is sa Shes . he wegeatE sire haw od iss Sek Seo ate Bk MS Man ge me se nea r 2 ™ Sheol fants Des ‘ Smenaegetts = ON Sans tite - In Memoriam of CROSBY STUART NOYES — The bridegrcom may forget the bride, Was made his wedded wife yeste’en; The monarch may forget his crown That on his head an hour has been; The mother may forget the child That smiles sae sweetly on her knee} But I'll remember thee, dear Noyes, And a’ that thou hast done for me. William Robertson Smith. Gass DD AS Book ie ey 2 1S63a William R. Smith, U.S. Botanic Garden, WadoilbGTon, D. Q, THE NATURAL LAWS OF HUSBANDRY. BY JUSTUS von LIEBIG. EDITED BY JOHN BLYTH, M.D., PROFESSOR OF CHEMISTRY IN QUEEN’S COLLEGE, CORK. NEW YORK: D. APPLETON AND COMPANY, 448 & 445 BROADWAY. 1863. : oe, hens, EDITOR'S PREFACE. ———0+e—-—— N the following work Baron Liebig has given to the public his mature views on agriculture, after sixteen years of experiments and reflection. The fundamental basis of the work is still the so-called Mineral Theory, which holds that the food of plants is of inorganic nature, and that every one of the elements of food must be present in a soil for the proper growth of a plant. The discovery of the remarkable power of absorption possessed by arable soils has necessarily led to a modification of the views re- garding the mode in which plants take up their food from the soil. As the food of plants cannot exist for any length of time in solution in soils, it is clear that there cannot be a circulation of such solution towards the roots, but the latter must go in search of food. Hence the great impor- tance of studying the ramification of the roots of plants, and the mode of growth of the different classes of plants culti- vated by man. The first chapter is devoted to the consid- eretion of the growth of plants, of the formation of their roots, and of their power of selecting food, and the part played by the mineral matters which are absorbed. If the food of plants is not in solution in the ground, we can conceive that those portions of the soil traversed by the numerous root ramifications will be more or less ex- hausted of food elements, whilst the immediate neighbour- 4 EDITOR’S PREFACE. ing portions are still rich in them. If, therefore, a suc- ceeding crop is to grow equally well on all parts of a field, there must be a thorough mixing of the exhausted and of the unexhausted portions of soil. This is effected by mechan- ical means, by manures, or by certain chemical compounds. Hence the necessity of becoming acquainted with the na- ture and properties of the soil and subsoil. The second chapter is devoted to this subject. The soil consists of arable surface soil and subsoil. In the former is accumulated the nutriment of plants chiefly cultivated for the food of man. This accumulation is affected by the absorptive power of the arable soil for mineral matters, by which soluble salts are removed from solution, and even chemical decomposition of the most stable compounds is brought about, and the bases or acids are retained by the soil in a firm state of combination. It is the presence of food in the soil in this state of phys- ical combination which is alone available for the nutrition of plants. On the abundant or scanty supply of food in | this state depends the fertility or sterility of a soil. In fertile soils food is present also in another form, in which it is not immediately available for the nutrition of plants. It exists as chemical compounds which are not soluble in water, or acids until rendered so by the action of power- ful chemical agents, or to a much smaller extent by the slower process of the decomposing action of the weather. When the food is eliminated by disintegration (by fallow and mechanical operations) from this inert state of chem- ical combination, it passes into that of physical combination with the earthy particles before it is absorbed by the plant. Each kind of soil has its own absorptive power for causing the food to pass into a state of physical combina- tion. When manure is applied, its greater or less disper- sion throughout the soil will depend on this power. In general it is absorbed and fixed by the upper few inches EDITOR’S PREFACE. 5 of the soil, a smaller quantity penetrates to the lower lay- ers, and scarcely any at all to the deep layers and subsoil. Hence when a subsoil is exhausted, manure cannot restore its fertility. From this peculiar property of soils of ar- resting the circulation of solutions of the food of plants, arises the necessity of employing means for the distribu- tion of food, and for the uniform mixture of the different layers of the soil. The manner in which this is effected by mechanical operations, by organic matter, by manures, by certain chemical salts, &c., is pointed out in chapters sec- ond, third, and twelfth. The quantity of food in a state of physical combination in any fertile soil is only limited. Continuous cultivation without replacement of all the mineral matters removed in the crops destroys fertility, either by causing the abso- lute loss of the assimilable food, or by altering the proper relative proportions between the different elements of food, to such an extent that the due growth of all parts of the plant is altered. For the successful growth of a plant in all its parts, every element of food is required. Not one substance has any superior fertilising power over another. The average crop of an unmanured field is always regu- lated by that element of food which is present in minimwmn quantity. The effect of a manure when beneficial is merely to increase the relative proportion of this minimum ele- ment. If the minimum matter was known in each case, its direct application would be suflicient to increase the fertility of the soil. But as in general this point is not ascertained, the application of farm-yard manure is certain in producing a fertilising effect, simply because it is a com- plex mixture containing all the food elements of plants, and consequently whilst supplying other matters which are not immediately wanted, it also furnishes the minimum substance. In chapter fourth, is discussed the question of this altered composition of the ground by cultivation. Ge EDITOR’S PREFACE. In chapter eleventh, the fact that not one of the ele- ments of food by itself possesses any superior nutritive value over the others is further discussed. Nitrogenous food, like all the rest, must be present if a plant is to grow properly, but no excess of this element of food will of itself produce more abundant crops. The analyses of soils show that they abound in nitrogen. Were all other sources of this element wanting, there would still be a continued supply provided for in rain and dew, and in the many pro- cesses of oxidation going on at the surface of the earth. Probably, wherever we have a generation and circulation of carbonic acid, there is also a provision for the forma- tion of nitrogenous compounds. When Nature thus pro- vides for a supply of nitrogen without the aid of man, it is likely that exhaustion of all other elements of food in the soil will take place by cultivation before this occurs with nitrogen. The inefficacy of the mass of nitrogen in the soil cannot be attributed to its existing in two forms, in one only of which it is assimilable. This is proved by ex- periments with soils and with farm-yard manure. When the nitrogen of the soil is not available, some other cause must be sought for than its existence in a state in which it is sparingly assimilable. This cause will be found to be the absence of some other elements of food, which, upon being supplied, will at once render the seemingly inopera- tive nitrogen at once energetic. The diminution of the amount of available food ele- ments in the arable surface soil, by the cultivation and sale of corn, necessitates the restoration of the removed mineral matters. This is effected to a limited extent by foreign manuring agents, but chiefly by the formation of manure by means of fodder plants. By the system of rotation, green crops which draw their nutriment from the subsoil are introduced between the cereals. By the deep pene- trating roots of the former, the mineral matters of the EDITOR’S PREFACE. q subsoil are absorbed, and in the form of manure are trans- ferred to the arable surface soil. But if this process con- tinues, and the corn and cattle are still sold, and no re- placement from without is made of the lost mineral matters, the time will arrive, sooner or later, when the subsoil be- comes exhausted, and the surface soil having no longer a reservoir from which to draw supplies by means of fodder plants, is also unable to bear remunerative crops. This natural progress of the system of farm-yard manuring is fully discussed in chapter fifth. The reader must not sup- pose that the condemnation passed on the system of farm- yard manuring is meant to apply to farm-yard manure itself. The latter is the type of a valuable manure which cannot be replaced in every respect by any artificial mixtures in use. The remarks of the author only apply to the falla- cious hopes entertained of keeping up permanently the fertility of the soil by manure obtained by the system of rotation, whilst we continue still to sell the corn raised by such manure without bringing back to the soil any portion of the mineral matter sold with the corn and cattle. The excrements of man contain all the mineral matter not only of the corn, but also of the cattle sold from the land. Could we restore these excrements to the soil, a per- fect circulation of the conditions of life for plants and ani- mals would be established, and our fields would be retained in a permanent state of fertility. This problem has been solved by the Chinese and Japanese. Chinese rural life, as it is described by travellers, as well as the report of the Japanese system of husbandry given in Appendix G. by Dr. Maron, would scarcely lead us to wish for the improve- ment of agriculture upon the plan of these Orientals! The requirements of modern civilization would not permit the purchase of manuring matter, however valuable, at the cost of all domestic comfort. The sewers must, we fear, still receive what would be offensive to our English senses. 8 EDITOR’S PREFACE, But can the contents of these sewers not be made ayvail- able? ‘The great mass of water which necessarily accom- panies at present the fertilising matters, renders them of comparatively little value when compared with the expense of transport. But how to separate and concentrate these matters from the water is a problem which is at present occupying the earnest attention of scientific and practical men. The solutions hitherto proposed are far from satis- factory. The future of agriculture is, however, intimately connected with the right solution of this great sewage question. In conclusion, I have only to state that the foreign weights and measures have been, when necessary, trans- lated into their equivalents in English, but have been left unaltered when the point was only one of comparison, which could be equally illustrated by the foreign weights. J. BLYTH, M.D. QueEeEn’s CoLLeGE, Cork: March 16, 1863. PREFACE. ———or0e--- - N the sixteen years which have intervened between this work and the sixth edition of my ‘ Chemistry applied to Agriculture and Physiology,’ I have had sufficient op- portunity to become acquainted with all the obstacles which are opposed to the introduction of scientific teach- ing into the domain of practical agriculture. Among the chief of these may be reckoned the complete sep- aration which has always existed between science and practice. There has generally prevailed an idea that a smaller amount of information and intelligence is required for agri- cultural pursuits than for any other occupation ; nay, that the practical skill of the farmer is only likely to be injured ' when he has recourse to science. Whatever requires thought and reflection is regarded as theory, which being the opposite of practice, must, of course, be of little value. The natural result of such opinions is, that when the prac- tical man does attempt to apply scientific teaching, he is almost invariably a sufferer. He seems altogether to for- get that man does not become intuitively acquainted with scientific teaching, which, like the skilful use of any com- plex instrument, must be learned. The truth or error of the notions which guide our prac- is 10 PREFACE. tice cannot, however, be regarded as a matter of indiffer- ence. The more correct ideas which science has given us of the growth of plants, and the part played in the process by the soil, air, mechanical operations, and manure, is not re- garded in the light of an improvement by the practical man, simply because his ignorance does not enable him to appreciate the information. Unable to find out the con- nection between scientific teaching and the phenomena pre- sented in his daily pursuit, he naturally comes to the con- clusion, from his point of view, that there really exists no connection between them. The practical agriculturist is guided by facts observed in his own neighbourhood for a long period ; or, if his views are more comprehensive, he follows certain authorities whose system of husbandry is held to be the best. It never enters into his thoughts to submit this system to proof, for he has no standard of comparison at hand. What Thaer dis- covered to be useful in Méglin was held to be equally so for all Germany, and the facts which Lawes found to be true on a very small piece of land at Rothamsted have be- come axioms for all England. Under the dominion of tradition and of slavish submis- sion to authority, the practical man has lost the faculty of forming a right conception of the facts which daily pass before his eyes, and in the end can no longer distinguish facts from opinions. Hence, when science rejects his ex- planations of any particular facts, 1t is asserted that the facts are themselves denied. If science declares that we have made progress in substituting for deficient farm-yard manure its active ingredients, or that superphosphate of lime is no special manure for turnips nor ammonia for corn, it is imagined that the utility of these substances is contested. Long disputes have arisen about misconceptions of this PREFACE. 11 kind. The practical man does not understand the infer- ences of science, and considers himself bound to defend his own views. The contest is not about scientific principles, which he does not understand, but about the false concep- tions he has formed of them. ‘Until this contest is ended by agriculturists themselves taking an active part in the matter, science can offer no effectual aid. I am doubtful if this time has yet arrived. I built my hopes, however, on the young generation who enter upon practice with a different preparation from their fathers. As for myself, I have reached the age when the elements of the mortal body betray a certain tendency to commence a new circle of action, when we begin to think about putting our house in order, and must defer to no later period what we have still to say. As every investigation in agriculture requires a year before we shall have all the facts before us, I have scarcely any prospect of living to see the results of my teaching. The only thing that remains for me to do, under these cir- cumstances, is to place my views in such a manner be- fore the public, that there can be no possibility of mis- conception on the part of those who will give them- selves the trouble of becoming thoroughly acquainted with them. Many have reproached me with unjustly condemning modern agriculture as a system of exhaustion. From the communications addressed to me by many agriculturists as to their system of husbandry, I must exempt them from such an accusation. There are, however, but few among the general body who really know the true condition of their soil. Ihave never yet met with an agriculturist who kept a ledger, as is done as a matter of course in other industrial pursuits, in which the debtor and creditor account of every acre of land is entered. 12 PREFACE. The opinions of practical men seem to be inherited like some inveterate disease. Each regards agriculture from his own narrow point of view, and forms his con- clusions of the proceedings of others from what he does himself. JUSTUS von LIEBIG. Mounicn: March, 1863. Cee. NS. CHAPTER I. THE PLANT. Chemical and cosmic conditions of the life of plants—Conditions for the germina- tion of the seed ; moisture and oxygen, their action—Influence of the seed in the formation of the organs of absorption, and the production of varieties ; influence of climate and soil in producing varieties—Importance of a knowl- edge of the developement of roots , radication of different plants—Comparison of the process of vegetation in annual, biennial and perennial plants—Growth of the asparagus, as an example of a perennial plant ; storing of reserved food in its underground organs; use of this store—Meadow and woody plants— Growth of biennial plants ; turnips: Anderson’s experiments—Growth of an- nual plants ; summer plants: tobacco; winter wheat, its developement like biennial plants; oats; Arendt’s experiments ; Knopp’s experiments with maize in flower—The protoplastem (matter for forming cells); conditions for its formation: Boussingault’s experiments ; organic processes in plants, di- rected to the formation of the protoplastem—Absorption of food by plants not an osmotic process ,; marine-plants; duck-weed; land-plants; Hale’s experi- ments on absorption by the roots and evaporation from the leaves—Power of the root to exclude certain substances from absorption not absolute ; Forch- hammer, Knopp—Comportment of the roots of land and water plants to solu- tions of salts ; De Saussure, Schlossberger ; comportment of land-plants to so- Jutions of salts in the soil—Use of those mineral matters which are constant in different species of plants; iron, magnesia, iodine, and chlorine compounds— Absorption of matters by plants from the surrounding medium ; influence of the consumption of them by the plant; part played by the roots in their ab- sorption, . rs : : : is - : - PAGE 19 CHAPTER II. THE SOIL. The soil contains the food of plants—Soil and subsoil ; conversion of the latter into the former—Power of the sdil to withdraw the food of plants from solution in 14 CONTENTS. pure and in carbonic acid water ; similar action of charcoal ; process of surface attraction ; chemical decomposition often accompanies this attraction of the food of plants in the soil; general resemblance of the soil in its action to ani- mal charcoal—All arable soils possess the power of absorption, but in different degrees—Mode of the distribution of the food of plants in the soil ; chemically and physically fixed condition of the food—Only the physically fixed are ayail- able to plants, being made soluble by the roots—Power of the soil to nourish plants ; on what dependent—Comportment of an exhausted soil in fallow— Means for making the chemically fixed elements of food available to plants— Action of air, weather, decaying organic matters and chemical means—Distri- bution of phosphoric and silicic acids ; influence of organic matters—Action of lime—Process of the absorption of food from the soil by the extremities of the roots—Mechanical preparation of the soil; its influence on the growth of plants ; chemical means for preparing the soil—Rotation of crops ; its influ- ence on the quality of the soil ; action of draining—Plants do not receive their food from a solution circulating in the soil; examination of drain, lysimeter, spring and river water : bog water, food of plants contained in it ; Briickenauer spring water contains volatile fatty acids ; amount of food of plants in natural waters dependent on the nature of the soil through which they flow—Mnud and bog earth as manure , explanation of their action—Manner in which ‘plants take up their food from the soil ; experiments on the growth of plants in solu- tions containing their food ; similar experiments with soil containing the food in a physically fixed state—Intimate connection of natural laws—Average crop ; necessary quantity of assimilable food in the soil for the production of such ; importance of the extent of surface of the food in the soil ; the root sur- face—Quantity of food for a given surface of roots necessary for a wheat or rye crop—Analysis of the soil of a field—Difference between fertility and pro- ductive power of a field—Mode of estimating relative extent of root surfaces —Conversion of rye into wheat soil; quantity of food necessary for the pur- pose ; the plan impracticable—Immobility in the soil of the food of plants ; ex- perience in agriculture—Real and ideal maximum production—Conversion in practice of the chemically fixed food into an available form—Effect of amanure depends upon the property of the soil—Improper relative proportions of the different elements of food in the soil: effect of this upon the different culti- vated plants : means for restoring the proper relative proportions, . ahs CHAPTER III. ACTION OF SOIL ON FOOD OF PLANTS IN MANURE. Manures : meaning of the term; their action as food of plants and means for im- proving the soil—Effect on soils with different powers of absorption—Each soil possesses a definite power of absorption ; the distribution of the food of plants in the soil is inversely to the power of absorption ; means of counteracting the absorptive power—Absorption number, notion of ; comparison of in different fields ; its importance in husbandry—Soil saturated with food of plants ; its comportment with water—Quantity of food to saturate a soil—A saturated soil not required for the growth of plants—Manuring may be compared to the application of earth saturated with food—Importance of the uniform distribu- tion of food in manures; fresh and rotted stall manure ; compost ; importance of powdered turf for the preparation of manure—Quantity of food in un- CONTENTS. 15 manured fields and their powers of production ; increase of the latter appar- ently out of proportion to the manure added; experiments on this point: explanation ; composition of the soil and its absorptive power compared with the requirements of the plants to be cultivated on it; surface and subsoil plants, the tillage and manuring respectively required by each — Clover sickness; experiments of Gilbert and Lawes, their conclusions; value of them, A é F : M : ; : : opie 134 CHAPTER IV. FARM-YARD MANURE. The fertility of a soil depends upon the sum of ayailable food, the continuance of the fertility upon the total amount of all food in it—Chemical and agricultural exhaustion of the soil—Exhaustion of the soi! by cultivation, laws regulating its progression ; effect of the transformation in the soil of the chemically fixed into physically fixed elements of food ; effect on the progress of exhaustion by partial restoration of the withdrawn food of plants—Progress of the exhaustion by different cultivated plants—Cultivation of cereals, consequence of removing the grain and leaving the straw in the soil; intervening clover and potato crops ; effect of leaving in the ground the whole or a portion of these crops ; division of soils ; productive power of wheat fields increased by accumulating in them the materials derived from clover and potato fields ; cultivation of fodder plants ; their food partly derived from the subsoil ; addition of these in- creases the productive power of the surface soil—Natural connection between the cultivation of cereals and fodder plants, the influence on the fertility of land—Exhaustion of the soil removed by the restoration of the withdrawn mineral constituents ; the excrement of men and animals contains these ; their restoration depends upon the agriculturist, . : As F os 164 CHAPTER V. THE SYSTEM OF FARM-YARD MANURING. Questions to be solved—Experiments of Renning, their significance—Produce of unmanured fields—In fluence of preceding crops, of the situation, and climatic conditions, on the produce—Each field possesses its own power of production —Large crops, their dependence and continuation—Closeness of the food of plants, what is meant thereby—The closeness of the particles of food in the soil is in proportion to the produce—Produce of corn and straw influenced by the relations of the assimilated food and by the conditions of growth ; action of food supplied in manures—Potatoes, oats, and clover crops of the Saxon fields ; conclusions drawn from them as to the condition of the fields—Produce of these fields from farm-yard manure ; the increase of produce cannot be cal- culated from the amount of manure used—Restoration of the power of produc- tion of exhausted fields by the increase of the necessary elements of food pres- ent in the soil in minimum amount; advantageous use of farm-yard manure ~ in this respect ; explanation of the result—Action of manure as compared with quantity used : experiments—Rational system of cultivation—Depth to which the food of plants penetrates is dependent on the power of absorption of the 16 CONTENTS. soil ; the Saxon ficlds considered in this respect ; the power of absorption con- sidered in manuring—Change produced in the composition of the soil by the system of farm-yard manuring; the different stages of this system, the final result—Examples of these stages in the Saxon experimental fields—Cause of the growth of weeds ; remedies—The history of husbandry, what is taught by it—Present condition of European husbandry—Present production of the land compared with the earlier ; conclusions—Continuation of production regulated by a natural law—Law of restoration ; defective practice of it—Agriculture in the time of Charlemagne—Agriculture in the Palatinate—Corn fields in the valleys of the Nile and Ganges ; nature provides in them for the restoration of food of plants—Practical agriculture and the law of restoration—The sta- tistical returns of average crops afford an explanation of the condition of corn fields, ‘ = 5 : A : : . 184 CHAPTER VI. GUANO. Composition compared with that of seeds; small amount of potash in it; its ac- tion—Guano and bone-earth, similarity of their active ingredients—Guano acts quicker than bone-earth, or a mixture of the latter and ammoniacal salts , reason of this—Oxalic acid in Peruvian guano ; the phosphoric acid rendered soluble by its means—Peruvian guano, its effect on the cultivation of corn— Moist guano loses ammonia—Moistening guano with water acidulated with sulphuric acid; effect—Inactivity of guano in dry and very wet weather— Rapidity of its action asa manure,on what dependent--Comparison of the effect of farm-yard manure and guano; effect produced by mixing the two— Guano on a field rich in ammonia—Increased produce by guano, what it pre- supposes— Exhaustion of the soil by continuous use of guano—Mixture of guano with gypsum and with sulphuric acid—The Saxon agricultural experi- ments; theirresults, . ‘ : 2 2 : : 245 CHAPTER VII. POUDRETTE—HUMAN EXCREMENTS. Poudrette, nature of ; small amount of the food of plants in it—Human excrement, its value—Construction of the privies in the barracks at Rastadt—Calculation of the amount of corn produced by the excrement collected ; importance to the neighbourhood—Its effect not impaired by deodorising with sulphate of iron— The excrement of the inhabitants of towns as manure—Its importance, . 258 CHAPTER VIII. EARTHY PHOSPHATES, High agricultural value of phosphates—Phosphates of commerce ; selection of the kind to be used dependent on the object in view, and on the nature of the soil— The rapidity and the duration of the effect of the neutral and of the soluble phosphate (superphosphate) of lime—The Saxon manuring experiments, 262 CONTENTS. 17 CHAPTER IX. GROUND RAPE-CAKE, Nature and composition of ; the diffusibility of its constituents in the soil is com- paratively great—Its importance as a manuring agent is small—The Saxon agricultural experiments with rape-cake—The inferences from them, . 267 CHAPTER X. WOOD-ASH. The amount of the food of plants in it—Box-wood ash gives only the half of its potash readily to water—Convenience in mixing wood-ash with earth before applying it—Lixiviated ash, its value—Proper mode of applying ashes as a manure, . = ° 3 2 es F c - 2712 CHAPTER XI. AMMONIA AND NITRIC ACID. Source of the nitrogen of plants—Amount of ammonia and nitric acid in rain and dew : Bineau, Boussingault, Knop—Quantity of ammonia in the air—Quantity of nitrogenous food brought to the soil yearly by rain and dew ; more present in the soil than is removed by the crops—The general reason for decrease of productive power in soils—Classification of manures according to the amount of nitrogen ; assimilable and sparingly assimilable nitrogen ; the nitrogen theory ; only ammonia according to this theory is wanting; resemblance to the humus theory—Manuring experiments with compounds of ammonia by Schattenmann, by Lawes and Gilbert, by the Agricultural Union of Munich, and by Kuhlmann—The efficacy of a manure is not in proportion to its amount of nitrogen : experiments—Large amount of nitrogen in soils ; the experiments of Schmid and Pierre; the arable surface soil contains most nitrogen—Form of the ammonia in the soil ; Mayer’s experiments—Comportment of soil and farm-yard manure with the alkalies—The ineffective nitrogen of the soil made effective by the supply of ash-constituents that are wanting—Progress in ag- riculture impossible if dependent on a supply of ammoniacal compounds ; re- sults of Lawes’ experiment with salts of ammonia—The artificial supply of ammoniacal manures contrasted with the crops produced and the increase of population—Increase of nitrogenous food by natural means; formation of nitrite of ammonia by oxidation in the air according to Schonbein—Supply of food in excess necessary to produce corn-crops ; reasons—How the necessary excess of nitrogenous food for corn may be obtained from natural sources—The supply of nitrogen in farm-yard manure in the Saxon experiments correspond- ed to the crop of clover-hay—Loss of nitrogen in lime soils by oxidation ; utility of a supply of nitrogen to such soils—Effect of nitrogenous food on the aspect of young plants ; on potatoes—Empirical and rational systems of agri- culture, ° ; - 3 “ , 5 : : . 274 18 CONTENTS. CHAPTER XII. COMMON SALT, NITRATE OF SODA, SALTS OF AMMONIA, GYPSUM, LIME. Effect of these substances as elements of food; their effect on the condition of the soil—Kuhlmann’s experiments with common salt, nitrate of soda, and salts of ammonia; esperiments with the same substances in Bavaria ; conclusions : these matters are elements of food ; they are chemical means for preparing the soil; they cause the distribution of the food in the soil in the form proper for the growth of plants—Experiments by Pincus with gypsum and sulphate of magnesia on clover; decrease of flowers and increase of stem and leaves of clover by sulphates ; the crop is not in proportion to the quantity of sulphates used—Effect of gypsum not yet explained ; indication in the comportment of clover soils with solution of gypsum; such solution disperses potash and magnesia in the soil—Manures, their effect not explained by the composition of plants produced by them—Composition of the ash of clover manured with dif- ferent substances—Effect of lime ; experiments of Kuhlmann and Trager ; comportment of lime-water with soils, i . - : x 316 APPENDICES. Beech leaves und asparagus, their ash-constituents at different periods of growth— The amylum of the palm—Motion of sap in plants—Drain, lysimeter, river, and bog water, their constituents—Fontinalis antipyretica from two different waters, ash-constituents— Vegetation of maize in solutions of its food —Experiments on the growth of beans in pure and prepared turf, results—Japanese agriculture— The cultivated soil of the torrid zone, its exhaustibility, its manure—Analysis of clover by Pincus—Clover sickness, its causes, - : “ : 332 THE NATURAL LAWS OF HUSBANDRY. CHAPTER I. THE PLANT. Chemical and cosmic conditions of the life of plants—Conditions for the germina- tion of the seed ; moisture and oxygen, their action—Influence of the seed in the formation of the organs of absorption, and the production of varieties ; influence of climate and soil in producing varieties—Importance of a knowl- edge of the developement of roots ; radication of different plants—Comparison of the process of vegetation in annual, biennial and perennial plants—Growth of the asparagus, as an example of a perennial plant ; storing of reserved food in its underground organs ; use of this store—Meadow and woody plants Growth of biennial plants ; turnips: Anderson’s experiments~Growth of an- nual plants ; summer plants: tobacco; winter wheat, its developement like biennial plants; oats; Arendt’s experiments ; Knopp’s experiments with maize in fiower—The protoplastem (matter for forming cells) ; conditions for its formation; Boussingault’s experiments ; organic processes in plants, di- rected to the formation of the protoplastem—Absorption of food by plants not an osmotic process ; marine-plants ; duck-weed ; land-plarts; Hale’s experi- ments on absorption by the roots and evaporation from the leaves—Power of the root to exclude certain substances from absorption not absolute; Forch- hammer, Knopp—Comportment of the roots of land and water plants to solu- tions of salts ; De Saussure, Schlossberger ; comportment of Jand-plants to so- lutions of salts in the soil—Use of those mineral matters which are constant in different species of plants; iron, magnesia, iodine, and chlorine compounds— Absorption of matters by plants from the surrounding medium ; influence of the consumption of them by the plant; part played by the roots in their ab- sorption. O obtain a clear view of the theory and practice of Agriculture, we must keep in mind the most general chemical conditions of the life of plants. ° Plants contain combustible and incombustible con- stituents. Of the latter, which compose the ash left by all parts of a plant on combustion, the most essential elements are—phosphoric acid, sulphuric acid, silicic acid, potash, soda, lime, magnesia, iron, and chloride of sodium. 20 THE PLANT. The combustible constituents are derived from car- bonic acid, ammonia, sulphuric acid, and water. By the vital process of vegetation, the body of the plant is formed from these materials, which are there- fore called the food of plants. All the materials con- stituting the food of our cultivated plants belong to the mineral kingdom. The gaseous elements are absorbed by the leaves, the jiwed elements by the roots; the for- mer, however, being often constituents of the soil also, may reach the plant by the roots, as well as by the leaves. The gaseous elements form component parts of the atmosphere, and are, from their nature, in continual motion. ‘The fixed elements are, in the case of land- plants, constituents of the soil, and cannot of themselves leave the spot in which they are found. The cosmic conditions of vegetable life are heat and sunlight. By the cooperation of the cosmic and the chemical conditions, the perfect plant is developed from the germ or seed. The seed contains, within its own substance, the elements required to form the organs which are in- tended to take up food from the air and the soil. These elements are nitrogenous substances, similar in compo- sition to the casein of milk or the albumen of the blood; _ and also starch, fat, gum, or sugar, with a certain quan- tity of earthy phosphates and alkaline salts. The fari- naceous body, or so-called albumen of the seed of corn, as also the constituents of the cotyledons in lezuminous lants, become the roots and leaves of the nascent plant. f corn-seeds are set to germinate in water, and allowed to grow upon a glass plate furnished with fine perfora- tions, through which the roots may reach the water, the grain will go on growing for several weeks without receiving any incombustible element of food or any constituent of the soil. After three or four weeks the apex of the first leaf is seen to turn yellow; and upon examining the seed, nothing but an empty skin is found, for the starch has disappeared together with the cellu- lose (Mitscherlich). However, the plant does not die away, but new leaves are produced, often also a feeble GERMINATION AND GROWTH OF THE SEED. 21 stalk; the constituents of the first-formed, but now withering, leaves being applied to the formation of fresh shoots. Under favourable circumstances, seeds with very large and vigorous cotyledons abounding in nutritive matter (e. g. beans) may, by vegetation in water alone, be got to flower—nay, even actually to produce small seeds; this developement, however, is mostly unat- tended by a perceptible increase of substance, but de- pends solely upon a mere transposition of the elements of the seed. Nutrition is a process by which food is assimilated 5 a plant grows when its mass is augmented, and its mass is increased by absorbing materials from without, which are, from their nature, suited to become constituent ele- ments of the body of the plant, and to sustain those functions upon which their assimilation depends. The bud on a potato-tuber stands in the same rela- tion to the constituents of the tuber as the germ in a corn-seed does to the farinaceous matter of the albumen. While the bud is developed in the formation of the young plant, the amylum and the nitrogenous and min- eral constituents of the sap of the tuber are employed to form the young branches and leaves. A potato, which lay wrapt up in thick paper, in a box, in the Chemical Laboratory at Giessen—in a place absolutely dark, dry, and warm, where the atmosphere was seldom changed—was found to have produced, from each bud, a simple white shoot many feet long, showing no traces of leaves, but covered with hundreds of minute potatoes, which exhibited the same internal structure as tubers grown in a field; the cells consisted of cellulose, and were filled with minute starch granules. It is certain that the starch of the mother tuber, to have moved away from its position, must have become soluble ; but it is equally clear that in the developement of the shoots a cause was operative within them, which (in the absence of all outward causes whereon growth depends) reconyerted the dissolved constituents of the mother tuber into cellulose and starch granules. 29, THE PLANT. The conditions required for the germination of a seed are—moisture, a certain degree of heat, and access of air; where one of these conditions is excluded, the seed will not germinate. By the influence of the moist- ure which the seed absorbs, and which causes it to swell, a chemical action takes place in it; one of the nitrogenous constituents acts upon the others, and upon the amylum, so that by a transposition of the element- ary particles, the constituents are rendered soluble ; the gluten is converted into vegetable albumen ; the amy- lum and oil into sugar. If the oxygen of the air is ex- cluded, the changes either do not take place or they proceed in a different way. The seeds of land-plants, when submersed under water, or placed in.a soil cov- ered with stagnant water, which excludes the air, will not put forth their plumules. This is the cause es many seeds, lying deep in the ground or in bogs, will remain for many years without germinating, although the conditions of moisture and temperature be favour- able. It is often found that earth taken up from bogs, or brought up by the plough from the deep subsoil, and exposed to the atmosphere, becomes covered with vege- tation, arising from. seeds which, for their develope- ment, required free access of air. Lowness of tempera- ture tends to annul or retard the inflnence of the air upon the process of germination; whilst increase of temperature, with a proper supply of moisture, acceler- ates the chemical changes in the seed. No seed germi- nates below 32° Fahrenheit ; each germinates at a defi- nite temperature, and therefore in fixed seasons of the year. The seeds of Vicia faba, Phascolus vulgaris, and the poppy, lose the power of germinating when dried at 95° Fahrenheit; while barley, maize, lentil, hemp, and lettuce seed retain the power at that heat ; but wheat, rye, vetch, and cabbage seed will germinate even at 158° Fahrenheit. ; During germination, oxygen is taken up from the air around the seed, and an equal volume of carbonic acid is evolved. If seeds are set to germinate in glasses, with a slip PROCESS OF GERMINATION. 