PEINCIPLES OF MANURING MANURES AND THE PRINCIPLES OF MANURING BY C. M. AIKMAN, M.A., B.Sc., F.E.S.E, F.I.C. PROFESSOR OP CHEMISTRY, GLASGOW VETERINARY COLLEGE; EXAMINER IN CHEMISTRY, GLASGOW UNIVERSITY; AUTHOR OF 'FARMYARD MANURE,' ETC. WILLIAM BLACKWOOD AND SONS EDINBURGH AND LONDON MDCCCXCIV 0 TO SIR JOHN BEMET LAWES, BAKT,, D.C.L, LL.D., F.B.S., OF ROTHAMSTED, AND SIR J. HENRY GILBERT, M.A., LL.D., F.R.S., FORMERLY SIBTHORPIAN PROFESSOR OP RURAL ECONOMY, UNIVERSITY OF OXFORD, WHOSE FAMOUS INVESTIGATIONS DURING THE LAST FIFTY YEARS HAVE SO LARGELY CONTRIBUTED TO BUILD UP THE SCIENCE OF MANURING, THIS WORK, EMBODYING MANY OF THE ROTHAMSTED RESULTS, IS DEDICATED. 380432 PREFACE. WHEN the present work was first undertaken there were but few works in English dealing with its subject-matter, and hardly any which dealt with the question of Manuring at any length. During the last few years, however, owing to the greatly increased interest taken in agricultural education, the demand for agricultural scientific literature has called into existence quite a number of new works. Despite this fact, the author ventures to believe that the gap which the present treatise was originally de- signed to fill is still unfilled. Of the importance of the subject all interested in agriculture are well aware. It is no exaggeration to say that the introduction of the practice of artificial manuring has revolutionised modern husbandry. In- deed, without the aid of artificial manures, arable farming, as at present carried out, would be impos- Vlll PREFACE. sible. Fifty years ago the practice may be said to have been unknown ; yet so widespread lias it now become, that at the present time the capital invested in the manure trade in this country alone amounts to millions sterling. It need scarcely be pointed out, there- fore, that a practice in which such vast monetary interests are involved is worthy of the most careful consideration by all students of agricultural science, as well as, it may be added, by political economists. The aim of the present work is to supply in a concise and popular form the chief results of recent agricultural research on the question of soil fertility, and the nature and action of various manures. It makes no pretence to be an exhaustive treatise on the subject, and only contains those facts which seem to the author to have an important bearing on agricultural practice. In the treatment of its subject it may be said to stand midway between Professor Storer's recently published elaborate and excellent treatise on ' Agriculture in some of ' its Re- lations to Chemistry ' — a work which is to be warmly recommended to all students of agricultural science, and to which the author would take this opportunity of acknowledging his indebtedness — and Dr J. M. H. Munro's admirable little work on ' Soils and Manures.' In order to render the work as intelligible to the ordinary agricultural reader as possible, all tabular matter and matter of a more or less technical nature PREFACE. ix have been relegated to the Appendices attached to each chapter. The author's somewhat wide experience as a Uni- versity Extension Lecturer, and as a Lecturer in con- nection with County Council schemes of agricultural education, during the last few years, induces him to believe that the work may be of especial value to those engaged in teaching agricultural science. He has to express the deep obligation he is under, in common with all writers on Agricultural Chemis- try, to the classic researches of Sir John Bennet Lawes, Bart., and Sir J. Henry Gilbert, now in pro- gress for more than fifty years at Sir John Lawes' Experiment Station at Eothamsted. His debt of gratitude to these distinguished investigators has been still further increased by their kindness in per- mitting him to dedicate the work to them, and for having been good enough to read portions of the work in proof. In addition to the free use which has been made throughout the book of the results of these experiments, the last chapter contains, in a tabular form, a short epitome of some of the more important Eothamsted researches on the action of different manures. To the numerous German and French works on the subject, more especially to Professor Heiden's encyclo- paedic 'Lehrbuch der Dlingerlehre' and the various writings of Dr Emil von Wolff, the author is further much indebted. x PREFACE. Among English works he would especially mention the assistance he has derived from the writings of Mr E. Warington, F.E.S., Professor S. W. Johnson, Professor Arrnsby, the late Dr Augustus Voelcker, and others. He would also tender his acknowledg- ments to the new edition of Stephens' ' Book of the Farm/ and he has to thank its editor, his friend Mr James Macdonald, Secretary to the Highland and Agricultural Society of Scotland, for having read parts of his proof-sheets. It is also his pleasing duty to thank his friends Dr Bernard Dyer, Hon. Secretary of the Society of Public Analysts; Dr A. P. Aitken, Chemist to the Highland and Agricultural Society of Scotland ; Pro- fessor Douglas Gilchrist of Bangor ; Mr F. J. Cooke, late of Flitcham ; Mr Hermann Yoss of London ; and Professor Wright of Glasgow, for having assisted him in the revision of proof-sheets. ANALYTICAL LABORATORY, 128 WELLINGTON STREET, GLASGOW, January 1894. CONTENTS. PART I.— HISTORICAL INTRODUCTION. PAGE Beginning of agricultural chemistry ...... 4 Early theories regarding plant-growth 4 Van Helmont ......... 4 Digby 6 Duhamel and Stephen Hales ...... 8 Jethro Tull 9 Charles Bonnet's discovery of source of plants' carbon . . 11 Researches of Priestley, Ingenhousz, Se'ne'bier, on assimilation of carbon H-12 Publication of first English treatise by Earl Dundonald . . 13 Publication of Theodore de Saussure, * Chemical Researches on Vegetation,' 1804 . . .14 Theories on source of plant-nitrogen . . . . .15 Early experiments on this subject 16 Sir Humphry Davy's lectures (1802-1812) .... 17 State of agricultural chemistry in 1812 . . . . .17 Beginning of Boussingault's researches (1834) .... 21 Publication of Liebig's first report to the British Association . 24 Refutation of " humus" theory ..... 26 Liebig's mineral theory ....... 26 Liebig's theory of source of plants' nitrogen ... 27 Publication of Liebig's second report to British Association . 30 Liebig's services to agricultural chemistry . . .31 Development of agricultural research in Germany ... 32 The Rothamsted Experiment Station ..... 33 Xll CONTENTS. Sir J. B. Lawes and Sir J. H. Gilbert, the nature and value of their experiments 33 Review of the present state of our knowledge of plant-growth 36 Proximate composition of the plant . . . . .36 Fixation of carbon by plants . . . . . .37 Action of light on plant-growth, Dr Siemens' experiments 38 Source of oxygen and hydrogen in the plant . . 39-40 Source of nitrogen in the plant . . . . .40 Relation of the free nitrogen to leguminous plants . 42-44 Relation of nitrogen in organic forms, as ammonia salts, and nitrates to the plant ..... 46-50 Nitrification and its conditions ...... 51 Ash constituents of the plant ...... 53 Methods of research for ascertaining essentialness of ash constituents of plants 53 (a) Artificial soils, (6) water-culture .... 53-55 Method in which plants absorb their food-constituents . 55 Endosmosis . . . . . . . . .55 Retention by soils of plant-food ..... 57 Causes of retention by soils of plant-food .... 59 Manuring ......... 60 " Field " and " pot " experimentation .... 60 PART II.— PRINCIPLES OF MANURING. CHAPTER I.— FERTILITY OF THE SOIL. What constitutes fertility in a soil ...... 65 I. Physical properties of a soil . . . . . .66 Kinds of soils ......... 67 Absorptive power for water of soils ..... 67 Absorptive power for water of sand, clay, and humus . 68 Fineness of particles of a soil . . . . . .69 Limit of fineness of soil-particles . . . . .69 Importance of retentive power . . . . . .70 Power of plants for absorbing water from a soil, experi- ments by Sachs ........ 73 How to increase absorptive power of soils . . . .74 Amount of water in a soil most favourable for plant growth 75 ' Hygroscopic power of soils . . . . . .75 Capacity of soils for absorbing and retaining heat . . 76 CONTENTS. Xlll Explanation of dew ....... 77 Heat of soils 78 Heat in rotting farmyard manure 78 Causes of heat of fermentation . . . . .79 Influence of colour on heat-retaining power ... 80 Power of soils for absorbing gases 81 Gases found in soils . . . . . . .81 Variation in gas-absorbing power of soils ... 82 Absorption of nitrogen by soils ..... 82 Requirements of plant-roots in a soil . . . .83 Influence of tillage on number of plants in a certain area 86 Comparison of English and American farming . . 86 II. Chemical composition of a soil ...... 87 Fertilising ingredients of a soil . . . . . . 87 Importance of nitrogen, phosphoric acid, and potash in a soil 88 Chemical condition of fertilising ingredients in soils . 89 Amount of soluble fertilising ingredients in soils . . 90 Value of chemical analysis of soils . . . . .90 III. Biological properties of a soil ... 92 Bacteria of the soil . .... 92 Recapitulation of Chapter I , .96 APPENDIX TO CHAPTER I. NOTE I. Table of absorptive power of soil substances by Schiibler . 98 II. Table of rate of evaporation of water in different soils by Schiibler 99 III. Table of hygroscopic power of soils dried at 212° F. (Davy) 99 IV. Gases present in soil . . . . . . .100 V. Amount of plant-food in soils . . . . . .100 VI. Chemical composition of the soil 101 VII. Forms in which plant-foods are present in the soil . . 107 CHAPTER II.— FUNCTIONS PERFORMED BY MANURES. Etymological meaning of word manure 109 Definition of manures .... Different classes of manures ... .111 Action of different classes of manures 113 XIV CONTENTS. CHAPTER III.— POSITION OF NITROGEN IN AGRICULTURE. The Rothamsted experiments and the nitrogen question . . 115 Different forms in which nitrogen exists in nature . . .116 Relation of "free" nitrogen to the plant . . . .117 Combined nitrogen in the air . . . . . .118 Amount of combined nitrogen falling in the rain . . 119 Nitrogen in the soil . . . . . . . .120 Nitrogen in the subsoil . . . . . . .121 Nitrogen of surface-soil 121 Amount of nitrogen in the soil . . . . . .123 Soils richest in nitrogen 123 Nature of the nitrogen in the soil . . . . .124 Organic nitrogen in the soil . . . . . .125 Differences of surface and subsoil nitrogen . . .126 Nitrogen as ammonia in soils . . . . . .127 Amount of ammonia in soils ...... 127 Nitrogen present as nitrates in the soil . . . .128 Position of nitric nitrogen in soil . . . . .128 Amount of nitrates in the soil . . . . . .129 Amount of nitrates in fallow soils 129 Amount of nitrates in cropped soils . . . . .130 Amount of nitrates in manured wheat-soils . . . 131 The sources of soil-nitrogen 131 Accumulation of soil-nitrogen under natural conditions . 133 Accumulation of nitrogen in pastures . . . .134 Gain of nitrogen with leguminous crops . . . 1 35 The fixation of " free " nitrogen ..... 136 Influence of manures in increasing soil-nitrogen . . 136 Sources of loss of nitrogen . . . . • .137 Loss of nitrates by drainage . . . . . .137 Prevention of loss of nitrogen by permanent pasture and "catch-cropping". . . . . . . .138 Other conditions diminishing loss of nitrates . . .139 Amount of loss of nitrogen by drainage . . . .140 Loss of nitrogen in form of " free " nitrogen . . .141 Total amount of loss of nitrogen . . . . .142 Loss of nitrogen by retrogression .... Artificial sources of loss of nitrogen . . . . .144 Amount of nitrogen removed in crops . . . .144 CONTENTS. XV Losses of nitrogen incurred on the farm . . . .146 Loss in treatment of farmyard manure . . . .146 Nitrogen removed in milk . . . . . .147 Economics of the nitrogen question . . . . .147 Loss of nitrogen-compounds in the arts . . . .148 Loss due to use of gunpowder . . . . . .148 Loss due to sewage disposal . . . . . .149 Our artificial nitrogen supply . . . . . .150 Nitrate of soda and sulphate of ammonia . . . .150 Peruvian guano . . . . . . . .151 Bones 151 Other nitrogenous manures . . . . . .152 Oil-seeds and oilcakes . . . . . . .153 Other imported sources of nitrogen ..... 153 Conclusion ......... 153 APPENDIX TO CHAPTER III. NOTE. I. Determination of the quantity of nitrogen supplied by rain, as ammonia and nitric acid, to an acre of land during one year ........ 155 II. Nitrogen in soils at various depths . . . . .156 III. Nitrogen as nitrates in cropped soils receiving no nitro- genous manures, in Ib. per acre (Rothamsted soils) . 157 IV. Nitrogen as nitrates in Rothamsted soils . . .157 V. Examples of increase of nitrogen in Rothamsted soils laid down in pasture ....... 158 VI. Loss by drainage of nitrates ...... 158 VII. Examples of decrease of nitrogen in Rothamsted soils . 159 VIII. Amount of drainage and nitrogen as nitrates in drainage- water from unmanured bare soil, 20 and 60 inches deep 160 CHAPTER IV.