Cover Crop Adoption and Corn Yields: Evidence of State-Level Heterogeneity in the United States

Empirical evidence on the effect of cover crops on row crop yields in the United States (US) remain mixed, likely because of the various locations where past studies were conducted. Focusing on corn in the continental US, this study comprehensively examines state-level spatial heterogeneity in the impact of cover crop use on corn yields. Based on a novel county-level panel dataset from 2015 to 2023 that links satellite-derived measures of cover crop adoption to corn yields (and other control variables), we are able to employ a suite of econometric methods — including linear panel fixed effects models, a double machine learning approach, and an instrumental variable procedure — to achieve the study objective. We document substantial state-level spatial heterogeneity in corn yield response to cover crops. Positive yield effects are concentrated in the Plains and the western Midwest, whereas effects in most other regions are statistically insignificant or negative. We further show that soil pH levels and calcium carbonate (CaCO3) in the soil are strongly associated with these spatial patterns. Our results indicate that the productivity impacts of cover crops are not uniform across states and it likely depends systematically on soil conditions and production environments. These findings provide important policy implications in terms of targeting the level of support or subsidy required to encourage cover crop use across different states with varying soil endowments.