MAAK . . NY Pew Pork State College of Agriculture At Cornell University Dthaca, #2. WB. —=> Library \ Cornell University Library The original of this book is in the Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924003329830 Te, bse HOW CROPS FEED. A TREATISE ON THE ATMOSPHERE AND THE SOIL AS RELATED TO THE Nutrition of Agricultural Plants. WITH ILLUSTRATIONS, BY (Cane SAMUEL W: JOHNSON, M.A., PROFESSOR OF ANALYTICAL AND AGRICULTURAL CHEMISTRY IN THE SHEFFIELD SCIENTIFIC SCHOOL OF YALE COLLEGE; CHEMIST TO THE CONNEC- TICUT STATE AGRICULTURAL SOCIETY; MEMBER OF TRE NATIONAL ACADEMY OF SCIENCES. NEW YORK: ; ORANGE JUDD COMPANY, 1891. eh fa 7 Entered according to Act of Congress, in the year 1870, by ORANGE JUDD & CO., In the Clerk’s Office of the District Court of the United States for the Southern District ot New York, PREFACE. The work entitled “ How Crops Grow” has been re- ceived with favor beyond its merits, not only in America, but in Europe. It has been republished in England under the joint Editorship of Professors Church and Dyer, of the Royal Agricultural College, at Cirencester, and a translation into German is soon to appear, at the instiga- tion of Professor von Liebig. The Author, therefore, puts forth this volume—the com- panion and complement to the former—with the hope that it also will be welcomed by those who appreciate the sci- entific aspects of Agriculture, and are persuaded that a true Theory is the surest guide to a successful Practice. The writer does not flatter himself that he has produced a popular book. He has not sought to excite the imagi- nation with high-wrought pictures of overflowing fertility as the immediate result of scientific discussion or experi- ment, nor has he attempted to make a show of revolution- izing his subject by bold or striking speculations. His office has been to digest the cumbrous mass of evidence, in which the truths of Vegetable Nutrition lie buried out 5 VI PREFACE. of the reach of the ordinary inquirer, and to set them forth in proper order and in plain dress for their legiti- mate and sober uses. It has cost the Investigator severe study and labor to discover the laws and many of the facts which are laid down in the following pages. It has cost the Author no little work to collect and arrange the facts, and develop their mutual bearings, and the Reader must pay a similar price if he would apprehend them in their true signifi- cance. In this, as in the preceding volume, the Author’s method has been to bring forth all accessible facts, to present their evidence on the topics under discussion, and dispassion- ately to record their verdict. If this procedure be some- times tedious, it is always safe, and there is no other mode of treating a subject which can satisfy the earnest inquirer. It is, then, to the Students of Agriculture, whether on the Farm or in the School, that the Author commends his book, in confidence of receiving full sympathy for its spirit, whatever may be the defects in its execution, CONTENTS. EMTRODUCTION 25: iecccice saves ensteccssacsisaes: sasataissetaratseeestesewe sea onl DIVISION L THE ATMOSPHERE AS RELATED TO VEGETATION. CHAPTER I. ATMOSPHERIC AIR AS THE Foon oF Puanrs. § 1. Chemical Composition of the Atmosphere § 2. Relation of Oxygen Gas to Vegetable Nutrition § 3. “ Nitrogen Gasto “ § 4 « —_“ Atmospheric Water to Vegetable Nutrition... § 5. “ Carbonic Acid Gas. * “ § 6. e ‘¢ Atmospheric Ammonia to “ Ge Ts MOBO bieisisssincie siceiaid cic denis rade serene ban eaeee aineisia pion eee Ca poe ay 63 § 8. Compounds of Nitrogen and Oxygen in the Atmosphere................. Kt) § 9. Other Ingredients of the Atmosphere..............cececee 0 ceeseeeeeees ot § 10. Recapitulation of the Atmospheric Supplies of Food to Crops........... 94. § 11. Assimilation of Atmospheric Food.............. 0... aiisivible © afetrcie aisivie: 7 § 12. Tabular View of the Relations of the Atmospheric Ingredients to the Life OF PIANts a)... cc csiccasice: ware sewed wawees onsen a eedceda tides seme OS CHAPTER II. Tur ATMOSPHERE AS PHYSICALLY RELATED TO VEGETATION. § 1. Manner of Absorption of Gaseous Food by Plants........ daden gee ssiveusens 99 DIVISION I. THE SOIL AS RELATED TO VEGETABLE PRODUCTION. CHAPTER I. INTRODUCTORY........... POLO RCM ICE OO Cor is eeakew eens LOE vg VIIl HOW CROPS FEED. CHAPTER Il. ORIGIN AND FORMATION OF SOILS.........0. ccc ccueeeneeeee gael nes townie 106 § 1. Chemical Elements of Rocks....... ........ cece ec ce eee eee n seen eceeenes 107 § 2. Mineralogical Elements of Rocks ......... siedde Hameed VeeKeneas taeee eee 108 § 8. Rocks, their Kinds and Characters. .........-.....+ stay sraveteielebeateis Si6 eeng ll Z § 4. Conversion of Rocks into Soil .......... ed ota Staia aie’ eieeiaye~ 2e Weta evarasats ai Bivne tacos 122 § 5. Incorporation of Organic Matter with the Soil, and its Effects........... 185 CHAPTER III. Kinps or Soins, THEIR DEFINITION AND CLASSIFICATION. TION 6:03 sieaisielsa sprees enineloniwisine suiedatewadeaas steele Seamusie es one LSB § 2, Distinctions of Soils based upon Obvious or External Characters........ 146 « CHAPTER IV. PaysicaAL CHARACTERS OF THE SOML...........04 ceceecccereceecenv coer ceeneLOT § 1. Weight of Soils............. arb biiaeera tei cecaie -b8 is siewvanomsan oes: sinieniaisare lS § 2. State of Division............ eizerwtabesaeaducreie ad aieshee a-sidiaieiatecessie LO, § 8. Absorption of Vapor of Water..... acagetantentea ijeaceces aiteter aie braraNb CS FoleeSiatoscexerein 161 § 4. Condensation of Gases...........04 seeeeee Biasis'h aise Ajsateayiaays eiescumietosls 165 § 5. Power of Removing Solid Matters from Solution............ aspect Pee LTE § 6. Permeability to Liquid Water. Imbibition. Capillary Power........... 1%6 § %. Changes of Bulk by Drying and Frost.............cececeeeeeee sae wee es 183 § 8. Adhesiveness....... § 9. Relations to Heat... ' CHAPTER V. Tur Som as a SouRcE or Foop To Crops: INGREDIENTS WHOSE ELEMENTS : ARE OF ATMOSPHERIC ORIGIN. § 1. The Free Waiter of the Soil in its Relations to Vegetable Nutrition......199 § 2. The Air of the Soil... ............ 0... 00s sila avi Siete avctata Senne) ud § 8. Non-nitrogenous Organic Matters. Humus..... saudariaciwtnete abeididistuineceteatere 222 § 4. The Ammonia of the Soil. ........... GiSiaidlaswieis db macmadine e seewnabusemie viele . 238 § 5. Nitric Acid (Nitrates) of the Soil § 6. Nitrogenous Organic Matters of the Soil. Available Nitrogen... § %. Decay of Organic Matters.... .......0.. esse eee neee shane Bake eile aise § 8. Nitrogenous Principles of Urine § 9. Comparative Nutritive Value of Ammonia-Salts and Nitrates...,........300 221 CONTENTS. 1x CHAPTER VI. THE Som as A SouRcE oF Foop ro Crops: INGREDIENTS WHOSE ELEMENTS ARE DERIVED FROM Rocks. § 1. General View of the Constitution of the Soil as Related to Vegetable Nutrition ............. seraiare lara laterslaiargial la wieteiated eiewadeaialeele 5 Mean 305 § 2. Aqueous Solution of the Soil wo. ccs, cavnsaawanneuve enone veunesen pena vat 309 § 3. Solution of the Soil in Strong ACid8..........ccccece cece cece cee ceeeeeee 329 § 4. Portion of Soil Insoluble in Acids................ 2. assets eines asta 330 § 5. Reactions by which the Solubility of the Elements of the Soil fs al- tered. Solvent Effects of Various Substances. Absorptive and Fixing Power of Soils..... : § 6. Review and Conclusion...... INDEX. Absorption and displacement, law Absorpelys power of soils... ..... ae “ cause of 843, 354 os $8 * significance OF: 6 cayes a «874 AGGGIN GO, pisaceencian wlanracs 223 “© absorbed by soils............ 355 MAREN OR wasacs nm dias seam iecemaoe 165 Adhesiveness of soils.............. 184 Air, atmospheric, composition of.. 21 “« within the plant, composition ONS cess oiBlayaiers cine uy eeveiayasnrensid 45 Alkali-salts, solvent effect of.......130 Allotropism. -.....61¢0246+- -.. 66 Allnvium ........ Ammonia... .. wax woe 40). 54 ae absorbed by clay....243, 267 oe s * peat........360 ae ee “ plants... ..56, 98 te condensed in soils ...... 240 ce eonversion of into nitric ROTC oc sscjs:ig's njavsssic erereie 85 cy evolved from flesh decay- ing under charcoal.....169 = fixed by gypsum... ‘ in atmosphere........... ee * how formed.?7, 85 a of rain, etc........ ..... 60 ss of the soil, formation of.239 a se ny chemically combined.243 Ts . oe physically condensed.240 be ss “quantity of. .248 ae ck * solubility of .246 ee ee ++ volatility of. .244 Ammonia-salts and nitrates, nutri- fie VAlde Of i505 cosciss tonaaavs 300 Amphibole.............2-.0.0000 os 112 Analysis of soils, chemical indica- tions of................ 368 ** mechanical ... 147 Apatite........ sleicie lesa cfemmraweenacsies 116 APOCP end tate cc5. sxside wesaeban done 231 Apocrenic acid. . 227, 220: APRN. cas scenes sanckeracax cus 119 oe physical constitution... 99 Atmospheric food, absorbed....... 99 ‘* assimilated .... 97 Barley crop, ash ingredients of..... "864 BRAM oi awn evades omigerweeia 155 Marell 288 ios) cues dcccwadecrieces 91, 99 Micaroises sacar sean ery Ba sicict ekSys 109 INDEX. Mica slate........ ... Minerals... t7 119 ity 7a variable composition of.... Moisture, effect of, on temperature Nitrate of ammonia........... A, 73 se Re ‘* in atmosphere. 89 INDTREOS sa iecinciin: x, a yas ties sents 252 By as food jor plants.......... 271 ‘© formed in soil.... ..... 171, 179 “ In Wateris sient. ssecaiesiveses 270 ss losS:Ofs: es.ccscscs. saves Hawa 270 as reduction of......... 13, 82, 85 se se “in soil......... 268 tests for....... cece ee eee . B Nitric acid.... 0.0.2... 0... e eee ee eee "0 $e * as plant-food. . .90, 98 “ deportment towards the ’ BOIL sarsiscisiovarataacciaroqaterers 357 - ‘© in atmosphere........... 86 ye rain-water... Co FE Belkin. ccgwanaeey “« « «& & sources of. Nitric oxide...” Nitric peroxide. Nitrification............. me conditions of.... 265, 292 Nitrogen, atmospheric supply to plants.............66 95 “ combined, in decay .291, 292 se oe of the soil...2' ae combined, of the soil, available. .........+.. 283 ene combined, of the soil, (GK. we caeeeces cece 278 a combined, of the soil, quantity needed for crops.288 ee free, absorbed by soil.. .167 se “ assimilated by the BON 5 ocinsiaajesaionie 259 es “in soil..,......---+- 218 ee * not absorbed by vegetation..... 26, 99 is not emitted by liv- ing plants........ 28 Nitrogen-compounds, formation of, in atmosphere.%5, '(7, 83 XII Nitrogenous fertilizers, effect on cereals... 83 Nitrogenous organic matters of soil.274 Niteous-aeld 25 cocks ewes cavavs.« Nitrous oxide.... .. Oxidation, aided by porous bodies. 169, 170 Oxide of iron, acarrier of oxygen, .257 se ss hydrated, in the soil.350 Oxys gen, absorbed by hag sew sees: 9B. essential to growth. . cy supply weathering action of. “concerned in ‘oxidation of ni- TOTEN, ges sewn dais O55: 82 ‘* formed by chemical action.66, 67 ‘* produced by vegetation.67, 84, 99 ** relations of, to vegetable nu- trition............ Bjateatseeian 0 Pan, composition of.. Parasitic plants, nourishment of... 235 POAC: 5:5 iccsferaseinansd ondis Sosietey Sioa 155, 224 * nitrogen of... 1 Qh Phosphate of lime......... 116 Phosphoric acid fixed by the soil. . .35% oe ** presence in soil water.......... 815 Phosphorite...............00c00 wee 116 Plant-food, concentration of........ 320 te maintenance of supply .871 Platinized charcoal............ ... 170 Platinum sponge, condenses oxygen170 POPPLYTY! weiss ccsiicie sd esgaesc saavviees 120 Potash, quantity in barley crop.....363 Provence, drouths of.......... 198 Pyrites.... 115 PYTOKCNC. 6: oie:sc ois voice sist oieine ve 112 “ nitric acid in.. is phosphoric acid in Ree Ree bottom, soil of..... os Respiration of the plant............ 43 Rocks sciceaaserenpie ta wstanes: 106, 11% “ attacked by plants. ....200+2.140 XLV HOW CROPS FEED. Kocks, conversion into suils........ 122 Koots, direct action on soil........ 326 Saline incrustations.............66+ 179 Saltpeter......... Salts decomposed or absorbed by the soil SETI sie eavecaie's Sand filter... Sandstone... Serpentine........ Schist, micaceous, “ talcose.... te chlorite. Shales. . Sherry wine rezior Shrinking of soils.. N, “function in the soi “ of soil, liberated by strong tas Silk, hygroscopic ifs acinar Soapstone...... 0... cece rene ee Sod, temperature of * absorptive power of.... * aid to oxidation........ ‘+ aqueous solution of. ‘* condenses gases.... “ capacity for heat.. * chemical action in.. * composition of.... * exhaustion of..... © inett DASTB eeccae “ natural strength of... * origin and formation. “106, 122, 135 “ physical characters...........-- 157 ** porosity Of........... * portion insoluble in acids 3 “ relative value of ingredicnts... .367 * reversion to rock............06+ 32 * solubility in acids. . * source of food to crops. . ‘* state of division...... ......... Soils, sedentary.............0005 ‘* transported.. “weight of.. Solubility, standards of............308 Solution of soil in acids........ “ a ‘* water, . . Stentite.........cce cece eee eeee ence Swamp muck Sulphates, agents of oxidation..... 258 Sulphate of lime.... Sn)phur, in decay. Sulpburous acid. . Sulphydric acid .. Temperature of soil Transpiration Trap rock...... Ulmates........ -- Ulmic acid... . - -224, 226, 229 224, 226, 229 ULC vac eeeie ces + 294, 27% Uric acid 295, 27% AM Glnx.zivid exeesreseuisciaaeiert stustnnalaaae 293 preserved fresh by clay....... 293 its nitrogenous principles as- 7 similated by plants. Vegetation, antiquity of........ ‘e decay Of..........4. aa ae action on soil........ 140 Volcanic rocks, conversion to soil. .135 Wall fruits... 0.20000 scence ee eee 199 Water absorbed by roots....... 202, 210 “functions of, in nutrition of Plate, cocci cscs ewe 216 “© imbibed by soil....... .. ....180 “movements in soil.... ..... 1% “proportion of in plant, infiu- enced by soil............. Be OR BON sce: ce crceiee averse ‘ “bottom water. : © caplllaryccc cewee saaieness te hydrostatic..........-02 eee 199 “ Iygroscopic... . ...-.-2-5-- 201 ‘* quantity favorable to crops. .214 Water-currents..........66 cece eee 124 Water-vapor, absorbed by soil.161, 164 exhaled by plants.... 99 Ey not absorbed by plants......... 35, 99 i of the atmosphere.... 34 Weathering..............00008: 131-134 Wilting... ... Wool, hygroscopic. Zeolites......ccceceessceseveeeedl4, 349 HOW CROPS FEED. HOW CROPS FEED. INTRODUCTION. In his treatise entitled “ How Crops Grow,” the author has described in detail the Chemical Composition of Agri- cultural Plants, and has stated what substances are indis- pensable to their growth. In the same book is given an account of the apparatus and processes by which the plant takes up its food. The sources of the food of crops are, however, noticed there in but the briefest manner. The present work is exclusively occupied with the important and extended subject of Vegetable Nutrition, and is thua the complement of the first-mentioned treatise. Whatever information may be needed as preliminary to an under. standing of this book, the reader may find in “ How Cropa Grow.” * That crops grow by gathering and assimilating food is a conception with which all are familiar, but it is only by following the subject into its details that we can gain hinta that shall apply usefully in Agricultural Practice. * It has been at least the author's aim to make the first of this series of books prepare the way for the second, as both the first and the second are written tu make possible an intelligible account of the mode of action of Tillage and of Fertilizers, which will be the subject of a third work. 17 18 HOW CROPS FEED. When a seed germinates in a medium that is totally destitute of one or all the essential elements of the plant, the embryo attains a certain development from the mate- rials of the seed itself (cotyledons or endosperm,) but shortly after these are consumed, the plantlet ceases to in- crease in dry weight,* and dies, or only grows at its own expense. A similar seed deposited in ordinary soil, watered with rain or spring water and freely exposed to the atmosphere, evolves a seedling which survives the exhaustion of the cotyledons, and continues without cessation to grow, forming cellulose, oil, starch, and albumin, increases many times—a hundred or two hundred fold—in weight, runs normally through all the stages of vegetation, blossoms, and yields a dozen or a hundred new seeds, each as perfect as the original. It is thus obvious that Air, Water, and Soil, are capa- ble of feeding plants,.and, under purely natural conditions, do exclusively nourish all vegetation. In the soil, atmosphere, and water, can be found no trace of the peculiar organic principles of plants. We look there in vain for cellulose, starch, dextrin, oil, or al- bumin. The natural sources of the food of crops consist of various salts and gases which contain the ultimate ele- ments of vegetation, but which require to be collected and worked over by the plant. The embryo of the germinating-seed, like the bud of a tree when aroused by the spring warmth from a dormant state, or like the sprout of a potato tuber, enlarges at the expense of previously organized matters, supplied to it by the contiguous parts. : As soon as the plantlet is weaned from the stores of the * Since vegetable matter may contain a variable amount of water, either that which belongs to the sap of the fresh plant, or that. which is hygroscopically re- tained in the pores, all comparisons must be made on the ary, i. e., water-free substance. See *‘How Crops Grow,” pp. 53-5. INTRODUCTION, 19 mother seed, the materials, as well as the mode of its nu- trition, are for the most part completely changed. Hence- forth the tissues of the plant and the cell-contents must be principally, and may be entirely, built up from purely inorganic or mineral matters. In studying the nutrition of the plant in those stages of its growth that are subsequent to the exhaustion of the cotyledons, it is needful to investigate separately the nu- tritive functions of the Atmosphere and of the Soil, for the important reason that the atmosphere is nearly con- stant in its composition, and is beyond the reach of human influence, while the soil is infinitely variable and. may be exhausted to the verge of unproductiveness or raised to the extreme of fertility by the arts of the cultivator, In regard to the Atmosphere, we have to notice minutely | the influence of each of its ingredients, including Water in the gaseous form, upon vegetable production. The evidence has been given in “ How Crops Grow,” which establishes what fixed earthy and saline matters are essential ingredients of plants. The Soil is plainly the exclusive source of all those elements of vegetation which cannot as- sume the gaseous condition, and which therefore cannot ex- ist in the atmosphere. The study of the soil involves a con- sideration of its origin and of its manner of formation. The productive soil commonly contains atmospheric elements, which are important to its fertility; the mode and extent of their incorporation with it are topics of extreme prac- tical importance. We have then to examine the signif- icance of its water, of its ammonia, and especially of its nitrates. These subjects have been recently submitted to extended investigations, and our treatise contains a large ainount of information pertaining to them, which has never before appeared in any publication in the English tongue. Those characters of the soil that indirectly affect the growth of plants are of the utmost moment to the farm- er. It is through the soil that a supply of solar heat, with- 20 HOW CROPS FEED. out which no life is possible, is largely influenced: Water, whose excess or deficiency is as pernicious as its proper quantity is beneficial to crops, enters the plant almost exclusively through its roots, and hence those qualities of the soil which are most favorable to a due supply of this liquid demand careful attention. The absorbent pow- er of soils for the elements of fertilizers is a subject which is treated of with considerable fullness, as it deserves. Our book naturally falls into two divisions, the first of which is devoted to a discussion of the Relations of the Atmosphere to Vegetation, the second being a treatise on the Soil. DIVISION I. THE ATMOSPHERE AS RELATED TO VEGETATION. CHAPTER I. ATMOSPHERIC AIR AS THE FOOD OF PLANTS. § 1. CHEMICAL COMPOSITION OF THE ATMOSPHERE. A multitude of observations has demonstrated that from ninety-five to ninety-nine per cent of the entire mass (weight) of agricultural plants is derived directly or indi- rectly from the atmosphere. The general composition of the Atmosphere is familiar to all. It is chiefly made up of the two elementary gases, Oxygen and Nitrogen, which have been described in “ How Crops Grow,” pp. 33-39.* These two bodies are present in the atmosphere in very nearly, though not altogether, invariable proportions. Disregarding its other ingredients, the atmosphere contains in 100 parts By weight. By volume. Oxygen.........+65 7 ee re 20.95 Nitrogen.......... 16.83 keane owen 79.05 100.00 100.00 Besides the above elements, several other substances oc- * In our frequent references to this book we shall employ the abbreviation H.C. G. 21 22 HOW CROPS FEED. cur or may occur in the air in minute and variable quanti- ties, viz.: Water, as vapor...average Proper tion by WHEE 1)i00 Carbonic acid gas sa a 8 [10-000 Ammonia " “ te "|50- 000: 000 ? Ozone et fe ss ‘minute traces, Nitric acid “ oe 66 oe “6 “ Nitrous acid a “ oe “ iT3 it) Marsh gas cr “ nw ‘13 “ce “ In air of Carbonic oxide, a“ iT) a ac “ “ 1 Sulphurous acid, fe Me ss “ ee “ sons. Sulphydrie acid xe iS ne a Miller gives for the air of England the following aver- age proportions by volume of the four most abundant in- gredients.—(Hlements of Chemistry, part IL. p. 30, 3d Ed.) ORY ON os iesiciesises cindaine meting asin aun te 20.61 NGtrOS OM so icidisscie tie ctepe Vee aeedia. civie deeniete view TS Carbonic acid......... cece cece eee Seiswetee oie G04 Water-vapor......ceeees Bsc Sisceiehstayendie Rrateaions 1.40 100.00 ‘We may now appropriately proceed to notice in order each of the ingredients of the atmosphere in reference to the question of vegetable nutrition. This is a subject re- garding which unaided observation can teach us little or nothing. The atmosphere is so intangible to the senses that, without some finer instruments of investigation, we should forever be in ignorance, even of the separate exist- ence of its two principal elements. Chemistry has, how- ever, set forth in a clear light many remarkable relations of the Atmosphere to the Plant, whose study forms one of the most instructive chapters of science. § 2 RELATIONS OF OXYGEN GAS TO VEGETABLE NUTRITION. Absorption of Oxygen Essential to Growth.—The ele- ment Oxygen is endowed with great chemical activity. This activity we find exhibited in the first act of vegeta ATMOSPHERIC AIR AS THE FOOD OF PLANTS. 23 tion, viz: in germination. We know that the presence of oxygen is an indispensable requisite to the sprouting seed, and is possibly the means of provoking to action the dor- mant life of the germ. The ingenious experiments of Traube (H. C. G., p. 326.) demonstrate conclusively that free oxygen is an essential condition of the growth of the seedling plant, and must have access to the plumule, and especially to the parts that are in the act of elongation. — De Saussure long ago showed that oxygen is needful to the development of the buds of maturer plants. He ex- perimented in the following manner: Several woody twigs (of willow, oak, apple, etc.) cut = in spring-time just before the buds should unfold were placed under a bell-glass containing common air, as in fig. 1. Their cut extremities stood in water held in a small vessel, while the air of the bell was separated from the external atmosphere by the mercury contained in the large basin. Thus situated, the buds opened as in the free air, and oxygen gas was found to be consumed in considerable quan- Fig. 1. tity. When, however, the twigs were confined in an atmosphere of nitrogen or hydrogen, they decayed, with- out giving any signs of vegetation. (Hecherches sur la Vegetation, p. 115.) The same acute investigator found that oxygen is ab- sorbed by the roots of plants. Fig. 2 shows the arrange- ment by which he examined the effect of different gases on these organs. A young horse-chestnut plant, carefully lifted from the soil so as not to injure its roots, had the latter passed through the neck of a bell-glass, and the stem was then cemented airtight into the opening. The bell 24 HOW CKOPS FEED. was placed in a basin of mercury, C, D, to shut off its con- tents from the external air. So much water was intro- duced as to reach the ends of the principal roots, and the space above was occupied by com- mon or some other kind of air. In one experiment carbonic acid, in a second nitrogen, in a third hydro- gen, and in three others common air, was employed. In the first the roots died in seven or eight days, in the sccond ang third they perish- ed in thirteen or fourteen days, while in the three others they re- mained healthy to the end of threc weeks, when the experiments were concluded, (Recherches, p. 104.) Flowers require oxygen for their development. Aquatic plants send their flower-buds above the water to blossom. De Saussure found Fig. 2. that flowers consume, in 24 hours, several or many times their bulk of oxygen gas. This absorption proceeds most energetically in the pistils and stamens. Flowers of very rapid growth experience in this process, a considerable rise of temperature. Garreau, observing the spadix of Arum italicum, which absorbed 28} times its bulk of oxygen in one hour, found it 15° F. warmer than the surrounding air. In the ripening of fruits, oxygen is also absorbed in small quantity. The Function of Free Oxygen.—All those processes of growth to which free oxygen gas is a requisite appear to depend upon the transfer to the growing organ of mat- ters previously organized in some other part of the plant, and probably are not cases in which external inorganie bodies are built up into ingredients of the vegetable struc- ture. Young seedlings, buds, flowers, and ripening fruits, ATMOSPHERIC AIR AS THE FvOD OF PLANTS. 25 have no power to increase in mass at the expense of the atmosphere and soil; they have no provision for the ab- sorption of the nutritive elements that surround them ex- ternally, but grow at the expense of other parts of the plant (or seed) to which they belong. The function of free gaseous oxygen in vegetable nutrition, so far as can be judged from our existing knowledge, consists in effecting or aiding to effect. the conversion of the materials which the leaves organize or which the roots absorb, into the proper tissues of the growing parts. Free oxygen is thus probably an agent of assimilation. Certain it is that the free oxygen which is absorbed by the plant, or, at least, a corresponding quantity, is evolved again, either in the un- combined. state or in union with carbon as carbonic acid. Exhalation of Oxygen from Foliage.—The relation of the leaves and green parts of plants to oxygen gas has thus far been purposely left unnoticed. These organs like- -wise absorb oxygen, and require its presence in the atmos- phere, or, if aquatic, in the water which surrounds them; but they also, during their exposure to light, exhale oxygen. This interesting fact is illustrated by a simple experiment. Fill a glass funnel with any kind of fresh leaves, and place it, inverted, in a wide glass containing water, fig. 8, so that it shall be completely immersed, and displace all air from its interior by agitation. Close the neck of the funnel air-tight by a cork, and pour off a portion of the water from the outer vessel. Expose now the leaves to strong sunlight. Observe that very soon minute bubbles of air will gather on the leaves. These will gradually increase in size and detach themselves, and after an hour or two, enough gas will accumulate in the neck of the funnel to enable the experimenter to 2 Fig. 3. 26 HOW CROPS FEED. prove that it consists of oxygen. For this purpose bring the water outside the neck toa level with that inside; have ready a splinter of pine, the end of which is glow. ing hot, but not in flame, remove the cork, and insert the ignited stick into the gas. It will inflame and burn much more brightly than in the external air. (See H. C. G., p. 35, Exp. 5.) To this phenomenon, one of the most im. portant connected with our subject, we shall recur under the head of carbonic acid, the compound which is the chief source of this exhaled oxygen. § 3. RELATIONS OF NITROGEN GAS TO VEGETABLE NUTRITION. Nitrogen Gas not a Food to the Plant.—Nitrogn in the free state appears to be indifferent to vegetation. Priestley, to whom we are much indebted for our knowl- edge of the atmosphere, was led to believe in 1779 that free nitrogen is absorbed by and feeds the plant. But this philosopher had no adequate means of investigating the subject. De Saussure, twenty years later, having command of better methods of analyzing gaseous mix- tures, concluded from his experiments that free nitrogen does not at all participate in vegetable nutrition. Boussingault’s Experiments,—The question rested un- til 1837, when Boussingault made some trials, which, how- ever, were not decisive. In 1851-1855 this ingenious chemist resumed the study of the subject and conducted a large number of experiments with the greatest care, all of which lead to the conclusion that no appreciable amount of free nitrogen is assimilated by plants. His plan of experiment was simply to cause plants to grow in circumstances where, every other condition of de- velopment being supplied, the only source of nitrogen at ATMOSPHERIC AIR AS THE FOOD OF PLANTS. 27 their command, besides that contained in the seed itself, should be the free nitrogen of the atmosphere. For this purpose he prepared a soil consisting of pumice-stone and the ashes of stable-manure, which was perfectly freed from all compounds of nitrogen by treatment with acids and in- tense heat. In nine of his earlier experiments the soil thus prepared was placed at the bottom of a large glass globe, . B, fig. 4, of 15 to 20 gallons’ capacity. Seeds of cress, dwarf beans, or lupins, were deposited in the soil, and a proper supply of water, purified for the purpose, was add- ed. After germination of the seeds, a glass globe, D, of about one-tenth the capacity of the larger vessel, was filled with carbonic acid (to supply carbon), and was secured air- tight to the mouth of the latter, com- munication being had between them by the open neck at C. The apparatus was then disposed in a suitably lighted place in a garden, _ and left to itself for a period which va- ried in the different experiments from 14 to 5 months, At a the conclusion of the } trial the plants were py ‘ lifted out, and, to- Fig. 4. gether with the soil from which their roots could not be entirely separated, were subjected to chemical analysis, to determine the amount of nitrogen which they had assimilated during growth. The details of these trials are contained in the subjoined 28 HOW CROPS FEED. Table. The weights are expressed in the gram and its fractions. = 8 3, Bedee ale & tales ae Fe ration |e) we | ws sw: 3] Kind of Plant. 38 Re | SS] 88 S33 any § Experiment. $3 $2 gs Sa Iss S25 = 7 i“ =“ i 5 & 1} Dwarf bean. ........ 2months | 1] 0.780] 1.87 |0.0349'0.0340|—0. 2] Oat... --.. 2 10 | 0.377] 0.54 {0:0078'0.0067|—-0.0011 8 3 1 | 0.530 | 0.89 |0:0210'0.0189; 0.0021 4 3 Ot 1 | 0.618 | 1.13 |0:0245'0.0226/—0.0019 5 2% 4 | 0.139 | 0.44 {0.0031/0.0030|—0. 6 1% 2 | 0.825 | 1.82 |0.0480'0.0483]-+0.0003 7 2 -6 | 2.202 | 6.73 |0.1282/0.1246|—0. 8 7 weeks 2 | 0.600) 1:95 |0.0349/0.0339|—0..0010 9 1 | 0.343] 1 05 /0.0200/0.0204/-+0.0004 10 6 2 | 0.686 | 1.53 |0:0399'0:0397/—0.0002 1 2months | 1 | 0.792] 2.85 |0.0354'0.0360|-+0.0006 12 2% 1 0.665 2:80 |0.0298\0.0277/—0.0021 3y% a) y 13) | as manure 19 | 0.035} 0.65 |0.0013/0.0018| 0.0000. 5 months 2 ; er 14 Soe arare:! a4 susie tbe 0.1927/0.1697 —0.0130 Dal Obenicsechsnauin oe edad easnine 68 .... [11.920 | 30.11 |0.618510.5868|—0.0247 While it must be admitted that the unavoidable errors of experiment are relatively large in working with such small quantities of material as Boussingault here employed, we cannot deny that the aggregate result of these trials is de- cisive against the assimilation of free nitrogen, since there was a loss of nitrogen in the 14 experiments, amounting to 4 per cent of the total contained in the seeds; while a gain was indicated in but 3 trials, and was but 0.13 per cent of the nitrogen concerned in them.—(Boussingault’s Agronomie, Chimie Agricole, et Physiologie, Tome I, pp. 1-64.) The Opposite Conclusions of Ville.—In the years 1849, 60, °51, and °52, Georges Ville, at Grenelle, near Paris, experimented upon the question of the assimilability of free nitrogen. His method was similar to that first employed by Boussingault, The plants subjected to his trials were cress, lupins, colza, wheat, rye, maize, sun-flowers, and to- bacco. They were situated in a large octagonal cage made of iron sashes, set with glass-plates. The air was ATMOSPHERIC AIR AS THE FOOD OF PLANTS. 29 constantly renewed, and carbonic acid was introduced in proper quantity. The experiments were conducted ona larger scale than those of Boussingault, and their result was.uniformly the reverse. Ville indeed thought to have established that vegetation feeds on the free nitrogen of the air. To the conclusions to which Boussingault drew from the trials made in the manner already described, Ville objected that the limited amount of air contained in the glass globes was insufficient for the needs of vegetation; that plants, in fact, could not aitain a normal development under the conditions of Boussingault’s experiments. (Ville, Recherches sur la Vegetation, pp. 29-58, and 53-98.) Boussingault’s Later Experiments.—The latter there- upon instituted a new series of trials in 1854, in which he proved that the plants he had previously experimented upon attain their full development in a confined atmosphere under the circumstances of his first experiments, provided they are supplied with some assimilable compound of ni- trogen. He also conducted seven new experiments in an apparatus which allowed the air to be constantly renewed, and in every instance confirmed his former results.— (Agronomie, Chimie Agricole et. Physiologie, Tome I, pp. 65-114.) The details of these experiments are given in the follow- ing Table. The weights are expressed in grams. se. 13./=.|*. [88 - Duration {nc | si ae Kind of Plant. of (SSRs | RS) SS) SS | STS Baperiment.| 5 se BS | £2 | 89 | B28 = rf BTR [SS “Lupin... 10 weeks | 1 | 0.837 | 2.140/0.0196 0.0187|—0.0009 2\Bean.. 10 “| 1 | 0.720 | 2:000|0.0822 0.0325'-+-0:0003 3|Bean.. 12 “ | 1 | 0.748 | 2.847|0.0335 0:0341)-+0.0006 4\Bean.. 14 « |’ 4 | 0.765 | 2:240,0.0339 0. 0329'—0.0010 5lBean....... (18 | 2 | 1.510 | 5:160/0:0676 0.0668 —0. 0010 OLapliinasussenes wonaens taeinannedl 21 (Nan 1.780/0,0865 0.0824 —0 0021 q]Grandssen Pumice is a vesicular rock, having nearly the composi- tion of feldspar. . Tue Maenesian SErRrEs consisting of Quartz, Feldspar and Taic, or Chlorite. Talcose Granite differs from common granite in the substitution of talc for mica. Is a fragile and more easily ORIGIN AND FORMATION OF SOILS. 121 decomposable rock than granite. It passes through talcose gneiss into Talcose Schist, which resembles mica-schist in colors and in facility of splitting into slabs, but has a less glis- tening luster and a soapy feel. Chloritic Schist resembles talcose schist, but has a less unctuous feel, and is generally of a dark green color. Related to the above are Steatite, or soapstone,—nearly pure, granular talc; and Serpentine rock, consisting chiefly of serpentine. The above are the more common and wide-spread si- licious rocks. By the blending together of the different members of each series, and the related members of the different series, and by the introduction of other minerals into their composition, an almost endless variety of si- licious rocks has been produced. Turning now to the CrysTaLLingE Catcarrgous Rocks, we have Granular Limestone, consisting of a nearly pure car- bonate of lime, in more or less coarse grains or crystals, commonly white or gray in color, and having a glistening luster on a freshly broken surface. The finer kinds are employed as monumental marble. Dolomite has all the appearance of granular limestone, but contains a large (variable) amount of carbonate of magnesia. Tue FracmMentaL on SEDIMENTARY Rocks are as fol- lows: Conglomerates have resulted from the consolidation of. rather coarse fragments of any kind of rock. According. to the nature of the materials composing them, they may be granitic, syenitic, calcareous, basaltic, etc., etc. They pass into Sandstones, which consist of small fragments (sand), are generally silictous in character, and often are nearly 122 HOW CROPS FEED. pure quartz. The freestone of the Connecticut Valley is a granitic sandstone, containing fragments of feldspar and spangles of mica. Other varieties are calcareous, argillaceous (clayey), basaltic, etc., ete. Shales are soft, slaty rocks of various colors, gray, green, ! red, blue, and black. They consist of compacted clay. When crystallized by metamorphic action, they constitute arg illite. Limestones of the sedimentary kind are soft, compact, nearly lusterless rocks of various colors, usually gray, plue, or black. They are sometimes nearly pure carbon- ate of lime, but usually contain other substances, and are often highly impure. When containing much carbonate of magnesia they are termed magnesian limestones. They pass into sandstones through intermediate calciferous sand rocks, and into shales through argillaceous lime- stones. These impure limestones furnish the hydraulic cements of commerce. g§ 4. CONVERSION OF ROCKS INTO SOILS. Soils are broken and decomposed rocks. We find in nearly all soils fragments of rock, recognizable as such by the eye, and by help of the microscope it is often easy to perceive that those portions of the soil which are impalpa- ble to the feel chiefly consist of minuter grains of the same rock. Geology makes probable that the globe was once in a melted condition, and came to its present state through a process of cooling. By loss of heat its exterior surface solidified to a crust of solid rock, totally incapable of sup- porting the life of agricultural plants, being impenetrable to their roots, and destitute of all the other external char- acteristics of a soil. ORIGIN AND FORMATION OF SOILS. 123 ‘The first step towards the formation of a soil must have been the pulverization of the rock. This has been accom- plished by a variety of agencies acting through long pe- riods of time. The causes which could produce such re- sults are indeed stupendous when contrasted with the narrow experience of a single human life, but are really trifling compared with the magnitude of the earth itself, for the soil forms upon the surface of our globe, whose di- ameter is nearly 8,000 miles, a thin coating of dust, meas- ured in its greatest. accumulations not by miles, nor scarcely by rods, but by feet. The conversion of rocks to soils has been performed, 1st, by Changes of Temperature ; 2d, by Moving Water or Ice ; 3d, by the Chemical Action of Water and Air ; 4th, by the Influence of Vegetable and Animal Life. 1.