The olive tree is a medium-high woody tree (depending on the cultivation system), which generally consists of a single crown, although it may have one or more trunks. In addition, the leaves of the olive tree are perennial with a dark green shaft, a smooth texture and a greyish reverse. The fruit is of great interest both for table olives and for its oil content.
Olive trees go through a stage of sprouting (February-April), flowering (April-May), fertilisation and fruit set (May-June), fruit growth (June-September), fruit ripening (October-December) and vegetative rest (November-February).
Each stage has different nutritional requirements:
This is the central element of fertilisation and should be applied at critical times, from sprouting to prior to flowering and setting. A nitrogen application is also appropriate in autumn to stimulate the recovery of tree reserves. In addition, this nutrient increases the assimilation of other elements.
A lack of nitrogen produces leaves with a lighter colour and reduced size, which fall prematurely. An excess is also undesirable as it can make the tree more sensitive to frost and disease.
Phosphorus accelerates ripening and improves flowering and setting. Needs for phosphorus in olive trees are consistent throughout the cycle.
A lack of phosphorus results in very small, dark leaves and reduced stem growth.
It is essential in the formation of sugars, proteins and fats and is also involved in the closing and opening of the stomata. It has a direct effect on production, increasing the quality and size of the fruit and improving the oil content. When the fruit ripens, the application of potassium is appropriate, as a large quantity of potassium accumulates inside the fruit.
A lack of potassium causes a reduction of flowering and fruit size, leaves with yellow or reddish tips and necrotic areas at the apex and rim.
This forms part of the cell walls of the plant and therefore promotes the growth and formation of fruits. It is important to note that although the soil presents a large amount of calcium, it may be in a form that cannot be assimilated by the tree.
A calcium deficiency will cause intense chlorosis in leaves in the apical area, ranging between a greenish colour in young leaves and orange in older ones.
This is the central atom of chlorophyll and therefore has a direct influence on photosynthesis. In addition, it activates several enzymes and is involved in the turgidity of cells.
Magnesium deficiency is rare in olive groves, however when it occurs light green leaves may be observed from the apex to the base, along with a general reduction in growth.
Iron is not part of chlorophyll, but it is essential as it influences the formation of green pigmentation and other processes such as photosynthesis. The olive tree is not particularly sensitive to iron deficiency. A lack of iron can be due to a high soil pH, which may cause it to be blocked.
An iron deficiency causes clear symptoms of chlorosis that can lead to necrosis if the deficiency is very pronounced. This results in reduced growth of shoots and therefore reduced production.
Boron is the most important micronutrient for olive trees, being of great importance in the flowering and fruiting stages. Application of boron must therefore start at the pre-flowering stage.
A boron deficiency will cause leaves to display necrotic areas at their apexes. In addition to constriction being related to fertility, a boron deficiency drastically decreases production and can cause deformation in the fruit.
This activates a series of enzymes and is fundamental for the growth and development of a crop. As deficiency of this micronutrient affects the growth of olive trees, it is important to carry out the treatment in spring. A zinc deficiency produces yellow spots on the leaves and reduced shoot growth.