Kostas Chartzoulakis. Institute of Olive Tree of Greece

More than 90% of olives are cultivated in Mediterranean Basin countries, in which the impacts of climate change are more dramatic due to intense competition for natural resources (water and land, etc) between agriculture and other economic sectors. In this region insufficient rainfall can lead to water stress and impact the overall health and productivity of the olive trees. Extreme heat waves, changes in precipitation patterns or cold waves, pose significant threats to the overall viability and sustainability of olive groves. In addition the increasing drought periods increases irrigation needs. Although olive is not a water-demanding crop like avocados and citrus, not all phenological stages are equally resistant, and combinations of the duration and level of water stress are important. The flowering, fruit set, and oil accumulation stages are the most sensitive to water-stress conditions. Furthermore, the efficiency of irrigation is very low, since less than 65 % of the applied water is used by the crops. In order to overcome water shortage in agriculture it is essential to increase the water use efficiency and to use marginal waters (reclaimed, saline, drainage) for irrigation.

Considering the above, but also the economic, social and environmental role of olive cultivation in the Mediterranean countries, the challenges for both research and technology are among others to improve the sustainability and competitiveness of olive cultivation in terms of water management and adaptation to climate change. The research with the study, evaluation and highlighting of existing rich varietal potential of the olive in terms of resistance to drought, salinity and cold requirements in relation to the quantity and quality of the olive oil produced. Technology with innovative practices will increase the efficiency of fresh irrigation water - more per drop-, but also the utilization for irrigation of low quality waters (saline, treated and drainage water). Rainwater harvesting and storage techniques can play also a crucial role in sustainable irrigation practices, particularly in regions where rainfall is erratic or insufficient.

Research and technology the last decades have developed innovative irrigation techniques to improve irrigation efficiency in drought-affected olive orchards. More important are:

-   The shift from the gravity irrigation to modern pressurized networks. Drip irrigation improve conveyance efficiency, deliver water directly to the root zone of olive trees and saves water and energy by reducing losses from tree transpiration, evaporation and surface runoff. Its efficiency can reach 95% compared to 50-60% of traditional irrigation (furrow, basin, ect.).

-   The application of deficit irrigation (DI) technique, i.e. the irrigation below full-water requirements by eliminating irrigations that have little impact on yield, aiming at the maximum production per unit of water applied. Such techniques include deficit irrigation, partial root drying and subsurface irrigation and can save up to 30% irrigation water. The adoption of deficit irrigation implies appropriate knowledge of olive response to water deficits at the critical growth stages and need support to be implemented.

-  The application of fertigation, i.e. the application of fertilizers and agrochemicals though the irrigation system. It ensures precise amount at the olive root system, optimum

conditions for use, high fertilization efficiency, flexibility in timing of fertilizer application while minimize environmental pollution.

-  The use of precision irrigation technologies, like GPS, soil moisture sensors and remote sensing, which allow farmers to tailor their water and nutrient applications to the specific needs of different parts of their fields in real time, optimizing input use and crop yields.

-    The artificial intelligence (AI) and machine learning algorithms can also play a significant role in improving water efficiency. By integrating diverse data sets, from soil and weather conditions to olive characteristics, water quality and availability, irrigation system and mulching etc, these algorithms can provide farmers with sophisticated decision support tools. The decision (how much water and when to apply) is communicated to farmer’s smart phone and/or directly to smart electrovalves for irrigation.

-   The use of satellite imagery and drones on large olive groves can provide detailed information about olive health and water needs, enabling precise and timely interventions. This not only improves water and nutrient use efficiency but also enhances pest and disease management, further boosting olive productivity.

Besides, agricultural practices are related with the sustainable water management in olive culture and protection of the environment. Such practices are:

-  Recycling pruning material and olive fruit processing residues either directly as mulch and nutrition material and/or after composting to increase soil organic matter content.

-  Increasing CO2 capture from the atmosphere through photosynthesis and ‘storage’ it in plant tissue and soil by modification the olive tree pruning to reduce transpiration and the olive groves flora using natural vegetation or producing green soil cover cutting its biomass periodically and left on the ground.

-   Applying on olive groves little or zero tillage to minimize erosion and destruction of organic matter improving the soil water storage capacity.

The successful implementation of above technologies and practices often requires supportive policies, research and development, farmer training, and community engagement. Governments, agricultural extension services, research institutions, technology companies and farmers themselves all have crucial roles to play in adopting and advancing these technologies. Both, technological advances and agronomical practices can save irrigation water up to 40% compared to full irrigation without substantial reduction of the yield.