Pruning management in a high-density olive orchard

The effect of different pruning strategies and times on olive vegetative-reproductive behavior was studied in a 5-year-old high-density orchard (1250 trees ha(-1), cultivar 'Ascolana tenera'). Compared treatments were a) winter hedging and topping, b) summer hedging and winter topping, c) winter hedging and summer topping, and d) summer hedging and topping. Selective spring pruning to a conical shape of the canopy was used as a control. Results showed no significant differences between the tested treatments regarding the maximum canopy diameter (along and perpendicularly to the row). Topping significantly constricted the tree height recorded at the end of the season when compared with the control (3.5 +/- 0.46 m); in particular, summer application maintained the final tree height at 2.5 +/- 0.21 m. Summer topping and hedging significantly reduced the canopy volume compared with winter and selective spring (control) pruning. No significant differences between the treatments were recorded regarding the number of newly emitted sprouts on the central leader and primary branches, whereas the length of these sprouts was significantly shorter for the trees with summer topping. Vegetative re-sprouting was mainly recorded in the upper portion of the canopy (above 2.0 m), and the total length of the new sprouts in this portion was significantly different for summer and winter pruning (1.2 +/- 0.08 and 18.7 +/- 0.92 m, respectively). No significant differences between the treatments were registered for the seasonal vegetative growth of 1-year-old mixed shoots. Fruit yield per tree was significantly higher following the winter hedging and summer topping treatment compared with summer hedging and topping (47% increase) and selective spring pruning (control, 64% increase). Results suggest that correct pruning management (winter hedging and summer topping) contributes to maintaining a good vegetative-reproductive balance of young trees (reduced vegetative re-sprouting and high fruit production) in high-density olive orchards.