Including non-growing season emissions of N2O in US maize could raise net CO2e emissions by 31% annually

Nitrous oxide (N2O) is a significant greenhouse gas and the most important currently emitted ozone depleting substance, primarily via agricultural fertilization. Current N2O emission estimation methods at the national scale are predominantly via emission factors. Models estimating national-scale emissions are focused on growing season emissions. However, a substantial fraction of N2O can be emitted during non-growing season periods. Using newly published off-season N2O emission ratio maps and high-resolution nitrogen application data, this study explores the potential magnitude of underestimated N2O emissions if using only the default growing-season focused methodology. Although there is large variation at county scales (12%-35%), non-growing season national emissions are estimated at 31% of the total, a potential 12,000 Gg CO(2)e year(-1). Further work should better refine emission estimates spatially as well as fully integrate estimates across growing and non-growing seasons.