Coarse and fine sands comprise more than 70 percent of a sandy soil. From 25 to 35 percent of a clay soil is clay. Loams range in clay content from 10 to 25 percent, less than 50 percent sand, and from 25 to 50 percent silt. That, regardless of their organic matter, makes loam soils most desirable because they have the good features of both sands and clays, plus the silt. When a plowed field is in good tilth the soil is crumbly, mealy, porous, and ready to grow a crop.
Loams are ideal for good tilth.
Clay is both the angel and the villain in soils. Because its particles are so fine and have such tremendous capacity for holding infinitesimal films of water, it can cause trouble. If a clayey soil is plowed or cultivated when too wet, if livestock trample it in early spring, the microscopic particles are puddled into a solid mass. On the other hand, the clay particles in soil are the pantry in which plant foods are kept, and the storage place where chemicals are held, to be gradually released to nourish plants. Argonne National Laboratory, Division of Educational Programs, Harold Myron, Ph.D., Division Director.