INFLUENCE OF NEMATODE-BACTERIAL INTERACTIONS ON N AND P MINERALISATION IN SOIL AND ON DECOMPOSITION OF CROP RESIDUES DURING AEROBIC COMPOSTING

The chemical composition of the crop residues such as the N and lignin content is one of the important factors that influence microbial activity, including their efficiency and contribution to the decomposition process. The objective of the present study was to compare the effects of organic substrates of different carbon to nitrogen (C:N) ratios viz; cabbage (Brassica oleracea) leaves, Soybean (Glycine max) stover and paddy (Oryza sativa) straw on population densities of a bacterivorous nematode, Cephalobus persegnis and its effect on N and P mineralization in soil microcosms and rate of organic matter decomposition in aerobic composting. The bacterivorous nematode, C. persegnis enhanced the release of ammonium nitrogen (NH4+-N) in presence of soybean (Glycine max) stover and paddy (Oryza sativa) straw in soil microcosms. Sampling at 15-day intervals revealed a progressive increase in the population densities of C. persegnis up to 45 days, followed by a decline. The bacterial densities in soil were significantly low in presence of nematodes on all days of sampling indicating the grazing effect of the nematodes. The microbial biomass carbon (MBC) was significantly higher in the presence of nematodes, on all days of sampling. A second trial on the rate of decomposition of the above crop residues during aerobic composting revealed enhanced reduction in C: N ratios in presence of nematodes on 75 and 90 days of incubation, in paddy straw treatments.