title: Global assessment of nitrogen losses and trade-offs with yields from major crop cultivations.
abstract: Agricultural application of reactive nitrogen (N) for fertilization is a cause of massive negative environmental problems on a global scale. However, spatially explicit and crop-specific information on global N losses into the environment and knowledge of trade-offs between N losses and crop yields are largely lacking. We use a crop growth model, Python-based Environmental Policy Integrated Climate (PEPIC), to determine global N losses from three major food crops: maize, rice, and wheat. Simulated total N losses into the environment (including water and atmosphere) are 44TgNyr-1. Two thirds of these, or 29TgNyr-1, are losses to water alone. Rice accounts for the highest N losses, followed by wheat and maize. The N loss intensity (NLI), defined as N losses per unit of yield, is used to address trade-offs between N losses and crop yields. The NLI presents high variation among different countries, indicating diverse N losses to produce the same amount of yields. Simulations of mitigation scenarios indicate that redistributing global N inputs and improving N management could significantly abate N losses and at the same time even increase yields without any additional total N inputs.
authors.affiliation: Eawag, Swiss Federal Institute of Aquatic Science and Technology, Ueberlandstrasse 133, CH-8600 Duebendorf, Switzerland. Electronic address: wenfeng.liu@eawag.ch.
authors.forename: Wenfeng
authors.initials: W
authors.lastname: Liu
authors.affiliation: Eawag, Swiss Federal Institute of Aquatic Science and Technology, Ueberlandstrasse 133, CH-8600 Duebendorf, Switzerland; Department of Environmental Sciences, University of Basel, Petersplatz 1, CH-4003 Basel, Switzerland.
authors.forename: Hong
authors.initials: H
authors.lastname: Yang
authors.affiliation: School of Environmental Science and Engineering, South University of Science and Technology of China, Shenzhen 518055, China.
authors.forename: Junguo
authors.initials: J
authors.lastname: Liu
authors.affiliation: International Institute for Applied Systems Analysis (IIASA), Ecosystem Services and Management Program, Schlossplatz 1, A-2361 Laxenburg, Austria.
authors.forename: Ligia B
authors.initials: LB
authors.lastname: Azevedo
authors.affiliation: Blackland Research and Extension Center, Temple, TX 76502, USA.
authors.forename: Xiuying
authors.initials: X
authors.lastname: Wang
authors.affiliation: College of Water Sciences, Beijing Normal University, Beijing 100875, China.
authors.forename: Zongxue
authors.initials: Z
authors.lastname: Xu
authors.affiliation: Eawag, Swiss Federal Institute of Aquatic Science and Technology, Ueberlandstrasse 133, CH-8600 Duebendorf, Switzerland.
authors.forename: Karim C
authors.initials: KC
authors.lastname: Abbaspour
authors.affiliation: ETH Zürich, Institute of Terrestrial Ecosystems, Universitätstr. 16, CH-8092 Zürich, Switzerland.
authors.forename: Rainer
authors.initials: R
authors.lastname: Schulin
keywords: Global assessment; Major crops; N losses; NLI; PEPIC; Trade-offs