Comparing Cotton Evapotranspirations Estimated by Micrometeorological and Water Budget Methods


Abstract: This study aimed at comparing actual water consumption of cotton obtained by the water balance method under full and limited irrigation conditions, with that estimated by a micrometeorological method (energy balance), which is being widely used nowadays. Results indicated that in the first year the total irrigation water applied was 438 mm, whereas in the second year it was 199 mm. Deep percolation losses were were 6 and 0 mm, respectively, in the first and second year of the experiment. The evapotranspirations of cotton under full irrigation condition were 496 and 629 mm for the energy balance and water budget methods, respectively. Corresponding values under limited irrigation conditions were 404 and 394 mm. Strong relationships (R^2= 0.99) were found between the evapotranspirations estimated by water balance and micrometeorological methods. Consequently, as compared to the water balance approach, the energy balance method under full irrigation conditions produced lower evapotranspiration (ET). This could be a result of the field measurements of deep percolation included in ET calculation by water balance.

Keywords: Micrometeorology, Water Budget, Evapotranspiration, Cotton

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