Interaction of Soil Microbes and Insecticides in Rice-Brinjal Crop Sequence

Results of a study on the interaction of rynaxypyr, fipronil, cartap hydrochloride, carbofuran, phorate and chlorpyriphos with the soil microbial population are reported. The bacterial population in soil was the most susceptible towards insecticides compared to fungi and actinomycetes. Insecticides exerted negative effect on the population of soil microbes, the effect being more prominent up to 14 d after application. The population of microbes started to recover from 21 d after application. Mean reduction in total bacterial population ranged between 0.22 to 45.86 per cent over control. Cartap hydrochloride was relatively more toxic towards the bacterial community. Fungal population was less susceptible to insecticides, their mean reduction ranging from -1.13 to 30.02 per cent over control. Rynaxypyr was relatively more toxic towards fungal population, while carbofuran was the least. The actinomycetes population also showed relatively less susceptibility to insecticides.Carbofuran recorded toxicity towards actinomycetes population (44.27% mean reduction over control). Cartap hydrochloride was relatively less toxic (9.19% mean reduction over control).