A new procedure is proposed for estimating actual basal crop coefficients fromvegetation indices (Kcb VI) considering a density coefficient (Kd) and a crop coefficient forbare soil. Kd is computed using the fraction of ground cover by vegetation (fc VI), which isalso estimated from vegetation indices derived from remote sensing. A combined approachfor estimating actual crop coefficients from vegetation indices (Kc VI) is also proposed byintegrating the Kcb VI with the soil evaporation coefficient (Ke) derived from the soil waterbalance model SIMDualKc. Results for maize, barley and an olive orchard have shown thatthe approaches for estimating both fc VI and Kcb VI compared well with results obtained usingthe SIMDualKc model after calibration with ground observation data. For the crops studied,the correlation coefficients relative to comparing the actual Kcb VI and Kc VI with actual Kcband Kc obtained with SIMDualKc were larger than 0.73 and 0.71, respectively. Thecorresponding regression coefficients were close to 1.0. The methodology herein presentedand discussed allowed for obtaining information for the whole crop season, including periodswhen vegetation cover is incomplete, as the initial and development stages. Results show thatthe proposed methods are adequate for supporting irrigation management
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