The introduction of mechanical harvesting with a ride-on machine has represented, since the mid-1990s, the second “Olive Growing Revolution,” spreading high density also to olive growing, which until then was an exclusive model of viticulture and fruit growing. Super-intensive olive groves in fact, are similar to modern wine grape vineyards: high planting density (1200-2000 trees/ha), early entry into production (3rd year), and stabilization around the fourth-fifth year with a production of at least 8-10 t/ha of olives, regular rectangular planting frame (spacing 3.5-4.0 x 1.3-1.5 m) allowing the formation of a continuous vertical vegetal wall, the dimensions of which should not exceed a height of 3 m and a thickness of 1.5 m. The trunk must be free of branches to a height of 0.5 m from the ground to allow proper management and effective operation of the harvesting machine. In first-generation hedge olive fields (photo 1) (SHD), the central leader formation was the central axis: the olive tree grew according to a vertical axis that was not pruned until a height of 2.5 m, and around which the lateral branches of equal length grew freely. Recently, a new management criterion has been introduced, the Smarttree format, the management of which has introduced the second generation of super-intensive fields (SHD 2.0) (Photo 2).
This cultivation system is proposed with the aim of achieving total mechanization of olive grove management operations, including formation pruning. Rooted cuttings undergo various cuts in the nursery at a height of 50 cm, so that, by removing the apical dominance exerted from the growing apex, it achieves: (i) the development of lateral buds, (ii) rapid branching, and (iii) the formation of a completely homogeneous free vegetal wall, which can be mechanically managed from the same plantation.
This new system allows for reduced installation costs per hectare, as it does not require any special support structure, but rather a simple 90 cm bamboo cane driven into the ground at the time of planting. Additionally, pruning is carried out entirely mechanically, through regular apical (topping) and lateral (hedging) cutting operations, even in the formation phase. In 1994, the first hedge olive grove model only involved working with two cultivated varieties, Arbequina and Arbosana, which were subsequently added to one another. The sustainable application of high density in olive growing essentially depends on the availability of olive varieties with specific vegetative-productive characteristics, with even greater limitations than those necessary for discontinuous mechanical harvesting carried out with the trunk shaker. Plant-machine interaction studies, in the case of this new cultivation system, have led to the identification, to date, of 5 varieties adapted to this type of collection. These experimental studies, conducted for the first time in Italy by researchers from the University of Bari in 2001, continue with the aim of evaluating the suitability of a greater number of varieties for mechanical harvesting with a ride-on machine. The Italian varieties studied so far unfortunately have strong limitations mainly due to their medium-high vigor, which results in both significant damage to the vegetation, even in young plants, and unacceptable delay in entering production, as well as enormous difficulty in hedge management. However, there is scientific evidence of some promising Italian genotypes for their adaptation to the new cultivation system, from both productive and vegetative performance perspectives of the hedge. However, at least another five years of testing are needed to ‘promote’ new Italian candidates At the moment, the possession of such genetic characteristics is recognized in the Spanish varieties Arbequina, Arbosana, Sikitita, Oliana, and the Greek Koroneiki. Globally, over 90% of super-intensive olive groves today use either Arbequina or Arbosana for their cultivation.
Arbequina still occupies 65% of the world area cultivated with the super-intensive system, while Arbosana is already estimated to cover around 25% of its surface. In Italy, almost two-thirds of super-intensive olive groves are located in Puglia (Photo 3), where in 2016 more than 600 hectares were already occupied by Arbequina, while around 300 were occupied by Arbosana and the rest by Koroneiki. However, the range of varieties is rapidly improving, with the introduction of new varieties resulting from various genetic improvement programs.
The bio-agronomic characteristics that, together, constitute the quintessence of a variety adapted to super-intensive cultivation systems are:
- Reduced vigor
- Compact habit
- Rapid entry into production
- High productive potential
- Quality of the oil extract
- High rhizogenesis attitude
- Resistance to abiotic stress (cold, drought, salinity)
- Resistance to biotic stress (fruit fly, fungal diseases, bacterial diseases)
All of these represent the objectives of olive genetic improvement necessary for expanding the range of varieties available for super-intensive cultivation systems, and are fundamental for providing greater choice to farmers. Over the last two decades, Italian breeding efforts have only resulted in two new varieties proposed for high-density systems: Fs-17® and Urano/Tosca®. The first possesses bio-reproductive characteristics in line with the sought-after ideotype for high density, but lacks some vegetative parameters, such as expanded habit and sparse canopy density. The second, on the contrary, exhibits valuable vegetative characteristics, such as semi-dwarf habit and compact vegetation density, but has provided erratic and unsatisfactory productive results. The genetic improvement program between Agromillora Research and the University of Bari has led to the obtaining of numerous interesting selections. Among them, OAC-10, which was evaluated in the field as Lecciana (Photo 4). It was obtained by controlled crossing between Arbosana and Leccino and possesses peculiar vegetative and reproductive characteristics that make it suitable for hedge olive groves:
- Medium-low vigor, between Arbosana and Arbequina
- Erect and fairly compact behavior
- Early entry into production, by the 3rd year
- Low gynosterility (4%)
- High flower set (5%)
- Good fruit size, greater than 3 g
- High productivity per tree, like Arbequina
- Minimal damage to the olive during mechanical harvesting, less than Arbosana
- Limited branch damage, lower than Arbosana, similar to Oliana
- Medium-low susceptibility to fruit fly, like Arbosana
Lecciana has been found, in the field, to be self-incompatible. The optimal harvest time corresponds to 50% of the ripe epicarp (pigmentation index 2). This usually occurs in Puglia between the second week of November and the first week of December. At this stage of ripeness, the fruits have:
- Good pulp consistency (around 4 N), reducing damage during mechanical harvesting
- Weight of around 3.5 g and drop index less than 2 N/g, allowing for high mechanical harvesting efficiency
- Oil yields of 15%
Lecciana oil, extracted at this harvest time, possesses excellent sensory and chemical characteristics. In particular, acidity is around 0.3%, and the average fruitiness, pungency, and bitterness are high (4). Lastly, the oil of Lecciana has a high polyphenol content, exceeding 450 ppm during this harvest time. This not only imparts sought-after organoleptic attributes but also extends the shelf life of Lecciana oils, allowing for the extraction of nutraceutical oils, as they meet the necessary requirements according to the European Food Safety Authority (EFSA) for health claims. Considering the importance of olive growing in Italy, and especially in Puglia, high density stands as one of the possible solutions that can be employed to mitigate the issues affecting this sector. The introduction of these new varieties into the Italian olive context seems to yield promising results in terms of agronomic and economic sustainability. The adoption of high-density olive cultivation in Italy has so far faced a significant obstacle in the limited choice of varieties, all of which are of foreign origin. . Lecciana is the first variety with Italian parentage that can adapt to high-density cultivation systems, allowing for an 80% reduction in the use of specialized agricultural labor compared to the best intensive Italian plantations. The variety can be directly included in the law governing productions recognized as Italian.
Therefore, companies will be able to produce extra virgin olive oil Made in Italy with a 50% cost reduction compared to the best intensive plantations currently in production and made with Italian national varieties. Lecciana is the first Italian-origin genotype suitable for hedge olive cultivation, possessing the required vegetative and reproductive parameters and producing oils with excellent organoleptic and nutraceutical characteristics.
