秸秆还田年限及还田量对稻田净温室效应的影响

本文研究了不同秸秆还田年限（2 年和13 年）和还田量（0、1.6 、3.2和4.8 t/hm2）对稻田CH4和N2O排放、土壤固碳速率和净温室效应的影响。结果表明：稻田CH4排放量在第2年和第13年均随秸秆还田量的增加呈线性增加，但第13年单位秸秆还田量对CH4排放的平均促进效应比第2年降低3%；各处理N2O排放量在第2年无显著差异，第13年显著促进N2O排放55% ~ 171%，且随秸秆还田量的增加呈线性增加；土壤固碳速率在第2年随秸秆还田量的增加呈线性增加，但第13年下降80% ~ 84%，且各处理间无显著差异；净温室效应随秸秆还田量的增加呈线性增加，但从第2年到第13年经历了从汇到源的过程，这说明秸秆还田量对净温室效应的影响受还田年限调控，其增加的温室效应逐步完全抵消了土壤固碳的减排效益，加剧了全球气候变暖。因此，稻田在长期秸秆还田条件下是一个重要的碳源，亟待优化秸秆还田技术，进一步固碳减排，以实现农业可持续发展。

Effects of Straw Incorporation Years and Rates on Net Global Warming Potential in Paddy Fields

In this paper, the effects of different straw incorporation years (2 and 13 years) and rates (0, 1.6, 3.2, and 4.8 t/hm2) on CH4 and N2O emissions from paddy fields, soil organic carbon (SOC) sequestration rate and net global warming potential (Net GWP) were studied. The results showed that CH4 emissions increased linearly with the increase of straw incorporation rate both in 2 and 13 years, but the average promoting effect of unit straw incorporation amount on CH4 emissions in 13 years was 3% lower than that in 2 years. For N2O emissions, there was no significant difference in 2 years, but the emissions significantly increased by 55% ~ 171% and showed a linear increase with the increase of straw incorporation rate in 13 years. Meanwhile, the SOC sequestration rate increased linearly with the increase of straw incorporation rate in 2 years, but it decreased by 80% ~ 84% in 13 years without significant difference among the treatments. Therefore, the Net GWP showed a linear increase with the increase of straw incorporation rate, but it shifted from carbon sink in 2 years into carbon source in 13 years. The findings suggest that the effect of straw incorporation amount on the Net GWP was regulated by the duration, and the increased GWP gradually completely offset the emission reduction benefit of soil carbon sequestration and then exacerbated global warming. Therefore, the paddy field is an important carbon source after long-term straw incorporation, and it is urgent to optimize straw incorporation technology to further sequester carbon and reduce emissions to achieve sustainable agricultural development.