—Cuances oF TEMPERATURE, . The continued cooling of the globe after it had become enveloped ina solid rock-crust must have been accom- panied by a contraction of its volume. One effect of this shrinkage would have been a subsidence of portions of the crust, and a wrinkling of other portions, thus produc- ing on the one hand sea-basins and valleys, and on the other mountain ranges. Another effect would have been the cracking of the crust itself as the result of its own contraction. The pressure caused by contraction or by mere weight of superincumbent matter doubtless led to the production of the laminated structure of slaty rocks, which may be readily imitated in wax and clay by aid of an hydraulic press. Basaltic and trap rocks in cooling from fusion often acquire a tendency to separate into vertical columns, somewhat as moist starch splits into five or six-sided frag- ments, when dried. These columns are again transversely jointed. The Giant’s Causeway of Ireland is an illustra- tion. These fractures and joints are, perhaps, the first oc- easion of the breaking down of the rocks. The fact that: 124 HOW CROPS FEED. many rocks consist of crystalline grains of distinct min- erals more or less intimately blended, is a point of weak- ness in their structure. ‘The grains of’ quartz, feldspar, and mica, of a granite, when exposed to changes of tem- perature, must tend to separate from each other; because the extent to which they expand and contract by alterna- tions of heat and cold are not absolutely equal, and be- cause, as Senarmont has proved, the same crystal expands or contracts unequally in its different diameters. Action of Freezing Water.—lIt is, however, when wa- ter insinuates itself into the slight or even imperceptible rifts thus opened, and then freezes, that the process of dis- integration becomes more rapid and more vigorous. Wa- ter in the act of conversion into ice expands ;' of its bulk, and the force thus exerted is sufficient to burst vessels of the strongest materials. In cold latitudes or altitudes this agency working through many years accomplishes stupen- dous results, The adventurous explorer in the higher Swiss Alps fre- quently sees or hears the fall of fragments of rock thus loosened from the peaks. Along the base of the vertical trap cliffs of New Haven and the Hudson River, lie immense masses of broken rock reaching to more than half the height of the bluffs them- selves, rent off by this means, The same cause operates in a less conspicuous but not less important way on the surface of the stone, loosening the minute grains, as in the above instances it rends off enormous blocks. A smooth, clean pebble of the very compact Jura limestone, of such kind, for example, as abound in the rivers of South Bavaria, if moistened with water and exposed over night to sharp frost, on thawing, is muddy with the de- tached particles. 2.—Movine Water or Icr. Changes of temperature not only have created differ- ences of level in the earth’s surface, but they cause a con- ORIGIN AND FORMATION OF SOILS. 125 tinual transfer of water from lower to higher levels. The elevated lands are cooler than the valleys. In their re- gion occurs a continual condensation of vapor from the atmosphere, which is as continually supplied from tie heated valleys. In the mountains, thus begin, as rills, the streams of water, which, gathering volume in their descent, unite below to vast rivers that flow unceasingly into the ocean. These streams score their channels into the firmest rocks. Each grain of loosened material, as carried downward by the current, cuts the rock along which it is dragged so long as it is in motion. The sides of the channel being undermined and loosen- ed by exposure to the frosts, fall into the stream. In time of floods, and always, when the path of the river has a rapid descent, the mere momentum of the water acts pow- erfully upon any inequalities of surface that oppose its course, tearing away the rocky walls of its channel. The blocks and grains of stone, thus set in motion, grind each other to smaller fragments, and when the turbid waters clear themselves in a lake or estuary, there results a bed of gravel, sand, or soil. Two hundred and sixty years ago, the bed of the Sicilian river Simeto was obstructed by the flow across it of a stream of lava from Etna. Since that time the river, with but slight descent, has cut a chan- nel through this hard basalt from fifty to several hundred feet wide, and in some parts forty to fifty deep. But the action of water in pulverizing rock is not com- pleted when it reaches the sea. The oceans are in perpet- ual agitation from tides, wind-waves, and currents hke the Gulfstream, and work continual changes on their, shores. Glaciers.— What happens from the rapid flow of water down the sides of mountain slopes below the frost-line is also true of the streams of ice which more slowly descend from the frozen summits. . The glaciers appear like motion- 126 HOW CROPS FEED. less ice-fields, but they are frozen rivers, rising in perpet ual snows and melting into water, after having reached half a mile or a mile below the limits of frost. The snow that accumulates on the frozen peaks of high mountains, which are bathed by moist winds, descends the slopes by its own weight. The rate of descent is slow,—a few inches, or, at the most, a few feet, daily. The motion it- self is not continuous, but intermittent by a succession of pushes. In the gorges, where many smaller glaciers unite, the mass has often a depth of a mile or more. Under the pressure of accumulation the snow is compacted to ice.- Mingled with the snows are masses of rock broken off the higher pinnacles by the weight of adhering ice, or loosened by alternate freezing and thawing, below the line of perpetual frost. The rocks thus falling on the edge of a glacier become a part of the latter, and partake its mo- tion. When the moving mass bends over a convex sur- face, it cracks vertically to a great depth. Into the cre- vasses thus formed blocks of stone fall to the bottom, and water melted from the surface in hot days flows down and finds a channel beneath the ice. The middle of the glacier moves most rapidly, the sides and bottom being retarded by friction. The ice is thus rubbed and rolled upon itself, and the stones imbedded in it crush and grind each other -to smaller fragments and to dust. The rocky bed of the glacier is broken, and ploughed by the stones frozen into its sides and bottom. The glacier thus moves until it descends so low that ice cannot exist, and gradually dis- solves into a torrent whose waters are always thick with mud, and whose course is strewn with worn blocks of stone (boulders) for many miles. The Rhone, which is chiefly fed from the glaciers of the Alps, transports such a volume of rock-dust that its muddy waters may be traced for six orseven miles after they have poured themselves into the Mediterranean. 3.—CuemicaL Action or WaTER.anp AIR. = ORIGIN AND FORMATION OF SOILS. 127 Water acts chemically upon rocks, or rather upon their constituent minerals, in two ways, viz., by Combination and Solution. Hydration.—By chemically uniting itself to the mineral or to some ingredient of the mineral, there is formed in many instances a new compound, which, by being softer and more bulky than the original substance, is the first step towards further change. Mica, feldspar, amphibole, and pyroxene, are minerals which have been artificially produced in the slags or linings of smelting furnaces, and thus formed they have been found totally destitute of wa- ter, as might be expected from the high temperature in which they originated. Yet these minerals as occurring in nature, even when broken out of blocks of apparently unaltered rock, and especially when they have been di- rectly exposed to the weather, often, if not always, con- tain a small amount of water, in chemical combination (water of hydration). Solution.—As a solvent, water exercises the most im- portant influence in disintegrating minerals. Apatite, when containing much chlorine, is gradually decomposed by treatment with water, chloride of calcium, which is very soluble, being separated from the nearly insoluble phosphate of lime. The minerals which compose silicious rocks are all acted on perceptibly by pure water. This is ‘readily observed when the minerals are employed in the state of fine powder. If pulverized feldspar, amphibole, ete., are simply moistened with pure water, the latter at once dissolves a trace of alkali, as shown by its turning red litmus-paper blue. This solvent action is so slight upon a smooth mass of the mineral as hardly to be per- ceptible, because the action is limited by the extent of surface. Pulverization, which increases the surface enor- mously, increases the solvent effect in a similar proportion. A glass vessel may have water boiled in it for hours with- out its luster being dimmed or its surface materially acted 128 HOW CROPS FEED. upon, whereas the same glass* finely pulverized is attack- ed by water so readily as to give at once a solution alka- line to the taste. Messrs. W. B. and R. E. Rogers (Am. Jour, Sci., V, 404, 1848) found that by continued digestion of pure water for a week, with powdered feldspar, horn- blende, chlorite, serpentine, and natrolite,t these minerals yielded to the solvent from 0.4 to 1 per cent of their weight. In nature we never deal with pure water, but with wa- ter holding in solution various matters, either derived from the air or from the soil. These substances modify, and in most cases enhance, the solvent power of water. Action of Carbonic Acid.—This gaseous substance is absorbed by or dissolved in all natural waters to a greater or less extent. At common temperatures and pressure water is capable of taking up its own bulk of the gas, At lower temperatures, and under increased pressure, the quantity dissolved is much greater. Carbonated water, as we may designate this solution, has a high solvent power on the carbonates of lime, magnesia, protoxide of iron, and protoxide of manganese. The salts just named are as good as insoluble in pure water, but they exist in considerable quantities in most natural waters. The spring and well waters of limestone regions are hard on account of their content of carbonate of lime. Chalyb- eate waters are those which hold carbonate of iron in solution. When carbonated water comes in contact with silicious minerals, these are decomposed much more rapidly than by pure water. The lime, magnesia, and iron they contain, are partially removed in the form of carbonates. Struve exposed powdered phonolite (a rock composed of feldspar and zeolites) to water saturated with carbonic * Glass is a silicate of potash or soda. + Mesotype. ORIGIN AND FORMATION OF SOILS. 129 acid under a pressure of 3 atmospheres, and obtained a solution of which a pound* contained: Carbonate of soda, 22.0 grains. Chloride of sodium, 2.0 Sulphate of potash, Ly s “ soda, 48 “ Carbonate of lime, 45 “ “ ““ magnesia, 11 & Silica, 0.5 “ Phosvhoric acid and manganese, traces Total, 87.1 grains, Tn various natural springs, water comes to the surface so charged with carbonic acid that the latter escapes copiously in bubbles. Such waters dissolve large quantities of mineral matters from the rocks through which they emerge. Examples are seen in the springs at Saratoga, N.Y. According to Prof. Chandler, the “Saratoga Spring,” whose waters issue directly from the rock, con- tains in one gallon of 231 cubic inches: Chloride of Sodium (common salt) 398.361 “« Potassium, : 9.698 Bromide of Sodium, 0.571 Iodide of Sodium, 0.126 Sulphate of Potash, 5.400 Carbonate of Lime, 86.483, se “Magnesia, 41.050 ce “ Soda, 8.948 ee “ Protoxide of iron, .879 Silica, 1.283 Phosphate of lime, trace Solid matters, Carbonic acid gas, (407.647 cubic inches at 52° Fah.) Water, % 552.799 58,317,110 grains, “ce ‘The waters of ordinary springs and rivers, as well as those that fall upon the earth’s surface as rain, are, indeed, * The Saxon pound contains 7,680 Saxon grains. 6* 130 HOW CROPS FEED. by no means fully charged with carbonic acid, and their solvent effect is much less than that exerted by water sat- urated with this gas. The quantity (by volume) of carbonic acid in 10,000 parts of rain-water has been observed as follows: Accord- ing to Locality. Lampadius, 8 Country near Freiberg, Saxony. Mulder, 20 City of Utrecht, Holland. Von Baumhauer, 40 to 90 Ee “ ae Peligot, 5 ? The quantities found are variable, as might be expected, and we notice that the largest proportion above cited does not even amount to one per cent. In river and spring water the quantities are somewhat larger, but the carbonic acid exists chiefly in chemical com- bination as bicarbonates of lime, magnesia, etc. In the capillary water of soils containing much organic matters, more carbonic acid is dissolved. According to a single observation of De Saussure’s, such water contains 2°|, of the gas. In a subsequent paragraph, p. 221, is given the reason of the small content of carbonic acid in these waters. The weaker action of these dilute solutions, when con- tinued through long periods of time and extending over an immense surface, nevertheless accomplishes results of vast significance. Solutions of Alkali-Salis—Rain-water, as we have already seen, contains a minute quantity of salts of am- monia (nitrate and bicarbonate). The water of springs and rivers acquires from the rocks and soil, salts of soda and potash, of lime and magnesia. These solutions, dilute though they are, greatly surpass pure water, or even car- bonated water, in their solvent and disintegrating action. Phosphate of lime, the earth of bones, is dissolved by pure water to an extent that is hardly appreciable; in ORIGIN AND FORMATION OF SOILS. 131 salts of ammonia and of soda, however, it is taken up in considerable quantity. Solution of nitrate of ammonia dissolves lime and magnesia and their carbonates with great ease. In general, up to a certain limit, a saline so- lution acquires increased solvent power by increase in the amount and number of dissolved matters. This import- ant fact is one to which we shall recur at another time. Action of Oxygen.—This element, the great mover of chemical changes, which is present so largely in the at- mosphere, has.a strong tendency to unite with certain bodies which are almost universally distributed in the rocks, On turning to the analyses of minerals, p. 110, we notice in nearly every instance a quantity of protoxide of iron, or protoxide of manganese. The green, dark gray, or black minerals, as the micas, amphibole, pyroxene, chlorite, talc, and serpentine, invariably contain these prot- oxides in notable proportion. In the feldspars they exist, indeed, in very minute quantity, but are almost never en- tirely wanting. Sulphide of iron (iron pyrites), in many of its forms, is also disposed to oxidize its sulphur to sul- phuric acid, its iron to sesquioxide, and this mineral is widely distributed as an admixture in many rocks. In trap or basaltic rocks, as at Bergen Hill, metallic iron is said to occur in minute proportion,* and in a state of fine division, The oxidation of these substances materially hastens the disintegration of the rocks containing them, since the higher oxides of iron and of manganese occupy more space than the metals or lower oxides. This fact is well illustrated by the sulphate of protoxide of iron (cop- peras, or green-vitriol), which, on long keeping, exposed to the air, is converted from transparent, glassy, green crys- tals to a bulky, brown, opaque powder of sulphate of sesquioxide of iron. Weathering.—The conjoined influence of water, car- © This statement rests on the authority of Professor Henry Wurtz, of New York. 132 HOW CROPS FEED. boniec acid, oxygen, and the salts held in solution by the atmospheric waters, is expressed by the word weathering. This term may likewise include the action of frost. When rocks weather, they are decomposed or dissolved, and new compounds, or new forms of the original mat- ter, result. The soil is 9 mixture of broken or pulverized rocks, with the products of their alteration by weathering. a. Weathering of Quartz Rock.—Quartz (silicic acid), as occurring nearly pure in quartzite, and in many sand- stones, or as a chief ingredient of all the granitic, horn- blendic, and many other rocks, is so exceedingly hard and insoluble, that the lifetime of a man is not sufficient for the direct observation of any change in it, when it is ex- posed to ordinary weathering. It is, in fact, the least destructible of the mineral elements of the globe. Never- theless, quartz, even when pure, is not absolutely insoluble, particularly in water containing alkali carbonates or sili- cates. In its less pure varieties, and especially when as- sociated with readily decomposable minerals, it is acted on more rapidly. The quartz of granitic rocks is usually roughened on the surface when it has long been exposed to the weather. b. The Feldspars weather much more easily than quartz, though there are great differences among them. The soda and lime feldspars decompose most readily, while the potash feldspars are often exceedingly durable. The decomposition results in completely breaking up the hard, glassy mineral. In its place there remains a white or yellowish mass, which is so soft as to admit of crush- ing between the fingers, and which, though usually, to the naked eye, opaque, and non-crystalline, is often seen, under a powerful magnifier, to contain numerous transparent crys- talline plates. The mass consists principally of the crys- talline mineral, kaolinite, a hydrated silicate of alumina,(the analysis of which has been given already, p. 113,) mixed ORIGIN AND FORMATION OF SOILS, 133 with hydrated silica, and often with grains of undecompos- ed mineral. If we compare the composition of pure pot- ash feldspar with that of kaolinite, assuming, what is probably true, that all the alumina of the former remains in the latter, we find what portions of the feldspar have been removed and washed away by the water, which, to- gether with carbonic acid, is the agent of this change. Feldspar. Kaolinite. Liberated. Added, Alumina........ 18.3 183 0 Silica... ccsewe ves. 64.8 23.0 41.8 Potash.......... 16.9 16.9 Watereceersecis 6.4 6.4 100 42.7 58.7 64 It thus appears that, in the complete conversion of 100. parts of potash feldspar into kaolinite, there result 47.7 parts of the latter, while 58.7°|, of the feldspar, viz: 41.8°|, of silica and 16.9°|, of potash, are dissolved out. The potash, and, in case of other feldspars, soda, lime,- and magnesia, are dissolved as carbonates. If much water has access during the decomposition, all the liberated silica is carried away.* It usually happens, however, that a por- tion of the silica is retained in the kaolin (perhaps in a manner similar to that in which bone charcoal retains the coloring matters of crude sugar). The same is true of a portion of the alkali, lime, and oxide of iron, which may. have existed in the original feldspar. The formation of kaolin may be often observed in na- ture. In mines, excavated in feldspathic rocks, the fis- sures and cavities through which surface water finds its way downwards are often coated or filled with this sub- stance. ce. Other Silicious Minerals, as Leucite, (Topaz, Scapo- lite,) etc., yield kaolin by decomposition. It is probable P; ; that the micas, which decompose with difficulty, (phlogo- * We have seen (H. C. G., p. 121) that silica, when newly set free from combi- nation, is, at first, freely soluble in water, wh 134 HOW CROPS FEED. pite, perhaps, excepted,) and the amphiboles and pyrox- enes, which are often easily disintegrated, also yield kaolin ; but in the case of these latter minerals, the result- ing kaolinite is largely mixed with oxides and silicates of iron and manganese, so that its properties are modified, and identification is difficult. Other hydrated silicates of: alumina, closely allied to kaolinite, appear to be formed in the decomposition of compound silicates. Ordinary Clays, as pipe-clay, blue-clay, brick-clay, etc., are mixtures of kaolinite, or of a similar hydrated silicate of alumina, with a variety of other substances, as free silica, oxides, and silicates of iron and manganese, carbon- ate of lime, and fragments or fine powder of undecom- posed minerals, Fresenius deduces from his analyses of - several Nassau clays the existence in them of a compound having the symbol Al, O, 3 SiO,+H,O, and the follow- ing composition per cent. Silica, 57.14 Alumina, 31.72 Water, 11.14 100.00 Other chemists have assumed the existence of hydrated silicates of alumina of still different composition in clays, but kaolinite is the only one which occurs in a pure state, as indicated by its crystallization, and the existence of the others is not perfectly established. (S. W. Johnson and J. M. Blake on Kaolinite, etc., Am. Jour. Sci., May, 1867, pp. 351-362.) d. The Zeolites readily suffer change by weathering ; little is known, however, as to the details of their disinte-. gration. Instead of yielding kaolinite, they appear to be transformed into other zeolites, or retain something of their original chemical constitution, although mechanically dis- integrated or dissolved. We shall see hereafter that there: ORIGIN AND FORMATION OF SOILS. 135 is strong reason to assume the existence of compounds analogous to zeolites in every soil. e. Serpentine and Magnesian Silicates are generally slow of decomposition, and yield a meager soil. J. The Limestones, when pure and compact, are very durable: as they become broken, or when impure, they often yield rapidly to the weather, and impregnate the streams which flow over them with carbonate of lime. g. Argillite and Argillaceous Limestones, which have resulted from the solidification of clays, readily yield clay again, either by simple pulverization or by pulverization and weathering, according as they have suffered more or less change by metamorphism. § 5. INCORPORATION OF ORGANIC MATTER WITH THE SOIL AND” ITS EFFECTS. Antiquity of Vegetation.—Geological observations lead to the conclusion that but small portions of the earth’s surface-rocks were formed previous to the existence of vegetation. The enormous tracts of coal found in every quarter of the globe are but the residues of preadamite forests, while in the oldest stratified rocks the remains of plants (marine) are either most distinctly traced, or the abundance of animal forms warrants us in assuming the existence of vegetation previous to their deposition. The Development of Vegetation on a purely Mineral Soil.—The mode in which the original inorganic soil be~ came more or less impregnated with organic matter may be illustrated by what has happened in recent years upon the streams of lava that have issued from volcanoes. The lava flows from the crater as red-hot molten rock, often in masses of such depth and extent as to require months to. éool down to the ordinary temperature. For many years: 136 HOW CROPS FEED. the lava is incapable of bearing any vegetation save some almost microscopic forms, During these years the surface of the rock suffers gradual disintegration by the agencies of air and water, and so in time acquires the power to support some lichens that appear at first as mere stains upon its surface. These, by their decay, increase the film of soil from which they sprung. The growth of new generations of these plants is more and more vigor- ous, and other superior kinds take rvot among them, After another period of years, there has accumulated a tangible soil, supporting herbaceous plants and dwarf shrubs. Henceforward the increase proceeds more rapid- ly; shrubs gradually give place to trees, and in a century, more or less, the once hard, barren rock has weathered to a soil fit for vineyards and gardens. Those lowest orders of plants, the lichens and mosses, which prepare the way for forests and for agricultural vegetation, are able to extract nourishment from the most various and the most insoluble rocks. They occur abund- antly on all our granitic and schistose rocks. Even on quartz they do not refuse to grow. The white quartz. hills of Berkshire, Massachusetts, are covered on their moister northern slopes with large patches of a leathery lichen, which adheres so firmly to the rock that, on being forced off, particles of the stone itself are detached. Many of the old marbles of Greece are incrusted with oxalate. of lime left by the decay of lichens which have grown upon their surface. Humus,—By the decay of successive generations of plants the soil gradually acquires a certain content of dead. organic matter. The falling leaves, seeds and stems of vegetation do not in general waste from the surface as rapidly as they are renewed. In forests, pastures, prai- ries, and marshes, there accumulates on the surface a brown or black mass, termed humus, of which leaf-mold, swamp- muck, and peat are varieties, differing in appearance as in ORIGIN AND FORMATION OF SOILS. 137 the circumstances of their origin. In the depths of the soil similar matters are formed by the decay of roots and other subterranean parts of plants, or by the inversion of sod and stubble, as well as by manuring. Decay of Vegetation.— When a plant or any part of a plant dies, and remains exposed to air and moisture at the common temperatures, it undergoes a series of chemical and physical changes, which are largely due to an oxida- tion of portions of its carbon and hydrogen, and the formation of new organic compounds. Vegetable matter is considerably variable in composition, but in all cases chiefly consists of cellulose and starch, or bodies of simi- lar character, mixed with a small proportion of albuminous -and mineral substances. By decay, the white or light- colored and tough tissues of plants become converted inte brown or black friable substances, in which less or none of the organized structure of the fresh plant can be traced. The bulk and weight of the decaying matter constantly decreases as the process continues. With full access of air and at suitable temperatures, the decay, which, from the first, is characterized by the production and escape of carbonic acid and water, proceeds without interruption, though more and more slowly, until nearly all the carbon and | hydrogen of the vegetable matters are oxidized to the above-named products, and little more than the ashes of the plant remains, With limited access of air the process rapidly runs through a first stage of oxidation, when it becomes checked by the formation of substances which are themselves able, to a good degree, to resist further oxidation, especially under the circum- stances of their formation, and hence they accumulate in considerable quantities. This happens in the lower layers of fallen leaves in a dense forest, in compost and manure heaps, in the sod of a meadow or pasture, and especially in swamps and peat-bogs, The more delicate, porous and watery. the vegetable 138 HOW ¢ROPS FEED. matter, and the more soluble substances and albuminoids it contains, the more rapidly does it decay or humify. It has been shown by a chemical examination of what escapes in the form of gas, as well as of what remains as humus, that the carbon of wood oxidizes more slowly than its hydrogen, so that humus is relatively richer in carbon than the vegetable matters from which it origin- ates. With imperfect access of air, carbon and hydrogen are to some extent disengaged in union with each other, as marsh gas (CH,). Carbonic oxide gas (CO) is proba- bly also produced in minute quantity. The nitrogen of the vegetable matter is to a considerable extent liberated in the free gaseous state ; a portion of it unites to hydro- gen, forming ammonia (NH,), which remains in the de- caying mass; still another portion remains in the humus in combination, not as ammonia, but as an ingredient of the ill-defined acid bodies which constitute the bulk of humus; finally, some of the nitrogen may be oxidized to nitric acid. Chemical Nature of Humus.—In a subsequent chapter, (p. 224,) the composition of humus will be explained at length. Here we may simply mention that, under the in- fluence of alkalies and ammonia, it yields one or more bodies having acid characters, called humic and ulmic (also geic) acids. Further, by oxidation it gives rise to crenic and apocrenic acids. The former are faintly acid in their properties; the latter are more distinctly char- acterized acids. Influence of Humus on the Minerals of the Soil._— a. Disintegration of the mineral matters of soils is aided by the presence of organic substances in a decaying state, in so far as the latter, from their hygroscopic quality, main- tain the surface of the soil in a constant state of moisture. 6, Organic matters furnish copious supplies of carbonic acid,: the action of. which has already. been. considered ORIGIN AND FORMATION OF SOILS. 139 (p. 128). Boussingault and Lewy (Mémoires de Chimie Agricole, etc., p. 369,) have analyzed the air contained in the pores of the soil, and, as was to be anticipated, found it vastly richer in carbonic acid than the ordinary atmos- phere. , The following table exhibits the composition of the air in the soil compared with that of the air above the soil, as observed in their investigations, Carbonic acid in 10,000 parts of air (by weight), 6 Ordinary atmosphere............ cece cece ceee eee Air from sandy subsoil of forest..............c0006 38 EES Noam SE iad saan awe aera 14 & ‘surface-soil “cess iesscaveoe eaves 130 es ee * vineyard............0e eee 146 She oe ss “ old asparagus bed....... 122 it] cr be “ce a“ [Ts newly manured. 233 eis AEE as © pastOre sc seas ceive vee se 270 SS OEE as rich in humus...........665 543 a as newly manured sandy field, during dry weather....... 333 Berets “ newly manured sandy field, during wet weather....... 1413 That this carbonic acid originates in large part by oxi- dation of organic matters is strikingly demonstrated by the increase in its quantity, resulting from the application of manure, and the supervention of warm, wet weather. It is obvious that the carbonic acid contained in the air of the soil, being from twenty to one hundred or more times more abundant, relatively, than in the common at- mosphere, must act in a correspondingly more rapid and energetic manner in accomplishing the solution and disin- tegration of mineral matters. c. The organic acids of the humus group probably aid in the disintegration of soil by direct action, though our knowledge is too imperfect to warrant a positive conclu- sion. The ulmic and humic acids themselves, indeed, do not, according to Mulder, exist in the free state in the soil, but their soluble salts of ammonia, potash or soda, have acid characters, in so far that they unite energetical- 140 HOW CROPS FEED. ly with other bases, as lime, oxide of iron, ete. These alkali-salts, then, should attack the minerals of the soil in a manner similar to carbonic acid. The same is probably true of crenic and apocrenic acids. d. It scarcely requires mention that the ammonia salts and nitrates yielded by the decay of plants, as well as the organic acids, oxalic, tartaric, etc., or acid-salts, and the chlorides, sulphates, and phosphates they contain, act upon the surface soil where they accumulate in the manner al- ready described, and that vegetable (and animal) remains thus indirectly hasten the solution of mineral matters. Action of Living Plants on the Minerals of the Soil._— 1. Moisture and Carbonic Acid.—The living vegetation of a forest or prairie is the means of perpetually bringing the most vigorous disintegrating agencies to bear upon the soil that sustains it. The shelter of the growing plants, not less than the hygroscopic humus left by their decay, maintains the surface ina state of saturation by .Mmoisture. The carbonic acid produced in living roots, and to some extent, at least, it is certain, excreted from them, adds its effect to that derived from other sources. 2. Organic Acids within the Plant.—According to Zoller, (Vs. St. V. 45) the young roots of living plants (what plants, is not mentioned) contain an acid or acid- salt which so impregnates the tissues as to manifest a strong acid reaction with (give a red color to) blue litmus- paper, which is permanent, and thercfore not due to car- bonic acid. This acidity, Zéller informs us, is most in- tense in the finest fibrils, and is. exhibited when the roots are simply wrapped in the litmus-paper, without being at all (?) crushed or broken, The acid, whatever it may be, thus existing within the roots is absorbed by porous paper placed externally to them. Previous to these observations of Zdller, Salm Horst- mar (Jour. fiir. Prakt. Chem. XL, 304,) having found in the ashes of ground pine (Lycopodium complanatum), 38° |, of ORIGIN AND FORMATION OF SOILS. 141 ‘alumina, while in the ashes of juniper, growing beside the Lycopodium, this substance was absent, examined the rootlets of both plants, and found that the former had an acid reaction, while the latter did not affect litmus- paper. Salm Horstmar supposed that the alumina of the soil finds its way into the Lycopodium by means of this acid. Ritthausen has shown that the Lycopodium contains malic acid, and since all the alumina of the plant may be extracted by water, it is probable that the acid reaction of the rootlets is due, in part at least, to the presence of acid malate of alumina. (Jour. fir. Prakt. Chem. LITT. 420.) At Liebig’s suggestion, Zoller made the following ex- periments. A number of glass tubes were filled with water made slightly acid by some drops of hydrochloric acid, vinegar, citric acid, bitartrate of potash, ctc.; the open end of each tube-was then closed by a piece of moistened bladder tied tightly over, and various salts, in- soluble in water, as phosphate of lime, phosphate of am- monia and magnesia, etc., were strewn on the bladder. After a short time it was found that the ingredients of these salts were contained in the liquid in contact with the under surface of the bladder, having been dissolved by the dilute acid present in the pores of the membrane, and absorbed through it. This is an ingenious illustra- tion of the mode in which the organic acids existing in the root-cells of plants may act directly upon the rock or soil external to them. By such action is doubtless to be explained the fuct mentioned by Liebig in the following words: “We frequently find in meadows smooth limestones with their surfaces covered with a network of small fur- rows. When these stones are newly taken out of the ground, we find that each furrow corresponds to a rootlet, which appears as if it had eaten its way into the stone.” (Modern Ag. p. 43.) 142 HOW CROPS FEED. This direct action of the living plant is probably ex- erted by the lichens, which, as has been already stated, grow upon the smooth surface of the rock itself. Many of the lichens are known to contain oxalate of lime to the extent of half their weight (Braconnot). According to Gveppert, the hard, fine-grained rock of the Zobtenberg, a mountain of Silesia, is in all cases softened at its surface where covered with lichens (Acarospora smar- agdula, Imbricaria olivacea, etc.), while the bare rock, closely adjacent, is so hard as to resist the knife. On the Schwalbenstein, near Glatz, in Silesia, at a height of 4,500 feet, the granite is disintegrated under a covering of li- chens, the feldspar being converted into kaolin or washed away, only the grains of quartz and mica remaining unal- tered.* CHAPTER III. KINDS OF SOILS—THEIR DEFINITION AND CLASSIFI- CATION. § 1. DISTINCTION OF SOILS BASED UPON THE MODE OF THEIR FORMATION OR DEPOSITION. The foregoing considerations of the origin of soils intro- duce us appropriately to the study of soils themselves, In the next place we may profitably recount those defini- tions and distinctions that serve to give a certain degree of precision to language, and enable us to discriminate in some measure the different kinds of soils, which offer great diversity in origin, composition, external characters, * See, also, p. 186. KINDS OF SOILS. 143 and fertility. Unfortunately, while there are almost num- berless varieties of soil having numberless grades of pro- ductive power, we are very deficient in terms by which to express concisely even the fact of their differences, not to mention our inability to define these differences with ac- curacy, or our ignorance of the precise nature of their peculiarities. As regards mode of formation or deposition, soils are distinguished into Sedentary and Transported. The lat- ter are subdivided into Drift, Alluvial, and Colluviatl soils, Sedentary Soils, or Sodls in place, are those which have not been transported by geological agencies, but which remain where they were formed, covering or contiguous to the rock from whose disintegration they originated. Sedentary soils have usually little depth. An inspection of the rock underlying such soils often furnishes most valuable information regarding their composition and probable agricultural value; because the still unweathered rock reveals to the practised eye the nature of the min- erals, and thus of the elements, composing it, while in the soil these may be indistinguishable. In New England and the region lying north of the Ohio and east of the Missouri rivers, soils in place are not abundant as compared with the entire area. Nevertheless they do occur in many small patches. Thus the red-sand- stone of the Connecticut Valley often crops out in that part of New England, and, being, in many localities, of a friable nature, has crumbled to soil, which now lies undis- turbed in its original position. So, too, at the base of trap- bluffs may be found trap-soils, still full of sharp-angled ‘fragments of the rock. Transported Soils, (subdivided into drift, alluvial, and colluvial), are those which have been removed toa dis- tance from the rock-beds whence they originated, by the 144 HOW CROPS FEED. action of moving ice (glaciers) or water (rivers), and de- posited as sediment in their present positions. Drift Soils (sometimes called diluvial) are characterized by the following particulars, They consist of fragments whose edges at least have been rounded by friction, if the fragments themselves are not altogether destitute of angles. They are usually deposited without any stratifi- cation or separation of parts. The materials consist of soil proper, mingled with stones of all sizes, from sand- grains up to immense rock-masses of many tons in weight. This kind of soil is usually distinguished from all others by the rounded rocks or boulders (“hard heads”) it con- tains, which are promiscuously scattered through it. The “Drift” has undoubtedly been formed by moving ice in that period of the earth’s history known to geolo- gists as the Glacial Epoch, a period when the present sur- face of the country was covered to a great depth by fields of ice. In regions like Greenland and the Swiss Alps, which reach above the line of perpetual snow, drift is now ac- cumulating, perfectly similar in character to that of New England, or has been obviously produced by the melting of glaciers, which, in former geological ages and under a colder climate, were continuations on an immense scale of those now in existence. : A large share of the northern portion of the country from the Arctic regions southward as far as latitude 39°, or nearly to the southern boundaries of Pennsylvania and to the Ohio River, including Canada, New England, Long Island, and the States west as far as Iowa, is more or less covered with drift. Comparison of the boulders with the undisturbed rocks of the regions about show that the materials of the drift have been moved southwards or southeastwards to a distance generally of twenty to forty miles, but sometimes also of sixty or one hundred miles, from where they were detached from their original beds, KINDS OF SOILS. 