Productive farming; or, A familiar digest of the recent discoveries of Liebig, Johnston, Davy, and other celebrated writers on vegetable chemistry; showing how the results of tillage might be greatly augmented

CHAPTER I. Page Introductory Observations, 9

CHAPTER n.

Some Account of the Simple or Elementary Bodies found

(combined or uncombined) in Animals, Plants, and Soils, - 23

CHAPTER ni.

Plants and Animals are both alike endowed with Life ; the

Elementary Materials and many of the Proximate Principles •

of Animal and Vegetable matter are precisely identical — they have similar Organs essential to their growth and reproduction, and are nourished or destroyed by the same agencies, 33

CHAPTER IV.

Of the Elementary Composition of Water ; of the Composition of the Atmosphere; and of the artificial Application of Water to Grass Lands, 55

CHAPTER V.

Of the Nature of Vegetable Growth ; the true use of Vegetable Mould or Humus; and of the Sources of the Elementary Constituents of Plants, 60

CHAPTER VI.

Of the Sources of the Saline, Earthy, and other Unorganized

Constituents of Vegetables, 81

CHAPTER VII.

Of the necessary Relation between the Composition of a Soil and the Vegetables it is fitted to raise. Fallowing and Green Crops considered as Vegetable Manure, - - - 86

CONTENTS.

CHAPTER VIII.

Of the Nature and correct Use of the Excrements of Animals considered as Manure ; the Mode of its Action and Preservation. — Bone Dust, and dead Animal Matter, - - - 97

CHAPTER IX.

Of the comparative Value of Vegetable Manure, as contrasted

with Animal Excrements, ------- 116

CHAPTER X.

Of Manures of Mineral Origin, or Fossil and Artificial or Chemical Manures ; their Preparation, and the Manner in which they act. — Of Lime in its dift'erent States ; its Operation as a Manure. — Of Alkalies and Common Salt, as to their Action upon the Land, ----- . 119

CHAPTER XI.

jOf the Composition of Productive Soils, and of the Agency of the Elements in their Natural Formation from the Rocks upon which they rest, • 129

CHAPTER XII.

Of the Chemical Analysis of Soils, and how far this is practicable by tlie Farmer, 143

CHAPTER XIII.

Of Advertised " Fertilizers" for the Soil, - . • - 148

Preface

This book is a compilation. The object of its compiler has been the simplification of the more strictlyscientific and technical writings of the principal agricultural writers of the present age. Practical farmers require the simplest and most elementary statements. The position of the agricultural interest renders it desirable that the recent views of Professor Liebig, the distinguished chemist, who has effected a complete revolution in the physiology of vegetation, should be presented in a style free from difficulty, condensed and separated from such portions of his work as would only bewilder ordinary readers. How far the attempt may be successful, the world must judge. The published lectures of the late Sir Humphrey Davy have been freely cited, and such portions selected, as, while they do not clash with later discovery, may prove a useful addition. The writings of Mr. Johnston, whose little elementary book is well known, have been laid under contribution, as well as the lectures of Dr. Mason Good ; and such useful statements as have appeared at various periods in periodicals devoted to the furtherance of agricultural science. It is to be hoped, that without torturing the sense of previous writers, nothing will be found in these b PREFACE.

pages inconsistent with the doctrines of the learned German professor, whose writings, though admirably adapted for the perusal of those who are familiar with chemistry and physiology, are susceptible of being abridged and presented to the industrious farmer in a form less repulsive, because less learned, and consequently, more generally intelligible.

MODERN AGEICULTUUE

CHAPTER I.

Introductory Observations.

