NEMATODE-TRAPPING FUNGI IN ORGANIC AND CONVENTIONAL CROPPING SYSTEMS

Nematode-trapping fungi, nematodes, and microbial biomass were quantif ied in conventionally and organically managed field plots in the Susta inable Agriculture Farming Systems Project at the University of Califo rnia at Davis. There were four replicate plots (0.135 ha per plot) For each management system, and plots were sampled three rimes each year for 2 years. The hypothesis that nematode-trapping fungi would be more abundant in organically managed plots was partially supported: the nu mber of species of nematode-trapping fungi was slightly but significan tly greater in organic than in conventional plots, two species (Arthro botrys dactyloides and Nematoctonus leiosporus) were detected more fre quently in organic plots, and the population densities of A. dactyloid es and N. leiosporus were greater in organic than in conventional plot s. Two other species (A. haptotyla and A. thaumasia), however, tended to be more numerous in conventional than in organic plots, and the tot al density of nematode-trapping fungi was similar in organic and conve ntional plots. Bacterivorous nematodes were more abundant and microbia l biomass (substrate-induced respiration) was greater in organic than in conventional plots. Suppression of the root-knot nematode Meloidogy ne javanica, as measured in a bioassay, was not related to management system or population density of nematode-trapping fungi but was positi vely related to microbial biomass.