145 The surface of the country when covered with drift is often or usually irregular and hilly, the hills themselves being conical heaps or long ridges of mingled sand, gravel, and boulders, the transported mass having often a great depth. These hills or ridges are parts of the vast trains of material left by the melting of preadamite glaciers or icebergs, and have their precise counterpart in the moraines of the Swiss Alps. Drift is accordingly not confined to the valleys, but the northern slopes of mountains or hills, whose basis is unbroken rock, are strewn to the summit with it, and immense blocks of transported stone are seen upon the very tops of the Catskills and of the White and Green Mountains. Drift soils are for these reasons often made up of the most diverse materials, including all the kinds of rock and rock-dust that are to be found, or have existed for one or several scores of miles to the northward. Of these often only the harder granitic or silicious rocks remain in con- siderable fragments, the softer rocks having been com- pletely ground to powder. Towards the southern limit of the Drift Region the. drift itself consists of fine materials which were carried on by the waters from the melting glaciers, while the heavier boulders were left further north. Here, too, may often be observed a partial stratification of the transported materials as the result of their deposition from moving water. The great belts of yellow and red sand that stretch across New Jersey on its southeastern face, and the sands of Long Island, are these finer portions of the drift. Farther to the north, many large areas of sand may, perhaps, prove on careful examination to mark the southern limit of some ancient local glacier. ' Alluvial Soils consist of worn and rounded materials which have been transported by the agency of running water (rivers and tides). Since small and light particles are more readily sustained. in a current of water than 7 146 HOW CROPS FEED. heavy masses, alluvium is always more or less stratified or arranged in distinct layers: stones or gravel at the bottom and nearest the source of movement, finer stones or finer gravel above and further down in the path of flow, sind and impalpable matters at the surface and at the point where the stream, before turbid from suspended rock-dust, finally clears itself by a broad level course and slow progress. Alluvial deposits have been formed in all periods of the earth’s history. Water trickling gently down a granite slope carries forward the kaolinite arising from decompo- sition of feldspar, and the first hollow gradually fills up with a bed of clay. In valleys are thus deposited the gravel, sand, and rock-dust detached from the slopes of neighboring mountains. Lakes and gulfs become filled with silt brought into them by streams. Alluvium is found below as well as above the drift, and recent alluvium in the drift region is very often composed of drift mate- rials rearranged by water-currents. Alluvium often con- tains rounded fragments or disks of soft rocks, as lime- stones and slates, which are more rarely found in drift. Colluvial Soils, lastly, are those which, while consisting in part of drift or alluvium, also contain sharp, angular fragments of the rock from which they mainly originated, thus demonstrating that they have not been transported to any great distance, or are made up of soils in place, more or less mingled with drift or alluvium. § 2, DISTINCTIONS OF SOILS BASED UPON OBVIOUS OR EXTER- NAL CHARACTERS. The classification and nomenclature of soils customarily employed by agriculturists have chiefly arisen from con- sideration of the relative proportions of the principal KINDS OF SOILS. 147 mechanical ingredients, or from other highly obvious qualities, The distinctions thus established, though very vague scientifically considered, are extremely useful for practical purposes, and the grounds upon which they rest deserve to be carefully reviewed for the purpose of appreciating their deficiencies and giving greater precision to the terms employed to define them. The farmer, speaking of soils, defines them as gravelly, sandy, clayey, loamy, calcareous, peaty, ochreous, etc. Mechanical Analysis of the Soil.—Before noticing these various distinctions in detail, we may appropriately study the methods which are employed for separating the mechanical ingredients of a soil, It is evident that the epithet sandy, for example, should not be applied to a soil unless sand be the predominating ingredient; and in or- der to apply the term with strict correctness, as well as to know how a soil is constituted as regards‘ its mechanical elements, it is neccessary to isolate its parts and determine their relative quantity. Boulders, stones, and pebbles, are of little present or immediate value in the soil by way of feeding the plant. This function is performed by the finer and especially by the finest particles. Mechanical analysis serves therefore to compare together different soils, and to give useful in- dications of fertility. Simple inspection aided by the feel enables one to judge, perhaps, with sufficient accuracy for all ordinary practical purposes; but in any serious attempt to define a soil precisely, for the purposes of science, its mechanical analysis must be made with care. Mechanical separation is effected by sifting and wash- ing. Sifting serves only to remove the stones and coarse sand. By placing the soil in a glass cylinder, adding wa- ter, and vigorously agitating for a few moments, then letting the whole come to rest, there remains suspended in the water a greater or less quantity of matter in a state 148 HOW CROPS FEED. of extreme division. This fine matter is in many cases clay (kaolinite), or at least consists of substances resulting from the weathering of the rocks, and is not, or not chiefly, rock-dust. Between this impalpably fine matter and the grains of sand retained by a sieve, there exist numberless gradations of fineness in the particles. By conducting a slow stream of water through a tube to the bottom of a vessel, the fine particles of soil are carried off and may be received in a pan placed beneath. Increasing tle rapidity of the current enables it to remove larger particles, and thus it is easy to separate the soil in- to a number of portions, cach of which contains soil of a different fineness. Various attempts have been made to devise precise means of separating the materials of soils mechanically into a definite number of grades of fineness. This may be accomplished in good measure by washing, but constant and accurate results are of course only at- tained when the circumstances of the washing are uniform throughout. The method adopted by the Society of Agricultural Chemists of Germany is essentially the fol- lowing (Versuchs Stationen, VI, 144): The air-dry soil is gently rubbed on a tin-plate sievé with round holes three millimeters in diameter; what passes is weighed as jine-earth. What remains on the sieve is washed with water, dried, weighed, and designated as gravel, pebbles, stones, as the case may be, the size of the stones, etc., being indicated by comparison with the fist, with an egg, a walnut, a hazelnut, a pea, ete. Of the jine- earth a portion (30 grams) is now boiled for an hour or more in water, so as to completely break down any lumps and separate adhering particles, and is then left at rest for some minutes, when it is transferred into the vessel 1 of the apparatus, fig. 8., after having poured off the turbid water with which it was boiled, into 2, This washing ap- paratus (invented by Nobel) consists of a reservoir, A,. ‘KINDS OF SOILS. 149° made of sheet metal, capable of holding something more than 9 liters of water, and furnished at 6 with a stop-cock. By means of a tube of rubber it is joined to the series of Fig. 8. vessels, 1, 2, 3, and 4, which are connected to each other, as shown in the figure, the recurved neck of 2 fitting water-tight into the nozzle of 1 at a, ete. These vessels are made of glass, and together hold 4 liters of water; their relative volume is nearly 1:8: 27: 64, or = 1°: 2°: 3°: 4. 5 is a glass vessel of somewhat more than 5 liters, capacity. The distance between 0 and ¢ is 2 feet. The cock, 4, is opened, so that in 20 minutes exactly 9 liters of water 150 HOW CROPS FEED. pass it. The apparatus being joined together, and the cock opened, the soil in 1 is agitated by the stream of wa- ter flowing through, and the finer portions are carried over into 2, 3, 4, and 5, Asa given amount of water requires eight times longer to pass through 2 than 1, its velocity of motion and buoyant power in the neck of 3 are corre- spondingly less. After the requisite amount of water has run from A, the cock is closed, the whole left to rest sev- eral hours, when the contents of the vessels are separately rinsed out into porcelain dishes, dried and weighed.* The contents of the several vessels are designated as follows :t 1. Gravel, fragments of rock. 2. Coarse sand, 3. Fine sand. 4, Finest or dust sand. 5. Clayey substance or impalpable matter. In most inferior soils the gravel, the coarse sand, and the fine sand, are angular fragments of quartz, feldspar, amphibole, pyroxene, and mica, or of rocks consisting of these minerals. It is only these harder and less easily decomposable minerals that can resist the pulverizing agencies through which a large share of our soils have passed. In the more fertile soils, formed from sedimen- tary limestones and slates, the fragments of these strati- fied rocks occur as flat pebbles and rounded grains. The finest or dust-sand, when viewed under the micro- scope, is found to be the same rocks in a higher state of pulverization. * See, also, Wolff's ‘‘ Anleitung zur Untersuchung landwirthschaftlich-wichtiger Stoffe,” 186%, p. 5. + These names, applied by Wolff to the results of washing the sedentary soils of Wirtemberg, do not always well apply to other soils. Thus Grouven, (8¢er Salz- minder Bericht, p. 32), operating on the alluvial soils of North Germany, desig- nated the contents of the 4th funnel as ‘‘clay and loam,” and those of the 5th vessel as ‘‘light clayand humus.” Again, Schéne found (Bulletin, etc., de Moscou, p. 402) by treatment of a certain soil in Nébel’s apparatus, 45 per cent of “‘ coarse sand’ remaining in the 2d funnel. The particles of this were for the most part smaller than 1-10th millimeter (1-250th inch), which certainly is not coarse sand t KINDS OF SOILS. 151 ‘What is designated as clayey substance, or impalpable matter, is oftentimes largely made up of rock-dust, so fine that it is supported by water, when the latter is in the gentlest motion. In what are properly termed clay-soils, the finest parts consist, however, chiefly of the hydrous silicate of alumina, already described, p. 113, under the mineralogical name of kaolinite, or of analogous com- pounds, mixed with gelatinous silica, oxides of iron, and carbonate of lime, as well as with finely divided quartz and other granitic minerals. So gradual is the transition from true kaolinite clay through its impurer sorts to mere impalpable rock-dust, in all that relates to sensible char- acters, as color, feel, adhesiveness, and plasticity, that the term clay is employed rather loosely in agriculture, being not infrequently given to soils that contain very little kaolinite or true clay, and thus implies the general physi- eal qualities that are usually typified by clay rather than the presence of any definite chemical compound, like kaolinite, in the soil. Many soils contain much carbonate of lime in an im- palpable form, this substance having been derived from lime rocks, as marble and chalk, from the shells of mollusks, or from coral; or from clays that have originated by the chemical decomposition of feldspathic rocks containing much lime. Organic matter, especially the debris of former vegeta- tion, is almost never absent from the impalpable portion of the soil, existing there in some of the various forms as- sumed by humus. As Schone has shown, (Bulletin dela Societé des Natura- listes de Moscou, 1867, p. 363), the results obtained by Nobel’s apparatus are far from answering the purposes of science. The separation is not carried far enough, and no simple relations subsist between the separated portions, as regards the dimensions of their particles. If the soil were composed of spherical particles of one kind of matter, or 152 HOW CROPS FEED. having all the same specific gravity, it would be possible by the use of a properly constructed washing apparatus to separate a sample into fifty or one hundred parts, and to define the dimensions of the particles of each of these parts. Since, however, the soil is very heterogeneous, and since its particles are unlike in shape, consisting partly of nearly spherical grains and partly of plates or scales upon. which moving water exerts an unequal floating effect, it is difficult, if not impossible, to realize so perfect a mechanic- al analysis. It is, however, easy to make a separation of a soil into a large number of parts, each of which shall ad- mit of precise definition in terms of the rapidity of flow of a current of water capable of sustaining the particles which compose it. Instruments for mechanical analysis, which provide for producing and maintaining at will any desired rate of flow in a stream of water, have been very recently devised, independently of each other, by E. Schéne (loc. cit., pp. 334-405) and A. Muller (Vs. S¢., X, 25-51). The employment of such apparatus promises valuable re- sults, although as yet no extended investigations made with its help have been published. Gravelly Soils are so named from the abundance of small stones or pebbles in them. This name alone gives but little idea of the really important characters of the soil, Simple gravel is nearly valueless for agricultural purposes; many highly gravelly soils are, however, very fertile. The fine portion of the soil gives them their crop- feeding power. The coarse parts ensure drainage and store the solar heat. The mineralogical characters of the pebbles in a soil, as determined by a practised eye, may often give useful indications of its composition, since it is generally true that the finer parts of the soil agree in this respect with the coarser, or, if different, are not in- ferior. Thus if the gravel of a soil contains many pebbles of feldspar, the soil itself may be concluded to be well supplied with alkalies; if the gravel consists of limestone, KINDS OF SOILS. 153 we may infer that lime is abundant in the soil. On the other hand, if asoil contains a large proportion of quartz pebbles, the legitimate inference is that it is of compara- tively poor quality. The term gravelly admits of various qualification. We may have a very gravelly or a mod- erately gravelly soil, and the coarse material may be char- acterized as a fine or coarse gravel, a slaty gravel, a granitic gravel, or a diorite gravel, according to its state of division or the character of the rock from which it was formed. But the closest description that can thus be given of a gravelly soil cannot convey a very precise notion of even its external qualities, much less of those properties upon which its fertility depends. Sandy Soils are those which visibly consist to a large degree, 90°|, or more, of sand, i. e. of small granular fragments of rock, no matter of what kind. Sand usually signifies grains of quartz; this mineral, from its hardness, withstanding the action of disintegrating agencies beyond any other. Considerable tracts of nearly pure and white quartz sand are not uncommon, and are characterized by obdurate barrenness. But in general, sandy soils are by no means free from other silicious minerals, especially feldspar and mica. When the sand is yellow or red in color, this fact is due to admixture of oxide or silicates of iron, and points with certainty to the presence of ferruginous minerals or their decomposition-products, which often give considera- ble fertility to the soil. Other varieties of sand are not uncommon. In New Jersey occur extensive deposits of so-called green sand, containing grains of a mineral, glauconite, to be hereafter noticed as a fertilizer. Lime sand, consisting of grains of carbonate of lime, is of frequent occurrence on the shores of coral islands or reefs. The term sandy-soil is obviously very indefinite, including nearly the extremes hed 154 HOW CROPS FEED. of fertility and barrenness, and covering a wide range of variety as regards composition. It is therefore qualified by various epithets, as coarse, fine, etc. Coarse, sandy soils are usually unprofitable, while fine, sandy soils are often valuable. ' Clayey Soils are those in which clay or impalpable mat- ters predominate. They are commonly characterized by extreme fineness of texture, and by great retentive power for water; this liquid finding passage through their pores with extreme slowness. When dried, they become crack- ed and rifted in every direction from the shrinking that takes place in this process, It should be distinctly understood that a soil may be clayey without being clay, i. e., it may have the external, physical properties of adhesiveness and impermeability to water which usually characterize clay, without containing those compounds (kaolinite and the like) which constitute clay in the true chemical sense. On the other hand it were possible to have a soil consist- ing chemically of clay, which should have the physical properties of sand; for kaolinite has been found in crys- tals soca of an inch in breadth, and destitute of all cohesive- ness or plasticity. Kaolinite in such a coarse form is, how- ever, extremely rare, and not likely to exist in the soil. Loamy Soils are those intermediate in character between sandy and clayey, and consist of mixtures of sand with clay, or of coarse with impalpable matters. They are free from the excessive tenacity of clay, as well as from the too great porosity of sand. The gradations between sandy and clayey soils are roughly expressed by such terms and distinctions as the following: KINDS OF SOILS. 155 Clay or impalpable matters. Sand. Heavy clay contains %—20° |, 10— 25°], Clay loam se 60—75 25— 40 Loam ss 40—60 40— 60 Sandy loam * 25—40 60— 75 Light sandy loam contains 10—25 W— 90 Sand “ 0—10 90—100 The percentage composition above given applies to the dry soil, and must be received with great allowance, since the transition from fine sand to impalpable matter not physically distinguishable from clay, is an impercep- tible one, and therefore not well admitting of nice discrim- ination. It is furthermore not to be doubted that the difference between a clayey soil and a loamy soil depends more on the form and intimacy of admixture of the ingredients, than upon their relative proportions, so that a loam may exist which contains less sand than some clayey soils. Calcareous or Lime Soils are those in which carbonate of lime isa predominating or characteristic ingredient. They are recognizable by effervescing vigorously when drenched with an acid. Strong vinegar answers for test- ing them. They are not uncommon in Europe, but in this country are comparatively rare. In the Northern and Middle States, calcareous soils scarcely occur to an extent worthy of mention. While lime soils exist containing '75°|, and more of car- bonate of lime, this ingredient is in general subordinate to sand and clay, and we have therefore calcareous sands, calcareous clays, or calcareous loams. Marls are mixtures of clay or clayey matters, with finely divided carbonate of lime, in something like equal propor- tions.* Peat or Swamp Muck is humus resulting from decayed * In New Jersey, green sand marl, or marl simply, is the name applied to the green sand employed as a fertilizer. Shell mari isa name designating nearly pure carbonate of lime found in swamps, é 156 HOW CROPS FEED. vegetable matter in bogs and marshes. A soil is peaty or mucky when containing vegetable remains that have suf- fered partial decay under water. Vegetable Mold is a soil containing much organic mat- ter that has decayed without submergence in water, either resulting from the leaves, etc., of forest trees, from the roots of grasses, or from the frequent application of large doses of strawy manures. Ochery or Ferruginous Soils are those containing much oxide or silicates of iron; they have a yellow, red, or brown color. Other divisions are current among practical men, as, for example, surface and subsoil, active and inert soil, tilth, and hard pan. These terms mostly explain tlem- selves, When, at the depth of four inches to one foot or more, the soil assumes a different color and texture, these distinctions have meaning. The surface soil, active soil, or tilth, is the portion that is wrought by the instruments of tillage—that which is moistened by the rains, warmed by the sun, permeated by the atmosphere, in which the plant extends its roots, gath- ers its soil-food, and which, by the decay of the subter- ranean organs of vegetation, acquires a content of humus. Subsoil— Where the soil originally had the same char- acters to a great depth, it often becomes modified down to a certain point, by the agencies just enumerated, in such a manner that the eye at once makes the distinction into surface soil and subsoil. In many cases, however, such distinctions are entirely arbitrary, the earth changing its appearance gradually or even remaining uniform toa considerable depth. Again, the surface soil may have a greater downward extent than the active soil, or the tilth may extend into the subsoil. Hard pan is the appropriate name of a dense, almost impenetrable, crust or stratum of ochery clay or com- PHYSICAL CHARACTERS OF THE SOIL. 157 pacted gravel, often underlying a fairly fruitful soil. It is the soil reverting to rock. The particles once disjointed are being cemented together again by the solutions of lime, iron, or alkali-silicates and humates that descend from the surface soil. Such a stratum often separates the sur- face soil from a deep gravel bed, and pe:t swamps thus exist in basins formed on the most porous soils by a thin layer of moor-bed-pan. With these general notions regarding the origin and characters of soils, we may proceed to a somewhat extend- ed notice of the properties of the soil as influencing fertil- ity. These divide themselves into physical characters— those which externally affect the growth of the plant; and chemical characters—those which provide it with food. CHAPTER IV. PHYSICAL CHARACTERS OF THE SOIL. The physical characters of the soil are those which con- cern the form and arrangement of its visible or palpable particles, and likewise include the relations of these parti- cles to each other, and to air and water, as well as to the forces of heat and gravitation, Of these physical char- acters we have to notice: 1, The Weight of Soils. 2. State of Division. 8. Absorbent Power for Vapor of Water, or Hygro- scopic Capacity. 4, Property of Condensing Gases. . Power of fixing Solid Matters from their Solutions, . Permeability to Liquid Water. Capillary Power. . Changes of Bulk by Drying, etc. . Adhesiveness. Relations to Heat. OIA 158 HOW CROPS FEED. In treating of the physical characters of the soil, the writer employs an essay on this subject, contributed by him to Vol. XVI of the Transactions of the N. Y. State Agricultural Society, and reproduced in altered form in a Lecture given at the Smithsonian Institution, Dec., 1859. § 1. THE WEIGHT OF SOILS. The Absolute Weight of Soils varies directly with their porosity, and is greater the more gravel and sand they contain. In the following Table is given the weight per cubic foot of various soils according to Schitbler, and like- wise (in round numbers) the weight per acre taken to the depth of one foot (=43,560 cubic feet). WEIGHT oF Sorts per cubic foot per acre to depth of one foot. . Dry silicious or calcareous sand......... about 110 Ibs. 4,792,000 Half sand and half clay......... ........ te 96 4,182,000 Common arable land*, ................4 * 80 to 90 ‘* 3,485,000 to 3,920,000 LGAVY? C1AVE co ad dideerersaiouiveaddai actawaietestars es % 3,267,000 Garden mold, rich in vegetable matter... “ "0 “ 3,049,000 PURI crccewndide Ged. medeiensannsanwe 30 to 50 ‘ 1,307,000 to 2,178,000 From the above figures we see that sandy soils, which are usually termed “light,” because they are worked most easily by the plow, are, in fact, the heaviest of all; while clayey land, which is called “heavy,” weighs less, bulk for bulk, than any other soils, save those in which vegeta- ble matter predominates. The resistance offered by soils in tillage is more the result of adhesiveness than of gravity. Sandy soils, though they contain in general a less percent- age of nutritive matters than clays, may really offer as good * The anthor is indebted to Prof. Seely, of Middlebury, Vt., for a sample of one-fourth of a cubic foot of Wheat Soil from South Onondaga, New York. The cubic foot of this soil, when dry, weighs 8644 lbs. The acre to depth of one foot weighs 3,768,000 lbs. This soil contains a large proportion of slaty gravel. A rich garden soil of silicious sand that had been heavily dunged, time out of mind, Boussingault found to weigh 81 Ibs. av. per cubic foot (1.3 kilos per liter), This would be per acre, one foot deep, 3,528,000 Ibs. PHYSICAL CHARACTERS OF THE SOII. 159 nourishment to crops as the latter, since they present one- half more absolute weight in a given space. Peat soils are light in both senses in which this word is used by agriculturists. The Specific Gravity of Soils is the weight of a given bulk compared with the same bulk of water. A cubic foot of water weighs 624 Ibs., but comparison of this num- ber with the numbers stated in the last table expressing the weights of a cubic foot of various soils does not give us the true specific gravity of the latter, for the reason that these weights are those of the matters of the soil contained in a cubic foot, but not of a cubic foot of these matters themselves exclusive of the air, occupying their innumerable interspaces. When we exclude the air and take account only of the soil, we find that all soils, except those containing very much humus, have nearly the same density. Schéne has recently determined with care the specific gravity of 14 soils, and the figures range from 2.53 to.2.71. The former density is that of a soil rich in humus, from Orenberg, Russia; the latter of a lime soil from Jena, The density of sandy and clayey soils free from humus is 2.65 to 2.69. (Bulletin de la Soc. Imp. des Naturalistes de Moscou, 1867, p. 404.) This agrees with the density of those mineralé which constitute the bulk of most soils, as seen from the following statement of their specific gravity, which is, for quartz, 2.65; feldspar, 2.62; mica, 2.'75-3.10; kaolinite, 2.60. Calcite has a sp. gr. of 2.72; hence the greater density of calcareous soils. § 2. STATE OF DIVISION OF THE SOIL AND ITS INFLUENCE ON FERTILITY. On the surface of a block of granite only a few lichens and mosses can exist; crush the block to a coarse powder and a more abundant vegetation can be supported on it; 160 HOW CRoOrs FEED. if it is reduced to a very fine dust and duly watered, even the cereal grains will grow and perfect fruit on it. Magnus (Jour. fiir prakt. Chem., L, '70) caused barley to germinate in pure feldspar, which was in one exper'- ment coarsely, in another finely, pulverized. In the coarse feldspar the plants grew to a height of 15 inches, furmed ears, and one of them ripened two perfectly formed seeds. In the fine feldspar the plants were very decidedly strong- er. One of them attained a height of 20 inches, and produced four seeds, It is true, as a general rule, that a!l fertile soils contain a large proportion of fine or impalpable matter. The soil of the “Ree Ree Bottom,” on the Scioto River, Ohio, re- markable for its extraordinary fertility, which has remained nearly undiminished for 60 years, though yielding heavy crops of wheat and maize without interruption, is char- acterized by the fineness of its particles. (D. A. Wells, Am. Jour. Sci., XTV, 11.) In what way the extreme di- vision of the particles of the soil is connected with its fer- tility is not difficult to understand. The food of the plant as existing in the soil must pass into solution either in the moisture of the soil, or in the acid juices of the roots of plants. In either case the rapidity of its solution is in direct ratio to the extent of surface which it exposes. The finer the particles, the more abundantly will the plant be supplied with its necessary nourishment. In the Scioto valley soils, the water which surrounds the roots of the crops and the root-fibrils themselves come in contact with such an extent of surface that they are able to dissolve the soil-ingredients in as large quantity and.as rapidly as the crop requires. In coarse-grained soils this is not so likely to be the case. Soluble matters (manures) must be applied to them by the farmer, or his crops refuse to yield handsomely. It is furthermore obvious, that, other things being equal, the finer the, articles of the soi! the more space the grows PHYSICAL CHARACTERS OF THE SOIL. 161 ing roots have in which to expand themselves, and the more abundantly are they able to present their absorbent surfaces to the supplies which the soil contains. The fine- ness of the particles may, however, be excessive. They may fit each other so closely as to interfere with the growth of the roots, or at least with the sprouting of the seed. The soil may be too compact. | It will presently appear that other very important prop- erties of the soil are more or less related to its state of mechanical division. § 3. ABSORPTION OF VAPOR OF WATER BY THE SOIL. The soil has a power of withdrawing vapor of water from the air and condensing the same in its pores. It is, in other words, hygroscopic. This property of a soil is of the utmost agricultural im- portance, because, Ist, it is connected with the permanent moisture which is necessary to vegetable existence; and, 2d, since the absorption of water-vapor to some degree determines the absorption of other vapors and gases. In the following table we have the results of a series of experiments carried out by Schiibler, for the purpose of determining the absorptive power of different kinds of earths and soils for vapor of water. The column of figures gives in thousandths the quantity of hygroscopic moisture absorbed in twenty-four hours by the previously dried soil from air confined over water, and hence nearly saturated with vapor. Quartz sand, COaTSC........ 0. cc ccc e cece cece ne eneneras 0 GYPSUM op cciscds «sings seals eases eee sente s cam aea ee ses 1 TAU SANG is:o.ir6:5 siaararesarsie aacvarsconas os pate due Vie erernie aia Vinwrelewetyes 3 Plough. lands: swesme saan seews tw, s vedesaaies vance sees 23 Clay soil, (60 per cent clay)........... cc cece eee ee eenees 28 Slaty Marl. edcs cas esreiewesd schacisseisnaacua odessa aie ares o 33 Loam.....ssessesesecseeees sraieisie wath bia terelete ssl alsjowia siaters «. 3D 162 HOW ‘CROPS FEED. Fine carbonate of lime..............00005 sceeeeeceecces OD Heavy clay soil, (80 per cent alas Rawraye o siarersicvejecstione axdiarans . 41 Garden mold, (7 per cent bumuS)..........0:eeeeeeceeee 52 Pure: Clays < cwss caus caer esas + eo ewevssemes wore tasers 49 Carbonate of magnesia (fine powder)...-.-.--eeeeeeeees 82 FLUMUS vise) stasavinot seuss soees tothe veces see senses 4 120 Davy found that one thousand parts of the soils named below, after having been dried at 212°, absorbed during one hour of exposure to the air, quantities of moisture as follows : Sterile soil of Bagshot heath. ...........0ee ee eeeeees eve sD Coarse Bawa: cc eseoxied ean VeeUs do Phe uliteavi aed Seas 8 Pineisand ices seg sescges sieves Gees vaeeeee: wieeeeu seeka © 11 Soil from Mersey, Essex......... 20005 seve ececesec cece 13 Very fertile alluvium, Somersetshire............5...0.006 16 Extremely fertile soil of Ormiston, East Lothian......... 18 An obvious practical result follows from the facts ex- pressed in the above tables, viz.: that sandy soils which have little attractive force for watery vapor, and are there- fore dry and arid, may be meliorated in this respect by admixture with clay, or better with humus, as is done by dressing with vegetable composts and by green manuring. The first table gives us proof that gypsum does not exert any beneficial action in consequence of directly attracting moisture. Humus, or decaying vegetable matter, it will be seen, surpasses every other ingredient of the soil in absorbing vapor of water. This is doubtless in some de- gree connected with its extraordinary porosity or amount of surface. How the extent of surface alone may act is made evident by comparing the absorbent power of car- bonate of lime in the two states of sand and of an im- palpable powder. The latter, it is seen, absorbed twelve times as much vapor of water as the former. Carbonate of magnesia stands next to humus, and it is worthy of note that it is a very light and fine powder. Finally, it is a matter of observation that “silica and lime in the form of coarse sand make the soil in which they predominate so dry and hot that vegetation perishes PHYSICAL CHARACTERS OF THE SOIL. 163 from want of moisture; when, however, they occur as fine dust, they form too wet a soil, in which plants suffer from the opposite cause.”—(Hamm’s Landuwirthschaft.) Every body has a definite power of condensing moist- ure upon its surface or in its pores. Even glass, though presenting to the eye a perfectly clean and dry surface, is coated with a film of moisture. Ifa piece of glass be weighed on avery delicate balance, and then be wiped with a clean cloth, it will be found to weigh perceptibly less than before. Exposed to the air for an hour or more, it recovers the weight which it had lost by wiping; this loss was water. (Stas. Magnus.) The surface of the glass is thus proved to exert towards vapor of water an adhesive attraction. Certain compounds familiar to the chemist attract water with great avidity and toa large extent. Oil of vitriol, phosphoric acid, and chloride of calcium, gain weight rap- idly when exposed to moist air, or when placed contiguous to other substances which are impregnated with moisture. For this reason these compounds are employed for pur- poses of drying. Air, for example, is perfectly freed from vapor of water by lowly traversing a tube containing lumps of dried chloride of calcium, or phosphoric acid, or by bubbling repeatedly through oil of vitriol eontnined in a suitable apparatus. Solid substances, which, like chloride of calcium, carbon- ate of potash, etc., gather water from the air to such an extent ax to become liquid, are said to deliquesce or to be deliquescent. Certain compounds, such as urea, the char- _ acteristic ingredient of human urine, deliquesce in moist air and dry away again in a warm atmosphere. Allusion has been made in “How Crops Grow,” p. 55, to the hygroscopic water of vegetation, which furnishes another striking illustration of the condensation of water in porous bodies. The absorption of vapor of water by adild bodies is not 164 HOW CROPS FEED. only dependent on the nature of the substance and its amount of surface, but is likewise influenced by externd conditions. The rapidity of absorption depends upon the amount of vapor present or accessible, and is greatest in moist air. The amount of absorption is determined solely by tem- perature, as Knop has recently shown, and is unaffected by the relative abundance of vapor: i. e., at a given tem- perature a dry soil will.absorb the same amount of moist- ure from the air, no matter whether the latter be slightly or heavily impregnated with vapor, but will do this the more speedily the more moist the surrounding atmosphere happens to be. In virtue of this hygroscopic character, the soil which becomes dry superficially during a hot day gathers water from the atmosphere in the cooler night time, even when no rain or dew is deposited upon it. In illustration of the influence of temperature on tha quantity of water absorbed, as vapor, by the soil, we give Knop’s observations on a sandy soil from Moeckern, Sax- ony: 1,000 parts of this soil absorbed At 55° F. 13 parts of Hygreesopie mater, oc 66° iT Th 9 oe oe (34 "7° (73 10.2 oe (74 (74 “ (<4 88° cc 8.7 (74 “ ce “ Knop calculates on the basis of his numerous observa- tions that hair and wool, which are more hygroscopic than most vegetable and mineral substances, if allowed to ab sorb what moisture they are capable of taking up, contain the following quantities of water, per cent, at the temper- atures named : At 87° Fah., ‘7.7 per cent. (73 55° ‘19 15.5 “ [T 177 82° 74 19.3 “ “ PHYSICAL CHARACTERS OF THE SOIL. 165 Silk is sold in Europe by weight with suitable allowance for hygroscopic moisture, its variable content of which is carefully determined by experiment in each important transaction. It is plain that the circumstances of sale may affect the weight of wool to 10 or more per cent, § 4, CONDENSATION OF GASES BY THE SOIL. Adhesion.—In the fact that soils and porous bodies gen- erally have a physical absorbing power for the vapor of water, we have an illustration of a principle of very wide application, viz., The surfuces of liquid and solid matter attract the particles of other kinds of matter. This force of adhesion, as it is termed, when it acts up- on gaseous bodies, overcomes to a greater or less degree their expansive tendency, and coerces them into a smaller space—condenses them. Absorbent Power of Charcoal, ete.