However, lower permeability is usually associated with soils that clump together making it difficult to evenly distribute moisture, air, and nutrients. Soil normally contains large numbers of diverse microorganisms including bacteria, algae, fungi, protozoa, and actinomycetes. In well-drained soils, which are most appropriate for biopiles, these organisms are generally aerobic. Of these organisms, bacteria are the most numerous and biochemically active group, particularly at low oxygen levels. Bacteria require a carbon source for cell growth and an energy source to sustain metabolic functions required for growth.
Bacteria also require nitrogen and phosphorus for cell growth.
Although sufficient types and quantities of microorganisms are usually present in the soil for landfarming, recent applications of ex situ soil treatment include blending the soil with cultured microorganisms or animal manure. Soil microorganisms require moist soil conditions for proper growth. Excessive soil moisture, however, restricts the movement of air through the subsurface thereby reducing the availability of oxygen which is essential for aerobic bacterial metabolic processes. In general, soils should be moist but not wet or dripping wet. Bacterial growth rate is a function of temperature.