Distinct driving mechanisms of non-growing season N2O emissions call for spatial-specific mitigation strategies in the US Midwest.

• NGS N 2 O emissions accounted for 6–60% of the annual fluxes in the US Midwest. • NGS N 2 O emissions were controlled by distinct drivers in the southeast and northwest. • NGS precipitation 300 mm line was found to be a threshold for the divergence. • Intensive freezing effect is the dominant driver of NGS N 2 O emissions in the southeast. • The thawing effect is the dominant driver of NGS N 2 O emissions in the northwest. Agricultural N 2 O emission is a growing concern for climate change. Recent field evidence suggests that non-growing seasons (NGS) may contribute one-third to half of the annual N 2 O emissions, but implications on management adaptations remain unclear. Here we used an advanced process-based model, ecosys , to investigate the magnitude and drivers of NGS N 2 O emissions from the US Midwest. Results showed that simulated NGS N 2 O emissions accounted for 6–60% of the annual fluxes under continuous corn systems, peaking in counties with NGS precipitation (P NGS) around 300 mm. Divergent patterns of spatial-temporal correlations between NGS N 2 O emissions and environmental variables were shown in the southeast (P NGS > 300 mm) and the northwest (P NGS < 300 mm) of the study area by simulations. Causal analysis indicates that more intensive freezing caused by decreased air temperature (T a) is the dominant driver that leads to NGS N 2 O emissions increasing within the southeast of the study area, while increased P NGS and increased T a cooperatively result in soil moisture decreasing at soil thaws that enhances NGS N 2 O production within the northwest of the study area. Scenario simulations suggest that annual N 2 O emissions in the US Midwest are likely to reduce under climate change primarily due to the reduction of NGS N 2 O emissions. Our estimates on monetized social benefits inform the necessity to implement spatial-specific mitigation strategies, i.e. determining fertilizer timing and use of nitrification inhibitors (NI). Spring fertilizer application is more beneficial than fall fertilizer application for most counties, however, the latter can bring extra benefits to some counties in the west of the study area. Introducing NI with either spring or fall applications can greatly increase social benefits by reducing N 2 O emissions and N leaching. This study addresses possibly effective adaptations by providing seasonal- and spatial-explicit mitigation potentials. [Display omitted] [ABSTRACT FROM AUTHOR]