Nitrous oxide and methane emissions from different soil suspensions: effect of soil redox status

Four soil samples from fields of different land use [US (paddy field), Chin a (paddy field) and Belgium (maize and wheat fields)] were incubated as soi l suspension (soil:water ratio 1:4) to study the N2O and CHS emission under different soil redox potential conditions. The results show that the N2O e mission was regulated within a narrow redox potential range of +120 to +250 mV, due to the balance of N2O production and its further reduction to N-2. Methane emission occurred below a soil specific redox potential point, and the emission rates were inversely related to soil redox potentials. Both l inear and exponential relationships between CH4 emission and the soil redox potential were significant. By extrapolating the linear relationship of CH 4 emission against soil redox potential, the critical redox potentials for CH4 production were estimated at about -170 (US paddy soil), -150 (Chinese paddy soil), -215 (Belgian maize soil), and -195 mV (Belgian wheat soil), r espectively. In addition, the results indicate that a soil with a lower cri tical redox potential for CH4 production had a higher CH4 production potent ial. In this study, N2O and CH4 emissions were found to occur at a distinct ly different soil redox potential condition. The range of soil redox potent ial values where both N2O and CH4 emissions were low was different for diff erent soils, but it was situated between +120 and -170 mV. This is a wide r edox potential range enabling field management practices to minimize both N 2O and CH4 emissions from wetland ecosystems.