Agricultural chemistry

“ Most of the inorganic matter, therefore, which is withdrawn from the soil in a crop of corn is returned to it again, by the skilful husbandman, in the fermented straw,—in the same way as nature, in causing the trees periodically to shed their leaves, returns with them to the soil a very large portion of the soluble inorganic substances which had been drawn from it by the roots during the season of growth. ”

“ 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. ”

“ Taking a general view of the whole question, it is evident that a certain amount of vegetation may always be produced by means of mineral manures, and the quantity obtained is generally much beyond the normal produce of the soil. But it is still open to doubt whether the largest possible crop can be thus obtained, although the balance of evidence is against it, and in favour of the addition of ammonia, and other nitrogenous and organic substances, to the soil. ”

“ Lawes and Gilbert have taken a prominent position, hold that, as a rule, fertile soils, cultivated in the ordinary manner, contain a sufficient supply of mineral matters for the production of the largest possible crops, but that the quantity of ammonia and nitric acid which the plants are capable of extracting from the air is insufficient, and must be supplemented by manures containing them. ”

“ The mode in which it does this is entirely unknown, but it in all probability depends on very feeble chemical actions, and hence the importance of having the soil constituents, not in solution, but in such a state that they may be readily made soluble by the plants. Many of the minerals from which fertile soils are formed are probably not attackable by plants when in their natural condition, and even after disintegration the quantity of the essential elements of their food, which are present in an easily assimilable state, is at no one time very large. ”

“ Twenty tons of farm-yard manure, a quantity commonly applied, and often exceeded on well cultivated land, contain a sufficiency of organic matters to yield about 2-1/2 cwt. of nitrogen. A complete rotation, according to the six-course shift, contains almost exactly the same quantity of nitrogen, when we assume average crops throughout the whole, and it is thus made up. [K]
[Pg 161]
The supply is therefore quite sufficient for the requirements of the crop ”

“ 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. ”

“ Thus, it is a notorious fact that white crops exhaust, while grass improves the soil; but the improvement in the latter case is really dependent on the fact, that when the land is laid down in pasture, nothing is removed from it, the cattle which feed on its produce restoring all but a minute fraction of the mineral matters contained in their food; and as the plants derive a part, and in some instances a very large part, of their organic constituents from the air, the fertility of the soil must manifestly be increased, or at all events maintained in its previous state. ”

“ It is manifest that, as the crops removed from the soil all contain a greater or less amount of inorganic matters, they must be continually undergoing diminution, and at length be completely exhausted unless their quantity is maintained from some external source. In many cases the supply of these substances is so large that ages may elapse before this becomes apparent, but where the quantity is small, a system of reckless cropping may reduce a soil to a state of absolute sterility. ”

“ It grows nearly as well on clay soils and on lighter loams, and with the methods of dry farming followed in the arid regions of the Western States and Canada, it will succeed with less than its normal amount of rainfall.
It is now about a hundred years since chemistry was applied with any approach to exactitude to questions affecting agriculture; since for instance it was first definitely recognised that plants must 3 obtain from their surroundings the carbon, hydrogen, oxygen, nitrogen, phosphorus, sulphur, potassium, calcium, and other elements of which their substance is composed. ”

“ Science predicts the exhaustion of nitrogen and consequent failure of the food supply, and science promptly finds a way of making plants draw nitrogen from the boundless supplies of the air. The time may come when every farmer will send for his bottles or cakes of bacteria culture every spring as regularly as he sends for his seed, and when the work of inoculating the soil will be a familiar agricultural process, with discussions in the farmers' papers as to whether two bottles or one is best for a field of sandy loam with a southern exposure. ”

“ All of these bodies contain valuable plant foods and the phosphoric acid, potash, and nitrogen therein are to be determined by the methods already given for these bodies when they occur in, or are mixed with, organic matter. In general, stall manures are found to have a higher manurial value than is indicated by the amount of phosphorus, potash, and nitrogen which they contain. Through them there is introduced into the soil large quantities of humus bodies whereby the physical state of the soil is profoundly modified and its adaptability to the growth of crops, as a rule increased. ”

“ The soil is rapidly dried to arrest nitrification; it is not heated above 40° lest there should be dissipation of ammonia compounds, or a change in solubility. The normal limit to which the soil may be heated in place by the sun’s rays should not be exceeded in preparing a sample for an agricultural chemical analysis. ”

“ The agricultural press is greatly assisting in bringing about the adoption of the simpler system, and the laws of some States now require that the percentages of the actual plant food elements, as nitrogen, phosphorus, and potassium, shall be guaranteed in fertilizers offered for sale. It is one of those questions that are never settled until they are settled right; and it is only a question of time until the simple element basis will be used throughout the United States, or at least in the Central and Western States. ”

“ The organic nitrogen in superphosphates, special manures, and mixed fertilizers of a high grade is usually valued at the highest figures laid down in the trade values of fertilizing ingredients in raw materials; namely, eighteen and one-half cents per pound, it being assumed that the organic nitrogen is derived from the best sources ”

