Optimizing grain yields reduces CH(4) emissions from rice paddy fields

Microbial production in anoxic wetland rice soils is a major source of atmospheric CH(4,) the most important non-CO(2) greenhouse gas. Much higher CH(4) emissions from well managed irrigated rice fields in the wet than in the dry season could not be explained by seasonal differences in temperature. We hypothesized that high CH(4) emissions in the wet season are caused by low grain to biomass ratios. In a screenhouse experiment, removing spikelets to reduce the plants' capacity to store photosynthetically fixed C in grains increased CH(4) emissions, presumably via extra C inputs to the soil. Unfavorable conditions for spikelet formation in the wet season may similarly explain high methane emissions. The observed relationship between reduced grain filling and CH(4) emission provides opportunities to mitigate CH(4) emissions by optimizing rice productivity.