UC San Diego

Nitrogen oxides (NO_x) are among the most widely emitted pollutants in the world, yet their impacts on agriculture remain poorly known. NO_x can directly damage crop cells and indirectly affect growth by promoting ozone (O₃) and aerosol formation. We use satellite measures of both crop greenness and NO_x during 2018-2020 to evaluate crop impacts for five major agricultural regions. We find consistent negative associations between NO₂ and greenness across regions and seasons. These effects are strongest in conditions where O₃ formation is NO_x limited but remain significant even in locations where this pathway is muted, suggesting a role for direct NO_x damage. Using simple counterfactuals and leveraging published relationships between greenness and growth, we estimate that reducing NO_x levels to the current fifth percentile in each region would raise yields by ~25% for winter crops in China, ~15% for summer crops in China, and up to 10% in other regions.