Effect of irrigation and methods of weed management on weed dynamics and yield of summer rice (Oryza sativa) under system of rice intensification

A field experiment was conducted during the summer season of 2014 and 2015 to study the effect of irrigation and methods of weed management on weed dynamics, yield and nutrient uptake of rice (Oryza sativa L.) under system of rice intensification (SRI). Application of 50 mm water on the day before weeding operation was signifi- cantly superior to saturation (15 mm) on the day before weeding operation for grain yield (5.5 t/ha) owing to the lowest weed density (172.2/m2), weed dry weight (76.1 g/m2), and the highest number of panicles/plant (35.1) and filled grains/panicle (94). Pre-emergence application of pretilachlor @750 g/ha at 3 days after transplanting (DAT) followed by post-emergence application of chlorimuron ethyl + metsulfuron methyl @ 4 g/ha at 20 DAT proved to be most effective in minimizing the density of weeds (139.8/m2), their dry weight (65.5 g/m2) and enhancing weed- control efficiency (57.6%), grain yield (5.6 t/ha), N-P-K uptake of 66.1, 20.2, 23.0 kg/ha respectively by grain, net returns (52,714 /ha) and benefit: cost ratio (3.35).