— NITRIFICATION. Process of nitrification . . . . . . . .161 Occurrence of nitrates in the soil . . . . . .162 Nitre soils of India . . . . . . . . .162 Saltpetre plantations . . . . . . .163 Cause of nitrification . . . . . . . .165 Ferments effecting nitrification . . . . .167 Appearance of nitrous organisms . . . . .168 Nitric organism . . . . • • • .169 XVI CONTENTS. Difficulty in isolating them 169 Nitrifying organisms do not require organic matter . .169 Conditions favourable for nitrification — Presence of food-constituents . . . . . .170 Presence of a salifiable base . . . . . .171 Only takes place in slightly alkaline solutions . . .172 Action of gypsum on nitrification 173 Presence of oxygen 173 Temperature . . . . . . . . .175 Presence of a sufficient quantity of moisture . . .176 Absence of strong sunlight . . . . . .176 Nitrifying organisms destroyed by poisons . . .176 Denitrification . .177 Denitrification also effected by bacteria . . . .178 Conditions favourable for den itrifi cation . . . .178 Takes place in water-logged soils 179 Distribution of the nitrifying organisms in the soil . . .179 Depth down at which they occur . . . . .180 Action of plant-roots in promoting nitrification . . .181 Nature of substances capable of nitrification . . .181 Rate at which nitrification takes place . . . . .183 Nitrification takes place chiefly during summer . . 183 Process goes on most quickly in fallow fields . . .184 Laboratory experiments on rate of nitrification . . .185 Certain portions of soil - nitrogen more easily nitrifiable than the rest ........ 187 Rate of nitrification deduced from field experiments . .187 Quantity of nitrates formed in the soils of fallow fields . 188 Position of nitrates depends on season .... 188 Nitrates in drainage- waters . . . . . .188 Amount produced at different times of year . . .189 Nitrification of manures . . . . . . .190 Ammonia salts most easily nitrifiable . . . .191 Sulphate of ammonia the most easily nitrifiable manure . 191 Rate of 'nitrification of other manures . . . .192 Soils best suited for nitrification . . . . .192 Absence of nitrification in forest-soils . . . .193 Important bearing of nitrification on agricultural practice . 193 Desirable to have soil covered with vegetation . . .194 Permanent pasture most economical condition of soil . 194 Nitrification and rotation of crops 195 CONTENTS. XV11 APPENDIX TO CHAPTER IV. NOTE I. Old theories of nitrification . . . . . .196 II. Nitrification takes place in solutions devoid of organic matter 196 III. Oxidising power of micro-organisms in soils . . .197 IV. Effect of urine on nitrification in soils . . . .197 V. Solution used by Professor Frankland in cultivating nitri- ficative micro-organisms . . . . . .198 VI. Experiments by Boussingault on rate of nitrification . 198 VII. Nitrogen as nitrates in Rothamsted soils after bare fallow in Ib. per acre ........ 198 CHAPTER V.— POSITION OF PHOSPHORIC ACID IN AGRICULTURE. Occurrence of phosphoric acid in nature 199 Mineral sources of phosphoric acid ...... 200 Apatite and phosphorite ........ 200 Coprolites 201 Occurrence of phosphoric acid in guanos ..... 202 Universal occurrence in common rocks ..... 202 Occurrence in the soil ........ 203 Condition in which phosphoric acid occurs in the soil* . . 203 Occurrence in plants ........ 204 Occurrence in animals 205 Sources of loss of phosphoric acid in agriculture . . . 205 Loss of phosphoric acid by drainage . . . . .206 Artificial sources of loss of phosphoric acid .... 206 Amount of phosphoric acid removed in milk . . . . 207 Loss of phosphoric acid in treatment of farmyard manure . 208 Loss of phosphoric acid in sewage 208 Sources of artificial gain of phosphoric acid .... 208 APPENDIX TO CHAPTER V. NOTE I. Composition of apatite (Voelcker) 210 II. Percentage of phosphoric acid in the commoner rocks . 211 CHAPTER VI.— POSITION OF POTASH IN AGRICULTURE. Potash of less importance than phosphoric acid . . .212 Occurrence of potash 213 b XV111 CONTENTS. Felspar and other potash minerals 213 Stassfurt salts . . . . . . . . .214 Occurrence of saltpetre 215 Occurrence of potash in the soil . . . . . .215 Potash chiefly in insoluble condition in soils . . . .216 Percentage of potash in plants and plant-ash . . . .216 Occurrence of potash in animal tissue . . . . .217 Sources of loss of potash 217 Amount of potash removed in crops . . . . .218 Amount of potash removed in milk . . . . . .218 Potash manures ....... .218 APPENDIX TO CHAPTER VI. NOTE I. Amount of potash in different minerals .... 220 II. Quantity of potash obtained from 1000 Ib. of different kinds of vegetation in the manufacture of potashes . 220 PART III.— MANURES. CHAPTER VII.— FARMYARD MANURE. Variation in its composition ....... 223 Made up of three classes of constituents ..... 224 Solid excreta — Its nature 224 Difference in composition of the solid excreta of the different farm animals ...... 224 Causes of this difference ...... 225 Percentage of manurial ingredients in solid excreta of different animals . . . . . . .226 Urine — Its nature 228 Variation in its composition 229 Causes of this variation ....... 229 Manurial value of the urine of the different farm animals 230 Percentage of the organic matter, nitrogen, and mineral substances in the food, voided in the solid excreta and urine 232 Comparison of manurial value of total excrements of the different farm animals ...... 234 CONTENTS. xix Nature of changes undergone by food in process of digestion . . . 235 Litter— Its uses 236 Straw as litter, and its qualifications . . . .237 Composition of different kinds of straw .... 238 Loam as litter 239 Peat as litter 240 Comparison of properties of peat-moss and straw . . 241 The bracken-fern as litter . . . . . .241 Dried leaves as litter . . . . . . . 242 Manures produced by the different animals — Horse-manure — Amount produced ........ 243 Its nature and composition ...... 243 Amount of straw used for litter ..... 244 Sources of loss on keeping 245 How to prevent loss ....... 245 Use of " fixers," and the nature of their action . . 245 Coiv-manure — Amount produced ........ 248 Its nature and composition ...... 248 Amount of straw used as litter ..... 248 Sources of loss on keeping ...... 249 Advantages of short dung ...... 249 Pig-manure — Amount produced ....... 250 Its nature and composition ...... 250 Amount of straw used as litter . . . . .251 Sheep-manure — Amount produced ....... 251 Nature and composition ...... 251 Amount of straw used as litter ..... 252 Methods of calculating amount of manure produced on the farm 252, note Fermentation of farmyard manure — Action of micro-organic life in producing fermentation . 255 Two classes of bacteria active in this work, aerobics and anaerobies ......... 255 Conditions influencing fermentation — Temperature 256 Openness to the air . . . . • • .256 XX CONTENTS. Dampness . . . . . . . . . 257 Composition of manure ....... 257 Products of fermentation ....... 257 Analyses of farmyard manure — Dr Voelcker's experiments 259 Variation in composition - . . . . . . . 259 Amounts of moisture, organic matter (containing nitrogen), and mineral matter . . . . . . .260 Its inanurial value compared with nitrate of soda, sulphate of ammonia, and superphosphate . . . . .260 Comparison of fresh and rotten manure — The nature and amount of loss sustained in the process of rotting 261 Ought manure to be applied fresh or rotten ? . . . 262 Relative merits of covered and uncovered manure-heaps . . 263 Methods of application of farmyard manure to the field — Merits and demerits of the different methods . . .265 Setting it out in heaps . . . . . . .265 Spreading it broadcast, and letting it lie . . . . 266 Ploughing it in immediately . . . . . .267 Value and function of farmyard manure — As a supplier of the necessary elements of plant-food . 268 As a " universal " manure . ...... 269 Proportion in which nitrogen, phosphoric acid, and potash are required by crops . . . . . . .269 Proportion in which they are present in farmyard manure 270 Farmyard manure poor in nitrogen . . . . .270 Lawes' and Gilbert's experiments . . . . .271 How it may be best reinforced by the use of " artificials " . 271 Indirect value of farmyard manure as a supplier of humus to the soil 273 Its influence on soil-texture ...... 273 Its influence in setting free inert fertilising matter in the soil .......... 274 Rate at which farmyard manure ought to be applied . . 275 Lasting nature of farmyard manure ..... 276 Its economic value . . . . . . . . .276 APPENDIX TO CHAPTER VII. NOTE I. Difference in amount of excreta voided for food con- sumed ... 279 CONTENTS. xxi NOTE II. Solid excreta voided by sheep, oxen, and cows . .279 III. Urine voided by sheep, oxen, and cows . . . 280 IV. Percentage of food voided in the solid and liquid ex- crements ........ 281 V. Pig excrements 281 VI. Manurial constituents in 1000 parts of ordinary foods . 282 VII. Analyses of stable - manure, made respectively with peat-moss litter and wheat-straw .... 283 VIII. Analyses of bracken ' . 283 IX. Analyses of horse-manure ...... 283 X. The nature of the chemical reactions of ammonia 11 fixers" 284 XI. Analyses of cow-manure ...... 286 XII. Composition of 'fresh and rotten farmyard manure . 286 XIII. Comparison of fresh and rotten manure . . . 288 XIV. Lord Kinnaird's experiments . . . . .289 XV. Drainings of manure-heaps ...... 290 XVI. Amounts of potash and phosphoric acid removed by rotation from a Prussian morgen (.631 acre) . . 290 XVII. Composition of farmyard manure (fresh) . . . 291 XVIII. The urine (quantity voided) 291 CHAPTER VIII.— GUANO. Importance in agriculture ....... 293 Influence on British farming . . . . . . .294 Influence of guano not wholly good ...... 295 Value of guano as a manure ....... 296 Origin and occurrence of guano ...... 297 Variation in composition of different guanos .... 299 I. Nitrogenous guano — (a) Peruvian guano 300 Different deposits of Peruvian guano . . . 301 Appearance, colour, and nature of Peruvian guano . 303 Composition of Peruvian guano .... 304 (b) Other nitrogenous manures : Angamos, Ichaboe . 306 II. Phosphatic guanos — Occurrence of phosphatic guanos ..... 308 Inequality in composition of phosphatic guanos . . 309 " Dissolved " phosphatic guano ..... 310 " Equalised " or " rectified " guano ..... 311 XX11 CONTENTS. The action of phosphatic guauos as manures . . .312 Proportion of fertilising constituents in guano . . 314 Mode of application of guanos . . . . .315 Quantity of guano to be used ...... 317 Adulteration of guano . . . . . . .318 So-called guanos — Fish-guano 320 Value of fish-guano 322 Meat-meal guano ........ 324 Value of meat-meal guano ...... 324 Bat guano 325 Pigeon and fowl dung 325 APPENDIX TO CHAPTER VIII. NOTE I. Peruvian guano imported into United Kingdom, 1865- 1893 327 II. Guano deposits of the world ...... 327 III. Composition of concretionary nodules . . . .328 IV. Table showing gradual deterioration of Peruvian guano, 1867-1881 329 V. Composition of different guanos ..... 329 VI. Liebig's theory as to the action of oxalic acid in guano . 330 VII. Analyses of dung of fowls, pigeons, ducks, and geese . 331 CHAPTER IX.— NITRATE OF SODA. Amount of exports . . . . . . . . .332 Date of discovery of nitrate deposits ..... 333 The origin of nitrate deposits . . . . . . .334 Forbes and Darwin on the theory of their origin . . .335 Source of nitric acid in nitrate of soda ..... 337 Guano theory of origin of nitrate of soda ..... 337 Nitric acid in nitrate of soda probably derived from sea-weed . 339 Appearance of nitrate-fields .... ... 340 The method of mining the nitrate of soda . . . .341 Composition of caliche . . . . . . • .342 Extent of the nitrate deposits ....... 342 Composition and properties of nitrate of soda . . . .343 Nitrate applied as a top-dressing . . . . . .344 Nitrate of soda encourages deep roots ..... 344 CONTENTS. XX111 Is nitrate of soda an exhausting manure ? 345 Crops for which nitrate of soda is suited . . . . .346 Method of application of nitrate of soda ..... 347 Importance of having a sufficiency of other fertilising con- stituents .......... 348 Conclusions drawn ......... 349 APPENDIX TO CHAPTER IX. Total shipments from South America, 1830-1893 . . .351 Total imports into Europe and United Kingdom, 1873-1892 . 351 CHAPTER X.— SULPHATE OF AMMONIA. Value of ammonia as a manure ...... 352 Sources of sulphate of ammonia ...... 353 Ammonia from gas-works ....... 353 Other sources .......... 354 Composition, &c., of sulphate of ammonia .... 355 Application of sulphate of ammonia . . . . .356 APPENDIX TO CHAPTER X. Production of sulphate of ammonia in United Kingdom, 1870-1892 358 CHAPTER XI.— BONES. Early use of bones ......... 359 Different forms in which bones are used ..... 360 Composition of bones ........ 362 The organic matter of bones . . . . . . .363 The inorganic matter of bones ....... 363 Treatment of bones ......... 364 Action of bones ......... 365 Dissolved bones ......... 368 Crops suited for bones ........ 368 Bone-ash 369 Bone-char or bone-black ........ 369 XXIV CONTENTS. APPENDIX TO CHAPTER XI. NOTE I. Analysis of bone-meal 371 II. Analysis of dissolved bones 371 III. Composition of bone-ash ....... 372 IV. Composition of bone-char 372 CHAPTER XII.— MINERAL PHOSPHATES. Coprolites .......... 373 Canadian apatite or phosphorite . . . . . .374 Estremadura or Spanish phosphates 375 Norwegian apatite . . . . . . . . .376 Charlestown or South Carolina phosphate . . . .376 Belgian phosphate ......... 377 Somnie phosphate . . . . . . . . .378 Florida phosphate 378 Lahn phosphate . . . . . . . . .379 Bordeaux or French phosphate ...... 379 Algerian phosphate . . . . . . . . .379 Crust guanos .......... 379 Value of mineral phosphates as manures 380 APPENDIX TO CHAPTER XII. Imports of phosphates . . . . . . . .381 CHAPTER XIII.— SUPERPHOSPHATES. Discovery of superphosphate by Liebig ..... 382 Manufacture of superphosphate 383 Nature of the reaction taking place ...... 385 Phosphates of lime ......... 385 Reverted phosphate . . . . . . . .389 Value of reverted phosphate . . . . . . .391 Composition of superphosphates ...... 