The more one studies the soil, the more certainly it will be found that the earth has locked up in her bosom many secrets, and that these secrets will not be given up for the mere asking. As mysterious as the soil may appear at different times, it always is governed by certain laws. These principles once understood, the soil becomes an open book from which one may read quickly and accurately.
Uses of the Soil.
The soil has certain offices to perform for which it is admirably fitted. The most important of these offices are:
- To hold plants in place;
- To serve as a source of plant-food;
- To act as a reservoir for moisture;
- To serve as a storehouse for applied plant-food or fertilizer.
Some soils are capable of performing all these offices, while others are fitted for only a part of them. Thus a soil which is pure sand and almost entirely deficient in the essential elements of plant-food, may serve, if located near a large city, merely to hold the plants in position while the skillful gardener feeds the plants with specially prepared fertilizers, and supplies the moisture by irrigation.
Early in the study of soils an excursion, if possible, should be made into the woods. Great trees will be seen and under the trees will be found various shrubs and possibly weeds and grass. It will be noticed that the soil is well occupied with growing plants. The surface will be found covered with a layer several inches thick of leaves and twigs. Beneath this covering the soil is dark, moist, full of organic matter, loose, easily spaded except as roots or stones may interfere, and has every appearance of being fertile.
Soil Conditions as Found in Many Fields.
After examining the conditions in the forest, a study should be made of the soil in some cultivated field. It will be found that in the field the soil has lost many of the marked characteristics noticed in the woodland. In walking over the field, the soil will be found to be hard and compact. The surface may be covered with growing plants, for if the seeds which have been put into the soil by the farmer have not germinated and the plants made growth, nature has quickly come to the rescue and filled the soil with other plants which we commonly call weeds. It is nature's plan to keep the soil covered with growing plants, and from nature we should learn a lesson. The field soil, instead of being moist, is dry; instead of being loose and friable, it is hard and compact, and it appears in texture entirely different from the woodland soil. The cause of the difference is not hard to discover. In the woods, nature for years has been building up the soil. The leaves from the trees fall to the ground and form a covering which prevents washing or erosion, and these leaves decay and add to the humus, or vegetable mould, of the soil. Roots are constantly decaying and furnish channels through the soil and permit the circulation of air and water.
In the field, nature's lesson has been disregarded and too often the whole aim seems to be to remove everything from the soil and to make no returns. Consequently the organic matter, or humus, has been used up; the tramping of the horses' feet has closed the natural drainage canals; after the crop is removed, the soil is left naked during the winter and the heavy rains wash and erode the surface, and remove some of the best plant-food. After a few years of such treatment, the farmer wonders why the soil will not produce as liberally as it did formerly.
Experiment No. 1.—The fact that there is humus, or vegetable mould, in certain soils can be shown by burning. Weigh a potful of hard soil and a potful of lowland soil, or muck, after each has been thoroughly dried. Then put the pots on the coals in a coal stove. After the soil is thoroughly burned, weigh again. Some of the difference in weight may be due to loss of moisture, but if the samples were well dried in the beginning, most of the loss will be due to the burning of the humus.