23 of litmus paper fastened on the inside, the paper is red- dened, often after a very short time, owing to the dis- engagement of acetic acid: the most abundant and rapid evolution of free acid was found to take place in the germination of cruciferous plants, cabbage, and rape-seed (Becquerel, Edwards). Certain it is that the fluid contents of the cells of the roots, as well as the sap of most plants, have an acid reaction, from the presence of a non-volatile acid; the sap of the young spring shoots of the vine yields, upon evaporation, an abun- dant crystallization of bitartrate of potash. By the experiments of Decandolle and Macaire, which have not yet been controverted, it was shown that vigorous plants of Chondrilla muralis and Phaseo- lus vulgaris which had been taken from the ground, with their roots, and were allowed to vegetate in water, imparted to the water, after a week’s time, a yellowish tint, a smell like that of opium, and a harsh taste: whereas when the root was cut off at the stalk and both were placed in water, no such substances were given off as those which the entire plant had yielded. Lettuces and other plants, when taken out of the gound, and, with their roots previously washed clean, are allowed to vegetate in blue litmus tincture, will continue to grow in the liquid, apparently at the ex- pense of the constituents of the lower leaves, which wither away. After three or four days the litmus tinc- ture assumes a red colour, which, however, disappears again upon boiling the fluid: this would seem to indi- cate that the roots had given off carbonic acid. If the plants are left longer in the litmus tincture, the latter suffers decomposition, and becomes neutral and colour- less, while the colouring matter, separating in flakes, gathers round the fibres of the roots. The developement of a plant depends upon its first radication, and the choice of proper seeds is therefore of the highest importance for the future plant. A crop of the same wheat, reaped in the same year, and from the same field, will exhibit differences in the size of the grains, some being larger, others smaller; and 94 THE PLANT. among both kinds, some when broken up will present a mealy, others a horny appearance, the one being more, the others less completely developed. The cause is this—that the stalks in the same field do not all shoot into ear and flower at the saine time, and that some of them produce seeds much more maturely than others: hence the seeds of the one are far more developed, even in unfavourable weather, than the seeds of the others. A mixture of seeds unequal in their developement, or differing in the quantities of amylum, gluten, and inor- ganic matters which they severally contain, will pro- duce a crop of plants as unequal in their developement as the original seeds from which they sprung. The strength and number of the roots and leaves formed in the process of germination are (as regards the non-nitrogenous constituents) in direct proportion to the amount of amylum in the original seed. A seed poor in amylum will, indeed, germinate in the same fashion as another seed abounding in it; but by the time the former has succeeded, by the absorption of food from without, in producing roots and leaves as strong and numerous, the plant grown from the more amylaceous seed is again just as much more advanced in growth: its food-absorbing surface was larger from the begin- ning, and the growth of the young plant is in like pro- portion. Poor and sickly seeds will produce stunted plants, which again will yield seeds bearing in a great measure the same character. The horticulturist knows the natural relation which the condition of the seed bears to the production of a plant, which is to possess all or only some properties of the species: just as the cattle-breeder, who, with a view to propagation and increase of stock, selects only the healthiest and best-formed animals for his purpose; the gardener is aware that the flat and shining seeds in the pod of a stock gilly-flower will give tall plants with single flowers, while the shrivelled seeds will furnish low plants with double flowers throughout. The influence of soil and climate gives rise to differ- IMPORTANCE OF GOOD SEEDS. 25 ent varieties of plants, which, like races, are possessed of certain peculiarities, and are propagated by means of seed, as long as the conditions remain the same. Planted in another soil, or in a different climate, the new variety will lose again some one or other of its dis- tinguishing characteristics. The influence exerted by the condition of the soil in producing varieties of plants is observed most. fre- quently with seeds that pass undigested through the intestinal canal of animals which have eaten them, and then receive a different manuring according to the various nature of the excrements of divers animals with which they are returned to the soil: an instance is afforded by the Byrsonima verbascifolia (v. Martius). In the selection of seeds for planting it is always important to take into account the soil and climate from which they have been derived. In England seed- wheat from a poor soil is considered particularly well suited to a rich soil; rape-seed grown in colder regions or situations is sure to give a good crop in warmer localities. Clover secd and oats from mountainous dis- tricts are preferred to the same seeds from plains. Wheat from Odessa and from South Hungary is es- teemed in colder regions also. The planters on the Upper Rhine import their hemp-seed from Bologna and Ferrara. In like manner many German flax-growers, who wish to produce tall plants of uniform size, attach par- ticular value to linseed from Courland and Livonia, where the soil and the nature of the climate, especially the short hot summer, bring the flowering and fruit time near together ; so that the flowers, being simulta- neously and uniformly fructified, produce ripe and per- fect seeds. Everyone knows how much the weather, during the flowering period, influences the formation of seed. If, after the flowering has commenced, cold weather or rain sets in, retarding the full developement of the in- florescence, the flowers fertilised at a later period pro- duce no seeds, as the nutriment needed by them is 9 26 THE PLANT. applied by the flowers first fertilised for their own de- velopement. It is a fact, that many plants will not repay the trouble of cultivation, if the climatic condi- tions are not sufficiently favourable to effect the thorough ripening of all the flowers, but serve only to ripen part of them. With oats it often happens that in warm moist weather side-branches will spring from the axils of the leaves, when the principal culm is already shooting into ear; whence it happens, that at the end of the period of vegetation the plant is found to bear both ripe and unripe seeds. The condition of the soil, as to porosity or compact- ness, influences the radication of plants. The fine fila- ments of the root, which are often coated with cork-like matter, are lengthened by the formation of new cells at their extremities, and they are obliged to exert a certain ey to force their way through the particles of earth. : The root-fibrils will always extend in that direction in which they encounter the least resistance ; and this lengthening necessarily presupposes that the pressure wherewith the new-formed cells push aside the particles of earth, must be somewhat greater than the cohesion of the particles. The strength with which the root- fibres force their way through the soil, is not equally great in all plants. Those plants which have roots formed of very fine fibres are but imperfectly developed in stiff, heavy soils, wherein other plants with thicker and stiffer root-fibres will grow luxuriantly. The very resistance which the heavy soil opposes to the spreading of the roots of such plants tends to strengthen their fibres. Of the cereals, wheat, with a comparatively feeble ramification of roots in the upper layers of the soil, still forms the strongest roots, which often penetrate several feet down into the subsoil ; for a certain degree of com- pactness in the surface soil is favourable to the devel- opement of its roots. There are instances on record, where parts of a wheat-field had been trampled down RADICATION OF PLANTS. 27 in the winter by horses (by no means an uncommon occurrence in the foxhunting districts of England), so far as to destroy every trace of a wheat-plant, and yet next year’s crop turned out much more abundant on those very spots than in any other part of the field. It is evident that, to outlive an attack of this kind, a plant must have its principal roots spreading in the deeper layers of the soil. In the developement of its roots and the power of penetrating the deeper layers of the soil, the oat-plant stands next to wheat, and will flourish in a somewhat stiff soil; but as in the superficial layers also the roots of oats throw out a number of fine feed- ers, In a lateral direction, it is necessary that the top- soil should be rather light and open. A light, open loam, even if of no great depth, is particularly suited for barley, which forms a net-work of fine comparatively short root-fibres. Peas require a loose soil, with little cohesion about it, which will favour the spreading of the soft root-fibres in the deeper layers also; whereas the strong woody roots of the horse-bean will ramify in all directions, even in a heavy and more compact soil. Clover, grass-seeds, and small-sized seeds in general, put forth at first feeble roots of small extent, and require so much the greater care in preparing the soil, in order to ensure their healthy growth. The pressure of a layer of earth half to one inch thick suttices to prevent the developement of the seed sown in the ground. Such seeds require only just as much earth to cover them as will retain the needful moisture for germination. It is, therefore, found advantageous to sow clover together with corn of some kind; for as the corn is earlier and quicker in growth, its leaves shade the young clover plant, and protect it from the too intense action of the sun’s rays; thus affording more time for the extension and developement of the roots. The nature of the roots* of rapes, turnips, and tuberous plants, clearly points out the part of the soil from which they draw their chief supply of food. Potatoes are formed in the * Whenever the term ‘root’ is used in this work, the underground organs of plants are meant. 28 THE PLANT. topmost layer of the soil; whereas the roots of beets and turnips, sending their ramifications deep into the subsoil, will succeed best in a loose soil of great depth. Still, they will also grow well in soil naturally heavy and compact, which has been properly prepared for their reception. Among turnips, the Swedish variety is distinguished by the numerous fibres which the root- stock sends into the ground; and mangelwurzel, with its strong and rather woody root-fibres, is still better suited than Swedes for a heavy clay soil. On the length of roots but few observations have been made. In some cases it has been found that lucerne will grow roots thirty feet, rape above five feet, clover above six feet, lupine above seven feet in length. A proper knowledge of the radication of plants is the groundwork of agriculture; all the operations which the farmer applies to his land must be adapted to the nature and conditions of the roots of the plants which he wishes to cultivate. On the root he should bestow his whole care; upon that which grows from it he can no longer exert any influence; therefore, to secure a favourable result to his labours, he should pre- pare the ground in a proper manner for the develope- ment and action of the roots. The root is not merely the organ through which the growing plant takes up the incombustible elements of food required for its increase, but it may, in another not less important function, be compared to the flywheel in an engine, which gives regularity and uniformity to the working. It is in the root that the material is stored up to supply the growing plant with the needful elements for con- ducting the processes of life, according to the require- ments made upon it by the action of light and heat. All plants which give landscapes their peculiar character, and clothe the plains and mountain slopes with perennial green, have an underground develope- ment, according to the geological or physical condition of the soil, admirably adapted to their perennial exist- ence and propagation. Whilst annuals are propagated and multiplied by RADICATION OF DIFFERENT PLANTS. 29 seeds alone, and have always a true root easily known by its simplicity of structure, by the absence of buds, and by the comparatively short range of its fibres, the turf and meadow plants are propagated by shoots and runners of a peculiar nature, and in many of them propagation is independent of the formation of seed. As the strawberry, which will in a very short time cover extensive tracts of ground, sends forth from the stock above the root-bulb shoots in the shape of run- ners, which creeping along the ground, and producing here and there buds and roots, grow up as independent plants, so the perennial weeds, among which are here included the meadow and pasture plants, spread in a similar manner by corresponding underground organs. The creeping roots of the couch-grass (Z7riticum repens), the sea lyme-grass (/ymus arenarius), the trefoil (772- folium pratense), the common toad-flax (Linaria vul- garis), propagate their plants by suckers in all direc- tions from the mother-plant. The smooth-stalked meadow-grass (Poa pratensis) is propagated by a mother-stock, consisting of true roots, rooted runners, and creeping suckers; rye grass (Lolium) puts forth root-suckers in a stiff soil, and prostrate stolons in loose ound. Cat’s-tail grass (PAlewm) is found sometimes with bulbous, sometimes with fibrous many-headed roots, having a tendency to creep and to form mother- stocks. Timothy-grass grows stalk in the first year ; in the second, it forms sometimes bulbous, sometimes fibrous many-headed mother-stocks, which send forth creepers in all directions. In the same way, meadow- grass spreads partly by budding suckers, partly by stolons. } On comparing the vital processes in annual, bien- nial, and perennial plants, we find that the organic work in perennials is principally directed to the formation of the root. The seed of asparagus sown during autumn, in a fertile soil, will produce next year, from spring to the end of July, a plant about a foot high, the stem, twigs, and leaves of which from that time forward show no 30 THE PLANT. further increase. The tobacco plant, which is an an- nual, would from the same period to the end of August have produced a stem several feet high, covered with numerous broad leaves; and the turnip a broad crown of foliage. But the cessation in the growth of the asparagus plant is only apparent; for from the moment that the external organs of nutrition are developed, the root in- creases in extent and substance in far greater propor- tion to the over-ground organs than is the case with the tobacco plant. The food which the leaves have ab- sorbed from the air and the roots from the soil, having first been transformed into organisable matter, descends to the roots, in which there is gradually collected a sufficient store to enable the latter to furnish in the fol- lowing year from themselves and without the least sup-. ply of food from the atmosphere the material required for the production of a new perfect plant, with a stem half as high again and a much greater number of twigs and leaves. The organic labour of this new plant, during the second year, results in the generation again of products which are deposited in the root, and, propor- tionately to the greater extent of the organs of nutrition, are stored up in much greater quantity than the roots had originally supplied. The same process is repeated in the third and fourth years ; in the fifth and sixth years the store deposited in the roots has become sufficiently rich to produce in spring, when the weather is warm, three, four, and more stems as thick as a finger, with numerous branches covered with leaves. A comparative examination of the green asparagus plant, and of its withering stems in autumn, seems to indicate that at the end of the period of vegetation the remainder of the dissolved or soluble substances fit for future use, then still remaining in the overground organs, descend to the root. The green parts of the plant are comparatively rich in nitrogen, alkalis, and phosphates, whilst in the withered stems these sub- stances are found in small quantities only. The seeds PERENNIAL PLANTS. 31 alone retain comparatively large proportions of phos- phated earth and alkalis, being nothing else than the excess of those substances which the roots do not require for the next year. The underground organs of perennial plants are the economic gatherers of all the vital conditions necessary for certain functions. If the soil will allow, they always collect more than they give out; they never spend all they receive. These plants form their flowers and seeds when the roots have collected a certain excess of phos- phates, which may be given up without endangering the existence of the plant. An abundant supply of nourishment, by means of manuring, will accelerate the developement of the plant in one or another direction. Manuring a sward with ashes will draw from it clover plants ; if acid phosphate of lime is employed, French rye-grass will spring up in thickly serried blades. In all perennial plants, the underground organs are usually very much greater in mass and extent than those of annual plants. Whilst the roots of the latter die every year, the former preserve theirs in a state of readiness to absorb food at every favourable oppor- tunity. The circle from which a perennial plant draws its food enlarges from year to year; if one part of its roots finds little nourishment in a given spot, other parts draw their supply from other spots richer in the food required. Only a very small portion of the plants of a thickly covered meadow will produce stems; the far greater part will develope only tufts of leaves; and many will for years be confined to the production of underground suckers. For perennial grass and meadow plants, the produc- tion of underground suckers is of the highest impor- tance, since by them the plant is furnished with nutri- ment at a time when a scarcity of supply would endanger the life of annual plants. A good soil, and all other conditions of vegetable life, will of course exert the same favourable influence 382 THE PLANT. upon perennial as on annual plants; but the develope- ment of the former is not so much dependent upon acci- dental and passing states of the weather, as is the case with the latter. Unfavourable conditions will, indeed, check the growth of a perennial plant, but only for a time, until a favourable change ensues, when the plant will resume growing; whereas an annual plant, under the same circumstances, reaches the limits of its exist- ence and dies. The permanence of vegetation on our meadows, and the certainty of their produce under varying conditions of soil and weather, must be attributed to the great number of plants which are able to continue tor a shorter or longer period at a low stage of developement. While the one species of plants is developed above ground, producing flowers and seeds, a second and third species gather below the surface the conditions for a similar future growth. The one vegetation seems to disappear, to make room for another and a third, until for itself too the conditions for a perfect developement recur. The woody plants grow and are developed in a man- ner quite similar to the asparagus plant, with this dif ference, however, that they do not lose their stem when the period of their vegetation comes to an end. An oak-sapling, 14 foot high, was. found to have a root above 3 feet long. The stem and the root serve jointly as a magazine for storing up the organisable matter to be used next year in restoring all the external organs of nutrition. When the stems of lime trees, alders, or willows have been cut down, they will, if lying in shady moist places, shoot out afresh, often after the lapse of years, and produce numerous twigs a foot long cr more, covered with leaves. The pauses which occur in the seed-bearing of forest trees are similar to those which are observed in most perennial plants, which, when growing on a poor soil, will also take several years to collect the conditions necessary for the production of fruit (Sendtner, Ratze- burg). MINERAL MATTERS IN FALLEN LEAVES. 33 The loss of inorganic food-constituents, which the foliaceous trees suffer by the fall of the leaves, is trifling. When the leaves have attained their full formation, the cells of the bark receive a copious supply of amylum, which substance completely disappears from the cells in the boss of the leaf-stalk (H. Mohl). Even long be- fore the fall of the leaves, their sap is considerably diminished, while the bark of the branches is, just at that time, often actually overflowing with sap (H. Mont). In accordance with this fact, the analysis of the ash of the leaves shows that the amount of alkali and phosphoric acid in them decreases immediately before the fall; the fallen leaves contain such trifling quantities of these constituents, in comparison to their mass, that it is difficult to account for the injurious consequences arising from the raking up and removal of the fallen leaves in woods. (See Appendix A.) A similar reflux of the assimilative products appears to take place in the grasses; when from the intense heat of summer the leaves begin to decay, chemical analysis reveals in the yellow leaves scarcely any traces of nitrogen, phosphates, and alkalis; and, indeed, ani- mals instinctively turn from all kinds of fallen leaves, and refuse to feed on them. In annuals and biennials the organic action results in the production of fruit and seed, after which the activity of the root comes to an end ; in perennials, the production of seed is rather an accidental condition of their permanent existence. The biennial can bestow more time than the annual in gathering the material necessary for the production of seed and fruit, which closes the period of its exist- ence; but the time in which this takes place depends upon the state of the weather and the nature of the soil. The annual is uniformly developed in all its parts ; the food daily taken up is expended in increasing the overground and underground organs, which meanwhile take up a larger amount of food in proportion to the increase of their absorbent surface. With the growth of the plant, the conditions of increase inherent in the Q* 34 THE PLANT. plant itself become enlarged, and exert their influence in proportion as the external conditions are favourable. The developement of the biennial plants cultivated for their roots has three distinct periods; in the first period the leaves principally are formed ; in the second, the roots, in which are stored the substances needed to produce the flower and fruit during the third period. A series of experiments, made by Anderson, upon turnips, affords a clear view of the several directions in which the energy of a biennial plant tends at different periods of its growth. (‘Journal of Agriculture and Transactions of the Highland Society,’ No. 68, 69, new series, 5.) : These experiments were made to ascertain the total produce of vegetable substances obtained from turnips on one acre of ground. The turnips were gathered at four different stages of growth ; the first on July 7, the second, on August 11, the third, on September 1, and the fourth, on October 5. The following table shows the weight of leaves and roots in pounds, taken up at the end of the respective stages, and calculated upon one acre of ground. Weight of leaves. Weight of roots. I. Harvest after 32 days . .. . 219 pounds 7°2 pounds I. e Gili ues be an Looms 2,762 e Iil. re i(k a, SeatMap rman phan! ssh 710) 0) tac iG 14,400 ag IV. es LQ2 ws ae) REE 2 OBie, Shes 36,792 - The relative quantities of leaves and roots show that in the first half of the time of vegetation, sixty-seven days, the organic labour in the turnip plant is princi- pally directed to the production and developement of the external organs. From the 7th July to the 11th August, a period of thirty-five days, we find the increase to be 12,574 pounds in the leaves, and 2,755 pounds in the roots, which gives a daily increase of Leaves. Roots. 359 pounds. | 78 pounds. In this stage, accordingly, the production of leaves prevailed over that of roots to this extent, that out of GROWTH OF TURNIPS. 35 eleven parts of food absorbed by the plants, nine parts went to the leaves and only two parts to the roots. We find a very different proportion in the third stage ; for during twenty days the weight of the leaves has increased by 6,507 pounds, that of the roots by 11,638 pounds, which gives a daily increase of Leaves. Roots. 325 pounds. | 582 pounds. During this third stage the plants take up daily some- what more than double the amount of food taken up on any given day of the second stage, and this increase must stand in proportion to the daily enlargement of the surface of the roots and leaves; but the food absorbed is distributed in the plant in a very different manner. Of twenty-five parts by weight of food ab- sorbed and assimilated, nine parts only remain in the leaves, the other sixteen parts serve to increase the mass of roots. In exactly the same ratio as the leaves approached the limits of their developement, they lost the power of applying to their further growth the food which they had absorbed, and which now transformed into organ- isable matter was deposited in the roots. The same nutritive particles which went to form leaves, so long as the mass of foliage kept on increasing, now became constituent portions of the root. This migration of the constituents of the leaves and transformation into constituents of the root appear to be most clearly shown in the fourth stage. The total weight of leaves, which on the Ist September still amounted to 19,200 pounds, had by the 5th October, or within the space of thirty-five days, decreased by 7,992 pounds, that is 228 pounds a day; in other words, out of every thirty-four leaves ten had withered, while the roots had increased by 22,392 pounds, or 640 pounds a day—a daily increase much more considerable than during the third stage. It is evident that with the advance of autumn, with the lower temperature and diminished action of sun- 36 THE PLANT. light, the organic energy of the leaves decreased, and more than a third of the organisable matter collected in them descended to the roots, to be stored up for future use. If we compare the quantities of nitrogen, phosphoric acid, potash, common salt, and sulphuric acid, absorbed during the last ninety days by the turnips growing on one acre of ground, we find from Anderson’s experi- ments that the daily amount was as follows :— Absorbed by the entire plant in a day. Total increase. Second stage. Third stage. Fourth stage. Pounds. Tnvsubstance 5 pin cre eee 437 907 417 INitrOmeniemt eretcieisteieysee. 115 0-695 1:21 Phosphoric acid......... 0°924 1:10 1°25 Ota eecror spehey aia tereistlenekers 1:41 4:04 3:07 Sul MUriCiACIG 1.15 «aeons 1:12 1°57 1:52 ‘Srl Haguncaes Seer ne Cire Mee cach cas 0°84 1:98 alia ba Daily increase of roots in the fourth stage of growth. P Hospherie Potash. Sulphuge Salt. Supplied by the soil .. 1°25 3°07 1°52 1:10 Ws “¢ leaves 0°41 1°56 0°51 0°53 1°66 4°63 2°08 1:63 These figures show that the quantity of phosphoric acid taken up daily by the turnip plants growing on one acre of ground increases from the commencement of the second to the end of the fourth stage of growth, that is in ninety days from 0°924 to 1:25 pound a-day, which reckoned from one day to another makes the trifling difference of 00037 pound a-day. Anderson suspects that his estimate of the nitrogen in the leaves during the third stage was not quite cor- rect, and that it fell below the actual amount. If we PHOSPHORIC ACID AND POTASH IN GROWING TURNIPS. 37 add together the quantities of nitrogen absorbed in the last two stages, fifty-five days, we find a daily average of 1-02 pound of nitrogen, which is very nearly the same as in the preceding stage of growth. The quantity of potash increased from the 11th Au- gust till the Ist September, in a somewhat higher ratio than the amount of vegetable substance produced. From the 1st September till the 5th October the in- crease of the roots was nearly double what it had been in the preceding stage, but this is explained by the migration of the potash compounds from the leaves to the roots. It is evident that the increase of potash has a certain connection with the formation of sugar and the other non-nitrogenous constituents of the roots, but no definite proportion can be established between them. The absorption of sulphuric acid increased uniformly in the three last stages; that of salt was a little greater in the third than in the second and fourth stages. Without wishing to indicate the exact part per- formed in the process of vegetation by these various mineral substances, as also by lime, magnesia, and iron, we remark that, except in the case of potash, the absorp- tion of them was evidently uniform from day to day, yet showing every day a trifling increase corresponding to the daily increase of the food-absorbent surface up to the fourth stage of growth. The smallest increase was seen in phosphoric acid and nitrogen, both equally necessary for the formative processes going on in the turnip plant; and it is mani- fest that they must have served to bring into operation some more powerful agency, whose effects are revealed in the production and augmentation of the non-nitro- genous constituents. If we take the quantity of mineral substances ab- sorbed as the measure of their importance for the organic operations going forward in the plant, we must assign to sulphuric acid and common salt an influence equal to that of any of the others. Looking at the qualities of mineral constituents sev- erally taken up by the different parts of the plant in the 38 THE PLANT. various stages of growth, we observe the greatest dis- parities. In the second stage, a quantity of potash, amounting in the aggregate to 49°29 pounds, was ab- sorbed in 35 days; and of this, the roots were found to contain 8:02 pounds, equal to one-sixth—the leaves 41:27 pounds, equal to five-sixths. The same propor- tion—namely, about five to one—was found to exist between the weight of the leaves produced, and that of the roots. In the third stage, the weight of the roots produced exceeded that of the leaves; and of the 80 pounds of potash absorbed by the plants, 34 pounds, or more than one-third, remained in the roots. The same was found to be the case with phosphoric acid, and the other mineral constituents; that is to say, they were found distributed in varying proportions, corresponding to the growth and increase of the mass of the overground and underground organs of the turnip plants, which, in the various stages, are likewise not uniform. If we regard the mere increase of the leaves and roots in mineral substances, without reference to the total amount of them absorbed by the entire plant, it appears to be most irregular, and to proceed by ‘ fits and starts.’ The plant receives every day nearly the same quantity of phosphoric acid, nitrogen, salt, and sulphuric acid, which are distributed in the several parts of the plant, leaves, or roots, where they are re- quired for use. The chief difference observable is in the increase of potash, which in the third stage is out of all proportion greater than that of the other mineral constituents. It is highly probable that from the raw material— i.e. the carbonic acid, water, ammonia, phosphoric acid, sulphurie acid, with the cooperation of the alkalis, earths, &c.—the chemical process engenders in the plant simply a nitrogenous and sulphureous substance, belonging to the albumen group, and only one non- nitrogenous substance, belonging to the group of hydro- earbons. The former retains its character during the period of vegetation; while the non-nitrogenous NITROGENOUS SUBSTANCES IN TURNIPS. : 39 substance is converted into a tasteless, gum-like body, or into cellulose, or sugar—becoming a constituent of the leaves or of the roots, according as the organic energy preponderates in the overground or under- ground organs. If there is a relation between the phosphoric acid and the production of the nitrogenous constituents, the soil must contain, in its parts, definite proportions of both substances; and for the cultivation of turnips, the upper layers must necessarily be much richer in phos- phates than the lower. For in the first half of the period for vegetation, the branching of the roots is much less extensive than at a later period, and the root is in contact with a much smaller bulk of earth than after- wards; hence, if the root is to draw from this smaller bulk the same amount of nourishment as from the larger, the former must contain more of it, in propor- tion as the absorbent root-surface is smaller. The ash of all plants in whose organism large quan- tities of amylum, gum, and sugar are produced, is dis- tinguished from the ash of other plants by the prepon- derance of potash ; now, if the potash in the sap of the turnip plant formed a necessary agent in the formation of sugar and the other non-nitrogenous constituents, the quantity of that mineral matter absorbed in the third and fourth stages of growth is easily explained—because the formation of the non-nitrogenous constituents of the root was more active in these than in the former stages. That the production of the combustible constituents —the conversion of the carbonic acid and ammonia into non-nitrogenous and azotised substances—stands in a definite relation of dependence to the incombustible matter found in the ash, is an opinion which no longer requires special proof to support it. But the depend- ence is mutual. To say that the reason why the azotised or non-nitrogenous products are formed in large proportion is because the plant has taken up more phosphoric acid or potash, is just as correct as to assert that the plant takes up more phosphoric acid or potash because the other conditions required for the production 40 THE PLANT. of azotised or non-nitrogenous substances are found com- bined in its organism. To enable a plant to attain its maximum of growth, the soil must at all times yield, in an available form, the whole quantity of each of its constituents; and, on the other hand, the cosmic conditions—heat, moisture, and sunlight—must cooperate to transmute the absorbed substances into the organs of the plant. If the sub- stances that have passed from the soil into the plant cannot be turned to account, from the want of this co- operation, no fresh substances are absorbed; in un- favourable weather, the plant does not grow. No more does it grow, even though the outward conditions are favourable, if the soil contains no proper nourishment. In the second half of the period of developement, the roots of the turnip plant, having penetrated through the arable surface deep into the subsoil, absorb more potash than in the preceding stage. If we suppose that the absorbing spongioles of the root reach a stratum of soil poorer in potash than the upper layer, or not sufficiently rich in that material to yield a daily supply commensu- rate with the requirements of the plant, at first, indeed, the plant may appear to grow luxuriantly; yet the prospect of an abundant crop will be small, if the sup- ply of the raw material is constantly decreasing, instead of enlarging with the increased size of the organs. In the economy of the turnip, the root receives dur- ing the last month of vegetation nearly one-half of all the movable constituents of the leaves; and this consti- tutes, after the completion of its first year’s period of vegetation, a store of organisable matter for future use. During the spring of the following year the root begins to shoot, putting forth a slight leafy top, and a flower-stalk several feet high; with the developement and maturing of the seed, the plant dies. The chief bulk of the food stored up in the root is applied, in the second year or third period, in quite a different direc- tion; though, beyond the mere supply of water, the soil seems to take no part in this new act of life. All monocarpous plants—that is, all plants which -SUMMER PLANTS. 41 flower and produce seed but once—present, like the turnip plant, distinct periods of life, as regards the direction of organic activity in them. In the first, the plant produces the organisable matter required in the succeeding period ; in the latter, that which is required for the final functions of life. But these materials are not always stored up in the root, as is the case in the turnip; in the sago-palm they fill the stem; in the aloe (Agave) they collect in the thick fleshy leaves. The production of seed is, with many of these plants, much less dependent upon any fixed period of time, than upon the store of organisable matter collected in them in the time preceding. Favourable climatic con- ditions or propitious weather will hasten, while unfa- vourable cosmic conditions will retard, its production. The so-called summer-plants are monocarps which are able to gather in a few months the conditions re- quired for the production of seed. The oat-plant grows to maturity and bears ripe seed in ninety days; the turnip-rape only in the second year of its existence ; the sago-palm in sixteen to eighteen years; the aloe in iy to forty, often not till 100 years. (See Appen- dix B.) In many perennial plants, the outer part dies every year, while the root lives on. In the monocarpous lants, the root dies with the production of the seed. n these the production of seed is an indispensable, in the perennial plants more of an accidental, condition of continued existence. The economy of plants is regulated by laws which manifest their operation in the peculiar faculty of cer- tain organs to store up food for future use; so that all the external causes which seem to hinder their develope- ment, actually contribute in the end to insure their continued existence, 7. e. their propagation. The contents of the roots in perennial grasses and asparagus, may, in the different periods of the life of these plants, be compared to the farinaceous body or albumen in the grain of cereals; with this difference, however, that the skin does not become empty as is the 42 THE PLANT. case with the latter on germination, but is always re- filled and keeps increasing in size. The perennial plant always receives more than it expends; whereas the monocarpous plant spends its whole store in forming fruit. The fact that the roots of the turnip, in autumn, grow at the cost of the constituents of the leaves, readily explains the influence which the removal of leaves will exercise upon the crop at different stages of growth. The removal of a few leaves in August makes no great difference to the root, while the removal of leaves at the end of September causes the greatest dam- age to the root-crop. Metzler, who made very accurate comparative experiments upon this point, found that an early cutting of the leaves reduced the turnip crop by 7 per cent. only, while a late, or a second cutting, re- duced it by as much as 36 per cent. If, in the first year, instead of the turnips being re- moved from the field at harvest, the tops were merely cut off and the roots were left and ploughed in, the field would, on the whole, sustain a loss of soil constituents ; still the roots in the soil would retain the greater por- tion of them. A very different relation would arise, if at the end of the second year of vegetation the turnip tops were cut off, and the stem were removed together with the seed. For, at the end of the first year, the root would still retain the far larger portion of the azotised and also of the incombustible constituents, which would thus be left in the soil; but in the second year these materials would be carried into the over- ground part of the plant, and there be used for the production of the stem and the seed; hence, the re- moval of the latter would of course make the soil poorer, even though the roots were now left in it. Before the shooting and flowering, the root was rich in soil con- stituents ; after the production of seed, its store of them is exhausted. If the plant is cut off and the root left in the ground, before flowering, the soil retains the far greater portion of the nutritive matter which it had given to the plant; on the contrary, after flowering and THE TOBACCO PLANT. 43 the production of seed, the root retains only a small residue of these constituents, and the soil is correspond- ingly exhausted of them. As it is with the turnip, so is it with culmiferous plants. If they are cut off before flowering, a consider- able portion of the nutritive substances stored up in them remains in the root, which the soil of course loses, ifthe overground plant is removed after the ripening of the seed. The experience derived from the cultivation of tobacco gives a clear view of the processes in the devel- opement of an annual leafy plant. In the tobacco plant the overground and the under- ground parts grow with perfect equality ; the root gains in extent, in the same proportion as the stem lengthens and the leaves increase in number and size. There is no appearance of sudden changes in the direction of or- ganic activity, no shooting, but the phases of life in the plant follow in steady continuous progression. Even while the top of the stem bears ripe seeds, and the lower leaves have withered, the side shoots of the plant are often still putting forth flower-buds, the seeds of which will ripen at a much later period. The tobacco plant is remarkable for producing in its organism two nitrogenous compounds, of which the one, nicotine, contains neither sulphur nor oxygen; while the other, albumen, is identical with the sulphureous and oxygenised constituents of the cereals and other alimentary plants. The commercial value of tobacco leaves is in an in- verse ratio to the amount of albumen which they con- tain, that sort of tobacco being most highly esteemed by smokers which contains the least albumen; for the latter ingredient, in the burning of the dry leaves, emits on carbonisation a most disagreeable smell of burnt horn shavings. The leaves rich in albumen contain, as a rule, more nicotine than those which are poor in albu- men; they give the strongest kinds of tobacco, many of which cannot be smoked unmixed. The tobacco leaves cultivated in France and Ger- 44 THE PLANT. many are manufactured either into smoking tobacco or into snuff. For the fabrication of snuff, leaves which are rich in albumen and nicotine are preferred to those containing a smaller amount of those ingredients. The leaves intended for snuff are, either when still entire or after being ground to powder, subjected to a kind of fermentation, which takes place pretty speedily, with evolution of heat, if they are kept moistened with water. From the putrefaction of the albumen there arises a considerable quantity of ammonia, which is a principal ingredient of German snuff, and is also occa- sionally increased by the manufacturers, by moistening with carbonate of ammonia or caustic ammonia, to suit the taste of consumers. The leaves intended for smoking are also improved in quality by a slight process of fermentation, which serves to diminish the quantity of albumen in them. These preliminary remarks will help to explain the different methods of cultivating tobacco. The size of the leaf in length and breadth, its light or dark colour, the height of the stem, the amount of produce, and the greater or less proportion of albumen and nicotine, all depend very essentially upon the manuring of the plant. The plant succeeds best, in Europe, on light, sandy, humose, loamy, or marly soils. The strongest kinds, richest in albumen and nicotine, are grown on virgin land, and on heavy clay soil manured with bone-dust, shavings and clippings of horns and claws, blood, bristles, human excrements, oilcake, and liquid manure. In Havannah, tobacco is grown on virgin soil, on cleared forest lands, which are often burnt first, as is done in Virginia. The best qualities (the poorest in albumen) are yielded in the third year of cultiva- tion. From this it would appear, that animal manure abounding in nitrogen (ammonia) favours the produc- tion of nitrogenous constituents; but the soil, on the other hand, which is poor in ammonia, and probably CULTIVATION OF TOBACCO. 