Evaluation of herbicide mixtures for broad-spectrum weed control and yield in transplanted summer rice (Oryza sativa)

An experiment was conducted during the summer seasons of 2018 and 2019 at Cuttack, Odisha, to compare the efficacy of new formulation of penoxsulam 1.02% + cyhalofop-butyl 5.1% in different application rate with the existing ready-mix formulation of penoxsulam 1.02% + cyhalofop-butyl 5.1% (Vivaya). The composition of weed flora showed more prevalence of grasses viz. (43.3%) followed by sedges (29.4%) and broad-leaf weeds (27.3%). Leptochloa chinensis (L.) Nees was the most dominant weed (19.6%). Penoxsulam 1.02% + cyhalofop-butyl 5.1% (135 g/ha) at 15 days after transplanting (DAT) registered effective control of broad-spectrum of weeds. The new formulation and Vivaya were found at par in terms of reduction in weed density and biomass. There were no significant difference between two doses of formulation (120 and 135 g/ha) in controlling weeds. Crop-weed competition in weedy plot reduced the grain yield of rice to the tune of 32.2%. Post-emergence application of penoxsulam 1.02% + cyhalofop-butyl 5.1% (135g/ha) at 15 DAT resulted in increased grain yield by 32.1% over the weedy check and it was at par with the existing ready-mix formulation. The new formulation has no phyto-toxicity to rice crop. Thus, post-emergence application of ready-mix penoxsulam + cyhalofop-butyl at 135 g/ha could be recommended as an alternative to conventional manual weeding for broad-spectrum weed control in transplanted rice fields.