Effects of herbicides on weed control, crop yield and soil environment in transplanted aus rice

Abstract

Abstract : Weed control efficiency, crop yield and soil environment under four herbicide treatments, i.e. Rifit 250EC, Ronstar 25EC, Setoff 20WG, Butachlor 5G at recommended doses, in comparison to weed free, recommended weeding and control (unweeded) condition were studied in an experiment arranged in RCBD with four replications in BR26 transplanted aus rice at the BSMRAU experimental farm during May - September 2001. Application of Butachlor pre¬emergence showed the highest weed control efficiency as a result of lowest weed infestation in terms of weed density and weed biomass in the treated plots compared to other herbicidal weed control treatments. Weed free condition contributed to the highest grain yield of 4.47 t/ha. Butachlor application contributed to the second highest grain yield of 4.19 t/ha, however, statistically identical to weed free treatment as well as superior to other treatments. In terms of profitability of rice production herbicidal treatments showed higher BCR than conventional weed control treatments. Butachlor application resulted the highest BCR (1.22) over all other treatments. Herbicide application appeared to exert prolonged residual activity in soil attributing to lower microbial population in terms of biomass carbon as well as organic matter content in soil compared to conventional weed control treatments as observed through this study. Butachlor appeared as a viable alternative to conventional weed control practices. However, effects on soil environment also appeared as a concern regarding herbicide application in rice.