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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]

Accurate partitioning of the evaporation (E) and transpiration (T) components of evapotranspiration (ET) in remote sensing models is important for evaluating strategies aimed at increasing crop water productivity. A two-source energy balance (TSEB) model designed for row crops solves the energy balance of the soil-canopy-atmosphere continuum using surface brightness temperature. By solving the energy balance of the soil and plant canopy separately, the TSEB model can calculate E and T, which cannot be done with single-source models. However, few studies have tested the TSEB model where E or T measurements were available, which until recently has impeded its advance. This article reviews recent physically based advances of the TSEB model. The advances were tested using measurements of E, T, and ET by microlysimeters, sap flow gauges, and weighing lysimeters, respectively, at Bushland, Texas, for irrigated cotton having a wide range of canopy cover. Root mean square error (RMSE) and mean bias error (MBE) were 0.54 and -0.19 mm d-1, respectively, between measured and calculated E. RMSE and MBE were 0.87 and 0.31 mm d-1, respectively, between measured and calculated T. This was deemed an improvement over previous TSEB model versions, which overestimated E and underestimate T, resulting in RMSE and MBE of up to 3.8 and -3.5 mm d-1, respectively. Ongoing research includes testing the TSEB model using different remote sensing platforms, from ground-based to satellite scales. [ABSTRACT FROM AUTHOR]

This article is an introduction to the "Emerging Technologies in Sustainable Irrigation: A Tribute to the Career of Terry Howell, Sr." Special Collection in this issue of Transactions of the ASABE and the next issue of Applied Engineering in Agriculture, consisting of 16 articles selected from 62 papers and presentations at the joint irrigation symposium of ASABE and the Irrigation Association (IA), which was held in November 2015 in Long Beach, California. The joint cooperation on irrigation symposia between ASABE and IA can be traced back to 1970, and this time period roughly coincides with the career of Dr. Howell. The cooperative symposia have offered an important venue for discussion of emerging technologies that can lead to sustainable irrigation. This most recent symposium is another point on the continuum. The articles in this Special Collection address three major topic areas: evapotranspiration measurement and determination, irrigation systems and their associated technologies, and irrigation scheduling and water management. While these 16 articles are not inclusive of all the important advances in irrigation since 1970, they illustrate that continued progress occurs by combining a recognition of the current status with the postulation of new ideas to advance our understanding of irrigation engineering and science. The global food and water challenges will require continued progress from our portion of the scientific community. This article serves to introduce and provide a brief summary of the Special Collection. [ABSTRACT FROM AUTHOR]