Bio-efficacy of herbicides and their mixture on weeds and yield of rice (Oryza sativa) under rice-wheat cropping system

A field experiment was conducted during the rainy (kharif) seasons of 2014 and 2015 at Krishi Vigyan Kendra, Sohna, Siddarthnagar Uttar Pradesh, to assess the efficacy of bispyribac-Na, pretilachlor, penoxsulam, pyrazosulfuron, bispyribac-Na + ethoxysulfuron methyl, bispyribac-Na + almix (metsulfuron methyl 10% + chlorimuron ethyl 10% WP), pretilachlor followed by (fb) ethoxysulfuron methyl, pretilachlor fb almix, pyrazosulfuron fb manual weeding, pretilachlor + bensulfuron in transplanted rice (Oryza sativa L.). The highest grain yield (5.2 t/ha) was recorded in weed-free plot, being at par with bispyribac-Na + almix (25 g + 4 g/ha), pretilachlor fb almix (750 g and 4 g/ha), pyrazosulfuron (20 g/ha) fb manual weeding. Uncontrolled weed growth caused 41.9% reduction in the crop yield compared to weed-free treatment. Tank-mix application of bispyribac-Na + almix, pretilachlor fb almix, pyrazosulfuron fb manual weeding and bispyribac-Na + ethoxysulfuron methyl (25 g + 18.75 g/ha) proved better, showing a mean increase in grain yield of 9.54% than mean of alone application of bispyribac-Na, pretilachlor, penoxsulam (22.5 g/ha) and pyrazosulfuron (20 g/h). Tank-mix application of bispyribac-Na + almix being at par with application of pretilachlor fb almix reduced the weed density and weed dry weight compared to rest of the herbicides tested. Application of bispyribac-Na + almix, remaining at par with pretilachlor fb almix, pretilachlor fb ethoxysulfuron methyl, bispyribac-Na + ethoxysulfuron methyl (25 + 18.75 g/ha) at 25 days after transplanting (DAT) was the most effective in enhancing yield attributes and grain yield. The highest net return (44, 073/ha) and benefit: cost ratio (1.97) were also obtained using bispyribac-Na + almix. Application of penoxsulam (22.5 g/ha) at 12 DAT recorded the lowest weed-control efficiency and grain yield amongst the herbicides tested which was at par with alone application of bispyribac-Na, pretilachlor, pyrazosulfuron. Application of bispyribac-Na + almix 25 + 4 g/ha at 25 DAT, though on a par with pretilachlor fb almix and pyrazosulfuron resulted significantly higher N, P and K uptake than rest of the herbicides tested and weedy check.