Jas. F. W. Johnston

“ In these three soils, then, we have examples, first, of one which contains within itself all the elements of fertility; second, of a soil which is destitute, or nearly so, of certain substances,—which, however, can be readily added by the ordinary manures in general use,—and to which the elements of gypsum are especially useful, in aiding it to feed the potato and the turnip; and, third, of a soil not only poor in many of the necessary species of the inorganic food of plants, but too rich in one which, when present in excess, is prejudicial to vegetable life. ”

“ From the surface of the earth there are continually ascending vapours and exhalations of a more or less noxious kind; these the rains wash out from the air, and bring back to the soil, at once purifying the atmosphere through which they descend, and refreshing and fertilizing the land on which they fall. ”

“ The food of plants we have seen to consist essentially of two kinds, the organic and the inorganic, both of which we have insisted upon as equally necessary to the living vegetable—equally indispensable to its healthy growth. A brief glance at the purposes served by plants in the feeding of animals, will not only confirm this view, but will also throw some additional light upon the kind of inorganic food which the plants must be able to procure, in order that they may be fitted to fulfil their assigned purpose in the economy of nature. ”

“ The reader, therefore, will understand why a diet which will keep up the human strength is easiest compounded of a mixture of vegetable and animal food. It is not merely that such a mixture is more agreeable to the palate, or even that it is absolutely necessary,—for, as already observed, the strength may be fully maintained by vegetable food alone;—it is, that without animal food in one form or another, so large a bulk of vegetable food must be consumed in order to supply the requisite quantity of nitrogen in the form of gluten. ”

“ The fertilizing power of animal manures, in general, is dependent, like [Pg 178] that of the soil itself, upon the happy admixture they contain of a great number, if not of all, those substances which are required by plants in the universal vegetation of the globe. Nothing they contain, therefore, is without its share of influence upon their general effects, yet the amount of nitrogen present in each affords the readiest and most simple criterion by which their agricultural value, compared with that of vegetable matters and with that of each other, can be pretty nearly estimated. ”

“ It is thus evident that a crop of wheat will carry off from the soil—even suppose the whole quantity of ash left by each the same in weight—very different quantities of potash, soda, &c. from a crop of oats. It will take more of these, of sulphuric acid, and of certain other substances, from the soil. It will, therefore, exhaust the soil more of these substances—as barley and oats will of others—hence one reason why a piece of land may suit one of these crops and not suit the others. That which cannot grow wheat may yet grow oats. ”

“ It has been ascertained, however, that in our climate, on an average, not less than from one-third to three-fourths of the entire quantity of carbon contained in the crops we reap from land of average fertility, is really obtained from the air.
We see then why, in arctic climates, where the sun once risen never sets again during the entire summer, vegetation should almost rush up from the frozen soil—the green leaf is ever gaining from the air and never losing, ever taking in and never giving off carbonic acid, since no darkness ever interrupts or suspends its labours. ”

“ The dung of birds possesses the united virtues of both the liquid and solid excretions of other animals. It contains every part of the food of the bird, with the exception of what is absolutely necessary for the support and for the right discharge of the functions of its own body. It is thus fitted, therefore, to return to the plant a greater number of those substances on which plants live, than either the solid or the fluid excrements of other animals; in other words, to be more nourishing to vegetable growth. ”

“ On some kinds of food they thrive,—fed with others, they sicken or die. The soil must therefore be prepared for their special growth.
In an artificial rotation of crops, we only follow nature. One crop extracts from the soil a certain quantity of all the inorganic constituents of plants; but some of these in much larger proportions than others. A second crop carries off in preference a larger quantity of those substances which the former had left; and thus it is clearly seen, both why an abundant manuring may so alter the constitution of the soil, as to enable it to grow almost any crop ”

“ We have seen that all the elements which are necessary to the production of the woody fibre, and of the other organic parts of the plant, may be derived either from the air, from the carbonic acid and watery vapour taken in by the leaves, or from the soil, through the medium of the roots. In the air, however, only rare particles of inorganic or earthy matter are known to float, and these in a solid form, so as to be unable to enter by the leaves; the earthy matter which constitutes the ash, therefore, must be all derived from the soil. ”

“ From the compound substances, described in the preceding chapter, plants derive the greater portion of the carbon, hydrogen, oxygen, and nitrogen, of which their organic part consists. The living plant possesses the power of absorbing these compound bodies, of decomposing them in the interior of its several vessels, and of recompounding their elements in a different way, so as to produce new substances,—the ordinary products of vegetable life. Let us briefly consider the general structure of plants, and their mode of growth. ”

