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Title: Simulating soil water content, evapotranspiration, and yield of variably irrigated grain sorghum using AquaCrop

Author
item MASASI, BLESSING - Oklahoma State University
item TAGHVAEIAN, SALEH - Oklahoma State University
item Gowda, Prasanna
item WARREN, JASON - Oklahoma State University
item Marek, Gary

Submitted to: Journal of the American Water Resources Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/4/2019
Publication Date: 8/5/2019
Citation: Masasi, B., Taghvaeian, S., Gowda, P.H., Warren, J., Marek, G.W. 2019. Simulating soil water content, evapotranspiration, and yield of variably irrigated grain sorghum using AquaCrop. Journal of the American Water Resources Association. 55(4):976-993. https://doi.org/10.1111/1752-1688.12757.
DOI: https://doi.org/10.1111/1752-1688.12757

Interpretive Summary: Insert or attach to e-mail and send. Irrigation is crucial for the sustainable agricultural production in the Central and Southern High Plains of the Ogallala Aquifer region. In this study, a crop growth simulation model “AquaCrop” was calibrated and validated to predict soil water content, evapotranspiration, and yield for grain sorghum grown under different irrigation regimes and dryland conditions at two sites, one each in Central and Southern High Plains. Although the model tended to overestimate evapotranspiration rates early in the growing season, overall results indicated that it has the potential for use in irrigation planning and formulating deficit irrigation strategies. Soil water content was generally underestimated due to overestimation of evapotranspiration rates. However, trends in the soil water content closely followed that in the observed data. Prediction accuracy for predicting sorghum grain yield was acceptable for all irrigation and dryland treatments.

Technical Abstract: The use of models to simulate crop production has become important in the formulation and evaluation of deficit irrigation strategies in arid and semi-arid regions. However, applicability and performance of these models generally differ across regions, due to environmental differences and management factors. In this study, the AquaCrop model was used to simulate soil water content (SWC), evapotranspiration (ET), and yield for grain sorghum grown under different irrigation regimes and dryland conditions at two sites in Central and Southern High Plains. Prediction errors (Pe) for SWC were ranged from -25 to -5% in fully irrigated, -11 to -5% in limited irrigated and -20 to 17% in dryland treatments. Prediction errors (Pe) of less than 6%, -2%, and 25% were attained for seasonal ET simulations under fully irrigated, limited irrigated, and dryland conditions, respectively. However, the model tended to systematically overestimate ET, which appeared to be the main reason for underestimating SWC. The grain yield prediction accuracy was within previously reported ranges, with Pe values ranging from -9 to 2%, -13 to 22%, and -6 to -1.2% for fully irrigated, limited irrigated and dryland conditions, respectively. The RMSE for yield was 0.6 Mg ha-1, indicating acceptable accuracy. Overall performance of the AquaCrop model showed that it could be used as an effective tool for evaluating the impacts of variable crop and irrigation managements on the production of grain sorghum in the Central and Southern High Plains of the Ogallala aquifer region.