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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.

Author information

1
Beijing Key Laboratory of Farmland Soil Pollution Prevention and Remediation, College of Resources and Environmental Sciences, China Agricultural University, Beijing, China.
2
Department of Chemistry, University of Oslo, Oslo, Norway.
3
Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, Ås, Norway.
4
Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, China.

Abstract

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.

KEYWORDS:

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

PMID:
29171128
DOI:
10.1111/gcb.13966
[Indexed for MEDLINE]

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