Effects of water regimes on soil biological properties in a paddy field.

Effects of water regimes on soil biological properties were investigated in a field study during a rice (Oryza sativa L.) growing season in the Lower Reaches of Liaohe Plain.The number of bacterial-feeding nematodes at pre-tillage stage was higher in CK and FC than in MC and IC.Percolation-controlling markedly decreased the number of bacterial-feeding nematodes at yellow ripeness stage and that of fungal-feeding nematodes at pre-tillage stage.The number of fungal-feeding nematodes was found to be lower than that of bacterial-feeding nematodes in aquic brown soil.Percolation-controlling significantly decreased soil microbial biomass C at pre-tillage stage.Water regimes exhibited no effects on bacterial-feeding nematodes,fungal-feeding nematodes,microbial biomass C and microbial biomass N during rice tillering and heading stages.No significant correlations were found between the number of bacterial-feeding nematodes,fungal-feeding nematodes and C,N in microbial biomass.