Rice paddies account for approximately 9% of human‐induced methane (CH4) emissions. Nitrogen (N) fertilization affects CH4 emissions from paddy soils through several mechanisms, leading to conflicting results in field experiments. The primary drivers of these N‐related effects remain unclear and the contribution of N fertilization to CH4 emissions from the rice paddies has not yet been quantified for global area. This uncertainty contributes to significant challenges in projecting global CH4 emissions and hinders the development of effective local mitigation strategies. Here, we show through a meta‐analysis and experiments that the impact of N fertilization on CH4 emissions from rice paddies can be largely predicted by soil pH. Specifically, N fertilization stimulates CH4 emissions most strongly in acidic soils by accelerating organic matter decomposition and increasing the activities of methanogens. Accounting for the interactions between soil pH and N fertilization, we estimate that N fertilization has raised current area‐scaled and yield‐scaled CH4 emissions across the total global paddy area by 52% and 8.2%, respectively. Our results emphasize the importance of alleviating soil acidification and sound N management practices to mitigate global warming.

中文翻译：

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土壤 pH 值决定了氮对稻田甲烷排放的影响


稻田约占人为甲烷 （CH4） 排放量的 9%。氮 （N） 施肥通过多种机制影响水稻土的 CH4 排放，导致田间实验的结果相互矛盾。这些氮相关效应的主要驱动因素尚不清楚，氮肥对稻田 CH4 排放的贡献尚未在全球范围内量化。这种不确定性给预测全球 CH4 排放带来了重大挑战，并阻碍了有效的地方缓解策略的制定。在这里，我们通过荟萃分析和实验表明，氮肥对稻田 CH4 排放的影响在很大程度上可以通过土壤 pH 值来预测。具体来说，氮肥通过加速有机物分解和增加产甲烷菌的活性，最强烈地刺激酸性土壤中的 CH4 排放。考虑到土壤 pH 值和氮肥之间的相互作用，我们估计氮肥使当前全球稻田总面积的面积和产量 CH4 排放分别增加了 52% 和 8.2%。我们的结果强调了缓解土壤酸化和健全的氮管理实践对缓解全球变暖的重要性。