Olive oil ecological production criteria constitute the main topics, included in the management cycle of an olive orchard during the cultivation period, which are based on the protection of the environment and natural resources. The aim is to combine economic yield of the crop with the health of the producers and consumers, ensuring at the same time the quality of life of next generations.

Below is a concise list of ecological olive oil production criteria, some of the basic characteristics of which are described concisely later on.

1. Selection of propagation material

The vulnerability of an olive cultivar to enemies or diseases, to which a particular area is prone to, should be taken into consideration when setting an orchard, as it will inevitably result in increased cost of crop control, greater burden of chemicals and downgrading of the quality of the products. Furthermore, the use of healthy propagation material is obligatory.

2. Soil management

A decrease in the frequency of cultivation on sloping soil and the preservation of vegetative cover will result in the protection of the soil from erosion and the increase in rainwater infiltration. Tillage is recommended once a year (usually late in the winter).

No-tillage combined with mowing or chemical weed control is encouraged; where this is not possible, reduced mechanical soil tillage is recommended.

Tillage in strips on sloping areas is recommended to be used in the autumn once a year, whereas the vegetative residue should be either destroyed by herbicides or incorporated in the soil, early in the spring before it begins antagonizing the crop for water and nutrients.

Fig. 1. Different soil management systems

An important measure against erosion is the construction of terraces along the contour lines or the maintenance of old terraces that already exist in many olive orchards. (Fig.2).

Fig.2. Terraces in an olive orchard

3. Nutrients and irrigation water management

Securing nutrients and fertility of the soil in Environmentally Friendly Management Systems is achieved by applying organic fertilization (manure, compost, vegetative residue, green manure etc) or by the use of chemical fertilizers as little as possible, depending on the particular characteristics of every region.

Within the framework of Environmentally Friendly Management of olive orchards, the following measures are proposed:

• Soil analysis & plant diagnosis prior to fertilization.
• Tillage & use of compost made from vegetative residue, olive leaves, animal manure etc, for the preservation and improvement of the organic matter and the soil fertility.
• Green manure and vegetative residue incorporation in the soil.

Green manure is mainly made from leguminous plants such as clover, broad beans, vetch etc. However, it can also be made based on a crop rotation programme that includes leguminous and graminaceous plants. The selection of the species included in the crop rotation programme is based on the soil type and the climatic conditions. Crop rotation with leguminous plants constitutes one of the oldest methods of natural fertilization of a field with nitrogen.

The efficiency of irrigation in Environmentally Friendly Management Systems requires rational use of water resources and can be increased by proper programming of irrigation according to the real needs of the olive trees.

Drip irrigation must be applied where deemed necessary, whereas it is also deemed necessary to examine the possibility of applying deficit irrigation. Deficit irrigation is a technique to save water without significant losses in production, by which plants develop under a minimum supply of water, either for a specific period of time or during the whole cultivation period, and yields are slightly smaller.

4. Pruning

The proper pruning of trees contributes in maintaining the crop’s yield, good status of health and a decrease in the risk of the development of diseases and therefore in the use of pesticides.

The shape and the size that are given to the trees are dictated by the cultivar, the climatic conditions, the soil type, the cultivation technique that is applied, the harvesting method etc.

5. Crop control

High inputs of agrochemicals have led to important problems such as environmental stress (biodiversity, soil pollution, water contamination etc.)and to the presence of residue in products.

The control and successful management with insects and other pathogens in the olive crop, can be made with ecological management and combination of cultivation practices with integrated control, when this is necessary (ecological insect traps, pheromone traps, beneficial insects, approved products for spraying, soil solarization etc).

A more systematic observation of the population of insects through an appropriate network of traps and use of approved pesticides with fewer side-effects to the environment, constitute strategic choices in the upgrading of the efficiency and the decrease of risks to human health and ecosystems. The use of selected pesticides.

6. Protection of biological balance and preservation of the biodiversity of agroecosystem

Very often, fires are set in pastures in order to renew the biomass, putting in danger the flora and fauna of those areas. High density of grazing during the summer when vegetation is limited favours the further decrease in vegetation cover, thus increasing the risk of erosion and desertification.

Moreover, overgrazing can lead to a drastic limitation and also the extinction of certain vegetative species from the area, downgrading biodiversity and upsetting the biological balance of the ecosystem.

The preservation of natural vegetation around the margins of farms or in the dry stone-walls contributes in the indirect protection of olive trees from polyphagous insects. Olive trees constitute secondary hosts to these insects and are damaged by them mainly in intensive management systems, where total herbicide control is applied, which results in the extinction of primary hosts.

7. Olive mill wastewater

Evaporation in open evaporation tanks/ponds is the most common technique applied in Crete for handling pollution problems caused by olive mill wastewater, mainly because of its low cost of installation.

Also, after proper processing, liquid wastewater can become an excellent soil improvement amendment or can be used for partial replacement of fertilizers, due to their high bio load and nutritional value. Solid by-products of olive mill wastewater can be used for the production of fertilizing compost. Pilot units for the processing of wastewater have been built in many areas. There are many different methods to cope with this specific problem. However, the cost for their implementation has been a prohibitive factor for many of these methods.