"Assisted" olive harvesting

Summary: Between traditional hand-picking methods on the one hand and modern powered machinery on the other, there is a type of mechanical device for olive harvesting that can be considered "intermediate". These are harvesting tools, and are particularly widespread in Italy because they are suited to the special needs of our olive growing sector

In olive cultivation, harvesting is still today one of the main items on the expense list, so much so that on average it represents between 25 and 50% of the total cost of oil production in our traditional plants, which involve olive trees that are often hundreds and at times (particularly in the Salento region) thousands of years old.  Currently, moving machines are now available for high production levels, such as vibrating shakers that can be fitted to tractors, or telescopic lifting devices and moving harvesters that derive from grape harvesters. On the other hand, it must be noted that manual harvesting has been more or less abandoned, with the exception of certain rare varieties of high value, destined for the table. Thus, in effect, the preferred option today consists in the use of small hand-held tools, which were introduced to the market in the mid-Seventies, from which the current, more efficient, reliable and economical, tools derive. From a technical point of view they can be described in various ways: olive shaker combs, beaters or shakers;  these are managed by the operator and allow a considerably higher harvesting yield when compared with the hand-picking method. 

Electric or compressed air beaters are commercially available, along with motor-powered shakers or olive beaters; the latter are generally higher powered, but also involve more problems than the former. The spread of this equipment in Italy encountered certain difficulties, substantially because their use only becomes cost-effective in olive farms with over 3-4000 plants, whereas the situation in our country features much smaller farms. It would therefore be necessary to create dedicated systems from scratch to take advantage of the full potential of these new machines.

 

Harvesting methods

There are various methods for harvesting olives; allowing them to fall spontaneously is undoubtedly the oldest and most economical, but in this case the oil obtained is of low quality, with somewhat poor organoleptic and nutritional qualities, and a high level of acidity. Combing involves the use of vibrating rakes, which when passed between the branches of the tree detach the olives so that they fall into the collection nets laid on the ground at the foot of the tree itself. This is a simple method, but the yield in terms of product harvested per hour is somewhat poor. Beating consists in hitting the branches with mechanically activated rakes, so that again the olives fall into the collection nets. This is the method preferred at present, due to its high yield. The most recent beaters have heads made using state-of-the-art materials (carbon fibre or high elasticity resins) that are particularly "delicate" on the plant, avoiding damage to the branches, something that was almost inevitable with the metal heads, which are extremely rigid. Damage to the plant is further reduced using shakers, that is to say shaking devices fitted with a hook at the end that is hooked onto the main branches, so that the olives are made to fall by shaking.

 

Operating methods

The traditional internal combustion engine (of limited power) is the power source installed on olive shakers; this inevitably makes the equipment heavy, resulting in early and intense fatigue for the operator, so much so that only the strongest are able to maintain high production levels for the whole of the working day. In any case, it is possible to harvest more than 80% of the olives from a mature tree in just 5-10 minutes using an olive shaker.  The vibrations remain a critical aspect, to the extent that under current regulations on the subject the typical levels do not allow continuous use for more than 2-4 hours a day. The noise levels are also considerable, being almost always above 85 dB(A), so that it is necessary to use ear protectors.

As an alternative to this option, electric beaters have appeared on the market. These are lighter, quieter, more ecological and almost maintenance-free. They are normally powered via a cable from a 12 V battery, positioned on the ground or mounted on a small trolley. The new types of Li-ion battery have seen considerable success, thanks to the fact that they reduce the size and weight of the power supply unit, so that the operator can carry the battery pack fastened to his belt, or in a special backpack.

Pneumatic olive shakers normally use the same harvesting head as the electrical beaters, but are activated using compressed air from a compressor unit, either electrical or with an independent internal combustion engine, or connected to a tractor via a cardan shaft. In this case, the main disadvantage is the presence of the air pipe, which can get caught up in the vegetation, slowing the harvesting operations. On small farms, compressors with 4-6 CV petrol engines are used, while larger farms prefer tractor operation, or operation with a 12-16 CV diesel engine, capable of powering up to 6 beaters simultaneously. To increase productivity, a net laying/winding device connected to the tractor is also used to collect the olives.

 

Harvesting capacity and criteria used when choosing

Both with electrical and compressed air versions, the harvesting capacity (in the hopper) reaches up to 400 kg/person per day. Telescopic rods, which can reach a length of 3.5 m, allow harvesting heights of up to 5.5-6 m, in effect eliminating the need for ladders, to the advantage of working safety.

When purchasing, particular care must be given to selecting the type of end tool: the use of soft, light-weight materials for the harvesting comb means that modern tools minimise the impact on both olives and vegetation, even though their working life is on average shorter than the metal or carbon combs used previously. Other criteria that must be assessed with care relate to the weight of the tool (bearing in mind that the lightest machine is not always the most efficient in terms of its ability to detach the olives), and the level of vibration generated and transmitted to the operator's hand and arm area.