Weed dynamics, weed control efficiency and yield of aerobic rice as influenced by different weed management practices in eastern U.P

Aim: To identify the best sequence of pre-and post-emergence herbicides for achieving better weed control efficiency in aerobic rice. Methodology: A field experiment was conducted in Randomized Block Design with eleven treatment combinations, replicated thrice. The dominant weeds in field were C. dactylon, E. colona and E. crusgalli among grasses, C. rotundus, C. difformis and F maliaceae among sedges and C. axiilaris and P. niruri among broad-leaf weeds. Treatments consisting sequential application of two pre-emergence application [Pendimethalin (30 EC) 1.00 kg a.i. ha(-1); Butachlor (50 EC) 1.5 kg a.i. ha(-1)] followed by three post emergence herbicides [Bispyribac-Na (10% SC) @ 35 g a.i. ha(-1); 2,4-D Na salt (80 WP) @ 0.06 kg a.i. ha(-1);Almix (CME + MSM) (20 WP) 40 g a.i. ha(-1)] and straw mulching @ 4 t ha(-1); Mechanical weeding at 20 and 45 DAS, weed free and unweeded check. Results: Among herbicidal treatments, pre-emergence application of pendimethalin at 3-4 DAS fb Bispyribac-Na at 1520 DAS as post-emergence was most effective in minimizing weed density (4.81 m(-2)), biomass (6.20 g m(-2)), weed index (1.11%) and in enhancing the weed control efficiency (84.50%), grain yield (3.68 t ha(-1)) and straw yield (4.87 t ha(-1)) over rest of the treatments. Interpretation: Sequential application of pendimethalin at 3-4 DAS fb bispyribac-Na at 15-20 DAS is prominent in enhancing herbicide efficacy and reducing weed flora abundance resulting in higher weed control efficiency and grain yield due to their broad spectrum weed control.