—Charcoal serves to illustrate this fact, and some of its most curious as well as useful properties depend upon this kind of physical peculiarity. Charcoal is prepared from wood, itself ex- tremely porous,* by expelling the volatile constituents, whereby the porosity is increased to an enormous extent, When charcoal is kept in a damp cellar, it condenses so much vapor of water in its pores that it becomes difficult ‘to set on fire. It may even take up one-fourth its own weight. When exposed to various gases and volatile matters, it absorbs them in the same manner, though to very unequal extent. De Saussure was the first to measure the absorbing power of charcoal for gases. In his experiments, boxwood charcoal was heated to redness and plunged under mer- * Mitscherlich has calculated that the cells of a cubic inch of boxwood have no less than 78 sauare feet of surface. 166 HOW CROPS FEED. cury to cool. Then introduced into the various gases named below, it absorbed as many times its bulk of them, as are designated by the subjoined figures: AMMONIW: soared cocrene cand 90 Hydrochloric acid....... 85 Sulphurous acid......... 65 Hydrosulphuric acid..... 55 Protoxide of nitrogen....40 Carbonic acid............ 35 OXY SCN ss se eaey cede FeesGs 94% Carbonic oxide.......... 914 Hydrogen............0006 134 Nitrogen; cisc0is seguats sees V6 According to De Saussure, the absorption was complete in 24 hours, except in case of oxygen, where it continued for a long time, though with decreasing energy. The oxygen thus condensed in the charcoal combined with the carbon of the latter, forming carbonic acid. Stenhouse more lately has experimented in the same di- rection. From these researches we learn that the power in question is exerted towards different gases with very unequal effect, and that different kinds of charcoal exert very different condensing power. Stenhouse found that one gramme of dry charcoal ab- sorbed of several gases the number of cubic centimeters given below. Kind of Charcoal. Name of Gas. Wood. | Peat. | Animal. AMMO siece ss go cciase os sac ands ae eas eeiz eae 98.5 96.0 43.5 Hydrochloric acid.......... 2.66. cesses cee enee 45.0 60.0 Hydrosulphuric acid....... cece eee eee ewes 30.0 28.5 90 Suiphurois aCidss cee cecases ci pexweeypieee sence 82.5 27.5 17.5 Cay0010 ROG success sates Hx EV RRe ded cew wen 14.0 10.0 5.0 ORY CCD einaseieis seca jest dinid oacasadeor he. eedisiciaie shea arsiemnaiainie 0.8 0.6 0.5 The absorption or solution of gases in water, alcohol, and other liquids, is analogous to this condensation, and those gases which are most condensed by charcoal are in general, though not invariably, those which dissolve most copiously in liquids, (ammonia, hydrochloric acid). Condensation of Gases by the Soil.—Reichardt and Blumtritt have recently made a minute study of the kind and amount of gases that are condensed in the pores of various solid substances, including soils and some of their PHYSICAL CHARACTERS OF THE SOIL, 167 ingredients. (Jour. fur prakt. Chem., Bd. 98, p. 476.) Their results relate chiefly to these substances as ordinarily occurring exposed to the atmosphere, and therefore more or less moist. The following Table includes the more im- portant data obtained by subjecting the substances to a temperature of 284° F., and measuring and analyzing the gas thus expelled. 100 Grams 10 Yols, 100 Vols. of Gas contained : ae “vols. Nitro- Ozxy- Carbon- Car-- Substance » in Cc. gas. gen. gen. ic acid. bonic i oxide. Charcoal, air-dry, 164 _ 100 0 0 0 “ moistened and dried again, 140 59 86 2 9 3 Peat, 162 _- 44 5 51 0 Garden soil, moist, 14 20 64 3 24 9 “air-dry, 33 B4 65 2 33 0 Hydrated oxide of iron, air-dry, 38% 309 26 4 70 0 Oxide of iron, ignited, 39 52 83 13 4 0 Hydrated alumina, air-dry, 69 82 41 0 59 —_ Alumina, dried at 212°, 11 14 83 17 0 _ Clay, 383 = 6 1 uw — ‘© long exposed to air, 26 39 vA) 5 25 _ ** moistened, 29 35 60 6 3 _ River silt, air-dry, 40 48 68 0 18 14 u “moistened, 2A 29 67 0 81 2 again dried, 26 30 67 9 16 7 Carbonate of lime (whiting,) 1864, 43 52 100 0 0 _ ae eo ee 1865, 39 48 74 16 10 - ba «ss precipitated, 1864, 65 - 81 19 0 _ * fe oe ee 1865,- 51 52 vi 15 8 - Carbonate of magnesia, 729 125 64 q 29 _ Gypsum, pulverized, 1% - 81 19 0 _ From these figures we gather: 1. The gaseous mixture which is contained in the pores of solid substances rarely has the composition of the at- - mosphere. In but two instances, viz., with gypsum and precipitated carbonate of lime, were only oxygen and ni- trogen absorbed in proportions closely approaching those of the atmosphere. 2. Nitrogen appears to be nearly always absorbed in greater proportion than oxygen, and is greatly condensed in some cases, as by peat, hydrated oxide of iron, and car- bonate of magnesia. 168 HOW CROPS FEED, 8. Oxygen is often nearly or quite wanting, as in char. coal, oxide of iron, alumina, river silt, and whiting. 4, Carbonic acid, thongh sometimes wanting entirely, ‘is usually abundant in the absorbed gases, 5. In the pores of charcoal and of soils containing de- caying organic matters, carbonic acid is often partially re- placed by carbonic oxide. The experiments, however, do not furnish proof that this substance is not formed under the influence of the high temperature employed (284° F.) in expelling the gases, rather than by incomplete oxidation of organic matters at ordinary temperatures. 6. A substance, when moist, absorbs less gas than when’ dry. Inaccordance with this observation, De Saussure no- ticed that dry charcoal saturated with various gases evolv- ed a good share of them when moistened with water. Ground (and burnt ?) coffee, as Babinet has lately stated, evolves so much gas when drenched with water as to burst a bottle in which it is confined. The extremely variable figures obtained by Blumtritt when operating with the same substance (the figures given in the table are averages of two or tliree usually discordant results), result from the general fact that the proportion in which a number of gases are present in a mixture, in- fluences the proportion of the individual gases absorbed. Thus while charcoal or soil will absorb a large amount of ammonia from the pure gas, it will take up but traces of this substance from the atmosphere of which ammonia is but an infinitesimal ingredient. So, too, charcoal or soil saturated with ammonia by ex- posure to the unmixed gas, loses nearly all of it by stand- ing in the air for some time. This is due to the fact that gases attract each other, and the composition of the gas condensed in a porous body varies perpetually with the variations of composition in the surrounding atmosphere. It is especially the water-gas (vapor of water) which is a fluctuating ingredient of the atmosphere, and one which PHYSICAL CHARACTERS OF THE SOIL. 169 is absorbed by porous bodies in the largest quantity. This not only displaces other gases from their adhesion to solid surfaces, but by its own attractions modifies these adhesions. Reichardt and Blumtritt take no account of water-gas, except in the few experiments where the substances were purposely moistened. In all their trials, however, moist- ure was present, and had its quantity been estimated, doubtless its influence on the extent and kind of absorp- tion would have been strikingly evident throughout. Ammonia and carbonate of ammonia in the gascous form are absorbed from the air by the dry soil, to a less degree than by a soil that is moist, as will be noticed fully hereafter. Chemical Action induced by Adhesion.—This physical property often leads to remarkable chemical effects; in other words, adhesion exalts or brings into play the force of affinity. When charcoal absorbs those emanations from putrefying animal matters which we scarcely know, save by their intolerable odor and poisonous influence, it causes at the same time their rapid and complete oxida- tion; and hence a piece of tainted meat is sweetened by covering it with a thin layer of powdered charcoal. As Stenhouse has shown, the carcass of a small animal may be kept in a living-room during the hottest weather with- out giving off any putrid odor, provided it be surrounded on all sides by a layer of powdered charcoal an inch or more thick. Thus circumstanced, it simply smells of am- monia, and its destructible parts are resolved directly in- to water, carbonic acid, free nitrogen, and ammonia, pre- cisely as if they were burned in a furnace, and without the appearance of any of the effluvium that ordinarily arises from decaying flesh. The metal platinum exhibits a remarkable condensing power, which is manifest even with the polished surface of foil or wire; but is most striking when the metal is < 8 170 HOW CROPS FEED. brought to the condition of sponge, a form it assumes when certain of its compounds (e. g. ammonia-chloride of platinum) are decomposed by heat, or to the more finely divided state of platinum black. The latter is capable of condensing from 100 to 250 times its volume of oxygen, according to its mode of preparation (its porosity ?); and for this reason it possesses intense oxidizing power, so that, for example, when it is brought into a mixture of oxygen and hydrogen, it causes them to unite explosively. RELATIONS OF THE SOIL TO HEAT. 191 Schiibler made observations on the temperatures at- tained by various dry soils exposed to the sun’s rays, according as their surfaces were blackened by a thin sprinkling of lamp-black or whitened by magnesia. His results are given in columns 1 and 2 of the following table (vide p. 196,) from which it is seen that the dark surface was warmed 13° to 14° more than the white. We like- wise notice that the character of the very surface deter- mines the degree of warmth, for, under a sprinkling of lamp-black or magnesia, all the soils experimented with became as good as identical in their absorbing power for the sun’s heat. The observations of Malaguti and Durocher prove that the peculiar temperature of the soil is not always so closely related to color as to other qualities. They studied the thermometric characters of the following soils, viz.: Garden earth of dark gray color,—a mixture of sand and gravel with about five per cent of humus; a grayish- white quartz sand; a grayish-brown granite sand; a fine light-gray clay (pipe clay); a yellow sandy clay; and, finally, four lime soils of different physical qualities. It was found that when the exposure was alike, the dark-gray granite sand became the warmest, and next to this the grayish-white quartz sand. The latter, notwith- standing its lighter color, often acquired a higher temper- ature at a depth of four inches than the former, a fact to be ascribed to its better conducting power. The black soils never became so warm as the two just mentioned, After the black soils, the others came in the following or- ‘der: garden soil; yellow sandy clay; pipe clay; lime soils having crystalline grains; and, lastly, a pulverulent chalk soil. To show what different degrees of warmth soils may acquire, under the same circumstances, the following max- imum temperatures may be adduced: At noon of a July day, when the temperature of the air was 90°, a thermom- 192 HOW CROPS FEED. eter placed at a depth of a little more than one inch, gave these results: AD Quariz Sand cacaec cane dens meer ediasease + seit eRe In crystalline lime soil, In garden soil... .... ese c cece reece In yellow sandy clay... c. seavvvswsend: doe ne pequaeniiwas 100° In: Pipe Clay ixsacccececsewiceeaesdtak teats tera cawhsees 94° Ent Challe gol scsssisis sisls: seniors eiaievan Hoey e deeeais's ana wees oes 8z° Here we observe a difference of nearly 40° in the noon- day temperature of the coarse quartz and the chalk soil. Malaguti and Durocher found that the temperature of the garden soil, just below the surface, was, on the average of day and night together, 6° Fahrenheit higher than that of the air, but that this higher temperature diminished at a greater depth. A thermometer buried four inches indi- cated a mean temperature only 3° above that of the at- mosphere. The experimenters do not mention the influence of wa- ter in affecting these results; they do not state the degree of dryness of these soils. It will be seen, however, that the warmest soils are those that retain least water, and doubtless something of the slowness with which the fine soils increase in warmth is connected with the fact that they retain much water, which, in evaporating, appropri- ates and renders latent a large quantity of heat. The chalk soil is seen to be the coolest of all, its tem- perature in these observations being three degrees lower than that of the atmosphere at noonday. In hot climates this coolness is sometimes of great advantage, as appears to happen in Spain, near. Cadiz, where the Sherry vine- yards flourish. “The Don said the Sherry wine district was very small, not more than twelve miles square. The Sherry grape grew only on certain low, chalky hills, where the earth being light-colored, is not so much burnt; did not chap and split so much by the sun as darker and heavier soils do. A mile beyond these hills the grape de- teriorates,”—(Dickens’ Household Words, Nov, 13, 1858.) RELATIONS OF THE SOIL TO HEAT, 193 In Explanation of these observations we must recall to mind the fact that all bodies are capable of absorbing and radiating as well as reflecting heat. These properties, a!- though never dissociated from color, are not necessarily dependent upon it. They chiefly depend upon the char- acter of the surface of bodies. Smooth, polished surfaces absorb and radiate heat least readily; they reflect it most! perfectly. Radiation and absorption are opposed to each other, and the power of any body to radiate, is precisely equal to its faculty of absorbing heat. . It must be understood, however, that bodies may differ in their power of absorbing or radiating heat of different degrees of intensity. Lamp-black absorbs and radiates heat of all intensities in the same degree. White-lead absorbs heat of low intensity (such as radiates from a ves- sel filled with boiling water) as fully as lamp-black, but of the intense heat of a lamp it absorbs only about one- half as much. Snow seems to resemble white-lead in this respect. Ifa black cloth or black paper be spread on the surface of snow, upon which the sun is shining, it will melt much faster under the cloth than elsewhere, and this, too, if the cloth be not in contact with, but suspended above, the snow. In our latitude every one has had op- portunity to observe that snow thaws most rapidly when covered by or lying on black earth, The people of Cham- ouni, in the Swiss Alps, strew the surface of their fields with black-slate powder to hasten the melting of the snow. The reason is that snow absorbs heat of low intensity with greatest facility. The heat of the sun is converted from a high toa low intensity by being absorbed and then radiated by the black material. But it is not color that determines this difference of absorptive power, for indigo and Prussian blue, though of nearly the same color, have very different absorptive powers. So far, however, as our observations extend, it appears that, usually, dark-colored soils absorb heat most rapidly, and that the sun’s rays 9 194 IIOW CROPS FEED. have least effect on light-colored soils. (See the table on p. 196.) The Rapidity of Change of Temperature independently of color or moisture has been determined on a number of soils by Schiibler. A given volume of dry soil was heat- ed to 145°, a thermometer was placed in it, and the time was observed which it required to cool down to 70°, the temperature of the atmosphere being 61°. The subjoined table gives his results. In one column are stated the times of cooling, in another the relative power of retaining heat or capacity for heat, that of lime sand being assumed as 100. HUMCISAN oo:s.csds sama wceancasdee ands 83 hours 80 min...... 100 Quarts GANA: « sascoenass Aeees esse ee Be A Oe ede a vial 95.6 POUheL 6 2C1IY siacsied Nea tanvees avniniess Ae ee) Oe 6.9 APY URN nee one ea dgia Bea ha ee eS Bi SE BE ane weet 3.8 TAT TOs cao asd etakedinwanceuaaws Br BEY 280) is dias ae 71.8 Chey lew Lit esas cake densi coeveues DQ OT Mesias et 70.1 Cav Clay: cacihins stones sean saiss ee eer en 68.4 Pureeray clays. ees caove case caonsedsix TDS aaseterssareld 66.7 Garden earth... eee cece eee eee eee Dior 88! NG Sse adensd 64.8 Fine carb. limescses scenes ecdes sauat eID ys ewenad 61.3 HUB cec3o se bSiemdiciee de eioecie scien LOS Bo Be wenus 49.0 MAGN eS 10. scie cs wee i syris eis ow oe'e’ steers Be OE Re Eo eeisncle 38.0 It is seen that the sandy soils cool most slowly, then follow clays and heavy soils, and lastly comes humus. The order of cooling above given is in all respects identical with that of warming, provided the circumstances are alike. In other words these soils, containing no moist- ure, or but little, and exposed to heat of low intensity, would be raised through a given range of temperature in the same relative times that they fall through a given number of degrees. It is to be particularly noticed that dark humus and white magnesia are very closely alike in their rate of cooling, and cool rapidly; while white lime sand stands at the op- posite extreme, requiring twice as long to cool to the same extent. These facts strikingly illustrate the great differ. RELATIONS OF THE SOIL TO HEAT. 195 ence between the absorption of radiant heat of low inten- sity or its communication by conduction on one hand, and that of high intensity like the heat of the sun on the other. Retention of Heat.—Other circumstances being equal, the power of retaining heat (slowness of cooling) is the greater, the greater the weight of a given bulk of soil, i. e., the larger and denscr its particles. A soil covered with gravel cools much more slowly than a sandy surface, and the heat which it collects during a sunny day it carries farther into the night; hence gravelly soils are adapted for such crops as are liable to fail of rip- ening in cool situations, especially grapes, as has been abundantly observed in practice. Color is without influence on the loss of heat from the soil by radiation, because the heat is of low intensity. The porosity or roughness of the surface (extent of sur- face) determines cooling from this cause. Dew, which is deposited as the result of cooling by radiation of heat into the sky, forms abundantly on grass and growing vege- tation, and on vegetable mould, but is more rarely met with on coarse sand or gravel. Influence of Moisture on the Temperature of the Soil. — All soils, when thoroughly wet, seem to be nearly alike in their power of absorbing and retaining warmth. This is due to the fact that the capacity of water for heat is much greater than that of the soil. We have seen that lime sand and quartz sand are the slowest of all the in- gredients of soils to suffer changes of temperature when exposed to a given source of heat. (See table, p. 194.) Now, water is nine times slower than quartz in being affected by changes of temperature, and as the entire sur- face of the wet soil is water, which is, besides, a nearly perfect non-conductor of heat, we can understand that ex- ternal warmth must affect it slowly. Again, the immense consumption of heat in the forma- tion of vapor (see note, p. 188) must prevent the wet soil 196 HOW CROPS FEED. from ever acquiring the temperature it shortly attains when dry. From this cause the difference in temperature between dry and wet soil may often amount to from 10° to 18°. On this point, again, Schtibler furnishes us with the re- sults of his experiments. Columns 4 and 5 in the table below give the temperatures which the thermometer at- tained when its bulb was immersed in various soils, both wet and dry, each having its natural color, (Columns 1 and 2 are referred to on p. 191.) 1 2 3 4 5 6 Surface. Surface. Whit-|Black- Differ- Differ- ened. ened. | ence. Wet. | Dry. ence. Magnesia, pure white................ 108.7°} 121.3°) 12.6° | 95.2°} 108.77) 13.5° Fine carbonate of lime, white......... 109.2°| 122.9°] 13.7° | 96.1°| 109.4°| 13.3° Gypsum, bright white-gray............ 110.3°| 124.3°| 14.0° | 97.3°] 110.5°] 13.2° Plow' land, @rayi: 5 icceaunwis deci ve 107.6°} 122.0°| 14.4° | 97.7°| 111.7°| 14.0° Sandy clay, yellowish. ............. 0. 108.3°| 121.6°) 13.3° | 93.2°] 111.4°) 13.2° Quartz sand, bright yellowish-gray... [109.9°| 123.6°; 13.7° | 99.1°| 112.6°| 13.5° Loam, yellowish, .............2-2 0 ee 107.8°} 121.1°} 13.3° | 99.1°/ 112.1°) 13.0° Lime sand, whitish-gray.,............ 109.9°} 124.0°| 14.1° | 99.3°} 112.1°] 12.8° Heavy clay soil, yellowish-gray........ '107.4°| 120.4°} 13.0° | 99.37) 112.8°| 13.0° Pure clay, bluish-gray................. 106.3°) 120.0°} 13.7° | 99.5°] 113.07} 13.5° Garden mould, blackish-gray.......... |108.3°| 122.5°) 14.2° | 99.5°| 113.5°| 14.0° Slaty marl, brownish-red............. /108.3°] 123.4°) 15.1° }101.8°] 115.3°| 13.5° Humns, brownish-black............... 1108 .5°! 120.9°! 12.4° (103.6°| 117.3°| 13.7° We note that the difference in favor of the dry earth is almost uniformly 18° to 14°. This difference is the same as observed between the whitened and blackened speci- mens of the same soils, (Column 3.) We observe, however, that the wet soil in no case be- comes as warm as the same soil whitened. We notice further that of the wet soils, the dark-colored ones, humus and marl, are most highly heated, Further it is seen that coarse lime sand (carbonate of lime) acquires 3° higher temperature than fine carbonate of lime, both wet, prob- ably because evaporation proceeded more slowly from the coarse than from the fine materials. Again it is plain on comparing columns 1, 2, and 5, that the gray to yellowish brown and black colors of all the soils, save the first three, assist the elevation of temperature, which rises nearly RELATIONS OF THE SOIL TO HEAT. 197 with the deepening of the color, until in case of humus it lacks but a few degrees of reaching the warmth of a sur- face of lamp-black. According to the observations of Dickinson, made at . Abbot’s Hill, Hertfordshire, England, and continued through eight years, 90 per cent of the water falling be- tween April lst and October Ist evaporates from the sur- face of the soil, only 10 per cent finding its way into drains laid three and four feet deep. The total quantity of water that fell during this time amounted to about 2,900,000 Ibs. per acre; of this more than 2,600,000 evap- orated from the surface. It has been calculated that to evaporate artificially this enormous mass of water, more than seventy-five tons of coal must be consumed. Thorough draining, by loosening the soil and causing a rapid removal from below of the surplus water, has a most decided influence, especially in spring time, in warming the soil and bringing it into a suitable condition for the support of vegetation. It is plain, then, that even if we knew with accuracy what are the physical characters of a surface soil, and if we were able to estimate correctly the influence of these characters on its fertility, still we must investigate those circumstances which affect its wetness or dryness, whether they be an impervious subsoil, or springs coming to the surface, or the amount and frequency of rain-falls, taken in connection with other meteorological causes. We can- not decide that a clay is too wet or a sand too dry, until we know its situation and the climate it is subjected to. The great deserts of the globe do not owe their barren- ness to necessary .poverty of soil, but to meteorological influences—to the continued prevalence of parching winds, and the absence of mountains, to condense the atmospheric water and establish a system of rivers and streams. This is not the place to enter into a discussion of the causes that may determine or modify climate; but to illustrate 198 HOW CROPS FEED. the effect that may be produced by means within human control, it may be stated that previous to the year 1821, the French district Proveuce was a fertile and well-water- ed region. In 1822, the olive trees which were largely cultivated there were injured by frost, and the inhabitants began to cut them up root and branch. This amounted to clearing off a forest, and, in consequence, the streams dried up, and the productiveness of the country was seri- ously diminished. The Angle at which the Sun’s Rays Strike a Soil is of great influence on its temperature. The more this ap- proaches a right angle the greater the heating effect. In the latitude of England the sun’s heat acts most power- fully on surfaces having a southern exposure, and which are inclined at an angle of 25° and 30°. The best vine- yards of the Rhine and Neckar are also on hill-sides, so situated. Iu Lapland and Spitzbergen the southern side of hills may be seen covered with vegetation, while lasting or even perpetual snow lies on their northern in- clinations. The Influence of a Wall or other Reflecting Surface upon the warmth of a soil lying to the south of it was observed in the case of garden soil by Malaguti and Durocher. The highest temperature indicated by a ther- mometer placed in this soil at a distance of six inches from the wall, during a series of observations lasting seven days (April, 1852), was 32° Fahrenheit higher at the surface, and 18° higher at a depth of four inches than in the same soil on the north side of the wall. The average temper- ature of the former during this time was 8° higher than that of the latter. In another trial in March the difference in average temperature between the southern and north- ern exposures was nearly double this amount in favor of the former. As is well known, fruits which refuse to ripen in cold. elimates under ordinary conditions of exposure may attain. THE FREE WATER OF THE SOIL. 199 perfection when trained against the sunny side of a wall. It is thus that in the north of England pears and plums are raised in the most unfavorable seasons, and that the vineyards of Fontainebleau produce such delicious Chas- selas grapes for the Paris market, the vines being trained against walls on the Thomery system. In the Rhine district grape vines are kept low and as near the soil as possible, so that the heat of the sun may be reflected back upon them from the ground, and the ripen- ing is then carried through the nights by the heat radiated from the earth.—(Journal Highland and Agricultural Society, July, 1858, p. 347.) Vegetation.— Malaguti and Durocher also studied the effect of a sod on the temperature of the soil. They ob- served that it hindered the warming of the soil, and in- deed to about the same extent as a layer of earth of three inches depth. Thus a thermometer four inches deep in green-sward acquires the same temperature as one seven inches deep in the same soil not grassed. CHAPTER V. THE SOIL AS A SOURCE OF FOOD TO CROPS.— INGREDIENTS WHOSE ELEMENTS ARE OF ATMOSPHERIC ORIGIN. § 1. THE FREE WATER OF THE SOIL IN ITS RELATIONS TO VEGETABLE NUTRITION. Water may exist free in the soil in three conditions, which we designate respectively hydrostatic, capillary, and hygroscopic. , Hydrostatic or Flowing * Water is water visible as * I. e., capable of flowing. 2 200 HOW CROPS FEED, such to the eye, and free to obey the laws of gravity and motion. When the soil is saturated by rains, melting snows, or by overflow of streams, its pores contain hy- drostatic water, which sooner or later sinks away into the subsoil or escapes into drains, streams, or lower situations. Bottom Water is permanent hydrostatic water, reached nearly always in excavating deep soils, The surface of water in a well corresponds with, or is somewhat below, the upper limit of bottom water. Jt usually fluctuates in level, rising nearer the surface of the soil ia wet seasons, and receding during drought. In general, agricultural plants are injured if their roots be immersed for any length of time in hydrostatic water; and soils in which bottom water is found at a little depth during the season of growth are unprofitable for culture. If this depth be but a few inches, we have a bog, swamp, or swale. If it is one and a half to three feet, and the surface soil be light, gravelly, or open, so as to admit of rapid evaporation, some plants, especially grasses, may flourish. If at a constant depth of four to eight feet under a gravelly or light loamy soil, it is favorable to crops as an abundant source of water. Heavy clays, which retain hydrostatic watcr for a long time, being but little permeable, are for the same reasons unfavorable to most crops, unless artificial provision be made for removing the excess. Rice, as we have seen, (H. C. G., p. 252), is a plant which grows well with its roots situated in water. Hen- rici’s experiment with the raspberry (H. C. G., p. 254), and the frequent finding of roots of clover, turnips, etc., in cisterns or drain pipes, indicate that many or all agricultural plants may send down roots into the bottom water for the purpose of gathering a sufficient supply of j this necessary liquid. Capillary Water is that which is held in the fine pores of the soil by the surface attraction of its particles, as oil THE FREE WATER OF THE SOIL. 201 is held in the wick of a lamp. The adhesion of the water to the particles of earth suspends the flow of the liquid, and it is no longer subject to the laws of hydrostatics. Capillary water is usually designated as moisture, though a soil saturated with capillary water would be, in most cases, wet. The capillary power of various soils has al- ready been noticed, and is for coarse sands 25°|,; for loams and clays, 40 to '70°|,; for garden mould and humus, much higher, 90 to 300 °|,. (See p. 180.) For a certain distance above bottom water, the soil is saturated with capillary water, and this distance is the greater, the greater the capillary power of the soil, i. e., the finer its pores. Capillary water is not visible as a distinct liquid layer on or between the particles of soil, but is still recogniza- ble by the eye. Even in the driest weather and in the driest sand (that is, when not shut off from bottom water by too great distance or an intervening gravelly subsoil) it may be found one or a few inches below the surface where the soil Jooks moist—has a darker shade of color. Hygroscopic Water is that which is not perceptible to the senses, but is appreciated by loss or gain of weight in the body which acquires or is deprived of it. (H.C. G., p. 54.) The loss experienced by an air-dry soil when kept for some hours at, or slightly above, the boiling point (212° F.,) expresses its content of hygroscopic water. This quantity is variable according to the character of the soil, and is constantly varying with the temperature; in- creasing during the night when it is collected from the at- mosphere, and diminishing during the day when it returns in part to the air. (See p. 164.) The amount of hygros- copic water ranges from 0.5 to 10 or more per cent. Value of these Distinctions.—These distinctions be- tween hydrostatic, capillary, and hygroscopic water, are nothing absolute, but rather those of degree. Hygroscopic water is capillary in all respects, save that its quantity is 202 ; HOW CROPS FEED. small, and its adhesion to the particles of soil more firm for that reason. Again, no precise boundary can always be drawn between capillary and hydrostatic water, espe- cially in soil having fine pores. The terms are neverthe- less useful in conveying an idea of the degrees of wet- ness or moisture in the soil. Roots Absorb Capillary or Hygroscopic Water.—It is from capillary or hygroscopic water that the roots of most agricultural plants chiefly draw a supply of this liquid, though not infrequently they send roots into wells and drains. The physical characters of soils that have been already considered suffice to explain how the earth acquires this water; it here remains to notice how the plant is re- Jated to it. As we have seen (pp. 35-38), the aerial organs appear incapable of taking up either vapor-or liquid water from the air to much extent, and even roots continually exhale vapor without absorbing any, or at least without being able to make up the loss which they continually suffer. Transpiration of Water through Plants,—It is a most familiar fact that water constantly exhales from the surface of the plant. The amount of this exhalation is often very great. Hales, the earliest observer of this phenomenon, found that a sunflower whose foliage had 39 square feet of surface, gave off in 24 hours 8 lbs. of water. A cab- bage, whose surface of leaves equaled 19 square feet, ex- haled in the same time very nearly as much, Schleiden found the loss of water from a square foot of grass-sod to be more than 14 Ibs. in 24 hours. Schiibler states that in the same time 1 square foot of pasture-grass exhaled nearly 5} lbs. of water. In one of Knop’s more recent experiments, (Vs. St, VI, 239), a dwarf bean exhaled during 23 days, in September and October, 13 times its weight of water. In another trial a maize-plant transpir- ed 36 times its weight of water, from May 22d to Sept. 4th. According to Knop, a grass-plant will exhale its own THE FREE WATER OF THE SOIL. 203 weight of water in 24 hours of hot and dry ‘summer weather. The water exhaled from the leaves must be constantly supplied by absorption at the roots, else the foliage soon becomes flabby or wilts, and finally dies. Except so far as water is actually formed or fixed within the plant, its absorption at the roots, its passage through the tissues, and its exhalation from the foliage, are nearly equal in quantity and mutually dependent during the healthy: ex- istence of vegetation. Circumstances that Influence Transpiration.—a. The structure of the leaf, including the character of the epi- dermis, and the number of stomata as they affect exhala- tion, has been considered in “How Crops Grow,” (pp. 286-8). 6. The physical conditions which facilitate evapora- tion increase the amount of water that passes through the plant. Exhalation of water-vapor proceeds most: rapidly in a hot, dry, windy summer day. It is nearly checked when the air is saturated with moisture, and va- ries through a wide. range according to the conditions just named, ce. The oxidations that are constanily going on within the plant may, under certain conditions, acquire sufficient intensity to develop a perceptible amount of heat and cause the vaporization of water: It has been repeatedly noticed that the process of flowering is accompanied by considerable elevation of temperature, (p. 24). In general, however, the opposite process of deoxidation preponder- ates with the plant, and this must occasion a reduction of temperature. These interior changes can have no apprecia- ble influence upon transpiration as compared with those that depend upon external causes. Sachs found in some of his experiments (p. 36) that exhalation took place from plants confined in a limited space over water. Sachs be- 204 HOW CROPS FEED. lieved that the air surrounding the plants in these experi- ments was saturated with vapor of water, and concluded that heat was developed within the plant, which caused vaporization. More recently, Boehm (Sitzungsberichte der Wiener Akad., XLVIII, 15) has made probable that the air was not fully or constantly saturated with moist- ure in these experiments, and by taking greater precau- tions has arrived at the conclusion that transpiration abso- lutely ceases in air saturated with aqueous vapor. d. The condition of the tissues of the plant, as depend- ent upon their age and vegetative activity, likewise has a marked effect on transpiration. Lawes* and Knop both found that young plants lose more water than older ones. This is due to the diminished power of mature foliage to imbibe and contain water, its cells becoming choked up with growth and inactive. 2 é. Lhe character of the medium in which the roots are situated also remarkably influences the rate of transpira- tion. This fact, first observed by Mr. Lawes, in 1850, Joe. cit., was more distinctly brought out by Dr. Sachs at a later period. (Vs. S¢., I, p. 203.) Sachs experimented on various plants, viz.: beans, squashes, tobacco, and maize, and observed their transpi- ration in weak solutions (mostly containing one per cent) of nitre, common salt, gypsum, one-fifth per cent solu- tion) and sulphate of ammonia. He also experimented with maize in a mixed solution of phosphate and silicate of potash, sulphates of lime and magnesia, and common salt, and likewise observed the effect of free nitric acid and free potash on the squash plant. The young plants were either germinated in the soil, then removed from it and set with their rootlets in the solution, or else were kept in the soil and watered with the solution. The glass * Experimental Investigation into the Amount of Water given off by Plants during ther Growth, vy J. B. Lawes, of Rothamstead, London, 1850. THE FREE WATER OF THE SOIL. 205 vessel containing the plant and solution was closed above, around the stem of the plant, by glass plates and cement, so that no loss of water could occur except through the plant itself, and this loss was ascertained by daily weigh- ings. The result was that all the solutions mentioned, except that of free nitric acid, quite uniformly retarded transpiration to a degree varying from 10 to 90 per cent, while the free acid accelerated the transpiration in a cor- responding manner. Sachs experimented also with four tobacco plants, two situated in coarse sand and two in yellow loam. The plants stood side by side exposed to the same temperature, etc., and daily weighings were made during a week or more, to learn the amount of exhalation. The result was that the total loss, as well as the daily loss in the majority of weighings, was greater from the plant growing in loam, although through certain short periods the opposite was noticed. J. The temperature of the soil considerably affects the rate of transpiration by influencing the amount of absorp- tion at the roots. Sachs made a number of weighings up- on two tobacco plants of equal size, potted in portions of the same soil and having their foliage exposed to the same atmosphere. After observing their relative transpiration when their roots were at the same temperature, one pot ‘was warmed a number of degrees, and the result was in- variably observed that elevating the temperature of the soil increased the transpiration. The same observer subsequently noticed the entire sup- pression of absorption by a reduction of temperature tc 41° to 48° F. A number of healthy tobacco and squash plants, rooted in a soil kept nearly saturated with water, were growing late in November in a room, the tempera- ture of which fell at night to the point just named. In the morning the leaves of these plants were so wilted that they hung down like wet cloths, as if the soil were 206 a “ HOW CROPS FEED. completely dry, or they had been fora long time acted upon by a powerful sun. Since, however, the sail was moist, the wilting could only arise from the inability of the roots to absorb water as rapidly as it exhaled from the leaves, owing to the low temperature. Further ex- periments showed that warming the soil in which the wilted plants stood, restored the foliage to its proper tur- gidity in a short time, and by surrounding the soil of a fresh plant with snow, the leaves wilted in three or four ; hours. Cabbages, winter colza, and beans, similarly circum- stanced, did not wilt, showing that different plants are un- equally affected. The general rule nevertheless appears to be established that within certain limits the root absorbs more vigorously at high than at low temperatures. _ The Amount of Loss of Water of Vegetation in Wilt- ing has been determined by Hesse (Vs. St., I, 248) in case of sugar-beet leaves. Of two similar leaves, one, gathered at evening after several days of dryness and sun- shine, contained 85, 74°|, of water; the other, gathered the next morning, two hours after arain storm, yielded 89.57°|,. The difference was accordingly 3.8°|,. Other observations corroborated this result. Is Exhalation Indispensable to Plants ?