Chemical Weed Management in Transplanted Rice (Oryza sativa L.) under Rice – Mustard Cropping System

An experiment was conducted at instructional farm Uttar Banga Krishi Viswavidyalaya during kharif season, 2017 to find out a suitable chemical weed management practice in transplanted rice. The experiment was laid out in randomized block design having 12 treatments replicated thrice. The treatments were T1: Weedy check, T2: Weed free, T3: Bispyribac sodium 10% SC @ 20 g a.i ha-1 at 14 DAT, T4: Bispyribac sodium 10% SC @ 30 g a.i ha-1 at 14 DAT, T5: Butachlor 1.5 kg a.i ha-1 at 3 DAT, T6: Pendimethalin 1.0 kg a.i. ha-1 at 3 DAT, T7: Pretilachlor 0.60 kg a.i ha-1 at 3 DAT + 2,4-D sodium salt 0.50 kg a.i ha-1 at 30 DAT, T8: Butachlor 1.5 kg a.i ha-1 at 3 DAT + 2,4-D sodium salt 0.50 kg a.i ha-1 at 30 DAT, T9: Metsulfuron methyl 20% WP @ 8 g a.i ha-1 at 14 DAT, T10: Pretilachlor 0.60 kg a.i ha-1 at 3 DAT + Almix @ 20 g a.i. ha-1 at 21 DAT, T11: Butachlor 1.5 kg a.i. ha-1 at 3 DAT + Bispyribac sodium 10% SC @ 20 g a.i ha-1 at 21 DAT and T12: Almix @ 20 g a.i ha-1 at 21 DAT. The rice variety used in the experiment was MTU 1075. It was observed that different herbicides treatments influenced weed control efficiency, weed index and yield components in transplanted rice. The highest number of filled grains (113.12 panicle-1), 1000 grain weight (22.90 g), grain yield (5.07 t ha-1) and straw yield (7.15 t ha-1) of rice was recorded with weed free (T2) treatment being at par with T11, T4, T3 and T10. In mustard, plots under weed free i.e. T2 treatment in rice performed the best in terms of every yield attribute viz. number of siliqua (77.00 plant-1), number of seeds (20.41siliqua-1), 1000 seed weight (3.14 g) as well as seed yield (1067.46 kg ha-1) and stover yield (2157.40 kg ha-1) being statistically at par with the plots under treatment T11 & plots under treatment T4. It can be concluded that the treatment comprising combination of pre-emergence & post-emergence herbicide like T11 i.e. Butachlor 1.5 kg a.i. ha-1 at 3 DAT + Bispyribac sodium 10% SC @ 20 g a.i. ha-1 at 21 DAT or application of higher dose of efficient & highly effective post-emergent herbicide molecule like T4 i.e. Bispyribac sodium 10% SC @ 30 g a.i ha-1 at 14 DAT can be opted for sufficient control of weeds in transplanted kharif paddy in terai zone of West Bengal to maximize the economic return.