45 contains the nitrogen in the form of nitric acid, pro- duces leaves containing much less albumen and nico- tine. The effect of removing the tobacco plant from the rearing beds to the field is very striking. Transplanted into the new soil, the young tobacco plant proceeds in the first instance, like seed in the process of germina- tion, to produce roots; the leaves already formed wither on transplantation, and their movable constitu- ents, together with the store of organisable matter col- lected in the roots, are applied to the production of numerous branch radicles. A second transplantation has a still more favourable effect upon the underground organs of absorption. As the direction of the organic operations in sum- mer-plants is entirely turned to the formation of seed, and as this consumes the materials which give activity to the roots and leaves, the tobacco planter breaks out, when the plant has put forth six to ten leaves, the heart of the middle stem, on which the flowers and seed cap- sules grow. Stripped thus of the crown, the whole vigour of the plant is now directed to the buds between the leaves and stem, and these put forth side-shoots which are treated like the principal stem, that is to say, they are either broken away, or simply cracked by twisting. Thus the leaves retain the organisable matter subsequently produced, and increase in mass and size, while the amount of water in them diminishes. By the middle of September, the leaves lose their green colour and are spotted with yellow blotches, imparting a mar- bled look; they become parchment-like, feel dry to the touch, get flaccid, with the ends drooping to the ground, and, when arrived at full maturity, are viscous, clammy, and readily come off the stem. This treatment is variously modified, according to the several varieties of tobacco, and the different coun- tries in which it is grown. The so-called common Eng- lish tobacco, which is particularly rich in nicotine, 1s often allowed by planters to run to seed, in order to 46 THE PLANT. effect a separation of the nitrogenous constituents, the albumen forsaking the leaves and lodging in the seed. In the young shoots, buds, and generally in all parts in which the production of cells is most actively carried on, the sulphureous and nitrogenous constitu- ents (albumen) accumulate, and thus the younger leaves are always richer in these substances than the older. The leaves nearest the ground (sand-leaves) give a milder, the upper leaves a stronger tobacco. In those varieties which are not particularly rich in nicotine and albumen, the sand-leaves are of much less value than the upper leaves. A mild tobacco always means a tobacco poor in narcotic constituents. The course pursued by the European tobacco plant- er, who lays a superabundance of animal manure upon ~ his fields, is the exact reverse of that adopted by the American planter, who cultivates his plants upon a field that has never been manured. The one seeks to reduce or dilute the narcotic, sulphureous, and nitro- genous constituents of the leaves; the other to concen- trate them. Accordingly, the American planter breaks the lower leaves in their full vigour, when the plant has attained to half-erowth; the European planter at- taches the greatest value to the fully-developed upper leaves. As the tobacco plant, like all annuals, only yields up its whole store of organisable matter at the ripening of the seeds, the stem does not die after the loss of the leaves; but the materials still. remaining in it and in the roots cause the stem to send forth fresh shoots, and frequently even leaves, though small-sized ones. In the West Indies, Maryland, and Virginia, before the gather- ing of the leaves, the stems are notched immediately above the ground, so that they lean over without being severed from the root. In warm weather, the water in the leaves evaporates, and a motion of the sap ensues from the stems and roots towards the leaves, in which the sap is thus concentrated as the plant withers. The tobacco planters on the Rhine have found that a supe- MODE OF GROWTH OF WINTER-WHEAT. AT rior tobacco, poorer in albumen and _ nicotine, is pro- duced if, instead of breaking the leaves off in the field, the plant with the leaves on it is cut down just above the ground, and hung up to dry with the top down- wards. The stem will, under these circumstances, con- tinue to vegetate for a time, sending forth small shoots which gradually turn in an upward direction and put forth flower-buds. In these flower-buds the sulphureous and nitrogenous constituents are collected from the leaves, which lose these ingredients in the same propor- tion, and are thereby improved in quality. Of the plants cultivated for the sake of their seed, wheat holds the chief’ place. Winter-wheat is in its developement extremely like a biennial plant. In the biennial turnip we see that with the first leaves a corresponding number of root- fibres are produced ; and that after the formation of the leaf-top, the root begins to expand greatly in size and extent, immediately after which the flower and seed- stalk shoots forth. Very soon after winter-wheat is sown, the young plant puts forth the first leaves, which in the course of winter and the early months of spring increase to a tuft; to all appearance the vegetation of the plant seems to cease for weeks and months. When warm weather comes, the plant puts forth a soft stem, several feet high, furnished with leaves, and bearing at the top an ear set with flower-buds in which, after flowering, the seeds are formed. As the seed is developed, the leaves from the bottom upwards turn yellow, and die with the stem as the seed ripens. It cannot be doubted that while the growth of the plant appears to have ceased before the time of shoot- ing, the over and under ground organs are in constant activity ; food is incessantly absorbed, which, however, is but partially employed to increase the mass of leaves, but not to form the stem. There is, therefore, every reason to believe that the far larger portion of the or- ganisable matter produced in the leaves during this . 48 THE PLANT. period goes to the roots, and that this store is after- wards applied to the formation of the stalk. On the approach of warmer weather all the operations of life in cereal plants are quickened, and the quantity of food daily absorbed and worked up increases with the extent of the absorbing and elaborating organs. In spring many of the older leaves and of the root-fibres die in the portions of the soil exhausted by them; the root- tops send forth new buds, and with every new bud new rootlets, until the stalk-joints have. attained a certain length. From this time forward to the end of the pe- riod of vegetation, both the food absorbed by the plant, and the movable part of the materials formed in the leaves, stem, and root, go to form flowers and seeds. The observations of Schubart show that the roots of cereal plants, in the first period of vegetation, increase much more than the leaves. Schubart found that rye plants, which, six weeks after sowing, presented leaves 5 inches long, had meanwhile produced roots 2 feet in length. The vigour with which cereal plants send forth their stalks and side-shoots corresponds to the developement of the root. Schubart found as many as eleven side- shoots in rye plants, with roots 3 to 4 feet long; in others, where the roots measured 13 to 24 feet, he fond only one or two; and in some, where the roots were but 14 foot, no side-shoots at all. The action of a low temperature in autumn and win- ter, which puts a certain limit to.the activity of the outer organs, without altogether suppressing it, is essen- tial to the vigorous thriving of winter corn. It is a most favourable condition for future developement, if the temperature of the air is below that of the soil, so as to retard for several months the developement of the outer plant. Hence a very mild autumn or winter operates un- favourably upon the future crop, as the higher temper- ature encourages the developement of the principal stalk before the proper time, which shoots up thin, and ’ DIFFERENT STAGES OF GROWTH OF THE OAT-PLANT. 49 consumes the food which should have served to form buds and new roots, or to increase the store of organisa- ble matter in the roots. Thus stunted in its develope- ment, the root supplies less food to the plant in spring, as it takes up and gives out less in proportion to its smaller absorbent surface and more limited supply stored up in it ; and it retains the same feeble character in the succeeding periods of vegetation. The agricul- turist endeavours to meet the difficulty by grazing down or cutting these feeble plants; the formation of buds and roots hereupon begins anew, and if the external conditions are favourable, and the plant has time to fill the root with a fresh store of organisable matter, the normal conditions of growth are, in the agricultural sense, restored: Summer corn maintains, in the several periods of its developement, the same character as win- ter corn; only these periods are of much shorter dura- tion. Ahrend’s study of the oat-plant in its several stages of growth is instructive in this respect. He determined the increase in combustible and incombustible constitu- ents during the following periods: from germination to the beginning of shooting (end of the first stage, 18th June); from this time to shortly before the end of shooting (second stage, 80th June); immediately after flowering (third stage, 10th July); the commencement of ripening (fourth stage, 21st July) ; finally, to perfect maturity (fifth stage, 31st July). On the 18th June the plants were on an average 31 centimeters high (14 inch), the three lower leaves were nearly expanded, the two upper leaves were still folded up. Of the stalk- joints the three lower alone had an appreciable length (1, 2, and 3 centimeters), the three upper had but a ru- dimentary existence. Twelve days after (on the 30th June) the plant had attained double the height (63 cen- timeters); and ten days after this again, on the 10th July, after flowering, it had reached 84 centimeters. 1,000 plants respectively produce in gramimes :— 50 THE PLANT. Examined on —— Se > 18th June. | 30th June. | 10th July. | 21st July. | 8ist July I. stage. | 11. stage. | III. stage. | LV. stage. | V. stage. Constituents In 49 days, | In 12 days, | In 10 days, |} In 11 days, |In 11 days, before stalks full | flowering. | formation of} ripening. shooting. grown. seed. Grammes. | Grammes. | Grammes. | Grammes. | Grammes. Combustible... | 419 873 475 435 128 Incombustible. . 36°6 33°48 30°38 20°34 | 718 In one day. Combustible... 8°551 1275 47:50 89°45 12°8 Proportion . . 1 8:5 55 4°6 15, Incombustible. . 0°747 2-79 3°03 1:849 0°318 Proportion. . it 3°73 4-06 2°47 0:96 In looking at these figures we must remember that Ahrens could only determine what the overground part of the plant had received from the root, not, as Ander- son in the case of the turnip, what the whole plant had derived from the soil. The great disparity in the in- erease of combustible and incombustible substances evidently depends rather upon the unequal distribution of the materials absorbed, than wpon any disparity in the quantity derived from the soil. The whole period of developement comprised about 92 days, and we see that for more than the first half (49 days) the plant re- mains stationary at an apparently low stage of growth, the foliage alone being developed, and that not fully. In the next 12 days, from the 18th to the 30th June, the plant gains double the weight of incombustible con- stituents, and grows twice as high as in the 49 days preceding ; and within this short time, the overground parts absorb nearly the same quantity of incombustible constituents as they had previously taken up. In fact, the plant takes up 83 times the quantity of combustible matter, and 3# times more of ash constituents on one day of shooting, than upon one of the 49 previous days. We cannot suppose it at all likely that the external conditions of nutrition, the supply of food by the atmos- phere and from the ground, or the absorptive power of GROWTH OF THE OAT-PLANT. 51 the plant, should aiter and increase, by fits and starts, from one day to another. We are led rather to assume that the oat-plant is subject in its developement to the same law which we have observed in the case of the turnip, and that therefore, in the second half of the first stage of growth, the activity of the leaves was princi- pally directed to the production of organisable matter, to be stored up in the root in the shooting stage, and then supplied to the overground organs of the plant. The heightened assimilative or working power of the plant, consequent upon the higher temperature and brighter sunshine of summer, was attended by a pro- portionate increase in the supply of food; but the rela- tive proportion of the soil constituents remained much the same as in.the turnip plant. If we compare the respective quantities of potash, phosphoric acidyand nitrogen, which the overground parts of the oat-plant have received from the root and the soil, in the several stages of growth, i. e. to the commencement of flowering, thence to incipient ripen- ing, and finally to maturity, we find that 1,000 plants have received :—" In the I. and II. | Inthe I. and II. | In the V. stage, stages, 61 days. stages, 21 days. 10 days. Grammes. Grammes. Grammes. Bomse! wee. ey 34°11 13°2 00 Nitrogen .... 2... 25°0 24°9 54 Phosphoric acid... . 5-99 6°94 1:33 These proportions show that the daily increase of potash in the overground parts of the oat-plant was pretty nearly the same in the 21 days of the 3rd and 4th stages, as in the 61 days of the Ist and 2nd._ But for the phosphoric acid and the nitrogen a very difier- ent result is obtained; we find that the quantity of these two ingredients which passed into the stalk, the ear, and the leaves, amounted in the 21 days of the 3rd and 4th stages to as much as in the 61 days of the 1st and 2nd stages: in other words, the overground organs 52 ; THE PLANT. of the plant gained of these two ingredients, in the flowering and ripening time, three times as much each day as in the preceding period. Of the turnip-plant we know with tolerable certain- ty, that from the time when it sends forth a flower- stalk, the constituents of the stalk, as also those of the flowers and the seeds, are for the most part stored up in the root, and are supplied therefrom. It is highly probable that the corn-plant is similarly cireumstanced, and that from the flowering to the end of life it is fed, though not exclusively, by the root, which from the flowering time gives out what it had stored up in the preceding period. Kwop observed that Indian corn plants in flower, taken out of the ground and placed with their roots simply in water, produced ears with ripe seeds ; which proves that the materials serving for the production of seed were already present in the plant at the time of flowering. It is an established fact that a corn-plant, if cut off before flowering, relapses into that lower stage of vege- tation of a perennial plant, in which the root receives more organisable matter than it parts with.* The proportions of incombustible constituents and of nitrogen severally required by oats and turnips, are remarkably different both in the aggregate and during the various stages of growth. The facts established by Anderson for the turnip, and by Ahrends for the oat, are indeed not sufficiently numerous to warrant us in deducing any positive law of growth for those two plants: still a few inferences may easily be drawn from them. ‘The quantities of phosphoric acid and nitrogen in the turnip are, at the end of the first year of vegeta- tion, nearly in the proportion of 1:1); in oats, on the contrary, of 1:4. The oat-plant requires to the same quantity of phosphoric acid four times as much nitrogen * Buckmann (‘ Journ. of the Royal Agric. Soc.’) sowed wheat on a field in autumn 1849, which was continually cut down in 1850, so that the plants were never allowed to come to flower: they were left in during the winter 1850-51, and yielded an excellent crop in the year 1851. GROWTH OF TURNIPS AND OATS COMPARED. 53 as the turnip; and the latter to the same quantity of nitrogen four times as much phosphorie acid. It the developement of the oat-plant takes a similar course to that of the turnip, the former must have ac- cumulated in its underground organs before the time of shooting a store of organisable matter, similar to that laid up by the turnip at the close of the first year of vegetation. The mass of organic substances accumu- lating in these plants before the developement of the flower-stalk is manifestly much larger in the turnip than in the oat-plant. The former receives from the soil much more phosphoric acid and nitrogen; but the turnip had 122 days, the oat-plant only 50 days, up to the period of shooting for extracting these nutritive substances from the ground. Now if the turnips and oats growing on a hectare (24 acres) of land had daily received an equal amount of them, then, all other cir- cumstances being the same, the quantity of nutritive substances absorbed would be proportionate to the time of absorption. In this respect the nature of the root makes a great difference, according to the extent of ab- sorbent root-surface. The larger root-surface is in con- tact with more earthy particles, and can during the same time extract more nutritive substances than the smaller. The mass of vegetable substance produced, and especially the quantity of non-nitrogenous and azo- tised materials, depend upon the nature of the plants. If the absorbent root-surface of the oat-plant were 2°45 times greater than that of the turnip, the former would, under like circumstances, take up daily 2°45 times as much food as the latter, 1. e. the oat-plant would absorb in 50 days as much as the turnip in 122 days. Thus in equal times the power of two plants to absorb food is in proportion to their absorbent root-surface. The time of vegetation occupied by the turnip-plant comprises, in the first year, 120 to 122 days, and termi- nates at the end of July in the next year with the pro- duction of seed. If we take the whole time of vegeta- tion of the turnip-plant at 244 days, and suppose the time of vegetation of the oat-plant extended from 93 or 54 THE PLANT. 95 to 244 days, we find that this would give sufficient time for growing two oat crops, and advancing a third half way to maturity ; and a careful investigation. might perhaps reveal that the quantity of sulphureous and nitrogenous constituents produced in the oat-plant is not less than that obtained in turnip-plants from an equal area of ground. In the grains of the cereals the quantity of the sul- phureous and nitrogenous constituents is to that of the non-nitrogenous (the quantity of the blood-making sub- stances to the amylum), as 1:4 or 5; in the roots of turnips, or in the tubers of potatoes, as 1:8 or 10. In the latter, therefore, the quantity of the non-nitrogenous constituents is in proportion to the other constituents much greater. ; When at a certain temperature the organic process of germination begins in a grain of wheat, the embryo first sends down a number of rootlets, while the plumule rises upward in the form of a short stem, with two or three complete leaves. Simultaneously with the changes taking place in the embryo, the constituents of the farinaceous body (albumen) become fluid; the amylum is converted first into a substance resembling gum, then into sugar, while the gluten changes into albumen, and both together form protoplastem (Naege- li’s organic food elements), or the food of the cell. The fluidity of the new body enables it to find its way to the places where the formation of cells is going on. The amylum supplies the elements required to form the outer wall of the cell; the nitrogenous matter consti- tutes a principal ingredient of the cell contents. Simul- taneously with the roots and leaves, small leaf-buds arise upwards on the stem-joint, and small root-buds appear at the basis of the roots. i In the protoplastem of the wheat-plant the non- nitrogenous matter exceeds the azotised matter as five to one. Except water and oxygen, no substance from with- out takes any part in these processes. What the seed loses in carbon by the formation of carbonie acid in FIRST GROWTH OF-A GRAIN OF WHEAT, 55 germination is afterwards recovered almost entirely by the oung plant. The plant developed under these circumstances barely increases in substance to any appreciable degree, even though it may continue vegetating for weeks. The organs developed from a grain of wheat weigh all together, when dried, no more than the grain did before germination. ‘The relative proportion of the non-nitro- genous and azotised substances in them is almost the same as in the farinaceous body, the constituents of which have in reality merely assumed other fornis. The leaves, roots, stem, leaf-buds and root-buds collect- ively represent the constituent parts of the seed, trans- formed into organs and apparatus now endued with the power of performing certain operations which serve to carry on a chemical process, whereby external inorganic substances, with the cooperation of sunlight, are con- verted into products analogous in all their properties to the materials from which these organs themselves arose. The organic process of cell-formation presupposes the presence of the protoplasm, and is independent of the chemical process by which the latter is generated ; but this chemical process is indispensable to the con- tinuance of the cell-formation. In a young plant which has been developed in pure water alone, the chemical process must soon come to an end for want of the necessary external conditions. The leaves and roots in this case can do no work as formative organs. In the absence of food they generate no products upon which the* continued existence of the plant de- pends. When they have arrived at a certain state of developement, the cell-formation ceases in tlfemselves, although it is still continued in the new root-buds and leaf-buds. The latter stand to the movable contents of the previously existing leaves and roots in the same re- lation as the embryo of the wheat-seed to the faiina- ceous body. The non-nitrogenous and azotised constit- uents which represent the working capital of the exist- ing roots and leaves are transformed as these die into new organs, and new leaves are developed at the ex- 56 THE PLANT. pense of the constituents of the old ones. But these processes are of short duration ; after a certain number of days the young plant dies. The more immediate ex- ternal cause of its short duration is the want of food ; but another ¢nternal cause is the conversion of the non- nitrogenous soluble substances into cellulose or woody tissue, whereby it loses mobility. With the diminution of this soluble substance the most essential condition of cell-formation is impaired: when the whole has been consumed, the process comes to an end. The withered leaves, when burnt, leave behind a certain quantity of ash, showing that ‘they retain some mineral matter 5 there remains in them also a small portion of rps nous substance. The most remarkable thing in this developement is the part performed by the nitrogenous matter of the seed, which becomes a constituent element of the root- fibres, stems, and leaves, where its agency serves to bring about the formation of cells. After the death of the first leaves, it becomes a constituent of the new ones, performing in them the same part over again, so long as there remains materials for cell-formation. But the nitrogenous matter itself is not in reality worked up in the plant, and forms no actual tissue or component part of the cell. The experiments of Bousstneautr on the growth of plants, in the absence of all nitrogenous food (* Annal. de Chim. et de Phys.,’ ser. ‘if., xliii., p-. 149), though undertaken for a different purpose, are well adapted to remove all doubt about the very important power pos- sessed by the nitrogenous matter just now alluded to, viz. of maintaining “the vital process in the plant, even where the mass of the plant itself receives no increase. In these experiments lupines, beans, oats, wheat, and cresses were sown in pure pumice-stone dust, washed and burnt, with which was mixed a certain quantity of ash from stable-manure and from seeds similar to those sown. The plants were grown partly under glass bells, with | a constantly-renewed supply of air containing car- bonic acid. The air supplied and the water used for FUNCTION OF THE NITROGENOUS MATTER OF SEEDS. 57 the plants, were most carefully freed from ammonia. The results of these experiments were as follows :—In an experiment where the plants were grown under a glass bell, 4-780 grammes of seeds (lupines, beans, and eresses), containing 0°227 gramme of nitrogen, gave 16°6 grammes of dried plants; adding the amount of nitrogen in the soil, 0-224 gramme of that element was recovered. In another experiment, where the plants were grown in free atmospheric air, with the exclusion, however, of dew and rain, 4°995 grammes of seeds (lu- pines, beans, oats, wheat, and cresses) gave 18°73 grammes of dried plants. The seeds contained 0:2307 gramme of nitrogen; the plants and_ soil, 0°2499 gramme. In the first series of experiments all ele- ments of food were supplied to the plants, except nitro- gen; the chief conditions required to form unazotised matter were given, but those required to form azotised matter were altogether excluded. The growth of a wheat plant in pure water and at- mospheric air is unattended with any increase of weight. The normal seed-corn contains a certain quan- tity of potash, magnesia, and lime, which are required internally for the organic formative process ; but it has no excess of those mineral substances that could serve to effect the chemical process of a new production of protoplasm. Where the mineral substances are ex- cluded, the organs will absorb water, but neither car- bonie acid nor ammonia; at all events, these two latter substances, even though they be introduced into the plant by means of the water, exert no influence upon the internal process ; they suffer no decomposition, and no vegetable matter is formed from their elements. In Boussingault’s experiments, the action of the mineral substances supplied is unmistakable. The weight of the plants produced was nearly 33 times greater than that of the seeds sown: but the quantity of nitrogenous matter was the same as in the seeds. Hence we haye a clear production of non-nitrogenous substance 24 times more than the original weight of the seeds. A simple caleulation shows that the nitro- 3 58 THE PLANT. gen in the seed has, under these circumstances, caused the generation of 56 times its own weight of unazotised matter; or, what comes to the same thing (taking the amount of carbon in the latter at 44 per cent. only), the decomposition of 90 times its own weight of carbonic acid. The course of vegetation in these plants throws sufficient light upon the processes going on in their or- ganism ; in the first days their developement was vig- ourous, afterwards languid. The first-formed leaves withered after a time, and partly dropped off, fresh leaves being developed in their stead, which went on in the same way; and the vegetation seemed to reach a point where the newly developed parts existed at the expense of the decaying portions. A French bean, weighing 0-755 gramme, planted on the 10th May, had by the 80th July developed 17 leaves, of which the first 11 were then dead and gone. The plant flowered, and on the 22nd August, when nearly all the leaves had dropped off, produced a single small bean, which weighed 4 centigrammes, the ;';th part of the weight of the seed-bean. The entire crop weighed 2°24 grammes, very nearly three times as inuch as the seed- bean. In the case of a rye-plant it was very clearly observed how the unfolding of every fresh leaf was at- tended with the death of one of the old leaves. In the second series of experiments, the plants had absorbed (from the air) 1:92 milligramme of nitrogen, and produced 0.830 gramme more vegetable substance, giving 43 milligrammes of unazotised matter for every milligramme of nitrogen. The difference in the developement of a plant in pure water from that of one grown, as in Boussingault’s experiments, in a soil supplying the incombustible con- stituents of food, is clear and unequivocal. The organs first formed received in both cases their elements from the seed; in both, a certain quantity of mineral sub- stances and also of soluble unazotised matter was con- sumed to form cellulose in the leaves, roots, and stems ; and the proportion of the unazotised to the nitrogenous DIFFERENCE IN DEVELOPEMENT. 59 matter was altered. In the plant growing in water, there was a constant decrease of uwnazotised matter ; while in the other a certain quantity of that substance was generated anew. Nothing can be more certain than that in Boussingault’s experiments, the first-formed leaves acquired by the supply of mineral substances the faculty of absorbing and decomposing carbonic acid, a power not possessed by the plant developed in pure water ; and that as much soluble unazotised substance was reproduced as had been consumed in the formation of the leaves and roots by the conversion into cellulose of the store originally present. In the movable constituents of the plant, the rela- tive proportion between the unazotised and the azotised seed constituents was manifestly restored pretty nea as it existed in the sced; both matters passed through the stem into every new-formed leaf-bud, and took part in the developement of new leaves, by whose operation the consumption of unazotised matter was always made good again within a certain limit, so that the same pro- cess could be repeated again and again for months. In every one of the dead leaves (and root fibres) a certain quantity of the azotised substance remained behind, and in the last period of vegetation the floating remainder of this substance was collected in the pod and in the seeds. The supply of mineral substances had served to effect the continuance of the chemical process, and caused the production of unazotised substances. By the presence of these mineral bodies, and by the coop- eration of the azotised matters, new material was en- gendered from carbonic acid to form the cell-walls, and the term of life was prolonged to its proper limit. The most remarkable point is, that a quantity comparatively so small, of azotised substance derived from the seed, should so long be able to perform its assigned functions, apparently without suffering any alteration ; so that in the body of the living plant, made to produce and col- oe it, it would seem to possess a kind of indestructi- ity. 60 THE PLANT. If we consider, that, in the cited experiment with the French bean, a great part of the additional unazo- tised substances which were produced fell away in the dying leaves from the body of the plant, it will be seen that the supply of mineral substances was of no use to the bean-plant in the absence of nitrogenous food. Lastly, it is quite intelligible that the amount of azotised matter contained in a bean might perhaps suf- fice to sustain for years the vegetation of one of the conifers with persistent leaves, and to produce many hundred — perhaps many thousand—times its own weight of woody substance; and that such a plant upon a barren soil altogether unsuited for other plants, might thrive with a very sparing supply of, nitrogenous food, if the soil contained a proper store of those min- eral substances which are indispensable for the genera- tion of unazotised matter. The growth of a plant essentially consists in the en- largement and multiplication of the organs of nutrition, i. e. the leaves and roots. The enlargement of the first, or the production of a second leaf or root fibre, requires the same conditions as the production of the first. The analysis of the seeds teaches us with tolerable certainty what these conditions are. In the normal conditions of nutrition, the first roots and leaves, whose elements were supplied by the seed, produce from certain mineral sub- stances organic compounds, which become parts and constituents of themselves, or constituents of fresh leaves and roots, consisting of the same elements and having the identical properties of the first, i. e. they possess the same power to transform inorganic nutritive substances into organic formative materials. It is quite clear that the enlargement of the first leaves and roots and the production of new ones, must have required azotised and unazotised substances in the same proportioif as in the seed, which makes it probable that the organic operations of the plant under the do- minion of sunlight uniformly produce in all periods of erowth the same materials, 1. e. the constituent ele- ments of the seed, which serve to build up the plant, FUNCTION OF AZOTISED MATTER IN PERENNIALS. 61 being formed into leaves, stems, and root-fibres, or finally into seed. The soluble constituents of a bud, a tuber, or the root of a perennial plant, are identical with the seed constituents. The cereal plant produces azotised and unazotised substances in the same propor- tion as in the albumen (farinaceous body). The potato plant produces the constituents of the tuber, which are formed into leaves and branches or roots; or, if the ex- ternal conditions are no longer favourable to the forma- tion of leaves and roots, accumulate again in the under- ground stem, to form new tubers.* While the growth of the plant continues, the first as well as the last leaves and roots will, with a proper supply of food, maintain their existence, since they re- produce out of the nutriment supplied to them the identical constituents from which they themselves arose. The excess of these, which they do not require for their own enlargement, goes to those parts of the plant where the motion of the fluids or the cell-formation is most active,—viz., to the roots, the leaf-buds, or the extreme points of the roots and shoots; and, finally, as in the case of summer plants, to the organs of seed-formation which at the ripening of the seed absorb most of the movable seed-constituents existing in the plant. The supply of the incombustible elements of food led to the formation of unazotised matter, a portion of which was used to form woody tissue, whilst another por- tion remained available for the same purpose. The supply of nitrogenous food caused a corresponding production of nitrogenous matter, so that the protoplasm was con- stantly renewed, and, so long as the chemical process lasted, was increased. * Boussingault has observed that even seeds weighing two or three milligrammes, sown in an absolutely sterile soil, will produce plants in which all the organs are developed, but their weight, after months, does not amount to much more than that of the original seed, even if they vegetate in the open air; and the result is more marked if they grow ina confined atmosphere. The plants remain delicate, and appear reduced in all dimensions; they may, however, grow, flower, and even bear seed which only requires a fertile soil to produce again a plant of the natural size. (* Compt. rend.’ t. xliv. p. 940.) 62 THE PLANT. To enable a plant to flower and bear seed, it would appear necessary in the case of many plants that the activity of the leaves and roots should reach a period of rest. It is only after this that the process of cell-forma- tion seems to gain the ascendancy in a new direction ; and the constructive materials being no longer required for the formation of new leaves and roots, are used to form the flower and the seed. In many plants the want of rain, and the consequent deficiency of incombus- tible nutritive substances, will restrain the formation of leaves and hasten the flowering. Dry, cool weather favours the production of seed. In warm and moist climates the cereals sown in summer bear little or no seed; and on a soil poor in ammonia the root-plants more readily flower and bear seed than on a soil rich in that substance. If the normal processes of vegetation require a defi- nite proportion of unazotised and azotised materials in the protoplasm which is formed in the plant, it is evi- dent that the want or excess of the mineral substances indispensable for the production of those matters must exercise a very decided influence upon the growth of the plant, and upon the formation of the leaves, roots, and seed. Want of azotised and excess of fixed nutri- tive substances would lead to the formation of mnazo- tised materials in preponderating quantity ; but when these have assumed the form of leaves and roots, they retain a certain amount of nitrogenous matter, thereby impairing the seed formation, a principal condition of which is an excess of protoplasm. An excess of azotised food, with a deficiency of fixed nutritive substances, will be of no use to the plant itself, because the latter can for its organic operations make use of nitrogenous sub- stances only in proportion as they exist in the proto- plasin, and the contents of the cell are of no value to the plant in the absence of the materials required to form the cell-walls. In the process of animal life the organs of the body are constructed from the elements of the egg; the con- stituent parts of such constructed organs are azotised, ABSORPTION BY THE ROOTS OF PLANTS NOT OSMOTR. 63 whereas in the plant they contain no nitrogen. All processes of vegetative life tend simply to produce the elements of the seed. The plant only lives in generat- ing the egg-constituents and the egg itself; the animal only lives by destroying these very egg-constituents. On one and the same soil equally suited for the tur- nip and the wheat-plant, the former produces for the same amount of azotised substance twice as much un- azotised matter as the latter. It is manifest that if two plants produce within the same time different quanti- ties of hydrates of carbon (wood, sugar, and amylum), the organs of decomposition must be arranged in a man- ner not only to afford adequate room for the carbonic acid supplying the carbon, and for the water supplying the hydrogen, as well as to present a suitable extent of surface to the action of the light, but also to permit the liberated oxygen to escape as promptly as it becomes free. If we compare in this respect the leaves of a wheat-plant with those of a turnip-plant, we find a striking difference in their size, and in the amount of water respectively contained in them ; and a microscopic examination reveals still greater differences. The wheat- plant has erect leaves, which present to the light a much smaller surface than the leaves of the turnip- plant, which overshadow the ground, preventing the drying of the soil and the exhalation from it of carbonic acid. In the wheat-leaf the stomates are equally thick on both sides; in the turnip-leaf they are much more numerous, although smaller than in the wheat-leaf, and a far greater number of them are found on the lower than on the upper side. All the facts known respecting the nutrition. of plants tend to prove that it is not by a mere osmotic process that they absorb their food, but that the roots perform a very definite active part in selecting from the amount of food presented to them such matters and in such quantities as are best suited to the plant. The influence of the roots is most manifest in the vegetation of marine and fresh-water plants, whose roots are not in contact with the soil. 64 THE PLANT. These plants received their incombustible nutritive substances from a solution in which these elements are most uniformly mixed and diffused; and yet a com- parative analysis of the water and the ash-constituents of these plants shows that each species absorbs from the same solution different quantities of potash, lime, silicic acid, and phosphoric acid. The ash of duckweed was found to contain 22 parts of potash to 10 parts of chloride of sodium, whereas the water in which the plant had grown contained only 4 parts of potash to 10 parts of chloride of sodium, In the plant the relative proportion of the sulphuric acid to the phosphoric acid was 10 to 14; in the water, 10 to 3. : It is quite the same with marine plants. Sea-water contains for 25 or 26 parts of chloride of sodium 1:21 to 1°35 of chloride of potassium ; but the plants growing in it contain more potash than soda. The kelp of the Orkney Islands, which consists of the ashes of many species of fucus,* contains for 26 per cent. of chloride of potassium only 19 per cent. of chloride of sodium. Sea-water contains manganese, but in such exceed- ingly small quantity that it would certainly have escaped analysis, were it not invariably found among the ash-constituents of many marine plants. The ash of Padina pavonia (a species of tang) is found to con- tain of this mineral even more than 8 per cent. of the weight of the dried plant. ;, By the same power of selection the laminaria with- draw from the sea-water in which they grow the iodine compounds present in it in such exceedingly minute quantities. Chloride of potassium and chloride of sodi- um have the same form of crystallisation, and so many * See Gdédechen’s analysis of the ash of different species of fucus. (‘ Annal. d. Chem. und Pharm.’ liv. 351.) + To give some idea of the extraordinary power which this plant must possess to withdraw the manganese from sea-water, I need simply state that the quantity of this metal in sea-water is so exceedingly small, that I could find distinct traces of it only by subjecting the sesquioxide of iron, obtained from twenty pounds of sea-water, to a most searching analysis. (Forchhammer and Poggendorff, xev. p. 84.) OSMOSIS AND ABSORPTION BY ROOTS. 65 other properties in common, that without the aid of chemical means we cannot accurately distinguish the one from the other. But the plant clearly discriminates between the two salts, for it separates the one from the other, and for every one equivalent of potassium which it absorbs leaves behind in the water more than thirty equivalents of sodium. Manganese and iron, iodine and chlorine, are likewise isomorphous bodies ; yet the iodine plant separates one equivalent of iodine in sea- water from many thousand equivalents of chlorine. The known laws of osmosis, and of the diffusion or interchange of water and salts through a dead mem- brane or a porous mineral body, give no explanation whatever of the action exercised by a living membrane upon salts in solution, or how they pass through it into the plant. The observations of Graham (‘ Phil. Mag.’ ser. [V. August 1850) show that matters capable of exerting a chemical action upon animal membranes, such as carbonate of potash and caustic potash, causing them to swell and gradually decomposing them, facili- tate the passage of water to an extraordinary degree.* Graham remarks that the processes of alteration, decom- position, and new formation, which are incessantly taking place in the membranes and cells in all parts of the plait, and which we have no means of defining or measuring, must entirely change the osmotic process: the permeation of mineral substances through the living vegetable membrane must, therefore, be governed by very complex laws. Land plants act in the Same manner with respect to the soil in which they grow, as marine plants to sea- * The water in the tubes of his osmometer rose to 167 millimeters, when holding 1/10m. per cent. of carbonate of potash in solution; with 1 per cent. of that salt, it rose to 863 millimeters (88 inches, English). In another experiment, the water holding 1 per cent. of sulphate of potash in solution, rose to twelve millimeters ; upon the addition of 1/10 per cent. of carbonate of potash to the solution, it rose to 254-264 millimeters; the same potash solution by itself rose only to 92 millimeters. The notion of an osmotic equivalent is altogether inadmissible, if the membrane is chemically altered, Graham’s latest investigations on the dialysis of crystalline and amorphous bodies are extremely interesting, and promise to throw considerable light upon the processes in the animal organism, 66 THE PLANT. water. One and the same field presents to the plants growing in it, the alkalis, alkaline earths, phosphoric acid, and ammonia, in absolutely the same form and condition ; but the ash of no one species of plant ever shows the same relative proportions of component ele- ments as the ash of another species. Even the parasit- ical plants, which draw their mineral constituents in a certain state of preparation, from other plants on which they live, as the mistletoe (Viscwm album), do not com- port themselves to the latter as a graftling to a tree, but absorb from the sap very different proportions of min- eral constituents (‘ Annal d. Chem. und Pharm.’ liv. 363). Now, as the soil is perfectly passive in respect to the supply of these materials, there must be some ageney at work in the plant itself, which regulates the absorption according to the requirements of each plant. The observations made by Hales (see Appendix C.) show that the exhalation from the surface of the leaves and branches exercises a powerful influence upon the motion of the fluids, and upon the absorption of water from the soil. If the plant drew its mineral food from a solution moving about in the soil and passing imme- diately into the roots, then two plants of different spe- cies or kind, placed in the same conditions, would re- ceive the same mineral substances in the same relative proportions ; but, as we have seen, two plants belonging each to a different species contain these substances in the most dissimilar proportions. That a selection takes place in the absorption of food by the roots is a fact beyond dispute. In the case of aquatic plants, which grow under water, exhalation is altogether excluded as a possible operating cause of the passing of the food into the body of the plant. In these plants the absorbent surface must exercise very unequal powers of attraction upon the different materials, which are presented by the solu- tion in the same form and in a state of equal mobility ; or, what comes to the same thing, the resistance offered to their passage through the outermost cellular layers must be very dissimilar. The case cannot be different POWER OF SELECTION BY ROOTS NOT ABSOLUTE. 67 with the roots of land-plants, to judge from the unequal proportions of the substances severally absorbed by them. The power of the roots to preclude the passing of certain substances from the soil into the plant is not absolute. Forchhammer (Poggend. ‘ Annal.’ xcv. 90) detected exceedingly minute traces of lead, zinc and copper in the wood of the beech, birch, and fir; and tin, lead, zinc, and cobalt in that of the oak; but the fact that the outer rind or bark, in particular, is found to contain metals of this kind in perceptibly larger quantities than the wood, clearly points to the acci- dental nature of their presence, and to their taking no essential part in the vital processes of the plant. How small the quantities of these metals must be which the roots of these trees absorb may be judged from the fact that hitherto chemical analysis has not been able to detect traces of any other metal than man- ganese and iron, in the water of wells, brooks, or springs; and their appearance in these wood-plants, which during the growth of half a century or more have absorbed and evaporated an immense quantity of water, is the only proof we possess, that this water must actu- ally have contained these metals in some form or other. The observations of Dr SaussurE, ScHLossBERGER, and Herr, show that the roots of land and water plants absorb from very dilute saline solutions water and salt in proportions entirely different from those in the fluid; in all cases a greater proportion of water, and a less quantity of salt. In plants watered with very dilute solutions of salts of baryta, Daubeny found no baryta, whereas Knop in similar experiments detected this substance. The general result of all these experi- ments is that, of themselves, the plants have not the power of offering a permanent resistance to the chem- * ical action of salts and other inorganic compounds upon the exceedingly fine membrane of the root. Most land-plants in their natural state in the soil ean bear no salt solutions, as concentrated as in these experiments, without sickening and dying; and even 68 THE PLANT. carbonate of potash and ammonia, which we certainly know to be nutritive substances, act upon many plants as poison, even when present in the water which cireu- lates in the ground only in suflicient quantity to impart a blue tint to red litmus paper. On the other hand, it would be very wonderful if the roots of a plant outside the soil, and in conditions not suitable to their nature should, under the influence of evaporation, be impene- trable for salt solutions.* Those mineral substances which, like iron, are con- stant constituents of all plants, though present only in very small proportions, must be regarded very different- ly from those metals which Forchhammer found in woody plants. We know the part which iron performs in the ani- mal organism, in which it is present in comparatively no larger quantities than in the seeds of cereals; and we are fully convinced that, without a certain amount of iron in the food of animals, the formation of the blood corpuscles, the agents of one of the chief fune- tions of the blood, is impossible. Hence, by the law of dependence, which links together the life of animals and plants, we are compelled to ascribe to the iron in the plant also an active part in its vital functions so material that the absence of that metal would endanger the very existence of the plant. Hitherto chemistry has attributed a positive part in the vital process of plants to those incombustible sub- stances only which are common to all, and which differ only in the relative proportions in the plants. But * Tf the long limb of a syphon-shaped tube, filled with water and closed with thick pieces of pig or ox bladder tied over both openings, is placed in salt-water or oil, and the other limb is exposed to the air, the water evaporates in the pores of the bladder with which the short limb is closed. By the capillary action of the bladder, the water exuding in gaseous form is taken up again on the other side of the bladder, and a vacuum is thus created in the interior of the tube, whence there is an increased pressure upon the surfaces of both bladders, which forces the salt-water or the oil through the bladder into the tube. (‘ Researches into some of the Causes of the Motion of Fluids, by J. v. Liebig. Brunswick: Fr. Viewig & Son. 1848.’—p. 67.) A plant in similar conditions is just like a tube closed with penetrable porous membranes. IRON AND ZINC NECESSARY FOR PLANTS. 69 should the conjecture prove true that iron is a constant constituent of chlorophyll and of the leaves of many flowers, it may be assumed that other metals, found in- variably present in certain varieties of plants (as man- ganese in Pavonia, Zostera, Trapa natans, in many ligneous plants, several cereals, and in the tea shrub), take part in the vital functions, and that certain pecu- liarities depend upon the presence of those metals. The ash of Viola calaminaria, a plant which, in the parts about Aix-la-Chapelle, is held so strongly indicative of the presence of zinc, that the places where it grows are selected for opening new mines in search of zine ore, is found to contain oxide of zine. (Alex. Braun.) As chloride of sodium and chloride of potassiam cause some plants to thrive, so iodide of potassium manifestly performs a similar part in others; and if one plant may properly be called a chlorine plant, others may with equal propriety be termed iodine plants, or manganese plants.* (Prince Salm-Horst- mar.) The diversity in the amount of iodine in different varieties of fueus (Goedechens), or of alumina in various kinds of Lycopodium (Count Laubach), remains, indeed, unexplained ; but the power of plants to withdraw sub- stances like iodine, even in the smallest quantities, from the sea water in which they grow, and to accumulate and retain them in their organism, can only be ex- plained upon the assumption that these substances have entered into combination with certain constituent parts of the plants, whereby as long as the plant lives they are prevented from returning to the medium from which they were taken.t+ * The examination of the following water-plants revealed the presence of considerable quantities of manganese and iron in their ash, though the water in which they grew apparently contained no trace of manganese :— Victoria regia (in the leaf-stalk principally manganese, in the leaf iron) ; Nymphea cerulea, dentata, lutea ; Hydrocharis Humboldti ; Nelumbium asperifolium. (Dr. Zoller.) + With respect to the copper in the grains of wheat and rye, which Meier of Copenhagen has shown to be a constant constituent of both seeds, Forchhammer (Poggendorff’s ‘ Annal.’ xe. 92) remarks :—‘ It is an old and 70 THE PLANT. It might be supposed that plants become saturated with the substances absorbed from the air and from the soil; and that all materials offered by the soil in solu- tion, or made soluble by the cooperation of the roots, are absorbed without distinction. Upon this assump- tion, only that substance in the plant could of course pass into it from without, which is withdrawn from the solution within for a formative purpose. The investigations made by Schultz-Fleeth show that Vymphea alba and Arundo phragmites absorb from the same soil and water, the former nearly 18 per cent., the latter 4:7 per cent., of ash constituents ; and of these silicic acid in the most unequal proportion ; the ash of Wymphea alba containing less than 4 per cent. of that substance, while in the ash of Avrundo phragmites there are above 71 per cent. Upon the supposition just made, an equal amount of silicic acid is offered to the roots of both plants, and they both take up an equal quantity of it in proportion to the volume of the sap respectively. In the reed plant the silicic acid is incessantly withdrawn from the sap, and depos- ited in a solid state in the leaves, the margins of the leaves, the sheaths, &ec. As the sap within contains less silicic acid than the solution without, fresh quanti- ties of it are absorbed from the latter ; but not so with the Vymphea, because the silicic acid taken up by that plant is not consumed in it. If we accept the same reasons for the passage into the plant of carbonic acid and phosphoric acid, then it can possess no actual power of selection, but the per- meation of the nutritive substances will depend upon osmotic conditions. It certainly cannot be denied that the absorption of nutritive substances depends upon growth or increase approved practice to steep grains of wheat, intended for sowing, in a solu- tion of sulphate of copper. The usual explanation of this practice is, that sulphate of copper destroys the sporules of blight to which the wheat plant is liable, an explanation which it is not my intention to dispute. Still it might also be held, supposing copper to be an essential constituent of wheat, that the practice in question serves to supply the copper necessary for the vigorous growth of the plant.’ PASSAGE OF MATTERS INTO THE ROOTS. G1 in mass; for as it is certain that a plant will not grow if no food is offered to it, so it is equally certain that it will absorb no nutriment if the external conditions are not favourable to growth. Yet the view given above would force us to conclusions which are not founded in nature ; such as, for instance, (1) that there is actually around the roots a solution containing all the ash con- stituents of the plants; and (2) that the roots of all plants have a similar structure, and their sap is of the same nature. With regard to the roots, the most common observa- tions appear to show that they possess the power of selecting the proper mineral nutriment for the plant from the matters presented to them. All plants do not thrive equally well in the same soil; one kind succeeds best in soft water, another in hard water, or water abounding in lime; another only on marshy ground ; many on fields rich in carbon and carbonic acid, such as the turf-plants; others again on soil containing large quantities of alkaline earths. Many mosses and lichens will grow only on stones, the surfaces of which they sensibly change ; others, like AGleria, possess the faculty of extracting from silicious sandstone potash and the phosphoric acid so sparingly present in it. Roots of grass attack the felspar rocks, accelerating their disin- tegration. Rapes and turnips, sanfoin and lucerne, as also the oak and beech, receive the chief part of their food from the subsoil poor in humus; while the cereal and tuberous plants thrive best in the arable surface soil, and in soil abounding in humus. The roots of many parasitic plants are absolutely unable to extract from the soil their necessary food ; but this is prepared for them by the roots of the plants on which they grow. Others again, as certain fungi, grow only on vegetable and animal remains, whose azotised and unazotised sub- stances they use for their own construction. These facts, accepted in their true significance, seem sufficient to remove all doubt respecting the different action of the roots of plants upon the soil. We know that common Lycopodium (club-moss) and ferns absorb 72 THE PLANT. alumina; yet we also know that this substance, in the form in which it occurs in all fertile soils, is not soluble in pure water, or water containing carbonic acid; and that it cannot be detected in any other plant growing on the same soil by the side of the club-inoss. In like manner, Schultz-Fleeth could not discover in the water in which Arundo phragmites (one of the plants most abounding in silicic acid) was growing, sufficient silicic acid to yield a ponderable amount in the composition of 1000 parts of the water. CHAPTER ITI. THE SOIL. The ggi! contains the food of plants—Soil and subsoil , conversion of the latter into the former—Power of the soil to withdraw the food of plants from solution in pure and in carbonic acid water ; similar action of charcoal ; process of surface attraction ; chemical decomposition often accompanies this attraction of the food of plants in the soil, general resemblance of the soil in its action to ant- mal chareoal—Ali arable soils possess the power of absorption, but in different degrees—Mode of the distribution of the food of plants in the soil ; chemically and physically fixed condition of the food—Only the physically fixed are avail- able to plants, being made soluble by the roots—Power of the soil to nourish plants; on what dependent—Comportment of an exhausted soil in fallow— eans for making the chemically fixed elements of food available to plants— Action of air, weather, decaying organic matters and chemical means—Distri- bution of phosphoric and silicic acids ; influence of organic matters—Action of lime—Process of the absorption of food from the soil by the extremities of the roots—Mechanical preparation of the soil; its influence ou the growth of plants ; chemical means for preparing the soil—Rotation of crops ; its influ- ence on the quality of the soil ; action of draining—Plants do not receive their food from a solution circulating in the soil; examination of drain ; lysemeter, spring and river water : bog water, food of plants contained in it ; Briickenauer spring water contains volatile fatty acids , amount of food of plants in natural waters dependent on the nature of the soil through which they flow—Mnd and bog earth as manure ; explanation of their action—Manner in whieh plants take up their food from the soil ; experiments on the growth of plants in solu- tions containing their food ; similar experiments with soil containing the food ina physically fixed state—Intimate connection of natural laws—Average crop ; necessary quantity of assimilable food in the soil for the production of such ; importance of the extent of surface of the food in the soil ; the root sur- face—Quantity of food fora given surface of roots necessary for a wheat or rye crop—Analysis of the soil of a field—Difterence between fertility and pro- ductive power of a field—Mode of estimating relative extent of root surfaces —Conversion of rye into wheat soil; quantity ef food necessary for the pur- pose ; the plan impracticable—Immobility in the soil of the food of plants , ex- perience in agriculture—Real and ideal maximum production—Convers.on in practice of the chemically fixed food into an available form—Effect of amanure peyende upon the property of the soil—Improper relative proportions of the different elements of food in the sojl- effeet of this upon the different culti- vated plants : means for restoring the proper relative proportions. atom the soil plants receive the food necessary for their developement ; hence an acq:aintance with its chemical and physical properties is important in helping us to understand the nutritive processes of plants, and the operations of agriculture. As a matter of course, a 4 74 THE SOIL, soil to be fertile for cultivated plants, must, as a pri- mary condition, contain in sufficient quantity the nutri- tive substances required by those plants. But chem- ical analysis, which determines this relation, gives but rarely a correct standard by which to measure the fertility of different soils, because the nutritive sub- stances therein contained, to be really available and effective, must have a certain form and condition, which analysis reveals but imperfectly. Rough uncultivated ground, and soil formed from the dust and dried mud of the highroads, are speedily overgrown with weeds, and though often still unfit for the cultivation of cereal and kitchen plants, may yet prove not unfruitful for other plants, requiring, like clover, sanfoin, and lucerne, a large amount of food, and which are often seen thriving luxuriantly on the slopes of railway embankments formed of earth that has never been under cultivation. A similar relation is shown by the subsoil of many fields. In many of them the earth from the deeper layers improves the surface soil, and increases its fertility; in others, the subsoil mixed with the surface soil destroys the fertility of the latter. It is a remarkable fact that rough uncultivated soil, unsuited for cereal and kitchen plants, may by diligent cultivation during several years, and by the influence of the weather, become fertile enough to produce those plants which it formerly refused to bear. The dif- ference between fertile arable land and barren untilled soil is not the result of any dissimilarity in the nutritive substances which they contain; because in cultivation upon a large scale, to convert the untilled rough soil into fertile arable land, the ground, so far from being enriched, is rather impoverished by the cultivation of other plants on it. The difference ‘between the subsoil and the arable surface soil, or the crude and the cultivated soil, sup- posing that both contain the same amount of nutritive substances, can only be founded upon this, that the eul- tivated ground contains the nutritive substances of A SOIL WHEN SAID TO BE FERTILE. 75 plants, not only in a more uniform mixture, but also in another form. Now as from the influence of cultivation and weather above-mentioned, the rough soil acquires the power of furnishing the elements of food which it contains, in just the same quantity and in the same time as cultivated soil, a power which was formerly wanting in it with regard to certain plants, it cannot be denied that an alteration must have taken place in the original form and fashion of these elements. Suppose we have a soil consisting of disintegrated rocks: in the smallest particles of such a soil, the nutri- tive substances of plants, as potash for instance in a silicate, are retained in combination by the chemical attraction of silicic acid, alumina, &e. This attraction has to be overcome by one still more powerful, if the potash is to be liberated and made available for passing into plants. If we find that some plants are perfectly developed in a soil of the kind, which remains unfruit- ful for others, we are led to assume that the former are able to overcome the chemical resistances opposed to their growth, and that the latter are not. Further, if we find the same soil gradually acquiring the power of producing these latter plants also, we can assign no other reason than this, that by the combined action of air, water, and carbonic acid, aided by mechanical operations, the chemical resistances have been over- come, and the alimentary substances have been reduced to a form in which they are available for absorption even by plants endowed with the feeblest powers of vegetation. A soil can only then be said to be perfectly fertile for a given species of plant, e.g. wheat, when every part of its horizontal section which is in contact with the roots contains the amount of food required by the plant, in a form allowing the roots to absorb such food at the proper time, and in the proper quantity, during every stage of its developement. \ In a former section mention has been made of a property possessed by arable soil, viz. that when 76 THE SOIL. brought into contact with solutions of the articles of food most essential for plants in pure water or in water containing carbonic acid, it can withdraw these ele- ments of food from such solutions. This power throws light upon the form and condition in which these mate- rials are contained or combined in the soil. To estimate this property correctly in its bearing upon the lite plants, we must call to mind a similar property in charcoal, which, like arable soil, withdraws from many fluids colourimg matters, salts and gases. This power in charcoal depends upon a chemical attraction proceeding from its surface, and the materials withdrawn from the fluid adhere to the charcoal in exactly the same way that the colouring matter adheres to the fibre of coloured stuffs coated over with it. The property of decolorising coloured fluids, which animal wood and vegetable fibre share in common with charcoal, is perceptible in those kinds of charcoal only which possess a certain degree of porosity. Powdered pit coal, and the shining, smooth, blis- tered charcoal from sugar or blood, have hardly any decolorising action ; whereas porous blood-charcoal and bone-charcoal with its fine pores exceed all other varie- ties in this property. Among the wood-charcoals, those made from poplar or pine, having wide pores, are inferior to the charcoal of the beech and box tree ; all these varieties decolorise in proportion to the extent of surface which attracts colouring matter. The attractive force which charcoal exercises upon colouring matter is about on a par with the feeble aftinity of water for salts, which are dissolved by it, but without alteration of their chemical proper- ties. When dissolved in water, a salt simply assumes the fluid state, and its particles acquire mobility ; but in all other respects it retains its characteristic proper- ties, which, as is well known, are completely destroyed by the action of a stronger affinity than that of water. In this respect the attraction of charcoal resembles that of water, for both attract the dissolved matter. If the attraction of the charcoal is somewhat greater than ABSORPTIVE POWER OF SOILS. 17 that of the water, then the colouring matter is com- pletely withdrawn from the water; if the attraction of both is equal, a division takes place, and the attraction is only partial. The materials attracted by the charcoal retain all their chemical properties, and continue unaltered, mere- ly losing their solubility in water; yet very slight cir- cumstances, increasing in the least degree the attractive force of the water, are suflicient again to withdraw from the charcoal the materials absorbed by it, and which sunply coat its surface. By a slight addition of alkali to the water the colouring matter may be discharged from the charcoal which has been used to decolorise the fluid, and by treatment with alcohol, the quinine or strychnine absorbed by charcoal from a fluid may be again extracted. The arable soil possesses, in these respects, the same properties as charcoals. Diluted liquid manure, of deep brown colour and strong smell, filtered through arable soil, flows off colourless and inodorous ; and not merely does it lose its smell and colour, but the ammonia, potash, and phosphorie acid which it holds in solution, are also more or less completely withdrawn from it by the soil, and this in a far greater degree than by char- coal. The rocks which by disintegration give rise to arable soil, if reduced to a fine powder, are just as little possessed of this power as pounded coal. On the con- trary, contact with pure water or water containing car- bonic acid, deprives many silicates of potash, soda, and other constituents, a clear proof that the former cannot possibly withdraw the latter from the water. There is no perceptible connection between the composition of a soil and its power of absorbing potash, ammonia, and Phosphoric acid. A soil abounding in clay, with a small proportion of lime in it, possesses this absorptive power in the same degree as a lime soil with a small admixture of clay; but the amount of humus substances will alter the absorptive relation. By a closer observation we perceive that the absorp- tive power of arable soil differs in proportion to its res) THE SOIL. greater or less porosity ; a dense, heavy clay soil and a loose sandy soil possess the absorptive power in the smallest degree. There can be no doubt that all the component parts of arable soil have a share in these properties, but only when they possess a certain mechanical condition, like wood or animal charcoal; and that this power of absorption depends, as in charcoal, upon a surface attraction, which is termed a physical attraction, be- cause the attracted particles enter into no chemical combination, but retain their chemical properties.* The arable soil owes its formation to the disintegra- tion of minerals and rocks, brought about by the action of mighty mechanical and chemical agencies. Though the comparison may not be altogether apt, the rock may be said to stand in about the same relation to the arable soil resulting from its disintegration as the wood or the vegetable fibre to the humus resulting from its decay. The same causes which in the course of a few years convert wood into humus act also upon rocks, with this difference, however, that it requires the combined action of water, oxygen, and carbonic acid, for probably a thousand years, to produce from basalt, trachyte, fel- spar, or porphyry, the thinnest layer of arable soil (such as is found in the plains of river valleys and low lands) with all the chemical and physical properties suited for the nutrition of plants. Sawdust possesses the proper- ties of humus no more than powdered rocks have the properties of arable soil. No doubt sawdust may pass into humus and powdered stones into arable soil, but the two states are essentially distinct ; and no human art can imitate the operations which were necessary, during immense ages, to convert the divers kinds of rocks into arable soil. Arable soil, resulting from the disintegration of various kinds of rocks, bears the same relation, in * The term, ‘physical attraction,’ as used here, does not signify a peculiar attractive force, but merely designates the ordinary chemical affinity, which shows differences of degree in its manifestation. ARABLE SOIL COMPARED TO ANIMAL CHARCOAL. 79 respect of absorptive power for enorganic substances in solution, as the woody fibre altered by the action of heat bears to organic substances in solution. It has been stated, that from a solution of carbonate of potash or ammonia, or from a solution of phosphate of lime in carbonic acid water, the arable soil will with- draw the potash, ammonia, and phosphoric acid, with- out any chemical interchange with the constituents of the earth taking place. In this respect the action of arable soil is absolutely like that of charcoal. But it goes farther, for it is sufficiently powerful to sever the connection between the potash or ammonia and the mineral acid, for which they have the greatest affinity, the potash being absorbed by the soil just as though it were not combined with an acid. In this property arable soil is like animal charcoal, which, by means of the phosphates of the alkaline earths contained in it, decomposes many salts that are not affected by charcoals free from such phosphates; and, without doubt, the lime and magnesia compounds in- variably present in arable soil have a share in this de- composing power which it possesses. We must suppose that the attractive force of the earthy particles would not in itself be strong enough to separate, for instance, potash from nitric acid, and that it requires the additional attraction of the lime or mag- nesia to decompose the nitrate of potash. On the one side the soil attracts the potash, on the other the lime or magnesia in the earth attracts the nitric acid, and thus the combined attraction effects, as in innumerable instances in chemistry, a separation which could not have been brought about by a simple one. The process of decomposition effected by arable soil differs only in one respect from the ordinary chemical processes, namely, that in the latter, as a general rule, no soluble potash salt is decomposed by an insoluble lime salt, in such a manner that the potash is thereby made insoluble and the lime soluble. There is evident- ly here some other attractive force at work, which alters the effect of chemical affinity. If a solution of phos- 80 THE SOIL. phate of lime in water containing carbonic acid is filtered through a funnel filled with earth, the upper- most layer of the earth first takes up the phosphoric acid or the phosphate of lime from the fluid. Once saturated therewith it no longer stops the free passage of the dissolved phosphate of lime which now reaches the layer beneath ; the latter then again becomes satu- rated in the same way, and thus by degrees the phos- phate of lime is completely diffused throughout the earth in the funnel, so that every particle retains on its surface an equal proportion of this substance. If the phosphate of lime were of the colour of madder and the soil colourless, the latter would now actually present the appearance of a madder lake. Just in the same way potash is diffused through the soil when a solution of carbonate of potash is filtered through it; the lower layers receive what the upper do not retain. There is no need of any special disquisition to show that the phosphate of lime contained in a particle of bone-earth is diffused in exactly the same way through arable soil, with this difference, that the solution of phosphate of lime in rain-water containing carbonic acid is effected at the very spot where the particle lies, and spreads thence downward and in all directions. The potash and the silicic acid rendered soluble by disintegration, or by the action of water and carbonic acid upon silicates, are diffused through the soil in the same way, so is ammonia also, which is conveyed in rain-water, or is generated by the putrefaction of the azotised constituents in the decayed roots from the suc- cessive generation of plants grown on a field. Every soil must therefore contain potash, silicic acid and phosphoric acid in two different forms, namely, in chemical and in physical combination: in the one form, infinitely diffused over all the surface of the porous par- ticles of the soil; in the other, in the shape of granules of phosphorite, or apatite and felspar, very unequally distributed. In asoil abounding in silicate and in phosphate of lime, which has for thousands of years been exposed to FOOD PHYSICALLY AND CHEMICALLY COMBINED. 81 the dissolving action of water and carbonic acid, the component particles will be found everywhere physi- eally saturated with potash, ammonia, silicic acid, and phosphoric acid ; and it may occur, as in the case of the so-called. Russian black-earth, that the phosphate of lime dissolved but not absorbed is deposited again in concretions, or in a crystalline form in the subsoil. In this state of physical combination the alimentary substances are manifestly in the most favourable condi- tion to serve as food for plants; for it is clear that the roots, in all places where they are in contact with the soil, will find the necessary nutritive substances in the same state of diffusion and readiness as if these substan- ces were in solution in water, but at the same time not movable of themselves, and retained in the soil by so slight a force that the most trifling dissolvent cause brought to bear upon them suflices to effect their solu- tion and transition into the plant. If it is true that the roots of cultivated plants have no inherent power to overcome the force which retains together potash and silicic acid in the silicates, but that those elements of food only which are in physical com- bination with the soil can be taken up and made ayail- able for nutriment, this explains the difference between cultivated and uncultivated ground, or barren sub- soil. Nothing can be more certain than that the mechan- ical treatment of the soil and the influence of the weather serve to strengthen the causes which bring about the disintegration and decomposition of the minerals, and the uniform distribution of the elements of food contained in them and rendered soluble. The elements chemically combined in the minerals, are re- leased from that combination, and in the arable soil gradually resulting from this decomposition acquire the form in which they are available as food for plants. It is evident that only by degrees the rough ground can attain the properties of arable soil, and that the time required for this change depends upon the quantity of nutritive substances present, and upon the obstacles 4* 82 THE SOIL. which oppose their distribution, or their disintegration and decomposition. The perennial plants, and particu- larly the so-called weeds, consuming in proportion to ‘the time less food, and absorbing longer, will always thrive on a soil of this description long before annual or summer plants, which in their shorter period of vegetation require a far larger amount of nutritive sub- stances for their full development. The longer a soil is under cultivation, the more it becomes suited for the growth of summer plants, from the recurrence and operation of the causes by which the nutritive substances are converted from a state of chemical into one of physical combination. To be pro- ductive, in the fullest sense of the term, a soil must be able to afford food at all points in contact with the roots of the plants; and, however small the quantity of this food may be, it must necessarily be distributed through every part of the soil. The power of the soil to nourish cultivated plants is therefore in exact proportion to the quantity of nutritive substances which it contains in a state of physical satu- ration. The quantity of the other elements in a state of chemical combination distributed through the ground is also highly important, as serving to restore the state of saturation when the nutritive substances in physical combination have been withdrawn from the soil by a series of crops reaped from it. Experience proves that the cultivation of deep-root- ing plants, which draw their food principally from the subsoil, does not materially impair the fertility of the surface soil for a succeeding crop of cereal plants; but the successive cultivation of the latter will, in a com- paratively small number of years, render the soil incapa- ble of yielding a remunerative crop. With most of our cultivated fields this state of ex- haustion is not permanent. If the ground is left fallow for one or more years, especially if it is well ploughed and harrowed during the time, it recovers the power of yielding a remunerative crop of cereal plants. Chemical analysis leaves altogether unexplained the FOOD PHYSICALLY COMBINED. 83 causes of this fact, so highly important to agriculture, and which has been fully established by the experience of several thousand years. If the reason be that cereal plants feed on those substances only which are in physi- cal combination in the surface soil, then we can easily understand the remarkable fact of a field recovering its power of production without any supply of manure ; for though the nutriment in this form constitutes but a small portion of the soil by weight, yet it imparts nutri- tive qualities to a large volume of it; and it is quite intelligible that a soil not originally rich in nutritive substances physically combined, when drained of them by the innumerable underground absorptive organs of a plant, must very speedily become unsuited for the cultivation of that plant. Now as the cultivated soil is composed in the main of ingredients which are identical with the constituents of uncultivated ground, and as the agencies affecting the decomposition of these ingredients, and the trans- position of their constituents aflording food to plants are in constant operation, it 1s easy to conceive how, by the influence of such causes, an exhausted soil, which is in fact nothing else than a soil reduced to its crude state previous to cultivation, must regain the properties which it had lost. With the conversion of a fresh por- tion of the food elements from a state of chemical to one of physical combination, the field recovers the power of affording food to a fresh vegetation in such quantity that the crops are again remunerative to the agriculturist. An exhausted field which is again rendered produc- tive by fallowing, may accordingly be defined as land deficient in physically i nutritive substances necessary for a full crop, while containing an excess of such substances in a chemically combined state. The Fallowing season, therefore, means the time in which the nutritive substances pass over from the one state to the other. It is not the amount of nutritive substances that is increased in fallowing, but the number of parti- cles of their constituents capable of affording nutrition. 