If the soil of our farm is largely clay, what happens to the rain that falls on it? The clay takes the water in so slowly that most of it runs off and is lost. Very likely it carries with it some of the surface soil which it has soaked and loosened, and thus leaves the farm washed and gullied.
What can we do for our clay soils to help them to absorb the rain more rapidly? For immediate results we can plow them and keep them loose and open with the tillage tools. For more permanent results we may mix sand with them, but sand is not always to be obtained and is expensive to haul. The best method is to mix organic matter with them by plowing in stable manures, or woods soil, or decayed leaves, or by growing crops and turning them under. The organic matter not only loosens the soil but also adds plant food to it, and during its decay produces carbonic acid which helps to dissolve the mineral matter and make available the plant food that is in it.
Clay soils can also be made loose and open by applying lime to them.
=Experiment.=--Take two bottles or jars, put therein a few spoonsful of clay soil, fill with water, put a little lime in one of them, shake both and set them on the table. It will be noticed that the clay in the bottle containing lime settles in flakes or crumbs, and much faster than in the other bottle. In the same manner, lime applied to a field of clay has a tendency to collect the very fine particles of soil into flakes or crumbs and give it somewhat the open texture of a sandy soil. Lime is applied to soil for this purpose at the rate of twenty bushels per acre once in four or five years.
Which soils have the greater power to absorb or pump moisture from below?
=Experiment.=--Use the same or a similar set of tubes as in the experiment illustrated in Fig. 23. Fill the tubes with the same kinds of dry sifted soils. Then pour water into the pan or dish beneath the tubes until it rises a quarter of an inch above the lower end of the tubes (Fig. 24). Watch the water rise in the soils. The water will be found to rise rapidly in the sand about two or three inches and then stop or continue very slowly a short distance further. In the clay it starts very slowly, but after several hours is finally carried to the top of the soil. The organic matter takes it up less rapidly than the sand, faster than the clay, and finally carries it to the top. By this and further experiments it will be found that the power of soils to take moisture from below depends on their texture or the size and closeness of their particles.