Weed management in lowland rice

Abstract

Lowland rice ecosystem in India is infested with complex weed flora including semi-aquatic and aquatic weeds. Recently weeds having mimics with rice, perennial and other weeds which propagate by vegetative means are emerging as major threat. Weeds cause yield losses from 15 to 76% in rice crop. Besides, weeds remove about 21-42 kg N, 10-13.5 kg P and 17-27 kg K/ha in transplanted rice. Research on weed management in lowland rice in India has been reviewed in this paper with respect to weed flora and their impact, biology and ecology of weeds, weed management methods and future thrust areas of research and management. The weed flora in lowland rice is very much diverse and dynamic over times and places. Very limited information is available on biology and ecology of major weeds. Studies have been carried out on cultural, manual, mechanical, chemical means of weed management. Shortage of labours, lack of suitable weed control implements and problem of specific weeds have compelled the farmers to think for alternative strategies and herbicides have been the obvious choice to the farmers. Many herbicides either alone or in combinations as ready or tank mixed have been recommended in India. Studies on integrated weed management have also been undertaken. But majority of researches focused on herbicide based IWM. Future research and weed management in lowland rice should be focused on ecophysiology and biology of major weeds, HR genetically modified rice, integrated weed management, exploring biocontrol agents and screening and use of allelopathic and weed competitive rice cultivars.