Unusually high soil nitrogen oxide emissions influence air quality in a high-temperature agricultural region

Fertilized soils have large potential for production of soil nitrogen oxide (NO(x)=NO+NO(2)), however these emissions are difficult to predict in high-temperature environments. Understanding these emissions may improve air quality modelling as NO(x) contributes to formation of tropospheric ozone (O(3)), a powerful air pollutant. Here we identify the environmental and management factors that regulate soil NO(x) emissions in a high-temperature agricultural region of California. We also investigate whether soil NO(x) emissions are capable of influencing regional air quality. We report some of the highest soil NO(x) emissions ever observed. Emissions vary nonlinearly with fertilization, temperature and soil moisture. We find that a regional air chemistry model often underestimates soil NO(x) emissions and NO(x) at the surface and in the troposphere. Adjusting the model to match NO(x) observations leads to elevated tropospheric O(3). Our results suggest management can greatly reduce soil NO(x) emissions, thereby improving air quality.