Grace, P. R., M. C. Jain, L. W. Harrington, and G. P. Robertson. 2003. Long-term sustainability of the tropical and subtropical rice and wheat system: An environmental perspective. Pages 27-43 in J. K. Ladha, J. E. Hill, J. M. Duxbury, R. K. Gupta, and R. J. Buresh, eds. Improving the Productivity and Sustainability of Rice-Wheat System: Issues and Impacts. American Society of Agronomy Special Publication 65, Madison, Wisconsin, USA.
Arable lands in the Indo-Gangetic Plains are already intensively cropped with little scope for expansion because of the competing end uses of land for urbanization and industry. Evidence from long-term experiments in the region indicates that cereal yields are declining, which is in stark contrast to the needed increases in production to meet population demands in the future. The intensification of rice-wheat rotations has resulted in a heavy reliance on irrigation, increased fertilizer usage, and crop residue burning, which all have a direct effect on the variable that most affects global climate change – emissions of greenhouse gases. We estimate that the CO 2 equivalent emissions from a high-input conventionally tilled cropping system with residue burning and organic amendments would equal 8 mg C or 29 mg CO 2 per year if applied to 1 million hectares of the Indo-Gangetic Plains. In a no-till, residue-retained system, with 50% of the recommended NPK application, the total emissions would equal 3.7 mg C or 14 mg CO 2 per year, an effective halving of emissions as we move from a high- to low-input system with improved nutrient use and environmental efficiency. The transition to intensified no-tillage systems, with recommended fertilizer levels, can be both productive and environmentally sound in a world that is rapidly becoming aware of the significant effects of global climate change in both the short and long term.
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