Response of nitrous oxide emissions to individual rain events and future changes in precipitation

Authors: MILLER, LEE - UNIVERSITY OF MINNESOTA; GRIFFIS, TIMOTHY - UNIVERSITY OF MINNESOTA; ERICKSON, MATT - UNIVERSITY OF MINNESOTA; TURNER, PETER - UNIVERSITY OF MINNESOTA; DEVENTER, MALTE JULIAN - UNIVERSITY OF MINNESOTA; CHEN, ZICHONG - UNIVERSITY OF MINNESOTA; YU, ZHONGJIE - UNIVERSITY OF MINNESOTA; Venterea, Rodney - Rod; BAKER, JOHN; FRIE, ALEXANDER - UNIVERSITY OF MINNESOTA

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/14/2022
Publication Date: 5/18/2022
Citation: Miller, L., Griffis, T., Erickson, M., Turner, P., Deventer, M., Chen, Z., Yu, Z., Venterea, R.T., Baker, J.M., Frie, A. 2022. Response of nitrous oxide emissions to individual rain events and future changes in precipitation. Journal of Environmental Quality. 51(3):312-324. https://doi.org/10.1002/jeq2.20348.
DOI: https://doi.org/10.1002/jeq2.20348

Interpretive Summary: Nitrous oxide (N2O) is a gas that can be emitted from agricultural soils following application of nitrogen fertilizers. Nitrous oxide emissions are important because N2O is both a strong greenhouse gas and depletes stratospheric ozone. Because soil water content is a major regulator of N2O emissions, changing precipitation patterns have the potential to alter N2O emissions from agricultural regions. In this study, we examined the effects of future precipitation changes predicted by climate models for the Upper Midwest U.S. on N2O emissions from a corn cropping system grown in an indoor mesocosm over four growing seasons. Total growing season N2O emissions, soil moisture, and inorganic nitrogen content were not impacted by the future precipitation patterns. Instead, N2O emissions were most strongly correlated with soil water-filled pore space and nitrogen status. Critical soil nitrogen thresholds were observed that regulated the short-term response of N2O fluxes following individual rainfall events. The change in N2O emissions following rain was more likely to be positive when soil ammonium levels were above a critical concentration of 10 mg per kg and negative when soil ammonium levels were below that threshold. Results from this study will be useful for scientists and modelers in assessing the future response of agricultural systems and their greenhouse gas budgets to changing climate patterns.

Technical Abstract: Changing precipitation has the potential to alter nitrous oxide (N2O) emissions from agricultural regions. In this study, we applied the CMIP5 end-of-century RCP 8.5 (business as usual) precipitation projections for the Upper Midwest U.S. and examined the effects of mean precipitation changes, characterized by increased early season rainfall and decreased mid- to late-season rainfall, on N2O emissions from a conventionally managed corn (Zea mays L.) cropping system grown in an indoor mesocosm facility over four growing seasons. We also assessed the response of N2O emissions to over 1000 individual rain events. Growing season N2O emissions, soil moisture, and inorganic N content were not impacted by the future precipitation (FP) pattern. Instead, N2O emissions were most strongly correlated with WFPS and soil nitrogen status. Following rain events, the change in N2O emissions was more likely to be positive when soil NO3- was > 40 mg N kg-1 soil and soil NH4+ was > 10 mg kg-1 soil yet negative when soil NO3- was > 40 mg N kg-1 soil and soil NH4+ was < 10 mg N kg-1 soil. Similarly, hourly N2O emissions remained below 5 nmol m2 s-1 when combined NH4+ + NO3-was < 20 mg N kg-1 soil or NH4+ and NO3- were < 5 mg N kg-1 and 20 mg N kg-1 soil, respectively. Rain event magnitude did not substantially affect the change in N2O flux. It is near optimal soil WFPS combined with the soil nitrogen concentrations above the identified thresholds that favor higher N2O emissions.