391 Action of superphosphates . . . . . . .392 Action of superphosphate sometimes unfavourable . . . 395 Application of superphosphate . . . . . . .395 Value of insoluble phosphates ....... 396 Rate at which superphosphate is applied 397 CONTENTS. XXV APPENDIX TO CHAPTER XIII. NOTE I. The formulae, and molecular and percentage composition, of the different phosphates ...... 398 II. Reactions of sulphuric acid and phosphate of lime . . 398 III. Table for conversion of soluble phosphate into insoluble phosphate 399 IV. Action of iron and alumina in causing reversion . . 399 V. Relative trade values of phosphoric acid in different manures ......... 400 CHAPTER XIV.— THOMAS-PHOSPHATE OR BASIC SLAG. Its manufacture ......... 401 Not at first used 403 Discovery of its value as a manure 403 Composition of basic slag ....... 404 Processes for preparing slag ....... 406 Solubility of basic slag . . . . . . . .408 Darmstadt experiments with basic slag . • . . . . 410 Results of other experiments . . . . . . .413 Soils most suited for slag . . . . . . .414 Rate of application . . . . . . . . .414 Method of application . . . . . . . .416 APPENDIX TO CHAPTER XIV. Analysis of basic slag . . . . . . . .417 CHAPTER XV.— POTASSIC MANURES. Relative importance . . . . . . . .418 Scottish soils supplied with potash . . . . . .419 Sources of potassic manures . . . . . . .419 Stassfurt potash salts . . . . . . . .420 Relative merits of sulphate and muriate of potash . . .421 Application of potash manures ....... 422 Soils and crops suited for potash manures .... 423 Rate of application ......... 423 XXVI CONTENTS. CHAPTER XVI.— MINOR ARTIFICIAL MANURES. Scutch 427 Shoddy and wool-waste ........ 427 Soot 428 CHAPTER XVII.— SEWAGE AS A MANURE. Irrigation .......... 431 Effects of continued application of sewage .... 433 Intermittent irrigation . . . . . . . .434 Crops suited for sewage . . . . . . . .434 Treatment of sewage by precipitation, &c. .... 436 Value of sewage sludge ........ 439 CHAPTER XVIII. — LIQUID MANURE .... 442 CHAPTER XIX.— COMPOSTS. Farmyard manure a typical compost . . . . .446 Other composts ......... 447 CHAPTER XX.— INDIRECT MANURES. Lime 449 Antiquity of lime as a manure . . . . . .449 Action of lime ......... 449 Lime a necessary plant-food ...... 450 Lime of abundant occurrence ...... 452 Lime returned to the soil in ordinary agricultural practice 452 Different forms of lime 453 Caustic lime ......... 453 Lime acts both mechanically and chemically . . .455 I. Mechanical functions of lime ...... 455 Action on soil's texture ....... 455 Lime renders light soils more cohesive . . . .457 II. Chemical action of lime ....... 457 CONTENTS. XXV11 III. Biological action of lime . ' . . . . . .459 Action of lime on nitrogenous organic matter . .460 Recapitulation . . . . . . . . .461 CHAPTER XXL— INDIRECT MANURES— GYPSUM, SALT, ETC. Gypsum ........... 462 Mode in which gypsum acts . . . . . .462 Salt 465 Antiquity of the use of salt . . . . . . 465 Nature of its action ........ 465 Salt not a necessary plant-food . . . . . .466 Can soda replace potash ? . . . . . . .466 Salt of universal occurrence . . . . . .467 Special sources of salt . . . . . . .468 The action of salt 468 Mechanical action on soils . . . . . . .470 Solvent action . . . . . . . . .470 Best used in small quantities along with manures . .472 Affects quality of crop . . . . . . .472 Rate of application 473 CHAPTER XXII. —THE APPLICATION OF MANURES. Influence of manures in increasing soil-fertility . . .474 Influence of farmyard manure on the soil . . . .475 Farmyard manure v. artificials ....... 476 Farmyard manure not favourable to certain crops . . . 477 Conditions determining the application of artificial manures . 477 Nature of the manure . . . . . . .478 Nitrogenous manures . . . . . . . .478 Phosphatic manures . . . . . . . .480 Potash manures ......... 480 Nature of soil .......... 481 Nature of previous manuring . . . ... . . 482 Nature of the crop ......... 483 Amounts of fertilising ingredients removed from the soil by different crops ......... 484 Capacity of crops for assimilating manures .... 486 Difference in root-systems of different crops . . . 488 XXviii CONTENTS. Period of growth 489 Variation in composition of crops . . . . .490 Absorption of plant-food ....... 490 Fertilising ingredients lodge in the seed .... 491 Forms in which nitrogen exists in plants 491 Bearing of above on agricultural practice .... 492 Influence of excessive manuring of crops . . . . .492 CHAPTER XXIII. —MANURING OF THE COMMON FARM CROPS. Cereals ........... 493 Especially benefited by nitrogenous manures . . . 494 Power of absorbing silicates . . . . . .494 Barley 495 Period of growth ....... 495 Most suitable soil ....... 496 Farmyard manure not suitable 497 Importance of uniform manuring of barley . . 497 Norfolk experiments on barley 497 Proportion of grain to straw . . . . .498 Wheat 499 Rothamsted experiments ....... 500 Continuous growth ....... 500 Flitcham experiments . . . . . . .500 Oats 501 A very hardy crop ....... 502 Require mixed nitrogenous manuring . . . .502 Arendt's experiments 503 Aveniue ......... 503 Quantities of manures ...... 504 Grass 504 Effect of manures on herbage of pastures . . . .505 Influence of farmyard manure . . . . . .506 Influence of soil and season on pastures .... 507 Manuring of meadow land ...... 508 Baiigor experiments . . . . . . .508 Norfolk experiments . . . . . . 509 Manuring of permanent pastures ..... 509 Roots .510 Influence of manure on composition . . . .512 Nitrogenous manures increase sugar 512 CONTENTS. xxix Amount of nitrogen recovered in increase of crop . .513 Norfolk experiments 513 Manure for swedes . . . . . . .514 Highland Society's experiments 515 Manuring for rich crops of turnips . . . .516 Experiments by the author on turnips . . . .516 Potatoes 517 Highland Society's experiments . . . . .518 The Rothamsted experiments . . . . . .519 Effect of farmyard manure ..... 520 Manuring of potatoes in Jersey 521 The influence of manure on the composition . . 521 Leguminous crops ......... 522 Leguminous plants benefit by potash .... 523 Nitrogenous manures may be hurtful .... 523 Clover sickness ........ 524 Alternate wheat and bean rotation ..... 524 Beans . . .525 Manure for beans ....... 525 Relative value of manurial ingredients . . ' . 526 Gypsum as a bean manure ...... 526 Effect of manure on composition of crop . . . 527 Peas 527 Hops 528 Cabbages 528 APPENDIX TO CHAPTER XXIII. Experiments on bean-manuring . . . . . 530 CHAPTER XXIV.— ON THE METHOD OF APPLICATION, AND ON THE MIXING OF MANURES." Equal distribution of manures ....... 531 Mixing manures ......... 532 Risks of loss in mixtures ........ 533 Loss of ammonia ........ 533 Effects of lime on ammonia . . . . . .535 Loss of nitric acid ........ 536 Reversion of phosphates . . . . . . .537 Manurial ingredients should be applied separately . . . 538 XXX CONTENTS. CHAPTER XXV.— ON THE VALUATION AND ANALYSIS OF MANURES. Value of chemical analysis ....... 539 Interpretation of chemical analysis . . . . . .539 Nitrogen . . . . . . . . . . 540 Phosphoric acid ......... 541 Importance of mechanical condition of phosphate . . 542 Potash 542 Other items in the chemical analysis of manures . . . 543 Fertilisers and Feeding Stuffs Act ...... 543 Different methods of valuing manures . . . . . 544 Unit value of manurial ingredients ...... 544 Intrinsic value of manures ....... 545 Field experiments 545 Educational value of field experiments ..... 547 Value of manures deduced from experiments .... 548 Value of unexhausted manures ...... 549 Potential fertility of a soil 549 Tables of value of unexhausted manures ..... 551 APPENDIX TO CHAPTER XXV. NOTE I. Factors for calculating compounds from manurial in- gredients . . . . . . . . . 553 II. Units for determining commercial value of manures and cash prices of manures 554, 555 III. Manurial value of nitrogen and potash in different sub- stances .......... 556 IV. Comparative manurial value of different forms of nitrogen and potash ......... 557 V. Lawes' and Gilbert's tables for calculating unexhausted value of manures ........ 559 CHAPTER XXVI.— THE ROTHAMSTED EXPERIMENTS. Nature of experiments on crops and manures . . . .561 Soil of Rothamsted 561 Table I. List of Rothamsted field experiments . . .562 Wheat experiments — Unmanured plots 562 CONTENTS. XXXI Wheat grown continuously on same land (unmanured) . 562 Table II. Results of first eight years . . .562 ii III. Results of subsequent forty years . . 562 Table IV. Wheat grown continuously with farmyard man- ure (14 tons per annum) .... 564 ii V. Wheat grown continuously with artificial man- ures 565 Table VI. Experiments on the growth of barley, forty years, 1852-91 566 it VII. Experiments on the growth of oats, 1869-78 . 567 ii VIII. Experiments on root crops — Swedish turnips 568, 569 ii IX. Experiments on mangel-wurzel . . . 568, 569 .. X. Experiments with different manures on permanent meadow-land, thirty-six years, 1856-91 . . 570 .1 XI. Experiments on the growth of potatoes — average for five seasons, 1876-80 571 u XII. Experiments on growth of potatoes (continued) — average for twelve seasons, 1881-92 . . . 572 INDEX 573 PAET I. HISTORICAL INTRODUCTION MANUKES AND THE PEINCIPLES OF MANUEING. HISTOEICAL INTBODUCTIOJST. AGRICULTURAL CHEMISTRY, like most branches of nat- ural science, may be said to be entirely of modern growth. While it is true we have many old specu- lations on the subject, they can scarcely be said to possess much scientific value. The great questions which had first to be solved by the agricultural chemist were, — What is the food of plants ? and, — What is the source of that food ? The second of these two questions more easily admitted of answer than the first. The source of plant-food could only be the atmosphere or the soil. As the composition of the atmosphere, however, was not discovered till the close of last century, and the chemistry of the soil is a question which is still requiring much work 4 HISTORICAL INTRODUCTION. ere we shall be in possession of anything like a full knowledge of it, it will be at once obvious that the very fundamental conditions for a solution of the question were awanting. The beginning, then, of a true scientific agricultural chemistry may be said to date from the brilliant discoveries associated with the names of Priestley, Scheele, Lavoisier, Cavendish, and Black — that is, towards the close of last century. * Early Theories on Source of Plant-food. While this is so, and while we must regard the early attempts made towards solving this question as being, for the most part, of little scientific value, it is not without interest, from the historical point of view, to glance briefly at some of these old interesting speculations. The Aristotelian doctrine, regarding the possibility of dividing matter into the so-called four primary elements, /ire, air, earth, and water, which obtained in one form or another till the birth of modern chemistry, had naturally an important influence on these early theories. Van Helmont s Theory. Among the earliest and most important attempts made to solve the problem of plant-growth was that by Jean Baptiste Van Helmont, one of the best known of the alchemists, who flourished about the beginning of the seventeenth century. Van Helmont believed VAN HELMONT'S THEOKY. 5 that he had proved by a conclusive experiment that all the products of vegetables were capable of being generated from water. The details of this classical experiment were as follows : — " He took a given weight of dry soil— 200 Ib. — and into this soil he planted a willow-tree that weighed 5 Ib., and he watered this carefully from time to time with pure rain-water, taking care to prevent any dust or dirt falling on to the earth in which the plant grew. He allowed this to go on growing for five years, and at the end of that period, thinking his experiment had been conducted sufficiently long, he pulled up his tree by the roots, shook all the earth off, dried the earth again, weighed the earth and weighed the plant. He found that the plant now weighed 169 Ib. 3 ounces, whereas the weight of the soil remained very nearly what it was — about 200 Ib. It had only lost 2 ounces in weight." l The conclusion, therefore, come to by Van Helmont was that the source of plant-food was water.2 1 The History of the Chemical Elements. By Sir Henry E. Ros- coe, F.K.S. (Wm. Collins, Sons, & Co.) 2 Van Helmont's science was, however, of an extremely rudimentary nature, as may be evidenced by the belief he entertained that the smells which arise from the bottom of morasses produce frogs, slugs, leeches, and other things ; as well as by the following recipe which he gave for the production of a pot of mice: " Press a dirty shirt into the orifice of a vessel containing a little corn, after about twenty- one days the ferment proceeding from the dirty shirt, modified by the odour of the corn, effects a transmutation of the wheat into mice." The crowning point ill this recipe, however, lay in the fact that he 6 HISTORICAL INTRODUCTION. Diybys Theory. Some fifty years later an extremely interesting book was published bearing the following title : ' A Dis- course concerning the Vegetation of Plants, spoken by Sir Kenelm Digby, at Gresham College, on the 23d of January 1660. (At a meeting of the Society for promoting Philosophical Knowledge by Experi- ments. London : Printed for John Williams, in Little Britain, over against St Botolph's Church, 1669.) ' The author attributes plant-growth to the influence of a lalsam which the air contains. This book is especially interesting as containing the earliest rec- ognition of the value of saltpetre as a manure. The following is an extract from this interesting old work : — " The sickness, and at last the death of a plant, in its natural course, proceeds from the want of that balsam ick saline juice ; which, I have said, mak'es it swell, germinate, and augment itself. This want may proceed either from a destitution of it in the place where the plant grows, as when it is in a barren soil or bad air, or from a defect in the plant itself, that hath not vigour sufficient to attract it, though it be within the sphere of it ; as when the root has become asserted that he had himself witnessed the fact, and, as -an interest- ing and corroborative detail, he added that the mice were born full- grown. See 'Louis Pasteur: His Life and Labours.' By his Son- in-law. Translated by Lady Claud Hamilton. (Longmans, Green, & Co.) P. 89. DIGBY'S THEORY. 