The characteristics of yield-scaled methane emission from paddy field in recent 35-year in China: A meta-analysis

Methane (CH4) emission per unit yield (yield-scaled) from paddy field were not paid enough attention until now, which may simply serve to displace any lost production. Therefore, we conducted a meta-analysis of the characteristics of yield-scaled CH4 emission across recent 35 years in China. The results showed the yield-scaled CH4 emissions were the highest in southwest single rice region and then increased from north to south. The N fertilizer decreased yield-scaled CH4 emission mainly through increasing the yield. The organic amendments (biogas residue, manure, straw) increased CH4 emission without impacting the yield. So the yield-scaled CH4 emission increased. The midseason drainage decreased yield-scaled CH4 emission through increasing the yield and decreasing CH4 emission. The direct seeding had no impact on rice yield but increased CH4 emission, resulting in the increment of yield-scaled CH4 emission. Our results provided the important reference for future rice production with higher yield and lower CH4 emission in China. More efforts should be paid on the technical innovating and field experiment.