Nematode-trapping fungi in conventionally and organically managed corn-tomato rotations

We tested the hypothesis that nematode-trapping fungi would be more abundan t in organically-managed than in conventionally-rnanaged plots (corn-tomato rotation) in the Long Term Research on Agriculture Systems Project (Yolo C ounty, CA). The replicated plots were established in 1992, began receiving different levels of organic matter (Ilo organic amendments or incorporation of a winter legume crop plus composted manure) in 1993, and were sampled f or fungi four times, twice near harvest (Sep 1995 and Nov 1996) and twice n ear planting (May 1996 and 1997). Fungi were quantified using soil dilution and soil sprinkle plates combined with most probable number procedures. Th e following fungi were detected: ARthrobotrys haptolyla, A. oligospora, A. thaumasia, Dactylella leptospora, Harposporium anguillulae, Meristacrum sp. , Monacrosporium eudermatum, Nematoctonus leiosporus, and Stylopage sp. Art hrobotrys thaumasia was the most abundant (about 10 propagules/g of soil) f ollowed by A. oligospora (about 1 propagule/g of soil). Population densitie s of the other fungi were usually less than 1 propagule/g of soil. Except f or N. leisporus, which was detected more frequently in the organic plots, a nd Me? istacrum sp., which was more abundant in the organic plots, detectio n frequencies and population densities of nematode-trapping fungi were simi lar in conventional and organic plots.