7 so hard, obstructed and cold, as that it hath lost its vegetable functions. Now, both these may be renie- dy'd, in a great measure, by one and the same physick. . . . The watering of soils with cold hungray springs doth little good ; whereas muddy saline waters brought to overflow a piece of ground enrich it much. But above all, well-digested dew makes all plants luxuriate and prosper most. Now what may it be that endues these liquors with such prolifick virtue ? The meer water which is common to them all, cannot be it; there must be something else enclosed within it, to which the water serves but for a vehicle. Examine it by spagyric art, and you will find that it is nothing else than a nitrous salt, which is dilated in the water. It is this salt which gives foecundity to all things : and from this salt (rightly understood) not only all vegetables, but also all minerals draw their origine. By the help of plain salt-peter, dilated in water and mingled with some other fit earthy substance, that may familiarize it a little with the corn into which I endeavoured to introduce it, I have made the bar- renest ground far out-go the richest, in giving a pro- digiously plentiful harvest. I have seen hemp-seed soaked in this liquor, that hath in due time made such plants arise, as, for the tallness and hardness of them, seemed rather to be coppice-wood of fourteen years' growth at least, than plain hemp. The fathers of the Christian doctrine at Paris still keep by them for a monument (and indeed it is an admirable one) 8 HISTORICAL INTRODUCTION. a plant of barley consisting of 249 stalks, springing from one root or grain of barley ; in which they counted above 18,000 grains or seeds of barley. But do you think that it is barely the salt-peter, imbibed into the seed or root, which causeth this fertility ? no : that would be soon exhausted and could not furnish matter to so vast a progeny. The salt-peter there is like a magnet, which attracts a like salt which fecundates the air, and gave cause to the Cosmopolite to say there is in the air a hidden food of life."1 DuJiamel and Hales. The names of the French writer, Duhamel, and of the English, Stephen Hales, may be mentioned in passing as authors of works bearing on the question of veg- etable physiology. Both of these writers flourished about the middle of the eighteenth century. The writings of the former contained much valuable in- formation on the effects of grafting, motion of sap, and influence of light on vegetable growth, and also the results of experiments which the author had carried out on the influence of treating plants with certain substances. ' Statical Essays, containing Vegetable Staticks ; or an Account of some Statical Experiments on the Sap of Vegetables, by Stephen Hales, D.D.' (2 1 He then goes on to relate a number of experiments by Cornelius Drebel and Albertus Magnus, showing the refreshing power of this balsam, and then those of Quercitan with roses and other flowers, and his own with nettles. JETHKO TULLS THSOBY. 9 vols.), was published in London in 1738 ; and contain- ed, as will be seen from its title, records of experiments of very much the same nature as those of Duhamel. Jethro TulVs Theory. Some reference may be made to a theory which created a considerable amount of interest when it was first published — viz., that of Jethro Tull. The chief value of Tull's contribution to the subject of agricul- tural science was, that he emphasised the importance of tillage operations by putting forward a theory to account for the fact, universally recognised, that the more thoroughly a soil was tilled, the more luxuriant the crops would be. As Tull's theory had a very considerable influence in stirring up interest in many of the most important problems in agricultural chem- istry, and as it contained in itself much, the value of which we have only of late years come to understand, a brief statement of this theory may not be without interest. According to Tull the food of plants consists of the particles of the soil. These particles, however, must be rendered very minute before they become available for the plant, which absorbs them by means of its root- lets. This pulverisation of the soil goes on in nature independently of the farmer, but only very slowly, and the farmer has therefore to hasten it on by means of tillage operations. The more efficiently these opera- tions are carried on, the more abundant will the supply 10 HISTORICAL INTRODUCTION. of plant -food be rendered in the soil. He conse- quently introduced and advocated the system of horse- hoe husbandry. This theory, he informs us, was sug- gested to him by the custom, which he had noticed on the Continent, of growing vines in rows, and hoeing the intervals between these rows from time to time. The excellent results which followed this mode of cultiva- tion induced him to adopt it in England for his farm crops. He accordingly sowed his crops in rows or ridges, wide enough apart to admit of thorough tillage of the intervals by ploughing as well as by hand- hoeing. This he continued until the plant had reached maturity. As to the exact width of the interval most suitable, he made a large number of experiments. At first, in the cultivation of wheat, he made this interval six feet wide; but latterly he adopted an interval of lesser width, that finally arrived at being between four and five feet. He likewise experimented on each separate ridge as to which was the best number of rows of wheat to be sown, latterly adopting, as most convenient, two rows at ten inches apart. The great success which he met with in this system of cultivation induced him to publish the results of his experiments in his famous work, ' Horse-Hoeing Husbandry/ While Tull's theory was based on principles at heart thoroughly sound, he was carried away by his personal success into drawing unwarrantable deduc- tions. Thus he came to the conclusion that rotation DISCOVERY OF THE SOURCE OF PLANTS' CARBON. 11 of crops was unnecessary, provided that a thorough system of tillage was carried out. Manures also, ac- cording to him, might be entirely dispensed with under his system of cultivation, for the true function of all manures is to aid in the pulverisation of the soil by fermentation. The first really valuable scientific facts contributed to the science were made by Priestley, Bonnet, Ingen- housz, and Senebier. Discovery of the Source of Plants Carbon. To Charles Bonnet (1720-1793), a Swiss naturalist, is due the credit of having made the first contribu- tion to a discovery of very great importance — viz., the true source of the carbon, which we now know forms so large a portion of the plant - substance. Bonnet, who had devoted himself to the question of the function of leaves, noticed that when these were immersed in water bubbles were seen, after a time, to collect on their surface. De la Hire, it ought to be pointed out, had noticed this same fact about sixty years earlier. It was left to Priestley, how- ever, to identify these bubbles with the gas he had a short time previously discovered — viz., oxygen. Priestley had observed, about this time, the interest- ing fact that plants possessed the power of purify- ing air vitiated by the presence of animal life.1 The 1 Priestley, however, did riot realise that carbonic acid gas was a necessary plant-food ; on the contrary, he considered it to have a 12 HISTOKICAL INTRODUCTION. next step in this highly interesting and important discovery was taken by John Ingenhousz (1730-1799), an eminent physician and natural philosopher. In 1779, Ingenhousz published a work in London entitled * Experiments on Vegetables.' In it he gives the results of some important experiments he had made on the question already investigated by Bonnet and Priestley. These experiments proved that plant- leaves only gave up their oxygen in the presence of sunlight. In 1782 he published another work on 'The Influence of the Vegetable Kingdom on the Animal Creation/ l The source of the gas, which Bonnet had first noticed to be given off from plant-leaves, Priestley had identified as oxygen, and Ingenhousz had proved to be only given off under the influence of the sun's rays, was finally shown by a Swiss naturalist, Jean Senebier 2 (1742-1809), to be the carbonic acid gas in the air, which the plant absorbed and decomposed, giving out the oxygen and assimilating the carbon. deleterious action on plant -growth. Percival was really the first to point out that carbonic acid gas was a plant-food. 1 It is recorded as an instance of the scientific enthusiasm of the man, that he was wont to carry about with him bottles containing oxygen, which he had obtained from cabbage-leaves, as also coils of iron wire, with which he could illustrate the brilliant combustion which ensued on burning the latter in oxygen gas. 2 For a full account of Senebier's researches, see l Physiologic vegetale, contenant une description des organes des plantes, et une exposition des pheuomenes produits par leur organisation, par Jean Senebier.' (5 tomes. Geneve, 1800.) TREATISE ON AGRICULTURAL CHEMISTRY. 13 Publication of First English Treatise on Agricultural Chemistry. In 1795, a book dealing with the relations between chemistry and agriculture was published. This work was written by a Scottish nobleman, the Earl of Dundonald, and possesses especial interest from the fact that it is the first book in the English language on agricultural chemistry. The full title is as follows : * A Treatise showing the Intimate Connection that subsists between Agriculture and Chemistry/ In his introduction the author says : " The slow progress which agriculture has hitherto made as a science is to be ascribed to a want of education on the part of the cultivators of the soil, and to a want of knowledge, in such authors as have written on agriculture, of the intimate connection that subsists between the science and that of chemistry. Indeed, there is no operation or process not merely mechanical that does not depend on chemistry, which is defined to be a knowledge of the properties of bodies, and of the effects resulting from their different combinations." In quoting this passage Professor S. W. Johnson remarks : l " Earl Dundonald could not fail to see that chemistry was ere long to open a splendid future for the ancient art that had always been and always will be the prime supporter of the nations. But when he 1 How Crops Grow. By Professor S. W. Johnson. Macmillan & Co. (Introduction, p. 4.) 14 HISTORICAL INTRODUCTION. wrote, how feeble was the light that chemistry could throw upon the fundamental questions of agricultural science ! The chemical nature of the atmosphere was then a discovery of barely twenty years' standing. The composition of water had been known but twelve years. The only account of the composition of plants that Earl Dundonald could give was the following: ' Vegetables consist of mucilaginous matter, resinous matter, matter analogous to that of animals, and some proportion of oil. . . . Besides these, vegetables con- tain earthy matters, formerly held in solution in the newly-taken-in juices of the growing vegetables.' To be sure, he explains by mentioning in subsequent pages that starch belongs to the mucilaginous matter, and that on analysis by fire vegetables yield soluble alkaline salts and insoluble phosphate of lime. But these salts, he held, were formed in the process of burning, their lime excepted; and the fact of their being taken from the soil and constituting the indis- pensable food of plants, his lordship was unacquainted with. The gist of agricultural chemistry with him was, that plants ' are composed of gases with a small proportion of calcareous matter ; for although this dis- covery may appear to be of small moment to the prac- tical farmer, yet it is well deserving of his attention and notice.' " De Saussure. The year 1804 witnessed the publication of by far the most important contribution made to the science SOURCE OF PLANT-NITROGEN. - 15 up till this time. This was ' Eecherches Chimique sur la Vegetation/ by Theodore de Saussure, one of the most illustrious agricultural chemists of the century. De Saussure was the first to draw attention to the mineral or ash constituents of the plant; and thus anticipate, to a certain extent, the subsequent famous " mineral " theory of the great Liebig. The French chemist maintained that these ash ingredients were essential; and that without them plant-life was im- possible. He also adduced fresh experiments of his own in support of the theory, based on the