—It was for along time supposed that transpiration is indispensable to the life of plants. It was taught that the water which the plant imbibes from the soil to replace that lost by ex- halation, is the means of bringing into its roots the min- eral and other soluble substances that serve for its nutri- ment. There are, however, strong grounds for believing that the current of water which ascends through a plant moves independently of the matters that may be in solution, either without or within it; and, moreover, the motion of soluble matters from the soil into the plant may go on, THE FREE WATER OF THE SOIL. 207 although there be no ascending aqueous current. (H. C. G., pp. 288 and 340.) In accordance with these views, vegetation grows as well in the confined atmosphere of green-houses or of Wardian Cases, where the air is for the most part or entirely satu- rated with vapor, so that transpiration is reduced to a mini- mum, as in the free air, where it may attain a maximum, ‘As is well known, the growth of field crops and garden vegetables is often most rapid during damp and showery weather, when the transpiration must proceed with com- parative slowness. While the above considerations, together with the asser- tion of Knop, that leaves lose for the first half hour nearly the same quantities of water under similar exposure, whether they are attached to the stem or removed from it, whether entire or in fragments, would lead to the con- clusion that transpiration, which is so extremely variable in its amount, is, so to speak, an accident to the plant and not a process essential to its existence or welfare, there are, on the other hand, facts which appear to indicate the contrary. In certain experiments of Sachs, in which the roots of. a bean were situated in an atmosphere nearly saturated with aqueous vapor, the foliage being exposed to the air, although the plant continued for two months fresh and healthy to appearance, it remained entirely stationary in its development. (Ve. St., I, 237.) Knop also mentions incidentally (Vs. Sé, I, 192) that beans, lupines, and maize, die when the whole plant is kept confined in a vessel over water. It is not, however, improbable that the cessation of growth in the one case and the death of the plants in the other were due not so much to the checking of transpira- tion, which, as we have seen, is never entirely suppressed under these circumstances, as to the exhaustion of oxygen or the undue accumulation of carbonic acid in the narrow 208 HOW CROPS FEED. and confined atmosphere in which these results were noticed. On the whole, then, we conclude from the evidence be- fore us that transpiration is not necessary to vegetation, or at least fulfills no very important offices in the nutrition of plants. The entrance of watcr into the plant and the steady maintenance of its proper content of this substance, under all circumstances is of the utmost moment, and leads us to notice in the next place the Direct Proof that Crops can Absorb from the Soil enough Hygroscopic Water to Maintain their Life.—Sachs suffered a young bean-plant standing in a pot of very reten- tive (clay) soil to remain without watering until the leaves began to wilt. A high and spacious glass cylinder, having a layer of water at its bottom, was then provided, and the pot containing the wilting plant was supported in it, near its top, while the cylinder was capped by two semicircular plates of glass which closed snugly about the stem of the bean. The pot of soil and the roots of the plant were thus enclosed in an atmosphere which was constantly sat- urated, or nearly so, with watery vapor, while the leaves were fully exposed to the free air. It was now to ke ob- served whether the water that exhaled from the leaves could be supplied by the hygroscopic moisture which the soil should gather from the damp air enveloping it. This proved to be the case. The leaves, previously wilted, re- covered their proper turgidity, and remained fresh during the two months of June and July. Sachs, having shown in other experiments that plants situated precisely like this bean, save that the roots are not in contact with soil, lose water continuously and have no power to recover it from damp air (p. 36) thus gives us demonstration that the clay soil which condenses vapor in its pores and holds it as hygroscopic water, yields it again to the plant, and thus becomes the medium through which THE FREE WATER OF THE SOIL. 209 water is continually carried from the atmosphere into vegetation. In a similar experiment, a tobacco plant was employed which stood ina soil of humus. This material was also capable of supplying the plant with water by virtue of its hygroscopic power, but less satisfactorily than the clay. As already mentioned, these plants, while remaining fresh, exhibited no signs of growth. This may be due to the consumption of oxygen by the roots and soil, or possibly the roots of plants may require an occasional drenching with liquid water. Further investigations in this direc- tion are required and promise most interesting results. What Proportion of the Capillary and Hygroscopic Water of the Soil may Plants Absorb, is a question that Dr. Sachs has made the only attempts to answer. When a plant, whose leaves are in a very moist atmosphere, wilts or begins to wilt in the night time, when therefore trans- piration is reduced to a minimum, it is because the soil no longer yields it water. The quantity of water still con- tained in a soil at that juncture is that which the plant cannot remove from it,—is that which is unavailable to vegetation, or at least to the kind of vegetation experi- mented with. Sachs made trials on this principle with tobacco plants in three different soils, The plant began to wilt in a mixture of black humus (from beech-wood) aud sand, when the soil contained 12.3°|, of water.* This soil, however, was capable of holding 46°|, of capillary water. It results therefore that of its highest content of absorbed water 33.7°|, (=46—12.3) was available to the tobacco plant. Another plant began to wilt on a rainy night, while the loam it stood in contained 8°|, of water. This soil was able to absorb 52.1°|, of water, so that it might after * Ascertained by drying at 212°, 210 HOW CROPS FEED. saturation, furnish the tobacco plant with 44.1°|, of its weight of water. A coarse sand that could hold 20.8°|, of water was found to yield all but 1.5°|, to a tobacco plant. From these trials we gather with at least approximate accuracy the power of the plant to extract water from these several soils, and by difference, the quantity of wa- ter in them that was unavailable to the tobacco plant. How do the Roots take Hygroscopic Water from the Seil!—The entire plant, when living, is itself extremely hygroscopic. Even the dead plant retains a certain pro- portion of water with great obstinacy. Thus wheat, maize, starch, straw, and most air-dry vegetable substances, contain 12 to 15°|, of water; and when these matters are exposed to damp air, they can take up much more. Ac- cording to Trommer (Bodenkunde, p. 270), 100 parts of the following matters, when dry, absorb from moist air in 12 @ 48 7 iene nat hours. Fine cut barley straw, 15 2% 34 45 parts of water. Ts oe rye ty 12 20 27 99 “ee it3 “e ‘«« “white unsized paper, 8 12 17 19 “% “« & As already explained, a body is hygroscopic because there is attraction between its particles and the particles of water. The form of attraction exerted thus among different kinds of matter is termed adhesive attraction, or simply adhesion. Adhesion acts only through a small distance, but its in- tensity varies greatly within this distance. If we attempt to remove hygroscopic water from starch or any similar body by drying at 212°, we shall find that the greater part of the moisture is easily expelled in a short time, but we shall also notice that it requires a relatively much longer time to expel the last portions. A general law of attraction is that its force diminishes as the distance be- tween the attracting bodies increases, This has been ex- THE FREE WATER OF THE SOIL. 21% actly demonstrated in case of the force of gravity and electrical attraction, which act through great intervals of space, We must therefore suppose that when a mass of hygro- scopic matter is allowed to coat itself with water by the exercise of its adhesive attraction, the layer of aqueous particles which is in nearest contact is more strongly held to it than the next outer layer, and the adhesion diminish- es with the distance, until, at a certain point, still too small for us to perceive, the attraction is nothing, or is neutralized by other opposing forces, and further adhesion ceases. Suppose, now, we bring in contact at 2 single point two masses of the same kind of matter, one of which is satu- rated with hygroscopic water and the other is perfectly dry. It is plain that the outer layers of water-particles adhering to the moist body come at once within the range of a more powerful attraction exerted by the very surface of the dry body. The external’ particles of water attached to the first must then pass to the second, and they must also distribute themselves equally over the surface of the latter; and this motion must go on until the attraction of the two surfaces is equally satisfied, and the water is equally distributed according to the surface, i. e., is uni- form over the whole surface. If of two different bodies put in contact (one dry and one moist) the surfaces be equal, but the attractive force of one for water be twice that of the other, then motion must go on until the one has appropriated two-thirds, and the other is left with one-third the total amount of water. When bodies in contact have thus equalized the water at their disposal, they may be said to be in a condition of hygroscopic equilibrium. Any cause which disturbs this equilibrium at once sets up motion of the hygroscopic water, which always proceeds from the more dry to the less dry body. 212 HOW CROPS FEED. The application of these principles to the question be- fore us is apparent. The young, active rvots that are in contact with the soil are eminently hygroscopic, as is de- moustrated by the fact that they supply the plant with large quantities of water when the soil is so dry that it has no visible moisture. They therefore share with the soil the moisture which the latter contains. As water evaporates from the surface of the foliage, its place is supplied by the adjacent portions, and thus motion is es- tablished within the plant which propagates itself to the roots and through these to the soil. Each particle of water that flies off in vapor from the leaf makes room for the entrance of a particle at the root. If the soil and air have a surplus of water, the plant will contain more; if the soil and air be dry, it will contain less. Within certain narrow limits the supply and waste may vary without detriment to the plant, but when the loss goes on more rapidly than the supply can be kept up, or when the absolute content of water in the soil is re- duced to a certain point, the plant shortly wilts. Even then its content of water is many times greater than that of the soil. The living tobacco plant cannot contain less than 80°|, of water, while the soils in Sachs’ experiments contained but 12.3°|, and 1.5°|, respectively. When fully air-dry, vegetable matter retains 13°|, to 15°|, of water, while the soil similarly dry rarely contains more than 1-2"|,. The plant therefore, especially when living, is much more hygroscopic than the soil. If roots are so hygroscopic, why, it may be asked, do they not directly absorb vapor of water from the air of the soil? It cannot be denied that both the roots and fo- liage of plants are capable of this kind of absorption, and that it is taking place constantly in case of the roots. The experiments before described prove, however, that the higher orders of plants absorb very l.téle in this way, THE FREE WATER OF THE SOIL. 213 too little, in fact, to be estimated by the methods hitherto employed. Sachs explains this as follows: Assuming that the roots have at a given temperature as strong an attrac- tion-for water in the state of vapor as for liquid water, the amount of each taken up in a given time under the same circumstances would be in proportion to the weight of each contained in a given space. |e | OOS SESE IFES f} 2 | 35] ®e | = |e. | abs [aces less. a) . [Ss | 38 | S | Seg | S85 [Shea Sees ; Ss 3 § |S Sse: B| & § | §& | §& | 88 | SES SESS Sees grms. | grms. | grms. | grms. | grms. | grms. | grms. grms. 1..! 0.0033 0.0000 | 0.0033 0.0053 | 0.0020+ 0.397 a 1 2..| 0.0033 0.0083 | 0.0066 | 0.0063 | 0.0002t 0.720 1.8 2 3..! 0.0033 0.0066 | 0.0099 0.0097 ; 0.0002¢ 1.130 2.8 3 4..| 0.0033 0.0264 | 0.0297 0.0251 | 0.0046¢ 3.280 8.5 9 * N=Nitrogen. In the first Exp. a trifling quantity of nitrogen was gathered (as ammonia?) from the air. In the others, and especially in the last, nitrate of soda remained in the soil, 12* 274 HOW CROPS FEED. not having been absorbed entirely by the plants. Observe, bowever, what a remarkable coincidence exists between the ratios of supply of nitrogen in form of a nitrate and those of growth of the several crops, as exhibited in the last two columns of the Table. Nothing could demon- strate more strikingly the nutritive function of nitric acid than these admirable investigations. Of the multitude of experiments on vegetable nutrition which have been recently made by the process of water- culture (ZZ C. G., p. 167), nearly all have depended upon nitric acid as the exclusive source of nitrogen, and it has proved in all cases not only adequate to this purpose, but far more certain in its effects than ammonia or any other nitrogenous compound. § 6. NITROGENOUS ORGANIC MATTERS OF THE SOIL. AVAILABLE NITROGEN.—QUANTITY OF NITROGEN REQUIRED FOR CROPS. In the minerals and rocks of the earth’s surface nitrogen is a very small, scarcely appreciable ingredient. So far as we now know, ammonia-salts and nitrates (nitrites) are the only mineral compounds of nitrogen found in soils. When, however, organic matters are altered to humus, and become a part of the soil, its content of nitrogen ac- quires significance. In peat, which is humus compara- tively free from earthy matters, the proportion of nitrogen is often very considerable. In 32 specimens of peat ex- amined by the author (Peat and its Uses us Fertilizer and Fuel, p. 90), the nitrogen, calculated on the organic mat- ters, ranged from 1.12 to 4.31 per cent, the average being 2.6 per cent. The average amount of nitrogen in the air- dry and in some cases highly impure peat, was 1.4 per cent. This nitrogen belongs to the organic matters in NITROGENOUS ORGANIC MATTERS OF THE SOIL. 275 great part, but a small proportion of it being in the form of ammonia-salts or nitrates, : Tn 1846, Krocker, in Liebig’s laboratory, first estimated the nitrogen in a number of soils and marls (Ann. Ch. u. Ph., 58, 387). Ten soils, which were of a clayey or loamy character, yielded from 0.11 to 0.14 per cent; three sands gave from 0.025 to 0.074 per cent; seven marls contained 0.004 to 0.083 per cent. Numerous examinations have since been made by An- derson, Liebig, Ritthausen, Wolff, and others, with simi- lar results. In all but his latest writings, Liebig has regarded this nitrogen as available to vegetation, and in fact designated it as ammonia. Way, Wolff, and others, have made evi- dent that a large portion of it exists in organic combina- tion. Boussingault (Agronomie, T. I) has investigated the subject most fully, and has shown that in rich and highly manured soils nitrogen accumulates in considerable quantity, but exists for the most part in an insoluble and inert form. In the garden of Liebfrauenberg, which had been heavily manured for centuries, but 4°|, of the total nitrogen existed as ammonia-salts and nitrates. The soil itself contained— Total nitrogen, 0.261 per cent. : Ammonia, 0.0022 “ « Nitric acid, 0.00084 “ “ The subjoined Table includes the results of Boussin- gault’s examinations of a number of soils from France and South America, in which are given the quantities of am- monia, of nitric acid, expressed as nitrate of potash, and of nitrogen in organic combination. These quantities are stated both in per cent of the air-dry soil, and in lbs. av. per acre, taken to the depth of 17 inches. In another column is also given the ratio of nitrogen to carbon in the organic matters. (Agronomie, T I, pp. 14-21.) ‘276 HOW CROPS FEED. Ammonia, NrrRatrs, 2ND Orcanic NITROGEN oF various AorLs. 5 Nitrate of || Nitrogen in |-s . [Ammonia.|) “potash. |lorg. combin. a Soils. Ibs. Ibs. Ibs |g 88 per |per}} per |per|} per | per |S3§ cent. jacre/} cent jacre!|cent.| acre |RSS o {Liebfrauenberg, light gard. soil}0.0022| 100/|0.0175*| 875 9.3 g J Bischwiller, light garden soil... |0.0020} 100)/0.1526 |7630 7 ¢ | Bechelbronn. wheat field clay. /0.0009} 45//0.0015 | 5 2 & lArgentan, rich pasture......... 0.0060] 300)/0.0046 | 230 a [Rio Madeira, sugar field, clay|0.0090| 450//0.0004 | 20 3 2 | Rio Trombetto,forest heavy do. /0.0030} 183)|0.0001 5 9 © | Rio Negro, prairie v. fine gand.|0.003S} 190)/0.0001 5 6 & | Santarem, cocoa plantation.. 0.0083] 415//0.0011 | 55)/ 0. Ai <<} Saracca, near Amazon, loam.. |0.0042/ 210 none 0.182] 9100) 1:3.2 | Rio Cupari, rich leaf mould... ./0.0525/2875 ue 0.685] 34250) 1:18.83 = | Iles du Salut, French Guiana... |0.00S0] 400 |0.0643 |3215]/ 0.543) 27170) 1:11.7 w® | Martinique, sugar ficld......... 0.0055! 275/10.0186 | 930|| 0.112] 5590! 1:8 * The same soil whose partial analysis has just been given, but examined for nitrates at another time. It is seen that in all cases the nitrogen in the forms of ammonia ¢ and nitrates { is much less than that in organic combination, and in most cases, as in the Liebfrauenberg garden, the disparity is very great. Nature of the Nitrogenous Organic Matters. Amides. —AHitherto we have followed Mulder in assuming that the humic, ulmic, crenic, and apocrenic acids, are destitute of nitrogen. Certain it is, however, that natural humus is never destitute of nitrogen, and, as we have remarked in case of peat, contains this element in considerable quanti- ty,-often 3 per cent or more. Mulder teaches that the acids of humus, themselves free from nitrogen, are nat- urally combined to ammonia, but that this ammonia is with difficulty expelled from them, or is indeed impossible to separate completely by the action of solutions of the fixed alkalies. In all chemistry, beside, there is no example of such a deportment, and we may well doubt whcther the ammonia that is slowly evolved when natural humus is boiled with potash is thus expelled from a humate of ammonia. It is more accordant with general analogies to + Ammonia contains 82.4 per cent of nitrogen. } Nitrate of potash contains 13.3 per cent of nitrogen, NIIROGLINOUS ORGANIC MATTERS OF THE soln. 277 suppose that it is generated by the action of the alkali. In fact, there are a large number of bodies which manifest asimilar deportment. Many substances which are pro- duced from ammonia-compounds by heat and otherwise, and called amides, to which allusion has been already made, p. 276, are of this kind. Oxalate of ammonia, when heated to decomposition, yields oxamide, which contains the elements of the oxalate minus the elements of two molecules of water, viz., Oxalate of ammonia. Ozxamide. Water. 2 (N IL) C,O, = 2 (NH,) C, 0, + 2H,O On boiling oxamide with solution of potash, ammonia is reproduced by the taking up of two molecules of water, and passes off as a gas, while oxalate of potash remains in the liquid. Nearly every organic acid known has one or several amides, bearing to it a relation similar to that thus sub- sisting between oxalic acid and oxamide. Asparagine, a crystallizable body found in asparagus and many other plants, already mentioned as an amide, is thought to be an amide of malic acid. Urea, the principal solid ingredient of human urine, is an amide of carbonic acid. Uric acid, hippuric acid, gua- nine, found also in urine; kreatin and kreatinine, occurring in the juice of flesh; thein, the active principle of tea and coffee; and theobromin, that of chocolate, are all regard- ed as amides. Amide-like boaies are gelatine (glue), the organic sub- stance of the tendons and of bones, that of skin, hair, wool, and horn. The albuminoids themselves are amide- like, in so far, that they yield ammonia on heating with solutions of caustic alkalies. Albuminoids a Source of the Nitrogen of Mumus,— The organic nitrogen of humus may come from the albu- minoids of the vegetation that has decayed upon or in the 278 HOW CROPS FEED. soil, In their alteration by decay, a portion of nitrogen assumes the gaseous form, but a portion remains in an in- soluble and comparatively unalterable condition, though in what particular compounds we are unable to say. The loss of carbon and hydrogen from decaying organic mat- ters, it is believed, usually proceeds more rapidly than the waste of nitrogen, so that in humus, which is the residue of the change, the relative proportion of nitrogen to car- bon is greater than in the original vegetation. Reversion of Nitric Acid and Ammonia to inert Forms. —It is probable that the nitrogen of ammonia, and of ni- trates, which are reducible to ammonia under certain con- ditions, may pass into organic combination in the soil, Knop ( Versuchs St., III, 228) found that when peat or soils containing humus were kept for several months in contact with ammonia in closed vessels, at the usual tem- perature of summer, the ammonia, according to its quan- tity, completely or in part disappeared. There having been no such amount of oxygen present as would be necessary to convert it into nitric acid, the only explanation is that the ammonia combined with some organic substance in the humus, forming an amide-like body, not decomposable by the hypochlorite of soda used in Knop’s azometrical anal- ysis. Facts supporting the above view by analogy are not wanting. When gelatine (a body of animal origin closely related to the albuminoids, but containing 18 instead of 15°|, of nitrogen) is boiled with dilute acids for some time, it yields, among other products, sugar, as Gerhardt has demonstrated. Prof. T. Sterry Hunt was the first to suggest (Am. Jour, Sci. & Arts, 1848, Vol. 5, p. 76) that gelatine has nearly the composition of an amide of dextrin or other body of the cellulose group, and might be regard- ed as derived chemically from dextrin (or starch) by the union of the latter with ammonia, water being eliminated, viz. : NITROGENOUS ‘ORGANIC MATTERS OF THE SOIL, 279 ‘Carbohydrate. Ammonia. Water. Gelatine. C,, H,,O,, + 4NH, = 6H,O + 2(C,H,,N, 0,). Afterwards Dusart, Schiitzenberger, and P. Thenard, in- dependently of each other, obtained by exposing dextrin, starch, and glucose, to a somewhat elevated temperature (800-360°F.), in contact with ammonia-water, substances containing from 11.to 19°], of nitrogen, some spluble in water and having properties not unlike those of gelatine, others insoluble. It was observed, also, that analogous compounds, containing less nitrogen, were formed at lower temperatures, as at 212° F. Payen had previously observed that cane sugar underwent entire alteration by prolonged action of ammonia at common temperatures. These facts scarcely leave room to doubt that ammonia, as carbonate, by prolonged contact with the humic acids or with cellulose, and bodies of like composition, may form combinations with them, from which, by the action of alkalies or lime, ammonia may be regenerated. It has already been mentioned that when soils are boil- ed with solutions of potash, they yield ammonia continu- ously for a long time. Boussingault observed, as has been previously remarked, that lime, when incorporated with the soil at the ordinary temperature, causes its content of ammonia to increase. Soil from the Liebfrauenberg garden, mixed with ‘|; its weight of lime and nearly 4 its weight of water, was placed in a confined atmosphere for 8 months. On open: ing the vessel, a distinct odor of ammonia was perceptible, and the earth, which originally contained per kilogram, 11 milligrams of this substance, yielded by analysis 303 mgr. (See p. 265, for other similar results.) Alteration of Albuminoids in the Soil.—Albuminoids are carried into the soil when fresh vegetable matter is in- corporated with it. They are so susceptible to alteration, however, that under ordinary conditions they must speed- 280 HOW CROPS FEED. ily decompose, and cannot therefore themselves be consid- ered as ingredients of the soil. Among the proximate products of their decomposition are organic acids (butyric, valeric, propionic) destitute of nitrogen, and the amides leucin (C, H,, NO,) and tyrosin (C, H,, NO,). These latter bodies, by further decompo- sition, yield ammonia. As has been remarked, it is proba- ble that “the albuminoids, when associated as they are in decay with cellulose and other carbohydrates, may at once give rise to insoluble amide-like bodies, such as those whose existence in humus is evident from the consider- ations already advanced. Can these Organic Bodies Vield Nitrogen Directly to Plants ’—Those nitrogenous organic compounds that exist in the soil associated with humus, which possess something of the nature of amides, though unknown to us in a pure state, appear to be nearly or entirely incapable of feeding vegetation directly. Our information on this point is de- rived from the researches of Boussingault, whose papers on this subject (De la Terre végétale considérée dans ses effets sur la Végétation) are to be found in his Agronomie, etc., Vols. I-and II. Boussingault experimented with the extremely fertile soil of his garden, which was rich in all the elements needful to support vegetation, as was demonstrated by the results of actual garden waltnre. This soil was especially rich in nitrogen, containing of this element 0.26° Joy Which, were it in the form of ammonia, would be equivalent to more than 7 tons per acre taken to the depth of 13 inches; or, if existing as nitric acid, would correspond to more than 43 tons of saltpeter to the acre taken to the depth just mentioned. This soil, however, when employed in quantities of 40 to 130 grams (14 to 4} oz. av.) and shielded from rain and dew, was scarcely more capable of carrying lupins, beans, maize, or hemp, to any considerable development, AVAILABLE NITROGEN OF THE SOIL. 281 than the most barren sand. In eight distinct trials the crops weighed (dry) but 3 to 5 times, in one case 8 times (average 4 times), as much as the seed; while in sand, pumice, or burned soil, containing no nitrogen, Boussin- gault several times realized a crop weighing 6 times as much as the seed, though the average crop of 38 experi- ments was but 3 times, and the lowest result 14 times the weight of the seed. The fact that the nitrogen of this garden soil was for the most part inert is strikingly shown on a comparison of the crops yielded by it to those obtained in barren soil with aid of known quantities of nitrates. In a series of experiments with the Sunflower, Boussin- gault (Agronomie, etc., I, p. 233) obtained in a soil desti- tute of nitrogen a crop weighing (dry) 4.6 times as much as the seeds, the latter furnishing the plants 0.0033 grm. of nitrogen. In a second pot, with same weight of seeds, in which the nitrogen was doubled by adding 0.0033 grm. in form of nitrate of soda, the weight of crop was nearly doubled—was 7.6 times that of seeds. In a third pot the nitrogen was trebled by adding 0.0066 grm. in form of ni- trate, and the crop was nearly trebled also—was 11.3 times the weight of the seeds. In another experiment (p. 271) the addition of 0.194 grm. of nitrogen as nitrate of potash to barren sand with needful mineral matters, gave a crop weighing 198 times as much as the seeds. But in the garden soil, which con- tained, when 40 grms. were employed 0.104 grm., and when 130 grms. were used 0.338 grm. of nitrogen, the result of growth was often not greater than in a soil that contained ‘no nitrogen, and only in a single instance surpassed that of a soil to which was added but 0.0033 grm. The fact is thus demonstrated that but a very small proportion of the nitrogen of this soil was assimilable to vegetation. From these beautiful investigations Boussingault deems it highly probable that in this garden soil, and in soils 282 HOW CROPS FEED. generally which have not been recently manured, ammonia and nitric acid are the exclusive feeders of vegetation with nitrogen. Such a view is not indeed absolutely demon- strated, but the experiments alluded to render it in the highest degree probable, and justify us in designating the organic nitrogen for the most part as inert, so far as vege-» table nutrition is concerned, until altered to nitrates or ammonia-salts by chemical change. To comprehend the favorable results of garden-culture in such a soil, it must be considered what a large quantity of earth is at the disposal of the crop, viz., as Boussingault ascertained, 57 lbs. for each hill of dwarf beans, 190 Ibs. for each hill of potatoes, 470 lbs. for each tobacco plant, and 2,900 lbs. for every three hop-plants. The quantity and condition of the nitrogen of Boussin- gault’s garden soil are stated in the subjoined scheme. Available { Ammonia 0.00220 per cent = = Nitrogen ‘i a pet cent nitrogen { Nitric acid 0.00034 ‘“ 10009 ho. 0019 per ct. Inert nitrogen—of organic eompoinile, pie SACHS eee eat Meeeme enacts 0.2501 8% Total nitrogen...... ........ 32 diy Westend deedes oc pate bed 0.2610 per ct. Calculation shows that in garden culture the plants above named would have at their disposal in this soil quan- tities of inert and available nitrogen as follows: Weight of soil. Inert nitrogen. Available nitrogen. Bean (dwarf) hill 57 Ibs. 5 grama.* 1 gram. Potato, e 190 ** 2A2 we 3 grams. Tobacco, single plant, 470 ‘ 555 ee Lace Hop, three plants, 2900 ‘* 3488 oS 44 * 1 gram = 15 grains avoirdupois near ly. 17grams= 1 oz. 983 oh = 1 lb, he “a Indirect Feeding of Crops by the Organic Nitrogen of the Soil.—In what has been said of the oxidation of the organic matters of the soil, (whereby it is probable that their nitrogen is partially converted into nitric acid,) and of the effect of alkalies and lime upon them, (whereby ammonia is generated,) is given a clue to the understand- AVAILABLE NITROGEN OF THE SOIL. 283 ing of their indirect nutritive influence upon vegetation. By these chemical transformations the organic nitrogen may pass into the two compounds which, in the present ‘state of knowledge, we must regard as practically the ex- clusive feeders of the plant with nitrogen. The rapidity and completeness of the transformation depend upon circumstances or conditions which we understand but im- perfectly, and which are extremely important subjects for further investigation. Difficulty of estimating the Available Nitrogen of any Soil.—The value of a soil as to its power of supplying plants with nitrogen isa problem by no means easy to solve. The calculations that have just been made from the analytical data of Boussingault regarding the soil of his garden are necessarily based on the assumption that no alteration in the condition of the nitrogen could take place during the period of growth. In reality, however, there ig no constancy either in the absolute quantity of nitrogen in the soil or in its state of availability. Por- tions of nitrogen, both from the air and from fertilizers, may continually enter the soil and assume temporarily the form of insoluble and inert organic combinations. Other portions, again, at the same time and as continually, may escape from this condition and be washed out or gathered by vegetation in the form of soluble nitrates, as has al- ready been set forth. It is then manifestly impossible to learn more from analysis, than how much nitrogen is avail- able to vegetation at the moment the sample is examined. To estimate with accuracy what is assimilable during the whole season of growth is simply out of the question. The nearest approach that can be made to this result is to ascertain how much a crop can gather from a limited vol- ume of the soil. Bretschneider’s Experiments.—W e may introduce here a notice of some recent researches made by Bretschneider in Silesia, a brief account of which has appeared since the 284 HOW CROPS FEED. foregoing paragraphs were written. (Juhresbericht 4. Ag. Chem., 1865, 29.) Bretschneider’s experiments were made for the purpose of estimating how much ammonia, nitric acid, and nitro- gen, exist or are formed in the soil, either fallow or occu- pied with various crops during the period of growth. For this purpose he measured off in the field four plots of ground, cach one square rod (Prussian) in area, and sepa- rated from the others by paths a yard wide. The soil of one plot was dug out to the depth of 12 inches, sifted, and after a board frame 12 inches deep had been fitted to the sides of the excavation, the sifted carth was filled in again. This and another—not sifted—plot were planted to sugar bects, another was sown to vetches, and the fourth to oats. At the end of April, six accurate and concordant anal- yses were made of the soil. Afterwards, at five different periods, a cubic foot of soil was taken from each plot, and from the spaces between that bore no vegetation, for de- termining the amounts of nitric acid, ammonia, and total nitrogen. The results of this analytical work are given in the following Tables, being calculated in pounds for the area of an acre, and to the depth of 12 inches (English measures*) ; TABLE I, AMOUNT OF AMMONIA. aad nod Beet plot. Vetch plot. Oat plot. Vacant plot. End of April, 59 59 59 59 59 12th June, 15 48 41 32 28 30th June, 12 41 24 40 32 22d July, 9 29 39 22 29 13th August, 8 15 16 11 43 0 16 16 7 23 9th September, *It is plain that when the results of analyses made on a small amount of soil are calculated upon the 3,500,000 lbs. of svil (more or less) contaitned in an acre to the depth of one foot (see p. 158), the errors of the analyses, which cannot be absolutely exact, are enormously multiplied, What allowance ought to be made in this case we cannot say, but should suppose that 5 per cent wonld not be too much, On this basis differences of 200-300 lbs. in Table IV should be overlooked, AVAILABLE NITROGEN OF THE SOIL, 285 TABLE II. AMOUNT OF NITRIC ACID. ei plet, Beet plot. Vetch plot. Oat plot. Vasant plot. End of April, 56 56 56 56 56 12th June, 281 270 102 28 106 30th June, 328 442 15 93 318 22d July, 116 89 58 0 43 13th August, 53 6 a 14 81 9th September. 0 0 12 0 0 TABLE III. TOTAS- ASSIMILABLE NITROGEN (OF AMMONIA AND NITRIC ACID).” wed on Beet plot. Vetch plot. Oatplot. Vacant plot. End of April, 63 63 63 63 63 12th June, 84 109 60 33 50 30th June, 95 148 23 BY 108 22d July, 3t 4t 31 18 35 13th Angust, a1 14 31 13 56 9th September, 0 18 16 6 19 TABLE IV. TOTAL NITROGEN OF THE SOIL. He Plot, Beet plot. Vetch plot. Oat plot. Vacant plot End of April, 4652 4652 4652 4652 4652 12th June, 4861 5209 5606 6140 4720 30th June, 4667 144 5688 5514 4452 2d July, 5398 5485 4724 4924 13th August. BACT 6316 6316 6266 4412 9th September, 5164 4656 6522 5004 4294 From the first Table we gather that the quantity of ammonia, which was considerable in the spring, dimin- ished, especially in a porous (sifted) soil until September. In the compact earth of the uncultivated path, its diminu- tion was less rapid and less complete. The amount of nitric acid (nitrates), on the other hand, increased, though not alike in any two cases. It attained its maximum ing the hot weather of June, and thence fell off until, at the close of the experiments, it was completely wanting save in a single instance. The figures in the second Table do not represent the absolute quantities of nitric acid that existed in the soil 286 HOW CROPS FEED. throughout the period of experiment, but only those amounts that remained at the time of taking the samples. What the vegetation took up from the planted plots, what was washed out of the surface soil by rains, or otherwise removed by chemical change, does not come into the reckoning. Those plots, the surface soil of which was most occupied by active roots, would naturally lose the most nitrates by the agency of vegetation; hence, not unlikely, the vetch and oat plots contained so little in June. The results up- on the beet, and vacant ground plots demonstrate that in that month a rapid furmation of nitrates took place. It is not, perhaps, impossible that nitrification also proceeded vigorously in the loose soils in July and August, but was not revealed by the analysis, either because the vegetation took it up or heavy rains washed it out from the surface soil. In the brief account of these experiments at hand, no information is furnished on these points. Since moiést- ure is essential to nitrification, it is possible that a period of dry weather coming on shortly before the soil was analyzed in July, August, and September, had an influence on the results. It is certainly remarkable that with the ex- ception of the vetch plot, the soil was destitute of nitrates on the 9th of September. This plot, at that time, was thickly covered with fallen leaves. We observe further that the nature of the crops influ- enced the accumulation of nitrates, whether simply be- cause of the different amount of absorbent rootlets pro- duced by them and unequally developed at the given period, or for other reasons, we cannot decide.