Articles
Grapevine crop coefficient (Kc) determined by surface renewal method at different phenological periods
Article number
1150_9
Pages
61 – 66
Language
English
Abstract
Actual evapotranspiration values (ETa) are frequently obtained using the approach that combines reference evapotranspiration (ETo) and empirical crop coefficient (Kc) proposed by FAO. However, several studies carried out in grapevines showed that Kc values proposed by FAO do not agree with those obtained experimentally.
Therefore, a verification of FAO crop coefficients might be needed, in order to obtain more accurate ETa values.
In this context, the Surface Renewal (SR) method provides a simple, portable, robust, and low-cost method for determining Kc using the energy balance equation.
The SR method was used to obtain values of sensible heat flux (H) from high-frequency temperature readings (10 Hz) measured during the 2009-2010 growing season.
Then, latent heat flux (LE) values were determined as the residual of the energy balance equation using measured net radiation (Rn), and soil heat flux (G). The LE values were converted to actual evapotranspiration (ETa), then the Kc values were calculated as Kc=ETa/ETo, where ETo was calculated using the Penman-Monteith equation.
Average Kc values estimated with a calibrated SR method during fruit set, and veraison were 0.40, 0.70, respectively.
Estimated crop coefficients showed a good agreement with the experimental Kc obtained by an Eddy covariance (EC) system with differences around 10%. These results indicated that the calibrated SR method is a useful tool for estimating Kc values, which can be used to improve irrigation scheduling in vineyards.
Therefore, a verification of FAO crop coefficients might be needed, in order to obtain more accurate ETa values.
In this context, the Surface Renewal (SR) method provides a simple, portable, robust, and low-cost method for determining Kc using the energy balance equation.
The SR method was used to obtain values of sensible heat flux (H) from high-frequency temperature readings (10 Hz) measured during the 2009-2010 growing season.
Then, latent heat flux (LE) values were determined as the residual of the energy balance equation using measured net radiation (Rn), and soil heat flux (G). The LE values were converted to actual evapotranspiration (ETa), then the Kc values were calculated as Kc=ETa/ETo, where ETo was calculated using the Penman-Monteith equation.
Average Kc values estimated with a calibrated SR method during fruit set, and veraison were 0.40, 0.70, respectively.
Estimated crop coefficients showed a good agreement with the experimental Kc obtained by an Eddy covariance (EC) system with differences around 10%. These results indicated that the calibrated SR method is a useful tool for estimating Kc values, which can be used to improve irrigation scheduling in vineyards.
Authors
C. Poblete-Echeverría, D. Sepúlveda-Reyes, M. Zúñiga, S. Ortega-Farías
Keywords
actual evapotranspiration, sensible heat flux, latent heat flux, ‘Carménère’
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