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Feeding olive trees rationally, saving time and money

All nutritional elements are essential, but in different quantity to satisfy the needs of plants. It is therefore necessary to know “how much” but also “when”. Some suggestions by Prof. Luca Sebastiani from Scuola Superiore Sant’Anna

“There is no CONCIMAZIONE formula valid anywhere and no matter how” says Luca Sebastiani, professor of tree cultivations at the Scuola Superiore Sant’Anna in Pisa, Italy. All nutritional elements are essential
The essential nutritional elements: - are instrumental for the completion of the vital cycle - cannot be substituted by other elements in their function - are directly involved in the metabolism From carbonium and oxygen which constitute more than 90% of the dry substance, to MOLIBDENO E NICHEL, present in concentrations of 0.1 ppm, all elements are equally important for the plant. Evaluation of the nutritional status
The most important factors to evaluate the nutritional status of an olive tree are: - concentration of nutrients in the soil - fertility and chemical-physical properties of the soil - symptoms of lacks - concentration of nutrients in the leaves
The sole analysis of soils is insufficient to exhaustively clarify the nutritional status of the plants as it does not provide data on the available concentrations of the elements, and does not consider the accumulation properties of the plant. This analysis should be combined with an analysis of the leaves.
Where are the elements?
The understanding of the physiology of the plant and the definition of a plan for CONCIMAZIONE require the localization of the mineral elements: - nitrogen, phosphor and potassium are prevalently located in the leaves, branches and fruits
- calcium is prevalently located in the leaves and branches, very little in the fruit - iron is prevalently present in the TRONCO and roots
How does the concentration of the elements in the leaves vary during the year?
The content of certain elements, such as potassium and zinc, linearly decreases during the year, while it is stable for others such as copper, and it oscillates between a minimum and a maximum for nitrogen and BORO.

The fertilization
The fertilization should be planned in function of the analysis of the soil and leaves, and too much nitrogen is useless and could even be harmful. Sufficient doses could be 250 - 300 g per olive tree in adult and traditional cultivars, with ample SESTI (200-250 plants per hectare), while in modern olive groves the dose may reach 400-500 g of nitrogen per tree.

A fertilization based on the diagnosis of leaves often utilizes the leaves CONCIMAZIONE or FERTIRRIGAZIONE as distribution technique. Both methods allow to reduce the waste of CONCIME, and to maximize the effect of the nutrients when necessary to the plant. In the FERTIRRIGAZIONE, the plants are able to absorb the nutrients that are gradually and continuously administered in low doses, and to use them with an efficiency higher than 90%, against the 30-40% which can be obtained with the traditional techniques of CONCIMAZIONE. Though, special care is necessary to verify that the fertilizers are water soluble and that the pH of solutions is in the range between 5.5 and 7. It is also necessary to use fertilizers with micro nutrients in CHELATA form, that is not subject to process that do not allow them to be soluble, and to obtain the highest uniformity in the distribution because, given the doses, the micro nutrients can easily reach toxicity levels, as it is the case with BORO, which can easily accumulate in the roots.

As regards the leave CONCIMAZIONE, the fertilizers are absorbed with special efficiency in the very first hours following the application, and the phenomenon later maintains constant in the following 24-48 hours. In general this technique is used in the phases of MIGNOLATURA, ALLEGAZIONE, and nut INDURIMENTO, and it utilizes water soluble fertilizers in different concentrations: - Urea: 1,5 – 4% (low content of BIURETO) - Potassium Nitrate: 1-3% or Potassium Sulfate 4%. Nitrogen, not in excess
Two researches carried out contemporarily by Italian and Spanish researchers have shown that nitrogen in excess reduces the content of poliphenols in the fruit, whereas a surplus of nitrogen fertilization has no effect on the contents of the olive.

This means that more CONCIME does not always bring benefits to the tree, and that saving some euros for a soil or leaves analysis, is a good choice. On the contrary, the expected results will not be obtained in most cases and the fertilization will even have a negative effect.

by Alberto Grimelli
06 september 2010, Technical Area > Olive & Oil

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