Efficacy of herbicide mixtures on weed control, yield and water productivity of direct-sown summer rice

Rice is more susceptible to weed infestation than other food crops, necessitating the prioritization of effective weed management strategies. The potential for sustainable weed control through herbicide mixtures is a key consideration. A study was conducted at the ICAR-National Rice Research Institute, Cuttack, India, during the summer seasons of 2020 and 2021 to assess the efficacy of a new formulation of penoxsulam 1.02% + cyhalofop butyl 5.1% in comparison to the existing ready-mix formulation, penoxsulam 1.02% + cyhalofop butyl 5.1% (marketed as Vivaya). In terms of weed composition, grasses, sedges, and broadleaf weeds accounted for 45.0%, 27.2%, and 27.8%, respectively. Among these, Echinochloa crus-galli emerged as the dominant weed, constituting 23.2% of the total weed population. The application of penoxsulam 1.02% + cyhalofop butyl 5.1% at 135 g/ha demonstrated effective broad-spectrum weed control, particularly strong against sedges. In plots with crop-weed competition, the grain yield of rice was reduced by 37.5%. The new formulation and Vivaya showed comparable results in reducing weed density and biomass. Application of ready-mix penoxsulam 1.02% + cyhalofop butyl 5.1% at 135 g/ha as a post-emergence herbicide at 15 DAS resulted in a remarkable 45.9% increase in grain yield over the weedy check plots. Weed control with the new formulation of ready-mix penoxsulam 1.02% + cyhalofop butyl 5.1% at 135 g/ha recorded physical water productivity (0.44 kg/m³), economic water productivity (`8.65/kg), and net return (`57.00×103/ha), which were comparable to Vivaya. Thus, new formulations of penoxsulam 1.02% + cyhalofop butyl 5.1% were found to be safe and effective for controlling weeds in wet direct-seeded rice at a dose of 135 g/ha.