Environmental Drivers of Agricultural Productivity Growth: CO₂ Fertilization of US Field Crops

We assess the CO₂ fertilization effect on US agriculture using spatially-varying CO₂ data from NASA's Orbiting Carbon Observatory-2 (OCO-2) satellite covering the majority of US cropland under actual growing conditions. This study complements the many CO₂ enrichment experiments that have found important interactions between CO₂ and local environmental conditions in controlled settings. We use three empirical strategies: (i) a panel of CO₂ anomalies and county yields, (ii) a panel of spatial first-differences between neighboring counties, and (iii) a cross-sectional spatial first-difference. We find consistently high fertilization effects: a 1 ppm increase in CO₂ equates to a 0.5%, 0.6%, and 0.8% yield increase for corn, soybeans, and wheat, respectively. Viewed retrospectively, 10%, 30%, and 40% of each crop's yield improvements since 1940 are attributable to rising CO₂.