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Weed Management Strategies to Reduce Herbicide Use in Zero-Till Rice–Wheat Cropping Systems of the Indo-Gangetic Plains
- Virender Kumar, Samar Singh, Rajender S. Chhokar, Ram K. Malik, Daniel C. Brainard, Jagdish K. Ladha
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- Journal:
- Weed Technology / Volume 27 / Issue 1 / March 2013
- Published online by Cambridge University Press:
- 20 January 2017, pp. 241-254
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- Article
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In the rice–wheat (RW) systems of the Indo-Gangetic Plains of South Asia, conservation tillage practices, including zero-tillage (ZT), are being promoted to address emerging problems such as (1) shortages of labor and water, (2) declining factor productivity, (3) deterioration of soil health, and (4) climate change. Despite multiple benefits of ZT, weed control remains a major challenge to adoption, resulting in more dependence on herbicides for weed control. Alternative management strategies are needed to reduce dependence on herbicides and minimize risks associated with their overuse, including evolution of herbicide resistance. The objectives of this review are to (1) highlight and synthesize research efforts in nonchemical weed management in ZT RW systems and (2) identify future weed ecology and management research needs to facilitate successful adoption of these systems. In ZT RW systems, crop residue can play a central role in suppressing weeds through mulch effects on emergence and seed predation. In ZT rice, wheat residue mulch (5 t ha−1) reduced weed density by 22 to 76% and promoted predation of RW weeds, including littleseed canarygrass and barnyardgrass seeds. For ZT wheat, rice residue mulch (6 to 10 t ha−1) in combination with early sowing reduced emergence of littleseed canarygrass by over 80%. Other promising nonchemical approaches that can be useful in suppressing weeds in ZT RW systems include use of certified seeds, weed-competitive cultivars, stale seedbed practices, living mulches (e.g., sesbania coculture), and water and nutrient management practices that shift weed–crop competition in favor of the crop. However, more research on emergence characteristics and mulching effects of different crop residues on key weeds under ZT, cover cropping, and breeding crops for weed suppression will strengthen nonchemical weed management programs. Efforts are needed to integrate multiple tactics and to evaluate long-term effects of nonchemical weed management practices on RW cropping system sustainability.
Weeds and Weed Management of Rice in Karnataka State, India
- Adusumilli Narayana Rao, Suhas P. Wani, Mugalodi Ramesha, Jagdish K. Ladha
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- Journal:
- Weed Technology / Volume 29 / Issue 1 / March 2015
- Published online by Cambridge University Press:
- 20 January 2017, pp. 1-17
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Rice is one of the staple food crops of India, and Karnataka is one of the major rice-producing states. The primary method of rice establishment in Karnataka is transplanting, but farmers are opting to shift to direct-seeding of rice. Weed management is critical for realizing optimal yield of direct-seeded rice (DSR). The objective of this review was to synthesize the published literature on weeds and weed management in rice in Karnataka, identify improved weed-management technologies for delivery to farmers, and suggest research needs. Some 98 weed species are reported to be associated with rice in Karnataka. Weed control to date in Karnataka has mostly been based on herbicides. Hand-weeding was found to be effective in all methods of rice establishment. However, it is time-consuming, tedious, and costly because labor is becoming scarce and unavailable, and labor wages are higher. Several PRE and POST herbicides that were effective in other Asian countries were also found to be effective in managing weeds in rice established by different methods in Karnataka. Bensulfuron plus pretilachlor and pyrazosulfuron in aerobic rice and pendimethalin, thiobencarb, bispyribac-sodium, cyhalofop, fenoxaprop plus chlorimuron plus metsulfuron, and fenoxaprop plus ethoxysulfuron in dry-DSR were found effective in managing weeds. In wet-DSR, butachlor plus safener and pretilachlor plus safener were effective. Thiobencarb, pendimethalin, pretilachlor, azimsulfuron plus metsulfuron, bispyribac-sodium, butachlor, cinosulfuron, oxadiazon, and quinclorac were found promising for weed management in transplanted rice. Integration of herbicides with hand-weeding or intercultivation was found to be effective in rice established by different methods. Options that were found economical in managing weeds varied across the different rice-establishment methods. The need for developing location-specific, sustainable, integrated weed management and extension of available technologies for the farming community in Karnataka is emphasized.