LAUSR

Changing precipitation has the potential to alter nitrous oxide (N2 O) emissions from agricultural regions. In this study, we applied the Coupled Model Intercomparison Project phase 5 (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 N2 O 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 N2 O emissions to over 1000 individual rain events. N2 O emissions were most strongly correlated with WFPS and soil nitrogen status. Following rain events, the change in N2 O emissions, relative to pre-rain 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 was more likely to be negative when soil NO3 - was > 40 mg N kg-1 soil and soil NH4 + was < 10 mg N kg-1 soil. Similarly, hourly N2 O emissions remained below 5 nmol m-2 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 N2 O flux. Finally, growing season N2 O emissions, soil moisture, and inorganic N content were not impacted by the future precipitation (FP) pattern. It is near optimal soil WFPS combined with the soil nitrogen concentrations above the identified thresholds that favor higher N2 O emissions. This article is protected by copyright. All rights reserved.