experi- ments of Bonnet, Priestley, Ingenhousz, and Senebier, that plants obtain their carbon from the carbonic acid gas in the air, under the influence of the sunlight. He was of opinion that the hydrogen and oxygen of the plant were, probably, chiefly derived from water. He showed that by far the largest portion of the plant's substance was derived from the air and from water, and that the ash portion was alone derived from the soil. To Saussure we owe the first definite state- ment on the different sources of the plant's food. It may be said that the lapse of nearly a century has shown his views to be, in the main, correct. Source of Plant-nitrogen. There was one question, which, even at that remote period in the history of the subject, engaged the atten- tion of agricultural chemists — viz., the question of the source of the plant's nitrogen — a question which may 16 HISTORICAL INTRODUCTION. be fitly described at the present hour as still the burn- ing question of agricultural chemistry.1 As soon as it was discovered that nitrogen was a constituent of the plant's substance, speculations as to its source were indulged in. The fact that the air furnished an unlimited storehouse of this valuable element, and the analogy of the absorption of carbon (from the same source by plant-leaves), naturally sug- gested to the minds of early inquirers that the free nitrogen of the air was the source of the plant's nitrogen. As, however, no direct experiments could be adduced to prove this theory, and as, moreover, nitrogen was found in the soil, and seemed to be a necessary ingredient of all fertile soils, the opinion that the soil was the only source gradually supplanted the older theory. Little value, however, must be attached to these early theories, as they can scarcely be said to have been based on experiments of serious value. Indeed it may be safely affirmed, in the light of subsequent experiments, that it was impossible for this question to be decided at this early period, from the fact that analytical apparatus, of a sufficiently delicate nature, was then wholly unknown. Indeed it is only within the last few years that it has been possible to carry out experiments which may be re- garded as at all crucial. A short sketch of the development of our knowledge of the relation of nitrogen to the plant will be given further on. 1 See p. 40 to 45. &' INDEX. 577 Cress, experiments with, 41. Crimea, bones from, 360. Cropped soils, nitrates in, 157 — lost by drainage in, 141. Crops, capacity of, for assimilating manures, 486 ; difference in root- sy stems of, 488 ; manuring of com- mon farm, 493 - 530 ; period of growth of, 489 ; potash removed in, 218 ; suited for sewage, 434 ; variation in composition of, 490. Crusius on phosphoric acid removed from the farm, 207. Crust guanos, 308, 379. Crystalloids, 491. Cura?ao phosphates, 308, 330, 379. Darmstadt experiments with basic slag, 410-413. Darwin on origin of nitrate-fields, 335. Daubeny on mineral sources of phos- phoric acid, 200. Davy, Sir Humphry, lectures of, on agricultural chemistry, 17-19 ; on heat and water absorbing and re- taining properties of soils, 57 ; on hygroscopic power of soils, 99. Deherain, on nitrification, 52 ; on nitrification in sulphate of am- monia, 191 ; on rate of nitrification. 186. Denitrification, 177 ; conditions fav- ourable for, 178 ; effected by bac- teria, 178. Derby, Lord, introduction of Peruvian guano by, 301. Detmer on humus in soil, 47. Dew, action of, on guano, 300 ; ex- planation of, 77 ; most abundant in summer, 78. Dicalcic phosphate, 387 ; formula of, 398; molecular composition of, 398 ; percentage composition of, 398. Digby, Sir Kenelm, on value of nitrates to plants, 45 ; theory of, on plant-food, 6-8. Diorite, phosphoric acid in, 202, 211. Direct manures, 113. Dissolved-bone compound, 372. Dissolved bones, 368; composition of, 371. Dissolved guano, 310. Dolerite, phosphoric acid in, 202, 211 . Dolomite, phosphoric acid in, 202, 211. Downton experiments on sewage- sludge, 439. Drainage, average of thirteen years, 160 ; nitrates in, 160 ; nitrates lost by, 140 ; phosphoric acid lost by, 206 ; potash lost by, 217. Drainings of manure-heaps, analysis of, 290. Dried blood, 424 ; composition of, 424 ; manure for sugar-cane, 425 ; potash in, 219 ; rate of nitrification in, 192 ; source of nitrogen, 152 ; suited for horticulture, 425. Dried flesh, 425 ; nitrogen in, 425. Dried leaves, as litter, 242 ; compo- sition of, 242 ; nitrogen in, 242 ; phosphoric acid in, 242 ; potash in, 242. Ducks' dung, analysis of, 331. Duhamel and Hales, theory of, on plant-growth, 8. Dundonald, Earl, treatise by, on agri- cultural chemistry, 13. Dung and urine, composition of, 234. Dutrochet on absorption of plant - food, 55. Dyer, Dr Bernard, analyses of stable manure by, 283 ; experiments on peat as litter, 240 ; on nitrate of soda as manure for mangolds, 349. Earth, an adulterant of guano, 319 ; composition of solid crust of, 102. Ecuador, guano deposits at, 327. Egyptian guano, nitrogen in, 329; phosphoric acid in, 329. Elbe, waters of, phosphoric acid in, 206 ; potash in, 217. Elm-tree, water transpired by, 71. Enderbury Island guano, 309, 328; phosphoric acid in, 328. Endosmosis, 55. English farming, 86. Equalised guano, 311. Essex, coprolites from, 374. Estremadura phosphate, 375. Ethylamine, nitrification in, 182. Evaporation from soil, 71, 72, 98. Excreta, amount of nitrogen in, 149, 292 ; composition of, 226, 292 ; dif- ference in amount of, for food con- 2 0 578 INDEX. sumed, 279 ; liquid, in farmyard manure, 224 ; solid, in farmyard manure, 224 ; solid, undigested food in, 224 ; solid, voided by cows, 280, 292 ; solid, voided by horse, 292 ; solid, voided by oxen, 280 ; solid, voided by sheep, 280, 292. Factors for calculating manurial in- gredients into their different com- pounds, 553. Falkland guano, 308 ; nitrogen in, 330 ; phosphoric acid in, 330. Fallow-fields, nitrates formed in, 188. Fanning Island guano, 328 ; phos- phoric acid in, 330. Farmyard manure, 223-292 ; action of, on soils, 273 ; ammonia in, 258 ; amount produced on farm per year, 252 ; analyses of, 259, 286 ; appli- cation of, 264 ; ash of, 287, 288 ; carbonic acid gas in, 258 ; classes of constituents of, 224 ; compared with artificials, 476; composition of, 259 ; denitrification in, 179 ; depth to plough to, 267 ; effect of, on potatoes, 520 ; fertilising matter in, 270 ; fire-fang in, £264 ; fresh, composition of, 286, 288 ; functions of, 268 ; heat in fermentation of, 78, 253 ; humates in, 259 ; hurnic acid in, 258 ; inadequate source of nitrogen to soil, 271 ; indirect in- fluence of, 273 ; influence of, on soil, 475 ; Lawes, Sir J ohn, on composition of, 291 ; Lord Kin- naird's experiments with, 289 ; marsh-gas in, 258 ; mineral matter in, 260 ; moisture in, 260 ; nitric acid in, 259 ; nitrogen in, 260 ; ratio of, to ash ingredients, 271 ; organic matter in, 260 ; phosphor - etted hydrogen in, 258 ; phosphoric acid in, 260 ; potash in, 260 ; pro- ducts of decomposition of, 257 ; rate of application of, 275 ; re- trogression of nitrogen in, 142 ; rotten, composition of, 287, 288 — value of, 261 ; rotting, effects of, on, 262 ; solid excreta in, 224 ; sul- phuretted hydrogen in, 258 ; sup- plemented with nitrogen, 271 ; supplemented with phosphoric acid, 272 ; temperature, effect of, on soil, 79, 274 ; typical compost, 446 ; ulmates in, 259 ; ulmic acid in, 258 ; unfavourable to certain crops, 477 ; urine in, 228 ; value of, 268 ; variation in composition of, 223 ; water in, 258. Fatty acids in guano, 305. Felspars, 103 ; albite, 103 ; composi tion of, 103 ; labradorite, 220 ; oligoclase, 103, 214, 220; ortho- clase, 103, 214, 220; phosphoric acid in, 211 ; potash manures, 213; potash in, percentage of, 213, 220. Ferment, aerobic, 173, 255 ; anaerobic, 255. Fermentation, ammonium carbonate formed during, 245 ; in bones, 365 ; heat of, 79 ; of farmyard manure, 253 ; of guano, 299 ; tem- perature of, 256. Fern, bracken, as litter, 241. Ferric chloride, test for sulphocyan- ates, 355. Fertilisers and Feeding Stuffs Act, 543. Fertilising ingredients, amount of soluble, in soil, 90 ; amounts re- moved by different crops, 484, 485 ; chemical condition of, in soil, 89 ; lodge in seed, 491 ; in soil, 87. Fertility, of the soil, 65-97 ; poten- tial, of soil, 214, 549 ; properties necessary for, 66 ; supply of oxy- gen necessary for, 81. Field experiments, 545, 548 ; educa- tional value of, 547 ; on rate of nitrification, 187. Finger-and-toe prevented by lime, 461. Fire-fang in farmyard manure, 264. Fischer on absorption of plant-food, 55. Fish-guano, 320-323 ; application of, 323 ; consumption of, 152 ; manu- facture of, 321 ; nitrogen in, 321 ; phosphoric acid in, 321 ; production of, 322 ; source of nitrogen, 152 ; value of, 322. Fixers, 246 ; chemical reactions with, 284. Fleece, potash in, 217. Fleischer, Professor, on solubility of phosphates, 408. Flesh-guano, 320. Flint Island guano, 309. INDEX. 579 Flitcham experiments on growth of wheat, 500. Floated bones, 362, 365. Florida phosphate, 378. Fluorapatite, composition of, 210. Food, consumed by pigs, 281 ; dry matter of, voided in dung, 228 ; percentage of, in excrements, 281. Food-constituents, plant, necessary for nitrification, 170. . Forbes, David, on nitrate - fields of Chili, 334. Forest-soils, absence of nitrification in, 193. Fowl-dung, 320, 326; analysis of, 331. Fownes on phosphoric acid in rocks, 202. Frankland, P. F., experiments on nitrification, 52, 167, 198. Franklin, Benjamin, experiment of, with gypsum, 462. Frey Bentos, meat-meal guano from, 324. Gallopagos Islands, guano deposits at, 327. Garden earth, absorptive power of, 98 ; ammonia in, 128. Gas-liquor, ammonia in, 353. Gas-works, ammonia from, 353, 358. Gases, absorbed by soils, 81 ; present in soil, 100. Gazzeri on retention by soil of plant - food, 57. Geese-dung, analysis of, 331. Geic acid in humus, 47. Gelatin, nitrification in, 182 ; from bones, 364. Germany, agricultural research in, 32 ; bones imported from, 360 ; manufacture of meat-meal guano in, 324. Germination, influence of temperature on, 76 ; oxygen necessary for, 81. Gilbert, Sir J. Henry, on barley- manuring, 496 ; on Liebig's mineral theory, 28 ; on manuring of po- tatoes, 520 ; Presidential address of, 61 ; and see Lawes and Gilbert. Glauber on artificial production of nitre, 164. Glue, 364. Glycin, assimilated by plants, 47. Glycocoll, experiments with, 46. Gneiss, 106 ; phosphoric acid in, 207. Grandeau, Professor, on forms of plant-food in soil, 107 ; on loss of phosphoric acid, 207. Granite, 105 ; in guano, 303 ; phos- phoric acid in. 202, 211 ; potash in, 214. Grass, Bangor experiments on, 508 ; effect of manure on, 505 ; influence of farmyard manure on, 506 ; man- uring of, 504-510. Gray, Asa, on transpiration by plants, Great Cayman guano, 379. Green manures, 113. Grouven on guano, 313. Guanape Island guano, 302, 327 ; nitrogen in, 329 ; phosphoric acid in, 329. Guanine, 304 ; experiments with, 46. Guano, 293-331 ; action of, as a man- ure, 312 ; adulteration of, 318 ; ap- plication of, 315 ; bat, 325 ; com- position of, 305, 329 ; crust, 308 ; deposits of the world, 327 ; dis- solved, 310; equalised, 309; fer- mentation of, 299 ; fertilising con- stituents in, 314; fish, 320-323; importance of, in agriculture, 293 ; inequality in composition of, 309 ; influence of, on farming, 294 ; meat- meal, 324 ; mode of application of, 315 ; nitrification in, rate of, 192 ; nitrogenous, 300-308 ; origin of, 297; Peruvian, 300-306; phos- phatic, 308 ; quantity to apply, 317 ; rectified, 311 ; so-called, 320 ; source of phosphoric acid, 202 ; source of potash, 219 ; value of, as a manure, 296 ; variation in com- position of, 299. Gulf of Mexico, guano deposits at, 328. Gulls, guano from, 297. Gunning on sources of plant-nitrogen, 42. Gunpowder, exports of, 149 ; nitrogen lost in, 149 ; production, annual, of, 149 ; saltpetre in, 149, 333. Gypsum, 462-464 ; absorptive power of, 98 ; action of, mode of, 462— on nitrification, 173 ; an adulterant of guano, 319 ; as a fixer, 246, 247, 580 INDEX. 