Conversion of Traditional Olive Groves

In this way, the reconversion must be approached as a goal to make the olive grove mechanizable, increase production, and maximize profit through cost reduction. To achieve this, we begin by acknowledging a series of premises:

• We know that the best reconversion for a traditional olive grove with wide spacing is to remove them and replace it with an intensive olive grove that, with proper care, will provide us with the same or even more production than the traditional one in 7-8 years, with annual increases until reaching its maximum leaf volume.
• We know that not all farmers can carry out this type of transformation due to various reasons, especially economic ones due to the total loss of production for several years.
• We know that planting new single-stem olive trees among existing multi-stem olive trees faces greater challenges in development due to various reasons, especially due to competition for water and light.

With this in mind, this article proposes a reconversion of the traditional olive grove for planting frames of 12x12 m with 69 trees/ha, or 14x14 m with 51 trees/ha. We are referring to all olive trees with 3-4 stems or trunks, with the idea of transforming them into frames of 12x6 with 139 trees/ha and 7x7 with 204 trees/ha, respectively, with single-stem olive trees, and enabling mechanized harvesting using an inverted umbrella shaker. While we recognize that this system is not ideal, it minimizes the loss of production during the reconversion process, significantly reduces production costs, and increases production once the reconversion process is completed. In this regard, we propose a progressive transformation over a period of 8-10 years.

The steps to follow are as follows:

1. Determine the spacing of the olive grove to be converted. This can be known by measuring with a measuring tape (more accurate) or using an aerial photo from the Google Earth application (which can be done on the same plot screen). In photo #1, two rows of crossed olive trees have been measured, one measuring 177 m and divided by the number of gaps, 14, resulting in a measurement of 12.6 m. The other crossed row measures 95.6 m with 8 gaps, resulting in 11.9 m. The spacing of the plot in the photo is 12x12. The advantage of the aerial photo is that it allows the spacing to be calculated and the density increase to be replanned on the photo without having to visit the plot. 

Photo 1: Calculation of the spacing of a plot using the aerial photo from the Google Earth application. (PHOTO: Valencian Institute of Agricultural Research).

2. In the replanting of new olive trees, it is necessary to define:

· The main working aisle, which should be perpendicular to the slope of the plot. In the case of the conversion from 12x12 to 12x6, the main aisle will be 12 meters.

· The movement of machinery, especially the turns at the end of the row of olive trees, to minimize invasions and disturbances to the neighboring property.

F-2 Theoretical Design of a Conversion. (PHOTO: Valencian Institute of Agricultural Research).

3. Determine the centers of the rows by measuring from the center of the trees and mark a reference at the start and end of each row, which will serve as a guide for subsoiling the center of the row. Once the subsoiling is done, proceed to use a rake to smooth the terrain and break up clumps.
4. Mark the positions of the olive trees to be planted and dig the planting holes.
5. Use paint to mark the selected live trunk or base of life that will remain on each tree from the traditional olive grove. This choice is made based on its potential future mechanization. Factors considered include height, slimness, diameter, and trunk health. Within this selection, there may be olive trees that won't undergo conversion and their only solution will be uprooting.
6. Initiate pruning or cutting with the goal of promoting the development of the live trunk, encouraging the growth of shoots or suckers towards the empty space in the central zone of the olive tree. Annual cleaning of the head of the trunk or live trunk is recommended, selecting the best-oriented shoots and removing any obstacles that hinder their proper growth from the vegetation of other trunks. Ideally, this pruning or cutting system should start a few years before trunk cuts and planting. The aim of pruning and cutting is for the live trunk to have 4-5 branches around the head of the trunk, with angles of approximately 60 degrees to the horizontal. This is achieved through successive prunings. In the traditional pruning of an olive tree with multiple trunks, preference is given to olive trees with compact growth that facilitate harvesting, with branches that are not very vertical, and sometimes nearly horizontal. Occasionally, some branches may reach the center of the rows, and low-hanging branch remnants may be left very close to the ground. With mechanization using an inverted umbrella vibrator, pruning changes. Slim branches (60 degrees to the horizontal axis) are sought, as they vibrate better, visible trunks to aid the attachment of the vibrating clamp, and low-hanging lateral branches at a certain height so they do not touch the inverted umbrella, as any branch that touches the umbrella's folds does not vibrate. For harvesting with an inverted umbrella vibrator, olive trees need taller canopy heights, with a maximum canopy diameter limited to the umbrella diameter, and lower branches must be maintained at a greater height from the ground. For harvesting with an inverted umbrella vibrator, the pruning systems for formation, maintenance, and renewal differ from the conventional multi-trunk olive grove. In formation pruning, the cut is made above the sap vein to induce shoot regrowth in appropriate areas and topping to reduce vigor. 

The photo shows the live trunk marked in red (left), with a deformative pruning already initiated on the live trunk. We can also see that the other existing trunk has undergone conventional pruning, aiming not to hinder the vegetative growth of the main trunk. In this olive tree, the process of removing trunks or bases has already begun.

F-3: Note the slender (60º) insertion of the main branches suitable for proper vibration transmission

(PHOTO: Valencian Institute of Agricultural Research)

F-4: Tree with some branches inserted at too wide an angle that do not transmit vibration well

F-5: Branch resting on the canvas that prevents good vibration transmission

Details of the conversion of an olive grove 12x12

During this conversion, many of the live trunks are not entirely straight. It's common for them to be somewhat tilted. In others, the canopy volume is off-center in relation to the trunk axis. All these inevitable imperfections in this type of conversion influence the quality of shaking and gradually correct themselves naturally with proper pruning. It's crucial that pruning practices are controlled and guided by the person conducting the conversion, who must have a clear understanding of what they want to achieve and must do.