A simplified weighing lysimeter for monolithic or reconstructed soils
1998
Schneider, A.D. | Howell, T.A. | Moustafa, A.T.A. | Evett, S.R. | Abou-Zeid, W.
A simplified weighing lysimeter applicable to both monolithic and reconstructed soils was developed and tested in two lysimeters installed at Ismailia, Egypt and one installed at Bushland, Texts, USA. A monolithic lysimeter was used to measure reference grass evapotranspiration (ET) at Bushland because the dense subsoil and calcic horizon of the clay loam soil cannot be reconstructed. The desert sand at Ismailia allowed the use of reconstructed soils for measuring reference ET of alfalfa and ET of field crops. The main lysimeter components are the concrete foundation, deck scale, soil tank and enclosure consisting of a base, a tank and a top. The steel soil tank and enclosure are shop-fabricated, and the scale is commercially available. Field construction consists mainly of excavation, collection of the soil monolith, if needed, and installation of the concrete foundation. Field calibration of the Bushland lysimeter over a 214-mm (8.43 in.) ET range resulted in s(y/x) = 0.1 mm (0.004 in.) and r2 = 0.9999. Similar calibration of one of the Ismailia lysimeters over an 80-mm (3.2-in.) ET range resulted in s(y/x) 0.02 mm (0.0008 in.) and r2 = 0.9999. In initial tests, the Kimberly-Penman equation overestimated grass reference ET, and the Penman-Monteith equation slightly underestimated grass reference ET for the Bushland environment. Hourly grass ET measured with the Bushland lysimeter agreed closely with hourly grass ET calculated by the 1963 Penman equation.
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