With the current interruptions in the availability of agricultural water in Crete – generally attributed to insufficient snowfall on the mountains during the winter – the Cretan Regional Authority has issued an information bulletin on how to ensure the optimum results in olive cultivation. The lack of water for irrigation does not by any means imply a reduction in output, they say, so long as the appropriate amount of water is given when the trees most need it. “In this way we can achieve the optimum production while at the same time economising the use of water .” The full text of the announcement is as follows.

Information from the Region of Crete on the reduced irrigation of olive trees
Solution to the reduced availability of irrigation water

Olive cultivation in Crete is indicated, since it matches the climatic and soil conditions, while it can be productive even when the trees are not irrigated. However, in order to achieve high yields, it is necessary to ensure that sufficient moisture is available, especially during the dry period of the summer. Irrigation of olive trees, when correctly carried out, positively affects flowering and fruit production while contributing to a reduction in the annual alternation between large and small crop yields [alternate bearing], at the same time maintaining oil content at a satisfactory level.

The most critical stages of olive production annually, as regards the need for water, are as follows:
– Slightly before and up to flowering (March-May). In this period irrigation is necessary to ensure better flower development, better fruit formation and germination.
– From fruit formation until pit hardening (May-June), which is a period of intensive activity of the fruit.
– From oil biosynthesis to the harvest (August-September or until the first rains of the autumn) with the aim of increasing the oil content and the maximum final development of the fruit’s flesh.
– The olive’s smallest demands for water are during the phase of pit hardening (around July) and to the end of August. At this stage there is practically no effect on production and so we can minimise or omit the application of water.

Excessive watering throughout the irrigation period or in isolated applications is a decisive factor in the appearance of diseases, increased damage from the olive fly, accumulation of salts, loss of nitrogen and other nutritive elements and the growth of weeds. Moreover the qualitative characteristics of olive oil are negatively affected by excessive irrigation. Thus when olive irrigation is done empirically without scientific guidance, it results on the one hand in the waste of water resources and on the other in the risk of lost production.

Deficit irrigation and optimum production
In the case of reduced availability of water (in dry periods), deficit irrigation must be applied. Deficit irrigation means reducing the dosage of water to an amount which depends on the crop and its stage of development. It is a practice which when applied at the appropriate stage of development of the crop not only has no negative effect on the crop yield but can potentially improve the quality of the fruits and of the olive oil produced. Deficit irrigation in no case means reduced yield, but rather the application of the appropriate amount of water during the stages at which water for the crop is essential. In this way we achieve optimum yield while simultaneously economising the use of water.

Using deficit irrigation, the irrigation needs of mature olive trees can be reduced to typical values of 120-160 cu m per stremma per year.

The irrigation quantities are only estimates since the exact dosage and the frequency of irrigation are determined on the basis of meteorological data for each area, the type of soil (light, medium, heavy), the age of the trees and the time of the previous irrigation. At the same time the use of drip irrigation, as well as the annual maintenance of the irrigation network, can optimise the use of irrigation water, chiefly in areas with reduced water availability.

For further information, you can follow the Irrigation Bulletins issued weekly (on Thursday), for the whole of the irrigation period by the Institute of Olive Tree, Subtropical Plants and Viticulture in collaboration with the Region of Crete, which are posted on the website: https://www.crete.gov.gr/deltia-ardeysis-2024/

Issued by:
Region of Crete
General Directorate for the Primary Sector, Directorate for Agricultural Development
Department for Coordination and Implementation of Plant and Animal Production Activities
Heraklion, 17-07-2024
Contact: Katerina Xydaki
Telephone: 2813 407922
Email: xydaki@crete.gov.gr