|Evett, Steven - Steve|
Submitted to: International Evapotranspiration Irrigation Scheduling Conference
Publication Type: Proceedings
Publication Acceptance Date: 7/1/1996
Publication Date: N/A
Technical Abstract: Weighing lysimeters, designed for both monolithic and repacked soils and adaptable to both developing and industrialized countries, were installed and tested at Bushland, TX, USA, and Ismailia, Egypt. At Bushland, a monolithic lysimeter was required for measuring grass reference evapotranspiration (ET) because the dense, natural subsoil and a calcic horizon of the clay loam soil cannot be reconstructed. The fine sand at Ismailia allowed the use of a repacked lysimeter to measure alfalfa reference ET and the ET of field crops. The soil and enclosure tanks are of welded steel construction, the scale is a factory-assembled deck type, and the lysimeter sits on a simple, reinforced concrete pad. Field construction is minimized by shop-fabricating the steel tanks, by the ease of constructing the foundation and by using the commercially-available, factory-assembled scale. Field calibration of one lysimeter at Bushland and two lysimeters at Ismailia resulted in standard errors (Sy/x) <\= 0.1 mm and coefficients of determination (r**2) >\= 0.9999. In initial tests, the Bushland lysimeter provided data suitable for verification of hourly calculations of Penman type ET equations.