EVAPOTRANSPIRATION OF DEFICIT IRRIGATED SORGHUM AND WINTER WHEAT

摘要

Deficit irrigation commonly is used in regions with reduced or limited irrigation capacity to increase water use efficiency (WUE). This research measured winter wheat (Triticum aestivum L.) and sorghum (Sorghum bicolor L. Moench) water use (ET) and yields so WUE could berndetermined. Two precision weighing lysimeters were used to accurately measure the crop ETrnfrom fully irrigated (FULL) fields and deficit irrigated (DI) fields. The DI wheat was anrnirrigation cutoff at the jointing growth stage as might be used if available irrigation water wasrnbeing shifted to summer crops while the sorghum DI used a reduced irrigation rate (～50% FULLrnirrigation) as might occur with a lower irrigation capacity. Both crops were irrigated by a lateralmovernsprinkler system at Bushland, Texas. Wheat ET was decreased by 20% from 849 to 677rnmm with a 76% decline in irrigation. Sorghum ET decreased 10% from 621 mm to 560 mm withrna 48% decline in irrigation. WUE of sorghum for both grain and dry matter increased slightlyrnwith DI but seed mass, and harvest index were unaffected. DI irrigated wheat extracted soilrnwater to a depth of 1.7 m in the Pullman soil with some apparent root extraction to the 2.3-mrndepth. Sorghum extracted soil water mainly above 1.2 m in the Pullman soil profile if wellrnwatered, but DI sorghum extracted soil water to 1.7 m. Sprinkler DI of sorghum beginning withrna nearly full soil water content profile permitted the crop to better exploit the soil profile waterrnand minimize soil water deficit effects on crop yield in a year with typical summer rainfall forrnBushland (～210 mm) such that yield was not reduced by DI. Cutting off winter wheat irrigationrnin early spring with a near full soil water profile at jointing, permitted the wheat crop to fullyrnexploit the soil water reservoir when rainfall was normal.