Evaluation of an enclosed portable chamber to measure crop and pasture actual evapotranspiration at small scale

An enclosed portable chamber was constructed and calibrated to measure actual evapotranspiration (ET) from crop and pasture and then evaluated against established methods that are used to determine evapotranspiration. The chamber was equipped with variable speed electric fans to mix the air within the chamber during each ET measurement. The most appropriate fan speed was investigated. Pasture ET measured using the enclosed portable chamber compared well with predicted water loss using the water balance method for a 6-day period during winter 1997 in Armidale (NSW, Australia). Mean cumulative pasture ET for the 6-day period was 5.8 and 5.9 mm measured with the enclosed portable chamber and water balance method, respectively.