Nitrous Oxide and Methane Emissions as Affected by Water, Soil and Nitrogen

Abstract

Specific management of water regimes, soil and N in China might play an important role in regulating N 2O and CH 4 emissions in rice fields. Nitrous oxide and methane emissions from alternate non-flooded/flooded paddies were monitored simultaneously during a 516-day incubation with lysimeter experiments. Two N sources ( 15N-(NH 4) 2SO 4 and 15N-labeled milk vetch) were applied to two contrasting paddies: one derived from Xiashu loess (Loess) and one from Quaternary red clay (Clay). Both N 2O and CH 4 emissions were significantly higher in soil Clay than in soil Loess during the flooded period. For both soil, N 2O emissions peaked at the transition periods shortly after the beginning of the flooded and non-flooded seasons. Soil type affected N 2O emission patterns. In soil Clay, the emission peak during the transition period from non-flooded to flooded conditions was much higher than the peak during the transition period from flooded to non-flooded conditions. In soil Loess, the emission peak during the transition period from flooded to non-flooded conditions was obviously higher than the peak during the transition period from non-flooded to flooded conditions except for milk vetch treatment. Soil type also had a significant effect on CH 4 emissions during the flooded season, over which the weighted average flux was 111 mg C m −2 h −1 and 2.2 mg C m −2 h −1 from Clay and Loess, respectively. Results indicated that it was the transition in the water regime that dominated N 2O emissions while it was the soil type that dominated CH 4 emissions during the flooded season. Anaerobic oxidation of methane possibly existed in soil Loess during the flooded season.