Agricultural Science has for its objects all those changes in the arrangements of matter connected with the growth and nourishment of plants, the constitution of soils, the manner in which lands are enriched by manure, or rendered fertile by the different processes of cultivation; and no rational system of farming can be formed without the practical application of well-understood scientific principles. Such a system must be based on an exact acquaintance with the means of nutrition in vegetables, with the influence of soils, and the action of fertilizing materials upon them. The object of the farmer is, to raise from a given extent of land the largest quantity of the most valuable produce at the least cost, with the least permanent injury to the soil ; and the sciences of chemistry and geology throw light on every step he takes, or ought to take, in order to effect this main object. Whoever reasons upon agriculture is obliged continually to recur to these sciences. He feels that, without such knowledge, it is scarcely possible to advance one step ; and, if he be satisfied with insufficient views, it is not because he prefers them to accurate knowledge, but generally because they are more current. It has been said, and undoubtedly with great truth, that a philosopher would most probably make a very unprofitable business of farming ; and this, certainly, would be the case if he were a mere philosopher. But there is 2 good reason to believe, that he would be a more successful aj^riculturist than a person equally ignorant of farming, but ignorant of chemistry altogether: his science, as far as it "Went, would be useful to him.

The great purpose of chemical investigation in agriculture ought, undoubtedly, to be the discovery of improved methods of cultivation ; but to this end, not only practical knowledge but general scientific principles are alike necessary; nor is industry ever so efficacious as when directed by science ; as he who, journeying in the night, aided by the most intelligible directions as to the way, is more certain of his footsteps if he carry a lamp to explore his path. Science cannot long be despised by any persons as the mere speculation of theorists, but must soon be considered, by all ranks of men, in its true point of view, — as the refinement of common sense, guided by experience, gradually substituting sound and rational principles for vague popular prejudices. If land be comparatively unproductive, the sure method of determining the cause is, first to ascertain the exact nature and relative quantities of the ingredients which form the soil, (which can only be done by chemical analysis,) and then to supply such soil with the deficient materials requisite for the growth of such vegetables as it is best fitted to raise. The preparation of compost will only be of real use when materials, which do not afiford singly an efficient or convenient manure, are made to do so by their mixture. Every farmer has it in his power so to compound the best from his store of manuring materials, that the defects of his soil may not only be remedied, but that the crops may receive those substances in sufficient quantity which are required for their vigorous growth.

To do this, however, it is requisite to know not only the component parts of the soil, but also those of the crops. If these are not taken into account, no clear idea either of the composition, much less of the action of manure, will ever be obtained ; and many substances of real value will be tried, and, from misapplication, tend to useless, if not injurious results. Perhaps iron may be found in injurious excess, which may be rendered harmless by the addition of lime ; or an excess of sand may be neutralized by the addition of clay. Is there a deficiency of lime 7 The remedy is obvious ; or an excess of undecomposed vegetable matter may be removed by the judicious use of lime, by paring and burning. With the aid of chemistry, the precise value of any variety of limestone may be determined in a few minutes ; and so its fitness or unfitness, as one among many substances intended to fertilize the soil, may be determined by a less expensive experiment than waiting to observe its action upon the land. In the same way, peat earth of a certain consistence and composition is an excellent manure; but there are some varieties of peat which contain so large a quantity of iron as to be absolutely injurious, if not destructive to corn and grasses. Now, nothing can be more necessary, more useful, and fortunately more simple, than the mode of determining whether a metallic substance be present. More especially, it is solely by a reference to the elementary principles of chemistry, and the ascertained constitution of manures, vegetables, and the air and soil in which they live and thrive, that we can determine whether it is wiser to plough that manure into the land, to apply it in a fresh, or in a fermented and decomposing state.

We know, that soon as dung begins to decompose, it throws off its volatile or gaseous parts. It is necessary that what is thus lost should be examined. It may be (which is the fact) that such evaporation is not only the escape, but the actual loss of that which forms a most material ingredient in the food of plants : and so, whether this shall be supplied gradually to the growing vegetable, or suddenly, is a tantamount question in the mind of an intelligent agriculturist to the inquiry often agitated among practical farmers, and determined only by individual caprice or fancy, as to whether the produce of the stable or the farm-yard is best, when spread upon the soil in a fresh or in a putrid state. When, for instance, it is considered, that with every pound of the strongly-pungent smelling ammonia lost in the air, a loss of at least sixty pounds of corn must correspondingly be sustained, — and that with every pound of urine a pound of wheat might be produced, — not only must we feel surprise at the ignorance which prevails as to the fact, but equally so at the indifference manifested by those who are aware of the value of such manure as to the best mode of applying it. On some soils a plant will thrive, on others it will sicken ; and the same knowledge which will enable us to correct a faulty or weak vegetation, will enable us also to produce far more abundant results than occur under the most favourable ordinary and natural circumstances. Agriculture has hitherto never fairly sought aid from that science which is based on the knowledge of those substances which plants extract from the soil, and of those restored to the soil on which they grow by means of manure.

