Abstract:

This study employed the static dark chamber/floating chamber-gas chromatography method to monitor greenhouse gas emissions from agricultural wetlands, including conventional mid-season rice fields, rice-crayfish paddies, crayfish ditches, and aquaculture ponds in the Jianghan Plain from July, 2021 to Nov, 2022 at Jingzhou Agro-meteorology Experimental Station of Hubei. By examining CH₄ and N₂O emission characteristics and their overall greenhouse effect across different agricultural wetlands, this study provides technical references for accurately assessing carbon sequestration and emission reductions in rice-farming ecosystems, contributing to green and low-carbon development. The results showed that CH₄ and N₂O emission fluxes in rice-crayfish paddies were significantly higher than in aquaculture ponds and crayfish ditches, with CH₄ emissions in rice fields mainly concentrated during the early flooded stages of rice growth. In crayfish ditches and aquaculture ponds, CH₄ emissions primarily occurred during the high-density breeding periods in spring and summer, with the highest peak emissions recorded in rice-crayfish paddies (85.7 μg/(m²·h)), which were 1.4-9.8 times higher than other agricultural wetlands. The peak N₂O emissions were observed during the tillering and drying stages of rice fields, as well as during the pre-stocking dry pond, dredging, and sun-drying stages in aquaculture ponds, with the highest peak in conventional mid-season rice fields (285.3 μg/(m²·h)), which was 0.9-21.2 times higher than other agricultural wetlands. Cumulative CH₄ emissions ranked in the following order: rice-crayfish paddies, aquaculture ponds, conventional mid-season rice fields, and crayfish ditches. Cumulative N₂O emissions were highest in conventional mid-season rice fields, followed by rice-crayfish paddies, aquaculture ponds, and crayfish ditches. The overall greenhouse effect followed this ranking: rice-crayfish paddies, aquaculture ponds, conventional mid-season rice fields, and crayfish ditches. Rice-crayfish paddies and aquaculture ponds were identified as major sources of greenhouse gas emissions from agricultural wetlands. Reducing greenhouse gas emissions from these areas is the key to achieving agricultural emission reductions. Therefore, it is recommended to adopt shallow-water aquaculture in rice-crayfish paddies to shorten the flooding duration, reduce methane production by inhibiting methanogenic bacteria, and apply slow-release fertilizers and integrated organic-inorganic fertilization techniques to suppress N₂O generation during the sun-drying period. For aquaculture ponds, improving sediment management, dynamically adjusting feed input, and using microporous oxygenation devices to enhance the redox status of the water body can reduce the overall greenhouse effect caused by sedimentation of residual feed.

Key words: Jianghan Plain, agricultural wetland, greenhouse gas, comprehensive greenhouse effect