WEED CONTROL EFFICIENCY OF HERBICIDE MIXTURES IN TRANSPLANTED AMAN RICE VARIETIES

Abstract

A field experiment was carried out at the Agronomy field of Sher-e-Bangla Agricultural University, Dhaka, Bangladesh from July to December-2019, to investigate the efficacy of herbicide mixtures against weeds in transplanted aman rice varieties. The experiment consisted of two factors i.e., herbicide treatments 4 levels viz., weedy check(H0), Bispyribac-sodium WP @ 150 g ha -1 (H1), Acitachlor 14%+ Bensulfuron methyl 4% WP @ 750 g ha -1 (H3) and Pretilachlor 6% + pyrazosulfuron 0.15% WP @ 9.88 kg ha -1 (H4) and T. aman rice varieties 4 levels viz., Chinigura(V1), BR11(Mukta)(V2), BRRI dhan56(V3), and BRRI hybrid dhan6(V4). The experiment was laid out in a split-plot design placing herbicide mixtures in main plots and rice varieties in sub plots with three replications. Results indicated that thirteen weed species infested the experimental plots belonging to nine families where the most dominating were broadleaf and sedge weed species. Monochoria vaginalis was the most dominant weed with (36 and 18 m -2 having relative density (15.93 and 16.98 % respectively) in weedy check plot at 30 and 60 DAT, respectively. Application of different herbicides, rice varieties, and their combination significantly influenced weed control and crop performance. Applications of mixed herbicides gave superior rice yields over the single herbicide where Acitachlor 14% + Bensulfuron methyl 4% WP @ 750 g ha -1 reduced weeds growth and biomass significantly. Among rice varieties, BR11(Mukta) rice variety produced the highest grain yield(4.71 t ha -1 ) with better yield contributing parameters and grain yield. Application of Acitachlor 14%+ Bensulfuron methyl 4% WP @ 750 g ha in BR11(Mukta) rice variety produced the highest grain yield (5.57 t ha ), straw yield (6.76 t ha -1 ), biological yield (12.33 t ha 1 ), and harvest index (45.09%) which also recorded the highest gross return (1,46,010 Tk.), net return (88,699 Tk.) and benefitcost

ratio (2.55) comparable to other combinations. This indicated that herbicide mixture application in the best way of controlling complex weed flora and enhanced productivity and profitability in transplanted rice.