84 THE SOIL. What is here asserted of all the mineral nutritive substances without distinction applies equally to every soil constituent required by the plant. ‘The exhaustion of a field may often simply depend upon a deficiency of available silicic acid for the coming crop of cereal plants, while the other food elements may be super- abundant. It is evident from the nature of the process, that if the soil is altogether deficient in disintegrable silicates or soluble earthy phosphates, the action of time, the plough, and the weather in fallow will not restore fer- tility to a field, and that the effect of disintegrating causes will vary with the time they are in operation, and with the composition of the different soils. It clearly results from the foregoing observations, that one of the principal requirements of the practical farmer is to know the causes as well as the means whereby the useful nutritive substances present in his field, but not in a form available for nutrition, may be rendered diffusible and capable of doing their work. The presence of moisture, a certain degree of heat, and free access of air, are the proximate conditions of those changes by which the nutritive substances in chemical combination are made available for the roots. A certain quantity of water is indispensable to trans- pose the soil-constituents when rendered soluble; water, with the co-operation of carbonic acid, decom- poses the silicates, and makes the undissolved phos- phates soluble and diffusible through the soil. The organic remains decaying in the ground afford feeble but long-continued sources of carbonic acid ; but without moisture no process of decay can take place. Stagnant water, again, which excludes the access of air, prevents the generation of carbonic acid; and the pro- cess of putrefaction is attended with the generation of heat, whereby the temperature of the soil is perceptibly increased. By the aid of putrescent vegetable and animal re- mains, a field exhausted by culture will regain its fer- tility in a shorter time, and the use of farm-yard CONDITIONS FOR RENDERING FOOD AVAILABLE. 85 manure in time of fallow will promote the process. The dense shadow east by a leafy plant tends to retain moisture longer in the ground, and thus increases the action of the disintegrating agencies during the fallow season. In a porous soil abounding in lime the putrefactive process of organic matter proceeds much more quickly than in a clay soil; the presence of the alkaline earth, under these circumstances, serving to oxidise the car- bonaceous matter, and to convert the ammonia present in the soil into nitric acid. All kinds of lime, when lixiviated, give up nitrates to the water. Nitric acid is not retained by the porous earth, as is ammonia; but it is carried down combined with lime or magnesia by the rain-water into the deeper layers of the soil. While the formation of nitric acid taking place in the ground is useful for plants which, like clover and peas, draw their food (here in- cluding nitrogen) from a greater depth, yet for this very reason fallowing has a less beneficial effect, with a view to the culture of cereal plants, upon a lime soil rich in animal remains; for by the conversion of am- monia into nitric acid, and its removal, the ground be- comes poorer in one of the most important elements of the food of plants. The case is conceivable that a field of the kind, if not cultivated for a number of years, may ultimately have its productive powers impaired by a deficiency of nitrogenous food in the soil. The cause of the exhaustion of a field by the culture of any plant is always, and under all circumstances, dependent upon a deficiency of one or more nutritive substances in those portions of the soil which are in contact with the roots. A field in which these portions are deficient in phosphoric acid in the state of physical combination, will be found unsuited for the production of a proper crop, though it should contain abundance of available potash and silicic acid. The same results will follow from a want of potash, even though phos- phorie and silicic acids be plentiful; and equally so from a want of silicie acid, lime, magnesia, or iron, 86 THE SOIL. even where potash and phosphoric acid are in abund- ance. When the exhaustion of a field is not caused by the absolute deficiency of food elements, when even a more than adequate supply of all the needful nutriment is there, but not in the proper form, and where conse- quently fallowing will again render the crop remuner- ative, the farmer has means at his disposal to assist the action of the natural agencies, whereby the conversion of the food elements into the state of physical combina- ation is effected, and thus to shorten the fallowing season, or even in many instances to make it altogether superfluous. We have seen that the diffusion of earthy phos- phates through the soil is effected exclusively by water, which, if containing a certain amount of carbonic acid, dissolves these earthy salts. Now, there are certain salts, such as chloride of sodium, nitrate of soda, and salts of ammonia, which experience has proved to exercise, under certain condi- tions, a favourable action upon the productiveness of a field. These salts, even in their most dilute solutions, pos- sess, like carbonic acid, the remarkable power of dis- solving phosphate of lime and phosphate of magnesia ; and when such solutions are filtered through arable soil, they behave just like the solution of these phos- phates in carbonic acid water. The earth extracts from these salt solutions the dissolved earthy phosphates, and combines with the latter. Upon arable soil mixed with earthy phosphates in excess, these salt solutions act in the same way as upon earthy phosphates in the unmixed state, that is, they dissolve a certain proportion of the phosphates. Nitrate of soda and chloride of sodium suffer, by the action of arable soil, a similar decomposition to that of the salts of potash. Soda is absorbed by the soil, and in its stead lime or magnesia enters into solu- tion in combination with the acid. If we compare the action of arable soil upon galts MEANS FOR CAUSING THE DIFFUSION OF Foop. 87 of potash and salts of soda, we find that the soil has far less attraction for soda than for potash; so that the same volume of earth which will suffice to remove all the potash from a solution will, in a solution of chloride of sodium or nitrate of soda of the same alka- line strength, leave undecomposed three-fourths of the dissolved chloride of sodium and half of the nitrate of soda. If, therefore, a field exhausted by culture, which contains earthy phosphate scattered here and there, is manured with nitrate of soda or chloride of sodium, and by the action of rain a dilute solution of these salts is formed, a portion of them will remain undecomposed in the ground, and must in the moist soil exert an in- fluence, weak in itself, but sure to tell in the long run. Like carbonic acid generated by the putrefaction of vegetable and animal substances, and dissolving in water, these salt solutions become charged with earthy phosphates in all places where these occur. Now when these phosphates diffused through the fluid come into contact with particles of the arable soil not already saturated with them, they are thereby withdrawn from the solution, and the nitrate of soda or chloride of sodium remaining in solution again acquires the power of repeatedly exerting the same dissolving and diffusing action upon phosphates which are not already fixed in the soil by physical attraction, until these salts are finally carried down by rain-water to the deeper layers of the soil, or are totally decomposed. It is well known that chloride of sodium is present in the blood of all animals, and that it plays a part in the processes of absorption and secretion ; hence it may be regarded as indispensable for these functions. We find also that nature has endowed fodder-plants, tuber- ous and root-plants, which serve more particularly as food for cattle, with a greater power of taking up chloride of sodium from the soil than is possessed by other plants; and agricultural experience shows that the presence of a small amount of common salt is favourable to the luxuriant growth of these plants. 88 THE sOIL. Of nitric acid, it is generally assumed that it may, like ammonia, serve to sustain the body of the plant. Thus, chloride of sodium and the nitrates act in two distinct ways: one direct, by serving as food for the plant ; one indirect, by rendering the phosphates avail- able for the purposes of nutrition. The salts of ammonia act upon earthy phosphates in the same way as the salts just mentioned, but with this distinction, that their power of dissolving phos- phates is far greater; a solution of sulphate of ammo- nia will dissolve twice as much bone-earth as a solution of an equal quantity of chloride of sodium. However, as regards the phosphates in the soil, the action of the salts of ammonia can hardly be more powerful than that of chloride of sodiuin or nitrate of soda, since the salts of ammonia are decomposed by the soil much more speedily, and often even immediately ; so that, as a general rule, no solution of such a salt can be said to be actually moving about in the soil. But as a certain volume of earth, however small, is required to decompose a given quantity of salts of ammonia, the action of those salts upon this small volume of earth must be all the more powerful. While, then, the action of salts of- ammonia is barely perceptible in the somewhat deeper layers of the arable surface soil, that which they exercise on the uppermost layers is so much the stronger. Feichtinger observed that solu- tions of salts of ammonia decompose many silicates, even felspar, and take up potash from the latter. Thus, by their contact with the arable soil, they not only enrich it with ammonia, but they effect, even in its minutest particles, a thorough transposition of the nu- tritive substances required by plants. The vegetable and animal remains in a soil seem to exercise a remarkable influence upon the diffusion of silicates. The experiments made on this point show that the absorptive power of an arable soil for silicic acid is in an inverse ratio to the amount of organic re- mains in it; so that a soil rich in such remains will, when brought into contact with a solution of silicate of DEFICIENCY OR EXCESS OF SOLUBLE SsILICIC AciD. 89 potash, leave a certain amount of silicic acid unabsorbed, whereas an equal bulk of soil poor in organic remains will take up the whole of the silicic acid in the solution. The incorporation of decaying vegetable and animal matter will, therefore, in a soil containing disintegrable silicates, first of all accelerate the decomposition of the silicates, by the action of the carbonic acid generated in the process of decay, and then as these substances diminish the absorptive power of the soil for silicic acid, as soon as this acid has passed into solution, it is dis- tributed through the soil more widely than would have been the case had these substances not been present. On many fields poor in clay, the growth of grass for several years will, in consequence of the organic matters collecting in the soil, which serve to promote the distribution of the silicic acid, act more favourably on a succeeding crop of a cereal plant than a plentiful application of farm-yard manure, whose organic con- stituents, quite irrespective of the silicate of potash in the straw, are always in operation to effect the same object. On many other fields, especially on those abounding in lime, where there is no actual deficiency of silicie acid, but the quantity present is not properly distributed through the soil, a dressing of pulverised turf-waste often produces an equally favourable effect on a succeeding cereal crop as a plentiful application of farm-yard manure. Deficiency or excess of soluble silicic acid in the ground is equally injurious to the growth of cereal plants. A soil which would answer very well for horse-tail or common reed (Arundo phragmites, plants abounding in silica) is not on that account equally well suited for the superior kinds of meadow grass, or for cereals, although these demand a rich supply of silicic acid. Such a soil may be improved by drainage, which, by giving free access to air, decomposes and destroys the organic substances present in excessive quantity ; or it may derive benefit from a dressing of marl, or of burnt lime, slaked, or fallen to powder by moist air. 90 THE SOIL. Hydrated silicic acid loses its solubility in water by simple drying, and it frequently happens that the drainage of a marshy field will cause the siliceous plants (reeds and horsetail) to disappear. The action exerted upon the soil by hydrate of lime, or by lime slaked or fallen to powder in the air, is twofold. On a soil rich in humus constituents the lime combines, in the first place, with the organic compounds present, which have an acid reaction; it neutralises the acid of the soil, thereby causing the speedy disappearance of many weeds, such as bog-moss (Sphagnum) and reed-grasses, which flourish in a sour soil of this kind. Simple con- tact with acids powerfully promotes the oxidation of metals (copper, lead, iron), while contact with an alkali prevents it (iron coated with a dilute solution of carbon- ate of soda will not rust). Upon organic substances, the action is the very reverse: acids prevent, and alkalis promote, oxidation or decay. Excess of lime causes the aforesaid destruction of the humose con- stituents. In the same degree as the acid humus, by the action of lime, disappears from the ground, the absorptive power of the latter for hydrated silicic acid is increased 5 and the excess of this acid present loses its mobility in the soil.* The action of lime, as we see, is so complex, that from its favourable influence upon one field, it is scarcely ever possible to form an opinion of its probable action upon another field, the condition of which is unknown. This is possible only when the causes of its favourable action in the first case are clearly understood. When lime has improved the condition of a field, simply by neutralising the acid state of the soil, and * Jn an experiment made specially for the purpose, it was found that a litre (about a quart) of forest soil, containing 30 per cent. of humose con- stituents, absorbed from a solution of silicate of potash only 15 milli- grammes of silicic acid. But the same soil mixed with 10 per cent. of washed chalk (carbonate of lime) absorbed 1140 milligrammes; and when mixed with 10 per cent. of slaked lime instead of chalk, the absorptive power was increased to such a degree, that a litre absorbed 3169 milli-~ grammes of silicic acid. BENEFICIAL ACTION OF LIME. 91 destroying the injurious excess of vegetable remains, the farmer will in vain expect a favourable result from the application of lime in the following years, unless the same causes should recur which had originally impaired the fertility of the field. In a soil wherein there are putrescent and decaying substances not a single plant will thrive, except mush- rooms; and it seems that every chemical process going on in the neighbourhood of roots disturbs that of their own. Decaying substances in excess, by generating too much carbonic acid, injure even those plants which thrive particularly well in a humose soil containing a moderate quantity of humus.* Upon deep-rooting plants, such as turnips, clover, sanfoin, peas and beans, organic matters accumulating largely in the subsoil act very injuriously, especially in clay, where they decay much more slowly than in a lime soil. The process of decay is communicated to the sickening roots, in which spores of fungi find a suitable soil for their developement. When turnips are thus affected, they become the prey of certain insects, which deposit their eggs in the roots, causing in their develope- ment a strange alteration and disturbance of the vege- table process ; for in the diseased parts spongy tmuours arise, the inner substance of which becomes soft and emits a bad smell, and in this state serves to nourish the larva of the small fly. All these processes, however obscure in themselves, are put an end to by applying lime to such a field; a ig ted lime dressing will always attain this object. ields that are particularly rich in organic remains * Gasparini sowed a few grains of spelt in a pot with washed earth from Vesuvius; these produced plants which continued to grow in a healthy state. In another pot, filled with the same earth, he introduced a piece of bread; in this, all the roots in the immediate vicinity of the mouldering bread died away, and the other roots seemed to have turned off towards the sides of the pot. It is clear that spelt would not grow in a soil copiously mixed with bread; and if the decaying roots left by a spelt crop have the same effect, it is not difficult to conceive how the decaying remains which a plant leaves in the ground, may injuriously affect its own growth, or that of other plants. (Russell.) 92 THE SOIL. require a much larger supply of lime than others, to effect their restoration to a healthy state. It is certain, that in all such cases, the beneficial action of the lime is not attributable to an original deficiency of that body in the soil for plants growing on it; forin that case, considering the rapidity with which it is diffused through the soil, the effect would manifest itself very soon, and even in the course of the first year. But it takes several years before the favourable change in the condition of the soil is effected ; proving that the lime operates, not simply as food, but by producing an alteration in the soil, which requires time, that is, a succession of operations. On a drained marshy soil, in which lime has dimin- ished the excess of hydrated silicic acid, a second appli- cation will not produce the same result, because the offensive substances, once removed, will not return; while on a heavy, stiff clay or loam, the application may be repeatedly successful. These kinds of soil are thereby made more friable and richer in available potash. The nature of the change produced is most clearly shown in the hydraulic lime obtained by cal- cining native cement stones (a hard marl). These cement-stones consist of a mixture of lime and clay, the former being in larger proportion than in calcareous elay soil. After burning, if it is stirred up with a large quantity of water, the separated potash imparts to the fluid all the properties of a weak lye. Glay which before calcination with lime refused to dissolve in acids, is, after calcination, soluble in acids to the whole extent of the silicic acid present. A calcareous clay soil withdraws from a solution of silicate of potash much less potash after calcination than before, but a much larger quantity of silicic acid.* Besides the chemical agents mentioned here, which * At Bogenhausen, near Munich, loam was calcined in the air, and brought into contact with a solution of silicate of potash ; before calcina- tion, a litre of this earth took up 1148 milligrammes of potash, and 2007 milligrammes of silicic acid; after calcination, no potash, and 3230 milli- grammes of silicic acid. THE ROOT GOES IN SEARCH OF FOOD. 93 the farmer may employ to effect the proper distribution of the nutritive substances stored up in his field, and to make the earthy phosphates, the potash, and the silicic acid available to the roots of the plants, he further im- proves his land by the mechanical operations of agricul- ture, and by removing from the soil all obstacles that hinder the spreading of the roots, as well as those in- jurious agencies which interfere with their normal ac- tivity, or endanger their healthy condition. The effect produced by breaking up the ground by the plough, spade, hoe, harrow, and roller, depends upon the fact, that the roots of plants go in search of their food; that the nutritive substances have no loco- motion of their own, and cannot of themselves leave the place in which they are. The root, as if it had eyes to see, bends and stretches in the direction of the nutri- ment; so that the number, thickness, and direction of its filaments indicate the precise spots where they have obtained food.* The young root forces its way, not like a nail driven with a certain force into a plank, but by the addition of successive layers, which increase its mass from within outwards. The new substance, which lengthens the extremity of the root, is in contact with the soil. The newer the cells forming at the extremities, the thinner are their walls ; as they grow older, the cell-walls thicken, and their outer surface, becoming more woody, is coated in many cases with a layer of corky substance, which, being impenetrable by water, affords, to the soluble matter deposited within, some protection against os- motic influences. * Pieces of bone are often found completely enclosed by a network of turnip-roots. It is difficult to understand how this could have been accom- plished otherwise than by an attraction between the spongioles and the substance of the bone. The cells, or their contents, are incessantly attracted by the fresh surface of a substance, for which the contents have a chemical attraction. It is owing to this attraction that the roots wind round the piece of bone ; they form a root-ball rolled, not from without, but from within, by the new cells constantly formed upon contact with a substance for which they possess a chemical attraction. (Russell.) 94 THE SOIL. Absorption of nutriment from the soil is effected by the extremities of the roots, whose fluid contents are separated from the earthy particles around them by an exceedingly thin membrane alone; and the contact of the two is the more intimate, as the root-fibre during its formation exerts upon the earthy particles a pres- sure sufliciently powerful, under certain circumstances, to push them aside. The evaporation of water from the leaves produces a vacuum within the plant, whereby a draught is created, which powerfully assists the con- tact of the moist earthy particles with the cell-wall. The cell and the earth are pressed against each other. Between the fluid contents of the cells and the nutritive substances physically combined in the earthy particles, there manifestly exists a strong chemical attraction, which, with the cooperation of carbonic acid and water, causes the transference of the incombustible matters into the system of the plant. By the powerful chemical attraction of any body, we understand its entering into a chemical combination, in which it loses its original properties and acquires new ones. In the case of potash, lime, and phosphoric acid, such a combination must take place immediately upon their passage into the cell; for, as already stated, the sap of the roots is always slightly acid. In the sap of the root-shoots of the vine, we can always detect bitartrate of potash ; in that of others, oxalate or citrate of potash, or tartrate of lime; but we never find these bases combined in such saps with carbonic acid, nor can phosphate of lime or magnesia be detected. If the fresh sap of the potato-tuber is mixed with ammonia, no precipitate of phosphate of magnesia and ammonia is produced; but this precipitate makes its appearance as soon as the fermentation of the sap has destroyed the (azotised) substance with which the phosphate of magnesia is combined. Careful mixture and distribution of the nutritive substances present in the soil, are the most important means of rendering them effective. A piece of bone, weighing half an ounce, placed in DISTRIBUTION RENDERS FOOD EFFECTIVE. 95 a cubic foot of earth, has no perceptible influence upon its fertility ; but when uniformly distributed and phys- ically combined with the minutest particles of the same earth, it attains a maximum of eflicacy. ‘The influence of the mechanical operations of agriculture upon the fertility of a soil, however imperfectly the earthy parti- cles may be mixed by the process, is remarkable and often borders upon the marvellous. The spade, which breaks, turns, and mixes the soil, makes a field much more fruitful than the plough, which breaks, turns, and displaces the earth, without mixing it. The effect of both is increased by the harrow and the roller, so that, in the very same places where a crop has grown during the preceding year, a fresh crop will find nutriment ; in other words, the earth is not yet exhausted. The action of chemical agents in distributing the food-elements of plants is still more powerful than that of the mechanical. By applying, in proper quantities, nitrate of soda, salts of ammonia, and chloride of sodi- um, the farmer not only enriches his field with materials capable of taking part in the nutrition of plants, but he also effects # distribution of the ammonia and potash, thereby replacing or aiding the mechanical work of the plough, and the influence of the weather in the time of fallow. We are in the habit of calling ‘manures’ all those materials which, when applied to our fields, increase the crops; but the same effect is produced by the plough. It is evident that the mere fact of a favour- able influence exerted by chloride of sodium, nitrate of soda, salts of ammonia, lime, and organic matter, affords no conclusive proof that these have acted as nutritive substances. The work performed by the plough may be compared to the mastication of food by those special organs with which nature has endowed animals ; and nothing can be more certain than that the mechanical operations of agriculture do not add to the store of nutritive substances in a field, but that they act beneficially by preparing the existing nutri- ment for the support of a future crop. With equal 96 THE SOIL. certainty we know that chloride of sodium, nitrate of soda, salts of ammonia, humus, and lime, beside the ac- tion peculiar to their elements, perform also a kind of digestive function comparable to that of the stomach in animals, and in which they may partly replace each other. These substances, therefore, act beneficially upon those kinds of soil only in which there is a defect, not in the quantity; but in the form and condition of the nutritive elements; and they may accordingly in their permanent action be replaced by a mechanical commi- nution, or exceedingly fine pulverisation of the soil. The true art of the practical farmer consists in rightly discriminating the means which must be ap- plied to make the nutritive elements in his field effect- ive, and in distinguishing these means from others which serve to keep up the durable fertility of the land. He must take the greatest care that the physical condi- tion of his ground be such as to permit the smallest roots to reach those places where nutriment is found. The ground must not be so cohesive as to prevent the spreading of the roots. In a stiff, heavy soil, plants with fines slender roots will never thrive well, even though the supply of nutri- tive substances be ample; and in these circumstances, the beneficial influence of green manure and fresh sta- ble dung is unmistakeable. The mechanical condition of the soil is, in fact, altered in a remarkable way by the ploughing in of plants and their remains. . 429 635 385 97 862 1854. Clover-hay ... 365 1615 137 1824 —* Here, again, what strikes us first is that the returns from all the fields were different from one another, and that apparently they did not bear the most remote rela- tion to the quantity of manure applied. Nothing can be more certain than the fact that a field, exhausted by cultivation, will yield larger returns if dressed with farm-yard manure than if unmanured : * The clover crop failed from excessive wet. 204 THE SYSTEM OF FARM-YARD MANURING. now, taking the increase to be caused by manure, it is natural to suppose that the same quantity of manure would produce the same increase upon diiferent fields. The following table, however, shows that the same quantity of manure, upon the Saxon fields, produced results which differed very considerably. One hundred cot. of farm-yard manure gave increased produce. Cunnersdorf. | Mausegast. Kotitz. Oberbobritzsch.| Oberschéna. Ibs. Ibs. Ibs. Ibs. Ibs. 1851-53. Winter rye & t 1539 1070 988 515 501 O2Usioes- e 1852. Potatoes.'.. . 720 i223 917 696 628 1854. C@lOVierscrg.t ss 203 832 60 628 — No one looking at these numbers could divine that they were intended to represent the effects produced upon five different fields by an equal quantity of the same manure, and that too the universal manuring agent. Neither in the crop of rye-corn and straw, nor in that of potatoes, oats, and clover, is there the slightest resemblance or correspondence ; still less is it possible to discover what amount of manure has been instru- mental in producing the increased crops. The same quantity of farm-yard manure gave, in the years 1851 and 1853, at Miausegast double, at Cunners- dorf three times, the increase of cereal crops, corn and straw together, that was obtained at Oberbobritzsch : the increase of the potato crop at Miusegast was twice as large as in Ko6titz; of clover, four times more in Miusegast than in Cunnersdorf; and in Oberbobritzsch, ten times as much as in Kotitz. The enormous quantity of farm-yard manure put upon the field at Oberschéna failed to produce anything like the crop obtained from the unmanured field at Mausegast. CROPS FROM FARM-YARD MANURE VARY. 205 The composition of farm-yard manure, as we know from numerous analyses, is on the whole so much alike in all places, that we may suppose without great risk of error that in 100 ewt. of farm-yard manure every field receives the same nutritive substances and in the same quantities. The constituents of farm-yard manure act every- where in the same way upon the soil or the earthy par- ticles. Now this apparently involves an irreconcilable contradiction with the fact that the increase obtained by it is nevertheless everywhere different, and that the dung-constituents supplied will, on one field, set in motion and render available to the cereal or potato plants growing on it, twice or three times as many ele- ments of food as on another field. This fact does not refer to the Saxon fields alone, but applies generally. Nowhere, in no country, do the crops obtained by farm-yard manuring on different fields ever correspond, as the following table of the average produce of divers crops in different provinces of the kingdom of Bavaria will show. AVERAGE Crops IN Bavaria. (Seuffert’s Statistics.) One day’s work yields average produce in bushels.* | Wheat.| Rye. | Spelt. | Barley. | Oats. UppersBavaria « ., ois 4... <2) 146 lbs. 330—845 Ibs. BeBe oo cats Bet arate ok a 128 ‘* 290—300 ‘ YC". oso faon ohh. Bande 140 “ 818—325 ‘ Gian cate ees. cs ta. 2 88‘ 200—800 ‘* Spelt (in the husk).......... gis 174—220 * According to this scale, the weight of a Prussian bushel of wheat is 206 THE SYSTEM OF FARM-YARD MANURING. The crops produced by farm-yard manuring differ not only in every country, but even in every locality ; and, strictly speaking, every field dressed with farm- yard manure yields an average produce of its own. The action of farm-yard manure upon the increase of produce is intimately connected with the condition and composition of the soil; it varies, therefore, in dif- ferent fields, simply because the composition of the soil varies. To understand the action of farm-yard manure, it is necessary to remember that the exhaustion of a field arises from the loss of a certain amount of nutritive con- stituents, at the end of a rotation, inflicted upon the soil by preceding crops, which of course leave less avail- able food in the soil for the following crops. However, the loss of each individual constituent has not the same effect upon the exhaustion of the soil. The loss of lime which a calcareous soil suffers by a cereal or by clover, matters little to the growth of a succeeding plant that requires large quantities of lime to thrive well. The same applies equally to the loss of potash, magnesia, iron, phosphoric acid, nitrogen, on fields severally abounding in potash, magnesia, iron, phosphoric acid, or ammonia. Where a soil is abun- dantly provided with one of the mineral constituents, the amount of that constituent removed by the crops is so small a fraction of the whole mass, that the effect of the diminished store is not appreciable from one rotation to another. But practical experience shows that the crops do de- crease from one rotation to another, and that the land requires a fresh supply of certain ingredients by manur- ing, if it is again to produce as large harvests as before. Now, as a supply of lime cannot be expected to re- store the fertility of an exhausted field where lime con- stitutes the principal bulk of the soil, just as little as a supply of potash or phosphoric acid to a field abounding in potash or phosphoric acid, it is easy to understand 83 lbs., and that of the English quarter 425 Ibs., 100 lbs. (Zollv. weight =110+2 lbs. avoir.). CROPS, HOW GOVERNED. 207 that where the productive power of an exhausted field is restored, the fertilising effect is to be attributed sim- ply to the manure returning to the field those elements of food which the soil originally contained in the least proportion, and of which it has accordingly lost, by the preceding crops, comparatively the largest fraction. Every field contains a maximum of one or several, and a minimum of one or several, other nutritive sub- stances. It is by the minimum that the crops are goy- erned, be it lime, potash, nitrogen, phosphoric acid, magnesia, or any other mineral constituent; it regu- lates and determines the amount or continuance of the crops. Where lime or magnesia, for instance, is the mini- mum constituent, the produce of corn and straw, tur- nips, potatoes, or clover, will not be increased by a sup- ply of even a hundred times the actual store of potash, phosphoric acid, silicic acid, &c., in the ground. But a simple dressing with lime will increase the crops on a field of the kind, and a much larger produce of cere- als, turnips, and clover will be obtained by the use of this agent (just as is the case by the application of wood-ashes on a field deficient in potash) than by the most liberal use of farm-yard manure. This sufficiently explains the dissimilar action upon different fields of so composite a manure as farm-yard dung. Only those ingredients of farm-yard manure which serve to supply an existing deficiency of one or two of the mineral constituents in the soil act favourably in restoring the original fertility to a field exhausted by cultivation; all the other ingredients of the manure, which the field contains in abundance, are completely without effect. A field rich in straw-constituents cannot be made more productive by manuring with straw-constituents in the dung, whereas these constituents will prove most efficacious on fields deficient in them. If two fields have the same abundance of straw-con- stituents, but are not equally rich in corn constituents, 208 THE SYSTEM OF FARM-YARD MANURING. the same supply of farm-yard manure will not produce, by any means, equal crops of corn, because these must bear a relation to the corn-constituents supplied in the manure. Of these, both fields received the same amount in the same quantity of manure; but as the one field, of itself, was richer in corn-constituents than the other, the poorer of the two must receive much more manure to make it produce as large crops as the other. A comparatively small quantity of superphosphate will, on a field of the kind, serve to increase the produce to a much greater extent, than the most liberal use of farm-yard manure. Upon a field deficient in potash farm-yard manure acts by the potash contained in it ; upon a soil poor in magnesia or lime, by its magnesia or lime; upon one poor in silicie acid, by the straw in it; upon land poor in chloride or iron, by the chloride of sodium, chloride of potassium, or iron contained therein. This fact accounts for the high favour in which farm-yard manure is held by practical farmers. As the dung of the farm-yard contains, under all circumstances, a certain quantity of each of the mineral constituents withdrawn from the soil by the crops grown on it, its action is universally beneficial. It never fails to pro- duce the desired effect, and thus spares the practical man the trouble of devising more suitable and equally efficacious means for keeping up the fertility of his fields, with a less profuse expenditure of money and labour, or of raising his land, without additional outlay, to the highest attainable degree of fertility compatible with its composition. It is well-known in practice, that the produce of many fields may be increased by manuring with guano, bone-dust, rape-cake, and other substances containing only certain constituents of farm-yard manure; and their operation is explained, in effect, by the doctrine of minimum, which I have just laid down. But as the practical farmer is not acquainted with the law which regulates the operation of these manur- ERROR IN USING TOO MUCH MANURE. 209 ing agents as affecting the increase of produce, he can, of course, have no correct notion of their rational, which means their tfuly economical, use ; he puts on his land too much, or too little, or chooses the wrong agent. The error of employing too little manure needs no ex- planation ; for every one knows that the right propor- tion of manure will, with exactly the same labour and at a trifling additional outlay, ensure the maximum produce of which the land is capable. The error of using too much manure arises from the mistaken notion that the action of manures is propor- tionate to the quantities in which they are applied ; this is true up to a certain limit, but beyond this all the manure applied is simply thrown away, as far as any fertilising action is concerned. A manuring experiment made by Mr. J. Russetr, of Craigie House (‘ Journal of the Royal Agr. Soe. of England,’ vol. xxii. p. 86), may, perhaps, serve to illus- trate our meaning. In this experiment a field was divided into a number of plots of three rows each, all planted with turnips, some of the plots being left un- manured, the remainder dressed severally with different manuring agents, among others with superphosphate (bone-ash dissolved in sulphuric acid). The produce, calculated per acre, was as follows :— Produce per acre. No. of piots. Cwt. PE PUMIMATULC Or. ous selene sigs soe ..+..--- 9340 turnips (Swedes). Il. oe hogntic. cp hobookwodpane moe 820 BZ V. Manured with 5 cwt. of superphosphate.. 535 s Wil. - Be 5 ty oo, All oa Vil. i Br #8 eS .. 480 - VIll. ss a fvetels 5 Si EX. a 10 “ “c 490 “c As shown by the difference of 20 ewt. in the produce of the unmanured plots, the condition of the soil and the store of mineral constituents differed, to some ex- tent, in different parts of the field. Other experiments, which we cannot describe more particularly, showed that the soil was poorer in the centre of the field than on the sides. 210 THE SYSTEM OF FARM-YARD MANURING. The one great fact most clearly proved by the above table of produce is, that 3 ewt. of superphosphate gave nearly the same crop of turnips as 5 ewt.; and that a further increase of the manure to 10 cwt. produced no additional increase of the crop. No steps were taken, in these experiments, to ascer- tain which of the constituents of superphosphate of lime had the principal share in increasing the produce of the field. Magnesia and lime, as well as sulphuric and phosphoric acid, are equally indispensable elements of food for the turnip plant ; and I have observed that by manuring with gypsum and a little common salt or with phosphate of magnesia, a field will be made to give more abundant crops than-by employing superphos- phate of lime, although the latter unquestionably proves the most effective manure for most fields. To apprehend these facts correctly, we must remem- ber that the law of the mznimum does not apply to one constituent alone, but to all. Where, in any given case, the crops of any plant are limited by a minimum of phosphoric acid in the field, these crops will increase by augmenting the quantity of phosphoric acid up to the point at which the additional phosphoric acid bears a proper proportion to the next minimum constituent in the soil. If the additional phosphoric acid exceeds the corre- sponding quantity, for instance, of potash or ammonia in the soil, the excess will prove of no effect. Before the supply of phosphoric acid the available quantity of potash or ammonia was a little larger than the amount of phosphoric acid in the soil, and the excess of the alkalies was ineffective until the phosphoric acid was supplied ; similarly the excess of phosphoric acid must remain just as inoperative, as previously the excess of potash. Whilst the produce before was proportionate to the minimum of phosphoric acid, it is now in proportion to the minimum of potash or ammonia, or both alkalies. A few experiments made on Mr. Russell’s field might have settled the question. Had potash or ammonia THE LAW OF MINIMUM. 