The application of such principles will be the task of a future generation ; for what can be expected from the present, which recoils with seeming distrust and aversion from all the means of assistance offiered by chemical investigation ? A future generation will derive incalculable advantage from these means of help, and make a rational use of philosophical discoveries. Here a marked and wide difference exists between the progress of manufacture and the history of agricultural operations. We see the steam-engine multiply indefinitely the labour of the human hand — supersede and almost infinitely exceed the united power of brute exertion; invention has lacked no mechanism to produce myriads upon myriads of the same fabric ; thousands of piles of manufactured silks and cottons are produced annually, one factory supplying daily as many yards as would encircle the globe — strange advancement on the ancient spinning-wheel ; while the sons of the soil still toil on through the long summer months, and brave the winter's cold, to reap the same quantity of produce from the soil as their forefathers of a thousand years ago. We do not say that there is no limit to the capabilities of the earth's surface, but fearlessly maintain that such limit is yet far from realization ; and that not until prejudice be silent, and inteUigence more universal, can it be hoped that the broad acres of our island home will yield to science and skill all the treasures they contain.

At a recent meeting of one of the Irish agricultural associations, a Scottish agriculturist is reported to have said, among other things, that " If science were permitted to do for farming all of which science is capable, the clamour about repeal of the Corn Laws would soon cease, and the prospect of starvation before us would vanish." He observed, that " Great Britain, besides supplying her own population with food in abundance, would become an exporting country for ages to come : that unless a more rational system of farming be adopted throughout the country, we shall have want, and its offspring, crime, at our doors and on every side of us. The manufacturers are offering premiums on the increase of population. That population is increasing far beyond the supply of food necessary for it, [he might have added, at the rate of a thousand a day, while the surface of our island remains the same ;] and unless the government, or the great agricultural societies, take the matter in hand, and that speedily, we shall soon feel that, solely from lack of food for her manufacturing population, the greatness of this empire, so long the wonder and envy of the world, will become a thing to be talked of as a tale that has passed away."

Haifa century sufficed to Europeans, not only to equal, but to surpass the Chinese in the arts and manufactures; and this was owing merely to the application of correct principles deduced from the study of chemistry. But how infinitely inferior is the agriculture of Europe, even of boasted England, to that of China! The Chinese are the most admirable gardeners and trainers of plants, for each of which they understand how to prepare and apply the best adapted manure. Their agriculture is the most perfect in the world : and there, where the climate in the most fertile districts differs little from the European, very little value is attached to the excrements of animals. Patient observation of results, and a ready adoption of really useful plans ; steady persistence, not in antiquated methods and notions, but in all that has been found by experience to be beneficial, — has raised the agriculture of that country, long ago, to a position which would rapidly, nay, instantly, be ours, if science were permitted to achieve for us that which, with them, has been the slow growth of centuries of experiment.

The soil of England offers inexhaustible resources, which, when properly appreciated and employed, must increase our wealth, our population, and our physical strength. The same energy of character, the same extent of resources which have always distinguished Englishmen, and made them excel in arms, commerce and learning, only require to be strongly directed to agriculture, to ensure the happiest effects. We possess advantages in the use of machinery and the division of labour, peculiar to ourselves ; and these having been mainly instrumental in aiding one great division of human industry, we are justified in the assertion, that the steam-engine and machinery has not done more for trade, than science and skill, in various ways, may do for land. Although it is obvious to all reflecting persons, that machinery, which is science in another form, is a good thing, we cannot wonder if we find some ready to say, " I know it is a bad thing, for it deprived me of employment." To attempt to convince such a man would be difficult. It would be useless to argue with that man, that a number of individuals had gained, though he was a loser. His loss is to him evident ; and the gain spread over a vast surface of society is an argument which makes no impression upon him.

