This method can be adopted especially with low-growth plants, better if located on a plain and having a pre-arranged pruning (bushy or polyconical vase); each worker averagely collects 10 Kg of olives an hour (80/100 Kg/day). Olives are collected inside a hanging basket and this actually represents an excellent method which is however being dropped due to high costs and lack of workforce. Another type of harvesting is that with a “cloth“: olives are dropped from a tree over a cloth under the canopy (a bruising risk always exists for already ripened olives).
Olives are harvested after they have spontaneously fallen down ending up in the nets being placed during the entire harvesting period; it is regarded as one of the worst harvesting methods due to the fact that fruits are likely to rot as they come into contact with soil and get contaminated with bacteria and moulds resulting into a low-quality end product. This method suits those olive trees with thick plants or located on steep slopes; however olives more than often remain on the trees for too long and become excessively mature or old.
Fruits are removed from sprigs by using some sorts of ‘combs’ that can be actioned mechanically or by means of compressed air (vibration motion) and fall down inside the nets purposefully laid on the ground. This type of harvesting is particularly useful when branches are fairly tall even though this may cause the falling of leaves and branches as well as some damages to fruits; it is calculated that the harvesting productivity increases by approximately 50%.
Through this mechanical harvesting method, olives are vibrated and shaken falling down to the nets laid on the ground or hanging in the air (or inside a suction machine); the detachment of olives from the tree happens through the vibration of the trunk and branches by means of shakers hooked to the plant by vises that make the plant vibrate until olives drop.
This system requires trees of suitable shape and size according to the machinery but it is still scarcely used as, throughout the years, vibrations affect the health status of the plant. That said, the use of such equipment reduces costs since hand-picking collection accounts for approximately 60% on the overall production costs (olives being picked up are reportedly only 80-90%).
Negative factors that must be taken into account are:
1) olives with a small volume and firmly tied to the branch;
2) structure and size of the olive grove;
3) different state of the ripening