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

Abstract

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.

Management of Cereal Crop Residues for Sustainable Rice-wheat Production System in the Indo-gangetic Plains of India

“…Rice residue management in no-till systems (surface retention) provides multiple benefits, including soil moisture conservation, suppression of weeds, improvement in soil quality (Balwinder-Singh et al 2011a, Ram et al 2013Kumar et al 2013;Singh et al 2005;Verhulst et al 2011), reduction in greenhouse gas emissions equivalent to nearly 13 t ha -1 (Mandal et al 2004), and regulates canopy temperature at the grain-filling stage to mitigate the terminal heat effects in wheat (Gupta et al 2010;Jat et al 2009), and significantly improves the C sustainability index (Jat et al 2011). The suppression of weeds with straw mulch might help reduce herbicide requirements (Yadvinder-Singh et al 2010b).…”

Towards a No-Till No-Spray Future? Introduction to a Symposium on Nonchemical Weed Management for Reduced-Tillage Cropping Systems

“…For example, Kumar et al (2013) present data demonstrating that combinations of rice (Oryza sativa L.) residue and early wheat (Triticum aestivum L.) planting dates substantially reduced emergence of littleseed canarygrass. They also highlight breeding efforts aimed at improving weed-suppressive traits in both rice and wheat.…”

“…], and littleseed canarygrass (Phalaris minor Retz.) (Kumar et al 2013). A more mechanistic understanding of how integration of multiple nonchemical weed management tactics impact these problematic species will be helpful for the long-term viability of low-input and organic reduced tillage crop production.…”

Buttonweed emergence as affected by seed burial depth and straw on the soil surface

“…In those soybean areas under no-tillage where buttonweed is a difficult-to-control weed, the increase in straw amount on the soil surface has the potential to reduce buttonweed emergence and consequently, its establishment, avoiding subsequent interference with the crop. For instance, a study on rice under no-tillage showed that 5,000 kg ha −1 of superficial wheat straw reduced weed density from 22 to 76 % and promoted predation of rice-wheat weeds (Kumar et al, 2013). Other studies have also shown that weed suppression was species-specific and could be achieved with residue from different plant species being present on the soil surface (Campiglia et al, 2012;Mirsky et al, 2013;Anderson, 2014).…”