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Validating the use of an atmometer as an irrigation management tool

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Paper number  032142,  2003 ASAE Annual Meeting . (doi: 10.13031/2013.14014) @2003
Authors:   Mahbub Alam, Jeff Elliott
Keywords:   Evapotranspiration, evaporation, crop water use, irrigation scheduling

Evapotranspiration (ET) data obtained using commercially available atmometers with three types of fabric covers were compared to evapotranspiration estimated using weather data from an automated weather station. Atmometers were established in a replicated random design within the compound of an automated weather station. Three years average data show that evaporation from an atmometer with canvas 54 cover is within 5 percent of evapotranspiration calculated from weather data using modified Penman equation for alfalfa as a reference crop. The ET gage with canvas 54 cover gave under-estimation. Similarly, three years average from atmometer with canvas 30 cover was within 4 percent of ETo estimated for grass as a reference crop. The ETgage with canvas 30 cover however gave an overestimation. Gore-Tex covered atmometer established at 1m fixed height overestimated ETr more than 15 percent, some year as high as 30 percent. Individual ETgage units showed some variation, which may be attributed to manufacturing or data reading errors. Further analysis of data is waiting to establish the significance of the variation.

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