Besides chemistry, there is another science which has many relations to practical farming — the science of geology, or that which embodies all ascertained facts in regard to the nature and internal structure, both physical and chemical, of the solid surface of our globe. Though the substances of which soils chiefly consist are so few in number, yet every practical man knows how very diversified they are in character, how very different in value. Thus, in some of the southern Enghsh counties we have a white soil, consisting, apparently, of little more than chalk ; in the central part of the country, a wide plain of dark-red land ; in the border counties of Wales, and on many of our coal fields, tracts of country almost perfectly black; while yellow, white and brown lands give the prevailing character to the soils of other districts. These differences arise from the varying proportions in w^hich the sand, lime, clay, and iron which colour the soils have been mixed together. Now, geology explains the cause why they have been so mixed in different parts of the country — by what natural agency, and for what end ; and by its aid we can predict the general quality of the surface-soil, and, more than this, of the unseen sub-soil in the several parts of entire kingdoms. We may learn, if the soil be of inferior quality, and yet susceptible of improvement, whether the means of improving it are likely, in any given locality, to be attainable at a reasonable cost.

Whether we attempt to investigate the composition of natural bodies, or, confining our attention to the review of those general diversities so remarkable on the earth's surface, the division of them all into two grand classes, as simple or compound, is an essential preliminary to a correct comprehension of the subject. Those substances are simple, which cannot, by any known method, be separated, decomposed, or divided, in such a manner as to produce particles different in their properties from one another. On the other hand, those substances are compound which, by experiment, maybe resolved into particles of an unlike nature. Thus, marble is a compound body ; for by a strong heat it is converted into lime— an elastic fluid, which is carbonic acid gas, (itself also a compound,) being disengaged during the process. Vegetable substances, whether in their living or dead state, are mostly of a very compound nature, and consist of a great number of elements. For a period of many centuries, and even till a very late date, there were four substances held to be elementary, or simple. These were Fire, Air, Earth, and Water. Nobody could prove them so ; and yet, of these four bodies, all others in nature were supposed to be constituted. This system continued to be orthodox till very lately, when three of these imaginary elements, namely, Air, Water, and Earth, were proved to be compounds ; and, as we shall see in the progress of this work, a correct understanding of the properties of the atmosphere, and of its relative agency over vegetation, is indispensable to the adoption of such plans as are intended to increase the fertility of the soil.

As to fire, it is still unknown whether it be simple or compound, in what its essence consists, or by what causes its effects are produced. The study of temperature, of the relative dryness or moisture of the air, of the action of the sun's hewt over soils and vegetation, is closely identified with the science of agriculture. The influence of the changes of seasons and of the position of the sun on the phenomena of vegetation, demonstrates the effects of heat on the functions of plants. The matter absorbed from the soil can only enter the roots in a fluid state ; and when the surface is frozen, this mode of communication is suspended. The activity of chemical changes in living vegetables is likewise increased by a certain increase of temperature, as is evident if a stalk of henbane be partially immersed in hot water : its leaves will, for a time, become erect, and quickly forego their drooping arrangement, evidently referable to the increased rapidity with which fluids, under such circumstances, rise in the minute vessels of the vegetable. Heat, then, is rather to be regarded as an agency by which both compound and simple substances are alike affected. What the ancients considered to be simple bodies, are no longer considered to be such : but, in place of these four assumed substances, the chemists of modern times have elevated to the dignity of elements, or simple bodies, a far more numerous race. No one, however, asserts now-a-days, that even these are all absolutely simple. The term " element," intimates no more than that the body to which it is applied has never, in the opinion of modern chemists, been subject to further d vision or decomposition : that it has never been divided into particles, different from one another, or from the original substance. The number of simple, or elementary substances, at present known, and constituting visible Nature around us, xs fifty-four.

