Vegetative growth, fruit distribution and oil quality in the canopy of olive trees grown under super high-density cropping system

Ali Ben Dhiab [Integrated Olive production Laboratory, Institut de l’Olivier, Cité Mahrajène, Tunis, Tunisia]
Hanen Zaier [Integrated Olive production Laboratory, Institut de l’Olivier, Cité Mahrajène, Tunis, Tunisia]
Badii Gaaliche [Laboratory of Horticulture, National Agricultural Research Institute of Tunisia (INRAT), IRESA-University of Carthage, Tunis, Tunisia]
Mahdi Fendri [Integrated Olive production Laboratory, Institut de l’Olivier, Cité Mahrajène, Tunis, Tunisia]
Mohamed Ayadi [Integrated Olive production Laboratory, Institut de l’Olivier, Cité Mahrajène, Tunis, Tunisia]
Ajmi Larbi [Integrated Olive production Laboratory, Institut de l’Olivier, Cité Mahrajène, Tunis, Tunisia]

This three-year study was carried out in a commercial super-high density olive orchard located in the northeast of Tunisia. The experiment was designed to evaluate the variability in photosynthetically active radiation (PAR), vegetative growth, flowering, fruit distribution, fruit size and oil content among three layers of the tree canopy, i.e., bottom (0-1m), medium (1-2m) and top (>2m) canopy layers. Results exhibited that PAR decreased progressively from the upper to the bottom part of the canopy. This decrease was more accentuated during the second year of trial because of the significant increase of tree size. The variation in PAR availability within the canopy affected the vegetative growth, fruit set, average fruit weight, fruit maturity index, and oil content. However, the inflorescence characteristics, the percentage of staminate flowers and fruit drop were not influenced by the light decrease in the medium and bottom parts of the canopy. Fruit drop appeared to be less sensitive to PAR availability, but this parameter probably depended mainly on carbohydrate competition between fruits. Regarding oil composition, the chlorophyll, carotenoids, polyphenols and fatty acid composition were not affected by the decrease of light availability in the central and the basal parts of the canopy. In super intensive olive orchards, the adequate management of hedgerow vigour by correct pruning, fertilization and irrigation may allow a more regular productivity and, thus, a better economic sustainability of this orchard system.

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