THE BUSHLAND WEIGHING LYSIMETERS: A QUARTER CENTURY OF CROP ET INVESTIGATIONS TO ADVANCE SUSTAINABLE IRRIGATION.

In 1987-1989, the first irrigated crops were grown on the four large, precision weighing lysimeters at the USDA-ARS Conservation and Production Research Laboratory at Bushland, Texas, on the Southern High Plains (SHP). Thus began >25-years of full- and deficit-irrigated crop growth, energy and water balance, evapotranspiration (ET), yield, and water use efficiency (WUE) studies of major SHP crops, including alfalfa, corn and sorghum for both grain and forage, cotton, soybean, sunflower, and winter wheat. Alfalfa studies supported development of the ASCE Standardized Reference ET methodology. The lysimeter effort, led by Terry Howell, Sr., co-designed with Lynne Ebling and Thomas Marek and constructed by Arland Schneider, eventually grew to include a separate lysimeter to study short grass ET, again for the ASCE standard, and a 48-lysimeter facility to study soil type effects on crop water uptake, ET, and WUE using monoliths of four soils typical of SHP irrigated soils. The large lysimeters were managed to be representative of sprinkler-irrigated fields so as to develop crop coefficients used for irrigation scheduling by clients of ET networks developed by Texas A&M AgriLife in collaboration with the USDA-ARS. In addition, the lysimeters were used to test and further develop several technologies important to irrigation science, including soil water sensors, eddy covariance and Bowen ratio systems, scintillometers, thermal remote sensing based ET models, and hydrologic and crop simulation models. With the installation of subsurface drip irrigation systems on two of the lysimeter fields in 2013, the Bushland lysimeters are entering a new phase of advanced irrigation method and management studies. [ABSTRACT FROM AUTHOR]