Discrepant responses of methane emissions to additions with different organic compound classes of rice straw in paddy soil

Highlights: • We assessed the effects of HAA, CHO, lipid and AIOM of rice straw on CH₄ emissions. • Straw incorporation stimulates CH₄ emissions across organic compound classes. • Occurrence time of the stimulation varies depending on organic compound classes. • Incorporations of HAA and CHO exert the greatest intensities to stimulate CH₄ emission. Crop straw incorporation has become a prevailing agricultural practice that guarantees the food production and security. There is a significant body of work on the effects of straw incorporation on the methane (CH₄) emissions in paddy fields. However, it is unclear whether there are diverse links between CH₄ emission dynamics and incorporations of different organic compound classes of straw to paddy fields. In this study, soil incubations were conducted to assess the respective effect of incorporations of hydrolysable amino acid (HAA), dilute-acid extractable carbohydrate (DAC), lipid and acid-insoluble organic matter (AIOM) fractions of rice straw on the CH₄ emission in paddy soil. It is revealed that incorporations of HAA and DAC fractions exert the greatest intensities to stimulate the CH₄ emissions, which mainly takes place in the early period of incubation; on contrary, the incorporation of lipid fraction exerts the lowest intensity and mainly takes place in the late period. The pattern of CH₄ emission after incorporation of AIOM fraction occurs peaks both in the early and late periods of incubation. Our findings highlight that the time of occurrence and intensity of effects of rice straw incorporation on CH₄ emissions vary significantly depending on the different organic compound classes of rice straw, which may be key to proposing a promising management strategy for mitigating CH₄ emissions in paddy fields in the context of straw incorporation.