Effects of rising CO2 concentrations on water dynamics and yields for C3 and C4 crops under both irrigated and dryland conditions in the Texas High Plains

Authors: WEN, NA - China Agricultural University; QI, JUNYU - University Of Maryland; WANG, YUE - China Agricultural University; Marek, Gary; ALE, SRINIVASULU - Texas A&M Agrilife; FENG, PUYU - China Agricultural University; LIU, DE LI - Wagga Wagga Agricultural Institute; SRINIVASAN, RAGHAVAN - Texas A&M University; CHEN, YONG - China Agricultural University

Submitted to: Water Resources Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/4/2026
Publication Date: 1/6/2026
Citation: Wen, N., Qi, J., Wang, Y., Marek, G.W., Ale, S., Feng, P., Liu, D., Srinivasan, R., Chen, Y. 2026. Effects of rising CO2 concentrations on water dynamics and yields for C3 and C4 crops under both irrigated and dryland conditions in the Texas High Plains. Water Resources Research. 197. Article 106859. https://doi.org/10.1016/j.envsoft.2026.106859.
DOI: https://doi.org/10.1016/j.envsoft.2026.106859

Interpretive Summary: Increased atmospheric CO2 concentrations may influence both crop growth and crop water requirements by affecting stomatal conductance and leaf area. Although the effects of such changes are largely unknown, computer simulation modeling using the Soil and Water Assessment Tool (SWAT) model and Shared Socioeconomic Pathways (SSPs) may help develop management strategies to conserve limited water resources. Researchers from USDA-ARS Bushland, Texas, and university partners from the U.S., Australia, and China simulated the effects of increased CO2 concentration on yield and crop water use (ET) using an enhanced SWAT model and archived field data from Bushland, Texas. Analyses revealed that elevated CO2 had a more pronounced positive impact on crop yields under dryland conditions compared to irrigated conditions. However, results varied depending on crop type, water availability, and SSP Scenario. These findings offer valuable insights for decision-makers, helping them select crops that can boost yields while simultaneously promoting water-saving strategies under future climate conditions.

Technical Abstract: Elevated atmospheric CO2 concentrations can influence crop growth and water dynamics by affecting both stomatal conductance (gs) and leaf area index (LAI). However, the combined effects of reduced gs and increased LAI on C3 crops (such as summer soybean and winter wheat) and C4 crop (like summer grain sorghum) under varying water availability conditions have been largely understudied. This study developed and employed a modified SWAT-gs-LAI model that integrated a nonlinear gs-CO2 equation and an LAI-CO2 function. Using Shared Socioeconomic Pathway (SSP) climate scenarios, the model was used to evaluate the effects of elevated CO2 on evapotranspiration (ET), irrigation, and crop yield using archived field data from Bushland, Texas. Results showed that elevated CO2 had no apparent impact on ET under dryland conditions. However, under irrigated conditions, ET was reduced by 6.8-7.4 percent at 495 ppm CO2, 11.2-14.4 percent at 660 ppm CO2, and by 15.3-20.7 percent at 825 ppm CO2, along with a reduction in irrigation. Although elevated CO2 enhanced crop yield, its effect was more pronounced under dryland conditions than under irrigated conditions. Model simulations for future climate projections (2041-2100) indicated an increase in ET for dryland crops, including 6.8-9.4 percent for soybean, 7.0-9.3 percent for winter wheat, and 6.7-9.2 percent for sorghum compared to the baseline scenario. Irrigated summer soybean and sorghum also showed an increase in ET, while irrigated winter wheat saw a decrease ranging from 0.6 to 8.6 percent. The simulations also revealed a general reduction in irrigation across most crops. Crop yields generally responded positively to future climate change, except for irrigated sorghum, which declined by 4.8, 5.4, and 11.9 percent under SSP1-2.6, SSP2-4.5, and SSP5-8.5, respectively. C3 crops like soybean and winter wheat were more responsive to future climate than C4 crops like sorghum, under varying water availability conditions. These findings highlight the value of using a physically based model to predict crop growth and water dynamics under elevated CO2 and future climate scenarios.