Methane emissions from rice fields - Quantification, mechanisms, role of management, and mitigation options

This chapter reviews the information available on CH4 production and emissions in rice paddy soils and discusses the impact of soil and environmental factors, as well as agronomic and management practices. The chapter also illustrates the CH4 source strength of different rice ecologies and possible mitigation options. It is now well understood that emission of CH4 from rice paddies into the atmosphere are triggered by the microbiological processes of CH4 production in the anoxic layers of the soil, by aerobic CH4 oxidation in the oxic surface layers of the soil, and the floodwater. Methane produced in rice fields escapes to the atmosphere initially by ebullition and diffusion from the flooded soil but as rice plant growth proceeds, it is emitted primarily by diffusive transport through the rice plant. Furthermore, based on differences among cultivars, it is feasible to select and breed high yielding rice cultivars with a reduced CH4 transport capacity. This could be useful in formulating mitigation options and that may be realized in future rice breeding programs. © 2001, Elsevier Inc. All rights reserved.