The water risk profile of corn, soybean, and potato in Minnesota from 1951 to 2024

Abstract

Climate change is expected to alter crop phenology, temperature regimes, and water availability, posing challenges for agricultural water management. We focus on corn ( Zea mays L.; VT–R1), soybean ( Glycine max (L.) Merr.; R3–R4), and potato ( Solanum tuberosum L.; tuber initiation‐bulking) to evaluate whether precipitation has historically met evapotranspiration demands during these key sensitive growth stages in Central Minnesota and whether demands or gaps have changed between recent precipitation and crop evapotranspiration (ET). We analyzed accumulated growing degree days (AGDD, 1951–2024) and precipitation using planting windows of April 15–25 for potatoes and May 1–10 for corn and soybean. Field observations from 2023 and 2024 at Becker and Saint Paul confirm that recent years have more AGDD than historical norms. We then compare empirical field measurements with historical AGDD and precipitation data to estimate crop ET demands during the growth stages most sensitive to water stress. We found that rainfall rarely matched ET demands during these stages from 1951 to 2024, as median rainfall frequently fell below growth stage‐specific ET thresholds in addition to the low soil water capacity in central Minnesota. Across the studied counties, approximately 0.3 million acres, which is 77% of the half a million total irrigated acreage of Minnesota, lies in these counties. The high interannual and spatial variability meant that precipitation was not consistently aligned with peak crop demand. We also find no trend of increasing or decreasing water stress over this time period due to evaporative demand limitation. These findings substantiate, as expected, that corn, soybean, and potato grown in Central Minnesota generally have not met the crop‐water demand during the most sensitive growth stages without irrigation, and importantly, in the Central Sand Plains of Minnesota, crop water demand has not gotten riskier since 1951; it is just as risky as it has been historically, requiring irrigation scheduling aligned with crop growth stages and precipitation to sustain yields and build climate‐resilient agricultural systems.