The use of pruning intensity to improve the balance between vegetative–reproductive activities and the physiology and water relations of olive trees in a climate change scenario

In 2023, an experiment was carried out in central Italy to evaluate the effects of two different pruning intensities (“light” and “medium”) on the vegetative–productive behaviour and physiology of adult olive trees grown in dry conditions (without irrigation). The two pruning intensities corresponded to the following crown volumes: 10,500 m3/ha with “light” pruning and 8,500 m3/ha with “medium” pruning. Shoot growth was greater in trees subjected to “medium” pruning. During the summer period, the leaves of plants pruned with “medium” intensity showed higher values of relative water content (RWC), water potential, photosynthesis, transpiration and stomatal conductance than those of plants pruned with “light” intensity. At harvest, “medium”-intensity pruning resulted in a higher unit weight, pulp/stone ratio, and oil content and slower pigmentation and reduction in pulp hardness. Olives from trees pruned with “medium” intensity showed a lower ratio between resistance to detachment and fresh fruit weight, as a consequence of the greater fruit weight. Trees pruned with “light” intensity showed a higher olive yield than those pruned with “medium” intensity, but the difference disappears if yield is expressed as quantity of oil. “Medium” pruning resulted in greater productive efficiency of the trees, expressed as the quantity of both olives and oil produced per unit of canopy volume. In conclusion, in the conditions in which we operated, the pruning intensity was able to significantly influence both the vegetative–productive behaviour of the trees and the physiology of the trees. A canopy volume of about 8,500 m3/ha, obtained with “medium”-intensity pruning, seems to be the one able to ensure the best responses in terms of production and water status and functionality of the leaves. The results show that pruning can potentially contribute to the trees' adaptation to water availability and thus to the different conditions caused by climate change.