“ By means of the absorptive power of soils the farmer, if he puts on an excess of potash or phosphoric acid as a fertilizer, does not lose it but is able to reap some benefits from it in the next and even in succeeding crops. If it were not for this power the best method for applying fertilizers would be a much more 122complicated problem than it is at present ”

“ With the foregoing causes in full action, and an adequate supply of moisture, whether from rains, dews, or artificial irrigation, the crop will draw largely from the atmosphere for the supply of its required organic constituents. Carbon will be furnished from its carbonic acid; nitrogen from its ammonia; hydrogen from its vapor, dews, and ammonia; and oxygen from air, water, and soil.
The use of all these materials, together with the selection of the best varieties of seed, will give the first three requisites of a wheat crop; large measure, heavy weight, and much flour. ”

“ In all statements of percentages of the essential constituents of ash, as regards fertilizing materials, it should be specified whether the percentage is calculated on a crude ash, the pure ash, that is free of carbon and sand, or upon a basis excluding the carbon dioxid. For the purpose of fertilizer control, the analyst and dealer will be satisfied, as a rule, with the determination of the percentages of phosphoric acid and potash alone. To the other constituents of an ash is not assigned any commercial value. ”

“ An ammoniacal salt is only partly changed to a state suited to plant nutrition while organic nitrogen is forced to undergo a complete transformation before it becomes available to supply the needs of the growing plant. It is important, therefore, equally to the analyst, the merchant, and the agronomist, to know definitely the forms of combination in which the nitrogen exists and the relative proportion of the different combinations. ”

“ Availability of Phosphatic Fertilizers.—There is perhaps no one question more frequently put to analysts by practical farmers than the one relating to the availability of fertilizing materials. The object of the manufacturer should be to secure each of the valuable ingredients of his goods in the most useful form. The ideal form in which phosphoric acid should come to the soil is one soluble in water. ”

“ Neither crops nor animals can be made out of nothing, and no independent system of livestock farming can add to the soil a pound of any element of plant food, aside from nitrogen, and even this addition is due to the legume crops grown and not to the live stock.
Under the best system of live-stock farming about three-fourths of the nitrogen, three-fourths of the phosphorus, and one-third of the organic matter contained in the food consumed can be returned to the land if the total excrements, both solid and liquid, are saved without loss. ”

“ Field crops, as a rule, will require less of the salt than garden crops. There is an economic limit to the application which should not be passed. As a rule 250 pounds per acre will prove to be a maximum dressing. The character of the crop must also be considered. Different amounts are required for sugar beets, tobacco, wheat, and other standard [Pg 245] crops. It is rarely the case that a crop demands a dressing of Chile saltpeter alone. It will give the best effects, as a rule, when applied with phosphoric acid or potash. ”

“ The habitual use of chemical analyses of fertilizers is rendering nitrogen, potash, and phosphoric acid almost as familiar terms as air, soil, and water, and thus is contributing in no small degree to the education of farmers. ”

“ Western agriculturalists have not sufficiently appreciated the fact that the most rapid growth of plant food substances in the soil cannot occur at the same time and place with the most rapid crop increase, because both processes draw upon the available soil moisture, soil air and soluble potassium, calcium, phosphorus and nitrogen compounds. ”

“ But the cerealia, and plants grown for their roots, meet on our fields, in the remains of the preceding crop, with a quantity of decaying vegetable substances corresponding to their contents of mineral nutriment from the soil, and consequently with a quantity of carbonic acid adequate to their accelerated development in the spring. A further supply of carbonic acid, therefore, would be quite useless, without a corresponding increase of mineral ingredients. ”

“ The quantity of matter dissolved, whether organic or inorganic, during the few weeks in which corn plants organise the bulk of their solids, is small. From 93 to 97 parts in 100 of the dry matter, in a mature, perfect plant, including its seeds, cob, stems, leaves, and roots, are carbon (charcoal) and the elements of water. It is not only an important, but an exceedingly instructive fact, that the most effective fertilisers known in agriculture are those that least abound in the elements of water and carbon. ”

“ The former, at every time of the day during winter and summer, obtain carbon through their leaves by absorbing carbonic acid which is not furnished by the barren soil on which they grow; water is also absorbed and retained by their coriaceous or fleshy leaves with great force. They lose very little by evaporation, compared with other plants. On the other hand, how very small is the quantity of mineral substances which they withdraw from the soil during their almost constant growth in one year, in comparison with the quantity which one crop of wheat of an equal weight receives in three months! ”

“ But the steer eats grass and you eat the steer, so you get the grass, don't you? Your corn, wheat, oats, timothy, potatoes, so far as we know, can't touch free nitrogen in the air, but clover can and then feed it to those other crops.
"Let us look into how we got the phosphorus. On land that would not grow over six to eight bushels of wheat per acre we have succeeded once in growing forty-seven and three-fourths bushels to the acre, on all the land sowed, of wheat that sold away above the market price and weighed sixty-four pounds to the measured bushel, and never put on a pound of phosphorus. ”