Studies on Crop-Weed Competition in Rainfed Direct-Seeded Lowland Rice (Oryza sativa)

摘要

Rice (Oryza sativa L.) is grown in shallow lowland (water depth 0-25 cm) situation in Orissa partly under direct-seeded condition. Weed problems are critical in this situation because initially (before water accumulation), it is just like upland situation which encourages grassy weeds, some sedges and dicots. In order to formulate an appropriate strategy for weed management, it is necessary to find out critical period of weed competition, which is the optimum time at which weeds should be removed toprevent possible loss in yield. Knowledge on critical period of weed competition helps in reducing the labour requirement for weeding operations and maximizes the economic returns. While considerable work on crop-weed competition in rainfed upland rice (where short duration varieties are grown) was reported (Sharma et. al., 1977; Bhan, 1983 ;Tiwari and Singh, 1991), not much on rainfed lowlands, where long duration varieties are grown, was done. The present study embodies the research carried out in this direction.