This paper examines how climate change and adaptation through irrigation have affected corn yield growth within the US Corn Belt since the 1960s. We combine corn yield and irrigation data from the USDA National Agricultural Statistics Service with ERA5-Land gridded temperature data. We adopt an augmented long-difference framework to i) assess the impact of extreme temperature trends from 1960 to 2023 on corn yield growth in Corn Belt counties since the 1960s and ii) estimate the potential of irrigation to mitigate this impact. Our findings reveal significant upward trends in extreme degree-days (EDD) above 29◦C across more than half of Corn Belt counties. We highlight that the varying magnitudes of these trends, alongside differential adoption rates of irrigation between counties, have played a crucial role in explaining the disparities in long-term corn yield trends within the region. Specifically, we show that irrigation offsets about 80% of the adverse impact of EDD on corn yields. Based on a counterfactual analysis, we find that current corn yields are about 6.5% lower, on average, than they would be in a non-climate change scenario.
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