System-level effects In weed management In rice-wheat cropping in India

摘要

Rice-wheat is the principal cropping system of the Indo-Gangetic Plains and its sustainability is vital to the livelihoods of the farmers of the region and national food security. Changing rice establishment from transplanting to direct seeding offerslabour and water savings and zero-tillage in wheat may improve productivity. Studies over four cropping cycles confirmed that with intensive weed control, yields under wet seeding of rice were superior to transplanted rice, dry direct seeded and zero-tilled rice. Conventional and zero-tillage in wheat gave similar yields. The inclusion of appropriate early post emergence chemical weed control followed by manual weeding for rice improved yields over conventional hand weeding. Underlying the pattern of selective recruitment of weeds by method of rice establishment were the impacts of wheat tillage method. Densities of Echinochloa colona in rice were reduced with zero-tilled wheat whereas abundance of Caesulia axillaris increased. Over four cropping cycles of direct seeding there were noticeable increases in Ischaemum rugosum, Leptochloa chinensis and Fimbristylis miliacea in wet seeded rice, while Cyperus rotundas became incorporated into the weed flora of dry direct seeded rice with highest abundancein plots zero-tilled for wheat.