2008 Joint Annual Meeting (5-9 Oct. 2008): Integrated Weed Management in Direct-Seeded Rice Under Different Crop Establishment Methods in Rice-Wheat System of Indo-Gangetic Plain.

Direct drill-seeded rice (DSR) with reduced or no tillage saves water, labour, fuel and time without yield penalty and thus gives higher return compared to the conventional transplanted rice. It also maintains soil health and improves fertilizer use efficiency and is more adaptive to drought. However, weed management is a serious problem in DSR posing a threat to its yield stability. Therefore, an integrated weed management involving chemical, manual and mechanical methods to control complex weed flora in DSR is urgently required. A study was conducted to evaluate four methods of crop establishment (zero-till DSR, reduced-till DSR, unpuddled transplanting and puddled transplanting) and five methods of weed control (sesbania followed by 2,4-D @ 0.5 kg a.i. ha^-1 at 35 days after sowing, cyhalofop-butyl @ 90 g a.i. ha^-1, pretilachlor + safener @ 0.5 kg a.i. ha^-1, pendimethalin @ 1.5 kg a.i. ha^-1 plus one hand weeding, pendimethalin @ 1.5 kg a.i. ha^-1 alone, and weedy check) in rice in the northwest Indo-Gangetic plains during 2004-2006. In Sesbania treatment, it was used as an intercrop with rice up to its vegetative phase following by mulching after sprayed by 2,4-D.  Highest weed density was recorded in reduced till DSR, followed by zero-till DSR, unpuddled transplanting and puddled transplanting. Yield loss due to weed was 7% with pendimethalin @ 1.5 kg a.i. ha^-1 plus one hand weeding in unpuddled transplanting, 70% with pretilachlor + safener @ 0.5 kg a.i. ha^-1 in reduced till DSR and 80% with weedy check DSR compared to puddled transplanting. Weed density and dry weight were negatively correlated with rice yield. Weed spectrum was dominated by Echinochloa spp. and Cyperus spp. Pendimethalin @ 1.5 kg a.i. ha^-1 plus one hand weeding reduced density of Echinochloa spp. by 92% over weedy check followed by cyhalofop-butyl @ 90 g a.i. ha^-1 (89%), sesbania followed by 2,4-D (70%), pendimethalin @ 1.5 kg a.i. ha^-1 alone (67%) and pretilachlor + safener @ 0.5 kg a.i. ha^-1 (44%) in both the years. The study showed that pendimethalin @ 1.5 kg a.i. ha^-1 followed by one hand weeding could be effectively practiced for controlling weeds in DSR.