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.
Keywords: Global warming potential; Methane; Net ecosystem carbon balance; Nitrous oxide; Rice paddy.
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