Simulating the effects of agricultural production practices on water conservation and crop yields using an improved SWAT model in the Texas High Plains, USA

Authors: CHEN, YONG - Texas A&M University; Marek, Gary; MAREK, THOMAS - Texas A&M Agrilife; PORTER, DANA - Texas A&M Agrilife; Brauer, David; SRINIVASAN, RAGHAVAN - Texas A&M University

Submitted to: Agricultural Water Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/22/2020
Publication Date: 10/7/2020
Citation: Chen, Y., Marek, G.W., Marek, T.H., Porter, D., Brauer, D.K., Srinivasan, R. 2020. Simulating the effects of agricultural production practices on water conservation and crop yields using an improved SWAT model in the Texas High Plains, USA. Agricultural Water Management. 244. Article 106574. https://doi.org/10.1016/j.agwat.2020.106574.
DOI: https://doi.org/10.1016/j.agwat.2020.106574

Interpretive Summary: Declining well capacities in the southern Ogallala Aquifer have led to increased interest in alternative crop management strategies to extend limited groundwater resources on the Texas High Plains (THP). Field-scale research has shown that 1) less frequent irrigations using greater application depth and 2) varying planting dates to take advantage of seasonal precipitation patterns may result in profitable crop yields while decreasing irrigation water use. However, regional water use estimates associated with such strategies have not been performed. Researchers from Texas A&M and USDA-ARS Bushland used a Soil and Water Assessment Tool (SWAT) equipped with an improved auto-irrigation function to simulate the effects of the alternative management strategies on seasonal irrigation, crop water use (ET), and yield for corn, sorghum, and winter wheat in the Palo Duro watershed. Results indicated that in general, increased irrigation application depth reduced seasonal irrigation requirements and ET for all crops. Delayed planting of corn and sorghum resulted in decreased irrigation requirements while early planting increased irrigation requirements with similar yield results. Simulations also showed that earlier planting of winter wheat resulted in marked increases in yield. These practices may help to reduce withdrawals from the Ogallala aquifer in the THP while maintaining profitable yields.

Technical Abstract: A calibrated SWAT model equipped with an improved auto-irrigation function was used to evaluate the impacts of agricultural production practices on water balances and crop yields of corn, sorghum, and winter wheat for the Palo Duro watershed located in the Texas High Plains (THP). Fourteen scenarios were simulated including alternative irrigation application depths of 12.7 mm and 38.1 mm for irrigated corn, sorghum, and wheat and with different planting dates for irrigated corn, sorghum, wheat, and dryland wheat. Results indicated that using the greater irrigation depth (38.1 mm) led to reductions in seasonal irrigation requirements and crop water use (ETc) when compared with the baseline scenarios using an irrigation depth of 25.4 mm for corn, sorghum, and wheat. However, soil water content, surface runoff, and percolation were increased. The opposite was observed for simulations using the same hydrologic parameters but using an irrigation depth of 12.7 mm. Crop yields associated with the alternative irrigation depths were similar to those achieved with the baseline irrigation depth. Delayed planting of corn and sorghum resulted in the decrease of all the studied hydrologic parameters relative to the baseline. By contrast, the early planting scenarios resulted in increases in those variables generally. Simulated corn yields were relatively stable, but a 3.7% reduction in irrigated sorghum yield was found with late planting. Notably, the early planting of winter wheat resulted in a clear increase in both irrigated and dryland yields of 11.2% and 13.5%, respectively. However, the yields of irrigated and dryland wheat were reduced by 28.8% and 2.7%, respectively for the late planting. These findings suggest the greater irrigation application depth is promising for maintaining crop yields and reducing groundwater use from the Ogallala Aquifer. Also, the late planting of corn may benefit water conservation. Nevertheless, the early planting of wheat might be warranted to enhance yield in the THP.