The impact of pruning severity on yield and quality of Zard olive fruit

Pruning and determination of its appropriate intensity are necessary to increase vegetative growth and productivity of the trees as well as light availability for the leaves of the tree canopy. For this purpose, a randomized complete block design study with three replications was conducted on Zard olive trees during two consecutive years. At the first year, different pruning intensities, including control (without pruning), 15, 30 and 45% removal of canopy volume were applied on 20-year-old trees located in Rudbar Olive Research Station. The results showed that the numbers of male and female flowers as well as fruit and oil yield were affected by the pruning intensity. Accordingly, trees with 45% removal of canopy volume had the highest number of male and female flowers. However, the yield of trees at 30% removal of canopy volume was higher than other pruning treatments. The percentage of fruit oil in pruned trees did not show a significant difference compared to the control, but due to the high yield in trees with 30% pruning, oil yield efficiency was also high in this treatment. Among the various measured quality indices of oil, such as total antioxidant capacity, free acidity of oil, peroxide value and spectrophotometric indices of K270, K232, antioxidant capacity and peroxide values were increased by pruning treatment. The highest antioxidant capacity and peroxide value were observed in 30% and 15% pruning, respectively. It seems that 30% pruning intensity, can be considered as a suitable and balanced treatment.