Bromin Iodin F = i9 01 = 35.5 Br = 8o 1 = 127 HF HC1 HBr HI Oxygen Sulfur Selenium Molybdenum O = 16 5 = 32.1 Se = 79.2 Mo = 96 H2O H2S H2Se H2SO4 H2SeO4 H2MoO4 Nitrogen Phosphorus Arsenic Antimony N = 14 P = 31 As = 75 Sb = 120.2 NHs PH3 AsH3 SbH3 N2O6 P2O6 As2O6 Sb2O6 Carbon Silicon Titanium Germanium C = i2 Si = 28.4 Ti = 48 Ge = 72.5 SiH4 CO2 SiO2 TiO2 GeO2 Aside from the similarity of valence and other properties and of compounds formed, there is interest in the relation of atomic weights, especially in the second and fourth groups, and, even in the fact that the atomic weight of antimony is so nearly the sum of the other three in the group. 2 In 1907 Ramsay and Cameron, of England, reported that they had reduced copper, in the presence of radium emanation, into other elements of the same series: potassium, sodium, lithium. (See Nature, July, 1907, and Journal of the Chemical Society, September, 1907.) The correctness of Ramsay and Cameron's experiments has been called in question by Mme. Curie and Mile. Gleditsch; Comptes rendus, 147, 345 (1908); Science, December 4, 1908. CHAPTER II THE MORE COMMON ELEMENTS AND COMPOUNDS Important elements. Fifteen elements are of special interest and importance in the study of soil fertility, because they are commonly found in plants and animals and because they so largely constitute the soil and air and ocean and the common things of earth. Of these fifteen elements, ten are known to be essential to plant growth; eight of them constitute 98 per cent of the solid crust of the earth; four of them constitute 99. 6 per cent of the ocean, about 96.4 per cent being water (H2O) and 3.2 per cent common salt (NaCl); and two of them (nitrogen and oxygen) constitute 98.5 per cent by weight of the dry atmosphere, about 1.5 per cent of the air consisting of the recently discovered element, argon. The ten essential elements of plant food may be grouped as follows : C, H, O, obtained by plants from air and water. P, K, N, sometimes deficient in soils, and of money value as plant food. S, Ca, Fe, Mg, required in small amounts and not likely to be deficient in soils. The five other elements commonly present in plants are silicon, aluminum, sodium, chlorin, and manganese. The reader is earnestly advised to learn by groups * the name and atomic weight and the valence of each of these important elements, and the following table is constructed for this purpose. Aside from the name, symbol, atomic weight, and valence, Table 2 furnishes some extremely valuable and useful information concerning the occurrence and relative abundance of the elements which essentially constitute the crust of the earth, the ocean, the air, and the agricultural plants and animals. These data are based 1 The author consents to the students' memory key: "C. HOPK'NS' CaFe,-Mg, " if Mg stands for "Mighty good " and the omission of I, for modesty. THE MORE COMMON ELEMENTS AND COMPOUNDS 13 upon the recent computations of. Professor F. W. Clarke of the United States Geological Survey for the average composition of the ocean and of the earth's crust 1 to a depth of ten miles, essen- tially upon Sir William Ramsay's recent estimate for the average composition of air, and upon the author's compilations and com- putations for the average composition of shelled corn (maize). TABLE 2. THE MORE IMPORTANT ELEMENTS NAME SYMBOL ATOMIC WEIGHT (0=i6) VALENCE, OR NUMBER OF BONDS OCCURRENCE In Earth's Crust (Per Cent) In the Ocean (Per Cent) In the Air (Per Cent) In the Corn Ker- nel (Per Cent) Oxygen . . Carbon . . Hydrogen o c H 16 12 I 2 4 I 47.07 .20 .22 85-79 23.00 .OI 46.000 45.000 6.400 10.67 Nitrogen Phosphorus Potassium . N P K 14 31 39 3 or 5 3 «r 5 i trace .11 2.46 75-5° 1.760 .300 •340 .04 Magnesium Calcium . . Iron . . . Sulfur . . Mg Ca Fe S 24-3 40 56 32 2 2 2, 3» 6, or 7 2, 4, or 6 2.40 3-44 4-43 .11 .14 •°5 .125 .022 .008 .OO4 .09 Silicon . . Aluminum . Sodium . . Chlorin . Manganese Si Al Na Cl Mn 28.3 27 23 35-5 55 4 3 i i, 3, 5, or 7 2,-3, 6, or 7 28.06 7.90 2-43 .07 .07 .014 I.I4 2.07 .013 .013 Titanium Argon Ti A 48 40 4 (?) .40 1.48 Totals 99.36 2 99-99 99-99 3 99-99 1 United States Geological Survey Bulletin 330 (1908). The data for phos- phorus and potassium include analyses of 1671 and 2110 different samples, re- spectively, of representative rocks, some of which were kindly furnished to the author by Doctor Clarke since Bulletin 330 was published. 2 About sixty other elements (most of them very rare) must account for this deficiency. 3 Constant traces of helium, neon, krypton, and xenon are also found in the air, of which they may constitute five parts per million. Varying amounts of moisture, compounds of nitrogen, sulfur, chlorin, and more or less dust, also exist in the air. 14 SCIENCE AND SOIL It may well be stated here Jthat plants secure their supply of both carbon and oxygen from the carbon dioxid of the air. The .01 per cent of carbon (C = 12) shown in the table is equivalent to nearly .04 per cent of carbon dioxid (CO2 = 44). The hydrogen of plants is taken from the water absorbed by the roots. The corn plant secures its supply of nitrogen from the " trace " contained in the earth's crust, which, however, amounts to about .25 per cent, in the tilled stratum of a good soil. Under proper conditions legume plants secure more or less of their nitrogen from the air. The remaining six essential elements are secured only from the soil by all plants. Of the atmosphere, ocean, and solid crust (ten miles deep), the solid crust constitutes about 93 per cent of the whole ; while the entire atmosphere amounts to only .03 per cent. These addi- tional facts make possible a mathematical comparison between the supply and crop requirements of carbon and oxygen (in CO2) and nitrogen in the air, and emphasize the importance of the carbon cycle and of the circulation of some other elements, all of which is more fully discussed and explained in the following pages. A ready working knowledge, sufficient for everyday use, lies at the basis of success in every industry and profession. It is worth while to have in mind a few fundamental facts relating to the seven- teen elements named in Table 2, which constitute more than 99 per cent of earth, sea, and air, and of all plants and animals. Nothing can be made of nothing. Compounds consist of two or more elements, and the molecule of a compound must contain two or more atoms. If one knows the valence of the elements, he is then in control of much information of very great value in relation to compounds. Valence is the key to the understanding of compounds and chemical reactions. Table 2 gives this information for the very important elements. Three of these elements — hydrogen, potassium, and sodium — have only one bond, or hand, for each atom (H — , Na — , and K — ); while chlorin (Cl) may use i, 3, 5, or 7 bonds. Three other elements have only two bonds for each atom (O = , Mg = , and Ca=), these elements being strictly bivalent. Sulfur sometimes uses only two bonds (in H2S and CS2), but may use four or six. THE MORE COMMON ELEMENTS AND COMPOUNDS 15 Iron and manganese are alike peculiar, with a valence of 2, 3, 6, or 7. Aluminum is a trivalent element with three-handed atoms, while nitrogen and phosphorus may use either three or five bonds. This leaves only the strictly tetravalent family, carbon (= C = ), silicon ( = Si=), and titanium (=Ti = ).1 When an iron atom uses three hands, it is called -ic iron, but if it uses only two hands it is called -ous iron. Thus we have the ferrous chlorid (FeCl2) and ferric chlorid (FeCl3) ; also ferrous oxid (FeO) and ferric oxid (Fe2Og). Likewise, when phosphorus uses only three bonds, it is called -ous phosphorus, but with the five bonds in use it is -ic phosphorus, as in phosphorous chlorid (PClg) and phosphoric chlorid (PC16), which are also called phosphorus tri- chlorid and phosphorus pentachlorid, the endings, -ous and -ic, being unnecessary when the valence is specified in the number of chlorin atoms held. Matter may exist in three distinctly different forms or classes which might be called " monary " (single), "fo'nary" (double), and " /raiary," or ternary (triple). First, matter may exist in the form of free or uncombined ele- ments; as solid metallic iron, aluminum, magnesium, calcium, sodium, or potassium; as solid nonmetallic carbon, phosphorus, sulfur, or silicon; as liquid mercury or bromin; or as gaseous oxygen, nitrogen, hydrogen, or chlorin. This might be termed the " wonary " form, all atoms in the molecule being of the one element. Second, matter may exist in binary compounds ; that is, with 1 Argon is of interest chiefly because it is so very common and yet so recently discovered. Argon is everywhere present in the air and we respire more than an ounce a day of that element. It is an invisible gas, and because it is mixed with so much nitrogen (which it resembles somewhat) and oxygen, and cannot be seen, it would be less easily discovered than many other elements; but the chief difficulty in detecting it by chemical methods was due to its chemical inaction. Because of this inaction, it has been named argon, which means without action. When the ele- ment was discovered and very thoroughly investigated, the discoverers (Rayleigh and Ramsay, in 1894) concluded that the argon atom has no valence, — no hand with which to clasp the hand of another atom, either of argon or of any other element. In other words, they discovered that argon forms no compounds, and that the molecule of argon is monatomic (man or mono means one, as in monotone = one tone). Later investigations indicate, however, that argon has some weak affinities. 1 6 SCIENCE AND SOIL two elements represented in the molecule. In the name of such a compound both elements are expressed, and sometimes the name also includes the number of atoms of each of the elements in the molecule, as phosphorus pentachlorid (PC15) . As a rule, the name of one element is modified slightly so as to end in -id, a termination that means that the compound is binary, containing but two elements. (Any exception to this rule will be self-explanatory.) Thus' sodium chlorid must contain only two elements, sodium and chlorin, because of the names and the ending -id; and, since sodium must be monovalent and chlorin may be, the formula for the molecule is probably Na — Cl, which is correct for com- mon salt. As a matter of fact, chlorin is always monovalent in binary compounds with metals. Calcium oxid (quicklime) must be a binary compound of the two strictly bivalent elements, calcium and oxygen, and the molecular formula may be Ca=O, which is also correct. Calcium chlorid should be Ca=Cl2; and magnesium chlorid, Mg=Cl2; and potassium oxid, K2=O; hydrogen sulfid, H2 = S; sulfur dioxid, SO2 (O = S=O); and sulfur trioxid, SO8 (in which the sulfur atom must use six bonds), all of which are correct. More complex molecules, which, however, are easily understood, are aluminum oxid (A12O3) and phosphorus pentoxid (P2O6) . The aluminum atom has three bonds (or hands) , and the phosphorus uses five bonds in this oxid, while the oxygen atom is always bivalent, having but two hands. There are six bonds of union in aluminum oxid and ten bonds in phosphorus pentoxid, P\° thus: A1;>O, /O. Thus, if one knows the name, the atomic AlS04 = CaS04 + 2 H2O. X!OH H,!/ The dotted line shows how the two compounds are broken. The two hydrogen atoms are broken off from the sulfuric acid and the two hydroxyl groups are broken off from the calcium hydroxid, and each hydrogen atom (H — ) immediately joins hands with a hydroxyl group ( — OH) and thus are formed two molecules of water, 2(H — O — H). The bivalent calcium atom (Ca=) also grasps the two free hands of the radicle =SO4, and forms the compound CaSO4, which is calcium sulfate. Thus, from a base (alkali) and an acid, we have formed water and a neutral salt, neither acid nor alkaline. This is a typical reaction between a hydroxid acid and a hydroxid base, resulting in the formation of a salt. Many other salts may be formed by similar reactions between basic hydroxids, oxids, or free metals, on the one hand, and different kinds of acids, on the other hand, which may contain oxygen in the form of hydroxid only, or in both hydroxid and oxid form, or the acid may contain no oxygen, but only hydrogen joined directly to some nonmetallic element, as in hydrochloric acid (HC1) or hydrosulf uric acid (H2S) . Salts are the most abundant and important compounds. The earth's crust consists largely of insoluble mineral salts, called sili- cates. These are, as a rule, very complex salts, one of the simplest being common felspar, potassium aluminum silicate, KAlSi3O8. This double salt is the principal source of potassium, one of the essential elements of plant food. Common salt is sodium chlorid, NaCl. Epsom salt is magnesium, sulfate, MgSO4. Glauber salt is sodium sulfate, Na2SO4. Even limestone is a kind of salt, calcium carbonate, CaCO3. For convenience, the formulas of salts containing oxygen are 22 SCIENCE AND SOIL written with the oxygen in one group, as Na^SO^ but it may well be remembered that oxygen is regularly the linking element be- tween the metal and the nonmetal, and the structure of the mole- cule is better shown if written thus: A few more equations for typical reactions will show the various ways by which salts may be formed. Other similar acids and bases give similar products: Ca(OH)2 + H2SO4 = CaSO4 + 2 H2O. KOH + HNO3 = KNO3 + H2O. These equations represent, first, the reaction between the cal- cium hydroxid and sulfuric acid with the formation of calcium sulfate (gypsum, or land plaster), and, second, the reaction be- tween potassium hydroxid and nitric acid with the formation of potassium nitrate (saltpeter). In place of a hydroxid base, we may use an oxid of some metal, thus: CaO + H2SO4 = CaSO4 4- H2O. CaO + 2 HNO3 = Ca(NO3)2 + H2O. K2O + H2SO4 = K2SO4 + H2O. The salts formed are calcium sulfate, calcium nitrate, and potas- sium sulfate, and in each reaction only one molecule of water is formed, when the oxid base is used, in place of two molecules of water from the use of a bivalent hydroxid base. The base may be not only in the form of an oxid or hydroxid of the metal, but we may use the free metal itself as a base, thus : Fe + H2SO4 = FeSO4 + H2. Mg + 2 HN03 = Mg(N03)2 + H2. In these reactions the hydrogen atoms are displaced by the metal and liberated as a gas. While most acids contain oxygen either as a hydroxid (C1OH) or a hydroxid oxid (OC1OH orO2C!OH), a few acids, with the prefix hydro-, contain no oxygen; as, for example, hydrochloric acid THE MORE COMMON ELEMENTS AND COMPOUNDS 23 (HC1); but these acids also react with bases (metals, metallic oxids, or metallic hydroxids), as shown above for the oxygen acids, thus: Fe + 2 HC1 = FeCl2 + H2. CaO + 2 HC1 = CaCl2 + H2O. NaOH + HC1 = NaCl + H2O. In these reactions the salts formed are chlorids. The last equa- tion shows the reaction between sodium hydroxid, which is ordi- nary concentrated lye, a poisonous substance, and hydrochloric acid, which is also a poisonous substance; and the salt formed is sodium chlorid (NaCl), the common table salt, and the most abundant salt of the ocean. Hydrosulfuric acid (H2S) also forms many salts, called sulfids, as iron sulfid (FeS), calcium sulfid (CaS), etc. In all of these reactions the number of pounds of any base re- quired to react with a given amount of any acid is easily and accu- rately computed, and the amount of the salt to be formed and of the water or hydrogen to be liberated can also be told in advance, if one knows the atomic weights and the equation for the reaction. Thus, 40 pounds of sodium hydroxid will react with 36.5 pounds of hydrochloric acid, and form 58.5 pounds of common salt and 1 8 pounds of water. It will be seen that 76.5 pounds of materials are used, and that 76.5 pounds of products are formed. In like manner, all such equations must balance. In other words, the num- ber and kind of atoms and the total quantity of materials put into the reaction oh one side of the equation must be exactly the same as appear in the products on the other side of the equation. Acid salts are salts which still contain some of the hydrogen of the acid from which they were made. Thus, if we supply only one half as much potassium as would be required to react with a cer- tain amount of sulfuric acid, if an acid salt is possible, it will be formed: KOH + H2SO4 = KHSO4 + H2O. The sulfuric acid molecule has two hydrogen atoms, and, to make neutral potassium sulfate, both hydrogen atoms must be replaced with potassium atoms; but in the equation here shown, only one potassium atom is provided. Consequently, only one 24 SCIENCE AND SOIL hydrogen atom is replaced by potassium, and the compound formed is acid potassium sulfate (HKSO4 or KHSO4). The charac- ter of this compound is one half acid and one half salt. If applied to the soil, it would tend to make the soil sour, or acid, which is also true of the common acid phosphate of the fertilizer trade, which is further discussed under phosphorus. Common acids are so few in number that it is well worth while to memorize the formulas. The following are important in the study of soil fertility : HC1 . . . Hydrochloric acid (no oxygen). HNO8 . . Nitric acid. HNO2 . . Nitrous acid (less oxygen). H2SO4 . . Sulfuric acid. H3PO4 . . Phosphoric acid. H2CO3 . . Carbonic acid. H2SiO3 . . Silicic acid. H2S . . . Hydrosulfuric acid (no oxygen). The salts made from these acids, and their derivatives, by reac- tion with the bases represented by the six metals (iron, aluminum, calcium, magnesium, potassium, and sodium) constitute, in large part, the solid crust of the earth and the salts of the sea. One non- metallic oxid (SiO,j) and two oxids of metallic elements (Fe2O3 and ALjO3) are also found native in very considerable amounts. Some acids are strong and some are weak. The weakest acid is carbonic (H2CO3), but silicic (H2SiOg) and hydrosulfuric (H2S) are also weak acids; while hydrochloric (HC1), nitric (HNOg), sulfuric (H2SO4), and phosphoric (HgPOJ are all very strong acids. A strong acid may take a base away from a weak acid, thus : CaCO8 + H2SO4 = CaSO4 + H2CO8. Here we have the strong sulfuric acid reacting with calcium carbonate (limestone) to form a neutral salt, calcium sulfate, and the weak carbonic acid. The carbonic acid is so weak that it may break in two, forming water and carbon dioxid: H2CO3 = H2O + CO2. THE MORE COMMON ELEMENTS AND COMPOUNDS 25 Thus we may apply limestone (CaCO3) to an acid soil (containing organic acids, silicic acid, or acid silicates) , and the soil acids will take the base (calcium), and the liberated carbonic acid will break in two, the gas carbon dioxid (CO2) passing out of the soil into the air and thus leaving the soil with no acid in it. CHAPTER III PLANT FOOD AND PLANT GROWTH Oxygen. Oxygen is the most abundant element. It constitutes about one half the sum of all known matter. It forms chemical compounds with nearly all other elements,1 and is, in consequence, termed a chemically active element. In the free state (O2), it is a gas. In this form it constitutes about 23 per cent of the air. It is thus present everywhere and ready to form compounds with other elements, or to attack other compounds under favorable conditions. The compounds formed with oxygen may at ordinary temperatures be gases, such as carbon dioxid (CO2) , liquids, such as water (H2O) , solids, such as iron oxid (Fe^Og). All ordinary combustion consists of chemical reaction with oxygen, and the principal products formed are carbon dioxid and water. Water is eight ninths oxygen, and carbon dioxid is eight elevenths oxygen, as any one can determine for himself if he knows the atomic weights given in Table 2. The grain of corn is nearly one half oxygen (46 per cent). Carbon. This is -a very common element, but not very abundant as compared with nine other elements. Even titanium, a tetrava- lent element belonging to the same periodic group as carbon and silicon, is one half more abundant than carbon in the earth's crust. But titanium has no agricultural value, while carbon is one of the most important elements in the structure of plants and ani- mals. About 45 per cent of the corn kernel is carbon. Carbon in the free state is the principal element in coal and char- coal. Soft coal (bituminous) contains about 90 per cent of carbon, and hard coal (anthracite) contains about 97 per cent of carbon. Graphite, the " lead " used in lead pencils, is not lead, but car- 1 No oxygen compounds are known with fluorin, argon, or helium. 26 PLANT FOOD AND PLANT GROWTH 27 bon. It differs in some manner from the carbon in coal or char- coal, probably because of a different number, or a different arrange- ment, of the atoms in the molecule. The diamond is very pure carbon in crystallized form. Both the diamond and ordinary carbon may be converted into graphite, and small diamonds have been made artificially from ordinary carbon. Free carbon in any form burns with oxygen to form carbon dioxid (CO2), but with graphite and the diamond the reaction occurs only at higher temperatures than are necessary with ordinary carbon. Carbon in the free state has never been liquefied, but it has been volatilized at the temperature of 3500° Centigrade (6332° Fahrenheit). On the other hand, many of the compounds with carbon are liquids or gases at ordinary temperatures. Examples of liquid compounds are carbon disulfid (CS2), benzene (C6H6), and many other hydrocarbons contained in petroleum; while carbon dioxid (CO2) , methane (CH^) , and acetylene (C^Hg) are well-known gases containing carbon. In the solid form, carbon occurs not only in the free state, but also in compounds, of which two very important groups are the carbonates and the carbohydrates. Marble, limestone, chalk, and marl are different forms of calcium carbonate (CaCO3), one of the few compounds with a molecular weight of 100, and thus containing 12 per cent of carbon, 40 per cent of calcium, and 48 per cent of oxygen. Of these four materials marble is nearly pure calcium carbonate, while the others may be nearly pure or very impure. When calcium carbonate is heated, two bonds are broken and then joined in another way, so that the one compound (CaCO3) is broken into two (CaO) and (CO2), thus: =O becomes Ca: = O, or CaCO8 = CaO + CO2. The calcium oxid (CaO) is burned lime, or quicklime, which remains in the kiln; while carbon dioxid (CO2) is a gas which passes off into the air. It is easy to see that only 56 pounds of quicklime could be made from 100 pounds of pure limestone. 28 SCIENCE AND SOIL Limestone is a constituent of good soils, and if limestone is not present in a soil, then it should be applied; for, as already explained, carbonic acid is the weakest of all acids, and, consequently, if the soil contains limestone, it cannot be an acid soil, because the soil acids will take the base away from calcium carbonate (and also from any other carbonate), and the liberated carbonic acid is broken up into water and carbon dioxid. Magnesium carbonate and iron carbonate are found in rock deposits; while potassium carbonate (K2COg) is the lye (alkali) obtained from wood ashes, and sodium carbonate (Na2COg) is the most harmful alkali in alkali soils. The carbonic acid is so weak that the carbonates of the strongest bases (potassium and sodium) are almost as basic (alkaline) as the hydroxids of the same ele- ments (KOH and NaOH). The term hydrate used in the name of a chemical compound means that it contains water combined with some other constitu- ent, or that hydrogen and oxygen are present in the same propor- tion as in water (H2O). Thus, carbohydrates contain carbon and water. This very important group of carbon compounds, includ- ing sugar, starch, and cellulose (wood fiber) will be explained after hydrogen has been discussed. Hydrogen. Hydrogen is the third most important element in plants, constituting about 6.4 per cent of the corn kernel. Water is the only abundant source of hydrogen, although the element is found in the earth's crust in appreciable amount, chiefly in hy- drated mineral compounds containing, as the name indicates, water in combination with salts. In some cases the combined water corresponds to the amount that might be held in hydroxid form; as, for example, in the abundant mineral called gypsum, or land plaster, which is calcium sulfate crystallized with two molecules of water, CaSO4 : 2 H2O, or CaO2S(OH)4. Hydrogen in the free state (H2) is a gas. From Table i it will be seen that the molecule of hydrogen (H^ is lighter than the atom of any other element; and, according to the gas law, a given volume will be filled by the same number of molecules of hydrogen as of any other gas. Consequently, hydrogen gas is the lightest of all known gases, so that a balloon filled with hydrogen easily floats in the atmosphere of nitrogen (N.j) and oxygen (O2), one of which PLANT FOOD AND PLANT GROWTH 29 is fourteen times, and the other sixteen times, heavier than hy- drogen. At the ordinary temperature, hydrogen and oxygen gases can be mixed together and remain a mixture; but, if heated or ignited, the bonds which hold the atoms in molecules (H2 and Og) are broken, and the mixture explodes with terrific force and loud re- port. The only product of the explosion, or at least of the reac- tion, is water, H2O; and, if either gas was present in the mixture in excess of these proportions, the excess remains unchanged. The corn kernel contains 6.4 per cent of hydrogen, or about 97^ per cent of the three elements, oxygen, carbon, and hydrogen. Life. The fixation of carbon is the most important process in the growth of plants. By the term fixation is meant the changing of a gas or soluble substance to a solid or insoluble form by means that involve chemical reaction. (The fixation of atmospheric nitrogen, the fixation of soluble phosphorus in soils, and the fixation of po- tassium and other bases will be explained in the following pages.) The process known as the fixation of carbon is the more impor- tant, because it involves, not only the fixation of carbon itself, but likewise the fixation of both oxygen and hydrogen. Its im- portance is better appreciated by recalling that these three ele- ments compose about 95 per cent of the entire weight of most agricultural plants or crops. Both the carbon and oxygen utilized in plant growth are derived from the carbon dioxid contained in the air. It is truly remarkable that 90 per cent (90 pounds in 100) of our common crops must be secured from .04 per cent (4 parts in 10,000) of the air. The fixation of carbon, oxygen, and hydrogen takes place in the green parts of plants. The carbon dioxid enters through the breath- ing pores l on the under side of the leaf; and the water, composed 1 A breathing pore consists of two guard cells with a slit between them, passing through the outer coat of the leaf. These slits or openings are greatly influenced by the moisture and temperature of the air. In the absence of light they remain closed. When the breathing pores are open, the outside air has free access to the intercellular spaces and passages within the leaf. The number of breathing pores varies with different plants, ^.bout 17,000 per square inch have been found on oat leaves, 102,000 on corn leaves, and 216,000 per square inch on the leaves of red clover. They are found chiefly on the under side of leaves and on green stems, but sometimes in small numbers on the upper leaf surface and even on underground stems. 30 SCIENCE AND SOIL of hydrogen and oxygen, enters the leaf through the stem, having passed from the soil into the plant through the roots. As the carbon dioxid and water come together within the leaf, a chemical reaction occurs which may be illustrated by the following equation: H2=o +;o=c=o = H2co + oa. The dotted line shows how the bonds are broken. The two atoms of oxygen that are set free immediately join hands to form a mole- cule of oxygen (O2), which passes from the leaf into the outer air. The two hydrogen atoms (H2=) attach themselves to the group, =CO, forming the compound, H2CO, which may also be written CH2O, to show its hydrate character, and which might be called monose, but is commonly known as formic aldehyde. This reac- tion occurs only in the light and only in the presence of active living chlorophyll (the green coloring matter of leaves). In other words, this compound is formed under the influence of life, and by it we enter a new field known as organic chemistry. Organic matter. Organic matter consists of compounds formed by life processes, — compounds that are, or have been, living matter; whereas, inorganic matter consists of rocks, minerals, and metals, of salts, liquids, and gases, whose origin has no necessary connection with any living substance. Organic matter consists of carbon compounds,1 such as hydrocarbons (containing only hydrogen and carbon) , fats (containing much carbon and hydrogen with little oxygen), carbohydrates (containing carbon with hy- drogen and oxygen in proportion to form water — as the name in- dicates), and proteids, which contain not only carbon, hydrogen, and oxygen, but also nitrogen, and sometimes phosphorus and sulfur. These are the great groups of organic compounds compos- ing plants and animals. The carbohydrates are the most abundant in plants, while the proteids, although a necessary part of plants, are the most abundant compounds in animals. Aldehydes and carbohydrates. Formic aldehyde is only one of many aldehydes, which constitute a large class or series of organic compounds. The aldehydes are extremely active substances and 1 Many of the simpler carbon compounds can be made artificially. PLANT FOOD AND PLANT GROWTH 31 have power to attack and decompose other substance. Formic aldehyde is often used as a disinfectant, and a 40 per cent solution, known as " formalin," is employed (at the rate of one pound of formalin in 50 gallons of water) to destroy smut in seed oats, for example. A remarkable property of the aldehydes is the power of condensa- tion, by which two or more molecules are condensed into one. Thus, two molecules of formic aldehyde, or monose, 2 CH2O, may become one molecule of diose, C2H4O2; while three molecules may form one of triose, C3H6O3; and four may form tetrose, C4H8O4; and five, pentose, C5H10O5; etc. The condensation process is so rapid that formic aldehyde itself is found in plants only in very small amount, while the condensa- tion products constitute commonly 80 to 90 per cent of the entire plant. The ending -ose means sugar, and the prefix mon-, di-, tri-, etc., designate the number of carbon atoms in the molecule. The following may illustrate this series of carbohydrates: l CH2O, monose (formic aldehyde). C2H4O2, diose (unknown). C3H6O3, triose (glycerose). C4H8O4, tetrose (erythrose). C5H10O5, pentose (xylose). C6H12O6, hexose (glucose). £-12^240 12, lactose (milk sugar). C^HjgOy, sucrose (common sugar). Here we may see the possible development of the well-known glucose, milk sugar, and common sugar (obtained from sugar cane and sugar beets), as condensation products from monose, or formic aldehyde, formed in the living plant from carbon dioxid and water. 1 It cannot be considered as absolutely proven that formic aldehyde is always the first product of this fixation process; and, if it is, it seems that the first condensa- tion product results from the union of three molecules, because the compound that might be called diose is not found in plants and is not known to exist. The known facts are that carbon dioxid is condensed in the leaves of plants and that oxygen is given off in the proportions required for this reaction (aside from the oxygen normally exhaled), also that formic aldehyde is found in plant leaves, that aldehydes have the power of condensation, and that multiples of the formic aldehyde molecule are actually present in plants (as hexose) or represented (as in starch, cellulose, pentosans, etc.). 32 SCIENCE AND SOIL It may be noted that cane sugar differs from milk sugar by one molecule of water (HgO) . The sugars are a very important group of compounds, but perhaps the starches are a still more important group. Starch (C6H10O6) appears to differ from glucose (C6H12O6) by one molecule of water (H2O) , but it is known that the starch mole- cule is not simply C6H10O5, but some multiple of this formula, which is best written (C6H10O6)^, in which x stands for the number by which this formula should be multiplied, for as yet x is unknown, although the proportion or percentage of each element in starch is known. The formula for cellulose (plant fiber) must also be recorded as (CgHjoOg)^., but this x may be a different number than the x of the starch molecule. Growth. Rapidity of growth is related to leaf surface. Sugar, starch, and fiber constitute the great carbohydrate group of plant structure, and their formation is dependent primarily upon the fixation of carbon, with oxygen and hydrogen, in the leaf; . and, with all necessary things provided in proportionate amounts, this process goes on in direct proportion to leaf surface. In other words, under perfect conditions, a leaf four inches long will grow four times as much during the day as a leaf only one inch long; and, with sufficient moisture and with plant food provided in abundance, a pasture with the grass kept six inches long will furnish twice as much feed as one with the grass kept down to three inches. If the foundation principles and the controlling factors in plant growth can be known, then the ideal conditions for crop production may be provided much more nearly than is common. The ideal condition is to provide all controllable factors in such abundance or perfection that the crop yields will be limited only by the sun- shine and rainfall. With all other limiting factors removed, the average yield of corn in the corn belt would undoubtedly exceed ico bushels per. acre. (See the records of actual yields, in the follow- ing pages.) Carbon cycle. The carbon cycle includes both the fixation and the liberation of carbon. Animals feed upon plants and plant prod- ucts rich in carbon compounds, which in part are digested and car- ried into the blood to meet the oxygen inhaled through the lungs. The carbon is burned, or oxidized, to carbon dioxid, furnishing PLANT FOOD AND PLANT GROWTH 33 to the animal the energy or heat' equivalent to that of ordinary combustion in the furnace, of the same materials; and the carbon dioxid is then thrown off through the lungs into the air, again to become the source of carbon and oxygen for plants. Thus, the fixation of carbon by the plants on the one side, and, on the other, all forms of combustion, including the visible flame, the consump- tion and oxidation of food by animals, or the oxidation of organic matter in the soil, completes the endless carbon cycle. But for this carbon cycle, plant growth and crop production would soon cease. A simple computation reveals facts not com- monly appreciated : A column of air one inch square and the height of the atmosphere weighs 15 pounds, which is equivalent to 2160 pounds per square foot, or less than 95 million pounds per acre. In ten thousand pounds of average air there is less than four pounds of carbon dioxid (CO2) or about one pound of carbon. Consequently, there is less than 10,000 pounds of carbon in the air above one acre of land. In loo bushels of corn (5600 pounds), there are 2500 pounds of carbon. (See Table 2, or compute from the per cent of carbon in starch and fiber, C6H10O5.) Thus, the total supply of carbon over an acre of land is only equal to the needs of four such corn crops as are commonly produced on the best-treated corn-belt land in the best seasons, the grain only being considered, or to only two crops, considering both grain and stalks. If, however, only one fourth of the earth's surface is land, if only one fourth of the land is cropped, and if only one fourth of 100 bushels is the average crop, then the supply of carbon is sufficient, not for two years only, but for 128 years, which, however, still emphasizes the fact that the carbon cycle makes possible the continuation of plant life on the earth. A maintenance ration for animals is a supply of food sufficient only to support the animal body in health, to provide food materials for repairing the daily waste, and to furnish energy sufficient to keep the body warm and to maintain the circulation of the blood and other necessary activities. Plants also have some vital pro- cesses to provide for, and, to a limited extent, plants are consumers of energy day and night. Food materials are stored by the plant, chiefly to be utilized in subsequent plant development. Thus 34 SCIENCE AND SOIL sugars are converted into starch and stored away in roots, tubers, or seeds, to supply the future needs of the same plant or of new plants. At the proper time the plant reconverts the insoluble starch into soluble sugar 1 and carries it through the circulation to the point of consumption as food by the plant, either for energy, repair, or growth. Food materials are thus consumed or oxidized within the plant, and carbon dioxid is constantly given off from all its living parts, including the roots. During the day the fixation of carbon is commonly so great as to completely mask the liberation of carbon dioxid in the green parts of the plant. Vegetable fats. Before leaving the subject of the fixation of carbon, oxygen, and hydrogen, some further mention should be made of the group of compounds called fats, whose importance is exceeded only by that of carbohydrates and protein. The vegetable fats and oils show distinct relationship to a con- densation process similar to the formation of sugars and other carbohydrates from formic aldehyde, the photosynthetic product of the reaction between carbon dioxid and water in the leaves of plants. The following series of compounds will show this relation- ship: HYDROCARBONS FATTY ACIDS HCH3— Methane ........ HCOOH — Formic acid. CH3CH3— Ethane ........ CH3COOH— Acetic acid. C2HSCH3 — Propane ....... C2H5COOH — Propionic acid. C3H7CH3 — Butane ........ C3H7COOH — Butyric acid. C4H9CH3 — Pentane ........ C4H9COOH — Valeric acid. C5HUCH3 — Hexane ....... C5HUCOOH — Hexoic acid. C6H13CH3 — Heptane ....... C6H13COOH — Heptoic acid. C7H15CH3 — Octane ........ C7H15COOH — Octoic acid. CnH23CH3 — Dodecane ....... CnH^COOH — Laurie acid. C15H31CH3— Hecdecane ...... C15H31COOH — Palmitic acid. C17H35COOH — Stearic acid. — Oleic acid. Unsaturated ........ C17H31COOH — Linolic acid. — Linolenic acid. The hydrocarbons, which constitute the simplest series of carbon compounds, are shown for direct comparison with the fatty acid 1 Glucose sugars and sirups are manufactured in large quantities by use of strong acids for converting the starch into glucose. PLANT FOOD AND PLANT GROWTH 35 series. All of the compounds here illustrated are known. The two series differ only by the — COOH group in the fatty acid series in place of the — CH3 group in the hydrocarbon series. The — CH3 group is methane from which one hydrogen atom is removed, leaving the radicle — CH3, which is called methyl (one of the alkyl radicles), and acts as a monovalent radicle, replacing one hydrogen atom. It finds a place in many organic compounds, as in ethane (CH3— CH3), butane (CH3— CH2— CH2— CH3) , etc. The group, — COOH, is called carboxyl, or the acid group. It may be represented: — C— O — H II O This group also has one free bond and acts as a monovalent radicle. Whenever this group is contained in an organic compound, the compound is an acid. The hydrogen in the hydroxyl part of this group may be replaced by metals, thus forming salts. If the free hand in this carboxyl group is grasped by a hydrogen atom, the compound formed is formic acid, but if methyl ( — CH3) joins hands with carboxyl ( — COOH), the compound formed is acetic acid (CH3COOH) , the acid which gives to vinegar its sour taste. When lead (Pb) is used as a base to form a salt with acetic acid by re- placing the acid hydrogen of the hydroxyl group, the sourness is destroyed and the salt is known as sugar of lead, or lead acetate, (CH3COO)2Pb. When the hydroxyl group joins alkyl radicles ( — CH3, — C2H5, etc.), alcohols are formed, as methyl alcohol (CH3OH), called wood alcohol, and ethyl alcohol (C2H6OH), which is common alcohol. Common glycerin, which is also called glycerol (because it is an alcohol), is an organic compound consisting of a trivalent radicle, called glyceryl, united with three hydroxyl groups, C3H5(OH)3. Common animal fats consist chiefly of palmitic, stearic, and oleic acids combined with this radicle, =C3H5, and the fats themselves are called palmitin, stearin, and olein. The harder fats, like tallow, contain more stearin (C17H35COO)3C3H5, while the softer fats, like lard and butter, contain considerable olein, which differs from 36 SCIENCE AND SOIL stearin by having two less hydrogen atoms in each acid radicle. By itself, olein is a liquid or oil. The oil of corn contains about 4 per cent of stearin, 45 per cent of olein, and 48 per cent of linolin, which differs from olein by two hydrogen atoms, and from stearin by four hydrogen atoms, in each acid radicle. When these fats and oils are heated with a strong base (alkali) such as potassium hydroxid, three potassium atoms displace the glyceryl radicle (=C3H5) and form potassium stearate (C^H^COOK), potassium oleate (C17H33COOK), etc.; while the three hydroxyl groups unite with glyceryl to form glycerin, C3H5(OH)3. The salts formed by potassium or sodium with these fatty acids are what we call soap, the potassium compounds being soft soap, and the sodium, hard soap. While the fixation of carbon, oxygen, and hydrogen, resulting ultimately in the formation of carbohydrates and fats, is properly considered the most important process in plant growth, we may well remember that no fixation and no growth occur in the absence of the other seven essential elements of plant food. Indeed, from the standpoint of possible control of crop production, another tripod is more important than these three; namely, nitrogen, phosphorus, and limestone. Nitrogen. This element has received more consideration as plant food than any other essential element. In the free state (Ng) it is a gas, and in this form it constitutes three fourths of the air. The total supply of nitrogen over each acre of the earth's surface, if available, would meet the needs of a hundred-bushel crop of corn every year for 500,000 years; whereas the supply of carbon is sufficient for such crops for only two years. Nevertheless, carbon has no commercial value as plant food, while nitrogen in available form is worth 15 to 20 cents a pound in the markets. These facts only emphasize the need of science in agriculture. Nitrogen is not contained in the mineral matter of the earth, but it is a constituent of common organic matter. It is an essential part of the structure of every plant and animal, and is present in all crops and crop residues and, consequently, in the organic matter, vegetable matter, or humus, of the top soil; and it is from the decomposition products of this organic matter that nitrogen is PLANT FOOD AND PLANT GROWTH 37 furnished to most growing crops, by a process (nitrification) that is more fully explained in the following pages. Protein. Protein is the general name for organic nitrogen com- pounds, including the proteids, or final products, and the amids, or intermediate products. The amids and proteids of the protein group might be compared with the sugars and starches (and fibers) of the carbohydrate group in which the sugars are the intermediate form and the starches (and fibers) the more permanent form. Protein always contains nitrogen in addition to oxygen, carbon, and hydrogen. The chemical reactions involved in the formation of proteids are not yet well understood, although many of the intermediate products (amids) are well known, and some can be made arti- ficially. The amids are especially abundant in young or immature plants, and they are also liberated as intermediate decomposition products. Thus, carbamid, O=C=(NH2)2, which is also called urea, is a common nitrogen compound in urine, the medium by which most of the nitrogen waste is thrown off from the animal body. This compound might be considered as formic aldehyde, or monose (O=C = H2), in which the two hydrogen atoms are re- placed by two amido groups, and the amido group ( — NH2) may be considered as ammonia in which only two monovalent hydrogen atoms are joined to the trivalent nitrogen atom, thus leaving one free hand by which this group may be attached to other groups or atoms in the building of molecules. The hydroxyl group ( — OH) and water (OH2),in relation to oxygen, correspond to the amido group ( — NH2) and ammonia (NH3), in relation to nitrogen, and also to the methyl group ( — CH3) and methane (CH^, in relation to carbon. The amido group ( — NH2) acts as a monovalent radicle, and by replacing hydrogen atoms in various compounds forms new compounds called amids, or amido compounds, and these by con- densation or combination with other groups may form the final nitrogenous organic compounds called proteids, which constitute chiefly the flesh (not fat) and vital organs of animals, and the pro- tein of mature plants. It has been suggested that amido formic aldehyde, H2NCHO, or amido acetic aldehyde, CH2(NH2)CHO, or aspartic aldehyde (see aspartic acid and asparagin in the following list) may furnish the 38 SCIENCE AND SOIL initial molecules whose condensation produces proteids, but this is largely speculative. The following list illustrates some instructive relationships of important and well-known compounds: HCOOH, or H— C— OH .... Formic acid. II O CH8COOH, or H3=C— C— OH . . Acetic acid (the acid in vinegar). O CH2(NH2)COOH ...... Amido acetic acid. COOH COOH, or (COOH)2 ..... Oxalic acid. CH2COOH CH2COOH ...... . . Succinic acid. CH2COOH I CH(NH2)COOH ...... Amido succinic acid (the aspartic acid in pumpkin seed, beets, etc.). CH2CONH2 CH(NH2)COOH ...... Amido succinamic acid (the asparagin found in asparagus, in beans and peas, and in many seeds when ger- H minating). H— CT C— H C6H6, or | || ... Benzene. H— C. C— H H C6H5 — OH ........ Hydroxy benzene, or phenol (carbolic acid). C6H5 — NH2 ........ Amido benzene, or anilin. C6H3(OH)3 ........ Trihydroxy benzene, or pyrogallol (pyrogallic acid). C6H3(NH2)3 ........ Triamido benzene. C10H14N2 ......... Dipyridyl hexahydrid, or nicotin (the alkaloid of tobacco). C17H21NO4 ........ Morphin (the alkaloid of opium, from the poppy). C2iH22N2O2 ........ Strychnin (the alkaloid of nux vom- ica). Q^f^NesOreSs ....... Albumen, or the white of egg. (For- mula suggested by Schutzenberger ) PLANT FOOD AND PLANT GROWTH 39 Zein, the most abundant proteid in corn (Zea mays), has the following composition: Carbon .... 55.15 per cent. Hydrogen ... 7.24 per cent. Oxygen. . . . 20.77 per cent. Nitrogen . . . 16.22 per cent. Sulfur .... .62 per cent. According to this analysis, the molecule of zein might be repre- sented by the following formula: Ordinary corn contains n per cent of protein, of which about one half consists of the proteid zein. This nitrogenous substance has been separated, purified, and investigated with very great care, especially by Chittenden and Osborne (American Chemical Journal (1891), jj, 453, 529; (1892), 14, 20). The percentage composition represents the average of several closely agreeing analyses of what was believed to be very pure zein. Based on the percentage of sulfur, the molecular weight cannot be less than about 5000, and the formula given above or some multiple of it must be approxi- mately correct. Certainly the proteid molecule is exceedingly complex, and the number of different proteids is very large. They all contain nitrogen, usually about 16 per cent, and some of them contain also sulfur and phosphorus. Sulfur. This is an essential element for all plants, but the amount required for normal growth and full development is relatively very small, even when compared with the small percentage present in the earth's crust.' Most proteids (as zein, for example) contain sulfur, but the percentage is usually very low. It is present, however, in organic combination, and does not give the ordi- nary tests for sulfates, the form in which it is usually taken from the soil. Many of the simpler organic compounds of sulfur are well known, and some can be made artificially. The oil of onions and garlic, which gives to those plants their peculiar odor and taste, consists 40 SCIENCE AND SOIL chiefly of allyl l sulfid (C3H6)2S; and mustard oil is also composed of organic sulfur compounds. Phosphorus. Phosphorus is the Greek word for the morning star, and signifies light. The element phosphorus is closely asso- ciated with the beginning of all forms of mortal life. The nucleus of every living cell in plants and animals is rich in phosphorus. Nuclein, the phosphorized nitrogenous constituent of the cell- nucleus, contains as high as 10 per cent of the element phosphorus, although it may contain no sulfur. The following formula has been suggested byMiescher for nuclein derived from animal cells: Lecithin, C44H90O9NP, is a well-known organic phosphorus com- pound, which it is thought may have some controlling influence in the formation of fats and oils. Ordinary corn contains about 5 per cent of oil, of which 1.5 per cent consists of lecithin; that is, i^ pounds of lecithin are found in 100 pounds of the oil. It should be remembered that, while sulfur is contained in many proteids, phosphorus is present in every cell of every plant. The grain or seed of plants contains, as a rule, more than fifty times as much phosphorus as sulfur. The phosphorus of the corn kernel is found largely in the germ. In 1000 pounds of corn there are about 100 pounds of germs containing more than two pounds of the ele- ment phosphorus. About 95 per cent of the ash obtained from the burning of corn consists of the phosphates of potassium and magnesium. Hay, straw, and other coarse products usually contain more sulfur than the grain, but these coarser parts com- monly remain on the farm, while the grain is more likely to be sold. 1 The monovalent allyl group ( — CaHs) differs from "the trivalent glyceryl (sCsHs) only in having a double bond, as shown in allyl alcohol and glycerin (which might also be called glyceryl alcohol) : Allyl alcohol Glycerin CH2 CH2OH II I GH CHOH I I CH2OH CH2OH PLANT FOOD AND PLANT GROWTH 41 The proteid of milk, called casein, has the following composition : Carbon . . . . 53.30 per cent. Hydrogen . . . 7.07 per cent. Oxygen .... 22.03 Per cent. Nitrogen . . . 15.91 per cent. Sulfur 82 per cent. Phosphorus . . .87 per cent. A ton of wheat bran contains about 24 pounds of phosphorus, or 1.22 per cent. About 86 per cent of the total phosphorus in bran is soluble in water, and, according to Patten and Hart (New York State Agricultural Experiment Station Bulletin 250), this water-soluble phosphorus is contained in the salt of an organic acid, which is probably identical with a compound investigated by Posternak, and called by him anhydro-oxymethylene diphos- phoric acid, the formula being C2H8P2O9. As determined by Patten and Hart, the complex salt of this acid which constitutes the prin- cipal phosphorus compound in wheat bran, has the following composition, as found by the ultimate analysis of the isolated compound : Calcium 1.13 per cent. Potassium 2.60 per cent. Magnesium 5.80 per cent. Carbon I7-3Q per cent. Hydrogen 3.63 per cent. Phosphorus 16.38 per cent. Oxygen (by difference) . . . 53.16 per cent. The free acid was found to contain 10.63 Per cent °f carbon, 3.38 per cent of hydrogen, and 25.98 per cent of phosphorus, which corresponds fairly closely, especially in phosphorus, with the theoretical percentages, which any one can compute for the for- mula C2H8P2O9. The mineral part of animal bone consists largely of tricalcium phosphate, Ca3(PO4)2, which, when pure, contains 20 per cent of the element phosphorus, as can be easily computed by any one who knows the atomic weights. In 100 pounds of raw bone are about 42 SCIENCE AND SOIL 10 pounds of phosphorus. The phosphorus required by animals is, as a rule, supplied in the plants that serve as animal foods. The percentage of phosphorus in the earth's crust is small when compared with the requirements of plants, especially when we also consider that the phosphorus accumulates in the more concen- trated and more salable products, as in the seed or grain, and also in the flesh, bone, and milk, of animals. Phosphorus is usually taken up by plants in the form of phos- phates, but within the plant it enters into organic combination as shown above. The six elements thus far discussed in some detail — carbon, oxygen, hydrogen, nitrogen, phosphorus, and sulfur — are all non- metallic. Three of them — oxygen, hydrogen, and nitrogen — are gases in the free state, and the other three — carbon, phosphorus, and sulfur — are nonmetallic solids. Four other elements are also absolutely essential to the growth of all agricultural plants. Potassium and magnesium. These are metallic elements which have very important functions in plant growth and which are re- quired in considerable amounts. Both are stored in the seed in relative abundance, and are found in the ash of grains in the form of phosphates, although still larger amounts of potassium are stored in the coarser parts of plants (as in straw, cornstalks, etc.). It is not known that potassium and magnesium are essential constituents of protoplasm, but, like nitrogen and phosphorus, they are found in largest proportions in the embryo tissues. It is suggested that one of their essential functions may be as carriers of nitrogen and phosphorus in the form of definite salts (as nitrates and phosphates) capable of reaction with certain products result- ing from the fixation of carbon, oxygen, and hydrogen. Certainly it is not sufficient that phosphorus, for example, shall merely be carried in the form of some soluble phosphate into the laboratory (the leaf) of the plant, but the compound must be such that the metallic base will release the phosphorus at the proper time, in order that it may enter the organic combination and thus become a part of the living organism. It is known that organic acids are developed by the plant with which potassium and other bases carried into the plant in the form of nitrates, phosphates, etc., may unite, and do unite, at some time PLANT FOOD AND PLANT GROWTH 43 during the life of the plant; for some of the potassium that enters the plant roots as nitrates, phosphate, or sulfate is afterward found in the plant in organic salts, as tartrate (in grapes) , oxalate (in sorrel) , etc. There appears to be little or no evidence that any living organic compounds of potassium or magnesium exist. It is the common belief that potassium has large influence over the formation of carbohydrates; but the information is not suffi- cient to determine whether this influence is direct or very indirect, as in maintaining the general health of the plant by having some absolutely necessary part in reactions involving the transference of nitrogen or phosphorus from inorganic compounds to the living organic combination. The potassium contained in plants is in large part very easily removed by leaching with water, and hence peaty swamp soils consisting largely of organic matter are frequently very deficient in potassium. While potassium and magnesium are required by plants in very considerable amounts, as stated, and as shown in Table 2, yet, when measured by the average composition of the earth's crust and by average crop requirements, the supply of these two elements is very great. Calcium and iron. These elements are absolutely essential to the normal growth and development of all agricultural plants, but for the grain crops the amounts positively necessary are so extremely small and the quantities present in the earth's crust are so extremely large that it is rarely that either calcium or iron is furnished to such plants in amounts insufficient to perform their essential functions, except, of course, when they are artificially withheld, as in investigational work. Legume plants are a very marked exception, however, so far as calcium is concerned. Iron evidently has some important connection, direct or indi- rect, with the formation of chlorophyll (the green coloring matter of leaves) ; for, if iron is withheld from the plant, the leaves do not become green, and if later iron is supplied, the chlorophyll soon begins to develop. On the other hand, analysis has shown that the chlorophyll itself does not contain iron, and the somewhat common assumption that the green color of plants is due to the presence of iron compounds of that color is incorrect. The iron held in nuclein compounds is not dissolved out by dilute 44 SCIENCE AND SOIL hydrochloric acid, — a fact which indicates that the iron is a con- stituent of the living matter of plants. Animals also have a small but absolute requirement for iron. Aside from oxygen, iron is the most abundant essential plant- food element, constituting about 4^- per cent of the solid crust of the earth, although the amount required by plants is very insig- nificant. Thus, the earth contains more than 40 times as much iron as phosphorus, while the corn kernel contains nearly 40 times as much phosphorus as iron, so that the supply of phosphorus would be depleted as much by the removal of 100 crops as the supply of iron would be by 160,000 crops. While a very small supply of calcium is of vital importance, considerable amounts of that element are commonly taken up and deposited in the coarser parts of plants, as in straw, cornstalks, and hay, and large supplies of calcium are required for legumes, especially for clover and alfalfa. This larger use of calcium appears to be due, especially in grain crops, to its power as a base to unite with organic acids that might otherwise injure the plant; and the salts formed are commonly deposited, not in the seed or with stored food materials, but in the older tissues as inert matter. The common use of certain calcium compounds, such as burned lime and ground limestone, for correcting soil acidity should not be confused with the essential need of the element calcium as plant food. Even strongly acid soils often contain abundance of the ele- ment calcium for plant food, not in the form of carbonates, but in silicates, which, however, have no power to correct soil acidity. Aluminum, silicon, sodium, chlorin, and manganese. These elements are not known to be essential to plant growth, but they are commonly found in plants, although the amount of manganese is very small and that of aluminum still smaller. The opinion that silicon was essential and gave stiffness to the straw of cereals is not correct, and the report that manganese exerts a marked stimulating action on plant growth has not been verified upon more thorough investigation. Sodium is now known to be a nonessential, but there is still a possible question regarding chlorin. According to Pfeffer, " it remains for precise researches to determine whether a minimal amount is essential, or whether chlorin simply favors growth under special cultural conditions." PLANT FOOD AND PLANT GROWTH 45 Common functions. Some common functions may be performed by several elements. Thus, if there is need for a base to correct an excess of acid that has developed in the plant, sodium may serve as well as potassium, although with enough potassium provided, no sodium is needed. As already stated, the largest use of calcium appears to be in this line, in which, perhaps, manganese, magne- sium, or iron might serve equally well if they were present in the plant in sufficient amount. Likewise, in solvent compounds, chlorin may serve as well as nitrogen or phosphorus, but cannot take their place in living tissue. We shall also consider in the following pages the value to plants of certain materials when applied to certain soils, which serve not as plant food, but rather as soil stimulants, having power to liberate from the soil some essential plant-food element more rapidly than it would otherwise become available — an action that may result in temporary profit and ultimate land ruin. Caustic lime, salt, gypsum (land-plaster), and, under certain conditions, commercial fertilizers, and even farm manure, clover, and green manures, may act in part, at least, as soil stimulants; and, to guard against such injurious action, practice must be controlled by science (knowl- edge). CHAPTER IV THE EARTH'S CRUST NEARLY 98 per cent of the solid crust of the earth consists of silicates of the six metals, aluminum, iron, calcium, potassium, sodium, and magnesium (in this order of relative abundance); and the remainder is largely composed of the closely related titan- ates. Silicon. Silicon in the mineral matter constituting the earth's crust corresponds to carbon in the organic matter of the vegetable and animal kingdoms. In all of the great groups of organic com- pounds the molecule is built up by the linking power of the four- handed carbon atom, as, for example, in the hydrocarbon, hexane (C6H14): H H H H H H I I I I I I H— C— C— C— C— C— C— H I I I I I I H H H H H H Silicon is the second member of the carbon group * in the periodic system, as shown on page u, and its linking power is also very great, although alternating with oxygen and metals and restricted mainly to silicates. Thus, instead of the almost unlimited number of hydrocarbons, carbohydrates, and other numerous compounds of carbon, hydrogen, and oxygen (alcohols, fats, organic acids, etc.), there are but four such silicon compounds known: SiH4, SiO2, OSi(OH)2 or H2SiO3, and Si(OH)4 or H4SiO4, which differs from silicon dioxid by two molecules of water. 1 A most interesting compound is SiC, silicon carbid, so-called carborundum, formed by the union of the two tetravalent elements and, next to the diamond, one of the hardest known substances. 46 THE EARTH'S CRUST 47 The numerous natural polysilicates (poly- means many) compos- ing granite and most other rocks of the earth's crust are salts of polysilicic acids, although the acids themselves are not known to exist free from the basic elements or radicles. The following may illustrate a few of the possible combinations, the last three being known only in salts in which bases appear in place of the acid hydrogen : Silicon dioxid, SiO2 . . . . O = Si=O. Metasilicic acid, H2SiO3 . . O = Si = (OH)2. Orthosilicic acid, H4SiO4 . . (HO)2 = Si=(OH)2. Disilicic acid, H2Si2O6 . . . HO-Si=O3=Si-OH. Polysilicic acid, H4Si3O8 . (HO)2=Si=O2=Si=O2=Si=(OH)2. J (HO).' Si-°s = Si -°. - Si -°« = Si - r Among the most common mineral compounds found in granite is ordinary felspar, or orthoclase, or potassium aluminum poly- silicate, KAlSi3O8, or (KAlSi3O8)2, whose structural formula may be represented thus: /ox /o o o KX >Si< >Si< >Si< *'O ^O O> ^* H M 00 M VO ro HI '£ \O M HI ON || 80 o vo O O O O O O O O M 881 8 O O O oo \o o^ 2 I oj.5 HI O HI OO HI HI t**> ^" ^- **•»- co oo oo o ^o sa VO HI W Q\ V a c 32 0 0 •* o O O O O 80 o o o o o o o C en rovo ^" CS O OO CO ^" o ^ HI HI O 00 PJ S VO HI t-- HI 00 O CS Uco VO HI HI ON 1 0 0 §O O vO 80 o o o o o O O o o S M VO 04 O VO O O O OO O vo a M t^. ONOO 00 t— 1 ^" OO CS OO w HI ^f vo o CS HI OO VO HI CS CS HI ON CONSTITUENTS Phosphorus . Potassium 1 ... wo c ,5 '4 A 23 ^OHHCO Silicon . . Aluminum . Sodium . . Manganese . "S ~ cu Id 74 SCIENCE AND SOIL carbonates of calcium and magnesium, which may have con- stituted 75 to 90 per cent or more of the original rock, having been nearly or completely dissolved out (see Table 5). Two striking facts are revealed by the analyses of these ten soils from ten different geological formations: 1. The amount of phosphorus is very small compared with the requirements of large crops for many years, the amount varying from 720 pounds in the Gabbro soil to 1500 pounds in the Helder- berg limestone soil. Counting 17 pounds of phosphorus for 100 bushels of corn, the 720 pounds would be sufficient for only 43 such crops; or, if both grain and stalks are removed from the land and if one pound of phosphorus per acre is the yearly loss in drain- age water, the 720 pounds is sufficient for only 30 such crops; while the best soil contains sufficient total phosphorus in a 61- inch stratum for only 63 such crops. The average of the ten soils shows 1 1 oo pounds of phosphorus in two million pounds of soil, or about one half as much as in the average crust of the earth. 2. The amount of potassium is very large, varying from 20 to 50 times as much as the phosphorus. The 15,400 pounds of po- tassium in 6f acre inches of the poorest soil would be sufficient for 100 bushels of corn every year for 800 years, while the 57,400 pounds in the best soil would suffice for 3000 years, if it could be made available as needed and if only the grain were removed. If both grain and stalks were removed, these supplies are sufficient for 200 and 800 crops, respectively, counting 19 pounds of potas- sium for ico bushels of corn and 52 pounds for the stalks for such a crop, not including the loss in drainage, which, however, would be somewhat greater than for phosphorus. Six of these soils average nearly as rich in potassium as the earth's crust, while the poorest soil is about one third as rich. Several of these soils are less abundantly supplied with magne- sium and calcium than with potassium, not only in total amounts, but also in comparison with the requirements of some general farm crops. In some cases the soils contain less than one third as much magnesium, and less than one fifth as much calcium, as potassium; while corn contains more than one third as much magnesium as potassium, and clover hay contains almost as much calcium as potassium, and one fourth as much magnesium (see Table 13). SOIL COMPOSITION 75 TABLE 13. MINERAL PLANT FOOD IN WHEAT, CORN, OATS, AND CLOVER PRODUCE p^ 11 a,-, || in 3 s J3-*-x Bl s ^~* o-S 0 ° sf If Kind Amount SI fi $£ 0°-i PH^ 11 <0n S^ 3% ufe 11 fc 11 COflj Wheat .... Wheat straw . . Corn 50 bu. 2\ tons 100 bu. 12 4 17 13 45 IQ 4 4 7 I.O 9-5 i "? •3 i-5 .A .1 2.O 2 Corn stover . . . Oats 3 tons 100 bu. 6 II 52 16 10 A 21. 0 2 O 4-8 e 5-8 6 Oat straw . . . 2^ tons 5 52 7 15-0 2.8 3-° Clover hay . 4 tons 20 3 1 20 31 •5 117.0 4.0 6.4 Total in four crops 77 320 68 168. 14-3 15.2 Note the accumulation of phosphorus in the grain and straw and compare with potassium and with sulfur; also compare magnesium and calcium in this respect. OTHER EASTERN SOILS By the action of the different agencies of transportation, soil particles are often sorted into grades, as clay, silt, sand, and gravel, and in addition there are stony loams and other residual soils, and the cumulose soils (as peaty soils), which accumulate in swamps and bogs and consist largely of plant residues. In Table 14 is recorded a valuable series of analyses from the Cornell Experiment Station (Roberts' " Fertility of the Land," 1900, page 13), representing " the amounts of plant food in surface soils in New York State." TABLE 14. COMPOSITION OF SURFACE SOILS IN NEW YORK STATE Pounds in 2 Million (per Acre about 6f Inches Deep) Son, TYPE No. OF ANALYSES TOTAL NITROGEN POUNDS TOTAL PHOSPHORUS POUNDS TOTAL POTASSIUM POUNDS Clay loam II 2060 1360 234QO Loam 8 ^480 1480 3O2IO Sandy loam Gravelly loam Slaty loam 8 10 i 2500 5480 3OOO 1440 2170 IS7O 32620 26640 29050 Peaty soil 2 •5 , 22CKO 1800 l 3280' 1 Amounts in i million pounds. 76 SCIENCE AND SOIL These New York soils are somewhat richer in phosphorus than most of the older residual soils, and noticeably richer than the average loessial soils of the older formations. The ten samples of gravelly loam show an average phosphorus content of 2170 pounds in 2 million of soil, which is about the same as the average of the earth's crust. With one notable exception these soils are very rich in potassium, although not quite equal to the average loessial soils of the corn belt. Two of the common New York soils (loam and gravelly loam) exceed 5000 pounds per acre in the nitrogen content of the surface 6f inches, an amount which represents approximately the average of the most abundant prairie soils of the corn belt, while the three soils, clay loam, sandy loam, and slaty loam, contain about one half as much. In the peaty soil we find another very abnormal soil type, which it is instructive to compare with the barren soils of Germany and Maryland, with the depleted long-cultivated soils of India, Turkey, Russia, and Africa, with the coral limestone soil of the Bermuda Islands and the limestone soils of Cuba, and with the phosphatic soils of Tennessee and Kentucky. The peaty soil contains in a 6f -inch stratum nearly ten times as much nitrogen, nearly twice as much phosphorus, and only one tenth as much potassium as the general average of the most common American soils. The soil on the Experiment Station farm at the State College, Pennsylvania, contains 2320 pounds of total nitrogen, 1080 pounds of acid-soluble phosphorus, and 5600 pounds of acid-soluble po- tassium, in 2 million pounds of the surface soil (Frear, Penn. Dept. Agr. Report, 1906). While most of the phosphorus is usually soluble in the acid used (HC1 of 1.115 sp. 8r-)> on^y about one sixth of the total potassium contained in old soils is thus dissolved, as a general average, although the proportion varies greatly with different types of soil. Doctor Frear has subsequently furnished data showing that 2 million pounds of the fine earth in the surface soil on the Pennsylvania State College farm contain 50,700 pounds of total potassium. SOIL COMPOSITION 77 SOILS OF THE CENTRAL STATES The accompanying soil map of Illinois and Tables 15, 16, and 17 serve to illustrate in a very trustworthy manner both the uniform- ity and variation that may be expected among the most important soil types in the North Central States. This detailed information from Illinois applies with almost equal value to similar soils in many other states. With a north and south extension of nearly 400 miles in the center of the greatest agricultural region of the United States, Illinois occupies a unique position. In latitude it reaches almost from Vermont to North Carolina, Cairo being farther south than Richmond, and Beloit farther north than Boston. Cairo is within 35 miles of the Tennessee line, and 150 miles south of Covington, Kentucky. From Cairo to Mobile on the Gulf is no farther than from Beloit to the 49th parallel, which marks the northern boundary of the United States. The soils of Illinois are in large measure representative of the soils of the wheat belt, of the corn belt, and, in part, of the cotton belt. Cotton growing has been a commercial success in southern Illinois, and much spring wheat has been produced in the north end of the state, while central Illinois is the heart of the corn belt. Fourteen great soil areas are recognized in Illinois, including the extensive unglaciated regions in the southern and northwestern parts of the state, the lower, middle, and upper Illinoisan glacia- tions, the pre-Iowan and lowan glaciations, the early and late Wisconsin glaciations, with numerous moraines and intermorainal tracts, the deep loess deposits, and the early and late swamp and sand areas, and extensive and widely distributed bottom lands and terraces. As already explained, the material called loess constitutes the chief basis for nearly all of the upland soils of central United States. The principal differences among these soils of loessial origin are due to difference in age, topography, and climatic conditions. Some additional or subsequent differences have been brought about by variation in native vegetation and in systems of farming. Prairie and timber soils. The upland soils may be divided into prairie soils and timber soils, according to the character of the original vegetation; and with similar topography the difference in 78 SCIENCE AND SOIL vegetation is not due to original differences in the soil materials ; but rather the difference between prairie land and timber land is due to the influence of the vegetation upon the soil. The existence of prairies over areas naturally well surface-drained is due very largely, if not entirely, to the prairie fires, which were, as a rule, of annual occurrence and often a source of danger to the early settlers in prairie regions. The annual destruction of any seedlings that may have started effectually prevented the growth of forests on the prairie lands, and it is noteworthy that level areas or valleys on the northeast side of streams were usually timbered, while corresponding areas on the southwest were usually prairie, because of the prevailing southwest winds during summer and autumn. (See " Soils of Clay County, Illinois.") Prairie fires have no tendency to run down hill, and they make but little progress against the wind. The wild prairie grasses and weeds, including native legumes, developed an abundant root system to an average depth of 16 to 20 inches, varying somewhat with the latitude or length of season, the depth being greater in the latitude of central Illinois than in northern Illinois; and, with the partial decay of these roots, followed the marked accumulation of humus which characterizes the " black soil " of the prairie; while the smaller amount of humus is the chief characteristic of the timber soils. Rotting tree roots are subject to very complete decay, because of the large cavities and ready admission of air. Boring insects and burrowing animals also hasten the destruction, so that the small amount of leaf mold that remains constitutes the main source of humus for timber soils, and even this is exposed to rapid decay. Being poorer in organic matter, the upland timber soils are correspondingly poorer in nitrogen than the prairie soils. The prairie lands may be classified according to topography, as undulating prairies and flat prairies. The undulating prairie soil covers the nearly level or gently rolling prairie lands that were naturally fairly well surface-drained. It is usually markedly uniform in a given formation, and consti- tutes the most important soil of the corn belt. More or less of the clay and finer silt has been carried downward from the surface and accumulated in the subsoil, and some has been carried away by SOIL COMPOSITION 79 surface washing during many centuries and collected in lower lying flat areas. The exposure of the surface after the annual prairie fires permitted some slight surface washing which other- wise would not have occurred. The flat prairie soils occupy the lower lying level areas that were naturally poorly surface-drained and inclined to be swampy, espe- cially during the wet season of the year. This soil has been formed in part from deposits of fine earth and vegetable matter washed in from the surrounding higher land. The rank growing swamp grasses have, from the partial decay of their roots (and of more or less of their tops) , added much organic matter to this soil. The undulating prairie soils vary from a gray silt loam on tight clay in the older areas, to a dark brown silt loam, in the later forma- tions, and the common flat prairie soils vary with age from drab silt loam to black clay loam. Many other less extensive soil types occur here and there on the prairies, including, as extremes, sand dunes formed of wind-blown material from old shallow lake beds, gravel points, or exposed glacial till, bogs of peat or muck, and sometimes adjoining strips of plastic clay. Some intermediate types include deep silt loam, sandy loam, silt on clay, etc. These are of small importance compared with the very extensive and most common prairie soils reported in Tables 15, 16, and 17. There are three principal types of upland timber soils in most of the great loess-covered areas. One, a light gray silt loam, occupies the flat areas ; a second type, yellow-gray silt loam, covers the undulating or gently sloping lands; and the third (yellow silt loam) is hilly or steeply sloping and consequently subject to serious ero- sion, or surface washing, especially when under cultivation. In addition, there are the areas of deep loess (yellow fine sandy loam) covering the bluffs in many places along the larger river valleys; and other less extensive types are sometimes found. In northern Illinois and southern Wisconsin, in what is termed the lowan glaciation, considerable areas are found of a brown sandy loam, occupying in the main the undulating uplands. The top soil con- sists of brown sandy loam, containing some gravel in places and occasionally pieces of stone. The subsoil at a depth of three feet or more frequently contains much stone, the proportion increasing 8o SCIENCE AND SOIL with the depth, the disintegrating bed rock being found at 4 to 10 feet beneath the surface. The bed rock and some of the pieces found in the soil and subsoil consist of impure limestone. The soil is commonly recognized as drift, but it is certainly much modified by the residual material, and in places there is but little evidence of glacial or loessial deposit. Sand, swamp, and bottom lands. In the older formations, as in the Illinoisan glaciations and still farther south, the soil of the smaller river bottoms is chiefly a deep gray silt loam; while, in the more recently formed great soil areas, the principal bottom land soil is a brown loam. In both cases the bottom land resembles somewhat the top soil of the adjoining upland (which has con- tributed much to its formation) , modified by additions of humus and alluvium from other sources. Many other types of bottom land are also found, but usually they are less abundant. Extensive swamp regions are found in most of the Northern States, especially in Michigan, Wisconsin, and Minnesota, and in the northern parts of Ohio, Indiana, Illinois, and Iowa. These swamp soils vary almost from pure sand to pure clay, and almost from 100 per cent mineral matter to 100 per cent organic matter; and they also vary from moderately acid soils to marls containing more than 50 per cent of calcium carbonate, and not infrequently magnesium carbonate is present in sufficient amount to render the soil non-productive and place it in the alkali class. These different constituents vary quite independently, sand, peat, clay, peaty sand, sandy peat, peaty clay or clayey peat (muck), sandy clay, clayey sand, loam, sandy loam, clay loam, and peaty loam being among the possible soil types; and any of these may be acid or may contain " alkali." In addition we find such variations as deep peat, medium peat, and shallow peat, with sand or clay or sandy clay subsoil. In places there are broad, level, and very uniform areas of deep peat, of peat on sand, or of nearly pure sand; and in other places peat bogs and sand ridges alternate every few rods. Not infre- quently sand dunes (still subject to more or less wind action) are found in or adjoining these swamp regions; and in some sections there are more extensive sand regions, including considerable parts of counties in Ohio, Indiana, Illinois, and Wisconsin, and an area of several counties in the north central part of the lower peninsula of Michigan. SOIL COMPOSITION 81 In case of the most important soil types the averages reported in Tables 15, 16, and 17 are based upon analyses of a large number of composite soil samples. The two most extensive soil types in Illinois are the gray silt loam prairie (330) of the lower Illinoisan glaciation (the so-called hard-pan soil of "Egypt"), and the brown silt loam prairie (1126) of the early Wisconsin glaciation. The averages reported for the gray silt loam on tight clay of the lower Illinoisan glaciation represent 57 different soil samples. In 2 million pounds of the surface soil the potassium (the most constant constituent) varied from 23,120 to 26,440 pounds, the phosphorus varied from 700 to 1000 pounds, and the nitrogen varied from 2140 to 3500 pounds; and in every case the surface, subsurface, and subsoil were found to be acid. The data reported for the brown silt loam of the early Wisconsin glaciation are averages obtained by analyzing 90 different samples of soil collected in ten different counties, and representing more than 500 different borings. In 2 million pounds of the surface soil of this type the potassium varied from 31, 980 to 43,100 pounds, the phosphorus varied from 980 to 1620 pounds (or, if we disregard four samples, from 1020 to 1340 pounds), and the nitrogen varied from 3980 to 7520 pounds (or from 3980 to 6340, if we disregard two samples). The limestone has not been leached out of the early Wisconsin brown silt loam to such a depth as in the older gray silt loam. In one case limestone was present in the surface of the brown silt loam, and in three cases it was found in the subsurface, while it was more often present in the subsoil, although in many cases even the subsoil was found to be acid, but never to such a degree as is common for the subsoils of the older brown silt loams (middle and upper Illinoisan, pre-Iowan, and lowan). With unimportant exceptions, all samples of surface, subsur- face, and subsoil of the yellow silt loams (and the yellow fine sandy loam) of the hill lands were distinctly acid, the degree varying with the age of the soil. In the late Wisconsin glaciation both the brown silt loam and the yellow-gray silt loam samples were almost invariably slightly acid in the surface and subsurface, but exceedingly well supplied with carbonates in the subsoil. 82 SCIENCE AND SOIL TABLE 15. FERTILITY IN ILLINOIS SOILS Average Pounds per Acre in 2 Million Pounds of Surface Soil (o-6f Inches) l SOIL TYPE NO. Son, AREA OR GLACIATION SOIL TYPE TOTAL NITRO- GEN TOTAL PHOS- PHOR- US TOTAL POTAS- SIUM LIME- STONE PRESENT LIME- STONE RE- QUIRED PRAIRIE LANDS, UNDULATING 33° Lower Illinoisan Gray silt loam on tight clay 2880 840 24940 1160 426 Middle Illinoisan Brown silt loam 437° 1170 32240 70 526 Upper Illinoisan Brown silt loam 4840 1200 32940 70 626 Pre-Iowan . . Brown silt loam 4290 1190 35340 no 726 lowan . . . Brown silt loam 4910 I22O 32960 90 1126 Early Wisconsin Brown silt loam 505° II9O 36250 60 1026 Late Wisconsin Brown silt loam 6750 1410 45020 60 PRAIRIE LANDS, FLAT 329 Lower Illinoisan Drab silt loam 2800 710 26260 1300 420 520 II2O I22O Middle Illinoisan Upper Illinoisan Early Wisconsin Late Wisconsin Black clay loam Black clay loam Black clay loam Black clay loam 6760 7840 8900 143° 1690 2030 1870 31860 29770 37370 830 30 32530 980 TIMBER UPLANDS, ROLLING OR HILLY 135 Unglaciated Yellow silt loam 1890 950 3J45o 80 335 Lower Illinoisan Yellow silt loam 2150 950 31850 310 435 Middle Illinoisan Yellow silt loam 1870 820 33470 40 535 Upper Illinoisan Yellow silt loam 2OIO 840 34860 130 635 Pre-Iowan . . Yellow silt loam 2390 850 37180 30 735 lowan . . . Yellow silt loam 1910 910 3578o 30 H35 Early Wisconsin Yellow silt loam 1890 870 32720 60 864 Deep loess . . Yellow fine sandy loam . . . 2I7O 960 35640 70 1 The numbers given in Table 15 represent the total amount contained in 2 million pounds of the surface soil on the dry basis, with the exception of deep peat swamp soil, for which the amounts in i million pounds are used, because its spe- cific gravity is only one half that of ordinary soil, and of sand soil for which 2 \ million pounds are used, because it is about one fourth heavier than ordinary soil. SOIL COMPOSITION TABLE 15. FERTILITY IN ILLINOIS SOILS — Continued SOIL TYPE NO. SOIL AREA OR GLACIATION SOIL TYPE TOTAL NITRO- GEN TOTAL PHOS- PHOR- US TOTAL POTAS- SIUM LIME- STONE PRESENT LIME- STONE RE- QUIRED TIMBER UPLANDS, UNDULATING 1034 Late Wisconsin Yellow-gray silt + loam . . . 2890 810 47600 40 760 lowan . . . Brown sandy loam 3070 850 26700 IOO TIMBER UPLANDS, FLAT 332 Lower Illinoisan Light gray silt loam on tight clay . . . 1890 810 27280 45° SAND, SWAMP, AND BOTTOM LANDS J331 Old bottom lands Deep gray silt loam . . . 3620 1420 36360 440 i45i Late bottom lands Brown loam 4720 1620 3997° 2090 1481 Sand plains and dunes . . . Sand soil . . 1440 820 30880 200 1401 Late swamp . Deep peat . . 34880 1960 2930 X3° 1415 Late swamp . Drab clay . . 5760 1900 48080 36300 1400 Late swamp . Marly peat . . 20900 1520 920 1278000 A careful study of the mass of evidence recorded in Tables 15, 16, and 17 clearly reveals the fact that the most important and most extensive areas of Illinois soils are poor in phosphorus. The only soils well supplied with phosphorus are the black clay loams, the bottom lands, and the clay and peaty swamp soils. On the other hand, the supply of total potassium is very great in all of the soils reported upon, with the exception of the deep peat and the abnor- mal marly peat, which are markedly deficient in that element. It should be kept in mind that small bodies of peat soil surrounded by normal upland soils rich in potassium are likely to have received deposits of silt or clay by overflow from time to time, and as a rule they are not deficient in potassium, and shallow peat bogs with clay 84 TABLE 16. FERTILITY IN ILLINOIS SOILS Average Pounds per Acre in 4 Million Pounds of Subsurface Soil (6^-20 inches) Son. TYPE No. SOIL AREA OR GLACIATION SOIL TYPE TOTAL NITRO- GEN TOTAL PHOS- PHOR- US TOTAL POTAS- SIUM LIME- STONE PRESENT LIME- STONE RE- QUIRED PRAIRIE LANDS, UNDULATING 330 Lower Illinoisan Gray silt loam on tight clay 3210 1500 5357° 635° 426 Middle Illinoisan Brown silt loam 5800 1920 62590 no 526 Upper Illinoisan Brown silt loam 6480 2090 64820 1 20 626 Pre-Iowan . . Brown silt loam 4650 2O6O 72370 57° 726 lowan . . . Brown silt loam 5*40 1940 66220 360 1126 Early Wisconsin Brown silt loam 6560 2OOO 72780 90 1026 Late Wisconsin . Brown silt loam 6870 1960 96420 15° PRAIRIE LANDS, FLAT 329 Lower Illinoisan Drab silt loam 3160 1230 54420 3980 420 Middle Illinoisan Black clay loam 6180 2260 64070 2940 520 Upper Illinoisan Black clay loam 738o 2690 60760 70 II2O Early Wisconsin Black clay loam 7200 3090 71670 49300 1220 Late Wisconsin . Black clay loam 9100 2860 78840 1310 TIMBER UPLANDS, ROLLING OR HILLY 135 Unglaciated . . Yellow silt loam 2030 2120 67320 4850 335 Lower Illinoisan Yellow silt loam 2170 2000 67380 6630 435 Middle Illinoisan Yellow silt loam 1980 ISIO 65370 37° 535 Upper Illinoisan Yellow silt loam 1900 1610 72570 222O 635 Pre-Iowan . . Yellow silt loam 2290 i75o 76150 650 735 lowan .... Yellow silt loam 2I2O 1960 71180 1500 "35 Early Wisconsin Yellow silt loam 1870 159° 68600 3910 TIMBER LANDS, UNDULATING 1034 Late Wisconsin . Yellow-gray silt loam . . . 2710 1390 IIIIOO 34° 760 lowan .... Brown sandy loam . . . 3920 1590 543°° 620 SOIL COMPOSITION TABLE 16. FERTILITY IN ILLINOIS SOILS — Continued Sou, TYPE No. Son. AREA OR GLACIATION Son, TYPE TOTAL NITRO- GEN TOTAL PHOS- PHOR- US TOTAL POTAS- SIUM LIME- STONE PRESENT LIME- STONE RE- QUIRED TIMBER UPLANDS, FLAT 332 Lower Illinoisan Light gray silt loam on tight clay .... 1920 1240 58480 7200 SAND, SWAMP, AND BOTTOM LANDS I,w Old bottom lands Deep gray silt loam 2250 1830 68090 449° 1451 Late bottom lands Brown loam . . 6660 2160 77540 980 1481 Sand plains and dunes . . . Sand soil . . . 2070 1480 62690 50 1401 Late swamp . . Deep peat . . 64980 2940 7010 2IO subsoils are also well supplied with potassium, or may be by deep plowing; whereas broad areas of deep peat or of shallow or medium peat on sand are as a rule deficient in potassium. Most of the older soils (chiefly in southern and western Illinois) are markedly acid in the surface and subsurface, and exceedingly acid in the subsoil. The rolling or hilly timber uplands and the sand soil are very deficient in nitrogen, while the undulating prairie lands (except in the late Wisconsin glaciation), the undulating timber lands, and even the flat prairie lands in the oldest forma- tion, are only moderately well supplied with nitrogen. The black clay loams (especially in the more recent formations) are rich, and the peaty soils exceedingly rich, in humus and nitrogen. In the main the soils of central and northern Illinois are com- parable with similar soil types in Indiana and Ohio on the east, and with Iowa and eastern Nebraska soils on the west; and the soils of southern Illinois are comparable with similar types in Missouri and eastern Kansas on the west, and also with the loess- covered areas in southern Indiana, Kentucky, Tennessee, and northwest Mississippi; while some of the same soil types that are 86 SCIENCE AND SOIL TABLE 17. FERTILITY IN ILLINOIS SOILS Average Pounds per Acre in 6 Million Pounds of Subsoil (20-40 Inches) SOIL TYPE No. SOIL AREA OR GLACIATION Son. TYPE TOTAL NITRO- GEN TOTAL PHOS- PHOR- TOTAL POTAS- SIUM LIME- STONE PRESENT LIME- STONE RE- PRAIRIE LANDS, UNDULATING 33<» Lower Illinoisan Gray silt loam on tight clay . . 3240 2400 84300 21580 426 Middle Illinoisan Brown silt loam 344° 2680 90040 2OO 526 Upper Illinoisan Brown silt loam 3440 2790 98580 460 626 Pre-Iowan . . Brown silt loam 394° 33«o 102620 1650 726 lowan .... Brown silt loam 3540 2780 99780 1940 1126 Early Wisconsin Brown silt loam 34.20 2620 117880 66600 1026 Late Wisconsin Brown silt loam 363° 2630 160140 728000 329 Lower Illinoisan Drab silt loam 3400 1690 80830 15770 42O 520 II2O 1220 Middle Illinoisan Upper Illinoisan Early Wisconsin Late Wisconsin Black clay loam Black clay loam Black clay loam Black clay loam 3020 3I4° 349° 3180 303° 3640 363° 393° 94900 96220 111280 125370 149200 I2IO II7500 5470 TIMBER LANDS, ROLLING OR HILLY 135 Unglaciated . . Yellow silt loam 1970 3280 10543° 20660 335 Lower Illinoisan Yellow silt loam 2480 317° 99670 21500 435 Middle Illinoisan Yellow silt loam 2820 2810 99000 3700 535 Upper Illinoisan Yellow silt loam 2280 3270 100950 62IO 635 Pre-Iowan . . Yellow silt loam 2380 3400 I02IOO 5480 735 lowan .... Yellow silt loam 2490 3900 105030 3750 H35 Early Wisconsin Yellow silt loam 2450 2660 103830 44OO 864 Deep loess . . Yellow fine sandy loam .... 2730 3320 IO52IO 3620 TIMBER UPLANDS, UNDULATING 1034 Late Wisconsin Yellow gray silt loam .... 3240 2400 156740 1034000 760 lowan .... Brown sandy loam .... 4160 2440 81180 49700 SOIL COMPOSITION TABLE 17. FERTILITY IN ILLINOIS SOILS — Continued Son. TYPE No. SOIL AREA OR GLACIATION SOIL TYPE TOTAL NITRO- GEN TOTAL PHOS- PHOR- US TOTAL POTAS- SIUM LIME- STONE PRESENT LIME- STONE RE- QUIRED TIMBER UPLANDS, FLAT 332 Lower Illinoisan Light gray silt loam on tight clay . . 2IOO 2230 9055° 19750 SAND, SWAMP, AND BOTTOM LANDS I331 Old bottom lands Deep gray silt loam .... 2280 2620 101610 9060 i45i Late bottom lands Brown loam . . 4150 2410 119520 4620 1481 Sand plains and dunes . . . Sand soil . . . 3100 2230 94030 80 1401 Late swamp . . Deep peat . . . 9773° 3740 11510 290 found in the "Great American Bottoms" in southwestern Illinois, are found in the Mississippi Delta farther south. The terminal moraine of the Wisconsin glaciation extends from southern Edgar County, Illinois, to the center of Parke County, Indiana, thence in a southeast direction to the north line of Jen- nings County, thence northeast to the south line of Fayette County, and thence to the southeast corner of Franklin County. About two thirds of the state lies north of this line and resembles the timber uplands of northeastern Illinois, with a smaller propor- tion of prairie lands and considerable areas of swamp, especially' in the Kankakee river basin. South of the terminal moraine the state is largely loess covered, and resembles the timber lands of southern Illinois, except for a central area of residual soils in Monroe, Lawrence, Martin, Orange, Washington, Warrick, DuBois, Crawford, and parts of most adjoining counties. In the 1907 Report of the Indiana Geological Survey, Mr. Robert E. Lyons gives data from which the following table is derived : 88 SCIENCE AND SOIL TABLE 18. COMPOSITION OF SOUTHERN INDIANA SURFACE SOILS Pounds per Acre in 2 Million of Soil (About 6f Inches Deep) SOILS NUMBER OF ANALYSES TOTAL NITROGEN ACID-SOLUBLE PHOSPHORUS Limestone soil (Residual rolling) . . . 5 3080 !330 Limestone and shale soil (Residual rolling) i 3660 4990 Volusia silt loam (Residual shale, rolling) i 2300 1160 Miami silt loam (Loessial, level) . . . i 1160 134° Waverly silt loam (Stream valleys) . . . 2 445° 2162 Ohio river bottom land I 1840 2430 Aside from the bottom lands, these soils are as a rule markedly acid. The residual soil derived from limestone and shale is rich in phosphorus, and the bottom lands are also well supplied with that element. On the other soils much commercial fertilizer, chiefly bone meal and acid phosphate, is already being used. The upland silt loams are becoming very deficient in nitrogen and organic matter. Two analyses of the shale underlying some of the residual soils show an average potassium content of 64,500 pounds and only 3000 pounds of total calcium, in 2 million of shale. The rolling residual soil derived from shale (Volusia silt loam) and the level or gently undulating loessial soil (Miami silt loam) are very acid. A residual soil of sandstone origin is found in Martin, Lawrence, and some adjoining counties. In his discussion of Indiana soil types, Mr. Charles W. Shannon makes the following suggestive statement: " Large amounts of planer dust from the stone mills are being used as a lime application on the various soils with good results. The most noted of these experiments are in cases where from 1000 to 2000 pounds per acre of the dust was applied to fields of alfalfa and clover, and as a result much better stands were secured than in parts without the lime. This is a cheap source of lime for those who have access to the mills." As an average of 21 analyses the Ohio Experiment Station (Bulletin 150) finds, in 2 million pounds of the surface soil on the Station farm at Wooster, 1880 pounds of total nitrogen and 920 pounds of acid-soluble phosphorus; and Ohio Circular No. 79 re- ports data showing 31,000 pounds of total potassium in the same stratum. The average of 161 soils from various parts of Ohio shows 960 pounds of acid-soluble phosphorus in 2 million of soil. As a general average about 85 per cent of the phosphorus in such soils is soluble in the acid used, so that the total phosphorus probably amounts to about noo pounds. The average composition of three samples of surface soil from the loess-covered uplands at the Missouri Experiment Station at Columbia, in central Missouri, shows 2710 pounds of total nitro- gen, 690 pounds of total phosphorus, and 28,500 pounds of total potassium, in 2 million pounds of soil (Schweitzer, Missouri Bul- letin No. 5) . These amounts correspond closely with the average composition of the most common upland soils of southern Illinois; and the more highly productive corn belt soils of north central and northwest Missouri are more nearly comparable with the brown silt loams and black clay loams of the middle Illinoisan glaciation. An analysis 1 of the worn upland soil near St. Louis, Missouri, shows 1 1 60 pounds of nitrogen, 700 pounds of total phosphorus, and 35,200 pounds of potassium in 2 million of soil. This is about the average composition of the subsurface soil of the deep loess area in Illinois, and indicates previous loss of surface soil by washing. Professor Keyser has kindly furnished the author with some unpublished data concerning the soils of Nebraska, showing that the glacial silt loam of eastern Nebraska, which has been formed evidently from the weathering of the till of the Kansan glaciation, contains, in 2 million pounds of the surface, 3940 pounds of nitro- gen, 660 pounds of total phosphorus, and 23,000 pounds of potas- sium; while the ordinary loessial soil representing the most common corn belt type in the southeast part of the state (and probably of northeast Kansas as well) contains 5160 pounds of nitrogen, 1060 of total phosphorus, and 29,000 pounds of potassium, correspond- ing very closely to the brown silt loams in the loess-covered middle and upper Illinoisan glaciation. The common silt loam of the less humid region of central Nebraska contains 3680 pounds of nitrogen, 1520 of phosphorus, and 48,000 of potassium. A preliminary general soil survey of Iowa (Stevenson, Iowa 1 Reported by Doctor R. O. Graham, Bloomington, Illinois, as a commercial analysis. 90 SCIENCE AND SOIL Bulletin 82) shows five important soil areas in Iowa, which closely resemble similar areas in Illinois. (1) About one tier of counties bordering the Mississippi (with a western projection which includes most of Cedar, Johnson, Iowa, Poweshiek, and Jasper counties) is termed the Mississippi loess area, and resembles the loessial soil on the Illinois side. (2) Similarly, along the Missouri and Big Sioux rivers the two western tiers of counties are chiefly in the Missouri loess area. (3) The Kansan glaciation (overlaid with shallow loess on the less rolling lands) covers the southern third of the remainder of Iowa, and this resembles closely the lower Illinoisan, except that the older Kansan is more broken and has much more exposed till on the eroded hillsides. (4) The eastern part of the remainder of the state is covered by the lowan glaciation, and (5) the somewhat larger western part by the Wisconsin glaciation, both of which are also found in Illi- nois. In both states the lowan glaciation is characterized by its rolling topography and perfect surface drainage, and the Wiscon- sin by its level prairies which require much artificial drainage by tile and open ditches. Eight analyses of lowan soils, reported to the author by Doctor J. B. Weems while professor of agricultural chemistry in the Iowa State College, showed 900 pounds of acid-soluble phosphorus in 2 million of soil, as a general average. The several soil types repre- sented varied considerably, however, as would be expected from comparison with similar Illinois soils, the highest amount reported being 1600 pounds of acid-soluble phosphorus per acre in a 6f-inch stratum, corresponding to 1880 pounds of total phosphorus, if 85 per cent were acid-soluble. (This method of estimating total phosphorus from the acid-soluble phosphorus is never safe for application to individual soil samples, but it is approximately cor- rect for large averages of most common soils of central United States.) The acid-soluble potassium (which varies from less than one sixth of the total in old soils to more than one third of the total in more recent, less weathered soils) amounted to 4670 pounds as an average of the eight soils (the highest being 7800 pounds) in 2 mil- lion of surface soil, corresponding probably to 30,000 to 40,000 pounds of total potassium. The analysis of loess from Dubuque, SOIL COMPOSITION Iowa, shows 35,600 pounds of total potassium in 2 million (see Table n). Since the above was written the author has secured, through the kindness of Professor Stevenson, the unpublished data shown in Table 18.1 which present the average results of from one to six analyses of the most important soil types in the great soil areas of the state. Professor Stevenson writes: " The samples are believed to represent the most widely distributed type of the respective areas. We did not determine total potassium." (Two types, the uncovered glacial till, and the shallow loess, are included for the Kansan area.) TABLE 18.1. PLANT FOOD IN SURFACE SOILS OF IOWA Pounds per Acre in 2 Million (about 6f -inch Stratum) FORMATION OR SOIL AREA NUMBER OF ANALYSES TOTAL NITROGEN POUNDS TOTAL PHOSPHORUS POUNDS Kansan glaciation (exposed till) . . . lowan glaciation Wisconsin glaciation 31 5 i 2380 3940 7C2O 860 1160 1460 Loess on Kansan glaciation .... Mississippi loess 6 •2 3400 3IOO IO2O IO2O Missouri loess IO 4.420 I42O 1 Only two analyses for phosphorus in the Kansan till The Kansan drift is the oldest and the poorest in both nitrogen and phosphorus, while the Wisconsin is the newest and the richest, with the lowan intermediate in both respects. The Mississippi loess and the shallow loess on the less rolling parts of the Kansan glaciation are similar in composition and probably of similar origin (of the lowan age) , but the Mississippi loess is much deeper and of a more rolling topography, which insures a much better subsoil, physically, and may also account for the somewhat lower nitrogen content of the surface, through loss of organic matter by washing. The higher phosphorus content of the Missouri loess suggests that it owes its origin in part to deposits from the semi-arid plains of the northwest, the richer mineral soil having encouraged the more recent accumulation of nitrogen. 92 SCIENCE AND SOIL SOILS OF THE SOUTHERN STATES The average composition of twelve samples of soil from seven different counties in Kentucky outside of the Blue Grass Region shows 550 pounds of acid-soluble phosphorus in 2 million pounds of surface soil; and within the famous Blue Grass Region the supply of acid-soluble phosphorus amounts to 5200 pounds (nearly ten times as much) in 2 million of soil, as the average of 30 soil analyses, collected from five counties, these residual soils having been formed in part at least from the weathering of phosphatic limestone. The state of Tennessee may be divided geologically into five principal sections: (1) The great loess-covered undulating upland area of west Tennessee, lying chiefly between the Mississippi and Tennessee rivers. (2) The Central Basin, including most of ten counties (David- son, Trousdale, Jackson, Smith, Wilson, Williamson, Rutherford, Bedford, Marshall, andMaury) and parts of several adjoining coun- ties. The Central Basin includes much of the great phosphate beds of Tennessee. It resembles in some respects the Blue Grass region of Kentucky, and by some the Central Basin of Tennessee is claimed to be the original home of Kentucky blue grass. (3) The Highland Rim, surrounding the Central Basin. (4) The Cumberland Plateau, farther east. (5) The East Tennessee Valley, lying between the Cumberland Plateau and the Unaka Mountains on the eastern border of the state. Table 19 shows the plant food in representative soils of each of these great sections, the averages of several soil analyses being reported for the more important areas (Mooers, Tennessee Bulletin 78). The average composition of the yellow silt loam soil on the loess- covered Ozark Hills of southern Illinois shows 1890 pounds of nitrogen, 950 pounds of phosphorus, and 31,450 pounds of potas- sium per acre in 2 million pounds of surface soil, which is practi- cally the same as for the west Tennessee soil. It may be kept in mind, too, that the north line of west Tennessee is only 35 miles SOIL COMPOSITION 93 TABLE 19. COMPOSITION OF SURFACE SOILS OF TENNESSEE Average Pounds per Acre in 2 Million of Soil (about 6f -inch Stratum) SECTION OR AREA ORIGIN OF Son. . NITROGEN (Total) PHOSPHORUS (Total) PoTAssnni (Total) West Tennessee . . Loess deposit . . . 1890 890 3IO2O Highland Rim . . . Limestone .... 2IOO 660 24600 Central Basin . . . Limestone and phos- phate 2350 2030 18160 Cumberland Plateau . Sandstone .... 1700 380 7840 East Tennessee Valley Limestone and dolomite 2080 980 12130 Bottom land . . . Alluvial 2620 1840 34160 from the southern point of Illinois, and that much of the upland soil of northwest Mississippi is essentially of the same character. It will be noted that the average soil of the Central Basin is comparatively rich in phosphorus, while the soils of the Highland Rim, and more especially the sandstone soils of the Cumberland Plateau, are extremely deficient in phosphorus, and the latter is also very poor in potassium, as might be expected from its origin. The number of soil analyses entering the averages in Table 19 is not sufficient for final data, but in the main they are supported by larger numbers of analyses for acid-soluble plant food. Thus, the averages of 25 analyses of soils from eight counties in the Central Basin show 2020 pounds of acid-soluble phosphorus in 2 million of soil, while 700 pounds of phosphorus is the corresponding aver- age for 1 6 analyses of loessial soil from eleven counties in west Tennessee. The acid-soluble phosphorus in the samples whose total phosphorus content was determined (and thus afforded for use in Table 19) was 1710 pounds for the Central Basin and 750 pounds for the. west Tennessee soil, 84 per cent of the total having been dissolved by strong hydrochloric acid, in either case. On this basis, the general average of all samples would show 830 pounds of total phosphorus for west Tennessee and 2400 pounds for the Central Basin, in 2 million pounds of surface soil. Hilgard reports the average of 97 analyses of Mississippi soils showing 790 pounds of acid-soluble phosphorus in 2 million pounds of surface soil, but the more abundant upland soils average about 94 SCIENCE AND SOIL 700 pounds, while 4100 pounds of phosphorus per acre (in a 6f -inch stratum) have been found in an upland soil of limestone origin. The " black prairie " limestone soils found in limited area in northeastern Mississippi and in northwestern Alabama are as a rule well supplied with phosphorus. This formation is apparently an extension of that found so commonly in the broad Central Basin of Tennessee, which also extends into Kentucky, where it again expands into the great Blue Grass Region. An analysis made by Doctor H. C. White of a sample of soil representing the University farm of Georgia, collected in March, 1884, from land that " had been cleared in December (1883) of a second growth of oak and hickory," gave the following amounts per acre based upon the surface foot, which was assumed to weigh 3,528,000 pounds. TABLE 19.1. COMPOSITION OF GEORGIA SOIL (UNIVERSITY FARM) PLANT-FOOD ELEMENTS POUNDS PER ACRE FOOT POUNDS IN 2 MILLION Nitrogen 36<2 2OOO Phosphorus "^O 3OO Potassium 2IOOO I2OOO Magnesium C7OO 32OO Calcium 74OO 4IOO Iron 2Q7OO l6lOO Sulfur IIOO 6dO The original statement reports " sand and clay," and it must be assumed that the mineral elements as given above represent the amounts soluble in strong acid. The Texas Experiment Station has analyzed a considerable number of soil samples collected to represent six general groups or " series," as mapped and named by the United States Bureau of Soils. The following descriptions are taken from Texas Bulletin 99 "Norfolk soils. These are light-colored upland sandy soils, with a yellow clay or sandy clay subsoil, usually with good drainage. " Of the areas under study, the Norfolk soils are found in Anderson, Houston, and Bexar counties. They are widely distributed in the eastern part of the state. SOIL COMPOSITION 95 "Orangeburg soils. The Orangeburg soils are gray to brown upland soils, with a red or yellowish clay sandy subsoil. The red color of the sub- soil distinguishes the Orangeburg soils from the Norfolk soils. The red soils appear to be more productive, and are generally stronger than the correspond- ing soils of the Norfolk series. The Orangeburg soils are widely distributed, especially in East Texas. "Lufkin soils. The Lufkin soils are gray, with heavy, very impervious plastic gray and mottled subsoils. These soils are generally lower in agricul- tural value than the Norfolk and Orangeburg soils, perhaps on account of the nature of the subsoils. These soils are found in Houston, Lamar, and Travis counties, of the areas studied. " Susquehanna series. These are gray and brown surface soils with heavy plastic mottled subsoils. They differ from the Lufkin series in the color of sub- soil. They are generally of low productiveness. "Houston series. These are black calcareous prairie soils, very productive and durable. They are among the best soils of the state. Some of them have been in cultivation forty or fifty years without fertilizer, and though some of them have decreased somewhat in fertility, they are still productive. They are found, in areas surveyed, in Lamar, Hays, Travis, and Bexar counties. They are of general occurrence in the east-central portion of the state. "These soils appear to owe their productiveness to their content of lime and organic matter, and nitrogen. Some of these soils will become deficient in phosphoric acid. " Yazoo soils. These soils are bottom land, generally subject to overflow and very productive. The soils are mapped in only two areas, Anderson and Travis counties. " The following tabular statement gives the average amounts of total nitrogen, acid-soluble phosphorus, and acid-soluble potassium in 2 million pounds of the surface soil of these different soil types, based upon the analyses reported by Doctor Fraps. TABLE 19.2. AVERAGE COMPOSITION OF SOME TEXAS SOILS Pounds in 2 Million of Soil CONVENTIONAL NAME Son. TYPE TOTAL NITRO- GEN ACID- SOLUBLE PHOS- PHORUS ACID- SOLUBLE POTAS- SIUM Norfolk soils . . Orangeburg soils . Lufkin soils Susquehanna series Houston series Light sandy upland .... Gray -brown sandy upland Gray silt loam on tight clay . . Gray-brown silt loam on tight clay Black prairie 1000 1200 1000 1400 2800 180 440 180 260 C30 2OOO 620O 1800 3700 5600 Yazoo soils . Bottom land 1600 060 6700 96 SCIENCE AND SOIL With the exception of the bottom land, these soils are extremely poor in phosphorus; and, aside from the black prairie, they are also very poor in nitrogen. Hilgard reports 940 pounds of acid-soluble phosphorus in 2 million pounds of Louisiana soil, as an average of 35 analyses. The Geological Survey of Louisiana has furnished the data for the following statement, showing the total nitrogen, acid-soluble phosphorus, and acid-soluble potassium in 8 surface soils and 2 subsoils in Madison Parish, opposite Vicksburg. These are all alluvial soils deposited from the overflow of the Mississippi River. TABLE 19.3. COMPOSITION OF LOUISIANA SOILS IN MADISON PARISH Pounds in 2 Million of Soil DESCRIPTION OF SOIL TOTAL NITROGEN ACID-SOLUBLE Phosphorus Potassium Black soil on buckshot clay; virgin swamp, but good land when cleared Subsoil of same type 3986 1286 1450 1044 6562 4976 Dark gray soil on buckshot clay; once swamp; cultivated 9 years Subsoil of same 3334 95° 1174 928 5466 3570 Dark gray clay; virgin soil ; wooded swamp; overflow land Black waxy soil on dark gray clay; very fer- tile when thoroughly drained; i£ to 2 bales of cotton per acre 2286 2456 2662 1562 1244 1306 2OOO 2O24 1760 1234 1474 I2O6 8412 5134 4748 5084 4IOO 3806 Black soil on buckshot clay Brown silty loam ; old land Brown sandy loam ; cultivated 50 years . . Light brown sandy loam; once productive, but now worn out for corn and cotton In phosphorus content these soils resemble the late bottom lands of Illinois, but the nitrogen content is, as a rule, much lower in the Louisiana soils, and extremely low in the old, worn soils. It may be mentioned here that the Mississippi Experiment Station has conducted some field experiments on delta lands, concerning which the following is reported in Mississippi Bulletin 119: SOIL COMPOSITION 97 "The land on which the tests were made had been cropped in cotton for many years. A part of it is loam soil and is well drained. A test was also made on stiff buckshot land." "The average increase from 300 pounds of high grade cotton seed meal per acre for the three years (1906-8) has been 106 pounds of lint cotton. We have not been able to increase the size of the crop nor its earliness by the use of either phosphorus or potash." "The increase from the application of 300 pounds of cotton seed meal to the stiff buckshot land was 36 pounds of lint cotton per acre. This is not sufficient to make the use of the meal profitable on this character of land." As an average of 38 analyses of Arkansas soils, Hilgard gives 1400 pounds of acid-soluble phosphorus in 2 million of soil, sug- gesting bottom-land soils or some connection with the phosphate deposits of that state. SOILS OF THE NORTHERN STATES In the northern tier of states, where the soils are of more recent origin and where the climate of winter offers less exposure to weath- ering and leaching, the normal soils are, as a rule, richer in mineral plant food, as is indicated, for example, by comparing the soils of the late Wisconsin glaciation in northern Illinois with similar types in the older middle Illinoisan glaciation. Of course, the up- land timber soils are not comparable in nitrogen content with the black prairie soils. The late Doctor Robert C. Kedsie, one of the few great scientists who, with Doctor E. W. Hilgard and Doctor S. W. Johnson, helped to lay firm foundations for the American Agricultural Experiment Stations, reported analyses of 28 Michigan soils grouped in accord- ance with a general survey or classification of the soils of that state (Michigan Bulletin 99) : 1. The four southern tiers of counties are classed as theMichigan "wheat belt." 2. The area along the eastern shore of Lake Michigan, including especially the light porous soils upon which peaches of the finest quality are extensively produced, is termed the " peach belt." 3. Several counties in the Traverse Bay region, including much soil of the sandy-loam type, constitute the " potato district." 98 SCIENCE AND SOIL 4. The large tract of light, sandy lands in the north-central part of the Lower Peninsula is called the " Jack Pine Plains." 5. The peaty swamp soils, used especially for the growing of celery, peppermint, etc., are so designated. In Table 20 is given the average composition of the soils from each of these sections. The nitrogen reported is total, but the data for phosphorus and potassium represent only the amount soluble in acids, probably much stronger, however, than now commonly used. The amount closely approaches the total in case of phos- phorus, but probably represents less than one half of the total potassium actually present in the soil. (A larger proportion of the total potassium present in the newer, less-weathered soils is soluble in acid than of the total potassium in the older leached soils found in the states farther south.) TABLE 20. AVERAGE COMPOSITION or SOME MICHIGAN SOILS Pounds per Acre in 2 Million of Soil (about 6§ Inches) ACID- ACID- AREA Son, SECTION SOLUBLE SOLUBLE PHOSPHORUS POTASSIUM (i) Southern Michigan Wheat belt . . 4600 3600 27360 (2) Lake shore region . . Peach belt . . 1860 2330 22600 (3) Traverse Bay region . Potato district . 1260 1520 16400 (4) North-central tract . . Jack Pine Plains 740 290 4600 (5) Swamp areas .... Deep peat ] . 22OOO 2980 2660 1 The amounts given for deep peat represent the plant food in i million pounds of the material, the specific gravity of which is about one half that of ordinary soils. These striking and valuable results obtained in a very prelimi- nary general survey of Michigan soils clearly indicate the much greater possible value of an extended and detailed investigation of the soils of the state. The high phosphorus content of theMichigan soils, especially of the great area of the wheat belt (3600 pounds), is in marked contrast, not only with the extremely low phosphorus content of the Jack Pine Plains (290 pounds, — less than one tenth as much), but also with the small supply of phosphorus in the common upland soils of southern Illinois, central Missouri, and the western parts of Kentucky, Tennessee, and other southern states. SOIL COMPOSITION 99 In commenting on his study of Michigan soils, Doctor Kedsie said: " Chemical analysis of the soil is of value in determining whether the soil is capable of fertility or the contrary ; also in determining the measure of its possible fertility.1 There are certain ash elements which are absolutely nec- essary for plant growth, in the absence of any one of which vegetable growth is impossible; if the supply is relatively limited, plant growth will be limited correspondingly. Hence, chemical analysis of a soil is of importance in deter- mining possibility of fertility and of the relative fertility which may be secured under favorable conditions. . . . Chemical analysis will not always dis- tinguish between a fruitful and an unfruitful soil. A soil may be unproductive for physical reasons, though it may still contain all the chemical elements of fertility. " The Michigan wheat-belt soils include several different soil types, but among the nine soil samples analyzed from that area, the poor- est contained 260x3 pounds of acid-soluble phosphorus, or 500 pounds more than the average of the best Illinois soil. More than four times as much phosphorus is contained in the average Michigan wheat-belt soil (when these samples were taken) as is now con- tained in the common soils of southern Illinois. A preliminary general survey of Wisconsin soils (Whitson, Wisconsin Agricultural Experiment Station, Annual Report for 1905, pages 262-270) outlines seven different great soil areas in that state : (i) The unglaciated area of the southwest quarter (extending into northwestern Illinois) with three subdivisions in which residual sands, sandy loams, and clay loams, respectively, predominate; (2) the early, and (3) the late glaciations (each in two divisions based upon the underlying rocks), occupying largely the remaining three fourths of the state, and covered with glacial till, with little or no loess deposit; (4) separated sand areas of glacial origin, as in the south-central, extreme northern, and northwest parts of the state; (5) a loessial area covering a strip of upland along the Mississippi; (6) "red clay" areas of lacustrine origin between Green Bay and Lake Winnebago and on the Lake Superior shore; and (7) the scattered swamps of muck and peat. But few analyses of Wisconsin soils have been reported. An 1 Italics by C. G. H. ioo SCIENCE AND SOIL ultimate analysis of 'virgin soil from the Wisconsin Experiment Station Farm at Madison, in the late glaciation, shows 3600 pounds of nitrogen, 1500 pounds of phosphorus, and 36,300 pounds of potassium, in 2 million pounds of surface soil. Where the same soil had been heavily cropped in pot cultures (19 crops having been removed) the nitrogen was reduced to 2200 pounds and the phos- phorus to 1140 pounds, with no determinable change in total potassium content. The analysis of another soil from the late glaciation from northern Outagamie County showed 1400 pounds of nitrogen and 2380 pounds of acid-soluble phosphorus. This glaciation Professor Whitson regards as the best soil area in the state. Residual sand from Jackson County contained 1000 pounds of nitrogen, 870 of phosphorus, and 5100 of total potassium in 2 million of surface soil, and the glacial sand from Vilas County con- tained 1000 pounds of nitrogen, 1580 pounds of phosphorus, and 30,000 pounds of potassium, indicating that the residual sand is more largely quartz, while the glacial sand consists chiefly of sili- cate minerals. (Compare with Tennessee soils.) Red clay from Ashland County contained 1400 pounds of acid- soluble phosphorus in 2 million of soil; and peaty swamp soil from Sauk County contained 32,000 of nitrogen, 1230 pounds of acid- soluble phosphorus, and only 910 pounds of acid-soluble potassium, in i million pounds of the surface soil. The acid-soluble plant food has been determined in many Minne- sota soils (Snyder, Minnesota Bulletin 41), and a few analyses are reported showing the total plant food in representative soils. The average prairie soil o£ the Red River Valley in northwestern Minnesota contains 8200 pounds of nitrogen, 3340 pounds of phos- phorus, and 45,100 pounds of potassium in the surface 2 million pounds; and the average prairie soil in west-central Minnesota contains 5300 pounds of nitrogen, 1760 pounds of phosphorus, and 63,300 pounds of potassium. A general average for the soils of the east-central part of the state is 5600 pounds of nitrogen, 2460 pounds of phosphorus, and 29,000 pounds of total potassium; while the average southeastern Minnesota soils contain 4400 pounds of nitrogen, 1910 pounds of phosphorus, and 30,200 pounds of potassium, in 2 million pounds of surface. SOIL COMPOSITION 101 From the general glacial map of the United States it will be seen that southeastern Minnesota lies in the older lowan glaciation, while most of the remainder of the state is covered by the late Wisconsin glaciation. This may account for the marked difference in potassium content between the soils of eastern and western Minnesota. (See also Tables 15, 16, and 17 for a comparison of these areas in Illinois.) It will be noted that the Red River basin lies within the boundaries of the old glacial lake, " Agassiz." (See also Canadian soils.) The analysis of a sample composed of equal parts of two hundred representative soils from various parts of Minnesota showed 2360 pounds of acid-soluble phosphorus in 2 million of soil. SOILS OF THE WESTERN STATES The soils of the arid plains are, as a rule, rich in mineral plant food and poor in nitrogen, doubtless due to the fact that with but little rainfall there has been practically no loss of minerals by leaching, and but small accumulation of vegetable matter, in which the supply of nitrogen is contained. Headden (Colorado Bulletin 65) reports ultimate analyses of four Colorado soils, showing as an aver- age 2900 pounds of phosphorus and 39,50x2 pounds of potassium; but the average of six soils shows only 2000 pounds of nitrogen, in 2 million of surface soil. Widtsoe (Utah Bulletin 52) shows 37 analyses of Utah soils averaging 1850 pounds of acid-soluble phos- phorus and 2450 pounds of total nitrogen, in 2 million of soil, in the most fertile valleys. On the arid plains the supply of nitrogen is usually very much less. Doctor Widtsoe states that he, " in common with those who have traversed the wastes of western America, has traveled for days without seeing a trace of vegeta- tion, and such soils are almost devoid of organic matter and humus, and contain but small quantities of nitrogen." Hilgard gives 600 pounds of total nitrogen and 2000 pounds of acid-soluble phosphorus in 2 million of soil, as the average of 16 analyses of the arid soils of Colorado. As a rule, the soils of the arid region contain about 3 per cent of lime (CaCO3), or 30 tons of calcium carbonate in 2 million pounds of soil; and the Utah Station reports 18 soil analyses from one county, containing as an average more than 20 per cent 102 SCIENCE AND SOIL of calcium carbonate corresponding to 200 tons per acre to a depth of 6| inches. For 2 million pounds of surface soil, Hilgard's " Soils" gives the following amounts of acid-soluble phosphorus as the average of many analyses: Nevada, 2800; Wyoming, 1570; Montana, 1920; Idaho, 1400. Mr. E. E. Hoskins, while a student in the University of Illinois, analyzed a sample said to represent good " bench " land near Boise City, Idaho, finding 2350 pounds of nitrogen, 1320 of total phosphorus, and 41,400 pounds of potassium, in 2 million of soil. In the Pacific coast states, Hilgard reports (as acid-soluble) 1830 pounds of phosphorus and 10,790 of potassium for Washing- ton, 960 of phosphorus and 8960 of potassium for Oregon, in 2 million pounds of surface soil; also 2800 pounds of total nitrogen, 875 of acid-soluble phosphorus, and 10,100 pounds of acid-soluble potassium, in 2 million pounds of the surface soils of California, as an average of 262 analyses. THE SOILS OF CANADA It will be kept in mind, of course, that Canada comprises an immense territory (3,300,000 square miles, compared with 3,600,000 square miles in the United States, including nearly 600,000 square miles in Alaska) and includes vast areas that are uninhabited, and in part uninhabitable, although the more favored regions are sufficiently extensive ultimately to support a mighty nation. The Canadian Agricultural Experiment Station (known officially as the Dominion Experimental Farms, with headquarters at Ottawa) has made analyses of Canadian soils collected from Van- couver Island on the west to Nova Scotia on the east. Perhaps the most complete investigation has been made of the valley lands and Piedmont soils of British Columbia. In general, these soil investigations have been conducted with reference to uncultivated lands or lands put under cultivation in recent years. They do not represent the comparatively small areas of Canadian soil that have been long cultivated, some of which has already been much de- pleted or much fertilized. The samples have been collected with EUGENE WOLDEMAR HILGARD, A MAN OF SCIENCE Born at Zweibriicken, Bavaria, January 5, 1833 ; educated at Belleville, Illinois, and Heidel- berg, Germany ; state geologist and professor of chemistry of the University of Mississippi, 1855-1873 ; professor of geology and natural history of the University of Michigan, 1873- 1875; statii 75 ; professor of agriculture and director and chemist of the agricultural experiment tion, University of California, 1875-1906 ; chemist since 1906 ; author of " Soils " (1906) SOIL COMPOSITION 103 sufficient purpose, method, and discrimination to give much im- portance to the results, which are summarized as follows: TABLE 20.1. COMPOSITION OF CANADIAN SURFACE SOILS Pounds per Acre in 2 Million of Soil (about 6f Inches) ACID-SOLUBLE NUMBER OF TOTAL ANALYZED NITROGEN Phosphorus Potassium Calcium 21 British Columbia .... 