Research topic: soil

soil surface layer of the earth, composed of fine rock material disintegrated by geological processes; and humus , the organic remains of decomposed vegetation. In agriculture , soil is the medium that supports crop plants, both physically and biologically. Soil may be from a few inches to several feet thick. Components and Structure The inorganic fraction of soil may include various sizes and shapes of rocks and minerals; in order of increasing size these are termed clay , silt , sand , gravel , and stone. Coarser soils have lower capacity to retain organic plant nutrients,... Read more