Nitrous oxide emissions derived from N leaching

Much of the fertilizer and manure nitrogen (N) that is applied to crop fields leaves the field in runoff and leaching to groundwater. This N is transformed as it moves across the landscape through riparian zones, rivers and estuaries, and nitrous oxide (N2O) is produced along the way. In this paper we: 1) discuss the mechanisms that lead to these 'indirect' N2O emissions, 2) describe the Intergovernmental Program on Climate Change (IPCC) methodology for assessing these emissions, 3) review the data in support of the methodology, 4) discuss implications for mitigation and 5) summarize with a case study for the nation of Denmark. (au)