Influence of organic matter incorporation on the methane emission from a wetland rice field

Abstract

Methane (CH4) emission from Philippine rice paddies was monitored with a closed chamber technique during the 1992 dry and wet season. CH4 emissions were significantly higher in the dry season. Application of green manure stimulated CH4 emissions. In plots that received more than 11 t ha−1 of fresh green manure, CH4 emission was highest during the first half of the growing season. Significant amounts of CH4 may evolve during or immediately after transplanting, if the organic amendments are incorporated 1 to 3 weeks before transplanting. Laboratory incubations of soil cores show that CH4 production is highest near the soil surface. CH4 production in green manure treated fields is higher than in urea‐fertilized fields, but toward the end of the season this difference is less pronounced. Around panicle initiation, the fraction of CH4 produced, which was emitted to the atmosphere, is lower than at tillering or ripening. The impact of organic amendments on CH4 emissions at different locations of the world can be described by a dose response curve, if CH4 emission from organically amended plots is expressed relative to CH4 emission from mineral fertilized plots of the same location and season. Various organic amendments (e.g., straw, fermented residues) have a similar effect on CH4 emissions after correction for differences in easily decomposable carbon content.