5240 2360 6970 16700 6 Northwest Territory . . . 9180 1520 5670 4I30 I Manitoba 2OIOO 2f -JQ 17100 27000 6 Quebec 4^2O 1 7^0 74OO 6 Ontario (Muscoka only) 2700 1250 3650 6300 5 Maritime Provinces . . . 26OO 960 7300 157° In referring to the averages represented in this tabular state- ment, Professor Frank T. Shutt (Chief Chemist for the Dominion Experimental Farms since 1887) says: "They are not provincial averages; they are rather averages from large untilled areas in the several provinces, and may therefore serve to indicate the general character of much of the yet unoccupied lands of Canada." (Do- minion Experimental Farms Reports, 1897, page 169.) A study of the details shows much variation, but in the main these are counterbalanced so that the averages have much meaning. Professor Shutt states that the one sample from Manitoba " repre- sents the unfertilized and uncropped prairie soil of the Red River Valley, Manitoba," and adds: "It was taken from section 31, township 4, range i west. The uniformity in character of the soil over a very large area in Manitoba makes the data here presented of more than ordinary importance. " "We may safely conclude that there is here ample scientific proof of the well- nigh inexhaustible stores of plant food, and that this prairie land, as regards the elements of fertility, ranks with the richest of known soils. " Doctor George M. Dawson, Director of the Geological Survey of Canada, is quoted as follows: "Of the alluvial prairie of the Red River much has already been said, and the uniform fertility of its soil cannot be exaggerated. . . . The area of this lowest prairie has been approximately stated as 6900 square miles. " 104 SCIENCE AND SOIL Of course, these averages from the various Canadian provinces must be considered as tentative and very preliminary, but they must also be accepted as giving a reasonably correct general view of the invoice of soil fertility in the most extensive types of soil in those sections. Some other analyses made in part in connection with special investigations are discussed in another place. REVIEW OF SOIL COMPOSITION A general summary of the mass of evidence contained in the preceding pages concerning the composition of soils clearly sets forth a number of definite and assured facts bearing significant rela- tions to systems of permanent agriculture. One of these most clearly established facts is that potassium as an element of plant food belongs in the class with calcium and magnesium rather than with phosphorus and nitrogen. In all normal soils the supply of potassium is enormous. Thus, as an average of the Maryland soils reported in Table 12, representing ten different geological forma- tions, more or less abundant in most of the Atlantic states, we find 37,860 pounds of potassium and only 14,080 pounds of magnesium, 7840 pounds oL calcium, and noo -pounds of phosphorus, in 2 million pounds of soil. Measured by the total requirements of approximately maximum crops in a rotation of wheat, com, oats, and clover (Table 13), the potassium is sufficient for 473 years, the magnesium for 828 years, and the calcium for 187 years; while the total phosphorus is suffi- cient for the same crops for only 57 years. If we consider the plant food removed in the grain alone, assuming that the coarse products will remain on the farm, and also disregard the one abnormal mag- nesium soil (from serpentine), the relative plant-food supply is represented by 105 years for phosphorus, 3060 years for potassium, 2828 years for magnesium, and 6970 years for calcium. The complete analyses of the loess deposits at Dubuque, Iowa, and Kansas City, Missouri, which contain only moderate amounts of carbonates, show, as an average, 33,100 pounds of potassium, 13,400 pounds of magnesium, 23,500 pounds of calcium, and 1400 pounds of phosphorus, in 2 million of loess. In the following summary are reported the total phosphorus, SOIL COMPOSITION total potassium, total magnesium, and total calcium in the surface soil of the five most extensive soil types of Illinois. TABLE 20.2. CERTAIN PLANT-FOOD ELEMENTS IN ILLINOIS SURFACE SOILS Pounds per Acre in 2 Million of Soil (about 6§ Inches) Son. TYPE No. SOIL AREA OR GLACIATION Son. TYPE PHOS- PHORUS (Total) POTAS- SIUM (Total) MAGNE- SIUM (Total) CALCIUM (Total) 135 Unglaciated Yellow silt loam 95° 3X450 551° 439° 33° Lower Illinoisan Gray silt loam 840 24940 4690 3420 426 Middle Illinoisan Brown silt loam 1170 32240 7460 9280 526 Upper Illinoisan Brown silt loam I2OO 32940 9610 11060 1126 Early Wisconsin Brown silt loam IIQO 36250 8790 II450 General average IO7O T.iz6o 72IO 7Q2O Number of years' supply : (a) Fnr total rrnns . . r6 •joe 424 188 (b) F or grain only IO2 2475 1802 6600 It should be kept in mind that these data are based upon the average composition of many soil samples from every type, and that these are widely representative of the most extensive and important soil types in the Central states. They signify determined facts. As a general average of these soils, potassium is better supplied than magnesium for grain farming (in which all coarse products are returned to the land), and potassium is better sup- plied than calcium for a system in which all of the produce is re- moved. In normal soil types the relations existing among these four elements in the subsoil are not essentially different from those in the surface, except in subsoils that are rich in calcium and mag- nesium carbonates. Even in the almost unweathered glacial sub- soils of the principal types of the late Wisconsin glaciation (brown silt loam and yellow-gray silt loam ; see Table 17), 2500 pounds of phosphorus and 158,000 pounds of potassium are the relative and total amounts of those two elements per acre in a 2o-inch stratum. Measured by the average losses from the farm by selling maximum crops of corn and wheat, our two principal grains, the phosphorus in 6 million pounds of this subsoil is sufficient for 173 years, or one half as long as from 1565 to 1911, and the potassium is sufficient io6 SCIENCE AND SOIL for 9900 years, or as long as from 8000 years before Christ to 1903 years after Christ. In other words, on the absolute mathematical basis there is less of reason for applying potassium to normal soils as plant food than there is for applying magnesium and cal- cium for the sake of adding them also as plant food (see page 561). The use of potassium on soils actually deficient in that element (as peaty swamp soils) , and on some other soils as a soil stimulant, is discussed in the following pages. In brief, it may be said, of the plant-food elements supplied by the soil, that nitrogen and phosphorus are in one class; that potassium, magnesium, and calcium are far removed in a second class; and that iron is distinctly in a third class; while the nitrogen of the air, so far as concerns the supply for permanent agriculture, should be classed with carbon, hydrogen, and oxygen. The place of sulfur is not so easily determined. Measured by the soil's supply, sulfur would be classed with phosphorus and nitrogen; or measured by the crop demands, it would be classed with iron; but, if both supply and demand are considered, it must be classed with potassium, magnesium, and calcium. It is, however, known with certainty that more or less sulfur is carried into the air with the products of combustion and of decay,' and some sulfates are also carried into the atmosphere in the dust from evaporated ocean spray. Long- continued investigations at Rothamsted and elsewhere have shown that as an average rainfall brings to the soil, chiefly in the form of sulfates, about 7 pounds of sulfur per acre per annum, or i pound more than would be required for a zoo-bushel crop of corn (p. 57). NOTE. In New Hampshire Agricultural Experiment Station Bulletin 142 (December, 1909), Morse and Curry report 37,400 pounds of total potassium in two million pounds of surface soil of the uplands, and 50,000 pounds in two million of surface soil of the lowlands, in the vicinity of Durham, these amounts representing averages of ten and fifteen respective soil analyses of clays and clay loams. The summary of this bulletin contains the conclusions that the potassium in these soils is soluble enough to supply potassium for heavy crops of grass without artificial reenforcement, and that additional potassium when supplied in commercial fertilizers does not affect the yield or the composition of the grasses. CHAPTER VII AVAILABLE PLANT FOOD "AVAILABLE plant food" is an expression much used in connec- tion with commercial fertilizers, and the argument is commonly made that because the soil does net contain available plant food, we should therefore apply available plant food in commercial fer- tilizers. Instead of following this advice, however, the farmer should, as a very general rule, adopt a system of farming that will make available the plant food in the soil so far as practicable, and, if any element is actually deficient in the soil, apply that element in cheap form and in positively larger quantities than will be re- moved in large crops; and then make it, too, available by his method of farming. There are three methods of determining with some degree of satisfaction which elements, if any, are deficient in the soil: First, we may compute from the composition of the soil and the requirements of crops the probable durability of a soil with reference to any element of plant food. Thus, we may determine that the unglaciated yellow silt loam surface soil of Illinois, Kentucky, Tennessee, and other adjoining states, contains sufficient nitrogen for less than 20 large corn crops if only the grain were removed; while the potassium in the late Wisconsin brown silt loam is suffi- cient for more than 2300 such crops. Second, we can assume for a rough estimation that the equiva- lent of 2 per cent of the nitrogen, i per cent of the phosphorus, and | of i per cent of the total potassium contained in the surface soil can be made available during one season by practical methods of farming. Of course, the percentage that can be made available will vary very much with different seasons, with different soils, and for different crops; and yet with normal soils and seasons and for ordi- nary crops the above percentages represent roughly about the 107 io8 SCIENCE AND SOIL proportion that is liberated from our common soils of the element that limits the yield of the crop. In Table 21 are given the amounts of annually available plant food in Illinois soils as roughly estimated by this method of com- putation. Of course, these amounts would be smaller and smaller year by year in proportion as the total supply is decreased, and accordingly complete exhaustion is not only impracticable and unprofitable because of the continual reduction in crop yields, but it is mathe- matically impossible, just as it would be impossible to exhaust a bank account if only one per cent of the remaining deposit could be withdrawn each week. A peaty swamp soil containing 2930 pounds of total potassium per acre in the first 6| inches would liberate during the season, according to this estimate, about 7 pounds of potassium, which would be equivalent to a crop of 10 bushels of corn, which represents roughly about the average yield from such land when not treated with potassium, as is shown in the following pages. The common brown silt loam prairie soil, when well farmed, will average about 50 bushels of corn per acre, which would require n^ pounds of phosphorus and 74 pounds of nitrogen, while 12 and 96 pounds' represent i per cent of the phosphorus and 2 per cent of the nitro- gen, respectively, in the surface soil, where phosphorus is the first limiting element and nitrogen the second. These illustrations are given not to prove that this rough esti- mate is applicable, but rather to show the basis which suggests such a computation. It has some value, chiefly, perhaps, in that it helps one to understand why it is that with phosphorus enough in the surface soil for 50 crops, we obtain only half a crop as an average. On this basis we should try to keep sufficient phosphorus in the surface soil for 100 large crops, of which one per cent would then be sufficient for one large crop. This would require about 2300 pounds of phosphorus per acre, or but little more than is actually contained in the most productive Illinois corn-belt soil, as the early Wisconsin black clay loam in such counties as McLean, Champaign, Edgar, et al. While there are several agencies that tend to convert insoluble AVAILABLE PLANT FOOD 109 plant food into available forms, such as the products of decaying organic matter, including carbonic, nitric, and various organic acids, the different forms of lime, and most soluble salts, each of which is more fully discussed in its proper place, it is also known that the plant roots themselves influence the availability of plant food, probably by means of the carbonic acid or other substances which they excrete. The juices of plants are commonly distinctly acid, and the roots have some power to exude moisture, which certainly contains carbonic acid and very possibly contains no other solvents, although this question is not fully settled. Where growing plant roots lie in contact with the polished surface of marble (calcium carbonate) and some other materials (as prepared slabs of calcium phosphate), distinct etching occurs, as was early shown by Sachs and Czapek. Kossowitsch conducted an experiment in which he grew plants (peas, flax, and mustard) in two pots of sand which differed only by the addition of fine-ground rock phosphate to one. The plants were watered with the slow and constant application of like amounts of a dilute solution containing all essential plant-food ele- ments, except phosphorus. For the pot which contained no phos- phate this solution was, in this continuous process of watering, passed through a third pot of sand to which the fine-ground rock phosphate had also been added. Kossowitsch found that the plants made a much better growth in the pot where the roots were in direct contact with the phos- phate, thus showing that they exert a solvent action in addition to any that may be exerted by the nutrient solution. If, for example, the plant roots come in contact with, or exert an influence upon, the equivalent of only one per cent of the sur- face of the soil particles within the root range, this would offer an explanation of the relationship (which is very irregular in different soils and seasons) that exists between the total amount of any plant-food element in a given soil stratum and the amount secured by a given crop during the growing season. It is well known that soluble phosphates and soluble potassium salts, when applied to normal soils, are almost immediately con- verted into insoluble forms; and the higher availability of such soluble fertilizers is now Relieved to be largely due to the fact that no SCIENCE AND SOIL TABLE 21. ANNUALLY AVAILABLE FERTILITY IN ILLINOIS SOILS, ROUGHLY ESTIMATED Pounds per Acre SOIL AVAIL- AVAIL- AVAIL TYPE No. SOIL AREA OR GLACIATION Son. TYPE ABLE NITRO- ABLE PHOS- ABLE POTAS- GEN PHORUS SIUM PRAIRIE LANDS, UNDULATING 33° Lower Illinoisan . . Gray silt loam on tight clay 58 8 62 426 526 626 726 Middle Illinoisan . . Upper Illinoisan . . Pre-Iowan .... lowan Brown silt loam . . . Brown silt loam . . . Brown silt loam . . . Brown silt loam . 8? 97 86 08 12 12 12 12 8l 82 88 82 1126 1026 Early Wisconsin . . Late Wisconsin . . Brown silt loam . . . Brown silt loam . . . 101 135 12 M 9i IJ3 PRAIRIE LANDS, FLAT 329 Lower Illinoisan . . Drab silt loam . . . 56 7 66 420 520 1 1 20 I22O Middle Illinoisan . . Upper Illinoisan . . Early Wisconsin . . Late Wisconsin . . Black clay loam . . . Black clay loam . . . Black clay loam . . . Black clay loam . . . 108 i35 J57 178 14 i7 20 J9 80 74 88 93 TIMBER UPLANDS, ROLLING OR HILLY !3S Unglaciated .... Yellow silt loam . . . 38 10 79 335 Lower Illinoisan . . Yellow silt loam . . . 43 10 80 345 Middle Illinoisan . . Yellow silt loam . . . 37 8 82 535 Upper Illinoisan . . Yellow silt loam . . . 40 8 87 635 Pre-Iowan .... Yellow silt loam . . . 48 9 93 735 lowan Yellow silt loam . . . 38 9 89 "35 Early Wisconsin . . Yellow silt loam . . . 38 9 82 864 Deep loess .... Yellow fine sandy loam 43 10 89 TIMBER UPLANDS, UNDULATING 1034 760 Late Wisconsin . . . lowan Yellow-gray silt loam . Brown sandy loam . . 58 61 8 9 119 67 TIMBER UPLANDS, FLAT 332 Lower Illinoisan . . Light gray silt loam on tight clay .... 38 8 68 AVAILABLE PLANT FOOD in TABLE 21. ANNUALLY AVAILABLE FERTILITY IN ILLINOIS SOILS, ROUGHLY ESTIMATED — Continued SOIL AVAIL- AVAIL- AVAIL- TYPE No. Son, AREA OR GLACIATION Son. TYPE ABLE NITRO- ABLE PHOS- ABLE POTAS- GEN PHORUS SIUM SAND, SWAMP, AND BOTTOM LANDS 1331 Old bottom lands . . Deep gray silt loam . . 72 14 91 1451 Late bottom lands Brown loam .... 94 16 100 1481 Sand plains and dunes Sand soil .... 2Q 8 77 1401 Late swamp Deep peat . (?) » 20 7 1415 Late swamp . . . Drab clay US iQ 1 2O 1 The nitrogen in peat is so very slowly available that not even a rough estimate can be made here. they first dissolve in the soil water and spread over the surface of the soil particles before becoming insoluble, and thus they offer a much more extensive surface for contact with plant roots than would plant-food particles applied in insoluble form, unless very finely ground. Third, we may apply different elements of plant food to the soil and note the effect, if any, in increasing the yield of crops, and thus sometimes discover what element is most deficient in the soil. One might suppose that this would be the best method, but such is not the case. This method frequently gives erroneous results which, if followed, may lead to land ruin, because the substance applied may produce little or no benefit on account of the special plant-food element it contains, but it may act as a powerful soil stimulant and thus liberate from the soil some other entirely differ- ent element in which the soil is already becoming deficient. Thus have many lands been practically ruined by the use of land-plaster and salt, by the improper use of lime, and even by the use of clover merely as a soil stimulant. Some good illustrations of this action of soluble salts are shown in the following pages. "In considering the general subject of culture experiments for determining fertilizer needs, emphasis must be laid on the fact that such experiments should never be accepted as the sole guide in determining future agricultural practice. 112 SCIENCE AND SOIL If the culture experiments and the ultimate chemical analysis of the soil agree in the deficiency of any plant-food element, then the information is conclusive and final; but if these two sources of information disagree, then the culture experiments should be considered as tentative and likely to give way with increasing knowledge and improved methods to the information based on chemical analysis, which is absolute. " l The plant food in the subsurface and subsoil is unquestionably )f some value, but even the total supplies of nitrogen and phos- phorus that are held within the feeding range of ordinary plant roots are not unlimited when measured by crop requirements in permanent agriculture. However, the thing of first importance is to maintain a rich surface soil, for no subsoil is of much practical value if it lies beneath a worn-out surface. On the other hand, if the subsoil will act as a reservoir for moisture, then a rich top soil will produce large crops. Manures and fertilizers are applied to, and incorporated with, the plowed stratum only. On the Rothamsted fields' where chalk exceeding 100 tons per acre was applied to the land a hundred years ago, practically no calcium carbonate is found below the plowed soil even after a century of cultivation, although 50 tons of the chalk applied still remain in the surface soil ; and the land fertilized with nitrogen, phosphorus, and potassium, which has yielded more than 30 bushels of wheat per acre as an average of fifty years, contains, as an average, no more plant food in the strata below the surface 9 inches than is found in the same strata where the land has been unfertilized and has produced an average yield of only 13 bushels of wheat for the same fifty years. \i The supply of nitrogen in soils is contained only in the organic matter; and thus the amount of nitrogen in the subsoil of normal soil types is relatively small, as will be seen from a study of Tables 15, 16, and 17, six million pounds of subsoil containing, as a rule, less nitrogen than two million pounds of surface, except where the surface is much worn. The small amount of humus in the subsoil is also quite inactive, and the liberation of nitrogen from its decom- position is very slight. Furthermore, in all humid regions there is large loss of nitrogen in drainage waters; so that in practice the addition of nitrogen to the surface soil must be somewhat greater 1 "Cyclopedia of American Agriculture," Vol. I, page 475. AVAILABLE PLANT FOOD than that removed in crops, if the productive power of the soil is maintained. The phosphorus of the soil exists in both organic and mineral forms. While the supply of mineral phosphorus is likely to be smaller in the surface and subsurface than in the subsoil, the organic phosphorus, like nitrogen, varies with the organic matter, which, as a rule, decreases rapidly below the plowed soil. As a consequence, there is usually less phosphorus in the subsurface than in the sur- face, unless the surface is very poor in organic matter; and also there is less phosphorus in the subsurface than in the subsoil, unless the subsurface is much richer in organic matter. A larger supply of phosphorus in the surface than in the subsurface is suffi- cient to prove that plants secure some phosphorus from below the surface soil, because the excess of phosphorus in the surface is contained in the decomposition products of plant residues from the centuries gone by. Where the subsoil is richer in phosphorus than the subsurface, it indicates either that phosphorus has been lost from the subsurface by leaching or that the plant roots have with- drawn phosphorus from the subsurface to a greater extent than from the subsoil. With the brown silt loams and black clay loams of the corn belt, the surface stratum rich in organic matter is always richer in phos- phorus than the subsurface; and, with one exception, the subsur- face, which is also quite well supplied with organic matter, is richer in phosphorus than the subsoil, but the other upland soils contain less organic matter in the surface and much less in the subsurface, and the subsoil, with a single exception, is richer in phosphorus than the subsurface, equal weights of soil always being considered. The potassium is contained almost solely in the mineral part of the soil, and the supply regularly increases with depth, the sub- surface being richer than the surface and the subsoil still richer. CHAPTER VIII SOIL SURVEYS BY THE UNITED STATES BUREAU OF SOILS THE Bureau of Soils of the United States Department of Agricul- ture was organized in 1895, with Professor Milton Whitney as Chief. The energies of this Bureau have been devoted largely to making surveys of the soils in certain localities in most of the different states; and, second, to laboratory investigations in sup- port of a theory early announced by Whitney and Cameron, to the effect that practically all soils contain sufficient plant food for good crop yields, and that this supply will be indefinitely main- tained. The soil surveys are of general interest but of doubtful value to the local farmers and landowners, because they are reported with practically no information concerning valuable methods of soil improvement other than that based upon the actual practice al- ready in vogue, the Bureau having conducted no systematic field experiments and having reported practically no chemical analyses of the various soil types identified. The mechanical analyses which are almost invariably reported give little information of value fur- ther than to support the soil surveyor's classification of the soils into sandy soils, silty soils, clay soils, etc. Even the soil sur- vey, as conducted by the Bureau, is often too general or superficial in character to be of local use, differences in soils which are clearly recognized by the farmers being often ignored or overlooked. This will be better understood by examination of concrete illus- trations ; such, for example, as a comparison of the Bureau's map of Tazewell County, Illinois, published in the Report of Field Operations* for 1902, with that of McLean County, which joins Tazewell on the east, and which accompanies the Report for 1903; or by a comparison of the Bureau's map of Clay County, Illinois 114 SURVEYS BY THE UNITED STATES BUREAU 115 (1902), showing all of the upland, comprising 85 per cent of the county, as one soil type (Marion silt loam), with the detail soil map published by the University of Illinois Agricultural Experi- ment Station (1911), showing eleven different types of upland soil, most of which are commonly recognized by the local farmers, the most extensive type (gray silt loam on tight clay, or " typical " Marion silt loam) comprising only 37 per cent of the county. These upland soil types vary in agricultural value from $15 to $60 an acre. They vary in average composition from uoo pounds of nitrogen and 40x3 pounds of phosphorus to 3890 pounds of nitro- gen and 820 pounds of phosphorus in 2 million pounds of the sur- face soil. On more than 15,000 acres of the level upland prairie soil, surface drainage can be provided only with much diffi- culty, while 40,000 acres of .eroded timberlands are so rough that the soil ought not to be kept under cultivation. About 30 per cent of the upland is not underlain with tight clay, while the remainder has the subsoil sometimes called " hardpan " by the resident farmers. These facts are mentioned in order that the student may under- stand that the soil survey as made by the Bureau of Soils is not intended to be in sufficient detail for local, specific use. To quote Professor Whitney's language from a letter to the author under date of March 26, 1903: "In the work on the scale in which the Bureau is engaged, we cannot recog- nize differences that might and should be recognized in a more detailed survey of a limited area. It is necessary for us to show only important differences in the soils which will be of value to the people of large areas. " Nevertheless, the soil surveys of the Bureau have large value as a source of general information concerning the soils of the United States. The author has very great respect for the art of surveying soils, whether for general information over broad areas or for spe- cific use where the details are mapped. The accompanying map of the United States, showing " Soil Provinces," as published by the Bureau of Soils, is based in part upon the work of the United States Geological Survey. Within these 14 great soil provinces, the Bureau of Soils had recognized (previous to January i, 1908) different soil types to the number of n6 SCIENCE AND SOIL 715, most of which have been grouped into 86 soil series; and the following extracts from Bureau of Soils Bulletin 55 (1909), de- scriptive of these soils, cannot fail to be of interest and value to the student of American soils. CLASSIFICATION OF SOILS "The texture of the soil is expressed in the mechanical analysis by a separa- tion into seven grades, the sizes of which are arbitrarily fixed. The results of the analysis show the percentages of sand, silt, and clay. " "When, aside from texture, the physical and chemical properties of the soil and its method of formation are alike, we have what we call a soil series, extending from the coarse gravelly or sandy soils on the one side to the finer silt and clay soils on the other, and in such a series the texture of the soil deter- mines the distribution of crops. " It would be a comparatively simple matter to compare and classify soils according to the mechanical analysis or texture, but this standard alone is not sufficient, and the problem is in reality a very difficult thing, for in working out the relation of the soils to crops, other factors enter which must be recognized in the correlation. One of the most important of these is the structure or the arrangement of the mineral matter. In some soils the mineral particles have a granular arrangement of flocculated masses, making the soil loose and porous. In others the grains appear to have no such coherency, but exist in a compact form, making the soil hard and compact. We also have the gumbo and adobe soils and others that are exceedingly plastic. Then, again, the amount and character of the organic matter influences not only the productive capacity of the soil, but its adaptation to crops, while the color of the soil has to be considered as indicative of certain obsure chemical or physical relations that influence the adaptation and productivity. The drainage features also come in, often with material influence on the organic constituents, on the aera- tion, and on oxidation processes. " "The experienced soil-survey man can judge very accurately of the texture of the soil material, but even his judgment, before being accepted, is always confirmed by mechanical analysis. " Where soils have a common origin and differ only in texture and are alike in color and in physical properties other than those affected by texture, they are arranged in what we call a series having the soil generic name with qualifying textural terms. We have, for example, the Miami gravelly loam, the Miami fine sand, the Miami sandy loam, the Miami silt loam, and the Miami clay loam as prominent types in the Miami series. In this particular series we have fourteen types, and possibly two or three other types will be encountered. In the Norfolk series we have twelve types." "If the texture and structure of two soils is the same, and one differs in a marked degree from the series color, and that departure is fairly constant and Appalachian Mountains and Plateaus Northwestern Intermountain Regions M *, L F OF b M E X I C \0 k V9* \ ^ '. U -L, f ^ * 1 UNITED STATES SOIL PROVINCES Reduced from maps of U.S. Geological Survey Reduced from maps of U.S. Geological Survey and Bureau of Soils _ SCALE OF MILES _ o loo 200 §5o loo sbo V ** ^ 95 from 90 Greenwich 85 SURVEYS BY THE UNITED STATES BUREAU 117 typical of the area covered by the soil, this soil likewise is thrown out of the series, because we have reason to know, by observation of the growing crops, that this color difference stands for a difference in the chemical changes which go on in the soil and which are necessary for the welfare of certain crops. " In the classification of soils, therefore, the texture is used to determine the place in the series; the structure and color to determine what series the soil can be correlated with. " The following table gives the name and area of the soil provinces and the proportion of each that has been covered by the soil survey. It is not unlikely that as the work progresses and as our knowledge of the soils increases it will seem advisable to divide some of these provinces into two or more parts. SOIL PROVINCES OF THE UNITED STATES PROVINCE ESTIMATED AREA AREA SURVEYED Atlantic and Gulf coastal plains . . . River flood plains Acres 233000000 64000000 48000000 72OOOOOO 68000000 455OOOOOO 4IOOOOOO 107000000 109000000 76000000 365000000 58000000 2IOOOOOO 2IIOOOOOO Acres 25613666 8061247 7271798 6367009 6052926 2241 7832 5091882 1825850 1005600 1455428 2939840 H3H55 4593881 Per Cent 10 13 15 9 9 5 12 2 I 2 I 2 22 Piedmont Plateau Appalachian Mountains and plateaus . Limestone valleys and uplands . . . Glacial and loessial Glacial lake and river terraces .... Residual soils of Western prairie . . . Great Basin Northwestern intermountain region . . Rocky Mountain valleys and plains . . Arid Southwest Pacific coast Western mountain regions Total 1928000000 93828114 ATLANTIC AND GULF COASTAL PLAINS The Atlantic and Coastal plains together constitute one of the most impor- tant physiographic divisions of the United States. The Atlantic Coastal Plain extends from the New England states southward to the Florida Peninsula, where the Gulf Coastal Plain begins, and extends thence westward to the Mexican boundary line. It is, however, discontinuous, being interrupted by the alluvial bottoms of the Mississippi River. From the coast the Atlantic Plain extends inland to the margin-of the Piedmont Plateau; that is, to a line passing through Trenton, Baltimore, Washington, Richmond, Raleigh, Columbia, Augusta, and Macon. In its northern extension it is represented by a narrow belt, but widens in New Jersey, and attains its maximum breadth n8 SCIENCE AND SOIL of about 200 miles in North Carolina. The Gulf Plain extends up the Missis- sippi to the mouth of the Ohio, its inner boundary line passing through or near Montgomery, luka, Cairo, Little Rock, Texarkana, Austin, and San Antonio. The surface is that of a more or less deserted plain marked by few hills, slightly terraced with bluffs along streams. The inner margin of the Coastal Plain is usually from 200 to 300 feet above tide water, but sometimes rises to 500 feet. The drainage here is usually well established, and the surface is rolling to hilly, and consequently carved and eroded. There is a wide belt border- ing the coast where the elevations are mostly under 100 feet. North of the James River, where the Coastal Plain is narrow and deeply indented with tidal estuaries, drainage is usually well established and the surface is rolling, but in the broad southern extension, where the seaward slope is hardly more than i foot to the mile, drainage is apt to be deficient. Here rain water often remains upon the surface for a considerable time, although the conditions are not comparable with those of a true swamp. The soils in this level section, while composed largely of sand, are compact, usually deficient in organic matter, and not very productive. Many of the flat interstream areas possess such poor drainage that true swamps, such as the Dismal and Okefenokee, have .been formed. Near the coast and along the tidal estuaries, extensive marshes, separated from the ocean by sand barriers, are found. The Coastal Plain is made up of unconsolidated gravels, sands, and sandy clays, with less frequent beds of silts and heavy clays. The desposits on the Atlantic coast have been derived mainly from the erosion of the Piedmont Plateau and other inland areas, while the deposits on the Gulf coast have been derived mainly from transported glacial material and from western plains. The materials have been transported and deposited beneath the sea and subsequently exposed by the uplift of the ocean floor. In the more northern parts of the Coastal Plain, and even as far south as Virginia, the character of the deposits has been modified by glacial action and the flooded condition of the streams resulting from the melting of the ice. The Coastal Plain deposits range in age from Cretaceous to Recent. Al- though extensive areas of the older sediment are exposed at the surface to form soils, still by far the greater part of the materials is Quarternary or Recent in age. The soils are for the most part composed of sands and light sandy loams, with occasional deposits of silts and heavy clays. The heavy clays are found principally near the inner margin of the Coastal Plain. The silts, silty clays, and black calcareous soils, upon which the rice and sugar-cane industries of southern Louisiana and Texas are being so extensively developed, have no equivalents in the Atlantic division. Bastrop series. Brown soils with reddish brown to red subsoils occurring as nonoverflow terraces. Cotton, corn, sorghum, alfalfa, melons, and potatoes are successfully produced. Crockett series. Dark gray prairie soils underlain by mottled red sub- soils. Derived from slightly calcareous material, the soils of this series are SURVEYS BY THE UNITED STATES BUREAU 119 productive. Cotton and the general farm crops are the leading products. The gravelly soil is early and adapted to early truck. Elkton series. Light gray to white surface soils, with mottled whitish gray and yellow subsoils, overlying gravel and coarse sands. Gadsden series. Gray soils, with subsoils of similar texture occupying gentle slopes and depressions and formed by wash or creep from higher areas. This series occurs in rather local development, particularly in Florida, southern Georgia, and Alabama. They are very productive soils and well adapted to tobacco. No heavy members of the series have been encountered, and it is doubtful if any exist. Guin series. Gray soils with brown to yellowish red subsoils, occurring as rolling and hilly lands. Intermediate series between the Norfolk and Orangeburg series. Owing to the rather rough topography, these soils have not been developed as much as either of the other series, although they seem capable of producing better crops than they do now. Houston series. Dark gray or black calcareous prairies. One of the most productive series for Upland cotton and well adapted to alfalfa and other forage crops. Laredo series. Gray to light brown calcareous soils with gray subsoils. Good cotton, corn, and sugar-cane soils, and especially adapted to the early production of vegetables — cabbage and onions in particular. Lufkin series. Light-colored soils with heavy mottled gray and yellow subsoils. The soils of this series have only a moderate degree of productivity. Montrose series. Gray soils with heavy plastic mottled yellow subsoils. These soils are in part poorly drained, but where cultivated they produce moderate yields of cotton and corn. Myatt series. Gray soils with mottled yellow, gray, and whitish subsoils occurring in poorly drained areas around heads of streams and intermediate between uplands and bottom lands. The series seems to be of local extent and but little developed. Norfolk series. Light-colored soils with yellow sand or sandy clay sub- soils. This series contains some of the most valuable truck soils of the Atlantic and Gulf Coast states, and certain members of the series are adapted under certain climatic conditions to wheat, grass, tobacco, and fruit. Oktibbeha series. Gray soils with brown to yellowish brown heavy sub- soils related to Houston series in origin. The soils of this series are distinctly inferior to the soils of the Houston series and, as they appear to cover large areas in Mississippi and Alabama, present a difficult problem in soil improve- ment. Orangeburg series. Light-colored soils with red sandy clay subsoils. This series constitutes some of the best cotton soils of the South, and certain members of the series are particularly adapted to tobacco. Portsmouth series. Dark -colored soils with yellow or mottled gray sand or sandy clay subsoils. Where drainage is adequate, this series is adapted to some of the heavier truck crops, to small fruits, and to Indian corn. 120 SCIENCE AND SOIL Sassafras series. Yellowish brown surface soils with reddish yellow to light orange subsoils overlying gravel beds. Susquehanna series. Gray soils with heavy red clay subsoils which become mottled and variegated in color in the deep subsoil. Only one member of this series, the sandy loam, has been developed to any considerable extent. This one is used for fruit and general farm purposes, but the other members are particularly refractory and difficult to bring into a productive state. Webb series. Brown to reddish brown soils with reddish brown to red sub - soils, a semiarid prototype of the Orangeburg series. The soils of this series have not been used to any great extent, owing to lack of irrigation facilities. Wickham series. Reddish or reddish brown terrace soils overlying reddish, micaceous heavy sandy loam or loam subsoils. The soils of this series have a relatively high productivity for general farm crops. Wilson series. Dark gray prairie soils with mottled gray subsoils. The clay member of this series is a strong soil devoted to general farming, with cotton as the leading crop. The other members are used for cotton, but are inclined to be droughty. RIVER FLOOD PLAINS An extensive and characteristic group of soils, usually known as " bottom lands," is found in the flood plains of numerous rivers and streams of the United States. The largest development of this group occurs along the Mis- sissippi River, where the bottoms are often many miles in width. The soils have been formed by deposition from stream waters during periods of overflow. The texture of the material depends upon the velocity of the current at the time of the deposition. Where the current is very rapid, large stones and bowlders are borne along, and beds of gravel and sand are formed. Along the swift-flowing streams the texture of the soil changes often within short distances, but in wide bottoms large areas of very uniform soils are often formed. The soil material has usually been derived from various kinds of rocks, but in some instances is closely related to the surrounding geological formation. The red soils along the Red and other rivers in the Southwest have been formed by the reworking of the Permian Red Beds. In general, the soils along the streams which flow through the prairie region have a darker color than those along the streams which run only through the timbered sec- tions of the country. The difference in the origin, drainage, color, and organic-matter content has given rise to several series of alluvial soils in the humid portion of the United States. Congaree series. Brown or reddish brown soils found along Piedmont streams and representing wash from Cecil soils. Valuable and dependable corn soils, but too low and moist for cotton. Huntington series. Dark brown to yellowish brown soils occurring along streams in the Alleghany plateaus. Both the general farm crops and truck crops thrive on these soils. SURVEYS BY THE UNITED STATES BUREAU 121 Miller series. Brown to red alluvial soils formed from the reworking of materials derived from the Permian Red Beds. Very productive soils suit- able for cotton, corn, sugar cane, alfalfa, and vegetables; especially adapted to peaches. Ocklocknee series. Gray to yellowish brown soils found along streams in Coastal Plain Georgia, Alabama, and Mississippi. Cotton, corn, and pastur- age are the leading products. Wabash series. Dark brown or black soils subject to overflow. Very pro- ductive soils used for cotton, sugar cane, corn, wheat, oats, grass, alfalfa, sugar beets, and potatoes and other vegetables. Waverly series. Light -colored, alluvial soils subject to overflow. Less pro- ductive than the Wabash soils, but adapted to the same wide range of crops. Wheeling series. Brown to yellowish brown soils occurring on gravel ter- races along streams issuing from glaciated regions. Excellent soils for general farming, and fruit and truck growing. PIEDMONT PLATEAU Lying between the Atlantic Coastal Plain and the Appalachian Moun- tains and extending from the Hudson River to east-central Alabama is an area of gently rolling to hilly country known as the Piedmont Plateau. On the Atlantic side it is closely defined by the "fall line," which separates it from the Coastal Plain, but on the northwestern side the boundary is not sharp, although in the main distinct. In its northern extension the Piedmont Plateau is quite narrow, but broadens toward the south, attaining its greatest width in North Carolina. The surface features are those of a broad rolling plain that has been deeply cut by an intricate system of small streams, whose valley walls are rounded and covered with soil, although many small gorges and rocky areas occur. The altitude varies from about 300 feet to more than 1000 feet above sea level. The extreme northern part of the Piedmont region, in New Jersey, has been glaciated, but elsewhere the soils are purely residual in origin and have been derived almost exclusively from the weathering of igneous and metamorphic rocks. The chief exception is the detached areas of sandstones and shales of Triassic age. Marked differences in the character of the rock and the method of formation has given rise to a number of soil types, those derived from crys- talline rocks being the most numerous and widely distributed. Among these the soils of the Cecil and Chester series predominate. The principal types formed from the sandstones and shales are included in the Penn series. Cecil series. Gray to red soils with bright red clay subsoils, derived from igneous and metamorphic rocks. Constituting by far the larger portion of the province, these soils are well adapted to, and used for, cotton, export tobacco, and fruit, and the lighter members for truck crops. As a rule, they are not highly developed, but where properly handled the heavier members produce excellent crops of corn and grazing and hay grasses. 122 SCIENCE AND SOIL Chester series. Gray to brown surface soils with yellow subsoils, derived principally from schists and gneisses. The most valuable soils of the province for wheat and corn, and good for certain fruits. The most highly developed soils of the Piedmont Plateau. Penn series. Dark Indian red soils with red subsoils, derived from red sand- stones and shales of Triassic age. Excellent soils for general farm crops, particularly wheat, corn, and hay. APPALACHIAN MOUNTAINS AND PLATEAU The Appalachian Mountains are made up of a number of parallel ranges and intervening valleys, which extend in a general northeast and southwest di- rection from southern New York to northern Alabama. The elevation ranges from about 1500 to nearly 7000 feet above sea level, the highest point being attained in western North Carolina. Immediately east of the Appalachian Mountains, and usually separated from them by a valley, is a wide stretch of country known as the Alleghany Plateau. In a broad way this plateau is carved out of a great block of sedimentary rocks tilted to the northwest from the mountains. It is crossed by numerous streams. As they run in deep channels (all the larger ones being from 200 to 1000 feet in depth), the dissection of the plateau block is often minute. The rocks of the eastern ranges of the Appalachian Mountains are igneous or metamorphic in origin, while the western ranges, as well as the Alleghany Plateau, are made up of sedimentary rocks. Different series of soils have, therefore, been formed in different parts of these mountains and plateau. The igneous and metamorphic rocks give rise to the soils of the Porter series, while the Dekalb and Upshur series are formed from the weathering of the sandstones and shales of sedimentary origin. The character of the topography in the mountain and much of the plateau region is such that general farming is not practicable. These areas are, how- ever, well suited to grazing and fruit growing, and these are very important industries. Dekalb series. Brown to yellow soils with yellow subsoils, derived from sand stones and shales. Soils of this series are used, according to texture, elevation, exposure, and character of surface, either for the production of hay, for pasture, or for orchard and small fruits. Fayetteville series. Grayish brown to brown soils with yellowish or reddish brown subsoils. Adapted to apples, grapes, and small fruits, and give mod- erate yields of general farm crops. Porter series. Gray to red soils with red clay subsoils, derived from igneous and metamorphic rocks. This is the greatest mountain fruit series of the eastern United States. It is also used for general farming. Upshur series. Brown to red soils with red subsoils, derived from sand- stones and shales. Somewhat more productive than the Dekalb soils. Used for cotton, corn, wheat, and forage crops. SURVEYS BY THE UNITED STATES BUREAU 123 LIMESTONE VALLEYS AND UPLANDS The limestone soils are among the most extensively developed of any in the United States and occur in both broad upland and inclosed narrow valley areas. The greatest upland development is seen upon the Cumberland Plateau in eastern Tennessee and Kentucky and upon the Carboniferous formation in central Tennessee and Kentucky, northern Alabama and Georgia, and in Missouri. The valley soils are found principally in Pennsylvania, Maryland, and Virginia, and in the mountain section of eastern Tennessee and Kentucky and northern Alabama and Georgia. The topography of the plateau soils varies considerably. In the Cumberland Plateau and Highland Rim the sur- face is undulating ; in the region of the Ozark uplift in Missouri and Arkansas it is quite rough and hilly, and where there is an elevation of the surface, or where the plateau is deeply dissected by erosion, it presents a quite mountain- ous topography. The valley soils of the Appalachian region also show consider- able topographic relief, sometimes exhibiting mountainous surface features. The limestone soils are residual in origin, being derived from the weather- ing in place of limestone of differing age and composition. This is accom- plished by the removal through solution of the calcium carbonate of the lime- stone, leaving behind the more resistant siliceous minerals. These soils are remarkable for the fact that they contain but a very small percentage of the original limestone rock, the larger part having gone into solution. It has thus required the solution of many feet of rock to form a single foot of soil. Thus far the limestone soils east of Kansas and Texas and north of central Alabama and Georgia have been grouped in two important series, known as the Hagerstown and Clarksville. Clarksville series. Light gray to brown soils with yellow to red subsoils, derived mainly from the St. Louis limestone. While not as strong as the Hagerstown soils, this is a valuable series. Apples and peaches are commer- cially important. Tobacco is a leading product. General farming is firmly established in many extensive regions. Cumberland series. Brown surface soils, derived from thin deposit of sedimentary material overlying residual limestone subsoils. Used for cotton and other general farm crops, truck and fruit. Decatur series. Reddish brown to red soils with intensely red subsoils. Intermediate in value between the two series just described. Cotton, corn, wheat, oats, forage crops, blue grass, and peaches are the leading crops. Hagerstown series. Brown to yellowish soils with yellow to reddish sub- soils, derived from massive limestone. Among the most productive soils of the eastern United States. Fine wheat and general farming soils, and the seat of important apple orcharding interests. Blue grass is indigenous. GLACIAL AND LOESSIAL REGIONS The soils of the glaciated part of the country constitute one of the most important groups in the United States. The group includes all soils derived 124 SCIENCE AND SOIL directly from till or loess. The soils formed from the till are confined to that part of the country lying north of the southern limit of glacial action, but the loess soils occur also south of this line, especially along the Mississippi and Ohio rivers and in Kansas and Nebraska. The line of the southern extension of the ice sheet touches the Atlantic coast about New York City, passes through northern New Jersey, southern New York, and northwestern Pennsylvania, swings southward through Ohio to Cincinnati, crosses the Mississippi River at St. Louis, and follows the south side of the Missouri River into Montana, where it crosses the Canadian boundary line, then dips southward into Idaho as a long lobe in the mountainous nonagricultural region, and crosses the northwestern part of Washington, including the Puget Sound region. Practically all of the United States north of this line was covered in recent geological time by a great continental glacier, many hundreds, and even thou- sands, of feet in thickness. This great ice sheet, moving in a southern direction, filled up valleys, planed off the tops of hills and mountains, ground up the underlying rocks, carried the derived material both within and upon the ice, and finally deposited the gravel, sand, silt, and clay, as a mantle, varying in thickness from a few feet to more than 300 feet. Often this material has been transported hundreds of miles, and is wholly unrelated to the underlying rocks, but in some places the movement has been slight, and the drift consists very largely of the ground-up underlying rock. Over a large porportion of the area covered by the drift and also along the Ohio and Mississippi rivers and in Kansas and Nebraska, the surface material consists of a fine silty deposit, known geologically as "loess" and "Plains marl." In the classification of the glacial soils, three important series — Miami, Marshall, and Volusia — having distinct characteristics have been recognized and, in addition, quite a number of miscellaneous soils which cannot be put in any series. Marshall series. Dark -colored upland prairie soils. The principal soils of the great corn belt belong to this series, while in the Northwest the finest wheat soils are found in this group. They are among the best general farming soils of the entire country. Miami series. Light-colored upland timbered soils. The different mem- bers of this series are considered good general farming soils and have in ad- dition special adaptations for truck, fruit, small fruit, and alfalfa. Volusia series. Light-colored soils with yellowish sut soils, derived by feeble glacial action from sandstones and shales. The soils of this series are adapted to the production of potatoes, grass, oats, buckwheat, and, in the less elevated positions, to corn. GLACIAL LAKE AND RIVER TERRACES Another important group of soils occurs in the glacial region, principally as terraces around lakes, or along streams, or as deposits in areas which were formerly covered by water. At the close of the glacial epoch the lakes in this part of the United States were not only more numerous, but the waters of those which remain reached a higher level and covered areas that are now far above SURVEYS BY THE UNITED STATES BUREAU 125 their present shore lines. In some cases several distinct terraces, each one marked by an old shore line, are easily discernible, and represent successive stages in the lowering of the water level. The elevation above the lake varies from a few feet to more than 200 feet. The surface of each terrace is usually rolling to level, with a gradual slope toward the lake, but sometimes areas of a rough and broken character occur. The streams which cross these terraces have frequently, by their cutting, produced deep, steep-sided valleys, especially near the lakes. The soils of this group vary from typical beach gravels to offshore deposits of heavy clays. The material from which they are derived consists of glacial debris reworked and redeposited in the lakes or along streams. While this glacial material is made up of rocks of widely varying origin, a large proportion of it often consists of the country rock. In the eastern part of the Great Lake region the percentage of sandstone and shale fragments is usually very high, while in the western part more of the igneous rocks are present. This fact, together with differences in drainage conditions, has given rise to several series of soils. Clyde series. Dark -colored swamp soils formed from reworked glacial material deposited in glacial lakes. A special use for these soils is the pro- duction of sugar beets, while general farm crops, truck and canru'ng crops, are grown extensively. Dunkirk series. Light-colored reworked glacial material occurring as terraces around lakes and along streams. Good general farming soils and especially adapted to grapes and other fruits. Fargo series. Black calcareous soils rich in organic matter formed by deposition of material in glacial lakes. This is the most important group of soils in the Red River Valley, and includes exceptional soils for the production of wheat, barley, and flax. While these are the chief crops at present, the soil adaptations are by no means limited to small grain production. Timothy and vegetables may become more important products with the development of markets. Hudson series. Light brown to yellowish brown soils, with drab to yellow- ish subsoils. Merrimac series. Brown terrace soils underlain by gravel, formed prin- cipally of reworked glaciated crystalline rocks. Leachy soils of low general farming value, but especially adapted to trucking and apple orcharding in some sections. Sioux series. Dark-colored soils resting on dark or light-colored subsoils, with gravel beds usually within 3 feet of the surface. The crops produced on soils of this series range from early short-seasoned truck crops through special crops like alfalfa and sugar beets to the wide variety of general farm crops produced in the Central West. Superior series. Gray and red soils with red subsoils, formed from reworked glacial material deposited in glacial lakes. Not extensively developed, but known to include fine types for clover, timothy, and small fruits. 12(5 SCIENCE AND SOIL Vergennes series. Light-colored soils, with gray or whitish subsoils, derived from Champlain clay, or lighter deposits over these clays. This series includes the best hay and apple soils of the Champlain Valley. A wide variety of tillage crops is grown, but cultivation of the heavier members of the series is very difficult. RESIDUAL SOILS OF THE WESTERN PRAIRIE REGION This region consists of the nonglacial part of the prairie plains bounded on the north by the Missouri River, the southern limit of glaciers, and extending southward through Texas to the Rio Grande. On the west it merges into the Plateau region at very near the 2ooo-foot contour, and on the east is limited by the Gulf Coastal Plain and the Ozark Plateau. Its surface is gently rolling, with occasional low hills, and is cut by numerous stream channels. The rocks are of Carboniferous age, and consist of sandstones, shales, and limestones more or less interbedded. These rocks give rise to three series of soils, viz. Oswego, Crawford, and Vernon, together with a number of miscellaneous soils. In Kansas and Texas these soils are in some instances more or less modified by the admixture of gravel and sand from Tertiary deposits brought down from the higher areas farther west occupied by crystalline rocks. Crawford series. Brown soils with reddish subsoils, derived from lime- stones. The soils of this series range from rough areas suited mainly for pastures to fertile general farming, fruit growing, and trucking soils. Oswego series. Gray or brown soils, derived from sandstones and shales. The lighter members of this series are adapted to corn, oats, potatoes, truck, and fruit ; the heavier to these crops and wheat. Vernon series. Brown to red soils typical of the Permian formation. Soils of this series show a wide adaptation according to texture. General farm crops, including cotton, corn, wheat, Kafir corn, and sorghum are the leading prod- ucts. Small fruit, peaches, and truck are grown to some extent and are capable of marked extension. GREAT BASIN With the exception of one soil type recognized in the Laramie area, Wyoming, the soils in this group, so far as mapped, are confined to the Great Interior Basin region. They are derived from a great variety of rocks, and consist of colluvial soil of the mountain slopes, deep lacustrine and shore deposits of the Bonneville period, and of recent stream-valley sediments and river-delta deposits. When not situated above or outside the limits of irrigation, or rendered unfit for cultivation by accumulation of alkali or seepage waters, they are of great agricultural importance, and are devoted mainly to the production of grains, sugar beets, alfalfa, stone or other tree fruits, and vegetables. Bingham series. Porous dark or drab colluvial and alluvial soils under- lain by gravel or rock, occupying lower mountain slopes. The lighter types SURVEYS BY THE UNITED STATES BUREAU 127 when irrigable are devoted to orchard fruits, the heavier types to alfalfa and sugar beets. Jordan series. Light to dark -colored lacustrine desposits. These soils are utilized principally in the production of alfalfa, sugar beets, truck crops, and grains under favorable conditions for irrigation and drainage, but consider- able areas covered by some of the members of this series are not utilized on account of the accumulation of alkali, poor drainage, or because of their drift- ing character. Malade series. Dark-colored alluvial soils underlain by light-colored sands, sandy loams, or heavy reddish material. These soils are devoted chiefly to sugar beets, alfalfa, grain, and some orchard fruits. Redfield series. Red soils consisting of colluvial and alluvial materials derived from red sandstones and other rocks. The lighter members are adapted to the production of alfalfa, grain, and general farm crops when irrigable and well drained. The heavier members, as far as encountered, are poorly drained and have not been developed. Salt Lake series. Dark-colored soils underlain by stratified sediments of lacustrine origin. These soils, as far as encountered, occupy very low, flat positions around the lake, and have not been developed to any extent. NORTHWESTERN INTERMOUNTAIN REGION The most extensive and uniform soil types of this region consist of residual materials overlying and derived from extensive basaltic lava plains and in some cases from granite rocks or of ancient lacustrine sediments or extensive lake beds now more or less modified by erosion or aeolian agencies. Owing to erosion by streams and to movements of the earth's crust, these soils now generally occupy more or less elevated sloping or rolling plains. About the margins of the lacustrine or residual deposits they are covered by sloping plains and fans of colluvial wash from the adjacent mountain borders, while in the vicinity of the larger streams, which have carved and terraced the lacustrine beds and residual soils, occur other series of recent alluvial stream sediments derived from reworked materials of the lake beds or from the weathered prod- ucts of the mountains. It is the soils of this region that constitute a large portion of the great grain -producing lands of the Northwest. Bridger series. Dark-colored soils with sticky yellow subsoils, of colluvial and alluvial origin. These soils generally occupy elevated foot slopes or sloping valley plains and have not been developed to a great extent. They are most extensively used for the production of grain, and, when irrigated, are utilized in the production of alfalfa and other hay crops and, under favorable climatic conditions, are adapted to fruits. Gallatin series. Light to dark-colored soils with yellowish to dark com- pact subsoils, of recent alluvial origin from basaltic and volcanic rocks. These soils generally occupy low positions, very frequently poorly drained, often subject to overflow, and have not been extensively developed for agricultural 128 SCIENCE AND SOIL purposes. They are used chiefly for grazing and, to some extent, in the pro- duction of hay, grains, and in some sections for vegetables. Yakima series. Ash-gray to light brown soils derived principally from ancient lake sediments consisting of an admixture of volcanic dust and ba- saltic, andesitic, and granitic materials. Certain members of this series have been very successfully developed for hop culture, alfalfa, grass, grain, and fruit, while other members of the series, owing to their elevated position and general rough character, have not been developed at all. ROCKY MOUNTAIN VALLEYS, PLATEAUS, AND PLAINS The soils of the Rocky Mountain valleys, plateaus, and plains are derived from a wide range of igneous, eruptive, metamorphic, and sedimentary rocks. The plateau and plain types occupy a more or less elevated position, and have sloping, undulating, or irregular surface features. They are derived from underlying sedimentary rocks or consist of the remains of the ancient extensive mountain foot-slope material or of alluvial deposits along streams trenching and terracing the sedimentary rocks of the plateaus and plains. The mountain slope and intermountain types consist of residual and colluvial deposits or of ancient lacustrine or later stream sediments, occupying mountain foot slopes and narrow valleys. The soils of the mountain slopes are usually of little agricultural value, owing to their rough surface, elevated position, and the consequent imprac- ticability of irrigation. Those of the plateaus, valleys, and plains vary widely in economic importance, depending largely upon climatic features, topography, position, and water supply for irrigation. They range from grazing lands of nominal value to soils adapted to the most important and intensively culti- vated fruit, melon, sugar beet, and other special crops. Billings series. Compact adobe-like gray to dark or brown soils and sub- soils, formed mainly by reworking of sandstones and shales, and occupying old elevated stream terraces. This is an important series adapted to alfalfa and general farm crops and stock raising ; also used to a considerable extent in the production of sugar beets. Colorado series. Light gray to reddish brown soils and subsoils, derived from colluvial wash. Where irrigable, these soils are important soils in the production of alfalfa, sugar beets, melons, and, to a limited extent, fruits. A number of the soils of the series, however, are so situated as not to be suscep- tible to irrigation, and have not been developed for agricultural purposes. Finney series. Brown to nearly black soils derived from glacial material underlain by lighter-colored subsoils. The heavier soils may be dry farmed to advantage, and would become very productive with irrigation. The lighter soils have a broken surface, are porous, and easily drifted by the wind. They are best adapted to grazing. Fruita series. Reddish brown soils, formed by reworking of sandstones and shales, occurring as stream terraces. When well drained and free from SURVEYS BY THE UNITED STATES BUREAU 129 alkali, the members of this series are admirably adapted to the production of choice fruits, alfalfa, sugar beets, grains, and truck crops. Laramie series. Dark -colored soils, with light-colored gravelly subsoils, de- rived from colluvial mountain wash. These soils have not been extensively developed, owing to their elevation, and are used principally for grazing pur- poses. Laurel series. Light gray to black soils, underlain by river sands or gravels, occurring in flood plains along streams. Under favorable moisture conditions, these are fertile soils, adapted according to locality to corn, alfalfa, sugar beets, and truck crops, but the areas are often subject to overflow, and in some cases cannot be drained. Mesa series. Light gray to brown soils derived from old flood-plain de- posits, now elevated to form mesa lands. Where these soils have been devel- oped and are susceptible of irrigation, they are used mainly for alfalfa and sugar beets. One member of the series has been quite extensively and very successfully used for the production of apples and peaches. Morton series. Brown residual soils, derived from sandstones and shales- The soils lie in the semiarid region, and give good yields of wheat, flax, oats, and potatoes, when rainfall is sufficient. San Luis series. Reddish brown gravelly soils, formed from lacustrine sediments of volcanic rock materials. On account of the position and the danger from alkali, these soils have not been successfully developed, but have been used mainly for pasturage and forage crops. Wade series. Brown to dark brown alluvial soils, formed by reworking of sandstones and shales. Used for oats, flax, millet, and wheat. ARID SOUTHWEST The soils of the arid Southwest are mainly of colluvial, alluvial, and lacus- trine origin. They occupy mountain foot slopes, alluvial fans, debris aprons, or sloping plains of filled valleys, sloping or nearly level plains, and bottoms of stream valleys or sinks and drainage basins. The principal colluvial soils of this region are also common to the Pacific coast. The climate of the arid Southwest is characterized by semitropical desert conditions, and where the soils are not capable of irrigation, they have little or no present agricultural value. Gila series. Light to dark brown soils of flood-plain alluvium, underlain at varying depths by coarse sands and gravels. Under favorable irrigation and drainage conditions, the members of the Gila series are adapted chiefly to the production of alfalfa, potatoes, truck, and root crops. Imperial series. Light-colored or reddish soils formed from old marine or lacustrine sediments modified by more recent deposits, and underlain to great depths by heavy material. These soils are particularly adapted to alfalfa, sorghum, and other forage crops. India series. Light-colored soils usually underlain by coarser sands and 130 SCIENCE AND SOIL gravels, formed by colluvial and alluvial wash from granitic rock, mingled with some shale and sandstone. These soils are adapted to fruit, truck crops, sweet potatoes, melons, and alfalfa, under favorable conditions of irrigation and drainage. PACIFIC COAST The soils of the Pacific coast, including those of the coastal and interior mountain ranges, foothills, and valleys, have been classified into a number of series, varying in field characteristics, topography, origin and mode of formation, and agricultural importance. They range from residual and colluvial soils of the mountain sides, foot slopes, and foothills, to deep and extensive river flood plains and delta sediments, and ancient and modern shore and marine lacustrine deposits. While some of these series are confined to a single coastal or interior mountain range or valley, others are of wider range and extend over several different physiographic regions. The value of these soils and their adaptation to crops is dependent largely upon the possibilities of irrigation and upon local conditions of rainfall and temperature, all of which are to great extent dependent upon topography. They range in agri- cultural importance from those devoted only to extensive grain farming to the most valuable and intensively cultivated lands devoted to citrus and decid- uous fruits, vines, small fruits, and other special crops. Anderson series. Reddish gray or light red alluvial soils occupying prin- cipal valley plains and the bottoms of intermittent streams. Generally gravelly. The soils of this series, when not too gravelly, are adapted to the production of peaches, pears, prunes, and small fruits, but are, in so far as mapped at present, inextensive types of secondary agricultural importance. Fresno series. Light-colored soils with light gray, ashy subsoils, and alkali -carbonate hardpan, derived from old alluvial wash. Where protected from alkali accumulations, these soils have been very successfully used for vineyards and raisin grapes, and are particularly adapted to almonds, peaches, and apricots. Hanford series. Recent alluvium of flood or delta plains derived from a variety of rocks. The light-textured soils are light in color, and the heavy tex- tured soils are dark in color. The lighter members of the series are adapted to the same class of fruits and raisin grapes as the Fresno series. The heavier members of this series, however, are better adapted to alfalfa, sugar beets, celery, asparagus, and other truck crops. Maricopa series. Loose, dark-colored soils derived from unassorted col- luvial or partially assorted alluvial materials, generally derived from granitic or volcanic rocks. There are two heavy members of this series upon which alfalfa, grain, and sugar beets are important crops. The lighter members, when occupying positions so that they can be irrigated, are adapted to citrus and deciduous fruits ; also vines. Oxnard series. Dark-colored alluvial or colluvial soils derived from higher lying areas of sandstones and shales. Members of this series are used to a very SURVEYS BY THE UNITED STATES BUREAU 131 large extent for sugar beets and lima beans, and, where irrigation is not practi- cable, extensively used for grain. Placentia series. Reddish soils derived largely from the weathering of allu- vial and colluvial deposits, generally underlain by heavy compact red material with an impervious adobe structure. Large areas of these soils are devoted to dry farming of grain, and occur throughout southern California and in some of the coastal valleys, viz., Bakersfield, Salinas, and San Jose*. These are exten- sive areas under irrigation, which are valuable for producing both deciduous and citrus fruits. The heavier members of this series have been more success- fully used for grain production in southern California. They seem particularly well adapted to English walnuts and olives. The soils are usually well drained. The English walnut does not thrive on poorly drained soils. Redding series. Ancient alluvial valley deposits of red and deep red color, generally gravelly. Heavy red subsoils with hardpan. The soils of this series, when not carrying an excess of cobbles or underlain at shallow depths by hardpan, are excellently adapted to the production of choice peaches and small fruits. Sacramento series. Gray alluvial soils consisting of recent stream sedi- ments. The lighter members of this series are used mainly for the production of prunes, pears, and peaches. The members of the series having a medium texture are adapted to sugar beets, alfalfa, and prunes. The heavier members are at present poorly drained, and have not been highly developed, being used mostly for grain and grazing. Salem series. Residual, alluvial, or colluvial soils, either red or .dark in color, derived from rocks of basaltic, schistose, crystalline, or arenaceous character. These soils, so far as they have been encountered, seem particularly adapted to hops, potatoes, and have been used to some extent for apples, peaches, and grain. They have not been very highly developed in the areas in which they have been encountered. San Joaquin series. Compact red soils and subsoils derived from old marine sediments, usually underlain by red hardpan. These soils have been used almost exclusively for dry farming to grain on account of the general occurrence of hardpan and very stiff and impervious subsoils. Recently, in the Sacramento area, some members of this series have been very successfully used for the production of the Tokay grape and strawberries. Sierra series. Light gray to red and frequently gravelly soils, often under- lain by red adobe. Members of this series constitute some of the most valu- able deciduous fruit soils of the foothills in northern California. Sites series. Residual and colluvial soils of reddish gray or dark brown color, derived from sandstones, shales, conglomerates, and volcanic or altered ma- terial occupying low, rolling foothills and their valley slopes, usually underlain at shallow depths by sandstones, conglomerates, or heavy subsoils. The Sites loam and clay loam adobe are the important soils of this series and are pro- ductive, but, owing to their positions, are generally unirrigable and adapted to dry farming to grains. 132 SCIENCE AND SOIL Stockton series. Brown to black soils with heavy yellow subsoils, derived from old alluvial sediments. These soils have been used principally for the production of grain. The lighter members of this series have been adapted to fruit. Willow series. Brown soils consisting of wash deposited by intermittent foot- hill streams. These soils have been used almost exclusively for dry farming grain crops. Large ranches are being broken up and brought under irrigation, and alfalfa and sugar beets are likely to prove the most important crops. The following additional quotations from Bureau of Soils Bulle- tin 55 will serve to acquaint the student with the general charac- ter of the more detailed descriptions which are given of the soil types singly and in series: Leonardtown loam1 (Maryland, Virginia, Kentucky, — 196,834 acres). "The Leonardtown loam is a valuable upland soil of Maryland and Virginia. The surface is slightly rolling, the drainage in most areas is good, and altogether the land is well suited to general farming. The soil has a special value in the production of wheat and grass." Marion silt loam (Illinois, Missouri, — 695,040 acres). "A large pro- portion of southern Illinois is occupied by Marion silt loam. The type occupies level prairie land and is characterized by hard silty clay subsoil locally known as ' hardpan. ' It is low in organic matter, and this, combined with the impervious nature of the subsoil, causes crops to suffer in wet as well as dry seasons. Wheat, corn, and grasses are the principal crops, but the average yields are considerably lower than upon the black prairie soils. It seems especially well adapted to apples, and many large orchards have been planted. Strawberries also do well." Marshall series (glacial and loessial regions). "The Marshall series in- cludes the dark -colored upland glacial and loessial soils, which cover almost all of the great prairie region of the Central West. The soils of this series are characterized and distinguished from those of the Miami series by the relatively large quantity of organic matter in the surface soils, which gives them a dark brown to black color. The topography is level to rolling, and artificial drainage is necessary on many level and low -lying areas to secure the best results. The soils of this series are very productive and constitute the great corn soils of the country. "The Marshall silt loam, loam, and clay loam constitute the principal soil types throughout the great corn belt, and rank among the most productive of our general farming soils. In Iowa, Illinois, and Nebraska, corn, oats, clover, and timothy are the leading crops, while in Minnesota and the Dakotas wheat becomes of primary importance. The Miami (Marshall) black clay loam, when drained, is also an exceedingly fertile soil, being particularly well adapted 1 The Leonardtown loam and Leonardtown gravelly loam in the Norfolk, Vir- ginia, report are the Portsmouth silt loam. SURVEYS BY THE UNITED STATES BUREAU 1.33 to corn. The sandy loam and fine sandy loam, while not so well adapted to general farming as the heavier soils, are quite productive and have a wide crop adaptation. The sand and fine sand are well suited to truck crops, but give rather uncertain yields of general farm crops. "The acreage of the types so far encountered is as follows : AREA AND DISTRIBUTION OF THE SOILS OF THE MARSHALL SERIES SOIL NAME STATES IN WHICH EACH TYPE HAS BEEN FOUND TOTAL AREA (Acres) Marshall stony loam Gravel l . . . North Dakota, South Dakota .... Minnesota, North Dakota 84096 2s6o Gravelly loam . Sand .... Kansas, Minnesota, NorthDakota, Wisconsin Indiana, Iowa, Wisconsin I068l6 t?27'?6 Fine sand . . Indiana, Iowa, Minnesota, Nebraska, North Dakota C4272 Sandy loam . . Illinois, Indiana, Kansas, Minnesota, South Dakota 26l44O Fine sandy loam Indiana, Minnesota, Nebraska, North Da- kota • IIIl68 Loam .... Illinois, Indiana, Iowa, Michigan, Minnesota, Nebraska, North Dakota, South Dakota, Wisconsin l68o8?2 Silt loam 2 . . Colorado, Illinois, Indiana, Iowa, Kansas, Louisiana, Minnesota, Missouri, Nebraska, North Dakota, Wisconsin 44^4470 Clay loam . . Black clay loam 3 Clay .... Iowa, Minnesota, North Dakota, Wisconsin Illinois, Indiana, Iowa, Michigan, Minnesota, North Dakota, Ohio, South Dakota, Wis- consin North Dakota 600320 572176 76800 Total . . . 8057686 1 The soil mapped as Marshall gravel in Pontiac area, Michigan, is Miami gravelly sand. 2 Mapped as Miami silt loam in Clinton and St. Clair counties, Illinois, and as Fresno fine sandy loam in Lower Arkansas Valley area, Colorado. 3 The soil mapped as Miami (now Marshall) black clay loam in the Toledo area, Ohio, is Clyde clay. Miami series (glacial and loessial regions). "The Miami series is one of the most important, widely distributed, and complete soil series that has been established. The series is characterized by the light color of the surface soils, by derivation from glacial material, and by being timbered either now or originally. The heavier members of the series are better adapted to wheat 134 SCIENCE AND SOIL AREA AND DISTRIBUTION OF THE SOILS OF THE MIAMI SERIES Son. NAME STATES IN WHICH EACH TYPE HAS BEEN FOUND TOTAL AREA Miami stony sand . Michigan, New York, Washington, Wiscon- sin 100278 Stony sandy loam New York, Rhode Island, Vermont, Wash- ington 267^28 Stony loam . . Gravel .... Michigan, Minnesota, New York, Ohio, Rhode Island, Washington, Wisconsin Illinois, Wisconsin 879094 21^76 Gravelly sand i . QI242 Gravellysandy loam Indiana, Michigan, Minnesota, Washing- ton 58624 Gravelly loam 2 . Sand .... Fine sand . . . Indiana, Michigan, Ohio Indiana, Kansas, Michigan, Minnesota, Nebraska, Ohio, Wisconsin .... Illinois, Indiana, Iowa, Kansas, Michigan, Minnesota, Missouri, Nebraska, New York, Wisconsin 71232 795720 263<64 Sandy loam 3 Fine sandy loam 4 Loam 5 . . . . Silt loam 8 . . Indiana, Iowa, Michigan, Minnesota, Ohio, Washington, Wisconsin Indiana, Michigan, New York .... Indiana, Michigan, Wisconsin .... Illinois, Indiana, Iowa, Kentucky, Mis- souri, Nebraska, Rhode Island, Wiscon- sin 745460 130816 214720 IQCI488 Clay loam 7 . . Indiana, Iowa, Michigan, Ohio, Washing- ton, Wisconsin 1831818 Total . . . 7422760 1 Mapped as Marshall gravel in Pontiac area, Michigan. 2 The soil mapped as Miami gravelly loam in the Big Flats area and Syracuse area, New York, is the Dunkirk gravelly loam. 3 The soil mapped as Miami sandy loam in the Grand Forks area, North Dakota, is the Clyde fine sandy loam; in the Montgomery County area, Ohio, is Wabash sandy loam; and in Posey County area, Indiana, is Wabash fine sandy loam. 4 The soil mapped as Miami fine sandy loam in Posey County, Indiana, and Union County, Kentucky, is Waverly fine sandy loam; in the Boonville area, Indiana, is the Norfolk fine sandy loam ; in the Lyons and Syracuse areas, New York, is Dunkirk fine sandy loam; and in St. Claire County, Illinois, is Memphis silt loam. 5 The Miami loam in the Auburn, Lyons, and Syracuse areas, New York; the Columbus, Coshocton, Montgomery, Toledo, and Westerville areas, Ohio; the Fargo and Grand Forks areas, North Dakota; the Marshall, Minnesota, and Pontiac areas, Michigan; and the Viroqua area, Wisconsin, is Wabash loam. The soil mapped as Miami loam in Tazewell County, Illinois, is Sioux loam, and that mapped as Miami loam in the Janesville area, Wisconsin, is the Sioux sandy loam. 8 The soil mapped as Miami silt loam in the Syracuse area, New York, is Dunkirk SURVEYS BY THE UNITED STATES BUREAU 135 than the corresponding members of the Marshall series, but they do not pro- duce as large yields of corn. "The clay loam is the most important for general farming, and forms the principal type of soil in western Ohio and central and eastern Indiana. It is especially well adapted to small grain and grass crops. The silt loam is more rolling and hilly than the clay loam and is not so well suited to general farming. Wheat does better upon it than upon the Marshall silt loam, with which it is closely associated, but the yields of corn are considerably less. It is also well adapted to fruit, especially apples. The sandy loam and fine sandy loam are used for general agriculture, but are especially adapted to me- dium and late truck crops and fruit. The loam is suited to corn and potatoes, while small grain and grass are grown, but with less success than upon the clay loam. Strawberries and raspberries, as well as other small fruits, do well on this type. The stony sand, gravelly sand, and gravel are not of much agricul- tural value under present conditions. The stony loam is a good general farm- ing soil, is also well adapted to apples, and furnishes excellent pasture, while in New York alfalfa is grown upon it very successfully. The stony sandy loam and gravelly sandy loam are not strong soils, but are fairly well suited to light farming, fruit, and truck. The sand and fine sand are not adapted to general farming, but are the best early truck soils of this section. "The acreage of the different types so far encountered is shown in the preceding table." silt loam, and that mapped as Miami silt loam in Clinton and St. Claire counties, Illinois, is Marshall silt loam. 7 The soil mapped as Miami clay loam in Toledo area, Ohio, is Dunkirk clay loam, and that mapped as Miami clay loam in the Stuttgart area, Arkansas, is Crowley silt loam. CHAPTER IX SOIL ANALYSIS BY THE UNITED STATES BUREAU OF SOILS THE United States Bureau of Soils Bulletin 54 (December, 1908), on " The Mineral Composition of Soil Particles," contains data from which can be computed 1 accurately the total amounts of phosphorus, potassium, magnesium, and calcium, in the ignited surface soil of twenty-seven important soil types of the United States. The loss on ignition of ordinary soils usually approaches 10 per cent, and includes chiefly the combined water, organic matter, and more or less carbon dioxid, if carbonates are present; consequently, the results given on the basis of ignited soil are, as a rule, about one tenth higher than if given on the usual basis of dry soil. The following general statements regarding these soil samples are made by the Bureau of Soils (Bulletin 54, page 15) : "Our extensive collection of soils from important and well-marked soil types enables us to select samples fully representative of the soils of the country. Accordingly, agricultural soils of known character were selected so as to include those from various geographical sections and from a number of soil provinces. Thus we have taken soils from the Coastal Plains, the Piedmont region, glacial soils, nonglacial soils of the interior, and those of the arid region, the list comprising 27 soil types." " We have but two soils of the arid region to compare with the twenty-five of the humid region. The latter were collected to represent soils of all classes — those of low, of medium, and of high productivity; sandy soils, clay soils, calcareous soils, and those intermediate between these extremes. They may be taken as fairly well representing the humid soils. The two arid soils cannot be considered to represent so well those of the region because of their limited number and similarity of texture, both being fine sandy loams." "The Coastal Plains soils have resulted, to a large extent, from material washed from the Piedmont Plateau and deposited in water at lower levels. 1 The Bureau of Soils Report shows, for example (Bulletin 54, page 19), that Leonardtown loam contains 29.5 per cent of sand, 55 per cent of silt, and 15 per cent of clay, and that the total P^Os which these particles contain is .01 per cent in the sand, .02 per cent in the silt, and .03 per cent in the clay. 136 ANALYSIS BY THE UNITED STATES BUREAU They have suffered from decomposition and solution more than have the Piedmont and Appalachian soils, and there has often been a greater separation of the finer from the coarser particles. " "The tables show that the residual soils, Chester mica loam, Porter's black loam, and Cecil clay, contain more plant-food constituents than do the Coastal Plains soils. This is especially true of the phosphorus, the potassium, and the magnesium." "The sandy and the silty glacial soils are somewhat similar in percentage composition. Owing to the latter consisting to so large an extent of such fine particles, it might have been supposed that decomposition and leaching would have affected them more . . . but the silty soils are loessial for the most part, and were formed from material blown by winds from glaciated areas and deposited where now found, or of material that has since been reworked by water. Minerals rich in alkalis and alkaline earths, being relatively easily crushed, would form a larger percentage of these silty soils than they do of the original glacial soils ; so that even if there has been a tendency to impoverish them by leaching, their originally greater richness enables the loessial soils to compare well with those strictly glacial." In Table 22 are reported the total amounts of phosphorus, po- tassium, magnesium, and calcium found by the Bureau of Soils in 2 million pounds of ignited soil for the surface soil of each of the 27 type soils, and also the amounts in the acid-soluble portion of one subsoil, or underlying greensand marl. While these soils " were selected to represent all classes — those of low, of medium, and of high productivity," Bulletin 54 gives no information as to the agricultural value of the different soils. Fortunately, the Annual Reports of the Bureau of Soils contain the descriptions made by the soil survey men concerning the common crops and normal crop yields produced on each of these soils, and thus a correlation is made possible between chemical composition (as recently determined by actual ultimate analysis) and produc- tive capacity, of these important and extensive types of soil (as reported in previous years from field investigations). Even here the student is advised not to accept opinions expressed, predictions made, or conclusions drawn, unless clearly supported by chemical facts or by long-continued agricultural experience. In each of the following descriptions the first paragraph is quoted from Bureau of Soils Bulletin 54 (December, 1908), and the second paragraph is quoted from the Annual Report of the " Field 138 u 80 o M O O 10 »O ON M O O O O vo MO O OO ^f M. M CO o o o O CM *O M CM M 0 O 00 O CM t-. 00 vo CVl O 0 o o MO o CNI 1*0 §o o CM O vO 00 0 0 O vO O 10 00 vo 00 0^ -t 0 O M NO r^oo 10 vO M O O O O O O aM O O O ON !•» MO O t^ CM Tf tr) O CM MO MO TJ- O CM o o CM O r^ MO M 00 M o O 0 O vo Tt* IO ***• O M ^- o o o 00 00 O Tt CM CM MO CM M O 00 O vO **• CM O O vO O M O IO CVl O O Tt" M O 00 M o o 00 MO M O 0 0 CM VO T)- ON ONOO Tj- ONVO 0 o 0 O 0 CM CM MO to •>tOO o o o o o o 00 CM CM OO VO O Tj- t^ to rf MO w 00 vo - 00 O vO 10 o o o o o o 10 O CM oo o MO 80 o o o t- - ^& a e Marshall silt loam (prairie) Miami silt loam (timber lar Marshall black clay loam ( Marion silt loam (prairie) rt g • — • rt •*J~~' rt E -2 C rt 'tn i-S- ^ j5 o -c I V •-= ~c 2. ^_rt 11 '55 tn O Jjj 4) rt o ^ ^~.'~".S ^ £ C — rt <~f ^, •*-> (-1 O- 2 • 6 c c S rt S X C O . o rt _rt rt ^ — _o g g O "u %, fe D 41 tn — «J -^ M bC 3 '£ t 4> U _ rt JD C 3 — in >-, u •U 4> C C o o _c %c 7J 7J 00 -— »/-N rt rt 3 3 "rt '55 '5! -5 0 i-i^ S T?lT -c 4) 4> C C "rt "rt "rt ^^ in rt M 'rt-5 "rt "rt rt "rt rt "rt - tn In "O _ ' 4) 4> ouo ouu OO OO OO ooo 5 CO CO JHJJS£O 00 .do <3'| ^ <-> 8 »- - •^ S u LOCALITY lifornia, Fresno lifornia. Indio . rt 4, ^ ANALYSIS BY THE UNITED STATES BUREAU 139 Operations of the Bureau of Soils " for the year designated. For convenient reference, the number of pounds of phosphorus shown in Table 22 is given at the beginning of the second paragraph in each description, not that the supply of the one element always correlates with productive power, but because it does so more frequently than any other. SOILS OF THE ARID REGION Fresno fine sandy loam (California) "is composed largely of silt to fine sand. It is locally known as 'white-ash land,' from its color and its physical character. The soil has probably been derived from volanic ash, but light- colored loams and sands have also contributed to it. The soil lies flat and works well, unless it be puddled, when water penetrates it slowly and hard clods or lumps form on drying. The lower subsoil is heavier, a blue clay being encountered at the depth of a few feet. Because of the poor drainage or light rainfall, this soil generally contains alkali. " (1830 Ib. P.) "Was originally considered extremely productive, and is now, where the drainage is good. Some of the first colonists settled on this land through choice. " (Report for 1900, page 46.) India fine sandy loam (California) "is made up of clay, silt, and the fine grades of sand. The clay is so flocculated that the soil in its field condition is lighter than the mechanical composition would indicate. The soil was mainly formed by erosion from adjacent mountains, the material being deposited in a bay or arm of the sea, but it has been greatly modified by wind action. It contains micaceous grains and minute shells. The soil ranges in depth from 2\ to 5 feet and is underlain with sandy loam or sand. The surface usually has a uniform slope and is generally well drained, but its high capillary power draws much water to the surface, causing an accumulation of alkali by its evaporation. In the lower levels the alkali is present in injurious amounts. Owing to insufficient rainfall, the salts are not washed out of this soil so well as might be expected from its physical character. " (2090 Ib. P.) "Where not too strongly alkaline, it will produce in abundance any of the crops suited to the climate." (Report for 1903, page 1255.) COASTAL PLAINS SOILS Leonardtown loam (Maryland) "consists of a yellow silty loam, fine and powdery when dry, but puddling to a plastic mass when thoroughly wet. The subsoil consists of a brittle mass of interlocking clay lenses, lumps, and fragments, separated by seams and pockets of medium to fine sand. This subsoil is as impervious as clay, owing to its peculiar shingle-like structure. It is an upland soil, and is generally slightly rolling. " (160 Ib. P.) "Covers about 41 per cent of St. Mary County. . . . This 140 SCIENCE AND SOIL soil has been cultivated for upward of two hundred years, but it is now little valued and is covered with oak and pine over much of its area. It is worth from $i to $3 an acre. The cultivated areas produce small crops of corn, wheat, and an inferior grade of tobacco." To this statement of facts is added the opinion that " the generally low estimation in which land is held is probably wholly unjustified. ... In texture, in chemical composition,1 and in general agricultural value (when carefully and intelligently farmed) these lands compare favorably with the Hagerstown loam of western Maryland and Lancaster County, Pa., which are con- sidered the most valuable soils of the Atlantic States for general farm crops." (Report for 1900, page 33.) The Bureau of Soils also reports that 45,770 acres of this type of soil are found in Prince George County, which borders the District of Columbia on the east and south, concerning which the Bureau's Report for 1901 contains the following statements: "The soil is not adapted to tobacco, and has consequently been allowed to grow up to scrub forests, so that large portions of it are at present uncleared. Such unimproved lands can be bought for $1.50 to $5.00 an acre, even within a few miles of the District line. The soil has been badly neglected, and, when cultivated, the methods have not been such as to promote fertility. It is fre- quently acid, and needs lime and manure, or green crops turned under. When properly handled, as it is in a few places, good yields of wheat, corn, and grass are obtained." And to this statement of facts is also added the opinion that " upon the whole it is one of the most promising soils 2 of the local- 1 See Table 22 for chemical composition of the Leonardtown loam and the loam and clay of the Hagerstown series. — C. G. H. 2 Determinations of the water-soluble constituents in 36 samples of Leonardtown loam are included in the data which led Whitney and Cameron to draw the very erroneous conclusions that "practically all soils contain sufficient plant food for good crop yields, that this supply will be indefinitely maintained, and that the actual yield of plants adapted to the soil depends mainly, under favorable climatic conditions, upon the cultural methods and suitable crop rotations." (Bureau of Soils Bulletin 22, page 64.) The following quotations are taken from page 34 of Bureau of Soils Bulletin 22 (1903). They furnish some information as to what is done when this soil is "properly handled": "There is no apparent relation between the yield of crops and the soluble salt content of soils, even where the yields per acre differ as much as from 4 bushels to 25 or 30 bushels. ANALYSIS BY THE UNITED STATES BUREAU 141 ity, although it is not so considered by the resident farmers." (Report for 1901, page 45.) Norfolk sand (Maryland) "is a coarse to medium orange or yellow sand, having a depth of about 10 inches. The subsoil is coarse to medium, becom- " As bearing upon this point of the association or nonassociation of high analyti- cal figures with large crop yields, no more striking evidence occurs to us than the following letter written by Mr. Taylor, May 26, while in the field in St. Mary County, Md., and forming a part of his regular reports to the Bureau at Washington: "'At Park Hall, upon the farm of Mr. S — , who is recognized as one of the best farmers of the community, I secured some samples of the Leonardtown loam from a wheat field which will produce from 30 to 35 bushels per acre this season. The land was in tobacco last season, upon which barnyard manure and 400 pounds of fertilizer had been used. Nothing was added when the wheat was sown. The land was plowed about 8 inches deep. The soil lacked the usual grayish, ashy appearance of the Leonardtown loam, and, owing to cultivation, was loose and mellow to a depth of over two feet. One of these samples was compared with one taken from another wheat field upon the same type, where the yield would not be over 6 or 8 bushels. This latter land was farmed by negroes, was in wheat last year, and produced a fair crop, so it is said. No manure but a little guano was used last fall. The ground was uneven on the surface, and below the first 4 or 5 inches the soil was hard and compact. A comparison of the analyses is given below : PARTS PER MILLION OF OVEN-DRIED SOIL CONDITION PER CENT OF MOISTURE PHOSPHORIC ACID (P04) NITRIC ACID (NO,,) CALCIUM (Ca) POTAS- SIUM (K) Good wheat : First foot 14.2 2.0O 13.22 14.72 24.36 Second foot 10. 0 3.72 IO.QI 12. <2 24.80 Poor wheat : First foot 14.7 4-72 1C. -24 7.01 3^.40 Second foot IQ Q 4 14. II. l6 4.1^ r 30.38 . It will be noted that the poor soil shows more water-soluble plant food with all elements except calcium. Other data reported show that the pounds of water- soluble calcium per million pounds of oven-dried soil of the Leonardtown loam varied from 2.66 to 29.52 in the first two feet where the soil was in "good condition," and from 3.95 to 24.99 where the soil was in "poor condition. " It appears, however, that the conclusions of Whitney and Cameron even con- cerning the nonrelationship between crop yields and water-soluble plant food are wrong. Professor F. H. King, a most careful investigator of the highest integrity, as the result of two years' experiments, including many determinations made during the crop season, before severing his connection with the Bureau of Soils, was led to the following conclusions: 142 SCIENCE AND SOIL ing loamy at about 3 feet. It is a common type of soil in the Atlantic and Gulf Coastal plains. The surface is level to rolling, and the soil is well drained." "Our own observations, published by the Bureau of Soils (Bulletin No. 26), have demonstrated that four good soils, observed to produce two and a half times the yield per acre of corn and potatoes that four poorer soils did under identical treatment, also gave up, when washed three minutes in five times their weight of pure water, 2.58 times as much plant food. Not only was there this difference in the amount of plant food carried in water-soluble form in the best and in the poorer soils, but the amounts of this same plant food taken out of like areas of field by like numbers and like kinds of plants during the same time was 3.2 times as great in the sap of the plants which gave the highest yields." (Proceedings Jamestown Con- gress of Horticulture, 1907, page n.) The following tabular statement is a summary of Professor King's data secured under known conditions from the eight soils mentioned. (See Bureau of Soils Bulletin 26, page 120.) It should be stated that each value recorded for plant food determined is the average of 28 different determinations. These data are certainly far more trustworthy than the selected results from such miscellaneous samples as are referred to by Professor Whitney in Bulletin 22 (see above quotation). AVERAGE CROP YIELDS AND MEAN AMOUNT OF WATER-SOLUBLE PLANT FOOD IN FOUR POOR SOILS AND FOUR GOOD SOILS FOR THE SEASON OF 1903. — By F. H. King POOR SOILS STATE .... North Carolina Maryland Pennsylvania Wisconsin Son, TYPE . . . Norfolk Sandy Soil Selina Silt Loam Norfolk Sand Sassafras Sandy Loam 8,^ rt !s fc8 h Average of 4 Good Soils Hagerstown Clay Loam 2 8 •2 § w Janesville Loam 1 GOOD SOILS CROP YIELDS PER ACRE: AVERAGE OF FIVE PLOTS FOR EACH SOIL Corn, bu. . . . Potatoes, bu. . . 36.3 47-7 38.9 70.4 29.6 102.7 29-5 93-4 33-6 78.6 64-3 213.2 52-9 168.0 54-7 iS7-o 80.4 290.5 69-3 237.1 POUNDS OF WATER-SOLUBLE PLANT-FOOD ELEMENTS IN 4 MILLION POUNDS OF SOIL: AVERAGE OF 28 DETERMINATIONS FOR EACH SOIL Nitrogen . . . 8-3 6.0 8.1 7-7 7-5 21.3 15.0 23-7 34-6 11.9 Phosphorus . . 10.4 10.8 15.2 11.9 12. 1 22.2 I8.3 15-6 30.0 24.7 Potassium . . . 47-5 42.7 46.5 47.1 46.0 69-3 48.9 60.4 99.9 68.0 Magnesium . . 44-7 45-i 42.2 47-5 44-9 9I.I 78.0 69.1 115.2 IO2.I Calcium .... 91.6 114.9 94-5 TOO. 8 100.5 264.8 264.4 223.4 293.6 277.7 Sulfur .... 62.3 71.9 50.2 83.1 66.9 156.9 121. 