Page:Popular Science Monthly Volume 67.djvu/628

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622
POPULAR SCIENCE MONTHLY.

SOIL FERTILITY.
By J. B. DANDENO,

MICHIGAN AGRICULTURAL COLLEGE.

PROBABLY the most important single problem which confronts the farmer to-day is that of the conservation of the fertility of the soil. Fertility may be defined as that condition of the soil which yields the maximum of that material which the plant is capable of using for the best development of those qualities which the farmer desires. Strange as it may seem, just wherein this fertility consists is not yet fully known. Some years ago it was well known, that is to say, it was thought, that all that could be said had been said about it. At the present time, the more thoughtful and cautious among those studying the question of plant growth from a scientific standpoint are by no means settled upon the point. They recognize that there is yet much to be cleared up in regard to it, especially from the physical and the bacteriological sides. The question may be examined from the chemical, physical, bacteriological and ecological standpoints.

Much has been done in the chemical laboratory—too much, in fact, judging by the results obtained. It was thought that a knowledge of the chemical composition of the soil was the key to the solution of the problem. But it has never been decided just what the chemical composition should be to produce the best results, for the simple reason that it is not known exactly what the requirements of the plants are. Nor does a chemical analysis of the plant itself answer the question. There are certain elements which are no doubt necessary for proper growth, but the analysis of the content of the plant and of the soil does not give a very complete notion of the proper conditions under which certain substances should exist when in the soil. The chemical analysis of soils and fertilizers, though not without considerable importance, is now being relegated to the background in comparison with the physical and the bacteriological conditions. The so-called perfect fertilizers, as sold on the market to the farmer, have been looked upon with some distrust, mainly because they have not produced the results in the production of crops which might be expected from the chemical standpoint. The farmer becomes skeptical and again and again sends samples to the chemist to see if the materials have the proper chemical constituents. The chemist finds it all right, and it is all right from his point of view, but to the farmer the results are still unsatisfactory. It is as much to the futile results of the chemical analyses of soils and