Now, if these elementary, or simple substances are placed either artificially, or, as they are presented in the universe, naturally in contact with each other, they combine, or refuse to combine ; and by such combination, when it occurs, a great variety of compound substances are produced. Some combinations are effected instantly, some more slowly and with difficulty, and there are certain elements which can scarcely, by any means, be made to combine. The compounds produced by such combinations possess properties very different from those of the separate elements of which they are composed. Thus, carbonic acid, or the gas which sparkles in fermented liquors, combines very readily with pure caustic lime, and the product of the union is common chalk. So, if the proportions be varied, the same two elements produce the common air we breathe and the strongest aquafortis or nitric acid. The power, in virtue of which simple bodies can combine and produce compounds, is one of which the nature is totally unknown. Chemists have learned no more than that simple bodies, or bodies supposed to be simple, do combine ; but WHY they combine, or W'hat that is which makes them combine, they have not discovered. To the illustrious Dalton belongs the discovery that they do not unite at random, but always in definite proportions of each; so that, if the elements be represented by numbers, the proportions in which they unite may be expressed either by those numbers, or by some simple multiples of them. Thus, sugar and Indian rubber are compounds resolvable into precisely the same ultimate elements, only in different proportions ; and, as the following table will illustrate, nearly one half the weight of all vegetable productions which are gathered for food for man or beast, in their dry state, are but varying compounds of the same elementary or simple bodies, the names of which are appended over the annexed numbers. What the properties of these elements in their separate state may be, is not our immediate purpose.

Carbon. Hydrogen. Oxygen Nitrogen. Ash.

parts by weight in 1000 pounds of each of the above vegetable substances.

If we take the ash left by a known w^eight of wheat straw, or of hay, and mix it with the proper quantities of the four elementary substances named in the foregoing table, we shall certainly be unable, by this process, to lorm either the one or the other. The elements, therefore, into which all vegetable compounds are ultimately resolvable, are not merely mixed together; they are united in some closer and more intimate manner. To this more intimate state of union the term chemical combination is correctly applied. Again, woody fibre, gum, sap, and the various fluids and substances which form a plant, are themselves mostly resolvable into varying proportions of the same ultimate elements, which, taken together form the entire vegetable. Thus, sugar forms one of the proximate principles of the sugar cane, and India rubber is one of the proximate principles of a South American tree, which contains no sugar ; yet sugar and India rubber are essentially composed of the same materials. So, if charcoal be burned in the open air, it slowly disappears, and forms a kind of air or gas, known by the name of carbonic acid, an elastic fluid precisely identical with that which forms the froth in ginger beer or common yeast. Now^, this carbonic acid is formed by the union of the charcoal or carbon, while burning, with one of the elements composing common air, named oxygen; and in this new form, the elements carbon and oxygen are said to be chemically combined. Again, if certain vegetable and animal materials are mixed together, and left to the agency of the atmosphere, they react upon each other — perhaps become heated, as happens in a heap of stable dung, and are said to become decomposed. New compounds are formed from the union of previously existing elements; perhaps ammonia is one of the most common and obvious, as indicated by its effect upon our eyes and nostrils. This, then, is as purely a chemical process as the conversion of wood into vinegar, or into charcoal, or the change that occurs when the flour of grain is converted by the distiller into ardent spirits ; and in all well-directed attempts to fertilize the soil, a knowledge of these changes is absolutely necessary : at least, he who proceeds without it has disappointment in prospect, and gropes in the dark, with uncertainty for his guide.

