ABSTRACT
Soil biota refers to a highly diverse assemblage of organisms that spend at least part of their life cycle in or on the soil. As their numerical diversity suggests, soil biota undertake a wide range of functions, including the detrimental activities of pathogens, parasites, and other agricultural pests. Fertilizer, tillage, and pesticide inputs account for as much as 33, 17, and 10 percent, respectively, of total energy use in US agriculture. Soil organisms may inhabit surface layers of soil and litter or deeper soil horizons, or move throughout the soil profile. The total biomass of the soil biota constitutes a relatively small fraction of total soil organic matter. The functioning of detritus food webs is driven by inputs of organic matter. Cultivation of undisturbed soil brings about a number of changes in community structure and activity of indigenous soil biota. Some physical and chemical manipulations alter habitat conditions directly and may be useful for stimulating or suppressing biotic activity.
