The influence of some agronomic parameters on the efficiency of mechanical harvest on young olive trees

Olive mechanical harvest trials were carried out on 9-year-old olive trees to assess the influence on harvest yield of olive ripening stage, cultivar (Frantoio, Leccino and Maurino) and training system (vase and monocone). Trials were carried out in 1997, at three different times (mid-November, end-November and mid-December). A trunk shaker, able to execute orbital and multidirectional vibrations in succession, was used. During olive ripening detachment force, colour, oil and water content, weight and fruit-drop of olives were determined. These parameters and the harvest yields allowed the “amount of oil on the trees” to be determined. Oil quality was evaluated for each time period. After mechanical harvest, the characteristics of branches with undetached drupes were evaluated. The trunk shaker was used on young olive trees having a trunk diameter of 8-10 cm. The harvest yields were generally high, indicating that this technique is suitable over a broad period of time. In November the best harvest yields were obtained with the cultivar Frantoio that had the highest fruit weight and a relatively low fruit detachment force. In mid-November the Maurino cultivar, because of the low fruit weight, gave the worse results. Afterwards its low fruit detachment force allowed the same harvest yield to be obtained as of the other cultivars, so that by December there were no differences between the cultivars. The vase training system showed a slightly greater suitability to mechanical harvest compared to the monocone. This is most likely due to the higher deviations and distance from the main branch of fruiting branches in the monocone system. In all the cultivars, the oil obtained from olives harvested in the first two periods had a higher polyphenol content and was more fruity bitter and spicy than that obtained from olives harvested in the last period. The largest “amount of oil” harvestable by using the trunk shaker was obtained in all cultivars in the second period (end-November) which also had the best quality.