211 been the minimum, after manuring with superphos- phate, a suitable supply of potash or ammonia, or both, would have increased the produce. In this same series of experiments, 6 cwt. of guano, corresponding to 2 ewt. of superphosphate, gave a crop of 630 ewt. of turnips, or 130 ewt. more than the superphosphate ; but it is left in doubt whether this increase was attributable to the potash or the ammonia in the guano. To return to our Saxon experiments. If we look at the different quantities of dung applied severally on the five fields, we are naturally led to inquire the reason of this diversity. The most feasible answer, perhaps, is, that the far- mer gives as much manure as he has at his disposal, or that he regulates the quantity according to certain facts. If he has found by experience that a certain quantity of farm-yard manure will restore his land to its original fertility, and that more copious manuring will fail to give larger crops, in proportion to the addi- tional supply, or to the cost incurred in collecting the manure, he will stop at the smaller quantity. Hence it cannot be regarded as a mere accident that the farmer at Cunnersdorf contented himself with 180 ewt. of farm-yard manure, while the farmer at Ober- bobritzsch laid 314 ewt. upon his field. But if the quantity of manure to be applied is not dependent upon chance or caprice, but is regulated by the object in view, it is manifest that the proceedings of the farmer are governed by a law of nature unknown to him, except by its effects. It is in the composition and condition of the soil that we must seek the law which regulates the quantity of farm-yard manure required, at the outset of a fresh rotation, to restore a field to its former fertility ; and it is not difficult to see that this quantity must always be proportionate to the effective dung-constituents already present in the soil; a field largely abounding in them takes less manure than a poor field to give the same increased produce. _ Now, as farm-yard manure owes its most active 212 THE SYSTEM OF FARM-YARD MANURING. constituents to clover, turnips, and the grasses, the in- ference is pretty clear that the quantity of this manure required on a tield is in an inverse ratio to the produce of clover, turnips, or grass, which the field can give when unmanured. The Saxon experiments show that this inference cannot be far from the truth, in one respect at least ; for on comparing the produce of clover given by the unmanured plots with the quantity of farm-yard manure applied, we find :— Clover crops in 1854. Cunnersdorf. Miusegast. Kotitz. Oberbobritzsch. Oberschéna. Pounds.. 9144 5583 1095 911 — Quantity of manure applied in 1851. Cwt..... 180 194 229 314 897 The field at Cunnersdorf which contained the largest store of dung-constituents received the smallest; the field at Oberbobritzsch which gave the smallest crop of clover, the largest quantity of farm-yard manure. The crop of clover, however, is not the only factor to determine the amount of farm-yard dung required for manuring ; for one of the clover-constituents, silicic acid, which is indispensable to the cereal plants, is present only in trifling proportion, and hence the quan- tity of farm-yard manure (straw-manure) must bear a detinite ratio to the quantity of straw-constituents already present in the ground. If, in the Saxon experiments, we compare the in- creased produce of corn and straw obtained from the fields manured with farm-yard dung, we find :— Increase of produce by farm-yard manuring, per acre. Cunnersdorf. Kotitz. | Obverbobritzsch. Quantity of farm-yard manure.... 180 cwt. 229 ewt. 314 cwt. (Olea slabs Gandy ob dsodansodse doc 347 Ibs. 352 Ibs. 452 lbs. Sicha tedbecgdcoavoes odedabS ais 1743“ 1006 * 914 ‘ The field in Cunnersdorf, manifestly the richest in substanees nutritive for straw, gave the largest straw- RATIONAL SYSTEM OF FARMING. 9138 crop, although it had received the smallest quantity of farm-yard manure. In the increased produce, corn was to straw as 1: 5, clearly showing that sparing applica- tion of straw manure was the proper course to pursue here. This fact readily explains also why the field at Oberbobritzsch, comparatively poorer in straw-constitu- ents, required 85 ewt. of farm-yard manure more than the Kétitz field, to. enable it to maintain, in its in- creased produce, the same proportion of corn and straw (1 : 2) as in the crop from the unmanured plot. These considerations might, perhaps, lead the prac- tical] farmer to the conviction that he is, after all, not much of a free agent in the cultivation of his fields, and that the ‘ facts and circumstances’ which guide him in his proceedings are simply laws of nature, of whose existence he has scarcely any conception. In truth, it may be said that the agriculturist is a free agent only in his wrong-doings. If he acts in accordance with his own interest, he must allow himself to be guided, even though unconsciously, by the condition of his land; and the only matter for wonder is, how far the man of ‘ ex- perience’ has succeeded in this way. A system of farming, to be called truly rational, must be exactly suited to the nature and condition of the soil; for it is only when the rotation of crops or the mode of manuring is conformable to the composition of the soil, that the farmer has a sure prospect of realising the highest possible returns from his labour or from the capital invested. Now considering, for instance, the great difference in the condition of the soil at Cunnersdorf and Ober- bobritzsch, it is self-evident that the same rotation of crops which suits the one field, will not answer equally well for the other. If farmers would only make up their minds to ac- quire by experiments on a small scale,* an accurate knowledge of the productive power of their land for certain kinds or classes of plants, a few more experi- * In a field of pretty uniform composition, experiments of this kind may be made with flower pots sunk in the earth. 914 THE SYSTEM OF FARM-YARD MANURING. ments would readily enable them to discover what nutritive substances their land contains in minimum proportion, and what manuring agents ought to be ap- plied to ensure the production of a maximum crop. In matters of this kind the farmer must pursue his own course, and the proper course is the one that will most fully secure the object he has in view; he must not put the least faith in the assertion of any foolish chemist, who wants to prove to him analytically that his field contains an inexhaustible store of this or that nutritive substance. For the fertility of a field is not proportionate to the quantity of one or several food elements analytically shown to exist in it, but to that fraction of the total nutritive substances which the field is able to give up to the plants ; and the only means of determining that fraction is by the plant itself. The most that chemical analysis can do is to supply a few data for comparing the condition of two fields. The experiments made by the beet-root growers on the ex- tensive tract of land in Russia, known as the Zscherno- sem or ‘* Black soil, whose fertility for corn plants is proverbial, show that this earth, though analytically proved to contain upon the whole, to the depth of twenty inches, 700 to 1000 times the quantity of potash required for a full beet-root crop, is, after three or four years’ cultivation, so exhausted, that without manuring it will no longer yield a remunerative crop of beetroot.* In the produce of cereals there is only one proper proportion between grain and straw; but the unfavour- * With regard to the general opinion about the abundance and inex- haustibility of potash in land, the following announcement, in the ‘ Badische Centralblatt fiir Staats und Gemeinde-Interessen,’ May 1861, is not without interest. ‘In the District of Bretten.—The contracts which usually take place in the early part of the year for the cultivation of beetroot, are now fully open for competition in this district, and for good articles 30 francs the ewt. are offered this year, whereas last year only 26 franes were paid. Notwithstanding this rise of prices, and the premiums offered for superior roots, not many transactions have been concluded. The reason of this is quite intelligible, for the very injurious effects resulting to land on which this product has been cultivated, are too well known.’ The effects must have reference to fields which had been adequately manured, for otherwise no profitable returns can be expected. PERMEABILITY OF SOILS TO MANURES. 915 able proportions are many. It is clear that the mass and extent of the organs for the formation of grain (in other words, the bulk of the straw) must bear a definite relation to the product, that is, to the quantity of grain produced: any excess or deficiency in the amount of straw must always act injuriously upon the grain crop. When it is known that, on a given field, one part by weight of corn to two parts by weight of straw is the most favourable proportion for the production of rain, then, according to theory, the manuring of the eld should not be such as to cause any marked altera- tion of this relative proportion in the increased prod- uce; that is to say, the several manuring substances should be selected and laid upon the field in such quan- tity and relative proportion, that the composition of the soil may remain the same as it was before. It is well known that certain manuring substances are especially favourable to the formation of the herbaceous parts of plants, others to that of seed. Phosphates, as a general rule, increase the grain crop: whilst of gypsum it is well known that where that substance effects an increase in the produce of clover-hay, this increase is always attended with a marked diminution in the prod- uce of seed. The cultivation of potatoes or Jerusalem artichokes tends to reduce the excessive accumulation in the arable surface soil, of substances which promote the formation of the herbaceous parts of plants. Theoretically, therefore, it is not impossible to main- tain a certain uniformity of composition in the soil of a field; but this cannot be effected by carrying on the husbandry of an estate by the system of farm-yard manuring. It will hereafter be shown that by the con- tinuous and exclusive use of farm-yard manure, the composition of the soil is found changed after each rotation. The last point which claims our attention, in refer- ence to the Saxon experiments, is the difference in the permeability of the soil to the dung-constituents in the different localities. The depth to which the alkalies, the ammonia, and the soluble phosphates penetrate, 216 THE SYSTEM OF FARM-YARD MANURING. depends of course upon the absorptive power of the soil; now, assuming, for the sake of illustration, the soil of a field to be divided from the top downwards into distinct layers, which are not of course sharply sepa- rated from one another, we find that in some localities the dung-constituents stop in the upper layers, whilst in others they penetrate to the deeper layers of the ground. Thus, for instance, in the Cunnersdorf field the clover crop had derived no benefit from the farm- yard manure, being about only 4 per cent. larger than the produce given by the unmanured plot; whereas at Miiusegast the manuring caused an increase of 30 per cent., and at Oberbobritzsch of 200 per cent. This result shows that certain mineral constituents, indispen- sable for clover, penetrated much deeper into the ground at Miusegast and Oberbobritzsch: than at Cun- nersdorf and Kotitz; or, what comes to the same, that, in the two latter places, they were, on their way down- wards, retained by the upper layer of the soil. On comparing the crops given by the unmanured plot at Cunnersdorf with those obtained from the unmanured plots in the other localities, we see that the Cunners- dorf field contained nearly as large a store of straw constituents as the fields at Kétitz and Oberbobritzsch, while it was decidedly poorer in the principal grain constituents, namely, in phosphoric acid and, perhaps, also in nitrogen. Hence, with an equal supply of phosphates and ammonia on the three fields, the top- most layer of the ground at Cunnersdorf, being poorer in these constituents, would retain a great deal more of them than that of the other two fields. The increase in the potato crop and in the produce of oat-grain and straw, on the Cunnersdorf field, clearly indicates that certain dung-constituents made their way to that layer of the soil from which the roots of the oat- plant principally derive their food, which layer, being richer in corn and straw constituents than the arable surface soil, permitted a small proportion of nutritive substances to pass through it and thus reach the clover. If we compare with this the field at Kotitz, and look COMPARISON OF RESULTS IN AGRICULTURE. 217 at its extraordinarily scanty crop of oat-grain and straw, we see at once that in the latter field the deeper layers of the soil were much poorer in corn and straw con- stituents, but that the topmost layer was much richer in corn constituents than the land at Cunnersdorf. Although the Kotitz field received above 25 per cent. more farm-yard manure than the Cunnersdorf field, yet only a very insignificant portion of that manure found its way down to the clover, as the layer above had retained the substances nutritive to clover, and these had principally served to benefit the oat- eat The increase in the produce of oat-grain at 6titz was more than double that obtained from the Cunnersdorf field. At Miusegast the relations were similar; from the uncommon abundance of corn and straw constituents in the arable surface soil, the absorp- tive or retentive power of the latter for the dung-con- stituents in solution was comparatively less, and a con- siderable proportion of these substances was thus per- mitted to reach the deepest layers. The uniform rise of the successive crops obtained from the manured field at Oberbobritzsch evidently shows a very uniform dis- tribution of active dung-constituents, such as might be expected in a soil which, though not exactly sandy, yet contained a larger proportion of sand than any of the other experimental fields. It is easy to see, that by knowing the absorptive power of the arable soil in these several fields, the farmer is enabled to determine beforehand to what depth the nutritive substances supplied in the manure will penetrate into the ground; and it follows, as a matter of course, that he is able to apply with greater effect the mechanical means at his disposal for promot- ing the distribution of these elements in the soil, in the right places and in the proper manner. It would answer no good purpose to expatiate still further on this point ; my object has been to direct the attention of the farmer to the different facts or phenom- ena which are presented by his land during the process of cultivation; because a closer observation of each 10 218 THE SYSTEM OF FARM-YARD MANURING. phenomenon will lead him to reflect upon the cause of it. This is the way to obtain an accurate knowledge of the state and condition of the soil. Observation and reflection are the fundamental con- ditions of all progress in natural science; and agricul- ture presents, in this respect, ample room for discov- eries. What must be the feelings of happiness and contentment of the man who, by skilfully turning to proper account his intimate knowledge of the peculiari- ties of his land, has succeeded, without increased appli- cation of labour or capital, in gaining from it a perma- nent increase of produce? For such a result is not only a personal advantage to himself, but a most im- portant benefit conferred upon all mankind. How paltry and insignificant do all our discoveries and inventions appear, compared to what is in the power of the agriculturist to achieve! All our advances in arts and sciences are of no avail in increasing the conditions of human existence ; and though a small fraction of society may by their means be gainers in material and intellectual enjoyment, the load of misery weighing upon the great mass of the people remains the same. A hungry man cares not for preaching, and a child that is to learn anything at school must not be sent there with an empty stomach. Every step in advance, however, made by agricul- ture serves to alleviate the sufferings and troubles of mankind, and to make the human mind susceptible and capable of appreciating the good and the beautiful that art and science present to us. Improvements in agriculture constitute the only solid foundation for fur- ther progress in all other branches of knowledge. We now proceed to consider the changes brought about in the composition of the soil of a given field by cultivation by the system of farm-yard manuring. The cause to which the restoration of the power of produc- tion in the soil by farm-yard manure is attributable, is the same in the case of all soils, without exception, however widely the rotations may differ, or whatever be the nature of the crops cultivated upon them. » MINERAL MATTERS RESTORED BY MANURE. 219 By the cultivation of cereals, and the removal of the corn-crops, the arable surface soil loses a certain por- tion of corn-constituents, which must be restored to it by farm-yard manure, if the future crops are to be kept up to the mark of the preceding ones. This restoration is effected by the cultivation of fod- der-plants, such as turnips, clover, grass, &e., on which the cattle on the farm are fed, and the constituents of which are drawn, in large proportion, from the deeper layers of the ground, where the roots of the cereals cannot penetrate. These fodder plants are consumed either on the field itself, as turnips in England, or in the stalls. A frae- tion of the nutritive substances contained in these plants remains in the body of the animals fed upon them, while the remainder, ejected in the form of solid or liquid excrements, constitutes farm-yard manure, the principal bulk of which, however, consists of straw which has served for litter. In Germany animals are not fed upon potatoes themselves, but upon the refuse from the distilleries of potato spirits, which contains all the nutritive substances taken away from the soil in the potato crop, together with the constituents of the barley-malt that have been used in the process of mashing. Since the whole of the straw taken away in the crops of the preceding rotation is, as a general rule, returned to the arable soil in the shape of farm-yard manure, the field is, at the outset of the new rotation, as rich as before in the conditions for the production of straw; and there exists, under these circumstances, no ground for a diminution of the straw-crops. With regard to the clover, turnips, potato-waste, &e., upon which the stock on a farm is fed, there re- mains, as already stated, in the bodies of the horses, cattle, &e., and full-grown animals in general (which no longer materially increase in weight), only a very small fraction of the constituents of the food consumed ; but in the young cattle sent to market, in the bodies of the sheep, in the milk and cheese, a portion of these 220 THE SYSTEM OF FARM-YARD MANURING. constituents is retained, which is not returned to the soil in the farm-yard manure. The loss of phosphoric acid and potash which the soil sustains by the sale of cattle and of animal products (wool, cheese, &c.), may be estimated at one-tenth of the quantity of these min- eral constituents contained in the potatoes, turnips, or clover; and even this estimate is, perhaps, too high. At all events, it is risking no great error to assume that nine-tenths of all the constituents of the clover, potatoes, or turnips, are returned to the field in the farm-yard manure; whence the arable surface soil, after manuring, is richer for the new rotation in the mineral constituents of potatoes, clover, and turnips, than it was before, as the constituents of the two latter plants have been brought up from the deeper layers of the ground. The far greater portion of the active dung-constitu- ents is retained by the upper layers of the soil, the deeper layers getting back very little of what has been taken from them; the power of the latter, therefore, to produce as large crops of clover or turnips as before is not restored. The soil constituents which the animals have derived from the turnips, clover, potatoes, &c., and which re- main in their bodies, are very nearly identical, in quantity and quality, with those of the cereals; hence the loss sustained by the land may be estimated as equal to the corn-crops sold, plus the corn-constituents which the fodder-plants have given up to the animals on the farm. The restoration of the power of a field to produce a crop of corn as large as the last naturally presupposes that the conditions required for the production of the new crop should remain the same in the very layer of the soil which supplied the preceding crop; in other words, the substances nutritive to corn which were taken away must be fully returned to the arable surface soil. If farm-yard manure contained only the constituents of straw and potatoes, and nothing else, manuring a THE ELEMENTS OF FOOD IN FARM-YARD MANURE. 221 field with it could merely restore the productive power of the arable soil for straw and potatoes, but not for corn. Under these circumstances it would remain as rich as before in food elements for straw and potatoes, but would be poorer for corn to the extent of the whole quantity of corn-constituents taken away in the crops. If farm-yard manure is to restore the former produc- tiveness of a field for corn, it must necessarily contain an amount of corn-constituents corresponding to the loss sustained, that is to say, as much or even more than has been removed. The amount of the elements of food for corn con- tained in the farm-yard manure naturally depends upon the sum of these elements which have passed over into manure, from the cattle feeding upon clover or turnips. Where this supply exceeds the loss sustained, the arable soil is actually made richer in corn-constituents ; but in that case it is enriched also in the conditions for an increased produce of straw and tuberous plants. Where, therefore, the farm-yard manure (by the clover or turnip constituents in it) increases the amount of phosphoric acid and nitrogen in the arable soil, it in- creases, in a much greater proportion, the quantity of potash and lime, and to some extent also that of silicic acid ; and since, as already stated, the whole of the straw-constituents removed from the field are brought back to it in that manure, higher crops of corn, straw, and potatoes are the natural result. This increase of the produce of all cultivated plants drawing their principal food from the arable surface soil, may go on for a very long time, but in all fields it has a certain appointed limit. The time comes, sooner or later, for every field, when the subsoil (which is to the clover or turnips what the arable surface soil is to the cereals), suffering a continued drain upon its stores of phosphoric acid, potash, lime, magnesia, &c., begins to lose its produc- tive power for clover or turnips; and thus the nutritive substances, taken away from the arable surface soil in the corn crops, are no longer replaced from the store 222, THE SYSTEM OF FARM-YARD MANURING. which existed in the deeper layers, and was brought up by the clover or the turnips. But the high returns of corn given by a field do not necessarily decline with the incipient failure of the clover; for where the arable soil of a field has, after every rotation, received from the clover or turnips more corn-constituents than it had lost by the corn-crop, there may be a gradual accumu- lation of an excess of these elements of food sufficient to conceal altogether from the farmer the true condition of hisland. By introducing into his rotation vetches, white- clover, and other fodder-plants that derive their food from the upper layers of the soil, he succeeds in keeping up his live stock, and he indulges in the notion that all things go on in his field just as before, when the clover or the turnips yielded good crops. This is of course simply a delusion, as there is no longer an actual re- placement of the loss sustained. His high corn-crops are now gained at the expense of the nutritive sub- stances accumulated in excess in the arable surface soil which are set in motion by the fodder-plants introduced into the rotation, and are uniformly distributed again in the arable soil after each rotation, by means of the farm-yard manure. His dung-heap may happen to be of larger bulk and extent than formerly, but as there is now no further supply of nutritive substances brought up from the sub- soil or the deeper layers by the clover or turnips, the power of the manure to restore the original fertility of the arable soil is continually decreasing With the ultimate consumption of the excess of corn-constituents accumulated in the arable soil, the time comes when the corn-crop begins to diminish, whereas the produce of straw is comparatively higher than before, as the conditions for the formation of straw have been steadily increasing. Of course, the farmer cannot fail to remark the diminution of lis corn-crops, which induces him to have recourse to drainage, to improved tillage, and to the substitution of other cultivated plants, in lieu of clover and turnips. If the subsoil of his fields will permit it, RESULTS OF FARM-YARD MANURING. 223 he now includes in his rotation lucerne and sainfoin, whose still longer and more widely spreading roots enable them to reach yet deeper layers of the ground than the red clover; until finally he employs the yel- low lupine, which may truly be called the ‘hunger- lant.’ . A new increase of produce is the result of these ‘im- provements’ in his system of cultivation by farm-yard manuring, which the farmer looks upon as a great ad- vance. A fresh store of nutritive substances, brought up from the deeper layers of the soil, may possibly ac- cumulate again in the arable surface soil; but these deeper layers also will be gradually exhausted, and the accumulated store in the arable surface soil will also be consumed. This is the natural termination of cultivation by the system of farm-yard manuring. The fields of the Saxon experiments afford very fair illustrations of the different conditions to which-arable land in general is brought, by a pure system of farm- yard manuring. The field at Cunnersdorf is in the first stage, the Miiusegast field in the second, the fields at Kotitz and Oberbobritzsch in the third stage, of cultivation by farm-yard manuring, to which we have referred. At Cunnersdorf the arable soil exhausted by the preceding cultivation becomes with every new rotation richer in the conditions required for the production of grain; not only does the clover replace the loss sus- tained by the removal of the corn-crops, but a remark- able excess of all nutritive substances will gradually accumulate in the arable soil; and, after a series of years, with the same system of cultivation by farm-yard manuring, the field will be brought to the condition of the land at Miiusegast; which means, that the arable soil will acquire a high productive power for corn and other crops, while the produce of clover will decrease. The fields at Kotitz and Oberbobritzsch most probably were in former times in the same condition as the Mau- segast field is at present; not that they ever yielded 224 THE SYSTEM OF FARM-YARD MANURING. crops as large as the latter gives, but merely that the unmanured plots have, at some antecedent period, given better crops than in the year 1851. Without an addi- tional supply of mineral elements derived from mea- dows or other fields not included in the rotation, the produce must go on continually decreasing, as the sup- ply of mineral constituents brought up by the clover from the subsoil, in these two places, is far from suf- ficient to make up for what is taken away in the corn- crops. In the following calculation it has been assumed that of the crops obtained, rye and oats were actually removed, and of potatoes and clover one-tenth was car- ried away in the form of cattle.* Cunnersdorf. Phosphoric acid. Potash. Ibs. lbs. Ibs. The arable soil lost by removal of 1176 rye-grain.. 10:2 55 oy us 2019 oats...... 15:3 77 ce ee zy potatocrop 2°3 11+ fs He = clover crop 4:0 20+ JNO FLOR SR OGeb Gogano oso: Bete 31°8 16°3 The arable soil had returned to it, in 345 of 9144 lbs. ofvelover=hay ieee ickcte.ce fietcre eters ote ore iced sree ou) OOFLO 95°5 Balance in'excess ..........2-- bAIndS 4°38 79°2 The arable soil of the Cunnersdorf field received, accordingly, in the farm-yard manure, more phosphoric acid and more potash than had been carried off by the corn-crops. In this calculation, it is a question of no importance how much of the rye or oats was carried off. More * The amount of phosphoric acid and potash is estimated in the cal- culation as follows :— Rye » Oats Potatoes. Clover-hay. Corn. Straw. Corn. Straw. Phosphoric acid....... 0864 0712 0-75 0-12 0-14 0°44 Potash ste ncmie shower 047 0°52 0°38 0:94 0°58 1:16 + The quantity of potash is calculated here upon the proportion of phosphoric acid in corn, one part by weight of potash to two parts by weight of phosphoric acid. MINERAL MATTERS LOST IN CROPS. 225 than the field produced could not be carried away, and if less were removed the only effect would be that phos- phorie acid and potash would accumulate all the more in the field. Mausegast. Phosphoric acid. Potash. : Ibs. lbs. The arable soil lost by the rye-grain, barley-grain, zy potatoes, yh; clover... -..2.-.eccecerecess “4 18:1 The arable soil received in 3; of the clover crop .. 22:0 62°0 PGGSSa) 19 AidstelsSatsicistatels sleralets SO ANU LE 13-4 Gain 43°9 Phosphoric acid. Potash. Ibs. Ibs. The arable soil lost in the rye, oats, and in the 45 of the potatoes and clover ...........-.0- ats). -) Sea Oe 12:7 Tereaarved ithe clovers si cscs cece cases one 8°5 11:0 NGOS ates corach tetas Stns ad citiasieei eaters 179 17 The calculation is about the same for the field at Oberbobritzsch as for Kotitz. While the arable soil at Miusegast, in consequence of the large clover crops pro- duced by it, still continues to gain in potash, the corn- crops are gradually reducing the rich store of potash in the Kotitz field. These three fields show the effect of a pure system of farm-yard manuring, from which is excluded all sup- ply of manure extraneous to the farm itself. An additional supply of fodder purchased from other farms, or hay grown on natural meadows, answers the same purpose as an additional supply of manure. It is self-evident that we cannot give more farm-yard manure to a field than it produces, unless we take the constituents of the manure from some other field, which in that case must lose just as much as the former field gains. If we direct our attention to manured fields, we find that they give larger corn-erops, and in many cases also larger clover or turnip-crops; the arable soil losing more by the removal of the corn-crop, and receiving 10* 226 THE SYSTEM OF FARM-YARD MANURING. more back by the increased produce of farm-yard ma- nure, still the ultimate results remain the same. In the system of cultivating by rotation of crops, it is found that, for a long time, the arable soil grows with each period of rotation very much richer than it is by nature, in potash as well as in lime, magnesia (the prin- cipal constituents of clover and turnips), and in silicic acid. These substances are the principal conditions for the formation of roots and leaves; their accumulation in the soil tends to make the ground rank and prone to grow weeds,* as the farmer says, an evil which arises as a necessary consequence from cultivation by the sys- tem of farm-yard manuring, and which can only be met, as he thinks, by a rotation of crops. It is generally supposed that the best remedy is the hoe; but though mechanical application may retard the developement of weeds for a time, it cannot effectually prevent them. The hoe has some share in removing them, but not all. * The most noxious of these weeds are the wild radish (Raphanus raphanistrum), the corn cockle (Agrostemma cithago), the corn-flower or blue-bottle (Centaurea cyanus), the German camomile (Matricaria chamo- milla), and the corn camomile (Anthemis arvensis). All these plants con- tain, in their ash, as much potash as is found in clover, and 7 to 18 per cent. of chloride of potassium, a salt which forms one of the principal constituents of the urine of animals, and which is brought to the field in the farm-yard manure. II. I. Matric. | Matric. | Anthemis| Centaurea} Agrostemma cham. cham. arvensis. | cyanus. cithago, Per cent. ash ..... 8°51 9°69 9°66 7°32 13°20 The ash contains: | Potash eae eter 25.49 32°386 | 30°57 36°536 22°86 Chloride of potas- OMIM Bao 4c 18°4 14°25 715, 11°88 755 Phosphoricacid..| 5° 7:80 9°94 6°59 6°64 Phosphate of iron; 2°39 2°39 477 2°34 | 1:80 (Ruxine, ‘ Annal. d. Chem. und Pharm.’ vol. lvi. p. 122.) SUCCESSION OF CROPS IN ROTATION. 227 The succession of crops in rotation is always made dependent upon the cereals; the preceding crops are selected of such a kind that their cultivation will not injure, but rather improve, the succeeding corn-crop. * The selection of the particular kind, however, is always governed by the condition of the soil. In a field abounding in stalk and leaf constituents, it is often found useful to have wheat preceded by tobacco or rape, rye by turnips or potatoes, since these plants by drawing from the soil a large amount of leaf and stalk constituents serve to restore a more suitable proportion between the straw and corn constituents for the future cereal crop, and at the same time to diminish, in the arable soil, those conditions which favour the growth of weeds. . The preceding observations relative to the produce given by the Saxon fields, both in the unmanured and manured state, afford, in my opinion, a perfect insight into the nature and results of cultivation by the system of farm-yard manuring. In the condition of these fields in their several stages, we may see reflected the history of agriculture. In the first period, or on a virgin soil, corn-crop is made to succeed corn-crop, and when the produce be- ins to fail, the culture is simply transferred to a fresh field. The increasing requirements of the growing population, however, gradually put a check upon this plan, and compel a steady cultivation of the same sur- face; a system of alternate fallowing is now resorted to, and efforts are made to restore the lost fertility of the soil, by manuring with the produce of the natural meadows. After a time, this expedient begins to fail, and leads to the cultivation of fodder-plants, the sub- soil being thus turned to account as an artificial mead- ow. The cultivation of fodder-plants proceeds, at first, without interruption ; after a time, longer and longer intervals are interposed between the clover and turnip crops ; finally, the cultivation of fodder-plants comes to an end, and with it the system of cultivation by farm- yard manuring. The ultimate result is the absolute 228 THE SYSTEM OF FARM-YARD MANURING. exhaustion of the soil, inasmuch as the means for in- creasing the produce of the soil gradually pass away from it by this system. Of course, the progress by which these different stages are reached is extremely slow, and the results are felt only by the third and fourth generation. When there are woods near the arable land, the peasant seeks to turn the fallen leaves to account as manure; he breaks up the natural meadows which are still rich in elements of food for plants, and converts them into arable land ; then he proceeds to burn down the forests, and to manure his fields with the ashes. When the gradual exhaustion in the productive power of the land has led to a corresponding decrease in the population, the peasant cultivates his land once every two years as in Catalonia, or once every three years as in Andalu- sia.* No intelligent man who contemplates the present state of agriculture with an unbiased mind, can remain in doubt, even for a moment, as to the stage which hus- bandry has reached in Europe. We find that all coun- tries and regions of the earth where man has omitted to restore to the land the conditions of its continued fer- tility, after having attained the culminating period of the greatest density of population, fall into a state of barrenness and desolation. Historians are wont to attribute the decay of nations to political events and social causes. These may, indeed, have greatly contrib- uted to the result ; but we may well ask whether some far deeper cause, not so easily recognised by historians, * The Emperor Charles V. gave orders that the meadows recently turned into arable land should be restored to their former condition. Even before the time of Charles V. orders of the same nature had been issued by the first Catholic Kings, and at a still earlier period by Pedro the Cruel of Castile. In the beginning of the fifteenth century, Henrique of Castile pro- hibited the exportation of cattle, on pain of death; and as early as the commencement-of the fourteenth century, King Alonzo Onzeno had issued ordinances for the preservation of meadows and pastures. (‘ Bilder aus Spanien von Karl Freiherrn von Thienen, Adlerflycht.’ Berlin: Dunker, p. 241.) All in vain! for what avails the power of even the mightiest monarchs against the irrepressible action of a law of nature ? FALSE DOCTRINES. : 229 has not produced these events in the lives of nations, and whether most of the exterminating wars between different races may not have sprung from the inexorable law of self-preservation? Nations, like men, pass from youth to age, and then die out—so it may appear to the superficial observer; but if we look at the matter a little more closely, we shall find that, as the conditions for the continuance of the human race which nature has placed in the ground are very limited and readily exhausted, the nations that have disappeared from the earth have dug their own graves by not knowing how to preserve these conditions. Nations (like China and Japan) who know how to preserve these conditions of life do not die out. Not the fertility of the earth, but the duration of that fertility, lies within the power of the human will. In the final result, it comes very much to the same thing, whether a nation gradually declines upon a soil constantly diminishing in fertility, or whether, being a stronger race, it maintains its own existence by exter- minating and taking the place of another people upon a land richer in the conditions of life. It can hardly be ascribed to caprice or chance that the cultivator in the Awertas of Valencia obtains three crops yearly from the same soil, while in the immediate neighbouring district the ground is tilled only once in three years ; or that the Spaniards burned down forests in sheer ignorance, in order to use the ashes to restore the fertility of their fields. (See Appendix G.) Everyone who is at all acquainted with the natural conditions of agriculture, must perceive that the method of culture practised for centuries in most countries could not but inevitably impoverish and exhaust even the most fruitful lands ; can it then be supposed that there will be any exception in the case of cultivated lands in Europe, and that like causes will not produce like effects ? Under these circumstances, is it right or reasonable to pay any attention to the doctrines of superficial wise- acres, who, with their wretched chemical analyses find 230 THE SYSTEM OF FARM-YARD MANURING. an inexhaustible supply of nutritive substances in any given soil, even in one which can no longer produce clover, turnips, or potatoes, and yet may be rendered capable of producing these plants by manuring with ashes or lime in the right places ? In the face of the daily experience which shows that the corn-fields, if theysare to remain fruitful, must be manured after a short series of years, it is a crime against human society, a sin against the public welfare, to dis- seminate the doctrine that the fodder-plants, which fur- nish manure to the corn-fields, will constantly find upon the field the conditions of their own growth, that the law of nature applies to one kind of plant only, and has no bearing upon the other. The teaching of these men has no other result than to keep agriculture in the low position which it now occupies. In England it is a mere mechanical handicraft, and in that country manure is regarded as merely the oil which smoothes the wheels and keeps the machine in motion. . In Germany agriculture is a jaded horse, treated with blows instead of fodder ; nowhere is its real beauty and the intellectual aspect of its pursuit recognised. Not merely for its utility, but on account of this very intellectual nature of its pursuit, it stands above all occupations ; and its practice procures, to the man who understands the voice of nature, not only all the advan- tages for which he strives, but also those pleasures which science alone can afford. In human society, ignorance is undoubtedly the fundamental, and therefore the very greatest evil. The ignorant man, however rich he may be, is not protected from poverty by his wealth; while the poor man, who has knowledge, becomes rich by its means. Uncon- sciously to the ignorant farmer, all his industry, care, and toil only hasten his ruin; his crops gradually di- minish, and at length his children and grandchildren, no wiser than himself, are unable to maintain them- selves upon the homestead where they were born; their land passes into the hands of the man who has knowl- edge; for by knowledge capital and power are acquired, CORN NOT INCREASED BY FARM-YARD MANURING. 231 and by these, as a matter of course, the helpless are ex- pelled from the inheritance of their forefathers. As an animal cannot care for himself, the law of nature takes care of him, and is his master; but not so with man, who, if he understands the intentions of God in his creation, is master of the law of nature, which yields to him a complete and willing obedience. The animal brings into the world his perceptions and in- stincts, which grow up with his growth, and without any effort of his own; but to man the Creator gave the gift of reason, and this distinguished him from the brutes. This is the divine talent, which he should put out to interest, and of which it is said, ‘ He that hath, to him shall be given; but from him that hath not, shall be taken away even that which he hath.’ It is only the interest procured by means of this ‘ talent’ that gives man power over the forces of the earth. Error arising from want of knowledge is excusable, for no one adheres to it after recognising its existence ; and the struggle between error and dawning truth arises from the natural striving of men for knowledge. In this contest truth must grow stronger, and if error pre- vails, this only proves that truth has yet to grow, not that error is truth. At all times the ‘ better’ has always been the ene- my of the ‘good ;’ but men do not comprehend for all that why, in so many cases, ignorance is the enemy of reason. There is no profession which for its successful prac- tice requires a larger extent of knowledge than agricul- ture, and none in which the actual ignorance is greater. The farmer who practises the system of rotation, depending exclusively upon the application of farm-yard manure, needs very little observation, nay only to open his eyes, in order to be convinced, by innumerable proots, that whatever may have been the outlay of labour and industry applied to the production of farm-yard manure, his fields have not been thereby increased in the power of bearing crops. If farm-yard manure was actually able to render a 232 THE SYSTEM OF FARM-YARD MANURING. field permanently richer in nutritive substances than it is by nature, we might expect that a course of manur- ing for fifty years would necessarily produce a steady increase in the crops. Now, if farmers who practise the system of rotation, laying aside all bias and prejudice, would compare their present with their former crops, or with those obtained by their fathers or grandfathers, none of them would be able to say that the crops have increased, and only few that the average has remained the same. Most of them would find, that on the average, the straw-crops have turned out higher, but the corn-crops lower, and proportionately lower than they formerly were higher ; and that the surplus money which their parents gained by the former high crops, the result of their improve- ments, as they supposed, must now be paid out again, to purchase manuring substances, which, as people formerly thought, could be ‘ produced.’ Now, how- ever, they begin to learn that though such substances may be produced for a time, they cannot be reproduced in perpetuity. " In like manner, the farmer whose richer ground has enabled him to carry out the three-field system, and whose rich meadows guarantee a supply of manure, . who obtains as abundant harvests and as large a weight .of corn as the farmer who adopts the system of rotation, and thus surmises that his management has procured what the ground gives of its own free will, will inevi- tably discover that his fields may be exhausted of the conditions of their fertility, and that it is quite erroneous to suppose that all the farmer’s art consists in convert- ing manure into corn and flesh. A simple law of nature regulates the permanence of agricultural produce. If the amount of produce is in proportion to the surface presented by the sum total of nutritive substances, in the soil, the permanence of the crops will depend upon the maintenance of that pro- portion. This law of compensation, the replacement of nutri- tive substances which the crops have carried away from RECORDS OF CHARLEMAGNE. " 983 the soil, is the foundation of rational husbandry, and must, above all things, be kept in view by the practical farmer. He may renounce the hope of making his land more fruitful than it is by nature, but he cannot expect to keep his harvests up to their average if he allows the necessary conditions for them to diminish in his land. All those farmers who cherish the notion that the produce of their fields has not declined, have not hither- to been able to appreciate the force of this law. As- suming that they have an excess of nutritive substances to deal with, they think they may continue drawing upon it, until a failure becomes visible, and then they fancy it will be time enough to talk of compensation. This view results from want of understanding the nature of their own acts. There surely can be no doubt that to manure a field which already contains an excess of nutritive substances is opposed to a rational system of cultivation; for what end could be gained by increasing the nutritive sub- stances in a field where a portion of the elements already existing cannot, on account of their mass, come into operation ? But how can sensible men talk of excess when they are obliged to use manure in order to keep up their harvests, and when their crops decline if they employ no manure ? The simple fact, say others, that in certain districts, © as in Rhenish Bavaria, agriculture has flourished since the time of the Romans, and that the ground there is just as rich, nay, gives higher crops than in other lands, is a proof how little reason there is to fear want or ex- haustion by continued culture ; for if such a thing were likely, it would make itself manifest there sooner than elsewhere. Bet in the cultivated lands of Europe agriculture is at all events still very young, as we know with the greatest certainty from records of the time of Charle- magne. His ordinances respecting the management of his own estates (capitulare de villis vel curtis im- peratoris), wherein directions are given to the stewards, 934 THE SYSTEM OF FARM-YARD MANURING. as also the official reports to the Emperor (specimen breviarti rerum fiscalium Caroli Magni), sent in by inspectors expressly appointed to survey those estates, are irrefragable proofs that there was then no agricul- ture worth the name. Very little is said in the Capitu- lare about the cultivation of corn, with the exception of millet. It is reported in the Breviariwm, that at Stefanswerth (a domain of the Emperor), comprising 740 acres (jurnales) of arable land and meadow, capa- ble of supplying 600 cartloads of hay, the commissioners found no corn in store, but on the other hand a large number of cattle, 27 sickles great and small, and only seven broad hoes, to till 740 acres of land! Upon another estate were found 80 baskets of last year’s spelt, equivalent to 400 lbs. of flour (=14 bushel, or somewhat more than 3 hectolitres), 90 baskets of spelt of the current year, from which 450 lbs. of flour could be made. On the other hand, there were 330 hams ! The crop or stock upon another domain amounted to 20 baskets of spelt (=100 lbs. of flour) of the preced- ing year, and 30 baskets of spelt, of which one was used for seed. It is easy to see that in those days the breeding of cattle was the chief object, and that the cultivation of corn occupied a very subordinate position in husbandry.* A deed of the period shortly after Charlemagne says on this point: ‘ Every year, three yokes of land upon an estate ? should be ploughed and sown with seed fur- nished by the lord of the manor. (See ‘die Getreide- Arten und das Brod von Freih. von Bibra.’ Nurem- berg: Schmid. 1860.) Hence we possess not a single trustworthy proof that any one field in Germany or France (perhaps we may make an exception in favour of Italy) has served for the cultivation of corn from the time of Charlemagne to our own age; and the argument for the inexhausti- * It is worthy of remark that Charlemagne introduced, upon his estates, the three-field system, with which he had become acquainted in Italy. EXHAUSTION OF RHENISH BAVARIA. 235 bility of land is almost childish, because it assumes that corn may be continuously taken from a field, without restoring the conditions of reproduction. A field does not necessarily become unfruitful for corn because it has yielded large corn-crops; but it ceases to yield corn- crops if it does not receive compensation for the corn- constituents which have been removed. This compen- sation is facilitated by the breeding of cattle, in propor- tion to the extent to which this is carried, and especially when the cultivator is acquainted with the operation of manure. In the time of Charlemagne this was well known, for the winter-crops were manured with dung, distinguished as cattle-dung (called gor) and horse-dung (dost or deist). Besides, the practice of marling was then common in Germany. With regard to the special instance of Rhenish Bavaria as proving the inexhaustibility of the soil, I had an opportunity last autumn, at a meeting of the Society of Naturalists at Spires, of making particular inquiries about the actual condition of the neighbour- hood. henish Bavaria, from the slopes of the Hardt mountains to the Rhine, comprises a district of great fertility : the region is inhabited by an extremely in- dustrious population, distributed in small towns and villages. Almost every artisan, even to the tailor and shoemaker, possesses a small plot of ground, on which he raises his potatoes and vegetables. The export of corn from this district is never thought of, but on the contrary corn and a large quantity of manure are im- ported from Mannheim, Heidelberg, and elsewhere. The manuring substances obtained from the houses of the towns and villages are carefully treasured and employed, so that there can be no fear of exhaustion, since the removed nutritive substances are restored to the fields. In spite of all this, in no part of Germany is the want of manure more felt than there. On the highways chil- dren are constantly seen with little baskets, following the horses and swine, to gather the manure dropped by those animals. In the year 1849, during the political agitation in the Palatinate, the peasants had no more 236 THE SYSTEM OF FARM-YARD MANURING. urgent request for the improvement of their condition to lay before the magistrates, than a petition to be al- lowed to collect ‘forestings, that is, to carry off the natural manure from the forests for the benefit of their fields. They urged that without this (very pitiful) ad- dition to their manure, the future prospects of agricul- ture in the Palatinate were endangered. In fact, a great quantity of manure is laid out upon the vineyards and tobacco fields, which give none in return ; hence the increasing want. There can be no doubt that in the earliest periods most of our cultivated fields gave a suecession of abun- dant crops, without manuring, as in the case even now, with many fields in the United States of America. But no fact has ever yet been more clearly established by experience than this, that in the course of a few genera- tions all such fields are found perfectly unsuited for the growth of wheat, tobacco, and cotton, and that they re- cover their fertility only by manuring. I know full well that recorded facts have as little weight with ignorant ‘ practical men’ as those of politi- cal history with practical statesmen, who also act ac- cording to ‘circumstances and contingencies,’ and are simply led when they fondly believe they lead. Still, the reflecting mind cannot fail to be struck by the cir- cumstance, that it is just in countries where the land is most positively known to have given for above 4000 years, without manuring by the hand of man, an unin- terrupted succession of abundant crops, that the full action of the great law of restitution is most clearly seen. We know, most positively, that the corn-fields in the valley of the Nile and the basin of the Ganges re- main permanently fruitful, simply because nature has taken upon herself to restore the lost condition of pro- ductiveness to the soil in the mud deposited by the inundation of these rivers which gradually raises the land. All the fields that are not reached by the river lose their productiveness unless manured. In Egypt, the . THE SOIL NOT INEXHAUSTIBLE. 237 amount of the crop to be expected is calculated from the height of the water of the Nile; and in the East Indies a famine is the inevitable consequence whenever there happens to be no inundation. Nature herself, in these striking instances, points out to man the proper course of proceeding for keeping up the productiveness of the land. (See Appendix H.) The notion of our ignorant practical husbandmen, that the soil contains ample store of the elements of food to enable them to pursue their system of agriculture, is due partly to the excellent quality of the land, but also to their skill in robbing it. The man who attempts to gain money by filing the weight of one gold piece from a thousand, cannot plead, in extenuation, that it is re- marked by no one, but if discovered he is punished by the law ; for everybody knows that the fraudulent act, repeated a thousand times, would ultimately leave nothing of the gold pieces. A similar law, from which, moreover, there is uo escape, punishes the agriculturist who would make us believe that he knows the exact store of available food elements in his land, and how far it will go; and who deceives himself when he fancies he is enriching his field by bestowing on the arable sur- face soil the matters taken from the deeper layers. There is another class of agriculturists consisting of men with a small stock of knowledge joined to a limited understanding, who, indeed, fully recognise the law of restitution, but interpret it after their own fashion. They assert and teach that part of the law only, and not the whole, applies to cultivated fields ; that certain constituents, unquestionably, must be restored to the soil to keep up its productiveness, but that all the others are found in the earth in inexhaustible quantities. They generally base their opinion upon some unmeaning chemical analysis, and demonstrate to the simple agri- ceulturist (for whom alone such disquisitions are intend- ed) how rich his fields still are in some one or other of the mineral constituents, and for how many hundred thousand crops the store will still suffice ; as if it could be of the least use for any one to know what the soil 238 THE SYSTEM OF FARM-YARD MANURING. contains, if the amount of the available food elements that serve to produce the crops, which is the really im- portant point, cannot be determined. . With such absurd assertions they absolutely hood- wink our ‘ practical’ farmers, who, but for them, might see clearly into matters, but who appear only too will- ing to accept any assertion that will only leave them at peace, and save them the trouble of ‘ thinking.’ I remember a case where a swindler offered to sell to a wealthy gentleman, at a high price, a mine of almost pure oxide of aluminium, after having shown him, from, chemical works, that oxide of aluminium was indispensable for the production of the metal alumin- jum, the market price of which was as much as 41. per pound, and that the ore of the mine offered for sale con- tained nearly 80 per cent. of that valuable metal. The purchaser was not aware that the ore in question is gen- erally known as ‘ pipe-clay,’ an article of almost nom- inal value, and that the high price of the metal arises from the many changes through which the oxide has to pass to effect its reduction to the metallic state. It is generally the same with the great stores of pot- ash in the soil. The alkali in the ground, to answer the intended purpose, must, by the agriculturist’s art, be converted first into a certain form, in which, alone, it is available as food for plants; and if he does not understand how to effect this conversion, all the potash in his soil is of no earthly use to him. The notion that the farmer need only restore to his land certain substances, without troubling himself about the rest, might not be prejudicial if those who enter- tained it confined the application to their own farms ; but, as a matter of instruction to others, it is untrue and quite exceptionable. It is calculated for the low intellectual standard of the practical man, who, if he in any way succeeds, by certain alterations, in his system, or by the use of certain manuring agents in obtaining better results than another, attributes his success to his own sagacity rather than to the superior quality of his land. He does not even know that the other has tried IGNORANT PRACTICAL MEN. 239 the very same plans as himself, only without attaining so favourable a result. Our ignorant practical husband- man starts upon the assumption that all fields are the same in condition as his own, and that, therefore, the same system which answers on his farm ought to do equally well on every other; that the manure which he finds useful ought to be equally useful to others; that the deficiencies in his field are the same in all other fields; that what he exports from his land, others ex- port from theirs ; and what he is called upon to restore to his soil, others are equally called upon to restore to theirs. Although he knows next to nothing of the condition of his own land, with which it would, indeed, require many years of careful observation to become familiar, and is most profoundly ignorant about the condition of the land in any other part; although he never has troub- led himself with reflecting upon the causes of his sue- eess in the cultivation of his fields, and is quite aware that the advice of agriculturists from other parts, respecting manuring, rotation of crops, and the general treatment of his own land, is not of the slightest use to him, because, as he has found, it is not at all applicable to his district; yet all this does not prevent him from wanting to instruct others, and persuade them that his system is.the only true one, and that they need only do as he does to obtain equally favourable results. The foundation of all such views is a total miscon- ception of the nature of the soil, the condition and com- position of which present an infinite variety of shades. The fact that many fields that happen to be rich in silicates, and in lime, potash, and magnesia, are, by the growth of corn upon the common farm-yard manuring system, drained only of phosphoric acid and nitrogen, and that the farmer need only look to the replacement of these matters without troubling his mind about the rest, has already been fully discussed. This fact no one can dispute: but it is utterly inadmissible to apply it to the case of other fields, and to make other farmers be- lieve that they, too, need not trouble their minds about 240 THE SYSTEM OF FARM-YARD MANURING. supplying to ¢hezr land potash, lime, magnesia, or silicic acid, and that salts of ammonia and superphosphate of lime will suffice to restore the productiveness of all exhausted fields. A farmer may, therefore, be quite justified in con- sidering that his field can never grow poorer in potash because he never takes any from it, or that it actually contains a superabundance of potash since every rota- tion tends to accumulate in the soil a fresh amount of that ingredient ; but it is childish of him to think him- self justified by this circumstance in assuring another agriculturist, about whose system of cultivation he knows nothing, that the fields of the latter equally con- tain a superabundance of potash. There are millions of acres of fertile land (sand and clay-soil), in which the proportion of lime or magnesia in the soil does not exceed that of phosphoric acid, and where provision must be made for replacing the former as well as the latter. Again, there are millions of acres of fertile land, which, like calcareous soils in general, are exceedingly poor in potash, and become absolutely barren without a proper supply of this ingredient. There are, on the other hand, millions of acres of fertile fields abounding so richly in nitrogen that any additional supply of that element would be mere waste. Ashes will not promote the growth of clover on fields abounding in potash, whilst the application of manur- ing agents containing phosphoric acid will have that effect ; on the other hand, ashes will make clover grow on land deficient in potash, where bone-earth proves useless ; and a simple supply of lime containing mag- nesia will often suffice to restore the productiveness for clover where the land is deficient in lime and mag- nesia. When a farmer, besides corn and flesh, grows and sells other produce, the nature of the required supply of mineral elements is thereby necessarily altered. In the average potato produce of three hectares of land we take away the seed-constituents of four wheat crops, besides about 600 lbs. of potash, and in the average MATTERS TO BE RESTORED VARY. 241 turnip produce of three hectares the seed-constituents of four wheat-crops, besides about 1000 Ibs. of potash. A supply of phosphorie acid alone will not suttice, in this ease, to keep up the productiveness of the land. The grower of commercial plants, such as tobacco, hemp, flax, the vine, &c., must in like manner strictly attend to the law of restitution, which, properly inter- preted, does not imply that he should bestow the same anxious care upon the replacement of all constituents alike which have been taken away in the crops. It would, for instance, be the height of absurdity to re- quire the tobacco planter who grows his crops on a lime or marl soil, to replace the lime carried off in the leaves of the plant. But it tells him that not all that goes by the name of manure is useful for his fields, and it shows him the difference between manures: it informs him of the loss inflicted upon the soil by the preceding crop, and the supply required to insure future harvests ; it teaches him never to allow himself to be guided in his proceedings by the opinions of persons who do not take the slightest interest in him and his land, but always to act upon his own observations. A careful study of the weeds that spring up spontaneously in his fields may frequently prove more useful in this respect than a heap of hand-books on agriculture. If after the foregoing statements the condition of the cultivated land in Europe, and the decline towards which agriculture is tending by the prevailing system of farm-yard manuring, should still be a matter of doubt to many persons unacquainted with the natural sciences, and who trust only to definite numbers as palpable facts, that doubt may, perhaps, be removed by statistical data on the corn produce of the land in different parts of Germany, which have been collected partly by order of the government. For a correct appreciation of the importance of these data in the matter, it is necessary in the first place to understand clearly what is meant by an ‘average’ crop. By this term is designated the aver- age produce, expressed in numbers, of a field, or a i 9AD THE SYSTEM OF FARM-YARD MANURING. number of fields, or all the fields of a district or coun- try. The figure which represents it is found by adding together the produce of all the fields for a number of years, and dividing the sum total by the latter. There is accordingly a special average produce tor every dis- trict, by which the next year’s crop is judged. Thus we talk of a full, or a half, or a three-quarter average, as the produce happens to come up to the calculated average, or fall one-half or one quarter below it. The question as to the actual condition of our corn- fields may therefore be put thus: Has there been any change in the figure which at any previous period ex- pressed the average produce of the land, and in what sense? Is that figure higher now than formerly, or has it remained the same or fallen? If the figure is higher, this is of course a sign of an improved condition of the land; if it remains the same, the condition has under- gone no change; and if it is lower, there can be no doubt that the condition of the land in that district has declined. I select for my purpose the statistical data of the produce of the Hessian Rhine district, one of the most fertile provinces of the Grand Duchy of Hesse, with an excellent wheat soil, and inhabited by a most indus- trious and generally well educated population. (¢ Sta- tistische Mittheilungen iiber Rheinhessen, von F. Dael, DLL.’ Mayence: 1849. Flor. Kupferberg.) These data embrace a period of fifteen years, from 1833 to 1847; they refer accordingly to the time when guano was not yet used as manure in Germany. ‘The use of bone-earth was at that time also still very limit- ed, and hardly worth taking into account. A produce of eleven grains of wheat to every two grains sown, of five and a half accordingly, was held to be an average crop for the Hessian Rhine district. (20 malters = 14 bushels = 5120 hectolitres per hectare = 2471 English acres.) Taking the figure 1 to express an average crop, the amount of produce reaped in the Rhine district of Hesse was :— MEAN OF AVERAGE CROPS IN RHINE HESSE. 243 1833. 1834, 1835, 1836, 1837. 1838. 1839. 0°85 O78 0°88 0-72 0°88 073 0°61 1840. 1841. 1842, 1343. 1844, 1815, 1346. 1847, 1:10 0°40 0°90 0-74 1°02 0°63 0-75 0°88 which gives a mean for the fifteen years of 0°79 of the former average. The productiveness of the wheat land in the Rhine district of Hesse has therefore declined somewhat more than one-fifth. I know all that may be urged against the accuracy of these figures severally, and their trustworthiness col- lectively ; but if they contain errors, the impartial observer must see that these must tend to the plus as well as to the menus side, and that it would be most extraordinary in the presence of plus errors that all the estimates should have fallen out on the minus side. There is, however, a very simple, and at the same time infallible and irrefutable, proof of the correctness of the conclusions drawn from these figures, in the fact that the enltivation of wheat is on the decrease, that of rye on the increase, in Rhine Hesse, and that many fields on which wheat was formerly grown are now turned into rye fields. Properly understood, the change from wheat to rye always argues a deterioration in the quality of the soil ; the farmer begins to grow rye in a wheat field only when the latter no longer gives remunerative wheat crops. i Rhine Hesse, a 44 fold produce of rye is consid- ered an average crop; a wheat soil, therefore, capable of giving only four-fifths of an average wheat-crop, can produce a full average rye-crop. Now the average produce of rye in the fifteen years is 0°96, which pretty nearly corresponds with the full average. For spelt, the mean was 0°79 of the average ; for barley, 0°88; for oats, 0°88; for peas, 0°67; for pota- toes, on the other hand, 0°98; and for colewort and turnips, 0°85. The statistical data collected in Prussia and Baya- 944 THE SYSTEM OF FARM-YARD MANURING. ria, which are most reliable, give the same result ; and I have not the slightest doubt that it would hold equally true with France and other countries, England includ- ed. ‘The visible gradual deterioration of the arable soil cannot but command the serious attention of all men who take an interest in the public welfare. It is of the utmost importance that we do not deceive ourselves re- specting the danger, indicated by these signs, as threat- ening the future of the populations. An impending evil is not evaded by denying its existence or shutting our eyes to the signs of its approach. It is our duty to examine and appreciate the signs: if the source of the evil is once detected, the first step is thereby taken to remove it for ever. CHAPTER VI. GUANO. Composition compared with that of seeds; small amount of potash init; its ac- tion—Guano and bone-earth, similarity of their active ingredients—Guano acts quicker than bone-earth, or a mixture of the latter and ammoniacal salts ; reason of this—Oxalie acid 111 Peruvian guano ; the phosphoric acid rendered soluble by its meaus— Peruvian guano, its effect on the cultivation of corn— Moist guano loses ammonia--Moistening guano with water acidulated with sulphuric acid; effect—Inactivity of guano in dry and very wet weather— Rapidity of its action asa manure,on what dependent--Comparison of the effect of farm-yard manure and guano; effect produced by mixing the two— Guano on a field rich in ammonia—Increased produce by guano, what it pre- supposes—Exbaustion of the soil by continuous use of guano--Mixture of guano with gypsum and with sulphuric acid--The Saxon agricultural experi- ments; their results. ERUVIAN guano generally contains 33 to 384 per cent. of incombustible, and 66 to 67 per cent. of volatile and combustible ingredients (water and ammo- nia). The latter consist principally of uric acid, oxalic acid, a brown matter of uncertain composition, and guanine. The uric acid amounts occasionally to as much as 18 per cent., the oxalic acid generally to 8 or 10 per cent. of the weight of the guano. The relation of uric acid to vegetation is not known, but it is hardly likely that this substance can have a perceptible share in the fertilising action of guano. To account for this action, then, we have only the ammonia and the incom- bustible constituents left to consider. An analysis of two samples of guano, made by Dr. Mayer and Dr. Zoeller, in my own laboratory, showed 100 parts of guano ash to contain :— BOtasiitests cesiaen aartsian « cosas wo | 256 to;. 2°08 UG eh eet ner eake clei sicisie. spices 8) O4'00)). BOO Ma enema occ as stan. Metactstsiale vicicts « poy po ROh sen Phosphorio AClGs ccc ss ees seee ss 41°00 * 4000 246 GUANO. If we compare with this the composition of the ashes of various seeds, we see at once that the incombustible constituents of guano do not altogether replace the soil constituents carried off in the seeds. In 100 parts of seed ash are contained,— Wheat. Peasand beans. Rape. IHN ho ante ouuocounaGe 30 40 24 NO seaoAS Goo obapoo ded 4 6 10 Maonesia ic. cn ee ciaehis 12 6 10 Phosphoric acid......... 45 36 36 The principal difference between the ash of guano and that of these seeds lies in the deficiency of potash and magnesia in the former. Agriculturists are generally agreed about the neces- sity of potash for vegetation, and that a supply is re- quired by fields poor in that ingredient, or drained of it; but the question as to the importance of magnesia for seed formation has not, as yet, met with the same attention, and special experiments in this direction would be very desirable. The fact that much more magnesia is found in the seeds than in the straw unmis- tukably shows that it must play a definite part in the formation of the seed, which might, perhaps, be ascer- tained by a careful examination of seeds of the same variety of plants containing different amounts of mag- nesia. It is a well-known fact that the seeds of the several species of cereals having the same proportion of nitrogen, do not always contain the same nitrogenous compounds, and it is possible that the nature of the lat- ter may, in the formation of the seeds, be essentially in- fluenced by the presence of lime or of magnesia, so that the differences in the proportions of both of these alka- line earths may have a certain connection with the pres- ence of the soluble nitrogenous compounds (albumen and casein), or of the insoluble (gluten or vegetable fibrine). Of course, the quantity of potash and soda present would have to be taken into account in an in- vestigation of the kind. The fertilising action of guano is generally attributed to the ammonia in it, and to the other ingredients rich in nitrogen; but accurate experi- OXALATE OF AMMONIA IN GUANO. 247 ments made to elucidate this point, by the General Committee of the Agricultural Society of Bavaria, which we shall hereafter have occasion to mention, have shown that whilst the use of guano was found, in many cases, to increase very considerably the produce of corn and straw of a field, the application of an am- moniacal salt containing an amount of nitrogen cor- responding to that in the guano produced no perceptible effect on the crop of the same cereal, grown in the same year, upon another plot of the field, when com- pared with the produce of a third unmanured plot of the same field. Though the part which the ammonia in the guano plays, in many cases, in increasing the produce, cannot be questioned ; yet it is equally certain, on the other hand, that in many other instances the fertilising action of guano must be attributed principally to its other con- stituents. If the ash of guano is compared with calcined bones, or bone-earth, it is found that the difference between the two is not very great ; yet an amount of bone-earth containing the same proportion of earthy phosphate as in guano, or even two to four times that quantity, has not the same action as the latter manure. Even a mix- ture of bone-earth with ammoniacal salts in sufficient proportion to make the amount of nitrogen and phos- phorie acid equal to that contained in the guano, though more efficacious than bone-earth alone, has still a dif- ferent action from guano. The great distinction be- tween the two lies in the greater rapidity of the action of the guano in the first year, and often even in the course of a few weeks, whilst in the year after it is barely perceptible ; that of the bone-earth, on the other hand, is comparatively slight in the first year, but in- creases in the following. The cause of this difference of action is the oxalic acid in Peruvian guano, which often amounts to from 6 to 10 per cent. If guano is subjected to lixiviation, the water dissolves sulphate, phosphate, and oxalate of am- monia, which latter salt crystallises out abundantly 248 GUANO. upon evaporating the solution. But if the guano is moistened with water, without lixiviating, and is then left to itself, it is found, upon extracting with water portions of the mixture from time to time, that the pro- portion of the oxalic acid in the solution gradually de- creases, Whilst that of the phosphoric acid increases. A decomposition takes place in this moistened condition of the guano, through the agency of the sulphate of am- monia, by which the phosphate of lime is converted into oxalate of lime and phosphate of ammonia. Peruvian guano is, in this respect, a very remarkable mixture, which could scarcely have been more ingeniously com- pounded for the purposes of the nutrition of plants ; for the phosphoric acid in it becomes soluble only in a moist soil, through which it then spreads in form of phosphate of potash, phosphate of soda, and phosphate of ammonia. The action of guano may rather be compared to a mixture of superphosphate of lime, ammonia, and salts of potash, which, indeed, in many cases, is equal to it. On a soil abounding in lime, guano is, however, decid- edly more advantageous than superphosphate of lime, since the latter, upon coming in contact with the car- bonate of lime in the soil, is at once converted into neu- tral phosphate of lime, which requires to meet with another solvent at the place of formation to effect its diffusion through the soil, whilst phosphate of ammonia spreads through a lime soil just as if there was no car- bonate of lime in it. The phosphate of ammonia formed when guano is moistened with water (PO,+3NH,0), loses in the air one-third of the ammonia. It is owing to this circumstance that guano, when quite dry, will keep without alteration; whereas, when it has been fraudulently moistened, to increase the weight, it loses, by keeping, considerably in ammonia. If guano, just before its application on the field, is moistened with water and a little sulphuric acid, suf- ficient to give the water a slightly acid reaction, the decomposition now mentioned, which otherwise requires days and weeks, is effected in a few hours. ADDITION OF GUANO TO FARM-YARD MANURE. 249 That guano should not produce much effect in very dry weather needs no explanation, because, without water, no substance will act in the ground; that it should, however, equally fail in very wet weather, is, undoubtedly, owing in part to the fact that the oxalic acid is washed out, as an ammoniacal salt, by the rain water, and that there is, accordingly, a corresponding quantity of phosphoric acid not made soluble. By the above simple and cheap means the injurious influence of wet weather upon guano may be completely guarded against, inasmuch as the water and sulphuric acid en- sure the conversion into a soluble form of the whole of the phosphoric acid, which could have been brought in to that condition by the oxalic acid. The rapidity with which a nutritive substance em- ployed in the shape of manure produces an effect, de- pends essentially upon the speed with which it spreads through the soil, and this, again, upon its solubility ; hence it is easy to understand why guano surpasses, in these respects, many other manures. As regards certainty of action, guano will not bear comparison with farm-yard manure, which, from its nature, is effective in all cases; for farm-yard manure restores to the land all the soil constituents of the pre- ceding rotations, though not in the same proportions, whereas guano restores only sorne of them, and cannot, therefore, replace farm-yard manure. As guano, how- ever, contains, with the exception of a certain quantity of potash, the chief constituents (phosphoric acid and ammonia) of the exported corn and flesh, the addition of a certain proportion of guano to farm-yard manure may serve to restore the proper composition of the lat- ter, and, with it, also that of the soil. Let us suppose, for the purpose of illustration, that a hectare of land has been manured with 800 ewt. of farm-yard manure, containing, according to Voelker’s analysis, 272 kilogrammes of phosphate, and that the field has, at the end of the rotation, returned the same quantity of farm-yard manure of the same composition, and has lost by the corn and the animal produce export- 11* 250 GUANO. ed, altogether 135 kilogrammes of phosphates ; the pro- ductive power of this field, in so far as it depends upon the phosphates, would not only remain unaltered, but would even be considerably increased, by adding to the 800 cwt. of farm-yard manure supplied to it at the com- mencement of a fresh rotation, 400 lbs. of guano (with 34 per cent. of phosphates in it). Kilogrammes. The farm-yard manure supplied to the land. . 272 of phosphates. In the produce exported the field lost : : ea ep iy There remained in the arabie soil : : Fe oh bSiF) " In the new rotation was added by the fresh supply of 800 ewt. of farm-yard manure Es : E 2 ef By the addition of the 400 Ibs. of guano . ; qo USS . Altogether © 08°)". COR ibad e At the beginning of the new rotation the arable soil contained, accordingly, twice as much phosphates as at the beginning of the preceding one. It will thus be seen that, under these circumstances, where a field receives back, in the farm-yard manure, a larger share of phosphate than it has lost in the crops, the action of guano upon it will grow feebler from year to year, until at last it ceases to be appreciable. But the case is very different as regards the applica- tion of guano on fields to which a smaller quantity of phosphates is returned in the farm-yard manure than has been lost in the crops, and that have, for instance, been cultivated for half a century upon the farm-yard manuring system. It has already been explained, that on such fields certain constituents of the fodder plants and of straw, more particularly soluble silicie acid and potash, are continually increasing in the arable soil, whilst by the export of corn and flesh its store of min- eral substances is reduced hy the quantity contained in the exported matters. The two sets of constituents had jointly produced the crop. By taking away the seed- constituents a corresponding amount of the straw and fodder constituents was, accordingly, rendered ineffec- tive. In fields of this description, manuring with guano not only brings up the amount of produce to the former standard, but frequently even increases it to a surprising REASON OF THE EFFECTIVE ACTION OF GUANO. 