285 ; decomposes double silicates, 463 ; favourable to clover, 464 ; as an oxidising agent, 464. Hales, Stephen, theory of, on plant- growth, 8. Hampe, Dr, on nitrogen in plants, 46. Harting on sources of plant-nitrogen, 42. Heat, of soils, 76-78 ; of fermenta- tion, 78. Heiden, Dr, on application of farm- yard manure, 265 ; on fixation of bases and acids by soil, 59 ; ou loss of ammonia from dung, 249 ; on per- centage of food voided by animals, 253 ; on straw as litter, 244, 249. Hellriegel, on amount of water in soils, 75 ; on barley, 498 ; on ni- trogen in plants, 44. Helmout, Van, theory of, on source of plant-food, 4. Henslow, Professor, on coprolites, 374. Heraus on organisms in soil, 95. Herbage, effect of manure on, 505. Herrings as manure, 321. Herve-Mangon, experiments on action of light on plants by, 38. Hilgeustock on tetracalcic phosphate, 405. Hippuric acid, experiments with, 46 ; in farmyard manure, 257. Hire, De la, on evolution of gases by plants, 11. Hofmeister on horse excrements, 243. Hoof-guano, source of nitrogen, 152. Hoofs and horns, manure from, 425. Hops, manuring of, 528 ; potash re- moved by, 217 ; slow-acting man- ures benefit, 528. Horn, capable of nitrification, 182 ; as manure, 425 ; nitrogen in, 426 ; phosphoric acid in, 426. Hornblende, 105. Horse-dung, alkalies in, 226 ; com- position of, in dry state, 227 ; hot, 225 ; nitrogen in, 225, 226 ; phos- phoric acid in, 226 ; water in, 225, 226. Horse-manure, 242 ; amount produced per day, 243 ; amount produced per year, 243 ; analyses of. 283 ; dry matter in, 243 ; dry nature of, 245 ; fermentation rapid in, 245 ; mineral matter in, 243; nitrogen in, 243, Horse-urine, alkalies in, 230 ; com- position of, in dry state, 231 ; fer- tilising ingredients in, 232 ; nitrogen in, 230 ; phosphoric acid in, 230 ; water in, 230. Hosaus on assimilation of ammonia, 50. Howland Island guano, 309, 328 ; phosphoric acid in, 330. Huanillos, guano from, 302, 327 ; nitrogen in, 330 ; phosphoric acid in, 330. Huano, 297. Hueppe on organisms in soil, 95. Hughes, John, on bracken-fern as litter, 241 ; on composition of bracken, 283. Humates in farmyard manure, 259. Humboldt, A., discovery of Peruvian guano by, 300. Humic acid in farmyard manure, 258 ; in humus, 47. Humin in humus, 47. Humus, absorptive power of, 68, 98 ; evaporation from, 99 ; nature of, in soil, 47 ; soils improved by addi- tion of, 273. Huou Island guano, 309, 328 ; phos- phoric acid in, 330. Huxtable and Thompson on retention of plant-food by soil, 57. Hydrated silicates, 107, 459. Hydrochloric acid as a fixer, 245. Hydrogen, amount of, in plants, 40 ; source of, in plants, 40. Hygroscopic power of soils, 75. Ichaboe guano, 307 ; nitrogen in, 329 ; phosphoric acid in, 329. Independence Bay guano, 302, 327 ; nitrogen in, 329 ; phosphoric acid in, 329. India, nitre soils of, 162. Indirect manures, 113, 114, 449-473. Ingenhousz, John, experiments by, on nitrogen in plants, 41 ; on oxygen evolved by plants, 12. Insoluble phosphate, 386; value of, 396. Iodine, in ash of plants, 55 ; in nitrate of soda, 340, 342. INDEX. 581 Iquique, nitrate of soda from, 333. Iron in ash of plants, 54 ; necessary for plant-growth, 55 ; reversion in superphosphates caused by, 390, 399. Iron-works, ammonia from, 353, 355, 358. Irrigation, 431 - 433 ; intermittent, 434 ; subsoil, 432. Jamieson, Professor, experiments with coprolites, 380. Jarvis Island guano, 309, 328 ; phos- phoric acid in, 330. Jersey, manuring of potatoes in, 521. Johnson^ Professor S. W., on appli- cation of superphosphate, 395 ; on Earl Dundonald, 13 ; on nitrogen in buffalo-horn shavings, 426 ; on nitrogen in soils, 123 ; on solubil- ity of basic slag, 408 ; value of organic nitrogen to plant, 46. Jurgensen on nitrogen in excreta, 234. Kainit, as a fixer, 247 ; potash in, percentage of, 214, 220, 421 ; rate of application of, 423. Kaolin clay, analysis of, 104. Karmrodt/ analysis of Chincha Island guano, 305 ; of concretionary nod- ules, 328. Karnallite, potash in, 220. Kellner, experiments on nitrification by, 52. Kelp, potash in, 420. Kieserite, 420. Kinuaird, Lord, experiments by, with farmyard manure, 289. Kitchen-garden soil, nitrogenous mat- ter in, 122. Knop on condition of nitrates in soil, 138. Koosaw River, phosphates from, 376. Kreatin assimilated by plants, 47. Kuria Muria guano, 309, 328. Labrador, guano deposits at, 328. Labradorite, 214 ; potash in, 220. Lacepede Island guano, 309, 328 ; phosphoric acid in, 330. Lahn phosphate, 379. Lava, phosphoric acid in, 202, 211. Lawes, Sir J. B., and Gilbert, early researches of, at Rothamsted, 34 ; experiments with farmyard man- ure, 271 ; experiments with Per- uvian guano, 301 ; inauguration of Rothamsted experiments by, 33 ; on composition of farmyard man- ure, 291 ; on manuring of wheat, 483 ; on motion of plant's sap, 56 ; on percentage of food in excreta, 233 ; on rate of nitrification, 186 ; on sources of plant-nitrogen, 43 ; on sulphate of ammonia, 356 ; on unexhausted manures, 550, 557-559. Lawes, Sir J. B., experiments with guano by, 301 ; manufacture of superphosphate by, 382 ; on ap- plication of superphosphate, 395 ; on bones, 359 ; on composition of farmyard manure, 291 ; on farm- yard manure, 477 ; on loss of ni- trates, 142 ; on sources of nitrogen, 154. Leather, as manure, 428 ; nitrogen in, 428. Leaves, dried, as litter, 242; nitro- gen in, 242 ; phosphoric acid in, 242 ; potash in, 242. Legrange, Charles, on extent of ni- trate-fields, 343. Leguminous plants, benefited by basic slag, 414 — by potash, 523 ; fixation of free nitrogen by, 42 ; gain of nitrogen with, 135 ; manuring of, 522-527, 530 ; nitrogenous manures hurtful to, 523. Lehmann on ammonia as plant-food, 50, 352. Leipzig, bones from, 361. Leones, guano deposits at, 327. Leucite, potash in, 220. Lias chalk, phosphoric acid in, 211. Liebig, criticism of humus theory by, 25 ; dissolved bones discovered by, 361 ; first report to British Associ- ation, 24 ; manufacture of super- phosphate from bones by, 359 ; mineral theory of, 26-29 ; on am- monia as a manure, 352 ; on im- portation of bones by Britain, 360 ; researches of, in agricultural chem- istry, 23-32 ; services of, to agri- cultural chemistry, 31 ; theory of manures by, 29 ; theory of, on ro- tation of crops, 29. Light, action of, on plant-growth, 38. 582 INDEX. Lime, 449-461 ; abundant occurrence of, 452 ; action of, 461 — contradic- tory, 450 — not thoroughly under- stood, 449 — on nitrogenous organic matter, 460 — on soil's texture, 455 ; antiquity of, as a manure, 449 ; binding effect of, 457 ; biological action of, 459 ; caustic, 453 ; chem- ical action of, 457 ; decomposes minerals, 458 ; different forms of, 453 ; effect of, on soils, 112 ; fixed by soils, 58 ; in ash of plants, 54 ; mechanical functions of, 455 ; mild, 453 ; necessary for nitrification, 171, 459 — for plant-growth, 55, 450 ; neutralises acidity in soils, 458 ; phosphates of, 385-388 ; pig excrements contain, 281 ; prevents clay puddling, 456 ; returned to soil, 452 ; soils contain, 450-452. Limestone, analyses of, 106 ; evapora- tion of water from, 99 ; occurrence of, 452. Linseed, imports of, 153 ; manurial constituents of, 282. Linseed-cake, manurial constituents of, 282. Liquid manure, 442-444. Lithia in ash of plants, 55. Litter, loam as, 239 ; peat as, 240 ; straw as, 236 ; uses of, 236. Lloyd on fattening animals, 253. Loam, as litter, 239 ; evaporation of water from, 99 ; poor in fertilising matter, 239. Lobos, guano deposits at, 327. Lobos de Afuera guano, 302, 327. Macabi Island guano, 302, 327 ; ni- trogen in, 329 ; phosphoric acid in, 329. Maercker, Professor, on destruction of nitrifying organisms, 177. Magnesia, fixed by soils, 58 ; in ash of plants, 54 ; in pig excrements, 281 ; necessary for nitrification, 171; necessary for plant -growth, 55 ; sulphate of, as a fixer, 246, 285. Maize, absorbs ammonia, 352 ; fer- tilising ingredients removed from soil by, 485 ; manurial constituents in, 282 ; source of nitrogen, 153. Maiden Island guano, 309, 328 ; phosphoric acid in, 330. Malpighi on importance of atmo- spheric air for germination, 39. Malt-dust, manurial constituents in, 282. Manganese, oxide of, in ash of plants, 04. Mangels, fertilising ingredients re- moved from soil by, 485 ; guano a manure for, 318 ; mauurial con- stituents in, 282 ; manuring of, 346, 511, 513, 514 ; Rotham- sted experiments on growth of, 568. Manitoba soils, nitrogen in, at various depths, 156 ; rate of nitrification in, 186. Manure, cow, 247 ; farmyard, 223- 292 ; horse, 243 ;' liquid, 442-444 ; meaning of word, 109 ; pig, 250 ; sewage, 430-441 ; sheep, 251 ; stable, from peat-moss, 283 — wheat-straw, 283. Manures, action of, 61 ; analysis of, interpretation of, 539-544 ; appli- cation of, 474-492 ; method of, 531- 538 ; cash prices of, 555 ; equal distribution of, 531 ; functions of, 109 ; increase soil - fertility, 474 ; intrinsic value of, 545 ; lasting effects of, 483 ; methods of valuing, 544 ; minor artificial, 424 - 429 ; mixing of, 531-538 ; nitrogenous, 293 - 359 ; phosphatic, 359 - 417 ; potassic, 418 - 423 ; quantities of, applied to oats, 504 ; unexhausted, 549-552, 558 ; units for determining commercial value of, 554 ; valuation of, 539-559 ; value of, deduced from experiments, 548 ; various classes of, 111-114. Manurial constituents of various foods, 282. Manurial ingredients, unit value of, 544. Manuring of, barley, 495-498 ; beans, 525-527, 530 ; cabbages, 528 ; cere- als, 493-504 ; clover, 524 ; common farm crops, 493-530 ; grass, 504- 510 ; hops, 528 ; leguminous crops, 522-528 ; mangels, 511, 513, 514 ; oats, 493 - 504 ; peas, 527 ; pota- toes, 517-522 ; roots, 510 - 517 ; turnips, 510, 511, 513-517 ; wheat, 499-501. INDEX. 583 Maraeaibo guano, nitrogen in, 330 ; phosphoric acid in, 330. Marl, phosphoric acid in, 211. Marsh -gas from farmyard manure, 258. Meadow -hay, fertilising ingredients removed from soil by, 485 ; man- urial constituents in, 282 ; Roth- amsted experiments on manuring of, 570. Meadow-land, benefited by basic slag, 414, 508 ; manuring of, 508 ; Nor- folk experiments on, 509. Meat-meal guano, 320, 324 ; com- position of, 152 ; imports of, 324 ; manufacture of, 324 ; nitrogen in, 324 ; phosphoric acid in, 324 ; rate of nitrification in, 192 ; source of nitrogen, 152 ; value of, 324. Mechi on liquid manure, 442. Mejillones guano, 309, 327 ; phos- phoric acid in, 330. Mene, on sources of plant - nitrogen, 42. Menhaddo. guano manufactured from, 322. Mexico phosphate, 308, 328. Mica, analysis of, 105 ; potash in, 214, 220. Micro-organisms, convert ammonia into nitrous acid, 167 ; convert nitrous acid into nitric acid, 168 ; effect fermentation, 80 ; effect fix- ation of free nitrogen, 44 ; effect nitrification, 161 ; oxidising power of, 197. Mild lime, 453. Milk, nitrification in albuminoids of, 182 ; nitrogen removed in, 147 ; phosphoric acid removed in, 207 ; potash removed in, 218. Mineral phosphates, 373-381 ; value of, as a manure, 380. Mineral salts necessary for nitrifica- tion, 52. Minor artificial manures, 424-429. Mixing manures, 532-538 ; ammonia lost in, 533 ; nitric acid lost in, 536 ; phosphates reverted in, 536. Moisture, atmospheric, action on guano, 300 ; in farmyard manure, 260 ; in manures, 543 ; necessary for nitrification, 52, 176. Molds, 94. Mona guano, 309. Mond, Ludwig, on nitrogen in coal, 354. Monks guano, 327; phosphoric acid in, 330. Monocalcic phosphate, 386 ; formula of, 398 ; molecular composition of, 398 ; percentage composition of, 398 ; reversion of, with iron and alumina compounds, 399 — with tricalcic phosphate, 399. Mulder on humus in soil, 47, 126. Miiller, A., on nitrogen in soil, 121, 124. Munro, Dr J. M. H. , on nitrification, 52 ; on sewage-sludge as manure, 439 ; on urine voided, 292. Muntz, on ammonia in air, 118 ; on nitrifying organisms in soil, 180 ; on oxidising power of micro-organ- isms, 197. Muriate of potash, application of, 423 ; forms calcium chloride, 422 ; harmful effects of, 421 ; more con- centrated than sulphate, 422. Mustard, 139. Navassa phosphate, 308, 328, 379. Nesbiton composition of guano, 301, New Granada, guano deposits at, 327. New Zealand, meat-meal guano from, 324. Nile, nitrates in waters of, 159. "Nitraries,"163. Nitrate - fields, appearance of, 340 ; origin of, 334. Nitrate of soda, 332 - 351 ; amount exported from Chili, 151, 332, 351 ; amount imported into Britain, 151, 351 ; appearance of fields of, 340 ; application of, 347 ; Chili and Peru chief source of, 161 ; composition of, 343 ; crops suited by, 346 ; dis- covery of deposits of, 333 ; extent of deposits of, 342 ; encourages deep roots, 344 ; formation of fields of, 334-340 ; method of applying, 347 ; method of mining, 341 ; nitric acid in, source of, 337 ; nitrogen in, percentage of, 343 ; not an exhaust- ing manure, 345 ; origin of fields of, 334 ; properties of, 343 ; quantity to apply, 348 ; shipments of, 351 ; soils benefited by, 348 ; source of 584 INDEX. nitrogen, 150 ; top - dressing with, o44. Nitrates, amount lost by drainage, 140 ; amount produced at different times, 189 ; amount in soil, 129 ; conditions diminishing loss of, 139 ; constantly formed in soil, 138 ; in barley -soils, 158 ; in cropped soils, 130, 157 ; in drainage-waters, 160, 188 ; in fallow-soils, 129 ; in man- ured wheat-soils, 131, 157 ; in soil, 129, 162 ; lost by drainage, 137 ; most formed in summer, 139 ; nitrogen as, in Rothamsted soils, 198 ; position of, in soil, 188 ; quantity formed in fallow -fields, 188. Nitre, beds, 163 ; occurrence of, 162 ; soils of India, 162. Nitric acid, amount of, supplied to soil by rain, 155 ; derived from sea- weed, 337 ; formed from ammonia, 118 ; formed from nitrous acid, 168 ; in farmyard manure, 259 ; in soil, 128 ; lost in mixing manures, 536 ; most important nitrogen compound for plants, 161 ; relation of, to plants, 50 ; source of, in nitrate of soda, 337. Nitrification, 51, 52, 161-198 ; action of gypsum on, 173 ; alkalinity necessary for, 172 ; in asparagin, 182 ; bearing of, on agriculture, 193 ; in bones, 182 ; cause of, 165 ; conditions favourable for, 170 ; deuitrification, 177 - 179 ; effected by micro-organisms, 51, 167 ; in ethylamine, 182 ; in fallow-fields, 184 ; food - constituents necessary for, 170 ; field experiments on rate of, 187 ; in gelatin, 182 ; in horn, 182 ; laboratory experiments on rate of, 185 ; in manures, 190, 192 ; in milk albuminoids, 182 ; mineral salts necessary for, 52 ; moisture necessary for, 52, 176 ; old theories on, 196 ; organic matter not neces- ary for, 169, 196 ; oxygen necessary for, 52, 173 ; plant-roots promote, 181 ; in rape-cake, 182 ; rate of, 183 ; rotation of crops, bearing of, on, 195 ; soil best suited for, 192 ; in subsoils, conditions favourable for, 181 ; substances capable of, 181; in summer, 183 ; sunlight, effect of, on, 176 ; temperature necessary for, 52, 175 ; in thiocyanates, 182 ; hi urea, 182 ; in wool, 182. Nitrifying organisms, depth found at in soil, 180 ; distribution of, in soil, 179 ; effect of poisons on, 176 ; organic matter not required by, 169. Nitrobaeter, 167. Nitrogen, 115-160 ; absorbed by soil, 81, 131 ; accumulates in pastures, 134 ; in air, 116 ; as ammonia in soils, 127 ; amount of, in plants, 40; amount of, in soil, 123; arti- ficial supply of, 150 ; in bat guano, 325 ; in bones, 363, 364 ; combined, in air, 118 ; combined, in rain, 119, 155 ; condition of, in manures, 540 ; converted into nitrates in soil, 51 ; in cow - dung, 226 - 228 ; in cow excrements, 278 ; in cow - urine, 230 ; difference between surface and subsoil, 126 ; different forms of, 45, 116 ; dissolved in rain, 131 ; in dried blood, 424 ; in farmyard manure, 260; in fish -guano, 321; fixation of free, 136 ; forms of, in plants, 491 ; free, relation of, to plant, 117; gain of, with legumin- ous crops, 135 ; in guanos, 329 ; in hoofs and horns, 426 ; in horse- dung, 226 - 228 ; in horse - man- ure, 243 ; in horse - urine, 230 ; importance of, in soil, 88 ; in lean flesh, 424 ; in leather, 428 ; least abundant of manurial ingredients in soil, 271 ; loss of, artificial sources of, 144 ; loss of, by crops, 144 ; loss of, on farm, 146 ; loss of, sources of, 137-150 ; loss of, total amount of, 142 ; lost in the arts, 148; lost in free condition, 141; lost in treating farmyard manure, 146; lost in milk, 147; lost by retrogression, 142 ; in Manitoba soils, 156 ; in meat - guano, 324 ; nature of, in soil, 124 ; as nitrates in soil, 128 ; as nitrates in cropped soils, 130, 157 ; as nitrates in Eoth- amsted soils, 198 ; as nitrates in wheat - soils, 157 ; in nitrate of soda, 343 ; nitric, in soil, 128 ; organic, absorbed by plants, 47 ; organic, in soil, 125 ; original INDEX. 