Strong mitigation of greenhouse gas emission impact via aerobic short pre-digestion of green manure amended soils during rice cropping

Highlights: • Aerobic short pre-digestion of biomass amended paddy over 10 days significantly decreased CH₄ flux. • Aerobic short pre-digestion did not change N₂O flux and soil C stock. • Aerobic short pre-digestion did not affect rice productivity. • Aerobic short pre-digestion significantly decreased net global warming potential. To increase soil carbon (C) stock, cover crop cultivation during the fallow season and its biomass incorporation as green manure (GM) is strongly suggested in mono-rice paddy. On the other hand, biomass application can highly increase greenhouse gas (GHG) emission, in particular methane (CH₄) during irrigated cropping season. Aerobic short pre-digestion of biomass applied soils was very effective to suppress CH₄ emission. However, its effect on other GHG (CO₂ and N₂O) emissions was not clear. To assess the integrated influence of aerobic short pre-digestion of green manured soils on global warming impact, cover crop biomass as GM was amended with different time interval before flooding (0–30 days) and aerobically decomposed under upland condition. Aerobic short pre-digestion over 10 days significantly decreased seasonal CH₄ flux, but did not affect N₂O emission. As aerobic pre-digestion days became longer, net ecosystem C balance (NECB) which implies the difference between C input and output was slightly increased, but not statistically different. The net primary productivity of rice plant as a C input source was not significantly differentiated by aerobic short pre-digestion. As a C output source, the respired C loss that was composed with CO₂-C and CH₄-C emission was not considerably discriminated among 0–30 days of aerobic short pre-digestion. As a consequence, due to big reduction of CH₄ emission, aerobic short pre-digestion significantly decreased net GWP which means integration of seasonal CH₄ and N₂O fluxes and NECB as CO₂ equivalent. In conclusion, aerobic short pre-digestion of biomass applied soil could be a sustainable management practice to decrease GHG emission impact without SOC stock change in temperate rice paddy field.