6 104.9 217.9 l83.I ANALYSIS BY THE UNITED STATES BUREAU 143 (520 Ib. P.) " Very poorly adapted to general farm crops, and little success is attained with either corn or wheat, and none of the grasses do well. " (Report for 1901, page 46.) Norfolk loam (Maryland) "is a mellow brown sandy loam to a depth of about 9 inches. The subsoil to 36 inches is a medium to heavy loam, which is often underlain by fine yellow sand. In the area from which the samples were taken it has a slight elevation and is gently rolling. It is usually well drained. " (610 Ib. P.) "The principal crop grown is wheat, which yields 20 to 30 bushels per acre on the heaviest phase of the type in fair seasons and from 15 to 20 bushels on the lighter areas, these yields depending largely on the amount of fertilizer used. ... It responds readily to applications of fertilizer and lime." (Report for 1903, page 172.) Orangeburg sandy loam (Alabama), "locally called 'red lands,' is a brown to a reddish brown light sandy loam, 4 to 15 inches deep, resting on a friable brick -red sandy clay subsoil. The surface is rolling. It is generally well drained, although there is a tendency to form a 'plow sole' or ' hardpan.'" (520 Ib. P.) "Practically all of this type is under cultivation, and is highly prized for the production of cotton. The yields are not so high in some in- stances as on the Houston clay and other prairie types, but it is considered a safer soil from year to year than the prairie type. Cotton yields from one half to i bale per acre. As much as ij bales per acre has been produced where the land has been heavily fertilized. Very little corn is grown, as it is claimed that the yields are generally light. The difficulty here, as with the Orangeburg fine sandy loam, is that the soil proper is shallow." (Report for 1905, page 436.) In the same report (page 438) the Orangeburg fine sandy loam, mentioned above, is described as follows: " Cotton is the principal crop grown on the Orangeburg fine sandy loam. The yields range from one fourth to i bale per acre, depending upon the amount of fertilizers used and the methods of cultivation. It is not considered a good corn soil, and, as a result, not much corn is planted. Corn yields range from 10 to 20 bushels per acre." Crowley silt loam (Louisiana) "usually has a surface of about 16 inches. It is of a brown color when wet, but ash gray when dry. It is composed of fine sand and silt, with sufficient clay to render it rather impervious. If stirred when wet, it puddles somewhat. This soil is underlain by a clay of mottled brown and yellow color, with brick -red streaks and blotches. The subsoil is highly impervious and the surface level, so that the soil has very poor drainage. The samples analyzed are from level prairies in southern Louisiana. " (1220 Ib. P.) "From the time that the Crowley silt loam was first cul- tivated, rice has been the only crop to receive attention. Nothwithstanding this continued annual cropping with the same crop, without attempting in any way to maintain the productiveness of the soil, there has as yet been no de- crease in yields." (Report for 1903, page 470.) I44 SCIENCE AND SOIL Orangeburg fine sandy loam (Texas). "Varies in color, being red, brown, or gray. It is a light sandy loam, generally carrying iron concretions. The subsoil is red, friable, sandy clay. The type occupies the upland and has good natural drainage." (960 Ib. P.) " Cotton is the principal crop raised upon this soil. Yields from one half to three fourths of a bale per acre are secured. Corn does fairly well. " (Report for 1903, page 495.) GLACIAL OR LOESSIAL SOILS Shelby silt loam (Missouri) " is a silty soil of medium depth and of a light gray color when dry; dark gray when wet. It grades into a stiff, impervious silty clay, plastic and waxy when wet, friable and loamy when dry. The sub- soil is a dark mottled clay. It is level or gently rolling. The original growth on this type of soil was the prairie grasses. " (1920 Ib. P.) "The following yields are secured on this soil in good seasons : Hay, from 2 to 3 tons; corn, from 35 to 40 bushels; oats, 30 to 60 bushels; wheat, 15 to 20 bushels, but uncertain; Kafir corn, 20 to 40 bushels; mil- let, 30 to 40 bushels of seed per acre. The Shelby silt loam is a typical grass soil." (Report for 1903, page 884.) Marshall loam (Minnesota) "is a somewhat heavy loam from 10 to 12 inches in depth and of a dark brown color. Under this is a stiff, sticky yellow subsoil to a depth of about 3 feet. Below this is a stiff bowlder clay, mottled yellow and gray. The type is generally rolling and well drained. Bowlders and glacial gravel occur to some extent over this soil." (1830 Ib. P.) "The Marshall loam is the safest soil in the area, as it is the surest to produce at least an average crop. . . . The Marshall loam, taken as a whole, excels all other soil types of the area in the production of wheat, on account of the superior quality of the grain produced." (Report for 1903, page 820.) Marshall silt loam (Wisconsin) "is a mealy, chocolate-colored silt loam with a dark brown tint when moist. It contains a large amount of silt, and becomes somewhat sticky when wet. It is about 10 inches deep. The sub- soil is a sticky, reddish-yellowish silty clay, about 3 feet deep, and rests upon a glacial gravel or, the disintegrating limestone of the region. The soil probably owes some of its distinguishing characteristics to the influence of this limestone. The type is rolling and well drained. It was originally covered with the prairie grasses of the region. " (2450 Ib. P.) "It is one of the strongest and most fertile soil types of the region, forming the larger portion of the original rolling prairie of southern Wisconsin. It produces, under average seasonal conditions, from 50 to 60 bushels of corn, from 40 to 50 bushels of oats, about ij tons of hay, and 1200 pounds of tobacco. " (Report for 1902, page 557.) Miami silt loam (Wisconsin) "is a very silty loam, light brown when wet, and light gray when dry. Its depth is about 8 inches. It is underlain by several ANALYSIS BY THE UNITED STATES BUREAU 145 feet of stiff, yellow, silty clay that is always mottled with gray, showing poor drainage and aeration. This type originally consisted mainly of timber lands and oak openings. " (2100 Ib. P.) "The crop yields on the Edgerton (Miami) silt loam average from 45 to 50 bushels of corn per acre, about 40 bushels of oats, from i to i£ tons of hay, and from noo to 1200 pounds of tobacco." (Report for 1902, page 55 7-) Marshall black clay loam (Illinois) "is a heavy, somewhat sticky, granular clay loam, containing a large percentage of silt and organic matter. It has a depth of about 18 inches. The subsoil is a mottled yellow or drab-colored sticky, silty clay. This soil type has formed where the natural drainage was poor. The surface is level. In its original condition it was wet and swampy and required thorough drainage. " (2970 Ib. P.) "There are few soils more productive than the Miami (Mar- shall) black clay loam. Some areas have been cropped almost continuously in corn for nearly fifty years without much diminution in the yields, but the effect will undoubtedly be seen if the practice is continued much longer." (Report for 1903, page 787.) Marion silt loam (Illinois, gray silt loam on tight clay) "consists of a light brown to whitish very silty loam, containing very little organic matter. Its depth averages 12 inches. The soil cakes on drying, but breaks down into flourlike dust when pulverized. The subsoil is heavier, and contains more clay. It is so impervious to water as to be locally called hardpan. The lower subsoil is a hard, silty, mottled yellow clay, often containing iron concretions. Below 4 or 5 feet, more or less gravel is found. The type is level or slightly rolling. The soil has very poor natural drainage, owing to the rather impervious subsoil and the level surface. While of loessial origin, this soil has been largely formed from sandstones and shales ground up by glaciers." (1050 Ib. P-) "The average yield of corn is not much more than 15 bushels per acre. . . . The Marion silt loam is not a strong soil, and is not well adapted to general farming purposes. The small yield of corn indicates that it is not a good soil for that crop, although the profit from corn, according to many farmers, is as much as from other crops. " (Report for 1902, page 542.) Miami sand (Ohio) "is a coarse to medium loose and deep yellowish sand. It is underlain by a yellow sand of about the same texture. It is level to rolling, and consists of glacial material somewhat modified by wind action. It occupies elevated positions, and is well drained. " (2360 Ib. P.) "Grass, corn, wheat, truck, and fruit are grown on this soil. The quality of these is good, and in some cases better than the produce grown on the other soils in the area, but the yield is usually 15 to 30 per cent less, and crops sometimes are cut short or fail because of susceptibility to drought. The yield of wheat ranges from 10 to 20 bushels per acre, and of corn from 20 to 45 bushels per acre. . . . This soil yields from 75 to 120 bushels per acre of an excellent quality of potatoes. " (Report for 1902, page 394.) W abash loam (Ohio) "is a dark brown to black soil of good depth, and con- 146 SCIENCE AND SOIL taining a small proportion of the coarser grades of sand. The subsoil is a heavy brownish yellow loam overlying a fine gravelly loam. It is a bottom land, frequently occurring as terraces. It is generally well drained. It con- sists of glacial drift redeposited by stream action." (1570 Ib. P.) "One of the more fertile soils of the area. Some of the fields, tilled for more than half a century and only moderately manured, still produce abundantly. . . . Corn yields from 40 to 100 bushels per acre, with the aver- age production probably about 75 bushels, and wheat from 20 to 35 bushels per acre." (Report for 1902, page 395.) Volusia silt loam (Ohio) "is a gray to brown silty loam with an average depth of 8 inches. The subsoil is a light yellow silty loam, mottled with gray in its lower portions. It has resulted in most part from the glaciation of shales. Its mechanical constituents closely resemble in size those of the soils derived from the loess, being composed largely of silt. This is doubtless due to the silt in the shales from which this soil type comes in large part. " (1480 Ib. P.) "The average yield of wheat is about 20 bushels per acre, and yields as high as 30 bushels are not uncommon. Corn, under the best cultural methods, will average 40 to 45 bushels per acre. Oats will yield an average of 50 bushels per acre, although larger yields are often reported. From 100 to 150 bushels of marketable potatoes per acre is the average produc- tion of this crop." (Report for 1904, page 559.) Podunk fine sandy loam (Connecticut) "is an alluvial soil, formed by the reworking by running water of glaciated granites, gneisses, and schists. It contains an abundance of micaceous mineral particles visible to the eye. It is underlain by fine sand. The soil is of a dark brown color and is well drained. The tobacco field from which the sample came had been heavily fertilized for years. " (1920 Ib. P.) "The type is entirely under cultivation and produces good crops of corn, late truck, cucumbers for pickling, and tobacco. The area in the latter crop is large, and the yields range from 1700 to 1900 pounds in the open field." (Report for 1903, page 54.) RESIDUAL SOILS Oswego silt loam (Kansas) "consists of a dark gray silty loam, varying from very shallow to 10 inches deep, which grades into a stiff clay, becoming more impervious with depth. It becomes hard and compact on drying, but it is easily broken up into a mellow loam if plowed when in proper condition of moisture. This is an upland type, and occupies gently rolling prairies. Owing to the topography of the country, the type has good surface drainage. The Oswego silt loam is derived from the weathering of the underlying rock, this usually being shales, with occasional interbedded layers of sandstone and limestone. (1050 Ib. P.) "The Oswego silt loam is not a strong soil It is better adapted to wheat than to any of the other crops grown in the area, but, even with wheat, commercial fertilizer costing about $1.25 an acre is used on ANALYSIS BY THE UNITED STATES BUREAU 147 this soil, while none is deemed necessary on the other soils." (Report for 1903. Page 897.) W abash silt loam (Kansas) "varies from 12 to 24 inches in depth and con- sists of a dark brown to black heavy silt loam. It is easily cultivated and readily kept in good tilth. The subsoil consists of a compact and rather heavy brown or yellowish silt loam. It occurs as long, narrow, tracts in the creek valleys and along the outer edges of the river valleys. The type occupies a rather low position in. stream valleys and on gentle slopes. Its surface is nearly level or gently sloping. It forms first bottoms of smaller streams and second bottoms of larger ones. It is well drained naturally. The type has been deposited by water, the surface consisting largely of material washed from the surrounding hills, which are made up of shales and limestones. This wash from the hills is continually adding to the type. " (1140 Ib. P.) "Corn is the most important crop, and yields from 30 to 75 bushels per acre, 40 to 45 bushels being an average yield in ordinary seasons. Alfalfa, a very important crop on this type, yields 3 to 5 cuttings a year, and averages about i ton per acre for each cutting. The average an- nual yield is probably 3 or 4 tons of cured hay per acre. Wheat yields from 20 to 35 bushels per acre. . . . The land is cropped constantly, but as yet the yields have not diminished greatly, although no fertilizer and very little manure is used. The soil is naturally rich in organic matter, which may account for its continued productiveness. Corn is often cropped year after year on this type, and no system of rotation is used." (Report for 1906, page 932.) Hagerstown day (Kentucky) "has a heavy texture, and varies from 3 to 12 inches in depth. It is yellow or brown in color. The subsoil is a heavy yellow clay, extending to a depth of 3 or more feet. This soil type is derived from limestones and shales. These rocks offer considerable resistance to disinte- gration, and the soil may therefore be more thoroughly leached than would be the case were the rocks more readily decomposed. The surface is rather rough, rounded hills being dominant features. Surface washing has been great, and the soil is generally shallow, the depth depending on its position. This is a residual soil, being formed from the breaking down in place of the underlying limestones and shales." (3490 Ib. P.) "Tobacco yields from 800 to 1200 pounds; wheat from 25 to 35 bushels; corn from 25 to 40 bushels; and hay from i? to 2 tons to the acre. . . . On the stony phase of this soil the same crops are produced, but the yields are lower — tobacco, 500 pounds ; corn, about 25 bushels ; wheat, less than 12 bushels. . . . The Hagerstown clay is a good grain and grass land, but it is rapidly deteriorating from continuous surface washing. . . . Unless better methods are speedily adopted, this soil type will soon reach the condition of its stony phase, locally known as the ' barren limestone' land. " (Report for 1903, page 626.) Hagerstown loam (Tennessee) " consists of brown or yellowish brown mellow loam from 9 to 12 inches deep. It is underlain by a yellow to reddish yellow 148 SCIENCE AND SOIL stiff loam or light clay loam, -which becomes a more pronounced red in depth. Traces of chert are found in both soil and subsoil. This type was formed by the slow weathering of limestones. In this soil the weathering has been so complete and the leaching so excessive that the lime of the disintegrated stone has been largely washed from the soil. The type has a moderately rolling sur- face, and has good surface drainage, but the subsoil is rather impervious. The underlying limestone comes near the surface in some places, owing to erosion. " (1050 Ib. P.) "The Hagerstown loam is all used in the extensive system of general farming which is practiced throughout the area. Corn yields from 15 to 30 bushels, with a probable average of 22 bushels per acre. Wheat yields from 5 to 20 bushels, with an average of 10 bushels, and the compara- tively small amount of hay which is grown yields an average crop of i ton per acre." (Report for 1903, page 584.) Houston clay (Alabama) "has resulted from the weathering of rotten limestones or chalks of Cretaceous time. Owing to its proximity to the soft and easily broken down lime rock, this soil is highly calcareous, and often contains lime concretions, especially in the subsoil. It may be considered to be of comparatively recent origin .and as a residual Coastal Plains soil. The soil is a gray, brown, or black loamy clay, 6 inches deep. This is underlain with 3 feet or more of heavy gray or mottled yellow clay. The surface is gently rolling and the drainage very good. Agriculturally, the soil is lighter than would be expected, from its high clay content. This may be due to floccula- tion by the high percentage of lime present. " (5150 Ib. P.) "The Houston clay, while clodding badly when plowed too wet, and requiring care in its management, is a very strong and productive soil." (Report for 1905, page 464.) Cecil clay (North Carolina) "is found on uplands, gentle slopes, and roll- ing lands of the Piedmont Plateau. The Cecil clay is a residual soil, result- ing from the disintegration of a number of rocks, differing in mineralogical characters. Granites, gneisses, schists, and other somewhat similar rocks have contributed to the formation of this type, and so thorough have been the dis- integration and decomposition that the same red clay results from all. There is such a gradual change from soil to the parent rock that there is generally no sharp line between the two. The soil consists of a heavy red loam, contain- ing many sand grains of the original minerals forming the rocks from which the soil is derived. It is shallow, averaging about 5 inches. The subsoil is a stiff, tenacious red clay to a depth of 3 or more feet. It becomes heavier at greater depths. Natural drainage is fairly good, probably due to the sand and rock fragments contained in soil and subsoil." (960 Ib. P.) "The soil is generally thin, but can be deepened by proper methods of cultivation and by green manuring. When so deepened, it assumes the properties of a heavy clay loam, and is very productive. It requires, however, considerable care and labor to maintain its fertility." (Report for 1901, page 55.) ANALYSIS BY THE UNITED STATES BUREAU 149 The average yields of corn, wheat, and oats are reported as 18, 12, and 20 bushels, respectively, per acre. In the description of this same type of soil for the Leesburg area of Virginia, the follow- ing statements were recorded by the field men of the Bureau of Soils : "The soil responds readily to applications of lime, and is much benefited by its use. Much commercial fertilizer, as well as lime and barn-yard manure, is used on this soil. In fact, so much acid phosphate has been added of late years that the land has become quite sour, and it is hardly possible to obtain a stand of grass or clover without the use of lime. " (Report for 1903, page 221.) Porter's black loam (Virginia) "is a loose, mellow black loam, averaging about 12 inches deep. The subsoil is slightly heavier and of a light brown to yellowish color. In depressions and coves, where wash from the higher ground has accumulated, there is no sharp distinction between soil and subsoil, the loose black loam being several feet deep. Both soil and subsoil contain frag- ments of the rocks whose decomposition has formed the soil — granites, gneisses, and schists. This type occurs principally in the coves of the Blue Ridge Mountains, but is also found upon the tops and upper slopes. " (4630 Ib. P.) "Locally the Porter's black loam is called 'black land' and ' pippin land,' the latter term being applied because, of all the soils in the area, it is preeminently adapted to the production of the Newtown or Albe- marle Pippin. This black land has long been recognized as the most fertile of the mountain soils. It can be worked year after year without apparent im- pairment of its fertility." (Report for 1902, page 210.) Chester mica loam (Maryland) "as its name indicates, is characterized oy a great quantity of micaceous particles. It is derived from granites, gneisses, and other micaceous rocks over which the type lies. It is strictly a resid- ual soil and consists of a brownish loam 10 to 15 inches deep, underlain by a lighter colored, heavier loam, also containing mica. The surface varies from gently rolling to somewhat hilly. " (1130 Ib. P.) "It is not naturally a strong soil, but is susceptible of being made quite fertile and productive through intelligent tilling and manuring." (Report for 1901, page 222.) Collington sandy loam (New Jersey) "has resulted from the weathering of the greensand, or glauconite, of New Jersey. The subsoil, which comes within 6 or 8 inches of the surface, is a sticky, tenacious, claylike material, yel- lowish or greenish in color. Owing to its relations to the greensand deposits, this type differs from the other Coastal Plains soils. " (From 260 Ib. P. in surface to 27,600 Ib. P. in lower subsoil.) " Since millions of tons of this greensand marl have been employed as fertilizers, it is at once evident that any soil possessing a subsoil of this material will contain more than the ordinary amounts of potash and lime. When, in addition to this, its phys- ical structure is also well adapted to crop production, it would seem that a particularly valuable soil was formed. . . . The marl specimen was collected SCIENCE AND SOIL as a sample to show the amounts of plant foods in the material actually used as a fertilizer. The potash content is not high for a greensand marl, but the phosphoric-acid content is unusually high. The subsoil analysis (by acid digestion) reveals the fact that the lime, potash, and phosphoric acid of the original material have been extensively dissolved and removed, though fair amounts still remain. " (Report for 1901, page 139.) Unless otherwise stated, the above quotations from the soil survey field men and from Bureau of Soils Bulletin 54 refer specifi- cally to the areas in which the samples analyzed (Table 22) were collected. In general, there is very distinct correlation between the compo- sition of these extensive soil types and their natural productive- ness as recorded by the soil surveyors themselves some years be- fore the chemical analyses were made. It should be kept in mind that the data reported in Table 22 are for amounts in 2 million pounds of ignited soil, and are thus somewhat higher than, and not strictly comparable with, the results of analyses of the ordinary dry soil. It is important, also, to know that most of the 27 type soils described are found not only in the state and area in which these analyzed samples were taken, but are widely distributed throughout the respective formations, as the Coastal Plains, glacial areas, Piedmont, or other regions. Thus the 1903 Report of Field Operations of the Bureau of Soils mentions that Norfolk sand was found that year in New York, Delaware, Maryland, Virginia, North Carolina, Georgia, Florida, and Alabama; and Marshall black clay loam has been reported for Ohio, Indiana, Michigan, Wisconsin, Illinois, Iowa, Minnesota, South Dakota, and North Dakota. The Bureau of Soils includes in the one soil type (Marshall silt loam) the common brown silt loams of the Middle and Upper Illinoisan glaciations, of the Pre-Iowan, lowan, and Early Wiscon- sin glaciations, in Illinois, as well as soil in the Janesville and Viroqua areas of Wisconsin, in the Grand Island and Staunton areas of Nebraska, and in the Jamestown area of North Dakota, with other areas in Colorado, Minnesota, Kansas, Missouri, Iowa, Indiana, and Louisiana; but it is apparent that the ultimate chemical composition of the soil is not considered among the characteristics required by the Bureau for a soil type. Thus the Marshall silt loam (brown silt loam) of the Middle Illinoisan glacia- ANALYSIS BY THE UNITED STATES BUREAU 151 tion contains 1 1 70 pounds of total phosphorus in 2 million of dry soil (see Table 15), while 2450 pounds are reported in 2 million pounds of ignited soil of the Wisconsin area (see Table 22). Doctor Fraps finds 480 pounds of acid-soluble phosphorus in 2 million pounds of the Houston day of Texas from samples furnished him by the Bureau of Soils, while Table 22 shows 5150 pounds of total phosphorus in 2 million pounds of ignited Houston clay of Alabama. The Texas soil is evidently very deficient in phosphorus, but this is certainly not the case with the Alabama soil, which, it will be seen, outranks in phosphorus content every other soil reported in Table 22. The Bureau of Soils has not reported the ultimate chemi- cal analyses of different samples of the same type soil from different areas, so that it is impossible to make any such comparative study from the Bureau's data alone. In the author's opinion, the exact chemical data from which Table 22 is derived, and the careful descriptions given of the type soils analyzed, constitute the most valuable contribution of the United States Bureau of Soils to American agriculture. This absolute invoice of plant food, together with the description of physical properties, crop adaptations, and topographic features, furnishes a basis for the intelligent consideration of possible permanent and profitable systems of agriculture. Actual field experiments, to determine the rate at which the plant food can be made available, are lacking, and no report is made of the nitrogen content of the soils or of the limestone present or required. The percentages of " lime " (CaO) and magnesia (MgO) are given in Bulletin 54, but these signify little or nothing in relation to lime. Even the very acid Marion silt loam of Clay County, Illinois (gray silt loam on tight clay), is reported by the Bureau to contain .56 per cent of CaO (5.6 tons in 2 million pounds of soil), whereas it contains neither calcium oxid nor calcium carbonate, the calcium present existing usually in acid silicates. In general, the work of the Bureau of Soils has been directed toward a study of crop adaptation, in accordance with a somewhat prevalent notion that every soil is intended to grow some definite crop or crops, and that success will be attained if the proper crop is found for the special soil. While all must recognize that the natural adaptation of soil and crop is an important factor in many 1 52 SCIENCE AND SOIL cases, in the author's opinion it is a matter which has been given undue consideration in comparison with other extremely important factors. Even in the common practice of agriculture, soils at first well adapted to the growing of a certain crop do not remain so adapted. The fact is too well known to need illustration that specific crops are often grown with success for years finally to fail and be aban- doned for some other successful crops, which in turn finally give way to others. Thus good wheat land finally becomes poor wheat land, but still remains good for timothy hay, which in turn gives way to red top, and this may be followed by partial abandonment of the land for crop production. At any stage in this process of soil depletion, the land may be restored to its original power to produce wheat, by adopting the proper systems of soil enrichment. When land refuses longer to grow any crop wyhich it has formerly produced writh satisfaction and profit, the landowner should, as a very general rule, find out wrhat the trouble is, and then proceed to remedy it; but, instead of meeting and overcoming such diffi- culties, the American farmer has literally run away from them; either by seeking newer lands or by adopting any other crop which the land would still produce. The most common staple crops can be grown on almost any soil if it is well drained, well watered, and sufficiently rich. Of course, the matter of crop adaptation must not be ignored, but if we would grow either plants or animals, we must not neglect the food supply. CHAPTER X CROP REQUIREMENTS FOR NITROGEN, PHOSPHORUS, AND POTASSIUM A STUDY of Table 23 is sufficient to make one familiar with the requirements of the more important crops of the United States for the three plant-food elements that are now recognized as having money values in commercial fertilizers. Information is also given regarding the amounts of these three elements in different parts of the crop, as in grain, straw, corn stover, and cotton stalks and lint, in order that it may be known with some degree of accuracy how much of each element is removed from the soil in crops and how much is sold from the farm in different kinds of farm produce. The ideal practice is to return to the soil, either directly or in farm manure, all plant food not sold from the farm. The data given in Table 23 are on the basis of pounds per acre for crop yields which are large, but which, when the best condi- tions are provided, have been and may be produced with very great profit, — yields that may well stand as ideals, desirable and pos- sible to be attained. Approximately proportionate amounts of plant food would be required for any other yields. Thus, if it is preferred to plan to make possible yields only one half as large, then the amounts given in Table 23 may be divided by two. (In Section 3 of the Appendix, data are reported showing the more com- plete composition of a much larger number of crops, but the re- sults there given are derived from a smaller number of analyses than are represented for the crops reported in Table 23; and, consequently, some differences are to be expected.) The value of the elements is computed on the basis of the present market prices for plant food from the most abundant natural deposits, delivered in car-load lots to central Illinois, and in suit- able condition for direct application to the land. Nitrogen in sodium nitrate 15 cents a pound. Phosphorus in ground raw phosphate ... 3 cents a pound. Potassium in kainit 6 cents a pound. 154 SCIENCE AND SOIL TABLE 23. FERTILITY IN FARM PRODUCE Approximate maximum amounts removable per acre annually PRODUCE ] 3OUNDS MARKET VALUE Nitro- Phos- Potas- Nitro- Phos- Potas- Total Kind Amount gen phorus sium gen phorus sium Value Corn, grain 100 bu. IOO 17 19 $15.00 $ -51 fc I.I4 $16.65 Corn stover 3T. 48 6 52 7-20 .18 3.12 10.50 Corn crop l 148 23 71 22.20 .69 4.26 27-I5 Oats, grain 100 bu. 66 II 16 9.90 •33 .96 11.19 Oat straw . . 4T. 31 5 52 4.65 •15 3.12 7.92 Oat crop 07 16 68 14.55 .48 4.08 IQ.II Wheat, grain . 50 bu. 7 1 71 12 13 10.65 •36 *f.V .78 y 11.79 Wheat straw . 2*T. 25 4 45 3-75 .12 2.70 6-57 Wheat crop 96 16 58 14.40 .48 3-48 18.36 Soy beans . . 25 bu. 80 13 24 I2.OO •39 1.44 13-83 Soy bean straw 2JT. 79 8 49 11.85 .24 2-94 15-03 Soy bean crop . i59 21 73 23-85 •63 4-38 28.86 Timothy hay . 3T. 72 9 7i IO.80 •27 4.26 15-33 Clover seed 4 bu. 7 2 3 1.05 .06 .18 1.29 Clover hay 4T. 1 60 2O 120 24.OO .60 7.20 31.80 Cowpea hay . 3T. 130 14 98 19.50 .42 5.88 25.80 Alfalfa hay 8T. 400 30 192 6O.OO i. 08 11.52 72.60 Cotton lint . . 1000 Ib. 3 0.4 4 •45 .01 ' .24 • 70 Cotton seed 2000 Ib. 63 II 19 9-45 •33 1.14 10.92 Cotton stalks . 4000 Ib. IO2 18 59 15-3° •54 3-54 19.38 Cotton crop . 1 68 29.4 82 25.20 .88 4.92 31.00 Potatoes . . 300 bu. 63 13 90 9-45 •39 5-4° 15-23 Sugar beets 20 T. IOO 18 i57 15.00 •54 9.42 24.96 Apples . . . 600 bu. 47 5 57 7-05 •15 3-42 10.62 Leaves . . . 4T. 59 7 47 8.85 .21 2.82 11.88 Wood growth . Atree 6 2 5 .90 .06 •3° 1.26 Total crop . 112 IA 109 1 6. 80 42 6 Zd 21: 76 Fat cattle . . 1000 Ib. 25 T- 7 i 3-75 •T- .21 w*ot .06 *O' /** 4.02 Fat hogs . . 1000 Ib. 18 3 i 2.70 .09 .06 2.85 Milk .... i oooo Ib. 57 7 12 8-55 .21 •72 9.48 Butter . . . 400 Ib. 0.8 0.2 O.I .12 .OI .01 .14 1 To this might also be added 1000 pounds of corncobs, containing 2 pounds of nitrogen, less than J pound of phosphorus, and a pounds of potassium. CROP REQUIREMENTS 155 The figures given in Table 23 are based upon averages of large numbers of analyses of normal products, of which some have been made by the author and his associates, and many others by various chemists in America and Europe. These averages are trustworthy for large crops of good quality. Abnormal or special crops may vary considerably from these averages. Thus, we have high-protein corn and low-protein corn, one strain requiring 50 per cent more nitrogen, and somewhat more phosphorus, than the other (Illinois Bulletins 87 and 128); and it has been shown, for example, that alfalfa and cowpeas are not only much more productive, but also much richer in nitrogen, when grown on normal soils with the proper root-tubercle bacteria than without bacteria. On the whole, however, it is as nearly correct to say that a fifty-bushel crop of wheat requires 96 pounds of nitrogen and 16 pounds of phosphorus as it is to say that a measured bushel of wheat weighs 60 pounds. It may be said that other similar crops resemble somewhat closely those given in Table 23 as to plant-food requirements. Thus rye and barley are not markedly different in requirements from wheat and oats, considering equal yields in pounds of grain and straw. Other root crops may be compared with sugar beets, other grasses with timothy, hay from other annual legumes with cowpea hay, and other biennial and perennial legumes may be compared in a general way with red clover and alfalfa. How many years would be required to sell as much phosphorus from the farm in cotton lint yielding 2 bales (of 500 pounds each) per acre as in 4 tons of clover hay, which may be produced in the two cuttings in one season? Compare the nitrogen and potassium contained in 100 bushels of corn and in 20 tons of sugar beets. Compare wheat and clover in plant-food requirements. Assuming that two thirds of the nitrogen used by the clover plant is deposited in the tops and only one third in the roots, and that a given soil will furnish as much nitrogen to a growing clover crop as to a growing wheat crop, what is the effect upon the total nitrogen content of the soil of growing clover if all of the tops are removed ? Compute the cost of commercial nitrogen for a 5o-bushel crop of corn, assuming that 40 per cent of the nitrogen applied will be lost in drainage waters. CHAPTER XI SOURCES OF PLANT FOOD IF the productive capacity of American soils is to be maintained, elements of plant food which are present in such small amounts as to limit the crop yields even under good systems of farming must be returned to the soil as needed, and information is given in Table 24 to show the average quantities in pounds of the different valu- able elements of plant food contained in one ton of average fresh farm manure, rough feeds and bedding, and other fertilizer ma- terials. In computing the value of plant food in these materials, nitrogen is counted at 15 cents a pound and potassium at 6 cents a pound; while phosphorus is counted at 3 cents a pound in raw rock phos- phate, at 10 cents a pound in bone meal, and at 12 cents a pound in acid phosphate, these prices being based upon the usual average market values for the standard fertilizing materials in such quanti- ties as ought to be purchased by farmers, either singly or by two or more uniting. From the data given in Tables 23 and 24 it is a simple matter to compute the amounts of average manure or other fertilizers neces- sary to be applied to the land to replace the plant food removed in any rotation of crops. Observe, for example, that a four-year rotation, including corn for two years, oats with clover seeding the third year, and clover for hay and seed crops the fourth year, would require 39 tons of manure to supply the nitrogen, 41 tons to supply the phosphorus, 40 tons to supply the potassium, assum- ing the yields given in Table 23, and counting that the clover se- cures from the air as much nitrogen as is removed in the hay and seed crops. Observe that one ton of raw rock phosphate or one ton of steamed bone meal contains more phosphorus than 100 tons of average manure. Observe that 250 pounds of phosphorus can be purchased for $7.50 in ground natural rock phosphate, for $25.00 156 SOURCES OF PLANT FOOD in steamed bone meal, for $30.00 in acid phosphate, and for $65.00 in " complete " fertilizer. TABLE 24. FERTILITY IN MANURE, ROUGH FEEDS, AND FERTILIZERS NAME OF MATERIAL POUNDS PER TON MARKET VALUE PER TON Ni- tro- gen Phos- phor- us Po- tas- sium Nitrogen Phos- phorus 'otassium Total Value Fresh farm manure . . IO 2 8 $ 1.50 $ .24 $ .48 $ 2.22 Barnyard manure l . IO 3 8 1.50 •36 .48 2-34 Corn stover .... 16 2 17 2.40 .24 1.02 3.66 Oat straw 12 2 21 1.80 .24 1.26 3.-?o Wheat straw .... IO 2 18 1.50 .24 1.08 \J tJ 2.82 Clover hay .... 40 5 3° 6.00 .00 i. 80 8.40 Cowpea hay .... 43 5 33 6-45 .60 1.98 9-°3 Alfalfa hay .... 5° 4 24 7-5° .48 1.44 9.42 Dried blood .... 280 42.00 42.00 Sodium nitrate . . . 310 46.50 46.50 Ammonium sulfate . . 400 60.00 60.00 Raw bone meal . . . 80 180 12. OO iS.OO 30.00 Steamed bone meal . . 20 250 3-00 25.00 28.00 Acidulated bone meal . 40 140 6.00 16.80 22.80 Raw rock phosphate 250 7-50 7-5° Acid phosphate . . . 125 15.00 15.00 Double superphosphate 400 48.00 48.00 Basic slag phosphate . 1 60 16.00 16.00 Potassium chlorid . . 850 51.00 51.00 Potassium sulfate . . 850 51.00 51.00 Kainit 200 I2.OO I2.OO Wood ashes 2 . . . . 10 IOO i. 20 6.00 7.2O "Complete" fertilizer3 33 88 33 (?) (?) (?) 23.00 (?) 1 About two tons of fresh farm manure are required to produce one ton of com- mon barnyard manure six months old, with losses about as indicated. 2 Wood ashes also contain about 1000 pounds of lime (calcium carbonate) per ton. 3 This is the average composition and the average selling price of twelve brands of so-called "complete" fertilizer offered for sale in Illinois. Only 70 pounds of the phosphorus is guaranteed available, 18 pounds being insoluble. The cost of 88 pounds of phosphorus in raw rock phosphate would be $2.64. 158 SCIENCE AND SOIL If the element calcium becomes deficient in the soil (and it does in some cases), the most economic source is ordinary limestone ; and, if magnesian limestone is applied, both calcium and mag- nesium are thus added to the soil. Kainit also supplies magnesium. Sulfur would be furnished in applications of acid phosphate, land-plaster, potassium sulfate, or kainit, as well as in magnesium sulfate and sodium sulfate, both of which are sometimes to be had as waste products or by-products. Iron sulfate (FeSO4) is a common by-product in certain manu- facturing processes, and strenuous efforts have been made from time to time to encourage its use as a fertilizer. Since numerous investigations have been conducted both in Europe and America to ascertain its fertilizing value, it is easily possible to select, from the many results thus secured, some few which indicate appre- ciable or even marked benefit. These results, however, have failed of verification. As a general average, iron sulfate produces less benefit than land-plaster, and sometimes detrimental effects are shown. A fair consideration of all results of carefully con- ducted experiments certainly leads to the conclusion that the use of iron sulfate as a fertilizer cannot be recommended in systems of soil improvement ; although, like common salt (NaCl), it may sometimes produce a stimulating action sufficient to cover the cost where it can be secured at less expense than land-plaster, common salt, or other soluble salts. PART II SYSTEMS OF PERMANENT AGRICULTURE FOR practically all of the normal soils of the United States, and especially for those of the Central states, there are only three con- stituents that must be supplied in order to adopt systems of farm- ing that, if continued, will increase, or at least permanently maintain, the productive power of the soil. These are limestone, phosphorus, and organic matter. The limestone must be used to correct acidity and sometimes to supply the element calcium. The phosphorus is needed solely for its plant-food value. The supply of organic matter must be renewed to provide nitrogen from its decomposition and to make available the potassium and other essential elements contained in the soil in abundance, as well as to liberate phosphorus from the raw mineral phosphate naturally contained in or applied to the soil. Other fertilizer materials have some value, and sometimes great 'value, on uncommon or abnormal soils, and certain other substances are powerful soil stimulants, especially on soils deficient in organic matter; and, if applied with intelligence, they may sometimes be used temporarily with advantage and justification, but they are unnecessary and, as a very general rule, they are unprofitable, in good systems of soil improvement. There are, of course, numerous and more or less extensive areas of abnormal soils, such as the residual sands and the peaty swamp lands (both of which are very deficient in potassium), and also soils exceedingly rich in phosphorus, as in the geologic neigh- borhood of the natural phosphate deposits in the Central Basin of Tennessee and the Blue Grass Region of Kentucky. 159 CHAPTER XII LIMESTONE CALCIUM carbonate, in the form of chalk or marl, has been used for soil improvement since the beginning of agricultural history. Large use has been made of these natural materials in England and France, especially. An English record of 1795 mentions the " pre- vailing practice of sinking pits for the purpose of chalking the surrounding land therefrom," and states that " the most experi- enced Hertfordshire farmers agree that chalking of lands so circum- stanced is the best mode of culture they are capable of receiving." On the famous Rothamsted Experiment Station it has been found that the fields that had received liberal applications of this natural limestone a century ago are still moderately productive, while certain fields remote from the chalk pits which show no evidence of such applications are extremely unproductive. Director Hall of the Rothamsted Experiment Station states that many of the farmers in that vicinity are still reaping profitable crops from lands enriched by the heavy applications of chalk made by their ancestors many years ago. There appears to be no record that these easily pulverized lime- stone materials have ever been burned in order to increase their agricultural value. The productive power and durability of the natural limestone soils is indicated by the time-honored truth, " A limestone country is a rich country." Where such natural materials as chalk and marl have not been accessible, more or less use has been made of water-slacked or air- slacked lime; because, by burning and slacking, limestone rock may be reduced to powdered form and thus distributed over the land. With the development of rock-crushing and rock-grinding machinery, pulverized natural unburned limestone can be had, and where this material can be gotten at reasonable cost, it replaces all other forms of lime used for the improvement of nor- mal soils. 160 LIMESTONE 161 In the " Georgical Essays " (1777 edition), we find an article by T. Henry, F.R.S., on the " Action of Lime and Marl as Manures," in which the following statements occur: "The lime, that we may come nearer to nature in our imitation, should not only be slacked, but be exposed to the open air, and often turned for several months, that it may recover its air; for it requires a long series of time be- fore it recovers the whole of which it has been deprived in calcination "I find that Doctor Home thinks that lime produces little effect on vegeta- tion till it is become effete. It may be known to have recovered its air by its no longer forming lime water, and by effervescing violently with acids without growing hot. If, however, the method described in the last note be used, it will be sufficient, if the lime be fallen, without waiting for the recovery of its air, as this point will be acquired during the long time which the mixture is to be exposed to the action of the atmosphere. . . . "Upon the whole, may we not conclude that lime, in most cases, is a stronger manure, when it has recovered the air of which it has been deprived in calci- nation, than it is when brought fresh from the kiln ; and that when procured for the purposes of agriculture, its efficacy and permanency will in general be increased, by mixing it, in its effete state, with the other ingredients which enter into the composition of marl?" -. ' ' \ " When limestone is burned, the calcium carbonate (CaCO3) is decomposed, the carbon dioxid (CO2) passes off as a gas, leaving the product calcium oxid (CaO), which constitutes 56 per cent by weight of the limestone used. When exposed to the moisture of the air or soil, the quicklime (CaO) quickly takes up water and forms calcium hydroxid, Ca(OH)2, sometimes called hydrated lime, which means merely water-slacked lime. The product is the same whether the slack- ing (hydrating) is performed by the manufacturer at large expense, or by the farmer at little or no expense. When slacked lime is exposed in the air or soil, carbon dioxid is gradually absorbed, and the calcium carbonate is thus reformed. Thoroughly air-slacked lime is exactly the same material as fine- ground limestone. In other words, no matter what form of lime we apply to the soil, the benefit derived during the subsequent months or years is due to one and the same compound, calcium carbonate. These facts alone would be sufficient, perhaps, to lead one to use ground natural limestone in preference to the disagreeable caustic 1 62 SYSTEMS OF PERMANENT AGRICULTURE lime, but there are other facts worthy of the most careful consid- eration. Burned lime, whether fresh or hydrated, is known always as caustic lime. According to Webster's Dictionary, the word caustic means " capable of destroying the texture of anything or eating away its substance by chemical action." This definition well describes the action of caustic lime upon the organic matter of the soil. The lime breaks down the organic compounds and unites with the liberated carbon dioxid or other acid products. Not all of the reactions involved are understood, but the general effect is well known, and its long recognition in European countries has given rise to the proverbial expressions, "Lime, and lime without manure, Will make both farm and farmer poor," and " Kalk macht die Vater reich, aber die Sohne arm." (Lime makes the fathers rich, but the sons poor.) Caustic lime is not only a powerful agent in hastening the de- struction of organic matter, but it also has some power to increase the solubility of phosphorus and potassium, all of which may be of special help to legume crops; and if such crops are grown and removed from the land and the decaying roots and residues used as a further stimulant for the production of wheat, corn, or other crops, more rapid progress can be made toward land ruin than where no lime is used. On the other hand, even caustic lime can be used with profit if ample provision is made to replace the organic matter destroyed and also to restore the phosphorus (and potassium if necessary) removed in the crops. The caustic action of slacked lime on the skin or flesh is familiar to all, but a child can play in ground limestone as safely as in the soil of the garden. The chief reason, and usually the only justifiable reason, for applying lime to soils is to correct, or neutralize, soil acidity. The fermentation and decay of nearly all forms of organic matter is accompanied by the formation of acids, including carbonic acid, nitric acid, and various organic acids, such as the well-known lactic acid of sour milk, acetic acid of vinegar from apple juice, various LIMESTONE 163 acids in ensilage and sauerkraut, etc. Souring is usually the first stage in the process of decay of organic matter. Thus, there are two principal effects produced by applying lime to soils : one of these is to furnish a base for neutralizing the acids that may exist in the soil or that may form in such necessary processes as nitrification, and the other is a more active decomposi- tion or destruction of the soil itself, especially of its organic matter or humus content. To correct the acidity of sour soils is certainly a very desirable and profitable use of lime. Clover, alfalfa, alsike, cowpeas, soy- beans, and most other valuable legumes will not thrive on soils that are strongly acid. To be sure, such crops can be made to grow on acid soils by liberal applications of farm manure or other fer- tilizers, but the nitrogen-gathering bacteria of such legume plants do not properly develop and multiply in acid soils, and consequently the legumes do not have the power which they should have to accumulate large quantities of atmospheric nitrogen by means of the root-tubercle bacteria. Furthermore, the process termed nitrification by which the nitrifying bacteria transform the in- soluble organic nitrogen, in farm manure and plant residues, into soluble nitrate nitrogen, the form in which it becomes available as plant food, is greatly promoted by the presence of limestone and retarded by acid conditions. The use of some form of lime for correcting the acidity of soils, and thus encouraging nitrification and the growth of clover and other legumes with their wonderful power to enrich the soil in nitrogen, is certainly good farm practice. Any form of lime which is finely divided and can be thoroughly mixed with the soil will serve this purpose, whether it be ground limestone, marl, or chalk, or fresh-burned lime, water-slacked lime, or air-slacked lime. The one effect of lime, due to its basic property, results in a building-up process, through the increased growth of legumes and nitrogen-gathering bacteria; while the other effect, the decompo- sition of the soil, produced by its caustic property, is in all respects a destructive process, serving only to destroy humus and to liber- ate and reduce the stock of plant food stored in the soil. Whether this second effect is desirable, will depend upon the soil itself. On soils which are exceedingly rich in organic matter, such as peaty 1 64 SYSTEMS OF PERMANENT AGRICULTURE soils and other swamp soils, it would seem altogether rational to make temporary use of caustic lime to hasten the decomposition of the soil and consequent liberation of nitrogen, if such treatment is necessary, which is not usually the case. There may possibly be conditions under which soils contain large amounts of phosphorus and potassium which are too slowly available for profitable crop production, and in such cases it might be good farm practice for a time to make use of lime to hasten the liberation of these mineral elements of plant food. We should bear in mind, however, that this use of lime on a soil which is already deficient in nitrogen, or other plant food, only serves to still further exhaust the soil of its meager supply of these elements. Without a doubt, this is the most common condition and the most common effect of the continued use of caustic lime. It is true that the immediate effect is usually somewhat increased crops, but it should be borne in mind that when a farmer pays out money for lime to be used for this purpose, he is purchasing a stimulant which will ulti- mately leave his land in worse condition than before, especially in the loss of nitrogen and organic matter. Of course, the landowner must be governed somewhat by the cost of the material. As a rule, pulverized limestone will be both the best and the most economical form of lime to use, wherever it can easily be obtained. If caustic lime be used, we should make special provision to maintain the humus in the soil by making even larger use of farm manure, legume crops, and green manures. It might be expected that burned lime would produce a greater increase in the crops for the first year or two than would be pro- duced by the ground limestone, more especially where the mineral elements, phosphorus and potassium, are not applied; for the reason stated, that ground limestone produces only the milder ac- tion, chiefly of correcting the acidity of the soil and thus encourag- ing the multiplication and activity of the nitrogen-gathering and nitrifying bacteria; whereas, the burned lime not only produces this same effect, but it also acts as a powerful soil stimulant, or soil destroyer, attacking and destroying the organic matter and thus liberating plant food from the soil, usually resulting in more or less waste of valuable nitrogen and humus. The most extended investigation ever conducted relating to the LIMESTONE use of burned lime and ground limestone in comparative tests is reported by the Pennsylvania Experiment Station (Report 1902). Four plots were treated with burned lime (slacked before being spread) at the rate of two tons per acre once in four years. Four other plots were treated with ground limestone at the rate of two tons per acre every two years. A four-year rotation was practiced, consisting of corn, oats, wheat, and hay, the hay being mixed timothy and clover, seeded on the wheat land in the spring. By having four sets of plots, each crop was grown every year. Seven products were obtained and weighed each year; namely, corn, corn stover, oats, oat straw, wheat, wheat straw, and hay. TABLE 25. PENNSYLVANIA EXPERIMENTS WITH BURNED LIME AND GROUND LIMESTONE Twenty Years' Produce per Acre CORN OATS WHEAT HAY, Grain Stover Grain Straw, Grain Straw (19 yr-) (Bushels) (Tons) (Bushels) (Tons) (Bushels) (Tons) None 8lQ 18.8 678 14.3 27O 13.2 24.0 Burned lime .... 699 16.5 6l7 I7.8 318 14.6 23.6 Ground limestone . . 798 18.6 733 20.4 331 16.6 29.2 Thus, after twenty years' results had been obtained (1882 to 1901), the Pennsylvania Station reports data showing that with every product a greater total yield had been obtained from the plots treated with limestone than from those treated with caustic lime. Furthermore, with every product whose total yield for the last eight years was greater than the total yield of the first eight years, the limestone produced a greater increase than the caustic lime; and with every product whose total yield for the last eight years was less than the total yield of the first eight years, the decrease was less where limestone was used than where caustic lime was applied (oat straw alone excepted). This is significant, in that it demonstrates the tendency of caustic lime with continued use to exhaust or destroy the fertility of the soil. In discussing these investigations, Doctor Frear of the Pennsylvania Station says: 1 66 SYSTEMS OF PERMANENT AGRICULTURE " In each case the yields with the carbonate of lime showed superiority under the conditions of this experiment over those following an equivalent application of caustic lime. " After these experiments had been in progress for sixteen years, the soil of each of the four plots in each test was sampled for analy- sis. The average nitrogen content for the four plots receiving ground limestone was found to be 2979 pounds per acre to a depth of 9 inches, while only 2604 pounds were found in the soil treated with caustic lime. This difference of 375 pounds of nitrogen is equal to the nitrogen contained in 37! tons of farm manure. In other words, the data indicate that the effect of caustic lime as compared with ground limestone was equivalent to the destruction of 37^ tons of farm manure in 16 years, or more than two tons a year to the acre. Or, if we count the soil nitrogen worth 15 cents a pound (a fair market price), there is a liberation of more than $7.00 worth of nitrogen for every ton of burned lime used during the 1 6 years. The estimation of humus in these soils, based upon the determi- nation of organic carbon (multiplied by Wolff's factor, 1.724), showed the soil receiving limestone to contain 38.9 tons of humus per acre to a depth of 9 inches (counting 300,000 pounds of soil to the acre-inch), while only 34.2 tons of humus remained in the soil treated with caustic lime. If 4 tons of farm manure contain only i ton of dry matter (average fresh farm manure contains about 75 per cent of water), and if 2 tons of dry matter would be re- quired to make i ton of humus (when exposed to the weather, manure usually loses half of its dry-matter content within one year or less), then this difference of 4.7 tons of humus would be equal to 37.6 tons of fresh farm manure, which represents the loss from the destructive action of caustic lime as compared with ground limestone. During the 20 years, the land treated with ground limestone produced per acre 99 bushels more corn, 116 bushels more oats, 13 bushels more wheat, and 5.6 tons more hay, than the land treated with caustic lime. Counting 35 cents a bushel for corn, 30 cents for oats, 70 cents for wheat, and $6.00 a ton for hay, the value of the produce from the limestone treatment was $112.15 more than that from the land treated with caustic lime. The total ultimate LIMESTONE 167 effect of the caustic lime for the 20 years was an actual decrease in the yields of all crops except wheat; while the ground limestone produced an increase in all crops except corn, on which the de- crease was only one sixth as much as with caustic lime. If it is true, as indicated by the Pennsylvania experiments, that 8 tons of burned lime, applied during 16 years, released 375 pounds of nitrogen and destroyed organic matter equivalent to 37 tons of farm manure, or more than $7.00 worth of nitrogen and 4^ tons of manure destroyed for each ton of burned lime used, as compared with ground limestone ; and if larger crops were obtained where limestone was used, especially where the practice is extended over several years, and if the ground limestone is sustaining the productive capacity of the soil much better than the burned lime ; then, as a very general rule, we should avoid applying caustic lime to the land, but make liberal use of ground limestone where needed to correct the acidity of the soil and to furnish a natural base, although, as used in these Pennsylvania experiments, without manure and with no return of plant food, the increase in crop yields produced by ground limestone has not been sufficient to pay for the heavy applications. The Maryland Experiment Station has recently reported experi- ments with different kinds of lime, covering eleven years, with a rotation of corn, wheat, and hay (timothy and clover), 1400 pounds of calcium oxid (burned lime) and equivalent amounts of calcium carbonate (ground oyster shells and shell marl) having been applied per acre at the beginning. Four crops of corn, three of wheat, and four of hay were harvested during the eleven years, with the follow- ing total results per acre: TABLE 25.1. MARYLAND EXPERIMENTS WITH LIME PRODUCE IN ELEVEN YEARS KINDS OF LIME USED Corn (Bushels) Wheat (Bushels) Hay (Tons) 4 Crops 3 Crops 4 Crops None . . 08 1.2 2.6o Caustic lime burned from stone ' . . 128 32 3-°9 Caustic lime burned from shells l . . 129 34 3.82 Calcium carbonate in ground shells 148 42 3-97 Calcium carbonate in shell marl . . 145 43 4.29 1 Average of two plots. 1 68 SYSTEMS OF PERMANENT AGRICULTURE In commenting on these results, Director Patterson of the Mary land Experiment Station says: " It will be noted that the car- bonate of lime gave decidedly better results than the caustic lime." Neuffer, of Heilbronn, Germany, has published a book entitled, " Das Kalksteinmehl im Dienste der Landwirtschaft " (The Use of Ground Limestone in Agriculture), in which he advises that ground limestone, and " not burned lime," should be used in the improvement of soils deficient in lime. Porter and Grant, in a recent Farmers' Bulletin issued by the Agricultural Department of the County Council of Lancaster, England, report experiments on manured and unmanured meadow lands, showing that ground limestone is more profitable as an application to grass lands than burned lime, and that it can be economically used on grass lands which are in need of lime. No trustworthy investigations support the use of burned lime in preference to ground limestone; although we have ample in- formation showing that on many soils a moderate use of burned lime in connection with a liberal use of farm manure and green manures yields profitable returns, which would, no doubt, be still more profitable if the burned lime were replaced with ground limestone. The most abundant impurity of limestone is magnesium car- bonate, which sometimes occurs in equal molecular proportion with calcium carbonate, in what is called dolomite (CaCO3 MgCO3) . Limestones containing considerable amounts of magnesium car- bonate are also called magnesian limestones, even though the proportion of magnesium may be less than in dolomite. Dolomitic limestone is usually slightly heavier than ordinary limestone, and it is scarcely attacked by cold hydrochloric or acetic acid, while pure calcium carbonate is rapidly decomposed, the carbon dioxid being liberated as a gas. The molecular weights are 100 for calcium carbonate and 84 for magnesium carbonate, and consequently 84 pounds of the latter has the same power to correct soil acidity as 100 pounds of the former; or 92 pounds of dolomite will correct as much soil acidity as loo pounds of pure ordinary limestone. To determine the amount of limestone present in the soil, or to determine the value of a sample of limestone for use on acid soils, LIMESTONE 169 it is usually sufficient to determine the content of carbonate carbon (or carbon dioxid) and compute from this the equivalent amount of calcium carbonate. Of course, this computation would show that 100 pounds of pure dolomite would be equivalent to about 109 pounds of pure limestone. Agricultural writers have placed upon record the general opinion that magnesian lime is very likely to produce injurious effects when used upon the soil. In his comprehensive and very valuable treatise upon "The Agricultural Use of Lime," Doctor William Frear includes the fol- lowing comments (Report Pennsylvania State College, 1899-1900, pages 14 to 176) : "Lloyd states that lime (CaO) is the only material of value in burnt lime and applies the adjective ' bad ' to a lime containing 60 per cent of lime (CaO) and 30 per cent of magnesia (MgO). Low says of the magnesian limestone of England: 'If applied after being calcined, in the same quantity as other limes, it produces a temporary sterility, burning, as it were, the soil ; hence, it is termed hot lime and is applied in much smaller quantity than other kinds of lime.' This action he attributes, after Sir Humphry Davy, to the longer period of causticity commonly supposed to occur with magnesia. In the form of car- bonate, he says, 'magnesia seems to exercise a highly favorable action; and magnesian limestone may perhaps be regarded as the most valuable of any, since a smaller quantity of it suffices for the ends proposed.' "The subject is quite fully discussed by Storer (Agriculture, 1897, Vol. 2, page 135), who notes that it was early observed by English chemists that certain limestones which had sometimes been found in practice to injure crops, contained magnesia, and that Tennant, on applying calcined magnesia to various soils with different crops, found that his plants either died, were un- healthy, or vegetated very imperfectly ; also, that Knop found, in growing plants by water culture (i.e., in very dilute solutions of plant foods), that magnesium salts are distinctly harmful unless accompanied by abundance of lime, potash, or ammonia salts; by themselves, the magnesium salts caused peculiar mal- formations of the plant roots, followed shortly by the death of the plants. "Storer notes, on the other hand, that Sir Humphry Davy found that the very magnesian limestones to which objection was made, gave very beneficial results on certain soils, and that magnesia, though injurious when present in caustic condition in considerable quantity in ordinary soils, may be beneficial when mixed with peat or where present as carbonate. " In a recent investigation at Rothamsted, Ashby reports a larger fixation of nitrogen by Azotobacter when magnesium carbonate was present than when calcium carbonate was used. For each 1 70 SYSTEMS OF PERMANENT AGRICULTURE gram of carbohydrate (mannite) consumed, 8.92 milligrams of nitrogen were fixed in 6.6 days with magnesium carbonate, and 5.80 milligrams in 4.6 days with calcium carbonate. Ashby says (Journal of Agricultural Science, January, 1907, pages 46, 47) : "With magnesium carbonate there was 50 per cent more nitrogen fixed, and a delay of two days in development. . . . One must conclude, therefore, the magnesium carbonate not only neutralizes more effectually than calcium car- bonate any trace of acidity due to foreign organisms in the early stages of culture, but also prevents butyric fermentation; but at first it inhibits the growth of Azotobacter itself. " Table 26 gives the results of an investigation concerning magne- sium carbonate conducted with the assistance of the author's students and associates at the University of Illinois. The experi- ment bears upon two lines of inquiry — (i) the value of magne- sium carbonate for soil improvement, and (2) methods of correcting this " alkali" when present in injurious amounts. Several series of 4-gallon pots were filled with the common brown silt loam prairie soil from the University farm, and to five of the six pots in each series was added magnesium carbonate in amounts varying from .4 per cent to 2 per cent of the dry soil. In addition, Series C and F received calcium sulfate in such an amount as to maintain the ratio of MgO to CaO = 4 to 7, in ac- cordance to Loew's advocated optimum ratio. After the crop of 1904 was harvested, the pots in Series F were thoroughly leached in order to remove magnesium, more or less of which was expected to react with the calcium sulfate, leaving the harmless calcium carbonate. The data recorded in Table 26 show a distinct and persistent benefit from the use of magnesium carbonate up to .8 per cent of the soil, while with 1.2 per cent the plants are very seriously injured and with 1.6 per cent they are usually so nearly killed as to produce no grain, and they are practically all killed with 2 per cent of mag- nesium carbonate. The application of i per cent of magnesium carbonate would require 10 tons per acre for the surface 6| inches, but if the material were applied and mixed with only the surface inch by a light har- rowing, it would require only i| tons per acre for i per cent. Since pure dolomite would contain only 46 per cent of magnesium LIMESTONE 171 TABLE 26. ILLINOIS POT-CULTURE EXPERIMENTS Magnesium Carbonate in Brown Silt Loam Prairie Soil POT " ALKALI " APPLIED AMEND- ADDITIONAL YIELDS OF WHEAT GRAIN, GRAMS PER POT No. MEN 5 Kind Cent 1904 1905 1906 1907 1908 O. 1908 R. SERIES A: MAGNESIUM CARBONATE i None .O None None I5-23 10.93 11.50 6.30 8.60 9.61 2 MgCOs •4 None None 21. 02 10.97 13.20 9-35 17.18 19.18 3 MgCOs .8 None None 24.88 12-57 12. 60 iQ-35 8.16 21.09 4 MgCOs 1.2 None None 4-15 9.02 9.40 14.00 .00 10.63 5 MgCO3 1.6 None None .00 .00 .10 2.IO 3-0° 12.86 6 MgCOs 2.0 None None .00 .00 .00 2.50 .70 2.72 SERIES C: MAGNESIUM CARBONATE AND CALCIUM SULFATE i None .O None None 11.22 8.94 12.20 12.91 8.00 6.18 2 MgC03 •4 CaSO4 None 27.00 12.02 IO.OO 8.79 15.00 16.32 3 MgCOs .8 CaSO4 None 24.85 *3-47 I5-70 8.42 14.86 21.15 4 MgC03 1.2 CaSO4 None 5-59 11.25 17.80 IO.I8 6.52 22.50 5 MgCOs 1.6 CaSO4 None .00 2.03 1.16 8.58 1.42 11.98 6 MgCOs 2.0 CaSO4 None .00 .00 •50 6.68 .62 3-32 SERIES F : MAGNESIUM CARBONATE AND CALCIUM SULFATE — LEACHED I None .0 None None 13.00 8.51 14.20 6.67 15.12 17.40 2 MgC03 •4 CaSO4 Leached 17.12 13.38 11.40 12.39 12.72 12.64 3 MgCOs .8 CaSO4 Leached 22.35 14.32 8.30 12. 60 I3-50 15.80 4 MgCOs 1.2 CaSO4 Leached 6.72 14.18 10.20 16.66 12.78 14-57 5 MgC03 1.6 CaS04 Leached 3-73 n-54 II. 10 10.75 10.24 I3-24 6 MgCOs 2.O CaSO4 Leached .00 14-15 10.70 9-52 10.22 13.20 1 Leached after 1904. carbonate, while most magnesian limestones contain a lower per- centage, and since thorough harrowing or disking will mix the ma- terial with at least 2 or 3 inches of soil, there is no likelihood of any but beneficial effects from initial applications of 5 or 6 tons to the acre, and subsequent applications of 2 tons per acre every four or five years would probably never produce injury. On the other hand, it is highly probable .that the element magnesium 172 SYSTEMS OF PERMANENT AGRICULTURE applied in dolomitic limestone may produce quite as much benefit for its own sake as will the element potassium on most soils where it proves more or less beneficial. (The limestones in Pennsylvania and in the northern parts of Ohio, Indiana, and Illinois are, as a rule, more or less magnesian, containing, as an average, perhaps 30 per cent of magnesium carbonate and 60 per cent of calcium car- bonate, with 10 per cent of impurities, which would be equivalent to a purity of 95 per cent for the common limestone.) As an experiment, the double decomposition and leaching proved a success, as is clearly shown in Series F, pot 6 being changed from a sterile condition to as productive soil as any. It should be re- membered that high temperatures may occur at a critical period, and consequently seasonal variations are marked even in glass- house cultures. Loew's ratio finds little support from these data. Incidentally, it may be stated that during the progress of these experiments, several resistant plants have developed, wrhich explains some apparent discrepancies in the yields of wheat from pots near the border line of injury; and consequently the seeds of these resistant plants have been used in part throughout one or more series. In 1908, one half of each pot was planted with ordinary (O.) wheat, and the other half with the resistant (R.) strain, and, consequently, double the weights harvested are re- corded for the 1908 yields. AMOUNT OF LIMESTONE TO APPLY From the information thus far secured, no fixed limits can be placed upon the amounts of limestone to use as an initial applica- tion to acid soils. One ton to the acre is more than enough to destroy the acid commonly contained in the plowed soil, provided the limestone is sufficiently fine and thoroughly mixed with the soil; but, as a rule, it is less expensive to apply more limestone and then to allow the mixing to go on more slowly by the neces- sary processes of plowing, disking, harrowing, etc., in the regular farm operations, keeping in mind also that the heavier the appli- cation, the longer it will last. About one half of the water that falls in rain and soaks into the soil is brought back to the surface from lower depths by capillary LIMESTONE 173 action and evaporated. More or less acidity is thus brought up from the acid subsoil, especially in time of drouth, and there should be sufficient limestone in the surface to destroy this acidity as it rises. Quantitative determinations have shown that to correct the total acidity contained in much of the upland soil of southern Illinois to a depth of 40 inches would require more than 10 tons of limestone per acre. It is not necessary to apply such amounts, because the limestone does not descend very much below the plowed soil, and the rise of acidity from below is only occasional and not rapid. It may be said, however, that 10 tons of ground limestone per acre would not only do no harm, but would probably produce somewhat larger crops than any lighter application. As much as 10 tons per acre has been applied on an experiment field in southern Illinois, and the crop yields on that field have been larger during the last three years than on any other experiment field in that area. Two to four tons per acre, however, have usually produced much benefit. The author has used 2 to 3 tons per acre of magnesium lime- stone on his own southern Illinois farm (gray silt loam on tight clay), and as much as 10 tons per acre of the same material has been used on another farm with evident benefit. He advises an appli- cation of at least 2 tons of ground limestone per acre, where the addition of limestone is necessary, believing that less than this will not give satisfactory results in practice. Heavier applications will give greater profits per acre, but probably less profit per ton of limestone used. These two factors, it may be noted, are commonly opposed to each other in many farm operations. Thus, farm manure gives the greatest profit per acre in heavy applications, but the greatest profit per ton in light applications. With little manure and much land we apply the manure lightly, but, with a small area of land and large supplies of manure, we apply it heavily. So, with ground limestone: If one must cultivate much land and can use but little limestone, apply 2 tons per acre, and plan to apply more in later years; but, if one cultivates less land and wishes to improve it more rapidly, apply 4 to 10 tons of limestone per acre, and it will give more marked results and will last much longer. 174 SYSTEMS OF PERMANENT AGRICULTURE The amount and frequency of subsequent applications will de- pend upon the rate of loss by leaching and by removal in crops. The soil of the Rothamsted Experiment Station, England, is underlain with a bed of calcium carbonate, in the form of chalk, at a depth of 8 feet or more; but, nevertheless, the overlying residual soil material is normally deficient in limestone to a depth of several feet. A century or more ago certain fields were given heavy appli- cations of chalk, dug out of pits excavated for the purpose, and the fact that some of these fields still contain 50 tons of calcium car- bonate per acre in the plowed soil and continue to produce good crops, with fair treatment, is proof sufficient that there is no danger of applying too much ground limestone. During a period of 40 years, from 1865 to 1905, large numbers of analyses have been made of the Rothamsted soils. During that time, according to Director Hall and Doctor Miller (Proceedings of the Royal Society, 1905, Vol. 77), there have been the following losses of calcium carbonate from nine different plots on Broadbalk Field, where wheat is grown every year: TABLE 27. LOSSES OF CALCIUM CARBONATE FROM BROADBALK FIELD, ROTHAMSTED, FROM 1865 TO 1905 PLOT No. SOIL TREATMENT TONS PER ACRE IN 40 YEARS POUNDS PER ACRE PER ANNUM 2b Farm manure- II.8 CQO 7 Unmanured 16 o 800 C Minerals 176 878 6 Minerals and single ammonium salts . 23-5 1174 7 Minerals and double ammonium salts 20. 2 IOIO 8 Minerals and treble ammonium salts 23-5 1174 9 Minerals and single nitrate .... "•3 564 10 Double ammonium salts .... 20.9 1045 ii Double ammonium salts and acid phosphate 28.6 14.20 The loss of calcium carbonate during the period of 40 years ranges from 11.3 to 28.6 tons per acre. The average annual loss where ammonium salts have been applied is 1170 pounds, but with no ammonium salts the average loss is only 710 pounds a year, or about one ton per acre in three years. LIMESTONE From eight plots on Hoos Field, where barley is grown every year, the following losses of calcium carbonate have occurred: TABLE 28. LOSSES OF CALCIUM CARBONATE FROM Hoos FIELD, ROTHAMSTED, FROM 1865 TO 1905 PLOT No. Son. TREATMENT TONS PER ACRE IN 40 YEARS POUNDS PER ACRE PER ANNUM Ol Unmanured 22.7 n8q O4 Minerals 14. =! 723 Al Ammonium salts IC..Q 703 A4 Minerals and ammonium salts is.o 7 CO Ni Sodium nitrate 1^.4 772 N4 Minerals and sodium nitrate II. I "^4 Ci Rape cake IS.O 7">O 7-2 Farm manure 17.0 848 The average of the eight plots on Hoos Field shows for 40 years an average annual loss of 800 of calcium carbonate per acre. The ammonium salts have not markedly increased the average loss on this field above that from the nitrate plots or the untreated land. The investigations reported also include Agdell Field and Little Hoos Field, both of which have lost calcium carbonate in about the same amount as Broadbalk and Hoos. Practice based upon these results would require an application of two tons per acre of ground limestone about every five or six years, in order to replace the regular losses. The loss of calcium carbonate from soils is largely due to leach- ing. The soil waters contain carbonic acid (H2COg) formed by the absorption of carbon dioxid (CO2) from the atmospheric air and from the soil air. This carbonic acid has power to react with cal- cium carbonate and form calcium bicarbonate, .CaH2(CO3)2, which is soluble in water, thus: H— O H— O\ / Ca^ >C=0 + >C=0 = Ca< TJ r\s \f >= O H— O' H— O = O 1 76 SYSTEMS OF PERMANENT AGRICULTURE In all humid regions where water passes through the soil, there is loss of calcium carbonate, leached out in the form of soluble bicarbonate. The " lime " carried in solution in " hard " waters from surface wells appears as a crust or scale in the teakettle, the soluble bicarbonate being decomposed by heat and the insoluble normal carbonate thus precipitated. Even virgin soils in old soil formations are often not only deficient in limestone, but they are sometimes found to be exceedingly acid, and thus require heavy applications of limestone to correct or neutralize the acids in the soil. Usually these soil acids exist in part, at least, as organic acids (humic acid etc.), but it is very evident that they are not always entirely organic, because the acidity often markedly increases while the organic matter decreases, with depth of soil, as will be seen from Tables 15, 16, and 17 (see soil types 330, 135, and 335), in which the measure of acidity is shown by the " limestone required," and the organic matter is indicated roughly by the nitrogen. Thus, in the lower Illinoisan yellow silt loam, limestone required to correct the acidity increases from 310 pounds in the surface to 3315 pounds in the subsurface, and to 7200 pounds in the sub- soil, considering 2 million pounds of each; while the nitrogen de- creases from 2150 pounds in the surface to 1085 pounds in the subsurface, and to 827 pounds in the subsoil; and, as a matter of fact, the organic carbon decreases from 23,400 pounds in the sur- face, to 9710 pounds in the subsurface, and to 6190 pounds in the subsoil, 2 million pounds of each being considered. Detmer assigns to humic and ulmic acids the molecular formula C60H54O27, and to their salts such formulas as Ag8C60H46O27, and Ca3(NH4)2C60H46O27. These would correspond to Ca4C60H46O27. On this basis, if all of the organic carbon in the subsoil were in the form of humic acid, it would be equal to less than one half of the acidity found. These computations are based upon the average of many analyses of soil samples from this type. Individual samples show as high as six times as much acidity as could be accounted for from the total organic carbon if in the form of humic acid. Acid silicates .(see acid salts), formed from polysilicates (see under silicon), from which some basic elements may have been removed and replaced with acid hydrogen, by reaction with soluble LIMESTONE 177 organic acids, or possibly by the long-continued weak action of drainage waters charged with carbonic acid, do exist in the soil, and the evidence thus far secured indicates that they account for most of the acidity of soils that are at the same time strongly acid and very deficient in humus. Calcium bicarbonate may be formed by the action of carbonic acid on silicates containing calcium, even though no limestone is present. It is well known that plants have power to secure calcium, as plant food, from acid soils containing calcium in silicates but not containing limestone. Of course, it is not necessary to apply limestone to soils that already contain abundance of calcium carbonate, but it should be applied to soils that show acidity in the top soil and subsoil. Not infrequently slight acidity exists in the surface, and sometimes in the subsurface also, where the subsoil contains very large amounts of limestone. From present information we cannot strongly advise the application of limestone to such soils, although it would cer- tainly do no harm, and for some crops might be beneficial. But where the subsoil also is strongly acid, liberal applications of lime- stone should be made. While a small amount of acidity in the sur- face may not be a serious injury when the rainfall is abundant, there is apparently in humid regions some rise of acidity from strongly acid subsoils in times of partial drouth, corresponding somewhat to the "rise of alkali " in arid regions, where the water leaves the soil only by evaporation from the surface. If, however, the subsoil contains abundance of limestone, some calcium bi- carbonate will be brought upward into the subsurface or surface soil with the capillary rise of the soil moisture, and this will be left as normal carbonate when the water evaporates, and may serve to reduce the acidity of the subsurface or surface soil, at critical times, as in time of drouth. Clover and alfalfa are plants that are very sensitive to acid conditions when dependent for most of their nitrogen upon the bacteria, Pseudomonas radicicola, but these crops are grown very successfully upon such soils as the brown silt loam of the early Wisconsin glaciation and the brown silt loam, -yellow-gray silt loam, and yellow silt loam, of the late Wisconsin; whereas they are complete failures on the lower Illinoisan gray silt loam prairie, 178 SYSTEMS OF PERMANENT AGRICULTURE and very unsatisfactory crops for all soils with strongly acid sub- soils, although, as already stated, such crops can be grown for a time on such soils if liberally fed with farm manure or other fer- tilizers. The legume plants, themselves, are not so sensitive to acid conditions, but, rather, the bacteria depended upon to furnish nitrogen; and while these will sometimes live and even form tuber- cles, they seem to develop but little power to fix nitrogen under such unfavorable conditions. THE TIME TO APPLY LIMESTONE The answer to this question can be no more definite than to a similar question concerning farm manure. We should consider the matter of hauling and spreading limestone in relation to the other necessary farm work, keeping in mind conditions of weather, roads, and land. It is applied but once during the crop rotation and for the benefit of all crops, although its most direct benefit is for the legumes, the other crops receiving large indirect benefit if the legume crops are returned to the soil. It is sometimes applied in winter or spring, but, as a rule, it is more satisfactory to apply it during the summer or early fall, when the land is dry, the roads are good, and the days are long. It is not best to apply it in intimate connection with phosphate, because the limestone will retard the availability of the phosphorus, although this effect is temporary, and in any case the two materials must ultimately become mixed if applied to the same land. The phosphate may well be applied with organic matter (manure or clover), mixed with the surface soil by disking, and then plowed under, and the limestone may then be applied after plowing and well mixed with the surface soil in the preparation of the seed bed, where wheat and clover are to be seeded, or where corn is to be followed by oats and. clover, the oats being disked in without re- plowing. Thus the limestone is well distributed in the first 3 or 4 inches of the soil where the atmospheric nitrogen enters and where the nitrogen-fixing bacteria do much of their work, while the phos- phate is mixed with the decaying organic matter in the next 3 or 4 inches of soil where the plant roots feed in large degree. Another good way is to apply the phosphate for corn and the limestone for wheat about three years later. LIMESTONE 179 METHODS OF APPLYING LIMESTONE No single method need be followed in applying limestone to the land, but it should be spread as evenly as practicable. This may be done by hand with a light shovel, either from the wagon or from small equal-sized piles placed at regular intervals. Thus, a pile of 100 pounds every 33 feet each way makes two tons to the acre. It can easily be thrown 16 or 18 feet with a shovel. A spreader made for the purpose of applying ground limestone or rock phosphate is very useful: There are some fairly satisfactory machines on the market at the present time. Several spreaders are manufactured that serve well for applying ashes, slacked lime, or other light materials, but most of them are not suited for han- dling such heavy materials as limestone and rock phosphate. The directions given below are similar to those published by the Ohio Experiment Station for a " home-made " spreader which any farmer can have made, and which is more satisfactory for spreading these heavy materials than some of the machines on the market. Make a hopper similar to that o^an ordinary grain drill, measur- ing inside 8^ feet or n feet long with sides about 21 inches wide and about 20 inches apart at the top. The sides may be trussed with -|-inch iron rods running from the bottom at the middle to the top at the ends of the hopper. Let the bottom be 5 inches wide in the clear, and cut in it crosswise a row of diamond-shaped holes, 2 inches wide, 2\ inches long, and 4 inches apart (6 inches between centers). Make a second bottom with holes in it of the same size and shape as those of the main bottom, and so shaped that they will register. Let this second bottom slide loosely under the first, moving upon supports made by leaving a space for it above bands of strap iron 12 inches apart, which should be carried from one side to the other under the hopper to strengthen it. The upper bottom piece may be of about 8-inch sheet steel, and the lower one may be Of smooth, seasoned hard wood, about i inch thick and 7 inches wide, reenforced with strap iron if necessary, and well oiled or painted. To this under strip, attach a V-shaped arm, extending an inch in front of the hopper, with a half-inch hole in the point of the V, in which drop the end of a strong lever, bolting i So SYSTEMS OF PERMANENT AGRICULTURE the lever loosely but securely to the side of the hopper, and fasten to the top of the hopper a guide of strap iron, in which the lever may move freely back and forth. The object of this lever is to regulate the size of the openings by moving the bottom board. Make a frame for the hopper, with a tongue to it, similar to the frame of an ordinary grain drill. Get a pair of old mowing-machine wheels with strong ratchets in the hubs, and with pieces of round axle of sufficient length to pass through the frame and into the ends of the hopper, which are to be welded to a square bar of iron about if inches in diameter and the length of the inside of the hopper. The axles should be fitted with journals, bolted to the under side of the frame. Make a reel to work inside of the hopper by securing to the axle, 12 inches apart, short arms of |-inch by i-inch iron, and fastening to these arms four beaters of f-inch square iron, about an inch shorter than the inside of the hopper, the reel being so adjusted that the beaters will almost scrape the bottom of the hopper, but will revolve freely between the sides. The arms may be made of two pairs of pieces, bent so as to fit around the axle on opposite sides, and secured by small bolts passing through the ends and through the beater, which is held between them. The diameter of the completed reel is about 5 inches, and it serves as a force feed. Two pieces of oilcloth may be tacked to the bottom of the hopper, one in front and one behind, of sufficient width to reach nearly to the ground, in order to reduce the annoyance of the flying dust to man and team. Another piece may be buttoned across the top of the hopper in windy weather, if desired; but the dust of limestone or of natural phosphate is certainly no worse than the dust of the field. A sort of second force feed has been evolved from the extensive experience of Illinois farmers in building home-made machines: Two pieces of sheet steel, each about 6 inches wide and the length of the machine, are used as a V-shape bottom for the hopper, forming nearly a right angle at the lowest point. One piece is stationary and the other is given an endwise motion back and forth by means of a small wheel with a heavy rim waving in and out horizontally and running through a slotted piece firmly attached to the movable sheet steel. Two very small wheels LIMESTONE 181 forming the sides of the slot serve to reduce the friction, and a lever is arranged to throw this mechanism out of gear. One of the pieces of sheet steel is provided with an adjustment by means of which a crack is opened of any desired width, the entire length of the bottom. Thus the stone falls, not through holes or in streaks, but in a perfect broadcast. Several of these home-made machines are in use. The draft is more than with the reel alone, but they are undoubtedly more satisfactory than anything on the market. The cash expense for such a machine, aside from the mower wheels with axle and ratchets, has varied from less than $10 to more than $20, depending on cost of material and labor. Farmers with some mechanical skill hire only the necessary blacksmithing. HINTS ON SPREADING LIMESTONE (AND PHOSPHATE) In hauling and spreading limestone it is of first importance to save time and labor. As a rule, it is more economical to purchase both limestone and raw phosphate in bulk, and have it shipped in paper-lined box cars. Wetting will do no harm except to give trouble in spreading. Bags are expensive and easily damaged, and with tight wagon boxes the use of bags is wholly unnecessary. As a rule, the plan should be to haul the limestone direct from the car to the field, and spread it at once. Only two days are allowed to unload a car, although an extra day's car service costs only one dollar. With a haul of two miles or less, and with two men, one boy, and two teams, with three wagons and one spreader, 30 tons of ground limestone can be taken from the car and spread over 10 to 15 acres of land in two or three days, provided the roads and other condi- tions are favorable. One man is kept in the car loading the limestone into a wagon. The boy with one team hauls the loaded wagon to the field, leaves it there, and takes an empty wagon back to the car, hitching at once to the loaded wagon and leaving the empty wagon to be loaded. The other man and team remain in the field with the spreader, spreading one load while the boy is gone for the next. If an extra team is at hand, the man at the car may drive to meet the empty wagon and thus save some time. 182 SYSTEMS OF PERMANENT AGRICULTURE When spreading across a forty-acre field, the loaded wagon should either be hauled to the middle line of the field, or half of the loads should be hauled to one side and the other half to the oppo- site side of the field, using an extra wagon. The spreader hopper should hold at least 1000 pounds on the half-rod machines, or 1333 pounds on the n-foot machines, so that by driving 80 rods, the load will amount to at least two tons per acre. Starting from the middle of the field, one hopperful will spread to the side (40 rods) and back, when the spreader must be backed up to the wagon and refilled. Four such drives (320 rods) with the half-rod machine, or three drives (240 rods) with the n-foot machine, will spread a two-ton load over an acre. If the roads are good, two tons can be hauled at a load with a good team and wagon. If necessary to draw the loaded wagon to the middle line of the field, a four-horse team is provided by adding the spreader team. For making applications from one half ton to two or three tons per acre of limestone or rock phosphate, an arrangement of this sort is very satisfactory. For heavier applications one can go over the ground twice, or it can be spread by hand. For longer dis- tances, one or more additional teams are needed on the road. Where manure is to be spread, rock phosphate may well be spread with it. The phosphate may be sprinkled over the manure from day to day as it is being made in the stall or covered feeding shed, or the manure spreader may be partly filled with manure, phosphate then being sprinkled on sufficient for the load, the load com- pleted, and then spread on the land. It should be kept in mind, however, that, if any leaching occurs after the phosphate is mixed with the manure and before the manure is spread on the land, some loss may ensue of the added phosphate; while if the phosphate is taken directly from the car and spread on the land where manure has been or is to be applied, it can later be plowed under with the manure with no danger of loss of phosphate. NOTE. Limestone is soluble in soil water containing carbonic acid, and if ground to pass a sieve with about 10 meshes to the linear inch, it is sufficiently fine, provided the product contains all of the finer material. Fineness correlates with loss by leaching as well as with " availability," while the coarser particles are more durable and serve as centers of alkalinity. (See pages 174, 198, 561.) CHAPTER XIII PHOSPHORUS PHOSPHORUS is the only element that must be purchased and returned to the most common soils of the United States. Phos- phorus is the key to permanent agriculture on these lands. To main- tain or increase the amount of phosphorus in the soil makes pos- sible the growth of clover (or other legumes) and the consequent addition of nitrogen from the inexhaustible supply in the air; and, with the addition of decaying organic matter in the residues of clover and other crops and in manure made in large part from clover hay and pasture and from the larger crops of corn and other grains which clover helps to produce, comes the possibility of liberating from the immense supplies in the soil sufficient potas- sium, magnesium, and other essential abundant elements, supple- mented by the amounts returned in manure and crop residues, for the production of large crops at least for thousands of years; whereas, if the supply of phosphorus in the soil is steadily de- creased in the future, in accordance with the past and present most common farm practice, then poverty is the only future for the people who till the common agricultural lands of the United States. And this does not refer to the far-distant future only, for the turning point is already past on most farms in our older states and on many farms in the corn belt ; and lands that have passed their prime with sixty years of cultivation will decrease rapidly in pro- ductive power and value during another sixty years of similar exhaustive farm practice. The world's supply of phosphorus exists in three principal sources: First are the supplies in the various soils, concerning which the reader of the preceding pages will have sufficient posi- tive knowledge for intelligent thought. Second are the natural beds of calcium phosphate, varying in purity from a few per cent, to as high as 80 per cent, of tricalcium phosphate, Ca3(PO4)2. 183 1 84 SYSTEMS OF PERMANENT AGRICULTURE Third are the extensive deposits of phosphatic iron ores con- taining more or less ferric phosphate, FePO4, the phosphorus being recovered in the slag produced in the conversion of pig iron into steel. About three fourths of the phosphorus taken from the soil by crops of corn, wheat, or other cereals, is deposited in the grain or seed, about one fourth remaining in the straw or stalks. If the grain is sold, three fourths of the phosphorus required for the crop is sold with it; and, likewise, when grain is bought and brought to the farm, a like proportion of phosphorus is brought with it. When crops are fed to animals, as a general average about three fourths of the phosphorus, three fourths of the nitrogen, and practically all of the potassium are returned in the manurial excrements. Thus, if sufficient grain is bought and fed, and if the manure is saved and applied to the land, the soil can be made richer in phosphorus year by year, and in most sections some instances can be found of farmers who succeed in maintaining or increasing the fertility of their soil by this practice. If they have the neces- sary knowledge and skill and material equipment and sufficient capital, they may feed stock for the open market, or if this is not profitable, they may produce pure-bred stock to sell at higher prices for breeding purposes. In any case, live-stock farming can never be permanently profitable to a large proportion of the farmers in a great agricultural country, because the world cannot live on meat and dairy products only, and the relative supply and demand always compels the sale of much grain from most farms. Conse- quently, this system of adding phosphorus to one farm by taking it from other farms must be of limited application; and live-stock farmers who feed only the produce from their own land gradually reduce the phosphorus of the soil at least by the amount sold in the animal products. A still more limited supply of phosphorus is secured for use in soil improvement by utilizing the bone meal prepared by the pack- ing houses. This, of course, also comes from the soil originally. It is made chiefly from bone scraps which have no value for other uses. The best bone is worth several times as much for the manu- facture of buttons, cutlery, toilet articles, etc., as for fertilizer purposes. Probably not more than one tenth of all the phos- PHOSPHORUS 185 phorus shipped off from American farms in animal products is returned to the soil in bone fertilizers. The mineral matter in bone consists chiefly of tricalcium phosphate, with a small amount of calcium carbonate. There is practiced more or less adulteration of bone fertilizers by admixture of raw rock phosphate or acid phosphate. There are three principal forms of bone meal'offered for sale — (i) raw bone, (2) steamed bone, and (3) acidulated bone. Raw bone meal. Raw bone meal contains about 9 per cent of phosphorus, 4 per cent of nitrogen, and much organic matter, including more or less fat, which tends to retard decomposition. The most common application of bone or other ordinary commercial fertilizer is 200 pounds per acre. Since 9 per cent means 9 pounds per hundred, this application would amount to 18 pounds of phosphorus per acre, or one pound more than is contained in 100 bushels of corn. Since 200 pounds is one tenth of a ton, raw bone meal contains about 180 pounds of phosphorus per ton. Hence, the rule: To convert per cent into pounds per ton, double the per cent and add one cipher. It is always advisable to memorize pounds per ton and to think in those amounts, rather than in per cent. At 10 cents a pound for phosphorus and 15 cents for nitrogen, a ton of raw bone meal costs about $30, which is $18 for the phosphorus and $12 for the nitrogen. Nearly i| tons of raw bones are required to make one ton of steamed bones, the loss in weight consisting of fat, flesh, glue, and other organic matters rich in nitrogen. Steamed bone meal. Steamed bone meal contains from 12 to 14 per cent of phosphorus, and it should average at least 12^ per cent, or 250 pounds of phosphorus per ton, costing $25 at 10 cents a pound for the element phosphorus. Thus, 200 pounds of steamed bone per acre supplies 25 pounds of phosphorus, or two pounds more than is required for a hundred-bushel crop of corn (grain and stalks). By steaming bones the nitrogen is largely removed in the organic matter, only about .8 per cent, or 16 pounds per ton, being found in good steamed bone, an amount within the legal limits of error in some fertilizer laws, and too small to justify consideration in the purchase price, especially when nitrogen can be secured from the inexhaustible supply in the air by using leg- 1 86 SYSTEMS OF PERMANENT AGRICULTURE umes in crop rotations. To supply sufficient nitrogen for a hun- dred-bushel crop of corn would require 9 tons of steamed bone meal, costing about $225. The phosphorus in raw bone and steamed bone exists in the form of the insoluble tricalcium phosphate, but because of the porosity and fine division of the bone particles and the presence of decom- posing organic matter in intimate contact with the extensive sur- face within the pores, phosphorus is liberated quite readily from bone meal, steamed bone being more active because of the removal of the fat and because it is usually more finely ground than raw bone. Acidulated bone meal. Acidulated bone meal (" acid bone ") is made by adding to a ton of bone meal sufficient sulfuric acid to convert a part of the insoluble tricalcium phosphate into the sol- uble monocalcium phosphate, or at least into the more readily available dicalcium phosphate. The bone meal thus treated is said to be mildly acidulated. As an average, it contains about 140 pounds of phosphorus and 40 pounds of nitrogen per ton. Much of the so-called " dissolved bone " sold in the fertilizer trade is made from phosphate rock, and this is no detriment to the product so far as the soluble portion is concerned, but the insoluble portion is more rapidly available if derived from bone than from rock. In the acidulated and most readily available form, phosphorus sells at about 12 cents a pound. Other bone products include bone black, dissolved bone black, and bone ash. Tankage from the packing houses varies from nearly pure bone to a high percentage of nitrogenous organic matter, including dried blood, meat, and mixed offal. Some further data will be found under nitrogen fertilizers. Three principal kinds of phosphorus fertilizer are derived from phosphate rock. These are (i) the fine-ground natural rock, (2) acid phosphate, and (3) double superphosphate. Natural phosphates. Natural phosphate beds are widely dis- tributed over the earth, some of the most important deposits being in Tennessee, South Carolina, Florida, and Canada, also in France, Belgium, Norway, Spain, and North Africa. The present annual production of the world amounts to about three million tons, of which two million tons are produced in the United States, about PHOSPHORUS 187 one million for home consumption, and an equal amount for exportation, chiefly to Great Britain, Germany, and other parts of Europe. It is estimated that the total phosphate deposits of the world thus far discovered will still furnish 'somewhere from 200 million to 500 million tons of high-grade phosphate rock. Some phosphate deposits have recently been found in Wyoming, Idaho, and Utah, and doubtless still other extensive deposits will be discovered in various parts of the earth; but, nevertheless, the world's total supply of high-grade phosphate is apparently very limited when measured by crop requirements, as evidenced by the enormous shipment of phosphate from America to Europe, despite the exten- sive and long-continued search by geologists for any undiscovered European deposits. (See also Appendix.) Facts worthy of careful consideration are that the Chilian gov- ernment derives a large revenue from export duties on sodium nitrate, from the world's greatest natural deposits of combined nitrogen, an element which the Chilian landowners can always secure, however, from the inexhaustible atmospheric supply; whereas, from the United States we are exporting half of our total production of phosphates with no restrictions, although we are thus shipping away from our lands the only element we shall ever need to purchase in order to maintain the fertility of our own soils. The laws of Norway greatly restrict the exportation of phosphate from that country. To restore to the soils of the United States the phosphorus removed by the corn crop alone, would require the annual applica- tion of our total annual production of phosphate rock, counting 23 pounds of phosphorus for a hundred-bushel crop of corn, and 2\ billion bushels as the average corn crop of the United States. The Florida phosphates are classed chiefly as hard rock and soft rock, the South Carolina phosphates as land rock and river rock; and the Tennessee phosphates as brown rock and blue rock. The quality is usually expressed as percentage of purity; that is, percentage of tricalcium phosphate. The South Carolina land rock is the lowest in phosphorus, averag- ing less than 50 per cent calcium phosphate, or less than 10 per cent of phosphorus. The South Carolina river rock and the Florida 1 88 SYSTEMS OF PERMANENT AGRICULTURE soft rock average 50 to 60 per cent pure; while the Florida hard rock and the Tennessee brown rock contain from 60 to 75 per cent of calcium phosphate. The Tennessee blue rock varies from less than 50 to more than 70 per cent, or from 200 to 300 pounds of phosphorus per ton of rock. The Florida soft rock contains chiefly phosphates of iron and aluminum, while in the other rocks the phosphorus is largely in the form of tricalcium phosphate. Aside from the deposits of high-grade phosphate, containing 45 or 50 to 75 or 80 per cent of calcium phosphate, there are known to exist very much more extensive deposits of lower grade phos- phates and phosphatic limestones containing from less than 10 per cent to 40 per cent or more of calcium phosphate, correspond- ing to from 2 to 8 per cent of phosphorus, or from 40 to 160 pounds of phosphorus per ton of rock. At present, these deposits have no market value, because, if the phosphate costs $4.00 per ton fine- ground and on board cars at the mine, and if the freight charges are $3.00 per ton, the freight on two tons of low-grade rock would amount to $6.00; while the delivered cost of one ton of high-grade rock supplying the same amount of phosphorus would be only $7.00, leaving but 50 cents a ton for the low-grade rock, which would barely pay for the expense of easy quarrying and grinding. As the supplies of high-grade phosphate become exhausted and prices advance, the lower grades will no doubt be utilized in this country as they are in Europe, where 35 to 40 per cent Belgian phosphate is now one of the chief commercial grades. About 62^ per cent calcium phosphate, or \2\ per cent of phos- phorus, is the average grade of the fine-ground natural rock phos- phate now used in Illinois, and to some extent in other states, for direct application to the soil in intimate connection with abundance of decaying organic matter, as farm manure, clover, or other green manures. In this form the element phosphorus costs the farmer about 3 cents a pound. The information thus far secured amply justifies the adoption of a system of farming in which fine-ground natural phosphate rock should be applied at the rate of 1000 to 2000 pounds per acre every three to six years, for three or four successive crop rotations, after which the application may be reduced one half, or to 200 pounds per acre for each year in the rotation, which would still PHOSPHORUS insure a small increase rather than a decrease in the future1 years. More specific data concerning the use of raw rock phosphate, the results of the most careful experiments, and the comparative value of different forms of phosphorus are more fully discussed in the following pages, after some consideration of organic matter. Acid phosphate. Acid phosphate is the name of a manufactured product, not of a chemical compound. Chemically, there are two acid phosphates of calcium, (i) the monocalcium phosphate, CaH4(PO4)2, and (2) the dicalcium phos- phate, Ca2H2(PO4)2. These chemical compounds, together with tricalcium phosphate and tetracalcium phosphate, phosphoric acid, phosphorus pentoxid, and phosphorus, itself, form a very impor- tant and interesting series. For the sake of simplicity and uni- formity, two atoms of phosphorus are given in each case, this being necessary in some cases: NAME FORMULA MOLEC- ULAR WEIGHT PHOS- PHORUS (Per Cent) Phosphorus P2 62 IOO.OO Phosphorus pentoxid . . . . P2O5 142 4"?. 66 Phosphoric acid H6(PO4)2 1 06 31.63 Monocalcium phosphate .... Dicalcium phosphate CaH4(PO4)2 Ca2H2(PO4), 234 272 26.50 22.43 Tricalcium phosphate Cas(PO4)2 3IO 20.00 Tetracalcium phosphate .... Ca3(CaO)(P04)2 366 16.94 Of these substances, tricalcium phosphate is the only one that occurs in nature. The element phosphorus takes fire when exposed to the air, two atoms of phosphorus uniting with five atoms of oxygen to form phosphorus pentoxid, sometimes called phosphoric oxid. This compound is the most powerful dehydrating agent known in chemistry, having power to abstract water from many other substances. It unites with water to form true phosphoric acid, H3PO4, or H6(PO4)2. This is one of the strong acids, and if it comes in contact with calcium carbonate, for example, it takes up one, two, and, finally, three bivalent atoms of calcium in place of the univalent hydrogen atoms, and thus forms acid monocalcium I go SYSTEMS OF PERMANENT AGRICULTURE phosphate, acid dicalcium phosphate, or the neutral tricalcium phosphate, respectively, carbonic acid being liberated, which promptly decomposes into water and the gas, carbon dioxid. Tetracalcium phosphate is thought by some to be the compound in which phosphorus exists in basic slag phosphate, being essen- tially tricalcium phosphate loosely united with the CaO group (see under basic slag phosphate). In the manufacture of commercial acid phosphate, the phosphorus material most commonly used in mixed commercial fertilizers, one ton of ground raw rock phosphate is treated with about one ton of sulfuric acid, and the resulting material consists chiefly of mono- calcium phosphate and calcium sulfate (land-plaster), together with all of the impurities contained in the original materials, and this mixture is the ordinary acid-phosphate fertilizer: Ca3(PO4)2 + 2 H2SO4 = CaH4(PO4)2 + 2 CaSO4. This equation shows only the general reaction between the chemical compounds, tricalcium phosphate and sulfuric acid, but impurities are always present, and both the impurities and the calcium sulfate are included in acid phosphate, in which the phos- phorus is held chiefly in the water-soluble compound, monocalcium phosphate. The reaction may be expressed in two equations, the two molecules of sulfuric acid being added separately, thus showing dicalcium phosphate as an intermediate product. Small amounts of both dicalcium phosphate and tricalcium phosphate usually remain in acid phosphate, and a considerable part of the sulfuric acid used reacts with impurities which consist chiefly of silicates of the abundant metals, aluminum, iron, calcium, magnesium, potassium, and sodium. Sometimes calcium carbonate is among the impurities. As a rule, about one fourth of acid phosphate consists of phosphates (chiefly monocalcium phosphate), while three fourths consist of calcium sulfate and impurities. The readily available phosphorus in acid phosphate has a market value of about 12 cents a pound. This includes the phosphorus soluble in water and also that dissolved by ammonium citrate solution, which is sometimes called the " citrate-soluble " or the " reverted." The term reverted is properly applied to dicalcium PHOSPHORUS 191 phosphate formed from monocalcium phosphate by reaction with tricalcium phosphate: CaH4(P04)2 + Ca3(P04)2 = 2 Ca^PO,),. On long standing, this sort of reaction evidently takes place if an excess of tricalcium phosphate was left in the original product, and consequently the percentage of water-soluble phosphorus may be greater in fresh acid phosphate than in that which has been stored for some time, the dicalcium phosphate, or " reverted," being sol- uble in citrate solution, but not in water. If the raw phosphate rock contains 12 per cent of phosphorus, the acid phosphate made from it will contain about 6 per cent of phosphorus. The most common grade is known as 14 per cent acid phosphate, which the fertilizer agent would say means that the acid phosphate con tains 14 per cent of " phosphoric acid," by which, however, is meant not 14 per cent of true phosphoric acid, H3PO4, but 14 per cent of phosphorus pentoxid, P2O5, which is equivalent to 6.1 per cent of the element phosphorus, corresponding to 122 pounds of phosphorus per ton of acid phosphate, which sells at about $15 a ton. Where 250 pounds of phosphorus cost $7.50 in fine-ground natural rock phosphate, the same amount of phosphorus will usually cost $30 in the two tons of acid phosphate.1 Double superphosphate. Double superphosphate consists chiefly of monocalcium phosphate, CaH4(PO4)2, and a moderate amount of impurities. It is richer in phosphorus than any other fertilizer material. It is made (i) by treating low-grade phosphate rock with an excess of sulfuric acid, by which true liquid phosphoric acid is liberated. This is leached out of the mass, and (2) this true phosphoric acid is applied to high-grade phosphate rock, thus: (1) Ca3(P04)2 + 3 H2S04 = H6(P04)2 + 3 CaSO4; (2) Ca3(P04)2 + 2 H6(P04)2 = 3 CaH4(P04)2. 1 Both acidulated bone and acid phosphate are sometimes called superphos- phate; and in England "super" (meaning literally over or higher) is the common term for acid phosphate, somewhat as photographers use the term "hypo" (mean- ing under or lower) for sodium thiosulfate, formerly incorrectly called hyposulfite of soda. SYSTEMS OF PERMANENT AGRICULTURE By this means the impurities of the low-grade phosphate and the calcium sulfate formed in the first reaction are left behind, and the monocalcium phosphate is then formed as a condensation prod- uct, with only the impurities of the high-grade phosphate and a small amount of calcium sulfate made from the excess of sulfuric acid which is carried with the phosphoric acid. In practice, double superphosphate is made to contain about 20 per cent of the ele- ment phosphorus, corresponding to about 75 per cent of mono- calcium phosphate, and to 400 pounds of phosphorus per ton of product. This material is not made in the United States, but is produced to a considerable extent in Germany. It has advantage over ordinary acid phosphate in long-distance shipping, and it also permits the use of phosphate rock containing more iron and alumi- num than can be used for the manufacture of common acid phos- phate on account of the deliquescent properties of the products. Slag phosphate. Basic slag phosphate results as a by-product when pig iron, made from phosphatic iron ores and thus contain- ing considerable phosphorus, is converted into steel by the basic process in which an excess of lime is used. By proper methods a slag is produced which may contain about 8 per cent of phosphorus, or 160 pounds per ton. It is commonly held that the phosphorus is in the form of tetracalcium phosphate, Ca4O(PO4)2, whose struc- tural composition might be represented thus: Tetracalcium Tricalcium Phosphoric phosphate phosphate acid Ca— O-)P=O / >° Ca< H Ca H— cr Whether these formulas express the relationship of tetracalcium phosphate to tricalcium phosphate and to phosphoric acid, is not fully known, and it is even questioned if the phosphorus in basic PHOSPHORUS 193 slag exists in the form of tetracalcium phosphate. However, an excess of calcium oxid is present, and the phosphorus in slag under suitable conditions can be made available. No doubt, the lime produces some benefit for its own sake on certain classes of soil. In value, the phosphorus is rated at 10 cents a pound, the same as in bone meal. The iron ores from the Lake Superior region, which are used in the Illinois Steel Works, contain too small an amount of phosphorus to give value to the slag produced, but some phosphorus-bearing ores are used in Pennsylvania, and slag phosphate has been pro- duced and used in that state to a limited extent for several years. In Europe very large quantities of slag phosphate are produced and sold under the name of Thomas slag, although Jacob Reese, who for many years controlled the production in Pennsylvania, claimed priority over the European discovery. The conditions under which the different forms of phosphorus should be used are discussed in the following pages. CHAPTER XIV ORGANIC MATTER AND NITROGEN THE organic matter of the soil may be considered in two classes, active and inactive, although no very sharp line can be drawn between them. The most active organic matter consists of such substances as decaying plant roots and crop residues, green manures and animal manures, incorporated with the soil. These products decay rapidly in the soil and in the process of decomposition liberate not only plant food which they contain, including nitrogen, phosphorus, and potassium, but they also set free other decomposition products, such as carbonic acid, nitric acid, and organic acids, which have power to dissolve more or less additional plant food from the mineral part of the soil. The inactive, or less active, organic matter consists of the more resistant organic residue that remains after several years and that decomposes very slowly. If present in large quantity, its gradual decomposition may still supply sufficient nitrogen to meet the needs of good crops, although its power to liberate mineral plant food from the soil may not provide adequate supplies of available phosphorus, potassium, etc. Thus, we find that one soil may at the same time be richer in organic matter and less productive than another soil, even though the two soils are alike in other respects. Three tons per acre of fresh, actively decaying organic matter may be more effective for a year or two than thirty tons of old and less active humus. The term humus is not synonymous with organic matter. Humus includes only that part of the organic matter that has passed the most active stage of decomposition and completely lost the physical structure of the materials from which it is made, and has thus become, as a rule, thoroughly incorporated with the soil mass. 194 ORGANIC MATTER AND NITROGEN 19$ It is the decay of organic matter, and not the mere presence of it, that gives " life " to the soil. Partially decayed peat produces no such effect upon the productive power of the soil as follows the use of farm manure or clover residues. DECAY OF ORGANIC MATTER A matter that has led to much confusion and misunderstanding is the common talk of " available plant food," as distinct from the total supply, whereas there is no line of distinction. The question as to the amount of available plant food contained in the soil at any given time is very insignificant in comparison with the ques- tion how to make plant food available. The plant food removed from the soil by a crop is not available when the crop is planted, but it must be made available during the growing season. Plant food is made available by chemical and biochemical processes, of which ammonification and nitrification are among those best understood. For the exact information we now have regarding these processes, we are indebted to the researches of Pasteur and Schlosing and Miintz of France, Winogradsky of Russia, Warington of England, and others. The nitrogen in the soil is almost entirely in organic compounds; that is, the nitrogen is united or combined with other elements, notably carbon, hydrogen, and oxygen, with small amounts of phosphorus, and sulfur, in the form of partially decayed organic matter; but plants cannot use these insoluble organic compounds of nitrogen occurring in the soil. There are at least three different kinds of microscopic organisms (called bacteria), and also three different steps, or stages, involved in the process of nitrification, the nitrogen being changed from the organic compounds, first into the ammonia l form (NH3) , second into the nitrite form, as Ca(NO2)2, and third, into the nitrate form, as Ca(NO3)2. During the process the nitrogen is separated from the carbon and other elements composing the insoluble or- ganic matter, and is united or combined with oxygen and some alka- line element to form the soluble nitrate, such as calcium nitrate, 1 Technically this first step (ammonification) is preliminary to, and not a part of, nitrification proper. 196 SYSTEMS OF PERMANENT AGRICULTURE which is one of the most suitable compounds of nitrogen for plant food. This, then, is the general process of nitrification (including am- monification and nitrification proper) , in which the ammonifying and nitrifying bacteria transform or transfer the nitrogen from insoluble organic compounds into soluble nitrate compounds in which it may serve as available plant food. Each specific class of bacteria performs a distinct function. Thus, the ammonifying bac- teria serve only to convert organic nitrogen into ammonia nitrogen; the nitrite bacteria (also called nitrous bacteria) serve only to convert ammonia nitrogen from ammonia or ammonium salts into nitrous acid (HNO2) or nitrites; and the nitrate bacteria (also called nitric bacteria) serve only to convert nitrous acid or nitrites into nitric acid (HNO3) or nitrates. While we may assume that the nitrogen passes through the forms of nitrous and nitric acid, those acids are never present in detectable quantities, the presence of a salifiable base being essential for the progress of these biochemical reactions. The final product is al- ways a nitrate, except under artificial conditions, when nitrites may be obtained in quantity in the absence of the nitrate bacteria. Under the natural conditions existing in normal soils, even nitrites can scarcely be detected, because of the quickness with which they are converted into nitrates. The nitrate that is formed may be calcium nitrate, magnesium nitrate, potassium nitrate, sodium nitrate, or even ammonium nitrate, depending upon which base is present in the most suitable form. In the nitrification of ammonium carbonate, (NH4)2CO3, the reaction will stop when* only one half completed if no other base is present, the final product being ammonium nitrate, NH4NO8. (NH4)2 CO3 + 3 O = NH4NO2 + CO2 + 2 H2O. NH4NO2 + O = NH4NO3. To continue the process beyond this point would require the formation of appreciable amounts of free nitric acid, of which the bacteria seem incapable. In the production of lactic acid in the souring of milk, the lactic bacteria are capable of continuing the ORGANIC MATTER AND • NITROGEN 197 process until the solution contains about .7 per cent of free lactic acid, beyond which they become inactive; but, if the free lactic acid is neutralized by the addition of some base, the bacteria again become active. In the process of nitrification there is required, not only the presence of calcium or some other alkaline element or group, in suitable form (as in carbonates) , but also a good supply of the ele- ment oxygen; for calcium nitrate contains but one atom of calcium (Ca) with two atoms of nitrogen (N)2, and six atoms of oxygen (O3)2, in each molecule, as indicated in the formula Ca(NO3)2. Magnesium nitrate, Mg(NO3)2, potassium nitrate, KNO3, and all other nitrates also contain oxygen. The supply of oxygen for the formation of nitrates in the process of nitrification comes from the air, and, aside from the killing of weeds, one of the most important effects of cultivation, or tillage, is that it permits the air more freely to enter the soil, and thus promotes nitrification. Another absolute requirement for the process of nitrification is the presence of phosphorus and probably of other mineral food supplies necessary to the growth and multiplication of the bacteria themselves. It is known that without phosphorus there can be neither growth nor life. These minute forms of plant life do not utilize the carbon dioxid of the air by means of the sun's energy; but they derive energy from the oxidation of the nitrogen com- pounds, and by means of this energy they are able even to decom- pose carbonates, if necessary, and to derive their supply of carbon from this source for the formation of their own organic bodies; but for all of this the mineral plant food must be supplied. (As a rule, the carbohydrates furnish the necessary carbon for bacterial growth.) An important consideration in this general connection is the fact that in the conversion of sufficient organic nitrogen into nitrate nitrogen for a hundred-bushel crop of corn, the nitric acid, if formed, would be alone sufficient to convert seven times as much insoluble tricalcium phosphate into soluble monocalcium phosphate as would be required to supply the phosphorus for the same crop. While this specific reaction could not occur in quantity, because the acid monocalcium phosphate would prevent nitrification, the suggestion is of interest in that it affords a quantitative comparison ig8 SYSTEMS OF PERMANENT AGRICULTURE between one of the decomposition products of organic matter and the process of making insoluble plant food available, thus: Ca3(P04)2 + 4HN03 = CaH4(P04)2 + 2 Ca(NO3)2. In accordance with this equation, 56 parts of nitrogen are equiva- lent to 62 parts of phosphorus in the reaction; whereas, when measured by the requirements of the corn crop, 56 parts of nitro- gen are equivalent to less than 9 parts of phosphorus, or only one seventh of 62. Even though the nitric acid maybe at once neutralized by reac- tion with calcium carbonate, it is known that the liberated carbonic acid exerts an influence in the conversion of insoluble phosphates and potassium salts into soluble compounds. Of course, the quantity of organic acids and carbonic acid other- wise produced in the decay of organic matter is many times as great as that of nitric acid. (See also page 633.) Recent investigations of Hall, Miller, and Gimingham (Pro- ceedings Royal Society, 1908) seem to prove that nitrification proper does not occur in acid soils, and that crops growing on such soils must take up their supplies of nitrogen in the form of ammonium salts, formed in the process of ammonificatioh. It is shown, however, that there may be a small amount of nitri- fication in soils that are, on the whole, acid, but which contain here and there particles of calcium carbonate within whose limited sphere of influence the soil is alkaline and nitrification takes place. Under certain abnormal conditions, as under a slime or scum from sewage which prevents access of air, some denitrification may occur. In this process the denitrifying bacteria may even decompose nitrates in order to secure oxygen, and the element nitrogen may be liberated as free gas. Such loss may readily occur in the decay of manure in piles, but in normal soils there is prac- tically no denitrification. METHODS OF SUPPLYING ORGANIC MATTER There are three general methods of supplying organic matter to the soil in practical agriculture: ORGANIC MATTER AND NITROGEN 199 (1) By green manures and crop residues. (2) By accumulations in pasturing. (3) By applications of farm manure. So much has been said and written regarding the value of farm manure that it is common talk that the manurial value of the food is almost wholly recovered in the manure; and there is even a vague notion in the minds of some that the manure is worth more for soil improvement than is the food from which the manure is made; while it is very generally believed that pasturing land increases the fertility of the soil. The fact is that the most important and least appreciated method of maintaining or increasing the supply of organic matter in the soil is by the use of green manures and crop residues. This is best understood by considering the digestibility of common food stuffs and by applying mathematics to the data (see Table 29). TABLE 29. AVERAGE DIGESTIBILITY OF SOME COMMON FOOD STUFFS FOOD STUFFS PER CENT DIGESTED OF TOTAL IN FOOD DRY MATTER OF FOOD RECOVERED IN MANURE Dry Matter Nitrogen Per Cent Pounds per Ton Pasture grasses 71 66 67 61 61 60 48 43 60 63 79 64 70 Qi 61 70 67 81 57 62 74 3° ii 45 42 52 49 78 76 79 29 34 33 39 39 40 52 57 40 37 21 36 3° 9 39 58o 680 660 780 780 800 IO4O II4O 800 740 42O 720 6oO 180 780 Red clover, green Alfalfa, green Mixed meadow hay Red clover hay Alfalfa hay Oat straw Wheat straw Corn stover Shock corn Corn-and-cob meal Corn ensilage Oats Corn .... Wheat bran 200 SYSTEMS OF PERMANENT AGRICULTURE Thus, when pasture grasses containing one ton of dry matter are eaten, only 580 pounds of the dry matter consumed will be re- turned to the land in the droppings; and the manure made from one ton of dry clover hay contains only 780 pounds of dry matter instead of the 2000 pounds taken from the field. In other words, a ton of clover plowed under will add nearly three times as much organic matter to the soil as can possibly be recovered in the ma- nure if the clover is fed. In the case of oat straw, about one half is digested and one half recovered in the manure, while only one tenth of the dry matter of corn is found in the manure. It must be kept in mind, furthermore, that to return even these proportions of organic matter to the land requires that the manure shall be applied to the soil before losses occur by fermentation and decay. The Maryland Experiment Station allowed 80 tons of manure to lie in an uncovered pile exposed to the weather for one year, during which time the amount was reduced to 27 tons. Professor Shutt, Chief Chemist for the Experiment Stations of the Dominion of Canada, exposed two tons of manure containing 1938 pounds of organic matter, from April 29 to August 29, four months, during which time the organic matter was reduced by fermentation and decay to 655 pounds. During the same time the nitrogen was reduced from 48.1 pounds to 27.7 pounds. In ordinary farm practice more or less loss of organic matter is almost certain to occur unless the manure is applied to the soil within a day or two after it is produced. Because the nitrogen of the soil is contained in the organic matter and must be applied in that form in general farming, and because the figures are available, the per cent of nitrogen digested is shown in Table 29 for the common food stuffs named. The fact that 62 per cent of the nitrogen in red clover hay is digested means that only 38 per cent of the nitrogen in the food consumed will be recovered in the solid excrement. If the food ration consists of equal parts of corn and clover hay, the solid excrement will contain 31 per cent, or less than one third, of the nitrogen in the food. Of the remaining 69 per cent, about one third will be retained by the animal (or secreted in milk) and two thirds excreted in the liquid manure, as a general average in live-stock farming for animal ORGANIC MATTER AND NITROGEN 2OI products. Mature work animals excrete practically as much nitrogen as they consume. These facts certainly emphasize the importance of saving all liquid manure and the danger of loss of nitrogen in that form. In a series of digestion experiments (not yet published) con- ducted by the Illinois Experiment Station, with six milk cows, dur- ing a period of 1 5 days, the average daily consumption of food per cow was 19.67 pounds of dry matter contained in a ration of clover hay, corn silage, and mixed concentrates, including corn, oats, wheat bran, gluten meal, and linseed meal. The total dry matter recovered in the dung and urine amounted to 8.1 1 pounds, or 41.23 per cent. (With heavy feeding the digestibility is appreciably less than with lighter feeding.) Of the nitrogen consumed, 80.32 per cent was recovered in the dung and urine, and 20.12 per cent in the milk, indicating a slight loss from the animal bodies. Of the phosphorus consumed, 73.34 per cent was recovered in the manures and 22.28 per cent in the milk, only 4.38 per cent being retained by the animals. Of the potassium taken in the food, 76.02 per cent was recovered in the manures and 13.69 per cent in the milk, the balance, 10.29 per cent, probably having been largely excreted through the skin. The experiments were conducted the last half of June. (Consider- able amounts of commercial potassium salts were once regularly obtained from the washing of sheep wool.) Table 30 shows these results in more detail for ready comparison: TABLE 30. PLANT FOOD RECOVERED FROM FOOD CONSUMED BY MILK Cows Illinois Experiments: Average of 90 Days PLANT-FOOD ELEMENTS RECOVERED IN MILK RECOVERED IN DUNG RECOVERED IN URINE NOT RE- COVERED IN TOTAL MA- NURES Nitrogen, per cent 20.12 22.28 13.69 35-56 72.33 16.70 44.76 I.OI 59-32 19.68 26.66 23.98 Phosphorus, per cent Potassium, per cent As an average of the best three cows, the plant food not recovered in the total solid and liquid manures was 25.03 per cent of the 202 SYSTEMS OF PERMANENT AGRICULTURE nitrogen, 28.07 per cent of the phosphorus, and 28.45 Per cen^ of the potassium, of the food consumed, the differences being prac- tically accounted for by the larger amounts of milk produced by the best cows. However, the poorest cow of the six, in milk produc- tion, digested, during the three successive 5-day periods, 47.18 per cent, 44.77 per cent, and 52.54 per cent, respectively, of the total phosphorus consumed in the food; or, as an average of the 15-day period, only 52.94 per cent of the phosphorus taken in the food was recovered in the dung and urine from this cow. The Pennsylvania Experiment Station (Annual Report for 1899- 1900, page 321) reports digestion experiments with two milk cows during a period of 50 days, with the results shown in Table 31. The rations fed were three fifths mixed clover and timothy hay, and two fifths concentrates, including corn meal, buckwheat middlings, cotton-seed meal, and linseed meal. TABLE 31. PLANT FOOD RECOVERED FROM FOOD CONSUMED BY MILK Cows Per Cow for 50 Days: Average for 2 Cows: Pennsylvania Experiments NOT RECOV- PLANT-FOOD ELEMENTS CONSUMED IN 50 DAYS RECOVERED IN MILK RECOVERED IN DUNG RECOVERED IN URINE ERED IN TOTAL MANURES Nitrogen, pounds . . 67.96 IJ-39 21.46 36.07 10.43 Phosphorus, pounds . 9-73 2.06 6-75 •13 2.85 Potassium, pounds 37-68 3-76 5-93 28.38 3-37 Nitrogen, per cent . . TOO 16.76 31-58 53-06 I5-36 Phosphorus, per cent . 100 21.17 69-37 i-34 29.29 Potassium, per cent . 