Weed management in direct-seeded rice

摘要

Rice (Oryza saliva), the staple food of more than half of the population of the world, is an important target to provide food security and livelihoods for millions. Direct seeding of rice (DSR) refers to the process of establishing the crop from seedssown in the field rather than by transplanting seedling from the nursery. Before the advent of Green revolution and adoption of irrigation, rainfed rice was often broadcasted into moist soil and yields were low, variable and highly prone to weed competition. Weed spectrum and degree of infestation in rice field are often determined by rice ecosystems and establishment methods. Research evidences at different places has shown around 20-100% losses due to weeds such as Echinochloa spp., Leptochloa spp.,Cyanolis spp., Commelina sp., Digilaria spp. and Allernanthera sp in DSR. Integrated weed management approach based on the critical period of crop weed competition, involving different direct and indirect control measures, has been developed and widely adopted by farmers to overcome weed problem in DSR in a sustainable way. Stale seed bed combined with herbicide (paraquat/glyphosate) and zero till results in better control. About 53% lower density was recorded due to stale seed bed. Brown manuring of Sesbania reduces weed population by 50%. Mulches, crop rotation and rice cultivars like 'Narender 359' and 'Sarjoo 52' were found better for Indo- Gangetic plains. Application of penoxsulam 25 g/ha as broad-spectrum, azimsulfuron + metsulfuron-methyl for Cyperus spp., pendimethalin at 1.25 kg/ha for Echinochloa spp. were found suitable for chemical weed management.Weed-competitive and allelopathic rice varieties, seed priming for increased weed competitiveness, higher seeding density should be consideredas a management strategy.