Early Post Emergence Herbicide and Their Influence on Weed Population Dynamics in Transplanted Rice (Oryza Sativa L.)

In India weed problem is one of the most important biotic constraints that limits rice productivity [1]. Transplanted rice, in particular, is infested by heterogeneous type of weed flora under lowland ecosystems which reduces yield upto 48 per cent and an yearly loss of 15 million tonnes due to weed competition [2]. Prevention of weed competition and provision of weed free environment at critical period of rice growth is necessary for successful rice production. Transplanted rice is infested with wide range of weeds species viz., grasses, sedges and broad leaved weeds. Among different weed species some group of weeds posing acute yield reduction in the transplanted rice and particularly, Echinochloa crusgalli and Cyperus difformis are the most predominant and highly competitive weeds in transplanted rice ecosystem. Echinochloa crus-galli competes with rice crop right from the planting till harvest stage of the rice crop whereas the sedge weed Cyperus difformis competes with the crop during the early phase of rice crop because of its shorter life cycle. Hence, these weeds can be effectively managed using herbicides instead of other weed management options. Since, weed control in transplanted rice by mechanical and cultural is an expensive method. Especially at the time of peak period of labour crisis, sometimes weeding becomes delayed causing drastic reduction in grain yield. In this context, an attempt was made to evaluate application of early post emergence herbicide and their influence on weed population dynamics in transplanted rice.