The fruit detachment force/fruit weight ratio can be used to predict the harvesting yield and the efficiency of trunk shakers on mechanical olive harvesting

From 2004 to 2007, trials were carried out in order to assess the importance of some agronomical factors, namely canopy density (sparse, medium and dense), growth habit (erect, spreading and dropping) and fruit detachment force and weight, in determining the percentage of mechanically detached olives (harvesting yield) through the use of a trunk shaker. The investigation was carried out in Central Italy, by using adult average-sized trees of several olive cultivars (crown volume 23 m3 in average), characterized by differences in all the studied factors (canopy density, growth habit, fruit detachment force and weight). Fruit detachment force and weight were the most important factors affecting harvesting yield. The ratio between these two parameters resulted strongly and linearly related to the harvesting yield, explaining about 60% of the total variability. The results show that with trees with canopies up to around 13,000 m3/ha, which are very common in intensive olive orchards, it is necessary to have values of fruit detachment force/fruit weight ratio equal to or lower than 2.3 to ensure harvesting yields equal to or higher than 85%. Such value allows harvesting yields equal to or higher than 85%, which is considered the breakeven point of mechanical olive harvesting with trunk shakers. In conclusion, the results clearly demonstrated a linear relationship between the fruit detachment force/fruit weight ratio and the harvesting yield obtainable with trunk shakers and indicated that this ratio can be used as a powerful harvesting index to decide the best harvesting time to execute the mechanical harvesting with trunk shakers in intensive olive orchards.