“ To those who are now embarking in such numbers in quest of new homes in our numerous colonies, who hope to find, if not a more willing, at least a more attainable soil in new countries, no kind of agricultural knowledge can at the outset,—I may say, even through life,—be so valuable as that to which the rudiments of geology will lead them. ”

“ It is kindly provided by nature, that a certain proportion of this ingredient of bones is always associated with the gluten of plants in its various forms,—with the fibrin of animal muscle and with the curd of milk. Hence, man, in using any of these latter along with his vegetable food, obtains from them, with comparative ease, the quantity of the earth of bones which is necessary to keep his system in repair; while those animals which live upon vegetables alone, extract all they require along with the gluten of the plants on which they feed. ”

“ Hence pigeons’ dung will benefit vegetation in circumstances where dry flesh would in some degree fail. So the liquid excretions contain much important saline matter not present in the solid excretions,—not present either in such substances as horn, wool, and hair,—and, therefore, each must be capable of exercising an influence upon vegetation peculiar to itself.
Hence the practical farmer sees the reason why no one simple manure can long answer on the same land; and why in all ages and countries the habit of employing mixed manures and artificial composts has been universally diffused. ”

“ Practical men have long been of opinion that the digestion of food, either animal or vegetable,—the passing of it through the bodies of animals,—enriches its fertilizing power, weight for weight, when added to the land. Hence, in causing animals to eat up as much of the vegetable productions of the farm as possible, it is supposed that not only is so much food saved, but that the value of the remainder in fertilizing the land is greatly increased. ”

“ We have considered the various chemical changes which take place within the growing plant, during the formation of its woody stem, the blossoming of its flower, and the ripening of its seed or fruit,—and have traced the further changes it undergoes, when, the functions of its short life being discharged, it hastens to serve other purposes, by mingling with the soil, and supplying food to new races. ”

“ Hence, in cropping the mixed herbage, the animal introduces into its stomach portions of various plants—some abounding more in starch or sugar, some more in gluten or albumen, some naturally richer in saline, others in earthy constituents; and out of these varied materials the digestive organs select a due proportion of each, and reject the rest. Wherever a pasture becomes usurped by one or two grasses—either animals cease to thrive upon it, or they must crop a much larger quantity of food to supply the natural waste of all the parts of their bodies. ”

“ It may be that here and there it may fall in with the humour or natural bias of some one chemist to apply his knowledge to this most important art; but hitherto the appreciation of such efforts has, in general, been so small—the reception of scientific results and suggestions by the agricultural body so ungracious—that little wonder can exist that so many have quitted the field in disgust—that the majority of capable men should studiously avoid it. ”

“ There are two purposes which vegetable manure is generally supposed to serve when added to the soil. It loosens the land, opens its pores, and makes it lighter; and it also serves to supply organic food to the roots of the growing plant. It serves, however, a third purpose: it yields to the roots those saline and earthy matters which it is their [Pg 149] duty to find in the soil, and which exist in decaying plants in a state more peculiarly fitted to enter readily into the circulating system of new races. ”

“ There is a beautiful adjustment in the constitution of the atmosphere to the nature and necessities of living beings. The energy of the pure oxygen is tempered, yet not too much weakened, by the admixture of nitrogen. The carbonic acid, which alone is noxious to life, is mixed in so minute a proportion as to be harmless to animals, while it is still beneficial to plants; and when the air is overloaded with watery vapour, it is provided that it shall descend in rain. ”

“ The value of the grass in any given spot may increase for an indefinite period—but it will never improve beyond a certain extent—it will necessarily be limited, as all other crops are, by the quality of the land. Hence the mere laying down to grass will not make all land good, however long it may lie. The extensive commons, heaths, and wastes, which have been in grass from the most remote times, are evidence of this. They have in most cases yielded so poor a herbage as to have been considered unworthy of being enclosed as a permanent pasture. ”

“ Sometimes it is a porous sand or gravel, through which water readily ascends from beneath or sinks in from above; sometimes it is light and loamy like the soil that rests upon it; sometimes stiff and impervious to water. ”

“ The starch consists of carbon, hydrogen, and oxygen only; the gluten, in addition to these, contains also nitrogen.
When ground into flour, these substances serve for food to man; in the unbruised grain they are intended to feed the future plant in its earliest infancy.
When a seed is committed to the earth, if the warmth and moisture are favourable, it begins to sprout. It pushes a shoot upwards, it thrusts a root downwards, but, until the leaf expand, and the root has fairly entered the soil, the young plant derives no nourishment other than water, either from the earth or from the air. ”

