2.6.2. Estimated Stem Water Potential

The linear regression models were the basis for calculating the estimated SWP (SWPe). The SWPe was calculated from the CWSI\_T100% and CWSI\_T33% values per MC for the entire dataset, and its values were denoted SWPe\_T100% and SWPe\_T33%, respectively. Additionally, SWP was measured on three to four healthy trees of representative canopy size per MC in the north subplot and three trees per MC in the south subplot for each day of data collection. The SWP measurements served as a reference indicating the actual water status of each MC. The specific method and time of measurement is described in Section 2.6.1. The SWPe was subtracted from the measured SWP per MC per day, and descriptive statistics were used to evaluate the datasets: average, standard deviation, maximum, minimum, median, 25% and 75% quartile, mean squared error (MSE), and RMSE. Additionally, each measured SWP and SWPe value was compared to the optimal water status range of stage III, which was defined between −1.17 and −1.43 MPa and based roughly on [39]. Above-range values (>−1.17 MPa) indicated excessive moisture and possible over-irrigation; withinrange (optimal) SWP values (between −1.17 and −1.43 MPa) indicated sufficient water status; and below-range values (<−1.43 MPa) specified orchard water stress. The variance of each distribution was calculated.
