Low Tree Vigor, Free Palmette Training Form and High Planting Density Increase Olive and Oil Yield Efficiency in Dry, Sloping Areas of Mediterranean Regions

Exploiting biodiversity must be considered today an effective strategy to improve the sustainability of olive production systems. The evaluation of local cultivars, based on their vegetative and fruiting traits, along with an analysis of product quality, may contribute significantly to the development and diffusion of new olive-growing systems. The aim of this study was to evaluate growth, productivity, and olive oil quality of three Sicilian cultivars with different vigor/growth habit grown in four different combinations of training form and planting density. ‘Abunara’, ‘Calatina’, and ‘Nocellara del Belice’ olive trees were planted in four different intensive planting systems: 2 × 5 m trained to central leader (CLx2), 3 × 5 m trained to free palmette (FPx3), 4 × 5 m trained to small globe vase (GVx4), and 5 × 5 m trained to poly-conic vase (PVx5) and evaluated for seven years. Planting systems with low-density showed faster growth (trunk cross section area and canopy volume) than high-density systems. High-density systems had higher yield per hectare but lower yield per tree than low-density systems. ‘Calatina’ was the least vigorous but most productive cultivar. ‘Abunara’ and ‘Nocellara’ were relatively vigorous and suffered the tight spacings of high-density systems. Yield efficiency was generally high in ‘Calatina’, and it showed an increase with time in ‘Abunara’ and ‘Nocellara’ grown under the GVx4 and PVx5 systems. Fruit yield per hectare was highest in ‘Calatina’ grown under high-density systems. Oil yield was lower in ‘Nocellara’ than in ‘Abunara’ and ‘Calatina’. In terms of oil quality, ‘Calatina’ and ‘Abunara’ produced oils with higher oleic acid content than ‘Nocellara’. Generally, ‘Calatina’ has production characteristics of considerable interest, which, combined with low canopy volume and vigor, make it suitable for intensive pedestrian olive orchards with high levels of harvest and pruning mechanization and using different strategies and machines. Overall, for their management flexibility, these planting systems can contribute to improve sustainability of the olive industry even in sloping, dry areas of the Mediterranean.