* From the third Table may be gathered some idea of the total quantity of nitrogen that was present in the soil in * It is remarkable that the large-leaved bect plant had a great surplus of ni- trates, while the oat plot was comparatively deficient in them. Has this fact any connection with what has been stated (p. 84) regarding the unequal power of plants to provide themselves with nitrogenous food ? AVAILABLE NITROGEN OF THE SOIL. 287 a form available to crops. Assuming that ammonia and nitric acid chiefly, if not exclusively, supply vegetation with nitrogen, it is seen that the greatest quantity of available nitrogen ascertained to be present at any time in the soil was 148 Ibs. per acre, taken to the depth of one foot. This, as regards nitrogen, corresponds to the follow- ing dressings :— lbs. per acre. Saltpeter (nitrate of potash) - - 1068 Chili saltpeter (nitrate of soda) : 898 Sulphate of ammonia - - - 909 Peruvian guano (14 per cent of nitrogen) 1057 The experience of British farmers, among whom all the substances above mentioned have been employed, being that 2 to 3 cwt. of any one of them make a large, and 5 ewt. avery large, application per acre, it is plain that in the surface soil of Bretschneider’s trials there was Sormed during the growing season a large manuring of nitrates in addition to what was actually consumed by the crops. The assimilable nitrogen increased in the beet plots up to the 30th of June, thence rapidly diminished as it did in the soil of the paths. In the oat and vetch plots the soil contained, at none of the times of analysis, so much assimilable nitrogen as at the beginning of the experi- ments. In September, all the plots were much poorer in available nitrogen than in the spring. Table IV confirms what Boussingault has taught as to the vast stores of nitrogen which may exist in the soil. The amount here is more than fwo tons per acre. We ob- serve further that in none of the cultivated plots did this amount at any time fall below this figure; on the other hand, in most cases it was considerably increased during the period of experiment. In the uncultivated plot, perhaps, the total nitrogen fell off somewhat. This difference may have been due to the root fibrils that, in spite of the ut- 288 HOW CROPS FEED. most care, unavoidably remain in a soil from which grow- ing vegetation is removed. The regular and great increase of total nitrogen in the vetch plot was certainly due in part to the abundance of leaves that fell from the plants, and covered the surface of the soil. But this ni- trogen, as well as that of the standing crops, must have come from the atmosphere, since the soil exhibited no diminution in its content of this element. We have here confirmation of the view that ammonia, as naturally supplied, is of very trifling importance to vegetation, and that, consequently, nitrates are the chief natural means of providing nitrogen for crops. The fact that atmospheric nitrogen becomes a part of the soil and enters speedily into organic and inert combinations, also appears to be sustained by these researches. Quantity of Nitrogen needful for Maximum Grain Crops.—Hellriegel has made experiments on the effects of various quantities of nitrogen (in the form of nitrates) on the yield of cereals. The plants grew in an artificial soil consisting of pure quartz sand, with an admixture of ash-ingredients in such proportions as trial had demon- strated to be appropriate. All the conditions of the ex- periments were made as nearly alike as possible, except as regards the amount of nitrogen, which, in a series of eight trials, ranged from nothing to 84 parts per 1,000,000 of soil. The subjoined Table contains his results. EFFECTS OF VARIOUS PROPORTIONS OF ASSIMILABLE NITROGEN IN THE SOIL. Nitrogen in Yield of Grain, in ibs. 1,000,000 lbs. of soil. Wheat. Rye. Oats. Found | Calculated | Found | Calculated | Found | Calculated 0 0.002 — 0.218 — 0.830 —_— Increase Increase Increase q 0.553 0.926 0.832, 0.966 0.929 1.168 14 1.708 1.851 1.944 ° 1.933 2.605 2.336 21 2.167 2.717 2.669 2.899 3.845 3.503 28 3.763 3.703 4.172 3.866 6.211 4.671 42 6.065 5.554 5.162 5.798 7.039 7.007 56 7.198 7.406 7.163 7.732 9.052 9.842 84 9.257 9.257 8.698, 8.698 9.342 9.342 DECAY OF NITROGENOUS BODIES. 289 From numerous other experiments, not published at this writing, Hellriegel believes himself justified in assum- ing that the highest yield thus observed, with 84 lbs. of nitrogen in 1,000,000 of soil, might have been got with 70 lbs. of nitrogen in case of wheat, with 63 Ibs. in case of rye, and with 56 Ibs. in case of oats. On this assump- tion he has calewlated the yield of cach of these crops,| and the figures obtained (see Table) present on the whole a remarkable coincidence with those directly observed. § 7. DECAY OF NITROGENOUS BODIES. We have incidentally noticed some of the products of the decay of nitrogenous bodies, viz., those which remain in the soil. We may now, with advantage, review the subject connectedly, and make our account of this process more complete. It will be needful in the first place to give some ex- planations concerning the nature of the familiar trans- formations to which animal and vegetable matters are subject. By the word decay, as popularly employed, is under- stood a series of chemical changes which are very differ- ent in their manifestations and results, according to the circumstances under which they take place or the kinds of matter they attack. Under one set of conditions we have slow decay, or, as Liebig has fitly designated it, eren ausis ;* under others fermentation; and under still others putrefaction. Eremecausis* is a slow oxidation, and requires the constant presence of an excess of free oxygen. It pro- ceeds upon vegetable matters which are comparatively ©¥ rom the Greek, signifying slow combustion. 13 oa 290 HOW CROPS FEED. difficult of alteration, such as stems and leaves, consist- ing chiefly of cellulose, with but little albuminoids, and both in insoluble forms. What is said in a former paragraph on the “ Decay of Vegetation,” p. 187, applies in general to eremecausis. Fermentation is a term commonly applied to any seemingly spontaneous change taking place with vegeta, ble or animal matters, wherein their sensible qualities suffer alteration, and heat becomes perceptible, or gas is rapidly evolved. Chemically speaking, fermentation is the breaking up of an organic body by chemical decom. position, which may go on in absence of oxygen, and is excited by a substance or an organism called a ferment. There are a varicty of fermentations, viz., the vinous, acetic, lactic, ete. In vinous fermentation, the yeast-fungus, Zorvula cerevisie, vegetates in an impure solution of sugar, and causes the Jatter to break up into alcohol and carbonic acid with small quantities of other products. In the acctie fermentation, the vinegar-plant, Dycoderma vini, is believed to facilitate the conversion of alcohol into acetic acid, but this change is also accomplished by platinum sponge, which acts as a ferment. In the lactic fermentation, a fungus, Zenicilium glaucum, is thought to de- termine the conversion of sugar into lactic acid, as in the souring of mill. The transformation of starch ijuto sugar has been termed the saccha- rous fermentation, diastase being the ferment. Putrefaction, or putrid fermentation, is a rapid internal change which proceeds in comparative absence of oxygen. It most readily attacks animal matters which are rich in albuminoids and other nitrogenous and sulphurized prin- ciples, as flesh, blood, and urine, or the highly nitrogenous parts of plants, as seeds, when they are fully saturated with water. Putrefying matters commonly disengage stinking gases. According to Pasteur putrefaction is oc- casioned by the growth of animalcules ( Vibrios). Fermentation is usually and putrefaction is always a reducing (deoxidizing) process, for either the ferment it- self or the decomposing substances, or some of the prod- ucts of decomposition, are highly prone to oxidation, and DECAY OF NITROGENOUS BODIES. 291 in absence of free oxygen may remove this element from reducible bodies (Traube, Fermentwirkungen, pp. 63-78). In a mixture of cellulose, sugar, and albuminoids, ere- mecausis, fermentation, and putrefaction, may all proceed simultaneously. When the albuminoids decay in the soil associated with carbohydrates and humus, the final results of their altera- tion may be summed up as follows: 1. Carbon unites mainly with oxygen, forming carbonic acid gas, which escapes into the atmosphere. With im- perfect supplies of oxygen, as when submerged in water, carbonic oxide (CO) and marsh gas (CH,) are formed. A portion of carbon remains as humus. 2. Hydrogen, for the most part, combines with oxygen, yielding water. In deficiency of oxygen, some hydrogen escapes as 1 carbon compound (marsh-gas), or in the free state. If humus remains, hydrogen is one of its con- stituents. 3. a. Nitrogen always unites to a large extent with hydrogen, giving ammonia, which escapes as gaseous car- pbonate in considerable quantity, unless from presence of carbohydrates much humus is formed, in which case it may be nearly or entirely retained by the latter. Lawes, Gilbert, and Pugh, (Pz. Trans. 1861, IL, p. 501) made observations on the decay of wheat, barley, and bean seeds, either entire or in form of meal, mixed with a large quantity of soil or powdered pumice, and exposed in vari- ous conditions of moisture to a current of air for six months, They found in nine experiments that from 11 to 58°|, of the nitrogen was converted into ammonia, al- though but a trifling proportion of this (on the average but 0.4°|,) escaped in the gaseous form. b. In presence of excess of oxygen, a portion of nitro- gen usually escapes in the free state. Reiset proved the escape of free nitrogen from fermenting dung. Boussin- 292 HOW CROPS FEED. gault, in his investigations on the assimilability of free nitrogen, found in various vegetation-experiments, in which crushed seeds were used as fertilizers, that nitrogen was lost by assuming some gaseous form. This loss prob- ably took place to some slight extent as ammonia, but chiefly as free nitrogen. Lawes, Gilbert, and Pugh, found in thirteen out of fifteen trials, including the experiments just referred to, that a loss of free nitrogen took place, ranging from 2 to 40 per cent of the total quantity con- tained originally in the vegetable matters submitted to decomposition. In six experiments the loss was 12 to 13 per cent. In the two cases where no loss of nitrogen oc- curred, nothing in the circumstances of decay was discov- erable to which such exceptional results could be at- tributed. Other experiments (Phil. Trans. 1861, IL, p. 509) demonstrated that in absence of oxygen no nitrogen was evolved in the free state. c. Nitric acid is not formed from the nitrogen of or- ganic bodies in rapid or putrefactive decay, but only in slow oxidation or eremecausis of humified matters. Pelouze found no nitrates in the liquor of dung heaps. Lawes, Gilbert, and Pugh, (/oe. cié.).found no nitric acid when the seed-grains decayed in ordinary air, nor was it produced when ozonized air was passed over moist bean- meal, either alone or mixed with burned soil or with slaked lime, the experiments lasting several months. It thus appears that the carbon and hydrogen of organic matters have such an affinity for oxygen as to prevent the nitrogen from acquiring it in the quicker stages of decay. More than this, as Pelouze has shown (Comptes Rendus, XLIV., p. 118), putrefying matters rob nitric acid of its oxygen and convert it into ammonia. We have already remarked that putrefaction and fermentation are reducing processes, and until they have run their course and the organic matters have passed into the comparatively stable forms of humus, their nitrogen appears to be incapable of THE NITROGENOUS PRINCIPLES OF URINE. 293 oxidation. So soon as compounds of carbon and hydrogen are formed, which unite but slowly with free oxygen, so that the latter easily maintains itself in excess, then and _not before, the nitrogen begins to combine with oxygen. 4, Finally, the sulphur of the albuminoids may be at first partially dissipated as sulphuretted hydrogen gas, while in the slower stages of decay, it is oxidized to sul- phuric acid, which remains as sulphates in the soil, § 8 THE NITROGENOUS PRINCIPLES OF URINE. The question “ How Crops Feed ” is not fully answered as regards the element Nitrogen, without a consideration of certain substances—ingredients of urine—which may become incorporated with the soil in the use of animal manures, Professor Way, in his investigation on the “ Power of Soils to Absorb Manure,” describes the following remark- able experiment: “Three quantitics of fresh urine, of 2,000 grains each, were measured out into similar glasses, With one portion its own weight of sand was mixed ; with another, its own weight of white clay ; the third being left without admixture of any kind. When smelt immediately after mixture, the sand appeared to have had no effect, whilst the clay mixture had entirely lost the smellof urine. The three glasses were covered light- ly with paper and put in a warm place, being examined from time to time. In afew hours it was found that the urine containing sand had become slightly putrid; then followed the natural urine; but the quantity with which clay had been mixed did not become putrid at all, and at the end of seven or eight weeks it had only the pecu- liar smell of fresh urine, without the slightest putridity. The surface of the clay, however, became afterwards cov- 294 HOW CROPS FEED. ered with a luxuriant growth of conferve, which did not happen in the other glasses.” (Jour. Roy. Ag. Soe. of Eing., XI., 366.) Professor Way likewise found that filtering urine through clay or simply shaking the two together, allow- ing the liquid to clear itself, and pouring it off, sufficed to prevent putretaction, and keep the urine as if fresh for a month or more. Cloez found, as stated on p. 264, that in a mixture of moistened pumice-stone, carbonate of lime, and urea (the nitrogenous principle of urine), no nitrates were formed during eight months’ exposure to a slow current of air. These facts make it necessary to consider in what state the nitrogen of urine is absorbed and assimilated by vegetation. Urine contains a number of compounds rich in nitro- gen, being derived from the waste ot the food and tissues of the animal, which require a brief notice. Urea (CO N,H,)* may be obtained from the urine of man as a white crystalline mass or in distinct transparent rhombic crystals, which remain indefinitely unaltered in dry air, and have a cooling, bitterish taste like saltpeter. It is a weak base, and chemists have prepared its nitrate, oxalate, phosphate, ete. Urea constitutes 2 to 3 per cent of healthy human urine, and a full-grown and robust man excretes of it about 40 grams, or 1°], oz. av. daily. When urine is left to itself, it shortly emits a putrid odor; after a few days or hours the urea it contained en- tirely disappears, and the liquid smells powerfully of am- monia, Urea, when in contact with the animal matters * Carbon............ 20.00 Hydrogen......... 6.67 Nitrogen.......... 46.67 Oxy gets ceccavass 26.66 100.00 THE NITROGENOUS PRINCIPLES OF URINE. 295 of urine, suffers decomposition, and its elements, combin- ing with the elements of water, are completely transformed into carbonate of ammonia. Urea, Water. Carbonate of Ammonia. CO N,H, + 2H,O = 2(NH,), H,0,CO,. As we have learned from Way’s experiments, clay is able to remove from urine the “ferment” which occasions its putrefaction. Urea is abundant in the urine of all carnivorous and herbivorous mammals, and exists in small quantity in the urine of carnivorous birds, but has not been detected in that of herbivorous birds. Uric acid (C,H,N,O,)* is always present in healthy human urine, but in very minute quantity. It is the chief solid ingredient of the urine of birds and reptiles. Here it exists mainly as urate of ammonia.** The urine of birds and serpents is expelled from the intestine as a white, thickish liquid, which drics to a chalk-like mass. From this, uric acid may be obtained in the form of a white powder, which, when magnified, is seen to consist of mi- nute crystals. By powerful oxidizing agents uric acid is converted into oxalate and carbonate of ammonia, and urea. Peruvian guano, when of good quality, contains some 10 per cent of urate of ammonia. Hippuric acid (C,H,NO,)} is commonly abundant in the urine of the ox, horse, and other herbivorous animals. By boiling down fresh urine of the pastured or hay-fed cow to *|, its bulk, and adding hydrochloric acid, hippuric acid crystallizes out on cooling in four-sided prisms, of- ten two or three inches in length. * Carbon .......... 35.72 * Carbon......... 32.43 + Carbon............ 60.74 Hydrogen...,.... 2.38 Hydrogen...... 3.78 Hydrogen......... 4.96 Nitrogen.........33.33 Nitrogen .......37.84 Nitrogen ........., %.82 OxyPen..cevsayes 28.57. Oxygen........ 25.95 Oxygen ...........26.48 a 296 HOW CROPS FEED. Glycocoll or Glycine* is a sweet substance that re- sults from the decomposition of hippuric acid under the influence of various agents. It is also a product of the action of acids on gelatine and horn. Guanine (C,H,N,O) + occurs to the extent of about "|, per cent in Peruvian guano, and is an ingredient of the liver and pancreas of animals, whence it passes into the excrement in case of birds and spiders. By oxidation it yields among other products urea and oxalic acid. Kreatin (C,H,N,O,) { is an organic base existing in very minute quantity in the flesh of animals, and occa- sionally found in urine. Cameron was the first, in 1857, to investigate the assimi- lability of urinary products by vegetation. His experi- ments (Chemistry of Agriculture, pp. 189-144) were. made with barley, which was sown in an artificial soil, destitute of nitrogen. Of four pots one remained without a supply of nitrogen, another was manured with sulphate of ammonia, and two received a solution of urea. The pot without nitrogen gave plants 8 inches high, but these developed no seeds. The pot with sulphate of ammonia gave plants 22 inches high, and 300 seeds. Those with urea gave respectively stalks of 26 and 29 inches height, and 252 and 270 seeds. The soil in neither case contained ammonia, the usual decomposition-product of urea. Dr. Cameron justly concluded that urea enters plants un- changed, is assimilated by them, and equals ammonia-salts as a means of supplying nitrogen to vegetation. The next studies in this direction were made by the au- thor in 1861 (Am. Jour. Science, XLL, 27). Experiments were conducted with uric acid, hippuric acid, and guanine. * Carbon...........+ 39.73 + Carbon............ 82.00 $Carbon.. ........ . Hydrogen... ...... 3.81 Hydrogen... .. 6.6% Hydrogen.. ee Nitrogen. -46.36 Nitrogen. 18.67 Nitrogen... . Oxygen...........- 0.60 Oxygen........ ..- 42.66 Oxygen. ..........24. THE NITROGENOUS PRINCIPLES OF URINE, 297 Washed and ignited flower-pots were employed, to con- tain, for each trial, a soil consisting of 700 grms. of ignited and washed granitic sand, mixed with 0.25 grm, sulphate of lime, 2 grms. ashes of hay, prepared in a muffle, and 2.75 grms. bone-ashes. This soil was placed upon 100 grms. of clean gravel to serve as drainage. In each of four pots containing the above soil was de- posited, July 6th, a weighed kernel of maize. The pots were watered with equal quantities of distilled water con- taining a scarcely appreciable trace of ammonia. The seeds germinated in a healthy manner, the plants devel- oped slowly and alike until July 28th, when the addition of nitrogenous matters was begun. To No. 1, no solid addition was made. To No. 2 was added, July 28th, 0.420 grm. uric acid. To No. 8 was added 1.790 grm. hippuric acid, at four different times, viz: July 28, 0.358 grm., Aug. 26th, 0.358 grm., Sept. 16th, 0.716 grm., Oct. 3d, 0.3858 grm. To No. 4was added 0.4110 grm. hydrochlorate of gua- nine, viz: July 28th, 0.0822 grm., Aug. 26th, 0.0822 grm., Sept. 16th, 0.1644 grm., Oct. 3d, 0.0822 grm. The nitrogenous additions contained in each case, 0.140 erm. of nitrogen, and were strewn, as fine powder, over the surface of the soil, The plants continued to grow or to remain healthy (the lower leaves withering more or less) until they were re- moved from the soil, Nov. 8th, The plants exhibited striking differences in their devel- opment.. No. 1 (noadded nitrogen) produced in all seven slender leaves, and attained a height of 7 inches. At the close of the experiment, only the two newest leaves were perfectly fresh ; the next was withered and dead through- out one-third of its length. The newer portions of this plant grew chiefly at the expense of the older parts. No sign of floral organs appeared. 13* 298 HOW CROPS FEED. No, 2, fed with uric acid, was the best developed plant of the series. At the conclusion of the experiment, it bore ten vigorous leaves, six of which were fresh, and two but partly withercd. It was 14 inches high, and carried two rudimentary ears (pistillate flowers), from the upper one of which hung tassels 6 inches long. No. 3, supplied with hippuric acid, bore eight leaves, four of which were withered, and two rudimentary ears, one of which tasseled. Height, 12 inches, No. 4, with hydrochlorate of guanine, had six leaves, one withered, and two ears, one of which was tasseled. Height, 12 inches. The weight of the crops (dried at 212° F.), exclusive of the fine rootlets that could not be removed from the soil, was ascertained, with the subjoined results. 1 2 3 4 Without Hippurie Nitrogen. Uric Acid. Acid. Guanine. Weight of dried crop, 0.1925 grm. 1.9470 grm. 1.0149 grm. 0.9820 grm. a bi sued, 0.1644 ‘“ 1725 “ 0.1752 “ 0.1698 * gain, 0.0291 “ 1.7745 “ 0.8397 ‘ 0.8122 “ We thus have proof that all the substances employed contributed nitrogen to the growing plant. This is con- clusively shown by the fact that the development of pis- tillate organs, which are especially rich in nitrogen, occurred in the three plants fed with nitrogenous com- pounds, but was totally wanting in the other. The rela- tion of matter, new-organized by growth, to that derived from the seed, is strikingly seen from a comparison of the ratios of the weight of the seed to the increase of organs ized matter, the former being taken as unity. The ratio is approximatively for No. 1, 1: 0.2 fe 1: 10.2 ee 8; I 4,8 “ss “ 4 1 4.8 THE NITROGENOUS PRINCIPLES OF URINE. 299 The relative gain by growth, that o° No. 1 assumed as unity, is for No.1, — 1 wow Be 6 “OG 3, — 29 6 ce 4, oe 298 The crops were small, principally because the supply ofunitrogen was very limited. These experiments demonstrate that the substances added, in every case, aided growth by supplying nitro- gen. They do not, indced, prove that the organic fertil- izers entered as such into the crop without decomposition, but if urea escapes decomposition in a soil, as Cameron and Cloez have shown is true, it is not to be anticipated that the bodies employed in these trials should suffer al- teration to ammonia-salts or nitrates. Hampe afterwards experimented with urea and uric acid by the method of Water-Culture ( Vs. S¢., VII., 308; VIII, 225; IX., 49; and X.,175). He succeeded in pro- ducing, by help of urea, maize plants as large as those growing in garden soil, and fully confirmed Cameron’s conclusion regarding the assimilability of this substance. Hampe demonstrated that urea entered as-such into the plant. In fact, he separated it, in the pure state, from the stems and lcaves of the maize which had been pro- duced with its aid. Hampe’s experiments with uric acid in solution showed that this body supplied nitrogen without first assuming the form of ammonia-salts, but it suffered partially if not entirely a decomposition, the nature of which was not determined. Uric acid itself could not be found in the crop. Hampe’s results with hippuric acid were to the effect that this substance furnishes nitrogen without reversion to ammonia, but is resolved into other bodies, probably benzoic acid and. glycocoll, which are formed when hip- 300 HOW CROPS FEED, puric acid is subjected to the action of strong acids or ferments. Hampe, therefore, experimented with glycocoll, and from his trials formed the opinion that this body is di- rectly nutritive. In fact, he obtained with it a crop equal to that yielded by ammonia-salts, Knop, who made, in 1857, an unsuccessful experiment with hippuric acid, found, in 1866, that glycocoll is as- similated (Chem. Centralblatt, 1866, p. 774). In 1868, Wagner experimented anew with hippuric acid and glycocoll. His results confirm those of Hampe. Wagener, however, deems it probable that hippuric acid enters the plant as such, and is decomposed within it into benzoic acid and glycocoll ( Vs. St., XI., p. 294). Wagner found, also, that kreatin is assimilated by vegetation. The grand result of these researches is, that the nitrog- enous (amide-like) acids and bases which are thrown off in the urinary excretions of animals need not revert, by decay or putrefaction, to inorganic bodies (ammonia or nitric acid), in order to nourish vegetation, but are either immediately, or after undergoing a slight and easy altera- tion, taken up and assimilated by growing plants. As a practical result, these facts show that it is not necessary that urine should be fermented before using it as a fertilizer, 8 9. COMPARATIVE NUTRITIVE VALUE OF AMMONIA-SALTS AND NITRATES. The evidence that both ammonia and nitric acid are ca- pable of supplying nitrogen to plants has been set forth. It has been shown further that nitric acid alone can per- fectly satisfy the wants of vegetation as regards the ele- ment nitrogen. In respect to ammonia, the case has not Bx VALUE OF AMMONIA AND NITRIC ACID. 301 been similarly made out. We have learned that ammonia occurs, naturally, in too small proportion, either in the atmosphere or the soil, to supply much nitrogen to crops. In exceptional cases, however, as in the leaf-mold of Rio Cupari, examined by Boussingault, p. 276, as well as in lands manured with fermenting dung, or with sulphate or muriate of ammonia, this substance acquires importance from its quantity. On the assumption that it is the nitrogen of these sub- stances, and not their hydrogen or oxygen, which is of value to the plant, we should anticipate that 17 parts of ammonia would equal 54 parts of nitric acid in nutritive effect, since each of these quantities represents the same amount (14 parts) of nitrogen. The ease with which ammonia and nitric acid are mutually transformed favors this view, but the facts of experience in the actual feed- ing of vegetation do not, as yet, admit of its acceptance. In earlier vegctation-experiments, wherein the nitro- genous part of an artificial soil (without humus or clay) consisted of ammonia-salts, it was found that these were decidedly inferior to nitrates in their producing power. This was observed by Ville in trials made with wheat planted in calcined sand, to which was added a given ‘ quantity of nitrogen in the several forms of nitrate of potash, sal-ammoniac (chloride of ammonium), nitrate of ammonia, and phosphate of ammonia. Ville’s results are detailed in the following table. The quantity of nitrogen added was 0.110 grm. in each case. Nitrogen Straw and Average jin average Source of Nitrogen. Roots. |Grain.| crop. crop. I. 70) 6.2 Nitrate of Potash.......s.sss005 tor 19.2 es t 2.26.71} 0.221 | Salamthonine......sseeeeeeess § i tae 2-231 |. .18.83] 0.148 Nitrate of ammonia,........e++- noe 588 L 18.82] 0.188 Phosphate of ammonia.........- 4 ye RB 88] 3-27 | ..18.40| 0.188 302 HOW CROPS FEED. It is seen that the ammonia-salts gave about one-fourth less crop than the nitrate of potash. The potash doubt- less contributed somewhat to this difference. The author began some experiments on this point in 1861, which turned out unsatisfactorily on account of the want of light in the apartment. In a number of these, buckwheat, sown in a weathered feldspathic sand, was ma- nured with equal quantities of nitrogen, potash, lime, phosphoric acid, sulphuric acid, and chlorine, the nitrogen being presented in one instance in form of nitrate of potash, in the others as an ammonia-salt—sulphate, muriate, phos- phate, or oxalate. Although the plants failed to mature, from the cause above mentioned, the experiments plainly indicated the inferiority of ammonia as compared with nitric acid. Explanations of this fact are not difficult to suggest. The most reasonable one is, perhaps, to be found in the circumstance that clayey matters (which existed in the soil under consideration) “fix” ammonia, 7. e., convert it into a comparatively insoluble compound, so that the plant may not be able to appropriate it all. On the other hand, Hellriegel (Ann. d. Landw., VIL, 53, u. VIIL, 119) got a better yield of clover in artificial soil with sulphate of ammonia and phosphate of ammonia than with nitrate of ammonia or nitrate of soda, the quan- tity of nitrogen being in all cases the same. As Sachs and Knop developed the method of Water- Culture, it was found Ly the latter that ammonia-salts did not effectively replace nitrates. The same conclusion was arrived at by Stohmann, in 1861 and 1863 (Henneberg’s Journ., 1862, 1, and 1864, 65), and by Rautenberg and Kiihn, in 1863 (Henneberg’s Journ., 1864, 107), who ex- perimented with sal-ammoniac, as well as by Birner and Lucanus, in 1864 (Vs. St, VIIL, 152), who employed sulphate and phosphate of ammonia. The cause of failure lay doubtless in the fact, first noticed VALUE OF AMMONIA AND NITRIC ACID. 303 by Kuhn, that so soon as ammonia was taken up by the plant, the acid with which it was combined, becoming free, acted as a poison. In 1866, Hampe (Vs. S¢., IX., 165), using phosphate of ammonia as the single source of nitrogen, and taking care to keep the solution but faintly acid, obtained a maize-plant which had a dry weight of 18 grams, includ- ing 36 perfect seeds; no nitrates were formed in the solution. The same summer Kihn (Vs. Sé., [X., 167) produced two small maize-plants, one with phosphate, the other with sulphate of ammonia as the source of nitrogen, but his experiments were interrupted by excessive heat in the glass-house. In 1866, Beyer ( Vs. St., [X., 480) also made trials on the growth of the oat-plant in a solution containing bi- carbonate of ammonia, The plants vegetated, though poorly, and several blossomed and even produced a few Seeds. Quite at the close of the experiments the plants suddenly began to grow, with formation of new shoots. Examination of the liquid showed that the ammonia had been almost completely converted into nitric acid, and the increased growth was obviously connected with this nitrifi- cation. In 1867, Hampe ( Vs. St., X., 176) made new experi- ments with ammonia-salts, and obtained one maize-plant 2’|, ft. high, bearing 40 handsome seeds, and weighing, dry, 25'|, grams. In these trials the seedlings, at the time of unfolding the sixth or seventh leaf, after consum- ing the nutriment of the seeds, manifested remarkable symptoms of disturbed nutrition, growth being sup- pressed, and the foliage becoming yellow. After a week or two the plants recovered their green color, began to grow again, and preserved a healthy appearance until mature. Experiment demonstrated that this diseased state was not affected by the concentration of the nour- 304 HOW CROPS FEED. ishing solution, by the amount of free acid or of iron present, nor by the illumination. Hampe observed that from these trials it seemed that the plants, while young, were unable to assimilate ammonia or did so with diffi- culty, but acquired the power with a certain age. In 1868, Wagner (Vs. S¢., XI, 288) obtained exactly the same results as Hampe. He found also that a maize- seedling, allowed to vegetate for two weeks in an artificial soil, and then placed in the nutritive solution, with phos- phate of ammonia as a source of nitrogen, grew nor- mally, without any symptoms of disease. Wagner ob- tained one plant weighing, dry, 26'|, grams, and carrying 48 ripe seeds. In experiments with carbonate of ammoniag Wagener obtained the same negative result as Beyer had experienced in 1866. Beyer reports (Vs. St., XI., 267) that his attempts to nourish the oat-plant in solutions containing ammonia- salts as the single source of nitrogen invariably failed, although repeated through three summers, and varied in several ways. Even with solutions identical to those in which maize grew successfully for Hampe, the oat seed- lings refused to increase notably in weight, every precau- tion that could be thought of being taken to provide favorable conditions, It is not impossible that all these failures to supply plants with nitrogen by the use of am- monia-salts depend not upon the incapacity of vegetation to assimilate ammonia, but upon other conditions, unfa- vorable to growth, which are inseparable from the meth- ods of experiment. A plant growing in a solution or in pure quartz sand is in abnormal circumstances, in so far that neither of these media can exert absorbent power sufficient to remove from solution and make innocuous any substance which may be set free by the selective agency of the plant. Further investigations must be awaited before this point can be definitely settled. It is, however, a matter CONSTITUTION OF THE SOIL. 305 of little practical importance, since ammonia is so sparse- ly supplied by nature, and the ammonia of fertilizers is almost invariably subjected to the conditions of speedy. nitrification. CHAPTER VI. THE SOIL AS A SOURCE OF FOOD TO CROPS.—INGRE- DIENTS WHOSE ELEMENTS ARE DERIVED FROM ROCKS. § 1. GENERAL VIEW OF THE CONSTITUTION OF THE SOIL AS RELATED TO VEGETABLE NUTRITION. Inert, Active, and Rescrve Matters.—In all cases the soil consists in great part of matters that are of no direct or present use in feeding the plant. The chemical nature of this inert portion may vary greatly without correspond- ingly influencing the fertility of the soil. Sand, either quartzose, calcareous, micaceous, feldspathic, hornblendic, or augitic; clay in its many varieties; chalk, ocher (oxide of iron), humus; in short, any porous or granular material that is insoluble and little alterable by weather, may con- stitute the mass of the soil. The physical and mechanical characters of the soil are chiefly influenced by those ingre- dients which preponderate in quantity. Hence Ville has quite appropriately designated them the “mechanical ‘agents of the soil.” They affect fertility principally as- they relate the plant to moisture and to temperature. They also have an influence on crops by gradually assum- ing more active forms, and yielding nourishment as the result. of chemical changes. In general, it is probable 306 HOW CROPS FEED. that 99 per cent and more of the soil, exclusive of water, does not in the slightest degree contribute directly to the support of the present vegetation of our ordinary field products. The hay crop is one that takes up and removes from the soil the largest quantity of mineral matters (ash- ingredients), but even a cutting of 2} tons of hay car- rics off no more than 400 Ibs. per acre. From the data given on page 158, we may assume the weight of the soil upon an acre, taken to the depth of one foot, to be 4,000,000 Ibs. The ash-ingredients of a heavy hay crop amount therefore to but one ten-thousandth of the soil, admitting the crop to be fed exclusively by the 12 inches next the surface. Accordingly no less than 100 full crops of hay would require to be taken off to consume one per cent of the weight of the soil to this depth, We confine our calculation to the ash-ingredients because we have learned that the atmosphere furnishes the main sup- ply of the food from which the combustible part of the crop is organized. Should we spread out over the surface of an acre of rock 4,000,000 Ibs. of the purest quartz sand, and sow the usual amount of seed upon it, maintain- ing it in the proper state of moisture, etc., we could not produce a crop; we could not even recover the seed. Such a soil would be sterile in the most emphatic sense. But should we incorporate with such a soil a few thousand Ibs. of the mineral ingredients of agricultural plants, to- gether with some nitrates in the appropriate combinations and proportions, we should bestow fertility upon it by this addition and be able to realize a crop. Should we add to, our acre of pure quartz the ashes of a hay crop, 400 lIbs., and a proper quantity of nitrate of potash, we might also realize a good crop, could we but ensure contact of the roots of the plants with all the added matters, But in this case the soil would be fertile for one crop only, and after the removal of the latter it would be as sterile as CONSTITUTION OF TIE SOIT. 307 before. We gather, then, that there arc three items to be regarded in the simplest view of the chemical compo- sition of the soil, viz., the inert mechanical basis, the presently available nutritive ingredients, and the reserve matters from which the available ingredients are supplied as needed, In a previous chapter we have traced the formation of the soil from rocks by the eonjoint agencies of mechanical and chemical disintegration. It isthe perpetual operation of these agencies, especially those of the chemical kind, which serves to maintain fertility. The fragments of rock, and the insoluble matters generally that exist in the soil, are constantly suffering decomposition, whereby the elc- ments that feed vegetation become available. What, therefore, we have designated as the inert basis of the soil, is inert for the moment only. From it, by perpetual change, is preparing the available food of crops. Various attempts have been made to distinguish in fact between these three classes or conditions of soil-ingredients; but the distinction is to us one of idea only. We cannot realize their separation, nor can we even define their peculiar con- ditions. Weare ignorant in great degree of the power of the roots of plants to imbibe their food; we are equally ignorant of the mode in which the elements of the soil are associated and combined; we have, too, a very imperfect knowledge of the chemical transformations and decomposi- tions thet occur within it. We cannot, therefore, dissect the soil and decide what and how much is immediately available, and what is not. Furthermore, the soil is chem- ically so complex, and its relations to the plant are so com- plicated by physical and physiological conditions, that we may, perhaps, never arrive at a clear and unconfused idea of the mode by which it nourishes a crop. Nevertheless, what we have attained of knowledge and insight in this direction is full of value and encouragement. Deportment of the Soil towards Solvents.—When we 308 HOW CROPS FEED. put a soil in contact with water, certain matters are dis- solved in this liquid. It has been thought that the sub- stances taken up by water at any moment are those which at that time represent the available plant-food. This no- tion was based upon the supposition that the plant cannot feed itself at the roots save by matters in solution. Since Liebig has brought into prominence the doctrine that roots are able to attack and dissolve the insoluble ingredients of the soil, this idea is generally regarded as no longer tenable. Again, it has been taught that the reserve plant-food of the soil is.represented by the matters which acids (hydro- chloric or nitric acid) are capable of bringing into solu- tion. This is true in a certain rough sense only. The action of hydrochloric or nitric acid is indeed analogous to that of carbonic acid, which is the natural solvent; but between the two there are great differences, independent of those of degree. Although we have no means of learning with positive accuracy what is the condition of the insoluble ingredients of the soil as to present or remote availability, the deport- ment of the soil towards water and acids is highly in- structive, and by its study we make some approach to the solution of this question. Standards of Solubility.