100 9.98 15-74 75-32 8.94 In the Pennsylvania experiments both the nitrogen and potas- sium are slightly more than accounted for, but 8.12 per cent of the phosphorus in the food consumed was retained by the animals, probably in part for the formation of bones in unborn calves. As an average of both the Pennsylvania and Illinois experiments, only one third (exactly 33.57 per cent) of the nitrogen consumed was recovered in the dung, and nearly one half (48.91 per cent) was excreted in the urine. These facts are worth remembering, and also that 28 per cent of the phosphorus consumed was not recov- ered in the total manurial excrements. ORGANIC MATTER AND NITROGEN 203 Pennsylvania Bulletin 63 reports an experiment covering two months, with four steers, two fed on a cement floor with the manure kept tramped under their feet, and two on an earth floor from which the manure was piled into an adjoining stall and kept under cover. If we assume no loss from the litter used, the following percentages were recovered from the food consumed: PERCENTAGES RECOVERED OF PLANT FOOD IN FEED METHOD OF KEEPING MANURE NITROGEN PHOSPHORUS POTASSIUM On cement floor, tramped . . On earth floor, piled . . . Average per cent recovered 84.8 54-o 8l-3 69.0 91-5 71.0 69.40 75-15 81.25 Of the total dry matter used for feed and bedding, 40.35 and 31.03, or, as an average, 35.69 per cent was recovered in the manure. In Table 32 are given data (in part estimated) from an experi- ment by the Ohio Station (Bulletin 183) in which 28 steers were fed on a cement floor from December i, 1904, to June i, 1905, a period of six months, or 182 days, during which time the average weight of the steers increased from 872 to 1230 pounds. At best, these results can be considered only as approximations, except as to the composition of the manure and the phosphorus added in the raw rock, but they are of interest and of some value as indicating what can be accomplished under the conditions. The amounts of feed and bedding used were accurately weighed, but their plant-food content was computed from accepted averages from each material. "The steers were turned out of the stable once a day to get water, and were allowed to run in the yards from one to two or three hours, consequently some manure was left in the yards." One would assume from this that one tenth or more of the excrements were voided in the yards. An experiment with 100 sheep (averaging 84 pounds each) for a feeding period of 112 days was conducted by the Ohio Station, in which more definite data were secured. Of the feed, 26,936 pounds consisted of hays which were analyzed; while accepted averages were used only for the standard concentrates, including 20,057 pounds of corn, 905 pounds of cotton-seed meal; and 905 pounds 204 SYSTEMS OF PERMANENT AGRICULTURE TABLE 32. RECORD OF Six MONTHS' FEEDING OF 28 STEERS ON CEMENT FLOOR Ohio Experiment Station MATERIALS TOTAL AMOUNT (Pounds) DRY MATTER (Pounds) NITROGEN (Pounds) PHOSPHORUS (Pounds) POTASSIUM (Pounds) Wheat bran .... Corn meal .... Linseed meal . . . Cotton-seed meal . . Corn silage .... Corn stover .... Mixed hay .... Total feed .... 9448 48128 5593 5097 63231 4896 31814 8324 40909 5083 4685 15808 4406 26946 252-3 875-9 304.0 346.1 177.0 5°-9 448.6 1 2O. I 148.2 40.9 64.6 30.6 6.2 37-8 126.2 159.8 63-7 36.8 194.2 56.8 409-3 106161 2454.8 448.4 1046.8 Straw bedding . . . Raw rock phosphate . 39033 4753 35I31 4753 230-3 2O.6 564.6 165.2 Total supplied 146045 2685.1 1033-6 1212 Total manure .... 255203 49698 2006.0 799-0 1064 PERCENTAGES RECOVERED From total supplied •2A.O 74.7 77. "? 87.8 With phosphate excluded . . . 31.8 74-7 50.0 87.8 Corrected for loss in yards . . 35-3 83.0 55-6 97.6 of linseed meal; and for 3020 pounds of oat straw used for bedding. It is understood that the sheep were kept confined in the stables during the entire time. Eight different analyses were made of the manure, and the Ohio Station computes that, of the total plant food contained in the feed and bedding, 64 per cent of the nitrogen, 79 per cent of the phos- phorus, and 97 per cent of the potassium, were recovered in the manure. Wood, of the University of Cambridge, England, reports an experiment with four heifers to determine losses in making and storing farm manure (Journal of Agricultural Science, April, 1907). The experimental feeding began on January 31, 1906, and ended on April 25, 1906, a period of 84 days. During this time two of the animals consumed 13,720 pounds of mangels (containing 1784 ORGANIC MATTER AND NITROGEN 205 pounds of dry matter), 1176 pounds of hay, and used up 1963 pounds of straw as food and litter. The other two animals in an adjoining stall consumed exactly the same amounts of mangels and hay, 100 pounds less straw, and, in addition, 672 pounds of oil cake made from hulled cotton seed. The stalls in Which the animals were housed during the experi- ment were bricked up to the highest level reached by the accumu- lated manure. The floors were not cemented, but were made of clay which was well rammed, and through which, according to Wood's statement, " there could be little leakage of soluble con- stituents." The manure was kept tramped under the feet of the animals, sampled for analysis at the end of the feeding period without disturbing the mass, then left in the compact condition for six months (till November 6, 1906), when it was sampled and weighed (8075 pounds from lot i and 8106 from lot 2) and applied to the soil. Following are the essential results: LOT i. (CAKE NOT FED) CONSTITUENTS DRY MATTER NITROGEN PHOS- PHORUS POTASSIUM In total feed and bedding, pounds . . 4421.0 47-9 5-5 93- 1 Percentage found ' in fresh manure . 58.6 75-2 67-5 86.4 Percentage applied to the soil . . . 42.4 64.6 67-5 72.8 LOT 2. (CAKE FED) In total feed and bedding, pounds . . Percentage found l in fresh manure . Percentage applied to the soil . . . 4942.0 60.0 41.6 9°-3 78.5 51.6 14.8 69-3 69-3 105.0 71.1 1 Assuming no loss of phosphorus during storage. Wood computes that the following percentages from the oil cake fed were recovered and applied to the soil: Dry matter . . . . 29 per cent. Nitrogen 37 per cent. Phosphorus .... 70 per cent. Potassium 52 per cent. 206 SYSTEMS OF PERMANENT AGRICULTURE As a general average for dairy farming, cattle feeding, and sheep feeding, it is shown that practically one third of the organic matter, three fourths of the nitrogen, and three fourths of the phosphorus contained in the feed and bedding are recovered in the total manures. Nearly all of the potassium may be recovered except that sold in milk. (Some potassium may be excreted through the skin, especially in hot weather, but even this is washed off in the pastures by summer rains.) Emmet and Grindley have reported the -following suggestive data from digestion experiments with swine (Journal American Chemical Society (1909), 31, 577): COEFFICIENTS OF DIGESTIBILITY OF THE CONSTITUENTS IN THE FEEDS CONSUMED Per Cent Digested FOOD RATION ANIMAL DRY SUBSTANCE ORGANIC MATTER PROTEIN (Nitrogen) PHOS- PHORUS Ground corn Pie A 87.1 86.7 80.6 64 7 Ground corn PigB 86.5 86.2 76.9 65-4 Ground corn and middlings Ground corn and middlings Pig A PigB 87.3 86.8 87.6 87.2 84.4 82.4 74.6 77-7 Average of four .... 86.9 86.9 8l.2 70.6 It is common knowledge among farmers that swine fed largely on grain produce but little solid manure; and in these experiments only about 13 per cent of the organic matter, 20 per cent of the nitrogen, and 30 per cent of the phosphorus were recovered in the solid excrement. However, the existing data are not sufficient to justify the adoption of these determinations as representing the average digestibility by swine of the phosphorus contained in the grain rations. That the normal coefficient is high, is evidenced by the fact that, unlike most animals, swine normally excrete very appreciable amounts of phosphorus in the urine. The production, composition, care, and value of farm manure are discussed in a later chapter. ORGANIC MATTER AND NITROGEN 207 THE FIXATION OF FREE NITROGEN As already stated, the nitrogen naturally in the soil is contained essentially in the organic matter. Any process which tends to decompose or destroy this organic matter, such as nitrification or other forms of oxidation, will also tend to reduce the total stock of nitrogen in the soil, whether removed by cropping or lost by leach- ing. Because of this fact, the matter of restoring nitrogen to the soil becomes of very great importance. Of course, a part of the nitrogen removed in crops may be returned in the manure produced on the farm; and nitrogen may also be bought in the markets in such forms as dried blood (14 per cent), sodium nitrate (15!- per cent) , and ammonium sulf ate (20 per cent) ; but when we bear in mind that such commercial nitrogen costs from 1.5 to 20 cents a pound, and that one bushel of corn contains about one pound of nitrogen, it will be seen at once that the purchase of nitrogen cannot be considered practicable in general farming, although in market gardening, and in some other kinds of intensive agriculture, commercial nitrogen can often be used with very marked profit. Considering all of these facts, and the additional facts that there are about seventy-five million pounds of atmospheric nitrogen resting upon every acre of land, and that it is possible to obtain unlimited quantities of nitrogen from the air for the use of farm crops, and at small cost, the inevitable conclusion is, that the inex- haustible supply of nitrogen in the air is the store from which we must draw to maintain a sufficient amount of this element in the soil for the most profitable crop yields. It is often stated that legume plants, such as clover, have power to obtain free nitrogen from the air. This is not strictly true. Red clover, for example, has no power in itself to get nitrogen from the air. ,It is true, however, that certain microscopic organisms * which commonly live in tubercles upon the roots of the clover plant do have the power to take up free nitrogen and cause it to unite with other elements to form compounds suitable for plant food. 1 Among the scientists who were prominent in making these discoveries regard- ing the action of bacteria in the fixation of free nitrogen were Hellriegel, Willfarth, and Nobbe in Germany, Atwater in America, Lawes and Gilbert in England, and. Boussingault and Ville in France. 208 SYSTEMS OF PERMANENT AGRICULTURE The clover plant then draws upon this combined nitrogen in the root tubercles, and makes use of it in its own growth, both in the tops and in the roots of the plant. These nitrogen-fixing bacteria live in tubercles upon the roots of various legume plants, such as red clover, white clover, alfalfa, sweet clover, cowpeas, soy beans, vetch, field peas, garden peas, field and garden beans, etc. The tubercles vary in size from smaller than a pinhead to larger than a pea, varying somewhat with the different kinds of plants, being especially small upon some of the clovers, and large upon cowpeas and soy beans. The tubercles are, of course, easily seen with the eye, but the tubercle is only the home of the bacteria, somewhat as the ball upon the willow twig is the home of the insects within. The bacteria themselves are far too small to be seen with the unaided eye, although they can be seen by means of the powerful microscope. Several million bacteria may inhabit a single tubercle. It is not necessary to see the bacteria, because if we find the tubercles upon the roots of the plant, we know that the bacteria are present within, otherwise the tubercle would not be formed.1 It has also been demonstrated that, as a rule, there are different modifications of nitrogen-fixing bacteria for markedly different species of legume plants. Thus, we have one kind of bacteria for red clover, another for cowpeas, another for soy beans, and still a different kind for alfalfa. There are some noteworthy exceptions to this rule. Thus, the bacteria of alfalfa (Medicago saliva) and of common sweet clover (Mellilotus alba) are interchangeable, and apparently identical, as are also the bacteria of cowpeas (Vigna unguicidata) and the widely distributed native partridge pea (Cassia chamaecrista) , relationships of much importance in connection with soil inocula- tion for alfalfa and cowpeas. There is evidence that, by a compara- tively long process of breeding, or evolution, the bacteria which naturally live upon one kind of legume may gradually develop the power to live upon a distinctly different legume to which they were not at first adapted. This change which has been brought about 1 A few plants form starchy nonbacterial tubers, which may be of large size, like the potato and artichoke, or of smaller size, as on the rootstalks of nut grass (Cy per us rotunda). ORGANIC MATTER AND NITROGEN 209 with some certainty in artificial cultures, and which very possibly occurs to some extent in farm manure from legume hay, may fur- nish bacteria with feeble action for a time, but ultimately, no doubt, with full power. Of course, this process of forcing bacteria to live upon a legume to which they are not naturally adapted has little or no practical value, because it is unnecessary, if there is a species of bacteria which naturally live upon the same legume. On the other hand, if, by any such process of breeding, or evolution, a species of nitrogen-fixing bacteria could be developed which could live on a nonleguminous plant, as corn, for example, it would be of incalculable value. As yet, the efforts of bacteriologists, working on this problem, have given only negative results, so far as known to the author. Attention is called to the fact that there are numerous instances where two different kinds of plants live together in intimate part- nership relation. If only one of the two plants receives benefit from this relationship or association, then the plant receiving the benefit is called a parasite. Thus the mistletoe is a parasite upon the elm or gum or other tree on which it lives. The mistletoe draws its nourishment from the tree. The tree is injured rather than benefited by the mistletoe. Dodder is also a parasitic plant, living upon other plants, except during the early part of its growth. Ticks and lice are common examples of animal parasites, living upon other animals. In some cases a relationship exists which is not parasitic, but symbiotic. The term symbiosis, which is commonly used by biologists to define this relationship, means living together in mutual helpfulness. The association of bees and flowers may serve to illustrate this mutual helpfulness, although this is not an example of intimate symbiosis. Thus, the bees obtain their food from the flowers and, in turn, the flowers, many of them, are in- capable of producing seed or fruit unless the pollen is carried from the male flower to the female flower by bees or other agencies. It is well known that plant lice and ants are mutually helpful. Likewise, the association of nitrogen-fixing bacteria and legume plants is a relationship of mutual helpfulness, and this is one of the best illustrations of what is meant by symbiosis. The legume furnishes a home for the bacteria and also furnishes in its juice or 210 SYSTEMS OF PERMANENT AGRICULTURE sap most of the nourishment upon which the bacteria live. The bacteria, on the other hand, take nitrogen from the air, contained in the pores of the soil, and cause this nitrogen to combine with other elements in suitable form for plant food, which is afterward given up to the legume for its own nourishment. Another illustration of remarkable parasitism, if not, indeed, one of true symbiosis, is found in the common lichens living upon rocks and trees. The lichen is not a single plant, but two plants, — one an alga, which lives upon the wood or stone, and the other a fungus, which lives upon the alga. Algae also live in the free state separate from fungi, and the present opinion of botanists seems to be that when the two are associated in the form of lichens, this association is not detrimental, but rather beneficial, to the alga, as well as to the parasitic fungus. If this is true, then it is another case of true symbiosis. (It is now known that some fungi have power to feed upon atmospheric nitrogen, and probably those in lichens furnish combined nitrogen to the algae upon which they live.) In the symbiosis of legume plants and nitrogen-fixing bacteria we have a partnership or relationship of immeasurable value to agriculture. Here is a class of plants (legumes) that are capable of consuming or utilizing nitrogen in quantities larger than could possibly be obtained from ordinary soils for any considerable length of time. They have no power in themselves of taking nitrogen from the atmosphere, and to them the symbiotic relation with this low order of plants (the nitrogen-fixing bacteria, Pseu- domonas radicicola), is especially helpful, and for the best results it is absolutely necessary. INOCULATION FOR NITROGEN FIXATION While it is true that nitrogen-fixing bacteria are essential to the most 'successful growing of legumes, it is also true that, as a very general rule, the proper bacteria for the ordinary legumes are already present in the most common soil, especially where the particular legume has been grown in the vicinity for several years, or where manure made from the legume has been applied. This applies especially to alfalfa in the alfalfa country of the West, to ORGANIC MATTER AND NITROGEN 211 cowpeas in the cowpea country of the South, and to the clovers throughout the Central and Eastern states. Where the special legume has not been grown successfully in the vicinity; or even on fields where the legume has not been grown for many years, and where neither manuring, overflow, nor dust storms have brought the bacteria from other fields, it is worth while to consider inocula- tion. The bacteria for clover, cowpea, and vetch are now very widely distributed over the United States (in part because of the par- tridge pea and wild vetches); but for alfalfa (except in alfalfa regions) and for soy beans, the question of inoculation should always be considered. For inoculating alfalfa, either alfalfa soil or sweet-clover soil can be used, care being taken to use only well- infected soil, collected where the plants have been growing for several years, well provided with root tubercles. The accumulated practical experience of the past twenty years, and the data thus far reported from many comparative experi- ments, combine to prove that the simplest and surest and most economical method of inoculation is by means of well-infected natural soil, collected where the plants are thrifty and free from noxious weed seeds, although the danger of carrying weed seeds or plant diseases by overflow, by wind storms, and in purchased ma- nures and farm seeds is probably a hundred times greater than by using infected soil for inoculation. The amount of soil used varies from 100 pounds to a wagon load to the acre. It may be applied broadcast with some degree of uniformity, and it should be mixed with the surface soil without delay, as by harrowing or disking, because exposure to the sunlight tends to destroy the bacteria. Successful seed inoculation can be performed with fresh, properly prepared artificial cultures, but, as a rule, this method has proved unsatisfactory. Some years ago German promoters undertook to establish the business of selling nitrogen bacteria for seed inocu- lation, and more recently American promoters have widely ad- vertised similar products, but failure is the most common report from their use. For large seeds, such as soy beans, a very satisfactory method of inoculation, suggested by the Illinois Experiment Station, is to thoroughly moisten the seed with a 10 per cent solution of glue, 212 SYSTEMS OF PERMANENT AGRICULTURE immediately sift over them sufficient dry, pulverized, infected soil to absorb all of the moisture, thus furnishing a coating of infected soil for every seed. The seed should be shoveled over a few times, then screened, and planted within a day,, or spread out to dry, after which they may be kept as long as though not covered with dust. The coat of thoroughly infected soil provides a much better inoculation than is common from the use of artificial cultures, and it does not interfere with drilling the seed immediately after treatment. If this method is used for inoculating small seeds, such as alfalfa, greater care must be taken to screen them afterward to prevent clusters of seeds from remaining glued together. If seeds are moistened, they should either be planted very soon thereafter or spread out and thoroughly dried, otherwise they are likely to mold and lose vitality. Infected soil should never be long exposed to bright sunshine, which is very destructive to all forms of bacteria. There has been much discussion during recent years concerning the development of unusually virile bacteria, but even if it were possible to develop and maintain in the soil bacteria of greater nitrogen-fixing power, it is a question whether the discovery would have great practical value (especially after the first year) , for the simple reason that bacteria multiply with such tremendous rapid- ity that we may soon have many times the number of bacteria that are really needed to do the work. In other words, the increase "in numbers may result in just as great efficiency as would result from any increased power of the individual bacteria. One who carefully studies the formation of root tubercles on plants growing on soils in varying conditions or degrees of infection will observe that on plants sparsely infected the individual tubercles or clusters develop to enormous size, comparatively speaking; while in well-infected soils the individual tubercles are much smaller, and clusters scarcely form. It is also observed that the marked effect on the growth, color, and composition of the plant is produced even though only a half-dozen large tubercles form on the roots. It is very evident that the relationship between the bacteria and the host plant is such that if the soil is sparsely infected, so that the roots come in contact with but few bacteria, and but few tubercles are started, those few tubercles will be so enlarged, either in individuals or as ORGANIC MATTER AND NITROGEN 213 clusters, that the multiplication and activity of the bacteria are sufficient to meet the needs of the host plant so far as nitrogen is concerned. Of course, as soon as the soil becomes well infected, the plant roots come in contact with large numbers of bacteria, and many tubercles are formed, but most of them remain smallj and no large clusters are formed, because the bacteria in the large num- ber of small tubercles are apparently capable of furnishing all the nitrogen needed by the host plant. If the other elements were provided in greater abundance, the tubercles would undoubtedly become enlarged, as much as necessary to supply the nitrogen needed to balance the supply of the other plant-food elements util- ized by the plant. NITROGEN FROM SOIL AND AIR Experiments or demonstrations almost without number have been performed to determine the amounts of nitrogen taken from the air by various legume plants when grown in sand cultures essentially free of combined nitrogen, but there are much less data concerning the relative amounts of nitrogen taken from the soil and from the air by legume crops grown on normal cultivated land. There are two methods by which such information can be se- cured with a fair degree of satisfaction. One of these is to deter- mine the amounts of nitrogen in infected plants and in similar plants not infected, grown on the same type of soil; and the other is to compare the total nitrogen content of a nonleguminous crop with that of a crop of infected legume plants, grown at the same time on similar soil. Though not strictly exact, these methods furnish practically correct information. In Table 33 are shown the results of a field experiment to de- termine the amount of nitrogen taken from the air by alfalfa when grown on the common corn-belt prairie land (Illinois Bulletin 76). The difference between the amount of nitrogen contained in the crop from the inoculated soil, on the one hand, and in the crop from the uninoculated soil, on the other hand, represents the amount of nitrogen secured by the bacteria. In no case will this give too much credit to the bacteria; but, if any unavoidable cross inoculation 214 TABLE 33. FIXATION OF NITROGEN BY ALFALFA IN FIELD CULTURE Illinois Experiments on Common Prairie Land PLOT No. TREATMENT APPLIED DRY MATTER IN CROPS (Pounds) NITROGEN IN DRY MATTER (Per Cent) NITROGEN IN CROPS (Pounds) NITROGEN FIXED BY BACTERIA (Pounds) ia ib 20, 2b 3« 3& None 1180 2300 1300 2570 1740 3290 I.8S 2.70 2.O2 2.65 2.03 2.71 2I.8l 62.04 26.20 68.02 35-4° 89.05 Bacteria 40.23 Lime . Lime, bacteria 41.82 Lime, phosphorus .... Lime, phosphorus, bacteria 53-65 occurred during the progress of the experiment, these amounts might understate the effect of the bacteria. It is very probable, however, that the increased root development, induced by remov- ing the nitrogen limit in plant growth, would make it possible for the infected plants to secure somewhat more soil nitrogen than otherwise. (Note the effect of phosphorus in the record.) How- ever, this, too, should perhaps be placed to the credit of the bac- teria, even though it is not atmospheric nitrogen, because if such nitrogen existed in the soil solution, it would soon have been lost in drainage waters if not taken up by the enlarged root system of the growing crop. Slightly more than one third of the total nitrogen contained in the crop from the inoculated unfertilized plot was secured from the soil, with larger proportions and larger actual amounts for the other plots. It should be borne in mind that nitrogen is required for root growth as well as for growth above ground, and that three other crops of alfalfa were cut from these plots during the season, this cutting having been made on May 28. Evident cross inoculation occurred before a second cutting was obtained; but the data given in Table 33 indicate that plot.ifr secured about 172 pounds of nitrogen from the air during the season, the yield of air-dry hay having been 2563 pounds for the first cutting and 10,980 for the ORGANIC MATTER AND NITROGEN 215 season. The value of this " gathered " nitrogen amounts to $25.80 l per acre at 15 cents a pound. Similarly, plot 36, yielding 3625 pounds of air-dry hay in the first cutting and 17,060 per acre for the season, "gathered" 252 pounds of nitrogen from the air, worth $37.80 at 15 cents a pound. The Illinois Station also conducted a series of pot cultures in- cluding 12 inoculated pots and 12 similar uninoculated pots, the results of which support very well the field experiments reported in Table 33. (See Illinois Bulletin 76.) The Dominion of Canada Experiment Stations (Report for 1905) as an average of twenty-one pot cultures increased the nitrogen content of the soil from .0392 per cent to .0457 by growing mam- moth clover for two successive seasons, and turning it all back into the soil. This amounted to 179 pounds' increase of nitrogen per acre to a depth of 9 inches, but it should be noted that the soil was extremely poor in nitrogen, containing only 784 pounds in 2 mil- lion at the beginning. In a similar plot experiment for two full seasons, two cuttings of mammoth clover and all residues being returned to the soil each season, the nitrogen content was increased from .0437 to .0580 per cent, making a gain of 175 pounds per acre to a depth of 4 inches; but only 874 pounds of nitrogen were contained in 2 million of soil at the beginning; so that in both of these experiments the results are not very different than would be secured in sand cultures. The clover was reseeded each year and grown without a nurse crop. The average annual fixation reported amounts to less than 90 pounds per acre. In another experiment by the Illinois Station (Bulletin 94) six sets of immature cowpea plants (10 plants in each set) were carefully collected, tops and roots. Three sets were infected, the others not infected. The plants were taken from a catch crop grown after oats had been harvested, on land that had been heavily cropped with corn and oats until nitrogen had become a limiting element, especially for a catch crop grown after oats. As a general average, the infected plants contained 86 parts of nitrogen in the tops, 5 parts in the roots, and 9 parts in the tubercles, while in direct comparison the noninfected plants contained 25 parts of 1 "They not only work for nothing and board themselves, but they pay for the privilege." — DAVENPORT. 2i6 SYSTEMS OF PERMANENT AGRICULTURE nitrogen in the tops and 2 parts in the roots, thus indicating that 73 per cent of the nitrogen contained in the infected plants was secured by the bacteria. The nitrogen in the dry matter of the infected plants varied from 4.09 to 4.33 per cent in the tops, from 1.45 to 1.53 per cent in the roots, and from 5.76 to 6.05 per cent in the tubercles; while the nitrogen in the dry matter of the noninfected plants varied from 2.32 to 2.69 per cent in the tops, and amounted to .88 per cent (in each of three lots) in the roots. From an experiment with soy beans by the Wisconsin Station (Report for 1907), it is computed that only 14 per cent of the nitrogen contained in .well-infected plants was secured from the air. The yield of dry matter was practically the same, but the infected plants were richer in nitrogen and protein, and thus of better quality. "The soy beans were grown on low, rich soil in these experiments." The Michigan Station (Bulletin 224) reports data showing that 33 per cent of the nitrogen in soy beans was secured by the bacteria, on well-infected plants. As an average of 20 untreated plots in one test, and of 16 plots treated with phosphorus and potassium in another test, both over a period of 25 years, in a four-year rotation of corn, oats, wheat, and hay (mixed clover and timothy), the Pennsylvania Experiment Station reports the following yields in pounds per acre per annum : POUNDS PER ACRE TREATMENT CORN OATS WHEAT HAY Ears Stover Grain •Straw Grain Straw None 2956 3783 IQSS 2801 J°33 1279 1403 1762 815 1108 1265 1776 2783 4138 Phosphorus, potassium . If we compute the nitrogen in the three uncultivated crops (see Table 23) , adopt the estimate that the hay was three fourths clover and one fourth timothy, and assume the soil nitrogen for the hay crops to be as indicated by a curve projected from the amounts furnished to the oats and wheat crops, then the clover must have secured from the air 66 per cent of its nitrogen when grown on ORGANIC MATTER AND NITROGEN 217 untreated land, and 64 per cent on land treated with phosphorus and potassium, the average annual yields of nitrogen per acre being 29.1 pounds for oats, 25.9 for wheat, and 50.1 for hay, on untreated land, and 36.15 pounds for oats, 35.5 for wheat, and 75.5 pounds for hay, on treated land. While the calculation of 65 per cent is probably near the truth for the treated land, where the nitrogen is likely to be the limiting element in crop production, the marked reduction in yield of nitrogen between the oats and the wheat crops on the untreated land is probably not a true index of the change in available soil nitrogen, because on these plots phos- phorus is certainly the limiting element for wheat, as will be seen from later discussion. In any case, we are safe in concluding that soil which will fur- nish from 26 to 36 pounds of available nitrogen for a crop of oats or wheat will also furnish approximately as much for the hay crops, whether timothy or clover. Clover and other legumes take available nitrogen from the soil in preference to the fixation of free nitrogen from the air, the latter being drawn upon only to supplement the soil's supply and thus balance the plant-food ration. In other words, the legumes have no nitrogen limit in yielding power when properly infected, but with abundance of available soil nitrogen constantly provided to fully balance other essential elements or factors, there is little or no development of root tubercles, and little or no fixation of free nitro- gen occurs. From the experimental data here presented or referred to, and from many other calculations approximating exactness, the con- clusion may be drawn that on normally productive soils at least one third of the nitrogen contained in legume plants is taken from the soil, not more than two thirds being secured from the air. This proportion would apply to the nitrogen content of the roots as well as to the tops; so that, if one third of the nitrogen of the entire plant is in the roots and stubble, and two thirds in the crop harvested, the soil would neither gain nor lose in nitrogen because of the legume crop having been grown, the soil having furnished as much nitrogen to the plant as remains in the roots and stubble. When grown on richer soils, such legume crops leave the soil poorer in nitrogen; but on poorer soils, furnishing less than the 218 SYSTEMS OF PERMANENT AGRICULTURE normal amount of available nitrogen, the growing of such legumes would enrich the soil in proportion to its poverty. In other words, to the soil that hath not, shall be given; but, from the soil that hath, shall be taken away. When properly infected, legume plants have power to make nor- mal growth and full development on soils absolutely devoid of nitrogen, if available mineral plant food, limestone, moisture, aeration, and all other essential factors are provided in abundance or perfection; and the statement sometimes made that the pres- ence of soluble nitrogen is necessary, in order to give clover a start, is not correct, as witness the accompanying illustrations of clover growing in purified quartz sand void of nitrogen, with all plant food provided except nitrogen, the culture on the right marked " Bac- teria " having been well inoculated with the clover bacteria; while the middle culture was started in exactly the same manner, except that it was not inoculated. In the culture on the left, all plant food was provided, including nitrogen. NITROGEN IN TOPS AND ROOTS OF LEGUMES From data already given it will be seen that in the study of immature cowpeas at the Illinois Station, the infected plants contained only 14 per cent of their total nitrogen in the roots with more than half of this in the tubercles themselves, at that stage of growth. As the plants approach maturity, the tubercles decay, and only the shell, or outer coat, remains, the nitrogen being absorbed largely by the host plant, but in some part evidently by companion ORGANIC MATTER AND NITROGEN 219 plants, as timothy or blue grass, whose roots may come in contact with the decomposing tubercles. In case of the noninfected cow- peas, only 7 per cent of the nitrogen was found in the roots at that stage of growth. Pot-culture experiments by the Dominion of Canada Experiment Station, with plants planted May 20 and harvested August 4, showed that very poorly infected horse beans contained 19 per cent of their nitrogen and 18 per cent of their organic matter in the roots, while better infected plants made a larger yield and contained 25 per cent of their nitrogen and also 25 per cent of their organic matter in the roots; whereas well-infected mammoth red clover contained 40 per cent of its nitrogen and 35 per cent of its organic matter in the roots. In a field experiment with mammoth clover, seeded with barley in the spring and harvested May 25 the following year, the Cana- dian Station found, per acre, 123.8 pounds of nitrogen in the tops and 48.5 pounds in the roots, to a depth of four feet, corresponding to 72 per cent in the tops and 28 per cent in the roots. As an average of four determinations with red clover, the Con- necticut Station found 28 per cent of its nitrogen, 35 per cent of its phosphorus, and 21 per cent of its potassium in the roots and stubble. As an average of two determinations by the Illinois Station, the red-clover roots found in the surface soil (o to 7 inches) contained 25 per cent of the total nitrogen of the plants, while only one per cent of the total was contained in the roots in the subsurface stra- tum (7 to 20 inches). In the case of nearly mature cowpeas, 12 per cent of the total nitrogen was found in the surface roots (o to 7 inches) , and i per cent in the subsurface (7 to 20 inches) ; and the corresponding figures for nearly mature soy beans were 8 per cent and i per cent. In Table 34 are recorded the data from an Illinois investigation of sweet clover, in which determinations were made of the total dry matter and nitrogen; (i) in the tops as they would ordinarily be cut with a mower, (2) in the surface residues, consisting of stubble and fallen leaves and old stems, (3) in the large roots in the plowed soil to a depth of seven inches, (4) in the smaller roots in the plowed soil, and (5) in the roots of the subsurface stratum from 7 220 SYSTEMS OF PERMANENT AGRICULTURE to 20 inches in depth. The investigation was made when the sweet clover was full grown and nearly mature. The crop was started the previous season, sweet clover being a biennial plant. TABLE 34. ILLINOIS INVESTIGATIONS OF SWEET CLOVER (MELLILOTUS ALBA) PARTS OF PLANT DEPTH (Inches) DRY MATTER PER ACRE NITROGEN PER ACRE Pounds Per Cent of Total Pounds Per Cent of Total Tops harvested . . . Surface residues . . Total tops .... 9029 1338 174 23 10367 8l 197 86 Large surface roots Small surface roots Total surface roots Subsurface roots . . Total roots .... o to 7 o to 7 o to 7 7 to 20 o to 20 I568 24I 17 5 1809 60 1 14 5 22 9 10 4 2410 J9 31 14 Total tops and roots .... 12777 100 228 IOO It will be seen that the yield of sweet clover is very large, amount- ing to 6.4 tons of total dry matter, of which, however, the roots contain only 1.2 tons per acre, or less than one fifth of the total. The tops of sweet clover are nearly as rich in nitrogen as full- grown red clover (40 pounds per ton) , but the roots contain only one seventh, or 14 per cent, of the total nitrogen. Nearly 24 per cent of the total nitrogen was found in the roots, stubble, and sur- face residues (largely of the previous season's growth). The sweet clover used in the investigation was well infected; but, in a previous experiment on the same soil (brown silt loam prairie of the early Wisconsin glaciation), it was found that the yield of sweet clover was almost exactly doubled by thorough inoculation, and the percentage of nitrogen in the infected plants was also about one half more than in the noninfected plants, showing that on this soil about two thirds of the nitrogen required for this large crop was secured from the air. While sweet clover makes a fair quality of hay, if cut sufficiently early in its growth, and is also used for pasture with some success ORGANIC MATTER AND NITROGEN 221 when nothing better can be had, it is not to be compared with red clover or alfalfa for either purpose, but it does give promise of great value as a green manure crop, and it seems appropriate to emphasize the fact that the 6.4 tons of dry matter furnish as much humus-forming material and as much nitrogen as would be furnished by 25 tons of average farm manure. In the Wisconsin experiments above referred to, the infected soy beans contained in their roots about 4 per cent, 6 per cent, and 5 per cent, of their nitrogen, phosphorus, and potassium, respec- tively; and in the Michigan experiments the corresponding figures are about 4 per cent, 6 per cent, and 6 per cent, respectively. From an exhaustive investigation of the crimson-clover plant (Trifolium incarnatum) , Penny (Delaware Bulletin 67) reports the following average results' for fall-seeded crops harvested about May 15, when nearly in full bloom: TABLE 35. COMPOSITION OF CRIMSON CLOVER IN BLOOM Delaware Experiments : Pounds per Acre PARTS OF PLANT AIR-DRY MATTER NITROGEN PHOS- PHORUS POTASSIUM Tops, pounds . 4CI2 IO3 76 7O Roots, pounds 2O22 41 3-1 IS Total, pounds 6S34 144 io.7 8s PERCENTAGE OF TOTAL Tops, per cent 60 72 71 82 Roots, per cent '. . 21 28 20 18 The proportions were found to vary considerably, but this gen- eral average shows the crimson-clover roots (to a depth of 24 inches) to contain less than one third of the organic matter, nitrogen, and phosphorus, and less than one fifth of the potassium of the entire plant. It was found that 77 per cent of the roots were in the first 6 inches of soil, and 1 3 per cent in the second 6 inches, 7 per cent in the third, and 3 per cent in the fourth 6 inches. In Table 36 are recorded much additional information concern- 222 SYSTEMS OF PERMANENT AGRICULTURE TABLE 36. COMPOSITION OF PLANTS (Tors AND ROOTS) Delaware Experiment Station : Crops seeded July 22 CROP, AND DATE OF HARVEST PARTS OF PLANT POUNDS PER ACRE AND PER CENT IN ROOTS Air-dry Matter Nitro- gen Phos- phorus Potas- sium Cowpeas Nov. 7 Tops 3718 301 9 65.2 4-2 .1 7-2 1.0 .1 39-2 I.9 .1 Roots o to 8 inches . * . Roots, 8 to 12 inches .... Per cent in roots 8 6 13 8 Soy beans Nov. ii Tops 6790 717 39 130.9 8.8 •5 I6-S 1.0 .0 38.3 1.4 .1 Roots o to 8 inches Roots, 8 to 12 inches .... Per cent in roots 10 6J 5* 4 Vetch Nov. 19 Tops 3064 584 16 108.0 12.8 •4 9.8 2.0 .1 65-i 5-7 .2 Roots o to 8 inches Roots, 8 to 12 inches ... . Per cent in roots 17 ii 18 8 Crimson clover Nov. 20 Tops 5372 38i 32 128.2 5-7 •5 25-9 .8 .1 69.7 3-2 •3 Roots, o to 8 inches Roots, 8 to 12 inches .... Per cent in roots 7 6 3* 5 Alfalfa Nov. 20 TODS . 2267 1972 8 54-8 40.2 .2 5-7 3-7 .0 26.7 7-9 .0 Roots, o to 8 inches Roots, 8 to 12 inches .... Per cent in roots 47 42 39 23 Red clover Nov. 22 Tops . 2819 1185 27 69.8 32'5 •7 8-3 4-3 .1 38.6 8.0 .2 Roots, o to 8 inches Roots, 8 to 12 inches .... Per cent in roots 3° 32 35 18 Cow-horn turnip Nov. 15 Tops 2565 2902 64.4 44-7 6.2 5-1 66.6 Si.8 Roots Per cent in roots 53 4i 45 44 Rape Nov. 1 6 Tops 5533 864 116.2 13.2 18.3 2.2 123.0 10.9 Roots, o to 8 inches Per cent in roots *& IO II 8 ORGANIC MATTER AND NITROGEN 223 ing the composition of the tops and roots of the most important field legumes. It summarizes a series of investigations by Penny and Close, and confirms much other data relating to these crops and bearing directly upon the problems of supplying the soil with organic matter and nitrogen. As an average of all determinations, it is safe to say that about one third of the nitrogen of the red-clover plant is contained in the roots and stubble, and that the growth of clover above ground contains, before rotting or leaching, about 40 pounds of nitrogen to the ton of air-dry substance. Alfalfa contains a somewhat larger proportion of its nitrogen in the roots, at least during the first year of its growth; and possibly the total nitrogen of the alfalfa roots would average one half as much as the total removed in the crops, even when the plants are several years old, considering the entire root system, which com- monly reaches a depth of 20 feet or more with old plants. Alfalfa hay contains 50 pounds of nitrogen per ton. In the case of such annuals as cowpeas and soy beans, not more than one tenth of the nitrogen is found in the roots and stubble, as a rule. The crop above ground contains (when thoroughly air-dry) about 43 pounds of nitrogen per ton for cowpeas and about 53 pounds per ton for soy beans. Extensive experiments are in progress in Illinois to determine, under actual field conditions, what systems of grain farming (with green manures and crop residues) and what systems of independent live-stock farming will increase or maintain the organic matter and nitrogen of the soil; but these are investigations that require time, and but few results have as yet been published. A series of pot cultures has been reported (Illinois Bulletin 115) which illustrates the fact that legume green manures may take the place of commercial nitrogen. The soil used in these experiments was the yellow silt loam from the unglaciated area of southern Illinois (Pulaski County), which, as will be seen from Table 15, is quite deficient in nitrogen. The field from which this soil was collected had been under cultivation for about 75 years, during which time the average yield of wheat had decreased from about 25 bushels to 5 bushels per acre. In the pot-culture experiments, catch crops of cowpeas were 224 SYSTEMS OF PERMANENT AGRICULTURE planted on certain pots every year after the wheat was harvested, the legumes being turned under before sowing wheat for the next year. From a study of Table 98, it will be seen that practically no gain has been made except where nitrogen has been supplied, either directly in commercial form or indirectly by means of legume treatment. It should be borne in mind that no legume treatment preceded the 1902 wheat crop. The catch crop of cowpeas which was planted after the 1902 wheat crop and turned under later in the fall, produced a marked effect upon the 1903 wheat crop. This effect became more marked in 1904 and 1905, when every pot receiving legume treatment outyielded the pot receiving lime- nitrogen treatment. Previous to 1905, the addition of phosphorus to nitrogen or legume treatment always increased the yield. The addition of potassium still further increased the yield more or less. The effect of both phosphorus and potassium has been less where decaying organic matter has been provided in the legume treatment than where the nitrogen has been supplied in commercial form (dried blood) carrying but little organic matter. The last line in the table gives the yield from a pot of virgin soil collected from a piece of unbroken virgin sod land adjoining the cultivated field from which the soil in all the other pots was taken. NITROGEN FIXATION BY NONSYMBIOTIC BACTERIA Aside from the fixation of free nitrogen by the bacteria living in symbiotic relationship with legume plants, there are at least three groups of bacteria that have nitrogen-fixing power without this relationship. First, and possibly of greatest importance, are the legume bacteria themselves, which continue to fix nitrogen in pure cultures entirely separated from legume plants, and very probably also continue thus to fix some nitrogen in the soil, even after the legume plants have been destroyed, the bacteria drawing their nutriment from the decaying organic matter. Second, is the anaerobic group of bacteria discovered by Wino- gradsky in 1893, and called Clostridium; but these have little ORGANIC MATTER AND NITROGEN 225 agricultural significance, because they develop only in the absence of free oxygen. » Third, is the azotobacter, an aerobic group described by Beijer- inck in 1901, of which Lipman has recently found some additional species, one of which (Azotobacter vinelandii) appears to be quite active in the fixation of free nitrogen when the best artificial condi- tions are provided. (See Lipman's " Bacteria in Relation to Coun- try Life," page 199.) Beijerinck has found, " as a result of improved technique for the determination and study of the distribution of the organism, that azotobacter fixes nitrogen, and that there is a distinct relation between the distribution of this organism and leguminous plants." The author questions if there may not be a relationship between the legume bacteria and the azotobacter. (See Experiment Station Record, 1909, Vol. 20, page 920.) Whether any of these nonsymbiotic bacteria are of appreciable agricultural importance under practical conditions, is not fully established. It is known, however, that a supply of organic matter is essential for their development, and the organic matter of the soil which must be decomposed in order to furnish their necessary supplies of carbonaceous food may also furnish part or all of the nitrogen which they require. (See also pages 434-440.) CHAPTER XV ROTATION SYSTEMS FOR GRAIN FARMING ABOUT three fourths of the farmers of central United States are so-called grain fanners. There has always been a large proportion of grain farmers; and, furthermore, there always will be, and al- ways must be, for the world does not live by meat alone, nor even upon meat and dairy products; bread is the staff of life. Notwithstanding these well-known facts, whenever the grain farmer of central United States has asked for information as to how he could maintain the fertility of his soil, the reply has always been, " Become a live-stock farmer." While this may or may not be good advice for the individual farmer, it is certainly not good advice for all the farmers of the state or nation. On the other hand, grain farming is not only profitable, — and often more profitable than live-stock farming, — but there are methods, and profitable, practical methods, by which the grain farmer can not only maintain the fertility of his soil, but even make it more productive than it ever was even in its virgin state. Let us consider the simple three-year rotation: (i) corn, (2) oats, and (3) clover, which is becoming somewhat common in the Illinois corn belt; or (i) corn, (2) wheat, and (3) clover, the most common crop rotation of Ohio. Of course, as many fields should be provided as there are years in the rotation, so that every crop may be represented every year. We may assume yields of 100 bushels per acre of corn and oats, 50 bushels of wheat, 4 tons of clover, and 4 bushels of clover seed; or these yields may be divided by two, the same proportions being maintained. With the smaller yields the corn, oats, and clover seed will remove 86£ pounds of nitrogen; while, in accordance with the average data thus far obtained, we may count that the clover secures 40 pounds of nitrogen from the air for each ton of hay it 226 ROTATION SYSTEMS FOR GRAIN FARMING 227 would produce, the nitrogen contained in the roots and stubble being no more than that furnished by the ordinary corn-belt soil. If the two regular cuttings would make two tons of clover hay; and if the growth of clover during the previous season (after wheat or oats harvest) and during the autumn (after the clover-seed harvest) and the following spring (before plowing for corn) would make another half-ton of clover hay, or two and one half tons in all, then 100 pounds of nitrogen would be secured from the air to balance the 86 \ or 89 pounds removed in the grain and seed. In other words, from 13 to 15 per cent more nitrogen is returned by the clover than is removed in the grain and seed. On normal soils the only addition to this system that is neces- sary in order to establish a permanent agriculture is the applica- tion of 20 pounds of phosphorus for the lower yields, or 40 pounds for the larger yields, these amounts being ample to replace the phosphorus removed in the grain and seed and to cover all possible loss by leaching. For the smaller yields, 200 pounds per acre of steamed bone meal or 200 pounds of raw rock phosphate or 400 pounds of acid phosphate, every three years, will be more than sufficient to maintain the phosphorus content of the soil; and twice these quantities would be ample for the larger yields after the productive power of the soil has been raised to that point. To do this may require much heavier initial applications of phosphorus, or moderately heavy applications for the first four or five rotations. Thus, an application of one ton of good rock phosphate (12^ per cent phosphorus) every three years would add 1250 pounds of phosphorus per acre in 15 years, or more than 1000 pounds above the amount removed in the grain or seed for the larger yields in the rotation. In other words, the phosphorus content of the aver- age Illinois surface soil should be doubled in 15 years under this system, and the annual cost of phosphorus ($2.50) would be no more than is commonly paid by farmers in the Eastern and Southern states for so-called " complete " fertilizers. If the phosphorus applied produced increased yields of 7 bushels of corn and equiva- lent values of other crops, the cost would be covered by the in- creased crops. (See actual results reported in later pages.) This system requires that the ears of corn shall be husked and the stalks returned to the soil, that the oat straw and clover straw 228 SYSTEMS OF PERMANENT AGRICULTURE shall also be returned to the land after threshing out the grain or seed, and that the regular crop of clover shall be mowed and left lying on the land. If necessary, to prevent too rank a growth (which might smother the plants), the clover may be mowed twice before the seed crop is allowed to grow. If the larger yields are considered, the same rotations hold, ex- cept that the richer soil would very possibly furnish a larger pro- portion of the nitrogen required by the clover plant. With some modifications, these two three-year rotations may be combined in a six-year rotation of (i) corn, (2) corn, (3) oats, (4) clover, (5) wheat, and (6) clover, which avoids the necessity of seeding wheat on the corn ground, a task sometimes difficult to accomplish. If necessary, this may be reduced to a five-year rotation, either by omitting one corn crop, or by plowing under the clover in the spring of the fifth year as late as practicable for corn. With the former change it will be less difficult, and with the latter more difficult, to maintain the nitrogen, than with the six-year rotation. A four-year rotation, which the author prefers for the general conditions in the North Central states, includes the four crops, wheat, corn, oats (or barley), and clover, in the order given. Clover should also be seeded on the young wheat in the early spring, and plowed under (after disking, if necessary to insure capillary connection) as late as practicable the next spring before planting corn. In grain farming only the seed crop of clover is removed from the land, and the phosphate is plowed under with the clover residues for the wheat. All of the threshed straw (from wheat, oats, and clover) is hauled from the threshing directly to the field, where it may be thrown off in windrows, and soon afterward spread over the land as uniformly as necessary. It may be used for a top dressing for wheat, or it may be applied in moderate amounts to the land from which wheat has been harvested, where the young clover is growing as a green manure for the following corn crop. Judgment must always be exercised in the matter of applying large amounts of straw, or of plowing under heavy crops, or applica- tions of coarse material, which may do damage if turned under too late in the spring, especially if the season is dry or if the soil is deficient in lime. ROTATION SYSTEMS FOR GRAIN FARMING 229 For southern Illinois and other Southern states, a four-year rota- tion of (i) corn, (2) cowpeas (or soy beans), (3) wheat (or oats), and (4) clover is very satisfactory; and a three- year rotation, in which it is more difficult to maintain the nitrogen, is (i) wheat, (2) corn, and (3) cowpeas; or (i) cotton, (2) corn and cowpeas, and (3) oats and cowpeas, in either of which soy beans may be sub- stituted, and should be substituted in case of danger from cowpea wilt or other disease; and similarly, alsike or sweet clover may be sometimes substituted for red clover in case of clover sickness, which is more fully discussed later on. In these rotations consider- able use can be made of legume catch crops. Thus red clover or sweet clover may be started with the wheat and plowed under the following spring as green manure for corn, or cowpeas can be grown after the wheat is harvested. Clover or vetch or cowpeas (or a mixture of legumes) can be seeded in the corn at the time of the last cultivation and plowed under late the following spring before seeding the regular cowpea crop; and, where cotton is to follow, some legume catch crop could be seeded after the regular cowpea crop is harvested, allowed to grow during the late fall, winter, and early spring, and plowed under for cotton. If necessary, not only the cotton stalks, but also the cotton seed may be returned to the land, the lint of itself being of much greater value than any grain crop. (Two bales of cotton, or 1000 pounds of lint, worth $100, is no larger crop, comparatively, than 100 bushels of corn, worth $40, as a ten-year average price in Illinois.) Any one who is familiar with agricultural practice can estimate closely the probable or possible crop yields, and with the yields determined and with the disposition of the crops, catch crops, and crop residues decided upon, any one can compute very closely from the data given in Table 23 as to the probable maintenance of the nitrogen supply. Two factors of opposite effect — (i) the loss of nitrogen, espe- cially by leaching, and (2) the addition of nitrogen in rain and by fixation of free nitrogen independent of legume plants, especially by the azotobacter (factors which tend to counterbalance each other) — are discussed on another page. From all of the facts it will be understood that there is just as much reason and as much satisfaction in computing that a 50- 230 SYSTEMS OF PERMANENT AGRICULTURE bushel crop of corn removes from the soil 74 pounds of nitrogen arid that eight tons of average manure, or two tons of clover, plowed under will return 80 pounds of nitrogen to the soil, as there is in estimating the quantity of corn and hay that will be required to feed a car load of steers for eight months. The average American grain farmer " changes " his crops more or less by occasionally substituting oats or barley for corn or wheat. He rarely even plows under a catch crop of clover, often burns his straw and corn stalks, and makes almost no effort to restore to the soil the fertility removed in crops. The supply of active organic matter rapidly decreases.. Consequently the land soon reaches a condition of low productiveness, and he is correctly termed a " soil robber." He knows his soil is running down, but he hopes it will last as long as he does. The average live-stock farmer is forced to keep more or less of his land in meadow and pasture, and in the residues and grass and clover roots supplies some fresh organic matter, which, as it decays, hastens the decomposition of the old humus and also the liberation of mineral elements from the soil. By these means and by the better avoidance of insect injuries and plant diseases, he produces larger crops when corn or other grains are grown, which may reduce the fertility of his soil even more rapidly than the smaller crops of the grain farmer; but he does not know it, and, as he makes a good show on new, rich land for two generations or more, he is incorrectly held up as a " soil builder." In actual practice most of the farm rarely, if ever, receives an application of manure. " Farm manure is good enough, but there's not enough of it " is the common report of experienced live-stock farmers. This inadequacy of the manure supply is due not only to the large destruction of organic matter when fed to animals, but also in part to unavoidable losses of manure and in part to unnecessary waste. In planning systems of permanent agriculture of wide applica- tion, a distinction should be kept in mind between the ordinary live-stock farmer, who markets his own farm produce in the form of meat, wool, or dairy products, and the stock breeder, who sells breeding animals at higher prices, or the stock feeder, who often buys both stock and feed and is to that extent not a farmer but a manufacturer. CHAPTER XVI LIVE-STOCK FARMING IF a four-year rotation is practiced, including two crops of corn, followed by oats, with clover seeded the third year, and clover for hay and pasture the fourth year, and all crops used for feed and bedding, the nitrogen balance can be determined by simple com- putations based upon facts established within narrow limits by such data as have been cited in the preceding pages. We may assume 5o-bushel crops of corn and oats, and i^ tons of hay in the first cutting, with i ton additional for all previous and subsequent growth, the same as for the grain system; or here, too, we may double the assumed yields and maintain the same proportions. With the lower yields the three grain crops and the i^ tons of clover hay would contain 256 pounds of nitrogen. Under the most careful system of saving manure, three fourths of this, or 192 pounds, can be returned directly to the land, and to this may be added 30 pounds of nitrogen added to the soil in the manure from the one ton of pastured clover, making 222 pounds added by pastur- ing and manuring. If we consider that the nitrogen contained in the clover hay was taken from the air, the real draft upon the soil is only 196 pounds. In this system about 13 per cent more nitro- gen is returned in the manure and pasture than is removed from the soil by the three grain crops. If the rotation is extended to five years by sowing clover and timothy and pasturing the fifth year, assuming the growth to be three fourths clover the fourth year and the pasture herbage to be only one fourth clover the fifth year, the outcome with respect to nitrogen would be 256 pounds removed from the soil and 267 pounds returned in the manure and pasture droppings during the five years, if we disregard the strong probability that timothy, growing as a companion crop, secures some portion of its nitrogen from the decaying tubercles of the clover roots. 231 232 SYSTEMS OF PERMANENT AGRICULTURE If we assume that three fourths of the produce harvested is used for feed and one fourth for bedding, and that one third of the or- ganic matter consumed by animals is recovered in the manure or droppings, then the four-year rotation under live-stock farming would add organic matter to the soil at the rate of i^ tons a year, while the three-year rotation of corn, oats, and clover, under the grain system, would add organic matter at the rate of if tons a year. Thus, it will be seen that the grain system under a three-year rotation of corn, oats, and clover, or of corn, wheat, and clover, or under a four-year rotation of wheat (and clover), corn, oats (or barley), and clover; or under a six-year rotation of corn, corn, oats, clover, wheat, and clover, will maintain the nitrogen as well, and the humus, or organic matter, somewhat better, than the live- stock system under the four-year rotation of corn, corn, oats, and clover, or under the five-year rotation of corn, corn, oats, clover, and timothy, with all produce either harvested or pastured. Furthermore, the most uncertain feature in these methods is in regard to saving the manure. The computations here given pro- vide for practically no loss of solid or liquid excrement, for no loss by fermentation or fire-fanging, which may occur even under cover, and for no loss by leaching of manure exposed to the weather in the open barnyard. It is common knowledge that a large part of the value of manure is frequently lost before it is applied to the land. The author has diligently inquired at many farmers' meetings for several years for a man who had applied manure made from crops grown on his own farm to all of the cultivated land on a 160- acre farm, — not to all during one year or during one rotation, but even during all the time he had farmed the land. Very few men have been found who could answer that all of their cultivated land had been thus manured, — not more than one in a thousand. In nearly all sections of the country a farmer can be found, here and there, — sometimes one in ten, and sometimes only one in a hundred, — who feeds all the crops he raises and also all that he can buy at reasonably low prices from his neighbors, who supple- ments all this with more or less purchased bran and shorts, oil meal, cotton-seed meal, etc., and who is thus able to produce sufn- LIVE-STOCK FARMING 233 cient manure of good quality to maintain or even to increase the fertility of his own farm. In specially favored localities, a few farmers haul manure from town, or even ship it from the larger cities, especially for use in market gardening, and they, too, are thus enabled to enrich their lands at the expense of many other farms; but no extensive state or nation ever has or ever can maintain sufficient live stock; even in country and city combined, to furnish manure with which to maintain the productive power of all the farm lands. Even under the best system of independent live-stock farming; that is, without dependence upon the purchase of supplementary food stuffs or the use of manure from town, it is necessary to pur- chase and apply some phosphorus in order to replace that sold in the animals and animal products, butter and cream being the only important farm products that do not contain appreciable amounts of phosphorus. In order to increase the phosphorus content of normal soils, phosphorus should be applied in live-stock farming the same as in grain farming, but to merely replace that sold in animal products will require applications of only one half as much phosphorus as is required for grain farming, assuming that all of the grain and clover and part of the corn stover and oat straw are eaten by the live stock. Thus, for the larger yields, the loss of phosphorus would be about 20 pounds per acre in four years with live-stock farming, and 30 pounds in three years with grain farming, as can readily be determined by computation from the data given in Table 23 and the results of the digestion and feeding experiments with dairy cows by the Illinois Station, with dairy cows and steers at the Pennsylvania Station, and with sheep at the Ohio Station, from which we must conclude that as an average at least one fourth of the phosphorus contained in the feed is not recovered in the manure. In comparison with these permanent systems of agriculture, it is worth while to compute the results of a four-year rotation of three crops of corn and one of oats, seeded with clover to be plowed under the next spring, assuming that the corn is husked and the stalks burned (except the third year, when the stalks are disked down for oats), that the oat crop is all removed, and that the total growth 234 SYSTEMS OF PERMANENT AGRICULTURE of clover would equal one ton of hay per acre. This will be recog- nized as the " best " common system of grain farming followed in past years in the heart of the corn belt. And not infrequently the live-stock farming has been like unto it, except that the corn stalks have been pastured before being burned or disked down, the clover has been pastured the first fall, cut for hay the next summer, and pastured again before plowing for corn, and 10 loads per acre of rotted and leached manure have been applied occa- sionally to the high places, where the land is getting thin and where the clover fails to catch. Another most significant fact should be considered in this com- parative study of grain farming and live-stock farming; namely, that 1000 bushels of grain has at least five times as much food value and will support five times as many people as will the meat or milk that can be made from it. (Not more than one fifth of the nitrogen consumed in the food of animals is retained, as a rule, in the milk or other edible animal products, and the proportion saved of carbonaceous food is usually still less.) In his American lectures on the " Agricultural Investigations at Rothamsted, England, during a Period of Fifty Years," which were published as Bulletin 22, Office of Experiment Stations, United States Department of Agriculture, Sir Henry Gilbert " summarizes the results of very numerous experiments " conducted at Rothamsted with growing and fattening cattle, sheep, and swine. From this summary we obtain the following data: DISPOSITION OF 100 POUNDS OF DRY SUBSTANCE IN FOOD CONSUMED Summary of Rothamsted Feeding Experiments ANIMALS USED IN EXPERIMENTS . . CATTLE SHEEP SWINE Dry substance found in animal increase, pounds . . 6.2 8.0 I7.6 Dry substance found in excrements, pounds . . . . 36.5 31.9 I6.7 Dry substance destroyed by the animal, pounds . . . 57-3 60. i 65-7 Average per cent of fat in the fat animal .... 3° 33 44 Thus, a large proportion of the food digested is destroyed by the animal and must be exhaled or thrown off as carbon dioxid, water, urea, etc. Of the small percentage of the food that is LIVE-STOCK FARMING 235 actually retained in the animal tissues, only one half to two thirds may serve as human food, after discarding the offal and non- edible parts. On the other hand, the carbohydrates of the food contribute largely to the formation of animal fat, the energy value of which is about 2^ times that of carbohydrates; so that, in case of fat swine, the edible food produced is equivalent to about 20 per cent of the dry substance in the ration consumed by the ani- mal; while, in the production of fat cattle, less than 10 per cent of the dry matter in the ration consumed is represented in the human food produced. These data do not answer questions as to the comparative value of vegetable and animal food for human nutrition; but 50 cents for a piece of steak, with 10 cents for potatoes, and no extra charge for bread, must roughly represent the relative cost of the materials; and perhaps the vegetarian would hold that the steak might as well be replaced by peas or beans costing 10 or 15 cents. With all of these facts considered, it seems evident that live- stock farming must and should continue to decrease, except on rough lands not suited to cultivation, in semiarid sections where the average produce is not worth harvesting otherwise, or in espe- cially favored sections near the cities where dairy farming is profitable and may easily be made permanent because of the addi- tion of manure hauled from town or made from purchased feeds. It should be understood, however, that America still produces a large surplus of grain suitable for human food, and for some years to come more or less of this, especially of corn, will be most profit- ably marketed through the production of live stock. For the live-stock farmer, all must agree with the following statement from Mumford's " Beef Production" (page 13): "When we remember that the production of manure of the looo-pound steer for a six-months' feeding period varies from three to four tons, we can appreciate what a factor farmyard manure may become in increasing the revenues of the farm, and that profits and losses in cattle feeding should not stop with a consideration of the cost of cattle and feed and their selling price." CHAPTER XVII THE USE OF PHOSPHORUS IN DIFFERENT FORMS HAVING determined how to correct soil acidity (when necessary) and how to keep the soil sweet, by means of ground limestone; having determined how to maintain or increase the supply of or- ganic matter and nitrogen in the soil, by means of farm manure in live-stock farming, or by means of legume crops and catch crops and crop residues in grain farming, or by a combination of these in mixed or diversified farming, which is sometimes preferable and more profitable than either alone; and having determined the absolute necessity of maintaining or increasing the supply of phos- phorus in the soil by direct applications exceeding the amounts removed in crops harvested, — the next most important question, and the only remaining exceedingly important question, is, What form or forms of phosphorus shall be used? There are four general sources of phosphorus for use in soil improvement: (i) farm manure, (2) bone meal, (3) phosphate rock, and (4) basic slag phosphate. The first two are themselves farm products, and at the best only provide that the phosphorus taken from the soil shall be returned to the soil, and if there is any loss whatever, the ultimate effect, applied to the state or country as a whole, must be a reduction in the general average fertility of the soil. To supply to a 40-acre field 1000 pounds of phosphorus (25 pounds per acre) in the form of manure made from purchased corn, would require an investment of more than $3000 at 40 cents a bushel for corn. While the purchase of grain and other food stuffs provides a method by which soils can be positively enriched in phosphorus, and while there is usually more or less profit from feed- ing, so that the phosphorus thus obtained may really cost nothing in the end, nevertheless, it is worth while to keep in mind that this method requires large capital, special equipment, such as buildings, 236 USE OF PHOSPHORUS IN DIFFERENT FORMS 237 water supply, and fences, and some knowledge and skill in the live- stock line, including business ability in the purchase and sale of stock and animal products, in addition to the requirements for the production of crops. The addition of phosphorus in farm manures is undoubtedly one of the best methods for those who are able to practice it, and by use of liberal proportions of grain and other concentrates rich in phosphorus, especially bran from different grains, cake or meal from various seeds from which the oil has been expressed, very considerable amounts of phosphorus are added. It is important, however, to understand and to keep in mind that average farm manure is poor in phosphorus in comparison with its content of nitrogen and potassium, especially when made from the produce that remains after part of the grain has been sold from the farm, and more especially when used in connection with a rotation in- cluding legume crops and on soils abundantly supplied with po- tassium but poor in phosphorus. In other words, under such con- ditions average farm manure is a very poorly balanced fertilizer, and if used even in moderate quantities the production of stalks or straw is likely to be excessive in comparison with the yield of grain; and the small grains are also likely to lodge, because the unbalanced ration produces weakness even in straw of large growth. Considering the more concentrated phosphorus products, there are four classes to be kept in mind: (i) natural bone, (2) natural rock phosphate, (3) basic slag phosphate, and (4) acid phosphate. In the first group are raw bone meal, steamed bone meal, bone tankage, and phosphatic guanos. In the second group are the va- rious natural mineral phosphates, as the hard and soft phosphates of Florida, the land rock and pebble phosphate of South Carolina, the brown and blue phosphates of Tennessee, and the apatite of Canada. The third group consists of basic slag only, sometimes called Thomas phosphate. The fourth group includes all acidulated phosphates, such as acidulated bone meal, acidulated bone black, acidulated bone ash, common acid phosphate, and double super- phosphate. The term dissolved is often used for acidulated goods. Non-acidulated bone black and bone ash are best considered as belonging to the second group with the natural mineral phosphates- In groups i and 2, the phosphorus is present chiefly in the same 238 SYSTEMS OF PERMANENT AGRICULTURE compound, tricalcium phosphate, Ca3(PO4)2, the difference be- tween these two groups being the presence of more or less organic matter within the pores of the bone, while the products in group 2 contain little or no organic matter. In group 3 the phosphorus is contained in a basic or alkaline compound or mixture, and in group 4 the phosphorus exists chiefly in monocalcium phosphate, an acid salt. This form of phosphorus is soluble in water, and even the dicalcium, or " reverted," phosphate is soluble in very weak solvents (as in neutral ammonium citrate solution) ; while all prod- ucts in groups i, 2, and 3, are known as insoluble forms of phos- phorus. About seventy years ago Sir John Lawes, independent of a suggestion previously made by Liebig, treated bone meal with sulfuric acid and formed an acid phosphate that proved of greater benefit to the turnip crop grown on the Rothamsted soils than the crushed bone or coarse bone meal then in use; and in 1842 a patent was taken out by him for treating mineral phosphates with sulfuric acid in order to increase their availability in crop production. Acidulated bone meal has been much used as a fertilizer, but gradually its use has given way, largely because the most success- ful and influential farmers in our Eastern states have insisted that in the long run fine-ground pure raw bone meal was more profit- able than acidulated bone. It is always recognized that the acidu- lated bone gave the best results the first year, but, on the basis of equal cost, the raw bone proved much more durable, and hence, more profitable in the end, especially where good rotations were practiced and some effort made to keep the soil supplied with organic matter. In more recent years steamed bone meal is replacing the raw bone, because, as a rule, it gives better results, due in part to its larger phosphorus content and in part to the fact that it is usually more finely ground than the raw bone. There are still to be found those who argue that " if one wishes to benefit himself, he should use acidulated phosphates, but if he wishes to benefit his grand- children, he should use bone." However, the farmers' demand for " pure raw bone " and for " steamed bone meal " continues to increase, and this steady demand is based upon long- continued USE OF PHOSPHORUS IN DIFFERENT FORMS 239 experience in the practice of agriculture. These products are everywhere looked upon as safe fertilizers. They never injure the soil, and where most used they are classed with farm manure in that regard. And this is a correct view, for farm manure and bone are two important products from the same source. In other words, from the fertility standpoint, animals separate crops roughly into manure and bone, and if we return the bone with the manure, we thus return practically all of the fertility removed by the crop, except a part of the nitrogen, which it is not necessary to return directly, because the legumes are able to secure it from the air. Basic slag phosphate, a by-product in the manufacture of steel from pig iron containing considerable quantities of phosphorus, has been used as a phosphorus fertilizer since 1882. Recent investigations1 by Director Hall of Rothamsted have con- vinced him that the typical phosphorus compound in basic slag is a double phosphate and silicate of calcium of the composition Ca3(CaO) (PO4)2CaSiO3, but the more common teaching has been that a tetracalcium phosphate, Ca3(CaO) (PO4)2, exists in the slag. In any case the slag contains very considerable proportions of lime, which undoubtedly greatly assists in the disintegration of the product after being incorporated with the soil, thus bringing the phosphate into an extremely finely divided state. The presence of lime in the slag is of itself of some benefit on certain soils, al- though as a source of lime it is, of course, very expensive and very insignificant, compared to ground limestone. The use of slag phosphate is quite likely to give disappointing results for the first year or two, resembling natural bone in this regard; but like bone, also, it gives very satisfactory results with continued use, and no prejudice has developed regarding its use on account of any supposed injury to the soil. Herbert Ingle, in his "Manual of Agricultural Chemistry," makes the following significant statements (page 162): "Many attempts to improve basic slag as a manure have been made, some directed to the removal of the iron, others the sulfur, while others have attempted 1 This statement is based upon the information given by Director Hall in con- nection with his course of lectures before the Graduate School of Agriculture of the Association of American Agricultural Colleges and Experiment Stations, held at Cornell University, July, 1908. His final conclusions should not be assumed in advance of publication by him. 240 SYSTEMS OF PERMANENT AGRICULTURE to render the phosphorus 1 more soluble, by treatment with sulfuric acid. Prac- tically all these attempts have been abandoned, and the only process through which the slag is passed is that of grinding. This must be thoroughly done, for it is found that the availability of the phosphorus depends very largely upon the fineness of subdivision. A sample should contain at least 80 or 90 per cent of powder which passes through a sieve of 100 meshes to the linear inch, i.e. 10,000 to the square inch. Thomas phosphate has given excellent results, especially in soil somewhat deficient in lime and rich in organic matter." The total quantity of basic slag phosphate now used in Europe as a phosphorus fertilizer amounts to several million tons a year. Ground natural rock phosphate has not been put to direct use as a fertilizer to any large extent, but the subject merits and re- ceives a thorough consideration in the following pages. Numerous trials both in Europe and America extending over only one or two years, without addition of organic matter, and in direct com- parison with acid phosphate or bone meal containing an amount of phosphorus equal to the total amount in the raw phosphate used, have not, as a rule, given satisfactory results, and in conse- quence the direct use of this material has been discouraged by some investigators, and the Association of German Agricultural Experiment Stations has even passed formal resolutions discourag- ing the general use of nonacidulated rock phosphate (Landwirt- schaftlichen Versuchs-Stationen, 67, 329). The mineral phosphates differ from bone, in that they lack the organic matter in porous structure; and they differ from slag in that they are not mixed or combined with caustic lime capable of slacking and disintegrating into extremely small particles. The fact is, however, that wherever fine-ground natural rock phosphate has been used liberally ; that is, somewhat in proportion to equiva- lent values in comparison with acid phosphate, and in connection with decaying matter, it has given satisfactory results, even during the first rotation, and, with continued use, it proves to be the most economical and profitable form of phosphorus to use in the adop- tion of systems of permanent agriculture. In the study of this extremely important question it is well to keep in mind some broad fundamental facts. Thus, the phos- 1 Substituted for "phosphoric acid," both here and in several other quotations from different writers. — C. G. H. USE OF PHOSPHORUS IN DIFFERENT FORMS 241 phorus contained in the soil is not in the form of acid phosphate, but largely, at least, in the form of pulverized or disintegrated rock; and yet it is the common experience that this phosphorus can be made available by large use of clover and other green ma- nures. It is an interesting and absolute fact, too, that phosphatic marls, containing phosphorus in the ordinary insoluble mineral form, have been much used for centuries for direct application to the land. It is recorded by writers that, when the Romans first invaded Britain, " the natives were found using phosphatic marls to obtain better crops." The United States Bureau of Soils states that millions of tons of the greensand marl of New Jersey have been used " as a natural fertilizer"; and, according to the Bureau's analysis of a specimen " collected as a sample to show the amount of plant food in ma- terial actually used as a fertilizer," this marl contains less than i per cent (18 pounds per ton) of acid-soluble potassium, and but little more calcium and magnesium than could be combined in the phosphates present. Evidently, the fertilizing value of the marl is due very largely to its phosphorus content, which amounts to 28.6 pounds per ton. In comparison it may be noted that one ton of the most common corn-belt soil contains about 1.2 pounds of phosphorus, 8 pounds of acid-soluble potassium, and 35 pounds of total potassium; and that 200 pounds (the average application) of the most common " complete " commercial fertilizer contain about 8|- pounds of total phosphorus and 3^ pounds of potassium. An analysis by the Bureau of Soils of the greensand marl of Prince George County, Maryland, shows about J pound of phos- phorus and 42.6 pounds of acid-soluble potassium, in one ton. The following statements are quoted from the Report of the Bureau of Soils for 1901, pages 186-187: "It is probable that the New Jersey greensand marls would, on the average, have a phosphorus content fifty times as great as the corresponding marls from Maryland." "In the Prince George area this greensand marl, which occurs along the numerous stream cuttings and natural cliffs, has only been used to a slight extent as a source of fertilizer. ... In other areas, both in the United States and foreign countries, the greensand marl has long been utilized as an inex- pensive though effective medium for restoring impoverished soils. " 242 SYSTEMS OF PERMANENT AGRICULTURE There are several points especially favorable to the use of natural rock phosphate where proper conditions can be provided: The first is the fact that phosphorus in fine-ground raw phos- phate can be obtained, delivered to the heart of the corn belt, for about 3 cents a pound, or for $7.50 for a ton of phosphate contain- ing 250 pounds of phosphorus, or perhaps $9.00 for a ton contain- ing 300 pounds of phosphorus; while phosphorus will cost about 10 cents a pound in steamed bone meal, 12 cents a pound in acid phosphate, and about 30 cents a pound in ordinary so-called com- plete fertilizers. In the adoption of systems of permanent agri- culture, one can easily afford to apply to the soil, in natural phos- phate, larger quantities of phosphorus than are removed in the largest crops, and thus provide a truly permanent system with respect to phosphorus. The second point is that lower grades of phosphate can be used for direct application to the soil than can be utilized in the manu- facture of acid phosphate. For acid-phosphate manufacture the raw material must be not only high in phosphorus, but it must be low in certain forms of impurities, such as iron and aluminum compounds, which, if present, require much larger use of sulfuric acid and also make an unsatisfactory product; but phosphates of moderate phosphorus content and even with considerable iron and aluminum present, which have hitherto been left on the dump piles as worthless, are now being used for direct application to the land in connection with liberal amounts of farm manure or clover or other forms of decaying organic matter. Other low-grade phos- phates are being mined and ground for direct use. If 12^ per cent phosphate (62^ per cent tricalcium phosphate) is worth $7.50 per ton, then 10 per cent phosphate (50 per cent pure) is worth $6.00 a ton; and even 8 per cent phosphate (160 pounds of phos- phorus per ton) is worth $4.80 a ton, which would allow $2.00 a ton for the fine-ground phosphate on board cars in bulk at the mine, and $2.80 for freight, the average rate from theTennessee phosphate district to southern Illinois points. The possibility of using these low-grade phosphates, of which there are immense deposits, is of enormous importance in the general adoption of permanent sys- tems of soil improvement. A third point in favor of raw phosphate, in common with bone USE OF PHOSPHORUS IN DIFFERENT FORMS 243 and slag, is that it is free from acidity and has no tendency to injure the soil. This is a minor advantage, because, if acidity develops from the continued use of acid phosphate (and it does), it can be corrected at small expense by the addition of any form of lime. Another point, previously mentioned, of fundamental signifi- cance is the simple fact that a form of phosphorus originally present in all natural soil material is finely divided natural rock phosphate, and through all agricultural history the principal source of phosphorus in plant growth has been this same natural phosphate. On most normal soils one of the chief benefits of farm manure and green manures is undoubtedly due to their power to liberate phosphorus from these insoluble natural phosphates of the original soil. In considering culture experiments, whether field cultures or pot cultures, three points should be kept in mind : (1) What are the limiting factors of plant growth under the conditions of the experiment? (2) Does the applied fertilizer increase the crop yield by direct or indirect action? (3) In case of insoluble fertilizers, are the conditions such that the plant food applied will be made available to the crop? Thus, an experiment to determine the comparative agricultural value of different forms of phosphorus cannot be expected to fur- nish satisfactory evidence if conducted on a soil in which nitrogen is the element that limits the crop yield; or, even though phos- phorus is the first limiting element, the results cannot be conclu- sive if the nitrogen limit is but little higher. For example, if the conditions are such that the soil will furnish phosphorus for only 40 bushels of corn per acre, and sufficient nitrogen for only 45 bush- els per acre, the yield cannot be increased above 45 bushels by the addition of phosphorus alone, no matter what form is applied or how much becomes available. In other words, one phosphate fertilizer might supply phosphorus for only 5 bushels, and another sufficient for 25 bushels, increase, but the results of the culture experiment would show no such difference, because beyond the 45 bushels the yield is limited by a second entirely different factor. The second point is important with every form of experiment. Thus, a student reported having found silver in an unknown solu- 244 tion because the addition of hydrochloric acid produced. a white precipitate. The Professor asked: "How do you know that this precipitate is not due to lead or mercury? " and the student replied, " Because I was not testing for lead or mercury at all." Similarly one may apply wood ashes to ascertain if the soil is deficient in potassium, or he may turn under a spring growth of clover to ascertain if the soil needs more nitrogen, and from the increased yield he may think both of these elements are deficient; but in the one case the increase may be due, not to the potassium as plant food, but to the basic or alkaline properties of the lime and other carbonates in correcting soil acidity, and in the other case not to the nitrogen supplied, but to the liberation of phos- phorus from the meager supply in the soil by the action of decaying organic matter. It is never safe to assume that the action of soluble fertilizers, such as sodium nitrate, acid phosphate, kainit, or other potassium salts, is due entirely to the respective plant-food elements for which those materials are valued, especially when heavy applications are made, as must be done with sodium nitrate and kainit if suffi- cient nitrogen and potassium are thus provided to meet the needs of good crops, more than 900 pounds of sodium nitrate and 700 pounds of kainit being required for a hundred-bushel crop of corn. About 400 pounds of acid phosphate would be required for such a crop, and this would contain more manufactured land-plaster (calcium sulfate) than monocalcium phosphate, as will be seen by computation from the reaction expressed by the equation: Ca3(PO4)2 + 2H2SO4 = CaH4(PO4)2 + 2CaSO4. Dried blood and steamed bone meal are among the most trust- worthy materials for culture experiments to determine if the soil is in need of nitrogen or phosphorus, and potassium sulfate is probably the least objectionable form of potassium, although solu- tions of such soluble salts have some power to liberate phosphorus contained in, or applied to, the soil, and by this indirect action to bring about more or less increase in crop yields not due to potas- sium as plant food. Steamed bone meal contains a small amount of organic nitrogen, but even if it were all made available, the USE OF PHOSPHORUS IN DIFFERENT FORMS 245 amount in 200 pounds would be sufficient to increase the yield of corn by one bushel, while such an application would contain more phosphorus than a hundred-bushel crop of corn. In Tables 37, 38, and 39 are recorded in detail the results of the world's most important and complete investigation thus far reported concerning the use and comparative value of raw rock phosphate. These experiments were begun by the Ohio Agricul- tural Experiment Station in 1897, and through the kindness of Director Thorne the author is able to include twelve years' data in these tables. In these experiments a three-year rotation of corn, wheat, and clover has been followed on three separate tracts of land, so that every crop may be represented every year. One plot in each series receives 8 tons per acre of manure "taken from the open barn- yard, where it has been accumulating during the winter," and applied to the clover sod in the spring, to be plowed under for corn. Another plot receives at the correct time 8 tons per acre of manure " taken from box stalls, where it has accumulated under the feet of animals kept continuously in the stalls." Two other plots in each series receive the same kind and quantity of manure with each ton of which 40 pounds of fine-ground raw rock phosphate have been mixed, and two other plots receive ma- nure with each ton of which 40 pounds of acid phosphate have been mixed. Every third plot in each tract or series receives no manure or other fertilizer. In the tables are reported the yields of corn, wheat, and clover, the experiment having been started in 1897 on section A, and in 1898 on sections B and C. Clover failed the first three years, and in its place soy beans were grown, and they were plowed under. The hay crop harvested in 1907 was soy beans, grown because of clover failure. Chemical analysis and the results of other field experiments show that the Wooster soil is most deficient in phosphorus, with nitrogen as the second limiting element. In considering the data given in Tables 37, 38, and 39, it should be kept in mind that each table gives results that are complete and entirely independent. Thus, by using three different tracts 246 SYSTEMS OF PERMANENT AGRICULTURE of land, the experiment was conducted in triplicate; and even each of the triplicate tests was in a sense duplicated in that a double comparison is made between the two forms of phosphorus, the test with yard manure being entirely independent of the test with stall manure. For convenience the average yield of each crop is given by plots for each series of plots separately. Thus, as an average of four corn crops in Series A, plot 15 with yard manure alone produced 41.5 bushels, and plot 2 with yard manure and raw phosphate produced 54.9 bushels, showing by direct comparison a gain of 13.5 bushels due to the raw phosphate. Further comparison shows average gains of 2.1 bushels of wheat and .58 ton of clover hay by raw phosphate and yard manure above the yields made where un- treated manure was used. A similar comparison shows average gains of 5 bushels of corn, 3.9 bushels of wheat, and .37 ton of hay by raw phosphate and stall manure above the yields where stall manure alone was used. Acid phosphate also produced marked gains, the average gross increase being somewhat greater than with the raw phosphate, but the net profit being slightly less on Series A. Attention is called to the fact that 8 tons of manure per acre have been applied every three years to all manured plots. This does not do full justice to the phosphate plots, because these plots have yielded as an average about one fourth more produce than the plots receiving manure alone, and from this increased produce about one fourth more manure can be made in regular farm prac- tice. Consequently, after the first rotation, the applications of manure should be larger on the phosphate plots in proportion to the produce of the previous rotation; whereas, to apply equal amounts of manure to plot 15 and plot 2, for example, means essentially that some of the produce from plot 2 is used to make part of the manure that is applied to plot 15. In the above comparison to determine the effect of the phos- phorus used, the yields with manure alone are subtracted directly from the yields with manure and phosphorus. As an average of many tests, this direct method of comparison is perhaps as good as any indirect method, but where a small number of tests on only a few fields are to be considered, probably an indirect method of USE OF PHOSPHORUS IN DIFFERENT FORMS 247 u 0 PI t^- H \r. \o t^* ^0 to co t>- r^ cooo co 0 < P NO oo M N0_ P« Os Ox w NO tO M HI ON M HI HI o PI -g"l HI NO M oo i>- to 1^X0 M PI IO M NO PI CM to Tf IO CO HI O 00 10 0 M rt- HI < < go-, HI 00 ON "^T Hi t~- HI ¥-8- oo oo PI 00 HI o o_ < sll oo NO' M PI Tt PI HI t^» HI HI M3 PI ONNO PI NO PI M CO PI IO PI \O IO ON Tt PI pj NO ON PI H z H PI oo NO M 10 Tt^S 10 ON ON ON PI co ON ON HI NO < o 25 ON 06 M rj- PI •^ ON HI HI NO CO HI O PI HI O PI -si PI ON CO t-» O t-coS CO HI Tj- IO CO OO 00 NO l~~ ON f» CO PI ON O t^ PI r^ < 41 PI ON CO PI t^*. 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J3 C *T a, p «c ««i o o i; °«s a S2« ua,£ USE OF PHOSPHORUS IN DIFFERENT FORMS 249 H NO *•» oo f> t^\O t^ MOO 00 O 00 t^NQ 00 to t^ u o £ CM CM to O (^ •* O O HI HI HI HI M N HI CM 00 PO «N) 4 -si O ON Tl- o •* d O 00 00 10 u-> 10 CM «N1 CM TJ- PCOO HI PC to m 0 M Tf M vO U . -s 9 S3 IO CM t^ M O 10 HI l^ N 1^ Tf M ro N IO N to f*3 ON PC HI IO CM NO tO HI ^ CM M «* CM 00 •* t^ PC W 0 **• O j^ O 10 Tj- 1000 00 O to t>- PC PCNO Tf t^ u 1 HI CM to t 0 <*) HI N GO HI »O HI H M oo oo CM ON H «^ -si 00 H •* r~T> J^vO r^ t^ fO Tf M rf "t l^NO O •* ON CM NO PC PO O CM CM HI u «g°- •Bis ^05 M -OM M H O PC HI Tj- oo «s§ D a B3 LO **• 00 53> S£ PC M t^ H oo oo HI *O cs fO t M CO O 00 r^ Tf CO io •* HI IO CM 10 Tt- O Tf CM H «# HI ON t~- «. 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CM t^ HI «^ ^ — ^ • -o *%i 1-1 PLOT No. SOIL TREATMENT . 1898 Corn, bu. . 1899 Wheat, bu. 1900 Soy beans (tun dJS •= -.-^- ~ cd (U F aj > S^-2 U^U M N ro Qs O\ O HI >- H (0 j4! _r rt S^-2 U^U Tf vo\O ON ON O< M M f-t 3 3-<=> -O ~ E"I d$ t^OO aa M *-l •* >2 > rt . rt^- -^ « g^ b o rr ^ U^ffi e 2 £2 r^ rt rt OJ 4J D >.>,>, •oo " 8 - 3 -5 C «H P- OJ 2 o ° •§-•§.» o ^a ^ S *r D-, O y3 n_ i O 0« a, «e 7 One ton of raw phosphate CO4O 47 8 Two tons of raw phosphate CIQO ec o (b) Average of 26 Otherwise Fertilized Plots One ton of lime 3 7oo 43.8 Two tons of lime 1880 4.C.Q One ton of raw phosphate £460 <2 7 Two tons of raw phosphate C7CQ 62.2 Even if we assume that the lime produced no increase, the effect of the raw phosphate is very marked. On the " otherwise unfer- tilized " land one ton of raw phosphate per acre produced 1.41 tons more clover and 15.1 bushels more oats, the value of which, at $6 per ton and 30 cents a bushel, respectively, would amount to $12.99, or enough to pay for two tons of ra\v phosphate at $3.50 per ton where the freight rate does not exceed $3 (as in southern Illinois). The two-ton application produced markedly greater effect on the oats, but not on the clover. These results include two entirely separate series of plots, and each reported yield is the average from a large number of plots. The data must not be considered as ex- ceedingly trustworthy, but we must agree with Director Thome's statement that " it looks as though we were getting something worth while there." Knowing that the effect of lime where needed 260 SYSTEMS OF PERMANENT AGRICULTURE is usually marked on both clover and oats, the " increase " given for phosphate must be regarded as quite unusual. Not more than one tenth of the phosphorus applied would be removed in the two crops. These results point toward the possibility of adopting profitable systems of permanent agriculture; and yet the most common fertilizer practice among the farmers of Ohio is to apply about 7 pounds of soluble phosphorus per acre, with 3 or 4 pounds each of nitrogen and potassium, in 200 pounds of "complete" fertilizer about twice during a four-year or five-year rotation. In the Rural New Yorker for June 5, 1909, Director Thorne reports an average yield of 2440 pounds of clover hay with lime applied, and 5112 pounds where rock phosphate is used, with no other fertilizers; and where nitrogen or potassium had been applied, the yield with lime was 2606 pounds and with rock phosphate, 5488 pounds, although where lime and a " complete " fertilizer, including nitrogen, potassium, and 480 pounds of acid phosphate, were used, the total yield of clover hay was only 4259 pounds. The following comment is made by Thorne: "This experiment thus indicates that floats (raw phosphate) may be very usefully employed for the combined purpose of carrying lime and phosphorus, the increase over the limed land being more than enough in this one crop to pay for one ton of floats per acre, which quantity has seemed to be as effective as the larger quantity, although the two tons of lime have produced a larger yield than the one ton, though not enough larger to pay the additional cost. This experiment, therefore, is confirming those of the Maryland and Illinois stations in showing that floats may be profitably used as a carrier of phos- phorus on acid soils well stocked with organic matter, but the meager effect produced upon cereal crops preceding clover would call for caution in de- pending upon floats alone. " Of course, more clover means more humus and more nitrogen if the clover is plowed under either directly or in manure; and, while the cereal crops preceding clover are quite certain to be un- satisfactory, they are sure to be increased after plowing under the larger amount of clover or manure with phosphate. The data reported by Thorne in these experiments do not show what increase was produced by lime alone, all plots having been treated either with lime or with raw phosphate, and consequently there seems to be no support for the suggestion that the effect of the raw phos- phate is in part due to the lime which it carries. In fact, the ordi- USE OF PHOSPHORUS IN DIFFERENT FORMS 261 nary high-grade raw phosphate carries very little, if any, lime, about 7 per cent of calcium carbonate being the largest amount in any high-grade phosphate known to the author. Tricalcium phosphate is a neutral substance which has practically no power to correct soil acidity, except as the phosphorus is converted into the dicalcium or monocalcium compound and removed from the soil by the growing crop. Furthermore, the most marked benefit from the use of raw rock phosphate in Illinois is not on markedly acid soils, but on the most common corn-belt prairie land, as on the Urbana and Gales- burg experiment fields on brown silt loams, which are practically neutral soils valued at $150 to $200 an acre. The Ohio investigations with raw and acid phosphates are in a class by themselves. No others have been conducted anywhere in the world that can compare with these in agricultural value. Many experiments with various phosphates have been carried on for a single season, and some for several years, but, as a rule, no farm manure has been used, and no adequate provision made for a supply of decaying organic matter. Where nitrogen has been sup- plied, it has usually been in some commercial form, such as sodium nitrate. One exception to this is found in the Maryland experi- ments, which have been conducted on one field since 1895, eleven years' results having been reported by Director Patterson (Mary- land Bulletin 114). Aside from single plots treated with different acid phosphates and reverted phosphates in the Crimson Clover Series, there is a strictly comparable triplicate test with (i) raw bone meal, (2) slag phosphate, (3) no phosphate, (4) South Caro- lina raw rock phosphate, and (5) Florida soft rock phosphate (containing phosphates of iron and aluminum). Equal amounts of phosphorus were used in all tests, 65^ pounds of phosphorus per acre having been applied only at the beginning of the experi- ment. The surface soil contained 1300 pounds of phosphorus in 2 million pounds of the soil. The following crops were grown: Corn in 1895. Wheat in 1899. Corn in 1903. Corn in 1896. Hay in 1900. Wheat in 1904. Corn in 1897. Hay in 1901. Hay in 1905. Crop failure in 1898. Corn in 1902. Corn in 1906. 262 SYSTEMS OF PERMANENT AGRICULTURE In one series of tests, crimson clover was regularly seeded in the corn to be plowed under later as a green manure, and in another series rye was employed in a similar manner, the third test being made without special provision for organic matter. Table 42 gives a summary of these investigations for all forms of phosphorus that were used under the three different conditions: TABLE 42. MARYLAND EXPERIMENTS WITH DIFFERENT FORMS OF PHOSPHORUS Twelve Years' Work : Yields per Acre : Average of Three Plots Six CORN CROPS, Av. Two WHEAT CROPS, Av. THREE HAY TOTAI AVER- T*» XT T> A T T« Av. YIELD Grain Stover Grain Stover (Tons; (Tons) (Bu.) (Tons) (Bu.) (Tons) 8, 13, 18 Raw bone meal . . . 39-6 1.25 23.6 1.22 1.85 6.41 9, 14, 19 Slag phosphate . . . 39- * 1.22 22.6 1.24 i-95 6.46 10, 15, 20 No phosphorus . . . 40.0 I.I7 12. 1 •n 1.44 5.10 II, l6, 21 S. C. rock phosphate 39-7 1.25 2O. I 1.07 1-95 6.26 12, 17, 22 Florida soft rock . . . 42-5 1.27 19.9 •94 1.89 6.19 Here are represented thirty-three separate tests (three plots for eleven years) for each form of phosphorus. As an average, the raw rock has given nearly the same results as the bone and slag. The average increase in yield is very marked with wheat, less marked with hay, and practically no effect is seen with corn. The value of the total increase in twelve years is about ten times the cost of the raw rock phosphate, at Illinois prices, and still more at Mary- land prices, for farm produce. In commenting upon his experi- ments, Director Patterson says: "The results obtained with the insoluble phosphates has cost usually less than one half as much as that with the soluble phosphates. "The results show decidedly that plants are able to utilize insoluble rock phosphates. "The use of an abundance of organic matter in the soil when insoluble phosphates are applied was evidently a necessity for their best effects. "Soluble phosphates produced the best yield of wheat. "Florida soft phosphate produced the best yield of corn. "Reverted phosphates produced the best yield of hay. USE OF PHOSPHORUS IN DIFFERENT FORMS 263 "Insoluble South Carolina phosphate rock produced a higher total average yield than dissolved South Carolina rock. "Florida soft phosphate is chiefly an aluminum-iron phosphate which occurs in large quantities deposited in many parts of that state. It is not well adapted to treatment with acid for making soluble phosphates, as the aluminum and iron make a sticky mass which is hard to dry and keep in a good mechan- ical condition. The Florida soft rock has been largely used as a fertilizer in its natural condition in some parts of that state on the light, sandy land, giving good results. When used in this way, there has been applied at the same time heavy dressings of the native mucks from the swamps and lakes. This muck furnishes nitrogen as well as the much-needed organic matter. In order to have a complete fertilizer, there is also applied some German potash 1 salt. " The Pennsylvania Experiment Station has reported the results of an experiment extending over twelve years (1884 to 1895), in which four different kinds of phosphorus were used in a four-year rotation of corn, oats, wheat, and hay (clover and timothy). Only one field was employed, so that each crop was grown only three times during the twelve years. The four forms of phosphorus were (i) acid phosphate made from bone black, (2) " reverted " phosphate made by mixing equal weights of dissolved bone black and quicklime twelve hours before application, (3) fine-ground bone meal (containing 8 pounds of nitrogen and 35 pounds of phosphorus in 300 pounds of bone), and South Carolina ground raw rock phosphate. The amounts applied per acre in each four years were 28 pounds of soluble and " reverted " phosphorus, and 35 pounds in bone and raw rock. No special provision was made for supplying decaying organic matter, but 94 pounds of nitrogen (102 pounds on the bone-meal plots) and 83 pounds of potassium (in potassium chlorid) were applied per acre, each four years, to all phosphorus plots and also to two comparison plots that received no phosphorus. In addition, there were two plots that received no application of plant food. The entire experiment was carried on in duplicate. One half of the fertilizer for the rotation was applied to the corn crop and the other half to the wheat crop. Table 430 gives the average yields of all products harvested dur- 1 Most peat soils and some sands are extremely deficient in potassium, and it is also difficult to liberate potassium that may exist locked up in coarse sand grains, as suggested, for example, by the Illinois experiments at Momence, p. 474. — C. G. H. ing the entire twelve years, and Table 436 gives the average re- sults for the last four years. TABLE 43. PENNSYLVANIA EXPERIMENTS WITH DIFFERENT FORMS OF PHOS PHORUS: YIELDS PER ACRE: AVERAGE OF DUPLICATE PLOTS (o) Average of Twelve Years' Work PLOT Nos. PLANT FOOD APPLIED CORN, 3-YEAR AVERAGE OATS, 3- YEAR AVERAGE WHEAT, 3-YEAR AVERAGE HAY, 3- YEAR AVERAGE (Tons) Grain (Bu.) Straw (T.) Grain (Bu.) Straw (T.) Grain (Bu.) Straw (T.) A &G B &H C &I D &J E &K F &L NK and dissolved bone black NK and "reverted" bone black NK and bone meal .... NK and raw rock phosphate . Nitrogen and potassium only . None 48.9 49.6 52.0 47.6 40.7 13.1 •97 •97 1.04 •95 •83 .CI 43-8 47.1 49-4 48.2 45-5 38.8 .67 .66 .80 .78 .61 •55 28.2 29.9 31.6 31.6 30.6 22.5 I-SI 1. 60 1.67 1.67 1.40 .98 1.58 1.65 1.68 i-57 1.25 1.02 Average of Last Four Years A &G NK and dissolved bone black 49-3 .98 33-6 .89 22.7 1.61 2.05 B &H NK and "reverted" bone black 54-3 1.03 38.3 .87 25-4 i-5i 2.36 C &I NK and bone meal .... 55-o 1. 08 39-1 I.OO 25-9 i-75 2.40 D &J NK and raw rock phosphate . 50.0 •95 39-2 .91 26.3 1.69 2.13 E &K Nitrogen and potassium only . 41.4 .83 30.8 •59 23-9 1. 21 i-93 F &L None 12. Q .4.7 22.2 6n 21.4 I. O3 I.4X By computation it will be found that the cost of the nitrogen and the potassium for four years was $24.06 per acre ($25.26 on the bone-meal plots); while the phosphorus for four years cost $3.36 in soluble or reverted form, $3.50 in bone ($4.70 including the cost of nitrogen), and $1.05 in the raw rock phosphate, at the prices mentioned in Table 24. At safe prices for increase in produce based upon zo-year aver- ages for the corn belt : corn 35 cents a bushel, oats 30 cents, wheat 70 cents, and hay $6 (about $3 per ton being allowed for stacking, baling, marketing, and loss), the value of the increase produced in four years by $24 worth of nitrogen and potassium is $11.72 per acre as an average of the twelve years, and $10.19 per USE OF PHOSPHORUS IN DIFFERENT FORMS 265 acre for the last four years; while the value of the increase pro- duced by $1.05 worth of raw phosphate (above the increase pro- duced by the nitrogen and potassium) was $5.85 per acre as an average of the twelve years, and $8.41 for the last four years. As an average of all crops, the raw phosphate produced larger yields than the acid phosphate (dissolved bone black) and prac- tically the same yields as the reverted phosphate (including lime) ; but the bone-meal plots gave slightly larger average yields, the increase from $4.70 worth of bone meal being $8.41 per acre for four years as an average of the entire period, and $11.47 Per acre for the last four years, above the increase produced by nitrogen and potassium alone. When used in addition to nitrogen and potassium, $1.05 worth of raw phosphate produced net profits amounting to $4.80 per acre every four years as an average of the twelve years, and $7.36 for the last four years; while the corresponding net profits from $4.70 worth of bone meal were. $3. 71 for the twelve years' average and $6.77 for the last four years. Thus, the greatest total net profits were from the raw phosphate. On the basis of money invested in phosphorus, the net profits from raw phosphate were 457 and 700 per cent, and from bone meal they were 79 and 144 per cent, re- spectively. In no case was the net profit from the use of phosphorus sufficient to cover the net loss from the use of nitrogen and potassium, so that the total result was a net loss in all cases. It must be kept in mind, too, that the effects produced by phosphorus when used in addition to nitrogen and potassium (over and above those produced by nitrogen and potassium alone) are usually greater than the effects produced by phosphorus when used alone, as is fully shown by other experiments hereinafter discussed. On the other hand, these Pennsylvania investigations clearly indicate that if the nitrogen were secured from the inexhaustible supply in the air and turned under in the form of farm manure, legume crops, or other residues, and if the potassium can be liber- ated from the practically inexhaustible supply in the soil by the decay of this same organic matter, then the use of phosphorus would not only be profitable in itself, but the total result of the system should yield large net profits. 266 SYSTEMS OF PERMANENT AGRICULTURE The soil of the farm of the Pennsylvania State College is a resid- ual clay loam from the disintegration, weathering, and leaching of impure limestone. The soil contains 85 to 90 per cent of fine earth and 10 to 15 per cent of small stones, quartz, silicates, etc. In 2 million pounds of the fine earth of this surface soil there are 1090 pounds of acid-soluble phosphorus and 50,700 pounds of total potassium, an amount equivalent to $3000 worth of commercial potassium salts. The following comments concerning these experiments are made by the Pennsylvania Station (Annual Report for 1895, page 210), on the basis of prices prevailing at that time: "The yearly average for the twelve years gives us a gain per year of $2.83 from insoluble phosphorus l (ground bone), $2.45 from insoluble phosphorus (South Carolina rock), $1.61 from reverted phosphorus, and 48 cents from soluble phosphorus, thus giving us considerably better results from the two forms of insoluble phosphorus than from the reverted or soluble forms, thus indicating that the insoluble phosphorus is of more value as a manure than is often supposed, and that it is worthy of more attention than has been given to it in the past." In 1894, the Rhode Island Experiment Station began an inves- tigation to ascertain the relative value of eight different forms of phosphorus, and a ninth form (double superphosphate) was intro- duced in 1895. Tne experiment included the common raw rock phosphate (containing tricalcium phosphate), raw and roasted aluminum phosphate (containing also some iron phosphate), basic slag phosphate, steamed bone meal, and three acid phos- phates (one made from raw rock, one from bone meal, and one from bone black), besides the double superphosphate. The fol- lowing statements from Rhode Island Bulletin 114 give further information : "According to the original plan of Ex-Director Flagg, like money values of phosphate were to be compared, and the applications were made for several years upon that basis. Owing, however, to the widely varying market prices from year to year, it was decided in 1898 to change the plan of the experiment so as to make it a comparison of like amounts of phosphorus.2 1 Substituted for " phosphoric acid" here and elsewhere. 1 Substituted for "phosphoric acid" here and elsewhere, with equivalent amounts. USE OF PHOSPHORUS IN DIFFERENT FORMS 267 "The crops of 1894 and 1895 were Indian corn and oats, respectively. In the autumn of 1895 the land was replowed and seeded to clover and grass, as follows: SEED PER ACRE Timothy 12 quarts Red top 6 pounds Medium red clover . . 12 pounds "Owing chiefly to the dryness of the soil, a stand of clover was not secured, and medium red clover was sown again, the next April, at the same rate. "On account of the fact that some of the phosphates contained soluble phosphorus while others were pratically insoluble in water, all of the more insoluble phosphates were sown broadcast after plowing, and were then thor- oughly harrowed into the soil before seeding. These applications were made sufficiently large to cover the crop requirements for three years that the land was expected to be left in grass. It was planned to divide the application of soluble phosphates into three parts, one third to be applied annually as a top dressing, in the spring, together with the nitrogenous and potassic manures which have been applied annually at like rates to all of the plots in both series. Owing to the change in the plan of the experiment in 1898, the land was left for an additional year in grass. In the spring of 1899 such quantities of phosphates were applied as were supposed, based upon their composition, to equalize the amount of phosphorus upon all the plots. It was discovered, however, in 1902, that the assistant to whom the calculations were intrusted in 1899 omitted to take into account the applications of the insoluble phosphates which had been made in the autumn of 1896, and owing to this oversight the complete equalization of the phosphorus was not finally accomplished until the spring of 1902. The total amount of phosphorus which was applied per plot (two fifteenths acre) to all excepting the two check plots, from 1894 to 1902 inclu- sive, amounted to 43 pounds, or to 322? pounds per acre. " Thus, from 1894 to 1898, the experiments are a comparison of equal money values of different phosphates ; from 1899 to 1901 the common raw phosphate plots contained about one third more applied phosphorus than the soluble phosphorus plots, about one fifth more than the bone-meal and slag plots, and slightly more than the aluminum phosphate plots. The entire experiment was carried on over two series of plots, one series having been given one ton of burned lime per acre in 1894, while the other series remained unlimed. In 1901, fourteen different kinds of plants were grown, from 3 to 8 rows of each having been planted across all of the plots in both series. In Tables 44 and 45 are given the number of pounds har- vested of the different kinds of produce. 268 . SYSTEMS OF PERMANENT AGRICULTURE en CO I Q TJ W X! 1 | El W - 3 -3 a § o W dn Q O a & ^ 2 i ' U ills cs oo 't oo NO 00 ON ON 'I-OO M r^O'4'cocoOOO NO co co t^* O H NO f^i "^ M CS CS M M C~l M NO OO W NO ^ M M OO M M *!l| \O ON ^* co f^* CS O CS M Tf VO IONO M ON to l^- IO CS COOO i ON M M M M ^ t^ 00 IO CS 10 t^ Q " <§"- f *SS t^» co M Q OO OO NO CS M CS ON TLO ^ M CS CO O ON O M O IO M CS "M M M J1 M O ON H NO t^ 00 00 CS Ills Tt M M ON ON IO CS T}- O NO O co co VO M "t" O OO ^ ONNO CO IO t~*- CO CO IO ON M - " M M M M ^° CO NO jgB^ ON M O O co NO O NO CS t^OO VO t^ H CO M ON l~- M TfOO HI ON ON U1OO ^1" co ^ CS cs t^. o t-» 00 O ON ^fcg — CS dig co cs Tf* NO O NO O CS "^f ON Tj" ^f IO CO CO CS NO O VO l~- NO O OO ^OO IO co CS CO ^J" '^ M t^» f^» jj ON M CS CS M M V~ M CS CO CS ON 10 M oo oo CS M Q g"< 111 Cfl NO co r~- rf M oo cs NO ON OO 00 O 00 >0 CS M IO CS to f- ONIOMOOHNOCO t^ IO ^f ^^ ONNO ^"*»v^ OO M CS M M M °° H CO CONQ NO M M III IO IO CO ON M O NO ON M O 1-1 CS IONO CO co M NO O VONO NO^vo^OOco 10 ^- CONO M NO NO -J M M CS CS M M £J M Tj- NO ON ON !>. 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The results of the Galesburg field are in harmony with those thus far secured from many other University of Illinois soil experiment fields in different parts of the state, and they are also in harmony with numerous practical tests by progressive Illinois farmers who make adequate provision for supplying the soil with decaying organic matter. Thus, as an average of four independent tests on each experiment field, Tennessee raw rock phosphate increased the yield of corn in 1908 by 12.1 bushels per acre on the Galesburg field, by 11.9 bushels on the Myrtle field for first-year corn and 9.3 bushels for second-year corn, by 16.0 bushels on the Rockford field for first-year corn and 7.6 bushels for second-year corn, by 3.5 bushels on the Antioch field, by 9.1 on the Auburn field, and by 8.4 bushels on the Urbana field. These experiment fields are in six different counties, and they have been in operation from four to six years. The average yield of corn in 1908 was 67.3 bushels where raw phosphate has been applied and' 57.5 bushels without phosphorus. The phosphate applied thus far adds phosphorus to the soil at the rate of 60 pounds or more per year, while 16 pounds are required for a 68-bushel crop and about 2 pounds for the ic-bushel increase. Thus, the value of the increase ($3.43) will pay the cost of the phosphate (less than $2) and leave 50 per cent net profit, and with 70 per cent of the phosphorus left in the soil. The effect on wheat and clover is almost as marked as on corn. Of course, more clover means more nitrogen secured from the air, and it may also mean more manure to return to the soil. Mean- while, the untreated land grows poorer year by year. In Table 51 are given the results reported by the Illinois Experi- ment Station (Circular 97) from a series of pot cultures conducted for the purpose of comparing equal money values of raw rock phos- phate and steamed bone meal. In the Illinois field experiments, the standard annual application of phosphorus is 25 pounds per acre in 200 pounds of steamed bone meal and nearly equal money values of other forms of phosphorus. The 25 pounds is based upon the requirements of a loo-bushel crop of corn, with i or 2 pounds for lo-s in drainage. In pot cultures very large crops are commonly USE OF PHOSPHORUS IN DIFFERENT FORMS 287 produced, and to meet the needs of such crops the applications of plant food are made three times as large as in field experiments. The soil used was from the gray silt loam prairie of the lower Illinoisan glaciation, and wheat was the crop grown in the pots. The phosphate used is known as the Tennessee blue rock. In cer- tain pots the phosphorus was turned under with a good growth of clover; in other pots with farm manure, and in others with both clover and manure. TABLE 51. COMPARATIVE EFFECTS OF STEAMED BONE MEAL AND RAW ROCK PHOSPHATE, IN CONNECTION WITH CLOVER AND MANURE PARTIAL TREATMENT APPLIED SERIES 100, WITHOUT POTASSIUM, WHEAT YIELDS SERIES 200, WITH POTASSIUM, WHEAT YIELDS Grams per Pot Increase in Grams Grams per Pot Increase in Grams None IO.O I6.3 14-7 14.2 22.2 . 