Fred Brown Jr., age 11, of Lancaster, Pa., for his question:
HOW IS SOIL MADE?
Soil is one of the most important natural resources. of any country. And that's the reason why so great an effort is being made to conserve soil. When the soil becomes unable to grow good cops, not enough food can be produced to feed the people. The strength of the nation can then decline.
Soil is the material that covers most of the land surface of the earth. It is made of rock and mineral particles of many sizes mixed with living things and their remains.
Soil is shallow in some places and deep in others. It can be red or it can be very black. It may be mostly sand or mostly clay.
It takes a long time for soil to be made. It takes thousands of years to form even a shallow layer of soil by having a moist and mild climate turn stone into soil. In places where it is very cold or very dry, soil forms only with great difficulty, or not at all.
Soil is actually formed in two ways. The action of the weather on rocks causes them to decompose, or break down. As the surface of the rock becomes softer, it decays to become soil. Such soil is called residual soil.
Soil surfaces may also be made when wind, water or glaciers carry soil from one place to another. Soil deposited by rivers and streams is called alluvium. Soil moved by glaciers is called till. And fine soil, blown about by the wind before it is deposited, is called loess.
Many soils when first deposited will not support much plant life.
Air helps to make soil because it contains oxygen, carbon dioxide, nitrogen and moisture. Water helps break rocks into smaller pieces.
Plants increase the value of soil by sending their roots out which breaks it up and makes it better for growing things. When the plants die, they decay and form humus. This organic material makes the soil more fertile.
Animals also play a part in making soil. Body wastes of many animals enrich the soil. When the animal dies, its body decays and adds important materials to the soil.
Perhaps the most valuable of all animals are the earthworms. To obtain food, earthworms take soil into their bodies and pass it out again in a finely pulverized state.
To be considered sandy soil, the soil must be at least half sand. Clay soil must be at least half clay. But most soils are a mixture of silt, sand and clay.
Topsoil is necessary for agricultural use. This type of soil has been made rich with the addition of decayed vegetation or animal material.