Now, chemical affinity is not only evident in the changes which masses of dead inorganic matter produce upon each other: it is found to be actively at work in the phenomena of vegetation ; thus proving that the growth of plants is more completely a chemical process than might have been imagined : and, as our further illustrations will tend to prove, the same law of affinity is equally operative upon animal structure, which, like that of plants, is not more truly alive than they. The sap consists of a number of ingredients dissolved in water by chemical attraction ; and it appears to be in consequence of the operation of this power, that certain principles derived from the sap are united to the vegetable organs. By the laws of chemical attraction, different products of vegetation are changed and formed during the process of growth : vegetable and animal remains are decomposed by the action of air and water or exert upon those fluids a mutual agency essential to the change ; rocks are broken down and converted into soils, and soils are more finely divided and fitted as receptacles for the roots of plants. The repulsive energy of solar heat or of that generated during chemical changes of constant occurrence, serves as the only counterbalance to that at' traction which pervades the particles of all living or dead matter : and thus the harmonious circle of growth and decay is produced by their mutual operations. The difl^erent influence of the different solar rays on vegetation is but partially understood. There are rays transmitted from ihe sun which do not impart light, and which yet produce more heat than the visible rays. The effect of these invisible rays is purely chemical and independent of the heat they produce. Thus, potatoes, which sprout in a comparatively dark cellar, send out nearly colourless shoots. Plants kept in the dark in a hot-house, grow luxuriantly, but never acquire their natural colours ; their leaves are white or pale, and their juices watery and sweet. So the upper surface of most leaves is darker than the lower, upon the same principle that the belly of a fish is whiter than its back.

The most obvious instance of Electrical Agency in external nature occurs in thunder and lightning. Electrical changes are of constant occurrence ; but as yet the effects of this power, not as accidental, but as essential to healthy vegetation, have not been correctly estimated. No doubt the germination of seeds, as well as the growth of plants, is materially modified by the peculiar electrical condition of the earth and the atmosphere, and by the varying state of each. It is known that corn will sprout more rapidly and readily in water positively electrified — that is, charged with electricity in excess or beyond its natural quantity ; and that if, by artificial means, water be deprived of its natural amount of electricity, its power of stimulating the growth of seeds is thereby diminished. Experiments made upon the atmosphere show that clouds are usually deficient of electricity ; and as when a cloud is in one state of electricity, the surface of the earth beneath that cloud is brought into the opposite state, it is probable that, in common cases, the surface of the earth is charged with the electric fluid in excess.

We have spoken of Chemical affinity : it is sometimes well named Elective or Chemical attraction, in as much as it is but an exemplification of one form of that law which maintains the order of the universe. It is the expression of the fact, that certain elements of unlike nature combine with each other when placed in contact, or (figuratively speaking) refuse to combine with any other, electing even the proportions in which only such combinations can occur. This affinity is but one division of the great law of attraC' Hon. In this aspect, there are Jive forms in which the relations of all bodies to each other may be arranged. We begin with that which compels the heavenly bodies to rotate round the sun ; or a stone when thrown upwards to fall to the ground — in other words, to gravitate towards the earth's centre. Next, there is the attraction of cohesion : thus, particles of oil will rise through water, and having reached the ransje of each other's attraction, will unite into one common and separate body. It is this form of attraction which gives roundness to the drops of dew, or of the rain as it falls, and is the sole cause of the arched form of the rainbow. In the same way, drops of water or of quicksilver placed upon a dry plate, have a tendency to unite, not only when they touch, but to run together when placed near each other. So, perfectly smooth and polished plates of glass or metal have a strong tendency to cohere. It is by the same means that the great number of rocks seem to be produced that enter into the substance of the earth's solid crust. The lowermost rocks are united by an intimate crystallization which is the most perfect form of cohesive or aggregate attraction that can exist among the particles of solid bodies. The next form of attraction is observed as occurring between bodies unlike in their nature, solids and fluids, capillary attraction, as when sap rises in the minute vessels forming the stem of a tree against its own weight, or in other language, overcoming the attraction of gravitation downwards. The Latin word which signifies a hair, is used in this instance to form the word denoting the extreme tenuity and delicacy of these narrow vessels, as only in such could fluids rise : hence the reason and the wisdom of this arrangement.