Efficacy of various herbicides on weed composition, weed control efficiency, weed index and production potential in wet-seeded post-flooded kharif rice

To ascertain the effect of herbicides on weed composition, weed control efficiency, weed index and production potential in direct seeded post-flooded rice, a field experiment was conducted at Instructional-cum-Research (ICR) Farm, Assam Agricultural University, Jorhat, in post-flooded seasons of 2020 and 2021. A randomized block design (RBD) with three replications was used to set up the experiment. The study included twelve different weed management strategies viz., weedy check (T1), weed free (T2), pretilachlor 30.7 EC with safener PE (pre-emergence) fb 1 manual weeding at 30 DAS (days after sowing) (T3), pretilachlor 30.7 EC with safener PE fb1 mechanical weeding at 30 DAS (T4), pretilachlor 30.7 EC with safener PE fb bispyribac-sodium 10 SL @ 25 g a.i./ha PoE (post-emergence) (T5), pretilachlor 30.7 EC with safener PE fb penoxsulam 2.5 OD @ 1000 ml/ha (T6), bispyribac-sodium 10 EC @ 25 g a.i./ha PoE + pyrazosulfuron @ 20 g a.i./ha PoE (20 DAS) (T7), bispyribac-sodium 10 EC @ 25 g a.i./ha PoE+ pyrazosulfuron @ 20 g a.i./ha PoE + one spot hand weeding (T8), penoxsulam 2.5 OD @ 1000 ml/ha + almix @ 20 g/ha (T9), trifamone 20 WG + ethoxysulfuraon 10 EC(Pre-mix) @ 225 g/ha + one spot hand weeding (T10), two mechanical weeding at 15 and 30 DAS (T11) and almix (Metsulfuron+ Chlorimuron) @ 20 g/ha + need based one spot hand weeding (T12). Among the treatments apart from weed-free treatment (T2), application of bispyribac-sodium 10 EC @ 25 g a.i. ha-1 PoE + pyrazosulfuron @ 20 g a.i. ha-1 PoE (20 DAS) (T7) at 60, 90 DAS and at the time of harvest recorded the lowest weed index, weed dry weight, highest weed control index and highest yield without any crop injury. Unwedded plots reduced the grain yield up to 42.96% in 2020 and 50.72% in 2021.