FLUXES OF METHANE FROM RICE FIELDS AND POTENTIAL FOR MITIGATION

Methane (CH4) is an important greenhouse gas. Flooded rice fields (pad dies) are a significant source of atmospheric CH4; estimates of the an nual emission from paddies range from less than 20 to 100 million Tg, with best estimates of 50 +/- 20 Tg. The emission is rile net result o f opposing bacterial processes: production in anaerobic microenvironme nts, and consumption and oxidation in aerobic microenvironments, both of which occur sequentially and concurrently in flooded rice sails. Wi th current technologies, CH4 emission from rice fields will increase a s production increases. Ova the next 25 years rice production will hav e to increase by 65% from the present 460 Mt/y to 760 Mt/y in 2020. Th e current understanding of the processes controlling CH4 fluxes, rice growth and rice production is sufficient to develop mitigation technol ogies. Promising candidates are changes in water management, rice cult ivars, fertilization, and cultural practices. A significant reduction of CH4 emission from rice fields, at the same time that rice productio n and productivity increase at the farm level, is feasible, although t he regions where particular practices can be applied, and the trade-of fs that are possible, have still to be identified.