## 3 Results and Discussion  
For data of all studied parameters, analysis of variance indicated a significant interaction among cultivar, planting system, and year. Hence, data and statistics are presented in graphs made of four different panels, each with a different planting system and containing data of the three cultivars. As expected by the end of the seven years of trial, TCSA was generally higher in GV and PV systems with 3D training forms than in CL and FP systems with 2D forms (Figure 2). This is in part due to the canopy shape and in part to the in-row distances, as they both induce tree growth reductions by foliage and root growth limitations, respectively. In terms of TCSA, 'Calatina' trees always grew less than 'Abunara' and 'Nocellara' trees, especially in the FPx3, GVx4, and PVx5 systems (Figure 2). Similar results were obtained by [PERSON] et al. [28]. 'Abunara' and 'Nocellara' trees had always similar TCSA, with the sole exception in CLx2 and at the end of the seven years of trial, where 'Nocellara' trees had smaller TCSA than 'Abunara' trees (Figure 2A). The latter indicates that high densities (smaller canopy and root allotted space) and the compact CL form depress growth of 'Nocellara' trees, which have the tendency to grow open with wide cro  
Figure 2: Trends of trunk cross-section area (TCSA) 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 Tukey’s honestly significant difference (HSD, \(p\) < 0.05). tree spacing and a better total light interception, determining a greater vegetative growth above and below ground. 'Calatina' was more growth efficient than 'Abunara' and 'Nocellara' in all systems, especially at higher densities (FPx3 and CLx2). Growth efficiency of 'Abunara' and 'Nocellara' were similar in all four systems (Table 1). Canopy surface, an indication of the leaf area exposed to solar radiation, followed the same trend of canopy volume (low levels for 'Calatina') except for the FPx3 system, which in this case, did not show differences among cultivars (Table 1). The canopy/soil surface ratio, an indication of the amount of foliage per unit of soil surface and thus a sort of vertical shading index, was also generally low in 'Calatina' compared to the other two cultivars. On the contrary, the canopy surface/volume ratio tended to be higher in 'Calatina' than in 'Abunara' and 'Nocellara', especially in the FPx3 and GVx4 systems. Both these last two parameters suggest a better use of the occupied space in terms of light interception for 'Calatina' compared to 'Abunara' and 'Nocellara'. In terms of pruning weight, differences were generally non-significant, with 'Calatina' showing the tendency to generate fewer prunings than the other two cultivars, especially in CLx2, FPx3, and GVx4 (Table 1). Yields per tree (average of the seven years) were generally highest in PVx5 (16.1 kg) and lowest in CLx2 (9.5 kg), with FPx3 and GVx4 showing similar intermediate levels (11-13 kg). This is generally expected, as it follows tree allotted space and canopy size: more space, bigger canopy, greater yield. Yields tended to be higher in 'Calatina' than in the other two cultivars in CLx2 and GVx4 during years 2016 to 2018 (Figure 3A,C), showing greater yield precocity of 'Calatina' under those two systems. Interestingly, 'Calatina' had high yields per tree until the sixth year of trial also in GVx4 and PVx5 systems, but in the seventh year, 'Abunara' and 'Nocellara' showed higher yields than 'Calatina' (Figure 3D). This may be in part explained by the evident alternate bearing in the vigorous cultivars. FPx3 was the planting system that showed relatively more regular yields with nearly no sign of alternate bearing, especially in 'Calatina' (Figure 3B).