A field experiment was conducted during two consecutive kharif seasons at AB block Farm, Bidhan Chandra Krishi Viswavidyalaya, Kalyani, Nadia, West Bengal, India during 2019-20 and 2020-21, to study the effect of different post emergence herbicides for broad spectrum weed management in transplanted rice. The experiment was laid out in a randomized block design with ten treatments and replicated thrice.  reatments comprises T1 : Bispyribac sodium 38% + Chlorimuron ethyl 2.5 + Metsulfuron methy l 2.5% (43% WG) 34.4 g ai/ha at 20 DAT, T2 : Bispyribac sodium 38% + Chlorimuron ethyl 2.5 + Metsulfuron methyl 2.5% (43% WG) 43 g ai/ha at 20 DAS, T3 : Bispyribac sodium 38% + Chlorimuron ethyl 2.5 + Metsulfuron methyl 2.5% (43% WG) 51.6 g ai/ha at 20 DAS, T4 : Penoxsulam 1.02% + Cyhalofop-butyl 5.1% OD 135 g ai/ha at 20 DAT, T5 : Bispyribac Sodium 10 % SC 25 g ai/ha at 20 DAT, T6 : Bispyribac Sodium 10 % SC 38 g ai/ha at 20 DAT, T7 : Metsulfuron Methyl + Chlorimuron ethyl 10 % WP + Surfactant 4 g ai/ha at 21 DAT, T8 : Metsulfuron Methyl + Chlorimuron ethyl 10 % WP + Surfactant 5 g ai/ha at 21 DAT, T9 : Hand weeding (twice at 20 and 40 DAP), T10 : Weedy check. Among the different herbicidal treatments, T2 and T3 recorded highest weed control efficiency. Two times hand weeding at 20 and 40 days after showing was found highest grain yield and straw yield (4190.18 and 6707.04 kg/ha) and it was on par with chemical application of Bispyribac sodium 38%+ Chlorimuron ethyl 2.5 + Metsulfuron methyl 2.5% (43% WG) 43 g ai/ha WG @ 51.6 & 43 g a.i. ha-1 (4179.06 and 6785.78 kg/ha) and (4152.78 and 6631.88 kg/ha) followed by rest of the treatments excluding control (1523.43 and 3463.70 kg/ha). 

Highlights

• Herbicidal treatments significantly reduced weed infestation compared with the weedy check and improved crop productivity
• Bispyribac sodium + Chlorimuron ethyl + Metsulfuron methyl (43% WG) at 43 and 51.6 g a.i. ha⁻¹ recorded the highest weed control efficiency among herbicidal treatments.
• Grain and straw yields under these herbicidal treatments were statistically comparable with two hand weedings at 20 and 40 days after transplanting.
• Effective chemical weed management markedly enhanced rice yield compared with the weedy check treatment.