title: Spatially explicit estimates of N2 O emissions from croplands suggest climate mitigation opportunities from improved fertilizer management.
abstract: With increasing nitrogen (N) application to croplands required to support growing food demand, mitigating N2 O emissions from agricultural soils is a global challenge. National greenhouse gas emissions accounting typically estimates N2 O emissions at the country scale by aggregating all crops, under the assumption that N2 O emissions are linearly related to N application. However, field studies and meta-analyses indicate a nonlinear relationship, in which N2 O 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 N2 O emissions from croplands. We estimate 0.66 Tg of N2 O-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 N2 O 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 N2 O emissions suggests that relatively large increases in N fertilizer application would generate relatively small increases in N2 O emissions. As aggregated fertilizer data generate underestimation bias in nonlinear models, high-resolution N application data are critical to support accurate N2 O emissions estimates.
authors.affiliation: Institute on the Environment (IonE), University of Minnesota, St. Paul, MN, 55108, USA.
authors.forename: James S
authors.initials: JS
authors.lastname: Gerber
authors.affiliation: Institute on the Environment (IonE), University of Minnesota, St. Paul, MN, 55108, USA.|Department of Natural Resources and Environmental Management, University of Hawai'i at Manoa 96822, 1910 East West Road, Honolulu, HI, USA.
authors.forename: Kimberly M
authors.identifier: 0000-0003-2162-1378
authors.initials: KM
authors.lastname: Carlson
authors.affiliation: INRA, AgroParisTech, University Paris-Saclay, UMR 211, F-78850, Thiverval-Grignon, France.
authors.forename: David
authors.initials: D
authors.lastname: Makowski
authors.affiliation: Department of Earth and Planetary Sciences, Harvard University, 20 Oxford Street, Cambridge, MA, 02138, USA.|Department of Organismic and Evolutionary Biology, Harvard University, 16 Divinity Avenue, Cambridge, MA, 02138, USA.
authors.forename: Nathaniel D
authors.initials: ND
authors.lastname: Mueller
authors.affiliation: INRA US 1116 AGROCLIM F-84914, Avignon Cedex 9, France.
authors.forename: Iñaki
authors.initials: I
authors.lastname: Garcia de Cortazar-Atauri
authors.affiliation: International Institute for Applied Systems Analysis (IIASA), Schlossplatz 1, A-2361, Laxenburg, Austria.
authors.forename: Petr
authors.initials: P
authors.lastname: Havlík
authors.affiliation: Commonwealth Scientific and Industrial Research Organisation (CSIRO), St. Lucia, QLD, 4067, Australia.
authors.forename: Mario
authors.initials: M
authors.lastname: Herrero
authors.affiliation: INRA US 1116 AGROCLIM F-84914, Avignon Cedex 9, France.
authors.forename: Marie
authors.initials: M
authors.lastname: Launay
authors.affiliation: Institute on the Environment (IonE), University of Minnesota, St. Paul, MN, 55108, USA.
authors.forename: Christine S
authors.initials: CS
authors.lastname: O'Connell
authors.affiliation: Institute of Biological and Environmental Sciences & ClimateXChange, University of Aberdeen, 23 St. Machar Drive, Aberdeen, Scotland, AB24 3UU, UK.
authors.forename: Pete
authors.initials: P
authors.lastname: Smith
authors.affiliation: Institute on the Environment (IonE), University of Minnesota, St. Paul, MN, 55108, USA.
authors.forename: Paul C
authors.initials: PC
authors.lastname: West
mesh_terms: D017954:Africa South of the Sahara; D002980:Climate; D018556:Crops, Agricultural; D005061:Europe, Eastern; D005308:Fertilizers; D009585:Nitrogen Dioxide; D009609:Nitrous Oxide
chemical_list: D005308:Fertilizers; D009609:Nitrous Oxide; D009585:Nitrogen Dioxide
keywords: N2O; climate change; emissions; flooded rice; greenhouse gas; manure; meta-analysis; nitrogen; nitrous oxide; sustainable agriculture