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

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 the greater irrigation depth (38.1 mm) led to reductions in seasonal irrigation requirements and crop evapotranspiration (ETc) when compared to 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 of the same hydrologic variables but with an irrigation depth of 12.7 mm. Crop yields associated with the alternative irrigation depths were similar to those achieved with the baseline. 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 showed the increase 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 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.