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<p>Ammonia (NH<sub>3</sub>) emissions from agricultural lands represent a major environmental concern, with current emission models heavily relying on inherent soil pH as a key determinant based on chemical equilibrium principles. Here, analyzing 1792 field measurements across global croplands, we demonstrate that soils with inherently higher pH generally have lower NH<sub>3</sub> emissions. We identify enhanced nitrification as the key mechanism, where higher pH promotes rapid NH<sub>3</sub> oxidation, thereby reducing substrate availability for NH<sub>3</sub> volatilization. This biological process can reduce NH<sub>3</sub> emissions by 11% per unit increase in inherent soil pH. In paddy rice, nitrification is inhibited due to the flooded environment, leading to higher emission factors (EF) than upland crops, with EF positively correlating with pH above approximately 7.5. Our findings highlight that current emission inventories may substantially misestimate NH<sub>3</sub> emissions by oversimplifying pH effects and overlooking biological processes.</p>

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Enhanced nitrification in higher pH soils moderates ammonia emissions in global croplands

  • 期刊论文

  • 出版模式：

    开放获取

  • 发表日期：

    2025年12月18日

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  • Xiaodong Ge,
  • Danni Xie,
  • Jan Mulder,
  • Lei Duan

摘要

Ammonia (NH3) emissions from agricultural lands represent a major environmental concern, with current emission models heavily relying on inherent soil pH as a key determinant based on chemical equilibrium principles. Here, analyzing 1792 field measurements across global croplands, we demonstrate that soils with inherently higher pH generally have lower NH3 emissions. We identify enhanced nitrification as the key mechanism, where higher pH promotes rapid NH3 oxidation, thereby reducing substrate availability for NH3 volatilization. This biological process can reduce NH3 emissions by 11% per unit increase in inherent soil pH. In paddy rice, nitrification is inhibited due to the flooded environment, leading to higher emission factors (EF) than upland crops, with EF positively correlating with pH above approximately 7.5. Our findings highlight that current emission inventories may substantially misestimate NH3 emissions by oversimplifying pH effects and overlooking biological processes.