23-3 I6.5 22-7 19.4 19-5 24.1 23-3 6-3 4-7 4-2 12.2 13-3 6-5 12-7 9-4 9-5 I3-1 i3-3 "•3 18.4 18.4 18.2 21.9 21.9 18.1 19.1 19-3 19.0 25-3 25-3 !-3 8.4 8.4 8.2 11.9 11.9 8.1 9.1 9-3 9.0 15-3 15-3 Clover Rock phosphate Clover, bone meal Clover, rock phosphate . . Manure Clover, manure Manure, bone meal Manure, rock phosphate .... Clover, manure, bone meal . . . Clover, manure, rock phosphate . . It will be seen that the untreated soil (pot 101) yielded 10 grams of wheat. Where clover was turned under (102), the yield was in- creased by 6.3 grams, and where bone meal was turned under with clover (105), the yield was 22.2 grams, the increase of 12.2 grams being nearly 'double that produced by clover without bone meal. Where raw rock phosphate was turned under with clover (106), the wheat yielded 23.3 grams, making a total increase of 13. 3 grams over the yield of the untreated soil. Of this increase 6.3 grams should be credited to the clover and 7 grams to the rock phosphate, by one computation; or 4.2 to the phosphate and 9.1 to the clover, by the other route. Thus, rock phosphate used alone produced an 288 SYSTEMS OF PERMANENT AGRICULTURE increase of only 4.2 grams, which, added to the increase of 6.3 grams due to clover alone, makes only 10.5 grams.' In other words, the sum of the gains which they make when used separately was 2.8 grams less than the increase produced when the rock phosphate and clover were turned under together. Somewhat similar results are produced with clover and bone meal when used separately and together; also with bone meal and potassium, and with rock phosphate and potassium. Such marked combined action does not appear, however, from other combinations, possibly because of other limiting factors. As a general average, the rock phosphate has made slightly better gains than the steamed bone meal. The pots used in these investigations are io|- inches in diameter, consequently i gram per pot corresponds to i pound per square rod, or to 160 pounds per acre. The actual yields in grams per pot are given, but the results may also be computed to bushels per acre. It should be remembered that pot cultures constitute an intensive form of agriculture. They are carried on under almost complete control, except in very warm weather, when too much shade may be required to avoid too high temperature. The yields obtained are usually two or three times as much as can be expected in the field under ordinary weather conditions. They are not, however, larger than could be obtained in the field under perfect weather conditions. The largest yield reported in Table 51 is 25.3 grams per pot, or 67 bushels of wheat per acre. Pot culture yields have been produced corresponding to 142 bushels of wheat, and to 230 bushels of oats, per acre. Doctor Alfred M. Peter of the Kentucky Station has kindly furnished the author the following data secured by him with the cooperation of Mr. S. C. Jones of the Kentucky Geological Survey: KENTUCKY EXPERIMENTS: POT CULTURES TREATMENT APPLIED CROP YIELDS: GRAMS PER POT Kind Amount Tobacco (Leaves and Stalks) Wheat (Grain Only) Alfalfa Hay None .... none 4.0 grams 10.5 grams 4-8 IO.O 12-9 6.8 9-5 I2.O 6.7 1 1 -5 IO.2 Acid phosphate .... Raw phosphate .... USE OF PHOSPHORUS IN DIFFERENT FORMS 289 The soil used in these pot cultures (which were 2-gallon jars) was a residual limestone soil from Christian County, Kentucky, and contained 870 pounds of total phosphorus and 32,120 pounds of potassium in 2 million pounds of surface soil. The results are of interest; but, as Doctor Peter writes, " it must be understood that they are only single experiments carried out one season, and must be valued accordingly." The Wisconsin Agricultural Experiment Station (Bulletin 174) also reports a single year's experiment with field cultures showing that manure and raw phosphate increased the yield of rutabagas by 27 per cent and the yield of potatoes by 47 per cent above the yield from manure alone, and the opinion is expressed that " these results leave no doubt that the use of phosphate supplementing manure is beneficial." In describing IVf r. J. F. Jack's Virginia farm, Joseph E. Wing, the well-known agricultural writer, makes the following state- ments (Breeders' Gazette, June 2, 1909) : "Proud as we are of Woodland Farm, I find acre after acre of alfalfa on Mr. Jack's farm as good as our best. I find it as good as the best that I ever saw in California. Is it all good? No. There are acres that are thin, stunted. What cause ? He is seeking that now. Doubtless there are areas that are too poorly drained, there are places yet sour, and some land needs more feeding. No doubt at all of that. He has not limed liberally at all times. Last year, for example, some men told him that they had a prepared lime that was two times as effective as ordinary lime. He had been using a ton to the acre ; he bought this lime, at a higher price, and used but 1000 pounds. Then he learned to his sorrow that the lime was simply slacked at the kilns, was so-called 'agricultural lime' and had only about half the strength of fresh burned lime. So it seems sure that much of his land has had too little lime. He finds that lime carbonate, that is, simply ground limestone, gives him as good results as anything, and that fortunately is cheap." ""What an interesting thing it is to find this old Eastern land being newly dis- covered. . . . But here the soil must be fed, do not forget that ! The natives forgot it, hence their sorrow now." "Business methods apply to farming as well as to anything else. Farming is a business, and, with present prices for things, a paying business. It pays to buy lime (Mr. Jack is getting his ground limestone delivered to him for $2.90 this year) to make land sweet, to buy phosphorus, to sow legumes, to build soil. Alfalfa is as easily set in Virginia as in any other state, and it grows splendidly when the land is made sweet with lime, filled with decaying vegetable matter or humus, given inoculation and phosphorus." 290 SYSTEMS OF PERMANENT AGRICULTURE " Alfalfa will make land in Virginia yield good returns on a valuation of $200 per acre, or more, and land that was worth $30 per acre can be set in alfalfa at a cost of about $15 per acre, including lime, fertilizer, seed, and the growth of crimson clover. Enthusiasm and faith, with carbonate of lime, phosphorus, and clovers, can make a land beautiful to the eye, inspiring to the soul, and filling to the purse." "One most valuable result seen here is apparently that untreated Tennessee phosphate rock is giving as good results as phosphorus in any other form, using not the same amounts, but the same cost equivalents. In fact, there seems de- cided gain from the use of the raw phosphate." This temporary superiority of raw phosphate was doubtless due to some liberation by one green manuring. Later Mr. Wing says : "The results as they now show are about like this, speaking roughly: Acid phosphate leads by far. Bone meal comes next. Whether slag phosphate or Tennessee rock follows I do not know, but both are far in the rear of either bone meal or acid phosphate." (Breeder's Gazette, Nov. 8, 1911.) NOTE. On the author's Poorland Farm, including about 320 acres in the prairie section of southern Illinois (gray silt loam on tight clay), limestone is applied at the rate of 2 to 3 tons per acre, and raw rock phosphate at the rate of i ton per acre, every six years. After the phosphorus content of the plowed soil has been increased from 800 pounds per acre to about 2000 per acre, the application of that element will probably be reduced to an amount which will simply maintain the supply. Thus far the use of n car loads of raw phosphate and 17 car loads of ground limestone has given as satisfactory results as one could reasonably expect during the first crop rotation. For this special soil a six-year rotation is planned, as follows: First year Corn (and legume catch crop). Second year Part oats or barley, part cowpeas or soy beans. Third year Wheat. Fourth year Clover, or clover and timothy. Fifth year Wheat, or clover and timothy. Sixth year Clover, or clover and timothy. The plan may be a grain system where wheajt is grown the fifth year, only clover seed being harvested the fourth and sixth years, or it may be changed to a live stock system by using a field for pasture and meadow the last three years, all manure produced being applied to the pasture land to be plowed under for corn. While the untreated land has produced about one third of a ton per acre of poor hay (part timothy and redtop, part foul grass, sorrel, and other weeds), the treated land has produced more than i$ tons per acre of clean clover and timothy hay. A car load of limestone or phosphate is purchased with less hesitation than a cow or a horse, and at about the same cost. A careful study of the literature of agricultural science from European countries reveals no investigations with the use of raw rock phosphate that compare in value with those conducted by USE OF PHOSPHORUS IN DIFFERENT FORMS 291 any one of the seven states, Ohio, Maryland, Pennsylvania, Rhode Island, Maine, Massachusetts, or Illinois. There are three essential points to be kept in mind concerning the use of raw rock phosphate: First, all rock is not phosphate rock, and the farmer should purchase only guaranteed material, and he should know how much phosphorus is contained in the ground rock he applies to the land, if necessary by taking 100 teaspoonfuls from 100 different parts of the car load (including different depths), thoroughly mixing, and sending half a pound of this to a reliable commercial chemist for analysis. Second, the rock should be very finely ground, and it should be purchased upon a guarantee that at least 90 per cent of it will pass through a sieve with 100 meshes to the linear inch (10,000 meshes to the square inch), which is no finer than is required for slag phos- phate. Third, raw phosphate should not be expected to give marked benefits except when used in connection with adequate supplies of decaying organic matter. It has practically no value as a top dressing, but must be plowed under and thoroughly incorporated with the soil where the roots feed. Of course, it will supply only the element phosphorus, and will not take the place of any other deficient element, nor act as a soil stimulant to liberate other plant food from the soil, although it sometimes contains small amounts of carbonate, and then has some tendency to correct soil acidity, but in this it is insignificant compared to the effect of ground limestone. The following interesting discussion concerning the use of raw rock phosphate, from the viewpoint of the fertilizer manufacturer, was published in pamphlet form and widely disseminated in 1908, by the National Fertilizer Association. It was also published in full in the American Fertilizer, August, 1908, and in part in Ar- mour's Farmer's Almanac for 1909. It is reproduced in complete form in the following pages, because it deserves to be read by every careful student of soil fertility. Its cautions against the use of raw phosphate as a source of immediately available plant food are commended. It also serves to emphasize the fact stated in the introduction, that, " if the independent farmer is to adopt and 292 SYSTEMS OF PERMANENT AGRICULTURE maintain permanent systems of profitable agriculture, he cannot accept ' parrot ' instruction," not even when offered by the fer- tilizer agent. The fact that acid phosphate and " 2-8-2 " fertilizers are still used in the Eastern and Southern states, largely as soil stimulants and for a single crop, or for one year's effect only, fairly raises the question whether agricultural practice in those states is not influ- enced more by the "arguments" of the fertilizer agent than by the established facts and principles from the experiment stations. RAW ROCK PHOSPHATE, "FLOATS" PUBLISHED BY THE NATIONAL FERTILIZER ASSOCIATION For years the raw rock question has cropped out spasmodically, in different parts of the world, like the measles or some other affliction. Sometimes it was the result of the recommendation of some impractical theorist who occupied a position that brought him before the farmer — oftener it was foisted on an unsuspecting farming community by some one who was either directly or indirectly interested in an offgrade phosphate mine, and who used his official position to further the interests of the rock mine at the expense of the farmer. But no matter what started its use, the result has always been the same — no benefit derived from its use — a distrust of legitimate fertilizers, and a distinct set-back to agricultural interests which has taken several years to overcome. In the following pages we give you the opinions of foreign experiment station men as well as those of our own country. Both statistics and your good common sense tell you that the older the state or country, the more fertilizers are used and the greater the knowledge they have of their use. The mere fact that in these older communities, both abroad and in this country, the use of legitimate fertilizers has increased rapidly from year to year for a hundred years conclusively shows their value. The fact that wherever raw rock has been used, its use has been abandoned, shows its worthlessness. Read what authorities who know have to say on this subject. RESOLUTION passed by the Association of German Agricultural Experiment Stations, in congress assembled, September 14, 1907, at Dresden, Germany: "As a result of the extensive advertising which is done by certain parties ad- vocating the use of RAW ROCK PHOSPHATE, the association passed the follow- ing resolution: "THE ASSOCIATION HAS CONCLUDED, FROM FERTILIZER EXPERIMENTS AT HAND WITH RAW PHOSPHATE FERTILIZER, THAT THERE IS SHOWN NO PROFIT- USE OF PHOSPHORUS IN DIFFERENT FORMS 293 ABLE FERTILIZER EFFECT, APART FROM THOSE OF ACID SOIL. IN CONSEQUENCE THEREOF THE ASSOCIATION FEELS IT SHOULD DISCOURAGE THE USE OF RAW PHOSPHATE ON OTHER SOILS." See 6;th Volume (5-6), page 329, " LANDWIRTSCHAFTLICHER VERSUCHS STATION." The Association of German Agricultural Experiment Stations represents the highest authority on agricultural matters in Germany, and undoubtedly the best in the world. German investigators, particularly Dr. Von Liebig, were the authors of most of the fundamental principles underlying fertilization and agriculture, — and it is to them that we largely owe the progress made in this direction. In view of the well-known thoroughness of German agricultural investigators, and the fact that the Association of German Agricultural Experiment Stations is universally regarded as the world's highest authority on such matters, their opinion on the use of RAW PHOSPHATE as a fertilizer is of great importance to the American farmer. On account of the high price of land in Germany intensive farming is every- where practiced. The farmers must, of necessity, use fertilizer containing plant food in available condition. Their selection of fertilizers is based on in- numerable experiments covering over a hundred years. The difference in crop yields per acre in Germany as compared with the United States is conclusive evidence of the soundness of their methods of fertilization. The average wheat yield per acre in Germany for the ten years 1895 to 1904, inclusive, was 27.2 bushels, as compared with 13.4 bushels in the United States for the same period. On oats the yield per acre in Germany was 46.0 bushels, as compared with 29.2 bushels in the United States for the same period. (See pages 671 and 678, "Statistical Matter," reprint from Year Book of Department of Agriculture for 1905.) 1 The soils of Germany have been cropped for hundreds of years, while a large portion of those in this country are virgin or comparatively fresh. Proper fertilization is the secret of the higher yield per acre in Germany. If the United States is to maintain its supremacy in agriculture, farmers in this country will have to properly fertilize their crops, — and they can well take heed to the experience of their German brothers in this respect. Before using raw rock, therefore, you would do well to ascertain its true fertilizing value — the availability of the plant food it is supposed to contain — and especially to consider the decision of the German experimenters after years of careful testing. From the standpoint of furnishing available plant food, RAW ROCK PHOS- PHATE is not a fertilizer. The report of the twenty-fourth annual meeting of the Association of German Agricultural Experiment Stations, at which the 1 The ten-year average yield of corn in the great state of Georgia, where more manufactured acidulated commercial fertilizers are used than in any other state, is ii bushels per acre. — C. G. H. 294 SYSTEMS OF PERMANENT AGRICULTURE resolution quoted was passed, states that from "real exact experiments," con- ducted by such authorities as P. Wagner, Tacke, Bottcher, Lemmerman and others, "but little fertilizing effect was shown." Further experiments made by Czerhati, L. Rey, Clausen, and others, led to similar results just stated. The same report states that, "From the present experiments it can be con- cluded with certainty that the general use of earthly phosphates (RAW ROCK PHOSPHATE) cannot be considered as phosphoric acid fertilization." Phos- phoric acid is the only element this material contains, and if IT is NOT available it is useless for fertilizing purposes. The experiment station officials of Germany have gone on record against the use of RAW ROCK PHOSPHATE in no uncertain tone. Their opinion is shared, with but one or two exceptions, by all the experiment stations in this country. If THIS material cannot be recommended for German soils, where proper fertilization has been studied for so many years, is it not folly to attempt its use on the comparatively fresh soils of this country ? This report also refers to some recent experiments conducted by parties en- deavoring to promote the sale of raw rock phosphate in Europe. In comment- ing on the so-called tests or experiments, the German report states — that they "were carried out with but very little exactness." They further class these experiments as "entirely unfounded, have been rejected by scientific agricul- turists, and especially by Wagner, Tacke, and Bottcher, in a manner not to be misunderstood." The said representations of these promoters are classed as "A very serious deception," and misleading to the farmers. The efforts to promote the sale of RAW ROCK PHOSPHATE in this country — in the light of world-wide failure to show any appreciable fertilizing effect — can only be classed, in the language of the German experimenters, as "a very serious deception," and misleading to the farmers. Not alone in Germany have experiments with RAW ROCK PHOSPHATE proven very unsatisfactory. Professor F. H. Storer, in Volume I of his book "Agri- culture," in speaking of the value of raw phosphate USED IN CONNECTION WITH MANURE, as compared with superphosphate, says: "This question would seem to have been answered long ago, in so far as good land is concerned, by the common English practice of using superphosphates." Again, later, in comparing the effects of the same materials for fertilizing purposes in European countries, he says: "For Europe at least, i.e., for fertile districts, the question has been decided fully long ago and most emphatically in favor of superphosphate. It has been decided by the long-continued experi- ments of a multitude of farmers, and their conclusion has been plainly expressed by the ever increasing demand for superphosphate." l 1 Director Hall of Rothamsted, in his " Fertilizers and Manures " (1909), .page 118, says: "The mineral phosphates have been but little employed directly as manures, though there is plenty of evidence that when they are really finely ground, they are effective enough on soils retaining plenty of water." — C. G. H. USE OF PHOSPHORUS IN DIFFERENT FORMS 295 Coming down to our country, we find that experiments with RAW ROCK PHOSPHATE — with scarcely any exception — have proven unsatisfactory. Experiments conducted by the Maine Experiment Station, covering several years on various crops, designed to show the relative availability of phosphoric acid as supplied in acid phosphate, floats (raw rock phosphate), and redonda phosphate, were summarized as follows : "In every case the acid rock (Acid Phosphate) gave the best returns. The gain was especially marked with the family Gramineae, three members of which (barley, corn, and oats) yielded nearly double the amount produced by the Floats or Redonda. The effect upon sunflowers and buckwheat was equally marked. If we compare the amount of dry matter produced by the acid rock with that produced by the Floats for all crops grown, we find the balance in favor of the acid rock to be FIFTY -TWO PER CENT. In other words, the effect of the available phosphoric acid as compared with the insoluble phosphate was to increase the product MORE THAN ONE HALF." 1 The Georgia Experiment Station, commenting in Bulletin No. 2, concern- ing field experiments with phosphates and kainit applied to cotton, states: " Of phosphates, Acid Phosphate appears to lead, slag comes next, and the FLOATS ARE LAST." 2 A later Georgia Bulletin (No. 31), in reviewing a comparison of superphos- phate with Tennessee soft phosphate, states : "Superphosphate in a complete fertilizer was compared with one, one and a half and two times the same amount of Tennessee soft phosphate. The latter (Tennessee soft phosphate) was ap- plied in each case at a loss." 2 In the Annual Massachusetts Experiment Station Report for 1902, concern- ing an experiment with various kinds of phosphates which were applied in equal amounts of phosphoric acid, there is the following regarding raw rock phosphate : "Tennessee phosphate and Florida soft phosphate gave results very much inferior to all the others." This was an experiment on onions. In the Massachusetts Annual Report for the following year (1903), concern- ing the same experiment continued on cabbages, the previous year's results are confirmed: "That Tennessee phosphate and Florida soft phosphate proved very much inferior to all others." 3 1 This quotation is taken from page 72 of the 1898 Report of the Maine Experi- ment Station; while on page 57 of the 1900 Report occur the following statements: " For the first year the largest increase of crop was produced by soluble phosphoric acid. For the second and third years, without further addition of fertilizers, better results were obtained from the plots where stable manure and insoluble phosphates were used." — C. G. H. 2 These are single-year tests. The following quotation might also be made from page 161 of Georgia Bulletin No. 25 : "Florida Soft Phosphate appears to be equally as valuable as Acid Phosphate, the difference, if any, being rather in its favor. " — C. G. H. 3 On the other hand, the South Carolina raw rock phosphate produced a much larger yield than acid phosphate, especially of marketable cabbage, as shown in Table 49. — C.G. H. 296 SYSTEMS OF PERMANENT AGRICULTURE In Scott County, Indiana, an experiment to determine the relative value of raw rock phosphate and acid phosphate was started in 1904 and continued for four years. Equal values of rock phosphate and acid phosphate were ap- plied in ONE application the first year — corn and wheat alternating. The actual amount of plant food applied was 286 pounds of total phosphoric acid in the rock phosphate and 100 pounds phosphoric acid in the acid phosphate. There were three plots in the experiment — one fertilized with rock phosphate, one with acid phosphate, one unfertilized. Notwithstanding the fact that the first year's corn crop was a total failure on all plots, the results on wheat showed a gain of fourteen bushels per acre with acid phosphate as against only nine bushels for the rock phosphate over the unfertilized plot. The profit per acre in four years from rock phosphate was $11.55; * the profit in four years from acid phosphate was $13.50. In Marion County, Indiana, another experiment for the same purpose was started, and crops harvested for two years? Only one application of fertilizer was made, the entire amount being applied the first season. As in Scott County, equal values of rock phosphate and acid phosphate were applied. The results speak for themselves, and they are given in the table below as taken from Circular No. 10 of the Indiana Experiment Station. The yields are given in bushels per acre: CORN WHEAT Amount per acre J9O4 1905 Unfertilized 20 3 Rock phosphate, 1000 Ib 20 6 Acid phosphate, 715 Ib 27 16 The value of the increase per acre, figuring corn at 35 cents and wheat at 80 cents per bushel, on the plot fertilized with acid phosphate, was $12.85 Deducting cost of acid phosphate 5.00 Net return on the increase $7.85 Value of the increase with rock phosphate . . . . ' . . 2.40 Deducting cost of rock phosphate 5.00 Or a net loss of $2.60 per acre On the total yields the results were as follows: Unfertilized $9.40 per acre 8 Raw rock phosphate 6.80 per acre 3 Acid phosphate 17.25 per acre 1 This is a very fair profit considering that about two thirds of the raw rock phosphate will remain in the soil after the acid phosphate is completely exhausted. It should also be noted that the cost of the acid phosphate was figured at $14 per ton, and the cost of the raw phosphate at $10 per ton. — C. G. H. 3 Italics mine. — C. G. H. 1 Cost of rock phosphate and acid phosphate deducted. USE OF PHOSPHORUS IN DIFFERENT FORMS 297 These figures show that the rock phosphate was applied at a dead loss of $2.60 per acre — the unfertilized yield value being $2.60 per acre more than the rock phosphate. The yield with acid phosphate was $7.85 more than the UNFERTILIZED, and $10.45 Per acre niore than the RAW ROCK PHOSPHATE. These results are from experiments primarily intended to show the value of raw rock as a fertilizer. They are self-explanatory, and show conclusively the FOLLY OF CONSIDERING THIS MATERIAL AS A FERTILIZER. Further, these results were obtained from 100 pounds of phosphoric acid in acid phosphate as compared with 286 pounds of raw rock phosphate. The practical farmer, interested in the proper use of commercial fertilizers, can easily figure that where acid phosphate gave such remarkable returns on experiments covering a series of years, it will pay him a handsome profit to invest judiciously in fertilizers every year giving such good returns. Tennessee has some of the largest phosphate deposits in the world. In this state where the value of phosphate is so well understood, Professor C. A. Mooers, chemist and agronomist of the Agricultural Experiment Station at Knoxville, in a recent letter to THE AMERICAN FERTILIZER has the following to say with regard to the use of this material in its crude state : "A bill was introduced in the Legislature, just adjourned, to allow the sale of ground rock phosphate as a fertilizer. In presenting this matter to the Agricultural Committee, the Commissioner of Agriculture and myself took the position that it would not be desirable to tag this material, as that would, to a certain extent, stamp it with the State's approval. Our position is better under- stood when it is considered that a very large part of the fertilizers used in this State are for wheat, and, as is well known, RAW PHOSPHATE ROCK, as ordinarily used, GIVES NO RETURNS ON THIS CROP. Other large amounts are used, es- pecially in West Tennessee, by the truckers, and for garden crops also RAW PHOSPHATE WOULD BE INADVISABLE. Fertilizers have been used in this State for many years, but our farmers have not studied the matter to any great ex- tent, so that many of them would buy a fertilizer just BECAUSE IT WAS CHEAP, especially if it had the State's tag on it. "Our results on leguminous crops, which are supposed to be better able to make use of the so-called insoluble forms of phosphoric acid than others, do not warrant the general use of RAW PHOSPHATE. I have recently corresponded with a number of station men who are interested in the use of fertilizers, and I find that the general opinion is AGAINST THE USE OF THIS MATERIAL, although under special conditions, such as are found on a decidedly acid soil, its use may be advisable." The state of Alabama is one of the oldest of the states using commercial fertilizers. Bulletin No. 24, issued May 15, 1908, contains an article on "Raw Phosphate Rock as a Fertilizer." Following are extracts from this article: "Many parties have written to this office for information as to the relative fertilizing value of the raw phosphate, as compared with the acidulated phos- phates, and the writer has invariably advised caution in the employment of this particular kind of phosphate. 298 SYSTEMS OF PERMANENT AGRICULTURE "The samples of this material which have reached this laboratory have al- most invariably exhibited a poor mechanical condition, the particles being coarse and irregular in size. As the fineness of division of this phosphate has a most important influence upon its availability to the plant, purchasers of this material have been advised to only use the rock which has been pulverized to a state of practical impalpability, the material in this condition being commonly designated by the name of 'floats.' "A typical analysis of the raw phosphate rock sent to this laboratory this season is given herewith : Citrate-soluble phosphoric acid 0.68 per cent Acid-soluble phosphoric acid 23-55 Per cent Total phosphoric acid 24.23 per cent "It will be noted that nearly all of the phosphoric acid in this phosphate is in an insoluble or acid-soluble condition, and there is SCARCELY A TRACE OF WATER SOLUBLE PHOSPHORIC ACID TO BE FOUND IN THIS RAW PHOSPHATE. "With regard to the comparative availability of raw phosphate rock, it might be stated that the Experiment Station at Auburn has, during the past few years, carried out under its supervision more than one hundred cooperative soil and crop tests in a great many different localities in the State with a view to deter- mining the comparative efficiency of raw phosphate and acid phosphate for fer- tilizing purposes. These tests have been carried out upon quite a variety of soils, and upon most soils the RAW PHOSPHATE HAS FAILED TO GIVE ANYTHING LIKE AS GOOD RESULTS AS THE ACID PHOSPHATE. "In the case of acid phosphate, the ready solubility of most of the phos- phoric acid contained therein promotes its rapid and thorough distribution through the top layer of the soil, and hence the plant food is so well dissemi- nated that it is brought within easy reach of the root system of the plant, whereas in the case of the crude insoluble phosphate the diffusion and dis- tribution of the phosphoric acid is necessarily slow, and much of the phos- phate is left unutilized at the end of the season in which it is applied. "For the above reasons IT is DEEMED INADVISABLE TO EMPLOY THE CRUDE PHOSPHATE to any great extent upon any given soil until comparative tests of the crude rock and acid phosphate have been made upon that soil, and, even under these conditions, it will- probably be found necessary to use much larger amounts of phosphate rock than are ordinarily employed to secure a satis- factory return from its application." While the experience of the German Experiment Stations, combined with a majority in this country, show emphatically that raw rock phosphate has little or no fertilizing value, in addition the method of applying followed by users of this material in this country is MOST EXTRAVAGANT AND WASTEFUL. The method followed would soon exhaust the known or visible supply of phosphate rock. Further, the enormous quantities necessary to apply per acre, instead of being scattered over and benefiting millions of acres, would be wasted on comparatively few. USE OF PHOSPHORUS IN DIFFERENT FORMS 299 On the other hand, this crude material, when properly treated with sulfuric acid and converted into acid phosphate, to be used either as straight acid phosphate or in mixed fertilizers, becomes a source of available plant food of greatest value. Raw rock phosphate, as mined and sold by certain operators, does not contain plant food immediately available to growing crops. It is only by proper handling and treatment with sulfuric acid that this material is con- verted into fertilizer furnishing plant food available to various crops and soils. Reputable fertilizer manufacturers decry the use of raw rock phosphate as a fertilizer, knowing that it will NOT prove satisfactory, as borne out by exten- sive experiments of the world's best agriculturists. They have gone on record against its use, and any lack of results on the part of those using this material should not vitiate against the use of commercial fertilizers rightly prepared, furnishing available, nourishing plant food for all crops. (Signed). THE NATIONAL FERTILIZER ASSOCIATION. The author feels that no further comment is necessary regarding this statement from the National Fertilizer Association. The facts are presented in very complete form in the preceding pages, and the reader must draw his own conclusions. For other illustra- tions of the possibility of erroneous conclusions being drawn by such German investigators as advance theories or reach conclu- sions without sufficient facts, reference may be made to Chapter 31, and also to Sir Henry Gilbert's very interesting and complete discussion of the sources of fat in the animal body, based upon Rothamsted investigations in which 327 different animals were dissected, 10 different selected carcasses having been subjected to chemical analysis, following the analysis of the foodstuffs provided during long feeding periods. (See Office of Expt. Stations Bui. 22.) OHIO EXPERIMENTS WITH MANURE AND PHOSPHATES, 1897-1911 VALUE OF THREE CORN,1 CORN, WHEAT, HAY, CROPS Son. TREATMENT 15-YEAR AVERAGE 14- YEAR AVERAGE 1 4- YEAR AVERAGE II-YEAR AVERAGE 1909 Corn 1 909 Corn (Bushels) (Bushels) (Bushels) (Tons) Excluded Included None 33-0 34-4 II. 2 1.30 $27.68 $27.19 Manure alone .... 54-6 56.0 2I.O 1.80 45.10 44.61 Manure, rock phosphate 62.4 62.5 25-7 2.28 53-54 53-51 Manure, acid phosphate 62.0 63.8 26.1 2.25 54-iQ 53-47 1 Because of irregular insect injury, the Ohio Station prefers not to include the 1909 corn crop in the general average. (For'details, see pages 245 to 258.) CHAPTER XVIII THEORIES CONCERNING SOIL FERTILITY ABOUT three hundred years ago Van Helmont, a Flemish alche- mist, planted a five-pound willow tree in 200 pounds of dry soil. ' He watered it with rain water for five years, and then found that the tree had gained 164 pounds and that the soil had lost only 2 ounces, in weight. Therefore, he concluded, water is the source of plant food. While it seemed to him that his evidence was strong and positive, all know now that his conclusion was wrong, and that the air, the water, and the soil are all essential sources of plant food. It will be noted that 2 ounces removed from the 200 pounds of soil correspond to 1250 pounds from 2 million pounds of soil. Later, Bradley, in his " General Treatise of Husbandry and Gardening," argued that water could be distilled or evaporated, which was not the case with willow trees; and, hence, that water is not the food of plants. He held that air must be the food of plants. About two hundred years ago, Jethro Tull, the inventor of the first seed drill, taught that neither water nor air could be the food of plants because they were furnished alike to all plants; whereas, two adjoining fields produced very different yields because one was impoverished soil while the other had been enriched. Tull wrote as follows: "It is agreed that all the following materials contribute in some manner to the increase of plants, but it is disputed which of them is that very increase of food: (i) Niter, (2) Water, (3) Air, (4) Fire, (5) Earth. . . . " Niter is useful to divide and prepare the food, and may be said to nourish vegetables in much the same manner as my knife nourishes me, by cutting and dividing my meat; but when niter is applied to the root of a plant, it will kill it as certainly as a knife misapplied will kill a man ; which proves that niter is, in respect of nourishment, just as much the food of plants, as white arsenic is the food of rats, and the same may be said of salts. 300 THEORIES CONCERNING SOIL FERTILITY 301 "Water, from Van Helmont's experiment, was by some great philosophers thought to be it. But these were deceived, in not observing that water has always in its intervals a charge of earth, from which no art can free it. " Air, because its spring, etc., is as necessary to the life of vegetables as the vehicle of water is, some modern virtuosi have affirmed, from the same and worse arguments than those of the water philosophers, that air is the food of plants. . . . "Fire. No plant can live without heat, though different degrees of it be necessary to different sorts of plants. Some are almost capable of keeping company with the salamander, and do live in the hottest exposures of the hot countries. Others have their abode with fishes under water, in cold climates; for the sun has his influence, though weaker, upon the earth covered with water, at a considerable depth, Which appears by the effect the vicissitudes of winter and summer have upon the subterraqueous vegetables. " But that fire is the food of plants, I do not know any author has affirmed, except Mr. Lawrence, who says: 'They are true fire-eaters'; and even he does not seem to intend that this expression of his should be taken literally." "Earth. That which nourishes and augments a plant, is the true food of it. "Every plant is earth, and the growth and true increase of a plant is the addition of more earth." "Too much earth, or too fine, can never possibly be given to roots . . . and earth is so surely the food of all plants, that with the proper share of the other elements, which each species of plants requires, I do not find but that any common earth will nourish any plant." "The mouths, or lacteals, being situate, and opening in the convex super- ficies of roots, they take their pabulum, being fine particles of earth, from the superficies of the pores, or cavities, wherein the roots are included. . . . These particles, which are the pabulum of plants, are so very minute and light, as not to be singly attracted to the earth, if separated from those parts to which they adhere, or with which they are in contact (like dust to a looking glass, turn it upwards, or downwards, it will remain affixed to it), as these particles do to those parts, until from thence removed by some agent. "A plant cannot separate these particles from the parts to which they adhere, without the assistance of water, which helps to loosen them. "As to the fineness of the pabulum of plants, it is not unlikely that roots may insume no grosser particles than those on which the colors of bodies depend; but to discover the greatness of those corpuscles, Sir Isaac Newton thinks, will require a microscope that with sufficient distinctness can represent objects five or six hundred times bigger than at a foot distance they appear to the naked I eye." In general, Jethro Tull taught that the soil particles are the food • (pabulum) of plants, and that, if the soil were made sufficiently fine by cultivation, the plants could then absorb these fine particles of earth and produce large crops continuously. In answer to the 302 arguments of his critics that the agricultural practice of his time was the result of long experience and consequently must be cor- rect, he expressed a fundamental truth in the following words: "The experience of 1700 years no more proves this practice to be right, than the long experience of cattle drawing by their tails proved that practice right, before drawing by traces was by experiment proved to be better: for nothing can be depended on as experience, which has not been tried by experi- ment." He also classes himself with those who " cannot believe that a man will become bald by being shaved at the wrong time of the moon, without more experience than 'has been made for it these 1700 years past/) - Another century passed, during which the humus theory ad- vanced by Thaer and others gained some recognition. The humus of the soil was held to be the source of carbon and carbonaceous matter for the plant. Humus and water were considered the only sources of plant food, and the productive power of the soil was believed to depend solely upon its humus content. In the "Georgical1 Essays" (Edition of 1777) by Doctor A. Hunter, which also includes many essays or reports by other " philosophical farmers," we find the following interesting state- ments : "The ancient writers gave us excellent comments upon the husbandry of their times. Hesiod wrote very early upon Agriculture. Mago, the Carthagin- ian general, composed twenty-eight books upon the same subject, which were translated by order of the Roman Senate. Upon these models Virgil formed his elegant precepts of husbandry. "Cato, the Censor, wrote a volume upon Agriculture. Columella has left us twelve books upon rural matters. Varro's treatise will ever be esteemed. . . . "The celebrated Sully calls Agriculture one of the breasts from which the State must draw its nourishment. That great man could not possibly have given us a more happy simile. . . ." "Colbert entertained a different notion of policy. Esteeming manufacturers and commerce as the sinews of the State, he gave all possible encouragement to the Artisan and the Merchant, but forgot that the manufacturer must eat his bread at a moderate price. The farmer being discouraged, the necessaries of 1 Georgical, like the proper name George (Latin Gear gins'), meaning husband- man or farmer, is derived from the Greek yij (ge-, as in geology), the earth, and tpytiv (ergein, as in energy), to work. The Georgics of Virgil are poems on agri- cultural affairs. THEORIES CONCERNING SOIL FERTILITY 303 life became dear; the public granaries became ill stored; manufactures lan- guished; commerce drooped; a numerous army soon consumed the scanty harvest; and, in a short time, Industry fell a sacrifice to the ill-judged policy of the minister. "From that period to the present, the French nation have constantly been availing themselves of their mistake. Under the genial influence of the King, Societies are erected in every province. Men of the first distinction do not dis- dain the cultivation of their own lands. M. de Chateauvieux and Duhamel are the greatest ornaments of their country. — Let us imitate the virtues of that fash- ionable nation. . . ." f "The art of husbandry boasts an origin coeval with the human race. Its age, however, seems to have contributed but little towards its advancement, being at present extended but a few degrees beyond its primitive institution. Until the philosopher condescends to direct the plow, Husbandry must remain in a torpid state. . . . " I take it upon me to say, that, to be a good husbandman, it is necessary to be a good chymist. Chymistry will teach him the best way to prepare nourish- ment for his respective crops, and, in the most wonderful manner will expose the hidden things of nature to his view. The principles of Agriculture depend greatly upon chymistry; and without principles, what is art, and what is science ? , "Directed by instinct, the animal seeks its own proper food ; but the vegetable, not being possessed of the power of motion, must be satisfied with the nourish- ment we give it. To direct this upon rational principles, is the business of the philosopher. The practical farmer will suffer himself to be instructed as soon as he perceives the practice correspond with the theory laid down to him. Let us expect no more of him. Men of limited education commit great errors when they attempt to reason upon science. In husbandry, effects are constantly applied to improper causes. Hence proceed the errors of our common farmers. To overcome these is the peculiar province of the philosopher; who, in his turn, must support his reasoning by facts and experiments. "I lay it down as a fundamental maxim, that all plants receive their principal nourishment from oily particles incorporated with water, by means of an alka- line salt or absorbent earth. ... It may be asked, whence do natural soils receive their oily particles? I answer, the air supplies them. During the summer months, the atmosphere is full of putrid exhalations arising from the steam of dunghills, the perspiration of animals and smoke. Every shower brings down these oleaginous particles for the nourishment of plants." " The ingenious Mr. Tull, and others, have contended for earth's being the food of plants. If so, all soils equally tilled would prove equally prolific. Water is thought, by some, to be the food of vegetables, when in reality it is only the vehicle of nourishment." After pointing out the great value of oil meals, rape cake, etc. (and later of fish scrap), for soil improvement, and after noting c SYSTEMS OF PERMANENT AGRICULTURE that all seeds contain oil, and that hemp, rape, and flax (rich in oil) are very exhaustive crops, Doctor Hunter adds, much to his credit as a scientist: "As I have not the vanity to think my experiments sufficiently conclusive, I embrace this opportunity to request assistance of the practical farmer, in order that the merits of the invention may be fully determined. Should my theory concerning the food of plants be thought erroneous, the compost (made in part of crude whale oil, 'train oil') will of course be disregarded. But, on the con- trary, should it be agreed to that oil, made miscible with water, constitutes the chief nourishment of vegetables, then the invention will probably become the subject of future experiment. "Though theory may direct our inquiries, yet experience must at last deter- mine our opinions, for which reason I propose to enlarge my experiments; and as I have no other view but the investigation of the truth, I shall lay them faith- fully before the public, whether they prove successful or not." Among the " Georgical Essays," the two reports which follow are of special interest. The first bears upon the oil theory, and both show evidence of the search for truth, and indicate the approach- ing dawn of chemical science. The editor says that the 1777 edi- tion is a reprint, and that " this volume contains several additional papers"; so it is not clear that Doctor Hunter knew of these experiments. "A COMPARATIVE VIEW OF MANURES " BY A. YOUNG, ESQ. "In the year 1771, 1 marked out a rood of land into divisions, and sowed them with oats. The variety of manures made use of in this experiment are marked as follows: PRODUCE PER ACRE No. B. P. 1. 40 cubical yards of farmyard compost, and dung ... 40 2\ 2. 20 ditto . 51 i 3. 10 ditto 45 o 4. 10 ditto 46 i 5. 10 loads of bones, each 40 bushels 63 i 6. 20 ditto 57 o 7. 200 bushels of lime 38 if 8. 40 yards of chalk 31 r 9. No manure 30 z\ 10. 80 yards of chalk 25 2\ n. 120 ditto 27 a THEORIES CONCERNING SOIL FERTILITY 305 PRODUCE PER ACRE No. B. P. 12. 40 yards of chalk, earth mixed with train oil, six months ago, and often turned 33 o£ 13. 40 ditto, earth mixed with urine, four months ago, and often turned 37 2 14. 40 ditto, earth alone . . ? 33 oj 15. 40 ditto, earth from the farmyard 37 2 16. 1 20 ditto, red gravelly loam 29 T£ 17. 160 ditto 31 i " N.B. The season was remarkably dry, which circumstance certainly had a j considerable effect upon the different crops." . J "ON BONES USED AS A MANURE "By ANTHONY ST. LEGER, ESQ. F" During a long course of speculative and practical Agriculture, in which, with critical exactness, I employed myself in making experiments upon almost every kind of manure, I was fortunate enough to discover that bones are su- perior to all the manures made use of by the farmer. "Eight years ago I laid down to grass a large piece of very indifferent lime- stone land with a crop of corn (Wheat, presumably) ; and, in order that the grass seeds might have a strong vegetation, I took care to see it well dressed. From this piece I selected three roods of equal quality with the rest, and dressed them with bones broken very small, at the rate of sixty bushels per acre. Upon lands thus managed, the crop of corn was infinitely superior to the rest. The next year the grass was also superior, and has continued to preserve the same superiority ever since, insomuch that in spring it is green three weeks before the rest of the field. J "This year I propose toplow up the field as the Festuca sylvatica (prye grass) has overpowered the grass seed originally sown. And here it will be proper to remark that, notwithstanding the species of grass is the natural prod- uce of the soil, the three roods on which the bones were laid have hardly any of it, but, on the contrary, have all along produced the finest grasses. Last year I dressed two acres with bones, in two different fields prepared 'or turnips, sixty bushels to the acre, and had the pleasure to find the turnrps greatly superior to the others managed in the common way. I have no doubt but these two acres will preserve their superiority for many years to come, if I may be allowed to prognosticate from former experiments most carefully con- ducted. "I also dressed an acre of grass ground with bones last October (1774) and rolled them in. The succeeding crop of hay was an exceeding good one. However, I found from repeated experience that, upon grass ground, this kind of manure exerts itself more powerfully the second year than the first. "It must be obvious to every person, that the bones should be well broken Ul L 306 SYSTEMS OF PERMANENT AGRICULTURE before they can be equally spread upon the land. No pieces should exceed the size of marbles^ To perform this necessary operation, I would recommend the bones to be sufficiently bruised by putting them under a circular stone, which, ^ being moved round upon its edge by means of a horse, in the manner that tan- ners grind their bark, will very expeditiously effect the purpose. At Sheffield it is now become a trade to grind bones for the use of the farmer. Some people break them small with hammers upon a piece of iron, but that method is in- ferior to grinding. (-To ascertain the comparative merit of ground and unground bones, I last year dressed two acres of turnips with large bones, in the same field where the ground ones were used ; the result of this experiment was, that the unground material did not perform the least service; while those parts of the field on which the ground bones were laid were greatly benefited. "I find that bones of all kinds will answer the purpose of a rich dressing, but those of fat cattle I apprehend are the best. The London bones, as I am in- formed, undergo the action of boiling water, for which reason they must be much inferior to such as retain their oily parts; and this is another of the many proofs given in these essays that oil is the food of plants. The farmers in this neighborhood are become so fond of this kind of manure, that the price is now advanced to one shilling and fourpence per bushel, and even at that price they send sixteen miles for it. "I have found it a judicious practice to mix ashes' with the bones; and this winter I have six acres of meadow land dressed with that compost. A cart load of ashes may be put to thirty or forty bushels of bones, and when they have heated for twenty-four hours (which may be known by the smoking of the heap) let the whole be turned. After laying ten days longer, this most excellent dress- ing will be fit for use." Jj In 1822, William Corbett, in his compilation of the writings of JethroTull, made the following statements: "Mr. Tull's main principle is this, that tillage will supply the place of manure; and his own experience shows that a good crop of wheat, for any number of years, may be grown every year upon the same land without any manure from first to last." " Mr. Tull continued his wheat crops to the harvesting of the twelfth upon the same land without manure; and when he concluded his work, he had, as he in- forms us in a memorandum, the thirteenth crop coming on, likely to be very good." It may be stated, however, that, after the time of Jethro Tull and before Corbett's republication of the Tullian methods and theories, some truly scientific facts had been discovered. In fact, chemistry had begun to assume the character of an exact science. Priestly had discovered oxygen and also identified as oxygen the gas which others had previously observed is given off from the THEORIES CONCERNING SOIL FERTILITY 307 leaves of plants under the influence of sunlight;1 Senebier had shown that the carbon of the plant is derived from the carbon dioxid of the air; and De Saussure had analyzed the ash of many plants, had shown that these ash constituents were derived from the soil, and that, though small in quantity as compared with the amount of material furnished to the plant by the air and water, the ash constituents were also essential to plant growth. De Saussure's publication in 1804 of his " Reserches Chimique sur la Vegetation" gave to the world the first definite and approxi- mately correct statement concerning the requirements and sources of plant food. While Davy's lectures on Agricultural Chemistry (first published in 1813) did much to extend the existing knowledge, and the investigations of Bousingault and Lawes began to develop (about 1835), it remained for Liebig to bring together the work of all and present it in a more comprehensive form in his " Organic Chemistry in its Application to Agriculture and Physiology," published in 1840. Thus, while Liebig is popularly known as the "Father of Agri- cultural Chemistry," the more fundamental contributions to knowl- edge concerning soil fertility and plant growth have been made by Senebier (of Switzerland), De Saussure (of France), Lawes and Gilbert (of England) , and Hellriegel (of Germany) , the last being the discovery (in 1886) of nitrogen fixation by the root-tubercle bacteria of legumes. Liebig devoted much effort toward the proof of his theory that the ammonia of the air is the source of nitrogen for plants; but in this he failed, and Lawes and Gilbert's laboratory and field investigations at Rothamsted, which were in part planned for the purpose of disproving Liebig's nitrogen theory, clearly established the fact that in the main the soil must furnish nitrogen as well as the mineral elements of plant food. The following quotations from Liebig's writings are interesting; and they are also instructive, in that they well illustrate the weak- ness of drawing quantitative deductions and specific conclusions from qualitative data and general observations. Thus wrote Liebig: 1 Any one may observe the bubbles of oxygen formed upon fresh leaves placed under water in the sunlight. 3o8 SYSTEMS OF PERMANENT AGRICULTURE ( "Let us picture to ourselves the condition of a well-cultured farm, so large as to be independent of assistance from other quarters. On this extent of land there is a certain quantity of nitrogen contained both in the corn and fruit which it produces, and in the mefi and animals which feed upon them, and also in their excrements. We shall suppose this quantity to be known. The land is culti- vated without the importation of any foreign substance containing nitrogen. Now, the products of this farm must be exchanged every year for money, and other necessaries of life, for bodies, therefore, which contain no nitrogen. A certain proportion of nitrogen is exported with corn and cattle; and this ex- portation takes place every year, without the smallest compensation ; yet after a number of years, the quantity of nitrogen will be found to have increased. Whence, we may ask, comes this increase of nitrogen ? The nitrogen in the ex- crements cannot reproduce itself, and the earth cannot yield it. Plants, and con- sequently animals, must, therefore, derive their nitrogen from the atmosphere. "The last products of the decay and putrefaction of animal bodies present themselves in two different forms. They are in the form of a combination of hydrogen and nitrogen, — ammonia, in the temperate and cold climates, and in that of a compound, containing oxygen, nitric acid, in the tropics and hot climates. The formation of the latter is preceded by the production of the first. Ammonia is the last product of the putrefaction of animal bodies; nitric acid is the product of the transformation of ammonia. A generation of a thousand million men is renewed every thirty years : thousands of millions of animals cease to live and are reproduced in a much shorter period. Where is the nitrogen which they contained during life? There is no question which can be answered with more positive certainty. All animal bodies, during their decay, yield the nitrogen, which they contain to the atmosphere, in the form of ammonia. Even in the bodies buried sixty feet underground in the church- yard of the Eglise des Innocens, at Paris, all the nitrogen contained in the adi- pocere was in the state of ammonia. Ammonia is the simplest of all the com- pounds of nitrogen ; and hydrogen is the element for which nitrogen possesses the most powerful affinity.) "The nitrogen of putrefied animals is contained in the atmosphere as ammonia in the form of a gas which is capable of entering into combination with carbonic acid, and of forming a volatile salt. Ammonia in its gaseous form as well as all its volatile compounds are of extreme solubility in water. Ammonia, there- fore, cannot remain long in the atmosphere, as every shower of rain must con- dense it, and convey it to the surface of the earth. Hence, also, rain water must, at all times, contain ammonia, though not always in equal quantity. It must be greater in summer than in spring or in winter, because the intervals of time between the showers are in summer greater; and when several wet days occur, the rain of the first must contain more 'of it than that of the second. The rain of a thunderstorm, after a long-protracted drought, ought for this reason to contain the greatest quantity, which is conveyed to the earth at one time. . . ." "If a pound of rain water contain only one fourth of a grain of ammonia, THEORIES CONCERNING SOIL FERTILITY 309 then a field of 40,000 square feet must receive annually upwards of 80 Ib. of ammonia, or 65 Ib. of nitrogen; for, by the observations of Schubler, which were formerly alluded to, about 700,000 Ib. of rain fall over this surface in four months, and consequently the annual fall must be 2,500,000 Ib. This is much more nitrogen than is contained in the form of vegetable albumen and gluten, in 2650 Ib. of wood, 2800 Ib. of hay, or 200 cwt. of beet root, which are the yearly produce of such a field, but it is less than the straw, roots, and grain of corn which might grow on the same surface, would contain. "Experiments, made in this laboratory (Giessen) with the greatest care and exactness, have placed the presence of ammonia in rain water beyond all doubt. It has hitherto escaped observation, because no person thought of searching for it.1 All the rain water employed in this inquiry was collected 600 paces southwest of Giessen, whilst the wind was blowing in the direction of the town. When several hundred pounds of it were distilled in a copper still, and the first two or three pounds evaporated with the addition of a little muriatic acid, HC1, a very distinct crystallization of sal-ammoniac (NH4C1) was, ob- tained : the crystals had always a brown or yellow color. "Ammonia may likewise be always detected in snow water. Crystals of sal-ammoniac were obtained by evaporating in a vessel with muriatic acid several pounds of snow, which were gathered from the surface of the ground in March, when the snow had a depth of 10 inches. Ammonia was set free from these crystals by the addition of hydrate of lime. The inferior layers of snow, which rested upon the ground, contained a quantity decidedly greater than thftse^vhich formed the surface. uf'It is worthy of observation, that the ammonia contained in rain and snow water possesses an offensive smell of perspiration and animal excrements, — a fact which leaves no doubt respecting its origin. . . ." "We find this nitrogen in the atmosphere, in rain water, and in all kinds of soils, in the form of ammonia, as a product of the decay and putrefaction of pre- ceding generations of animals and vegetables. We find, likewise, that the pro- portion of azotized matters in plants is augmented by giving them a larger supply of ammonia conveyed in the form of animal manure. "No conclusion can then have a better foundation than this, that it is the ammonia of the atmosphere which furnishes nitrogen to plants." ) As an average of 15 years, the total amount of nitrogen brought to earth in rain and snow was found to be 3.97 pounds per acre per annum, at Rothamsted. Other records, varying from 3 to 7 years, have shown 3.45 pounds per acre per annum on the Barbados Islands, 3.54 pounds in British Guiana, 3.69 pounds in Kansas, 5.42 pounds in Utah, and 3.64 pounds in Mississippi; while the records from Paris show 8.93 pounds, and those from Gembloux, 1 " It has been discovered by Mr. Hayes in the rain water in Vermont." — W. 3io SYSTEMS OF PERMANENT AGRICULTURE Belgium, 9.20 pounds, both of which are doubtless influenced by the atmosphere from the cities with their numerous factories and other sources of pollution. Professor Shutt reports 4.32 pounds of nitrogen per acre in one year's precipitation at Ottawa, Canada, in 37.35 inches, of which 3.24 pounds were found in 24.05 inches of rain and 1.08 pounds in 13.3 inches of snow water (corresponding to about 133 inches of snow), the average composition being based upon analyses of 46 samples of rain water and 32 samples of snow water. Of the nitro- gen found in rain water, 61 per cent existed in free ammonia, 22 per cent in nitrate (and nitrite) form, and 17 per cent as organic nitrogen, the corresponding percentages for snow water being 56, 34, and 10. Liebig also discussed very interestingly and, in the main, very erroneously, the reasons for the value of crop rotation. In 1840 he wrote as follows: "Of all the views which have been adopted regarding the cause of the favor- able effects of the alternations of crops, that proposed by M. Decandolle alone deserves to be mentioned as resting on a firm basis. " Decandolle supposes that the roots of plants imbibe soluble matter of every kind from the soil, and thus necessarily absorb a number of substances which are not adapted to the purposes of nutrition, and must subsequently be expelled by the roots, and returned to the soil as excrements. Now as excrements can- not be assimilated by the plant which ejected them, the more of these matters which the soil contains, the more unfertile must it be for plants of the same species. These excrementitious matters may, however, still be capable of as- similation by another kind of plants, which would thus remove from the soil, and render it again fertile for the first. And if the plants last grown also expel substances from their roots, which can be appropriated as food by the former, they will improve the soil in two ways. " Now a great number of facts appear at first sight to give a high degree of probability to this view. Every gardener knows that a fruit tree cannot be made to grow on the same spot where another of the same species has stood ; at least not until after a lapse of several years. Before new vine stocks are planted in a vineyard from which the old have been rooted out, other plants are cultivated on the soil for several years. In connection with this it has been ob- served, that several plants thrive best when growing beside one another; and, on the contrary, that others mutually prevent each other's development. Whence it was concluded, that the beneficial influence in the former case depended on a mutual interchange of nutriment between the plants, and the injurious one in the latter on a poisonous action of the excrements of each on the other respectively. THEORIES CONCERNING SOIL FERTILITY "A series of experiments by Macaire-Princep gave great weight to this theory. He proved beyond all doubt that many plants are capable of emitting extractive matter from their roots. He found that the excretions were greater durihg the night than by day, and that the water in which plants of the family of the Leguminosce grew, acquired a brown color. Plants of the same species, placed in water impregnated with these excrements, were impeded in their growth, and faded prematurely, whilst, on the contrary, corn plants grew vigorously in it, and the color of the water diminished sensibly; so that it appeared, as if a certain quantity of ^ie excrements of the Leguminosce had really been absorbed by the corn plants.jThese experiments afforded as their main result, that the characters and p*j^>erties of the excrements of different species of plants are different from one another, and that some plants expel excrementitious matter of an acrid and resinous character; others mild (douce) substances resembling gum. The former of these, according to Macaire-Princep, may be regarded as poisonous, the latter as nutritious. "The experiments of Macaire-Princep are positive proof that the roots, prob- ably of all plants, expel matters, which cannot be converted in their organism either into woody fiber, starch, vegetable albumen, or gluten, since their ex- pulsion indicates that they are quite unfitted for this purpose. But they cannot be considered as a confirmation of the theory of Decandolle, for they leave it quite undecided whether the substances were extracted from the soil, or formed by the plant itself from food from another source. It is certain that the gummy and resinous excrements observed by Macaire-Princep could not have been contained in the soil ; and as we know that the carbon of a soil is not diminished by culture, but, on the contrary, increased, we must conclude that all excrements which contain carbon must be formed from the food ob- tained by plants from the atmosphere. Now, these excrements are compounds, produced in consequence of the transformations of the food, and of the new forms which it assumes by entering into the composition of the various ;ans. "M. Decandolle's theory is properly a modification of an earlier hypothesis, hich supposed that the roots of different plants extracted different nutritive substances from the soil, each plant selecting that which was exactly suited for its assimilation. According to this hypothesis, the matters incapable of as- similation are not extracted from the soil, whilst M . Decandolle considers that they are returned to it in the form of excrements. Both views explain how it happens that after corn, corn cannot be raised with advantage, nor after peas, peas ; but they do not explain how a field is improved by lying fallow, and this in proportion to the care with which it is tilled and kept free from weeds; nor do they show how a soil gains carbona-0 fifi f\ 1887-1896 . 43 • •* 1897-1904 .... 46 I 59-7 5°-4 THEORIES CONCERNING SOIL FERTILITY 327 YIELDS OF CEREALS ON RITTERGUT TREBSEN, NEAR LEIPZIG YEAR WHEAT (Bu.) RYE (Bu.) BARLEY (Bu.) OATS (Bu.) I766—I 77 "? 13. 2t; 12.33 21.71 23.48 1776-1785 1 736-1 7(K . 16.63 13.98 14.47 13.67 20.44 l6.77 23-45 IQ.l6 1 796—1800 13.89 IS- 16 I5.l6 17.00 1814-1816 15.28 15.68 2^.41 28 -- i»45 1049 1883-1892 25-51 27.03 2°-75 23.06 3O.95 56-25 44.64 1803-1804 , 29.81: 28.36 3O.95 54-74 180^—1800 . 35.85 30.45 35-3Q 51.15 i 000—1004 , 36.14 32.52 43.23 57.80 YIELDS OF CEREALS ON ANOTHER GERMAN ESTATE 1800-1810 21.15 14.64 19.80 17.22 1810—1820 20.02 11.76 20.92 17.44 1820-1830 1830-1840 1840—1850 23-25 18.82 23.10 17.76 15.04 10.84 21.29 16.37 20.87 14.84 13.86 27.58 1850-1855 1855-1860 26.40 25. 27 23.12 24.16 32-75 27.71 33-46 34-44 1860-1865 29.77 30.48 37.85 44.52 1865-1870 27.45 26.48 36.17 55.72 1870-1875 1875-1880 29.92 28.12 28.32 24,72 35-71 29.38 51-38 7O.48 1880-1885 1885-1894 25-57 3^.70 25.12 20.^2 36.45 41.06 45.08 43.06 AVERAGE YIELDS OF CEREALS IN GERMANY 1881-1885 21.7? 18.56 20.07 36.06 1886-1890 22.6=C IQ.O4 20.07 40.42 i8oi-i8(X 2A.7O 21.28 2I.SJ4 40.88 I896—I9OO 26."^ 23.04 32.49 45. 08 AVERAGE YIELDS OF CEREALS IN FRANCE 1815-1824 11.86 IO.IO 14. 4C 17.12 1825-1834 13.44 12.34 14.64 17.78 1835-1844 , 14.30 I3.OI 1^-02 2O. IO 1855-1864 I ^ QO 14 II 10 QO 24.03 1865-1874 I5.8l 14 6< IQ.7S 24.40 1875-1876 . 1 6. 60 1^.71 IQ.OO 23.6l 328 SYSTEMS OF PERMANENT AGRICULTURE first definite information which could serve as a scientific basis for systems of soil improvement. The few records from 1800 to 1825 are of little or no value, but the averages from 1825 to 1834 show very clearly the application of definite knowledge as com- pared with the averages previous to 1800; while the further marked increase for the ten years ending 1844 clearly shows that the teach- ings of Davy, Bousingault, and Liebig were being applied on the Trebsen estate as well as by Sir John Lawes at Rothamsted. The most satisfactory data are from the third German estate, showing lo-year or 5-year averages for practically all of the last century, from which it is plain to see that the first distinct increases date from the publication of Liebig's teachings in 1840. While the larger private estates would perhaps be the first to adopt the teachings of science, the records show general increases for both Germany and France. The average yields of wheat of late years for England, Germany, and France are 32.2, 28.0, and 19.8 bushels per acre, respectively, or, as a general average, about double the average of 100 years ago. It is safe to credit this in- crease very largely to the use of plant food, including the more general use of atmospheric nitrogen by legume crops during the last quarter century. The average yield of wheat in the United States is 13.7 bushels for the ten years, 1899 to 1908. A second factor1 of much importance in crop improvement, though very subordinate to that of plant food, is the improvement in seed by selection and breeding. A German economist has esti- mated that, as an average, seed improvement has produced a gain of 25 per cent. In exceptional cases, as with the sugar beet, very remarkable progress has been made by breeding, the average sugar content of the beet having been raised from about 4 per cent to 12 per cent or more. The following extracts from an address by President Creelman, of the Ontario Agricultural College, to the Ontario Agricultural and Experimental Union, December, 1908, is well worthy of care- ful consideration (Report for 1908, page 62) : 1 Other factors of improvement are of doubtful consequence, including correc- tion of toxic bodies. Tillage and crop-rotation have been the rule for centuries in old countries. Isolation of such bodies signifies little. The soil is earth's waste- basket, wherein we may find almost every substance, toxic or nontoxic. THEORIES CONCERNING SOIL FERTILITY 329 "SOME OBSERVATIONS OF FARMING IN SOUTHERN EUROPE "Italy has been practicing the art of agriculture since the early, early days of the old, old civilization, hundreds of years before the Christian era began, and agriculture is still the most important industry in Italy, as 85 per cent of all the Italian soil is productive land. Dairying is not one of the leading lines, however, nor is any other kind of stock raising. Oxen and asses are still the principal beasts of burden, and wine the largest crop. "And yet, the agricultural products of Italy are varied, and in the aggregate amount to a very large total. Remember that Italy is only twice the size of the State of New York, and you will realize that not much land is wasted when the following crops are produced annually: Wheat 143,400,000 bushels Corn 85,600,000 bushels Oats 19,360,000 bushels Rye and barley 18,400,000 bushels Rice 26,000,000 bushels Other cereals 18,000,000 bushels Total cereals 310,760,000 bushels Potatoes 19,360,000 bushels Hemp 111,000,000 pounds Flax 30,000,000 pounds Cotton .< 22,000,000 pounds Tobacco 7,250,000 pounds Olive oil 74,500,000 gallons Wine 666,000,000 gallons "But, like the Swiss and the French, the peasant people are a frugal, thrifty race ; and while the rich eat wheat bread, the work-people are content with bread made from corn or rye. "Legumes everywhere. In looking about to find how the fertility of the soil was maintained, in districts where live stock was not common, and hence farm manure was far from plentiful, I noticed that everywhere leguminous crops (or pulse) were the rule. I also discovered that in some form it was eaten every, day by rich and poor alike. All the time I was in Italy I never once sat down to a dinner without being served with peas or beans or lentils, or some other variety of leguminous annual. I found also that the poorer classes consume large quantities of pulse, it being used to a large extent as a substitute for meat." The increases in these European crop yields since about 1825 to 1840 should be a most effective object-lesson to the American farmer to " go and do likewise "; and if he will talk with any man who has had experience in western European agriculture during the last quarter century, he will promptly receive the positive assur- 33° SYSTEMS OF PERMANENT AGRICULTURE ance that no successful farmer in those countries thinks of trying to farm without liberal applications of plant food, especially of phosphate fertilizers, and, as a rule, either farm manure or green manure. Often commercial nitrogen and potassium are also used, in part because of the very high value of farm produce and also because of the low price of potassium salts, Germany's supply of which is estimated to be sufficient to meet the present con- sumption of the world for 190,000 years. In comparison with these European records, marked contrast appears in the average crop yields of the state of Kansas during 48 years. Professor W. J. Spillman, of the United States Bureau of Plant Industry, has called attention to these statistics in the following words: "The following table of figures is interesting: "YIELDS PER ACRE — AVERAGE FOR STATE OF KANSAS CROP 1860-1889 (Bu.) 1880-1908 (Bu.) DECREASE (Per Cent) Corn T.A.2 21 6 -26.0 Wheat 1C. 2 n.8 22.8 Oats 12.8 2I.O 32.2 "These figures are in general agreement with data collected from other sections of this country. When rich virgin soil is brought into cultivation and farmed without any reference to the conservation of fertility, good yields are obtained for about forty years. Then begins a decline, and the yield ultimately sinks down to a point where there is no profit for the farmer. ... In the case of each of the three crops above mentioned the average yield for the past nine years is slightly greater than for the preceding ten years. This indicates that the . Kansas farmer is slowly but surely improving his system of farming. Dairying and the feeding of beef cattle, also hay raising are becoming more prevalent, and there is every reason to believe that before another generation has passed the Kansas farmer will have rehabilitated his soil and have developed suitable systems of farming that will keep Kansas near the forefront in agriculture." (Hoard's Dairyman, May 14, 1909.) While the average yields are probably approximately correct and the results are exceedingly striking, in the author's opinion these Kansas results have little significance, because of the enor- mous increase and westward extension of the area put under cul- THEORIES CONCERNING SOIL FERTILITY 331 tivation in Kansas during the fifty years, as briefly indicated by the following tenth-year records: ACREAGE OF CEREALS IN KANSAS YEAR CORN WHEAT OATS 1862 . 17036^ O^6o 2036 1868 1878 360388 240^482 98525 I 7 3081 2 9880 4441 QI 1888 600"? 20 7 1120119 16^6814 1808 7277601 4624731 KX4QOO IOCS 7CK7<^c; 60 30 'Kl 8311^0 When we consider that eastern Kansas, the part first settled, is in the humid section of the United States, and that the later years include the records from the central and western parts of the state where semiarid conditions prevail, it will be seen that the average yields computed by Professor Spillman may serve best to illustrate the possibility of drawing erroneous conclusions from the use of general statistics unless full consideration is given to all important factors. The explanation for the slight increase in the average yields of the last nine years of the period, as compared with the preceding ten years, is very possibly to be found in the increased rainfall in the semiarid region, as is well illustrated by the very interesting and very instructive diagram (shown on an- other page) of the rainfall record at North Platte, Nebraska, for the thirty-four years, 1875 to 1908 (Nebraska Bulletin 109, April, 1909), from which it will be seen that the ten years, 1890 to 1899, included eight years below normal and averaged only 15.35 inches, while the following nine years, 1900 to 1908, show but three years below normal, and average 21.21 inches. It should be kept in mind that meat and dairy products bring much larger returns in Maryland than in Kansas, and until the well-situated, well-drained, and well-wa'tered farm lands of Mary- land and Virginia have been rehabilitated by these methods of live-stock farming (which farmers have been familiar with for centuries) ; until such soils as the Leonardtown loam, comprising 41 per cent of St. Mary County, Maryland, where, to quote the 332 SYSTEMS OF PERMANENT AGRICULTURE language of the Bureau of Soils, " it is worth from $i to $3 an acre," which also covers 45,770 acres of land in Prince George County, adjoining the District of Columbia, where it " can be bought for $1.50 to $5 an acre, even within a few miles of the District line," - until this Leonardtown loam, which, according to Whit- ney's latest decision (Bureau of Soils Bulletin 55, page 116, Febru- ary, 1909), " is a valuable upland soil of Maryland and Virginia; the surface is slightly rolling, the drainage in most areas good, and altogether the land is well suited to general farming"; until this land which, according to the analyses of the Bureau of Soils (Bulletin 54, page 19), contains in 2 million pounds of the surface soil only 160 pounds of total phosphorus and 1000 pounds of total calcium; that is, sufficient total phosphorus and total calcium in the plowed soil of an acre for about 8 crops of clover, with such yields as we can and do produce on our best-treated land in good seasons (4 tons in 2 cuttings), — until these impoverished lands surrounding the National Capital have been rehabilitated and changed in value from $1.50 to $150 an acre, by crop rotation, or even by live-stock farming without the purchase of plant food in feed or fertilizers, — until these results have actually been accom- plished, the student of agriculture is earnestly warned against accepting any predictions that the farmers of Kansas or of any other states are actually enriching their soils because they are practicing live-stock farming to a greater or less extent. The student is urged to have faith in the exact data of scientific inves- tigations, such, for example, as those conducted for more than 60 years at Rothamsted, England, and for about 30 years at Urbana, Illinois, and at State College, Pennsylvania, full records of which are given in the following pages. Of course the small commercial countries of Europe which retain practically all of their own fertility and import much more in food stuffs and fertilizers can markedly enrich their soils, just as some of our small states can build up some small areas of culti- vated lands; but as the average yield of corn in the great state of Georgia is only n bushels per acre, so the average yield of wheat on the " black soils " of Russia, for the 20 years, 1883 to 1902, is' 8^ bushels per acre, and as a rule this land lies fallow every third year. The following comment is recorded on page 27 of Bulletin 42 THEORIES CONCERNING SOIL FERTILITY 333 of the Bureau of Statistics, United States Department of Agri- culture: "It may be claimed that this extremely low average yield in European Russia is caused by the total failure of crops in famine years, and that these should have been omitted in calculating the average for a series of years. But the extreme variability of the average yield is no less a characteristic feature of Rus- sian agriculture than its very low yield; and the famine years have been so frequent as to become a permanent feature of Russian agriculture, each one of the five-year periods including at least one famine year, and some even two." It may be added that in famine years the average yield of wheat in Russia is 6^ bushels, the lowest recorded average yield being 5^ bushels per acre. In India the average yield of cotton on the " black cotton soils " is less than 100 pounds of lint per acre. The following extract from an article written by Saint Nihal Singh of India (see Wallaces' Farmer, April 30, 1909) is given as a faithful description of the present condition of our cousins in India, the Eastern Branch of our own Aryan1 race, " the sons of Japheth ": "If the American farmer were to seek contrast to his life and labor, he would find it on the farm in India ; and the contrast would be as clearly defined as that which exists between day and night." "Almost all the farm land has to be irrigated. While the rainfall is heavy at seasons, it is uncertain, and prolonged drouths make irrigation positively neces- sary." (In the main the water for irrigation is collected in ponds or large shal- low wells during the rainy season, and then drawn to the fields by oxen or carried by hand as needed. When the monsoons fail and the wells or reservoirs are not filled, at least partial crop failure results, and famine is likely to follow. — C. G. H.) " The farm in India is very small in area. It is very rarely larger than ten or twenty acres — often it is only two or three acres. 1 " The languages of all these branches or groups of people are akin ; that is to say, they are descendant of one original tongue, once spoken in a limited locality, by a single community, but where or when it is impossible to say. "Many words still live in India and England that have witnessed the first separation of the northern and southern Aryans, and these are witnesses not to be shaken by any cross examination. The terms for God, for house, for father, mother, son, daughter, for dog and cow, for heart and tears, for axe and tree, identical in all the Indo-European idioms, are like the watchwords of soldiers. We challenge the seeming stranger; and whether he answer with the lips of a Greek, a Ger- man, or an Indian, we recognize him as one of ourselves. There was a time when the ancestors of the Celts, the Germans, the Slavonians, the Greeks and Italians, the Persians and Hindus, were living together beneath the same roof, separate from the ancestors of the Semitic and Turanian races. " — MAX MULLER. 334 SYSTEMS OF PERMANENT AGRICULTURE "As to the nature of the crops grown in the country: wheat, corn, various kinds of peas and lentils, cotton, and sugar cane are grown exclusively in north- ern India, except such portions where the lands are low and the rainfall heavy where rice is grown. Rice is the principal crop in southern India." "Considering the amount of hard drudging work that the Indian farmer puts into his work, the yield l from the labor is pitifully disappointing." "At harvest time extra hands are needed and they are employed by the far- mer, who agrees to pay them a certain amount of grain to compensate them for their labor. If payment is made in coin, it seldom exceeds two and a half annas (five cents 2) a day. The income of the average East Indian, according to gov- ernmental statistics, is only fifty cents a month, and farmers, as a community, live in the most miserable poverty. "There are 450,000 square miles of waste land in Hindustan, or nearly one fourth of the country, that is to-day uncultivated, though capable of yielding rich harvests. The people of India do not know enough to bring these lands under cultivation. The soil that is in use is never allowed to lie fallow, even for a brief space of time. Crops follow one another in quick rotation. The farmer lacks the knowledge and resources to enrich his land by means of fer- tilizers. The only fertilizer that he knows about is cow dung and, unfor- 1 Nitya Gopal Mukerji, Professor of Agriculture and Agricultural Chemistry in the Civil Engineering College at Sibpur, Bengal, India, in his "Handbook of Indian Agriculture" (1907), reports "the area under food grains in India at 164 million acres and the produce of grain per acre per annum at 840 lb., and the population at 350 millions." There are about 70 million acres of rice and nearly 30 million acres of wheat. The average yields are estimated at 17 bushels of rice (of 60 lb. each), about 10 bushels of wheat, and 7 to 12 bushels of corn, per acre, and in the main the crops are grown under irrigation. The following quotations from Mukerji are of interest: "The farmer aims at doing without manures (the English term for commercial fertilizers) as much as possible, at keeping up the fertility of his land simply by feeding his cattle with nourishing oil cakes and utilizing all the cattle dung, urine, and litter in manuring his fields. By growing leguminous crops and by adopting a judicious system of rotation he also tries to avoid the purchase of manures (fer- tilizers)." " The reported fertility of Indian_ soils is more a myth than a reality. Where the soil has been in cultivation for many years, the virgin richness has disappeared, except where it is irrigated by canals (e.g., the Eden Canal) bringing rich desposits of silt, or annually flooded by rivers leaving such deposits (e.g., in eastern Bengal). As a rule, Indian soils yield poor crops. "In the famine of 1770, in nine months, ten million people died in Bengal. The famine of 1784 was of such a bad type that four seers (8 lb.) of wheat were sold for a rupe (48 ct.), and the deaths from starvation were innumerable. The most recent of all famines, viz., that prevailing in some part of India or other from 1897 to 1900, has been severer than the famine of 1874-1878." * The anna is about 3 cents, but it sometimes depreciates to less than 2 cents. — C. G. H. THEORIES CONCERNING SOIL FERTILITY 335 tunately, he is able to spare little of this for enriching the field, for timber is scarce in most parts of India and the cow chips are used for fuel. "When these old-fashioned methods are taken into consideration, it is easy to understand why agriculture does not pay in India. Since 95 per cent of the people of Hindustan are engaged in farming or allied industries, it is easy to realize why the people of India live in excruciating poverty. Famine rages in the country all the year round, and it will continue to do so until the East Indian agriculturist is taught to use better methods. As it is, only one out of 147 women and only ten out of 100 men farmers are capable of reading and writing, and only one out of every five villages in India has a schoolhouse. "The home life of the farmer is so filled with desperate poverty that it lacks all picturesque details. . . . The house usually consists of but one room or, at best, two or three, and all of these are most rudely furnished. There are no carpets on the floor, which is of dirt, uncovered by boards or even by matting. The men and women usually squat on the floor, using small, narrow pieces of gunny sacks to sit on. The bedstead is home-made and may be described as a cot made in the most elementary manner of bamboo laced across with coarse twine. The same room is used for storing goods of all descriptions, preparing and eating food, and for sitting and sleeping purposes. Not unoften the cattle are given a corner in the room. Since the married sons of the father live at home, the shortage of space compels two or three families to herd together in the same apartment. "Life for the woman is especially filled with drudgery. She gets up between three and four o'clock in the morning. While the husband is feeding the stock she milks the cows. Over night the milk has been boiled and allowed to curdle. The woman puts it into an earthen pot and churns it. Buttermilk forms an important item of the scanty breakfast. About the only thing that the farmer eats along with the whey is corn or wheat bread, which, unlike in this country, is made thin like a pancake and six or eight inches in diameter. Both men and women take a bite of this bread and pour down a quantity of buttermilk. In eating no knives, forks, spoons, are employed. The fingers are made to perform the various eating operations." "The life of great hardship and excruciating poverty that farmers in India are obliged to lead makes them subnormal. They lack vim and vitality. In their waking moments they are only half awake. Through insufficient nutrition they are unable to do the hard physical work they would be able to do otherwise. Naturally the people in India are fatalists by religion. They look upon life as an adversity that has to be shouldered as best it can be. They are not afraid of death; in fact, they long for death, for they believe that on the other side of existence they would lead a happier and a better-fed life. Thus do the people of India live and labor." In China, the fourth great agricultural country comparable with the United States in extent and necessary self-dependence, there are areas of arable upland plains, sometimes 100 square miles or 336 more in extent, that are not now populated, the reclamation of which has been called the " Problem of China." The information available is not sufficient to determine to what extent the waste lands of India and China represent abandoned farms that were once cultivated, but it is fully known that to some extent this is the case. On the other hand, the Chinese have main- tained well the fertility of much of the lands they are now culti- vating. The explanation is found in the following quotations, taken largely from Sir Humphry Davy's "Agricultural Chemistry" (1827) and from Davis, Fortune, and other writers, through extracts published in the works of Baron Justus von Liebig (1840 to 1859) : "The Chinese, who have more practical knowledge of the use and application of manures than any other people existing, mix their night soil with one third of its weight of a fat marl, make it into cakes, and dry it by exposure to the sun. These cakes, we are informed by the French missionaries, have no disagreeable smell, and form a common article of commerce of the empire." — DAVY. "Davis, in his 'History of China,' states that every substance convertible into manure is diligently husbanded. 'The cakes that remain after the expression of their vegetable oils, horns, and hoofs reduced to powder, together with soot and ashes, and the contents of common sewers are much used. The plaster of old kitchens, which in China have no chimneys, but an opening at the top, is much valued : so that they will sometimes put new plaster on a kitchen for the sake of the old. All sorts of hair are used as manure, and barber's shavings are carefully appropriated to that purpose. The annual produce must be considerable, in a country where some hundred millions of heads are kept constantly shaved. Dung of all animals, but more especially night soil, is esteemed above all others. Being sometimes formed into cakes, it is dried in the sun, and in this state becomes an object of sale" to farmers, who dilute it previous to use. They construct large cisterns or pits lined with lime plaster, as well as earthen tubs sunk in the ground, with straw over them to prevent evaporation, in which all kinds of vegetable and animal refuse are collected. These, being diluted with a sufficient quantity of liquid, are left to undergo the putrefactive fermentation, and then applied to the land." " Human urine is, if possible, more husbanded by the Chinese than night soil for manure; every farm, or patch of land for cultivation, has a tank where all substances convertible into manure are carefully deposited, the whole made liquid by adding urine in the proportion required, and invariably applied to the soil in that state. The business of collecting urine and night soil employs an immense number of persons, who deposit tubs in every house in the cities for the reception of the urine of the inmates, which vessels are removed daily with as much care as our farmers remove their honey from the hives. The night soil is collected in the same way, as well as on the roads and by-places, THEORIES CONCERNING SOIL FERTILITY 337 persons being always on the alert with baskets and rakes to avail of the least particle that appears. The Chinese get as much off their land as it is capable of producing, and this is done by the liberal use of manure and application of much more labor in working the soil than in other countries. The reason they do not use dung is that they have comparatively no animals." "It is quite impossible for us in Europe to form an adequate conception of the great care which is bestowed in China upon the collection of human excre- ments. In the eyes of the Chinese, these constitute the true sustenance of the soil (so Davis, Fortune, Hedde, and others tell us), and it is principally to this most energetic agent that they ascribe the activity and fertility of the earth." "Except the trade in grain, and in articles of food, generally there is none so extensively carried on in China as that in human excrements. Long, clumsy boats, which traverse the street canals, collect these matters every day, and dis- tribute them over the country. Every coolie who has brought his produce to market in the morning carries home at night two pails full of this manure on a bamboo pole. I11 The estimation in which it is held is so great that everybody knows the amount of excrements voided per man in a day, month, or year ; and a Chinese would regard as a gross breach of manners the departure from his house of a guest who neglects to let him have that advantage to which he deems himself justly entitled in return for his hospitality. The value of the excrements of five people is estimated at two Teu per day, which makes 2000 Cash l per annum, or about twenty hectoliters (440 gals.), at a price of seven florins." w "Every substance derived from plants and animals is carefully collected by the Chinese and converted into manure. Oil cakes, horn, and bones are highly valued, and so is soot, and especially ash. To give some notion of the value set by them upon animal offal it will be sufficient to mention that the barbers most carefully collect, and sell as an article of trade, the somewhat con- siderable amount of hair of the beards and heads of the hundreds of millions of customers whom they daily shave. The Chinese know the action of gypsum and lime; and it often happens that they renew the plastering of the kitchens for the purpose of making use of the old matter for manure." — DAVIS. "During the summer months all kinds of vegetable refuse are mixed with turf, straw, peat, weeds, and earth, collected into heaps, and when quite dry, set on fire ; after several days of slow combustion the entire mass is converted into a kind of black earth. This compost is only employed for the manuring of seeds. When seedtime arrives, one man makes holes in the ground; another follows with the seed, which he places in the holes ; and a third adds this black earth. The young seed planted in this manner grows with such extraordinary vigor that it is thereby enabled to push its rootlets through the hard solid soil, and to collect its mineral constituents." — FORTUNE. "The Chinese farmer sows his wheat, after the grains have been soaked in 1 The Chinese coin tsien (pronounced chen), called cash by foreigners, is valued at about one tenth of a cent. — C. G. H. 338 SYSTEMS OF PERMANENT AGRICULTURE liquid manure, quite close in seed beds and afterwards transplants it. Oc- casionally, also, the soaked grains are immediately sown in the field properly prepared for their reception, at an interval of four inches from each other. The time of transplanting is toward the month of December. In March the seed send up from seven to nine stalks with ears, but the straw is shorter than with us. I have been told that wheat yields 120 fold and more, which amply repays the care and labor bestowed upon it." — ECKEGERG, in Report to the Academy of Sciences at Stockholm, 1765. "In Chusan, and the entire rice districts of Chekiang, and Keangaoo, two plants are exclusively cultivated for the purpose of serving as green manure for the rice fields; the one is a species of Coronilla, clover is the other. Broad fur- rows, similar to those intended for celery, are made, and the seeds are planted on the ridges in patches, at a distance of five inches from each other. In the course of a few days germination begins, and long before the winter is gone the entire field is covered with a luxuriant vegetation. In April the plants are plowed in ; and decomposition soon begins, attended with a most disagreeable odor. This method is adopted in all places where rice is grown." — FORTUNE. ^.^ "These extracts," said Liebig, "which, from want of space, cannot be further extended, will probably suffice to convince the German agriculturist that his practice, when compared with that of the oldest agricultural nation in the world, stands somewhat in the position of the acts of a child to those of a full-grown and experienced man." A communication dated Chengtu, Szechuan, China, July 4, 1907, from Elrick Williams (formerly associated with the author, as student and teacher, at the University of Illinois) contains the following information: "One of the first things which attract the attention of a foreigner on reach- ing China is the simple form of closets and 'outhouses' in vogue. Private ones consist of a square box in which is placed an earthenware vessel usually smaller than a bushel basket. A stranger will notice that it is empty every morning, even at an early hour. Greater still is one's astonishment to note along the streets convenient places for accommodating one's necessity in this regard. They are, of course, very simple. Along the river where there are multitudes of trackers (men who tow the boats), one finds earthenware vessels set in the ground behind a half circle of matting about three or four feet high. Enter- prising farmers put these in to reap the passing reward. Last, but by no means least, is the man with the dung basket and fork. The man may be a woman or child but the majority are grown men. They haunt the streets, alleys, lanes, or loafing places of men, and the feeding places of beasts. I have seen a woman run down a steep hill with a basket in order to be nearest to a squatting tracker. Before he is twenty feet away, often the prize is gathered up. 339 "Human manure is the most highly prized, although a friend told me that the manure from silk worms was even more valuable. Dog manure, pig manure, cow manure, and water buffalo manure are prized in about this order." Thus do the people of China follow the products of the land to the place of consumption and return to the soil every possible recoverable residue, and to this are added a large use of legume crops and applications of muck, marl, lime, etc., and silt deposits on overflowed or irrigated lands. (See also page 594.) The following quotations from circular letters from Doctor Al- fred M. Peter, Head of the Division of Agricultural Chemistry of the Kentucky University Agricultural Experiment Station, will be of interest to the student (see also pages 263-267, Vol. i, Journal of Industrial and Engineering Chemistry, April, 1 909) : "LEXINGTON, KY., January 21, 1909. "DEAR SIR: " In a ' Hearing before the Committee on Agriculture of the House of Repre- sentatives,' 1908, Doctors Whitney and Cameron of the Bureau of Soils have made statements to the effect that the recent teachings of the Bureau in regard to soil fertility are generally accepted throughout this country and Europe, and that they are being widely taught in the Agricultural Colleges of this country. The teachings referred to, with which you are, no doubt, familiar, may be sum- marized in the following statements: " i. That all soils contain enough mineral plant food in available form for maximum crops, and that this supply will be indefinitely maintained. " 2. That the real cause of infertility is the accumulation in the soil of poison- ous excreta from plant roots. " 3. That it is not ever necessary to add fertilizers for the purpose of increas- ing the plant food in the soil, the good effect of fertilizers being due to their power-of neutralizing or destroying these toxic substances or their activity. " 4. That soil fertility can be maintained indefinitely by practicing a system of rotation by which a crop is grown each year that is not injured by the ex- creta of the preceding crop. " In order to ascertain just how extensively these views are accepted and taught in our Agricultural Colleges and Experiment Stations, the writer is sending this letter to professors of agriculture, agronomists, and agricultural chemists in all such institutions on the "Organization Lists." It is proposed to publish a summary of the data obtained, without giving names of institutions or individ- uals. Will you kindly assist by telling me whether or not these views are ac- cepted and taught by you or your institution, or by referring this letter to some one who will give me an authoritative answer ? " Yours very truly, (Signed) "ALFRED M. PETER." SYSTEMS OF PERMANENT AGRICULTURE " LEXINGTON, KY., February 18, 1909. "DEAR SIR: " Replies to my letter of January 21 have now been received from 104 in- dividuals in the United States and Canada, including 35 Agricultural Chemists, 25 Agronomists, 21 Professors of Agriculture, 9 Soil Specialists, both chemists and physicists, 8 Experiment Station Directors, not otherwise classified, 3 Directors of Farmers' Institutes, i Professor of Vegetable Pathology, i of Hor- ticulture, and i of Natural Science. Out of these only two indorse the Bureau's views without qualification and say they are taught in their institutions as estab- lished facts. These two are from minor or branch institutions, however, not one of the Land-grant Colleges or State Experiment Stations being willing to accept or teach them in the sense in which they have been put forward by the Bureau. About half recognize more or less truth in the doctrines, and present and discuss them in advanced teaching. Most of them recognize the value of the Bureau's work on toxic substances and consider them a possible factor in soil fertility, though not the most important one. The rest either say they do not accept and teach the Bureau's views on these subjects, or oppose them. The Agricultural Colleges and Experiment Stations in 47 States and Terri- tories of the United States are represented in these answers, showing a very general interest in the subject of the inquiry. It is apparent that while the Bureau's views on soil fertility are not being accepted and taught as established, in these institutions, they are being generally presented and discussed in ad- vanced teaching of agriculture. " In a letter to me dated January 28, a copy of which has been sent to you, Doctor Cameron takes exception to my presentation of the Bureau's teachings and explains his position in this matter. Doctor Whitney in a letter to me ap- proves Doctor Cameron's letter, so it may be taken as an authoritative ex- pression of the Bureau's views. If, after reading it, you desire to modify your opinion already expressed to me, I will be glad to hear from you before making my final publication. « ,r , " Yours very truly, (Signed) "ALFRED M. PETER." From the numerous exact quotations hereinbefore given the student will be able to determine for himself how fairly Doctor Peter has summarized the teachings of the Bureau of Soils. Under date of July 3, 1909, Doctor Peter wrote the author as follows: " About half of my correspondents wrote me again to say that Doctor Cameron's letter had made no change in their views. I did not hear from any one who desired to change his expression of opinion." The persistent and long-continued teaching of the Federal Bureau of Soils, that the fertility of the soil can be indefinitely maintained without the restoration of plant food, is widely pro- mulgated by inspired press reporters and other prolific writers and THEORIES CONCERNING SOIL FERTILITY 341 gladly accepted by land agents and by landowners inexperienced in the management of truly depleted soils. And why not ? No doctrine could be more pleasing, — an in- exhaustible national asset ! — a self-maintaining food supply ! — a dish from which we can eat and eat, to-day, to-morrow, and for- ever ! — a bank account which requires for its maintenance only the rotation of the check book among the members of the family ! — a " philosopher's stone " that creates an infinite supply of golden grain from finite quantities of baser materials ! The possible enormous and irreparable damage of such teach- ing lies in the fact that even our remaining supply of good land will ultimately be depleted by the present practices beyond the point of self-redemption, thus repeating the history of our aban- doned Eastern lands, where the rotation of crops was the com- mon rule of practice for more than a hundred years. The following extracts are typical : " SOILS NOT WEARING OUT " A most comprehensive bulletin has recently been published by the Na- tional Department of Agriculture dealing with the question of soil composition." " The facts and figures presented in this bulletin tend to show that there is not any immediate danger of the soils of the United States wearing out. " "Considering the fact that the farms of the United Kingdom have been under cultivation for a thousand years or more, it is held by Professor Whitney that continuous cropping does not necessarily tend to decrease production." " We believe that Professor Whitney's statements will come as a surprise to a great majority of our readers, because the average man labors under the belief that soils are gradually wearing out ; on the other hand, it is a fact that our leading farmers, in every state in the Union, are not only able to main- tain their crop yield, but they are increasing it from year to year." " It is true that there may be annually some loss.of mineral elements, but in ordinary good soils, such as our clays and loams, the supply of these minerals is so great that a five-hundred or even a thousand-year period will not reduce the supply to a point where production is materially affected." — The Home- stead, October 28, 1909. " FERTILITY OF SOIL " Artificial Fertilizers Said to be all Wrong " Special Correspondence. "WASHINGTON, Nov. 17. — Artificial fertilizers — phosphates and nitrates, chiefly — act upon the soil as drugs act upon the human body, according to 342 SYSTEMS OF PERMANENT AGRICULTURE investigations just completed by the Bureau of Soils of the Department of Agriculture. " Although there are some experiments and some tabulation of results yet to be made, the scientists have gone far enough to evolve a theory that may upset present-day methods of agriculture. " The new theory is based on a series of experiments that have been con- ducted during the summer and for several years prior to this season. They intend to show that there are natural agencies at work in the soil that will replenish worn-out 'soil tissues' just as the worn-out tissues of the body in man are replaced by agencies inside. Only in the case of man there is usually a limit to this process, whereas, in soils, the scientists have observed some wonderful results from soils long ago abandoned as useless. " Sensible rotation of crops will produce much better and more lasting results than the artificial fertilization of soils, say the experts" — Freeport (Illinois) Daily Buttetin, November 19, 1909. " SECRETARY WILSON ON EASTERN FARMING " Secretary of Agriculture Wilson has been traveling through some of the Eastern States for the purpose of studying farming conditions, and is quoted as saying: ' ' It was a beautiful country that we passed through, but the farms gener- ally did not show prosperity. Many of the districts looked depopulated. We saw plenty of children in the villages, but few in the rural regions. The coun- try looked deserted. In fact, interest in agriculture appears to have declined.' ' The soils in this state are not exhausted. In some cases they have be- come unproductive by failure to rotate crops, and again because there has been no change of seed. I am told that many farmers hereabout have planted seed from the same source for fifty years. In the West they know the value of changing seed. We have searched the world for seeds which would flour- ish in all climates and conditions, and we are going to increase our production by making use of them.' " — Wallaces1 Farmer, November 5, 1909. In conclusion it may be stated that the four great fundamental facts of plant nutrition still stand against every test: thus, Sen6- bier's proof of the fixation of carbon, oxygen, and hydrogen by photosynthesis, De Saussure's discovery of the presence and abso- lute necessity of mineral plant food, Lawes and Gilbert's proof that the soil must furnish the nitrogen for most plants, and Hell- riegel's discovery of the fixation of free nitrogen by the bacteria of legumes always lead to the same conclusion whenever, wherever, or by whomsoever they are repeated. They are fully recognized as absolutely established facts, at least as well established as the fact that the earth is round. SIR JOHN BENNET LAWES (1814-1900) PART III SOIL INVESTIGATION BY CULTURE EXPERIMENTS IN the preceding pages we have considered the subject of soil fertility in large part from the chemical and mathematical stand- point (the last chapter being disregarded). Thus, we have dis- cussed briefly the chemical composition of earth, air, water, plants, and animals; the essential plant-food elements and their relative abundance in plants and in plant and animal products and resi- dues, also in normal and abnormal soils; and the sources and forms of materials whose use is necessary for the adoption of systems of permanent agriculture on ordinary lands under general farming. We have thus far referred to field or pot-culture experiments mainly to cite the existing evidence concerning the possibility and practicability of using methods or materials regarding which the scientific, agricultural, and commercial interests are not agreed. Before taking up a study of various factors that influence crop production, including the use of special fertilizers for special soils and crops, it seems wise to consider in detail the results of some of the long-continued field experiments with general farm crops on ordinary normal soils; and, after wandering through the wilder- ness of the last chapter, the seeker after truth will welcome the positive data from thoroughly scientific cultural investigations, not from 20-day cultures in pound pots or water extracts or even from single-year tests, but the definite yields of mature crops year after year for twenty, thirty, and even for sixty years. At the same time the author begs some consideration for the question if we need prepare to avoid in America a repetition of the Dark Ages that followed the high civilization of the Mediter- ranean countries, until relieved by the discovery of the New World, and that still exist for the masses in Russia, India, and China. 343 CPTAPTER XIX THE ROTHAMSTED EXPERIMENTS ROTHAMSTED is the oldest agricultural experiment station. It was formally established in 1843, nme years before the first German experiment station was started at Mockern (Leipzig), although some experiments had been conducted at Rothamsted at least as early as 1837, and more extensive field experiments were begun in 1840. The published records report all of the crops grown on Broadbalk field since 1839, and the exact yields of produce are recorded since 1844, so that the records now cover about two thirds of a century. It was in 1843 that John Bennet Lawes, the proprietor of the Rothamsted estate and founder of the experiment station, secured the services of Doctor Joseph Henry Gilbert; and this associa- tion, which continued to the end of the century, made the names, Lawes and Gilbert, almost synonymous with Rothamsted. The earlier extensive investigations of De Saussure concerning the mineral constituents of plants, followed by the discussion and further investigations of Sir Humphry Davy and others, and the confident announcement of well-defined theories by Baron Justus von Liebig, were among the important factors that influenced the general plans that were adopted for the Rothamsted field experi- ments. Lawes and Gilbert did not concur in Liebig's theory so far as concerns the element nitrogen, and the central plan in most of the Rothamsted field experiments is based upon this difference of opinion; and, while the accumulated information showing the correctness of Lawes and Gilbert's views is exceedingly full and complete, some other important facts find little proof in the Rothamsted data. 344 SIR JOSEPH HENRY GILBERT (1817-1901) THE ROTHAMSTED EXPERIMENTS 345 Notwithstanding this somewhat restricted character of the general plans, the records of Rothamsted are the greatest source of knowledge concerning many of the most fundamental problems of soil fertility; and in justice to the American farmer and student of permanent agriculture, the author cannot do less than to repro- duce the following records of Rothamsted investigations that seem to bear most directly upon the maintenance of soil fertility as measured by crop yields: 1. Crops grown in rotation on Agdell field, with records since 1848. 2. Wheat grown continuously on Broadbalk field, with records since 1844. 3. Wheat alternating with fallow on Hoos field, with records since 1851. 4. Barley grown continuously on Hoos field, with records since 1851. 5. Potatoes grown continuously on Hoos field, twenty-six years' records (1876 to 1901). 6. Hay grown continuously on the permanent Park, with records since 1856. 7. Experiments with root crops on Barn field, with records since This mass of valuable data is given in order that one who so desires may study these results from any point of view and draw his own conclusions. Space is also taken for a brief discussion of the summaries of the Rothamsted laboratory investigations, and frequent reference to these data must be made for proof of estab- lished principles. AGDELL FIELD ROTATION CROPS * The Agdell field includes two series of six plots each. On one series a four-year rotation is practiced, as follows : First year .... Swede turnips (rutabagas). Second year .... barley. Third year .... clover (or beans). Fourth year .... wheat. 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B | i: H Z ~ •Y. H 10 ON co r-» vo IO iovO vO oo oo oo oo oo 0 N M 0 (N 8 M 10 ON "5 t^ l^. t^-OO oo oo oo oo X, t>. "JC 00 0 S -o O H -C M lo ON ON ON ON 00 00 00 fO & H £ l-~ 8- M O N T3 CO THE ROTHAMSTED EXPERIMENTS 353 The cropping of the other series is the same, except that fallow cultivation is practiced instead of growing clover or beans the third year. In the tabular statements the one is termed the " legume " system, and the second the " fallow " system. Crosswise, Agdell field is divided into three sections of four plots each. One section is unfertilized, the second or middle section received a phosphorus fertilizer for the first nine rotations (36 years) and a mixed mineral fertilizer, including phosphorus, po- tassium, magnesium, and sodium, during the last six rotations (24 years), while the third section of four plots has received both the mixed minerals and nitrogen during the entire sixty ye'ars. The fertilizers are all applied for the turnip crop, that is, only once every four years. In each of the three sections two plots (one legume and one fal- low) have had the turnip crops all removed (leaves and roots) ; while the other two plots (one legume and one fallow) have had the turnips all fed off by sheep, all other crops having been removed from all plots as regularly harvested. In 1904 the plan was adopted of removing the turnips from all of the plots, thus simplifying the experiments as shown in the tables. In 1850, only, clover was grown on the entire field, including the series since in fallow every four years. The twelve individual plots were each one fifth acre in size and nearly square; so that, as conducted since 1904 (or evidently since 1901), the six individual plots are each two fifths acre in size and about twice as long as wide. In 1848 Norfolk white turnips were grown on the " legume " series and Swede turnips on the " fallow " series. The exact yields are recorded in Tables 52 and 53; but in computing the average yields for the first twenty years (5 rotations) the 1848 yields from the fallow series were used for both series, as otherwise the averages would not be comparable. The clover was regularly cut twice during the season (three times in 1874). Undoubtedly the frequent failure of the clover1 crop has to a considerable extent foeen caused by clover "sickness." 1 For many years the best farmers of England and Continental Europe have practiced the substitution of some other legume, as beans, yellow trefoil, etc., in alternate rotations, thus seeding clover on the same land only once in about eight years. 