251 extent, when the soil contains a large store of other as- similable food elements, which require only-the presence of the guano constituents to make them available for nutrition. In the increased produce thus obtained, there is, of course, carried off, together with the guano constituents, also a part of the store of the other food elements; and upon repeated manurings with guano the fertilising effect of that agent must therefore neces- sarily become feebler in the same proportion as the quantity of these other food elements decreases in the ground. The fertilising action of all compound ma- nures is rarely dependent upon one constituent alone ; and as guano contains, in its ammonia and phosphorie acid, two food elements, which require the presence of each other to be available, manuring with guano insures the action of the phosphoric acid, because the particles of the latter are In immediate contact with ammonia particles, that are at the same time also available to the roots ; and in the same way the phosphoric acid insures and increases the action of the ammonia. In a soil abounding in ammonia, manuring with phosphates alone possessing the same degree of solubil- ity, will produce the same effect as guano. When ammonia salts fail to produce any effect on a field whilst guano is found to act favourably, there is reason to attribute the beneficial effect of the guano principally to the phosphoric acid in it; but in the reverse case the conclusion would not hold equally good, because the salts of ammonia produce two dif- ferent kinds of effects; they may, under certain cireum- stances, considerably increase the amount of produce, and yet the favourable effect may not be positively at- tributed to the action of ammonia as such (see page 86). The presence in the soil of a sufficient quantity of potash and silicic acid is always presupposed when guano increases the produce of corn; and on a soil rich in potash and magnesia, the application of guano alone insures a succession of crops of such plants, which, like potatoes, require for their growth chiefly potash and magnesia. feadows and corn fields which gave at first large 252 GUANO. crops with guano, become at last, by the continued use of this agent, frequently so drained of' silicic acid and potash, as to lose for many years their original produc- tiveness. At the same time it cannot be denied that there may be many soils which, for several years, by the aid of guano alone, might be made to produce high cereal crops before this state of exhaustion appears ; but it will at last inevitably come, and it will then be very difficult to repair the damage. In 800 ewt. of farm-yard manure with which a hec- tare of land is mannred in a rotation of crops, the soil receives (according to Voelker’s analysis) the same quantity of phosphates and of nitrogen as in 800 kilo- grammes (15°7 ewt.) of guano; in other words, there is as much of these two elements of food for plants con- tained in 1 lb. of the latter agent as in 50 Ibs. of farm- yard manure. Guano, therefore, contains these ele- ments in the most concentrated form, and permits the application of them to certain parts of the field more conveniently than by farm-yard manure, as is often ad- vantageously done after putting in the seed. In many places, guano is mixed with gypsum to reduce its over- powerful action. The gypsum divides the guano par- ticles and causes them to be more equally distributed over the field; but there is no real diminution of the chemical action of the ammoniacal salts; the gypsum decomposes the oxalate and the phosphate of ammonia into sulphate of ammonia and phosphate and oxalate of lime. The phosphate of lime formed in this way is in a state of infinitely fine division, in which it is most suitable for the roots of plants; however, a small por- tion only of the phosphoric acid is converted into this state, and with the removal of the oxalic acid, ceases, also, the beneficial influence which the latter exercises in promoting the diffusion of the phosphoric acid. It will, therefore, be found much more effective to moisten the guano with water to which a little sulphuric acid has been added, and to mix it, after twenty-four hours, with saw-dust, turf-dust, or mould, instead of gypsum, and to strew this mixture over the surface of the field. The rain water dissolves out the phosphat GUANO AND SULPHURIC ACL. 253 of ammonia, which slowly sinks into the ground, and all parts of the soil with which the solution comes in contact are enriched at the same time with phosphoric acid and ammonia. If to the saw-dust, turf-dust, &ce., gypsum is added, it decomposes with the phosphate of ammonia into very finely-divided phosphate of lime and sulphate of ammonia, which are separated by the rain water; the soluble sulphate of ammonia penetrating deeper into the ground and carrying down with it a small quantity of the phosphate of lime, whilst the main bulk of the latter is left on the top. On land poor in potash, the addition of wood ashes to the guano, moistened with water and sulphuric acid, will be found beneficial, as the carbonate of potash de- composes with the phosphate of ammonia into carbonate of ammonia and phosphate of potash, and the potash does not interfere with the phosphoric acid penetrating into the soil. The results obtained, in the Saxon experiments, by manuring with guano, afford aclear insight into all the pe- culiarities observed in the action of this manuring agent. If we compare the produce severally obtained by manuring with guano and with farm-yard manure (see page 186), we are led to the following considerations on the condition of the experimental field :— Manuring with guano. Cunnersdorf. Mausegast. Kotitz. Oberbobritzsch. Ibs Ibs. Ibs. Ibs Quantity of guano t 379 411 4}1 616 Sppliedt sia sie 1851, ABV EN CORI a laic, see sted: The effect of guano upon the straw produce was here out of all proportion greater than that of farm-yard manure, whilst the produce of corn was smaller. It is quite evident that one constituent acting more power- fully in the direction of the formation of straw was supplied to the field in larger proportion in the guano than in the farm-yard manure. Experiments with superphosphate (excluding ammonia), or with an am- moniacal salt (excluding phosphoric acid), would have shown to which of these two elements the difference in the produce was owing. At Oberbobritzsch the increase of produce was— Corn. Straw. Ratio. Ibs. Ibs. Ibs. By farm-yard manure (314 ewt.)... 452 918 = 1:2 By euano (G1G1DS)-<—.c<..-2 erat tse 938 2812 =i 8 As the quantity of guano used at Oberbobritzsch was about 50 per cent. more than in the preceding experi- ments, no comparison as to amount can be made between the produce of this field and that of the others. What is again remarkable here is the similarity of the condition of this and the Miusegast field; on both, 256 GUANO. farm-yard manure gave straw and corn in the propor- tion of 1:2; guano, in the proportion of 1:3. As regards the power of the soluble guano constituents to pass through the soil, we find from these experiments the same conditions existing as with those of farm-yard manure. At Cunnersdorf and Kotitz the whole guano constituents hardly produced any effect upon the clover crop; whilst at Miusegast and Oberbobritzsch a per- ceptible increase was the result. Silicic acid, which gives strength and firmness to stalks and leaves, is not one of the ingredients of guano; hence, after manuring with guano, the tendency of the cereals to lodge, so much dreaded by agriculturists, is observed on many fields poor in silicic acid, whilst on others abounding in this substance it does not occur. On many soils this tendency may be cured by dressing with lime before applying the guano; and in other cases it may be lessened by mixing dung made from straw with the guano. If we calculate the increase in the produce of cereals, potatoes, and clover, obtained severally in the years 1851 to 1854, from 100 lbs, of guano we find 100 lbs. of guano gave increase of produce. Cunnersdorf. Mausegast. Kétitz. Oberbobritzsch. lbs Ibs. Ibs. Ibs. 1851 and 1853. Ryevandsoats.-) 1088 646 ob4 731 1852. Potatoes). scicus calc oe 326 225 112 646 1854. Clowerinets: oie wires 36 172 89 670 These results show that the same quantity of guano has an equally dissimilar effect upon different fields as farm-yard manure, and that it is quite impossible to draw from the crops obtained any inference as to the quality or quantity of the manuring agent employed to produce them. The field at Mausegast had received INCREASE OF PRODUCE BY GUANO. 257 the same amount of guano as the Kotitz field, both, accordingly, the same quantity of nitrogen and phos- phorie acid ; yet in cereals and potatoes the increase of produce was twice as great, and in clover much greater in the former than in the latter. : How very little the crops will enable us to draw comparisons between the effects of the several constitu- ents of one and the same manuring agent, may be clearly seen from the results of the experiments at Cunnersdorf and Oberbobritzsch. At Cunnersdort, 100 Ibs. of guano gave an increase of produce in cereals, potatoes, and clover, containing— Phosphoric Nitrogen. Potash. acid. Lime. Ibs. Ibs. lbs. Ibs, Increase of produce... 92 16:1 3:°5 3°6 The guano contained... 13°0 FOn S120 12:0 More in the manure. . 3°8 — 85 8-4 less in the crops. Lessin the manure... — 14:1 — — more in the crops. At Oberbobritzsch, 100 lbs. of guano gave an increase of produce, containing— Phosphoric Nitrogen. Potash. acid. Lime. Ibs. Ibs. lbs. lbs. Increase of produce... 23°0 15°5 Gre 211659 The guano contained.. 13°0 PO A 0 eae) More in the manure... — _ 5:9 — less in the crops. Less in the manure... 10°0 13° _ 4-9 more in the crops. The difference in the effect produced by the guano on the two fields is most strikingly exhibited by these tables. At Cunnersdorf the produce reaped contained 30 per cent. less, at Oberbobritzsch 77 per cent. more nitrogen than the manure applied. CHAPTER VII. POUDRETTE—HUMAN EXCREMENTS. Poudrette, nature of ; small amount of the food of plants in it—Human excrement its value—Construction of the privies in the barracks at Rastadt—Calculation of the amount of corn produced by the excrement collected ; importance to the neighbourhood —Its effect not impaired by deodorising with sulphate of iron— The excrement of the inhabitants of towns as manure—Its importance. JDOUDRETTE, sold as manure, should consist simply of the desiccated excrements of man made into a transportable form. This is not the case, however, as most poudrettes contain, in reality, only a comparative- ly small proportion of excrementitious matter. To show this, it will suffice to point out that the poudrette of Montfaucon, which is one of the best sorts, contains 28 per cent., that of Dresden from 43 to 56 per cent., that of Frankfort above 50 per cent., of sand. No kind of poudrette is ever met with in commerce containing more than 3 per cent. of phosphoric acid, and the same amount of ammonia. The construction of privies in dwelling-houses (at least, in Germany) does not make it practicable to keep out the sweepings and other rub- bish of the house; besides, when emptying the pits, it is often the practice, after taking out the fluid contents, to throw into the residuary mass some solid porous body, such as brown-coal or turf-dust, to make it drier and more convenient for removal. All additions of the kind, of course, diminish the percentage of effective and available food elements, and inerease the costs of trans: port. The privy pits, moreover, are but rarely water- tight, and permit the greater part of the urine and VALUE OF HUMAN EXCREMENTS. 259 other fluid contents to leak away, thus causing the loss of a good deal of the most valuable matter, such as the potash salts, and the soluble phosphates. The follow- ing statement will show the great value of the excre- ment of man. In the fortress of Rastadt and in the soldiers’ barracks in Baden generally, the privies are so constructed that the seats open, through wide funnels, into casks fixed upon carts. By this means the whole of the excrements, both fluid and solid, are collected without the least loss. When the casks are full, they are replaced by empty ones.* The food of the soldier, in Baden, consists chiefly of bread, but also of certain daily rations of meat and vegetables. As the body of an adult does not increase in weight, it needs no particular calculation to make out that the collected excrements must contain the ash- constituents of the bread, meat, and vegetables, and also the whole of the nitrogen of the food. To produce a pound of corn, the soil has to furnish the ash-constituents of that pound of corn; if we sup- ply these ash-constituents to a suitable field, the latter will thereby be enabled to produce, in a number of years, one pound of corn more than it would have done without this additional supply of ash-constituents. The daily ration of a soldier, in Baden, is 2 lbs. of bread; the excrements of the 8000 men of the different garri- sons contain accordingly, per day, the ash-constituents and the nitrogen of 16,000 lbs. of bread, which returned to the soil will fully suffice to reproduce the same quan- tity of corn as had been used, in form of flour, to bake * The price of acart is from 100 to 125 florins = £8 6s. 8d. to £10 8s. 4d. It will last about five years. The original outlay incurred by the Army administration in Baden, in 1856 and 1857, for the carts and casks amounting to about £370, was speedily repaid out of the proceeds of the manure. The collective number of the garrisons of Constance, Freiburg, Rastadt, Carlsruhe, Bruchsal, and Mannheim, averages about 8000 men. The receipts for manure sold were in 1852, £285; in 1853, £315; in 1854, £443 ; 1855, £400; 1856, £668; 1857, £668; 1858, £680; £50 or £60 | are to be deducted from these receipts annually for cost of maintenance, repair, ‘&c., of the carts, &e. (‘ Journ. of the Agric. Soc. of Bavaria,’ April 1860. Page 180.) 260 POUDRETTE—HUMAN EXCREMENTS. the 16,000 lbs. of bread. Reckoning 14 lb. of corn to 2 lbs. of bread, the excrements of the soldiers in the Grand Duchy of Baden give, therefore, annually, the ash-constituents required for the production of 43,760 ewts. of corn. The peasants about Rastadt and the other garrison towns, having found out at last by experience the pow- erful fertilising effect of these excrements upon their fields, now pay for every full cask a certain sum (still rising in price every year), which not only has long since repaid the original outlay, besides covering the annual cost of maintenance, repairs, &ec., but actually leaves a handsome profit to the department. The results brought about in these districts are highly interesting. Sandy wastes, more particularly in the vicinity of Rastadt and Carlsruhe, have been turned into smiling corn-fields of great fertility. Assuming, for the sake of illustration, that the peasants had to fuar- nish the whole corn produced by means of this manure, to the military administrations of the several garrison towns, there would thus be established a perfect circu- lation of these conditions of life, which would provide 8000 men with bread, year after year, without in the least reducing the productiveness of the fields on which the corn is grown, because the conditions required for the production of corn being thus always returned to the soil, would continue to circulate and yet always re- main the same.* What is said here about the corn-constituents ap- plies, of course, equally to the constituents of meat and vegetables, which, returned to the field, will reproduce as much meat and vegetable matter as has been con- sumed. The same relation that exists between the in- * When, some years ago, an order was suddenly issued by the authori- ties of the city of Carlsruhe, to deodorise and disinfect the pits and cess- pools with sulphate of iron, before being emptied, the farmers refused at first to pay any longer for the contents, which they argued were by this treatment deprived of their fertilising virtue. Experience has shown that this is not the case, and the disinfected dung commands as high a price now as the article in its pure state did formerly. The dung in the privy carts requires no disinfecting. LOSS OF MANURE BY CARELESSNESS. 261 habitants of the barracks in Baden and the fields sup- plying them with bread, exists equally between the in- abitants of towns and the country around. If it were practicable to collect, without the least loss, all the solid and fluid excrements of all the inhabitants of towns, and to return to each farmer the portion arising from the produce originally supplied by him to the town, the productiveness of his land might be maintained almost unimpaired for ages to come, and the existing store of mineral elements in every fertile field would be amply sufficient for the wants of the increasing populations. At any rate, that store is, at present, still sufficient to do so, although the number of farmers who take care to cover by an adequate supply of suitable manures the loss of mineral matters sustained by the land in the crops grown on it, is but small in proportion to the whole agricultural population. However, sooner or later, the time will come when the deficiency in the store of these mineral matters will be important enough in the eyes of those who are, at present, so void of sense as to be- lieve that the great natural law of restoration does not apply to their own fields; and the sins of the fathers, in this respect, will also be visited upon their posterity. In matters of this kind, inveterate evil habits are but too apt to obscure our better judgment. Even the most ignorant peasant is quite aware that the rain falling upon his dung-heap washes away a great many silver dollars, and that it would be much more profitable to him to have on his fields what now poisons the air of his house and the streets of his village; but he looks on unconcerned, and leaves matters to take their course, because they have always gone on in the same way. CHAPTER VIII. EARTHY PHOSPHATES. High agricultural value of phosphates—Phosphates of commerce ; selection of the kind to be used dependent on the object in view, and on the nature of the soil— The rapidity and duration of the effect of the neutral and of the soluble phos- phate (superphosphate) of lime—The Saxon manuring experiments. HE earthy phosphates are among the most impor- tant agents for restoring the impaired productive- ness of land; not that they influence vegetation in a more marked manner than other mineral elements, but because the system of cultivation pursued by the corn and flesh producing farmer tends to remove them from the soil in larger proportion than other constituents. In choosing among the phosphates of commerce, the farmer should always keep in view the object which he intends to accomplish, as some sorts will answer better for certain purposes than others. The so-called superphosphates are commonly phos- phates to which a certain quantity of sulphuric acid has been added, to convert the insoluble neutral lime salt into a soluble acid salt. When mixed with a salt of ammonia and a salt of potash, they are often called guano or ammoniacal superphosphates. A good super- phosphate generally contains from 10 to 12 per cent. of soluble phosphoric acid. On land poor in clay and lime the superphosphates are particularly suitable for supplying the upper layer of the soil with phosphoric acid. Their effect upon the produce of potatoes and of cereals on such fields is equal to that of Peruvian guano. For turnips and rape, which derive advantage PROPERTIES OF BONE-DUST. 263 from the presence of sulphuric acid, they have a special value. On chalky soils, the free phosphoric and sul- phuric acids are immediately neutralised, by which they are deprived of one of their essential properties, viz., their ready diffusibility, which renders them so valuable a manure for other soils. Among the neutral phosphates bone-dust holds the first rank. When bones are exposed, under high pres- sure, to the action of steam, they lose their toughness, and swell up into a soft gelatinous mass, which, after drying, may be readily ground to a fine powder. In this form it spreads, with great rapidity, through the soil; it dissolves in water to a small but perceptible extent, without requiring the presence of any other solvent. What dissolves, under these circumstances, in water, is a combination of gelatine with phosphate of lime, which is not decomposed by the arable earth, and therefore penetrates deep into the ground—a prop- erty wanting in the superphosphate. In the moist ground, however, the gelatine speedily putrefies, being converted into ammonia compounds, and the phosphate of lime is then retained by the arable earth. Bone-dust is the agent best adapted to supply phosphate of lime to the deeper layers of the arable soil, for which pur- pose the superphosphates are not suitable. Bone-earth, or bone-ash, is the name applied to bones freed, by cal- cination, from the glue or gelatinous part. The animal charcoal of sugar refineries belongs to this category. It must be reduced to the finest powder to render it fully available for manuring purposes. To effect its more speedy distribution through the soil, the presence of a decaying organic substance is necessary to supply the carbonie acid required for its solution in rain water. An excellent way is to mix the powder with farm-yard manure and let the mixture ferment. Among the phos- phates of commerce, the guano coming from the Baker and Jarvis Islands are distinguished, before others, by their acid reaction and greater solubility. They con- tain only a small quantity of an azotised substance, no uric acid, and small proportions of nitric acid, potash, aw 264 EARTHY PHOSPHATES. magneisa, and ammonia. The Baker guano contains as inuch as 80 per cent., the Jarvis guano 33 or 34 per cent. of phosphate of lime; the latter having, besides, 44 per cent. of gypsum. In diffusibility, these guanos, when equally finely powdered, approach nearest to bone- dust: their condition also enables the farmer who wishes to accelerate their action, to convert them most readily into superphosphates (100 parts by weight of Baker guano require 20 to 25 per cent. of concentrated, or 30 to 40 per cent. of the lead chamber sulphuric acid). The influence of these neutral phosphates upon the produce of a field is generally less marked in the first than in the following years, as it takes a certain time to effect their diffusion through the soil. The speedier or slower manifestation of their action upon a field depends, in a great measure, upon the state of fine- ness of the powder, to which they have been reduced, the greater or less porosity of the soil, the presence in it of decaying matters, and careful tillage; but, under any circumstances, they require a certain store of sol- uble silicic acid, and of soda and potash in the soil. The subjoined table giving the produce obtained, in the years 1847-50, by H. Zenker, at Kleinwolmsdorf, in Saxony, shows the difference between guano and bone-dust as regards rapidity and duration of action. In the first year the guano gave the larger produce, which became smaller in each following year; in the first year the crop from the bone-dust was smaller, but in the succeeding years the increase was most remarkable. Bone-dust (822 lbs.). Guano (411 Ibs.). fom oe Straw. = Com. Straw. = Ibs. lbs. Ibs. Ibs. 1847. Wanterscorm. .<.scon 2798 4831 2951 4711 1848. Barley eiolatrals mar eheveteneretone 2862 3510 2484 3201 1849. Vetchesiicin. icon Abo 1591 5697 1095 4450 1850. Wantericorni- > ener 1351 2768 (32 2481 PRODUCE FROM GUANO AND BONE-DUST. 265 The 411 Ibs. guano contained 53, and the total pro- duce 271 lbs. of nitrogen, or very nearly five times more. ‘The bone-dust contained 87 lbs. of nitrogen, whereas in the total produce there were 342 lbs., or nearly nine times more. The bone-dust gave in the crops altogether 71 lbs. of nitrogen more than the guano. Between the quantity of nitrogen in the manure and the amount of the crops reaped, there is, therefore, no connection whatever. Inthe Saxon experiments, the plots manured with bone-dust gave the following results :— Manuring with bone-dust. Cunnersdorf. Kotitz. Oberbobritzsch.| Mausegast. Q Ibs. Ibs. Ibs. lbs. uantity of bone-dust 9 9 TEGO ras Stes al sista tf axe ee oe le 1851 4 C002) 30 ee 1399 1429 2280 1982 See UUEV clea lois ai/ate sass, ar 4167 3707 5036 4365 1852. PEQEMORE MS octe dace sous 00 18250 19511 11488 19483 1853. OE s vx y= oes 2846 | 1108 1718 1405 OO SURA WIS Sins c's t's cht 8 3105 1224 1969 1905 1854. OIG eae 10393 2186 7145 5639 Increase of produce over the unmanured field (see p. 186). Mausegast. Cunnersdorf. Kotitz. Oberbobritzsch.| (1853, barley instead of oats.) lbs. lbs. Ibs Ibs 1851 A MEOOUIL S32 sata a cveneie 227 165. TTT _— PES HENS Wite oS o'c.e's) «, «oft 1216 694 2021 oe 1852. Potatoes:. .. <<... eedraiate 1583 934 1737 2587 1853. MOR COR on «oe See sere 827 — 190 116 te RINAWio ws. fa) of etce'al ore 642 — 157 65 1854 Clover ...... dave grms. grains. grms. grains. 1 litre* of Bogenhausen earth took up | 2°824=43°5 2259=34788 Ue Schleissheim earth ...... 2°397=37'0 1917=29521 Hl earth from Botanic Gardens | 3:000=46°2 2400=36960 Sa subsoil from Bogenhausen . | 8°288=50°6 2630=40502 1 ae Wheater sori cieratal.i:.. 2°471=38°0 1976=30430 Ace OUMUCE AWOWGEL sic ayers slcieis.e @ 6°301=97°0 5040=77616 The investigation into the alterations produced in the earth by the absorption of lime, more especially as regards potash and silicic acid rendered soluble, is not yet terminated. * ] Litre = 1 cubic decimétre= 61 cubic inches. Ao IP oP EN. Dt Cot 33 APPENDIX A (page 33). EXAMINATION OF BEECH-LEAVES AT DIFFERENT STAGES OF GROWTH. (DR. ZOELLER.) Beech leaves and asparagus, their ash-constituents at different periods of growth— The amylum of the palm—Motion of sap in plants—Drain, lysimeter, river, and bog water, their constituents—Fontinalis antipyretica from two different waters, ash-constituents— Vegetation of maize in solutions of its food—Experiments on the growth of beans in pure and prepared turf, results—Japanese agriculture— The cultivated soil of the torrid zone, its exhaustibility, its manure—Analysis of clover by Pincus—Cloyer sickness, its cause HE beech tree (/fagus sylvatica), from which the leaves ex- amined were gathered, stands in the Botanical Garden of Munich. The leaves marked I. period were taken from the tree of four different sizes, on May 16, 1861. The smallest leaves a were just unfolded from the leaf-bud, whilst those marked d were fully expanded. There were between a and d a difference of four days’ growth. The other two sets, marked severally b and c, were in size and period of growth intermediate between a and d. The leaves of the I. period were very delicate, and of yellowish green colour. The leaves of the II. period were gathered on July 18, those of the III. period on October 15, 1861. The leaves of each period possessed among themselves the same size and firmness of structure. The colour of the July leaves was dark green, of those of October somewhat lighter. The leaves of the IV. period were from the same tree, but had been gathered in the end of November, 1860. They had withered on the tree, and were quite dry. EXAMINATION OF BEECH-LEAVES. 333 One hundred parts by weight of the fresh beech leaves con- tained :— I. Period. Il. Ill. - —~—_—_—_————.,, Period. Period. a b e d Dry substance ...........+ 80°29 22°04 21°58 21°52 4413 43:23 VU nears 69°71 77°96 T8:47 T7846 55°87 56°77 One thousand fresh leaves contained, in grammes :— Dry substance ..........00 10°01 15°90 §=82°63 = 60°00 -:116°16 = 117°53 \)/ AUIS S SACS S pSaOe sre Boot 22°61 57°26 118°91 218°31 147°04 154°33 Total weight of 1000 leaves.. 82°62 73°16 15154 278°31 263°20 271°86 Ash of dry leaves percent... 465 540 582 576 757 1015 The amount of water in the air-dried leaves of the IV. period was 11°89 per cent. The quantity of ash left by the dried leaves was 8°70 per cent. For the ash analysis of the leaves of the period I., an equal number of leaves }, c, d, were incinerated. One hundred parts of the ash of the leaves contained :— I. Period. | II. Period. | IIT. Period. | IV. Period. 16th May, 1Sth July, 14th October,| End of Noy., 1861. 1861. 1861. 1860. Sadat so 2. nome 2°30 2°34 1-01 —* Parapet kk 29°95 10°72 4-85 0:99 Mapnesia..........-.--- 3:10 3°52 2°79 713 Iria) hee ne tec 9°83 26°46 84°05 84°13 Sesquioxide of iron..... 0°59 ool 0°94 1:10 Phosphoric acid........ 24°21 5°18 8°48 1°95 Sulphuric acid ......... —* ‘3 —_ 4-98 SIROTA CRE: C3 OREN eee 1°19 13°37 20°68 24°37 Carbonic acid and con- 7 stituents not deter- 28°83 87°50 32°20 25°35 FMATIED! 8555 4 odie eyerm is otal wot) do) cind' sx 10000 100-00 100-00 100°00 _—$—$ * Not determined. 334 APPENDIX A. Analysis of the ash of the leaves of the horse-chestnut and the walnut-tree, by E. Starrer. (‘An. der Chem. und Pharm.,’ vol. 1xxvi. p. 372.) | Horse-chestnut. Walnut-tree. Spring. Autumn. Spring. Autumn, Moisture in 100 parts of fresh substance, 82°09 56°27 82°15 63°31 dried at 212° Fahr... | Pepecnts ofaskintiet) rare | ass | ron | “2ato Ficten bubetan caer ctyleah oae8 752 w719 | 7008 100 parts of ash con- tained— POtaS be mae itecerieie stir 46°38 14:17 42°04 25°48 Ij De geassdioodosdodoe 13°17 40°48 26°86 53°65 Magnesia....... o4g0006 5°15 7-78 4°55 9°83 INNIS Sonos ob ob IDC 0°41 0°51 0-18 0°06 Sesquioxide of iron..... 1°63 4°69 0°42 0°52 Sulphuric acid ......... 2°45 1°69 2°58 2°65 PIC C FACTS eererenete ete ere 1°76 13°91 1:21 2°02 Phosphoric acid........ 24°40 8°22 21°12 4°04 Chloride of potassium... 4°65 8°55 1:04 1°73 Motalisd apie\adich! tee 100:00 100-00 100-00 99°98 Analysis of the ash of flowering asparagus shoots, and of withered shoots with ripe fruit.—Dr. ZOELLER. ; nba Flowering |Autumnshoots shoots. with ripe fruit. Moisture in 100 parts of the fresh substance, ? 6 dried at /Qvo Mah es cerecets ly coacieeonete t eres nee Per cents of ash of the fresh substance......... 0-946 4°13 Per cents of ash of the dried substance......... 6°050 10°13 100 parts of ash contain— Sodan wishares x seers rf isersteictorsvstone:evels speroteyaatclees 5-11 5°25 Potash ccrcie cmismicite ce aleters cio atereiewsisre sie eaiste tie. « 84°40 a le(re IMG ONES aie eieclcieleeielel= etefalsteeioieieislotersieteletelersrsi Gb aaobs5 sabac 0°266 | 03801 | O°384 | 0°303 | 0°226 | 0°224 SS ALL toyole sie lverieteaisisielee tne 0°155 | 0°237 | 0°155 | 0°105 | 0°062 | 0:088 SWisieagodes sHeduseas 4:068 | 4:226 |10°829 | 7-463 | 2°998 | 4°644 Less the amount of oxy- gen equivalent to the +| 0:051 | 0°053 | 0884 | 0°039 | 0-071 | 0°053 chlorine five «ae spieh ici ISUITWANO ae aeors ceo OEG 4-017 | 4°163 | 9°945 | 7-424 | 2°927 | 4°691 Loss and carbonic acid 4:968 | 4°051 | 4:253 | 0°257 | 1:987 | 3°410 SHAS G Sunpee Spoon 8985 | 8214 |14°198 | 7671 | 4°864 | 8-001 1,000,000 litres of water, passed through 10 inches of the soils already described, contain— ig II. III. VE Vv. VI. grms. | grms. | grms. | grms. | grms. | germs. Solid residue left at 212° F. 307. 86 | 328°46 |504°58 | 439°76 | 294-42 | 259-35 Ash contained in it....... 925°83 | 248°69 | 436°84 | 3874°04 | 224°21 | 200-71 Sodanteductivtesiot ccmeiaciee 8°56 9°79 |116°92 | 71°85 | 18-22 755 Potashys4. ane eee 2°56 2°63 1°20 2°00 1:93 0°94 WIEN cooooosbos 8005 IASQOM isl | 16131)" Tbe) “2s -e sie Lime va vecsposbllevete enovelsiene iets 82°78 | 98°65 | 83°73 | 102°59 83°41 | 85°73 Oxidejofiron.s..):.teeneen 3°94 3°31 3°69 4°75 5°81 3°79 Chlorine. eee eeeee UG T(VE 9:47 | 139:49 | 10°18 | 19-18 771 Phosphoric acid.......... _ = 0°31 _ 0-42 | 0°48 INTURICEACIGEcreeierreeteln cere — _ — |187°04 — — Sulphuric/acrds ce O8SST-0 am 61F0-0 000-001} 6690-0 | 000-001 | £060-0 | 000-001} $180-0 | 000-00L | GFE63-0 | 000-001 | Sé9ST-0 660-89 | sLPFO-0 | sGl-67 | c0S70-0 | c0G-Ih | sS0-0 | 94¢-11 | 9660-0 | 109-82 8¢-6 £G00-0 0¢-0L | £600-0 06-8 6100-0 | 186-16 | €S640-0 | 8&6.) T&L10-0 901} 90vI} 90v1} 90v1y 90vd} 901} | 6Z0-T 6200-0 | 098-8 200-0 | — = = a 97-6 0600-0 | STT-0 96000-0 | ¢9L-T 6800-0 61-1 6100-0 16.6 1600-0 OL-T 6000-0 | 898-6L | 88460-0 | 186-0 48000-0 a) 36L-L 26100-0 | sol. 26900-0 | 216-6 z8L00-0 | §&1-0 06000-0 | 801-0 11.000-0 ‘a a =) 1G-& 6600-0 61L- 9600-0 | 686.9 1210-0 | 990-1 9100.0 B SPL 0100-0 LT-OL | 6600-0 76-81 | FS10-0 | 181-7 | 0880-0 | £96-6 €9700-0 a 69-11 | $310.0 T¥-9 8200-0 O8-1L | 9600-0 | $2¢.6 69900-0 | 06-8 686 10-0 B 181-8 11900:0 | 194-4 18F00-0 | 1ST) 18200-0 | GE8.T €1700-0 | 196-1 86100-0 FL-G _$100-0 62-9 _8£00-0 10-8 _$200-0 661-0 £9100-0 008-0 6100-0 19}JVUL |*SOTIMALAS| *19}CUE |SOTMTIVIS) *1097CUT |‘SOMMUTBIS) *10q;0U1 |‘souIMBIS| “10}]vUN |‘souTUIeIs PILOS Jo 000T PILOs Jo 000T PITOs Jo 000L P}Os Jo 000T PILOS Jo 000T "qu00 Jog uy ‘yued log ul yuo. Log ul ‘ued Jog ul yued 10g ul se a ———S$ Jur ae | er ‘puns ‘10};vUI a[qnOsuy z ‘epog r Ja}jeu oluvsi0ul Jo AyWUCNb yrjo, *** anpiser pros jo AyyWUVNb [eyoy, O0SILL-O [[Sisleeniaieieieie sce TOI BOL CLUBS oasfeyouy oy} W01 ———_—_ —___ — 348 ‘Z[I 94} WOT ny ‘NOSNHOG ‘9 ‘HL udsay OY} WoL ne “19ST 04} WOT ONO 04} MOI ——_—_—_—___—__—_ =—— “NIDLSLLI A ————____—_——_. ‘sdan Mand fo sashywup- eee ewes et weee eee seer eases wesc reesesee eereeoseesee eeeeesoscees ee fee eseesseee teeees* prog orang ****plov o1oydsoyg see" prov ornydjng “*9** TOIL JO opIxg see eeeee es cemmmnpy eevee eses BISOUSU I Pe awry seeeeeeeerss Ustiog ss eeccceces unissejod jo eprlolqp TIBCOO SUNG IIH seFalg ales jo apluolyy MOSS WATER. 349 IV.—Moss Water from the neighbourhood of Schleissheim.—Dnr. WITTSTEIN. The composition of the water was found to be as follows:— In 1000 grammes In 100 parts of of water. solid matter. WhlormGe Gf BOGIUIN Se iciccceeccccaeclesss 0:00280 1101 JIN MELD Pe ARCHOS TORR OREO Oar 0:00022 0°086 REN sateen oes orcihs crone «hci lel alee stumtotelovelae one 0:00551 2°167 LUNTIG a St AR POBRDOOEE COOBODOSE OSD OBE baeC 0'05266 20°728 VI SETIGU Muir Statere oiators reya aretclolaveleie atars aot Yo 0°00921 3°627 J ALI OT GeROR OCI IEDRISTOCOCIOBCIOE Irate 0°00029 07114 PST Ob TPO ois etal ciai Cad > MgO CaO KO SO Absorbed : = Gels =17; —— =24 MgO CaO MgO IV. Period. From July 27 to August 1.—At the commence- ment the plant weighed 147 grammes, had eleven leaves, with a surface of 1160 square centimétres; water exhaled = 1 litre; to the solution was added 0:1 gramme of phosphate of iron; the roots became distinctly reddish yellow. The plants received twice as much KOPO,; as in the second period. A B Cc i WiT OGG il-akaeeedseEceD Sodc 1:0800 ? ? Sulphuric acid .............. 0°2475 0-1874 071101 WAOSPHOTIC ACIG sae ocsercene - 071250 0°0000 0°1250 MATE eters fot ss a ty orclasy ee sie are oeadis i 071188 0°2232 Magnesia 0-0719 0°0446 GEARS sis cidve.e1sis araue (alate aisiaie «(erate ‘ 071296 0°4222 2°4628 0°4617 0°9211 Proportions between bases and acids,— é CaO KO so Given: US ep - = 21 MgO CAO a MgO CaO KO so Absorbed : 0; —~=18; —— = 2:3 fake” Oak MO To ascertain how far the results from this artificial mode of cultivation may be compared with those produced under natural circumstances, maize of the same kind was planted in the garden in the middle of May. The latter were exposed to the same at- mospheric conditions as the experimental plants. On August 1, a plant from the garden of the same period of vegetation as the ex- BD4 APPENDIX E. perimental plant, with also fifteen leaves, and visible male flowers, weighed 1260 grammes, that is to say, seven times as much as the artificially reared plant. The stem of the garden plant from the lower knot to the summit of the flower-stalk measured 150 centi- metres, being three times the height of the experimental plant. V. Period. From August 1 to 10.—At the commencement the plant weighed 173 grammes; the stem was 52 centimétres high ; in the middle of the period the plant had fifteen large fine green leaves, with a surface of 1420 square centimétres. In this period double the quantity of water (2 litres) was exhaled, and as the older roots were distinctly reddish yellow in colour, the plant re- ceived no more phosphate of iron, but thrice as much phosphate of potash as in the second period. On August 6 and 7, the male flower, consisting of seven single ears, was fully expanded from the sheath, the stem was strong, and 70 centimétres high. On August 7, a fully formed female flower appeared; on bai 9, the anthers began to shed their pollen. A B Cc IGA HOGA See asus Seoneoaee 1:0800 ? 2 Sulphuric acid . eee, OATS 01640 0°0835 Phosphoric acid.. ofl SLO ae 0-0020 071855 GUM OM asain cise ere 0°3420 01236 0°2184 Magnesia ....... evens aen Oalelae 0:0790 0°0370 otashisnsnccrcemetrdercnjee siete 0°5927 0°1894 0°4033 2°5662 0°5580 09277 Proportions between bases and acids, CaO KO see SOs Given: ——— = 29; = 2: iven 20 i Ga iy e ‘ 2-1 CaO KO SO; b ‘bh d: = 5:9 OSS 1: a 3 Absorbe 20 > Ga Se ae 2 As the plant in this period flowered, and earlier experiments had shown that maize dug up at the ‘period of flowering, and placed in river water furnished still ripe seeds, and also by the ad- dition of the salts which the plant in each period had taken up in proportion to its increase in weight in the first four periods, it ap- peared that it must contain fully as much salts as the plant in its normal condition in the field takes up, if placed from this period only in distilled water. VI. Period. From August 10 to 16.—At the commencement the plant weighed 255 grammes, and had 15 fully expanded leaves with a surface of 2640 square centimétres: 2 litres of water were exhaled. On August 10, the anthers had almost completely shed their pollen. The stem shot up rapidly, and on the 12th it measured to the tip of the flower 1 métre in height. On the 13th a second EXPERIMENTS ON VEGETATION IN soLuTIONS. 3855 female flower appeared, which was surrounded with paper to pro- tect it from dust. On August 16 the height of the plant was 1:1 mettre; it did not grow any more. The fruit-bearing stalk was, on August 16, already 2 decimétres long, and had below a thickness of 4 centimetres. On August 16 the water was drawn off and analysed. Present. Not present. 0-016 gramme potash. Sulphuric acid (only indistinct opales- 0-008 Ks lime. cence with chloride of barium). 0:001 + phosphoric acid. Magnesia. Iron and silicic acid. From the circumstance that in this solution there was no silicic acid, it is plain that the glass vessel had furnished none to the fluid by decomposition in the course of one to two weeks. VII. Period. From August 16 to September 4,— Weight of plant on 16 August.............5..5 980 grammes. § Pp g g ee = OOP ae at 9 o’clock a.m. 316 ac “cc “ 99 “ “ 9 “ce pm. 320 “cc ac ae 98 “ . “ 9 “oe “ce 830 ac “c “c 1 Sept. «“ 9 “ «é 827 “ce “ce “ce 4 “ “cc 9 “ss ce 317 “ From September 1 the weight diminished by the drying of the leaves, and as this decrease was accidental, the plant was not thenceforward weighed. The leaves shrivelled. The plant had exhaled 34 litres of water in the period. At this time it was placed in a vessel containing 1°5 litres of water, to determine what salts returned to the water by endosmone. The water was kept up at the same level by daily additions, and at last was allowed to exhale until the residue was 1 litre. In this litre were found 0.031 carbonate of lime, and 0.007 carbonate of magnesia. Both salts were left in the basin undissolved after evaporation, and after the residue had been treated with water. 5 In the water with which the residue left on evaporation in the ban had been extracted, the following substances were found in solution :— 0020 lime : together with organic matter which 00006 phosphoric acid reduced a solution of oxide of copper 0°0034 potash and potash. Tn this last solution not a trace of iron, sulphuric acid or mag- nesia was found. As the preceding analyses indicate, the solution of nutritive matters for graminew must have the following com- position :— MgOSO; + 4CaONO; + 4KONO; + xKOPOs (Compare ‘Chem. Central Blatt, 1861,’ s. 465, 564, and 945.) * At all periods the plants threw off organic substances, but chiefly in the last periods, ‘ 3856 APPENDIX E. I].—Experiments of Stohmann. The experiments of Stohmann agree in their main results with those of Knop. According to these experiments, the maize plant grows to full maturity if in the beginning of May the seed which has germinated in water, and has shot forth roots, is placed in a solution containing the food of maize in the proportions in which they exist in the ashes, if at the same time there has been added to it so much nitrate of ammonia that to every part of phosphoric acid in the solution there are two parts of nitrogen, and if finally it has been diluted with distilled water to a concentration of three parts of solid matter per 1000 parts. The plants must’ grow in a sunny spot, and the water exhaled by the leaves must be daily replaced by distilled water, and the solution tested as to its reac- tion. The solution must always react, slightly acid, and be main- tained in this condition by the addition from time to time of a few drops of phosphoric acid. If these conditions are fulfilled, there is no necessity for any artificial source of carbonic acid, but by means of the atmospheric carbonic acid alone there are produced fully formed plants which, under favourable circumstances, attain a height of 7 feet.* The experiments of Stohmann were more especially directed to the influence exercised on the growth of the maize plant by the withdrawal of one element of food. In this point the results differ from those of Knop. Whilst in the experiments of the latter, maize was found to grow perfectly without silicic acid, soda, or ammonia, Stohmann made use of silicic acid in all his experiments, and found further that by the complete withdrawal of ammonia and even soda the plants grew quite well. On withdrawing ammonia completely and replacing it by nitric acid, Stohmann found that the plants grew perfectly well for the first ten to twelve days, then they became of a pale yellowish green, and the vegetation proceeded extremely slowly. If after a month’s vegetation a little ammonia (in the form of nitrate or acetate) was given to the plants, they died very quickly. Without this supply of ammonia the blanched, sickly vegetation continued; the plant did not die, and yet it could not be said to live.t In the experiments made without soda, it was found that the plant could dispense with this substance at first, but its pro- gress was soon arrested if the soda was completely withdrawn. The nitrate of lime of the normal solution was in another experi- ment replaced by a corresponding quantity of nitrate of magnesia. The growth of the maize plant was after a short time much re- tarded, only a few small, thin leaves being developed. By the ad- dition of a little nitrate of lime to the growing plant, the most * According to Knop maize plants growing in a watery solution give off carbonic acid continuously from their roots. + Compare Knop, ‘Chem. Central Bl. 1862,’ s, 257. * EXPERIMENTS ON VEGETATION IN sOLUTIONS. 3857 remarkable change was however produced. Scarcely five lours elapsed before the growth of the plant, which had been stationary for four weeks, awakened to a new life, and proceeded from this time forth in the best manner possible. A plant without the after addition of nitrate of lime remained stationary, making no progress whatever: the maize plant, therefore, requires lime immediately after the commencement of its growth. In an experiment in which the magnesia was replaced by nitrate of lime, the same result was obtained as when lime was wanting. In this case, also, the vegetation was very poor. A supply of mag- nesia in the form of nitrate, exerted here also the most favourable action, only the effect was not so quickly produced as in the case of lime. Even by the complete withdrawal of nitric acid the maize plant did not grow. In these experiments it is true the alkalies, as well as the alkaline earths, were in part supplied in the form of sulphates and chlorides. Chlorine and sulphuric acid, however, are required only to a limited extent in the vegetable organism. The same holds good in the experiment without nitrogen.