Diurnal variation of remotely sensed ET and some indices on sweet cherry trees in subhumid climate conditions

In this study, an experiment was conducted in sub-humid condition, several observations made to determine Tc, spectral indexes, LWP and daily ET of sweet cherry trees with different irrigation treatments (T1 and T2). The results showed that, Tc-Ta were increased from sunrise to noon and decreased from noon to sunset throughout the day on DOY 171-172 (T1-T2) and DOY 233-234 (T2). However, it was increased from sunrise to sunset on DOY 233-234 for T1 treatment. It is very close the values of ET(d) and ET(cum) which were determined based on remotely sensed data with daily ET values determined by soil water budget for Gisela 5 rootstock. The cherry trees with non-water stress condition (T2) have had also the highest spectral index values and the tree with water stress condition (T1) has had the lowest spectral index values. According to statistical analysis, most significant relationships were determined between LWP-SAVI (r = 0.88 for T1; r = 0.77 for T2), ET(i)-LWP (r = 0.89 for T1; r = 0.92 for T2), ET(i)-SAVI (r = 0.88 for T1; r = 0.70 for T2) and ET(i)-Tc-Ta (r = 0.85 for T2). Based on these findings, the canopy temperature of sweet cherry trees is more sensitive to water stress than leaf water potential and spectral indexes and daily ET for sweet cherry trees may be defined with remotely sensed data. Spectral indexes may be used efficiently to monitor vegetation growth periods and may be beneficial to determine ET of sweet cherry trees.