SOILS ARE COMPLEX BIOGEOCHEMICAL MATERIAL ON WHICH PLANTS MAY GROW. THEY HAVE STRUCTURAL AND BIOLOGICAY PROPERTIES THAT DISTINGUISH THEM FROM THE ROCKS AND SEDIMENTS FROM WHICH THEY NORMALLY ORIGINATE. THEY ARE DYNAMIC ECOLOGICAL SYSTEMS, PROVIDING PLANTS WITH SUPPORT, WATER, NUTRIENTS, AND AIR. THEY SUPORT ALL ECOSYSTEMS ON LAND INCLUIDING LARGE POPULATION OF MICROORGANISMS THAT RECYCLE THE MATERIALS OF LIFE.