—Before proceeding to details, some words upon the limits of solubility and upon what is meant by soluble in water or in acids will be appropri- ate, The terms soluble and insoluble are to a great de- gree relative as applied to the ingredients of the soil. When it is affirmed that salt is soluble in water, and that glass is insoluble in that liquid, the meaning of the state- ment is plain; it is simply that salt is readily recognized to be soluble and that glass is not ordinarily perceived to dissolve, The statement that glass is insoluble is, however, only true when the ordinary standards of solubility are re- ferred to. The glass bottle which may contain water for AQUEOUS SOLUTION OF THE SOIL. 309 years without perceptibly yielding aught of its mass to the liquid, does, nevertheless, slowly dissolve. We may make its solubility perceptible by a simple expedient. Pulver- ize the bottle to the finest dust, and thus extend the sur- face of glass many thousand or million times; weigh the glass-powder accurately, then agitate it for a few ininutes with water, remove the liquid, dry and weigh the glass again, We shall thus find that the glass has lost several per cent of its original weight (Pclouze), and by evapo- rating the water, it will leave a solid residue equal in weight to the loss experienced by the glass. g 2. . = AQUEOUS SOLUTION OF THE SOIL. The soil and the rocks from which it is formed would commonly be spoken of as insoluble in water. They are, however, soluble to a slight extent, or rather, we should say, they contain soluble matters. The quantity that water dissolves from a soil depends upon the amount of the liquid and the duration of its contact; it is therefore necessary, in order to estimate properly any statements respecting the solubility of the soil, to know the method and conditions of the experi- ment upon which such statements are based. We subjoin the results of various investigations that exhibit the general nature and amount of matters soluble. in water. In 1852 Verdeil and Risler examined 10 soils from the grounds of the Institut Agronomique, at Versailles. In each case about 22 Ibs. of the fine earth were mixed with pure lukewarm water to the consistence of a thin pap, and after standing several hours with frequent agitation the water was poured off; this process was repeated to the third time. The clear, faintly yellow solutions thus obtained were evaporated to dryness, and the residues were analyzed with results as follows, per cent:. 310 HOW CROPS FEED. Per cent of Ash. 3 g& be! Name of Field, eyl Syl By §3 S ele. gis BS SS) 58 > 4 Se slgyl & Ses) | 55/85) 5) $e | | (S88! § (Bg) § SS3] 3] 48) Se] Rs] S81] 3 Sse] 2 ka! & Mall ...[Walk] 43.00[57.00 48.92} 25..60 4,27 1.55) 0.62) 7.63) 5.49/3.97) — Pheasant 70.50/29 90/31 .49,35.29) 2.16] O.47jtrace | 3.55]13.67/4.23) — TUTE, scpcisisias 35.00/05 .00}48.45) 6.08) 2.75) 1.21] — 6.19]25.71/5.06) — Sues Ave..} 44.00/56.00/43.75] 6.08] 6.32} 2.00,trace | 14.45/15.61/4.13] — itchen Gard.) 87.00/63.00)51 -60/12.35 11.20)trace jtrace | 13.51)19.60/7.23 trace Sulerys, (Galy 23.00167.00)18.70/24.25/18.50! 3.72) 0.50) — [21.60/4.65, — Clay soil of | 43.00/52.U0/18.75/45.61] 3.83] 0.95] 1.55) 9.14) 5.00/7.60] 7.60 Lime soil, do.| 47.00/53.00]17.21/48.50] 9.00|trace | — 6.21] 5.50) — 8,32 Peat bog..... 46.00/54.00]24.43,30.61) 0.92) 5.15)trace 6.06) 8.75)7.45) — Sand pit..... 47.04152.06 2231 /24.59 8.10! 1. _ 4.05:15 5816.47) — Here we notice that in almost every instance all the mineral ingredients of the plant were extracted from these soils by water. Only magnesia and chlorine are in any case missing. We are not informed, unfortunately, what amount of soluble matters was obtained in these experiments. We next adduce a number of statements of the pro- portion of matters which water is capable of extracting from earth, statements derived from the analyses of soils of widcly differing character and origin. I. Very rich soil (excellent for clover) from St. Martin’s, Upper Austria, treated with six times its quantity of cold water (Jarriges). II. Excellent beet soil (but clover sick) from Schlan- stacdt, Silesia, treated with 5 timcs its quantity of cold water (Jarriges). Ill. Fair wheat soil, Seitendorf, Silesia, treated with 5 times its weight of cold water (Peters). IV. Inferior wheat soil from Lampersdorf, Silesia— ‘B-fold quantity of water (Peters). V. Good wheat soil, Warwickshire, Scotland—10-fold quantity of hot water (Anderson). VI. Garden soil, Cologne—3-fold amount of cold water (Grouven). AQUEOUS SOLUTION OF THE SOIL. 311 VII. Garden soil, Heidelberg—3-fold amount of cold water (Grouven). VII. Poor, sandy soil, Bickendorf—3-fold amount of cold water (Grouven). IX. Clay soil, beet field, Liebesnitz, Bohemia, extract- ed with 9.6 times its weight of water (R. Hoffmann), X. Peat, Meronitz, Bohemia, extracted with 16 times its weight of water (R. Hoffmann). XI. Peaty soil of meadow, extracted with 8 times its weight of water (R. Hoffmann). XII. §$andy soil, Moldau Valley, Bohemia, treated with twice its weight of water (R. Hoffmann). XIII. Salt meadow, Stollhammer, Oldenburg (Harms). XIV. Excellent beet soil, Magdeburg (Hellriegel). XV. Poor beet soil, but good grain soil, Magdeburg (Hellriegel). j XVI. Experimental soil, Ida-Marienhiitte, Silesia, treat- ed with 2} times its weight of cold water (Killenberg). XVII. Soil from farm of Dr. Geo. B. Loring, Salem, Mass., treated with twice its weight of water (W. G. Mixter). MATTERS DISSOLVED BY WATER FROM 100,000 PARTS OF VARIOUS SOILS. S ’ - a ra 8a] 2 (8 SEslgs s/| 8/3] s | 88] § |Ss] § Se8i88] 8 Fle /s/ 3 | ss] 8 [Ss] & Bssies S|] /@!] $ [Ag] 8 [Sq] B SSsiSs] & 18 2 /13 8 2 1 5 11 5 63] 134 5 214) 3 54 |trace |trace |trace 4y%| 6%] 2) 51 6 1 | 4 4 — |trace 1 2 2 23) 43 10 |trace | 1 2 — |trace 1 11 3 18) 46 34 718 13 = = 36] 136 17 3/9 T%| 5 2%) 64%! 13%] 1 22) 87 23 ly! 7 44%) 1%; 1%} 1 2 30) 110 8 Y%| %| 3s84\trace 1 1%] 20 - 10 ‘ 33% «8%| 44) 9 5 3%| 18 |trace | — 40) 14% 1 1 |4 12 {trace 302 |trace | 77% | 449/1095 92 21 24 |trace |trace | 11 2 | 230; 425- 1 2% 1 |trace |trace |trace |trace | — 33; 39% "9 16 | 476 — | 407 44 — | 170/1393 19 3/3 5 1 4 4 20 3 88| 150 5 | 3 4 1 5 3 15 2 83] 147 6%, 2 | 1 3 Yl BY; 3Y%| 12 ud 12) 53 2 ley! 1 ‘iol 7% 1%! 17 | 121 55% 312 HOW CROPS FEED. The foregoing analyses (all the author has access to that are sufficiently detailed for the purpose) indicate 1. That the quantity of soluble matters is greatest—400 to 1,400 in 100,000—in wet, peaty soils (X, XI, XII), though their aqueous solutions are not rich in some of the most important kinds of plant-food, as, for example, phos- phoric acid. 2. That poor, sandy soils (VIII, XII) yield to water the least amount of soluble matters,—40 to 45 in 100,000. 3. That very rich soils, and rich soils especially when recently and heavily manured as for the hop and beet crops (I, II, V, VI, VU, IX, XIV, XV, XVD,, yield, in general, to water, a larger proportion of soluble matters than poor soils, the quantity ranging in the instances be- fore us from 50 to 150 parts in 100,000. 4, It is seen that in most cases phosphoric acid is not present in the aqueous extract in quantity sufficient to be estimated; in some instances other substances, as mag- nesia, chlorine, and sulphuric acid, occur in traces only. 5. In a number of cases essential elements of plant- food, viz., phosphoric acid and sulphuric acid, are wanting, or their presence was overlooked by the analyst. Composition of Drain-Water.—Before further discus- sion of the above data, additional evidence as to the kind and extent of aqueous action on the soil will be adduced, The water of rains, falling on the soil and slowly sinking through it, forms solutions on the grand scale, the study of which must be instructive. Such solutions are easily gathered in their full strength from the tiles of thorough drained fields, when, after a period of dry weather, a rain- fall occurs, sufficient to saturate the ground. Dr. E. Wolff, at Moeckern, Saxony, made two analyses of the water collected in the middle of May from newly laid tiles, when, after a period of no flow, the tiles. had AQUEOUS SOLUTION OF THE SOIL. 313 been running full for several hours in consequence of a heavy rain. The soil was of good quality. He found: in 100,000 PaRTs OF DRAIN-WATER. Rye field. Meadow. Organic matters, 2.6 3.2 Carbonate of lime, 21.9 4.4 cs “ magnesia, 3.1 1.4 “s ‘** potash, 0.3 0.5 “ “ soda, 19 14 Chloride of sodium, 2.3 trace Sulphate of potash, 1.2 trace Alumina, Oxide of iron, i 0.8 0.6 Silica, 0.7 0.4 Phosphoric acid, trace 1.9 34.8 13.8 Prof. Way has made a series of elaborate examinations on drain-waters furnished by Mr. Paine, of Farnham, -Surrey. The waters were collected from the pipes (4-5 ft. deep) of thorough-drained fields in December, 1855, and in most cases were the first flow of the ditches after the autumn rains. The soils, with exception of 7 and 8, were but a few years before in an impoverished condition, but had been brought up to a high state of fertility by ma- nuring and deep tillage. (Jour. Roy. Ag. Soc., XVII, 183.) IN 100,000 PARTS OF DRAIN-WATER. 1 2 3 4 5 6 q Wheat | Hop Ep Wheat | Wheat | Hop | Hop field. | field. | fiel Jield. | field. | field. | field. Potash sins sarsicayccen ost trace |trace | 0.03 | 0.07 trace | 0.31 |trace Soda. 1.43 | 3.10 | 3.23) 1.94 2.03 | 2.00 | 4.57 Lime... 6.93 |10.24 | 8.64] 2.28 3.60 | 8 31 |18.50 Magnesia sc 2cc0 cseersa sree 0.97 | 8.31 | 8.54] 0.58 0.30 | 1.33 | 8.5% Oxide of iron and alumina.} 0.59 { 0.07] 0.14] none! 1.85 | 0.50] 0.71 SHIGA. acssecstncvassiase sy wield wipe 1.85 | 0.64] 0.78 | 1.71 2.57 | 0.93 | 1.21 Chlorine..... cNestaeiaytateuaialne a6 1.00 | 1.57 | 1.84] 1.16 1.80 | 1.73 | 8.74 Sulphuric acid,...i. 5 .1.<<4 06 2.35 | 7.35 | 6.28 | 2.44 1.84 | 4.45 |13.58 Phosphoric acid............ trace | 0.17 |trace | trace | 0.11 | 0.09 | 0.17 Nitric acidicesicciess'eaessreens 10.24 21.05 ]18.17 | 2.78 4.93 |11.50 /16.35 Ammonia .. .......5 seeee 0.025 | 0.025) 0.025) 0.017% | 0.025 | 0.025] 0.009 Soluble organic matter..... 10.00 |10.57 {17.85 | 8.00 8.14 | 8.28 110.57 BOA caves 2c aencwise? 34.885 |58.095160.525! 21.227 | 27.195 |39.455!"72,979 314 HOW CROPS FEED. Krocker has also published analyses of drain-waters collected in summer from poorer soils. He obtained IN 100,000 PARTS: a b é d € J Organic matters, 2.5 2.4 1.6 0.6 6.3 5.6 Carbonate of lime, 8.4 8.4 12.7 w.9 71 8.4 Sulphate of lime, 20.8 21.0 11.4 1.7 U7 7.2 Nitrate of lime, 0.2 0.2 0.1 0.2 0.2 0.2 Carbonate of magnesia, 7.0 6.9 4.7 par 2.7 1.6 Carbonate of iron, 0.4 0.4 0.4 0.2 0.2 0.1 Potash, 0.2 0.2 0.2 0.2 0.4 0.6 Soda, 14 1.5 1.3 1.0 0.5 0.4 Chloride of sodium, 0.8 0.8 0.7 0.3 0.1 0.1 Silica, 0.7 0.7 0.6 0.5 0.6 0.5 Total, 42.1 42.5 33.7 15.3 25.8 4.7 Krocker remarks (Jour, fir Prakt. Chem., 60-466) that phosphoric acid could be detected in all these waters, though its quantity was too small for estimation. aand bare analyses of water from the same drains—a gathered April 1st, and b May 1st, 1853; ¢ is from an ad- joining field; d, from a field where the drains run con- stantly, where, accordingly, the drain-water is mixed with spring water; e and fare of water running from the sur- face of a field and gathered in the furrows, Lysimeter-Water.— Entirely similar results were ob- tained by Zoller in the analysis of water which was col- lected in the Lysimeter of Fraas. The lysimeter* con- .Sists of a vessel with vertical sides and open above, the upper part of which contains a layer of soil (in these ex- periments 6 inches deep) supported by a perforated shelf, while below is a reservoir for the reception of water. The vessel is imbedded in the ground to within an inch of its upper edge, and is then filled from the diaphragm up with soil. In this condition it remains, the soil in it being exposed to the same influences as that of the field, while the water which percolates the soil gathers in the reservoir * Measnrer of solution. 1 AQUEOUS SOLUTION OF THE SOIL. 315 below. Dr. Zoller analyzed the water that was thus col- lected from a number of soils at Munich, in the half year, April 7th to Oct. 7th, 1857. He found IN 100,000 OF LYSIMETER-WATER: Potash, 0.65 0.24 0.20 0.55 0.38 Soda, 0.71 0.56 0.7%4 2.37 0.60 Lime, 14.58 5.76 %.08 6.84 9.23 Magnesia, 2.05 0.89 0.18 0.29 0.51 Oxide of iron, 0.01 0.63 0.83 0.5% 0.43 Chlorine, 5.5 0.95 2.08 3,94 3.58 Phosphoric acid, 0.22 - _ - _ Sulphuric acid, 1.75 2.71 2.8 2.93 3.35 Silica, 1.04 1.13 1.5 0.95 0.93 Organic matter, with some \ 20.4 12.59 18.6% 12.08 10.19 nitric and carbonic acids, Total, 47.23 25.46 29,26 30.52 29,15 The foregoing analyses of drain and lysimeter-water exhibit a certain general agreement in their results, They agree, namely, in demonstrating the presence in the soil-water of all the mineral food of the plant, and while the figures for the total quantities of dissolved matters vary considerably, their average, 36} parts to 100,000 of water, is probably about equally removed from the ex- tremes met with on the one hand in the drainage from a very highly manured soil, and on the other hand in that where the soil-solution is diluted with rain or spring water, It must not be forgotten that in the analyses of drain- age water the figures refer to 100,000 parts of water; whereas, in the analyses on p. 311, they refer to 100,000 parts of soil, and hence the two series of data cannot be directly compared and are not necessarily discrepant. Is Soil-Water destitute of certain Nutritive Matters ? —We notice that in the natural solutions which flow off from the soil, phosphoric acid in nearly every case exists ‘in quantity too minute for estimation; and when estimat- ed, as has been done in a number of instances, its propor- tion does not reach 2 parts in 100,000, This fact, together with the non-appearance of the same substance and of oth- 316 HOW CROPS FEED. er nutritive elements, viz., chlorine and sulphuric acid, in the Table, p.311, leads to the question, May not the aqueous solution of the soil be altogether lacking in some es- sential kinds of mineral plant-food in certain instances? May it not happen in case of a rather poor soil that it will support a moderate crop, and yet refuse to give up to water all the ingredients of that crop that are derived from the soil ? The weight of evidence supports the conclusion that water is capable of dissolving from the soil all the sub- stances that it contains which serve as the food of plants. The absence of one or several substances in the analytical statement would seem to be no proof of their actual ab- sence in the solution, but indicates simply that the sub- stance was overlooked or was too small for estimation by the common methods of analysis in the quantity of solu- tion which the experimenter had in hand, It would ap- pear probable that by employing enough of the soil and enough water in extracting it, solutions would be easily obtained admitting of the detection and estimation of ev- ery ingredient. Knop, however, asserts (Chem. Central- blatt, 1864, 168) that he has repeatedly tested aqueous solutions of fruitful soils for phosphoric acid, employing the soils in quantities ranging from 2 to 22 Ibs., and water in similar amounts, without in any case finding any traces of it. On the other hand Schulze mentions having inva- riably detected it in numerous trials; and Von Babo, in the examination of seven soils, found phosphoric acid in every instance but one, which, singularly enough, was that of a recently manured clay soil, Inno case did he fail to detect lime, potash, soda, sulphuric acid, chlorine, and nitric acid; magnesia he d:d not look for. (Hof? mann’s Jahresbericht der Ag. Chem., I. 17.) So Heiden, in answer to Knop’s statement, found and estimated phosphoric acid in four instances in proportions AQUEOUS SOLUTION OF THE SOIL. 317 ranging from 2 to 6 parts in 100,000 of soil.. (Jahresbe- richt der Ag. Chem., 1865, p. 84.) It should be remarked that Knop’s failure to find phos- phoric acid may depend on the (uranium) method he em- ployed, a method different from that commonly used. Can the Soil-water supply Crops with Food ?— As- suming, then, that all the soil-food for plants exists in solu- tion in the water of the soil, the question arises, Does the water of the soil contain enough of these substances to nourish crops? In case of very fertile or highly manured fields, this question without doubt should be answered af- firmatively. In respect of poor or ordinary soils, how- ever, the answer has been for the most part of late years in the negative. While to decide such a question is, per- haps, impossible, a closer discussion of it may prove ad- vantageous. Russell (Journal Highland and Ag. Soc., New Series, Vol. 8, p. 584) and Liebig (Ann. d. Chem. u. Pharm., CV, 138) were the first to bring prominently forward the idea that crops are not fed simply from aqueous solutions. Dr. Anderson, of Glasgow, presents the argument as follows (his Ag. Chemistry, p. 113): “Tn order to obtain an estimate of the quantity of the substances actually dissolved, we shall select the results obtained * by Way. The average rain-fall in Kent, where the waters he examined were obtained, is 25 inches. Now, it appears that about two-fifths of all the rain which falls escapes through the drains, and the rest is got rid of by evaporation.+ An inch of rain falling on an English acre weighs rather more than a hundred tons; hence in the course of a year, there must pass off by the drains about 9 1,000 tons of drainage water, carrying with it, out of the reach of plants, such substances as it has dissolved, and * On drain-waters, eee p 318. ‘+ From Parke’s measurements, Jour. Roy. Ag. Soc., Hng., Vol. XVIL, p. 127%. 318 HOW CROPS FEED. 1,500 tons must remain to give to the plant all that it holds in solution. These 1,500 tons of water must, if they have the same composition as that which escapes, contain only two and a half pounds of potash and less than a pound of ammonia, It may be alleged that the water which re- mains lying longer in contact with the soil may contain a larger quantity of matters in solution; but even admit- ting this to be the case, it cannot for a moment be sup- posed that they can ever amount to more than a very small fraction of what is required for a single crop.” The objection to this conclusion which Anderson al- ludes to above, but which he considers to be of little mo- ment, is, perhaps, a serious one. The soil is saturated with water sufficiently to cause a flow from drains at a depth of 4 to 5 ft., for but a small part of the grow- ing season, The Indian corn crop, for example, is planted in New England in the early part of June, and is harvest- ed the first of October. During the four months of its growth, the average rain-fall is not enough to make a flow from drains for more, perhaps, than one day in seven. During six-sevenths of the time, then, there is a current of water ascending in the soil to supply the loss by evapora- tion at the surface. In this way the solution at the sur- face is concentrated by the carrying upward of dissolved matters. A heavy rain dilutes this solution, not having time to saturate itself before reaching the drains, Ac- cordingly we find that the quantity of matters dissolved by water acting thoroughly on the surface soil is greater than that washed out by an equal amount of drain-water ; at least such is the conclusion to be gathered from the experiments of Eichhorn and Wunder. These chemists have examined the solution obtained by leaving soil in contact with just sufficient water to saturate it for a number of days or weeks. (Vs. S¢., II, pp. 107- 111.) The soil examined by Eichhorn was from a garden near AQUEOUS SOLUTION OF THE SOIL. 319 Bonn, Prussia, not freshly manured, and was treated with about one-third its weight (36.5 per cent) of cold water for ten days. Wunder employed soil from a field of the Experiment Station, Chemnitz, Saxony. This soil had not been re- cently manured, and was of rather inferior quality (yield- ed 15 bushels wheat per acre, English). It was also treated with about one-third its weight (34.5 per cent) of water for four weeks. The solutions thus procured contained in 100,000 parts, Bonn. Chemnitz. Silica, 480 2.57 Sulphuric acid, 10.02 — Phosphoric acid, 3.10 traces Oxide of iron and alumina, trace 1.17 Chloride of sodium, 5.86 4.76 Lime, 12.80 8.36 Magnesia, 3.84 3.74 Potash, 11.54 0.75 Soda, 1.10 3.04 If we assume with Anderson that 1,500 tons (= 3,360,000 Ibs.) of water remain in these soils to feed a crop, and that this quantity makes solutions like those whose composition is given above, we have dissolved (in pounds per English acre) from the soil of Bonn. Chemnitz. Silica, 161 86 Sulphuric acid, 343 = Phosphoric acid, : 104 ? Oxide of iron and alumina, 39 Chloride of sodium, 197 160 Lime, 430 281 Magnesia, 129 126 Potash, 387 5 Soda, 37 102 These results differ widely from those based on the com- position of drain-water. Eichhorn, by a similar calcula- tion, was led to the conclusion that the soil he operated with was capable of nourishing the heaviest crops with 320 HOW CROPS FEED. its aqueous solution. Wunder, on the contrary, calculat- ed that the Chemnitz soil yields insufficient matters for the ordinary amount of vegetation; and we see that as respects potash, the wants of grass and root crops could not be satisfied with the quantities in our computation, while sulphuric acid and phosphoric acid are nearly or en- tirely wanting. We do not, however, regard such calcu- lations as decisive, either one way or the other. The quantity of water which may stand at the actual service of a crop is beyond our power to estimate with anything like certainty. Doubtless the amount assumed by Ander- son is too large, and hence the calculations relative to the Bonn and Chemnitz soils as above interpreted, convey an exaggerated notion of the extent of solution. Proper Concentration of Plant-Food,— Let us next inquire what strength of solution is necessary for the sup- port of plants. As has been shown by Nobbe (Vs. S¢., VIII, p. 337), Birner & Lucanus (Vs. S¢., VIII, p. 184), and Wolff ( Vs. S¢t., VIII, p. 192), various agricultural plants flourish to extraordinary perfection when their roots are immersed in . a solution containing about one part of ash-ingredients (together with nitrates) to 1,000 of water. The solutions they employed contained the following substances in the proportions stated (approximately) be- low: In 100,000 parts of Water. Nobbe. , Birner & Lucanus. Wolff. ’ Lime, 16 19 19 \ Magnesia, 3 614 21g Potash, 31 16 16 v Phosphoric acid, q 24 14 . Chlorine, 21 none 2 \ V Sulphuric acid, 6 13 4 » Oxide of iron, Mu lg XK Nitric acid, 314 36 51 anaes a, 116 115 * 109 Nobbe found further that the vigor of vegetation in his a al. u AQUEOUS SOLUTION OF THE SOIL. 321 solution was diminished either by reducing the proportion of solid matters below 0.5, or increasing it to 2 parts in 1,000 of water. The proper dilution of the food of plants for most vigorous growth and most perfect development is thus approximately indicated. We notice, however, considerable latitude as regards, the proportions of some of the most important ingredients which are usually present in least quantity in the aqueous solution of the soil. Thus, phosphoric acid in one case is thrice as abundant as in the other. We infer, therefore, that the minimum limit of the individual ingredients is not fixed by the above experiments, especially not for or- dinary growth. Birner and Lucanus woniauitedts other results ( Vs. St., VIL, p. 154), which throw much light on the question un- der discussion. They compared the growth of the oat plant, when nourished respectively by a rich garden soil, by ordinary cultivated land, by a solution the composition. of which is given above, and lastly by a natural aqueous solution of soil, viz., a well-water. Below is a statement of the weight in grams of an average plant, produced in these various media, as well as that of the grain yielded by it. Dry crops compared Weight of aver- Weight of with seed, the latter age plant, dry. dry Grain. taken as unity. Gafden.......... 5.27 1.23 193 Biel ncseey ce ovo 1.% 0.63 64 Solution......... 3.75 1.53 137 Well-water....... 2.91 1.25 106 We gather from the above figures that well-water, in quantities of one quart for each plant, renewed weekly, gave a considerably heavier plant, straw, and grain, than a field under ordinary culture ; the yield in grain being double that of the iatter, and equal to that obtained in a rich garden soil. 14* 322 HOW CROPS FEED. The analysis of the well-water shows that the nutritive solution need not contain the food of plants in greater proportion than occurs in the aqueous extract of ordinary soils, The well-water contained, in 100,000 parts, ‘ Lime, - - - - - 15.14 Magnesia, -~ - - - : 1.53 Potash, - - - - - 2.13 Phosphoric acid, : - - + 0,16 Sulphuric acid, - - T45 Nitric acid, - - - - - 6.02 We thus have demonstration that a solution containing but one-and-a-half parts of phosphoric acid to ten million of watcr is competent, so far as this substance is concern- ed, to support a crop bearing twice as much grain as an ordinary soil could produce under the same circumstances of weather. Do we thus reach the limit of dilution ? We cannot answer for agricultural plants, but in case of some other forms of vegetation, the reply is obvious and striking. Various species of Fucus, Laminaria, and other ma- rine plants, contain iodine in notable quantities. This element, so much used in photography and medicine, is made exclusively from the ashes of these sea-weeds, one establishment in Glasgow producing 35 tons of it annu- ally. The iodine must be gathered from the water of the ocean in which these plants vegetate, and yet, although the starch-test is so delicate thit one part of iodine can be detected when dissolved’in 300,000 parts of water, it is not possible to recognize iodine in the “ bitterns” which remain when sea-water is concentrated to the one-hund- reth of its original bulk, so that its proportion must be less than one part in thirty millions of water! (Otto’s Lehrbuch der Chemie, 4te, Aufl., pp. 743-4.) AQUEOUS SOLUTION OF THE SOIL. 323 Mode whereby dilute solutions may nourish Crops.— There are other considerations which may enable us to reconcile extreme dilution of the nutritive liquid of the soil, with the conveyance by it into the plant of the req- uisite quantity of its appropriate food. It is certain that the amount of matters found in solution at any given moment in the water of the soil by no mcans repre- sents its power of supplying nourishment to vegetation. If the water which has saturated itself with the solu- ble matters of the soil be deprived of a portion or all of these matters, as it might be by the absorptive action of the roots of a plant, the water would immediately act anew upon the soil, and in time would dissolve another similar quantity of the same substance or substances, and these being taken up by plants, it would again dissolve more, and so on as long and to such an extent as the soil itself would admit. In other words, the same water may act over and over again in the soil, to transfer from it to the crop the needful soluble matters. It has been shown that the substances dissolved in water may diffuse through animal and vegetable tissues independently of each other, and independently of the water itself. (H.C. G., p. 340.) Deportment of the Soil to renewed portions of Water. —It remains to satisfy ourselves that the soil. is capable of yielding soluble matters continuously to renewed por- tions of water. The only observations on this point that the writer is acquainted with are those made by Schulze and Ulbricht. Schulze experimented on a rich soil from Goldberg, in Mecklenburg (Vs. St., VI., 411). This soil, in a quantity of 1,000 grams (= 2.2 lbs.) was slowly leached with pure water, so that one liter (= 1.056 quart) of liquid passed it in 24 hours. The extraction was con- tinued during six successive days, and each portion was separately examined for total matters dissolved, and for phosphoric acid, which is, in general, the least soluble of the soil-in gredients, 324 HOW CROPS FEED. The results were as follows, for 1,000 parts of extract, Portion of Total Organic aqueous matters and Phosphoric extract. dissolved. volatile. Inorganic. acid. 1 0.535 0.340 0.195 0.0056 2 0.120 0.057 0.063 0.0082 3 0.261 0.101 0.160 0.0088 4 0.203 0.083 0.120 0.0075 5 0.260 0.082 0.178 0.0069 6 0.200 0.077 0.123 0.0044 1.579 0.740 0.839 0.0414 We see that each successive extraction removed from the soil a scarcely diminished quantity of mineral mat- ters, including phosphoric acid. In case of a poor soil, we should not expect results so striking, as regards quan- tity of dissolved matters, but doubtless they would be similar in kind. This is shown by the investigations that follow: Ulbricht gives ( Vs. St., V., 207) the results of the simi- lar treatment of four soils, 1,000 grams of each were put in contact with four times as much pure water for three days, then two-thirds of the solution was poured off for analysis, and replaced by as much pure water; this was repeated ten times. Partial analyses were made of some of the extracts thus obtained ; we subjoin the pub- lished results : Dissolved by 40,000,000 parts of water from 1,000,000 parts of— Loamy Sand from Heiusdorf. 1st 2d 3d 4th 7th 10th Extract. |Extract.|Extract.|Extract.|Extract | Extract. Potash........0.05 3014 15 15 8 4 Soda........ vee] 84 14 21 18 11 Lime...... 2a] 9 39 38 39 Magnesia 301g 12 10 10 Phosphoric acid...} trace. 14 3 3 Total......... 190 81g 87 78 AQUEOUS SOLUTION OF THE SOIL. 325 Loamy Sand from Wahlsdorf. Potash............ 23 12 18 6 4 Soda.............. 26 16 20 16 6 DON Csi sceis's sareiara ze 116 43 39. 42 48 Magnesia......... 3614 15 14 12 14 Phosphoric acid.. vi | 3 4 | 4 | | Total......... | 208% | 89 9 | 80 | | Loamy ferruginous Sand from Dahme, containing 41g of humus, Potash........ asiee q 6 7 v 3 Soda.............. 41 11 26 17 8 HIM} s cseewrscsces 96 70 55 48 62 Magnesia.......... 14 10 9 7 8 Phosphoric acid..] trace. 2 trace. 1 Total......... 158 99 97 80 Fine Sandy Loam from Falkenberg. Potash............ 1 11 9 9 S0d8e 5 ssxees sees 47 12 12 8 Lime....... 47 27 19 18 Magnesia. “17 8 5 6 Phosphoric acid.. 3 2 trace. | trace. Total......... 129 60 45 at | | As Schulze remarks, it is practically impossible to ex- haust a soil completely by- water. This liquid will still dissolve something after the most prolonged or frequently renewed action, as not one of the components of the soil is possessed of absolute insolubility, although in a sterile soil the amount of matters taken up would presently be- come what the chemist terms “traces,” or might be such at the outset. The two analyses by Krocker, a and 8, p. 314, made. on water from the same drain, gathered at an intervai of one month, further show that water, rapidly percolating the soil, continuously finds and takes up new portions of all its ingredients. In addition to the simple solution of matters, the soil suffers constantly the chemical changes which have been already noticed, and are expressed by the term weather- 326 HOW CROPS FEED. ing. Matters insoluble in water to-day become soluble to-morrow, and substances that to-morrow resist the action of water are taken up the-day after. In this way there is no limit to the solution of the soil, and we cannot there- fore infer from what the soil yields to water at any given moment nor from what is taken out of it by any given amount of water, the real extent to which aqueous action operates, during the long period of vegetable growth, to present to the roots of a crop the indispensable ingredi- ents of its food. The discussion of the question as to the capacity of water to dissolve from the soil enough of the various in- gredients to feed crops, while satisfactorily establishing this capacity in case of rich soils, and making evident that in poor soils most of the inorganic matters are pre- sented to vegetation by water in sufficient quantity, does not entirely satisfy us in reference to some of the needful elements of the plant, especially phosphoric acid. It is therefore appropriate, in this place, to pursue fur- ther inquiries into the mode by which vegetation acquires food from the soil, although to do so will somewhat inter- rupt the general plan of our chapter. *~ Direct action of Roots upon the Soil.—In noticing the means by which rocks are converted into soils, the action of the organic acids of the living plant has been mentioned. Since that chapter was written, further evi- dence has been obtained concerning the influence of the plant on the soil, which we now proceed to adduce. Sachs (Haperimental Physiologie, 189) gives an ac- count of observations made by him on the action of roots on marble, dolomite (carbonate of lime and magnesia), magnesite (carbonate of magnesia), osteolite (phosphate of lime), gypsum, and glass. Polished plates of these substances were placed at the bottom of suitable vessels and covered several inches in depth with fine quartz sand. Seeds of various plants were planted in the sand and kept DIRECT ACTION OF ROOTS UPON THE SOIL. 327° moist. The roots penetrated the sand and came in con- tact with the plates below, and branched horizontally on their surfaces. After several days or weeks the plates were removed and examined. ©The plants employed were the bean, maize, squash, and wheat. The carbonates of lime and magnesia and the phosphate of lime were plains ly corroded where they had been in contact with the roots, so that the course of the latter could be traced with- out difficulty. Even the action of the root-hairs was mani- fest as a faint roughening of the surface of the stone either side of the path of the root. Gypsum and glass were not perceptibly acted on. Dietrich has made a scries of experiments (Hoj'mann’s Jahresbericht, VI, 3) on the amount of matters made solu- ble from basalt and sandstone, both coarsely powdered, and kept watered with equal quantities of distilled water, when supporting and when free from vegetation, The crushed rocks were employed in quantities of 9 and 11 Ibs.; they were well washed before the trials with dis- tilled water, and access of dust was prevented by a layer of cotton batting upon the surface. After removing the plants, at the termination of the experiments, each sam- ple of rock-soil was washed with the same quantity of water, to which a hundredth of nitric acid had been added. It was found that the plants employed, especially lupins, peas, vetches, spurry, and buckwheat, assisted in the decomposition and solution of the basalt and sand- stone. Not only did these plants take up mineral mat- ters from the rock, but the latter contained besides, a larger amount of soluble matters than was found in the experiments where no plants were madé to grow. The cereal grains had the same effect, but in less degree. In the subjoined table we give the total quantities of sub- stances dissolved under the influence of the growing vegetation. These figures were obtained by adding to what was found in the washings of the rock-soils the ash 328 HOW CROPS FEED. of the crops, and subtracting from that sum the ash of the seeds, together with the matters made soluble in the same soils, which had sustained no plants, but which had been treated otherwise in a similar manner. MATTERS DISSOLVED BY ACTION OF ROOTS. On 9 lbs. of On 11 Ibs. of sandstone. basalt. Of 8 lupin plants ..............0e eee 0.608 grams, 0.749 grams. “3 pea Be eliea dessin lS hecsa,nayease 0.481 =“ 0.713‘ Ospurry xecswese cewsnsnmas ve 0.268 0.365 STO DUCE WH EM ce cewineiesisaesieciernsee 0,282 0.327 © Ayvetch. “© siswenwemaneenmar eng 0.221 =“ 0.251 = gD “Sweat ME eccdeveavaesrnesoredssslerwes nye 0.027,“ 0.196 ‘“* “« 8rye UO eaeeia nd ene sebiodneais 0.014 0.1382‘ These trials appear to show conclusively that plants exert a decided effect on the soil. We are not informed, however, what particular substances are rendered soluble under this influence. We conclude, then, that the direct action of the roots of a crop may in all cases contribute toward supplying it with food, and in many instances may be absolutely essential to its satisfactory growth. Further Notice of Matters Soluble in Water.