Herbicide options for controlling weeds in transplanted rice (Oryza sativa) under North Eastern Plains Zone

A field experiment was conducted during the rainy seasons of 2012 and 2013 at research farm of Regional Station, Indian Agricultural Research Institute, Pusa, Samastipur, Bihar, to evaluate suitable herbicide options for controlling weeds in transplanted aromatic rice (Oryza sativa L.). The experiment comprised 8 treatments, viz. pendimethalin 30 EC pre-emergence (PE) @ 1.0 kg a.i./ha, butachlor 50 EC (PE) @ 1.5 kg a.i./ha, oxydiargyl 80 WP (PE) @ 0.10 kg a.i./ha, bispyribac-sodium 10 SC post-emergence (PoE) @ 0.025 kg a.i./ha, ethoxysulfuron 15 WDG (PoE) @ 0.018 kg a.i./ha, pendimethalin (PE) @ 0.75 kg a.i./ha followed by (fb) bispyribac-sodium 10 SC (PoE) @ 0.025 kg a.i./ha, weed free and a weedy check. Sequential application of pendimethalin (PE) fb bispyribac-sodium (PoE) was observed to reduce the Jungle rice [Echinochloa colona (L.) Link] density by 87.6 and 82.7% as compared to weedy check at 30 and 90 days after transplanting (DAT) of crop respectively. At the same time, the density of bermuda grass [Cynodon dactylon (L.) Pers.], false daisy [Eclipta alba (L.) Hassk.] and barnyard grass [(Echinochloa crussgalli (L.) Beauv] were also reduced significantly by this treatment. Single application of ethoxysulfuron (PoE) significantly reduced the population of smallflower umbrella sedge (Cyperus difformis L.) at all growth stages of rice as compared to the other herbicide used. Among the herbicide treatments, significant higher weed-control efficiency (WCE) was recorded with the sequential application of pendimethalin (PE) fb bispyribac-sodium (PoE) to the tune 92.4 and 88.2%, respectively as compared to weedy check at 30 and 90 DAT of crop. Minimum total weed dry biomass (21.1 g/m²) and highest weed-control efficiency (84.8%) were also recorded with application of pendimethalin (PE) fb bispyribac-sodium (PoE). Sequential application of preand post-emergence herbicide had significant effect on yield and yield attributes of aromatic rice as compared to single application of pre-or post-emergence herbicides.