## 2 Materials and Methods
### Watering Regimes  
The experiment involved four watering treatments (Table 1).  
The first treatment, C, involved olive trees grown under rainfed conditions. The first deficit irrigation treatment T\({}_{1}\), or the producer's practice treatment, refers to the method of adding water based on the years of producer experience in grove irrigation and visual inspection of the grove without precisely determined regimes. Second deficit irrigation treatment T\({}_{2}\) (SAN-technology) refers to reduced irrigation according to phenological stages (Table 2): 80% of Etc before flowering, fruit growth and oil accumulation in the fruit and 50% of Etc between these stages. T\({}_{3}\) refers to the irrigation treatment involving compensating  
Figure 1: Monthly rainfall and monthly reference evapotranspiration in 2019 and 2020, from Zman, Dugi otok. ETo—reference evapotranspiration (obtained from the PinovaMeteo meteorological station [23]).  
100% of the water lost by evapotranspiration (ET\({}_{\text{c}}\)) during the entire irrigation period to calculate the amount of water saved using other treatments.  
Water was supplied in all irrigation treatments by drip irrigation, with 29 self-compensating drippers placed for each tree around the canopy (flow rate of 2.8 L/h). The amount of water used in all treatments was measured by flow rate meters F0550 (Conrad Electronic SE, Wels, Austria).  
The amount of water used in each treatment (IR) was determined using the following Formula (1) [31]:  
\[\text{IR}=\text{ETc}-\text{EP}-\text{R} \tag{1}\]  
where ETc is evapotranspiration, EP is effective precipitation and R is available water. Effective precipitation (EP) used in the calculation was 70% of the total precipitation recommendation for olive trees grown in the Mediterranean [31].  
Evapotranspiration (ETc) was calculated using the Formula (2) [31; 32]:  
\[\text{ETc}=\text{ETo}\times\text{Kc} \tag{2}\]  
where ETo is reference evapotranspiration obtained from the PinovaMeteo meteorological station [23] and Kc is corrective factor for olive trees [32]. The Kc value for the months of March, April and May was 0.76, for June it was 0.70, for July and August 0.63, for September 0.72, for October 0.77 and for November 0.75 [32].  
Available water (R) used in the calculation was obtained using the following Equation (3):  
\[\text{R}=0.70\times\text{AWC} \tag{3}\]  
where AWC is available water capacity obtained using the following formula (4):  
\[\text{AWC}=\frac{\text{PC}-\text{PWC}}{100\times\text{Dr}} \tag{4}\]  
where PC refers to field water capacity (% volume), PWC refers to permanent wilting point (% volume), and Dr refers to the depth at which the majority of root system is located.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Treatment 1 **} & **2019** & **2020** & **2019** & **2020** \\ \hline \multicolumn{6}{c}{**Amount (I)**} & **Rate Number** & **Saved Water (I)**} \\ \hline C & 0 & 0 & 0 & 0 & 800 & 1800 \\ T1 & 448 & 1393 & 5 & 11 & 352 & 407 \\ T2 & 560 & 1261 & 8 & 19 & 240 & 539 \\ T3 & 800 & 1800 & 8 & 19 & 0 & 0 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Amount of water added per tree, number of rates and the amount of water saved as compared to T3 over the two-year period (2019 and 2020).  
\begin{table}
\begin{tabular}{l c c c} \hline \hline \multirow{2}{*}{**Phenological Stages**} & **BBCH 1 ** & **2019** & **2020** \\ \hline Flowering & 61–68 & 3/5–15/5 & 2/5–12/5 \\ Fruit set & 69 & 16/5–20/5 & 13/5–19/5 \\ Pit hardening & 75 & 10/7–23/7 & 11/7–20/7 \\ Oil accumulation & 79–89 & 10/8–10/9 & 10/8–10/9 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Dates of phenological stages in olive cv. Coratina during 2019 and 2020.