Spatially explicit estimates of N2O emissions from croplands suggest climate mitigation opportunities from improved fertilizer management |
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| Authors: | James S Gerber Kimberly M Carlson David Makowski Nathaniel D Mueller Iñaki Garcia de Cortazar‐Atauri Petr Havlík Mario Herrero Marie Launay Christine S O'Connell Pete Smith Paul C West |
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| Affiliation: | 1. Institute on the Environment (IonE), University of Minnesota, St. Paul, MN, USA;2. Department of Natural Resources and Environmental Management, University of Hawai'i at Manoa 96822, Honolulu, HI, USA;3. INRA, AgroParisTech, University Paris‐Saclay, UMR 211, Thiverval‐Grignon, France;4. Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA, USA;5. Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, USA;6. INRA US 1116 AGROCLIM F‐84914, Avignon Cedex 9, France;7. International Institute for Applied Systems Analysis (IIASA), Laxenburg, Austria;8. Commonwealth Scientific and Industrial Research Organisation (CSIRO), St. Lucia, QLD, Australia;9. Institute of Biological and Environmental Sciences & ClimateXChange, University of Aberdeen, Aberdeen, Scotland, UK |
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| Abstract: | With increasing nitrogen (N) application to croplands required to support growing food demand, mitigating N2O emissions from agricultural soils is a global challenge. National greenhouse gas emissions accounting typically estimates N2O emissions at the country scale by aggregating all crops, under the assumption that N2O emissions are linearly related to N application. However, field studies and meta‐analyses indicate a nonlinear relationship, in which N2O emissions are relatively greater at higher N application rates. Here, we apply a super‐linear emissions response model to crop‐specific, spatially explicit synthetic N fertilizer and manure N inputs to provide subnational accounting of global N2O emissions from croplands. We estimate 0.66 Tg of N2O‐N direct global emissions circa 2000, with 50% of emissions concentrated in 13% of harvested area. Compared to estimates from the IPCC Tier 1 linear model, our updated N2O emissions range from 20% to 40% lower throughout sub‐Saharan Africa and Eastern Europe, to >120% greater in some Western European countries. At low N application rates, the weak nonlinear response of N2O emissions suggests that relatively large increases in N fertilizer application would generate relatively small increases in N2O emissions. As aggregated fertilizer data generate underestimation bias in nonlinear models, high‐resolution N application data are critical to support accurate N2O emissions estimates. |
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| Keywords: | climate change emissions flooded rice greenhouse gas manure meta‐analysis N2O nitrogen nitrous oxide sustainable agriculture |
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