## 2 Materials and Methods
### Harvest Assessment and Nutritional Analysis  
At maturity, a total of twenty trees, ten per irrigation treatment and location, were harvested (October 2022). Several agronomic and quality parameters were determined at harvest: fresh weight per tree (Yield_FW, kg tree\({}^{-1}\)), number of bunches per tree (Bunch, bunch tree\({}^{-1}\)), and average bunch weight (Yield_raw, kg tree\({}^{-1}\)). Thereafter, the samples were peeled and dried for 24 h at 60 \({}^{\circ}\)C to avoid mycotoxin contamination and weighed again to obtain the dry weight (Yield_DW, kg tree\({}^{-1}\)). The size was determined as the number of pistachios present in one ounce (commercial caliber, 28.35 g). The percentage of open husk, closed husk, and empty nuts was also determined (Split, Non_Split, and Blank) and the weight of open husk, closed husk, and empty nuts per tree (DW_split, DW_non_split and DW_blank, kg tree\({}^{-1}\)) were calculated at a representative subsample of twenty five nuts.  
Regarding nutritional quality, the numerous parameters of a sample of pistachio nuts collected from the studied trees were evaluated in the physicochemical laboratory of the 'Instituto Tecnologico Agrario de Castilla y Leon'. On the one hand, the fiber (g 100 g\({}^{-1}\)) was calculated using the enzymatic-gravimetric method via sequential enzymatic digestion with \(\alpha\)-amylase, protease, and amyloglucidase, and the fat content (Fat, g 100 g\({}^{-1}\)) was obtained through petroleum ether extraction using the Ankom sealed bag system. On the other hand, the protein content (PROT, g 100 g\({}^{-1}\)) was calculated from nitrogen quantification (Dumas combustion method) by multiplying the value obtained with the coefficient 6.25 [46], and the carbohydrates content (CBH, g 100 g\({}^{-1}\)) was determined through the difference of other major components (CBH = 100 \(-\) Ash-Humidity-PROT-Fat), in which ash and humidity content were determined gravimetrically.  
Furthermore, macro and micronutrients, such as calcium (Ca, mg kg\({}^{-1}\)), magnesium (Mg, mg kg\({}^{-1}\)), phosphorus (P, mg kg\({}^{-1}\)), potassium (K, mg kg\({}^{-1}\)), sodium (Na, mg kg\({}^{-1}\)), iron (Fe, mg kg\({}^{-1}\)), and zinc (Zn, mg kg\({}^{-1}\)), were determined. To that end, in the ETHOUS UP microwave digestion system (Milestone, Sorisole, Italy), 500 mg of dry material was digested at 200 \({}^{\circ}\)C in a Teflon container. The solutions were then cooled to room temperature and diluted. To conclude, the nutrient content was measured using an Agilent Technologies Varian 720-ES inductively coupled plasma-optical emission spectrometer (ICP-OES; Santa Clara, CA, USA).  
Finally, after acid digestion via dry route, several fatty acids expressed by percentage were measured, including palmitic, palmitoyl, stearic, oleic, linoleic, and linoleic, through gas chromatography with a flame ionization detector (GC-FID).  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Vegetation Index** & **Formula** & **Measure** & **References** \\ \hline Normalized Difference & \(=\frac{(NIR-R)}{(NIR+R)}\) (1) & Quantity, quality, and development & [15] \\ Vegetation Index (NDVI) & \(=\frac{(NIR-Green)}{(NIR+Green)}\) (2) & Water and nitrogen consumption & [20] \\ Normalized Difference Red & \(=\frac{(NIR-RE)}{(NIR+RE)}\) (3) & Measuring the amount of chlorophyll & [21] \\ Crop Water Stress & \(=\frac{T_{1}-T_{\text{dry}}}{T_{\text{dry}}-T_{\text{wet}}}\) (4) & Relative transpiration rate & [22; 23; 45] \\ \hline \hline \end{tabular}
\end{table}
Table 3: Vegetation indices (VIs) employed in this work. \(R\), reflectance in the red (660 nm); _NIR_, near-infrared (760 nm); _RE_, red edge (around 715 nm); \(T\), average canopy temperature acquired using the UAV thermal imagery after removal of ground pixels; _T_net, lower canopy temperature; _T_dry, temperature of the upper limit of the canopy.