“ When wheat is cut down, the quantity of straw left in the field, in the form of stubble and roots, is sometimes greater than the quantity carried off in the sheaf. Upon a grass field two or three tons of hay may be reaped from an acre; and if we suppose only a tenth part of this quantity to die every year in the form of roots or parts of roots, or of excretions from roots, we can easily understand how the vegetable matter in the soil thus gradually accumulating, should at length become very considerable in quantity. ”

“ All that he eats as food is intended merely to renovate or replenish his system, to restore that which is daily removed from every part of his body by natural causes. In the full grown state, every thing that enters the body must come out of the body in one form or another. The first part of the food that escapes is that portion of its carbon that passes off from the lungs during respiration. ”

“ Planting.—It has been observed that lands which are unfit for arable culture, and which yield only a trifling rent as natural pasture, are yet in many cases capable of growing profitable plantations, and of being greatly increased in permanent value by the prolonged growth of wood. Not only, however, do all trees not thrive alike on the same soil, but all do not improve the soil on which they grow in an equal degree. ”

“ By a manure is to be understood whatever is capable of feeding or of supplying food to the plant. And us plants require earthy and saline as well as vegetable food, gypsum and nitrate of soda are as properly called manures as farm-yard dung, bone-dust, or night-soil. ”

“ But while agriculture has a right to use such language, she has herself preliminary duties to perform. She has no right in one breath to deny the value of chemical theory to agricultural practice, and in another to ask the sacrifice of time and labour in doing her chemical work. Chemistry is a wide field, and many zealous lives may be spent in the prosecution of it without at all entering upon the domain of practical agriculture. ”

“ Every one understands why the roots send out fibres in every direction through the soil,—it is in search of water and of liquid food, which the spongy fibres suck in and send forward with the sap to the upper parts of the tree. It is to aid these roots in procuring food that, in the art of culture, such substances are mixed with the soil where these roots are, as are supposed to be necessary, or at least favourable, to the growth of the plant. ”

“ Granite generally forms hills and sometimes entire ridges of mountains. When it decays, the rains and streams wash out and carry down the fine felspar clay, and leave the (quartz) sand on the sides of the hills. Hence the soil in the bottoms and flats of granite countries consists of a cold, stiff, wet, more or less impervious clay, which often bears only heath, bog, or a poor and unnutritive pasture. The hill sides are either bare or covered with a thin, sandy, and ungrateful soil, of which little can be made by the aid even of skill and industry. ”

“ That any dry vegetable matter, therefore, does not produce an immediate effect, ought not to induce the practical farmer to despise the application to his land—either alone, or in the form of a compost—of every thing of the kind he can readily obtain. If his fields are not already very rich in vegetable matter, both he and they are likely to be ultimately benefitted by such additions to the soil. ”

“ We have spoken of soils as consisting chiefly of sand, lime, and clay, with certain saline and organic substances in smaller and variable proportions. But the study of the ash of plants (see chap. iv.) shews us, that a fertile soil must of necessity contain an appreciable quantity of at least eleven different substances, which in most cases exist in greater or less relative abundance in the ash both of wild and of cultivated plants. ”

“ When the young grass throws up its leaves into the air, from which it derives so much of its nourishment, it throws down its roots into the soil in quest of food of another kind. The leaves may be mown or cropped by animals, and carried off the field, but the roots remain in the soil, and, as they die, gradually fill its upper part with vegetable matter. ”

“ Even on the natural mixture of starch and gluten in fine white bread, dogs have been unable to live beyond 50 days, though others fed on household bread, containing a portion of the bran—in which earthy matter more largely resides—continued to thrive long after. It is immaterial whether the general quantity of the whole food be reduced too low, or whether one of its necessary ingredients only be too much diminished or entirely withdrawn. ”

“ The manure of the cow, taking it mixed, is not so rich in nitrogen as that of man,—because the cow in the stall, large though it be, and great the bulk of food it consumes, does not give off much more carbon by respiration than an active full grown man. Hence the proportion of carbon in the excretions of this animal is greater than in those of man. ”

“ Dry sands and clays, and blackish garden mould, become warmed to nearly an equal degree under the same sun; brownish red soils are heated somewhat more, and dark-coloured peat the most of all. It is probable, therefore, that the presence of dark-coloured vegetable matter renders the soil more absorbent of heat from the sun, while the colour of the dark-red marls of the new and old red sandstones may, in some degree, aid the other causes of fertility in the soils which they produce. ”