—The analyses we have quoted show that every chemical ele- ment of the soil may pass into aqueous solution. They ’ also show that some substances are dissolved more easily and in greater quantity than others. In general, chlcrine, nitric acid, and sulphuric acid, are most readily and completely taken up by water, and, for the most part, in combination with lime, soda, and, magnesia. In spme cases, sulphuric acid appears to exist in a difficultly soluble condition (Van Bemmelen, Vs. St., VIIL, 263). ' Potash, ammonia, oxide of iron, alumina, silica, and phosphoric acid, are the substances which are usually soluble in but small proportion. These, together with ACID SOLUTION OF THE SOIL. 329 lime, magnesia, and soda, it is difficult or impossible to wash out completely from a soil of good quality. Very poor soils may be deficient in soluble forms of any or several of the above ingredients, and therefore readily admit of nearly complete extraction by a small amount of water. Certain soils contain soluble salts of iron and alumina (sulphates and humates) in considerable quantity, and are for that reason unproductive. Such are many marsh lands, as well as upland soils containing bisulphide of iron (iron pyrites), of the kind that readily oxidizes to sulphate of protoxide of iron (copperas). § 3 SOLUTION OF THE SOIL IN STRONG ACIDS. The strong acids, hydrochloric (muriatic), nitric, and sulphuric, by virtue of their vigorous affinities, readily remove from the soil a considerable quantity of all its mineral ingredients. The quantity thus taken up is greatly more than can be dissolved in water, and is, in general, the greater, the more fertile the soil. Exceptions are soils consisting largely of carbonate of lime (chalk soils), or compounds of iron (ochreous soils). The differ- ent acids above named exercise very unlike solvent effects according to their concentration, the time of their action, the temperature at which they are applied, and the chemi- . eal nature and state of division of the soil. The deportment of the minerals which chiefly constitute the soil towards these acids will enable us to under- stand their action upon the soil itself. Of these minerals quartz, feldspar, mica, hornblende, augite, talc, steatite, kaolinite, chrysolite, and chlorite, when not altered by weathering, nearly or altogether resist the action of even hot and moderately strong hydrochloric and nitric acids, 330 HOW CROPS FEED. On the other hand, all carbonates, sulphates, and phos- phates, are completely dissolved, while the zeolites and serpentine are decomposed, their alkalies, lime, etc., enter- ing into solution, and the silica they contain separating, for the most part, as gelatinous hydrate. According to the nature of the soil, and the concentra- tion of the reagent, hydrochloric acid, the solvent usually employed, takes up from two to fifteen or more per cent. Very dilute acids remove from the soil the bases, lime, magnesia, potash, and soda, in scarcely greater quantity than they are united with chlorine, and with sulphuric, phosphoric, carbonic, and nitric acids. Treatment with stronger acids takes up the bases above mentioned, par- ticularly lime and magnesia, in greater proportion than the acids specified. We find that, by the stronger acids, silica is displaced from combination (and may be taken up by boiling the soil with solution of soda after treat- ment with the acid). It hence follows that silicates, such as are decomposable by acids, (zeolites) exist in the soil, although we cannot recognize them directly by inspec- tion even with the help of the microscope. To this point we shall subsequently recur. g 4. PORTION OF SOIL INSOLUBLE IN ACIDS. When a soil has been boiled with concentrated hydro- chloric acid for some time, or until this solvent exerts no further action, there may remain quartz, feldspar, mica, hornblende, augite, and kaolinite (clay), together with other similar silicates, which, in many cases, are ingredients of the soil. Treatment with concentrated sulphuric acid at very high temperatures (Mitscherlich), or syrupy phos- phoric acid (A. Miller), decomposes all these minerals, quartz alone excepted. By making, therefore, in the first CHEMICAL ACTION IN THE SOIL. 331 place, a mechanical analysis, as described on page 147, and subjecting the fine portion, which consists entirely or in great part of clay, to the action of these acids, the quan- tity of clay may be approximately estimated. Or, by “melting the portion insoluble in acids with carbonate of soda, or acting upon it with hydrofluoric acid, the whole may be decomposed, and its elementary composition be ascertained by further analysis, Notwithstanding an immense amount of labor has been expended in studying the composition of soils, and chiefly in ascertaining what and how much, acids dissolve from them, we have, unfortunately, very few results in the way of general principles that are of application, either to a scientific or a practical purpose. In a number of special cases, however, these investigations have proved exceed- ingly instructive and useful. ae WVVS A REACTIONS BY WHICH THE SOLUBILITY OF THE ELEMENTS OF THE SOIL IS ALTERED. SOLVENT EFFECT OF VARIOUS SUBSTANCES THAT ARE COMMONLY BROUGHT TO ACT UPON SOILS. THE AB- SORPTIVE AND FIXING POWER OF SOILS. Chemical Action in the Soil.—Chemistry has proved that the soil is by no means the inert thing it appears to be. It is not a passive jumble of rock-dust, out of which air and water extract the food of vegetation. It is not simply a stage on which the plant performs the drama of growth. It is, on the contrary, in itself, the theater of ceaseless activities; the seat of perpetual and complicated changes. A large share of the rocks now accessible to our study at the earth’s surface have once been soil, or in the condi- tion of soil. Not only the immense masses of stratified limestones, sandstones, slates, and shales, that cover so 332 HOW CROPS FEED. large a part of the Middle States, but most of the rocks of New England have been soil, and have supported vege- table and animal life, as is proved by the fossil relics that have been disinterred from them. We have explained the agencies, mechanical and chemi- cal, by which our soils have been formed and are forming from the rocks, By a reverse metamorphosis, involving also the codperation of mechanical and chemical and even of vital influences, the soils of earlier ages have been so0- lidified and cemented to our rocks, Nor, indeed, is this process of rock-making brought to a conclusion. It is going on at the present day on a stupendous scale in vari- ous parts of the world, as the observations of geologists abundantly demonstrate. If we moisten sand with a so- lution of silicate of soda or silicate of potash, and then drench it with chloride of calcium, it shortly hardens to a rock-like mass, possessing enough firmness to answer many building purposes (Ransome’ s artificial stone). § g 33 3 ; & > &. 8 : és g¢ § § bk BSS 5 q =x OR & @E oF S Barley Grain, 43.75 8.1 1.7 3.1 1.2 0.3 14.2 1.2 0.5 Straw, 100.00 12.0 4.6 3.0 4.3 1.9 6.0 2.8 2.6 Total, 143.75 20.1 6.3 6.1 8.5 2.2 20.4 4.0 3.1 In the account of Hellriegel’s experiments, it is stated that the maximum barley crop in some other of his trials, corresponds to 8,160 lbs. of grain, or 154 bushels of 53 Ibs. each per acre. This is more than 44 times the yield above assumed. The above figures show that no essential ash-ingredi- ent of the oat crop is present in larger quantity than potash. Phosphoric acid is quite the same in amount, * These figures are employed by Anderson, and are based on Scotch statistics REVIEW AND CONCLUSION. 365 while lime is but one-half as much, and the other acids and bases are still less abundant. It follows then that if 71 Ibs. of available potash in 1,000.000 of soil are cnough for a barley crop 44 times greater than can ordinarily he produced under agricultural conditions, the same quantity of phosphoric acid, and less than half that amount of lime, ete, must be ample. Calculating on this basis, we give in the following statement the quantities required per acre, taken to the depth of one foot, to produce the max- imum crop of Hellricgel (1), and the quantities needed for the average crop of 33 bushels (2). The amounts of nitrogen arc those which Hellriegel found adequate to the wheat crop. See p. 289. 1 2 lbs lbs. Potash, 248 55 Soda, % 17 Magnesia, %6 17 Lime, 105 23 Phosphoric acid, 250 55 Sulphuric acid, 49 11 Chiorine, 38 8 Nitrogen, 245 54 If now we divide the total quantities of potash, etc., found in an acre, or 3,500.000 lbs. of the soil analyzed by Baumhauer, by the number of pounds thus estimated to be necessarily present in order to produce a maximum or an average yield, we have the following quotients, which give the number of maximum barley crops and the number of average crops, for which the soil can furnish the re- spective materials. ; The Zuider Zee soil contains enough Lime for 1864 naximum and 6138 averaye barley crops, : Potash “144 “ “648 “ “ Phosphoric acid “65 “ « 992 & “« “ Sulphuric a «64 ee ss ORQ « “ Nitrogen in ammonia ‘ % ee « 31 tt “ “ We give next the composition of one of the excellent 366 HOW CROPS FEED. wheat soils of Mid Lothian, analyzed by Dr. Anderson. The air-dry surface-soil contained in 100 parts: ili Cay -ssikists ib pbiarl adele aeray ao Red eiedieainagiee sales MAIMG io, cserasafereicuin avd aes & tak vert Sia ce auatih graye Magnesia. Potash; :42°2 staawawnwe peas aaeomes Sulphuric acid Phosphoric acid......... ee re OES ae 0.480 Chlorine traces We observe that lime, potash, and sulphuric acid, are much less abundant than in the soil from the Zuider Zee. The quantity of phosphoric acid is about the same. The amount of sulphuric acid is but one-twentieth that in the Holland soil, and is accordingly enough for 15 good bar- ley crops. Lastly may be instanced the author’s analysis of a soil from the Upper Palatinate, which was characterized by Dr. Sendtner, who collected it, as “the most sterile soil in Bavaria.” Watetis.: sees vasa eves sews tae aw eae ii eee cae we 0.535 Oxide of iron-and alumi cceccaecvavesicas > caren 1.640 TLIMG: + cscs Gaiess sats aeese da oes Te wise Salas eRe 0.096 Magnesia. A APWOTIE APIs ccaestcasanvats casio ececanewws loede trace PHOSPWOrie NCH so. se cscais ose siorsie wniciars oie diane wera s wie wis trace Chlorine BARA crwth aces vame asa euiwas add ieee name gvaen 100.000 Here we note the absence in weighable quantity of magnesia and phosphoric acid, while potash could not éven REVIEW AND CONCLUSION. 367 be detected by the tests employed. This soil was mostly naked and destitute of vegetation, and its composition shows the absence of any crop-producing power. Relative Importance of the Ingredients of the Soil. —From the general point of view of vegetable nutrition, all those ingredients of the soil which act as food to the plant, are equally important as they are equally indispens- able. Absence of any one of the substances which water- culture demonstrates must be presented to the roots of a plant so that it shall grow, is fatal to the productiveness of a soil. : Thus regarded, oxide of iron is as important as phos- phoric acid, and chlorine (for the crops which require it) is no less valuable than potash. Practically, however, the relative importance of the nutritive elements is mcas- ured by their comparative abundance. Those which, like oxide of iron, are rarely deficient, are for that reason less prominent among the factors of a crop. If any single substance, he it phosphoric acid, or sulphuric acid, or pot- ash, or magnesia, is lacking in a given soil at a certain time, that substance is then and for that soil the most im- portant ingredient. From the point of view of natural abundance, we may safely state that, on the whole, availa- ble nitrogen and phosphoric acid are the most important ingredients of the soil, and potash, perhaps, takes the next rank. These are, most commonly, the substances whose absence or deficiency impairs fertility, and are those which, when added as fertilizers, produce the most frequent and remarkable increase of productiveness. In a multi- tude of special cases, however, sulphuric acid or lime, or magnesia, assumes the chief prominence, while in many in- stances it is scarcely possible to make out a greater crop- producing value for one of these substances over several others. Again, those ingredients of the soil which could be spared for all that they immediately contribute to the 368 HOW CROPS FEED. nourishment of crops, are often the chief factors of fer- tility on account of their indirect action, or because they supply some necessary physical conditions. Thus humus is not in any way essential to the growth of agricultural plants, for plants have been raised to full perfection with- out it; yet in the soil it has immense value practically, since among other reasons it stores and supplies water and assimilable nitrogen. Again, gravel may not be in any sense nutritious, yet because it acts as a reservoir of heat and promotes drainage it may be one of the most import- ant components of a soil. What the Soil must Supply.—It is not sufficient that the soil contain an adequate amount of the several ash-in- gredients of the plant and of nitrogen, but it must be able to give these over to the plant in due quantity and pro- portion. The chemist could withont difficulty compound an artificial soil that should include every element of plant-food in abundances, and yet be perfectly sterile. The potash of feldspar, the phosphoric acid of massive apatite, the nitrogen of peat, are nearly innutritious for crops on account of their immobility—because they are locked up in insoluble combinations. Indications of Chemical Analysis.—The analyses by Baumhauer of soils from the Zuider Zee, p. 362, give in a single statement their ultimate composition. We are in- formed how much phosphoric acid, potash, magnesia, etc., exist in the soil, but get from the analysis no clue to the amount of any of these substances which is at the dispo- sition of the present crop. Experience demonstrates the productiveness of the soil, and experience also shows that a soil of such compusition is fertile; but the analysis does not necessarily give proof of the fact. A nearer approach to providing the data for estimating what a soil may sup- ply to crops, is made by ascertaining what it will yield to acids, REVIEW AND CONCLUSION. 369 Boussingault has analyzed in this manner a soil from Calvario, near Tacunga, in Equador, South America, which possesses extraordinary fertility. He found its composition to be as follows: Nitrogen in organic combination, 0.248 Nitric acid, 0.975 Ammonia, 0.010 Phosphoric acid, } 0.460 Chlorine, 0.395 Sulphuric acid, 0.023 Carbonic acid, ; : traces Potash and Soda, Soluble in acids. 1.030 Lime, 1.256 Magnesia, 0.875 Sesquivxide of irou, 2.450 Sand, fragments of pumice, and clay insoluble in acids, 83.195 Moisture, 3.150 Organic matters (less nitrogen), undetermined substances, and loss, 5.938 100.000 This analysis is much more complete in reference to ni- trogen and its compounds, than those by Baumhauer al. ready given (p. 362), and therefore has a peculiar value. As regards the other ingredients, we observe that phos- phoric acid is present in about the same proportion; lime, alkalies, sulphuric acid, and chlorine, are less abundant, while magnesia is more abundant than in the soils from Zuider Zee. The method of analysis is a guarantee that the one per cent of potash and soda does not exist in the insoluble form of feldspar. Boussingault found fragments of pumice by a microscopicexamination. This rock is vesicular feld- spar, or has at least a composition similar to feldspar, and the same insolubility in acids. The inert nitrogen of the humus is discriminated from that which in the state of nitric acid is doubtless all assim- ilable, and that which, as ammonia, is probably so for the most part. The comparative solubility of the two per cent of lime and magnesia is also indicated by the analysis, 16* 370 HOW CROPS FEED. Boussingault does not state the kind or concentration, or temperature of the acid employed to extract the soil for the above analysis. These are by no means points of indifference. Grouven (lter & 3ter Salzmiinder Berichte) has extracted the same earth with hydrochloric acid, con. centrated and dilute, hot and cold, with greatly different results as was to be anticipated. In 1862, a sample from an experimental field at Salzmiinde was treated, after be- ing heated to redness, with boiling concentrated acid for 3 hours. In 1867 a sample was taken from a field 1,000 paces distant from the former, one portion of it was treat- ed with boiling dilute acid (1 of concentrated acid to 20 of water) for 3 hours. Another portion was digested for three days with the same dilute acid, but without applica- tion of heat. In each case the same substances were ex- tracted, but the quantities taken up were less, as the acid was weaker, or acted at a lower temperature. The follow- ing statement shows the composition of cach extract, cal- culated on 100 parts of the soil. EXTRACT OF SOIL OF SALZMUNDE. Hot strong acid. Tiot ditute acid. Cold dilute acid. Potash, 635, 116 029 Soda, 127 067 -020 Lime, 1.677 1.046 1.098 Magnesia, 687 Bete) .23T Oxide of iron and alumina, 7.931 3.189 -680 Oxide of manganese, 030 085 071 Sulphnric acid, 059 -03) -020 Phosphoric acid, 059 O81 .057 Silica, 1.735 BE 1% Total, 12.990, 5.308 2.357 The most interesting fact brought out by the above fig- ures, is that strong and weak acids do not act on all the ingredients with the same relative power. Comparing the quantities found in the extract by cold dilute acid with those which the hot dilute acid took up, we find that the latter dissolved 5 times as much of oxide of iron and alumina, 4 times as much potash, 3 times as much soda, REVIEW *AND CONCLUSION. 3871 twice the amount of magnesia, sulphuric acid, and phos- phoric acid, and the same quantity of lime. These facts show how very far chemical analysis in its present state is from being able to say definitely what any given svil can supply to crops, although we owe nearly all our pre- cise knowledge of vegetable nutrition directly or iidi- rectly to this art. The solvent effect of water on the soil, and the direct action of roots, have been already discussed (pp. 309 to 328). It is unquestionably the fact that acids, like pure water in Ulbricht’s experiments (p. 324), dissolve the more the longer they are in contact with a soil, and it is evident that the question: How much a particular soil is able to give to crops? is one for which we not only have no chemical answer at the present, but one that for many ‘years, and, perhaps, always can be answered only by the method of experience—by appealing to the crop and not to the soil. Chemical analysis is competent to inform us very accurately as to the ultimate composition of the soil, but as regards its proximate composition or its chemical consti- tution, there remains a vast and difficult Unknown, which will yield only to very long and laborious investigation. Maintenance of a Supply of Plant-food.—By the recip- rocal action of the atmosphere and the soil, the latter keeps up its store of available nutritive matters. The difficultly soluble silicates slowly yield alkalies, lime, and magnesia, in soluble forms; the sulphides are converted into sulphates, and, generally, the minerals of the soil are disintegrated and ‘fuxed under the influence of the oxy- gen, the water, the carbonic acid, and the nitric acid of the air, (pp. 122-135). Again, ihe atmospheric nitrogen is assimilated by the soil in the shape of ammonia, ni- trates, and the amide-like matters of humus, (pp. 254-265), The rate of disintegration as well as that of nitrifica- tion depends in part upon the chemical and physical char- acters-of the soil, and partly upon temperature and mete- 3872 HOW CROPS FEED, orological conditions. In the tropics, both these processes go on more vigorously than in cold climates. Every soil has a certain inherent capacity of production in general, which is chiefly governed by its power of sup- plying plant-food, and is designated its “natural strength.” The rocky hill ranges of the Housatonic yield once in 30 years a crop of wood, the value of which, for a given locality and area, is nearly uniform from century to cen- tury. Under cultivation, the same uniformity of crop is seen when the conditions remain unchanged. Messrs. Lawes and Gilbert, in their valuable experiments, have obtained from “a soil of not more than average wheat- producing quality,” without the application of any ma- nure, 20 successive crops of wheat, the first of which was 15 bushels per acre, the last 173} bushels, and the average of all 164 bushels. (Jowr. Roy. Ag. Soc. of Hng., XXV, 490.) The same investigators also raised barley on the same field for 16 years, each year applying the same quan- tity and kinds of manure, and obtaining in the first 8 years (1852-59) an average of 44% bushels of grain and 28 cwt. of straw; for the second 8 years an average of 51 bushels of grain and 29 cwt. of straw; and for the 16 years an average of 48! bushels of grain and 28} cwt. of straw. (Jour. of Bath and West of Eng. Ag.Soc., XVI,2i4.) The wheat experiments show the natural capacity of the Rothamstead soil for producing that cereal, and de- menstrate that those matters which are annually removed by a crop of 16} bushels, are here restored to availability by weathering and nitrification, The crop is thus a measure of one or both of these processes.* It is probable * In the experiments of Lawes and Gilbert it was found that phosphates, sul- phates, and carbonates of lime, potash, inaynesia, and soda, raised the produce of wheat but 2 to 3 bushels per acre above the yield of the unmanured soil, while sulphate and muriate of ammonia increased the crop 6 to 10 bushels. This re- sult, obtained on three soils, viz., at Rothamstead in Herts, Holkham in Nor- folk, and Rodmersham in Kent, the experiments extending over periods of §, 8, and 4 years, respectively. shows that these soils were, for the wheat crop, rela- tively deficient in assimilahle nitrogen. The crop on the nnmanured soil was therefore a measure of nitrification rather than of mincral disintegration. Py REVIEW AND CONCLUSION. 373 that this native power of' producing wheat will last unim- paired for years, or, perhaps, centuries, provided the depth of the soil is sufficient. In time, however, the silicates and other compounds whose disintegration supplies alka- lies, phosphates, etc., must become relatively less in quan- tity compared with the quite inert quartz and alumina- silicates which cannot in any way feed plants. Then the crop will fall off, and ultimately, if sufficient time be al- lowed, the soil will be reduced to sterility. Other things being equal, this natural and durable pro- ductive power is of course greatest in those soils which contain and annually supply the largest proportions of plant-food from their entire mass, those which to the great- est extent originated from good soil-making materials, Soils formed from nearly pure quartz, from mere chalk, or from serpentine (silicate of magnesia), are among those least capable of maintaining a supply of food to crops. These poor soils are often indeed fairly productive for a few years when first cleared from the forests or marshes; but this temporary fertility is due to a natural manuring, the accumulation of vegetable remains on the surface, which contains but enough nutriment for a few crops and wastes rapidly under tillage. Exhaustion of the Soil in the language of Practice has a relative meaning, and signifies a reduction of producing power below the point of remuneration. A soil is said to be exhausted when the cost of cropping it is more than the crops are worth, In this sense the idea is very indef- inite since a soil may refuse to grow one crop and yet may give good returns of another, and because a crop that re- munerates in the vicinity of active demand for it, may be worthless at a little distance, on account of difficulties of transportation. The speedy and absolute exhaustion of a soil once fertile, that has been so much discussed by spec- ulative writers, is found in their writings only, and does not exist in agriculture, A soil may be cropped below the 374 HOW CROPS FEED. point of remuneration, but the sterility thus induced is of a kind that easily yields to rest or other meliorating agen- cies, and is far from resembling in its permanence that which depends upon original poverty of constitution. Significance of the Absorptive Quality.—Disintegration and nitrification would lead to a waste of the resources of fertility, were it not for the conserving effect of those physical absorptions and chemical combinations and re- placements which have been described. The two least abundant ash-ingredients, viz., potash and phosphoric acid, if liberated by the weathering of the soil in the form of phosphate of potash, would suffer speedy removal did not the soil itself fix them both in combinations, which are at once so soluble that, while they best serve as plant-food, they cannot ordinarily accumulate in quantities destruct- ive to vegetation, and so insoluble that the rain-fall cannot wash them off into the ocean. The salts that are abundant in springs, rivers, and seas, are naturally enough those for which the soil has the least retention, viz., nitrates, carbonates, sulphates, and hydro- chlorates of lime and soda. The constituents of these salts are either required by vegetation in but small quantities as is the case with chlo- rine and soda, or they are generally speaking, abundant or abundantly formed in the soil, so that their removal does not immediately threaten the loss of productiveness. In fact, these more abundant matters aid in putting into circulation the scarcer and less soluble ingredients of crops, in accordance with the general law established by the researches of Way, Eichhorn, and others, to the effect that any baxe brought into the so:l in form of a freely sol- uble salt, enters somewhat into nearly insoluble combina- tion and liberates a corresponding quantity of other bases. “The great beneficent law regulating these absorptions appears to admit of the following expression: those bodies which are most rare and precious to the yrowing plant are ms REVIEW AND CONCLUSION. 375 by the soil converted into, and retained in, a condition not of absolute, but of relative insolubility, and are kept avail- able to the plant by the continual circulation in the soil of the more abundant saline matters. “The soil (speaking in the widest sense) is then not only the ultimate exhaustless source of mineral (fixed) food, to vegetation, but it is the storehouse and conservatory of this food, protecting its own resources: from waste and from too rapid use, and converting the highly soluble matters of animal exuvie as well ag of artificial refuse (manures) into permanent supplies.”’* By absorption as well as by nitrification the soil acts therefore to prepare the food of the plant, and to present it in due kind and quantity. * The author quotes here the concluding paragraphs of an article by him ‘On Some points of Agricultural Science,” from the American Journal of Science and Arts, May, 1859, (p. 85). which have historic interest in being, so far as he is aware, the earliest, broad and accurate generalization on record, of the facts of soil-absorption. NOTICE TO TEACHERS. At the Author’s request, Mr. Louis Stadtmuller, of New Haven, Conn., will undertake to furnish collections of the minerals and rocks which chiefly compose soils (see pp. 108-122), suitable for study and illustration, as also the apparatus and materials needful for the chemical experiments described in ‘‘ How Crops Grow." A Valuable Periodical for everybody in City, Village, and County. DUOC iy h | iculturigt. T he American Agticulturigs (ESTABLISHED 1842.) THE LEADING INTERNATIONAL PUBLICATION FOR THE FARM, GARDEN, AND HOUSEHOLD. A MONTHLY MAGAZINE of from 48 to 64 pages in each number, containing in each volume upward of 700 pages and over 1000 original engravings of typical and prize-winning Horses, Cattle, Sheep, Swine, and Fowls; New Fruits, Vegetables, and Flowers; House and Barn Plans ; New Implements and 5 Lar eeene Contrivances ; and many pleasing and instructive pictures for young and old. 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Land Mcasurer for Farmers, Cloth. 8 60 Quinn. Money in the Garden.......... 150 Rawson. Success in Market Gardening. 1 00 Robinson, Facts for Farmers........ 5 00 Robinson, W. Mushroom Culture... . 650 Roe, E, P. Play and Profit in My Garden.. 1 50 The Home Acre........scsceeeees . 150 ERoosevelt, Five Acres Too Much....... . 150 Stewart, F. L. Sorghum and Its Products........... tienenranl a . 1 56 Stewart, Henry. Irrigation for the Farm, Garden and Orchard. vee 1B Storer, Agriculture in Some of Its Relations with Chemistry. 2 vols... 5 CG Tanner, The Abbotts’ Farm ......csseesesvenevecenececsees pares oor 1 co Ten Acres Enough......... 103 Terry. ABC of Potato Culture.......sssseesseeseevereeee seveveeevecs 40 The Soil of the Farm ......... ccc ccc cne cee ecen eens sen eeenceneeens 10 'Tisomas. Farm Implements and Machinery . .. 150 Tobacco Culture. Paper..........06+ wowisne 12D: Wodd. Young Farmers’ Manual. 3 vols. inaeen: 4 BO Treat. Injurious Insects of the Farm and Garden... Peer me 0 1} ORANGE JUDD COMPANY’S CATALOGUE, Vaughn. Celery Manual........eseeeee Wille. School of Chemical Manures....... High Farming without Manures..... Artificial Manures.,......... oveceses Ware. The Sugar Beet.......-....eeeee+ aie ania’ Waring. Book of the Farm..,...,.cccccceuveee Draining for Profit and Health......... ot enesoeecees —— Elements of Agriculture...... ig tearatrersinse ui islodaaiacata eieiaiswrayra cidicsiaistoy 100 Farmers™ Vacations ssecssevensayraceers Uivialeear eines gta loiceiaieetjannae 8 00 Warington. Chemistry of the Farm..,..... Sor aia tatenaverate 1 00 White. Gardening for the eli jasicendetd occa euelan tepodeet 2 00 LANDSCAPE GARDENING. Elltott. Handbook of Practical Landscape Gardening........... ajeinieaien 150 Kemp. Landscape Gardening............seeeseceees an Long. Ornamental Gardening for Americans ....... Vaux and Parsons, Concerning Lawn ee Welidenmann, Beautifying Country Homes......../.ssscscecesesees "40 00 ORANGE JUDD COMPANY’S CATALOGUE, LIST OF BOOKS Pertaining to Rural Life. ORANGE JUDD COMPANY, Publishers, 52 & 54 Lafayette Place, New York. Our i12-page full descriptive : catalogue mailed to any * address on application, [Any of these books will be forwarded by mail, postpaid, on receipt of price.] CATTLE, SHEEP, AND SWINE. Allen, L. F. American Cattle. Revised Edition..............ceceeees $2 50 Armatage, Prof. Geo. Every Man His Own Cattle Doctor. 8vo. Hall airecee) 45. asgessccenieknsnesauagwee eee eseenmeene 7 50 Armsby. Manual of Cattle Feeding...........ccccscuveccelecteneen cee 175 Coburn, F. D. Swine Husbandry. Revised Edition..., ............. 1% Curtis. Hints on Cheese Making.......... caatafatelicteickarajarainicictetaimiacueanainiSeie 5 Dadd, Prof. Geo. H. American Cattle Doctor. 12mo.............. 150 American Cattle Doctor. 8vo. Cloth........... cesceeeseeer ees 2 50 Flint, C.L. Milch Cows and Dairy Farming....... ....... -seeeseees 2 00 Gresswell, G. and A. Diseases and Disorders of the Ox........... 6 00 Guenon. Milch Cows............0002-005 Bid in-orainrone atWlASiStSleTeID sie’ d azo nisvernays 1 00 Harris, Joseph. On the Pig.. ........... s\aradanaserevegcbeanbdarolpiereesien wake 150 Mazard. Butter and Butter Making............+6 Aaiielaale gars igytonlaiies 25 Jennings. ‘Cattle and their Diseases .. 125 Sheep, Swine, and Poultry..... ona 1:25 Jersey, Alderney, and Guernsey Cow.. waaies 150 Keeping Ome Cow. ...... cic. ices cence cece eneteeteeneteererseee 1 00 Martin, R. B. Ung-Raising and Pork-Making........,.......-eeee0- 40 MeClure. Diseases of the American Horse, Cattle, and Sheep. wishin 1 2 MEiles, Stock Breeding .......csccscccscoccnsceccovscctesscrcescanseues 1 50 Murray, A. J. Cattle and their diseases..........-.--ssceseeeseeeeees 2 00 Powers, Stephen. The American Merino for Wool and Mutton. A practical and valuable work Randall. Practical Shepherd Sheldon. Dairy Farming.. Shepherd, Major W. Prairia Hexperiences 1 in n Handling Cattle and ORANGE JUDD COMPANY'S CATALOGUE, Steel, Treatise on Diseases of the Sheep.. rpaictslaresniays wrdiniate a Piaissels $4 50 Stewart, E. W. Feeding Animals. . .............. ++. 200 Stewart, Henry. Shepherd's Manual. Enlarged Edition............ 150 Dairyman’s Manual........ ......06 eine area: ‘ The Sheep. Its Varieties and Merieeniea Boards..... Warfield. Cattle Breeding....... dai Repiacontae eee setae iieya Willard. Practical Dairy Husbandry....... Sin aia oid avelavare ete ina aussie ainsi 3 00 Practical Butter BooOk......cscsescceccscecsesvecceescsscsssenees 1 OO DOGS, ETC. ' Ashmont, Dogs: Their Manag t and Treatment in Di veee 200 Dalziel, H. The Fox Terrier..... saben eeneeenseneneseeneeeeteencaras 80 The Greyhound........cscccccccccccrevevacssesssnccecetecsecese 1 00 ——— The St. Bernard..... aisiasdior Strep rere laeiers Aieie cisiaidreoaermrerciacs Wereiasdwlavcrs’vias Lae) ——- The Collie......... a etSriaavaretetees —— _ Diseases of Dogs.........csccccvecsncccessaccesrecene gj cinabiagstajor sr 80 Dog—The Varieties and Management iogtemsetuencesaenn ers . 80 Dogs of Great Britain, America, and Other Countries, Compiled from Stonehenge and other Standard Writers. The most Complete Work ever Published on the Dog. 12mo. Floyd, Wm. Hints on Dog Breaking. 12m0..............-0005 Forester, F. The Dog, by Dinks, Mayhew, and Histelilasan. Sens. sees Hallock, C. Dog Fanciers’ Directory and Medical Guide. 18mo.. 25 Wammond, 8. Dog Training. 12mo........ i esiansebranete er Gusta 1 Oo Sill, J. W. Manag t and Di of the Dog. 12mo. 2 00 House and Pet Dogs....... ae Hutchinson, G.N. Dog Breaking. Byo. iS Ed:stone. The Dog. Illustrated. 12mo... Laverack, E. The Setter. 4to...........5 -.. . Mayhew, E. Dogs. Their Management. 16mo. 5 Mercer. The Spaniel and its Training .................06. 1 00 Points for Judging Different Varieties of Dogs. 50 Shaw, T. Vero. [Illustrated Book of the Dog. 4to,...... Stables, Gordon. Our Friend, the Dog. 8vo.... Practical Kennel Guide........ eeseenee Ladies’ Dogs as Conipanions... Ee Stonehenge. The Dog in Health and Disease. Wynn. History of the Mastiff......... Wouatt. On the Dog........ erie Ach HORSES, RIDING, ETC. Anderson, E. L. Modern Horsemanship. 8v0..............200000+ . 5 50 Armatage, Geo. Every Man His Own Horse Doctor, together with Blaine’s Veterinary Art. 8vo. Half morocco,.........sseeeeeecceee 7 50 Ballou, Eugene, Equine Anatomy and Physiology................+ 1 00 Battersby, Col. J.C. The Bridle Bits. A valuable work on horse- manship. Fully illustrated. 12mo............... eis einen aig aponee 100 Baucher, F. Method of Horsemanship. 12mo........ seisatieaiaa easaiasts 100 Chawner, BR. Diseases of the Horse, and How to Treat Them. 12mo 1 25 Clarkke. Horses’ Teeth........sscscsetecsceccssegeteeetteneceeeees seeee 2 00 ORANGE JUDD COMPANY'S CATALOGUE. Curtis, Horses, Cattle, Sheep and Swine............cceeeeeees Dadd, G. H. American Reformed Horse Book. 8vo.... Modern Horse Doctor, 12m0..........:.-ceeeeeeeee Du Hays, C. Percheron Horse. New and Revised Edition. 12mo... 50 Dun, Finley. Veterinary Medicines; Their Actions and Uses. . American Edition. 8vo............ aueey a eeeee red saseeccecvccccens OOO —— Veterinary Medicines; Their Actions and Uses. English FGUHON,, BVO. isisis a saticad av ecscwaretumnes teainmeiade en a ote:vincordimnarasiasarae'e (BOO Feek. Every Man His Own Trainer............ dw igicgyma anos seemed vox 250 Fleming, Geo. Operative Veterinary Surgery. Part1. 8vo......... 3 50 Veterinary Obstetrics. 8vo.......... sirasala bia atdrave REESE ERT winks 6 00 Gleason, 0. R. How to Handle and Educate Vicious Horses... ..... 50 Gresswell, Geo. and Chas, Veterinary Pharmacopeia, Materia Medica and Therapeutics. 8V0.........cceeecceeceeeerecsneneeesenss 3 50 J.B.and A. Bovine Prescriber for the Use of ‘Veterinarians and Veterinary Students. 16M0 ............cee seers wcsasivceoases 1100 Equine Hospital Prescriber................ RimbeleTeAeRiE Kegs G 1 00 —— Manual on the Theory and Practice of Equine Medicine. 8vo.. 3 50 J. B., Albert and George. Diseases and Disorders of the Horse. 8vo........... aiats eussmiaeea aren ntavece oie sbtsraroum iaeoasicsin senvecsscces 2 00 J.B. Veterinary Pharnacdioey and Therapeutics. 16mo..... 1 50 May Seed. How to Develop Speed in Trotters and Pacers............-+ 100 Heatley, Geo. S. Every Man His Own Veterinarian. 12mo... - 2 50 Herbert, H. W. Hints to Horse Keepers. 12mo. .......... 175 Horse, The; Its Varieties and Management. Boards.... 7 Howden, P. The Horse ; How to Buy and Sell. 12mo.... 1 00 Jennings, KR. Horse Training Made Easy. 16mo............ . 100 The Horse and His Diseases. 12M0...........seeeee eveeeceeese 125 Law, J. Farmers’ Veterinary Adviser. 8vo......... aiaty eteerarn necacEe 3 00 Lehndorff. Horse Breeding Recollections. 8V0...........sssseeeee0. 125 Liautard, A. Animal Castration. 12m0.........0.....sceceeeseesees 2 00 — Chart of the Age of Domestic Animals..,............ sheedasicrcat: 100 On the Lameness of the Horse............+ a sisi nib ee diesinareiresauejerts) 200. Magner, D. Art of Taming and Educating the Horse. 8vo........... 5 00 Standard Horse and Stock Book...... Sesubheuinse peReRwoRiN eens 5 00 Manning. The Ilustrated Stock Doctor and Live Stock Encyclopaedia 4 25 Martin, Geo. A. The Family Horse. 12mo........... serial Gigeaw wee 1 00 Marvin, Training the Trotting Horse...... aieletseeaibloytiaaie ueoiwinnaie a Riana 3 50 Mayhew, E. Mlustrated Horse Management. 8vo........ sates weae 800 Illustrated Horse Doctor. 8vo........ eiaie Se jelaiwraineteteua sieidintepseiareaie 3 00 McClure, BR. Diseases of American Horses. 12M0....+......0cee eee 1 25 American Gentleman's Stable Guide. 12mo..... Seevaceaisd see 100 WicFadyean, J. WE. Anatomy of the Horse. 8V0..........-...00005 6 50 Miles, Wanly. Stock Breeding. 12m0..........:cseeeeeeeeeee ener Miles. The Horse’s Foot, and How to Keep it Sound.................65 Practical Horse Shoer.......... io tS aide here ose levaacvatar sn aha ghirserals F Rarey and Knowlson. Horse Tamer and Farrier. 16mo eee seen 5D Riley, HM. On the Mule. 12mo..............:..22eeeeeeee odnaeabalaiatevaies 150 Robertson, W. The Practice of Equine Medicine. 8vo... ¥ 6 50 FRussell. Scientific Horse-Shoeing........ 2. ccs ceeeeceeneeeeees neers 3 00 Saddle Horse, The. Complete Guide to Riding and mralning sseeee 100 Sandors. Horse Breeding. 12M0............ceceecseeseeseeenteeseeses 2 00 ORANGE JUDD COMPANY'S CATALOGUE, Sidmey, S. The Book of the Horse. 4t0...........0..6 aiatieorata eavmnseees $8 00 Stonehenge. Every Horse Owner's Cyclopedia. 8vo...... die aeenewa DCO On the Horse in the Stable and the Field. English Edition. 8vo 3 50 On the Horse in the Stable and the Field. American Edition. LZMO 5 s5:sy;njeis gig iacecelgnsrerecarareiviaratess Hale xiaticibiate ee ia Wiemnse eiaee eaiey Recess saeeee 2 00 Strangeway and Vaughn, Veterinary Anatomy. 8yvo.. Tellor. Diseases of Live Stock. Cloth, $2.50; Sheep..... Terry. Winter Care of Horses and Cattle Williams, W, Principles and Practice of Veterinary Medicine. Principles and Practice of Veterinary Surgery. 8v0......... Woodruff. The Trotting Horse in America. 12mo........ Woods, Rev. J3.G. Horse and Man.........cssseeeeee Youatt, History, Treatment and Diseases of the Horse.. — andSkKinmer,. The Horse. 8V0........cccceeseeeeees wiageins te 1% and Spooner. The Horse. 12mo.......... Cares seseveeeee 150 Zundel, A. The Horse's Foot and its Diseases. 12m0................ 2 00 POULTRY, PIGEONS AND BEES. American Standard of Perfection in Poultry........ cesses 100 Beal, S. Profitable Poultry-Keeper. 12mo...........+-+ « 150 Burnham, New Poultry Book........ Cook, Prof, A. J. Manual of the Apiary.. Cooper, Dr. J. W. Game Fowls....... Felch, I. K. Poultry Culture........ Johnson, G. MM. 'T. Practical Poultry- Keeper. Paper King. Bee-Keeper’s Text Book........ccsseeseceee igre piety Langstroth, On the Honey and Hive Bee.. Lewis. Practical Poultry Book..............see0e0 Sinden ieomes: 1 50 Newman. Beeand Honey. Paper, 50 cts. Cloth....... aie bisdossanichecaecieadhs 1) Poultry. Breeding, Rearing, Feeding, etc. Boards. sincera ‘ysioiected wie sibiots . 50 Profits in Poultry and their Profitable Management. Most complete work extant.......ccssececcecc cee rereetecrececsncnes 1 00 Quinby. Mysteries of Bee-Keeping Explained. (Edited by L. C. Root.) 1 50 Rankin, Jas, Duck Culttre...........ccseessenseeeeseesteeeeeresees 50 Root, A. HT. ABC of Bee Culture........, sec cceeeeeeeeeseeeerecseeees LO Stoddard, H. H. An Egg-Farm. Revised and Enlarged............ 50 Wright, L. Illustrated Book of Poultry. Colored Plates. Demy. 4to 12 50 Tilustrated Book of Poultry........cscccocccveccsvceecceccsseses DOO — Practical Poultry-Keeper........cccceucceeececses iuidale ieiesinrweceny 200. Practical Pigeon-Keeper......sscccssececessovcscsvssereecccceces 1 50 RSs MXR Sa AA RNS A BARONE SERS a : PRRAVVVE QA ACT QO CQ CAS Ww AN AK AWCCE[E[EC@