Weed management in different rice establishment methods under two nitrogen levels

摘要

Rice ecosystems are characterised mainly according to the water regimes as lowland rice, irrigated lowland rice, rainfed upland rice etc. Lowland rice is mainly transplanted or wet seeded on puddled soil, while upland rice is direct seeded on dry soil. Transplanting is labour intensive while, weeds are more serious problem in direct seeded rice cultivation. As a compromise between these two methods, throwing of rice seedling (broadcast planting) is practiced in Japan and China. A wide range of weed species infest rice crop and yield losses of 16 and 61 per cent have been reported in transplanted and direct seeded rice respectively due to uncontrolled weeds (Chiang, 1981). Further, the weed flora and crop losses are found to be influenced very much by the systems of rice cultivation (Ali and Sankaran, 1984).