Tillage and Crop Establishment Affects Sustainability of South Asian Rice-Wheat System

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 aft er 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 (similar to 1225US$) and T3 and T4 had the lowest (747-846 US$) in the rice-wheat system. Zero-tillage on fl at 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 fl at beds (T5) must improve before adoption occurs.