Midseason drainage (MSD) has been proven as an effective strategy for mitigating methane (CH) emissions in paddy fields. However, its efficacy under milk vetch ( L., MV) incorporation, a paddy green manure widely cultivated in East Asian countries, remains uncertain. A three-year field trial was conducted, including five treatments: common level of chemical fertilizer with continuous flooding (CF-F), MV incorporation and reduced chemical fertilizer with continuous flooding (MVCF-F) or with 5 (MVCF-D5), 10 (MVCF-D10), and 15 (MVCF-D15) days of MSD. The results showed that the MVCF-F treatment enhanced rice productivity and soil fertility but promoted CH emissions relative to the CF-F treatment. However, compared with the MVCF-F treatment, the MVCF-D5, MVCF-D10, and MVCF-D15 treatments significantly decreased average CH emissions by 20%, 31%, and 35%, respectively. Furthermore, the MVCF-D5 and MVCF-D10 treatments led to a significant reduction in CH production potentials (PPs) and an increase in CH oxidation potentials (OPs). Compared to the MVCF-F treatment, the two treatments significantly decreased gene copy numbers from 23.44 × 10 copies g to 12.62 × 10 copies g and 11.26 × 10 copies g, while increasing gene copy numbers from 11.32 × 10 copies g to 18.94 × 10 copies g and 20.56 × 10 copies g, respectively. The results from the partial least squares-path model revealed that the reduction in CH emissions under MSD was mainly due to a decrease in CH PPs rather than an increase in CH OPs. The copy numbers, negatively regulated by soil Eh, was essential in regulating CH PPs. These findings provide evidence that MSD with a rational duration, even under exogenous carbon input through MV incorporation, can still effectively mitigate CH emissions in paddy fields. Considering that MSD with 15 days sacrificed the yield-increasing benefits of MV incorporation, MSD with 10 days is advisable in the study area.

中文翻译：

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季中排水能否减少掺入紫云英（Astragalus sinicus L.）的稻田的甲烷排放？

季中排水 (MSD) 已被证明是减少稻田甲烷 (CH) 排放的有效策略。然而，其在东亚国家广泛种植的稻田绿肥紫云英（L.，MV）中的功效仍不确定。进行了为期三年的田间试验，包括五个处理：普通化肥连续淹水（CF-F）、MV掺入和减量化肥连续淹水（MVCF-F）或加5（MVCF-D5）， 10 (MVCF-D10) 和 15 (MVCF-D15) 天的 MSD。结果表明，相对于 CF-F 处理，MVCF-F 处理提高了水稻生产力和土壤肥力，但增加了 CH 排放。然而，与MVCF-F处理相比，MVCF-D5、MVCF-D10和MVCF-D15处理使平均CH排放量分别显着降低了20%、31%和35%。此外，MVCF-D5 和 MVCF-D10 处理导致 CH 生产潜力 (PP) 显着降低，而 CH 氧化潜力 (OP) 增加。与MVCF-F处理相比，两种处理显着降低了基因拷贝数，从23.44×10拷贝g至12.62×10拷贝g和11.26×10拷贝g，同时基因拷贝数从11.32×10拷贝g增加至18.94×10拷贝g。分别为 20.56 × 10 份 g 和 20.56 × 10 份 g 。偏最小二乘路径模型的结果表明，MSD 下 CH 排放量的减少主要是由于 CH PP 的减少，而不是 CH OP 的增加。受土壤 Eh 负调控的拷贝数对于调节 CH PP 至关重要。这些发现证明，即使在通过MV掺入的外源碳输入下，具有合理持续时间的MSD仍然可以有效减少稻田的CH排放。考虑到15天的MSD牺牲了MV掺入的增产效益，因此研究区建议进行10天的MSD。