the other hand, has been discovered. It is this: Denitrifying bacteria are slow workers when oxygen finds its way freely into the soil or wherever decomposition takes place. If this be true, is it not good farming to till so carefully the land that air may find easy access to all parts of it? If water excludes air from the soil, is it not in line of good practice to get rid of it by drainage? Certainly, this is the best method of battle. And a method that allows nitrates to accumulate and that weakens the ravages of all forms of reducing bacteria. The conclusion, then, is this: if nitrates and ammonium saltsthe forms that just suit plant roots-are to be protected in the soil, it is necessary to loosen and fine and open the land to air and oxygen. If these plant foods are to be increased, organic matter must be added in abundance but with this caution: you must send air into the soil; you must till it; you must drain it well; you must make its texture of the highest quality. And then plants will like this soil as a home. In it, organic matter quickly will be decomposed, and at the same time, the nitrogensupply content increased and protected, because that soil is mellow and open and of good tilth; because the things that do good and discountenance the evil of the nitrogenliberating bacteria, have been secured and supplied with great abundance. Who shall withhold this method of nitrogen increase and nitrogen protection? This great power is in your hands. Who shall hinder you from using it. The fault, dear Brutus, is not in our stars, But in ourselves, that we are underlings. CHAPTER XIV NITRIFICATION: NITROGEN MADE READY FOR PLANTS Every one familiar with the growing of crops knows that organic matter, when thoroughly decomposed and mixed with the soil, increases the producing power of the land; especially is this the case when nitrogen compounds are present in considerable quantities. We have discussed the manner in which organic matter is decomposed in the soil. Bacteria do the work: they break into pieces every sort of organized life. A question now arises: What becomes of these simpler forms, now pulled apart and disorganized? One phase of this question has been answered already: some of the nitrogen has been given freedom: it has disappeared from the soil. The mineral substances, that were contained in the organic matter, are left in the soil. They cannot get away into the air. They will be available at once to plants, or else lost through drainage waters. They may join with other elemental forms already in the soil, and so remain until called into use by the enticing demands of future generations of plants. The carbon compounds remain either in the soil or return to the air as rapidly as they are released from their combinations by decomposition bacteria. This departure may be in the form of marsh gas or of carbon dioxide. In either case, it offers no service to growing plants so long as it remains in the soil. We now reach the important part of our question, and out of it grows a second. What becomes of the nitrogen compounds that remain in the soil? That we shall attempt to answer now. Just after decay nitrogen compounds are not ready for plants. When nitrogen compounds are reduced from their complex forms-plant or animal tissue-by decomposition bacteria, they are unavailable plant food, still. They must be made to combine with more oxygen: they must be oxidized. Scientific men call this process nitrification. Organic compounds of nitrogen, when applied to the soil and decomposed, eventually oxidize to a nitrate, and then become usable plant food. The chemical process. In this disorganization of the higher and complex compounds, nitrogen compounds, like those of other elements, are reduced to more simple ones, reaching, finally, a point where nitric acid is formed. This acid now unites with bases or metals, producing compounds now known as nitrates. The common nitrates are: potassium nitrate (KNO), sodium nitrate (NaNO3), calcium nitrate (Ca(NO3)2), and ammonia nitrate (NH4NO3). Nitrification is a biological process.-Nitrification, at first, was thought to be a chemical process. The chemist had learned that he could do this same work in his laboratory he could oxidize, under certain conditions, nitrous bodies into nitric acid bodies: he could oxidize unavailable plant food into available nitrogen plant food. But, in recent days, many things have been discovered about soil bacteria. Further study has revealed the fact, that some of these many busy bodies of the soil are back of this oxidization process: some of them cause nitrification: some of them change unavailable nitrogen into the desired form. One way of proving this theory is this: secure a sample of soil which when mixed, divide into two parts. One lot now is sterilized by heating, that all bacteria may be killed. The other lot is undisturbed. Both lots are treated alike in all other respects from now on. When compared later, it will be found that the treated lot shows no increase of nitrates-of available food; while the other lot-where bacteria were permitted to go on— shows an increase in this respect. Hence, nitrification, now, is believed to be a biological process: to be actually caused, governed and controlled by the bacterial life of the soil. Moreover, it is a two-fold process, for the reason that two sets of bacteria are at work. One set oxidizes ammonium compounds into nitrous acid-nitrite; the other oxidizes the nitrites into nitrates the final form. A Russian scientist has demonstrated that these two sets are completely separated, that neither crosses the line into the other's territory, that each class does its own work, only. In short, that neither class is able to do the other's work, even if it would do so. NITRIFYING BACTERIA A.-Nitrococcus B. and C.-Nitric bacteria B The bacteria that cause nitrification. These workers are known now as nitrobacteria. The two classes are: Nitrous bacteria, called also nitrosomonus, and nitric bacteria, called also nitrobacter. As stated before, nitrous bacteria begin the work of nitrification: they change ammonium compounds into nitrites. When this is done, their work stops: they go no farther, for they cannot. However, nitrification is not stopped, for at this point the nitric bacteria take up the work, change nitrites into nitrates, thereby completing the work originally begun by putrefaction bacteria. A striking peculiarity of the nitrobacter is this: they need no organic food. So far as now known, they comprise the only living form that is able to live in an environment wholly devoid of organic matter. Decomposition bacteria cease their labors when the organic matter is used up, but these, the nitrobacteria, only begin their work when such becomes the case, and so this is proved: nitrifying bacteria are inactive in the presence of organic matter for they labor only when it has been completely destroyed. Nitrogen-starved soils may contain much nitrogen.— All agricultural soils contain some nitrogen. Some may show considerable quantities and others but little. And often the latter class produce the best crops. A question naturally arises: why is this so? In the first place, other conditions being secured, crops are dependent upon a plentiful supply of nitrates in the soil. These, as has been shown, pass through various changes before reaching the final usable state. Nitrogen compounds may be present in the soil in great abundance, but until these are changed to nitrates, they are useless to plants. Hence, nitrification is essential. The bacteria must be stimulated in this work. It may be, decomposition of the organic supplies is slow; if so, decomposition bacteria must be induced to work with more energy. Tillage may help; lime may help. But the fault may be elsewhere: the decomposition bacteria may have completed their effort; they may have done every bit of work possible to do. Maybe the nitrobacteria-the, nitrifying agents are at fault. They must be induced to greater effort. If the soil is acid, the explanation is at hand, for these bacteria never work in sour lands. Liming the land may answer the question. And then tillage will help. It will admit the air, which certainly can do no harm, for air is just |