Stage-Specific Effects of Air Pollution on Crop Yields and the Role of Seed Technology

This study estimates month-specific yield associations between U.S. corn yields and five air pollutants: fine particulate matter (PM2.5), ground-level ozone at 60 and 80 ppb thresholds (AOT60 and AOT80, respectively), nitrogen dioxide (NO2), sulfur dioxide (SO2), and carbon monoxide (CO). We draw on data that combine an extensive commercial variety trial dataset of 210,207 observations from 17 U.S. states (2000-2023) with EPA Air Quality System monitor measurements. Our findings show that the aggregate effect of pollutants during the growing season is mostly negative yet minor or statistically insignificant; however, monthly decomposition uncovers systematic heterogeneity. For PM2.5, March exposure is associated with a 1.3 bu/acre yield reduction per μg/m3, while August exposure is associated with a 1.0 bu/acre increase, a seasonal pattern consistent with an aerosol scattering channel. The August AOT60 coefficient is −0.030 bu/acre per ppb·hour, with a more pronounced negative effect under AOT80. NO2 shows negative associations in March and August; SO2 and CO show none. Interestingly, the estimates provide little evidence that genetically engineered varieties mitigate yield losses from air pollutants; if anything, they suggest larger losses, except for the PM2.5 interaction.