Impacts of meteorological forcings on simulated soil moisture stress for rainfed crops at a U.S. Corn Belt site

Authors: Schreiner-Mcgraw, Adam

Submitted to: Vadose Zone Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/21/2026
Publication Date: 2/24/2026
Citation: Schreiner-Mcgraw, A.P. 2026. Impacts of meteorological forcings on simulated soil moisture stress for rainfed crops at a U.S. Corn Belt site. Vadose Zone Journal. 25. Article e70082. https://doi.org/10.1002/vzj2.70082.
DOI: https://doi.org/10.1002/vzj2.70082

Interpretive Summary: Crops are sensitive to dry conditions and precipitation and temperature patterns that promote dry conditions can lead to crops experiencing multiple stresses. One such stress is soil water stress, where there is not sufficient water for crop growth. While it is known that water stress in the topsoil is increasing across the U.S. Corn Belt, crops in rainfed production systems use water from below the topsoil to supplement their water needs when topsoil water is low. It is not well known how water availability across the whole root zone responds to changes in precipitation or air temperature. In this study, I used a three-dimensional hydrologic model of the subsurface to evaluate how water in the entire root zone changes with changes to the weather driving the model. Consistent with previous results, I found that water stress in the topsoil increases as precipitation becomes less frequent. But I also found that water in the deeper root zone was not affected by the simulated precipitation changes. This suggests that management strategies that increase connectivity between the topsoil and shallow groundwater will be important for sustaining crop production in the face of dry weather.

Technical Abstract: Temperature and precipitation change can increase crop water stress leading to declines in crop yield. In the U.S. Corn Belt, previous studies have found that the topsoil is drying. But crops, even in systems with restrictive soil layers, access water from beneath the topsoil and it is poorly understood how weather variability will affect water availability throughout the entire root zone. To investigate these impacts, I built an integrated surface water-groundwater model of a field in the Central Mississippi River Basin (CMRB). Using stochastically downscaled precipitation forcings, I found that in the topsoil (top 30 cm), less frequent precipitation leads to soil water more frequently dropping below the stress point. Increased precipitation during the spring did not impact the simulated soil moisture because soil was already near saturation at that time, meaning that additional precipitation primarily increased runoff. The shallow groundwater and soil layers beneath the topsoil did not experience drying, though unquantified recharge pathways limit the interpretation of groundwater results. Overall, this study showed that less frequent, more intense precipitation increases topsoil moisture stress. But the moisture in the critical zone below the topsoil is not likely to be affected, meaning it can be an important water source to sustain crop yields in places with unreliable precipitation. Thus, improvements to genetics and management that facilitate deep root growth should be investigated to sustain agricultural production in the future.