The relative contributions of the soil fauna to microbial turnover and nutrient mineralization are directly related to the demographics of the soil biota (Coleman et al. 1983). Many invertebrates (e. g., earthworms, termites, and ants) play an important role for soil fertility; they produce macropores (e. g., galleries, chambers) and organomineral structures that influence hydraulic properties, macroaggre­gation, and organic matter dynamics in soil (Lavelle 1997, 2002). The importance of earthworms in enhancing nutrient availability and raising the rate of nitrogen turnover through the breakdown and incorporation of organic matter into the soil was demonstrated (Basker et al. 1992). Leroy et al. (2007) and Moreira et al. (2008) reported a significant increase of earthworm density and biomass after compost application. Earthworms can affect other soil-inhabiting invertebrates by altering their resource base, affecting soil structure, by direct ingestion, and by dispersing them (Blair et al. 1995); a direct effect of earthworm activities following compost application is an increase in the number of trophic groups of soil-inhabiting arthropods (phytophages, predators, omnivores, and saprovores) (Gunadi et al. 2002). Nematodes play a role in decomposition and nutrient cycling; free-living nematodes that feed on bacteria and fungi (as opposed to plants) contribute as much as 27% of the readily available nitrogen in the soil and promote rhizosphere colonization of beneficial rhizobacteria (Ekschmitt et al. 1999; Knox et al. 2003). Compost supply stimulates nonparasitic nematodes and encourages predator nema­todes and parasitic fungi which specifically destroy the eggs of certain parasitic nematodes (Fuchs et al. 2004). By boosting the key functional species in soil defined as “ecosystem engineers” (Jones et al. 1994), compost allows optimal conditions for plant health and growth.