Herbicide mixture mediated soil environment analysis in wet direct-sown rice

Abstract

Direct-sown rice is the possible alternative to the conventional puddled transplanted rice as it saves resources viz. water, labour and time. Pre-germinated (sprouted) seeds are sown on puddled soil in wet direct-sown rice. But weed infestation is the major yield compromising factor under this environment as the weeds emerge simultaneously with the rice and compete from the beginning. Among the weed control methods, herbicide-based weed control is the most effective and efficient method. However single herbicide application in a long run leads to weed flora shift and development of herbicide resistance in weeds. In contrast, herbicide mixtures with different mode of action are the possible alternative to reduce the herbicide resistance and to broaden the weed control spectrum season long. But soil environment aspect is important for sustainable rice farming using herbicide mixtures. This investigation was done in Research farm of ICAR – National Rice Research Institute, Cuttack, Odisha in wet season of 2016. The experiment was laid out in randomized complete block design with nine treatments viz. herbicide mixture florpyrauxifen-benzyl + cyhalofop-butyl in four doses i.e. 120, 150, 180 and 360 g/ha; florpyrauxifen-benzyl in two doses i.e. 25 and 30 g/ha; bispyribac-sodium at 30 g/ha; weed free and weedy check; replicated thrice. Soil environment parameters viz. microbial-biomass carbon, FDA hydrolase activity, dehydrogenase activity and urease activity were studied before, 4, 10, 20 and 30 days after herbicide treatments. The herbicide mixture florpyrauxifen-benzyl + cyhalofop-butyl at 150 g/ha (4.91 t/ha) was found to be the most effective herbicide showing no detrimental effect on soil environment of wet direct-sown rice after 10 days of application and yielding at par with the weed free (5.27 t/ha).