Rice-wheat {Oryza sativa L-Triticum aestivum L.) rotation is the major production system in Asia, covering about 18 million ha. Conventional practice of growing rice (puddled transplanting) and wheat (conventional till, CT) deteriorate soil physical properties, and are input-and energy-intensive. Zero-tillage (ZT) along with drillseeding have been promoted to overcome these problems. A 7-yr permanent plot study evaluated various tillage and crop establishment (CE) methods on soil physical properties with an aim to improve soil health and resourceuse efficiency. Treatments included transplanting and direct-seeding ot rice on flat and raised beds with or without tillage followed by wheat in CT and ZT soil. Bulk density (D|j) of the 10-to 20-cm soil layer was highest under puddled treatments (1.74-1.77 Mg m"') and lowest under ZT treatments (1.66-1.71 Mg m"'). Likewise, soil penetration resistance (SPR) was highest at the 20-cm depth in puddled treatments (3.46-3.72 MPa) and lowest in ZT treatments (2.51-2.82 MPa). Compared with conventional practice, on average, water-stable aggregates (WSAs) > 0.25 mm were 28% higher in ZT direct-seeding with positive time trend of 4.02% yr~'. Infiltration was higher (0.29-0.40 cm h~') in ZT treatments than puddled treatments (0.18 cm h"'). The least-limiting water range was about double in ZT direct-seeding than that of conventional practice. Gradual improvement in soil physical parameters in ZT system resulted in improvement in wheat yield and is expected to be superior in longrun on system (ricc+wheat) basis. Further research is needed to understand mechanisms and requirements of two cereals with contrasting edaphic requirements in their new environment of ZT direct-seeding.

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Rice (Oryza sativa L.)–wheat (Triticum aestivum L.) is the major cropping system occupying 13.5 million ha in the Indo‐Gangetic Plains of South Asia. Conventional‐tillage practices are resource and cost intensive. A 7‐yr study evaluated six treatments (T) involving three tillage methods and two rice establishment methods on crop yield, water productivity, and economic profitability in a rice–wheat rotation. Average rice yields in the conventional practice of puddling and transplanting without (T1) and with (T2) mid‐season alternate wetting‐drying were highest (7.81–8.10 Mg ha−1) and increased with time (0.26 Mg ha−1 yr−1) in T2. Compared to T1, rice yields in direct drill‐seeding with zero‐tillage averaged 16% lower on flat (T5) and 43% lower in raised beds (T3). Rice yield in raised beds (T3 and T4) decreased with time (0.14–0.45 Mg ha−1 yr−1). Conversely, wheat yielded 18% higher after zero compared to conventional‐tillage. Treatment 2, despite low soil matric potential during vegetative development, had higher water productivity with 25% less water use compared with T1 and 19% less compared with other treatments. Conventional‐tillage and crop establishment practices had higher net cash return in rice but in wheat it was higher with zero‐tillage. Overall, T2 and T5 had the highest net returns (∼1225US$) and T3 and T4 had the lowest (747–846 US$) in the rice–wheat system. Zero‐tillage on flat beds (T5), however, would conceivably be more sustainable than the conventional T2 in the long‐run. Yields of zero‐tillage with direct‐seeding of rice on flat beds (T5) must improve before adoption occurs.

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Soil quality degradation associated with resources scarcity is the major concern for the sustainability of conventional rice-wheat system in South Asia. Replacement of conventional management practices with conservation agriculture (CA) is required to improve soil quality. A field experiment was conducted to assess the effect of CA on soil physical (bulk density, penetration resistance, infiltration) and chemical (N, P, K, S, micronutrients) properties after 4 years in North-West India. There were four scenarios (Sc) namely conventional rice-wheat cropping system (Sc1); partial CA-based rice-wheat-mungbean system (RWMS) (Sc2); CA-based RWMS (Sc3); and CA-based maize-wheat-mungbean (Sc4) system. Sc2 (1.52 Mg m−3) showed significantly lower soil bulk density (BD). In Sc3 and Sc4, soil penetration resistance (SPR) was reduced and infiltration was improved compared to Sc1. Soil organic C was significantly higher in Sc4 than Sc1. Available N was 33% and 68% higher at 0–15 cm depth in Sc3 and Sc4, respectively, than Sc1. DTPA extractable Zn and Mn were significantly higher under Sc3 and Sc4 compared to Sc1. Omission study showed 30% saving in N and 50% in K in wheat after four years. Therefore, CA improved soil properties and nutrient availability and have potential to reduce external fertilizer inputs in long run.

HighlightsHigher cereal productivity can be achieved with lower environmental footprint through conservation agriculture.Wheat productivity and profitability can be increased by zero-tillage and early sowing.Kharif maize appears to be a suitable and profitable alternative to rice in northwest India.Productivity and resource efficiency of transplanted rice can be improved by BMPs.Directly sown rice has potential to save water, energy and global warming potential compared to transplanted rice.

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.