Paddy ponding water management to reduce methane emission based on observations of methane fluxes and soil redox potential in the Red River Delta, Vietnam*

Abstract

AbstractReducing methane (CH4) emissions from paddy fields that contribute to the greenhouse effect has been addressed recently through the application of the alternate wetting and drying irrigation method. However, in poorly drained areas, such as the Red River Delta in Vietnam, the soil cannot be dried immediately, and so CH4 can continue to be produced unintentionally. Therefore, the purpose of this case study was to identify the optimal ponding water management schedule to reduce CH4 emissions by using the measured data of ponding depth, soil redox potential (Eh), and CH4 fluxes from field experiments and to show its effects on CH4 emission and water conservation. Observations in the winter–spring cropping season showed that the non‐flooding period of 3–8 days suppressed CH4 emission, and the continuous flooding period of 14–22 days caused CH4 re‐emission. Information regarding the non‐flooding period to be maintained and the flooding period to be avoided to suppress CH4 emission was not obtained for the summer–autumn cropping season due to abundant rainfall. The proposed schedule could suppress CH4 emission by 27%–85% and increase the amount of conserved water by up to 18% compared with traditional flooding protocols, but it may increase irrigation water due to the frequency and the amount of re‐flooding.