Evapotranspiration of Deficit Irrigated Sorghum

Deficit irrigation commonly is used in regions with reduced or limited irrigation capacity to increase water use efficiency (WUE). This research measured sorghum (Sorghum bicolor L. Moench) water use (ET) and yield so WUE could be determined. Two precision weighing lysimeters were used to accurately measure sorghum ET from a fully irrigated field (FULL) and a deficit irrigated field (DI; ~50% irrigation) that was irrigated by a lateral-move sprinkler system at Bushland, TX in 1993. Sorghum ET decreased 10% from 621 mm to 560 mm with a 48% decline in irrigation. WUE for both grain and dry matter increased slightly with DI but seed mass, and harvest index were unaffected. Sorghum extracted soil water mainly above 1.2 m in the Pullman soil profile if well watered, but DI sorghum extracted soil water to 1.7 m. Sprinkler DI beginning with a nearly full soil water content profile permitted the crop to better exploit the soil profile water and minimize soil water deficit effects on crop yield in a year with typical summer rainfall for Bushland (~210 mm) such that yield was not reduced by DI.