Nematode community as potential indicator of compost maturity and quality

Composting is the heat-producing, aerobe disintegration of organic materials by several organisms which form a complex and fast changing community. Up to now only the dynamics of the bacterial community have been thoroughly investigated in relation to composting processes. This research focuses on the taxonomical composition and the succession of the nematode community during the composting process. Nematodes show several characteristics which make them ideal bio-indicators to analyze the ecosystem quality. Furthermore, the nematode diversity and density in mature compost are considered crucial to construct a solid soil food web. To characterize the nematode community, a compost heap prepared according to the CMC-method (Controlled Microbial Composting) was surveyed at different time intervals and at the same time several variables (temperature, pH, conductivity and moisture) were determined. The quantitative and taxonomical analyses of the compost samples clearly showed an abundant presence of nematodes in compost (except during the heat peak at more than 71 °C). However, major shifts in the nematode community occurred during the process. Three clear phases could be distinguished after the heat-peak. At the beginning of the process, directly after the heat peak, the nematode population is primarily built by bacterial feeding enrichment opportunists (cp-1) (Rhabditidae, Panagrolaimidae, Diplogasteridae) immediately followed by bacterial feeding general opportunists (cp-2) (Cephalobidae) and the fungal feeding general opportunists (Aphelenchiodidae). Thereafter, the bacterial feeding-predator opportunistic nematodes (Mononchoides sp.) became dominantly present. Finally, at the most mature stage, the fungal feeding Anguinidae is the most prominent group. These changes in nematode community and the associated indices illustrate the potential of nematodes to assess the compost maturity and quality. The biology of compost is an important criterion of mature compost especially when compost is used to inoculate the soil. Especially the remarkable high number of predatory nematodes, provided by certain stages of the composting process, can be an important factor of the suppressive capacity of compost