Nitrogen is the most important and irreplaceable nutritious element for the vegetative growth and fruitation of the olive grove.
- ● it promotes vegetation, which is essential for the formation of the reproductive organs and fruit growth.
- ● it increases the number of flower buds that will give inflorescence
- ● it promotes the formation of perfect flowers, thereby increasing the fertilization and fruit setting
- ● it increases the fruit number and weight, thereby increasing the yield
- ● in combination with rational lopping and irrigation, it decreases alternate bearing of olive trees
The olive trees absorb large quantities of Nitrogen from the soil throughout the year, however they are particularly demanding and express real `’ hunger” for this element in specific stages of their annual vegetative and reproductive cycle.
- ● in the period of morphologic differentiation of flower buds (Feb. – Mar.)
- ● in the period of blossoming – fruit setting (Apr. – May)
- ● in the period of core hardening (Jun. – Jul.)
The sufficient supply of Nitrogen to the olive grove, during the stages described above, exerts a decisive effect on the quantity and quality of the final product.
Phosphorus is a component of important tree enzymes and proteins. It is directly or indirectly involved in a series of metabolic processes, and more specifically in those related to reproduction and energy transport. High concentrations of phosphorus are found in the young developing tissues.
From a functional perspective:
- ● It supplies the tree with the required energy for all its activities.
- ● It contributes to the root and timber formation.
- ● It contributes to the fruit setting, their strong retention and the production precocity.
Although in most Greek territories it does not constitute a restrictive factor for olive tree growth, phosphorus administration to the irrigated olive groves that are treated with rich Nitrogenous fertilizations and to table olive cultivars, constitutes a critical factor for the size, weight, precocity and qualitative characteristics of the fruit. In the rainfed olive groves and more specifically in soil rich in Calcium Carbonate (CaCO3) it should be administered it is granted in regular time intervals, so that the high levels of soil fertility are maintained.
Potassium, similar to Nitrogen, constitutes an irreplaceable element for olive trees. It presents high mobility within the tissues and subcellular structures, and participates in a plethora of physiological functions. It is implicated in the activation of many enzymes, in the production and transport of photosynthesis products, in water uptake and utilization and in the tree’s water balance. As a result of its multidimensional function, its sufficiency in the olive tree:
- ● Increases the fruit size and weight
- ● Increases the oil content of the fruit
- ● Improves oil’s qualitative characteristics
- ● Increases the resistance of trees to drought, frost and attacks from enemies and diseases
Olive tree has elevated annual needs in Potassium, particularly during the period of fruit growth and maturation, when more than 60% of the available Potassium migrates to the fruit.
In the oil producing cultivars it is essential to administer Potassium in equal quantities with that of Nitrogen, specifically in the year that increased fruit production is expected, so that the production of small fruit is avoided, the oil production is increased and the nutritious exhaustion of trees that leads to alternate bearing is decreased.
In table cultivars, the annual administration of Potassium is imposed, in order to achieve satisfactory production and improvement of the fruit’s qualitative characteristics.
Boron is the most important trace element for Olive trees, and the most essential one for flower formation, and smooth development of fertilization and fruitsetting processes. It participates in the transport of carbohydrates within the tree, the synthesis of plant hormones, the growth of young tissues, the pollen production and germination and in the fruit growth. Boron deficiency constitutes the most frequent nutrient deficiency of the olive trees and directly affects the fertility of the olive grove, thereby dramatically decreasing the production.
Boron administration in the form of borax (250-400g. tree), or by using complex fertilizers that contain Boron, is considered essential in the basic fertilization of olive trees, as much in the humid acidic, as in the calcareous soil.
Foliar sprayings with Boron during the formation of new vegetation, and at the beginning of blossoming, have also a positive outcome.