Page:Popular Science Monthly Volume 67.djvu/630

624 this operation is the clearing the field of weeds, but, aside from this, the soil is much more productive and, it may be said, more fertile. What is done to the soil in the process of cultivation is to break up the lumps and allow the air to permeate freely, to retain the moisture by making the surface portions fine and porous, thus acting as a 'Campbell blanket,' to mix so thoroughly that the physical affinity of the soil substances becomes changed, the soil being renewed to a very large extent. In this way a farmer can control the fertility without adding any fertilizer. Similar to this is the case already mentioned where the farmer plows under a field of rye. He increases the fertility without adding any fertilizer.

Land should never be allowed to bake or become hard on the surface. If so, air is kept from the roots of the plants. Baking of the soil can be largely controlled by the farmer with certain crops. It occurs, more or less, after rain, depending upon the character of the soil. This crust should be broken up, and kept broken up, by cultivation. In hoeing weeds a man is fertilizing the soil. Weeds, therefore, may be of considerable indirect benefit.

The fable of the farmer dying when on the point of revealing great hidden treasure to his sons illustrates the point. When about to die he told his sons that immense treasure lay buried in the ground on the farm, but death came just before he was able to tell the exact spot. His sons then dug through every inch of soil, over and over again, with the greatest diligence, but did not find any such treasure as they expected to find. The result, however, of such thorough digging was great abundance in the crops. They really did unearth the treasure, but in a far different way from that which they expected.

The bacterial content plays also a very important role in the process. Comparatively little is known in regard to the interrelationship existing among these organisms, and of their relations with plants. The processes of nitrifying and denitrifying are in themselves important, but these are probably only an extremely small part of the bacteriological question. And chemical analysis of soils does not throw much light upon it. It is a more complicated problem than a mere chemical one.

Root-tubercles and their production, although a bacterial proposition, require, because of their importance, special mention. The organism which produces the tubercle is capable of extracting nitrogen from the air and rendering it available for the plant upon which the nodule is produced. And these nodules are capable of being produced on many plants of the 'bean' family, such as clover, alfalfa, peas, vetches and the like. The cultivation of such crops, therefore, is productive of additional fertility in nitrogen. The soil, of course, should contain the bacteria peculiar to the plant upon which they work. The soil may contain them already; if not, it should be inoculated. Each farmer,