354 INVESTIGATION BY CULTURE EXPERIMENTS The fertilizers applied per acre every four years (for the turnip crop only) have been about as follows, where used: (a) FERTILIZERS FOR AGDELL FIELD, POUNDS PER ACRE, 1892 AND PREVIOUSLY ELEMENTS AND MATERIALS UNFERTILIZED MINERALS (Phosphate only MINERALS AND previous to 1884) Nitrogen .... None None 140 Phosphorus None 28 45 Potassium None 125 147 Ammonium sulfate . . None None IOO Ammonium chlorid . . None None IOO Rape cake None None 2000 Acid phosphate .... None 350 35° Potassium sulfate . . . None 300 300 Magnesium sulfate . . None IOO IOO Sodium sulfate .... None 200 2OO (b) FERTILIZERS FOR AGDELL FIELD, POUNDS PER ACRE, 1896 AND SINCE Nitrogen None None 1 4O Phosphorus None 40 57 Potassium None 2IO 232 Ammonium sulfate . . None None IOO Ammonium chlorid . . None None IOO Rape cake None None 20OO Acid phosphate .... None 500 500 Potassium sulfate . . . None 500 500 Magnesium sulfate . . None 200 2OO Sodium sulfate .... None • IOO IOO Exceptions to these tabular statements are as follows: In 1848, about 40 pounds of nitrogen, 20 pounds of phosphorus, and 60 pounds of potassium were applied, with no magnesium or sodium salts. In 1852, about 30 pounds of phosphorus and only 100 pounds of sodium sulfate were applied, otherwise the applications for 1852 were the same as shown in table, except as explained below. In 1884, the applications of alkali minerals were made for the first time to the middle section and for that year were double the THE ROTHAMSTED EXPERIMENTS 355 regular amounts; that is, 600 pounds of potassium sulfate, 200 pounds of magnesium sulfate, and 400 pounds of sodium sulfate. In 1896 and in 1900, 600 pounds of basic slag phosphate were applied instead of 500 pounds of acid phosphate. The sixty years' data from Agdell field are exceedingly valuable in the study of many important soil fertility problems. No ex- haustive discussion can be given here, but these results will be referred to for many years at least as the greatest source of informa- tion concerning the effect of long-continued crop rotation. A few of the plainly indicated conclusions may be noted. (1) On the unfertilized land the rotation of crops does not main- tain the fertility of the soil, the yields of every crop having de- creased with the possible exception of beans. The yield of Swede turnips dropped from about 10 tons per acre in 1848 to less than 2 tons in 1852, and never equaled 3 tons per acre afterward. That is to say, the turnips have always been grown at a loss since the first year, the best yields being scarcely worth harvesting. The barley yields have decreased from more than 40 bushels, 1849, to 15 bushels as an average of the last 20 years, but the decrease has been very gradual. The yield of legumes has been very irregu- lar, but, with the exception of the beans in 1898, has markedly decreased, the clover from 2.8 tons in 1850 to less than one half ton per acre as an average of the crops grown during the third 2o-year period. The yield of wheat has been greatly influenced by several condi- tions, but during the sixty years has decreased as an average by 8 bushels in the legume system and by 16.5 bushels in the fallow system, if we assume that the difference between the averages for the first 20 years and the last 20 years represents the decrease of 40 years. The lowest average yield is for the second 20 years, but this period includes the abnormally low yields of 1879 (when the best fertilized plots averaged only 13.5 bushels) and two other rather poor years. It should be kept in mind, too, that the wheat crop comes in the next year after legumes or fallow, and thus has the most favored place in the rotation. (2) The application of mineral plant food has as an average main- tained the yields of legumes and of the following wheat crops. 356 INVESTIGATION BY CULTURE EXPERIMENTS Even the yield of turnips has been fairly good and practically maintained since 1852 in the legume system, but it should be noted that the yield of Swede turnips fell off nearly 10 tons from 1848 to 1852 (see fallow series only for Swedes in 1848). In case of the barley the influence of the legumes grown three years before is less apparent, and the barley yields have decreased during the sixty years by 22 bushels in the legume system and by 31 bushels in the fallow system, if we consider that the averages for the first and third 2o-year periods are 40 years apart. (3) Where both minerals and nitrogen have been applied (al- ways to the turnip crop only), the yield of turnips has been appre- ciably increased; and, if allowance be made for the failure of 1868, the increase has been somewhat regular; while the barley crop, which follows the turnips, has apparently suffered approximately in proportion to the increasing drafts upon the soil by the turnips, and with as near approach to regularity. The fact that this marked decrease in yield appears in the barley straw as well as in the grain clearly indicates that the abundant supplies of minerals applied and liberated from the soil make it possible for the enormous turnip crop to appropriate so much of the available nitrogen supply that the quick-growing spring barley is limited in yield by lack of nitrogen. In the case of the legumes the average yields have dis- tinctly decreased where commercial nitrogen has been supplied. This raises the question whether the larger crops of turnips and barley where nitrogen was supplied have not removed such large amounts of the mineral elements that the yield of the legumes (which have power to balance their own nitrogen ration) is thereby limited. In this connection it may be noted that, as an average, the yields of both clover and beans have been better where the full minerals alone are applied (middle section since 1884) than where nitrogen also has been added. The yield of wheat following the legumes has been well maintained, not only where both minerals and nitrogen are applied, but also where minerals alone are used. (4) On the unfertilized land the fallow system has given better average yields of turnips, of barley, and of wheat than the legume system, throughout the entire sixty years, except for the wheat in the last twenty. The fallow system also gave better results THE ROTHAMSTED EXPERIMENTS 357 on the phosphorus plots with wheat and turnips, and practically the same yields of barley, as the legume system, clearly indicating that where the soil contains a fair supply of nitrogen in proportion to its phosphorus content the legume crops add little if any nitro- gen to the soil in excess of what they take from the soil, when the regular legume crops are all removed. Ultimately, however, with the continued reduction of the absolute or relative supply of nitro- gen, in comparison with other essential elements, a point is reached below which the legumes leave in the roots and stubble more nitro- gen than they have taken from the soil. In soils practically devoid of available nitrogen only legumes can be grown, and their total content of nitrogen must, of course, be taken from the air. It is evident that nitrogen has become so depleted in the unfer- tilized land that the legume residues are now furnishing the wheat crop with some nitrogen taken from the air, but this effect does not extend to the turnips or barley crop. On the other hand, where an abundant supply of minerals makes possible the production of large crops of legumes, the atmospheric nitrogen stored in the legume crop residues (or possibly gathered subsequently as sug- gested elsewhere) not only maintains the yield of wheat but mark- edly affects both the turnips and the barley, although the yield of barley is steadily decreasing. As a general average on unfertilized land the wheat after clover or beans has yielded about 10 per cent less than after fallow; but the clover residues have increased the yield of wheat by 18 per cent on the mineral plots and by 13 per cent on the plots receiving minerals and nitrogen, compared with the fallow system; whereas the wheat yields after beans have averaged less than after fallow on all plots. These results are in accord with the data already given, showing that the roots and stubble of annual legumes, such as cowpeas and soy beans, contain much less nitrogen and organic matter than the roots and residues of red clover, alfalfa, and sweet clover. (5) The fallow system is unquestionably very exhaustive of the soil's supply of nitrogen. During the first twenty years the fallow system produced as an average larger crops than the legume system, but the decrease in yield under the fallow system has in most cases been more marked than under the legume system. 358 INVESTIGATION BY CULTURE EXPERIMENTS This is especially noticeable on the mineral section, where best provision is made for rapidly exhausting the' nitrogen by removing other limits to crop production. With barley under the fallow system the yield for the last twenty years averages no more where minerals are supplied than where no fertilizer is used, thus indi- cating the same nitrogen limit for that crop, and emphasizing the fact that no amount of phosphorus or other elements can increase the yield of crops where nitrogen has become the limiting element. In the case of wheat, the yield is still greater where the minerals are supplied, because wheat is the first crop grown after the year of fallow cultivation, the principal effect of which is to liberate nitrogen from the residue still contained in the soil humus; and whatever weeds are allowed to grow, during the fallow year or other years, will help to save soluble nitrogen from loss in drainage water; and if the volun- teer herbage includes any legume plants, some atmospheric nitrogen would thus be added. Of course if any growth of this character were larger on the mineral plots than on the unfertilized land, the effect would be greatest on those plots in the increased growth of the wheat, turnips, and barley. It is pointed out by Dyer (Results of Investigations on the Roth- amsted Soils, Bulletin 106 of the Office of Experiment Stations, United States Department of Agriculture) that where barley is grown every year on Hoos field the most common weed on the plot receiving minerals without nitrogen is yellow trefoil, which grows even while the barley crop is supposed to occupy the land; and that Sir Henry Gilbert had expressed the opinion that very appreciable quantities of nitrogen were added to the soil by that leguminous plant, which grows persistently as a weed on that plot despite the efforts to eradicate it. Since the above was written, Director Hall, of Rothamsted, has kindly furnished the specific information that the fallow portion of Agdell field is kept plowed, and is therefore practically free from weeds during that year; but when wheat is grown, " there is a good deal of wild yellow trefoil, particularly in certain seasons, and on the plots receiving mineral manures only." He states that this trefoil was so abundant in 1907 that after the wheat harvest he had it cut and weighed separately, and found that the amounts per acre (including, presumably, the wheat stubble etc.) were THE ROTHAMSTED EXPERIMENTS 359 1330 pounds on the unfertilized land, 2633 pounds where minerals alone are used, and 718 where both minerals and nitrogen are applied. These figures relate only to the fallow plots. On the legume plots there was very much less trefoil. Director Hall states that the amounts that grew on the fallow plots in 1907 are rather exceptional, but that in every crop of wheat or barley there is some of this wild legume, " which must have some influence upon the nitrogen content of the soil." (6) The effect of feeding off the turnips by pasturing with sheep is a distinct benefit to succeeding crops wherever the yield of tur- nips amounts to much. This effect is most marked, of course, on the mineral plots, where nitrogen is very deficient, and it is also most marked on the barley crop, which follows immediately after the turnips, although the influence can usually be seen on the legumes and wheat, and even on the following turnip crop. Before leaving Agdell field we may well try to view these results from the financial standpoint, particularly during the last twenty years, because the world affords no other data from crop-rotation experiments in which can be studied 2o-year averages secured after a preliminary period of forty years. (See also page 419.) In Table 59 the turnips are valued at $1.40 per ton, the clover hay at $6 per ton, the barley at 50 cents a bushel, the beans at $1.25 a bushel, and the wheat at 70 cents a bushel. At these prices, the turnips and beans were more valuable per acre than the wheat. Nitrogen is figured at 15 cents a pound, phosphorus at 12 cents, and potassium at 6 cents; and it is assumed that the magnesium and sodium salts cost the same as the extra salts in kainit at $15 a ton. These various prices may be modified and the results re- calculated to fit different local conditions. No values are allowed for the straw of barley, beans, or wheat, or for turnip leaves; but in computing the value of increases it is assumed the increase in these by-products would be worth as much as the extra cost of harvesting, threshing, etc. At the prices used in Table 59, the use of minerals in the legume system has more than doubled the value of the crops produced during the last 20 years, the average of which really represents the condition just fifty years from the beginning, in 1848. While the effect upon turnips is to change a practical failure into a crop which almost pays for the minerals the first year, the residual effect upon the other crops is to nearly double their total value. TABLE 59. ROTATION CROPS ON AGDELL FIELD, ROTHAMSTED Average per Acre of Third 2o-year Period, 1888 to 1907 Son. TREATMENT UNFERTILIZED MINERALS MINERALS AND NITROGEN System Legume Fallow Legume Fallow Legume Fallow Swede turnips, pounds . Barley, bushels . . . Clover hay (3), pounds Beans (2), bushels . . Wheat, bushels . . . 967 13-7 770 16.0 24-3 2502 15-9 25275 22.2 3895 28.3 38.4 20629 15-9 4I731 29.2 3479 19.6 36-4 46523 24.1 23-5 28.0 32.1 Swede turnips, value Barley, value .... Clover, value (f) . . . Beans, value (I) . . . Wheat, value .... Value in four years . . $ .68 6.85 i-39 8.00 17.01 $ i-75 7-95 $I7-69 II. IO 7-OI I4-I5 26.88 $14.44 7-95 $29.21 14.60 6.26 9.80 25.48 $32.57 12.05 16.45 19.60 22-47 S33-83 $26.15 $76-83 $41.99 $35.35 $67.09 Value of increase $43-00 17.88 $15.84 17.88 $5i-52 42.24 $40.94 42.24 Cost of treatment Profit or loss ( — ) $25.12 -$2.04 $9.28 -$1-30 In this system the minerals have paid for themselves and made a net profit of 140 per cent on the investment. They have also fully maintained the average yield of legumes, wheat, and turnips since 1852, but the system fails to maintain the supply of nitrogen, and because of this the barley has markedly de- creased in yield. One may assume with reasonable confidence that if the turnip leaves, the wheat and barley straw, the bean straw, and perhaps part of the clover crop, had been returned to this land to furnish nitrogen and decaying organic matter, the barley yields might also have been maintained and the turnip crops kept equal to that of 1848, thus providing a permanent system; whereas, under the system practiced, it seems certain that the yield of turnips must decrease in time; and in the opinion of the author the nitrogen supplied by the legume residues will ultimately be insufficient to THE ROTHAMSTED EXPERIMENTS ' 361 maintain the yield of wheat, unless the azotobacter or some other nitrogen-fixing agency is more efficient than our present knowl- edge indicates; or unless the leguminous weeds are allowed to grow in sufficient quantity to furnish and maintain the nitrogen balance. The application of commercial nitrogen does not solve the prob- lem for present conditions of general farming in the United States, because at reasonable average prices the addition of $21 of nitro- gen has increased the average crop values by only $8.52 under the only profitable system, notwithstanding the additional phosphorus and potassium also supplied in the rape cake. As would be ex- pected, the applied nitrogen produced a more marked effect in the fallow system, which is so very exhaustive of the soil nitrogen; and in this case the minerals and nitrogen produced slightly less loss than the minerals alone; so that, if produce from the mineral plots could be figured at prices which would show some profit, it would then be profitable to add the ammonium salts and rape cake. The question remains whether a liberal supply of decaying or- ganic matter in connection with the phosphorus fertilizer would not have rendered the use of potassium sulfate and other salts unnecessary or unprofitable, especially since much of the potassium removed in crops would be returned in the straw and leaves. Since there has been a recent change on Agdell field, by which the practice of pasturing off the turnips has been discontinued, Director Hall is considering the plan of applying to the " fed " plots, in addition to the regular fertilizers, amounts of farm manure equivalent to the root crops, straw, and clover hay pro- duced on those respective plots, because that would more closely agree with ordinary farming practice in England. In passing from the Agdell rotation field to the continuous wheat-growing on Broadbalk field, attention is called to the fact that as an average of the third 2o-year period the unfertilized plot 3 on Broadbalk produced 12.2 bushels of wheat per acre (see Table 62), which at 70 cents a bushel would be worth $34.16 in four years; whereas the average value of the rotation crops produced on unfertilized land during four years (as an average of the third 2o-year period on Agdell field) was only $33.83 in the 362 INVESTIGATION BY CULTURE EXPERIMENTS legume system, and $26.15 in the fallow system, at the prices used in Table 59. (See also comparative statement of prices on page 359.) 17.58 TURNIP CROP OF 1908 ON AGDELL FIELD, ROTHAMSTED; 6isx CROP IN 4-YEAR ROTATION; TONS PER ACRE Unfertilized Mineral plant food Minerals and nitrogen Counting from the left, lots 1,3, and 5 were grown on land where the rotation is turnips, barley, clover, and wheat, while lots 2, 4, and 6 were grown on land where the rotation is turnips, barley, fallow, and wheat. The six lots were all produced on plots of ground of equal size. Plots i and 2 have received no fertilizer. Plots 3 and 4 received only a phosphorus fertilizer for the 36 years, 1848 to 1883, but since that time they have received mixed minerals, including phosphorus, potassium, magnesium, and sodium. (The average yield of turnips in 1880 was i% tons for plots i and 2, and the average yield of plots 3 and 4 for the same year was 1 2% tons per acre.) Plots 5 and 6 have re- ceived mixed minerals and nitrogen since 1848. These are the rotation experiments referred to by Professor Whitney on page 22 of U. S. Farmers' Bulletin 257, as follows: "In other experiments of Lawes and Gilbert they have maintained for fifty years a yield of about 30 bushels of wheat continuously on the same soil where a complete fertilizer has been used. They have seen their yield go down where wheat followed wheat without fertilizers for fifty years in succession from 30 bushels to 12 bushels, which is what they are now getting annually from their unfertilized wheat plot. With a rotation of crops without fertilizers they have also maintained their yield for fifty years at 30 bushels, so that the effect of rota- tion has in such case been identical with that of fertilization." In commenting upon these statements, Director A. D. Hall, of the Rothamsted Experiment Station, says: "I cannot agree with Professor Whitney's reading of the results on the Agdell field in the least. The figures he quotes for wheat are hardly justifiable as approximations, and are in spirit contrary to the general tenor of the par- ticular experiment. In my opinion the results on the Adgell rotation field are directly contrary to Professor Whitney's idea that rotation can do the work of fertilizers." (See Report of the Committee of Seven, including Woll of Wiscon- sin, Van Slyke of New York, Lipman of New Jersey, Davidson of Virginia, THE ROTHAMSTED EXPERIMENTS 363 Ross of Alabama, Peter of Kentucky, and Penny of Pennsylvania, appointed by the Association of Official Agricultural Chemists, "to consider in detail the questions raised"; published in full in Circular 123 of the University of Illinois Agricultural Experiment Station.) BROADBALK FIELD Undoubtedly Broadbalk is the best-known experiment field in the world, and plots 2 and 3 are the most often referred to. While the continuous growing of wheat on the same land is not to be considered the best practice, the records given in Table 60 show very clearly that it is possible. These plots are compared with most of the others for a period of 55 years. Perhaps the most interesting and instructive results are the average yields of 12.9 bushels on the unfertilized land, 35.5 bushels with farm manure, and 37.1 bushels with the heaviest applications of commercial plant food. Plots 5, 6, 7, and 8 differ only in the amount of nitrogen applied; and, with successive additions of 43 pounds of nitrogen per acre, the average yields increase from 14.9 bushels with no nitrogen applied, to 23.8 bushels with 43 pounds of nitrogen, to 32.8 bushels with 86 pounds of nitrogen, and to 37.1 bushels with 129 pounds of nitrogen. The average yield of 55 crops is only 2 bushels more per acre where 792 pounds of mixed mineral fertilizers have been applied every year than where no fertilizer of any kind has been used. These data are in striking contrast with the results from Agdell field, where, as an average of the last 20 years, the increase with minerals alone is 83 per cent of the total increase with min- erals and nitrogen, while on Broadbalk the minerals alone have produced an average increase which is only 8 per cent of the in- crease from minerals and nitrogen (plot 8). With the fallow system on Agdell field the results are tending in the same direction as those from Broadbalk, and most markedly, of course, where all crops were removed. This must emphasize a fact which it is exceedingly important to keep in mind while studying the results from Broadbalk field; and indeed, when studying the data from not only the Rothamsted fields but from nearly all of the oldest soil experiment fields in 364 INVESTIGATION BY CULTURE EXPERIMENTS fc 3 o pq 00 0 •* 01 o PO to i» 00 O ON O " PO " 00 PI Pi bo^o "^ -2 PI PI PO ro Ol ro ro >-> ro PI a _o S S S o r~ 1^ n IO ONO t^ n O « O t^O M t- ON O O n-sS 3 a_o -g H » PO Os PO M PO PO • a PI TJ- PI '„- O P* to M t-«- PO * PO O 00 ii3 ^H tn £ 3 S "> C 0 H o § t^o =6 J| -. C, rotolo'il o o O- . «-» 1- to tooo _, 5 "o 13 SP *& c ... Ot « P "S "S PO30 PI ^- PI 00 ? f«rf ?°°. nio PO Tj- .2 oo «g g .ti >> "2 « 3 o .2 rt r PI so 0 0 PO t^- PI 10 j O O 00 M Tj- 1 1 X H Oi oo PI PO -H •* PO POOO M PI PO ro 00 O I-- M t-. « 01 01 ro PI 1 1 S -5 o 2 • o P* rt O C 42 «* r 01 « too ro O to ON i ON O ON IO Tf HI 1 < "> » HOC ro ro PO IH to •* 01 to M Pi ro PO — O O ^ — 1 1 ° g g^ °^ M PI NO «•. o o 10 ON OsOO OO M 1 rj- to to roo t^ M- •* £ ^ « 0 p 30 H Oi PO M M 01 ro ro PI PI PI PO PI 0 PO i?ro 0 &1 o £-§ § r N SO w O IO i-t IOOO 0 TJ- to ^ TCO to ro 0 r- 0 M S M ™ "^ <"£ §H 21 10 0 •* ro PI 00 M PI PO PO X t— 00 10 M -0 i/~ Tf IO f^O O M ro M 01 00 "ti ^- ro O ^ < 25 X) H 5i T)- ro M 00 w 01 PO ro CJ 00 ONO ON IO M M 01. 01 PI t^ PI PI PO to CNO a, 3 'J K o •— > o « » HM il oo to O •* ro •* tooo M PI ro ro ^" t*-. »-l IO M ON PI O PI »- M PI ro PO ro 01 00 10 «."o I? t^u .2 O w _ 4J i-j r PI M «~- •* M W ON OI PO t~- M 00 ^t o 'S O jj M o poi 00 O PI ONO w M M PI PO (•-• M IOO O W 01 PI PI 01 ^42 ^^a, PI H to to IO l~" ON to >H ON POOO *t N N N 03 "ON. OT 2 SO H°0 PO t-« M 01 ro T)- PI PI PO ro ro to 00 O 'o N 3 1) *4-1 . n « PI O Tf CS! t^ M OI ^t Tf CN to 43 S3 "B S <2* 2°f Tt 10 OO t^ TfO M PI ro ro POOO PO PI ro PI PI PO PO PO $"£ 1st u 1 i 01 i | 1 N 3 IM w 4, ^ PO"^ * 6 n N < « li sU o PI PI 01 01 ON CN ON C- «~» ON w ro 0 c O PI 't PI PI PI PI M ro 01 O ON O •^d S"'S . ° ^ U~ ^, C 3 W) ^1 Ml C^g S TfOO PI c 5 oo oo oo oo oo O O oo oo O O PO OO 00 ON Sc-5 >"> 5 o «3 i> -r ~ S "H 5; u S . ^,0 < JC CU -y •SI . 1 |f: 3 2 rt co to cfl •^•o -^ ti o x-^ "D "3 c '"' 'S ri o C oo SOIL TREATMENT EVERY Y (Except on Plots 17 and 18, receive Keverse ireatment on nate Years) Farm manure (15.7 tons) Unfertilized .... Minerals (P, K, Mg, Ca, S Amm. salts and minerals Amm. salts and minerals . Amm. salts and minerals . Nitrate and minerals . . • 43 .- .- ^ @* tn (ft * 9 .$9 CD 09 n C. to t/) tft tfi I e a s s Amm. salts in fall, and mil Nitrate and minerals Minerals 1 (after amm. salt. Amm. salts l (after mineral Rape cake (1889 pounds) . )TES. The "minerals" i n sulfate, and too Ib. of s jsium, and 14 Ib. of sodiu >ts 12, 13, and 14 receive, i 95 per cent pure), and 28 monium sulfate and amm 2 Ib. of potassium, pplied in alternate years. S 01 PO too t^oo 9 O " PI PO T)- too 00 OO V M 2s K||SJSi^ ft' £s 2^§ THE ROTHAMSTED EXPERIMENTS 365 w a H 0 a 3 W £ ! NO CM O NO O 00 to O 00 CM (-- 0 rj- CO O >O t^ 00 O CM 1 *^ « * N. 0 "I NOTE. Average yields of straw for the eight years, 1844 to 1851, were 2979 Ib. from plot 2, also 1736 Ib. from plot 3, and 2654 Ib. from plot 10. 1 Applied in alternate years. * This is three fourths of actual yield on half plots after fallow. CM M CO ON HI CM tO Tj- £ HI CM CM tO CM GO O HI CM HI tO o o. ON 00 ro ON to O NO H M f^ O ON ON HI to HI NO to CM O M tovo 00 V) M l/~ t^NQ NO OO to O to "^- HI to to T}- IONO to to 00 Tj- 10 IO J^ NO CM CM IONO O Tt ON Tj- NO o M \f to oo TT O CM ON T)- O T)- CM O 0 ON CM ON CM HI LOCO ON fO M 00 ONNO O OO HI H CM Tt CM CM CM tO HI O to CM CO IO Tj-00 to I NO 'to Tj- IO 1O l-l tooO O NO to r^. to Tt* r^. CM CM r^ CNl Tj- to 10 •o OO CM O to Hi to HI HI ON to CM CO Tt" Tj- tO t ON O H t^. CM T}- IO IO O M tO HI t^- O O co ro rf to 1 IO CM NO t"-* tO NO t^ TJ- to M HI N to 0 M ONNO O NO OO 00 CM Tj- T)- to to ON CM ON ON w H CM CM HI CO O CM CO •* rooo ON CM HI 10 ON (O CM CM I 'O -t O ON ON to M ON CM OO OO T> OO O HI t^. CM to TJ- -c' ?> OO to O ONOO 00 O t^ ^ CM CM 00 r- ON HI HI w HI CM CM ON NO •* M ON rt- Hl tO HI tO t^- r^ ON o to CM to to CM AVERAGES - N NO 10 ll 00 o O «>C 00 — Ov »^ M M Tf CM HI ON M CM Tf CO Tf CM GO CM CM tONO t-- M CM fO Tj- to to tONO HI t^ CM 00 Tj-00 HI CM CM tO CM o ^ ui o oo 0 •* CO HI 00 Tt HI M t^ ON M ON O '2*Jti2 r— CM ON O ON ON O to HI CM «*• Tj- too O to O Tj- IO CO tO CM r- H GO OO ON CM to to CO to ° z « w^-> gop- — ; — ; 3 Amm. salts m fall, and minerals Nitrate and minerals . Minerals1 (afteramm. salts) . Amm. salts l (after minerals) Rape cake (1889 pounds) Farm manure (15.7 tons) Unfertilized . . . . . CJ u D II.4 9.2 J3-7 12.4 32.0 29.8 34-i 30.1 13-3 II. I 1871, '75, '79, '83 19.9 20.5 25-8 (Note Changes) Minerals Minerals and 86 Ib. N iQQ, TSr>i-i 12-5 12.7 10.4 8.4 15-9 18.4 14.0 14.2 39-6 42.4 35-3 3*-7 37-8 38.4 39-4 35-3 34-9 38.0 32-7 30.8 1887/91/95, '99 1900-1907 1903-1907 . 28.9 27.2 4°-5 I8.3 20. 2 32-9 1844-1875 . 1876-1907 14.8 "•5 21.4 14.7 30.2 24-5 28.1 23.6 29-3 34-8 33-4 35-8 37-5 36.8 1844-1907 J3-1 17-5 27.2 25-7 32.2 34-6 37-i 1 Average of 15 crops. 2 Average of 13 crops (1852-1864). 3 Average of 3 crops (1855, '59, '63). In Table 64, the average wheat yields from the plots indicated are grouped in two ways. First are given the averages of all years for those plots or twin plots (on Hoos field) which furnish a con- tinuous record ; and, second, the averages are given only for those years when wheat was grown on Agdell field. There are a preliminary and a final period of 8 years each, and three 1 6-year periods intervening. These figures show that the middle i6-year period (1868-1883) gives averages clearly below the normal, and that the average of the four years within that period are still lower, thus proving that even two 1 6-year periods may not positively establish by crop yields whether land is growing better or poorer. A comparison of the first and second 1 6-year periods indicates that all plots are growing poorer; while a com- parison of the second and third 1 6-year periods indicates that all plots are growing better. In the lower part of Table 64 are recorded the average yields for all wheat crops grown in two 32-year periods, and these figures are the best that can be secured. They show decreases of 6.7 bushels with the wheat and fallow plot (Hoos field), 5.7 bushels with the fallow system, and 4.5 bushels with the legume system, on Agdell field, and 3.3 bushels decrease with unfertilized continuous wheat, which, however, is a greater percentage decrease than on either of the Agdell plots. It should be kept in mind, however, that wheat is the only profitable crop now grown on the unfertilized Agdell plots. The yields increased slightly on the farm manure plot and very considerably where minerals and legumes were used on Agdell field. Finally, in the last line, are recorded the general average of all wheat crops grown on these plots since the experiments were be- gun, with extremes differing by 24 bushels, a difference which in 64 years amounts to 1500 bushels more wheat from the applica- tion of plant food than could be obtained without it, in the same system of cropping. Table 65 gives, in brief, some of the very interesting and valuable weather records of Rothamsted, and for comparison is given the very trustworthy average rainfall records for northern, central, and southern Illinois, and Tennessee, as representing a wide range of latitude in central United States, with the average precipitation (including snow measured as water) varying from 33.48 inches in northern Illinois to 53.69 in Tennessee. (See also map showing average annual precipitation in the various parts of the United States.) The 5 OO OO PI co co PI O 8COOO O OO O Pi O I-- « 0. M PI M CO H X o M 00 •* 10 vO «"> «O O O vo o' O 8M H Tj- Ooo co ^ c 8> ro M H M CO « 0 H 1 « t^ ro ^ "^ t^ M ir> VO l~~X « PI O co ro O T}- Pi vo O t^ co t^ O 1^ 1O c 1 0, M M Pi H M Q « 11 TJ- ro O M CO W M O 1^- ir. i/-, PI vox) •* •<*• co OOO 00 O t- O O« I/I o> M M M Tf.H M vo M M «*> M Ell. - ' t IT2 t^ N t^ O vr> O vo vo vo O Pi vo\O t~-*O CO rj-00 VO OO 00 M M t»J t^ 9 8ilM N M M M PI PI * IH I -§6«-i? C4 t^ C<^ Qs ff) OOO 00 M vo <^O r^ M CO t^>\O PI O O PI VO PI OO vo $ w £g > Ml>g £< rt^2 - N M M M PI Pi P) PI PI fO PI PI CC « H ft 2 00 Tj- O 00 VO ff) •& « O r^ co M 00 vO •<*• O O O PI t~- vo PI 00 O H CO < 0- W M CO CO H H P» PO M PI PI LO C1 r^ VOOO M V) d rj- rooO O M M 0 •*vO PI 00 00 O •* O t^OO tf CO •* o H H M « PI PI PI M •* PI co t^ « V 1 ^8 O CO CO O O covO t~- CO M p| rj- coo ^r PI 10 O PI O 1-1 CO PI t^- in Ov J Ov Tj- M M M CO M M VO Tj- PI 00 0) 1 10 r}- 10 t^ PI CO Ov vo PI CO vo t^-O H O •* •* VO t-~ CO O N O PI H -t <* .H i M CO PI M Tf H ro PI HI PO tH 0 M TtO t^ CO vo O **• vo Pi Pi OO PI M O O ; VOOO VO O O 00 O co O en *£2 PI M CO H PI vO •* co 0 c M M M M M w> &5 8 vo PI PI vo O \O •* P» PI O O 00 PI O O co O OO co "*• O O O 00 o Q£<2 PI CO M M CO PI 00 PI CO PI M •* M vo Osoo t^ co t-« t^-oo PI PI vo '3- Pl CO vr,\O M O 00 W VO M VO CO 01 O "£< S1* s PI M H H P4 PI M PI PI CO PI PI OO C) g« •5 "is S HI to PI O M VO M VO t^ M -tO O f>. M O OO O «^ O O O O PI ON O H PI PI CO CO 't rf co PI co PI PI PI tN. "> I13! VO PI PI CO oo oo ^f vo O O r^oo O PI ro vo TJ- vo t^ O t^ PI vooO o> M g 'S 00,0, PI PI Tj- CO rf rf co PI PI Pi co P« M * 3 •5 o'rt'S t^-oo 't r^ PI Pi O ro O Pi co O PI PI vr,O t-- Tf O •* PI O OO PI M 0 f2 £*£ PI PI CO CO •*•<*• CO PI co PI PI PI Tj ff> tea t^ rj- Pi w O* Ov t^ vo vo VO t^ t^ O 00 O O M •>*• co M PI O PI 00 * 0^ H M PI PI «j- CO co'PI CO PI PI H ro CO Bj >^ . '- <->!-, n Kit 1 fll = Alsl iii! J3 >_ J2 J3 !l|l #8 la J9 rt S en § 'S rt 3 E S2 c TJ 2" O u o e O 1 60 rt O J3 >? C O "9 J2 c§ N u h .-a . •£ rt |.s« 1 1 rt ^ °° is o M •s oo X "^ (^00 nj ««-i ri^ JG v^ (J rt •* •s^i 1) O & °° c *J CO JJ po.E ca LO *4H II o E P s 1 ^ s o. o3 ^ ^ o1^ "* i-c in tn . rt M 'S •~ o * CO 3 43 «S I, o B lit o ^ & o .£ w o s r. s g£ O M l& I- — r**» in O C co \*£ £ S ir different poi : ; minimum, 2 0 Q ^ C M 00 •- < •- O %s^ fj? l|s •£ z « ^ f- «2 ^ >\ co I§! .2 tf ll.§ tn 6C *J C S 2 i sj « r< '§ J3 O C -w 4) <*H Oj u •- J3 S ±> w; t; 2 S ti vo •" rt ^^ ^^ NS 4J >> r^ w • fe > O ^ "tr OO *T"! *-^ »* « « M 5T *^ V wj t/j O c '* -. oo . <« vo "5 °o o M .. O M O fj _, OO (U U. c rt »-" O & « K a •2 .^ co*" •H rt O — _g C 0 rt 8'a tn (j "° ^ ^S J3 "" •*-» *"! p£3 t^ H-E " 8 if t1 ^ s a S 378 INVESTIGATION BY CULTURE EXPERIMENTS annual rainfall at Rothamsted, and of this amount 50 per cent passes off in drains, at a depth of 40 inches, and 50 per cent is evaporated, from a soil kept free of vegetation. Roughly, the evaporation from a bare soil may be regarded as a constant, to be subtracted from the rainfall to find the drainage (and run-off, if any). Thus, if we regard 14.25 inches as the constant for evaporation at Rothamsted, the drainage should be 6.24 inches for 1898 and 24.44 inches for 1903, while the actual records show 7.90 and 23.59 inches, respec- tively. Of course the evaporation can be markedly reduced by culti- vating the surface as soon as practicable after each rain, in order to destroy the capillary connection and to maintain a dust mulch, and thus largely preventing the rise of moisture to the surface. On the other hand, evaporation is greatly increased by growing crops, so that during the growing season the drainage would be less on the ordinary field than from the bare soil.1 BARLEY EVERY YEAR ON Hoos FIELD, ROTHAMSTED Table 66 presents in summarized form the data secured from Hoos field, where barley has been grown every year since 1852. These experiments help to answer some important questions con- cerning which neither Agdell nor Broadbalk give any information. The yields, as an average of 55 years, vary from 14.8 bushels on the unfertilized land, and 15.7 bushels where only the sulfates of potassium, magnesium, and sodium were used, to 43.9 bushels with sodium nitrate and acid phosphate, and 47.7 bushels with farm manure (15.7 tons a year). As an average of the 3 •" « o b^ W ^ x ^ W M M < pq oo ft CC f^ 11 mo t w ro in r^ PI r~- t PI M r^O ro M PI Om (A 21 *"" 2" °* H? HI PI pi ro PI ro PI ro rSroJ?t PI m M T*"° 2 H? r. «-~ o « « O t HI t- tO O « t~- HI oO ro « m HI PI in i**o oo 1 t— rood <*3 OOO O PI M PI PI ro S ?« Jo OOO O M PI PI PI ro m PI M t PI 00 O I^ M S> O t^m M r~ in M M M O O PI O OO 00 O tOO 1^.00 o m t h 1 M 00 t O HI HI HI PI t H. 00 PI 0 0 H, 0 ro >n ro t ttSrs. PI m rOO OOO M O m o t^oo ro« o>n ro O ro PI O m ro PI M t 00 00 O 00 O 0 a Ov M HI HI PI M ro HI ro H ro pTp,?^ HI ro ^H, 2 > t— O «*• PI in HI \o HI r«^ M t^. I-H HI C ro m o O 0 moo rooO t^ t~- N O' »O m ro O r^ in in ro o M PI M PI PI t PI t PI in PI t fO ^f rO *t Pi O M M PI M M > : fo rot^.00 0 O M 00 00 m ro 00 « CO ^O PI t ro moo PI o 00 HI t^ Q- H HI 00 O O HI ro HI PI OC O 00 w M f> W ro O ro PI t roO O ro HI 01 10 C oo o o N>H °° *^ °* HI o O m O to rooo PI ro Pt ro t O O 00 ro\O C* IO Pi t *2?-S a 0 u^Og 0 0 00 PI rooo tin O 00 O PI M O lO 10 O t moo o a « « „ P, t < - M O 00 Ot-ro O w> t^ O OOON 00 M ^ o^ ! " PI in O t 2"? H?8 "S 3% t ?trOt fO ^ fO "^ t M M M - N *O M NO PI 0 00 0 HI t t 1^ t O IO N ^O H PI in PI o O O ^ o< *^ o* O 00 O 00 0 m O O ro ro PI O PI t PI rO fO fO fO fO N t O ro O O O HI HI PI HI Q ri^^ri, 0 t O M tOO O H! Q 0 JcS o S ^to 9--n- in t^ HI t t toe o to ro t^. PI O r^ ^^ * K4 M M M PI COP! t P. t N t roro-oro PI t HI M HI M H s.£|sa S^4^ ^Hl oo PI o PI PI t PI t q m t o PI PI t d ro in m rooo in 10 PI t ro HI d HI M HI p| < 2;i"l2t m PI M t W Tf O **• 4!£S O r-* pi PI ro in ro t^- in in r~ PI t PI PO t^- in M -« » t ot-m o \o o M t-OO 0 O 00 O t O O PI O PI ro 2>;«2» PI t-. t O PI PI PI ro StS^ ooo oo o t ttt in m HI Pi o ro HI HI + i c ;pSg2 O W O PI O PI O PI PI O O O 0 P< 0 PI co ^f- r>* ^ - c 00 : t 1 X jsMl O O O O ro ro ro ro ?5?5 ???? " T • • • -6 SOIL TREATMENT APPLIED EVERY YEAR Unfertilized Acid phosphate .... Alkali salts (K, MR, Na, S) Minerals (P, K, Mg, Na, S) "rt a c c "* rt rt rt C wi c/) to -3 .— i .— 1 1— t .™ rt rt rt O . . . E E E E E E E £ " ' J2 ' sHi J3 T3 "O "O •- c a c « oj rt rt E £ ^ £ _3 rt rt rt -o . . . if!! 4^-O 13 T3 rt C C C u rt rt rt "to" « 11 in 10 V U 3 3 a c rt rt S E S £ rt cc ?en effect: Ai over Oi . . horus effect: A 2 over Ax horus effect: Ni over Ni m effect: N2 over A2 . . . ual effect of manure : 7-1 ove g 6 oooo HI Pi ro t M N ro t M « PO t uuuu M PI M < H > H H J to O s i £ THE 00 o o> ROTH, Os tovo CO TJ- W O O to to to o H \MSTE r^ \n 381 OO CO to ON co d vO tovo vO to HI d CO Os r^ | d O CO d SO co IO d to O O to M H d O O O vO Os TJ- r^ 10 10 CS t-~CO H M H M so tO M so d 'tOO Tf OsCO to O M C» M CO Tj- OS OS M to HI d d co **• d SO d d d d HI SO \O to O d d Tj- OO O ON to ON d to HI O ON CO VO ONSO d HI « o OsOO VI to CO 1-1 CO to to ONCO d aJ^- M 00 OssO O 10 CO O Os M N N M coco co co OS 'I' f- M OO « M Os M CO N M Os toco O HI SO OS O Tfr 10 TtOO O d d d Tj- CO co so Tf to H CO HI to tO HI tO to O to to ON CO OO POCO so *n & •* O Tj- CO ON tOCO co to to t>. co coco CO so co « \O 00 CO M IO If M (X M N M O CO O O Os lOsO sO CO sO J^ H M HI M IO d O to HI OO COCO Os ON CO to M M d d co to %2 CO ON lOCO d ON CO ONOO-O so to to d to CO HI ? o. M d Ti- ON to Tt-oo d CO O toco M ^•00 sO CO c< O O d to IO HJ H TJ- r^ 10 t^ •*00 M sO CO tOCO 00 M N M M to M vO so cosO CO t» sO -^-00 co HI CO H CO •* ONCO 10 CO OO ON rt M to Tj-OO d d d d •*CO d CO NO O HI Tj- to coso ^ to HI Tj- d to QS. to d CO CO ON H Ht AVERAGES ^Sol N 1)00 *5 & JM M « CO 'fr rj- rj- O H M w M 00 Tj- to Tj- co co Os co to toOO to M N HI M OO CO ON CO HI O to IO HI CO HI CO d d d d CO •<*• O Tf to co M CO •*NO SO vO O CO •* ON HI to sO to OssO to S « » 0 O «0 o°° ro li°o -"00 >l w " ON HI co ON co w CO GO HI co M co H M M M t^. CO N N ON o Ifl M IO O O ioS»2 a >" " to M co if, to coco O ON M ON d M M CO OO 10 >o »o o Os Os so »ooo r-» M M HI M M W Tj- to O to Os to O Os HI O PI d N CO \O 00 CO to CO to w d rj-sO to to d d d d CO CO HI CO d d d CO W O M Tf SO O to to TJ- IO tooO Os TJ- d HI AVERAGE YIELDS «ilsl >H « - CO CO SO 10 00 O CO Tf \O O to d so CO r^. O OssO ^O so CO - M C( IH M O ZC O C* ao O^ t^. t-< ^O O 00 Os M CO HI PJ CO Tf d 10 CO •* •<*• HI HI TJ- IO to d d d d CO HI HI SO co **• H CO OO d co O to O to M CO d to OS Th to SO M Slf W M o J5 do o M UOO *- 0 . > M " Os •*<> so co to O ON tooO toco « Tf r^ co co O »OsO N Os »O co HI H H M 00 O to M tO M CO CO vO sO CO sO H P4 HI d COCO HI ON CO w sO d O d O d d d d d O ON ON rf Tf CO HI CO CO d d SO HI ON to to O IO TJ-SO OS to to O e« =0 O ex M Sw-SoO >H " « d to M HI vO O sO •* to Os to ON H SO IO M O O co ct 10 c» so >O M d M CS 00 to M Tfr •^" to to Tj- 00 O Os to HI d HI d toOO tosO HI HI Ht ON HI CO HI d d d d d d CO \O d HI CO Os IO ON M d CO O d to *O to toOO ^- CO o c5 *^ o oo M Soo — oo >< " " CO M IO M to Tt ON to to ON to ON coso r-« M N Os ^ to io M r^so M W M 04 to Tj- O H - « d d CO M Os O so so HI O IO M d d Tj- Tf ON ON to HI ON O to M co w *fr M M M M Os O d M M CO d CO d d Tj" CO d CO d CO to ONCO M d d d CO CO CO CO CO 00 HI O HI d HI H d 0 S^OSO IH a^ oc — oo Jx " M Os to co O so to O tOsO tOOO CO 10 CO t^ HI O IO CO P) M ^- C1) M CO M O CO to ON to SO IOOO CO d CO d fO co O to\O ON to CO O d Tj- d to CO CO CO CO ON ON to to ON ON d d to r^ toco co HI O CO t to to ONCO Tf Tj- H Son. TREATMENT APPLIED • EVERY YEAR HI M 1 « d Si rt °<^o£ • < •• •• ««H • u "o Z ° •• u aj . . z^tg . ^SSc§^H mil? P fi tn .2 .H > 11113° ^ PL, Pi CO Pi C/3 CO ef cvf . .fcfc t£ t£ 'SS i*x 1«^ .H o e« M 3-g^fi €34 c §^3 — G ^«S . J'rt.a a * a •111 a^-a «-U-OT3 a! C C C M rt rt td S») (/] V) ~ __ — .2 "c5 "5 "c5 g (/) t/3 « o . . . S £ S S S S E S «« Sodium nitrate . . . Nitrate and phosphate . Nitrate and alkali salts Nitrate and minerals as -o • C 3 .,, »> • o £•£ o, ca ca j£ 8-S^S §sl| ^^ a d £ u ^ T3 T3 "O aj C C C O aj rt rt D 4) a) D a,^ ^A M fl9 c$ cd 08 «uuu _>> • "5 o • " CO to O 00 ON u to to CO CO a a 3 3 a! rt ZZ So £* H d co Tf ooco M d CO Th «« H « CO Tf zzzz HI d CO •* OCJUU H d 1 1 to to 382 INVESTIGATION BY CULTURE EXPERIMENTS phosphate (compare O2 and 04 for the 3o-year and 25-year periods). Where nitrogen has been applied without phosphorus, the stimu- lating effects of the alkali salts is still apparent, probably because they continue to liberate some phosphorus from the soil. Where both nitrogen and phosphorus are provided, the effect of the al- kali salts is most marked, and here it is increasing, very possibly because all of the potassium needed by the larger crops is not liber- ated from the soil on account of lack of decaying organic matter. Here it will be seen, however, that the sodium in sodium nitrate without potassium (plot N2) produces even better results than the alkali salts, including potassium (plots A4 and N4), but this com- parison is complicated by the fact that ammonia nitrogen and nitrate nitrogen may have different effects, and the chlorin and sulfate radicle may also produce some effect. It is of special interest to compare the marked residual effect of farm manure on plot 7-1, Hoos field, with the absence of such an effect from the heavy applications of commercial fertilizers (in- cluding 172 pounds of nitrogen) on plot 16 of Broadbalk field. (See Table 62.) However, it should be kept in mind that plot 7-1 re- ceived 314 tons of manure during the 20 years (1852 to 1871), which is equivalent to almost 6 tons per acre a year for the entire 55 years- At 40 cents a bushel for barley, the manure applied to plot 7-2 has been worth about 85 cents a ton, while that applied to plot 7-1 has already paid $1.36 a ton for itself, not deducting interest on investment or counting the remaining residual effect, plot Ci being used as the basis for comparison. A comparison of plots N2 and 7-2 shows the marked superiority of the farm manure in a dry season (1893), while the commercial fertilizers give nearly as good results in normal or wet seasons, and probably would surpass the farm manure if the nitrogen were in- creased sufficiently. If the 43 pounds of nitrogen cost $6.45 and the 29 pounds of phosphorus $3.48, and if barley is worth 40 cents a bushel, the ammonia nitrogen has left a deficit of $1.97 a year for the 55 years, while phosphorus, in addition to nitrogen, has overcome $1.92 of the deficit, leaving a net loss of 5 cents per acre per annum. THE ROTHAMSTED EXPERIMENTS 383 The nitrate nitrogen practically paid for itself as an average of the first 30 years, but left a deficit of about $i a year for the subsequent 25-year period, of which, moreover, the last 15 years show an annual loss of $1.49. Phosphorus added to nitrate has paid for itself and 60 per cent net profit as an average of the 55 years, and the effect of phosphorus is apparently increasing where applied in this connection, which practically amounts to using it in addition to both nitrogen and potassium, assuming that the sodium has power to liberate potas- sium from the soil. If the nitrogen were secured from the air by clover, and if the potassium were liberated from the soil also by clover, plowed under directly or in manure, it is easy to see that applied phosphorus would be still more profitable, especially if the 29 pounds were applied in raw natural phosphate at a cost of 87 cents instead of in acid phosphate costing $3.48. It should be remembered always that computations based upon increases compared with the yields from unfertilized land may indicate profits that would not be wholly realized if the total yield of the unfertilized land is not sufficient to pay for its own cost. In other words, if it costs more than the value of 14.8 bushels of barley to secure that yield, then the financial deficit from the un- fertilized land must also be overcome before any profit can be had from the use of fertilizers. Furthermore, in planning systems of permanent agriculture, we must also consider whether the apparent increasing gains are due solely to improvement resulting from soil treatment, or in part to the general depletion of the unfertilized land. Probably nothing is more difficult for the average landowner to realize than that what appears to be profit is in part at least taken from his own capital. This is very clearly illustrated in the Hoos barley experi- ments. Thus, with nitrogen on plot Ai, during the 15 years (1892 to 1906), there appears to be an average increase in yield of nearly 8 bushels per acre above the unfertilized yield; but, by referring to the average for the first 10 years (1852 to 1861), it will be seen that the unfertilized yield has decreased by more than 12 bushels. On this basis, as an average of the last 25 years, the apparent in- crease from nitrogen is wholly represented in the decrease in pro- ductive power, and consequently in the decrease in value, of the unfertilized land. 384 INVESTIGATION BY CULTURE EXPERIMENTS POTATOES EVERY YEAR ON Hoos FIELD, ROTHAMSTED On another part of Hoos field potatoes were grown every year for 26 years (1876-1901). There were several changes in the va- rieties grown, so that but little importance, at most, should be attached to the yields in successive periods as indicating decreas- ing or increasing fertility, except in those cases where the change is so regular and so marked as to leave no room for doubt. It is especially to be kept in mind that the variety " White Beauty of Hebron " was grown only during the last five years (1897-1901). During the previous 21 years the varieties grown were " Rock " for 4 years, "Champion " for n years, " Button's Abundance " for 5 years, and " Bruce" for one year, and, in this order, from 1876 to 1896. Thus, the two five-year periods from 1882 to 1891 should be comparable, but, of course, seasonal variation renders even that possible comparison of doubtful value. The special object of the experiment was to ascertain the effect upon the yield of potatoes of different fertilizing materials, as indi- cated in Table 68, which shows the general plan, the treatment applied, and the yields obtained each year. One of the points most clearly indicated by the data in Table 68 is that " White Beauty of Hebron," grown from 1897 to 1901, was a very poor yielding variety. It may be said that 1879 was an exceedingly wet year at Rotham- sted, the rainfall being 2.79, 3.48, 5.55, 4.24, and 6.56 inches for the respective months April to August. In any consideration of these potato experiments, it should be kept in mind that potatoes are a market-garden crop, and constitute one form of intensive agriculture. An annual investment of $25 to $40 an acre for fertilizing materials is not beyond consideration for a crop that may yield 300 bushels, that may be worth $150 an acre. In the last lines of Table 68 are given the average yields for the first 6-year period and for the four successive 5-year periods, and, finally, the average for the 26-year period, followed by the several averages for the value of the increase and the cost of treatment. Since New York leads in the production of potatoes, the price THE ROTHAMSTED EXPERIMENTS 385 used in these computations is 50 cents a bushel (57.6 cents being the 10- year average farm price for New York State, and also for Ohio), and the cost of manure is figured at $2 a ton; but these figures should always be modified to meet average local conditions. They only help to summarize the results so as to bring to mind their economic importance. Thus, at the prices named, the treatment applied to plot 4 has cost $35.32 a year, and the increase produced has been worth $70 a year, or sufficient to pay the cost and leave practically 100 per cent net profit. The ammonium salts on plot 5 have paid but half their cost, and the sodium nitrate alone has but slightly more than paid for itself. By far the largest returns for money invested has been from acid phosphate on plot 9, which has paid for itself and added more than 600 per cent net profit as an average of the 26 years. Indeed, the acid phosphate alone exactly doubled the average yield of 26 years. The alkali minerals, including 300 pounds of potassium sulfate, ico pounds of magnesium sulfate (Epsom salt), and 100 pounds of sodium sulfate (Glauber salt) , have not paid their cost when used in addition to acid phosphate, the average annual increase of plot 10 over plot 9 being only 7 bushels, and the annual cost $7.90. The largest average yield and the largest net profit per acre is from plot 8, which produces as much on one acre as were grown on four acres of untreated land. It should be noticed, however, that, during the last 10 years of the experiment, the farm manure plots, 3 and 4, have forged ahead of the complete chemical fertilizers on plots 7 and 8. Director Hall makes the following statements in his book on " Rothamsted Experiments " (1905) : "In the Hoos field, experiments upon potatoes were begun in 1876, and con- tinued for twenty -six years ; they were then discontinued, because the crop on the plots receiving no organic manures had fallen to a very low ebb in conse- quence of the deterioration of the texture of the soil. But on the plots receiving farmyard manure, and even on those receiving only a complete artificial manure (plots 7 and 8), the crop was maintained in favorable seasons. No falling off was observed which could be attributed to the land having become 'sick' through the continuous growth of the same crop, or through the accumulation of disease in the soil." 386 INVESTIGATION BY CULTURE EXPERIMENTS 0 1H 145 g*,-~ a* 3 0 1 1 H l-l CO O r<3 H <~O Tf 10 Tt Tf (S OHM M « MINERALS OO UO O H U-> SO 00 -"tOO 00 H H H H SO tOOO P4 ^sO 00 H O H H 9> ACID PHOSPHATE (29 Ib. P) V i o \O ro t^ w r^OO «S P) •* •* Tf O C« M 1-1 HP) ACID PHOSPHATE o^.^o oo Tf t^ T--00 •^•00*^ H H H *•» fO ^fOO l^ t^sO t-» O\ O 00 aS \ 3<02 3£5w N ro VO OS ^ O uo O i-i ro TT ro M CO (-O M O ro FARM MANURE2 ds-7 T.) PI U-) P) TfSO J^ r^ 10 O O H H H H H O SO rOsO IO Os ON H 10 ro M H PI PI w FARM MANURE AND PHOSPHATE A« ~ ". ON^O Tf O O O\ O t~- ^ W vO M M M 0* M FARM MANURE 2 (iS-7 T.) VO IO J^OO .H l-l PI Tj" Q\ H p< P| H H SO SO ^ PI Os iO ON J^ 10 ro H P) M N w^ a 2IH ""' — < Z r- ta%2 - O\ O O M ir> O\ 10 ts O O\ O O l-l O N HO W « M Z Woo S£« « < ^ IOSO O *^ •* O Os t^ t^ H O sO ro PI 00 00 OO so SO OssO fH H z o z u i u B 0 [z; Tf ro t^ O O \O TT H O ro t *>• H H H u z 1 ro t^sO ON Tt t~- O\OO ro re IH OO H l^SO IO PI rC ^t P< s 3 w gg So << -r | U fc « a o 1 H B! Z M la i 8s 5 < J Sri i •j-. ti H HI 2 t H§ 2 1* O t^QO O O M i^ t^. t^ t^-cx5 oo oo oo oo oo oo oo <: ^ p« rj- ioso oo oo oo oo oo 00 00 00 00 OO t^-00 Os O H 00 00 00 O. Os 00 00 00 00 00 THE ROTHAMSTED EXPERIMENTS 387 o 1H . §2 u « *£ »o CM NO oo o HI HI O fO ^O ^O^O If HI '*f CS 00 »O CO ON O ^t HI HI H 800 ~ . *? 10 ON HI CM HI . B«R 0 5> N fi_ NO co co t^- co O OO ONNO O HI HI W \O 10 O O O HI IO Hi O CO COOO ON Tf HI M 0 M O 00 IO 10 co 00 ||gl NO IO HI IO O M HI CM HI CM <*o o oo 10 in ^ CS CO vO 00 HI M O ON O 00 N 10 O O 00 M O CM HI CM HI o"' M §00 N iO\o •^- r- a |Ji| s ONNO COOO CNI O NO to CO CO cs M r^so *^« M M HI oo ^1" NO O O CO NO O ON CM HI CM o- 1— 800 ~ . °! ^" CO TJ- gll OO ONOO t^NO ^f N \O POOO O NO ^ CM t— ON 0 0 00 O ON Us HI M HI HI . in! ?%*<*£ o o^ o o\ H CO O CO NO p & rr> 10 ON HI NO CM g|£ •^•00 xo Tf- o 00 rose t^vO NO CM 00 O •* H 8 CM - . ^ ^11 CM CM CO CM CM H HI CNI HI HI CM HI H HI f^. CO . W^ OS ^ Is Os **o w o ^o H C< CO C*( 04 ^f COOO ONOO M M O- O cs ON CO CM O< HI M CM HI OC O ^t ^^ 10 CO N co CM' HI VO CO » W « M ^ < " o M fO\O ^C ^ 'J- N CS CNI o ON IO O ^t M 01 o H O «o M XO CM vo i/S r^. 0 iH H Z 10 o^ ^-O t^** ^o co **O ^" fO ^ M ^O IONO t^- N W HI HI c .S S £ ei > > > > CS Go flS fly gj'oC! ." s CO W co ^" loO OO 00 CO 00 00 ON ON ON O O 00 00 00 ON ON rt O 388 INVESTIGATION BY CULTURE EXPERIMENTS It should be noted that the average yields on plots 3, 4, and 8 increased during the fifteen years previous to the last five, when the " Beauty of Hebron " variety was introduced; and, as an average, the farm-manure plots yielded higher during the five years ending 1896, than during the six years beginning 1876, notwithstanding the addition of acid phosphate during the earlier period. During the first six years the use of $150 worth of plant food on plot 8 produced $615 worth of potatoes, above the 85-bushel yield on the untreated land, which is also the lo-year average yield of potatoes for New York State. Even when used in addition to manure, during the first six years, acid phosphate, as well as phos- phate and nitrate, paid 100 per cent net profit on the investment; but no test was made with manure and nitrate without phosphate. These Rothamsted data furnish no information concerning the effect of potassium, except that it failed to pay its cost on plot 10. It might be said that all but 9 bushels of the i96-bushel increase on .plot 7 should be credited to the minerals (compare plot 5), but how much of this increase would have been produced by acid phosphate and ammonium salts is not revealed; on the other hand, nitrogen must be credited with the increase from plot 7 above plot 10; all of which means that phosphorus is the first limiting element and nitrogen the second, for the growth of potatoes on this normal soil. To maintain satisfactory soil texture and to provide for the liberation of potassium, magnesium, etc., from the immense supply in the soil, liberal applications of manure should be made, and for the improvement of the subsoil the growing of clover in rotation will produce benefits that manure cannot produce. On the other hand, in such intensive agriculture, there is large profit in a moderate use of commercial nitrogen, especially in such form as sodium nitrate, which also furnishes sodium as a soil stimulant. Whether one should use raw phosphate or acid phosphate, in connection with the manure, clover, and sodium nitrate, is not established, but the Rhode Island and Wisconsin data indicate that potatoes are able to utilize the raw phosphate to some extent, and (in Rhode Island) even without adequate provision for decaying organic matter. It would seem advisable, however, to use the acid phosphate until the raw rock has been more thoroughly tested for potatoes, especially considering that the expense for phosphorus, THE ROTHAMSTED EXPERIMENTS 389 even in acid phosphate, is one of the smallest items in the produc- tion of this expensive and valuable crop. RESIDUAL EFFECT OF FERTILIZERS ON Hoos FIELD Any one who has made himself acquainted with the 26-year potato experiments on Hoos field will naturally be interested in the further history of those plots. The data reported since 1901 are given in Table 69, following a summary of the soil treatment and potato yields. The barley yields for 1902 are in harmony with the common ex- perience that potatoes leave an excellent seed bed for a succeeding crop of barley or wheat; and the residual effect for one year is also very marked where nitrogen has been applied, as was the case with continuous wheat on plot 16 of Broadbalk field. Even the first barley crop on plots 9 and 10 are no better than on plots i and 2, clearly showing that nitrogen was the limiting element for the quick- growing barley crop. Aside from the farm-manure plots, much less residual effect is apparent after 1902; and, in all cases where the treatment is comparable, the barley yields of these plots in 1903 were less than on corresponding plots in the same field (Hoos) where barley had been grown every year for more than half a century. If we keep in mind that nine of the eighteen plots of continuous barley produced more than 36 bushels per acre in 1902, also that four of the ten plots where potatoes had been grown for 26 years produced less than 36 bushels of barley in 1902, and that the largest average yield of potatoes from the farm-manure plots (3 and 4), either for one year or for five years, was secured after pota- toes had been grown on the same land every year for more than fifteen years, then the following statement by Whitney seems clearly inapplicable: "One of the most interesting instances going to show that toxic substances are formed and that what is poisonous to one crop is not necessarily poisonous or injurious to another is a series of experiments of Lawes and Gilbert — the growing of potates for about fifteen years on the same field. At the end of this period they got the soil into a condition in which it would not grow potatoes at all. The soil was exhausted, and under the older ideas it was necessarily deficient in some plant food. It seems strang? that, under our old ideas 390 INVESTIGATION BY CULTURE EXPERIMENTS 3o"Z 3 o 1^ -^ to to M u to ON itS1 •K a nil ON H I y 00 gw 2 » < Q « & SH I B < O a NO CO 2^5" °5 S CN 111 HI SsSgf H oo tfsl ro l^<| CN •o HI? "t ON OS H S 3 J s 2(2 to •# IIPI CN ^1? ON NO Hi w H « as i H *i§|5 ON 2|s oo M S £ C-H VO W 0! M to N ^11 HI IP H to S; HI O oo 0 *^- 525 fc U U H ej o 2 < cd < u f^oo C^ o rt g-s rt £? cu ^ ^ *Q O 0 HO NO W M CN pJ,x vT 3 09 B. 00 en s M • to ro oi <0 H « O CM NO NO N ro as 00 *>• M O ON H t-i Tj- ON ON •*00 0 vO CN ro 1 •*-! a 4) T3 rt E CN OO CN \O HI CM Tt t>- 00 10 NO NO >lications M CN IH ON ON ^" IO M CN sf"3 > g _O 3 U a, c- < TfONtO ro to M vO o fc CN Tf w O O ON CN rO ^ w CN >. O ON to ro O ON CN c O M NO IO t^» ^ IO 00 NO 00 O CN ro w CN u OJ T}- CN to M O ~~f — pn r^ ro ON O\ ON C> THE ROTHAMSTED EXPERIMENTS 391 of soil fertility, if the soil became exhausted for potatoes, it should grow any other crop, because the usual analysis shows the same constituents present in all of our plants, not in the same proportion, but all are present and all necessary, so far as we know. This field was planted in barley, and on this experimental plot that had ceased to grow potatoes they got 75 bushels of barley." l While the avoidance of possible injury to plants from the pos- sible toxic substances that may possibly be excreted from the roots of the same kind of plants is by no means precluded from among the possible benefits of crop rotation, the Rothamsted data fur- nish little evidence in favor of such a theory, and even less in sup- port of the Whitney theory, that crop rotation alone will maintain the fertility of the soil. On the other hand, the residual effect of the farm manure applied to plot 3 (Table 69), previous to 1882, is still apparent after the removal of twenty-five crops, in com- parison with the unfertilized land. Clover was seeded in 1905 on plots 6, 8, and 10, and cowpeas on plots 5, 7, and 9. The cowpeas failed, and in 1906 clover was seeded on 5, 7, and 9. The clover yields thus far reported are recorded in Table 69. They are of some interest for comparison with the 1906 clover on Agdell field (Table 56), where clover " sickness " has been recognized by the Rothamsted Station as the probable cause of frequent failure during more than half a century. There is much evidence to show that soils frequently become " sick " from the continuous growing of flax and of certain legume crops. " Clover sick " land and " bean sick " land are expressions common to nearly all countries. Cowpea wilt and flax wilt are well understood fungous diseases, and the evidence thus far secured indicates that clover " sickness " is also due to a fungus rather than to any pos- sible toxic excreta. (See below.) HAY EVERY YEAR FROM PERMANENT MEADOW AT ROTHAMSTED In 1856, experiments were begun at Rothamsted in top-dressing meadow land with various fertilizing materials, as indicated in 1 From page 14 of Farmers' Bulletin 257, U. S. Department of Agriculture. The careful student is advised to secure a copy of this interesting bulletin and also Bulletins 22 and 55 of the U. S. Bureau of Soils in which are set forth in greater detail the unique theories of Whitney and Cameron concerning soil fertility. They should be read in connection with Circulars 72, 105, 123, 124, and 129, of the Uni- versity of Illinois Agricultural Experiment Station. 39* INVESTIGATION BY CULTURE EXPERIMENTS Table 70. The land was known to have been used for meadow and pasture for at least two centuries previous to the beginning of these experiments. The field was known as The Park, and consisted of normal, nearly level upland soil, very similar to Agdell, Broadbalk, Hoos, and other Rothamsted fields, except that The Park had not been heav- ily chalked in the earlier years, while the other Rothamsted fields (with the exception of Geescroft at least) had received chalk dress- ings probably amounting to 100 tons or more of calcium carbonate per acre. The Rothamsted Station has no knowledge of any grass seed ever having been sown on The Park, either before or since the beginning of the experiments. From 1856 to 1874 only the first crops were harvested and weighed as hay, the second crops having been fed off by sheep, as a rule, and the sheep having been con- fined upon the plots so that the droppings were returned to the respective plots. Since 1874, the second crops, when sufficient in amount to justify it, have also been harvested and removed as hay. On a few plots the treatment was not fully decided upon until a few years after the beginning of the experiments. Thus, plot u was divided in 1862, when the addition of sodium silicate was begun on 11-2. At the same time the application of potassium was discontinued on plots 8 and 10 and the sodium sulfate changed from 200 pounds to 500 pounds for 1862 and 1863 and then to 250 pounds. The periods represented in the first column of averages vary from 7 to 10 years. In studying the results from Table 70, it should be kept in mind that all applications have been made only as top-dressings; and, consequently, that benefit could be expected only from those materials which were sufficiently soluble to permit of their being carried into the soil to the depth where the plant roots secure considerable amounts of their food supplies. It should be kept in NOTES TO TABLE 70. The "minerals" regularly included 392 Ib. of acid phosphate (400 Ib. of basic slag, 1897 to I9°2), 500 Ib. of potassium sulfate (300 Ib. for 1878 and previously), 100 Ib. of magnesium sulfate, and 100 Ib. of sodium sulfate (200 Ib., 1856 to 1863), but where potassium was omitted (plots 8 and 10), the sodium sulfate was increased to 250 Ib. from 1864 to 1904. The farm manure applied to plots i and 2 was at the rate of 15.7 tons per acre for the eight years, 1856 to 1863. THE ROTHAMSTED EXPERIMENTS 393 PER CENT BY WEIGHT (Plus Weeds = 100) 0. o U 1 «_ rt t- IO rt U 1 | O CO Hi COO 0 0 HI NO r^ "00 rt • 1897). 4 Seven years 8 Farm manure and }.; 1862-1881 = i72lb. H. 10.- "is 1° *"" NO «O co w co NO M S3SSBJO NO rt CO rt 10 M rt COOO CM NO CM IO M 1-1 00 CM t^-00 K:ct5; rf H, 00 <5 00 10 ON ' 1 HI CM CM Hi 1^ C- ON ON ON ON ON 00 OO 00 CO O-OC NO M CO CM NO rt Averages, 1836-1902 wum^i t^. CO ON OO Hi rtl | 00 00 rt M HI O O co co 1 rt CO rtOO IO CONO 1 ' CM ON HI inn S3SSBJQ 00 IOOO O CM 101 | O NO t^ r^oo 10 ON CONO I 1 O"> O oo r-»NO OO' 00 6 1 CM 6 NO OO 00 1 ' NO t- 00 O 10 t^ OO ON ON O- rt CM 6 O 00 NO f^O « 00 CM CO 10 CNI NO HI CO rt O CM NO «-» IO 1 First crops, and second (if any). 2 Sodium silicate, 400 Ib. 3 Cut wheat straw, 2000 Ib. (omitted aftei (1898-1904). 5 Nine years (1896-1904). " Forty years (1856-1895). 7 No nitrogen applied after 1895 fish guano, once in four years, beginning with 1907 (?). " For 1856-1858 = 172 Ib.; 1859-1861 = 86 1 I ON Ul rt NO 00 CM IO IO IO HI rtOO CO CN) CM rtOO 00 rt OC CO t^ O- rt ON N w TtOC r^ ONNO rt IO CM 00 CO CM j u C O z> s ONO N rt O-OO CO CM 00 ON rt O ON O H4 o-oo oo 00 M CH IONO ON CM CONO HI NO OC M NO O cooc rt " ON O 1-1 CM 10 HI M NO O CO H. HI fe'f 00 rtOO TO O « W HI 0 ON O ON CM CO H. CO 10 HI rt CM OO 00 H, CO CM rt rt rt t^ 0 O CM M CM CO rt rJ-NO CM_ IONO oo CO CO CM . -NO W HI CO rt 30 10 NO O ON O- CM CO CM IO CONO CO *-< t^ rt rt CO CM 00 O CM CM O- O CM M CM 10 CM CM O t^ IO CONO 0 10 H. rt COOO CNJ rt ON rt lo co Two CUTTINGS 1 M "*O V) > £° % ^» OO *- O* CO CM NO NO -*00 NO ONNO O NO O rt Hi OO M CO O CM CO CO O CM CO ON rt CO 10 O- O O NO CM NO O IO COOO rt O IO rj rtNO OC 0 ON CO rtNO CN! ON O IO rt 10 CO 8£ £ t~+ O O* CM NO 00 CM O CM CM NO O ON IO CM IO ON CM rtOO OO O O O 10 HI 00 ON CO CO 00 NO CM H, 00 H. rt CM NO HI 00 CO r": O 6 c > \o o t^. 00 rt O CM 00 •* M U-) CM rt CO CM O NO rt 00 H. NO CO rt Tt CM CO CM 00 NO O CO « rt CO HI O> CO rf CM CO co O - rt rt O ON IO rtNO NO CM 00 NO IONO t^ CM NO NO O rt CM CM CO IO ON co r^ co 10 co -£ -vO *O >gog 00 CM O HI NO CM rt rt NO O ON Hi NO t^ Tt CM co co -t -to HI ONO CO co co NC X NO t 0 0 « 00 O ON ON O O 00 O O 00 10 00 HI o- CM NO IO NO OC NO 0 000 rt 10 CO (•qi) aaoy 83d SX1Vg 1VXOJ, ODD 0 C C CM O O a c CM CM "b ON ON O ON ON rt O-. rt ON O C ON rt C rtNO C M H, M f^ Ul O CO CM (•qi) CO U V "* O O C C 1) " §00 00 ODD C C C 0 0 O c c c NO NO ON O 00 00 CM CNI HI HI §!«5 a §?? C saxva HaxsAg IVNIJ 00 00 00 NO NO 00 00 OO 00 NO IONO oo oc oo NO CM NO CN! IONO IONO oo oo oo oo NO NO 00 10 10 IO 00 00 00 NO NO NO t^ IO IO oo oo oo Son. TREATMENT APPLIED PER ACRE EVERY YEAR (Excepting Changes as Noted) S (Manure, amm. salts); then amm. sa (Manure); then unfertilized . . Unfertilized c . . ni • • 0-3 • •J'3 ' • 'u ? 00 ^ (About 43 Ib. N till 1860 ; then 86 ^ 0 cTH <. O srb fc.^ 0 3 <. O tffc ,Q. PLOT Ib. Nothing applied for the Bar- i« 2 w .ra j>"^ i ° c a a c c lrf! No. ley, and no Manure, Rape Cake, or §0? Doo < in 0! t^ poo o o r . £ 0 £ «" Nitrogen applied for 187,4 or 1875. H£ HT >°Z f 1 H M r1 H c-1 C (v About 300 Ib. Potassium Sulfate w S. W w *° M N m ^> 10 till 1871 ; afterward 500 Ib.) O g• s N6 N7 N8 Nitrate and farm manure . Nitrate, manure, and phos- (?) (?) 86 86 86 86 94 86 550 942 SSo 1842 942 1442 M79 S5Q 20.85 22.90 I3-30 19.40 16.45 I7-30 I7-65 II.OO 23-45 25-05 I2.QO I7-70 14.65 14-55 14.80 10.15 20.95 22.55 13-65 18.40 15.60 15.20 15.80 10.90 29-65 25.80 12.80 14.20 12.90 12.05 12. 2O 6.00 26.90 28.05 18.25 18.95 16.15 16.45 16.05 11.45 30.32 31-24 22.51 18.57 19.84 21.03 1 1. 06 30.31 30.24 13-08 14.30 17-23 21.92 10.25 41.42 42.13 30.46 24.62 25-05 26.54 1 8.60 12.73 12.49 11.19 9-30 8.03 8.76 2.79 Sodium nitrate .... Nitrate and minerals . . . Nitrate and phosphate . . Nitrate, phosphate, and pot. sul •. . . Nitrate, phos., pot., amm. salts Sodium nitrate .... Ai A2 A3 A4 As A6 A7 A8 Amm. salts and farm manure Amm. salts, manure, phosphate Ammonium salts .... Amm. salts and minerals . . Amm. salts and phosphate . Amm. salts, phos., and pot. sul. Amm. salts, phos., and pot. sul. Ammonium salts . . . . (?) (?) 86 86 86 86 04 f6 400 792 400 1692 792 1292 1329 400 23.00 22.70 8.15 iS-SS 9.70 14.00 14.65 7-05 21-35 21.45 6.00 16.10 8.00 14.40 14.65 5-45 2O. IO 19.75 6-35 14.80 8.10 13-65 14.70 6.15 25.00 22.60 4-95 12.80 5-70 12.80 13-25 4-30 18.70 23-75 6-95 14-95 6.60 14.65 14-85 6. 20 24-34 30-15 16.08 6.93 15.46 16.51 6.01 25.69 30-95 12.29 3-85 16.38 16.95 6.36 33-52 41.68 26.68 10.88 25-22 26.52 9-87 11.05 11.94 11.48 6.42 10.07 10.84 2-53 AC i AC 2 AC 3 AC 4 ACs AC 6 AC? ACS Amm. salts, rape cake, and manuYe Amm. salts, cake, manure, (?) (?) i«3 183 183 183 IQI 183 400 79 400 169 79 129 1329 400 24-95 24.10 11.80 24.40 12.50 21.05 20.80 12.00 25-I5 24.90 0-95 26.00 11.25 24.10 23.60 21-45 21-55 10.40 22.35 10.50 19.65 20.50 n. so 28.55 26.25 9-85 28.65 10.35 25-80 24.25 p. 7" 20.50 25.80 7-85 24.2°; 7.60 20.70 2I.OO 8.70 26.54 34-15 3T-52 8.44 27-77 29-75 8.22 26.82 32.06 26.31 6-57 25.28 28.19 8.05 34-29 43-52 40.97 11.26 35-88 34.38 10.^0 10.98 11.19 n-55 5-45 9-52 9-S3 4.61 Amm. salts and rape cake . Amm. salts, cake, and minerals Amm. salts, cake, and phos. Amm. salts, cake, phos., and Amm. salts, cake, phos., and pot Amm. salts and rape cake . Ci C2 £3 cl C6 c? C8 Rape cake and farm manuie Rape cake, manure and phos. Rape cake (200x3 pounds) . Rape cake and minerals . Rape cake and phosphate . Rape cake, phos., and pot. sul Cake, phos., pot., amm.salts Rape cake (2000 pounds) . 9-35 20.75 10.35 21-55 21.40 10-75 19-35 11.50 16.30 I7-I5 9-75 20.80 28.25 11.05 26.11; II.So 22.30 22.65 n-45 22.25 24-75 8-95 20.85 8.00 18.05 18.15 8.30 25-13 30.57 24.08 9.89 21. l6 26.83 8.84 25.26 30.10 23-18 8.93 21.66 24.68 9-93 35-02 40.74 33-09 15-43 28.15 30-59 I3-24 0-73 10.36 11.03 5.i6 9.26 9-43 4.23 These data are presented for examination by the reader, and only a few special points will be referred to here. The records of 1885 and 1901 are not included in the averages because, owing to un- THE ROTHAMSTED EXPERIMENTS 401 favorable conditions, no nitrogen salts were applied for those years. For the same reason the records for plots N$ to N8 and A3 to A8 are not used for 1903. The Rothamsted Station reports that, owing to very heavy rains in November, 1894, flooding the lower parts of the experimental mangel field, and washing soil from the farm-manure plots, especially on to plot 03, and to a less degree on to plot N3, there is no doubt that the results from those plots are too high for 1895 and each year since. Of late years no data are reported from plot 3, but the No. 8 plots are sufficient. As explained in the table, 500 pounds of potassium sulfate has been applied since 1895, in addition to the other regular treatments, to plots Oa, N2, A2, AC2, and €2; and for 1903 and since the application of potassium and the extra nitrogen (8 pounds per acre) has been discontinued on plots Oy, Ny, Ay, ACy, and Cy, but in- stead those plots have received the full minerals, except potassium. The " minerals " regularly include 392 pounds of acid phosphate, 500 pounds of potassium sulfate, 200 pounds of magnesium sul- fate, and 200 pounds of common salt (sodium chlorid) ; but from 1896 to 1902 the acid phosphate was replaced throughout by slag phosphate. The mangel leaves are each year spread over the respective plot, and thus returned to the soil. It had been suggested that plants with large leaf surface, like the mangel, could probably secure sufficient nitrogen from the air, in the form of ammonia or possibly as free nitrogen, for their full requirement, provided a small amount of available nitrogen was furnished to give the plants a good start; and because of this the special 8 pounds of nitrogen were applied to plots Oy, Ny, Ay, and Cy until 1902, after which the treatment for those plots was changed as stated. Where no other nitrogen was supplied (plot Oy), the 8 pounds increased the yield of mangel-wurzel by 1.36 tons as an average of 25 years. At $1.50 per long ton this increase would be worth $2.04 per acre, while the nitrogen would cost only $1.20 at 15 cents a pound. Two points must be kept in mind, however; first, that the total crop on plot O8 was produced at a loss; second, that the increase from the phosphorus and potassium applied to plot O6 was worth less than 10 per cent of the cost of those elements. 402 INVESTIGATION BY CULTURE EXPERIMENTS Where organic nitrogen was applied in rape cake, the additional 8 pounds of soluble nitrogen produced only two thirds of a ton in- crease, which would be worth less than the cost of the nitrogen, at the price used. It may be stated that the first crop of mangel-wurzel (1876) on plot O8 was 5.45 tons, while the same plot produced 6.95 tons in 1898 and 7.75 tons in 1900. Plot N4 produced 25.05 tons in 1876, and several plots produced still higher yields, the highest being 31.45 tons on plot ACi. Since 1904, the 200 pounds of sodium chlorid has been omitted from one half of plot N4, which receives sodium in the nitrate. The subsequent yields for this half have been 24.69, 16.69, an^ 35- Z5 tons per acre for the years 1905-1907, or distinctly more than where the common salt was included, as will be seen from Table 716. Of special interest is the evident effect of the potassium applied to plots 2 for 1895 and since. The previous records indicate that the heavy applications of manure had furnished sufficient phos- phorus for the crops grown, and the yields since 1895 plainly show that potassium was the limiting element wherever nitrogen had been applied in addition to the farm manure. Since phosphorus is also applied to plots 2, it is impossible to determine what in- crease would have been made by potassium without the added phosphorus; but on plots A2, AC2, and C2 the yields since 1895 have averaged about 5 tons more than on the No. i plots. The sodium applied in the. sodium nitrate on plot Ni appears to produce almost the same effect as the potassium applied (since 1895) to plot A2. It will be observed that phosphorus produced an appre- ciable effect on N2 from 1876 to 1890. As an average, one ton (2000 pounds) of mangel-wurzel contains about 3.6 pounds of nitrogen, .5 pound of phosphorus, and 6.6 pounds of potassium, and the average requirements for such an enormous crop as grew on plot AC2 in 1907 would be about 175 pounds of nitrogen, 24 pounds of phosphorus, and 330 pounds of potassium, for the roots only. If we assume the farm manure to have 10 pounds of nitrogen, 2 pounds of phosphorus, and 8 pounds of potassium per ton of 2000 pounds, the annual applications now being made to plot AC2 contain about 340 pounds of nitrogen, 60 pounds of phosphorus, and 360 pounds of potassium. On this THE ROTHAMSTED EXPERIMENTS 403 basis, the crop of 1907 required for the roots alone, 180 pounds more potassium than was supplied in the manure and rape cake; and it seems remarkable that the 141 pounds of sodium on plot Ni produced almost as great an effect as the 210 pounds of potassium on plot AC 2. It is of interest to note that the total supply of potassium con- tained in the surface soil (6| inches deep) of the peat lands of New York or Illinois, for example, would be sufficient for less than 10 such crops as were grown on plots Ni, N2, A2, AC2, AC4, and C2, of Barn field, Rothamsted, in 1907; and that even the total potas- sium in 2 million pounds of the most common type of soil in the Illinois wheat belt (gray silt loam prairie, lower Illinoisan glacia- tion) would be sufficient for only 75 such crops, although it would be sufficient for 50 bushels of wheat per acre every year for 19 centuries, if the straw is returned to the land. ABANDONED LANDS AT ROTHAMSTED Since 1882, a piece of Broadbalk field, which had been cropped with wheat every year since 1844, has been abandoned to nature, except that trees and shrubs have been kept out. Likewise, a piece of Geescroft field, which had been used for beans from 1847 to 1881 (only four crops grown during the last n years), and for clover from 1882 to 1885, has been abandoned to volunteer vege- tation since 1885. Nothing has been harvested from these pieces of land, not even by pasturing, since they have been left to " lie out," or " run wild." The most marked difference that has developed between the herbage of the two fields is the absence of legumes on Geescroft and the abundance of legume plants on Broadbalk, although Broadbalk was abandoned with a wheat crop standing on it (of which some volunteer plants continued to appear for three or four years) , while Geescroft was in clover when abandoned. Observers (including Sir John Lawes *) commonly attributed the absence of 1 In 1900, when I had the deeply appreciated privilege of being shown over the Rothamsted fields by Sir John Lawes (about a month before his sudden death), he climbed the fence like a boy, to take me into Geescroft field and point out a few legume plants (of a. single species) the development of which he had been watching for two or three years. — C. G. H. 404 INVESTIGATION BY CULTURE EXPERIMENTS legumes on Geescroft to the fact that the land was legume " sick " from the effort to grow beans for more than 30 years, although some good crops of clover were grown from 1882 to 1885. Some interesting data concerning these two abandoned fields are given in Table 72. TABLE 72. ROTHAMSTED FIELDS, ABANDONED TO NATURE FOR 20 YEARS LAND BROADBALK FIELD GEESCROFT FIELD Character of Herbage, June, 1903 Grasses 59.64 per cent 25.31 per cent 15.05 per cent 95.26 per cent .43 per cent 4.31 per cent Legumes Miscellaneous .... Percentages in Soils from Broadbalk (1881) and Geescroft (1883) DEPTH (Inches) 0-9 9-18 18-27 0-9 9-18 18-27 Total nitrogen . . . Organic carbon . . . .108 i-i43 .070 .624 .058 .461 .I081 I. Ill .074 .600 .060 _ •44?' Percentages in Soils in 1904 Total nitrogen . . . •145 .096 .084 •131 .083 .065 Organic carbon . . . !-233 •°73 •551 1.494 .624 -438 Calcium carbonate . . 3-325 .126 .160 •I31 ~ 'This percentage was .108 in 1883 and .115 in 1885, the clover crops having been harvested and removed during the two years. It seems that the practice of chalking the land, which prevailed at Rothamsted a century or more ago, had not extended to Gees- croft field, and without much doubt this has been the chief factor in determining the character of the herbage, in part because of the chemical reaction of the soil and in part because of the physical difference, the Geescroft land being close-textured, poorly drained, wet, and cold, while the Broadbalk soil, because of the lime present, flocculates or granulates and drains well. (The adjoining regular plots are tile-drained on Broadbalk.) Hall states that " where nitrate of soda had been used (on Gees- THE ROTHAMSTED EXPERIMENT 405 croft field), the land became specially difficult to manage, remain- ing persistently wet, and then drying out with an excessively hard crust." From any estimates that can be based upon the percentages of nitrogen found in samples of soil from these fields, very large in- crease is shown; in fact, much larger than can be accounted for by any existing knowledge concerning nitrogen fixation. It is questioned if the samples collected in 1904 are strictly comparable with those taken 20 years before, because of the increasing porosity and looseness of the soil. Thus, the 9-inch stratum of 1881 might occupy 10 inches or more in 1904. Director Hall estimates that Geescroft field (even without legume plants) has gained a quantity of nitrogen " which at the lowest reckoning amounts to about 25 pounds per acre per year," and adds: "The nitrogen brought down in the rain would account for perhaps 5 Ibs. per acre per annum, a little more will come in the form of dust, bird-droppings, and other casual increments, while some may be due to fixation of atmospheric nitrogen by bacteria in the soil not associated with leguminous plants, like the Azotobacter chroococcum of Beijerinck and Winogradsky's Clostridium pasto- rianum. Two other causes may be at work, the absorption of atmospheric am- monia by soil and plant, and the rise of nitrates from the subsoil." In the author's opinion, the two most important factors involved are the difficulty of securing comparable samples and the mechani- cal addition of foreign substances, especially the dust of summer, and the dirty, drifting snow of winter, light trash (leaves, weeds, etc.), which blow about until they find a lodging place in such a small " wilderness " as the abandoned portions of these fields furnish. An extreme illustration of this is found in a Rothamsted note concerning the potato tops on Hoos field in 1877: "Tops withered, not weighed, each lot spread on its own plot, but high wind (October 14) blew all off before plowing." One experienced in farm practice will easily recall conditions under which field dust is drifted by the wind. The extent varies from the cloud which follows the harrow to the dust storm, during which a field, even of clay loam, in certain mechanical condition, may lose very appreciable amounts of its best soil, which requires 4o6 INVESTIGATION BY CULTURE EXPERIMENTS for its deposition and accumulation only an undisturbed lodging place, and dirty snowbanks form in such places near open fields. NOTES ON THE ROTHAMSTED FlELD EXPERIMENTS The records herein given must be considered at best as summaries of the Rothamsted field experiments. Aside from the experiments already mentioned, beans were grown every year from 1849 to 1859, and oats every year (except 1877, fallow) from 1869 to 1878, under different systems of fertilizing, on Geescroft field. The average yield of oats for the five years (1869 to 1873) range, in bushels per acre, from 19.9 (unfertilized) and 24.5 (minerals) to 47 (ammonium salts) and 59 (ammonium salts and minerals) ; and for the other four years from 13.1 (minerals) and 13.8 (unfer- tilized) to 28.9 (ammonium salts) and 38 (ammonium salts and minerals) . No oats were grown on this field from 1847 to 1868, and the first crop of oats (1869) varied, in bushels per acre, from 36.6 (unfer- tilized) and 45 (minerals) to 56.1 (ammonium salts) and 75.2 (ammonium salts and minerals). The records for the 9 years, 1860 to 1868, are: fallow, wheat, wheat, fallow, beans, wheat, beans, wheat, wheat; with no fertilizers applied during those years except farm manure for the beans in 1864. Experiments with legume crops, especially with beans and clover, have been in progress on Geescroft or Hoos fields (or both) most of the time since 1847. In summarizing their experimental results after more than fifty years, Lawes and Gilbert recorded the following statements (Rothamsted Memoranda, published in 1901) : "When the same description of leguminous crop is grown too frequently on the same land, it seems to be peculiarly subject to disease, which no conditions of manuring that we have hitherto tried seem to obviate." "The general results of the experiments on ordinary arable land in the field has been that neither organic matter rich in carbon as well as other constitu- ents, nor ammonium salts, nor nitrate of soda, nor mineral constituents, nor a complex mixture, supplied with manure, availed to restore the clover-yielding capabilities of the land; though, where some of these were applied in large quantity, and at considerable depths, the result was better than when they were used in only moderate quantities, and applied only on the surface. THE ROTHAMSTED EXPERIMENTS 407 "On the other hand, it is clear that the soil in the garden, which at the com- mencement contained in its upper layers about four times as much nitrogen as the arable land, and would doubtless be correspondingly rich in other constitu- ents, has supplied the conditions under which clover can be grown year after year on the same land for many years in succession. "The results obtained on the soil in the garden seem to sliow that what is called 'clover sickness,' cannot be due to the injurious influence of excreted matters upon the immediately succeeding crop. "That clover frequently fails coincidently with injury from parasitic plants or insects cannot be disputed; but it may be doubted whether such injury should be reckoned as the cause, or merely the concomitant, and an aggravation, of the failing condition." "When land is not what is called 'clover-sick,' the crop of clover may fre- quently be increased by top dressings of manure containing potash and super- phosphate of lime ; but the high price of salts of potash, and the uncertainty of the action of manures upon the crop, render the application of artificial manures (as top dressings) for clover a practice of doubtful economy. "When the land is what is called 'clover-sick,' none of the ordinary manures, whether ' artificial ' or natural, can be relied upon to secure a crop. "So far as our present knowledge goes, the only means of securing a good crop of red clover is to allow some years to elapse before repeating the crop upon the same land." In his book on the "Rothamsted Experiments" (page 146), Director Hall gives the complete data and the following summary of the clover grown year after year on a small plot of rich garden soil at Rothamsted: RED CLOVER ON RICH GARDEN SOIL, ROTHAMSTED Pounds per Acre YEAH s AIR DRY HAY DRY MATTER NITROGEN IN CROPS Average of Average of 25 years 25 years (1854-1878) . (1879-1903) . 7664 3924 M? 3270 179 101 During the fifty years there have been only two crop failures (1895 and 1900); but the plot required seeding only five times during the first twenty years (1854, 1860, 1865, 1868, and 1871), whereas since 1874 it has been seeded or reseeded almost every year, and sometimes two or three seedings in one year have been required to secure a stand. Late yields of dry matter are: 2887 4o8 INVESTIGATION BY CULTURE EXPERIMENTS pounds in 1901, 1169 pounds in 1902, and 1589 pounds in 1903; and Hall's book contains the following: "In March, 1897, and in July, 1899, a^ the plants were removed by hand, burnt and their ashes returned, and the soil was carefully picked over by hand for the Sclerotia of*the fungus, Sclerotinia trifoliorum, many of which were found. The soil was also dressed with carbon bisulfid as a fungicide, before fresh seed was sown. In 1903, which was a favorable year for the growth of clover, a fair plant was obtained by reseeding, and in the spring of 1904 the best crop for many years was cut from this plot." Director Hall expresses the opinion that the fungus named is not the only cause of " clover sickness." Finally, it should be understood that, while the Rothamsted field experiments have been conducted with extreme care, there are some possible sources of error, and the Rothamsted Station has been very careful to point these out where they are of probable consequence. Warrington, in his Rothamsted lectures (Bulletin No. 8, Office of Experiment Stations, United States Department of Agriculture), delivered before the Association of American Agri- cultural Colleges and Experiment Stations, in 1891, under the pro- visions of the Lawes Agricultural Trust, makes the following statements: "The earlier experimental fields at Rothamsted were not arranged as skill- fully as the later ones; thus, Broadbalk wheat field has long, narrow plots, and the influence of the manure of neighboring plots is in some cases distinctly felt. The barley experiments in Hoos field are the best laid out ; here the plots are nearly square; they have each an area of one fifth of an acre." (In the author's opinion, tenth-acre plots, 2 by 8 rods or i by 1 6 rods, or fifth-acre plots, 4 by 8 rods or 2 by 1 6 rods, are more satisfactory than square plots for field experiments, because greater uniformity between plots is thus secured; but in all cases a pro- tecting border of at least one fourth rod should completely surround every plot, the same crops being grown upon the border as upon the plot proper. This requires a half-rod division strip between plots, and wherever needed, an additional uncultivated strip of grass sod should be left between the plots.) On the Grass Park at Rothamsted an imaginary line is the only division between the plots, but the ground is never broken, and the fertilizers are applied as top dressings with exactness (a cloth screen A. D. HALL, DIRECTOR OF ROTHAMSTED EXPERIMENT STATION Author of " The Soil," " Fertilizers and Manures " THE ROTHAMSTED EXPERIMENTS 409 being placed on the line), and Director Hall states that the influ- ence of the fertilizers can scarcely be detected six inches over the line, either in the yield or in the character of the herbage, despite the exceedingly marked differences that have developed between the plots. THE CHEMISTRY OF ROTHAMSTED FIELD EXPERIMENTS While much chemical work has been carried on from the begin- ning by the Rothamsted Experiment Station in connection with the field experimentation, it has been directed more largely to investigations concerning the composition of the crops produced than to soil analyses. From most of the fields few soil analyses have been reported; but in the case of Broadbalk field some very complete and thorough investigations have been made of several plots. The results are briefly summarized in Table 73. The soil samples upon whose analysis the data in Table 73 are chiefly based were collected in 1893, fifty years from the beginning of definite plot experiments on Broadbalk field, although on several plots the final systems of treatment were not fully settled until 1852. For this reason the average yields are given for the forty- two years, 1852 to 1893, but tne plant food removed and applied is computed for the fifty years; and, in the main, estimation of plant food removed is based upon the analysis of the actual crops harvested. In computing from percentages found by analysis to pounds per acre, Doctor Dyer has used as the weight of fine dry soil per acre 2,590,000 pounds for the first 9 inches, 2,670,000 pounds for the second, and 2,790,000 pounds for the third 9 inches. The cor- responding weights, including stones, are 3,120,000, 3,040,000, and 3,000,000 in round numbers. (For the common silt loam soils of Illinois, we have found 300,000 pounds per acre-inch to be practi- cally correct. This would correspond to 2,700,000 pounds per acre for a 9-inch stratum, or 2 million pounds for a 6|-inch stratum.) In considering the composition of the soils represented in Table 73, it should be kept in mind that the nitrogen reported is total, while the phosphorus and potassium are the portions soluble in strong acid. In the case of phosphorus, this usually represents 4io INVESTIGATION BY CULTURE EXPERIMENTS nearly the total, but in different soils it may vary from the total to as low as 75 per cent of the total; while only from 15 per cent to 30 per cent of the total potassium is acid soluble, although in some abnormal soils, as certain peaty soils, it may reach 60 per cent or more of the total. Potassium varies greatly in this respect at different depths in the same field. Thus, on the gray silt loam prairie of the lower Illinoisan glaciation the percentage of the total potassium that is soluble in hydrochloric acid (specific gravity 1.115), during ten hours' digestion at the temperature of boiling water, varies from as low as 14 per cent in the surface soil to as high as 38 per cent in the subsoil of the same field. Because of these facts the determinations of potassium reported in Table 73 must not be considered as the basis for any final con- clusions, but the phosphorus data must be approximately correct, and the results for nitrogen are practically exact, except for pos- sible variation (from the field average) of the samples of soil col- lected. The data are all reported for 9-inch strata of soil, corre- sponding to the depths to which the samples were taken. Table 73 contains much information, but it is self-explanatory. Thus, plot 7, which has received both ammonia and the regular minerals (as more fully explained in the previous pages), produced an average yield of 32.8 bushels of wheat and 3668 pounds of straw, and 2450 pounds of nitrogen, 482 pounds of phosphorus, and 2117 pounds of potassium were removed in the crops during the fifty years; while there were applied 4300 pounds of nitrogen, 1336 pounds of phosphorus, and 4181 pounds of potassium. The appli- cations have been nearly double or more than double the amounts removed. If we compare plots 7 and 3, we find in the first 9 inches about 23 per cent more nitrogen, 71 per cent more phosphorus, and 19 per cent more potassium in plot 7 than in the unfertilized plot 3. On the other hand, in the lower strata, plot 7 contains distinctly less phosphorus than plot 3 or 4, but this difference is much less marked if plots 12, 13, and 14 be considered. The variations in the lower strata are too great to draw conclusions from any one plot, and this is more especially true as regards potassium. In the lower part of Table 73 are recorded some average results that should be more significant, at least for nitrogen and phos- THE ROTHAMSTED EXPERIMENTS 411 ^ U O < W .. 3 -o < o M > Q 2 < 2 POTASSIUM (Lb.) 1 .as •a<2 1 6ss ^sg'^ %£&$ £S~po£ PO •* to PI O H, 0 1 Os -o-o c s o o ftft so to C u H) u OS H, M O O PI i- 2 M 2 °~ a;ssi HI 00 O- Q' •0 Hi PI M t^oo oo PI sO O to 0 PHOSPHORUS (Lb.) 1 .ss r Wi M oo oo 0 M H, sO O 00 to O O-OO t^ HI OS OS PO PO O HI PI n 7 I/", -J- in in C C O O ft ft O 00 •* C 4> u u HI 6 pUO33g 1000 t^ OS HI PO 00 PO to to T}- o Os ro W O (A in -a -a c e o o ft ft c u I 6 pUODSg ON O W rj- Os PI O t^ HI 00 OS 0-00 M H, Os •* PI 00 sO t PI •* PI PI PI PI HI O 0 ssqouj 6 jsjij hH d O 10 r>. ^f »o w c* sO 00 PI Os O HI r^ r^ PI so PO HI Os O O PI II -t oS u; poj;ddy s|| e O O 0 g o o o o o o o o o o o o o 0 PO o -t I OS DI p3AOlU3>{ o o to O o o o o O to O to o o o o to to to o Os O Pi PI sO O 0 2 c s^ WHEAT, AVERAGE §? ( 0) *T!JJS PI O 00 PI 00 00 O POsO Os PI PI PO PO PO ne) n;wo SO 00 to 00 00 10 Os to H PI OC POM M" -3- PI OS HI ••t O i-i O PI PO PO PO SOIL TREATMENT APPLIED EVERY YEAR FOR 50 YEARS (OR LESS) ''^i in Amm. salts and phosphate . . Amm. salts, phos., and sodium . Amm. salts, phos., and potassiui Amm. salts, phos., and magnesi Farm manure (15.7 tons) . . Unfertilized Unfertilized since 1852 . . Minerals (P, K, Mg, Ca, Na, Amm. salts and minerals Ammonium salts . . . . Amm. salts since 1850 . . Average of plots receiving . . 1 Average of plots not receiving Excess Balance • ». >> o £ to ) C 3 in a C HI ft ft •a "ft ft oS C O OS "o 1 s u o 1-1 u |o C* CO ^" ,0,,8-S HI PI PO Tf 4i2 INVESTIGATION BY CULTURE EXPERIMENTS phorus. The line marked " average of plots receiving " includes the average of plots 7 to 14 for nitrogen, of plots 5, 7, and n to 14 for phosphorus, and of plots 5, 7, and 13 for potassium; while in the next line are given the averages for the plots as indicated (*) for the respective elements. By subtraction we find the excess or deficiency ( — ). The difference between the sum of the ex- cesses found in the three soil strata and the balance with respect to applications and removal in crops gives us the apparent loss in 50 years of the respective elements, and indicates an annual loss per acre of 55 pounds of nitrogen, 8|- pounds of phosphorus, and 59 pounds of potassium, — losses besides those which are ac- counted for in the crops removed. In terms of plant food applied, these losses amount to 63 per cent of the nitrogen, to 31 per cent of the phosphorus, and to 69 per cent of the potassium. There are two principal ways in which plant food may be lost from the surface soil, aside from removal in crops; namely, by leaching and by erosion (including erosion by wind action as well as by water). In addition, some mechanical mixing of surface and subsoil may occur, because of burrowing animals and insects, soil cracking, etc., and losses of nitrogen by dentrification are possible, though not probable to any important extent under normal conditions. In Table 74 is recorded the average composition of waters col- lected from the tile drains of Broadbalk field during the years 1866, 1867, 1868, and 1869. These averages represent the mean of a large number of analyses made by Doctor Augustus Voelcker. The results are given in Table 74 on the basis of 3 million pounds of water, which corresponds to a drainage of 13^- inches per acre, which is less than the average annual drainage (14.73 inches) from the uncropped bare soil of the Rothamsted drain gauge (see Table 65), and more than Dyer's estimate (10 inches) for the ordi- nary cropped soils at Rothamsted, but probably not more than the average for the cropped soils of central United States. The actual amounts found in pounds per million of drainage water will be secured by dividing these data by three. Some apparent relationships may be noted between the appli- cations and losses of certain elements, and also between certain elements in the drainage water, such as calcium and sulfur, but THE ROTHAMSTED EXPERIMENTS 413 -• - 1 00 ON oo co t^ m r-l M 00 co CONO NO O H 3 < W 5- K ON W TfvO c< PI PI IONO t-~ t^-00 £wS H M u "^ M PI NO CO CO PI OO OO CONO t^ HI HI C^ \O m co O oo ON ON ON M M HI M Th rl- t>. CO AH O co- co M PI PI PI PI H O *n l/"> rj- ro PI M CO M w <*^-' 00 O PI CO M O 00 00 00 00 00 0 0 H M $ co mNO •* O IONO MOP! H M HI ON NO Tj- PI M u 3 2U oj CV J O UH < H a in d 00 CO COOO NO t^- ON O •* moo 00 O co PI oo PI 00 HI 00 00 O O PI 00 00 t^ PI O NO HI Jl§ NO O HI HI CO PI t*~» ON ON CO O O oo Pi Pi co co •*!• £ O vn HI PI NO rO 10 HI COOO CO co TJ- ^- ^~ HI M CO «0 CO CO co < H ° H _oA 10 10 IO t^» ON in HI ON COOO •* J«SS CO M in in in O M « CO •* PI PI CO CO CO § 11*11 « c o c PI PI PI PI ON ON ON ON r^ ON M CO to o O PI 't M PI O ON CO ON t^- ^- t^ M ON O 2" c r. o c p< o pi o^T* o c • o r* CONO ON § -*00 PI a H I/- NO vO NO NO NO NO 00 00 oo 00 00 NO g 00 § 1? . . . . ^ "5 •=' 3 in < H g * S » s • V ro x £ K S en 3 2 t^ in H I* E e S Q. C DH • E »r . *- «" -o J2 _0 g O " ' 414 INVESTIGATION BY CULTURE EXPERIMENTS the points of chief interest are that from the four or five best yielding plots the annual losses per acre are probably not more than 50 pounds of nitrogen, i^ pounds of phosphorus, and 7 pounds of potassium. Dyer assumes an average drainage of 10 inches per annum for Rothamsted, which would reduce these figures by one fourth, but he also suggests that the losses in drainage are probably greater now than they were in 1866-1869. While the drainage certainly accounts for most of the loss of nitrogen, there remains not accounted for an annual loss of about 7 pounds of phosphorus and 50 pounds of potassium per acre. Dyer suggests that these losses are to be accounted for by descent into the subsoil. The data for potassium, representing the " acid- soluble" only, are too uncertain to warrant any conclusion. In the author's opinion it is not improbable that some of the potas- sium, applied as soluble potassium sulfate, may have reacted with silicates and formed compounds that are not dissolved by strong acid. This seems less doubtful when we consider the proper- ties of cement, and the changes that occur even in a short time in the " setting " of that material. The data afford practically no evidence for the "descent into the subsoil of either phosphorus or potassium. The phosphorus determinations so nearly represent the total amounts that they serve satisfactorily for general computations, and as an average they show less phosphorus in the subsoil of the plots where phos- phorus has been applied, although plots 5 and 14 are exceptions. At least most of the unused phosphorus remains in the plowed soil. Thus plots 4 and 5 have produced almost the same average yields, and plot 5 contains 1121 pounds more phosphorus in the first 9 inches, but only n pounds more in the second depth, than plot 4. The third depth shows a different relation, but this is reversed in the case of plots lob and n, whose average yields are not markedly different. With 2250 pounds of phosphorus in the surface 9 inches, it would require about one inch of erosion in 35 years to account for an annual loss of 7 pounds of phosphorus. This would also ac- count for 10 pounds additional loss in nitrogen, and it seems the most probable explanation. Land that has sufficient slope to provide any surface drainage will suffer some erosion if such drain- THE ROTHAMSTED EXPERIMENTS 415 age occurs when the land is not covered with vegetation. When- ever roily water leaves a field, some soil goes with it; and the loss of a tenth of an inch in three or four years is not improbable, even for nearly level land, if annually cultivated, especially if torrential rains sometimes occur (see record of Barn field) Whether one assumes 10 inches or 13 j inches of drainage, there is some degree of correlation between the computed calcium carbonate equivalent to the calcium found in the drainage water, as shown in Table 74, and the loss of calcium carbonate from the sur- face soil of Broadbalk field, as recorded in Table 27. While there are marked discrepancies, both methods agree that, as an average, more calcium is removed from the plots receiving ammonium salts. Analyses made of surface soil from the barley plots on Hoos field in 1889 show in 2 million pounds of soil 960 pounds of phos- phorus as an average in the 8 plots receiving no phosphorus, 1560 pounds as an average in the 8 plots receiving acid phosphate with- out rape cake, 1900 pounds as an average in the 2 plots receiving acid phosphate and rape cake, and 1540 pounds in the farm manure plot (7-2). Table 75 shows the nitrogen content of the surface 9 inches of the different plots on the Agdell rotation field. From the data thus far reported, the nitrogen content of the soil on Agdell field appears to be decreasing about 10 pounds a year, except on the legume plots which receive rape cake and ammonium salts, where an increase is shown on the " fed " plot amounting to 212 pounds in 16 years. While the individual variations are great, the results indicate a slightly larger loss of nitrogen in the legume rotation than with fallow, but where nitrogen is applied, the op- posite is shown. The factors of erosion and deposition and of difficulty in securing samples (by the method used) which fairly represent the average of the plot are sufficient to account for any of the changes indi- cated by these analytical data; and it may be stated that the to- pography of Agdell field suggests the possible influence of such factors. On the other hand, the indicated gain of 180 pounds of nitrogen per acre during seven years with the legume rotation on the unfertilized land, with all crops removed, has actually been 4i 6 INVESTIGATION BY CULTURE EXPERIMENTS TABLE 75. AGDELL ROTATION FIELD, ROTHAMSTED Nitrogen in Surface 9 inches; Pounds per Acre SYSTEMS AND SOIL TREATMENT Nov., 1867 (After Wheat) OCT., 1874 (After Clover or Fallow) NOV.-JAN., 1883-1884 (After Wheat) Legume, unfertilized, turnips removed Legume, unfertilized, turnips fed off . Legume, phosphorus, turnips removed Legume, phosphorus, turnips fed off . 3127 3IJ3 3185 33^2 33° 7 2849 2978 317° 3*39 2892 2897 3110 Average of four plots ?l8S 3076 3OIO Loss in 1 6 years 17s Fallow, unfertilized, turnips removed . Fallow, unfertilized, turnips fed off Fallow, phosphorus, turnips removed . Fallow, phosphorus, turnips fed off 3127 2959 2938 2976 3XI3 2976 2753 2702 2952 2724 2786 2947 Average of four plots 3OOO 2842 28 =n Loss in 1 6 vears 147 Plots receiving Minerals, Rape Cake, and Ammonium Salts Legume, turnips removed 30 ?8 -2006 -2QI2 Legume, turnips fed off 3T94 3293 3408 Average of two plots . . ... -2116 2IQC •22IO Gain in 16 years (04) Fallow, turnips removed 3OIO 2887 2918 Fallow, turnips fed off •2107 2Q4O 2986 Average of two plots ^IO4 2QI4 2Q1T2 Loss in 16 years 1^2 cited by a writer for the agricultural press in support of the teach- ing that crop rotation will maintain the fertility of the soil. Probably no information could now be furnished by the Roth- amsted Station that would be of greater interest to the agricul- tural world than the changes that have occurred in the nitrogen content of the Agdell plots since 1883. In Tables 76 and 77 are recorded the average composition of the Agdell crops (except barley not reported) and the Park hay, re- THE ROTHAMSTED EXPERIMENTS 417. spectively. The data are given in pounds per acre removed in the actual crops grown, — on the plots receiving both minerals and nitrogen in case of the Agdell field. TABLE 76. AVERAGE COMPOSITION OF CROPS GROWN ON AGDELL FIELD Pounds per Acre actually removed in the Crops Harvested CROPS ANALYZED CROP YIELDS (Approx.) NITRO- GEN (N) PHOS- PHO- RUS (P) PO- TAS- SIUM (K) MAG- NE- SIUM (Mg) CAL- CIUM (Ca) SUL- FUR (S) SODI- UM (Na) CHLO- RIN (Cl) Wheat, grain . . Wheat, straw Wheat crop . . Swede turnips Turnip leaves Turnip crop . . Beans, grain . . Bean straw . . Bean crop . . . Clover, first crop Clover, second crop Clover, both crops 30 bu. 1.9 T. 28.3 13-4 6.8 2.1 8.5 21.8 2.1 2.O •7 6.4 .2 2.1 .04 .62 .OI 3.28 41.7 75-5 18.5 8.9 8.6 1.9 30-3 65-7 11.9 4.1 3-7 •5 7-i 15.6 9.1 2-3 10-4 2-3 .66 7-5 • 7 3-29 5-2 5-5 i6T. 2T. 94.0 49.6 14.0 10.5 S-o •9 77.6 12.6 5-8 4-2 i-5 1.6 24.7 i-5 i7-5 12.7 1.0 I.I 8.2 .6 9-3 10:7 •9 2.2 23 bu. .9T. 63.6 i°33 56.0 5-9 7-8 4-5 18.4 58.6 26.5 3-1 ii. 6 5-9 19.0 92-5 36.8 2.1 3-7 2.1 9-9 1.9 .8 3-i ii 7 6.1 3-o T. 159-3 12.3 85.1 17-5 129-3 5-8 2-7 17.8 The results for wheat are the average of the eight crops grown from 1850 to 1879; for turnips, the average is for three crops (1864, 1872, and 1876); for beans, six crops (1854 to 1870 and 1878) ; and the clover data are averages of 1850 and 1874 for the first and second crops. In Table 77 the data represent, as a rule, in pounds removed per acre per annum, the averages for the 18 years, 1856 to 1873 (first crops only). This mass of data concerning actual results with mixed grasses is especially valuable for the use of the analytical mind. A cur- sory examination will show that, within the groups, the total yield of organic matter correlates better with the nitrogen and phosphorus removed than with most other constituents, while the amount of potassium removed seems to be controlled by the 4i8 INVESTIGATION BY CULTURE EXPERIMENTS < a If PI PI M oo o P) HI mo M P) in r- HI O "~ PO U" rt- Pi o o oo o C 00 00 •* tf T}- ov PI O PO PO •* P^ vO PO PO PO AZ in PO t^- inn, r-p. M Ov PI POvO O 00 0 HI oo r- rt •* PI OQ oo ° CO POM PI HI Ht t-l HI P4 PI ?5 HI PI PO to r*" oo m PI PO w 2 en \o 5s o s c/2 vO O 00 5-t ^ 0«| S-SS5 POOO t— PO PI t>. PO PI oo PI PO Pt mvO O CO PI m 0 ro COOO O O HI HI PI HI 00 OvOO C=i 00 0- 0 PO r- 0 r^* pi PO M Tj- 00 vO t-vo 0 H. HI oo m 0 0 0 2 » oo oo PO 00 00 m Ov ^- in m PI M •* »- 0 PI PO PO PO PI PI £_ ~ < M) a 2 i 6 z g a w HI O »t vo m PO HI PI £% --- PO Tj- m •* 00 «^ O 0 CO vJTR w > °I|B 00 PO O- 0 tj- PO PI M PO Tf O M W CO PO t PO vO 00 PI PI X •* O POOO TJ- in in rj- < ~c AH O a. < OS vO t- PO vo O in HI O O tf- CO P* oo in PO PI 0 0 PI PO t>» rO v> \O ro r^ 10 (N r^ in PO M O IO CO OO O PI PO vO -t o PI Ov in o- oo •* i^ PI rf in m m 00 00 ro m **• PO rf m "« 2 Q S rf V 0 C O o « PI PI PI Ov Ov O 10 O Ov -t O PI 0 Ov 9 PI t-^. t^ pi Ov PI PI Ov t^ PI VO Tf & 2' W fStfl « c HI M N HI n U ll s "• °c d-d- 3 c o o a c o o c c none none \o POO OO ^OO vO vO 00 00 ne With every crop there has been a decrease in yield, varying from £ bushel of wheat, or 4 per cent of the crop, to 14 bushels of corn, or 33 per cent of that crop. The average yearly value of produce from one acre has decreased from $11.05 to $8.18; and this $2.87 represents the total decrease, not for a 24-year period, but for a PENNSYLVANIA FIELD EXPERIMENTS 429 TABLE 80. PENNSYLVANIA EXPERIMENTS : FOUR-YEAR ROTATION Records per Acre for Three Complete Rotations, 1897 to 1908 TREATMENT FOR EACH FOUR YEARS AVERAGE OF 12 YEARS FROM FOUR ACRES Plot No. Important Elements Applied Ni- tro- gen per Acre (Lb.) Form of Nitro- gen Applied "lorn Av. Bu. per Acre Oats Av. Bu. per Acre Wheat Av. Bu. per Acre Hay Av. Lb. per Acre Value of the Four Crops Value if Un- fertil- ized Value of In- crease Cost of Treat- ment Profit or (-Loss) z • 9 4 S'one . . N (48 Ib.) P (42 Ib.) K (166 Ib.) 23.6 25.8 35-8 25-5 2I.O 23-5 30.8 24.9 9.1 10.7 15-5 10.4 155° i6co 2950 1820 825.58 28.64 41.47 29.14 $25-58 26.06 26.54 27.03 48 Dried blood . 2.58 14-93 2. II $ 7.20 5-04 0.96 (-4.62) 9.89 6 7 8 0 IO II 12 NP . . NK . . PK . . 48 48 Dried blood . Dried blood . 37-6 28.8 45-i 38.6 35-5 28.3 37-2 29.9 19.6 12.3 19.7 14-5 3470 2340 4360 3070 47-94 34-20 53-82 41.84 27-51 27.99 28.48 28.96 20.43 6.21 25-34 12.88 12.24 17.16 15.00 (?) 8.19 (-10.95) 10.34 12.88 Manure for 10 years prior to 1882 NPK . . NPK . . NPK . . NPK . . 48 96 144 60 Dried blood . Dried blood . Dried blood . Blood and bone 44-5 44-8 46.5 47-9 37-7 38.5 38-7 37-5 22.6 25-3 27.2 22-7 4340 4060 4320 4330 55-73 57-12 59-89 56.90 29.44 29-93 30.41 30.80 26.29 27.19 29.48 26.01 22.20 29.40 36.60 23.16 4-09 (-2.21) (-7.12) 2.85 y Land-plaster (CaSO4), 640 Ib. . 29.6 24.4 I2.O 2140 32.50 31-38 1. 12 1. 60 (-.48) 14 IS None . . PK . . 28.5 43-9 47.2 38.7 23.6 33-9 35-5 33-8 12. 1 19-3 25-4 22.6 2110 4440 4150 3300 31.86 52.37 57-40 40. 6£ 31-86 31-77 31.68 31-50 2O.OO 25-72 1 8.09 15.00 3.60 22.2O 5.60 22.12 (-4.H) 16 Yard manure, 12 tons .... 17 NPK . . 48 IDried blood . 18 10 Yard manure, 16 tons .... 45-i 44-7 50.2 46.1 37-9 36.5 38.5 36.5 27.O 25-3 27.9 27.7 4440 4020 4710 3980 59-38 56.37 62.78 58.42 31-50 31-42 31-33 31-24 27.88 24-95 31-45 27.18 4.80 29.40 6.00 36.60 23.08 (-4-45) 25-45 (-9.42) NPK . , 96 IDried blood . 20 21 Yard manure, 20 tons .... NPK . . 144 IDried blood . 22 »3 Lime (CaO), 2 tons; yard ma- nure, 12 tons Lime (CaO), 2 tons 52.6 23-3 37-3 21.9 25-3 I4.I 4650 2340 61.26 31.62 3i-i5 31.06 30.11 .56 12. 6c 9.00 17-51 (-8.44) 24 25 26 «7 28 None . . PK . . NPKNa . NPKNa . NPKNa . 23-3 44.1 47-7 48.2 49.0 25.2 35-7 36.8 37-4 38.2 I3-I 20.5 23-6 26.2 27-1 2030 4200 4410 4460 4450 1 30.98 53-10 57-49 59.81 60.93 30.98 3i-i7 31-36 31-55 3i-74 21.93 26.13 28.26 29.19 15.00 22.20 29.40 36.60 6-93 3-93 (-1.14) (-7-41) 48 96 144 Sodium nitrate Sodium nitrate Sodium nitrate U CM U 10 K) M O O PK . . NPK . . NPK . . NPK . . 40-5 44.6 42.6 36.8 34-2 35-3 36.0 37-Q 26.1 25-7 37-i 25.2 I8.7 23-3 24-3 21.6 3850 3740 3010 2960 49.08 53-73 51-75 47.98 3i-93 32.12 32.31 32.50 17-15 21. 6l 19.44 15.48 15.00 22.2O 29.40 36.60 2.15 (-.59) (-9-96) (-21.12) 48 96 144 Amm. sulfate Amm. sulfate Amm. sulfate 33 34 35 36 Land-plaster (CaSO4), 640 Ib. . Ground limestone (CaCO3), 4 tons 24.7 28.8 50. 1 24.6 12.9 15.8 24.6 15-3 20SO 2470 4690 2130 31-66 36.26 59.96 33-27 32.69 32.88 33-07 33-27 (-1.03) 3.38 26.89 1.60 6.00 23.16 (-2.63) (-2.62) 3-73 NPK . . None . . 60 Blood and bone 12-year period. Of course, the actual decrease will grow less and less as soil depletion continues, even though the per cent of decrease remain constant, for, as already stated, it is as impossible to com- pletely exhaust a soil as it would be to exhaust a bank account under a contract that only 2 per cent of the remaining deposit 430 INVESTIGATION BY CULTURE EXPERIMENTS could be withdrawn at any one time. (Two per cent per annum is approximately the rate of decrease in crop values from the 20 un- fertilized plots in these experiments.) There are only four combinations of commercial plant food that have maintained the productive power of the soil, and these are all combinations of the three elements; plot n (with dried blood, 144 Ib. N), plots 27 and 28 (with sodium nitrate, 96 and 144 Ib. N), and plots 12 and 35 (with bone and blood, 60 Ib. N). However, as an average of the 24 years, the increase was not sufficient to pay for the cost of treatment on any of these plots. It appears, however, that during the second 1 2-year period plots 12 and 35 have, as an average, paid the cost of the plant food and left a net profit of $3.29 from the four acres. Thus it will be noted that the only plots receiving commercial plant food that has paid its cost even for the second 1 2-year period and that has also fully maintained the crop yields are those treated with ground bone. The difference in favor of ground bone is not sufficient to show that it is distinctly better than acid phosphate, but we may surely conclude that the in- soluble bone is at least as good as the acidulated form. During the first 1 2-year period the net profit from the use of manure decreased as the amount of manure increased above 12 tons, but during the second 1 2-year period the value of the 1 2-ton application is more than twice as much as during the previous 12 years, and the greatest net profit per acre is where the heaviest applications are made (counting 30 cents a ton for manure), but the value per ton is still greatly in favor of the lighter application, the first 12 tons being worth $2.14 a ton and the next 8 tons only 72 cents, compared with $1.14 and 4 cents, respectively, for the first 12 years. While the larger amounts of manure show a distinct cumulative effect ($56.31 to $62.78, or $6.47 a year from the four crops), the lightest application has but little more than maintained the earlier crop yields, the markedly greater apparent profit dur- ing the second 12 years being due to the decreased yields of the unfertilized land. In Table 81 is given a summary of the effect of treatment over the 24-year period, and also a concise statement showing the actual or absolute profit or loss from every system, based upon the aver- age yields secured during the second 1 2-year period in comparison PENNSYLVANIA FIELD EXPERIMENTS 431 TABLE 81. PENNSYLVANIA EXPERIMENTS : FOUR-YEAR ROTATION Summary of Financial Results from Soil Treatment in Four-year Rotation TREATMENT FOR EACH FOUR YEARS FROM FOUR ACRES, ONE EACH OF CORN, OATS, WHEAT, AND HAY I I; i a 3 4 6 7 Important Elements Applied Ni- tro- gen per Acre (Lb.) Form of Nitrogen Applied Effect of Treatment (Av. of 24 Years, 1885 to 1908) Value of the Four Crops Av. of 2d 12 Yr. Value if Un- fertil- ized Av. of ISt 12 Yr. Value of Increase of 2d over ist 12 Yr. Cost of Treat ment For Permanent Systems Profit Loss Profit Loss None . N (48 Ib.) P (42 Ib.) K(i661b.) 825.58 28.64 41.47 29.14 $37-77 38-15 38.53 38.91 *=: $12.19 16.71 2. 10 19.73 48 Dried blood . . 7-13 4.18 (-9-5I) ( o& 7.20 5-04 9.96 7.28 NP . . NK . . PK . . 48 48 Dried blood . . Dried blood . . 5.06 5-32 12.02 11.77 47-94 34-20 53-82 41.84 39-29 39-67 40.05 53-23 8.65 (-5.47) 13.77 (-11.30) 12.24 17.16 15.00 — 3-59 22.63 1-23 ii-39 — 8 9 10 II ia y 14 y Manure for 10 years prior to 1882 . NPK . NPK . NPK . NPK . 48 06 144 60 Dried blood . . Dried blood . . Dried blood . . Blood and bone . — •33 6.98 13.10 2.88 55-73 57-12 59-89 56.90 40.81 41.19 41-57 41-95 14.92 15.93 18.32 14.05 22.20 29.40 36.60 23.16 — 7.28 13-47 18.28 8.21 Land-plaster (CaSO4), 640 Ib. . . .12 32.50 4a-33 (-0.83) i. 60 — "•43 None . PK . . . . . i. 20 16.15 31-86 52.37 57-40 49.68 42.71 42.64 42-57 42.50 (-10.85) 9-73 14.83 7.18 15.00 3.60 22.20 10.85 5-27 15.02 8.33 11.23 1 6 17 18 Yard manure, 12 tons NPK . 48 Dried blood . . Yard manure, 16 tons 16.27 16.73 9-15 14.79 59.38 56.37 62.78 58.42 42.43 42.36 42-29 42.22 16.95 14.01 20.49 16.20 4.80 29.40 6.00 36.60 12.15 14.49 15-39 20.40 iSL 20 21 22 33 24 2.S 26 27 sL 39 30 ji 3_2_ 33 34 NPK . 96 | Dried blood . . Yard manure. 20 tons NPK . 144 | Dried blood . . Lime (CaC 12 tons Lime (CaC )), 2 tons; yard manure, 9.64 10.45 61.26 31.62 42-15 42.08 19.11 (-10.46) 12.60 9.00 6.5i 19-46 None . PK . . NPKNa NPKNa NPKNa 2-59 30.98 53-10 57-49 59.81 60.93 42.00 42.26 42.52 42.78 43-04 (-11.02) 10.84 14.97 17.03 17.89 15.00 22.20 29.40 36.60 1 1. 02 4.16 7-23 12.37 18.71 48 96 144 Sodium nitrate . Sodium nitrate . Sodium nitrate . 1.49 7.22 13-99 — PK . . NPK . NPK . NPK . 48 96 144 Ammonium sulfate Ammonium sulfate Ammonium sulfate 1.70 4.68 "•37 23.16 49.08 53-73 51-75 47-98 43-30 43-56 43-82 44.08 5.78 10.17 7-93 3.00 15.00 22.20 29.40 36.60 — 9.22 12.03 21.47 32.70 Land-plaster (CaSO4), 640 Ib. . . Ground limestone (CaCO3), 4 tons E 2.83 3-29 3-74 31-66 36.26 59.96 33-27 44-34 44.60 44.86 45-13 (-12.68) (-8.34) 15.10 (-11.86) i. 60 6.00 23.16 E 14.28 14-34 8.06 11.86 35 3f> NPK . None . 60 Blood and bone . with yields of the unfertilized land during the previous 12 years. By this means only are we able to avoid the exaggerated influ- ence which is always credited to the soil treatment when com- parison is made with the decreasing productiveness of unfertilized check plots. 432 INVESTIGATION BY CULTURE EXPERIMENTS For this purpose these Pennsylvania data are probably the most valuable the world affords; and, in the author's opinion, this volume presents no more significant facts than are contained in Table 81. The decrease in productive value of the unfertilized plot is markedly uniform, notwithstanding the variation among those plots, the average decrease in value per acre per annum being $2.87 and the widest variation from that average being 18 cents. Plot 8, which had received manure during the 10 years previous to 1882, shows the same decrease as the other four unfertilized plots, the average for the four others being $11.46, while plot 8 shows $11.39. The average yield of the No. 8 plots during the second 1 2-year period is slightly less than the average yield of the four other unfertilized plots during the first period. From Table 81, it will be seen that, for permanent systems of farming, no form or combination of commercial plant food has been used with profit, the annual loss from four acres varying from $2. 46 with phosphorus alone, $3.59 with phosphorus and nitrogen, and $5 (as an average) with phosphorus and potassium, to $20.40 and $32.70 with the complete fertilizer carrying the largest amounts of dried blood and ammonium sulfate, respectively. Manure costing 30 cents a ton shows net profit in all cases, but the profit is greatly reduced by the addition of caustic lime at $4.50 a ton; although the lime produced sufficient increase to pay $2.14 a ton for it for use with manure, and the effect of the lime- manure treatment is distinctly cumulative, especially upon the clover and timothy, the yield of hay from the lime-manure plots being 640 pounds higher during the second 12 years than during the earlier period, and 500 pounds more than from the manure alone during the second period. Would ground limestone at less cost produce a greater benefit, and would the use' of phosphorus also with farm manure or green manure produce still greater net profit? The Ohio investigations answer the latter question with a most emphatic affirmative. (See Tables 37, 38, 39, and 396.) Thus it will be noted that, as an average of the same 12 years (1897 to 1908), the value of the produce per acre per annum is $14.35 where 12 tons of manure are used in the Pennsylvania PENNSYLVANIA FIELD EXPERIMENTS 433 four-year rotation, $13.76 where 8 tons of manure are used in the Ohio three-year rotation (corn, wheat, and clover, — see Table 396), and 17.29 where 40 cents worth of raw phosphate, or 80 cents' worth of acid phosphate, was used in connection with 8 tons of manure in the Ohio rotation. From Table 81 it can easily be determined that the absolute value per ton of manure for permanent systems is $1.24 for the smallest amount used, $1.06 for the medium amount, and $1.02 for the heaviest application. For the additional 8 tons (12 to 20) the manure was worth 71 cents a ton. Based upon comparison with the yields from the untreated land during the last 12 years, the 12 tons of manure for the Pennsyl- vania four-year rotation were worth $2. 