Soil Nitrous Oxide Emissions by Atmospheric Nitrogen Deposition over Global Agricultural Systems

Agricultural soil is the main source of nitrous oxide (N2O) emissions which contribute to global warming and stratospheric ozone depletion. In recent decades, atmospheric nitrogen (N) deposition has increased dramatically as an important agricultural soil N input, while its effect on soil N2O emissions in the current and future climate change remains unknown. Here, we conducted a thorough analysis of the effect of N deposition and climate change on soil N2O emissions as well as their trends. Soil N2O emissions induced by N deposition accounted for 25% of global cropland soil N2O emissions. Global soil N2O emissions over croplands increased by 2% yr(-1) during 1996-2013, of which N deposition could explain 15% of the increase. The emission factor of N deposition was similar to 7 times that of N fertilizer plus manure (similar to 1%) through a more direct way, since N deposition including nitrate (NO3-) and ammonium (NH4+) could be directly used for nitrification and denitrification. By 2100, N deposition will increase by 80% and cropland soil N2O emissions will increase by 241% under the RCP8.5 scenario in comparison with the 2010 baseline. These results suggest that, under the background of increasing global N deposition, it is essential to consider its effects on soil N2O emissions in climatic change studies.

Automated summary

Agricultural soil is the main source of nitrous oxide emissions, with atmospheric nitrogen deposition as an important factor in increasing soil N2O emissions. The study shows that N deposition accounts for a significant portion of global cropland soil N2O emissions and predicts a substantial increase in emissions due to N deposition and climate change by 2100.