585 source of, m soil, 133 ; in oxen excrements, 280 ; in pasture-lands, 158 ; peat-soils richest in, 123 ; in Peruvian guano, 302, 306, 307, 329 ; in pig-dung, 226-227 ; position of, in agriculture, 115-160; relative manurial value of, 556; Rotham- sted experiments on, 115 ; in scutch, 427 ; in sewage, 431 ; in sewage-sludge, 439 ; in sheep -dung, 226 - 228 ; in sheep excrements, 280 ; in sheep-urine, 230 ; in soil, 120 ; in soil, portion of, easily nitrifiable, 187 ; in soils at various depths, 156 ; in soot, 428 ; source of, in plants, 15, 16, 40-52 ; sources of soil, 131-137 ; in straw, 237, 243 ; in subsoil, 121 ; in surface - soil, 121 ; in swine-urine, 230 ; in wool- len rags, 427. Nitrogenous guano, 300-308, 329. Nitrogenous manures, application of, 478 ; benefit cereals, 494 ; hurtful to leguminous crops, 523. Nitrogenous organic substances, in Chincha guano, 305 ; in concretion- ary nodules, 328. Nitros omon as, 167. Nitrous acid, converted into nitric acid, 168 ; formed from ammonia, 167. Nobbe, on fixation of free nitrogen, 136 ; on potash in soil, 108. Nollner on origin of nitrate - fields, 339. Norfolk, coprolites from, 374 ; experi- ments on barley, 497 — on meadow- land, 509 — on turnips, 513. North America, guano from, 298, 328. Norwegian apatite, 375. Oak-tree, water transpired by, 71. Oat-straw, composition of, 238 ; man- urial constituents in, 282. Oats, Arendt's experiments with, 503 ; avenine in, 503 ; fertilising ingre- dients removed from soil by, 485 ; hardy crop, 502 ; manurial con- stituents in, 282 ; manuring of, 501-504 ; nitrogen removed in crop of, 148 ; require mixed nitrogenous manures, 502 ; source of nitrogen, 153 ; Rothamsted experiments on growth of, 567. Oficinas, 342. Ohlendorff, introduction of dissolved guano by, 311. Oilcakes, imports of, 153 ; source of nitrogen, 153. Oil-seeds, source of nitrogen, 153. Oligoclase felspars, 103, 214 ; com- position of, 103 ; potash in, 220. Organic matter, in bones, 363 ; in dung, 228, 260 ; in manures, 543 ; not necessary for nitrifying organ- ism, 169. Orthoclase felspars, 103, 214 ; com- position of, 103 ; potash in, 220. Ox-dung, fertilising ingredients in, for food consumed, 228. Ox-urine, fertilising ingredients in, 232. Oxalic acid in guano, action of, 330. Oxen, excrements of, 280 ; food aided by, 280 ; solid excreta voided by, 280 ; urine voided by, 280. Oxidation, 79 ; products of, 79, 80. Oxygen, absorbed by plant-roots, 81 ; absorbed by soil, 81 ; evolved by plants, 11 ; necessary for fertility, 81 ; necessary for nitrification, 52, 173 ; percentage of, in plants, 39 ; source of, in plants, 39. Pabellon de Pica, guano from, 298, 302, 327; nitrogen in, 330; phos- phoric acid in, 330. Pacific Islands, guano from, 298. Pacific Ocean, sea-weed in, 339. Palagonite as potash manure, 213. Palm-kernel meal, manurial constit- uents in, 282. Pasteur, on fermentation in urine, 255 ; on nitrification, 166. Pastures, accumulation of nitrogen in, 134 ; benefited by basic slag, 414 ; deficient in lime, 451 ; effect of manure on herbage of, 505 ; nitro- gen in, 158 ; permanent, 138, 194 — manuring of, 509 ; season influ- ences, 507 ; soil influences, 507. Patagonian guano, 308, 327 ; nitrogen in, 330 ; phosphoric acid in, 330. Patent phosphate meal, 405. Patillos, guano deposits at, 327. Patos Island, guano deposits at, 328 ; phosphoric acid in, 330. Patterson on superphosphate, 399. 586 INDEX. Payen and Boussingault on composi- tion of dried flesh, 425. Peas, mamirial constituents in, 282 ; manuring of, 527 ; phosphorus in, 205 ; source of nitrogen, 153. Peat, absorbing properties of, 239 ; adulterant of guano, 317 ; analysis of stable-manure from, 281 ; litter, 239 ; nitrogen in, 240 ; retaining properties of, 240 ; soils, 123. Pelicans, guano from, 297. Penguin Island guano, 330 ; nitrogen in, 330 ; phosphoric acid in, 330. Penguins, guano from, 297. Percival on carbonic acid in plants, 12. Peru, guano deposits in, 327 ; guano first used in, 297 ; nitrate of soda from, 161, 162. Peruvian guano, 300-306 ; appearance of, 303 ; composition of, 304-306 ; deposits of, 301 ; imports of, 151, 297 ; source of nitrogen, 151. Peters and Eichhorn on solvent power of salt, 471. Petzholdt on sources of plant's nitro- gen, 42. Pfeffer on action of light on plant - growth, 38. Phoenix Island guano, 309. Phosphate of iron in Chincha guano, Phosphate of lime, in Algerian phos- phate, 379 ; in apatite, 374 : in Belgian phosphate, 377 ; in bones, 364 ; in Cambridge coprolites, 374 ; in Carolina phosphates, 376 ; in crust guanos, 379 ; in Estremadura phosphate, 375 ; in Florida phos- phate, 378 ; hi French phosphates, 379 ; in Lahn phosphates, 379 ; in Somme phosphate, 378 ; reverted in mixing manures, 537. Phosphates of lime, 385-388, 398 ; im- portance of mechanical condition of, 542. Phosphates, mineral, 373-381 ; imports of, 381 ; value as a manure, 380. Phosphatic guano, 308, 330. Phosphatic manures, application of, 480. Phosphoretted hydrogen in farmyard manure, 258. Phosphoric acid, 199-211 ; in ash of plants, 54 ; in basic slag, 404 ; in bat guano, 325 ; in bones, 363 ; condition of, in soil, 203 ; in cow- dung, 226-228; in cow excre- ments, 280 ; in cow-urine, 230 ; in farmyard manure, 260 ; in fish- guano, 321 ; fixed by soils, 58 ; gain of, 208 ; in guano, percentage of, 329, 330 ; guano a source of, 202 ; in hoofs and horns, 426 ; in horse- dung, 226-228; in horse - nrine, 230; importance of, 88; loss of, artificial sources of, 206— by drain- age, 206 — in farmyard manure, 208 — in milk, 207— in sewage, 208— sources of, in agriculture, 205 ; in meat-guano, 324 ; mineral sources of, 200; necessary for plant-growth, 55 ; occurrence of, in animals, 205 — in nature, 199 — in plants, 204 — in soil, 203 ; in oxen excrements, 280 ; in pig-dung, 226, 227 ; in pig excre- ments, 281; in pig-urine, 230; po- sition of, in agriculture, 199-211 ; relative trade values of, in manures, 400 ; in rocks, 202, 211 ; in sewage- sludge, 441; in sheep-dung, 226— 228 ; in sheep excrements, 280 ; in sheep-urine, 230; statement of, in analyses of manures, 541. Phosphorite, 201, 374. Phosphorus, in albuminoids, 205; in animals, 205; in beans, 205; in peas, 205; in plants, 204; in pig- iron, 401. Physical properties of soils, 66-87. Pichard on action of gypsum on ni- trification, 173. Pig-dung, composition of, 226 ; in dry state, 227. Pig excrements, 281 ; composition of, Pig-manure, 250; amount produced per day, 251 ; mineral matter in, 251 ; nitrogen in, 251 ; poor in nitrogen, 251. Pig-urine, composition of, 230 — in dry state, 231. Pigeon-dung, 320, 325; analysis of, 331. Pigs, excrements of, 281; food con- sumed by, 281. Pisagua, nitrate-fields at, 340. Plant, action of light on, 38 ; amount INDEX. 587 of hydrogen in, 40— nitrogen in, 40 — oxygen in, 40 ; ash constituents of, 53-55; carbon fixed by, 37, 38; food, absorption of, by, 55; phos- phoric acid in, 204 ; potash in, 216 ; proximate composition of, 36; re- lation of ammonia to, 48-50 ; source of hydrogen in, 40— nitrogen in, 40-52— oxygen in, 39, 40. Plant-food, absorption of, 490; amount of soluble, in soil, 100 ; early theories on source of, 4; retained by soil, 57. Plant-roots, grow downwards, 84; nitrification promoted by, 181; openness required by, 83; room required by, 85; soil in relation to, 84. Pliny, on lime as a manure, 449 ; on salt as a manure, 465. Pockets a source of phosphoric acid, 202. Poisons, effect of, on nitrifying organ- isms, 176. Polstorff on ash constituents of plants, 53. Polyhallite, potash in, 220, 420. Porphyry, in guano, 303 ; phosphoric acidX 202, 211. Potash, 212-220, 418-423; in ash of plants, 54 ; in barilla, 420 ; chloride of, 218 ; condition of, in soil, 216 ; in cows' excrements, 280 ; in drain- age-waters, 217 ; in farmyard man- ure, 260 ; in felspars, 220 ; in fleece, 217 ; fixed by soils, 58 ; importance of, in soil, 88; in kelp, 420; less important than phosphoric acid, 212 ; manures, 218, 418-423 ; muri- ate of, 218, 421 ; necessary for nitri- fication, 171 ; necessary for plant- growth, 55; occurrence of, 213; in ocean, 213; in oxen excrements, 280; in pig excrements, 280; in plants, 216 ; position of, in agricul- ture, 212-220; relative manurial value of, 556; Scottish soils sup- plied with, 419 ; in sheep excre- ments, 280; soda replaces, 466; sources of loss of, 217 ; in Stassfurt salts, 214 ; statement of, in analyses of manures, 542 ; in sugar-beet ref- use, 219 ; sulphate of, 218, 421 ; in wood-ashes, 218, 220, 419. Potash manures, 218, 418-423 ; appli- cation of, 422, 480— rate of, 423; barilla , as, 420; crops suited for, 423 ; relative importance of, 418 ; soils suited for, 423; sources of, 419 ; Stassfurt salts as, 420 ; wood- ashes a source of, 419. Potassium phosphate in concretionary nodules, 328. Potassium sulphate, in Chincha guano, 305 ; in concretionary nodules, 328. Potatoes, effect of farmyard manure on, 520 ; fertilising ingredients re- moved from soil by, 485; grown with covered manure, 289 ; High- land Society's experiments on, 518 ; manurial constituents in, 282 ; man- uring of, 517-522— in Jersey, 529 — influences composition of, 521 ; po- tash removed in, 217 ; Rothamsted experiments on, 519, 571. Precipitated ammonium phosphate in concretionary nodules, 328. Precipitated phosphate, 330, 387. Precipitation, treatment of sewage by, 436. Priestley, discovery of evolution of oxygen by plants, 11 ; on nitrogen in plants, 40. Prussiate of potash, manufacture of, 353. Pugh on sources of plant-nitrogen, 42. Punta de Lobos guano, 302 ; nitrogen in, 303 ; phosphoric acid in, 303. Punta de Patillos, guano deposits at, 327. Pyroxene, potash in, 220. Quartz, evaporation of water from, 99. Queensland, meat-meal guano from, 324. Quercitan, experiments of, with roses, 8. Rape -cake, capable of nitrification, 182 ; manurial constituents in, 282. Rape-seeds, imports of, 153. Raza Island guano, 328 ; phosphoric acid, 330. Rectified guano, 311. Relative trade values of phosphoric acid, 400. 588 INDEX. Resin in guano, 305. Retentive power of soils for water, 70-73. Retrogression, nitrogen lost by, 142. Reverted phosphates, 389-391 ; deter- mination of amount of, 391 ; for- mation of, 387 ; value of, 391. Rhine, nitrates in waters of, 158. Rice-meal, an adulterant of guano, 319 ; manurial constituents of, 282. Rocks, phosphoric acid in, 202. Roots, influence of manures on com- position of, 512 ; manuring of, 510- 522 ; Norfolk experiments on, 513 ; potash removed in, 217. Rotation of crops, bearing of, on nitrification, 195. Rotations, phosphoric acid in, 290 ; potash removed in, 290. Rothamsted, alternate Avheat and bean rotation at, 524 ; ammonia in rain at, 49 ; barley experiments at, 566 ; Broadbalk Field, alteration in composition of, 159— manuring of, 159 — produce of wheat on, 159 ; early experiments at, 33-36 ; ex- periments, 560 - 572 ; experiments with nitrate of soda at, 347 ; ex- periments on nitrogen question at, 115 — mangel - wurzel, 568 — oats, 567 — potatoes at, 519 — value of nitrogen in farmyard manure, 271 ; increase of nitrogen with manures at, 137, 513 ; nitrates in barley- soils of, 158 ; nitrates in cropped soils of, 130, 157 ; nitrates in drain- age of, 189 ; nitrates in wheat-soils of, 131, 157 ; nitrogen as nitrates in soils of, 129, 198 ; nitrogen, de- crease of, in soils, 159 ; nitrogen in pasture at, 126 ; pasture, increase of nitrogen in, 158 ; retrogression of nitrogen at, 142 ; soil, nature of, 561 — nitrogen in, at various depths, 156 ; total amount of nitrogen lost at, 142 ; turnip experiments at, 568 ; unmanured fallow-land loses nitrogen by drainage at, 141 ; wheat experiments at, 500, 562-565. Roy on sources of plant-nitrogen, 42. Rubidia in ash of plants, 55. Ruffle, John, on superphosphate, 388. Rye, manurial constituents in, 282. Rye-grass suited for sewage, 435. Rye-straw, summer, composition of, 238 ; winter, composition of, 238. St Helena, experiments at, with Peruvian guano, 301. Saldanha Bay guano, 328 ; nitrogen in, 329 ; phosphoric acid in, 329. Salinas, 335. Salm - Horstmar, Prince, on water- culture, 54. Salt, 465-473 ; action of, on crops, 472 ; adulterant of guano, 319 ; amount applied, 473 ; antiquity of use of, 465 ; an antiseptic, 468 ; application of, 472 ; clarifies water, 470 ; coagulates clay, 470 ; decom- poses minerals, 470 ; a germicide, 468 ; indirect action of, 468 ; me- chanical action of, 470 ; nature of action of, 465 ; not a necessary plant -food, 466 ; occurrence of, 467 ; prevents rapid fermentation, 471 ; quantity to apply, 473 ; sol- vent action of, 470 ; sources of, 468. Saltpetre, formation of, 164 ; occur- rence of, 215 ; plantations, 163. Sand, absorptive power of, 68 ; an adulterant of guano, 319 ; cal- careous, absorptive power of, 98 ; siliceous, absorptive power of, 98. Sandy soils deficient in lime, 451. Sandwich Islands, guano deposits at, 328. Saragossa Sea, sea-weed in, 339. Saussure, De, on absorption of gases by soil, 81 ; on nitrogen in plants, 41 ; researches on plant-food by, 15. Sawdust an adulterant of guano, 319. Scheibler, Professor, on basic slag, 404. Schloesing and Muntz, on nitrifica- tion, 51, 166 ; experiments on rate of nitrification by, 185 ; on denitri- fication, 179 ; on ferments effecting nitrification, 167 ; on fixation of free nitrogen, 42 ; on ammonia in air, 119, 132 ; on nitrogen absorbed by soil from air, 132 ; on tempera- ture favourable for nitrification, 175. Schoenite, potash in, 220. Schlibler, on absorptive power of soils, 98 ; on retentive power 'of soils, 98. INDEX. 