14 a ton; while, for the same 12 years, the 8 tons of manure, in the Ohio three-year rotation, were worth $1.82 a ton for the yard manure and $2.41 a ton for the stall manure. (See Tables 37, 38, and 39.) Director Thorne has emphasized the fact that the Ohio experi- ments at Wooster were started on fields that had for many years been under exhaustive tenant husbandry, and the unfertilized plots at Wooster during the last 12 years are more nearly compar- able with those at State College during the same 12 years than dur- ing the first 12 years. Thus the average annual produce per acre for the same three crops, corn, wheat, and clover, was $10.35 f°r the first 12-year period and $7.77 for the second 12-year period, in Pennsylvania; while for the last 12 years the average value in Ohio has been $8.06, these values being based upon the normal unfertilized plots, the No. 8 plots at State College, and the No. i and No. n plots at Wooster (see Table 40) not being included. If the oats are included, the Pennsylvania figures would be $10.47 for the first 12 years and $7.61 for the second period. In Pennsylvania Bulletin 90 (1909), Director Hunt summa- rizes the results of the first 25 years covered by these experiments. The following tabular statement, containing figures based upon Pennsylvania values, may be of special interest to the student of Eastern conditions. The upper part of this table shows the total weights of the seven products harvested, including ear corn, corn stover, oats, oat straw, wheat, wheat straw, and hay; and the lower part shows the total 434 INVESTIGATION BY CULTURE EXPERIMENTS values at 75 cents per 100 pounds of ear corn, 32 cents a bushel for oats, $1.33 per 100 pounds of wheat, $2.50 a ton for corn stover and straw, and $10 a ton for hay. TABLE SIP. PENNSYLVANIA FIELD EXPERIMENTS PLANT FOOD APPLIED UN- FERTIL- IZED NITRO- GEN (48 Lb.) PHOS- PHORUS (42 Lb.) POTAS- SIUM (166 Lb.) NITRO- GEN AND PHOS- PHORUS NITRO- GEN AND POTAS- SIUM PHOS- PHORUS AND POTAS- SIUM BLOOD (48 Lb. N), PHOS- PHORUS, POTAS- SIUM BLOOD (96 Lb. N), PHOS- PHORUS, POTAS- SIUM BLOOD d44 Lb. N), PHOS- PHORUS, POTAS- SIUM YEARS POUNDS OF TOTAL PRODUCTS FROM FOUR ACRES. (Averages) 1882-86 1887-91 1891-96 1897-01 1902-06 14679 T4339 12611 9562 9848 14479 14060 11461 8326 8955 14628 15204 14647 12229 12907 14598 14476 12404 8780 958l 16176 16469 16622 14038 14358 I5031 15959 12840 10450 11778 16577 17090 17764 15440 16368 16889 17492 18352 15867 T6335 17994 18706 I94I5 16981 17780 17933 19210 19786 17221 18008 1882-06 I22IO "457 13922 11967 15534 12814 16647 16986 I8I37 18653 YEARS VALUES OF TOTAL PRODUCTS FROM FOUR ACRES. (Averages) 1882-86 1887-91 1892-96 1897-01 1902-06 $75-35 75-46 64.29 49.16 50.88 $73.61 74-13 58-57 42.36 45-5° $74-76 79.66 75-58 61.80 67.28 $73.90 74.61 61.34 43-63 47-3° $83-35 86.15 85-75 71.91 74.83 $74.82 77-85 62.88 5I-85 54-13 $85.34 87.56 89.08 76.81 83.73 $85.20 87.81 90-75 77.92 83.87 $89.21 93-49 95-59 83.07 90.92 191-53 94-70 96-56 85.25 95.87 1882-06 $63.03 $58.84 $71-79 $60.16 880.40 $64.31 $84.51 $85.10 $90.47 $02.79 1887-96 1897-06 $69.88 50.02 $66.35 43-93 $77-62 65-54 $67.98 45-47 $85.95 73-37 $70.37 52.99 $88.32 80.27 $89.28 80.90 $94-54 87.00 $95.63 90.56 The last two lines in the table are ic-year averages computed by the author, all other figures being copied from Pennsylvania Bulletin 90. In his discussion of these experiments, Doctor Hunt makes the following comments (Bulletin 90, page 14) : "The most striking fact brought out by this table is that the application of 48 pounds of phosphoric acid and 100 pounds of potash in alternate years to a rotation consisting of corn, oats, wheat, and mixed hay (timothy and clover), namely, to the corn and wheat, has, during twenty-five years, maintained the crop-producing power of the soil. There is no evidence thus far to show but what the supply of nitrogen can be indefinitely maintained on this limestone soil by means of a rotation containing clover, provided the mineral fertilizers are abundantly supplied." PENNSYLVANIA FIELD EXPERIMENTS 435 These statements, if true, are of tremendous significance to American agriculture, for they refer to the oldest experiments of the kind in the United States; furthermore, the phosphorus- potassium plot is repeated four times in every series, so that the average results are from 16 different plots of normal soil every year for twenty-five years, and they must be considered highly trust- worthy. The small amount of limestone contained in this Penn- sylvania soil can very easily be supplied to any other soil by the direct application of ground limestone. It will doubtless be agreed by all that the results of the first few years at the beginning of a rotation and fertilizer experiment are not to be considered as comparable with the subsequent results. There are several reasons for this; but, for the present purpose, it is sufficient to consider that nitrogen may not have been a limit- ing element for all crops at the beginning. The data given in Table 8iP are not satisfactory for making any study of this special point, because the averages for the unfertilized land include the results from plot 8 which is represented to have received annual applications of manure during the ten years previous to 1882, because of which the addition of nitrogen alone appears (from Table 8iP) to have actually decreased the crop yields, which is not the case if we accept the system of comparison adopted for Tables 78 to 81. It must be evident from every point of view that nitrogen was not the limiting element for all crops at the beginning of these experiments. It is evident, however, that phosphorus was the principal limiting element at the beginning. Now, for the sake of simplicity, let us assume that from a given type of very uniform soil (see Table 87) sufficient phosphorus will become available during the season (1903) to meet the needs of a 54-bushel crop of corn (plot 102), while sufficient nitrogen will be liberated for a 62-bushel crop. The application of nitrogen with- out phosphorus could not be expected to appreciably increase the yield (plot 103), while the addition of sufficient phosphorus with- out nitrogen should increase the yield from 54 to 62 bushels, but unless nitrogen was also supplied, the yield could not be expected to go above 62 bushels. However, by applying nitrogen in addition to phosphorus, the yield might be still further increased (as to 69 436 INVESTIGATION BY CULTURE EXPERIMENTS bushels on plot 106) to a point where perhaps the supply of avail- able phosphorus again becomes the limiting factor. In other seasons or in later years, these conditions may become reversed, with nitrogen as the most limiting element, and phosphorus with little or no effect except in addition to nitrogen. (Note the results for 1907 and 1908, in Table 87.) We can conceive of conditions under which the supply of nitro- gen naturally liberated from the soil, when supplemented by that secured from the air by clover grown in the rotation, will meet the needs of the crops grown for several years, during which the nitro- gen does not become the limiting element to any marked degree, and it must be plain that in such case the crop yields give little or no information concerning the maintenance of nitrogen in the soil. Thus, it is only after nitrogen becomes the limiting element, in any given system, that the crop yields become an index as to the possible permanency of the nitrogen supply. In soils that are markedly deficient in phosphorus, that element may still remain the limiting element after the first small appli- cation has been made, provided the increased supply of available phosphorus is not sufficient to raise the crop yields to the point where nitrogen, for example, becomes the limiting factor; and it is easily conceivable that the increase produced by supplying po- tassium in addition to phosphorus, in the Pennsylvania experi- ' ments, was due, in part at least, to the power of potassium salts to hold the phosphorus in available form. Even where heavy applications of potassium were made, the sodium nitrate was more effective than dried blood, and, if only sodium nitrate had been added with phosphorus, the sodium would very probably have produced nearly as marked results as were produced by potassium. There are too marked variations among duplicate plots on the Pennsylvania field to justify fine distinctions, and even on more uniform land there are many factors involved with different crops and different seasons; but we dare not ignore the fact (Table 8iP) that the average value of the crops from four acres receiving phos- phorus-potassium treatment decreased from $88.32 to $80.27 during ten years, from 1891-1892 to 1901-1902, which are the middle points of the two lo-year periods. Whether we consider the values or the pounds of products, the apparent decrease is PENNSYLVANIA FIELD EXPERIMENTS 437 approximately 10 per cent in 10 years, and if this rate of decrease continues, we may expect the average values to drop during suc- cessive lo-year periods from $80 to $72, to $65, to $59, to $53, and to $48, in the next 70 years. It will be noted that the dividing point between the two lo-year periods in Table 8iP is exactly the same as between the two 12- year periods referred to in Tables 79 and 80; and it may also be noted that, as an average of the four phosphorus-potassium plots, the average yields during the second 1 2-year period show 6.4 bushels less corn, 8.3 bushels less oats, and 25 pounds less hay, but with 3.5 bushels more wheat, than during the first 12 years. These figures mean that for each rotation (four years) the yields have decreased by 2.1 bushels of corn, 2.8 bushels of oats, and 8 pounds of hay, while the yield of wheat shows an increase of 1.2 bushels. The algebraic sum shows, as an average, that each re- curring rotation produces $2.36 lower crop values from an acre of land than during the preceding four years. All this must remind us of the mineral plot on Agdell field, where the yields of turnips and legumes are still well maintained, and the wheat yield has appreciably increased, while only the barley has very markedly decreased. Mathematically, it is not possible for the roots and stubble of the clover crop to furnish sufficient nitrogen for the other four crops, — timothy (associated with the clover), corn, oats, and wheat; but the question again arises, whether important amounts of atmospheric nitrogen may not be fixed that are not thus ac- counted for. It is fully established that the azotobacter (and possibly other similar bacteria) fixes measurable quantities of free nitrogen under favorable conditions; and it is also fully es- tablished that the bacteria which commonly live in symbiotic relationship with legume plants can fix appreciable amounts of free nitrogen, under suitable artificial conditions, and entirely independent of legume plants. It is thus conceivable that these may fix nitrogen to a greater or less extent while they continue to live, not in the tubercles of growing clover, but upon the dead and decaying residues; and, if such is the case, it is exceedingly probable that the presence of carbohydrate matter (as in plant residues) and a liberal supply of available mineral plant food in a 438 INVESTIGATION BY CULTURE EXPERIMENTS limestone soil, will furnish the very favorable conditions, although the data thus far reported from Agdell field (Table 75) show a greater average loss of nitrogen (245 pounds from the surface 9 inches only) from the phosphorus plots than from the untreated plots (105 pounds) in the legume rotation; while, as an average of the four plots, the fallow rotation lost less nitrogen than the legume system. It should be kept in mind, also, that the organic matter of the soil contains nitrogen as well as carbon, and that the amount of combined nitrogen liberated from this organic matter may be nearly or quite sufficient to meet the needs of the bacteria that can be supported by the carbonaceous food. In laboratory cultures the fixation of nitrogen amounts to about 10 milligrams for each gram of sugar (mannite) consumed by the "free-living" bacteria.1 Thus the amount of nitrogen fixed is equal to about i per cent of the carbonaceous food consumed; whereas the organic matter of the soil contains, as a rule, more than 2 per cent of nitrogen. On Broadbalk field the nitrogen 2 content of the surface 9 inches decreased during 28 years (1865 to 1893) by 285 pounds (from 2722 to 2437) on plot 3 (unfertilized), by 265 pounds (from 2782 to 2517) on plot 5 (minerals), and by 63 pounds (from 3034 to 2971) on plot 7 (minerals and 86 pounds of nitrogen) ; while the only in- creases shown are 633 pounds (from 4343 to 4976) on plot 2 (farm manure), and 131 pounds (from 2991 in 1865 to 3015 in 1881 and to 3122 in 1893) on plot 14, which receives ammonium salts (86 Ib. N), acid phosphate, and magnesium sulfate. (The possibility of erosion or deposit from surface washing should not be over- looked. Compare the nitrogen content of plots u, 12, 13, and 14 with respect to each stratum, as shown in Table 73.) 1 In this connection attention is called to the point that if increased growth of plants is caused by the use of pyrogallol, as reported from the unverified experi- ments of Whitney and Cameron, it may be due to the fixation of free nitrogen by the nonsymbiotic bacteriv that find in pyrogallol a suitable carbonaceous food supply. It is known that the addition of sugar to ordinary soil deficient in nitrogen will increase the growth of nonleguminous plants because of the increased nitrogen fixation by the "free-living" bacterh. J All of these determinations were made by the older soda-lime method and are considered trustworthy for comparison, but the 1893 analyses reported in Table 73 were made by the newer Kjeldahl method, which gives somewhat higher and more nearly correct results. PENNSYLVANIA FIELD EXPERIMENTS 439 As already stated, a study of the present nitrogen content of the soil of Agdell field will probably furnish more satisfactory informa- tion than can be secured from any other source at this time. It is very evident that the loss of nitrogen in drainage water usually exceeds the addition in rainfall; and, unless there are sources of nitrogen other than can be found by the analysis of the legume plants (tops, roots, and tubercles), we must make provision to supply a sufficient excess of nitrogen in farm manure, crop resi- dues, or otherwise, to meet the needs of large crops and to overcome the loss in drainage from rich land. In Bulletin 221 of the New Jersey Agricultural Experiment Station, issued July, 1909, Voorhees and Lipman report in detail the results of ten years' investigations with twenty culture experi- ments (in triplicate) in which corn, oats, wheat, and timothy were grown in rotations in 60 cylinders, each 4 feet long and 23^ inches in diameter, set in the earth and open at both ends, so as to approach natural conditions for drainage. Cow manure, fresh and leached, and cow dung (solid excrement), fresh and leached, were used with and without sodium nitrate, ammonium sulfate, and dried blood, in various combinations. At the beginning of the experiment, in 1898, the surface soil (8 inches deep) contained 155.47 grams of nitrogen in each cylinder. The amounts of nitrogen applied during the ten years varied from 38.25 grams in the leached dung to 58.31 grams in the fresh manure and sodium nitrate combined. The total amounts of nitrogen removed in the sixteen crops harvested during the ten years varied from 21.88 to 36.70 grams; and the total loss of nitrogen, other than that contained in the crops removed, varied from 25.12 to 39.38 grams. Thus, in these long-continued and very carefully conducted experiments the absolute chemical control shows loss of nitrogen by leaching far in excess of possible additions by rain- fall, azotobacter, etc. After a full consideration of the data accumulated in these experiments with respect to their bearing upon the question of denitrification, the authors make the following statements: "We must conclude, therefore, that at least with cow manure, used at the rate of sixteen tons per annum for a period of ten years, no destruction of ni- trates takes place. In view of the long duration of the experiment, and of the 440 INVESTIGATION BY CULTURE EXPERIMENTS comparatively large amounts of manure used in the course of the ten seasons, we must assume that denitrification is not a phenomenon of economic importance, in general farming and under average field conditions. ... We have no hesita- tion in emphasizing again the view expressed above that under the wide range of field conditions, denitrification is not a phenomenon of economic significance to the general farmer." With our present knowledge we should not do less than to base our practice upon the known mathematical and chemical facts concerning the nitrogen requirements of crops and the nitrogen content of manures, legume crops, and crop residues, keeping in mind, of course, that there are some soils, such as peaty lands and others excessively rich in organic matter, which should be cropped for years with little or no return of nitrogen. CHAPTER XXI OHIO FIELD EXPERIMENTS ASIDE from the experiments outlined in Table 40, which deal especially with manure, alone and reenforced with different mate- rials, the Ohio Experiment Station has conducted, for 15 years, two very extensive and valuable investigations by means of plot experiments, relating to the maintenance of soil fertility. In one of these a five-year rotation is practiced on five separate fields or series, each of which contains 30 tenth-acre plots about i by 16 rods, each of the five crops, corn, oats, wheat, clover, and timothy, being represented every year (excepting the clover and timothy for the first two years). In the other investigation, potatoes, wheat, and clover are grown in a three-year rotation on three separate series, each of which contains 34 tenth-acre plots of the same shape. Each of the crops is represented every year (ex- cept wheat the first year and clover the first two years) . The detail plan of these experiments and the average results secured for the 15 years (1894 to 1908) are shown in Tables 82 and 83. Seasonal variations are too great to justify an attempt to de- termine from the data secured in fifteen years (only 13 years with clover and timothy) whether the productive power of the soil is increasing or decreasing. It will be recalled that Jethro Tull grew 13 crops of wheat in succession on the same land without the use of manure or fertilizers, and from the data secured the conclusion was drawn, " that a good crop of wheat, for any number of years, may be grown every year upon the same land without any manure from first to last." A more recent similar illustration is furnished by the Minnesota Experiment Station, showing average yields of 14.7 bushels of wheat from 1893 to 1898, and 17.2 bushels from 1899 to 1904, where wheat was grown every year without manure or fertilizer. 441 442 TABLE 82. OHIO EXPERIMENTS: FIVE-YEAR ROTATION Average Records per Acre for Three Rotations, 1894 to 1908 TREATMENT FOR EACH FIVE YEARS AVERAGE YIELDS PER ACRE FROM FIVE ACRES C y. ~z G* i a _J_ 4 S 6 Elements Applied (Lb.) Forms of Plant Food, if not Stand- ard1 a a 1 « (2 Wheat Grain, 14 Years (Bu.) o i! « 1 Wheat Straw, 14 Years 8ot 1 (Bu.) Clover Hav, 13 Years (Lb.) Value of the Three Crops Value if Unfertilized Value of Increase Cost of Treatment Profit from Treatment Price of Potatoes Nitrogen Phosphorus Potassium 3°^ S°? I 9 Ji_ 4 6 83 170.8 185.5 184.8 3°-9 36-4 32.7 3°-5 3°-7 36.4 3610 3840 345° $83.70 92.65 88.68 $83.70 83.29 82.88 *B 9-36 5-80 • • — 20 (P) 2.40 4-98 6.96 .82 9.87 3-56 (K) .is 38 20 20 — (X) '?i-3 178.3 1 86. i 2970 3200 3810 3240 3500 3670 82.46 85.48 92.32 82.46 80.65 78.84 4.83 13.48 5-70 8.10 (-.87) 5-38 1-47 IO.22 (NP) 8 g 58 83 83 " 157-2 192.8 174-8 28.4 36.1 34-4 2760 3350 3220 3330 3540 3610 77-03 93-73 87-35 77-03 77-39 77-75 16.34 9.60 7-38 10.68 8.96 (-1.08) 15.85 1.98 (PK) (NK) 10 II 12 38 02 20 20 83 83 (NPK) . . 160.6 184.3 100.8 29.6 38.6 38-4 2740 3720 3850 3070 3490 3660 78.11 92.78 95.10 78.11 77-75 77-39 I5-03 17.71 13.08 16.68 1-95 1.03 6.91 7-51 13 14 IS 5» Si 3° .50 125 i »S (Extra on potatoes) . (All on potatoes) 157-3 196.2 194.9 28.8 38.3 36.8 2670 3800 3520 3230 3700 3700 77.04 96.77 95-33 77.04 75-54 74.04 21.23 21.29 i8.75 18.75 2.48 2-54 10.85 11.24 If) 17 IS 148.5 157-8 162.2 27.2 31-3 32.5 2450 3050 3130 2980 3480 3860 72.53 79-69 82.00 72.53 71-03 69-53 Yard manure, 4 tons on wheat Yard manure, 8 tons on wheat 8.66 13.46 i. 20 2.40 7.46 11.06 9.69 14-54 II) 20 .'I 25 as 2O 20 83 83 143.0 189.2 181.7 24-5 34-0 34-i 24.1 34-9 34-8 2380 330° .1200 2180 3220 310° 2660 3430 3120 2790 3140 3130 68.03 90-85 87-74 68.03 68.64 69.25 22.21 18.40 11-13 11-13 11.08 7-36 19.94 14-34 Oil meal, 460 Ib. 22 33 ->4 148.7 181.9 181.6 60.85 88.42 88.23 69-85 69.65 69-45 7.64 7-65 »s »5 2O 20 83 83 Dried blood . . Amm. sulfate . . 18.77 18.78 11.13 11.13 14-45 14-57 »5 a6 27 146.2 176.0 185.8 24-7 35-6 37-o 2270 3350 3630 243° 3740 2700 3420 3250 2900 37io 69.25 87.98 91.29 69-25 70.00 70-75 38 38 2O 20 83 83 Raw bone meal . Acid bone black . 17.98 20.54 12.68 13.08 5-30 7.46 10.03 14.82 28 20 3» 2O ».? Basic slag . . . 151.2 184.8 24.9 37-6 71.49 92.80 71.49 72.24 20.65 12.68 7-07 14.09 30 Yard manure, 8 tons on potatoes 2OO.O 3i-9 3090 3700 93-43 72.99 20.44 2.40 18.04 26.60 31 ja Yard manure, 16 tons on wheat 160.3 1 88.0 24.8 33-4 2410 33io 2760 3450 73-73 90.13 73-73 70.29 19.84 4.80 15.04 22.27 .1.1 vl 25 20 83 Tankage .... 179.0 '35-o 33-4 23-2 3080 1990 2650 222O 85-03 63.40 66.85 63-40 18.18 10.73 7-45 M-57 1 The standard forms include both dried blood (usually 50 Ib.) and sodium nitrate (usually 200 Ib.), acid phosphate, and potassium chlorid, the applications being divided, in most cases, between the potatoes and wheat. hay, $6.00 a ton ; nitrogen, 15 cents a pound ; phosphorus, 12 cents (10 cents in raw bone, slag, and tankage) ; and potassium, 6 cents. The price of potatoes varies greatly, and for that reason the figures OHIO FIELD EXPERIMENTS 449 given in the last column of Table 83 are based upon the price of 50 cents a bushel for potatoes, while 30 cents a bushel is the price used in the other computations. Of course the increase in crop values resulting from treatment is not computed at the delivered price for marketable potatoes, but sometimes this would be justi- fied, because the treatment may largely increase the percentage of marketable potatoes, and even with other crops the improvement in quality, as well as in quantity, may be a factor of some impor- tance. In any case, potatoes belong to the crops of intensive agri- culture, the largest average yield (200 bushels) amounting to $60 an acre at 30 cents, and to $100 an acre at 50 cents a bushel.. Part of the field upon which these experiments have been con- ducted was virgin soil, cleared from forest for the purpose, and all of the land was fairly rich at the beginning. The average of 16 analyses of soil from the " East Farm," where the five-year rotation (Table 82) and reenforced manure experi- ments (Table 40) are conducted, and 5 analyses of soil from the " South Farm," where the potato-wheat-clover rotation experi- ments are under way, show that the South Farm soil contains about one half more acid-soluble phosphorus than the East Farm soil. It is also somewhat richer in acid-soluble potassium, while in total nitrogen the East Farm soil is slightly richer. By referring to the column headed " Value if unfertilized " (Table 83), it will be seen that the natural productiveness of the land varies markedly from plot i ($83.70) to plot 19 ($68.03) an^ plot 34 ($63.40); but the oft-repeated check plot (unfertilized) makes possible a comparison that could not be made without it. On the other hand, we can never be sure that the treatment applied to one plot (as phosphorus to plot 2, for example) has produced the same total increase as it would have produced if applied to some other plot (as to plot 20, for example) . Thus the actual total yield from plot 2 ($92.65) is greater than that from plot 20 ($90.85) , but the computed increase from plot 20 is more than twice as great ($22.21) as that from plot 2 ($9.36). The fact is that more plant food is removed from plot 2 than from plot 20, but this is also true, of course, with respect to the adjoining unfertilized control plots. These difficul- ties are emphasized, however, by comparing plots u and 20, both of which receive the three elements, nitrogen, phosphorus, and po- 450 INVESTIGATION BY CULTURE EXPERIMENTS tassium, in the standard forms (the nitrogen chiefly in sodium nitrate). The treatment for these two plots differs only by the addition of 13 pounds more nitrogen to plot n (plot u receives 50 pounds of dried blood for wheat, and plot 20 only 25 pounds). The total yields (except potatoes) are greater from plot n, and the total value of the three crops is greater from plot n ($92.78) than from plot 20 ($90.85); but the increase from plot 20 ($22.21) is much greater than from plot n ($15.03), and the net profit from 20 ($11. 08 or $19.94) is several times as great as from n ($1.95 or $6.91). In comparison with such plots as 14 and 27, it seems evident that plot 20 gives results above normal; while it is like- wise evident that plot n shows increases below normal, in com- parison with such plots as 8 and 24. These opposite abnormalities develop the striking discrepancy between n and 20. A study of the yearly details shows that for the first five years (1895 to 1899) the increase from treatment was greater every year in the wheat crops from plot n, the average difference being 3.6 bushels, whereas during the next five years (1900 to 1904) the in- crease in wheat was greater every year on plot 20, the average difference being 2.6 bushels. As an average of the four years, 1905 to 1908, the increase from plot 20 averaged 2.5 bushels more wheat than from n, although in two of these years the treatment gave about equal results on those plots. As an average of the first six years (1896 to 1901) plot n produced 79 pounds less clover than the unfertilized control plots, while on plot 20 the treatment produced an average increase of 630 pounds. These results and discrepancies serve to emphasize the uncer- tainty of drawing correct conclusions from a single field experiment, even when continued for several years. On the other hand, most of the results from this potato- wheat-clover rotation are concord- ant, and justify confidence. Indeed, there is marked agreement in most cases where direct comparison is possible. Thus the increases from like amounts of plant-food elements on plots 21, 23, 24, and 33 vary only from $18.18 to $18.78. In harmony with the results from all other sources, the use of phosphorus on normal soils proves highly profitable, the increase produced by phosphorus, both alone and in addition to other OHIO FIELD EXPERIMENTS 451 elements, being sufficient to pay for the phosphorus (even in acid- phosphate) and leave a net profit of 200 to 300 per cent. The use of commercial nitrogen or potassium, alone or in combination, is of doubtful advantage with potatoes at 30 cents, but at 50 cents for potatoes the potassium has been a good investment, although, with sufficient manure or clover plowed under to supply the nitro- gen, it is very probable that abundance of potassium would have been liberated from the soil. Potatoes draw heavily upon potassium, and ultimately, on level land which neither receives deposits from overflow nor loses par- tially exhausted soil by erosion, potassium must become so defi- cient as to limit the crop yield, even with the best efforts to main- tain adequate supplies of active organic matter; but the total supply of potassium in 2 million pounds of this Ohio soil is suffi- cient for 200 bushels of potatoes every year for more than 500 years, and the land has sufficient surface drainage to insure some soil erosion. Another series of long-continued and very valuable experiments have been conducted by the Ohio Station on the Strongsville experi- ment farm, on a quite different type of soil, of nearly level topog- raphy, higher clay content, and less perfect physical condition. The surface acre-foot of Wooster soil contains, as a general average, about 2770 pounds of nitrogen, 1700 pounds of acid-soluble phos- phorus, and 7310 pounds of acid-soluble potassium, while the corresponding figures for the Strongsville soil are 6520, 1700, and 6300. Thus the Strongsville soil averages more than twice as rich in nitrogen, but somewhat poorer in acid-soluble potassium, while the phosphorus content is practically equal in the two soils. Table 84 gives the average results obtained from a series of 5- year rotation experiments (1896-1897-1898 to 1907). The plant- food materials are 440 pounds of sodium nitrate (and 50 pounds of dried blood), 320 pounds of acid phosphate, and 260 pounds of potassium chlorid. (One plot (No. 12) receives 680 pounds of sodium nitrate.) The more marked effect of phosphorus on the Strongsville soil is doubtless due to the larger supply of organic matter, the decom- position of which tends to furnish nitrogen and liberate potassium. As an average, the crops from the best-yielding plots have removed 452 INVESTIGATION BY CULTURE EXPERIMENTS 30 pounds of phosphorus during the five years, or 50 per cent more than was applied. TABLE 84. EXPERIMENTS AT STRONGSVILLE, OHIO Data per Acre for Five-year Rotation: Increase Only, except as Noted CLOV- TIMO- CORN, OATS, ER, THY, PLANT FOOD APPLIED I2-YR. AVERAGE II-YR. AVERAGE AVER- IO-YR. AVER- IO-YR. AVER- (Bu.) (Bu.) AGE AGE (Tons) (Tons) Nitrogen, 76 Ib 1.18 -.OS — .24 .08 .OI Phosphorus, 20 Ib QCl IO.OQ 7.14 • 4S .16 Potassium, 108 Ib .20 .41 — .1C .os — .OI Nitrogen, phosphorus 10 46 14.38 0.72 . 30 .12 Nitrogen, potassium, I.4O 2.24 1.67 .06 — .02 Phosphorus, potassium 0 O4 IO. ^4 8.04 .34 .17 Nitrogen, phosphorus, potassium . . 12.07 14.69 IO.2I •39 •17 Nitrogen,1 phosphorus, potassium . . 11.36 14-51 12.85 .36 .11 Total yield from untreated land . . (26.94) (34.80) (5-62) (.68) (-75) 'On this plot 114 Ib. of nitrogen; otherwise the applications were: nitrogen, 76 Ib. ; phosphorus, 20 Ib. ; and potassium, 108 Ib. ; per acre, in five years. In general, it may be stated that the plant food applied in the Ohio experiments produced small effects the first few years. Thus, in the 5-year rotation at Wooster the largest increase in corn in 1904 was 3.5 bushels per acre, on plot 21, and in 8 cases out of 20 the treated plots produced lower yields than the untreated control plots. As an average of the first five years, phosphorus (on the No. 2 plots) produced increases per acre as follows: corn, 4 bushels; oats, 3.5 bushels; wheat, 3.1 bushels; clover, 390 pounds ; timothy, 186 pounds. These are about one half the effect for the i5~year average, as will be seen from Table 82. From a consideration of the Rothamsted and Pennsylvania data, it seems probable that more or less of this apparent average increase is due to a comparative decrease on the unfertilized plots, although the time is too short since the Ohio rotations and soil treatment have been fully under way to make trustworthy averages, because of seasonal variations; for, while land may be decreasing in normal productive power, a few favorable seasons following unfavorable years may furnish data that indicate increasing yields, as in the Minnesota experiments'ref erred to on a former page. CHAPTER XXII ILLINOIS FIELD EXPERIMENTS ASIDE from the old experiments on the University Farm, the Illinois field experiments have been in progress only for a few years, but they are of special interest and value because they are conducted in widely separated places and on different definite soil types of great extent and importance. Brown silt loam constitutes the most common prairie soil in the middle and upper Illinoisan, pre-Iowan, and early Wisconsin glaciations, and is found also in the lowan and late Wisconsin. It is called " the ordinary prairie land " by farmers throughout the corn belt, extending from Mattoon, Illinois, into Wisconsin, and from north-central Indiana into Nebraska and South Dakota. While the different brown silt loams are similar in many respects, they differ somewhat in chemical composition, varying with age or formation of the different areas, and it is noteworthy that in the older soil areas the brown silt loam is either no longer repre- sented (as in the lower Illinoisan glaciation), or it is replaced to some extent by a type of soil intermediate in character and value between brown silt loam and gray silt loam on tight clay. This intermediate type is well developed in places in the southern part of the middle Illinoisan glaciation and in the western part of the upper Illinoisan, but it is only one of many minor types whose exact location requires a detail soil survey. The top soil of the brown silt loam consists of a friable dark- colored and fairly uniform soil to a depth of 1 6 to 20 inches, with appreciably less organic matter at the lower depth. Below the top soil, from 16 or 20 inches to 40 inches and more, is the yellow, silty subsoil, somewhat less porous or friable than the top soil, but not very compact. This soil and subsoil have great capacity to absorb and retain water from heavy rains, and later to deliver the moisture to grow- 453 454 INVESTIGATION BY CULTURE "EXPERIMENTS ing crops as needed. In other words, the crops growing on brown silt loam soils are enabled to withstand drouths that would pro- duce very severe damage on such a soil as the lower Illinoisan gray silt loam on tight clay. Of course even the brown silt loam becomes much less absorbent and less retentive of moisture where the surface soil is allowed to become deficient in humus. As a general average (the late Wisconsin being disregarded) the brown silt loams contain in the surface soil of an acre (2 mil- lion pounds) about 4800 pounds of nitrogen, 1200 pounds of phos- phorus, and 34,000 pounds of potassium, amounts which, if they could be drawn upon at will, would furnish the nitrogen for 100 bushels of corn (grain only) every year for 48 years, the phosphorus for 70 years, or the potassium for 1790 years. For four tons per acre of clover hay each year, the nitrogen, if drawn only from the surface soil, would be sufficient for 30 years, the phosphorus for 60 years, and the potassium for 280 years. These data are for very large crops, and take into account only the plant food in the surface soil to a depth of 6f inches, but these crops are not loo large to try to raise, and the fertility of the surface soil must be maintained if we are to maintain a permanent, profit- able agriculture. We may reduce the crop yields to the lowest limit of profit on land valued at $150 to $200 an acre, but still the absolute limit in years is short for the nitrogen and the phosphorus in this most common prairie soil of the corn belt ; and, if such crops of corn and clover as are mentioned above had been removed from this land from the time Columbus discovered America until now, every pound of phosphorus contained in the soil to a depth of four feet would have been required for the crops grown. So far as the author has been able to learn, the oldest soil experi- ment field in the United States with an authentic record of its origin and with a present continuation of the experiments origi- nally inaugurated is on the campus of the University of Illinois, or rather it is surrounded by the University campus. In the biennial report for 1879 and 1880, on page 232, and under date of March 10, 1880, is the following: "The Farm Committee then submitted the following report: "To the Hon. Board of Trustees of the Illinois Industrial University: ILLINOIS FIELD EXPERIMENTS 455 "Your committee beg leave to submit the following recommendations from the Professor of Agriculture in regard to experiments for the coming season : . . . "Fifth. The formal commencement of what is designed to be a long-con- tinued experiment to show the effect of rotation of crops, contrasted with con- tinuous corn-growing, with and without manuring, and also the effect of clover and grass in a rotation. A commencement was made last year, and we are fortunate in having a piece of land more than usually well adapted for such a test. " The report was approved, and its recommendation concurred in." Thus, these oldest rotation experiments, begun, according to the official records, by Prof essor George E. Morrow, in 1879, completed a record of thirty-one years in 1909. Fortunately, these plots are located on the typical brown silt loam soil of the corn-belt prairie land. In Bulletin 13 of the Illinois Agricultural Experiment Station, published in 1891 and signed by Professor Morrow, the state- ment is made that from the beginning of these experiments plot No. 3 had " been in corn continuously," that plot No. 4 had been " in corn and oats alternately," and that plot No. 5 had " had this rotation: corn, 2 years; oats, i year; meadow (clover, timothy, or both), 3 years." The records also state that these plots had received " no manure or commercial fertilizers of any kind." The series originally contained seven other plots, and included a limited use of commercial fertilizers and farm manure, and other rotation systems. All but three of the original plots have been taken for campus or buildings. The Experiment Station was established in 1888, and in the re- ports made by Professor Morrow and his assistants relating to these experiments and published in 1888 to 1894 there is no record of crop yields previous to 1888. The most important thing, per- haps, is the record that the crop systems were followed during those early years. Since 1888 these crop systems for the three plots mentioned have been essentially maintained, with the modification on plot No. 5 during the later years of adopting the more simple rotation of corn, oats, and clover, one each year. From the recorded state- ments and the existing knowledge it is safe to say that all crops 456 INVESTIGATION BY CULTURE EXPERIMENTS have been removed, including the grain, hay, straw, and corn fodder, from 1879 to the present time, but records of yields are lacking in some cases. Originally, these plots were one half acre each in size, being 5 rods wide (north and south) by 16 rods long (east and west), but in 1904, because of the enlargement of the University campus, it became necessary to reduce the length to 9 rods in the central part of the original plots. At the same time one-half rod division strips were established between the plots, also a one-fourth rod cultivated or cropped protecting border around the plotted area, and each of the three plots was also divided in four quarters by half-rod division strips through the center in both directions. Thus, from each of the original plots four plots of one-twentieth acre each have been formed, with half-rod protecting strips. In each case the two plots on the north are continued as a duplicate test of the original system, without the use of manure or commercial fertilizers, while the two plots on the south are cropped the same, but they are now being improved by such applications of farm manure as can well be made from the crops grown, by the use of legume catch crops, applications of ground limestone to correct possible soil acidity, and by the use of phosphorus, applied for each year in the rotation in 200 pounds of steamed bone meal (on the east plot), or in 600 pounds of rock phosphate (on the west plot), per acre. The original plot numbers are 'retained, the untreated north part being known as 3N, 4N, and 5N; and the treated south part as 38, 48, and 58, respectively; and to each of these may be added W or E to designate the west or east half. InTable 85 are recorded the yields of these old plots for the last twenty-two years, from 1888 to 1909, including, since 1904, for each rotation system, the average of the untreated duplicates and of the treated parts. Seasonal influences are so great that no very satisfactory com- parison can be made between different years for the sake of deter- mining the effect of the different systems upon the productive power of the soil, 'and the thorough underdrainage provided for in 1904 must be expected to markedly increase the crop yields in subsequent seasons of excessive rainfall, such as 1907, for example, ILLINOIS FIELD EXPERIMENTS 457 TABLE 85. CROP YIELDS PER ACRE FROM THE OLDEST ILLINOIS EXPERIMENT PLOTS: URBANA SOIL EXPERIMENT FIELD YEARS Son. TREATMENT APPLIED CORN EVERY YEAR TWO-YEAR ROTATION THREE-YEAR ROTATION Corn (Bu.) Corn (Bu.) Oats (Bu.) Corn (Bu.) Oats (Bu.) Clover (Tons) 1879-87 1888 1889 1890 1891 54-3 43-2 48.7 28.6 49-5 48.6 37-4 4.04 I-Si 1.46 54-3 33-2 None 1892 1893 1894 33- 1 21.7 34-8 37-2 67.6 34-1 29.6 None . : 57-2 65.1 1895 1896 I897 42.2 62.3 40.1 41.6 22.2 34-5 None 47.0 1898 1899 1900 18.1 50.1 48.0 None 44.4 53-5 None 4i-5 1901 1902 1903 None 23-7 60.2 26.0 33-7 56.3 34-3 54-6 None 3,-vQ I. II 1904 1904 1905 I9°S 1906 1906 N. ^ None o i f Legume/ manure,2 | '^{lime, phosphorus2 J N \ None 21.5 17.1 24.8 3i-4 27.1 35-8 17-5 25-3 55-3 72.7 50.0 44-9 42.3 50.6 S. ^, Lgm., mnr., lime, phos. N \ None 34-7 52.5 1-43 3 r.743 S. %, Lgm., mnr., lime, phos. 1907 1907 1908 1908 1909 1909 N \ None 29.0 48.7 13-4 28.0 26.6 31-6 47-8 87.6 80.5 93-6 S. \ , Lgm., mnr., lime, phos. N ^ None 32.9 45-° 4O.O 44-4 S. 5, Lgm., mnr., lime, phos. N J None 33-0 64.8 •65 1.74 S. £, Lgm., mnr., lime, phos. 1910 1910 1911 1911 1912 1912 N. £, None 35-9 54-6 21.8 31-5 43-2 64.2 33-8 59-4 58.6 83-3 S. J, Lgm., mnr., lime, phos. N 5 None 28.6 46.3 20.5 37-9 S. J, Lgm., mnr., lime, phos. N. |, None 55-0 81.0 i-354 i-7o4 S. £, Lgm., mnr., lime, phos. 1 Legume catch crops first grown in 1904 to benefit 1905 crops. 2 Manure and phosphorus first applied to plot 58 for 1904 crop, but to plots 38 and 4$ for 1905 crop. 3Cowpea hay; the clover failed. 4 Soy-bean hay. 458 INVESTIGATION BY CULTURE EXPERIMENTS as compared with previous years. Thus, on the continuous corn plot the yield was 18.1 bushels in 1898 and 60.2 bushels four years later, and the largest recorded corn yield in the corn-oats-clover rotation was 80.5 bushels in the wet season of 1907. A fair comparison between different systems can usually be made in the same years, and the change in productive power under any system can best be ascertained by comparing the results from these old experiments with those from newer experiments, as shown in Table 86, when the effect of sixteen years' cropping can be noted. Every plot in the newer experiments produced more than 75 bushels of corn per acre in 1896, and the average in 1897 was about 70 bushels. Upon these facts is based the assumption that all of the older plots originally produced 70 bushels or more per acre. It is apparent that the legume catch crops (chiefly cowpeas) seeded in the corn decrease the yield for the first year at least, as shown in 1904 on plot 3 and, even in spite of the light manuring, on plot 4 in 1905. The general effect of the system of soil improvement adopted for the south half of each of these old plots is already very marked, an increase of 40 bushels of corn per acre being secured in 1907 from the treatment on plot 4, where the most marked effect is to be expected because no clover or other legumes had been grown previous to 1904 in this rotation, and the frequent change from corn to oats has helped to avoid the development of corn insects. Table 86 gives, for comparison, three-year averages for corn, including the 1901-7 corn crops grown in the three-year rotation on the old field. As an average of the three years where corn has been grown every year, the yield has been 27 bushels in the 29-year experiments and 35 bushels in the 13-year experiments. The lesson of these experi- ments is that 12 years of cropping where corn follows corn every year reduces the yield from more than 70 bushels to 35 bushels per acre, after which the decrease is much less rapid, amounting to only 8 bushels' reduction during the next 16 years. Undoubtedly the rapid reduction during the first 12 years of continuous corn- growing is due in large part to the destruction of the more active decaying organic matter, resulting ultimately in insufficient libera- tion of plant food within the feeding range of the corn roots. ILLINOIS FIELD EXPERIMENTS 459 TABLE 86. COMPARABLE CORN YIELDS FROM THE UNIVERSITY OF ILLINOIS EXPERIMENT FIELD AT URBANA: TYPICAL BROWN SILT LOAM PRAIRIE Three-year Averages: Bushels per Acre CROP YEARS CROP SYSTEM 13- YEAR EXPERIMENTS 29- YEAR EXPERIMENTS IQCX. —6, —7 Corn every year ^ bu. 27 bu. IQO3. — <\. ~7 Corn and oats 62 bu. 46 bu. 1901, -4, -7 Corn, oats, clover .... 66 bu. 58 bu. AVERAGE OF THREE CORN CROPS IN CORN-OATS-CLOVER ROTATION GRAIN FARMING LIVE-STOCK CROP YEARS SPECIAL TREATMENT WITH CROP FARMING WITH RESIDUES FARM MANURE IQO2. —3. —4 None 77.4 Gain 75 3 Gain IQO2, — ?, —4 Lime 78.4 80.8 I.O e.e 1902, -3, -4 Lime, phosphorus .... 88.0 10.6 88.8 13-5 1902, -3, -4 Lime, phosphorus, potassium . 90.1 12.7 9°-5 15.2 TOO? —6 —7 None 68 <; 80 c IQCX, -6, —7 Lime 72.3 3 8 ouo 848 A 1 1005, -61 ~7 Lime, phosphorus .... 90.4 21.9 93-2 12.7 1905, -6, -7 Lime, phosphorus, potassium . 93-8 25-3 95-6 15-1 TfloH — O —TO None CT C IOo8, — 0, — IO Lime OXO q8 i 66 74 O s 6 1908, -9, -io Lime, phosphorus .... 83.8 32.3 86.6 17-3 1908, -9, -io Lime, phosphorus, potassium . 86.7 35-2 90.9 21. 6 Where corn is followed by oats in a 2-year rotation the average yield of the three crops of corn is 46 bushels in the 29-year experi- ments, whereas in the 13-year experiments the average yield for the same three years is 62 bushels of corn per acre. In this case the destruction of humus is less rapid, and the development of the corn insects is discouraged by changing to oats every other year, so that the decrease in yield is less marked during the early years, although the reduction continues persistently with passing years. During the first ii years the yield decreased from more than 70 bushels to 62, and the next 16 years show a further reduction of 16 bushels. 460 INVESTIGATION BY CULTURE EXPERIMENTS With the 3-year rotation corn is grown for one year, followed by oats with clover seeding the second year, and clover alone the third year. During the first ten years under this system the yield of corn has decreased from more than 70 bushels to 66, and during the next 16 years the yield has further decreased to 58 bushels, the average reduction being only one-half bushel a year. In this sys- tem the most marked reduction in crop yields has not yet appeared, although it must be expected in the future because the clover crop is already beginning to fail on the oldest field, even in seasons when clover succeeds well on newer land under the same crop rotation. When clover fails, cowpeas are substituted for that year on that field, which thus provides a legume crop and preserves the 3-year rotation. In the lower part of Table 86 (third column) are included the average yields of corn for the last three years in a system of grain farming, in a 3-year rotation of corn, oats, and clover. This system, when fully under way, provides that the corn shall be husked and the stalks disked down in preparation for the seeding of oats and clover the second year. In harvesting the oats, as much straw as possible is left in the stubble, which may be mowed later in the summer to prevent the seeding of the clover or weeds. In the spring of the third year the clover is mowed once or twice before the usual haying time and left lying on the land. The seed crop, if successful, is harvested with a hay buncher attached to the mower, or in any other way to avoid raking, and afterward the threshed clover straw and oat straw (or at least as much as is practicable) are returned to the land, all of this accumulated organic matter to be plowed under for the following corn crop, which begins the next rotation. In addition to this, catch crops of annual legumes, such as cowpeas, may be seeded in the corn at the time of the last cultivation and disked in the next spring with the corn stalks. If biennial or perennial legumes are used as catch crops, the corn ground may be plowed for oats. (This is a practice of doubtful advantage where the corn is rank.) The corn yields reported for this system in Table 86 were secured where the system was not fully under way, the legume-catch crops being the only organic matter returned to the soil, aside from the residues necessarily left, except for the last crop rotation. By ILLINOIS FIELD EXPERIMENTS 461 using three different fields for this rotation, every crop may be grown every year, and the yields of corn reported are true three- year averages. With no special soil treatment aside from crop residues and catch crops, the yield of corn for 1908, 1909, and 1910 averaged 52 bushels. Where the equivalent of ^ ton per acre of ground limestone was applied (five years before) the corn has yielded 58 bushels per acre; and, with the phosphorus added for six years at the rate per annum of 25 pounds per acre of the element phosphorus (in 200 pounds of steamed bone meal) the average yield of corn has been 84 bushels per acre for the last three years. The yearly addition of 42 pounds of potassium in 100 pounds of potassium sulfate has further in- creased the yield to 87 bushels. Under the heading " Live-stock Farming," in Table 86, are re- corded the average yields of corn secured during the same three years where farm manure has been applied to the clover ground to be plowed under for corn. The plan of this system is to remove all crops from the land as usually harvested, including the corn and stover, oats and straw, and both first and second crops of clover. The amounts of manure applied to the different plots are determined by the crop yields secured during the previous rotation. While the system of cropping followed during the 16 years on these plots, and on those just described under " Grain Farming," has been approximately equivalent to a three-year rotation of corn, oats, and clover, the applications of manure have been made only for the last 6 years, from 1905 to 1910. If the average yields are decreasing on plots that receive only the amounts of manure that can be produced in practice from the crops grown, then the appli- cations of manure must also be reduced on such land ; whereas if the crop yields are increasing where both manure and phosphorus are applied, then the applications of manure for such plots may be increased in direct proportion. Where manure alone has been used in this rotation, the com has averaged 69 bushels per acre for the three years ; with lime added, the average is 75 bushels; with lime and phosphorus, the manured land has averaged 87 bushels of corn, and this was increased to 91 bushels by adding potassium. While potassium has usually made some increase in crop yields 462 INVESTIGATION BY CULTURE EXPERIMENTS on these fields, it has not nearly paid its cost. The most profitable yields are the 88 bushels in grain farming or the 90 bushels in the live-stock system (9-year averages). The effect of limestone has already been sufficiently uniform to recommend its use on this soil, and marked profit has resulted from the addition of phosphorus, which is applied in sufficient amount actually to en- rich the land, and not as a stimulant. Phosphorus has been ap- plied since 1902. Table 87 gives results obtained during seven years (1902 to 1908) from the Sibley soil experiment field, located in Ford County, on typical brown silt loam prairie of the Illinois corn belt. TABLE 87. CROP YIELDS IN ILLINOIS SOIL EXPERIMENTS: SIBLEY FIELD BROWN SILT LOAM PRAIRIE, EARLY WISCONSIN GLACIATION CORN, IO02 CORN, 1003 OATS, 1004 WHEAT, 1005 CORN, 1006 CORN, 1907 OATS, 1908 Plot Soil Treatment Applied Bushels per Acre IOI 102 None 57-3 60.0 5°-4 54-o 74-4 74-7 29-5 31-7 36-7 39-2 33-9 38.9 25-9 24-7 Lime I03 IO4 I°5 Lime, nitrogen .... Lime, phosphorus . . . Lime, potassium . . . 6o.c 61.3 56.0 54-3 62.3 4.9-9 77-5 92-5 74-4 32.8 36-3 30.2 41.7 44.8 37-5 48.1 43-5 34-9 36-3 25.6 22.2 1 06 107 108 Lime, nitrogen, phosphorus Lime, nitrogen, potassium Lime, phosphorus, potas- sium 57-3 53-3 58.7 69.1 5i-4 60.9 88.4 75-9 80.0 45-2 37-7 39-8 68.5 39-7 4i-5 72-3 Si-i 39-8 45-6 42.2 27.2 109 no Lime, nitrogen, phosphorus, potassium 58.7 60.0 65-9 60. i 82.5 85.0 48.0 4S.5 69-5 63-3 80. i 72-3 52.8 44.1 Nitrogen, phosphorus, po- tassium The standard applications for this and other Illinois soil experi- ments are 100 pounds of nitrogen (in dried blood), 25 pounds of phosphorus (in steamed bone meal) , and 42 pounds of potassium (in potassium sulfate), per acre per annum, but the phosphorus and potassium are usually applied in correspondingly heavier applica- tions once for the rotation. It is not necessary to take space here for a complete discussion of the data in Table 87. Previous to 1902 this land had been cropped with corn and oats ILLINOIS FIELD EXPERIMENTS 463 for many years under a system of tenant farming, and the soil had become somewhat deficient in active humus. While phosphorus was the limiting element of plant food, the supply of nitrogen be- coming available annually was but little in excess of the phosphorus, as is well shown by the corn yields for 1903 when phosphorus pro- duced an increase of 8 bushels, nitrogen without phosphorus pro- duced no increase, but nitrogen and phosphorus increased the yield by 15 bushels. After six years of additional cropping, however, nitrogen appeared to become the limiting element, the increase in 1907 being 9 bush- els from nitrogen and only 5 bushels from phosphorus, while both together produced an increase of 33 bushels of corn. By comparing the corn yields for the four years, 1902, 1903, 1906, and 1907, it will be seen that the untreated land has apparently grown less pro- ductive, whereas on land receiving both phosphorus and nitrogen the yield has appreciably increased, so that in 1907, when the un- treated rotated land produced only 34 bushels of corn per acre, a yield of 72 bushels, or more than twice as much, was produced where lime, nitrogen, and phosphorus had been applied, although . these two plots produced exactly the same yield (57 bushels) in 1902. While the actual yields might be quite different under dif- ferent seasonal conditions, the relative and increasing differences between the plots must be considered as representative and due to the difference in soil treatment. By comparing plots 101 and 102, and also 109 and no, will be seen the increase by lime, suggesting that the time is near when lime also must be applied to these brown silt loam soils. Because of the tremendous importance of this most common corn- belt soil to American agriculture and to the prosperity of the na- tion, space is taken to insert Table 88, giving all of the results thus far obtained from the Bloomington soil experiment field, which is • also located on the brown silt loam prairie of the Illinois corn belt. (Additional data are inserted on page 475.) The general results of the seven years' work on the Bloomington field tell the same story as those from the Sibley field. The rota- tions differ by the use of clover and cowpeas in 1906, and in dis- continuing the use of commercial nitrogen after 1905, on the Bloomington field, in consequence of which phosphorus without 464 TABLE 88. CROP YIELDS IN ILLINOIS SOIL EXPERIMENTS: BLOOMINGTON FIELD BROWN SILT LOAM PRAIRIE, EARLY CORN, CORN, OATS. WHEAT, CLOVER, CORN, CORN, WISCONSIN GLACIATION IOO2 1903 1904 1905 1906 1907 1908 Plot Soil Treatment Applied Bushels or Tons per Acre IOI None 30.8 63.0 EJ4.8 30.8 .•7Q 00.8 4O 1 102 Lime 37-0 60.3 60.8 28.8 .58 63.1 353 IOT, Lime, nitrogen ' . . . . 35-i 59-5 69.8 3°-5 .46 64-3 36-9 IO4 Lime, phosphorus . . . 41.7 73-o 72.7 39-2 1.65 82.1 47-5 105 Lime, potassium .... 37-7 56.4 62.5 33-2 •51 64.1 36.2 1 06 Lime, nitrogen,1 phosphorus 43-9 77.6 85-3 50.9 2 78.9 45-8 107 Lime, nitrogen/ potassium 40.4 58.9 66.4 29-5 .Si 64-3 31.0 108 Lime, phosphorus, potassium 50.1 74.8 70-3 37-8 2.36 81.4 57-2 109 Lime, nitrogen,1 phosphorus, potassium 52.7 80. o 90-5 5i-9 2 88.4 58.1 no Nitrogen,1 phosphorus, po- tassium 52-3 73- 1 71.4 5i-i 2 78.0 Si-4 1 No commercial nitrogen applied after 1905. 2 Clover smothered out by previous very heavy wheat crop. After the clover hay was harvested, all ten of the plots were seeded to cowpeas, and the crop was plowed under later on all plots as green manure for the 1907 corn crop. nitrogen (plot 104) produced nearly as large an increase as the increase by phosphorus with nitrogen (plot 106) ; whereas on the Sibley field phosphorus with nitrogen (plot 106) produced more than twice as large an increase as the increase by phosphorus with- out nitrogen. It should be stated that a draw runs near plot 1 10 on the Bloom- ington field, and the crops on that plot are sometimes damaged by overflow or imperfect drainage. Otherwise, all results reported in Tables 87 and 88, including more than 150 tests, are considered trustworthy, and they furnish much information and afford many interesting and instructive comparisons, as, for example, between plots 104 and 106 and between 108 and 109 on the Sibley field where no legumes are grown in the rotation; also, between plots 103 and 106 and between 107 and 109 on both fields. Wherever nitrogen was provided either by direct application or by the use of legume crops, the addition of the element phosphorus ILLINOIS FIELD EXPERIMENTS 465 produced very marked increases, the average value being, as a rule, more than double its cost in steamed bone meal, the form in which it was applied to these fields. On the other hand, the use of phosphorus without nitrogen will not maintain the fertil- ity of the soil (see plots 104 and 106, Sibley field), and a liberal use of clover or other legumes is suggested as the only practical and profitable method of supplying the nitrogen, the clover to be plowed under, either directly or as manure, preferably in connec- tion with the phosphorus applied, especially if raw rock phosphate is used. From the best treated plots, 100 pounds per acre of phosphorus have been removed from the soil in the seven crops. This is equal to 10 per cent of the total phosphorus contained in the surface soil of an acre. In other words, if such crops could be grown for 84 years, they would require as much phosphorus as the total supply in the surface 6| inches of soil. The results plainly show, however, that without the addition of phosphorus such crops cannot be grown year after year. Where no phosphorus was applied, the crops removed only 75 pounds of phosphorus in seven years, or nearly 1 1 pounds a year, equivalent to almost i per cent of the total amount (1260 pounds) in the surface soil. (See also Table 50, giving results of raw rock phosphate on brown silt loam.) The yellow-gray silt loams are found on the undulating upland areas that are, or were originally, timbered. The topography varies from nearly level to gently rolling, corresponding to the topography of the brown silt loam prairies. The yellow-gray silt loam varies from yellow to gray in the surface, and, as a rule, there is more or less " gray layer" in the subsurface (especially in the older formations). On the late Wisconsin glaciation, the loess covering being shallow, glacial material containing more or less gravel is frequently found in the subsoil within 40 inches of the surface. As shown in Table 15, the late Wisconsin yellow-gray silt loam (1034) contains in the surface 6| inches about 2900 pounds of nitrogen, 800 pounds of phosphorus, and 47,600 pounds of potas- sium. Compared with the more productive, more durable, and more valuable soils (as the early Wisconsin black clay loam), this soil is very poor in phosphorus and quite low in humus as 466 INVESTIGATION BY CULTURE EXPERIMENTS measured by the nitrogen or organic carbon, while it is extremely rich in potassium.1 The total supply of phosphorus in the plowed soil (6f inches deep) is less than would be required for 35 crops of corn yielding 100 bushels of grain and 3 tons of stover, while the total nitrogen content even to a depth of 40 inches is less than would be required for 60 such crops, or for less than 90 if only the grain were removed, although the total potassium to a depth of 40 inches is sufficient to meet the requirements of loo-bushel crops of corn every year for more than 4 thousand years, or for more than 16 thousand years if only the grain is removed. Notwithstanding these positive facts, based upon absolute chemical analysis, showing such an enormous supply of potassium and a relatively small supply of nitrogen, the addition of soluble potassium salts, while not yielding profitable results, has actually produced a larger average increase than has been produced by nitrogen applied in dried blood on the Antioch soil experiment field about five miles from the Wisconsin line, in Lake County, Illinois, on the late Wisconsin yellow-gray silt loam, thus affording a good illustration of the fact that systems of soil treatment for permanent agriculture should not be based solely upon previous culture experiments. This soil is deficient in active humus, and the soluble potassium 1 It is appropriate to mention in this connection that Doctor A. S. Cushman of the United States Department of Agriculture has recently emphasized (Science (1905), 22, 838; and U. S. Dept. of Agr. Bureau of Plant Industry Bulletin 104) the possibility of using powdered granite and felspar as a source of potassium for fertilizing purposes, although some previous experiments with felspar (Svenska Mosskidturfor. Tidskr. (1903), //, 360; (1904), 18, 33, 73) have not given en- couraging results. While it is by no means certain that granite averaging 4 per cent of potassium or felspar with 8 or 10 percent of potassium may not be used with profit under some conditions, as where it can be secured as waste or by-product at very low cost near lands actually deficient in potassium, it is worth while to know that at $3 per ton for powdered granite the surface 20 inches of the principal types of soil in the late Wisconsin glaciation already contains about $6000 worth of potassium per acre in the form of finely powdered granitic rock. In other words, two tons of this soil (or three tons of any silt loam soil in the Illinois corn belt) spread over an acre of land would supply as much potassium, and in the same form, as would be supplied by a ton of average powdered granite. While the phosphorus content of the surface soil of most $150 Illinois land can be doubled by investing $25 to $40 per acre in raw rock phosphate at $7.50 per ton, to double the potassium content by applying powdered granite at a cost of only $3 a ton would cost from $1200 to $1800 per acre. ILLINOIS FIELD EXPERIMENTS 467 salt acts in large part at least, if not entirely, as a soil stimulant rather than as plant food. As already shown by the results from Rothamsted, other soluble salts may produce the same effect. In Table 89 are given the results of seven years' work on the An- tioch soil experiment field. TABLE CROP YIELDS IN SOIL EXPERIMENTS: ANTIOCH FIELD SOIL YELLOW-GRAY SILT LOAM, UNDULAT- PLOT ING TIMBER LAND: LATE WISCONSIN GRAIN, BUSHELS PER ACRE No. GLACIATION Treatment Applied IQO2, Corn 1903, Corn 1904, Oats Wheat 1906, Corn 1907, Corn 1908, Oats IOI None 44.8 ?,66 17.8 18 «; •2C Q 12 4. 6c;6 IO2 Lime 45-1 38-9 12.8 10.. 1 31-5 9-5 61.6 IO3 Lime, nitrogen . .... 46.3 40.8 2.8 17.8 37-8 6 \ 60.3 IO4 Lime, phosphorus SO. I ^3.6 12.5; «.8 ^7.4 17.4 7O. Q 105 Lime, potassium 48.2 50.2 9-7 21.7 34-9 12.9 62.5 1 06 Lime, nitrogen, phosphorus . 56.6 62.7 15-9 15.2 59-3 20.9 49.1 107 Lime, nitrogen, potassium . . 52.1 54-9 10.3 11.8 39-o II. I 52.6 108 Lime, phosphorus, potassium 60.7 66.0 19.7 28.7 59-i I8.3 59-4 109 Lime, nitrogen, phosphorus, po- tassium 6l 2 69 i 21. Q 180 6< o 31 4 Cl Q no Nitrogen, phosphorus, potassium 59-7 71.8 37-2 16.3 66.3 28.8 55-9 Plot No. i is naturally better land than the others, and both i and 10 serve only as checks against the lime treatment. They are not used in studying the effects of plant food applied. The oats crop in 1904 and the 1907 corn crop were almost fail- ures. The low yields of wheat from plots 3, 6, 7, and 9, in 1905, were due to the fact that the wheat on these nitrogen plots grew very rank and lodged badly before it ripened. The straw on these plots also rusted badly, resulting in shriveled and light grain. The oats also lodged badly on the nitrogen plots in 1908. The total gains for seven years show very markedly the effects of soil treatment. After the first year the best treated plots pro- duced about twice as much as plot 2, which serves properly as a check plot, to which no nitrogen, phosphorus, or potassium is applied. Sand soil is found in considerable areas in Wisconsin and Michi- 468 INVESTIGATION BY CULTURE EXPERIMENTS gan and in northern Illinois, Indiana, and Ohio, sometimes on sand plains and also in sand dunes where the sand has been blown into ridges varying from narrow drifts to extensive sand-hill areas, often covering many square miles, as inTazewell, Mason, and Kankakee counties, in Illinois. In composition this soil averages about 1400 pounds of nitrogen, 800 of phosphorus, and 31,000 pounds of potassium in the surface 6f inches (2^ million pounds). The high percentage of potassium shows that this soil is not a pure quartz sand, but is, to a consider- able extent, of granitic origin. In composition this soil is extremely poor in nitrogen, rich in potassium, and fairly well supplied with phosphorus, if we consider its very porous character and the very deep feeding range afforded to plant roots. The Green Valley soil experiment field is located on sand-ridge soil in Tazewell County, Illinois. The soil varies from a very sandy loam to a slightly loamy sand that is easily drifted by the wind when not protected by vegetation. This field was broken out of pasture in 1902. In Table 90 are reported results secured in six years from contiguous and comparable plots in that part of the Green Valley field where nitrogen as well as other elements is supplied in commer- cial form. TABLE 90. CROP YIELDS IN ILLINOIS SOIL EXPERIMENTS: GREEN VALLEY FIELD SAND-RIDGE SOIL GRAIN, BUSHELS PER ACRE SOIL PLOT No. Treatment Applied IQO2, Corn 1903, Corn 1904. Oats 1905, Wheat 1906, Corn 1907, Corn 401 None 68 7 5^3 40-7 T«3 72.9 7C.2 402 Lime 68.2 42.0 35 -Q 19.0 I7.8 2Q-5 4O? Lime, nitrogen 686 6"v4 44-4 23.5 62.9 •?8.9 404 Lime, phosphorus 30. i 24.0 20.3 16.7 10.4 17. I 405 Lime, potassium 23.1 20. i i6.(j I6.5 8.4 12.8 406 Lime, nitrogen, phosphorus .... 57-4 69.8 51- Q 26.8 70.8 64.7 407 Lime, nitrogen, potassium .... 70.0 72.9 54-7 36.5 74.8 73-6 408 Lime, phosphorus, potassium . . . 49.8 39-6 36-9 13-7 18.3 27.7 409 Lime, nitrogen, phosphorus, potassium 69-5 69.8 47.8 36.2 66.4 73-6 410 Nitrogen, phosphorus, potassium . . 57-2 66.1 50.0 26.5 66.0 71.9 ILLINOIS FIELD EXPERIMENTS 469 Plots i (especially) and 2 in this series were naturally more productive than the other plots, it being the regular custom oi the Illinois Station to use the most productive land for the untreated check plots if any such differences are apparent when the field is established, as was the case in this instance. Plot i serves only as a check against the lime treatment, and the average of plots 2, 4, 5, and 8 gives a more reliable basis of comparison for ascertaining the effect of nitrogen. Potassium is evidently the second limiting element in this soil where decaying organic matter is not provided, but the limit of potassium is very far above the nitrogen limit. During the six years plot 7, receiving nitrogen and potassium, produced 291.3 bushels of corn (averaging 72.5 bushels a year), 54.7 bushels of oats, and 36.5 bushels of wheat, per acre. To pro- duce the increase of plot 7 over plot 5 would require about 75 per cent of the total nitrogen applied. Thus, there has been a loss of 25 per cent of the nitrogen applied, which is a smaller loss than usually occurs where commercial nitrogen is used. Without doubt, larger yields would have been produced, especially of corn, if 150 or 200 pounds of nitrogen per acre per annum had been used, which would have increased the cost of nitrogen to $22.50 or $30, re- spectively, per acre each year. It need scarcely be mentioned that commercial nitrogen is used in these and other experiments in Illinois only to help discover what elements are limiting the crop yields. It should never be purchased for use in general farming, but, if needed, secured from the atmos- phere by legume crops to be returned to the soil directly or in ma- nure. On three other series of plots on the Green Valley soil experi- ment field, a three- year rotation of corn, oats, and cowpeas is prac- ticed, every crop being represented every year. On plots receiv- ing lime and phosphorus and legume crops, as green manure, the yield of corn was 45.6 bushels in 1906 and 67.8 bushels in 1907, compared with 70.8 bushels and 64.7 bushels with lime, phosphorus, and nitrogen on plot 6 (see Table 90) and with 10.4 bushels and 13.1 bushels with no nitrogen on plot 4, for the respective years. On other plots receiving comparable treatment, where lime, phos- phorus, and potassium were used with nitrogen-gathering legume 470 INVESTIGATION BY CULTURE EXPERIMENTS crops as green manure, the corn yields in the three-year rotation were 54.6 bushels in 1906 and 51.5 bushels in 1907, compared with 66.4 bushels and 73.6 bushels on plot 9 with nitrogen applied, and compared with 18.3 bushels and 27.7 bushels on plot 8 with no nitrogen for the same years. The growing of legume crops and the use of farm manure (and possibly limestone) are the only recommendations made for the improvement of these well-drained sand soils, although further tests may show profit from potassium until more organic matter is supplied. As a rule, clover cannot be grown successfully on this land, but cowpeas and soy beans are well adapted to such soil, and they produce very large yields of excellent hay or of grain very valuable for feed and also for seed. Under the best conditions, with good preparation and heavy manuring, alfalfa can be grown on this sand soil, more than five tons of alfalfa hay per acre in one year having been grown on part of the Green Valley field. Both soy beans and alfalfa should be inoculated with the proper nitrogen-fixing bacteria. Heavy applications of ground limestone also may be especially beneficial in getting alfalfa started. (It should be kept in mind that residual sand soils, such as are found in the Coastal Plains soil province in the South Atlantic and Gulf States, are, as a rule, very deficient in mineral plant food, as well as in nitrogen.) Peaty swamp lands. Peat is chiefly of two kinds, one being known as moss peat and the other as grass peat. Moss peat consists largely of dead and decaying sphagnum moss, and grass peat of the residues of coarse swamp grass, sedge, flags, etc. Probably most of the beds in Ohio, Indiana, Illinois, and Iowa are grass peat, although there is some moss peat in northern Illinois. Indeed, in the detail soil survey of Lake County, Illinois, one swamp of several acres was found where the sphagnum moss is still growing luxuri- antly over a bed of moss peat. Where the soil consists very largely of decaying peat to a depth of 30 inches or more, it is called deep peat. As shown in Table 15, deep peat contains in one million pounds of surface soil about 35,000 pounds of nitrogen, 2000 pounds of phosphorus, and 2900 pounds of potassium. This shows in the ILLINOIS FIELD EXPERIMENTS 471 surface 6f inches of an acre about five times as much nitrogen as the early Wisconsin black clay loam prairie. In phosphorus con- tent these two soil types are about equal, but the peat contains less than one tenth as much potassium as the black clay loam. Thus, the total supply of potassium in the peat to a depth of 6f inches (2930 pounds) would be equivalent to the full potassium re- quirement (75 pounds) of a hundred-bushel crop of corn for only 39 years, or if the equivalent of only one fourth of i per cent of this is annually available in accordance with the rough estimate previously suggested, about 7 pounds of potassium would be liber- ated annually, or sufficient for about 10 bushels of corn per acre. In Table 91 are given all results obtained from the Manito (Mason County, Illinois) experiment field on deep peat, which was begun in 1902 and discontinued after 1905. The plots in this field were one acre l each in size, being 2 rods wide and 80 rods long, and untreated half-rod division strips were left between the plots, which, however, were cropped the same as the plots. TABLE 91. CORN YIELDS PER ACRE IN ILLINOIS SOIL EXPERIMENTS : MANITO' FIELD: TYPICAL DEEP PEAT SOIL PLOT No. SOIL TREATMENT FOR 1902 (Per Acre) CORN, IQO2 (Bu.) CORN, 1003 (Bu.) SOIL TREATMENT FOR 1904 (Per Acre) CORN, IQ04 (Bu.) CORN, 1005 (Bu.) FOUR CROPS (Bu.) I 2 None 10.9 10.4 8.1 10.4 None 17.0 12. 0 I2.O 10. 1 48.0 42.9 None Limestone, 4000 Ib. 3 4 5 Kainit, 600 Ib. . . Kainit, 600 Ib. ; acid- ulated bone, 350 Ib 3°-4 30-3 31.2 32.4 33-3 33-9 Limestone, 4000 Ib. ; kainit, 1200 Ib. Kainit, 1200 Ib. ; steamed bone, 395 Ib 49.6 53-5 48-5 47-3 47-6 52-7 159-7 164.7 166.3 Potassium chlorid, 200 Ib Potassium chlorid, 400 Ib 6 Sodium chlorid, 700 Ib II. I i3-i None 24.0 22.1 70.3 7 8 9 Sodium chlorid, 700 Ib !3-3 36.8 26.4 14-5 37-7 25.1 Kainit, 1200 Ib. . . Kainit, 600 Ib. . . Kainit, 300 Ib. . 44-5 44.0 4i-5 47-3 46.0 329 164.5 125.9 Kainit, 600 Ib. . . Kainit, 300 Ib. . 10 None I4-92 14.9 None 26.0 13.6 69.4 1 In 1904 the yields were taken from quarter-acre plots because of severe insect injury on the other part of the field. * Estimated from 1903; no yield was taken in 1902 because of misunderstanding. 472 INVESTIGATION BY CULTURE EXPERIMENTS The results of four years' tests as given in Table 91 are in com- plete harmony with the information furnished by the chemical composition of peat soil as compared with that of ordinary normal soils. Where potassium was applied, the yield was from three to four times as large as where nothing was applied. Where approxi- mately equal money values of kainit and potassium chlorid were applied, slightly greater yields were obtained with the potassium chlorid, which, however, supplied about one third more potassium than the kainit'. On the other hand, either material furnished more potassium than was required by the crops produced. The use of 700 pounds of sodium chlorid (common salt) produced no appreciable increase over the best untreated plots, indicating that where potassium is itself actually deficient, salts of other ele- ments cannot take its place. Applications of two tons per acre of ground limestone produced no increase in the corn crops, neither when applied alone nor in combination with kainit, neither the first year nor the second. Reducing the application of kainit from 600 pounds to 300 pounds, for each two-year period, reduced the yield of corn from 164.5 to 125.9 bushels. The two applications of 300 pounds of kainit furnished 60 pounds of potassium for the four years, or sufficient for 84 bushels of corn (grain and stalks). The difference between this and the 125.9 bushels obtained is 42 bushels, about what was obtained from the poorest untreated plot. The underdrainage provided for this experiment field was not sufficient for the best results, probably because of insufficient nitrification. In other experiments on peaty soil with imperfect drainage, the addition of $15 worth of nitrogen with potassium produced about 15 bushels more corn than where potassium alone was used. Peaty alkali soils. Aside from deep peat, there are many other types of peaty soil, as will be seen from the classification of Illinois soil types given in a previous chapter. Thus we find shallow peat and medium peat, underlain with clay, sand, rock, etc., and also sandy peat and peaty loam; and in some instances peaty soils also contain alkali, consisting chiefly of harmless calcium car- bonate with smaller amounts of injurious magnesium carbonate. In some cases these peaty soils actually contain a good percentage ILLINOIS FIELD EXPERIMENTS 473 of total potassium, more commonly in the subsurface or subsoil, but sometimes in the surface soil, also; and yet the untreated soil is unproductive, while the addition of potassium salts produces large and very profitable increases in the yield of corn, oats, etc. In pot-culture experiments the author has even been able by the addition of potassium sulfate to correct to a considerable extent the injurious property of magnesium carbonate that has been purposely applied to ordinary brown silt loam prairie soil which is known to contain abundance of available potassium. These facts are mentioned here because he recommends, in humid sections, trial applications of potassium salt to all classes of peaty and alkali soils that are unproductive after being well drained, whenever the supply of farm manure is insufficient. It should be understood that plenty of farm manure, preferably quick-acting, or readily decomposable, manure, such as horse manure, will supply potas- sium and thus accomplish everything that potassium salts can accomplish, and on some swamp soils manure produces good re- sults where potassium is without effect. In pot-culture experiments soils containing injurious amounts of magnesium carbonate have been treated with calcium sulfate (land-plaster) which brings about a double decomposition, or inter- change, forming the harmless insoluble calcium carbonate (lime- stone) and the very soluble magnesium sulfate, which is subse- quently leached out, leaving the soil productive. (Seepage 171.) The new Manito experiment field is on alkali soil consisting of peaty, clayey sand with some gravel, and containing sufficient total potassium for normal crop yields. In Table 92 are recorded the treatment applied and results obtained in 1907. TABLE 92. CORN YIELDS IN ILLINOIS SOIL EXPERIMENTS: NEW MANITO FIELD: PEATY ALKALI SOIL PLOT No. TREATMENT APPLIED FOR 1907 CORN (Bu. per Acre) 2OI 202 W. 2O2 E. 203 204 205 None .... 8.8 43-5 64.9 73-o •4.9 5-4 Manure, 6 tons . Manure, 12 tons Potassium sulfate, Calcium sulfate, 2 None .... 400 pounds to 16 tons 474 INVESTIGATION BY CULTURE EXPERIMENTS Plot 204 is divided into four equal parts and the calcium sulfate applied at the rate of 2 tons, 4 tons, 8 tons, and 16 tons per acre, at a cost of $6 per ton. It produced no benefit in 1907. Whether it will assist in the removal of the magnesium carbonate by double decomposition and leaching and thus improve the soil in time, time alone will tell. (The 1908-1911 crops show no benefit.) The 400 pounds of potassium sulfate are applied for a three- year rotation at an initial cost of $10. The increase of 66 bush- els of corn produced the first year, at 35 cents a bushel, amounts to more than twice the total cost of the potassium. The manure also gave very excellent results. In Table 93 are given all results obtained during six years' experiments on part of theMomence soil experiment field, located in Kankakee County, Illinois, near the Indiana line, on peaty swamp land which contains much decaying peat and coarse sand in the surface and subsurface, with a clayey sand subsoil resting on impure limestone, while the surface, subsurface, and subsoil contain more than half of the normal amounts of total potassium (19,000, 47,000, and 73,000 pounds, respectively, per acre). The soil contains but little alkali. After 1902 (when the corn was damaged by water) the land was tile-drained sufficiently well for ordinary years, but in the ex- tremely wet season of 1907 the corn was planted very late, and with the continued wet weather resulted in almost a complete failure. Potassium was not applied to plot 102 for 1902 and 1903, and was not applied to plot no for 1904. The untreated check plot 101 is naturally somewhat more productive than the other plots. These results from the newManito field and from theMomence field, on abnormal swamp lands, emphasize the fact that, although some principles are well established and can be applied with normal results on normal soils and on some abnormal soils (as the deep peat and sand ridge soils), there are complex problems still unsolved relating to soils and soil fertility. These problems may be chemical, physical, or biological, and their solution may require the application of science yet unknown. Thus, some essential element of plant food may be present in abundance but held in unavailable form by physical combination, as in grains of sand : or there may exist some still undiscovered ILLINOIS FIELD EXPERIMENTS 475 TABLE 93. CROP YIELDS IN ILLINOIS SOIL EXPERIMENTS: MOMENCE FIELD PLOT No. PEATY SWAMP LAND: SOIL TREAT- MENT APPLIED CORN (Bushels per Acre) 6 CROPS 1902 1903 1904 1905 1906 1907 Bu. Value 101 IO2 None 6.6 5-5 14.9 7-i 4.8 20.1 6.8 3S-9 6.8 -6 I no 7 3 Legume, lime . . . 14.9 8-3 49-1 61.9 48.9 3°-3 43-9 257-3 4 Legume, lime, phos- phorus 12. "? 4Q.4 ^7.2 4O.O 37.1 42.0 247 4 5 Legume, lime, phos- phorus, potassium . 19.9 n.6 44-7 56.5 40.9 38.1 50.6 262.3 Oats or Wheat, Bushels per Acre Oats Wheat Wheat Wheat Wheat Wheat Wheat Wheat Series Series Series Series Series Series Series in 200 300 200 IOO 200 300 IOO 6 Years I None IQ.I .4 6.7 1.2 r8 A.T. none 16 s 2 Legume V 18.8 •*t .6 / 7.1 O 10.8 o "v4 *T O 6.1 none L"' j -2O. O 3 Legume, lime . . . 19.8 •7 / IO.O 18.2 •j ™ 17.9 13-0 4-5 JW.V. 64-3 4 Legume, lime, phos- phorus 20. o 8.0 14.8 2<.6 ii. 3 1:5.6 8.? 8l.6 5 Legume, lime, phos- ~_; v o * o 3 phorus, potassium . 3!-7 II. O 17-5 30.0 15.0 15-6 9.8 98.9 average of the type, although large areas are to be found as badly worn as the field from which this soil was collected. This field has been under cultivation for about seventy-five years, and was still cropped when the soil was collected. During the earlier period of its cultivation the soil frequently produced 25 bushels of wheat an acre, but during the later years about 5 bushels has been the aver- age crop in normal seasons. Table 98 gives the results from six years' experiments with pot cultures on this type of soil. It is seen that practically no gain has been made except where nitrogen was supplied, either directly in commercial form or indirectly by means of legume treatment. It should be borne in mind that no legume treatment preceded the 1902 wheat crop. The catch crop of cowpeas, which was planted after the 1902 wheat crop and turned under later in the fall, pro- duced a marked effect upon the 1903 wheat crop. This effect be- came more marked in 1904 and 1905, when every pot receiving legume treatment outyielded the pot receiving lime-nitrogen treatment. The last line in the table gives the yields from a pot of virgin soil collected from a piece of unbroken virgin sod land adjoining the cultivated field from which the soil in all the other pots was taken. It is seen that the yields frorn this pot are gradually de- creasing, doubtless due to the exhaustion of the more active or- ganic matter in the soil. TABLE 98. CROP YIELDS FROM PULASKI COUNTY (ILLINOIS) SOIL Pot-culture Experiments YELLOW SILT LOAM HILL LAND OF THE UNGLACIATED AREA 1902 1903 1904 1905 1906 1907 WHEAT WHEAT WHEAT WHEAT WHEAT OATS (Grams) (Grams) (Grams) (Grams) (Grams) (Grams) Soil Treatment Applied None ? c A A 4 6 Legume, lime A IO 17 26 IO 37 Legume, lime, phosphorus . . 3 14 19 2O 18 27 Legume, lime, phosphorus, potas- sium 3 16 20 21 iQ 3° Lime, nitrogen 26 17 14 If n 28 Lime, phosphorus 3 6 4 6 4 8 Lime, potassium ..... 3 3 3 5 5 10 Lime, nitrogen, phosphorus . . 34 26 20 18 18 30 Lime, nitrogen, potassium . . .33 14 21 21 16 23 Lime, phosphorus, potassium 2 3 3 5 3 7 Lime, nitrogen, phosphorus, po- 34 31 34 21 20 26 tassium Virgin soil (no treatment) . . 24 17 15 17 13 6 The results from the pot cultures bear out very conclusively the results obtained from the field tests; namely, that marked improve- ment can be made on this soil by turning under legume crops where lime has been applied. Very striking results appear in the oat crop in 1907. Of interest in this connection is another series of pot-culture experiments, with soil from the worn hill lands of Henry County, FIELD EXPERIMENTS IN THE SOUTH 487 in northwestern Illinois, which furnish additional information concerning the general need of nitrogen for these hill lands. The plan of these experiments, the soil treatment applied, and the results obtained are all shown in Table 98.1, and they require no further comment. TABLE 98.1. OAT YIELDS FROM HENRY COUNTY (ILLINOIS) SOIL Pot-culture Experiments YELLOW SILT LOAM HILL LAND: UPPER ILLINOISAN GLACIATION OAT YIELDS Soil Treatment Applied . (Grams per Pot) None cr Lime 4 Lime, nitrogen 4"% Lime, phosphorus 6 Lime, potassium ' 5 Lime, nitrogen, phosphorus 78 Lime, nitrogen, potassium 46 Lime, phosphorus, potassium 5 Lime nitrogen phosphorus potassium .... 38 Nitrogen phosphorus potassium .... 31 None . ... c The Mississippi Experiment Station has reported in Bulletin 108 one year's experiments (1906) at Holly Springs in the northwest part of that state, on similar worn hill land where fertilizers were used for cotton, corn, and cowpeas. The following comments are made: "Phosphates hastened the maturity of cotton. On land with some decaying organic matter in it, phosphate alone gave good results, good enough to make it profitable. Potash alone, or in combination with nitrogen and phosphates, gave no apparent results. Nitrogen (cotton-seed meal) alone gave good re- sults. Cotton-seed meal and phosphates mixed gave good results." Similarly, in referring to the corn and cowpeas, the following statements are made: "The land was thin upland. A drought of seven weeks obtained when the corn was young. Where the soil contained organic matter, phosphates alone gave good results. Potash alone, or in combination, failed to show any appre- 488 INVESTIGATION BY CULTURE EXPERIMENTS ciable benefit. Nitrogen (cotton-seed meal) alone gave good results. A mix- ture of cotton-seed meal and phosphates gave good results." "The fertilizer test with peas was interfered with somewhat by the October storm, but it was apparent that both acid phosphate and crude, finely ground rock increased the growth of peas in a marked manner — apparently doubling the crop." In Iowa Bulletin 98, 1908, are reported the following yields of clover hay from the Leon experiment field on the loess and till soils of southern Iowa. TABLE 99. SOUTHERN IOWA FIELD EXPERIMENTS PLOT SOIL TREATMENT CLOVER HAY PER ACRE 401 a Loess None 2800 pounds 402 a Loess Lime 2400 pounds 403 a Loess Manure 4480 pounds 404 d Loess Phosphorus ^480 pounds 40^ a Mixed J Potassium 2600 pounds 406 a Mixed Phosphorus 4750 pounds 407 a Mixed Potassium 2480 pounds 408 a Mixed Phosphorus, potassium 4680 pounds 409 a 410 a Till Till Lime, nitrogen, phosphorus, potassium . . Nitrogen, phosphorus, potassium .... 6560 pounds 4600 pounds So6 b Till Lime 3520 pounds l8> 23 • • 17 1 80 182 6.1 3.68 I8.5 3, 8, 14, 19 ... 17 l62 211 7.0 3.68 I8.7 4, 9, 15, 20 ... 17 146 236 7-9 3.68 !7-3 5, 10, 16, 21 ... 17 J31 259 8.7 3.68 17.0 ii (unfertilized) ii. 6 "The plan of the experiment was to make up five different formulas and apply the same cost value of each different formula to corresponding successive plots." The same section of land (Div. B, Sect, i — East) was used for corn in 1900, and the report for that year states that " no plots were left unfertilized." The fertilizer (including 53 pounds FIELD EXPERIMENTS IN THE SOUTH 49 1 cotton-seed meal, 45 pounds of acid phosphate, and 2 pounds of potassium chlorid, in 100 pounds) was applied at the rate of 200, 400, and 600 pounds per acre, and the respective yields of corn were 35.8, 37.0, and 38.4 bushels per acre, from which the conclu- sion is drawn that " the results only confirm conclusions repeatedly reached in previous years that large doses of commercial fertilizers ' do not pay,' as a rule, when applied to corn on upland." In this connection the following rainfall records are of interest : TABLE 161. RAINFALL RECORDS AT EXPERIMENT, GEORGIA YEARS MAY (Inches) JUNE (Inches) JULY (Inches) AUGUST (Inches) TOTAL FOR THE YEAR IQOO IQOI IOO2 . 2.6l 6.09 .70 12.02 5-14 I QO 6.84 3.22 I ^4 4-45 6.27 4 QQ 62.33 53-40 47 O<\ 1QO? . 6.47 2.27 2.28 e 46 48.78 1QO4 . 2.43 .8? •2.64 6.91 20 06 IQCX . ^8 4.07 3.OI 2.02 42.77 1906 2.21 5-03 4.17 6.48 44-74 Averages, 1890 to 1906 .... 3.08 4.II 5-OO 5-93 46.47 The yearly records for 1900 and 1904 are the extremes for the seventeen years. In Table 102 are recorded the results of a series of fertilizer ex- periments with cotton, as reported in Georgia Bulletin 63. For the 1904 corn crop fertilizers were applied uniformly to all plots (except No. u) as follows, in pounds per acre: SODIUM NITRATE COTTON- SEED MEAL ACID PHOSPHATE POTASSIUM CHLORID Section 4 Section 5 17 21 156 IQ"> 130 162 6.2 8.0 In 1906 cotton was grown on at least part of the same land as in 1003, with the plan of experiment and results reported in Table 103. It is not clear whether these results may have been influenced 492 INVESTIGATION BY CULTURE EXPERIMENTS TABLE 102. GEORGIA FERTILIZER EXPERIMENTS WITH COTTON POUNDS APPLIED PER ACRE COST OF .FERTIL- YIELD VALUE 1904, EACH PLOT (4 Rows for Plot n?) Sodium Nitrate (With Seed) Cotton- seed Meal Acid Phos- phate Potas- sium Chlorid IZERS (Except Nitrate per Acre) COTTON (Pounds per Acre) CREASE AT 4^ PER POUND CORN (Bushels per Acre) NITROGEN TEST: DIVISION B, SECTION 4, EAST, 1003 1904 I, 6, 12, 17, 22 . I5.6 2OO 250 25.0 $4.15 1146 $15.04 20.3 2, 7, 13, l8> 23 . I5.6 160 306 30.6 4-15 1 1 2O 14.00 2O. I 3, 8, 14, 19 . . 15-6 120 362 362 4-15 1072 12.08 18-5 4, 9, 15, 20 . . 15-6 80 418 41.8 4-15 I°57 11.48 19-5 5, 10, 16, 21 . . I.S-6 40 474 47-4 4-15 1042 10.88 19.6 ii (unfertilized) I5.6 770 20.1 POTASSIUM TEST: DIVISION B, SECTION 4, WEST, 1903 I, 6, 12, 17, 22 . 19-5 195 520 65 $6.50 1503 $22.13 2, 7, i3» l8> 23 • 19-5 205 547 52 6.50 1438 19.71 3, 8, T4, 19 • • 19-5 215 574 39 6.50 1448 20.16 4, 9, J5, 20 . . 19.5 225 601 26 6.50 1488 21.96 5, 10, 16, 21 . . 19.5 235 628 13 6.50 I451 20.29 ii (unfertilized) 19-5 IOOO POTASSIUM TEST: DIVISION B, SECTION 5, WEST, 1903 I, 6, 12, 17, 22 . 19.5 195 520 65 $6.50 1556 $24.93 2, 7, 13, l8> 23 . 19.5 205 547 52 6.50 1639 28.66 3, 8, 14, 19 . . 19-5 215 574 39 6.50 1635 28.48 4, 9, 15, 20 . . 19-5 225 601 26 '6.50 1667 29.92 5, 10, 16, 21 . . 19.5 235 628 13 6.50 1693 31.09 ii (unfertilized) 19-5 1002 POTASSIUM TEST: AVERAGE, 1903 1,6, 12, 17, 22 . 19-5 195 520 65 $6.50 1529 $23.76 25-3 2, 7, X3, l8> 23 • 19-5 205 547 52 6.50 i538 24.16 25-5 3, 8, 14, 19 . . 19-5 215 574 39 6.50 i54i 24.30 25-3 4, 9, I5, 20 . . 19-5 225 601 26 6.50 i578 25.96 21.7 5. 10, 16, 21 . . 19-5 235 628 T3 6.50 1572 25.96 24.0 ii (unfertilized) 19-5 IOOI 22.2 by the residual effect of previous applications made in the " ni- trogen test," for example (Table 102). The use of fertilizers on corn in Georgia, if profitable at all, is evidently made possible only because the farm price of corn is very high (69 cents as a ten-year average), and the profit from the FIELD EXPERIMENTS IN THE SOUTH 493 TABLE 103. GEORGIA FERTILIZER EXPERIMENTS WITH COTTON (Division B, Sections 4 and 5, East, 1906) FERTILIZER FORMULA: Acid phosphate . . . 1000 Ib. Cotton-seed meal . . 498 Ib. Potassium chlorid . . 74 Ib. 1572 'b- APPLIED PER ACRE RESULTS PER ACRE Mixed Fertilizer Nitrate (With Seed) (Lb.) Yield of Seed Cotton (Lb.) Increase Due to Fertilizer (Lb.) Value of In- crease 1 Amount (Lb.) Cost 12 plots of 3 rows each . 1 2 plots of 3 rows each . 12 plots of 3 rows each . 2 plots of 4 rows each . 4OO 800 I2OO $4.00 8.00 I2.OO 22 22 22 22 1735 1890 2042 1454 28l 436 r-QQ 5<55 $10.11 15.69 21.17 1 At 10 cents a pound for lint and 70 cents a hundred for seed. use of fertilizers is found in the cotton crop, which it should be remembered is the most valuable per acre of all the general field crops grown in the United States (potatoes and tobacco being considered as truck or garden crops) . As an average seed cotton is about one third lint and two thirds seed, and a hundred-bushel crop of corn is more difficult to produce than 3000 pounds per acre of seed cotton, which would yield 1000 pounds (or 2 bales) of cotton lint. At ten cents a pound for cotton lint and 70 cents per 100 pounds for cotton seed, such a crop would be worth $114 an acre, or about three times as much as 100 bushels . of corn at the ten-year average price in the corn belt. Georgia produces less than 200 pounds of cotton lint per acre, on about 4^- million acres, the annual acreage being second only to that of Texas. Judging from the composition of the residual soils of Maryland, Tennessee, and Georgia, and from the statement by Director Red- ding concerning the value of farm manure reenforced with acid phosphate, it seems evident that large use of ground limestone and legume crops, the latter to be plowed under either directly or in farm manure, and liberal applications of phosphate, constitute the most essential factors for the permanent improvement of such land; although, under the present condition of most of the upland soils of Georgia and other Southern states, profitable use can no doubt be made of potassium, at least until the supply of active organic matter is greatly increased, and especially for the cotton crop, which pays such large returns for a comparatively small increase in yield per acre. 494 INVESTIGATION BY CULTURE EXPERIMENTS TABLE 104. ALABAMA FIELD EXPERIMENTS, 1905-1908 Averages per Acre per Annum LAU- DER- CULL- CHIL- Au- TAU- MONT- GOM- TALLA- MACON o DALE MAN TON GA ERY Co., A PLANT FOOD APPLIED COST Co., GRAY SILT Co., GRAY SANDY Co., GRAY SANDY Co., RED- DISH Co., BLACK OK RED GRAY SANDY DARK GRAY SANDY fc LOAM UP- SOIL SANDY PRAI- LOAM SOIL LAND SOIL RIE No. of Years in Trial 4 3 4 3 3 4 3 SEED COTTON PER ACRE, POUNDS I a Nitrogen (14 Ib.) l . . Phosphorus (16 Ib.) . $2.50 1.68 649 678 442 571 647 573 .0, 888 789 f\nf\ 464 484 635 587 468 625 ,.QT 4 5 6 7 8 (i Potassium (20 Ib.) . . Nitrogen, phosphorus . Nitrogen, potassium . Phosphorus, potassium Unfertilized .... NPK 1.50 4.18 4.00 3.18 s 68 374 796 1295 886 695 387 QI7 320 452 721 576 614 291 68? 4°3 646 657 618 57° 437 778 70O 829 801 716 679 880 576 503 628 644 382 74O 433 610 651 663 626 358 74.2 634 728 595 610 522 Q2S 10 NPK (*) . A Q7 80 1 7IO 718 808 689 7QO 89? INCREASE OF SEED COTTON PER ACRE, POUNDS T N $2. SO 27S 122 163 212 62 2O 2 —IT. 7 P i 68 204 2SI O4 II -2 82 1C A I4S 4 K I. "CO 4IQ 138 172 27 178 IQ2 I4S. e NP 4.18 Ql6 412 IQ2 IS2 IOQ 248 27,1 6 NK 4-OO SO4 274 163 124 238 27=; GO 7 PK 3.18 711 317 124 -58 2S8 2C^ 96 n NPK 5.68 "?3O 7Q2 ^41 2O I 7C7 ^84 4O3 Tri NPK(i) . 4. Q7 414 410 280 1 2O 307 472 771 VALUE OF INCREASE PER ACRE (AT 3.2 c. PER LB.) T N $2 SO 88c 7. OO S 23 6 78 I. QQ 6.46 —.41 0 P i 68 97-2 804 3 O2 T 6?, 2 63 4. 04 .63 A K I SO I 3 41 4 41 S 40 .7S S.7I 6.13 4.64 C NP ....... 4 18 20 31 13 22 6 16 4 87 3.40 7. "8 | ON co t^ T}- 10 PI 00 00 O 11 O* PI PO T(- to PO H V ,1 °^ « "• O *t **• 1- 11 PI PO PO PO p? p? Eo£r Pt PI M PI n PI Pl PI Pl M fO rt f\ t~~ PI 1- 90 to f« I - "~. S. I/-. to PI PO t^ to ^ PO PI to > W | w t^ PO Tj- to « 10 t « O « PI PI PO PO PO <; oo & PI COO " PI O Pl PI PI PI PI M PI CO Tf PI Pl PI PI (^ O ON PO to f» PI O t~- t^ t^. por^ 11 i 00 10 « I^-O t^O a 00—00 PO •* Tf CO co i-i •* o-> oo PO c- i O O PO PI PI PI I-I rj- Pl Pl Pl OC M PI Pl PI >- DO OO O « M M Tt- tox o tooo PI O 00 Pl -? 21 Tf « PI 10 Tf O PI P) f~ O & PI O 00 O POOO M O 1- « BQ •a "S CO PI O TJ- O M tOO t-- Tt-00 r~» O co to - jjj 1 O coto to >0 PO o o « o o PO to Tf Tf co M ON PO PO PO PO PO co co •* O* PI O CO CO Tf 1- •* < "f t to •t PI OO O IO to co r-. o O 00 O 00 «^ - OOO 00 00 M >H ,1 1 t-00 Pl to to T)- M 00 O PO CO to to O to to O 'too >O IO to PO PI O O CO tf •* Tt IO Tj- IO IO r^. coo n Tt 10 •* 10 >• rO r~- Tf w o •* o oo & t^oo & r~ O O 't t^ O O « t^ r^ U M > ? O P0«~- PO ON *t f^ O t^oo O PO to 10 O f\O oo or- tf M I E CD 00 r» o> o o 00 — O> i^-C O 3C r^oc c^ - 00 w PO PI ON PO PO t— M 00 M •* O PO t^ to O co T)- o « O < ?2^ i-O 0 0 PO >- Tt- 10 co O OO PO Tf O CO •* t Tf •* to too P! PO f PO PI PO t^. to IO CO co co Tt CO •* O to co co «^ CO co r~ r>. O PI to t^ «-«• O 00 PI O PO O PO t^- PI IN (N r--. 9 1 £•£•""' O^ O *t" O* t~~ M 11 11 IO 00 O O OOO t^. t^OO M 3 o 00 00 PO PI PI PO O PO '^. I/", I -- 1^. O O Pl to co n O to PI X o co Pi co PI Pi n to 00 00 « O M M M « M coo o PO to O t- t^O to too < H > 4> Tf R co Pi Pl ^ o « 'r ^ PO «- PI PI CO O O to r- to t^-oo to > a U J CO o 0> r-- PI to PI « rj- PO oo oc PI T to >O «^ 00 Tf O PO co PI CN PI oo o PI 00 00 00 00 M H E 00 t^ 0 O O 00 — O O •* « •* PI to- PI- o o o •- o to O «- O U H 2 00 «» PI PI w O - O O t~ O> 00 O1 3O « 00 O 00 CO t^.O O 00 PO O O ^ 00 °S 0 O 0 PI PI » O PI t^- PI O >-• fO PO O M to CO IO PI PI co CO Pl ° ° & Jl *5* 3 * !| u jj "-1 _ J2 £^ g* io. •a • tu '^ o a • ^JS J3 ^0 ^^ 0~ o o K 4- < CT ••a >i ~ tn tn & . f3 o oo o . 10 >- 5 . to . 1> " Sf-i u too* & -° C w g a> ' a v . s?1 {& e o s> :& : o ** s SciincSoor}' rC •a| 1 1 1 REATMENT APPLIED JIVE (Except i goo to 1904 (and no T Grain each Spring from 1899 to under in the Fall.) Mixed rotted yard manure, 15 Mixed fresh manure, 15 tons Unfertilized Raw phosphate to 1897 ; slag sir Sodium nitrate, 200 Ib., with r 1897 and with slag since, 500 1 Rotting manure, 6 tons, with r 1897 and with slag since, 500 1 Nitrate, 200 Ib., and ashes, 10 phosphate to 1897 and with sk Unleached wood ashes, 1500 Ib phate to 1897 and with slag si s-"5 • .2 o • T3 0 • 0 M . « airS • r&i : a«To . ^1^ 0-Q, .-o o 8 g.2 •5-= J=~ a-aat: 3"2r2«^ ~ 'C 'o c <«^ Fine-ground bone, 500 Ib. . Bone, 500 Ib. ; ashes, 1500 Ib. Sodium nitrate, 200 Ib. . . Potassium chlorid, 150 Ib. . Ammonium sulfate, 300 Ib. . . . .£ O o . to •£=„• ^IM o-o" B v O'c; « rt fljaa ^•328 "3 a Sj= « § 3 ft ci^lS'H 2 o rt G ic«U< § d M « PO Tf 10 O t^ 00 ON O 11 PI PO t too t^ 00 O O 11 £ « « CANADIAN FIELD EXPERIMENTS 509 plot 13 yielding only 1.2 bushels more wheat, 2.3 bushels more oats, and .4 bushel less barley than plot 4. The 300 pounds of cal- cium sulfate on plot 20 produced .4 bushel more wheat, the same yield of oats, and .9 bushel less barley than the 500 pounds of acid phosphate on plot 21. By referring to Table 78, we find that as an average of six 4-year periods, 640 pounds of calcium sulfate pro- duced practically no effect (12^ cents per acre in four years), while dissolved bone black carrying 42 pounds of phosphorus produced an average increase of $12.17. These results certainly indicate that phosphorus is not the limiting factor in crop yields on the Ottawa soil. The effect produced on oats by the fine-ground bone is probably due to the nitrogen contained in the bone. It is a common ob- servation that oats respond to nitrogen more rapidly than most other crops on the same soil, and it will be observed that sodium nitrate alone (plot 15) produced practically the same effect on oats as the nitrate and acid phosphate combined. Where nitrogen was provided, the raw phosphate (plots 5 and 7) produced a larger average increase on oats than did the acid phosphate (plots 10 and u), during the first nine years. A study of the results with wheat and barley indicate that potas- sium is the first limiting element for those crops. As an average of the first ten years, the largest yield of wheat was produced by po- tassium chlorid, aside from the farm-manure plots; and the second largest yield was with ashes (plot 14; compare with 13). Sodium chlorid also produced some increase in the yield of wheat, and with barley the 300 pounds of sodium chlorid produced the largest yield, aside from the two heavily manured plots. Even acid phosphate, containing much calcium sulfate and an acid salt of phosphorus, may liberate some potassium. It may be questioned whether potas- sium or nitrogen is most limiting for the barley crop, but it is plain that phosphorus is not the limiting element. Even during the sec- ond ten years, the 150 pounds of potassium chlorid or the 300 pounds of sodium chlorid rank higher than 500 pounds of bone or 500 pounds of acid phosphate, in either trial (plots 9 and 21), and also far above the slag phosphate (plot 4) . On plot 6 the raw phosphate was applied in connection with " actively fermenting " manure, and it may have produced some 5io INVESTIGATION BY CULTURE EXPERIMENTS effect, but this cannot be known, because there is no comparison plot on which the same amount of untreated manure was used. If we average plots i and 2, we find that 6 tons of phosphated manure on plot 6 produced more than 70 per cent as much in- crease as 15 tons on plots i and 2. Comparison with the Penn- sylvania and Ohio experiments does not help much in trying to decide if the raw phosphate was effective when mixed with the manure at Ottawa, in part because the applications are propor- tionately different, and in part because the manure itself produces different effects on different soils. With the data presented, any possible comparisons can be made by the student. Except for the oat crops which, as stated, usually respond readily to nitrogen, ammonium sulfate with the 60 pounds of nitrogen produced a smaller average effect than the sodium nitrate with 30 pounds of nitrogen, thus indicating that the sodium in the nitrate exerted appreciable influence. Apparently, iron sulfate produced some small effect, but it is doubtful if it is greater than would have been produced by 60 pounds of sodium chlorid. For this and other comparisons in- volving few plots, the author calls attention to the fact that there are some marked natural variations among the individual plots in these series; and in such cases no final conclusions can be drawn. In the oat series, plot 3 produced 9 bushels more oats per acre than plot 12 as an average for the first nine years, and 14 bushels more for the next ten years. Plot n in the oat series is evidently a plot which yields below normal. The quotations from Doctor Saunders show that some parts of the field were naturally wetter than others, and on page 51 of the Annual Report for 1897 the statement is made that " plots 12, 13, and 14 were on a piece of rising ground on light soil." The records for 1903 and 1904 give the yields for the last two years of green manuring with catch crops of clover, while 1906 and 1907 furnish later records after the fertilizer applications were renewed, beginning with 1905. In Table 107 are given probably the most significant data from the root crops (and potatoes) that were grown on alternating half plots in these series during the seven years, 1891 to 1897. CANADIAN FIELD EXPERIMENTS g r* Os 6S § 53 ON r*> 0 IO IT) IH "O W O^ O w O O O !O 10 fO N ff) H \O •«*• ON O a>O VO OvOO SO O -\O *~- ON O HI > •« < 0, -^ 00 sS S=5 O 0 0 OO OO - O OOO vo *~« 00 HI \O - 10 •* C> 00 VO •* t^ a £ be < =»c ?^n 00 O\ O i-i ro t-^\o f; O 10 O Tj- O -"fr « -4- O O O O O O HI N M \O ONNO 00 ' 30 10 M f. cs t^ t~~\o ^r ON •t 10 O O\ IO VOOO <*5 Ttoo i>- § g ~O "> S3 O\ O\ 1/1 O ^t H P) N HI Ov »O fi OO OO HI OO M •* o « o .a£ < rOO O CNVO Tt- ro O 00 OO <~O ON t^ »O t*5 t^ t^.NO P* v o M l-l • < bo** 2 3, fcg o o o» M *-• O O fO •^- ro w «^ °° CIJ3 . t^-\o •<*• M OO ONO « lO t^ M r^; tNi oo fO r^. o ONOO H ON 00 "^.3 00 r^oo 1~- ro\O HI O^ HI ro fOOO 00 O 1000 HI O M. M O a i $32 OO r^ rr. Ifl t^ T}- M N 00 cs O O Tf O ON O •* H HI M •'t OS — T; rtO rOO if. <3 O OO Tf O l~- IO 4s* t*- NO ro ON l~- PI vo t^oo t^ w ' M HI in Z h. 01 u. -; o 00 »o PD tr> TJ- ro TJ- o\ ro VO •* M t^« T VOOO NO HI 0 H 3° Ci -G «sj t^ O M P) CS M M tO HI OO HI C* O rv ^ O . O 5j ^ O ."R 8 . a 02 VO O ^ IT) . m-^ T ,- 8 ° 1 IT} rn S tL^ «J • 5 fe ~™ rt • Tf VO\O t^-OO ON O HI PHOSPHORIC Aero (P.OS) POTASH (K,0> Available Total "Superphosphate ....... 1.64 1. 00 2.50 .82 1.64 1.64 2.47 2-47 1.64 2.00 1.25 3-oo 1. 00 2.OO 2.0O 3.00 3-oo 2.OO 8.00 8.00 8.00 8.00 8.00 IO.OO IO.OO 8.00 IO.OO IO.OO 14.00 IO.OO 12.00 11.00 II.OO 10.00 II.OO 13.00 13.00 IO.OO II.OO II.OO 15.00 II.OO 2.OO I.OO 5.00 4.00 7.00 2.OO 3-0° IO.OO 1 Complete fertilizer 1 Sugar-beet grower , 1 Truck grower 1 Onion, potato, and tobacco . . . 1 Kentucky tobacco grower .... 1 Special tobacco fertilizer .... 1 Vegetable and tobacco grower . . . Ammoniated phosphate Special phosphorus and potash . . . O&rdcn city phosphate 2.OO n Diamond "S" phosphate .... 1 Insoluble phosphoric acid derived from animal bone. "Nitrogen (ammonia) in all the above brands derived from Blood and Bone. " Purchasers of fertilizers should profit by the fact that the higher the guaran- teed fertilizer analysis, the less the cost of the plant food obtained, allowing for equal distances of shipment. It pays, therefore, to buy fertilizers on the basis of analyses and not simply by the price per ton for some certain brand. By making a careful comparison of our analyses when buying fertilizers, 's will lead. "For the convenience of our customers in making comparisons of values of different fertilizers, we suggest the following as being approximate values: " (i) Pure Bone Fertilizers. If any one of these grades is desired, the values for the essential compound ingredients may be limited as follows: Ammonia at 15 c. per Ib. $3.00 per unit Phosphoric acid at 5 c. per !b i.oo per unit Potash, actual, at 6c. per Ib 1.20 per unit Ammonia at 15 c. per Ib 3.00 per unit "(2) Acidulated Fertilizers, which are more complex in their nature and manufacture, may be judged comparatively by the following: MANUFACTURED COMMERCIAL FERTILIZERS 523 Phosphoric acid, available, at 7 c. per lb $1.40 per unit Phosphoric acid, insoluble from bone, at 5 c. per Ib i.oo per unit Phosphoric acid, insoluble from rock, at i c. per lb 20 per unit Potash, actual, at 6c. per lb 1.20 per unit "Multiplying the minimum guarantees with the above valuations per unit, the total is the relative value per ton of 2000 pounds." Of these fertilizers, the "Special Bone Meal," containing 12 per cent of phosphorus, is a fair grade of steamed bone meal, and the "Garden City Phosphate" containing 6.1 per cent of available phosphorus and less than £ per cent of insoluble phosphorus represents the most common grade of acid phosphate on the mar- ket. At the prices given, a pound of phosphorus would cost about 1 1 cents in steamed bone meal and about 16 cents in acid phosphate. In some cases different brands have the same composition, even where sold by the same company. In fact, some of the larger fertilizer companies sell a dozen different brands of the same com- position, so that the total number of brands sold by all companies is very large, amounting to about goo in the state of Indiana and to more than 1800 in Georgia, which only emphasizes the fact that most farmers purchase fertilizers by name rather than on the basis of plant food. Probably half of all the fertilizers bought by American farmers have as an average the " 2-8-2 formula," as in the " Superphosphate " and " Eagle Wheat and Corn Grower." In some states, as in Illinois, a deficiency of i per cent below the miminum guarantee is " not considered evidence of fraudulent intent," but greater deficiencies subject the dealer to a severe pen- alty if prosecuted. (See Model Fertilizer Law, in the Appendix.) In most states the burden of " fertilizer inspection and control " is placed upon the agricultural experiment station, and some- times this burden has almost prevented the stations from con- ducting investigations concerning the soils of the state or in other important lines where exact information is needed. In other states, as in Pennsylvania, Ohio, and Illinois, the enforcement of fertilizer laws is placed with the State Board of Agriculture, and the ex- periment station is left free to conduct agricultural experiments and investigations. It may be added that there is grave doubt if the agricultural investigator should be compelled to depend, either in large part or in small part, upon the income from tonnage tax 524 VARIOUS FERTILITY FACTORS or brand tax of commercial fertilizers sold in his state, as a source of revenue for the support of his department of investigation. FORMS AND SOURCES OF COMMERCIAL NITROGEN Aside from the free nitrogen of the air,, there are four distinct " forms " of nitrogen : (i) organic nitrogen, (2) ammonia nitrogen, (3) nitrate nitrogen, and (4) cyanamid nitrogen. Aside from farm manure and crop residues, the chief sources of organic nitrogen are (i) dried blood and tankage from the slaughter houses or stock yards, (2) cotton-seed meal from the oil refineries in the South, and (3) fish-scrap in the Eastern and extreme West- ern states. (Near the coast seaweed often becomes the staple manure. It contains about as much nitrogen and phosphorus as farm manure, and nearly five times as much potassium.) Dried blood. A good grade of dried blood contains 14 per cent of nitrogen, while tankage is of various grades, ranging almost from blood to bone. It contains much of the offal, and may include the undigested contents of the stomach and intestinal tract. One common grade is "7 and 30" tankage, meaning 7 per cent of ammonia (NH3) and 30 per cent of " bone phosphate," Ca3(PO4)2, corresponding to 6 per cent each of nitrogen and phosphorus. A mixture containing about 2 parts of tankage, 3 or 4 parts of acid phosphate, i part of kainit, and i or 2 parts of filler will produce the " 2-8-2 formula," with about 2 per cent of "insoluble phosphoric acid derived from animal bone." The annual pro- duction of tankage and blood amounts to about i million tons. Dried peat. Train loads of dried peat are shipped from the peat beds of Illinois and elsewhere to the fertilizer factories for use as a filler; and as a filler it is said to be superior to all other materials, because it is a very effective absorbent and thus keeps the acidu- lated fertilizers in excellent mechanical condition. Dried peat con- tains from 3 to 4 per cent of nitrogen which may be "found" by analysis, although the nitrogen in peat is at best no more active than that in the ordinary organic matter of the soil, which usually amounts to 3000 to 5000 pounds per acre in the plowed soil, so that 50 pounds of peat in 200 pounds of "complete" fertilizer would not appreciably affect the crop. MANUFACTURED COMMERCIAL FERTILIZERS 525 Cotton seed. Cotton-seed meal contains about i£ per cent each of phosphorus and potassium. Sometimes the whole cotton seed, containing about 3 per cent of nitrogen, is used directly as a fertilizer, but as practically all of the plant food remains in the hulls and cake (after the oil is expressed) , the meal is now largely used, and more profitably, of course, unless the farmer pays more for his nitrogen than he received for the same amount in seed, which is likely to be the case if he buys ready mixed "complete" fertilizer. The annual production of cotton seed in the United States amounts to about 6 million tons. Fish scrap. Fish-scrap meal contains about 8 per cent of nitro- gen and 6 per cent of phosphorus. There are various other sources of organic nitrogen, some of which, like hoof meal, furnish avail- able nitrogen, while others, like hair, wool waste, and horn meal, are very slowly nitrified. Ammonium sulfate. Commercial ammonium sulfate is usually about 95 per cent pure, containing 20 per cent or more of nitrogen. It is obtained by washing coal gas through dilute sulfuric acid and concentrating the liquid until the ammonium sulfate crystallizes out. About 100,000 tons of ammonium sulfate is the present annual production from the gas plants and coke ovens in the United States, and the production is likely to largely increase, because most of the American coke ovens are still wasting the ammonia produced. Sodium nitrate. Sodium nitrate of commercial grade is about 95 per cent pure, and contains 15 per cent or more of nitrogen. It is obtained from the extensive nitrate beds of Chile, where it is found in very extensive deposits, thought to have resulted from the decomposition of seaweed in connection with sea salt. The impure material is leached and the nitrate secured by crystalliza- tion. The exportation began about 1830 and has quite steadily increased from 8000 tons in 1840 to about 2 million tons in 1908, the total exportation from 1830 to 1909 amounting to about 40 million tons, which is about one sixth of the estimated 1 amount re- maining in the Chilian and Peruvian beds. The export duty 1 The estimates of ten years ago placed the total supply at 81 million tons, but a so-called official report made in 1909 (American Fertilizer) estimates 246 million tons. 526 VARIOUS FERTILITY FACTORS yields an annual revenue of more than $20,000,000, or about three fourths of the total income of the Chilian government. Most of the sodium nitrate imported into the United States is used for the manufacture of explosives. Calcium nitrate. The artificial fixation of atmospheric nitrogen by an economic and practical method is a problem whose solution has been given much attention for many years; in fact, it has been the dream of many a chemist and a dream which has only recently been realized. Calcium nitrate is now produced to a limited extent (chiefly at Notodden, Norway, by the aid of cheap water power) by the Birkeland-Eyde process, in which a current of air is subjected to powerful electric action, which results in the formation of nitrogen tetroxid (as observed by Priestly as early as 1775), which by somewhat complex reaction with water and oxygen yields nitric acid. This is treated with lime to form calcium nitrate, which is obtained in crystallized form, Ca(NO3)2 4 H2O, containing about 12 per cent of nitrogen. Calcium nitrate is a highly deliquescent substance, and must be shipped in air-tight containers. In an experiment at Rothamsted 10 grams of calcium nitrate (produced at Notodden in 1906) absorbed 20 per cent of water and became liquid in 3 days, and in 10 days about 50 per cent of water had been absorbed. Calcium cyanamid. Calcium cyanamid is also a product result- ing from the artificial fixation of atmospheric nitrogen, by a pro- cess recently developed by Frank and Caro of Germany. The primary materials used in the process are limestone, coke, and nitrogen gas. Calcium carbid is first produced by heating a mixture of burned lime and coke to a very high temperature pro- duced by an electric furnace: CaO + 3 C = CaC2 + CO. The calcium carbid is finely ground and then placed in closed retorts and heated to the requisite temperature in an atmosphere of nitrogen, which reacts with the calcium carbid with the forma- tion of calcium cyanamid and separation of carbon : CaC2 + 2 N = CaCN2 + C. MANUFACTURED COMMERCIAL FERTILIZERS 527 The nitrogen gas is obtained from the air, either by passing air through a hot tube containing copper turnings, which remove the oxygen by forming copper oxid (the oxid being again reduced by substituting coal gas for air), or by the Linde liquid-air process, in which advantage is taken of the difference between the boiling points of nitrogen (— 194° C.) and oxygen (— 184° C), the nitro- gen being evaporated at the lower temperature. Potassium cyanid is a well-known substance with the formula KCN, or N=C — K, and the group or radicle, N = C — , is called cyanogen, somewhat as the group — NH4 is called ammonium, and the group — NH2 is called the amido group. Cyanamid contains the two groups, thus N = C — N=H2, and by replacing the two hydrogen atoms by one bivalent calcium atom, calcium cyanamid (N=C — N=Ca) is produced. Calcium cyanamid itself con- tains 35 per cent of nitrogen; and, if the product could be made with the one atom of free carbon as the only impurity, the nitro- gen would still reach 30 per cent, but about one third of the commercial article consists of other impurities (coal ash, lime, cal- cium carbid, sulfid, phosphid, etc.), the nitrogen being thus re- duced to about 20 per cent. An analysis of a commercial sample gave the following results: Calcium cyanamid (CaCN2) 57.0 per cent Carbon 14.0 per cent Lime (CaO) 21.0 per cent Silicon dioxid 2.5 per cent Iron oxid 4.0 per cent Calcium sulfid, phosphid, and carbonate . . . 1.5 per cent When first added to the soil the commercial calcium cyanamid with its impurities produces an injurious effect upon young plants, and to avoid this it is applied a week or two before seeding. For the same reason it cannot safely be used as a top-dressing. It has a tendency, because of its lime content, to absorb moisture and carbon dioxid from the air, and for protection is usually treated with a small amount of heavy petroleum. A ten-gram sample of calcium cyanamid exposed for 1 2 days at Rothamsted increased 30 per cent in weight, and some loss of ammonia occurred. 