Rice straw decomposition in paddy surface water potentially reduces soil methane (CH4) emission

Abstract

Background: Rice cultivation is considered significant methane (CH4) emission source. Rice straw (RS) incorporation into the soil is a critical factor that produces higher CH4 emissions. The RS waterlogging approach on the soil surface potentially reduces CH4 emissions due to increasing RS decomposition in aerobic conditions. However, the hypothesis has not been entirely determined. The study aimed to examine CH4 emissions under RS waterlogging on surface water compared with RS incorporation into the soil. Methods: We carried out a microcosm experiment in a screen-house with two treatments, including (i) RS incorporation into the soil and (ii) RS waterlogging on the soil surface in triplicates. We compared the CH4 emissions and CH4 accumulation for the off-growing and rice-sowing periods. Yield-scaled CH 4 emission was assessed based on total methane emission and rice yield. Results: The results demonstrated that RS waterlogging reduced CH4 emissions by 16.9% compared to RS incorporation. During the rice-growing period, total CH4 emissions from RS waterlogging accounted for 36% of the incorporation treatment. Under RS waterlogging, high CH4 emissions during the off-sowing stage were disclosed. The difference between yield-scaled CH4 emissions was not significant. Conclusions: RS waterlogging is a feasible option to alternate conventional RS incorporation toward lower CH4 emissions from rice production. Ameliorating CH4 emission mitigation by RS waterlogging during off-sowing is recommended for future works.