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1 March 2013 Weed Management Strategies to Reduce Herbicide Use in Zero-Till Rice–Wheat Cropping Systems of the Indo-Gangetic Plains
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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.

Nomenclature: Barnyardgrass, Echinochloa crus-galli (L.) Beauv.; littleseed canarygrass, Phalaris minor Retz.; sesbania, Oryza sativa L.; wheat, Triticum aestivum L.

En sistemas de arroz-trigo (RW) de las planicies Indo-Gangéticas del sur de Asia, se está promoviendo el uso de prácticas de labranza de conservación, incluyendo labranza cero (ZT), para solucionar problemas emergentes tales como (1) escasez de agua y mano de obra, (2) reducción de productividad, (3) deterioro en la salud del suelo, y (4) cambio climático. A pesar de los múltiples beneficios de ZT, el control de malezas continúa siendo uno de los mayores retos para la adopción de esta tecnología, lo que resulta en una mayor dependencia en herbicidas para el control de malezas. Se necesitan estrategias alternativas de manejo para reducir la dependencia en herbicidas y minimizar los riesgos asociados a su sobreuso, incluyendo la evolución de resistencia a herbicidas. Los objetivos de esta revisión son (1) resumir y resaltar los esfuerzos de investigación en el manejo no-químico de malezas en sistemas ZT RW e (2) identificar las necesidades futuras de investigación sobre ecología y manejo de malezas para facilitar el éxito en la adopción de estos sistemas. En sistemas ZT RW, el residuo del cultivo puede jugar un rol central en la supresión de malezas mediante efectos de cobertura sobre la emergencia y la depredación de semillas. En arroz ZT, la cobertura con residuos de trigo (5 t ha−1) redujo la densidad de malezas 22 a 76% y promovió la depredación de malezas de RW, incluyendo semillas de Phalaris minor y Echinochloa crus-galli. Para trigo RW, la cobertura con residuos de trigo (6 a 10 t ha−1) en c

Virender Kumar, Samar Singh, Rajender S. Chhokar, Ram K. Malik, Daniel C. Brainard, and Jagdish K. Ladha "Weed Management Strategies to Reduce Herbicide Use in Zero-Till Rice–Wheat Cropping Systems of the Indo-Gangetic Plains," Weed Technology 27(1), (1 March 2013).
Received: 21 April 2012; Accepted: 17 July 2012; Published: 1 March 2013

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