Efficacy of pre- and post-emergence herbicides on complex weed flora in direct-seeded rice (Oryza sativa) in the eastern plains

The efficacy of different herbicides as tank mixture was evaluated to control diverse and complex weed flora in direct-seeded rice (Oryza sativa L.) during 2014-2016 at research farm of ICAR Research Complex for Eastern Region, Patna. Pendimethalin followed by tank mixture of bispyribac + ethoxysulfuron provided better control on diverse weed flora under direct seeded rice (DSR), except some of the typical grassy weeds with a yield of 4.4 tonnes/ha and was followed by tank mixture application of bispyribac + azimsulfuron (4.0 tonnes/ha) with an increment of yield by 83 and 67 % over plots receiving pendimethalin alone (2.4 tonnes/ha). Tank mixture application of bispyribac + 2, 4-D and fenoxaprop + ethoxysulfuron (3.8 t/ ha) also produced 58% more grain yield over pendimethalin treated plots. It was also observed that pendimethalin followed by bispyribac in isolation could not able tocontrol Trianthema portulacastrum effectively (69/m(2)) but when applied in combination with ethoxysulfuron or azimsulfuron has effectively controlled this species (18 and 25/m(2)). Strong negative correlation (r = -0.96, P < 0.001) was obtained between weed dry matter at 45 days after sowing and yield during the years of experimentation. With linear regression, it was observed that rice crop likely to produce less than 40% grain yield if weed dry matter is more than 200 gm(2). Pendimethalin followed by bispyribac + ethoxysulfuron mixture produced similar grain yield (4.4 tonnes/ha) as that of weed free situation (4.5 tonnes/ha). At farmers' field bispyribac + ethoxysulfuron tank mixture produced significantly higher grain yield (4.3 tonnes/ha) as compared to bispyribac alone (3.3 tonnes/ha) and weedy check (2.2 tonnes/ha) too. The tank mixture of bispyribac with ethoxysulfuron needs further evaluation at different locations as the particular mixture has got potential to control diverse and complex weed flora in direct seeded rice.