Side effects of pencycuron on nontarget soil microorganisms in waterlogged soil: Field experiment

Field experiments with waterlogged rice were conducted during the wet seasons (June–October) of 2002 and 2003, in an alluvial clay loam soil treated with and without decomposed cow manure (DCM) at field rate (FR), 2-times FR (2FR) and 10-times FR (10FR) as foliar spray. Soil microbial biomass-C (MBC), ergosterol content and fluorescein diacetate hydrolyzing activity (FDHA) declined in all the treatment combinations including the control till day 30, when the field was waterlogged. After crop harvest at day 70, when the experimental plots became aerobic, the soil microbial parameters increased remarkably with all the treatment combinations. The microbial metabolic quotient (qCO2) and microbial respiration quotient (QR) under different treatment combinations showed distinct increasing trend up to day 30 followed by a sharp decrease at day 70 irrespective of DCM amendment. Thus, the toxic effect of pencycuron on microbiological parameters persisted till the field was submerged. After withdrawal of submergence at crop harvest, the microbial parameters measured in the present study improved remarkably. Present work thus demonstrated that pencycuron application might not cause any permanent detrimental effect on the studied soil microbiological parameters.