## 3 Results and Discussion
On the contrary, trees under the GVx4 and PVx5 systems showed a relatively high degree of alternate bearing (Figure 3C,D). \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**System**} & \multirow{2}{*}{**Cultvar**} & \multirow{2}{*}{**Canopy Volume**} & \multirow{2}{*}{**Growth Efficiency**} & \multirow{2}{*}{**Canopy Surface**} & \multirow{2}{*}{**S/V**} & \multirow{2}{*}{**Canopy/Soil**} & \multirow{2}{*}{**Prunings**} \\  & & & **(m\({}^{3}\))** & & & & \\ \hline \multirow{3}{*}{CLx2} & Abunara & 19.1 & 0.112 & 21.4 & 1.21 & 2.14 & 8.94 \\  & Calatina & 13.8 & 0.148 & 16.1 & 1.25 & 1.61 & 4.43 \\  & Noellara & 14.4 & 0.108 & 15.9 & 1.18 & 1.59 & 5.98 \\  & Abunara & 20.4 & 0.111 & 20.9 & 1.12 & 1.40 & 11.0 \\  & Calatina & 16.6 & 0.182 & 20.1 & 1.36 & 1.34 & 4.44 \\  & Noellara & 20.2 & 0.119 & 22.6 & 1.19 & 1.50 & 7.53 \\  & Abunara & 21.5 & 0.104 & 27.6 & 1.27 & 1.38 & 9.02 \\ GVx4 & Calatina & 14.5 & 0.134 & 20.8 & 1.48 & 1.04 & 4.80 \\  & Noellara & 19.6 & 0.099 & 25.8 & 1.31 & 1.29 & 10.8 \\  & Abunara & 23.1 & 0.110 & 29.0 & 1.25 & 1.16 & 11.0 \\ PVx5 & Calatina & 18.7 & 0.135 & 25.0 & 1.35 & 1.00 & 8.63 \\  & Noellara & 28.0 & 0.116 & 32.5 & 1.16 & 1.30 & 8.71 \\ Tukey HSD(\({}_{\alpha<0.05}\)) & 3.46 & 0.030 & 4.80 & 0.20 & 0.02 & 5.72 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Growth parameters for ‘Abunara’, ‘Calatina’, and ‘Nocellara del Belice’ olive trees grown as central leaders at 2 \(\times\) 5 m (CLx2), free palmete at 3 \(\times\) 5 m (FPx3), globe vase at 4 \(\times\) 5 m (GVx4), and polyconic vase at 5 \(\times\) 5 m (PVx5). Mean separation by Tukey’s honestly significant difference (HSD, \(p\) < 0.05). Yields per hectare of course followed the same trends as yields per tree but considered the different planting density of the various systems. In this case, trees in the CLx2 (9.5 t ha\({}^{-1}\)) and FPx3 (8.9 t ha\({}^{-1}\)) systems were significantly more productive than trees in the GVx4 (5.8 t ha\({}^{-1}\)) and PVx5 (6.4 t ha\({}^{-1}\)), with 'Nocellara' reaching the highest yields per hectare in 2021 under the PVx5 system (Figure 4A). Overall, 'Calatina' was the most productive cultivar, with yields cumulated over the seven years of 77.8 t ha\({}^{-1}\) compared to 62.8 t ha\({}^{-1}\) of 'Abunara' and 57.8 t ha\({}^{-1}\) of 'Nocellara' and was certainly the most productive cultivar in the first four years from planting in CLx2, FPx3, and GVx4. Furthermore, in terms of cumulated oil yields, 'Nocellara' was the least productive, with 9.83 t ha\({}^{-1}\) compared to 'Calatina' and 'Abunara', both with 10.1 t ha\({}^{-1}\). These results confirm previous findings from other studies [28]. Figure 3: Trends of fruit yield per tree across the seven years of trial for ‘Abunara’, ‘Calatina’, and ‘Nocellara del Belice’ olive trees grown as central leaders at 2 \(\times\) 5 m (CLx2, (**A**)), free palmette at 3 \(\times\) 5 m (FPx3, (**B**)), globe vase at 4 \(\times\) 5 m (GVx4, (**C**)), and polyconic vase at 5 \(\times\) 5 m (PVx5, (**D**)). Error bars represent standard errors of the means. Mean separation by [PERSON]’s honestly significant difference (HSD, \(p<0.05\)). As already pointed out by [PERSON] et al. [15], higher planting densities affected positively the yield per ha and negatively the yield per tree. 'Nocellara' and 'Abunara', which were more vigorous than 'Calatina', filled the assigned space in the rows earlier due to faster vegetative growth and higher canopy volume. This may decrease their efficiency later on during orchard life because of canopy overlapping and reciprocal tree shading [37]. Calatina was also the most yield-efficient cultivar, with some differences among planting systems (Figure 5). In particular, 'Calatina' was the most efficient from the second year onward in the FPx3 and GVx4 systems (Figure 5B,C); while it was the most efficient in the first four years, it lost some efficiency in the last three years under the CLx2 system (Figure 5A).