Performance of sequential application of pre and post-emergence herbicides for management of weeds in aerobic rice (Oryza sativa)

A field experiment was conducted during the rainy (kharif) season of 2014 and 2015 at Zonal Agricultural Research Station, V.C. Farm, Mandya, Karnataka, India, to study the performance of sequential application of herbicides in aerobic rice (Oryza sativa L.). Among the weed-management practices, hand-weeding at 20, 40 and 60 days after sowing (DAS) resulted in significantly lower density and dry weight of all categories of weeds, ensuing higher grain yield (5.57 and 5.42 t/ha, respectively); this was closely followed by pre-emergence application of pyrazosulfuron ethyl @ 25 g/ha and by post-emergence application of bispyribac-sodium @ 25 g/ha at 20 days after sowing (5.20 and 5.12 t/ha, respectively) during both the years. However, the higher net returns (₹48,210 and 47,040/ha, respectively) and benefit: cost ratio (2.62 and 2.58, respectively), during both the years were obtained from sequential application of herbicide treatment. Uncontrolled weed growth caused about 51% reduction in grain yield of aerobic rice during 2014 and 2015.