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Glob Chang Biol. 2018 Feb;24(2):e617-e626. doi: 10.1111/gcb.13966. Epub 2017 Nov 24.

Soil pH as the chief modifier for regional nitrous oxide emissions: New evidence and implications for global estimates and mitigation.

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Beijing Key Laboratory of Farmland Soil Pollution Prevention and Remediation, College of Resources and Environmental Sciences, China Agricultural University, Beijing, China.
Department of Chemistry, University of Oslo, Oslo, Norway.
Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, Ås, Norway.
Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, China.


Nitrous oxide (N2 O) is a greenhouse gas that also plays the primary role in stratospheric ozone depletion. The use of nitrogen fertilizers is known as the major reason for atmospheric N2 O increase. Empirical bottom-up models therefore estimate agricultural N2 O inventories using N loading as the sole predictor, disregarding the regional heterogeneities in soil inherent response to external N loading. Several environmental factors have been found to influence the response in soil N2 O emission to N fertilization, but their interdependence and relative importance have not been addressed properly. Here, we show that soil pH is the chief factor explaining regional disparities in N2 O emission, using a global meta-analysis of 1,104 field measurements. The emission factor (EF) of N2 O increases significantly (p < .001) with soil pH decrease. The default EF value of 1.0%, according to IPCC (Intergovernmental Panel on Climate Change) for agricultural soils, occurs at soil pH 6.76. Moreover, changes in EF with N fertilization (i.e. ΔEF) is also negatively correlated (p < .001) with soil pH. This indicates that N2 O emission in acidic soils is more sensitive to changing N fertilization than that in alkaline soils. Incorporating our findings into bottom-up models has significant consequences for regional and global N2 O emission inventories and reconciling them with those from top-down models. Moreover, our results allow region-specific development of tailor-made N2 O mitigation measures in agriculture.


emission factor; environmental factors; global meta-analysis; greenhouse gas estimate and mitigation; nitrous oxide; nonlinearity coefficient; soil pH

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