528 VARIOUS FERTILITY FACTORS Many pot-culture and field experiments have been made with calcium cyanamid which show that when properly used the nitrogen in this form has about the same value as in ammonium sulfate. When heated with water under pressure, calcium cyanamid decomposes with the formation of calcium carbonate and ammonia, as indicated by the following equation: CaCN2 + 3 H2O = CaCO3 + 2 NH3. For long-distance shipping the final product from the artificial fixation of atmospheric nitrogen is, in the opinion of the author> to be ammonium nitrate, made by using the ammonia thus pro- duced as a base for neutralizing the nitric acid obtained in the Birkeland-Eyde process. NH3 + HNO3 = NH4NO3. The ammonium nitrate thus formed, free from mineral im- purities, would contain 35 per cent of nitrogen. To produce this compound would require five plants: (i) for nitrogen gas, (2) for calcium carbid, (3) for calcium cyanamid, (4) for ammonia, and (5) for nitric acid. A publication issued June i, 1907, by the American Cyanamid Company, estimates that the original cost of a complete plant for the production of 10,000 tons per annum of calcium cyanamid would amount to $444,000, including: $155,000 for the calcium carbid plant, 70,000 for the Linde nitrogen plant, 145,000 for the calcium cyanamid plant, 74,000 for expense not itemized. This estimate of $444,000 does not include the cost of the power plant, it being assumed that a separate company will be organized to furnish the power by utilizing a natural waterfall. In connection with elaborated estimates as to the actual cost of producing cyanamid nitrogen in such a plant, the following state- ments are made in this publication : " Throughout all estimates of costs of operating it is assumed that power costs the Cyanamid Company $15 per 24-hour horse power per annum, meas- ured on the switchboard of the power company supplying the power. It is MANUFACTURED COMMERCIAL FERTILIZERS 529 assumed also that the power company and the works of the Cyanamid Com- pany are so close together that there will be no appreciable loss in electric transmission." " Thus the total estimated cost, including interest upon the estimated in- vestment of $444,000, is $45 per metric ton,' equivalent to 22^ cents per kilogram of nitrogen, or 10 cents per pound." It should be noted that this 10 cents per pound for cyanamid nitrogen is the estimated cost to the manufacturers, and that it includes no allowance for transportation of the finished product from the factory to the farmer, no allowance for the cost of adver- tising and selling, and no allowance for any profit to anybody. It should be noted, too, that the 4 million pounds of combined nitrogen which such a plant could produce in one year would be sufficient, if none were lost in drainage waters, to meet the " grow- ing demands " of the average corn crop of the United States for less than 200 minutes. A calcium cyanamid factory is located at Niagara Falls. SOURCES OF COMMERCIAL POTASSIUM There are three important sources of commercial potassium: (i) the German mines, (2) the salts recovered from the evapora- tion of sea water, and (3) wood ashes. Potassium salts of Germany. The very extensive salt deposits in the region of the Harz Mountains in northern Germany con- stitute at present by far the most important source of commercial potassium. These deposits were discovered by borings made near Stassfurt in 1857, and the potassium salts are found chiefly in strata overlying the much thicker stratum of common rock salt. It is estimated that these German salt deposits cover an area of a million acres, and that the supply of potassium which they con- tain is sufficient to supply the present rate of mining for 190,000 years. It is thought that these salt and potash beds were formed in ancient geologic time by the evaporation of sea water confined in lakes somewhat like the Dead Sea, or Great Salt Lake, except that there. was at times connection with the ocean which supplied the salt water. Evaporation carries off water vapor and leaves the salts in solution, but if the evaporation proceeds far enough, the 530 VARIOUS FERTILITY FACTORS less soluble salts, such as (i) calcium sulfate (gypsum) and (2) sodium chlorid (common salt), begin to separate in crystals which settle to the bottom; and with further evaporation of water the more soluble salts of potassium and magnesium finally separate in crystals which are deposited in strata above the principal salt deposits. After vast amounts of water had been evaporated and immense quantities of salts deposited, these accumulations sometimes be- came covered with drift material (clay etc.) several feet in thick- ness, and at a later period the sea water again, came in and by evaporation left a second stratum of calcium sulfate, and above it another immense salt deposit. The total thickness of these various strata is about 5000 feet at Stassfurt. There are many variations and irregularities, but in the main the lower stratum consists largely of calcium sulfate; next above is the sodium chlorid deposit of great depth; then a layer of the mineral polyhalite, composed of the sulfates of po- tassium, calcium, and magnesium, kieserite (magnesium sulfate), and finally a stratum varying from 50 to 130 feet in thickness, which consists largely of carnallite, a double salt of potassium and magnesium chlorid. In some places the overlying clay or earth became cracked, and water entered from the surface, so that more or less of the various salts were dissolved and redeposited in veins or pockets in com- pounds or forms not commonly found in the more general strata. Thus were formed comparatively small beds of kainit, sylvanite, and hartsalz. More than thirty different compounds or minerals are found in these Stassfurt deposits, and at least a dozen of these contain more or less potassium. By far the most abundant source of potassium is the carnallite stratum, but even the pockets or beds of kainit, sylvanite, and hartsalz are of great importance. The following are commonly accepted as the formulas which represent these minerals: Carnallite, KC1 MgCl2 6H2O. Kainit, K2SO4 MgSO4 MgCl2 6 H2O. Sylvanite, K2SO4 MgSO4 KC1 MgCl2 NaCl 6H2O. Hartsalz, KC1 MgSO4 NaCl H2O. MANUFACTURED COMMERCIAL FERTILIZERS 531 There are three principal potassium fertilizers brought to America from Germany: potassium chlorid, kainit, and potassium sulfate. The commerical kainit usually consists of two thirds of the mineral and one third sodium chlorid, and contains about 10 per cent of potassium. It is ground and used very generally for direct application. Potassium chlorid is obtained from carnallite, and potassium sulfate from kainit, by dissolving the minerals and allowing these salts to crystallize out at suitable temperatures. Commercial potassium chlorid is usually at least 80 per cent pure, while the sulfate has a purity of nearly 95 per cent. Each contains about 42 to 43 percent of potassium. Potassium sulfate is also produced from potassium chlorid and sulfuric acid in the manufacture of hydrochloric acid, for which sodium chlorid was formerly used. Sylvanite and hartsalz (hard salt) are sometimes ground and applied in the crude state, but the concentrated salts may also be derived from them by solution and recrystallization. Potassium-magnesium sulfate, or " double manure salt," is another Stassfurt preparation which is used to some extent. It contains, as found in the market, about 20 per cent of potassium. Its special value, like that of potassium sulfate, is for use in fer- tilizing those crops whose " quality " is injured by salts containing chlorin, particularly the tobacco crop. Wood ashes. Unleached wood ashes commonly contain 5 per cent of the element potassium (as carbonate), 50 per cent of cal- cium carbonate, and .5 per cent of phosphorus. On most soils they are likely to be more valuable for the lime than for their potassium content; and, when applied at the rate of a ton or more per acre, even the phosphorus added is more than that con- tained in 200 or 300 pounds of the common " complete " commer- cial fertilizer. Potassium from sea water. Where common salt is obtained from the evaporation of sea water, as has been done to some extent on the southern coast of France, potassium is secured as a by- product from the concentration of the " mother liquor," and one may conceive of unlimited supplies being produced in this manner where the climatic conditions and other natural advantages can be utilized, as on an arid coast and under a tropical sun, especially 532 VARIOUS FERTILITY FACTORS where tidal power could fill extensive reservoirs and where a mountain stream could serve to dissolve and remove the salt deposit after the " mother liquor " is drawn off for further con- centration. It is sometimes claimed that potassium salts, especially kainit, have some power to prevent damage from fungous diseases and injurious insects, but it may be questioned whether the effect is direct or indirect ; data already given show very conclusively that not only potassium salts, but also the salts of magnesium and sodium (usually to a smaller extent), produce marked benefit in many instances. In most cases, however, any influence which aids directly or indirectly in the proper nourishment of the plant will thus enable the plant itself better to resist attacks of insects or disease. The author has frequently observed that insect in- juries are much more apparent on corn grown on poor land than on adjoining plots treated with phosphorus in connection with farm manure or crop residues. Where the soil is markedly deficient in potassium, as compared with normal soils, as is the case with certain peaty swamp soils, and where the application of potassium salts on such soils produces marked benefit, while sodium salts produce practically no benefit (see Table 91), there can be no question regarding the need and value of potassium for its own sake; and even where the soil con- tains normal amounts of potassium, if enormous crops are to be grown that draw very heavily on potassium, as the 40 to 50 tons per acre of mangels on Barn field at Rothamsted (see Table Jib), the time will come when potassium must be returned. (This, how- ever, is also the case with magnesium and calcium.) On the other hand, where the plowed soil contains sufficient total potassium to meet the draft upon it for, say, two thousand years, and where sodium or magnesium salts produce about the same effect as potassium salts, and where potassium produces little or no effect if applied in connection with liberal amounts of decaying organic matter, the conclusion may be safely drawn that the addition of commercial potassium is not essential in adopting systems of permanent agriculture, for even the slight erosion that occurs on nearly level lands will possibly provide an absolutely permanent supply. CHAPTER XXVIII CROP STIMULANTS AND PROTECTIVE AGENTS A CLEAR distinction should be made betweeen the use of plant food in systems of permanent agriculture and the use of crop stimulants or crop " protectors." Unquestionably there are con- ditions under which the use of some particular substance, other than plant food, will produce a sufficient increase in the yield of the crop for which it is applied to more than pay the cost; and, further- more, the use of such material may in some cases be advisable, but it should be used with intelligence and full understanding of its effect. Land-plaster. Land-plaster (native calcium sulfate) is a well- known crop stimulant, but it contains neither nitrogen, phos- phorus, potassium, nor lime, supplies no plant food of commercial value and has no power to correct soil acidity, and its physical effect on the soil is probably injurious rather than beneficial. In fact, it is the common report that the soil tends to become hard and more compact with the long-continued use of land-plaster; but whether this effect is wholly due to the wearing out of the organic matter, or in some part due to the cementing properties of the calcium sulfate, cannot be stated with certainty. When de- hydrated, calcium sulfate becomes plaster of Paris, and it is a constituent of different cementing materials. The temporary beneficial effect of land-plaster is probably due to its chemical action in the soil. It may convert more or less of the supposedly difficultly available iron phosphate into the more readily available tricalcium phosphate, as indicated by the follow- ing equation : 2 FePO4 + 3 CaSO4 = Ca3 (PO4)2 + Fe2 (SO4)3. Very possibly this or some similar reaction occurs to a limited extent when calcium sulfate is applied to a soil containing iron 533 534 VARIOUS FERTILITY FACTORS phosphate. Another possible reaction may result in the liberation of potassium or magnesium from polysilicates, as roughly indicated by the following equation: AlFeMgNaKx+2 (SiO3)y (H2O)Z + CaSO4 = AlFeMgNaKxCa (SiO3)y(H2O) With large supplies of potassium present in polysilicates, heavy applications of calcium sulfate would doubtless liberate some potassium sulfate, although under the opposite conditions mass action would force the reverse reaction; that is, heavy appli- cations of potassium sulfate to a soil containing much calcium in polysilicates would liberate some calcium sulfate. The potassium sulfate liberated from the insoluble silicate, as indicated above, may serve directly as plant food, or it may react to increase the availability of phosphorus, thus : Ca3 (PO4)2 + 2 K2SO4 = CaK4 (PO4)2 + 2 CaSO4. These equations are given to show some of the possible reactions that may occur when a soluble salt is added to the soil. A dozen different reactions may be taking place at the same time within the same cubic inch of soil, and it is easily possible that, while one reaction is taking place in one part of the cubic inch, the reaction is running in reverse order in another part, depending upon the mass, composition, and concentration of the insoluble and soluble salts. If a solution of ammonium sulfate or potassium chlorid is per- colated through a stratum of soil, an examination will usually show that, while ammonium or potassium passed into the soil, calcium and magnesium have passed out in the percolate. If tricalcium phosphate be shaken with pure water, practically no phosphorus will be found in the filtrate; but if a solution of some neutral salt, such as sodium chlorid or potassium nitrate, be sub- stituted for the pure water, very appreciable amounts of phosphorus are dissolved. Land-plaster has been much used in some parts of the North Central and Eastern states, and for a time it usually gives quite profitable results; but finally, the element of real value that has been liberated by the action of the land-plaster becomes so depleted CROP STIMULANTS AND PROTECTIVE AGENTS 535 that even heavy applications of plaster fail to liberate sufficient for profitable crops, and thus the plastered land is made poorer than the untreated land. A common method of advertising has been to write the word PLASTER with a heavy application of the material in large letters on a cultivated field in view of the public road. In the larger, greener growth of grain crops or grass, the word PLASTER can be read by the passers-by; and thus the landowner is induced to plaster his whole field. If, however, he would only apply plaster year after year where the word was first written, the time would come when the word could not be read; and, if he still continued the applica- tions, ultimately he would again be able to read PLASTER, if we may judge from the testimony of common experience. Common salt. Common salt (sodium chlorid) is sometimes used as a crop stimulant, but its beneficial effect is likely to be even less durable than that of land-plaster. However, where common salt or other soluble salts, such as sodium sulfate or magnesium sulfate, or mixtures like kainit, are applied in connection with sufficient supplies of phosphorus, nitrogen, and lime, the effect of the stimu- lant must be confined chiefly to holding the phosphorus or other necessary elements in available form and to liberating potassium from the soil; and where the natural supply of potassium is ex- tremely large, the beneficial effect of the applied salt may continue for many years, as is well shown in the results from Rothamsted. Kainit. Kainit, of course, also supplies some potassium, and is thus in some part a fertilizer, though in large part a stimulant. To some extent this is also true of the common acid phosphate, which contains phosphorus mainly in the form of a soluble acid salt, and twice as many molecules of manufactured land-plaster : Ca3 (P04)2 + 2 H2S04 = CaH4(P04)2 + 2 CaSO4. It is difficult to conceive of a more effective combination than about 200 pounds per acre of a mixture of acid phosphate and kainit applied twice for each five-year rotation of corn, oats, wheat, clover, and timothy. With all crops removed, such a system would doubt- less as thoroughly deplete the soil as any that could be devised, clover itself, used in this way, being a very powerful soil stimulant. If anything could be added to hasten the action, an application 536 VARIOUS FERTILITY FACTORS of five tons of farm manure about once in ten years (spread very uniformly, and an occasional dressing of burned lime, would make this system of ultimate land ruin very complete. A mixture of 300 pounds of acid phosphate and 100 pounds of kainit in five years would, with the manure system, furnish about 5 pounds of nitrogen, 5 pounds of phosphorus, and 6 pounds of potassium per acre per annum; whereas, crops as large as we ought to try to produce would remove from the soil as a yearly average about TOO pounds of nitrogen, 20 pounds of phosphorus, and 80 pounds of potassium (see Table 13). When crops one half as large are produced under such a system of fertilization, the soil under the action of these stimulants must furnish about nine tenths of the nitrogen, half of the phosphorus, and six sevenths of the potassium required for the crops. An invoice of his stock of fertility will help the landowner to plan wisely for the future, because he can thus know in advance what the ultimate effect must be of such systems. Protective agents. As protective agents we may include materials which tend to ward off disease or insect enemies; and the effect may be produced by substances destructive to fungi or repellent to insects. Kainit is thought to act sometimes as a fungicide, and tankage is held by some to prevent attack from certain insects. Any treatment which hastens the normal growth of the plant usually helps the plant to resist or overcome the attack of insects or disease; and it is apparently true that imperfect or abnormal plants are more likely to suffer from such attacks than normal, healthy plants. It has been suggested that sucking insects prefer the concentrated sap of weak or somewhat withered plants to that of vigorous succulent plants. Doctor Forbes has suggested that the very dilute juice of a rapidly growing plant may constitute a starvation diet for healthy insects; in other words, that the capacity of the insect for such juice is not sufficient to furnish it with the amount of nutrition necessary for maintenance and reproduction. It is common observation that chinch bugs may attack and destroy wheat that would otherwise yield 10 or 15 bushels per acre, while wheat growing in the same field on land capable of producing 30 bushels or more per acre is not attacked. The author has noted in several different seasons that corn growing on land that will CROP STIMULANTS AND PROTECTIVE AGENTS 537 yield 40 to 60 bushels per acre has been very severely injured by the colaspis root worm, while no apparent damage was done on adjoining well-fertilized plots which produced 80 to 100 bushels per acre, although the insects were found in both parts of the field. In any or all of these ways small applications of fertilizers or stimu- lants may produce results in crop yields far beyond the direct nutrient value of the plant food applied. The practice is somewhat common in places of coating seed corn by stirring with a paddle dipped in warm tar, and to some extent castor oil has been used for the same purpose, the appli- cation being made two or three weeks before planting so that the oil coating may have time to " dry on." Turpentine has also been used, and some have advised putting powdered sulfur with the seed in the planter boxes. These of course are solely protective agents, if they have any value. Their use is based upon experi- ence, however, and not upon experiment, and thus far the practice seems to rest upon no better foundation than that of planting potatoes "by the moon," or "witching" for water, an "art" which fails to find water twice in the same place if the operator is blindfolded. CHAPTER XXIX CRITICAL PERIODS IN PLANT LIFE IN this connection we may well consider another cause of differences in crop yields quite out of proportion to the difference in soil treatment. There may be, and often are, critical periods in the life of plants, when some small measure of assistance may change prospective failure into marked success. Thus, it is not infrequently a question of life or death with the clover plant when the nurse crop is removed; and, while most of the plants may die at that time on untreated land, a good stand of clover may be saved where a very light application had been made of manure, fertilizer, or soil stimulant. The nutrient value of the application may not be sufficient for half a ton of clover, but the difference in yield may amount to one or two tons; and from the larger crop larger resi- dues are left on and in the soil, resulting in a larger crop of grain the following year. Thus, enormous credit may be given, which is not at all deserved, on the basis of total plant food concerned. One of the most critical periods in the life of the corn plant is at the time the ears are forming, and an ample supply of moisture appears to be especially necessary at that time. If a severe sum- mer drouth is coincident with this critical period, the yield of grain is likely to be small; and any soil treatment which has the effect either of hastening or retarding the development of the plant, and thus of bringing the earing time either before or after the drouth, may very markedly affect the crop yield. The farmer is usually most anxious for conditions under which his wheat will " fill " well, and since this is influenced very appre- ciably by the temperature during this critical period, it follows that very marked effects upon both yield and quality may sometimes result from any soil treatment that causes the wheat to " fill " either a few days earlier or a few days later than on the untreated land. On the other hand, the treatment, whether applied as a crop 538 CRITICAL PERIODS IN PLANT LIFE 539 stimulant or in a system of permanent soil improvement, may some- times be the means of bringing this critical period at the time when the weather conditions are most unfavorable, while the untreated land may mature a larger crop at the more favorable time. An instance has been reported of a field treated with half a ton per acre of raw phosphate having produced a crop of 45 bushels of oats free of rust, whereas only 20 bushels of badly rusted oats were produced from similar seed on adjoining untreated land. Two influences may help to produce this difference: the added phos- phorus tends to balance the food ration and thus to strengthen the oats against the fungous disease (and against lodging, as well), and also to hasten the maturity by which the crop escapes the rust which might attack the plants maturing later and perhaps under weather conditions more favorable for the development of the disease. As was stated by the author to the farmer who reported this experience, the marked difference in yield is not to be credited even largely to the phosphorus because of the plant food for its own sake, but rather to a combination of influences to which the added phosphorus proved to be the key. While such examples may serve temporarily as good advertise- ments for the treatment applied, they are just as misleading for wide application as are the occasional reports of damage to crops produced by applying manure. All of this serves to emphasize the importance of having some fundamental knowledge upon which to base definite systems of permanent agriculture. For this pur- pose we must rely primarily upon the absolute facts furnished by chemistry and mathematics and be guided only by the results of carefully conducted and long-continued experiments. Single examples can be found in support of almost any practice or theory that can be advanced; but a mere experience, though it be repeated, invariably with the same result, for fourscore times, furnishes no proof whatever that the octogenarian will live to celebrate another birthday. A small amount of readily available plant food, such as 50 pounds of sodium nitrate per acre as a top dressing for wheat on poor land in a cold spring, may produce a sufficient increase in yield to more than pay the cost of the nitrate. Likewise, 100 pounds of " am- moniated bone and potash," carrying perhaps 2 pounds of nitro- 540 VARIOUS FERTILITY FACTORS gen, 4 pounds of phosphorus, and 2 of potassium may be dropped in or near the hill of corn with a " fertilizer attachment " to the planter, and, under adverse conditions of soil and season, the crop increase may show some profit. It should be clearly understood, however, that all such systems of fertilizing are of themselves only an aid to soil depletion, because the " good start " thus given to the crop enables it to draw upon the soil itself for larger supplies of one or more elements of plant food than would be furnished by the untreated soil and the fertilizer applied. Quite independent of any such practices, the landowner should make ample provision for maintaining the fertility of the soil, on normal soil, by large use of phosphorus and farm manure or legume crops and crop residues, sufficient limestone being applied when necessary to prevent or correct soil acidity. Where this is done, however, the use of " starters " is usually unnecessary and unprofitable. Indeed, the dropping of a small quantity of fertilizer in the hill of corn for near it) is sometimes a source of damage, not so much because it may injure the seed or young plant, but because it does not encourage the normal development of the root system in proportion to the early growth of the plant, and as a consequence the crop may suffer from drouth later in the season much more than the unfertilized corn. CHAPTER XXX FARM MANURE THE value of farm manure is governed largely by four modify- ing and somewhat related factors. First, the composition of the materials used for feed and bedding. Second, the dryness, or dry-matter content, of the manure. Third, the preservation or stage of decomposition or waste of the manure. Fourth, the kind of animals producing the manure. As a general average a ton of fresh-mixed cattle and horse manure contains about 500 pounds of dry matter, 10 pounds of nitrogen, 2 pounds of phosphorus, and 8 pounds of potassium. It would be produced from about 810 pounds of air-dry feed (yielding 270 pounds of 'dry excrement) and 270 pounds of air-dry bedding (containing 230 pounds of dry matter). On this basis, four tons of air-dry feed and bedding (used in the proportion of 3 to i) would produce about 7^ tons of average fresh manure containing 25 per cent of dry matter and 75 per cent of water. Roughly, this represents the theoretically possible production of manure on the farm, if all crops grown are used for feed and bedding. If the crops sold from the farm amount to one third of the total produced, and if one fifth of the manure made is lost be- fore it is applied to the land, then for every ton of air-dry produce harvested and removed from the land one ton of manure could be returned. If we count 85 per cent of dry matter in the air-dry feed and bedding, and 66| as the average digestion coefficient for the dry matter in the food consumed (see Table 29), and 75 per cent of the nitrogen and phosphorus and 90 per cent of the potassium re- turned in the manurial excrements, then a ration of 500 pounds of clover hay and 310 pounds of corn, with 270 pounds of wheat 542 VARIOUS FERTILITY FACTORS straw for bedding, would make a ton of manure containing 500 pounds of dry matter, about 12 J pounds of nitrogen, 2 pounds of phosphorus, and p| pounds of potassium. Or a ration containing 500 pounds of timothy hay and 310 pounds of oats, with 270 pounds of oat straw for bedding, would make a ton of manure containing 500 pounds of dry matter, about n pounds of nitrogen, 1.7 pounds of phosphorus, and 9 pounds of potassium. Some loss of nitrogen is likely to occur by volatilization, and both nitrogen and potassium are very likely to be lost in the liquid excrement. For the most common rations used in live-stock farming, 10, 2, 8 represent very approximately the average pounds of the three elements, nitrogen, phosphorus, and potassium, in a ton of " aver- age fresh manure." By leaching and fermentation the dry matter, nitrogen, and potassium are lost in approximately the same pro- portion, but the phosphorus is lost only about half as rapidly, so that one ton of average yard manure, resulting from perhaps two tons of fresh manure, contains about 500 pounds of dry matter, 10 pounds of nitrogen, 3 pounds of phosphorus, and 8 pounds of potassium, one half of the dry matter, nitrogen, and potassium, and one fourth of the phosphorus having been lost. Wheat bran contains about 24 pounds of phosphorus per ton, so that, for every 100 pounds of bran used in the ration, nearly one pound of additional phosphorus will be found in the manure. This illustration and reference to the average composition of food stuffs will show how important the factor of food is in affecting the quality of manure. Most analyses of manure represent the product in a more or less decomposed state, in which case the phosphorus content is likely to be appreciably higher than in strictly fresh manure, and even manure commonly called fresh is likely to have lost some nitrogen and potassium in the liquid excrement. The following analyses include some accepted averages from the best authorities. While these general averages may be satisfactorily applied to large quantities of mixed manure, or in estimating the amounts of plant food in repeated applications of fresh or yard manure, respectively, they cannot safely be used for small single lots, unless the per cent of dry matter is determined and the character of the feed and bedding used is known. FARM MANURE 543 TABLE no. COMPOSITION OF FRESH MANURE Pounds per Ton AUTHORITY KIND OF MANURE DRY MATTER NITROGEN PHOS- PHORUS POTASSIUM Wolff Cows AC.O 68 I 4 66 S. W. Johnson .... Cornell Station .... Sir John Lawes . . . • . Voelcker Cows Horses Mixed Mixed 294 659 672 676 7-6 n-5 i4-3 12. 0 i-4 . 2-4 2.2 2.O 6.0 9.6 IO.O o s French data Mixed ZOO 7.8 1.6 7.5 UNIFORM BASIS Wolff Cows zoo 7-6 1.6 7.3 S. W. Johnson .... Cornell Station .... Sir John Lawes .... Voelcker Cows Horses Mixed Mixed 500 500 500 ZOO 12.7 8.7 10.7 0.7 2-4 1.9 i-7 2.2 9.0 7-3 7-5 7 I French data Mixed 500 7.8 1.6 7-5 General average .... 5O and could not be removed by leaching, except in the case of the dead-ripe wheat; while phosphorus as well as the other elements was apparently taken up in excess of the absolute needs of the plants and in part tolerated until removed by leaching. This is the most probable explanation for the difference in results from these experiments and those reported by Wilfarth, Romer, and Wimmer; and the author has taken the liberty of suggesting to Le Clerc and Breazeale that by extending these investigations in connection with fertilizer experiments, results of great scientific value and of far-reaching practical importance will probably be secured in relation to the absolute requirements of plants for the different elements essential to plant growth. It has long been recognized that the analysis of the plant or of the plant ash was not a sufficient guide for use in planning systems of fertilization; but, for certain of the elements, the analysis of the thoroughly leached plant at the proper stage of growth may give more satis- factory information; and, because of its very general character, it seems especially appropriate that it should be continued by the federal government, while local problems, such as county soil surveys, are perhaps better managed by the state institutions. The fact that phosphorus is most frequently the limiting element in plant growth or crop yield on most normal soils, especially for legume crops, suggests that the averages commonly accepted for the composition of crops probably represent the minimum amounts of phosphorus, as a rule. CHAPTER XXXII LOSSES OF PLANT FOOD FROM SOILS THERE . are four ways in which plant food may be lost or re- moved from the soil: (i) by removal in crops as already explained, (2) by leaching after solution in the rain water or soil water, (3) by mechanical erosion, either by surface washing or by wind action, and (4) by volatilization, a factor of minor importance, represented chiefly by the slight loss of nitrogen in ammonia or by denitri- fication, a process which may occur to a limited extent under some- what abnormal conditions. Loss of plant food from soils by the process of leaching is a matter of very great consequence, chiefly because large amounts of nitrogen may thus be lost every year in humid sections. Even under the best systems of farming more or less nitrogen is likely to pass off in drainage waters. The annual loss of lime by leaching is large (see Tables 27 and 28), and when long periods of time are con- sidered, the amounts of magnesium, potassium, and other elements removed from the soil by leaching (see Table 74) become very significant. The only practical method of preventing or reducing the loss by leaching is by the use of growing plants, the roots of which may absorb the plant food about as rapidly as it is made soluble. If desired, it may be then returned to the soil in the form of organic matter, afterward to become available when required to meet the needs of regular crops. The use of rye or rape as a green manure, by seeding in the fall and plowing under the next spring on land that would otherwise lie bare during the fall, winter, and early spring, is often profitable, in part because of the conservation of plant food that would otherwise be lost by leaching. This fact and principle is well illustrated by the following data from that great source of positive agricultural information, the Rothamsted Ex- periment Station. SS6 LOSSES OF PLANT FOOD FROM SOILS 557 TABLE 116. NITROGEN IN DRAINAGE WATERS: ROTHAMSTED EXPERIMENTS Average of 12 Years (or More) MONTH RAINFALL (Inches) BARE SOIL, 6o-lNCH GAUGE WHEAT LAND, NITROGEN (Per Mil- lion of Water) Drainage (Inches) Nitrogen (Per Million of Water) Nitrogen (Pounds per Acre) January 2.13 2.l6 1.70 2.25 1-93 1.74 •94 •79 8.9 9.I 8.9 9.0 3.88 3-57 1.89 1.61 3-1 4.0 2.0 1.9 February March April May 2.48 2-59 2.85 2.69 •79 .78 .62 .76 9.I 9.1 n.8 J3-3 1.63 i. 60 1.66 2.28 •9 • .1 .1 .1 June My . August September October November . . . 2.70 3.12 3.20 2-34 .82 1.68 2.32 1.88 13-4 11.9 11.4 10.6 2.50 4-53 5-98 4-51 3-9 4.6 3-6 4.8 December January-April .... Mav-August 8.24 10.61 11.36 5-4° 2-95 6.70 9.0 10.6 n.8 10.95 7.17 I7-52 2.8 •3 4.2 September-December . . January-December . . . 30.21 iS-05 10.5 35-64 2.4 While the drainage water from the bare uncropped soil of the drain gauge contained 11.4 parts of nitrogen per million during the summer months (June to August), the drainage water from the land on which wheat was growing (Broadbalk plots 3 and 4) con- tained only .1 pound of nitrogen per million pounds of water, as an average of the three months. After the wheat harvest, the loss of nitrogen in the field drains quickly rises to about 4 pounds per million. In loss per acre the differences are much greater, because during the growing season the quantity of drainage from the field is probably even less than that from the drainage gauge, and the data from the gauge show two to three times as much drainage during the other months. In Table 117 are recorded the amounts of water-soluble nitrogen found in the soil and subsoil of Hoos field, where the shallow-rooting white clover (Trifolium repens) had been grown for seven years and where the vetch and the deep-rooting alfalfa had been grown for 558 VARIOUS FERTILITY FACTORS six years, also of Agdell field after the wheat crop had been har- vested, in the legume system and the fallow system, for which the yields are recorded in Table 57. TABLE 117. SOLUBLE NITROGEN IN CROPPED SOILS RECEIVING NO NITROGEN FERTILIZER SINCE 1849 (Pounds per Acre) Hoos FIELD AGDELL FIELD Wheat Land DEPTH White Alfalfa Vetch Land Land, Land, Julv,' July, July, After After 1885 1885 1883 Clover, Fallow, Fall, 1883 Fall, 1883 First 9 inches II.S 8.9 IO.2 6.1 3.4 Second 9 inches . . . . J 1.4 y I.I 2.7 4.4 O't 2.1 Third 9 inches . . . . •9 .8 I.I 1.6 .8 Fourth 9 inches .... 1.9 .8 i-5 i-3 I.O Fifth 9 inches 7.1 I.O 2.< i.< .8 Sixth 9 inches / II. 3 .0 j 4.4 o .8 .6 Seventh 9 inches .... o J3-1 V .6 «t*«l 4-5 2.2 .8 Eighth 9 inches .... 12.6 .8 4-9 i-7 •9 Ninth 9 inches .... II. 2 •7 4.8 2-4 •7 Tenth 9 inches .... I0.y .6 5-i 2.1 2.0 Eleventh 9 inches . . . II. I •4 6.4 2.1 i-5 Twelfth 9 inches .... IO.O •4 6-5 2.8 3-8 0—9 inches II. 1 8.9 IO.2 6.1 -J A 9-36 inches J 4.2 • y 2.7 ^ 3 7 3 O'T' •2 Q ?-o feet . «t*« 87.! / 5-4 J'j 39-i I'J 15.6 O'V II. I The crops of white clover were too small to cut in 1880, 1883, and 1884, and in other years only a single cutting was harvested. Thus most of the rather small amount of produce was left to decay upon the white clover plot. Evidently 87.1 pounds of nitrate nitrogen has escaped beyond the reach of the white clover roots, while almost no soluble nitrogen (5.4 pounds) was found in the same stratum (3 to 9 feet) under alfalfa. The root system of vetch is perhaps even less extensive than that of white clover (see Table 36), but the annual decay of the roots possibly gives it the inter- mediate position in loss of nitrogen as indicated, although a different season may perhaps have given quite different results. The data 559 from Agdell field indicate that only small amounts of nitrogen escape from the wheat plant under the conditions, these results being in harmony with those reported in Table 116. On the University of Illinois experiment field at Urbana are two adjoining plots, one of which (No. 3) grew corn for 16 years, while the other (No. 105) was kept in pasture. In 1901 plot 3 con- tained 4000 pounds of nitrogen and plot 105 contained 4914 pounds in 2 million of surface soil, a loss of about one fifth of the total being thus indicated. Professor Shutt reports the nitrogen content of virgin soil and adjoining cultivated soil from the Northwest Territory of Canada. He says: "Regarding the cultivated soil, we possess a complete and authentic record of the cropping and fallowing since the prairie was first broken, 22 years ago. It has borne 6 crops of wheat, 4 of barley, and 3 of oats, with fallows (9 in all) between each. "Both samples were of a composite character and every precaution taken to have them thoroughly representative. It may, further, be added that there is every reason to suppose that the soil over the whole area examined was origi- nally of an extremely uniform nature; in other words, that at the outset the ni- trogen content was practically the same for the soils now designated as virgin and cultivated, respectively:" NITROGEN, POUNDS PER ACRE Virgin soil, to depth of 8 inches 6936 Cultivated soil, to depth of 8 inches 4736 Difference or loss due to cropping and cultural operation . . 2200 "The results show that the cultivated soil is to-day still very rich, yet com- pared with the untouched prairie it is seen to have lost one third, practically, of its nitrogen. This is highly significant. Humus and nitrogen must be re- turned, either as manure or by the occasional growth of certain enriching crops, or fertility will inevitably decline." (Dominion Experiment Farms, Report for 1905, page 128.) Shutt reports 3780 and 3240 pounds of nitrogen in the virgin and cultivated soils, respectively, of Grindstone Island, Magdalen Islands, Quebec; also 3160 and 2260 pounds of nitrogen from virgin and cultivated soils from Kent County, New Brunswick. The corresponding figures for acid-soluble phosphorus are 2160 and 1970 for the Quebec soils, and 2180 and 1070 for the New Bruns- 560 VARIOUS FERTILITY FACTORS wick soils. The New Brunswick soils are said to be representative of the district. In commenting upon the analytical data, Professor Shutt says : "Since we must suppose, from the information furnished, that the culti- vated soil was originally identical, or practically so, with the virgin soilt it is evident that great exhaustion of fertility has taken place, due, no doubt, to suc- cessive cropping without any adequate return of plant food." (Report for 1899, page 133.) It is certain that on sloping lands a very considerable part of the total loss of humus, nitrogen, and phosphorus is due to soil erosion, although this is the minor factor on nearly level lands. It should be kept in mind that in respect to loss of humus, and of the plant food contained in humus, sheet washing on uniform slopes may be even more effective than gullying, and that it is extremely important and necessary to prevent or at least to reduce to the minimum both forms of erosion, the sheet washing by means of cover crops, deep contour plowing, contour ridging, or terracing, if necessary, and the gullying by frequent dams and by keeping the draws in per- manent meadow. President Van Hise makes the following statements regarding the loss of phosphorus from Wisconsin soils, as determined by " quantitative studies ": "Whitson finds as the result of an average of nine typical tests that 'the sur- face 8 inches of virgin soil contains 1256 pounds of phosphorus per acre, while that of the cropped fields contains but 792 pounds, an average loss per acre on these cropped fields of 464 pounds, or 36 per cent of its original content. The average of cropping for these fields has been 54. 7 years.' In other words, during the past half century in Wisconsin one third of the original phosphorus of the soil has been lost in the cropped fields. What has been proved for Ohio, Illinois, and Wisconsin and other states where tests have been made is unques- tionably true for the other states in the country which have been settled for some time. "In what conditions will the soil of the United States be as to phosphorus content fifty years hence if this process of depletion be allowed to continue un- checked?" (See page 221 of "Conservation of Natural Resources," published by the American Academy of Political and Social Science, Philadelphia, 1909.) It may be noted that a loss of 464 pounds of phosphorus in 55 years is only 8^ pounds per annum; and, if we deduct i\ pounds for loss in drainage (see Table 74), the loss by cropping does not LOSSES OF PLANT FOOD FROM SOILS 561 exceed 7 pounds per acre, an amount sufficient only for a 30- bushel crop of corn, or i| tons of clover hay. It may be kept in mind that, so long as the surface soil contains more phosphorus than the subsurface, erosion helps to deplete the soil of phosphorus ; but when the phosphorus content of the surface becomes reduced by cropping to a point below that of the subsurface, then erosion tends to increase the phosphorus in the surface soil. In regard to erosion, President Van Hise says: "It is plain that we must not permit soil erosion to take place more rapidly than the soil is manufactured by the process of nature. To do this will be ultimately to destroy our soils. If nature manufactures the soil at the rate of one inch in a century, then the erosion must not exceed one inch in one century." Of course, this statement refers especially to residual upland soils and to the making of soils from the slow disintegration of the underlying rock. Most of the corn-belt subsoils include from 20 to 200 feet of loess and glacial drift above the bed rock. The loss of plant food by cropping and leaching is the most serious matter on most of the valuable agricultural soils. Lyon and Bizzell (Jour. Ind. and Eng. Chem., Oct., 1911) report a loss of ii pounds of potassium, 76 of magnesium, and 407 of cal- cium, from uncropped soil; and 8 pounds of potassium, 31 of mag- nesium, and 1 66 of calcium, from cropped soil (average for corn and oats), in drainage water per acre from a four-foot stratum of clay loam soil, from May 23, 1910, to May i, 1911 ; and Bartow (Illinois State Water Survey Bulletin) reports 90 analyses of Illinois well waters drawn chiefly from glacial sands, gravels, and till, showing, as an average, n pounds of potassium, 130 of magnesium, and 330 of calcium, in 3 million pounds of water (see Table 74). These data confirm the results of the Rothamsted investigations (pages 174, 175, 413), showing an excessive availability of magnesium and especially of calcium ; and they clearly indicate that in many cases those elements may be of much greater importance for soil improve- ment than potassium, even from the standpoint of plant food maintenance, and in addition to their value for correcting soil acidity. (See also pages 105 and 633.) CHAPTER XXXIII FIXATION OF PLANT FOOD BY SOILS WHEN soluble plant food is applied to the soil, it is as a very general rule changed into insoluble forms by reaction with the soil. Nitrogen in the form of nitrate is an exception to this rule, the only method of changing nitrate nitrogen to the insoluble form being by the growth of some plant which converts it into organic nitrogen, as already explained.1 The fixation of bases includes not only the metals, but also the ammonium group, the soluble base taking the place of some other element in an insoluble polysilicate, as illustrated in the following general equation: AlxFexMgxNaxCa (SiO3)x(H2O)x + 2 KC1 = AlxFexMgxNaxK2 (SiO3)x (H2O)X + CaCl2. This equation typifies the reaction of soluble potassium chlorid with a zeolitic compound, resulting in the fixation of potassium and the liberation of calcium, which passes off in the drainage waters in combination with the acid radicle which formerly carried the potassium. Other mineral bases and even ammonium may be fixed in a simi- lar manner, but the ammonium fixation is very temporary, because under usual conditions nitrification proceeds rapidly and the ammonia nitrogen passes into soluble nitrate nitrogen, a fact which is well illustrated by the following data from Rothamsted. The ammonium salts consisted of equal parts of the sulfate and chlorid. Warington makes the following comments: "At the first running of the drain pipe (after October 25) sufficient time had not elapsed for the complete decomposition of the ammonium salt and the fixation of the ammonia. Some undecomposed salt of ammonium is thus 1 Even low forms of plant life, as fungi and bacteria, may aid in this process. 562 FIXATION OF PLANT FOOD BY SOILS 563 TABLE 1 18. NITROGEN AND CHLORIN IN DRAINAGE WATER BEFORE AND AFTER THE APPLICATION OF AMMONIUM SALTS ON OCTOBER 25, 1880: PLOT 15, BROADBALK FIELD Pounds per Million of Water DATE OF COLLECTING DRAINAGE WATER AMMONIA NITROGEN NITRATE NITROGEN CHLORIN October 10 None 8.2 22.7 October 27, 6.30 A.M Q O ll.S 146.4 October 27, i.oo P.M October 28 6-5 2.i; 12.9 16. 7 116.6 QC.7 October 29 I. 6 8 j. o 8 Red clover .... Horse bean, Vicia . . Garden bean . . . Peanut kernels . . 85o 850 85o 85o 3°-S 40.8 39-o 38-0 6.3 5-3 4.2 3-3 "•3 10.7 IO.I 7.0 3-° i-3 i-3 1.8 i.i i.i 0.4 0.4 0.4 0.2 O.O9 O.O9 0.3 0.3 °-3 °-5 o-5 °-3 38.3 31.0 27.4 OIL SEEDS Cotton 850 -16 f. 4.2 8.4 3.1 1.2 O.I O.O4 T 6 0.5 11.8 Flax 850 12.8 5.7 8.0 2-7 1.8 O.I O.2 0.5 32.6 Hemp 850 26.1 7-i 7.6 i-S 7-5 0.04 2-5 0-3 46.3 STRAW Corn (Maize) . . . Oat 850 850 4.8 c.6 i-7 1.2 13-7 13.5 1.6 1.4 3-5 I.O I.O 0.6 6.2 11.4 0.4 i.e. 0.6 2-7 45-3 61.6 Wheat 850 4.8 I.O 5-2 0.7 I.O 0.4 14.4 0.4 n 8 46 o Rye 850 4.0 I.I 7.1 0.7 2.2 0.6 8.8 o.c o 8 18.2 Barley Buckwheat .... 850 850 6.4 13.0 0.8 2-7 8.8 20.4 °-7 1.2 *'3 6.9 0.7 i.i 10.90 1-4 1.2 0.8 i-5 4.1 45-9 Si-7 COBS AND CHAFF Corncobs .... Oat chaff .... Wheat chaff .... Rye chaff .... 850 850 850 850 2-3 6.4 7.2 5-8 0.09 0.6 i-7 2.4 1.9 3-7 6.9 4-3 O.I 0.9 0.7 0.7 O.I 2.8 1.2 2-5 0.04 1-4 0.04 0.6 23-S 34-8 30-9 0.07 2.1 i-3 O.2 O.2 0.8 0.4 4-5 71.2 92.0 82.7 HAY Redtop 850 IO-5 i.e 8.0 Red clover in flower . Alsike clover . . . Alfalfa, early bloom . Red clover, ripe Red clover, in bud Red clover, young . . White clover in flower From very young grass 850 850 850 850 850 850 850 850 19.7 24.0 23.0 12. S 24-5 35-5 23.2 2S-S 2-5 1.8 2-3 1.9 3-i 4-5 3-5 3-2 iS-7 9-4 12.3 8-3 21-5 2S-3 ii. i 26.3 3-9 3-i 1.9 4.2 4-7 4-7 3-6 2.8 14.6 9.8 18.2 "•3 IS-* 17.1 13-3 7.2 0.8 0.6 i-5 0.6 0.7 0.7 1.8 i.i 0.8 0.8 2.8 1.4 0.9 1.2 i-3 7.5 0.8 0.9 0.8 I.O I.I 1.4 3-3 I.O 2.2 2.2 1.9 !-3 2-4 3-3 2.6 8.4 57-6 40.0 62.0 44-7 68.4 82.3 61.1 82.4 GRASSES Timothy Rye grass .... Orchard grass . . . Rich pasture grass 300 300 300 218 5-4 5-7 7-2 I.O I.O 0.6 0.8 5-9 5-9 4-9 6.8 0.4 0.2 0-3 0.7 1.2 I.I 0.8 1.9 O.2 °-3 0.2 o-3 3-i 3-i 2.8 1.9 «-3 o-5 0.6 O.2 i.i 2.1 i-3 2.1 20.5 20.4 17.8 21. 1 604 APPENDIX TABLE i2ift. COMPOSITION OF PLANTS AND PLANT PRODUCTS (CHIEFLY AFTER VON WOLFF, 1889)— Continued (Pounds in 1000 of Produce) M >s i o A§ ~ gs S g H § 1 2 M PRODUCE SB i Is H £ og S H) § s O »J 5 5 W ^ S PI 9 Si ^ 'S " < D 1 o • ^ * fc A. 2 u c« Cfl C0 U LEGUMES Red clover, young . . 140 6.0 O.? 4-3 0.8 2.8 O.I 0-9 O.2 0.6 14.0 Red clover in bud . . 180 5-3 o-7 4-6 I.O 3-2 0.2 O.2 O.2 0.5 14.7 Red clover in flower . 200 4.8 0.6 3-7 0.9 3-4 O.2 O.2 O.2 0.5 Alsike clover . . . 1 80 5-3 0.4 2.O °-7 2.1 O.2 O.I O.2 °-S 8^6 Lucern, or alfalfa . . 260 7.2 0.7 3-8 o-S 6.1 0.4 0.8 O.2 0.6 19.2 White clover in flower 195 S-6 0.8 2.6 0.8 3-r 0.4 0.3 0.7 0.6 14-3 FRUITS Apple, entire fruit 169 0.6 O.I 0.7 O.I 0.07 0.4 0.04 0.4 2.2 Pear, entire fruit . . 169 0.6 O.2 O.I 0.2 0.08 0.05 O.2 3-3 Grape, entire fruit 170 1.7 O.O6 4-2 O.2 O.O7 O.2 O.I O.O/ O.I 8.8 Raspberries .... 1 80 1.5 2.1 2-9 Strawberries .... IOO T-5 o-S 2-5 ROOTS, TUBERS, BULBS Potato 250 - . O.7 4-8 0.3 O.2 O.2 o.oo O.2 O 3 9c Sugar beets .... i!6 / 0.4 3-2 0.4 O.I 0.9 0.4 o-3 •3 Turnips 80 1.8 O 7 2.4 O. T °-5 O.7 o c f\ A Rutabagas .... 2.1 o-S 2-9 O.2 0.6 O °-3 "•o °-3 o-S 7-5 Artichoke .... 2OO 3-2 0.6 3-9 O.2 O.2 O.2 0.9 0.7 0.4 9.8 Onion I4O 2.7 0.6 2.1 O.2 i.r O.2 0.3 O.I O.2 7-4 Beets I2O 1.8 O.3 4.O O.2 O.2 O. I o.oo i.i _ _ Carrots 150 2.2 *O 2.? O.2 0.6 O.2 o.oo T 1 O 4 9.1 8.2 Parsnip 2O7 5 A 0.8 J 0.8 O.2 o.oo 'O O. I O 4 Radish 67 •*t I .O O.2 1.7 O.I O.I O.7 "3 A O Horseradish .... 233 * -y 4-3 0.9 O 6.4 0.2 i '4 2.O 0.7 0.3 0.3 4-9 19.7 "VEGETABLES" Cabbage, outer leaves 110 2.4 0.6 4.8 0.4 2.0 I.O 0.05 i.i !-3 IS-6 Cabbage, heart . . IOO o-S 3-6 O.2 0.9 °-5 0.05 0.6 °-5 9.6 Cucumber, fruit . . 44 i!6 2.O O.I o-3 O.2 0.2 0.4 0.4 5-8 Lettuce 60 0.3 3.1 O.I 0.4 O.I 0.6 0.6 0.4 8.1 Asparagus, sprouts . 67 3-2 0.4 I.O O.I 0.4 O.I O.2 °-7 S-° Cauliflower, heart . . 96 4.0 0.7 3-0 O.2 0.4 0.4 O.I 0.4 0.3 8.0 MISCELLANEOUS Wheat flour .... 900 22.O 2-5 4-5 Wheat bran .... 875 25.0 12.2 13.0 Gluten meal .... 900 50.0 1.3 0.4 Hominy feed . . . 900 I6.3 4-3 4.0 Peanut-kernel cake . 900 76.7 8.7 r2-5 Soy-bean cake . . . 900 68.0 IO.O 15.0 • Rape cake .... 900 50.0 8.7 10.8 Linseed cake . . . 850 47-2 6.8 IO.I 4.8 3-° °-7 2-9 0.6 0.4 51.3 Cotton-seed cake . 850 62.1 12.7 12.6 5-9 2.0 0-3 2-5 66.4 Tobacco leaves . . 850 34.8 3-° 3S-4 6-5 37-5 3-5 4.0 3-5 9-4 140.7 Tobacco stems . . . 850 24.6 4-2 24-4 o-3 9-2 0.9 0.8 5-1 2.4 64.7 Flax stalks .... 850 1.8 7.8 1.2 4.8 0.8 0.8 1.8 T-3 31.1 Hemp stalks . . . 850 0.9 4-4 1.2 IT.4 O.2 1.4 0.4 0.6 3x-7 Hops, entire plant . . 850 25.0 2-5 14-7 4.2- 13-9 1.2 6.2 1.4 3-7 72.9 APPENDIX SECTION IV 605 STATISTICS OF AGRICULTURAL PRODUCTS1 CROP AREAS, YIELDS, AND VALUES, 1908 The final revised estimates of the Crop Reporting Board of the Bureau of Statistics, United States Department of Agriculture, based on the reports of the correspondents and agents of the Bureau, supplemented by information derived from other sources, indicate the acreage, produc- tion, and value, in 1908 and 1907, of important farm crops of the United States to have been as follows : CROP ACREAGE (Acres) PRODUCTION FARM VALUE, DEC. i Per Acre (Bu.) Total (Bu.) Per Bushel Total Corn, 1908 .... 1907 .... 101,788000 99,931000 26.2 25-9 2,668,651000 2,592,320000 $0.606 .516 $1,616,145000 i,336.9°i°o° Winter wheat, 1908 1907 30,349000 28,132000 14.4 14.6 437,908000 409,442000 •937 .882 410,330000 361,217000 Spring wheat, 1908 1907 17,208000 17,079000 13.2 13.2 226,694000 224,645000 .911 .860 206,496000 193,220000 Oats, 1908 .... 1907 .... 32,344000 31,837000 25.0 2.3-7 807,156000 754,443°°° .472 •443 381,171000 334,568000 Barley, 1908 .... 1907 .... 6,646000 6,448000 1,948000 1,926000 803000 800000 25-1 23.8 16.4 16.4 19.8 17.9 166,756000 153.597°°° 31,851000 31,566000 15,874000 14,290000 •554 .666 .736 •731 .756 .698 92,442000 102,290000 33.455°oo 23,068000 12,004000 9,975000 IOO7 . Buckwheat, 1908 . . 1907 . . Flaxseed, 1908 . . . 1907 . . . Rice, 1908 2,679000 2,864000 655000 627300 9.6 9.0 33-4 29.9 25,805000 25,851000 21,890000 18,738060 1.184 •956 .812 •858 30,577000 24,713000 17,771000 16,081000 1907 .... Potatoes, 1908 . . . 1907 . . . 3,257000 3,124000 85-7 95-4 278,985000 297,942000 .706 .617 197,039000 183,880000 Hay, 1908 .... i9°7 46,486000 44,028000 2 J-S2 *i-45 2 70,798000 2 63,677000 3 8.98 3 n. 68 635,423000 743.5°7°°o Tobacco, 1908 . . . 1907 . . . 875000 820000 4 820.2 4 850.5 4 718,061000 4 698, 126000 '.103 5.102 74,130000 71,411000 1 Figures furnished by the Bureau of Statistics, United States Department of Agriculture, except where otherwise credited. 2 Tons. * Per ton. * Pounds. 6 Per pound. 6o6 APPENDIX CORN AVERAGE YIELD PER ACRE OF CORN IN THE UNITED STATES (WITH TOTALS FOR 1909) STATE OR DIVISION 10- YEAR AVERAGES 1006 1907 Bu. 37-0 35-o 36.0 36.0 31-2 33-o 27.0 31-5 32.5 1908 1909 1910 CROP or 1909 1866- 1875 1876- 1885 1886- 1895 1896- I9°S Maine . ._ . . . New Hampshire . . Vermont Massachusetts . . . Rhode Island . . . Connecticut .... New York .... New Jersey .... Pennsylvania . . . North Atlantic Delaware .... Maryland .... Virginia West Virginia . . . North Carolina . . South Carolina . . . Georgia Florida South Atlantic . . Ohio Indiana Illinois Michigan .... Wisconsin .... Northeast Central Minnesota .... Iowa Missouri North Dakota . . . South Dakota . . . Nebraska .... Kansas Northwest Central Kentucky .... Tennessee .... Alabama Mississippi .... Louisiana .... Texas Oklahoma .... Arkansas South Central . . Bu. 29-3 35-5 36.0 34-6 26.9 3°-9 31-6 36.5 35-1 Bu. 33-8 35-5 35-3 32-S 30.8 29.1 30-4 32.8 32.6 Bu. 34-3 34-5 35-5 35-7 31-2 33-4 31-1 30-9 30.4 Bu. 35-1 34-0 35-1 35-9 31-9 35-8 30.3 34-3 34-5 Bu. 37-0 37-5 35-5 39-7 33-1 40.0 34-9 36.3 40.2 38^3" Bu. 40.5 39-0 4°-3 40.4 42.8 41-3 38.8 38.0 39- S 39-3 Bu. 38.0 35-1 37-o 38.0 33-2 41.0 36.0 32.7 32.0 Bu. 46.0 46.0 43-o 45-5 40.0 53-2 38-3 36.0 41-0 4°-3 Acres 17000 30000 65000 47000 IIOOO 60000 670000 290000 1,525000 Bushels 646000 1,053000 2,405000 1,786000 365000 2,460000 24,120000 9,483000 48,800000 34-2 32.0 30.9 33-5 3JJ 33-6 2,715000 91,118000 20.5 24-7 2O.O 29-3 14-3 9-7 ii-3 10.9 22.5 26.0 17.9 25.8 13-3 8.8 10.3 9-5 19.8 23-5 17.4 22.2 12.4 IO.2 II. 2 IO.2 26.8 32.0 2I.O 26.4 13-4 9-5 10.5 9-3 30.0 35-0 24-3 30-3 15-3 12.2 I2.O II.O 27-5 34-2 25-0 28.0 16.5 iS-i 13.0 1 1 -3 32.0 36.6 26.0 31-2 18.0 14.1 12.5 10.5 18.3 31-0 31-4 23.2 31-4 16.8 16.7 13.0 12.6 31.8 33-5 25-5 26.0 1 8. 6 18.5 14-5 I3-Q 19.4 2000OO 700000 2,040000 880000 2,898000 2,218000 4,400000 665000 6,200000 21,980000 47,328000 27,6-52000 48,686000 37,041000 61,160000 8,379000 17.4 14.4 13-9 15.0 16.9 17.8 18.5 14,001000 258,406000 35-3 32.3 29.9 32.2 31-4 32.6 29-9 27.2 31-8 30.4 28.8 28.9 29.0 26.7 27.4 34-8 34-0 34-5 32.2 33-2 42.6 30.6 36.1 37-o 41.2 34-6 36.0 36.0 30.1 32.0 38.5 3°-3 31-6 31-8 33-7 39-5 40.0 35-9 35-4 33-0 36.5 39-3 39-1 32.4 32.5 3,875000 4,913000 10,300000 1,976000 1,533000 153,062000 196,520000 369,770000 69,950000 50,589000 31.9 29.2 28.7 34-2 38.4 35-o 32-7 37-2 37-7 22,597000 839,891000 32.2 34-3 30.1 32.S 33-5 30.9 31-8 28.6 35-5 33-4 27-6 30.1 27.7 20. i 16.8 25.2 22.2 29.1 32-4 27.4 22.6 25.8 28.0 22.O 33-6 39-5 32.3 27.8 33-5 34-1 2.H.O 34-1 27.0 29-5 31-0 20. o 25-5 24.0 22.1 ~26T8 29.0 31-7 27.0 23.8 29-7 27.0 22.O 34-8 3i-5 26.4 3i.o 3i-7 24.8 19.9 26.7 32.7 36.3 33-0 14.0 25.0 25.8 19.0 IsTs 1,690000 9,200000 8,100000 195000 2,059000 7,825000 7,750000 58,812000 289,800000 213,840000 6,045000 65,270000 194,060000 154,225000 32.4 31-4 26.1 27.7 27.4 36,819000 982,052000 29-3 22.9 14.0 16.0 18.2 23-7 25-7 26.0 21.4 12.4 14.2 16.3 19.8 21.4 24-9 21-5 12.8 14.7 16.2 I9.O 19.2 25-5 21.9 12.6 14.7 16.3 17.7 23.5 17.8 33-0 28.1 16.0 18.5 17.2 22.5 33-3 23-6 24.8 28.2 26.0 15-5 17.0 17-5 2I.O 24.4 17-2 25.2 24.8 14.7 17-3 19.8 25-7 24.8 20. 2 29.0 22. 0 13-5 14-5 23.0 15.0 17.0 18.0 18.3 29.0 25-9 1 8.0 20.5 23.6 2O.6 16.0 24.0 21.5 3,568000 3,575000 3,233000 2,810000 2,226000 8,150000 5,950000 2,800000 103,472000 78,650000 43,646000 40,745000 51,198000 122,250000 101,150000 50,400000 23-4 19.7 I9.I 18.9 21-5 22.7 32,312000 591,511000 29-S 28.6 26.6 2S-3 20.4 21. 1 23-3 22.5 26.4 26.3 29.2 26.1 23.6 22.8 20.7 2O.2 19.9 24.2 20.7 24-3 21). 0 22.3 24.7 18.7 23.2 22.3 23.8 27.7 20. o 23.8 29.9 23-4 27.0 27.9 29.4 29-5 32.0 28.3 25-2 27.6 34-9 29.6 22.5 25-0 23-5 29.O 37-5 25-5 30.0 27.0 27-5 34-Q 27-5 23-4 28.0 2O.2 27.O 33-2 29.4 2Q.O 25-5 27.8 32.0 25-3 35-o 28.0 24.2 31-3 32.1 31-4 30.6 27.8 30.7 34-8 28.7 23.0 IO.O 19.9 23.0 32.5 30.3 32.0 28.0 25-5 37-5 24.7 5000 5000 135000 68000 13000 13000 6000 15000 17000 50000 175000 140000 3,267000 2,128000 417000 408000 180000 417000 522000 1,740000 Wyoming .... New Mexico. . . . Arizona Utah Washington .... Oregon California .... Western . . . United States . . 28.7 25-6 24-3 23.1 327000 9,398000 26.1 25-5 23-4 25.2 30.3 25-9 26.2 25-5 27.4 108,771000 2,772,376000 APPENDIX 607 CORN — Continued ACREAGE, PRODUCTION, VALUE, PRICE, AND EXPORTS OF CORN IN THE UNITED STATES, 1849-1909 Year Acreage Aver- age yield per acre Production Aver- age farm price per bushel, Dec. i Farm value Dec. i. Domestic exports, including corn meal, fiscal year beginning July i Per Cent of Crop ex- port- ed Acres Bu. Bushels Cents Dollars Bushels 7 632860 P.cl. 1866 867,946295 47.4 1.8 J86? 23.6 768,320000 57.0 437,769763 1.6 1868 34 887246 006,527000 46.8 8,286665 !869 874,320000 59.8 1870 28.3 1,094,255000 49.4 1871 991,898000 43.4 3-6 1872 30.8 X873 23.8 932,274000 44.2 1874 850,148500 58.4 1875 1,321,069000 36.7 484,674804 j876 1,283,827500 1877 1,342,558000 34.8 6.5 ^78 1,388,218750 87 884892 6.3 1879 1,547,001790 37-5 580,486217 6.4 I88o 27.6 1,717,434543 1881 1882 64,262025 18.6 1,194,916000 63-6 48.5 759,482170 783 867175 44,340683 3-7 2.6 !883 68 301889 46,258606 !884 69 683780 2<;.8 1885 .... 32.8 1886 36.6 41 368584 1887 !888 3.6 1889 1890 78,319651 27.0 2,112,892000 28.3 597,918829 103,418709 4-9 1891 1892 76,204515 27.0 2,069,154000 40.6 836,439228 76,602285 3-7 1893 1894 1895 72,036465 62,582269 22-.S 19.4 26.2 1,619,496131 1,212,770052 36.5 45-7 591,625627 554,719162 66,489529 28,585405 4-1 2.4 1896 28 2 7 8 1897 1898 24.8 28.7 1899 82,108587 86 1901 1902 91,349928 94.043613 I6.7 26.8 1,522,519891 2,523,648312 60.5 4°-3 921,555768 1,017,017349 952 868801 28,028688 76,639261 1.8 3-o 2.6 26 8 1905 28.8 86 368228 1907 si.6 1908 60 6 37,665040 1909 38,128498 1.4 1 Census figures of production. 6o8 APPENDIX CORN— Continued CORN CROP OF COUNTRIES NAMED, 1902-1906 COUNTRY 19O3 (Bu.) 1903 (Bu.) 19O4 (Bu.) 19O5 (Bu.) 19O6 (Bu.) United States . . Canada (Ontario) . Mexico .... Total No. America Argentina . . . Total So. America Austria-Hungary . France .... Italy .... 2,523,648000 21,159000 78,009000 2,244,177000 30,211000 90,879000 2,467,481000 20,880000 88,131000 2,707,994000 21,582000 85,000000 2,927,416000 24,745000 70,000000 2,622,906000 2,365,267000 2,576,492000 2814,576000 3,022,161000 84,018000 148,948000 175,189000 140,708000 194,912000 89,944000 J55. 355ooo 179,701000 146,369000 198,984000 139,126000 24,928000 71,028000 16,000000 68,447000 48,419000 25,272000 183,994000 25,360000 88,990000 14,000000 80,272000 50,464000 18,759000 89,757ooo 19,482000 90,545000 15,000000 19,598000 25,920000 21,300000 i39>307ooo 24,030000 97,265000 16,000000 59,275000 33,33 1000 31,880000 215,636000 14,581000 93,007000 16,000000 130,546000 70,501000 30,000000 Portugal .... Roumania . . . Russia (European) . Spain Total Europe Africa 429,716000 504,154000 303,858000 442,168000 618,0517000 36,899000 7,256000 36,118000 4,987000 38,862000 9,972000 37,6550°° 8,374000 37,700000 8,608000 Australia .... New Zealand . . Total Australasia Grand total . . 590000 627000 547000 506000 653000 7,846000 5,614000 10,519000 8,880000 9,261000 318,7311000 3,066,508000 3,109,432000 3,449,648000 3,886,163000 CORN, AVERAGE YIELDS PER ACRE, BUSHELS YEARS SOUTH CAROLINA GEORGIA IOWA ILLINOIS UNITED STATES 1866-1875 (10 years) 1876-1885 (10 years) 1886-1895 (10 years) 1896-1905 (10 years) 9-7 8.8 10.2 9-5 "•3 io-3 II. 2 10.5 34-3 31-8 30-1 32-4 29.9 27.2 29.0 34-5 26.1 25-5 23-4 25-2 1866-1885 (20 years) 1886-1905 (20 years) 9-3 9-9 10.8 10.8 33-o 31.2 28.6 3i-7 25-8 24-3 1866-1905 (40 years) 9.6 10.8 32.1 30.1 25.0 CORN, SINGLE-YEAR RECORDS 1899, bu. per acre 9.0 IO.O 31.0 36.0 25-3 1909, bu. per acre 16.7 13-9 3i-5 35-9 25-5 1899, acres of corn 1,857000 3,249000 7,815000 6,865000 82,109000 1909, acres of corn 2,218000 4,400000 9,200000 10,300000 108,771000 1899, bu. of corn 16,713000 32,495000 242,250000 247,150000 2,078,000000 1909, bu. of corn 37,041000 61,160000 289,800000 369,770000 2,772,360000 1899, price per bu. 450 490 350 360 37.20 1909, price per bu. 9°0 86^ 490 520 59-60 1899, value of crop $ 8,357000 $16,247000 $55, 7 17000 $64,259000 $ 629,210000 1909, value of crop 33,337ooo 52,598000 142,062000 192,280000 1,652,822000 APPENDIX 609 INTERNATIONAL TRADE IN CORN, INCLUDING CORN MEAL, 1902-1906 GENERAL NOTE. Substantially the international trade of the world. The exports given are domestic exports and the imports given are imports for consumption, as far as it is feasible and consistent so to express the facts. While there are some inevitable omissions from such a table as this, on the other hand, there are some duplications because of reshipments that do not appear as such in official reports. For the United Kingdom import figures refer to imports for con- sumption. EXPORTS COUNTRY YEAR BEGIN- NING 1902 (Bu.) 1903 (Bu.) 19O4 (Bu.) 1905 (Bu.) 1906 (Bu.) Argentina . . . Austria-Hungary . Belgium .... Bulgaria .... Netherlands . . . Jan. Jan. Jan. Jan. Jan. 46,959590 3,010624 4,346609 7,883279 4,726324 82,845915 310804 6,579655 5,089114 5,373*94 97,221783 174342 6,287688 9,762657 4,449009 87,487629 63218 8,078215 3,870090 4,278515 106,047790 22361 6,588557 5,658500 6,010176 Roumania . . . Russia .... Servia .... United States . . Uruguay .... Other countries Total .... Jan. an. Jan. July July 43,013192 44,148590 1,091588 76,639261 703770 1,528000 31,080198 25,349683 171767 58,222061 1,004063 1,086000 18,042377 18,633663 130225 90,293483 2,002431 1,009000 1,441437 7,372386 806115 119,893833 28519 4,100325 1 23,394301 29,878141 1,755446 86,367988 2 034696 23>547299 234,050827 217,112454 248,006658 237,420282 250,205255 IMPORTS Austria-Hungary . Belgium .... Canada .... Cape of Good Hope Cuba Jan. Jan. July }an. an. 5,87497i 14,583008 7,i54522 1,943896 1.1^0176 11,130274 20,323863 11,33353° 3,471281 610326 14,090377 I9,47433° I2,oo3574 1,236927 606 <; 1 7 18,511368 24,169780 11,779679 2,171601 7,118221 20,125507 2 15,233894 215007 2 489087 Denmark .... Ecrvot . Jan. Jan. ^,355050 51:266 8,772022 I4.2S37 9,284777 ^•?OI7 10,859257 18,855752 France Germany3 . . . Italy Jan. Jan. Jan. 8,674931 35,454243 8,216902 11,347114 37,527343 i i;.oQ2<;27 10,124353 30,450853 8.36SI2? 11,122512 36,538366 c OO287C 14,509103 44,883053 8 666763 Mexico .... Netherlands . . . Norway .... Portugal .... Russia Jan. Jan. Jan. Jan. Tan. 142102 I5,8i7237 637387 759967 13^822 496028 20,160078 765246 366605 41:7711: 476182 16,547198 555991 531889 62CC2O 1,454327 16,234785 544596 2,724050 2 2,079553 25,305233 718277 * 2,724050 * 4-27868 Spain Jan. Sweden .... Switzerland . . . Transvaal . . . United Kingdom . Jan. Jan. Jan. Jan. 191958 2,404644 1,306038 89,371445 189357 2,611202 2,197476 101,284919 234986 2,704457 1,422985 86,076697 491035 2,498380 1,277353 84,156490 564946 2,887291 4 i, 277353 97,736852 3>309436 7,42935! 2 7,090991 Total. . . . — — — 210,483315 257,°9I403 221,026621 243,057067 277,005211 1 Average, 1902-1905. 2 Preliminary. * Not including free ports prior to March i, 1906. * Year preceding. 6io APPENDIX WHEAT WHEAT CROP OF COUNTRIES NAMED, 1903-1907 COUNTRY 19O3 (Bu.) 1904 (Bu.) 19O5 (Bu.) 19O6 (Bu.) 1907 (Bu.) United States . . Canada .... Mexico .... Total No. America Argentina . . . Total So. America Austria-Hungary . Belgium .... Bulgaria .... Denmark .... France .... Germany .... Greece .... Italy 637,822000 85,271000 10,493000 552,400000 75,213000 9,393000 692,979000 113,441000 7,000000 735,261000 132,705000 7,000000 634,087000 96,606000 10,000000 733,586000 637,006000 813,420000 874,966000 740,693000 103,759000 129,672000 i5°,745°°° 134,931°°° 155,993000 119,113000 155.185000 160,834000 151,604000 178,636000 226,721000 12,350000 35,551000 4,461000 364,420000 130,626000 8,000000 184,451000 4,258000 307000 8,000000 73,700000 551,728000 10,885000 128,979000 5,538000 26,000000 46,524000 204,406000 13,817000 42,242000 4,302000 298,826000 139,803000 8,000000 167,635000 4,423000 2I2OOO 9,OOOOOO 53.738°°° 622,255000 11,676000 95-377°°° 5,135000 23,000000 35,624000 228,138000 12,401000 40,736000 4,083000 335,453°oo I35,947°°° 8,000000 160,504000 5,109000 329000 5,000000 103,328000 568,274000 11,280000 92,504000 5,529000 20,000000 57,422000 268,675000 12,964000 55,076000 4,161000 324,919000 144,754000 8,000000 176,464000 4,978000 303000 9,000000 113,867000 45°,963°°° 13,211000 140,656000 6,650000 25,000000 57,583000 185,059000 12,000000 30,000000 4,000000 369,970000 127,843000 8,000000 i?7, 543°°° 5,000000 200OOO 6,OOOOOO 42,237000 455,OOOOOO 8,375°°° 100,331000 5,953000 16,000000 53,860000 Netherlands . . . Norway .... Portugal .... Roumania . . Russia (European) Servia Spain Sweden .... Turkey (European) England .... Total United Kingdom . . Total Europe British India, includ- ing such native states as report . Cyprus .... Taoan . 50,321000 39,082000 62,188000 62,481000 58,275000 1,830,526000 1,747,262000 1,803,132000 1,826,422000 1,616,086000 297,601000 2,477000 9,600000 69,659000 35,000000 359,936oo° 2,176000 19,754000 44,494000 35,000000 283,063000 2,441000 18,437000 68,011000 35,000000 320,288000 2,410000 20,283000 57,427000 35,000000 315,386000 2,000000 22,932000 56,000000 35,000000 Russia (Asiatic) Turkey (Asiatic) . Total Asia . . Algeria .... Cape of Good Hope EcrvDt . 430,516000 477,550000 423,152000 451,586000 447,518000 34,035°°° 1,755000 12,000000 4000 294000 7,523000 25,484000 2,000000 12,000000 7000 486000 10,510000 25,579000 2,000000 12,000000 4000 483000 5,720000 34,080000 2,000000 12,000000 8000 542000 4,409000 31,120000 2,000000 12,000000 6000 500000 6,000000 Natal Sudan (Anglo- Egyp- tian) .... Tunis Total Africa . . Australia .... New Zealand . . Total Australasia Grand total . 55.61 1000 50,406000 45,705000 53,030000 51,626000 12,768000 7,69300° 76,488000 8,140000 56,215000 9,411000 70,681000 7,013000 68,185000 5,782000 20,461000 84,628000 65,626000 77,694000 73,967000 3,189,813000 3,152,127000 3,320,959000 3,435,401000 3,108,526000 APPENDIX 611 WHEAT — Continued ACREAGE, PRODUCTION, VALUE, PRICE, AND EXPORTS OF WHEAT IN THE UNITED STATES, 1849-1909 Year Acreage Aver- age yield per acre Production Aver- age farm price per bushel, Dec. i Farm value Dec. i Domestic exports, including flour, fiscal year beginning July i Per cent of crop ex- ported Acres Bu. Bushels Cents Dollars Bushels P.ct. A 5944 7-5 1866 9.9 R i 1867 1868 J86Q 18,321561 18,460132 1.6 2.1 3.6 212,441400 224,036600 145.2 108.5 76. q 308,387146 243,032746 26,323014 29,717201 12.4 13-3 1870 1871 1.6 I&J2 1873 1874 22,171676 2.7 281,254700 IO6.9 86.3 300,669528 26 «; ,881167 91,510398 32-5 I8?S 1876 26,381512 I.I 292,136000 89.5 06 ^ 261,396926 74,750682 25.6 1877 1878 77.6 •jc ft 1879 3.8 no. 8 !88o 498 549868 1881 ii 8 1882 3.6 88.4 1883 1.6 1884 39,475885 1885 1886 36,806184 68.7 •>•> 6 1887 68.1 1888 415,868000 88,600743 1889 69.8 1890 83.8 26 6 1891 83.9 1892 1893 1894 34,629418 34,882436 1.4 396,131725 53.8 213,171381 164,283129 4i.5 lgg5 1896 72.6 1897 so.s 1898 58.2 1899 58.4 1901 40,895514 5-o 748,460218 62.4 467*350156 234,772516 31.4 637,821835 18.9 8.0 74 8 66.7 1907 87.4 1908 92 8 114,268468 •5.8 87,364318 1 Census figures of production. 6l2 APPENDIX WHEAT — Continued AVERAGE YIELD PER ACRE OF WHEAT IN THE UNITED STATES (WITH TOTALS FOR 1909) STATE OR DIVISION 10- YEAR AVERAGES 1006 Bu. 24.8 22.3 2O.O l8.3 17-7 18.2 1007 Bu. 26.2 23-0 17-3 18.5 18.6 I008 Bu. 23-5 23.0 17-5 17-3 18.5 1909 Bu. 25.5 25.0 2I.O 17.9 17-0 17.9 I9IO Bu. 29.7 29-3 23-7 18.5 17.8 CROP OF 1909 1866- 1875 1876- 1885 1886- 1895 1896- 1905 Maine Vermont New York .... New Jersey .... Pennsylvania . . . North Atlantic Delaware .... Maryland .... Virginia West Virginia . . . North Carolina . . South Carolina . . . Georgia South Atlantic . . Ohio Indiana Illinois Michigan .... Wisconsin .... Northeast Central Minnesota .... Iowa Missouri North Dakota . . . South Dakota . . . Nebraska .... Kansas Northwest Central Kentucky .... Tennessee .... Alabama Mississippi .... Texas Oklahoma .... Arkansas South Central . . Montana .... Bu. 13-2 17.0 14.1 14.6 13-3 Bu. 13-7 16.8 15-5 13-3 13-4 Bu. 15.8 18.8 15-4 13-4 :3-6 Bu. 22.1 21.2 17-5 16.1 15.8 Acres 9000 1000 420000 IIOOOO 1,545000 Bushels 230000 25000 8,820000 i ,969000 26,265000 13-7 14.1 14.1 16.3 18.4 18.3 19.1 2,085000 37,309000 10.9 10.6 8-3 10.3 7.2 6.0 6.9 12.5 12.8 8.3 10.8 6.6 6.6 6.9 I2.I 13-3 8.8 10.3 6.2 5-7 6.1 16.0 15.0 10.3 10.8 7-5 7-7 7-9 16.0 16.0 12-5 12.7 9.1 9-3 IO.O 20.5 IQ.O 12.5 12.2 9-5 8-5 0.0 15.0 16.4 n.t 13-0 IO.O 9.0 9-2 14.0 14-5 II. 2 13-0 9-5 IO.O IO.O 17.0 17.4 12. i 12.5 11. II.O IO-S 118000 770000 790000 370000 570000 381000 245000 1,652000 11,165000 8,848000 4,810000 5,415000 3,810000 2,450000 8.9 8.9 9.0 10.6 12.4 14-3 12.3 n.8 13-3 | 3,244000 38,150000 I2.O II.O II.9 13-4 13-7 14.6 13-9 13-1 16.1 12.2 14.4 I3-Q 14-3 14.8 13-0 13-8 12.2 13-0 13-8 IS-7 20.4 20.7 19-5 13-1 16.3 I6.3 14-4 1 8.0 14-5 14.1 16.0 16.6 13.0 1 8.0 18.2 iS-9 IS-3 17.4 18.8 19-5 16.2 15.6 15.0 18.0 IQ. 2 1,480000 2,165000 1,810000 775000 179000 23,532000 33,124000 31,494000 14,570000 3,484000 12.3 13-9 14.2 13-3 19.1 15-8 15.6 16.6 15-9 6,409000 106,204000 15.0 12.6 12.8 14.8 15.7 13.1 12.8 10.2 II.4 II.9 13-9 II.9 13-7 I2.Q 12.8 I4-S II.O 10.8 12.8 13-3 I4-I 12.2 12.2 II. I IS-4 13-7 10.9 iS-7 14.8 13.0 13-4 22.0 IS-' 13.0 13-4 13-2 IO.O II. 2 18.1 II.O 12.2 12.8 17.2 IO.O 1 1.6 12.8 17.2 12.6 12.7 1 6.8 17.0 14.7 13-7 14.1 18.8 14.4 16.0 21. 0 13.8 5-0 12.8 16.1 14-0 12. 1 5,600000 439000 1 ,943000 6,625000 3,375000 2,640000 6,045000 94,080000 7,446000 28,562000 90,762000 47,588000 49,650000 87,203000 13-0 13-0 14.2 15-2 ! 26,667000 405,291000 9.2 7-7 7-6 9.2 12.8 10.3 9-7 6.6 6.4 6.2 10.8 7-i II. 2 8.3 6.9 6.9 10.4 11.4 8.6 1 1.2 9-5 9.1 9.4 12.3 14.1 9-1 I4.I 12.5 II.O IO.O n-5 13-7 10.8 12.0 9-5 IO.O II.O 7-4 9.0 9-5 9-7 1 1.6 IO.O li-S 14-5 II.O 1 1.6 IO.O II. I n.8 10.4 10.5 II.O 9.1 12.8 11.4 12.8 11.7 12. 0 14.0 IS.O 16.3 13-9 670000 800000 98000 IOOO 555000 1,225000 151000 7,906000 8,320000 1,029000 I IOOO 5,050000 15,680000 1,721000 8.6 8.2 9-7 ii-S 12.8 "•3 14-3 3,500000 39,717000 21.6 18.9 14.8 17.7 17-0 19.1 13-6 13-9 1 8.0 18.1 17.2 16.3 I7-S 13-0 19.8 20. i 19.2 14.7 15-2 17.6 17.4 18.4 17.6 16.7 12.4 26.9 22.6 23-1 19.6 21.6 23.4 25.9 23.8 23.0 18.4 "•3 24.0 28.7 32.5 25.0 25.2 27.4 3i-5 24-4 20.8 2O.O I7-I 20.8 28.8 28.5 29.0 24.0 25-9 28.8 32.0 25-3 26.0 23-4 15-0 24.2 25.4 21.0 25.0 26.7 26.S 30.0 28.2 18.8 20.8 14.6 30.8 28.7 29-S 24-S 25.0 25-9 28.7 27-8 23.2 20.2 I4.O 22.9 22.O 25.0 22.2 2O. O 22.3 22.4 29.0 22.4 17.2 21-5 18.0 2O.O 350000 80000 365000 41000 16000 235000 36000 520000 1,540000 810000 825000 10,764000 2,297000 10,758000 1,004000 400000 6,000000 1,033000 14,465000 35,780000 16,377000 11,550000 Wyoming .... Colorado New Mexico . . . Utah Nevada Idaho Washington .... Oregon California .... Western . . . United States . . 15.4 14-3 13-9 16.8 22.6 2O.2 4,818000 110,518000 II.9 12.3 12.7 I3-S IS-S 14.0 I4.O IS-8 I4.I 46,723,000 737,180000 APPENDIX 613 INTERNATIONAL TRADE IN WHEAT, INCLUDING WHEAT FLOUR, 1902-1906 EXPORTS COUNTRY YEAR BEGIN- NING 1903 (Bu.) 1903 (Bu.) 19O4 (Bu.) 1905 (Bu.) 19O6 (Bu.) Argentina . . . Australia . . . Austria-Hungary . Belgium .... British India . . Bulgaria . . . Canada .... Chile Jan. Jan. Jan. Jan. Apr. Jan. Jan. Jan. Jan. Jan. San. an. an. uly 25,672368 10,799165 5,S3427o i3»89°599 21,389010 9,320644 39,820238 1,043883 4,044662 37i3498°4 34,715888 114,872260 1,875580 202,905598 14,499026 65,421537 1,489763 5,532485 13,362799 50,684276 13,185710 24,452019 2,270728 7,956750 40,218462 31,860939 158,064833 2,016358 120,727613 9,3I1[307 90,115119 38,850166 3,984789 18,217597 83,128272 20,286368 21,110205 3,146416 8,640465 41,268227 26,718698 I74,334i82 3,098326 44,112910 10,955245 112,718476 32,506453 3,630659 18,496029 37,483073 17,508259 48,566652 706932 10,512765 53.95M47 65,246599 181,759796 3,520627 97,609007 I3,Il6253 89,128802 38,878679 4,059153 18,030378 32,213417 11,037613 42,224469 1 706932 10,350641 33,626290 '65,246599 3l37,I3°392 3,365644 146,700424 3 14,227728 Germany 2 . . . Netherlands . . Roumania . . . Russia .... Servia .... United States . . Other countries Total . . . 537,732995 546,555579 587,966975 697, 333027 646,927161 IMPORTS Belgium .... Brazil .... Denmark . . . Finland .... France .... an. an. an. an. an. 57,507743 10,845841 5,865624 3,026987 10,509786 59.797102 12,129189 5,467021 3,442443 18,516169 64,160454 i3,74535i 5,373202 3,4i376i 8,625293 64,976813 14,983303 4,691567 3,580581 7,347i85 68,178372 16,303441 5,648708 3,966877 11,732007 Germany 2 . . . Greece .... Italy an. an. an. an. an. 77,822604 6,396218 43,330190 2,427147 55.752861 72,501263 6,207668 43,I74711 9,l64759 58,552553 75,436433 5,207403 29,670497 6,702045 58,916277 85,136923 5,863742 43>I04i99 7,873865 70,380247 74,873885 7,924950 50,541670 5,622967 54,678154 Japan .... Netherlands . . Portugal . . . Spain .... Sweden .... Switzerland . . United Kingdom . Other countries Total . . . an. an. an. an. an. 336955 2,620395 7,953342 15,226501 200,577004 43,509254 2,748269 3,363238 8,658924 16,324627 217,100937 58,579453 3,282298 8,253950 8,446395 17,220343 219,713497 47,873864 4,672573 35,502385 7,515498 16,158553 212,089481 49,518455 1 4,672573 20,040928 8,216745 16,196009 208,920370 349,598374 543,7o8452 595,728326 576,041073 633,395370 607,116030 1 Year preceding. 2 Not including free ports prior to March i, 1906. 8 Preliminary. 614 APPENDIX WHEAT — Continued QUANTITY AND PERCENTAGE OF EXPORTS OF DOMESTIC WHEAT, 1907 AND 1908, BY LEADING PORTS CUSTOMS DISTRICT YEAR ENDING JUNE 30 — 1907 1008 (Preliminary) Bushels Per Cent of Total Bushels Per Cent of Total New York 18,679225 6,012732 7,198844 8,391450 5,026578 14,172021 2,622505 5,49693S 1,940582 7,028551 24.4 7.8 9-4 II.O 6.6 18.5 3-4 7.2 2-5 9.2 21,478019 14,699237 13,411581 12,357077 8,763989 8,112828 5,261870 5,020235 3,845004 7,262321 21.4 14-7 13-4 12.3 8.7 8.1 5-3 S-o 3-8 7-3 Puget Sound Willamette Philadelphia Boston and Charlestown New Orleans Duluth All other Total 76,569423 100. 0 100,212161 IOO.O AVERAGE YIELD OF WHEAT IN COUNTRIES NAMED,3 BUSHELS PER ACRE, 1898-1907 YEAR UNITED STATES * RUSSIA, EURO- PEAN2 GER- MANY2 AUSTRIA 2 HUNGARY PROPER 2 FRANCE l UNITED KING- DOM1 Average (1888 to 1897) 12.8 8.4 22.7 i5.6 17.9 17.6 30.1 1898 .... iz.i o 6 18 o «.8 12.1 8.7 28 4 17 8 ^n-8 IOOO 12.1 8.7 27. Q i ?.< 16.0 IO.2 2Q.I; I S.O 8.1 27 S 16 7 i c i 18 c 7I.O IOO2 14.? I I.I 1O.1 IO.O 20. 7 20. 2 77. Q IOO7 12. 0 17.8 22.8 71. 1 1904 12 S IO C 16 7 27.8 IOO1 14.. S 28 < 18 7 20 8 73. 0 1006 I ? C •24.7 IOO7 18 o ^•O Average (1898 to 1907) 13-9 9-3 28.4 i8.3 17.9 20.8 32-6 1 Winchester bushels. 2 Bushel of 60 pounds. 3 For the ten years, 1886 to 1895, the average yield of wheat was 27.7 bushels per acre in Holland, and 37.3 in Denmark; and for the succeeding ten-year period, 1896 to 1905, the average yield in Holland was 31.2 bushels, and in Denmark 40.6 bushels per acre, with only two years below a 4o-bushel average (35.2 bushels in 1898, and 29.2 in 1901). — C.G.H. APPENDIX OATS OAT CROP OF COUNTRIES NAMED, 1903-1907 COUNTRY 19O3 (Bu.) 1904 (Bu.) 19O5 (Bu.) 1906 (Bu.) 1907 (Bu.) United States . . Canada .... Mexico .... Total North America . . Austria .... Hungary proper . France .... Germany . . . Russia (European) Great Britain — England . . . Scotland . . . Wales .... Ireland .... Total United Kingdom . . Total Europe . Russia (Asiatic) Total Asia . . Total Africa . . Australia. . . . New Zealand . . Total Australasia Grand total . • 784,094000 211,192000 13000 894,596000 208,024000 18000 953,216000 234,099000 17000 964,905000 251,194000 17000 754,44300° 210,869000 17000 995,299000 1,102,638000 1,187,332000 i, 216, 1 16000 965,329000 128,330000 87,334000 300,366000 542,432000 728,049000 85,400000 36,379000 6,832000 58,816000 109,611000 62,775000 257,811000 477,852000 1,065,068000 86,728000 37,034000 7,661000 60,142000 123,880000 78,009000 269,581000 451,017000 851,667000 76,453000 36,390000 7,264000 60,754000 154,551000 87,733°°° 256,943000 580,875000 633,291000 84,102000 35,108000 8,063000 62,751000 170,657000 79,484000 314,132000 630,324000 820,621000 94,707000 36,056000 7,875000 60,080000 187,427000 191,565000 180,861000 190,024000 198,718000 2,268,425000 2,402,641000 2,203,967000 2,222,575000 2,493,53200° 71,734000 59,135000 84,995000 79,713000 85,176000 72,215000 12,116000 7,527000 22,452000 59,552000 14,309000 85,397000 12,077000 80,072000 12,418000 85,576000 12,008000 18,094000 15,583000 9,064000 15,012000 10,805000 13,108000 14,041000 I I, 5550°0 29,979000 33,677000 24,076000 23.9I3°°o 25,596000 3.378,034000 3,612,817000 3,5i2,849'ooo 3,S55,°94°°o 3,582,O4IOOO AVERAGE YIELD OF OATS IN COUNTRIES NAMED, 1898-1907 Bushels per Acre YEAR UNITED STATES 1 RUSSIA, 'EURO- PEAN2 GER- MANY* AUSTRIA * HUNGARY PROPER J FRANCE J UNITED KING- DOM1 Average (1888 to 1897) 25-7 16.8 36-9 23-9 25-3 29.2 43-i 1898 28.4 16.2 47.1 27.4 30.2 29.0 46.1 1800 . 10. 2 27.1 48.0 30.2 73.1 27.8 44.2 IOOO . S f. 20. 6 20. o 48.0 25.2 28.1 25.7 43-5 IOOI . 25.8 14.4 44.6 25.6 28.1 23.5 42.9 IOO2 . ?4.c 21.8 SO. I 27.7 34.O 29.2 48.3 1007 . 28.4 17.7 51-2 28.3 34.5 31.6 44.2 32.1 2=;. 7 46.2 24.3 25.6 27.2 44.2 TOO? • 74.O 20. 2 43.6 27.7 3I.I 28.6 43-9 IOO6 . 31.2 IS-1 55-7 34.1 34.3 27.0 46.1 I9«>7 23-7 19.7 58.2 35-7 29.7 31-8 45-i Average (1898 to 1907) 29.8 19.4 49-3 28.6 3°-9 28.1 44-7 Winchester bushels. 2 Bushels of 32 pounds. 6i6 APPENDIX BARLEY BARLEY CROP OF COUNTRIES NAMED, 1903-1907 COUNTRY 1903 (Bu.) 1904 (Bu.) 1905 (Bu.) 1906 (Bu.) 1907 (Bu.) United States . . Canada .... Mexico .... Total North 131,861000 39,035000 9,061000 139,749000 42,244000 7,355°°° 136,651000 45,389000 7,000000 178,916000 50,820000 7,000000 153,597°°° 45,235°°° 7,000000 America . . 1 79,95 7°o° 189,348000 189,040000 236,736000 205,832000 Austria .... Hungary proper . France .... Germany . . . Russia (European) Great Britain — England . . Scotland . . . Wales .... Ireland .... 73,873000 64,577000 43,345°°° 152,653000 350,486000 50,628000 7,739000 2,981000 6,076000 66,815000 49,915000 38,338000 135,409000 339,717000 48,511000 7,408000 3,077000 5,478000 70,469000 62,453000 40,841000 134,204000 338,836000 48,778000 8,257000 2,906000 7,181000 76,024000 69,747000 36,538000 142,901000 304,276000 5I,543°°° 7,803000 3,116000 7,21 1000 78,548000 63,078000 45,095000 160,650000 344,104000 51,912000 7,466000 2,885000 6,995000 Total United Kingdom . . 67,424000 64,474000 67,122000 69,673000 69,258000 Total Europe . 931,758000 841,070000 867,392000 907,895000 911,451000 Cyprus .... Japan 3,969000 3,122000 2,980000 2,778000 3,000000 90 544000 Russia (Asiatic) . 6,984000 6.538000 8,130000 7,763000 9,345000 Total Asia . . 70,728000 90,1512000 88,596000 94,558000 102,039000 Africa . .. . . 50,987000 52,097000 35,7°3°°° 44,102000 44,205000 Australia .... New Zealand . . 1,184000 1,172000 2,740000 1,197000 2,084000 1,164000 1,945000 1,056000 2,319000 1,068000 Total Australasia 2,356000 3,937000 3,248000 3,001000 3,387°°° Grand total . . 1,235,786000 1,176,964000 1,183,979000 1,286,292000 1,267,814000 AVERAGE YIELD OF BARLEY IN COUNTRIES NAMED, BUSHELS PER ACRE, 1898-1907 YEAR UNITED STATES ' RUSSIA, EURO- PEAN* GER- MANY* AUSTRIA * HUNGARY PROPER 2 FRANCE l UNITED KING- DOM l Average (1888 to 1897) 23.2 12.6 27.6 20. 2 20.3 21-5 34-4 1898 22. 0 37.4. 1800 2C.C 33 8 24.9 24.0 22.7 TS-8 1900 I I C 20. 2 21.8 •32.7 IOOI 2S.6 1 1.2 77.2 22-4 20. o 21. 1 72.7 1902 jc 6 24.6 24 7 24. ? 77. 0 loot I ? C 76 7 24.8 2? I 2?. 2 77.4 IQO4 27.2 77.7 22.8 10.8 22. 0 72.7 IOOS 26.8 24 C 7S.O 1006 28.7 14.1 7<1.2 26.1 26.8 20.8 76.2 1907 • 23.8 14.2 38.2 27-3 20-7 24.4 36.8 Average (1898 to 1907) 25-5 '3-7 34-4 23-9 23.8 22-9 34-9 1 Winchester bushels. 2 Bushels of 48 pounds. APPENDIX 617 RYE RYE CROP OF COUNTRIES NAMED, 1903-1907 COUNTRY 1903 (Bu.) 1904 (Bu.) 1905 (Bu.) 1906 (Bu.) 1907 (Bu.) United States . . Canada .... Mexico .... Total No. America Austria-Hungary . France .... Germany .... Russia (European) United Kingdom . Total Europe . Russia (Asiatic) Total Asia . . Australia .... New Zealand . . Total Australasia Grand total . . 29.363000 3,915000 136000 27,242000 2,995000 67000 28,486000 2,748000 70000 33,375000 2,273000 70000 31,566000 2,002000 70000 33,414000 30,304000 31,304000 35,718000 33,638000 132,267000 57,951000 389,923000 879,883000 2,000000 I37»963000 52,141000 396,075000 977,981000 2,000000 151,641000 58,116000 378,204000 708,692000 2,000000 !53, 515000 50,429000 378,948000 638,675000 2,000000 129,234000 58,578000 384,150000 776,000000 2,000000 1,594,370000 1,681,280000 1,436,406000 1,371,881000 1,479,851000 32,059000 30,457000 28,750000 28,169000 32,000000 32,059000 3°i457000 28,750000 28,169000 32,000000 78000 40000 131000 2IOOO 85000 33°°° 94000 • 65000 89000 43000 1 1 8000 152000 i i 8000 159000 132000 1,659,961000 1,742,193000 1,496,578000 I,435,927o°0 1,545,621000 AVERAGE YIELD OF RYE IN COUNTRIES NAMED, 1898-1907 (Bushels per Acre) YEAR UNITED STATES RUSSIA, EURO- PEAN GER- MANY AUS- TRIA HUN- GARY PROPER FRANCE IRE- LAND Average (1888 to 1897) . 13-5 IO.O 19.0 J5-5 16.3 17.1 25-4 1808 M.6 10.6 17 7 18 ? 2S S 1800 12.8 21 < 18 7 18 2 2S 8 IOOO IS. I 12.7 i c.i 2S.7 IOOI IS. 3 IO.3 n 8 16 7 27.3 IOO2 17 O 12. S 18 2 28.1 IQO7 IS. A. 18 2 18 2 18 i IQO4. I S 2 16 6 1905 I6.S IO.I i8.<; 27.O 1906 16 7 8.8 2S I 19 8 16 7 27 6 1907 16.4 10.8 25-7 18.8 16.2 18.2 27.0 Average (1898 to 1907) . 15-8 "•5 24.6 18.1 J7-5 17.2 26.7 NOTE. The student may well remember that the reported crop yields, acreage, and production are based upon estimates, while the statistics for im- ports and exports are based upon definite data. In census years the estimates are made with greater care and detail, but even these are largely estimates. In some cases the annual estimates are undoubtedly far from the facts, as is strongly suggested by comparing the federal "statistics" with the "statistics" 6i8 APPENDIX POTATOES POTATO CROP OF COUNTRIES NAMED, 1902-1906 COUNTRY 1902 (Bu.) 1903 (Bu.) 1904 (Bu.) 1905 (Bu.) 1906 (Bu.) United States . Canada .... Mexico .... Newfoundland Total North America . Chile 284,633000 51,206000 347000 1350000 247,128000 56,944000 539000 i,350000 332,830000 55,436oo° 527000 1,350000 260,741000 55,257000 400000 1,350000 308,038000 59,804000 400000 1,350000 337,536oo° 305,961000 390,143000 317,748000 369,592000 11,616000 584,619000 441,055000 1,596,969000 1,028,036000 10,349000 544,166000 426,422000 1,576,361000 887,600000 6,131000 520,461000 451,039000 I,333.326oo° 893,908000 6,532000 765,117000 523,876000 1,775,579000 1,032,888000 6,532000 709,237000 372,076000 1,577, 653°°° 939,717000 Austria-Hungary . France .... Germany . . Russia (European) United Kingdom : Great Britain . Ireland . . Total United Kingdom Total Europe . Japan .... Russia (Asiatic) . Total Asia . . Total Africa . Australia . . . New Zealand . Total Australasia Grand total . 119,250000 • 101,761000 108,779000 88,227000 133,961000 98,635000 140,474000 127,793000 128,005000 99,328000 221,011000 197,006000 232,596000 268,267000 227, 333°°° 4,280,644000 4,038,566000 3,843,081000 4,779,59°000 4,3°5>3I3000 7,418000 13,142000 9,824000 19,364000 11,274000 18,800000 16,255000 18,865000 16,255000 16,481000 20,560000 29,188000 30,074000 35,120000 32,736000 3,884000 3,541000 4,048000 4,071000 4,138000 12,039000 7,721000 14,973000 7,215000 16,777000 7,795000 11,071000 5,025000 10,016000 4,607000 19,760000 22,188000 24,572000 16,096000 14,623000 4,674,000000 4,409,793000 4,298,049000 5, J 59^5 7ooo 4,732,934ooo from some of the states which have crop-reporting boards, such as the Illinois State Board of Agriculture and the Iowa Weather and Crop Service. Thus in 1907, Illinois produced, according to the federal report, more than 40 million bushels of wheat, but less than 25 million bushels by the state report. In 1908 the federal estimate gave Illinois 9,450,000 acres of corn, while the state report was 6,780,000 acres. The same year the state of Iowa claimed to produce only 4,968,250 bushels of wheat, but in the federal report Iowa receives credit for 8,068,000 bushels. These are extreme variations, but they should serve to emphasize the fact that crop "statistics" should not weigh heavily as against actual data, such, for example, as the records of the long-continued field experiments of Rothamsted, Pennsylvania, etc. On the other hand, the United States crop statistics are probably as good as those from any nation ; and, while gross errors may appear in specific instances, APPENDIX 619 RICE RICE CROP OF COUNTRIES NAMED, 1902-1906 [Mostly cleaned rice. China, which is omitted, has a roughly estimated crop of 50,000,000,000 to 60,000,000,000 pounds. Other omitted countries are Afghanistan, Algeria, Brazil, Colombia, Federated Malay States, Madagascar, Persia, Russia (Asiatic), Trinidad and Tobago, Turkey (Asiatic and European), Venezuela, and a few other countries of small production.] COUNTRY 1903 (Lb.) 1903 (Lb.) 1904 (Lb.) 19O5 (Lb.) 1906 (Lb.) United States: Contiguous . . Hawaii .... 319,400000 33,400000 40,000000 560,800000 33,400000 48,700000 586,000000 33,400000 62,000000 378,000000 33,400000 62,000000 496,000000 33,400000 62,000000 Total No. America 401,600000 652,000000 690,800000 482,800000 600,800000 Total South America 85,600000 87,500000 95,100000 97,300006 120,500000 Italy 359.800000 417,100000 394,600000 478,800000 475,400000 Total Europe . . 1,038,300000 1,188,500000 1,167,500000 1,166,500000 1,215,000000 British India: British Provinces Native States . Japanese Empire Total Asia . . Total Africa . 72,688,000000 799,000000 13.295,300000 105,075,200000 22,200000 68,580,000000 838,000000 16,809,200000 104,887,800000 22,200000 71,561,000000 764,000000 18,658,700000 110,212,200000 22,200000 67,916,000000 640,000000 14,639,200000 102,147,900000 21,800000 67 ,464,000000 640,000000 17,185,900000 104,974,000000 21,800000 Grand total . . 106,626,400000 IO6,84I,OOOOOO 112,190,800000 103,919,100000 106,943,900000 they doubtless approximate the truth as a general rule, and are more trust- worthy, especially for purposes of comparison, than some state estimates. It should be kept in mind that certain crops, such as wheat, are now quite regularly fertilized in some of the Eastern and East Central states. Comparison of crop yields in different states is most significant when the acreage is also comparable. In 1907 the average yield of wheat per acre was 23 bushels in Vermont and only n bushels in Kansas; but Vermont raised one thousand acres and Kansas raised six million acres, and on many thousand acres the Kansas yield may have exceeded 30 bushels per acre. In 1905 the average yield of corn per acre was 42.7 bushels in Connecticut and only 39.8 bushels in Illinois; but Connecticut raised only 55,595 acres of corn, while Champaign County, Illinois, raised some 200,000 acres of corn, which made an average yield of 65 bushels per acre. South Carolina is authentically credited with having produced 239 bushels of air-dry corn on one acre of land in one season, but the average yield for the state for the 44 years, 1866 to 1909, is 10 bushels per acre. Even the average yield of corn for the United States has varied from 30.8 bushels per acre, in 1872, to 16.7 bushels, in 1901 ; and if these records were interchanged the average yield would become the same for two successive 2o-year periods, 25.0 bushels per acre. 62O APPENDIX SUGAR SUGAR PRODUCTION OF COUNTRIES NAMED, 1903-1904 TO 1907-1908 [European beet sugar, as estimated by Licht; United States beet sugar, from reports of Department of Agriculture on the Progress of the Beet-sugar Industry in the United States; production of British India (except 1907-1908) and of Formosa and Natal prior to 1905-1906 from official statistics; other data, from Willett & Gray. The estimates of Willett & Gray do not include the production of China, and some other less important sugar-producing countries.] COUNTRY 1903-4 (Tons1) 1904-5 (Tons1) 1905-6 (Tons1) 1906-7 (Tons1) 1907-8 (Tons1) CANE SUGAR United States: Contiguous — Louisiana 228477 771:000 37OOOO 230000 775OOO Texas 19800 Noncontiguous — Hawaii 328107 780^76 Porto Rico 130000 145000 2I30OO 2IOOOO 217000 Total United States (except Philippine Islands) . . . 706380 87SS76 938225 845871 984000 Mexico IO7S47 Cuba 1,040228 i 163258 I 17874.0 115 Total North America . . . 2,143911 2,410477 2,545l82 2,680175 2,609000 Total South America . . . 601134 590382 700001 610151 586000 Total Asia 2,876671 3,333672 2,926209 3,455446 3,481477 Total Africa 355747 25134° 317967 349000 270000 Total Oceania 163328 216213 230000 249000 276000 Total cane-sugar production 6,168791 6,820676 6,735°8i 7,360172 7,233477 BEET SUGAR United States Canada Total North America . . . 221535 2242O7 290812 443 I 63 421897 Austria-Hungary &8n?7? 60000 72877O France Netherlands Russia Other countries Total Europe . . . e 88l777 *7o&*7nn z: fi 4» f\jo j\j\j Total beet-sugar production 6,102868 4,932907 7,22446l 7,160163 6,006807 Total cane and beet sugar 12,271659 ". 753583 '3,959542 I4,52°335 I4,23°374 1 Tons of 2240 pounds, except beet sugar in Europe, which is shown in metric tons of 2204.622 pounds. APPENDIX 621 SUGAR — Continued PRODUCTION OF SUGAR IN THE UNITED STATES AND ITS POSSESSIONS, 1874-75 TO 1907-8 CANE SUGAR YEAR SUGAR (Long Tons) Louisiana (Long Tons) Other Southern States (Long Tons) Porto Rico (Long Tons) Hawaii, (Long Tons) Philippine Islands (Long Tons) TOTAL (Long Tons) 1874-1875. . . I 160047 3454 72128 11197 126089 273015 1875-1876. . . TOO' 72954 4046 70016 11639 128485 287240 1876-1877 . . . f IOO 85122 3879 62340 11418 121052 283911 1877-1878 . . . J 65671 5330 84347 I7I57 120096 292701 1878-1879 . . . 2OO 106908 5090 76411 21884 129777 340270 1879-1880 . . . I2OO 88822 3980 57057 28386 178329 357774 1880-1881 . . . 500 121867 61715 41870 205508 436960 1881-1882 . . . 1 , / 71373 5000 80066 50972 148047 355958 1882-1883 . . . J 5°° I i35297 7000 77632 51705 193726 465860 1883-1884. . . 535 128443 6800 98665 63948 120199 418590 1884-1885 . . . 953 94376 6500 70000 76496 200997 449322 1885-1886 . . . 600 127958 7200 64000 96500 182019 478277 1886-1887 • • • 800 80859 4535 86000 95000 169040 436234 1887-1888 . . . 255 I5797I 9843 60000 IOOOOO 158445 486514 1888-1889 . . . 1861 144878 9031 62000 I20OOO 224861 562631 1889-1890. . . 2203 124772 8x59 55000 I2OOOO M2554 452688 1890-1891 . . . 3459 215844 6107 50000 125000 136035 536445 1891-1892 . . . 5356 160937 4500 70000 "5598 248806 605197 1892-1893 . . . 12018 217525 5000 50000 I4OOOO 257392 681935 1893-1894. . . 19950 265836 6854 60000 136689 207319 696648 1894-1895 . . . 20092 3X7334 8288 525OO 131698 336076 865988 1895-1896 . 29220 237721 4973 50000 201632 230000 753546 1896-1897 . . . 37536 282009 5570 58000 2242l8 2O2OOO 809333 1897-1898 . . . 40398 3I0447 5737 54000 204833 I78OOO 793415 1898-1899 . . . 32471 245512 3442 53826 252507 93000 680758 1899-1900 . . . 72944 147164 2027 35000 258521 62785 578441 1900-1901 . 76859 270338 2891 80000 321461 55400 806949 1901-1902 . 164827 321676 3614 85000 3I75°9 78637 971263 1902-1903 . . . 194782 329226 3722 85000 391062 9OOOO ,093792 1903-1904 . . . 214825 228477 2 19800 130000 328103 84000 ,005205 1904-1905 . . . 216173 335000 2 15000 145000 380576 106875 ,198624 1905-1906 . . . 279393 330000 I2OOO 213000 383225 M5525 ,363I43 1906-1907 . 431796 230000 2 I3OOO 210000 392871 I450OO ,423167 1907-1908 . . . 413954 335000 2 I2OOO 217000 420000 135000 ,532954 1 Production uncertain ; not exceeding quantity stated. 2 Texas. 622 APPENDIX INTERNATIONAL TRADE IN SUGAR, 1902-1906 EXPORTS COUNTRY YEAR BEGIN- NING 1902 (Lb.) 1903 (Lb.) 1904 (Lb.) 1905 (Lb.) 1906 (Lb.) Austria-Hungary . Argentina . . . Belgium .... Brazil .... British Guiana . British India . . China .... Cuba Dutch East Indies Egypt .... Formosa . . . France .... Germany . . . Mauritius . . . Netherlands . . Peru Jan. Jan. Jan. Jan. Apr. Apr. Jan. Jan. Jan. Jan. Jan. Jan. Jan. Jan. Jan. Jan. 1,500,882186 91,919510 296,287771 301,498062 280,284480 55,645520 89,945867 1,781,561643 1,904,371591 98,521149 100,873254 804,993320 2,367,596256 331,172713 310,694069 258,738790 1,564,437691 66,888231 257,180695 48,256967 282,125760 57.474502 39,890000 2,118,279646 1,907,867045 86,469803 54,128545 469,129814 2,249,141034 375,505049 287,238939 281,482880 1,125,102823 40,368833 406,944665 17,331526 239,043840 57,211504 48,787467 2,459,166945 2,318,243282 50,620531 79,518816 636,360461 1,720,574091 435,923559 403,476558 290,916853 1,265,791878 4,847964 304,193682 83,216786 261,072000 64,546944 69,228800 2,412,915391 2,314,655085 67,821106 93,930689 658,062149 1,636,803746 361,987596 215,001603 295,935805 1,631,529629 233690 462,976753 187,278992 257,490912 58.660896 23,106000 2,643,700975 2,197,208868 10,495854 93,930689 617,793487 2,671,881051 410,917817 356,157015 295,935805 Philippine Islands Jan. Jan 217,486869 188,114307 iO7,862s84 191,917567 239,196273 41,433135 285,394747 41,433135 Russia .... Trinidad and Tobago . . . Other countries . Jan. Apr. i 288,610934 105,861392 617,792000 540,418988 90,460944 609,680000 398,854898 106,573936 569,646000 220,925074 81,179056 901,932101 206,854118 100,809856 952,547723 00 IMPORTS Australia . . . Jan. 208,551056 205,026640 85^98624 55,923056 94,: 3 7680 British India . . Apr. 549,868704 672,147168 724,262224 862,453200 1,090,152784 Canada .... July 388,370832 390,544660 346,752590 448,962523 423,6896:4 Cape of Good Hope Jan. 120,365406 104,629048 :o:, 46894: 82,805094 87,165626 Chile .... Jan. 97,002936 115,467959 I24,:396:9 75,6:0563 75,6:0563 China .... Jan. 607,880000 435,7:1467 509,959200 626,433333 896,422400 Denmark . . . Jan. 42,051621 77,3745i6 82,865:27 76,080072 45,254827 Egypt .... Jan. 22,84444: 16,920099 45,843510 86,880895 76,32:099 1'in land .... Jan. 6i,752745 72,691465 7:, 26353: 73,772007 83,322752 France .... Jan. 220,187363 288,073883 179,849557 179,460755 222,562321 Italy . Jan. aa Q i* Japan .... Jan. 47,355501 351,750533 *4»477532 523,:3:o67 4,920073 547,300400 1 1,25:729 289,129733 3 «,°323 * 7 104,8:6933 Netherlands . . Jan. 248,799655 203,06:092 208,329129 167,742700 1:8,406076 New Zealand . . Jan. 84,878074 88,197686 9^84:944 89,439230 93,329376 Norway .... Jan. 82,791956 83,524155 76,703054 77,993596 80,364:38 Persia .... Mar. 2 167,114080 179,4:2238 154,8:592: 154,2:74:5 154,2174:5 Portugal . . . Jan. 63,630016 68,7656:0 72,490231 70,0:: 389 70,0:: 389 Singapore . . . Jan. 93.271733 :o2, 369867 114,407600 1:7,958267 :: 7,958267 Switzerland . . Jan. 180,272161 192,0:5742 :75,444?o: i o:',o i i 375° 1310 5230 7760 33io 2090 Dorset (continued) Kimmeridge clay (87) . . . (88) . . . 2960 4360 2700 2790 4100 5230 3490 3050 2790 2700 33!° 33*° 2960 2OIO 2880 2790 2180 3920 4270 3920 2530 3920 2270 2350 2620 2700 1480 5580 3230 2960 3T4° 2180 33io 4270 5230 (71) (99) (95) (T7\ (51) \ll) (Q~\ (94) (°2) (Q.r.\ (35) V89.' (%} (50) (0) fe*,} (16) 157J feS\ (72) (5°) Calcareous grit (9) .... (40) . . (21) doo) (34) (60) (59) (52) (53) (29) (4) Cornbrash (10) d) (08) (Q6) (97) .... Greensand (79) (47) (48) (2) Junction greensand and marl- stone (31) (76) (28) .- . Fuller's earth (18) .... (23) .... (56) .... (46) .... (90) .... (26) .... Inferior oolite (91) .... (13) .... [unction inferior oolite and Midford sands (14) . . Midford sands (55) .... (54) .... (45) .... (5) .... (92) .... (a«) Wealden beds (33) .... (32) .... (84) .... (69) .... (22) .... Purbeck beds (27) .... Portland stone (66) .... Kimmeridge clay (3) ... (20) . . . (42^ . . . (85) • • • (86) ... APPENDIX 639 PHOSPHORUS IN SOILS IN THE UNITED KINGDOM (Continued) Pounds per Acre in 2 Million of Soil (about 6f Inches Deep) PHOS- DESCRIPTION AND LOCALITY DESCRIPTION AND LOCALITY (Original Sample Nos.) PHORUS (Lb.) (Original Sample Nos. PHORUS (Lb.) ENGLAND (Continued) Dorset (continued) Junction Midford sands and marlstone (6) .... (43) ..-• Marlstone (7) (70) (75) (78) Junction marlstone and lower Lias (24) . 270x3 2790 4270 549° 2880 4100 253° 3°5° 349° 4450 4620 Essex (continued) Saffron Walden ] .... Tendring 960 870 780 1400 1130 780 1310 Thaxted St. Osyth Yeldham Hampshire Newlands Manor, Lymington (4) 1480 1260 (44) • Lower Lias (17) West Mark, near Petersfield (5) (74) (93) Isle of Ely Black soils: White Fen Benwick . . . Littleport Fen . . . 2670 2480 3770 334° 2300 3260 1950 2140 1670 Durham Grange Hill plot (116) . . . Shield Ash plot (i) . . . (11) • • • 1130 79° 1130 Wryde Loam, Wisbeck Fen .... f Essex Birch 870 870 157° 1400 1220 2090 7^o (5) • • • • 1130 Flexford •580 (6) . . 1050 46O Wanborough 680 Hanging Leaves (265) . . . Castle Steads (267) .... 520 610 Raynes Park . . . . Horsley . .... 850 IOIO Davy Houses (266) .... East Tower Hill . . . . . 700 14.80 Chalk soils: Pepnv ?oo Scale IS7O Whitefield IOOO Fetcham 1680 Kirnblesworth (^55) • • 610 Puttenham I4.CO 1420 PnrVlp Part • Sutton I2OO Tower Hill ICKO 800 Back House 8^0 650 Tree Field . . . . . . 610 Gault soils, Alder Holt 1320 Pallace Leas Field-plot (i) . (2) . (6) . (8) . (12) . (13) . Oxford 870 700 520 520 520 440 Wiltshire Christchurch Allotment Sta- tion, Warminster . . . Boreham Road I ' • ' Horningsham 780 2960 2250 262O 22IO Heytesbury T.Q2O Wick. Farm: Headington (I) .... (II) .... Suffolk 43° 1050 Codford allotment soil . . . Chitterne allotment soils . . Imber allotment (i) . . . . (2) .... Corslev plot 4060 7920 3230 3510 1 1 7O Bramford i ^70 Clay soil, Warminster . . . 222O 2160 York warp soil 1940 642 APPENDIX PHOSPHORUS IN SOILS IN THE UNITED KINGDOM (Continued) Pounds per Acre in 2 Million of Soil (about 6f Inches Deep) PHOS- PHOS- DESCRIPTION AND LOCALITY PHORUS DESCRIPTION AND LOCALITY PHORUS (Lb.) (Lb.) SCOTLAND Lanark Cleghorn, near Lanark: Plot i OIO Argyll Birgidale Knock, Rothesay 2130 Plot 2 . . . IIOO Aberdeen Tarves 4IQO Dumbarton Wester Fintray, Kintore . . Fedderate, Maud 2470 32OO Drumfork, Helensburgh . . Nairn Easterboard, Croy .... 3920 II2O Tulloch, Lumphanan . . . Kincardine Fasque, Fettercairn .... 990 1870 IRELAND Cork Wexford Limestone soils, Shanagany . Old red sandstone, Killeigh . 1290 1360 Silurian clay slate soils: Bally-Carney Clonroche 1360 1460 Tipperary Limestone soils: Rockford 1400 St. Kieran's 1 1 -20 WALES Garden soil 2670 • AVERAGES OF ALL SAMPLES England (269 samples) Scotland (10 samples) Ireland (6 samples) Wales (i sample) . . 2230 2190 1.33° 2670 APPENDIX SECTION VII 643 AGRICULTURAL COLLEGES AND EXPERIMENT STATIONS IN THE UNITED STATES AND CANADA STATE OR TERRITORY NAME OF SCHOOL LOCATION OP SCHOOL ADDRESS OF AGRICULTURAL EXPERIMENT STATION Alabama . . . Alabama Poly technical Alabama (College), Institute .... Auburn Auburn Agricultural School of Alabama (Canebrake), the Tuskegee Normal Uniontown and Industrial In- stitute Tuskegee Institute Agricultural and Me- Alabama (Tuskegee), chanical College for Tuskegee Institute Negroes .... Normal Alaska, Sitka Arizona . . . University of Arizona . Tucson Arizona, Tucson Arkansas . . . Unversity of Arkansas . Fayetteville Arkansas, Fayetteville California . . . Branch Normal College University of California Pine Bluff Berkeley California, Berkeley Colorado . . . The State Agricultural Colorado, Fort Collins College of Colorado Fort Collins Connecticut . . Connecticut Agricul- Connecticut (Storrs), tural College . . . Storrs Storrs Connecticut (State), New Haven Delaware . . . Delaware College . . Newark Delaware, Newark State College for Col- ored Students . . . Dover Florida .... University of the State of Florida .... Gainesville Florida, Gainesville Florida State Normal and Industrial School Tallahassee Georgia . . . Georgia State College of Agriculture . . . Athens Georgia State Indus- trial College . . . Savannah Georgia, Experiment Hawaii College of Hawaii . . Honolulu Hawaii, Honolulu Idaho University of Idaho . Moscow Idaho, Moscow Illinois University of Illinois . Urbana Illinois, Urbana Indiana Purdue University . . Lafayette Indiana, Lafayette Iowa Iowa State College of Agriculture and Me- chanic Arts . . . Ames Iowa, Ames Kansas .... Kansas State Agricul- tural College . . . Manhattan Kansas, Manhattan Kentucky . . . State University . . Lexington Kentucky, Lexington The Kentucky Normal and Industrial Insti- tute for Colored Per- sons Frankfort Louisiana . . . Louisiana State Uni- Louisiana (State), versity and Agricul- Baton Rouge tural and Mechanical Louisiana (Sugar), New College Baton Rouge Orleans Southern University Louisiana (North), Cal- and Agricultural and houn Mechanical College . New Orleans APPENDIX AGRICULTURAL COLLEGE AND EXPERIMENT STATIONS IN THE UNITED STATES AND CANADA (Continued) STATE OR TERRITORY NAME OF SCHOOL LOCATION OF SCHOOL ADDRESS OF AGRICULTURAL EXPERIMENT STATION Maine .... The University of Maine Orono Maine, Orono Maryland . . Massachusetts . Michigan . . . Minnesota Maryland Agricultural College Princess Anne Acad- emy, Eastern Branch of the Maryland Agri- cultural College . . Massachusetts Agricul- tural College . . . Massachusetts Institute of Technology . . Michigan State Agri- cultural College . . The University of Min- nesota College Park Princess Anne Amherst Boston East Lansing Minneapolis Maryland, College Park Massachusetts, Amherst Michigan, East Lansing Minnesota, St. Anthony Park, St. Paul Mississippi . . Missouri . . . Mississippi Agricul- tural and Mechanical College Alcorn Agricultural and Mechanical College . College of Agriculture and Mechanic Arts of the University of Mis- souri Agricultural College Alcorn Columbia Mississippi, Agricul- tural College Missouri (College), Co- lumbia Missouri (Fruit), Moun- tain Grove School of Mines and Metallurgy of the University of Mis- souri Rolla Montana . Lincoln Institute . . Montana Agricultural College Jefferson Bozeman Montana, Bozeman Nebraska . . Industrial College of the University of Ne- braska Lincoln Nebraska, Lincoln Nevada . . . New Hampshire University of Nevada . New Hampshire Col- lege of Agriculture and the Mechanic Arts Reno Durham Nevada, Reno New Hampshire, Dur- ham New Jersey . . New Mexico New York Rutgers Scientific School (The New Jersey State College for the Benefit of Agriculture and the Mechanic Arts) . . New Mexico College of Agriculture and Me- chanic Arts . . . New York State College of Agriculture at Cor- nell University . . New Brunswick Agricultural College Ithaca New Jersey, New Bruns- wick New Mexico, Agricul- tural College New York (Cornell), Ithaca New York (State), Ge- neva APPENDIX 645 AGRICULTURAL COLLEGES AND EXPERIMENT STATIONS IN THE UNITED STATES AND CANADA (Continued) STATE OR TERRITORY NAME OF SCHOOL LOCATION or SCHOOL ADDRESS OF AGRICULTURAL EXPERIMENT STATION North Carolina . The North Carolina North Carolina (Col- College of Agriculture and Mechanic Arts . The Agricultural and West Raleigh lege), West Raleigh North Carolina (State), Raleigh Mechanical College for the Colored Race Greensboro North Dakota . North Dakota Agricul- North Dakota, Agricul- tural College . . . Agricultural College tural College Ohio .... Ohio State University . Columbus Ohio, Wooster. Oklahoma. . . Oklahoma Agricultural and Mechanical Col- Stillwater Oklahoma Stillwater Agricultural and Nor- mal University . . . Langston Oregon . . . Oregon State Agricul- tural College . . . Corvallis Oregon, Corvallis Pennsylvania The Pennsylvania State Pennsylvania, State Col- College State College lege Porto Rico . . University of Porto Rico San Juan Porto Rico, Mayaguez Rhode Island . Rhode Island College of Agriculture and Mechanic Arts . . Kingston Rhode Island, Kingston South Carolina . The Clemson Agricul- tural College of South Clemson College South Carolina, Clem- The Colored Normal, son College Industrial, Agricul- tural, and Mechani- cal College of South Carolina .... Orangeburg South Dakota . South Dakota State • College of Agricul- ture and Mechanic South Dakota, Brook- Arts Brookings ings Tennessee . . University of Tennessee Knoxville Tennessee, Knoxville Texas .... Agricultural and Me- chanical College of Texas College Station Texas, College Station Prairie View State Nor- mal and Industrial College Prairie View Utah . . . . The Agricultural Col- lege of Utah . . . Logan Utah, Logan Vermont . . . University of Vermont and State Agricul- tural College . . . Burlington Vermont, Burlington Virginia . . . The Virginia Agricul- tural and Mechanical College and Polytech- Virginia (College), nic Institute . . . Blacksburg Blacksburg The Hampton Normal Virginia (Truck), Nor- and Agricultural In- folk stitute Hampton 646 APPENDIX AGRICULTURAL COLLEGES AND EXPERIMENT STATIONS m THE UNITED STATES AND CANADA (Continued) STATE OR PROVINCES NAME OF SCHOOL LOCATION OF SCHOOL ADDRESS OF AGRICULTURAL EXPERIMENT STATION Washington . . State College of Wash- ington Pullman Washington, Pullman West Virginia West Virginia Univer- West Virginia, Morgan- sity Morgantown town The West Virginia Col- ored Institute . . . Institute Wisconsin . . . University of Wisconsin Madison Wisconsin, Madison Wyoming . . . Alberta .... University of Wyoming University of Alberta . Laramie Edmonton Wyoming, Laramie Alberta (Provincial), Edmonton (Dominion), Lacombe (Dominion), Leth- bridge British Columbia (Dominion), Agassiz Manitoba . . . Manitoba Agricultural Manitoba College Winnipeg (Dominion), Brandon (Provincial), Winne- Peg Nova Scotia . . Nova Scotia Agricul- Nova Scotia tural College . . . Truro (Dominion), Nappan (Provincial), Truro Ontario .... Ontario Agricultu- Ontario ral College . . . Guelph (Provincial), Guelph (Dominion central), Ottawa Prince Edward Island (Dominion), Char- lottetown Quebec .... MacDonald Agricul- tural College . . . St. Anne Quebec (College), St. Anne Saskatchewan University of Sas- Saskatchewan katchewan . . . Saskatoon (Dominion), Indian Head (Dominion), Rosthern (Provincial), Saska- toon INDEX Abandoned lands : eastern United States, 342, 591 Maryland, 140 Rothamsted, 403 Acid, defined, 20 Acid phosphate, 189 Acid salts, 23 Acidity of soils, 163, 566 determination, 627 test, 566 Acids, common, 24 Adobe soil, 65 African soils, 66 Agdell field, Rothamsted, 345 Agricultural colleges in the United States and Canada, 643 established by law, 518 Agricultural experiment stations in the United States and Canada, 643 established by law, 505, 518 Agricultural history, two periods, 590 Agriculture, permanent systems, 159 Aikman, early use of bones, 324 Air, composition, 13 Alabama, field experiments, 494 soils, 138 Albite, 47 Aldehydes, 30 Alkali, defined, 20 Alkali salt, fertilizer or stimulant, 364, 393, 402, 479, 533 Allyl, 40 Aluminum, 44 American agricultural colleges and experi- ment stations, 643 Amids and amido group, 37 Ammonification, 195 Ammonium sulfate, 525 Analysis of animal and plant products, 157, 602 Analysis of soils, 626 Analyzing, and testing soils, 565, 626 Animal and plant products, composition, 157, 602 Animal fats, 35 Animals destroy organic matter, 199 Anorthite, 47 Appearance of soils and crops in relation to fertility, 572 Arid and semiarid sections, rainfall records, 580, 582 Arid soils, 126, 129, 139 Arkansas soils, 97 Asbestos, 49 Ashes, composition, 602 fertility experiments, 508, 511 Asiatic soils, 66, 67 Association, National Fertilizer, report on raw phosphate, 292 Atom, defined, 3 Atomic bond, 4 Atomic weight, defined, 3 Atomic weights, table, 10 Available plant food, 107, 314, 366 Bacteria : denitrifying, 439 nitrifying, 195 nitrogen-fixing, 207 nonsymbiotic, or "free-living," 225, 437 Barley: Canadian experiments, 505 composition, 603 Rothamsted experiments, 378 statistics, 616 Barn field, Rothamsted, 398 Barren soils, 63, 367 Base, defined, 20 Basic slag phosphate, 192 Beans, composition, 417, 603 • fertility loss, 550 Bond, atomic, 4 Bone meal, 157, 185 Bones and other phosphates used in Eu- rope, 324 Bottom land soils, 62, 120, 138 Bradley's soil fertility theories, 300 Bran, wheat, composition, 41, 604 Breathing pores, 29 Broadbalk field, Rothamsted, 363 647 648 INDEX Bulbs, composition, 604 Bureau of Soils, United States Department of Agriculture: pot cultures, 513 soil analyses, 136 soil fertility theories, 313, 362, 367 soil surveys, 114 Butter, composition, 154 statistics, 623 Cabbage, composition, 604 experiments, 266, 278 Cake, oil, composition, 604 fertility loss, 205 statistics, 626 Calcium, 43 Calcium cyanamid, 526 Calcium determination, 632 Calcium nitrate, 526 California soils, 102, 138 Canadian colleges of agriculture, 646 experiment stations, 505, 646 field experiments, 505 soils, 103, 507, 559 Carbohydrates, 30 Carbon, 26 Carbon cycle, 32 determination, 628 fixation, 29 , supply as plant food, 33 Carbonates, 50 determination, 628 loss by leaching, 51, 174 test, 567 Carrots, composition, 604 field experiments, 511 Casein, 41 Central states soils, 77, 138 Cereal seeds, composition, 154, 603 Chaff, composition, 603 Chemical action, 3, 107, 194, 562 Chemical elements, 10 Chemistry, defined, i organic, 30 China, agricultural conditions and prac- tices, 335 Chinese philosophy, 594 Chlorin, 44 Chlorophyll, 43 Clarke, on composition of earth's crust, 13 Clay, 50, 55 Clover, composition, 75, 154, 417, 603 Clover sickness, 312, 406 Coal ashes, composition, 602 Coastal plains soils, 117, 138, 139 Cobs, corn, composition, 603 Colleges of agriculture, 518, 643 Colorado soils, 101 Combining weights of elements, 3 Commercial fertilizers, 517 Commercial plant food materials, 157 Common elements, 13 Common functions of elements, 45 Composition of animal and plant products, 157, 602 Compound, defined, 2 Connecticut, investigations with legumes, 219 soil, 138 Corn, composition, 13, 75, 154, 603 cost per bushel, 585 record yield, 619 statistics, 606 Corn cobs, composition, 603 Cotton, composition, 154, 497, 603 statistics, 624 Cotton seed, 154, 525, 603 Cotton-seed meal, 525, 604 Condition of soil, 576 Conservation of soil moisture, 577 Coral limestone soil, 65 Creelman, on farming in Southern Europe, 329 Crimson clover tops and roots, composi- tion, 221 Critical periods in plant life, 538 Crop residues, 199 statistics, 605 stimulants, 533 yields (see also statistics): Asia, 334 Europe, 326 Kansas, 330 Crops, composition, botanical, 393 chemical, 154, 417, 418, 602 Crysolite, 47 Curie and Gleditsch, on transmutation of elements, n Cyanamid, 526 Czapek, on availability of plant food, 109 Decandolle's soil-fertility theories, 310 Decay of organic matter, 195 Delaware investigations with legume plants, 221, 222 Denmark, wheat yield, 614 Dentrification, 439, 502 De Saussure's discovery of mineral plant food, 307 Digestion coefficients for organic matter, 199, 206 Dolomitic limestone, 169 Drainage reclamation possible in the United States, 583 Dry farming, 579, 581 Dyer, on manure used in England, 324 INDEX 649 Earth's crust, 13, 46 Eastern states soils, 72, 75, 138 Element system for reporting analyses, S^S. 599 Elements in air, ocean, and earth's crust, i3 of plant growth, 12 the more common, 13 transmutation, n English soils, 637 Equilibrium in nature, 62 Essential elements of plant food, 12 European crop yields (see also statistics), 326 European soils, 634 Experiment stations in the United States and Canada, 643 established by law, 505, 518 Factors in crop production, 435, 575 Famines, Indian, 334 Russian, 333 Farm manure, composition, 542 Cambridge University investigation, 205 Canadian experiments, 508, 511 dried, 545 English practice, 324 Illinois experiments, 201, 206, 459, 473, 480 Japan, human and compost, 594 Ohio experiments, 204, 256, 442, 448, 547 Pennsylvania experiments, 202,423,431 Rothamsted experiments, 364, 380, 390, 393. 399t 4oo, 407, 4" Fats, 34 Felspars, 47 Fertility theories, 300, 362, 366, 385, 389 Fertilizer Association's report on raw phosphate, 292 Fertilizer law, 599 Fertilizers, commercial, 157, 517 Fish-scrap fertilizer, 525 Fixation of plant food by soils, 562 of carbon, oxygen, and hydrogen, 29 of free nitrogen, 207, 225, 437 Flax, composition, 603, 604 sickness, 319 statistics, 605 Florida phosphates, 187, 188, 595 sand and peat soils, 498 Formula, chemical, defined, 7 France, crop yields (see also statistics), 327 soils, 635 Fruits, composition, 604 Functions that are common to different elements, 45 Gas law, 7 Georgia, field experiments, 489 soils, 94 Germany, crop yields (see also statistics), 326 soils, 634 Glacial material, 54 Glacial soils, 123, 138, 144 Glycerin, 40 Gneiss, 48 Grain farming, 226, 329, 345, 434, 459, 478, 483 Granite, 48 Graphite, 26 Grass, composition, 603 digestibility, 199 Green manuring, 199, 218 Ground limestone and burned lime, 165 Growth of plants, 32 Hall, on soil-fertility theories, 319, 362, 366, 385 Hay, composition, 75, 154, 417, 418, 603 Hay grown every year, Rothamsted, 391 Hay statistics, 605, 624 Heat factor in crop production, 576 Hellriegel's discovery of nitrogen-fixing bacteria, 307 Hill's view of agriculture, 594 History of agriculture, 590 Holland, soil, 63 wheat yield, 614 Home of plants, 576 Hoos field, Rothamsted, 378 Hops, composition, 604 Hornblende, 49 Hunter's soil-fertility theories, 302 Hydrate, defined, 28 Hydrogen, 28 Hydroxid, defined, 17 Idaho, phosphates, 595 soils, 102 Illinois, field experiments, 283, 453, 476 pot-culture experiments, 171, 287, 486, 487 soils, 82, 138 India, agricultural conditions, 333 soils, 66 Indiana soils, 88 Inoculation for nitrogen fixation, 211 Intermountain soils, 127 Iowa, field experiments, 488 soils, 89 Ireland, soils, 642 Iron, 43, 69, 73, 75, 106, 603 Iron sulfate as a fertilizer, 158, 505 Italian agriculture, 329 650 INDEX Irrigation, in India, 333, 583 possible in the United States, 583 Japan, agricultural practices, 594 Jethro Tull's soil-fertility theories, 300 Kainit, 530, 535 Kansas, crop yields (see also statistics), 330 soils, 138 Kentucky, pot-culture experiments, 288 soils, 64, 65, 92, 138 King, on Japanese agriculture, 594 on water-soluble plant food, 142 Kossowitsch, availability of raw phosphate, 109 Land-plaster, 256, 420, 505, 533 Land reclamation possible in United States, 583 Land values, 586 Law, constant proportions, 8 diminishing returns, 374 gas, 7 governing sale of fertilizers, 599 periodic, 9 solution, 314, 316, 366 Lawes and Gilbert, source of nitrogen for plants, 307 Leaching, rocks, soils, 49, 51, 174, 413, 556 plants, 549 Lecithin, 40 Legume plants, composition, 154, 218, 604 inoculation, 210, 218 nitrogen fixation, 207 tops and roots, 218 Legume seeds, composition, 154, 603 Liberation of plant food, 109 Liebig's soil-fertility theories, 308 Liebig's view of agriculture, 591 Life, 29 Life of soil, 195 Light factor in crop production, 576 Lime and ground limestone, 165 Lime burning, 27 Limestone, amount to apply, 172 how to apply, 179 loss by leaching, 51, 174, 561 magnesian, or dolomitic, 169 soils, 123, 147 spreader, 179 time to apply, 178 use in soil improvement, 160 Limiting factors in crop production, 435, 575 _ Lincoln's view of agriculture, 592 Lipman, on dentrification, 439 Live stock destroy food values, 234 organic matter, 199 Live-stock farming, 231, 459 Loess, characteristics, 54 composition, 69 in United States, 68 Loessial soils, 123, 144, 634 Losses of plant food, from manure, 200, 546, 547 from plants, 549 from soils, 411, 413, 556 Louisiana, field experiments, 495 soils, 96, 138 Machine for spreading limestone and phosphate, 179 Magnesian limestone, 169 Magnesium, 42 Magnesium determination, 633 in fertilizer experiments, 171, 364 Maine field experiments, 275 Maintenance rations, 33 Manganese, 44 Manganese separation, 633 Mangel-wurzel, composition, 402 field experiments, 400 Mann, on the use of raw phosphate, 504 Manure, losses from exposure, 200, 256, 508, 546, 547 preservatives and reenforcing materials, 256, 547 _ recovered in live-stock farming, 201 Manure in culture experiments, 256, 343 Manures (see farm manure and green manuring) Marl carbonates, 167 Marl phosphates, 241 Maryland, field experiments, 261 soils, 138, 141 subsoils, 73 Massachusetts field experiments, 278 Mellilotus for green manuring, 220 Mica, 49 Michigan, investigations with legume plants, 216, 221 soils, 97 Minnesota, soil experiments, 499 soils, 100, 138 Mississippi soils, 93 Missouri soils, 89, 138 Moisture factor in crop production, 577 Molecule, defined, 4 Montana soils, 102 Mountain soils, 122, 128 Nascent, defined, 4 National Fertilizer Association report on raw phosphate, 292 Nebraska rainfall, 331, 580, 582 soils, 89 Nevada soils, 102 INDEX 651 New Jersey, pot-culture experiments, 439 soil, 138 New York, investigation of phosphorus in wheat bran, 41 soils, 75 Nitrate of calcium, 526 Nitrate of sodium, 525 Nitrification, 195 Nitrogen, 36 Nitrogen and organic matter, 194 Nitrogen determination, 629 fixation by legumes, 207 by nonsymbiotic bacteria, 224, 405, 437 from air and soil, 213 gain or loss difficult to determine, 499 in animal and plant products, 154, 602 in drainage waters, 557, 563 in fertilizers, 157, 517 in rain, 309 in roots and tops of legumes, 218 in sweet clover, 220 recovered in live-stock farming, 201 retained by animals, 201 used in different amounts, 374, 423 used to give crops a start, 218, 401, 533 Nitrogenous compounds, 38 Nomenclature, 19, 565, 599 North Carolina soils, 138, 142 North Dakota investigations of flax sick- ness, 319 North Platte, Nebraska, rainfall, 331, 580 Northern states soils, 97, 138 Nuclein, 40 Oats, composition, 75, 154, 603 statistics, 615 Ocean, composition, 13 Ohio, field experiments, 245, 299, 441 investigations with manure, 547 soils, 88, 138 in pot-culture experiments, 513 Oil cakes, composition, 604 fertility loss, 205 statistics, 626 Oil seeds, composition, 603 Oils and fats, 34 Oregon soils, 102 Organic chemistry, 30 Organic matter, defined, 30 decomposition, 195 loss in digestion, 199 methods of supplying, 198 Organic matter and nitrogen, 194 Orthoclase, 47 Oxids, defined, 17 occurrence, 53 Oxygen, 26 Pacific coast soils, 102, 130, 138 Park field, Rothamsted, 391 "Parrot" instruction, 292 Pasturing land, 199 Peat, dried, 524 Peat soils, 75, 83, 98, 100, 470 Pennsylvania, field experiments, 263, 420 investigations with manure, 202, 203 soils, 76, 142 Pentosans, 31 Periodic law of chemical elements, 9 Permanent systems of agriculture, 159 Peter, on soil fertility theories, 339 Phosphate deposits, 597 Phosphate experiments: Canada, 505 Illinois, 283, 504 Indiana, 296 Kentucky, 288 Maine, 275 Maryland, 261 Massachusetts, 278 Ohio, 245, 442, 448, 452 Pennsylvania, 263 Rhode Island, 266 Phosphate production, 595 raw rock and slag must be fine-ground, 239 in practical agriculture, 289, 504 Phosphate report by National Fertilizer Association, 292 spreader, 179 supply, 597 Phosphates, 52, 186 low-grade, 188, 242, 598 natural, 52, 186 used in Europe, 324 Phosphatic limestone, 52 marl, 241 slag, 192 Phosphorus, 40, 52, 183, 236 Phosphorus compounds, 189 determination, 630 'in fertilizers, 157, 517 in plant and animal products, 154, 602 in wheat bran, 41 production, 595 retained by animals, 201 supply, 597 use in different forms, 237 used in Europe, 324 Photosynthesis, 29 Physical condition of soil, 576 Piedmont soils, 121, 138 Plant and animal products, composition, 157, 602 Plant food, 26 available, 107, 314, 366 652 INDEX Plant food, essential, 12 in crops, 75, 154, 602 in culture experiments, 236, 343 in sea weed, 524 lost from manure, 200, 546, 547 from plants, 549 from soils, 411, 413, 418, 556 Plant food, recovered in live-stock farm- ing, 199 retained by animals, 201 sources and cost, commercially, 157, 517 value, 154 water-soluble, 141 Plot experiments for testing soils, 569, 570 Potassium, 42 Potassium chlorid and sulfate, 531 Potassium determination, 631 Potassium, from sea water, 531 in fertilizers, 157, 517 in plant and animal products, 154, 602 Potassium salts of Germany, 529 Potato experiments, 384, 447, 511 Potatoes, composition, 154, 604 statistics, 605, 618 Prairie soils, 78, 82, 132, 138 Prefixes in chemical names, 19 Proportions, law of constant, 8 Protective agents, 536 Protein and proteids, 37 Quartz, 49 Radicle, denned, 17 Rain, composition, 309 Rainfall and drainage records, 309, 377, 413, 491, 557, 580, 582 Rainfall averages for the United States, 582 Rainfall in dry farming sections, 580, 582 Ramsay, on composition of air, 13 Ramsay and Cameron, on transmutation of elements, n Rate of growth, 32 Residual soils, 54, 126, 146, 149 Residues of crops used in soil improve- ment, 199 Rhode Island field experiments, 266 Rice, composition, 603 statistics, 619 Rock weathering, 49 Roman agriculture, 590 Root crops, compositidn, 417, 604 in Canadian experiments, 511 in Rothamsted experiments, 398 Roots and tops of legumes, composition, 218 Root tubercles, composition, 215 size, 213 Rotation crops grown in experiments: Agdell field, Rothamsted, 345 Illinois, 453 Louisiana, 495 Minnesota, 499 Ohio, 245, 256, 441 Pennsylvania, 421 Rotation crops, plant food required, 75 Rotation of crops and soil fertility, 318. 339, 362, 389, 435, 443 Rotation systems, 226, 231 Russia, agricultural conditions, 332 soils, 66 Rye, composition, 603 statistics, 617 Sachs, on availability of plant food, 109 Salt, common, 535 defined, 20 Salt deposits, 53, 529 Sand soils, 80, 98, 100, 138, 468, 498 Science, defined, i Scotland, soils, 63, 642 Seed factor in crop production, 575 Semiarid section, rainfall records, 331, 580, 582 S6nebier's discovery of carbon fixation, 307 Shale, 50 Shutt, on loss of organic matter and nitro- gen, 200, 559 Silicates in earth's crust, 47, 48 Silicon, 44, 46 Slag phosphate, 192 Snow, composition, 310 Soaps, 36 Sodium, 44 Sodium in fertilizer experiments, 364, 380, 402, 508 Soil analysis, methods, 626 classification, 54, 116 composition, 58, 138 depletion, 556 by natural agencies, 61 Soil fertility theories, 300, 362, 366, 385 formation, 54 materials, 55 provinces of the United States, 116 samples, method of collecting, 626 series, 116, 132 stimulants, 45, 158, 533 structure, 116 surveys, 57, 77, 114, 5^7, 555 texture, 116 types, 55 Soils of Africa, 66, 67 Canada, 103 central states, 77, 138 INDEX 653 Soils of eastern states, 72, 75, 106, 138 Europe, 63, 634 India, 66 Northern states, 97, 138 Rothamsted, 63, 411, 416 Russia, 66 South America, 67 southern states, 92, 138 Transvaal, 67 Turkey, 67 western states, 101, 138 Solution law, 314, 316, 366 South American soil, 67 South Carolina, phosphates, 187, 595 record yield of corn per acre, 619 Southern states soils, 92, 138 Spencer, on farming in semiarid region, 58i Spillman, on Kansas crop yields, 330 Spreader for limestone and phosphate, 179 Starches, 31 Statistics of agricultural products, 605 Steatite, 48 Sterile soils, 63, 367 Stimulants, 368, 394, 402, 479. 5°8, 533 Straw, composition, 157, 603 Structure of soils, 116 Success in farming, 584 Sugar beets, 155, 399, 604 Sugar statistics, 620 Sugars, 31 Sulfates and sulfids, 52 Sulfur, 39, 57, 106, 158 in rain, 106 Superphosphate, 191 Supply and demand of plant food, 59 Swamp soils, 80, 583 Sweet clover, content of nitrogen and or- ganic matter, 220 Symbol, denned, 7 Systems of permanent agriculture, 159 Temperature factor in crop production, 576 Tennessee, phosphates, 187, 188, 595 soils, 64, 93, 138, 367 Terminations in chemical names, 19 Terrace soils, 124 Testing soils, 565, 626 Texas soils, 95, 138 Texture of soils, 116 Timer's soil-fertility theories, 302 Theories concerning soil fertility, 300, 362, 366, 385 Timber soils, 79, 133 Tobacco, composition, 604 experiments, 288 statistics, 605 Transmutation of elements, n Transported soils, 54 Transvaal soils, 67 Tubercles on roots of legumes, 212, 215 Tubers, composition, 604 Tull's soil-fertility theories, 300 Turkish soil, 67 Turnips, composition, 417, 604 experiments, 346, 399 Utah, phosphates, 596 soils, 101 Valence, defined, 4 Value of land, 586 Van Helmont's soil-fertility theories, 300 Van Hise, on phosphates, 560 Vegetable fats and oils, 34 Vegetables, composition, 604 Vesuvius lava, composition, 67 Virginia, field results with raw phosphate, 289 soil, 138 Vital processes in plant growth, 33 Volcanic ash, 67, 138 Wales soil, 642 Washington soils, 102 Water (see moisture) Water-soluble plant food, 141, 513 Weathering of rocks and soils, 49, 61, 174 Webster's view of- agriculture, 594 Western states soils, 101, 138 Wheat, composition, 75, 154, 417, 603 Wheat bran, composition, 41, 604 Wheat grown every year: Canada, 505 Jethro Tull, 306 Minnesota, 499 Rothamsted, 363 Whitney, on potatoes at Rothamsted, 389 Whitney and Cameron's soil-fertility theo- ries, 313, 362, 367, 385 Whitson, on loss of phosphorus from Wis- consin soils, 560 Widtsoe, on arid soils and vegetation, 101 Williams, on value of manure in China, 338 Wilson, on abandoned lands, 342 Wing, on use of limestone and raw phos- phate, 289 Wisconsin experiments, 216, 221, 289, 560 soils, 99, 138 Wood ashes, 531, 602 Wyoming phosphates, 595 soils, 102 Zein, 39 Zeolites, 50 This book is DUE on the last date stamped below MOV 14 « mov i o MI, Form L-9-10m-5,'28 0£C4 195, i OCT28)952 4K ' REGIONAL LIBRARY FACILITY A 001 075 662 5 tJniversi Soutt Libi