Integrated weed management, a key to success for direct-seeded rice in the Indo-Gangetic Plains
2009
Singh, S. | Chhokar, R.S. | GopaL, R. | Ladha, J.K. | Gupta, R,K. | Kumar, V. | Singh, Megh
Water scarcity, labor shortage, escalating fuel prices, and soil fertility problems are causing increasing interest in shifting from puddled and transplanted rice (the traditional system) to direct-seeded rice (DSR). Weed control is a serious challenge to the success of DSR. Therefore, the development of an effective weed management program for DSR is needed. Field studies conducted at research stations and in farmers fields in the Indo-Gangetic Plains (western Uttar Pradesh, Haryana, and Bihar states of India) from 2002 to 2008 showed that complex weed flora caused yield losses in DSR of 65_92%. Studies revealed that for the success of DSR weeds can be managed by integrated weed management (IWM) approaches, which include stale seedbed techniques. the use of competitive varieties, water management, the use of weed-free seed. hand weeding, mulching, co-culture of Sesbania, and the application of recommended herbicides. Competitive cultivars of rice (Basmati group) effectively smothered weeds compared with short-stature high-yielding varieties. Stale seedbed techniques and straw mulching were found to be effective in reducing the density of grassy and broadleaf weeds. Brown manuring (broadcasting of Sesbania along with rice seeding and killing Sesbania, by spraying 2,4-D around 30 days after seeding) or mulching reduced weed density by 37-42% compared with a sole rice crop. Rice yield was greater when Sesbania was seeded 0 and 5 days after rice seeding compared with 10 days after rice seeding and a sole rice crop. Some herbicides found effective in DSR are pendimethalin. cyhalofop-butyl, fenoxaprop-ethyl, propanil, bispyribac, penoxsulam, triclopyr, carfentrazone, halosulfuron, bensulfuron, azimsulfuron, quinclorac, clomazone. 2,4-D, chilorimuron + metsulfuron, and molinate. The integration of herbicides with one hand weeding around 45 days after seeding was effective in reducing weeds and improving yield. For season-long and broad-spectrum sustainable weed management, an integration of different herbicides and weed control measures is needed as part of an IWM strategy. Continuous monitoring of weed flora is needed to identify shifts in weed flora due to a shift from conventional puddled transplanted rice to DSR and to focus on the emerging problematic new weed species that are even more difficult to control and that are competitive in nature, such as weedy rice.
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