589 Schulze on fixers, 246. Scutch, 427 ; manufacture of, 427 ; ni- trogen in, 427. Sea- weed, nitric acid in, 339. Seals, guano from, 297. Seed, fertilising ingredients lodge in, 491. Seine, nitrates in waters of, 158. Senebier, Jean, on carbon in plants, 12 ; on nitrogen in plants, 41. Sewage, 430-441 ; charcoal a filter for, 437; crops suited for, 434; de- nitrification in, 179 ; dry matter in, 431 ; effects of continued appli- cations of, 433 ; filters for, 437 ; irrigation with, 431-433 ; nitrifica- tion in, 166 ; nitrogen lost in, 149 ; phosphoric acid lost in, 149 ; puri- fied by soils, 435 ; treatment of, by precipitation, 436 ; value of, as a manure, 430. Sewage-sick land, 433. Sewage-sludge, 438-441 ; as a manure, experiments with, 438 ; nitrogen in, 439 ; phosphoric acid in, 439 ; pro- fitable treatment of, 441 ; value of, 439 ; water in, 438. Shale -works, sulphate of ammonia, from, 358. Shark's Bay guano, 309, 328. Sheep, excrements of, 280, 281 ; solid excreta voided by, 280 ; urine voided by, 280. Sheep-dung, alkalies in, 226 ; com- position of, in dry state, 227 ; most valuable excrement, 227 ; nitrogen in, 226 ; phosphoric acid in, 226 ; water in, 226. Sheep-manure, 251 ; amount produced per day, 251 — per year, 252 ; dry matter in, 252 ; mineral matter in, 252 ; nitrogen in, 252. Sheep-urine, alkalies in, 230 ; com- position of, in dry state, 231 ; most valuable urine, 231 ; nitrogen in, 230 ; phosphoric acid in, 230 ; water in, 230. Shoddy, 427; production of, 152, 425 ; nitrogen in, 152, 427. Sicily, bones from, 360. Sidney Island guano, phosphoric acid in, 330. Siemens, Dr, experiments by, with light on plants, 38. Silica, in ash of plants, 55 ; in Chincha guano, 305 ; jelly, 169 ; necessary for plant-growth, 55. Silicates, 102 ; absorbed by cereals, 494. Silicic acid fixed by soils, 58. Simon on humus in soil, 47. Slaked lime, 454. Slugs killed by lime, 461. Smut prevented by lime, 461. Soda, in ash of plants, 54 ; fixed by soils, 58 ; necessary for plant- growth, 55 ; nitrate of, 332 - 351 ; in salinas. 335 : replaces potash, 466. Sodium chloride in Chincha Island guano, 305. Sodium phosphate in concretionary nodules, 328. Sodium sulphate in concretionary nodules, 328. Soil, 65-108 ; absorptive power of, for water, 67, 98 ; acids fixed by, 58- 60 ; action of lime on, 453 ; am- monia absorbed by, 81 ; amount of soluble plant - food in, 100 ; arti- ficial, 54 ; barley, nitrates in, 158 ; bases fixed by, 58-60 ; best suited for nitrification, 192 ; biological properties of, 92-96 ; capacity for heat, 76-78 ; carbonic acid absorbed by, 81 ; chemical composition of, 87 - 92, 101 - 107 ; colour of, 80 ; cropped, nitrates in, 157 ; denitri- fication in, 177 ; evaporation from, 71, 72 ; farmyard manure, action of, on, 272 ; fertilising ingredients in, 87 ; fertility of, 65-108 ; fineness of, 69-70 ; gases in, 100 ; hygroscopic power of, 75-76, 99; improved by humus, 272 ; innueiice of farmyard manure on, 475 ; on nitrification, 180 ; manures increase fertility of, 474 ; nitrates in, amount of, 128- 131 ; nitrifying organisms in, 179 ; distribution of, 179 ; nitrogen ab- sorbed by, 81, 82, 131 ; nitrogen accumulates, 133 ; nitrogen in, amount of, 120-128 ; nitrogen least abundant of manurial ingredients in, 270 ; nitrogen at various depths in, 156 ; oxygen absorbed by, 81 ; phosphoric acid in, 203 — condition of, in, 203 — occurrence of, in, 203 ; 590 INDEX. peat, 123 ; possesses power of fixing ammonia, 57 ; potash in, 215 — con- dition of, in, 216 ; potential fertility of, 549 ; power of, for absorbing gases, 81 ; relation of, to plant- roots, 84 ; retention of plant-food by, 57 ; retentive power of, for water, 70-73 ; sewage purified by, 435 ; shrinkage of, 74 ; variation in absorbing powers of, 82 ; varieties of, 67 ; virgin, 133 ; water in, most favourable amount of, 75 ; water- logged, 179 ; wheat, nitrates in, 157. Soluble phosphate, 386. Sombrero phosphate, 308, 328, 330, 379 ; phosphoric acid in, 330. Somme phosphate, 378. Soot, 428 ; application of, rate of, 429 ; crops suited by, 429 ; nitro- gen in, 428. South America, guano deposits in, 327 ; meat-meal guano from, 324. Starbuck Island guano, 309, 328; phosphoric acid in, 330. Stassfurt salts, 214 ; potash in, 215, 420. Stead and Eibsdale on formation of basic slag, 407. Stoeckhardt, on composition of solid excreta, 226 ; on composition of urine, 229. Storer, Professor, on composition of birds' dung, 331 ; on composition of leaves, 242 ; on fish - guano, 323 ; on nitrogen removed in milk, 147. Straw, composition of, 238 ; imports of, 153 ; as litter, 236, 248 ; mineral matter in, 238, 243 ; nitrogen in, 237, 243 ; variation in composition of, 237. Subsoil, conditions favourable for nitrification in, 181. Suffolk coprolites, 374. Sugar-beet refuse, potash in, 219. Sulphate of alumina, a precipitant of sewage, 437. Sulphate of ammonia, 352-358 ; am- monia in, 355 ; application of, 356 ; composition of, 355; a concentrat- ed nitrogenous manure, 356 ; con- verted into nitrates, 356 ; from gas-works, 353 ; from iron-works, 355 ; from shale-works, 354 ; manure for cereals, 356 ; most easily nitri- fiable manure, 191 ; production of, 151, 358 ; properties of, 355 ; source of nitrogen, 149 ; sources of, 353, 354, 358 ; sulphocyanate of ammonia in, 355. Sulphate of lime a fixer, 246. Sulphate of magnesia, an adulterant of guano, 319 ; as a fixer, 246. Sulphate of potash, application of, 422 — rate of, 423 ; compared with muriate, 421 ; sources of, 218, 420. Sulphuretted hydrogen from farm- yard manure, 258. Sulphuric acid, action of, on bones, 382 — on guano, 311 — on tricalcic phosphate, 398 ; in ash of plants, 54 ; as a fixer, 245, 285 ; necessary for plant -growth, 55; superphos- phate manufactured with, 384, 388. Superphosphate, 382-400; action of, 392-395 — sometimes unfavourable, 395 ; application of, 395 — rate of, 397 ; composition of, 391 ; discovery of, 382 ; hastens early growth, 394 ; high -class, 392 ; low -class, 392 ; manufacture of, 383 - 385 — phos- phates suitable for, 384 ; medium- class, 391 ; production of, 382 ; reversion in, 389, 399, 400 — causes of, 389, 390 ; reverted in soil, 392. Surprise Island guano, 328. Swan Island guano, 328. Swedes, fertilising ingredients remov- ed from soil by, 485 ; manurial con- stituents in, 282 ; manuring of, 514. Swine-dung, alkalies in, 226 ; com- position of, 227 ; nitrogen in, 226 ; phosphoric acid in, 226 ; water in, 226. Swine-urine, alkalies in, 230 ; com- position of, 231 ; nitrogen in, 230 ; phosphoric acid in, 230; water in, 230. Sydney Island guano, 309. Syenite, 106 ; phosphoric acid in, 202, Sylvin, potash in, 220. Symbiosis, 44. Tamarugal, Pampa de, nitrate deposits in, 340. Tarapaca, nitrate deposits in, 340. Temperature necessary for nitrifica- tion, 52, 175. INDEX. 591 Tetracalcic phosphate, 387 ; occur- rence of, 387, 405 ; solubility of, 387. Thaer on application of farmyard manure, 275. Thiocyanates, nitrification in, 182. Thomas - Gilchrist process of steel- smelting, 402. Thomas-slag. See Basic slag. Tillage increases number of plants, 86. Timor Island guano, 309. Tobacco, potash in, 217. Torrefied horn, 426. Torrefied leather, 428. Tortola guano, 309. Trachyte, phosphoric acid in, 202, 211. Transpiration, by elm-tree, 71 ; by oak-tree, 71. Trees, as pumping-engines, 76 ; water transpired by, 71. Tricalcic phosphate, 386, 398. Tubercles on roots of plants, 44. Tull, Jethro, theory of, on plant- growth, 9-11, 69, 109. Turkey, dung produced by, 331. Turnips, fertilising ingredients re- moved from soil by, 485 ; manurial constituents in, 282 ; manuring of, 510, 511, 513 - 517 ; Kothamsted experiments on growth of, 568. Twigs, potash in, 217. Tyrosin, assimilated by plants, 47. Ulmates in farmyard manure, 259. Ulmic acid, in farmyard manure, 258 ; in humus, 47. Ulmin in humus, 47. Uncovered farmyard manure, 263, 289. Unexhausted manures, valuation of, 549-552, 558. Unit value of manurial ingredients, 544. Units for determining commercial value of manures, 554. Urate of ammonium in Chincha Is- land guano, 305. Urea, assimilated by plants, 46 ; in farmyard manure, 257 ; nitrification in, 182. Uric acid, experiments with, 46 ; in Chincha Island guano, 305. Urine, 228 ; amount voided, 291 ; composition of, varies, 228 ; con- tains digested manurial ingredients, 228, 232 ; devoid of phosphoric acid, 205 ; and dung, composition of, 234 ; influence of food on, 229 ; nitrification in, 197 ; nitrogen in, 292 ; potash in, 292 ; voided by cows, 280 ; voided by oxen, 280 ; voided by pigs, 281 ; voided by sheep, 280. Uruguay, meat-meal guano from, 324. Valuation of manures, 539-559. Vegetation, desirable to have soil cov- ered with, 194. Venezuela, guano deposits at, 327. Ville, Georges, on assimilation of ammonia, 50 ; theory of, on source of plant-nitrogen, 41. Vine, potash removed by, 216. Virgin soils, 133. Voelcker, Dr, analysis of apatite, 210 — of farmyard manure, 259 ; on action of superphosphate, 395 ; on fresh and rotted dung, 261, 286 ; on guano, 316 ; on salt as a manure, 473. Voss, Hermann, on manures used, 152. Wagner, Professor, on, application of basic slag, 416 ; assimilation of organic nitrogen, 46 ; experiments with basic slag, 408-413 ; fineness of basic slag, 409 ; manures, 412 ; relative manurial value of nitrogen compounds, 556 ; solubility of basic slag, 408. Wallace, Dr, on sewage purification, 436. Walruses, guano from, 297. Warington, E., on ammonia in rain, 49 ; on appearance of nitrous organ- isms, 168 ; on conditions favourable for nitrification, 181 ; experiments on rate of nitrification, 186 ; on composition of farmyard manure, 260 ; on manufacture of superphos- phate, 383 ; on manurial constitu- ents of foods, 282 ; on nitrification in alkaline solutions, 197 ; on ni- trogen in excrements, 233 ; on ni- trogen in soil, 122 ; on potash in wool, 227 ; researches of, on nitrifica- tion, 35, 52, 166-168, 180, 186. 592 INDEX. Water, absorbed by plants, 73 ; amount of, transpired by plant- leaves, 56 ; an adulterant of guano, 319 ; a carrier of plant-food, 55 ; in cow-dung, 226 — cow-urine, 230 ; from decomposition of farmyard manure, 257 ; in horse-dung, 226 — horse - urine, 230 ; necessary for plant, 67 ; in pig-dung, 226 — pig- urine, 230 — sheep - dung, 226 — sheep - urine, 230 ; transpired by elm-tree, 71 — oak-tree, 71. Water-culture, 54. Water-logged soils, 179. Waterloo, bones from, 360. Way, Thomas, on retention of plant- food by soil, 57, 59 ; on sewage, 437. West Indies, guano from, 298. Whales, guano from, 322. Wheat, fertilising ingredients removed from soil by, 485 ; Flitcham experi- ments on, 500 ; manurial constitu- ents in, 282 ; manuring of, 499-501 ; nitrogen removed in crop of, 145 ; requires nitrogenous manures, 499 ; Rothamsted experiments on, 500, 562-565 ; a source of nitrogen, 153. Wheat-soils, nitrates in, 157. Wheat-straw, analysis of stable man- ure made from, 283 ; composition of, 238 ; manurial constituents in, 282. White clover, growth of, promoted by lime, 451. Wiegmann on ash constituents of plants, 53. Wilfarth on nitrogen in plants, 44. Wilting, 73. Winogradsky, on nitrification, 52, 167, 169, 197 : on organisms in soil, 94. Wolff on, analysis of manure - heap draiiiings, 290 ; composition of fresh and rotten dung, 288 ; assimi- lation of organic nitrogen by plants, 47 ; relative manurial value of manurial compounds, 556 ; urine, 232. Wood-ashes as potash manure, 218, 419. Woodhouse, researches of, on nitrogen in plants, 41. Wool, capable of nitrification, 182 ; potash in, 217. Wool-waste, 427 ; nitrogen in, 427. Wooluey, on organisms in soils, 93, 95 ; on water in soils, 75. Wrightson, Professor, on application of basic slag, 414. Yeast, 94. Yorkshire, bones first used in, 359. Zeolites, potash in, 220. PRINTED BY WILLIAM BLACKWOOD AND SONS. IVERSITY OF CALIFORNIA LIBRARY BERKELEY Return to desk from which borrowed. This book is DUE on the last date stamped below. MAR 5 1948 LD 21-100m-9,'47(A5702sl6)476 380432 UNIVERSITY OF CALIFORNIA LIBRARY