Olive tree

Nitrogen (N), Phosphorus (P2O5), Potassium (K2O), Magnesium (MgO), Boron (B) and Zinc (Zn) are the main nutrients required by the olive tree.

Of the macronutrients, most critical are:

• Nitrogen (N): is the most important nutrient for the olive tree, essential for germination and production. It favours germination, bud differentiation and, finally, yield. Its most important effect, of course, is to increase the percentage of perfect flowers. A lack of nitrogen in the critical stages leads to reduced fruit set or alternate fruit bearing.
• Potassium (K₂O): an essential nutrient for many physiological processes in olive cultivation, such as the regulation of cellular osmotic potential and the activation of enzymes involved in photosynthesis, transpiration and respiration. Adequate potassium nutrition ensures resistance to abiotic stresses. In addition, it influences the physiological, quality and organoleptic characteristics of the fruit, which is why it is widely known as a ‘quality nutrient’. Its deficiency directly reduces production and adversely affects the quality and oil content of the fruit.
• While adult trees need less Phosphorus (P₂O₅): it affects all the physiological processes of the tree (energy supply), fruit setting, flower retention and early production.
• Magnesium (MgO): a critical nutrient for the photosynthesis process, also contributing to protein synthesis and the transport of phosphorus and carbohydrates.

In acidic soils additional requirements are needed:

• Calcium (CaO) applications.
• When Potassium is surplus, the application of Ammoniacal Nitrogen (NH₄⁺) is required.

Of the micronutrients, Boron (B) is the most important trace element for the olive tree. It is an essential element for the smooth development of flowering, pollination and fruit set. Its deficiency is the most common nutritional deficiency of the olive tree. Its effect is immediate, reducing the productive potential of the olive grove and significantly reducing the yield. If the deficiency is not treated in time, the leaves turn completely yellow, acquire a characteristic brown colour at the top and eventually fall off. Even in cases of mild boron deficiency, some fruits may ripen normally, but most will fall prematurely or be deformed. Therefore, the addition of Boron in the basic fertilisation of the olive tree is now considered essential. Foliar spraying with Boron during the flowering stage also gives spectacular results.

At the same time, the contribution of Zinc (Zn) is quite significant. Zinc is a key participant in several metabolic processes in the olive, playing an important role in the synthesis of tryptophan, a precursor compound of auxin (IAA). Zinc deficiency is quite common in calcareous soils.

For the normal development, excellent growth and maximum productivity of olive trees, the addition of all the necessary nutrients in the ideal quantity and proportion is essential.

A complete olive plantation nutrition programme includes the addition of nutrition products both through the soil and through the foliage. As soil applications, basic and surface fertilisation are now essential cultivation practices for the development of the crop, while foliar applications complement the above, aiming to further improve the processes of flowering, fruit set, fruit development and the concentration of higher oil content. At the same time, post-harvest applications are also decisive, aiming to store nutrients in the root and wood for the next growing season.

The effectiveness of fertilisation and the necessary corrective measures are always based on the recommendations of the agronomic adviser.

Because rational fertilisation of the olive tree is always assessed in relation to:

• The specificity of the area.
• Soil physico-chemical properties.
• Long-term observations.
• Rainfall.
• Tree age.
• Year of fruiting - load.
• Alternate bearing.
• Leaf diagnostics.