Soil is the unconsolidated mineral material on the immediate surface of the earth that serves as a natural medium for the growth of land plants. Soil is found on all surfaces except on steep, rugged mountain peaks and areas of perpetual ice and snow.

Soil is related to the earth much as the rind is related to an orange. But this rind of the earth is far less uniform than the rind of the orange. Soil is deep in some places and shallow in others. Soil can be red in Georgia and black in Iowa. It can be sand, loam, or clay. Soil is the link between the rock core of the earth and the living things on its surface. Soil is the foothold for the plants we grow and the foundation for the roads we travel and for the buildings we live in.

Soil consists of mineral...