Olive tree growing deals with a tree of great historical, economic and environmental importance, which is why it is deeply rooted in the traditional habits of every producer.
The organic cultivation of olive tree is based on methods of rejuvenation of the olive tree grove soil, the recycling of by-products and other available organic materials and the reproduction and protection of the natural environment.
It is the method of olive production that aims to produce an excellent quality olive oil (meaning extra virgin olive oil), free from pesticide residues, which undermine health, and reduces contamination of soil, water and air.
It also contributes to the preservation of the diversity of valuable plants of the area, wild animals and genetic material of the olive tree.
Creation of an organic olive tree grove
Suitable location: Before creating or setting up a new organic olive tree grove, it is necessary to study and take into account the soil-climatic conditions of the area.
Locations with limited sunshine, long periods of shading and frost-affected areas should be avoided as much as possible. Coastal areas and areas with cool weather and high relative humidity, especially during the summer and autumn months, should not be preferred, because such areas favour high infestations from Olive fruit fly (Thakos (Δάκος) in Greek).
It is also very important the principle that the location where the organic crop will be planted should not be affected or neighboured by conventional olive groves. In a sloping location protection measures must be taken against the transfer of rainwater from conventional olive groves or other conventional crops.
Also, if possible, the plantation should be isolated with a tall natural windbreaker, so that it is not affected by spraying that will be carried out in conventional olive groves or other crops.
Selection of soils and measures for their correction
The main concern of every olive tree grower is from the beginning of the conversion or planting of the organic olive grove to do all those actions to significantly improve the physical and chemical properties of the soil for normal nutrition and growth of trees.
We must keep in mind that the soil is a living organism with a number of important biological processes that in turn can feed the olive trees. Heavily used and damaged soils, with a limited concentration of organic matter, do not help the olive trees to grow and perform satisfactorily. Boring and cohesive soils that retain enough moisture cause rotting in olive trees and reduce or inhibit the prevention of various nutrients.
Soils poor in organic matter are corrected, either by adding organic matter or animal manure or by applying green fertilizer, which is done by incorporating in the soil a mixture of legumes (vetch, broad beans, peas, etc.) with grass plants, with the aim of increasing organic matter and nitrogen.
Green manure is the cheapest method due to the advantages it provides both to the ecological system (non-dependence on the imported expensive system of organic matter), but also in terms of cultivation (competition with some weeds, etc.).
Also, the addition of organic matter to the soil improves its structure, makes it easier to cultivate the soil from agricultural machinery and allows better absorption and retention of moisture.
Olive grove installation and varieties
The olive trees of the organic olive grove must be planted at regular distances. Dense planting does not help their normal ventilation. In sparse planting, the entire area of the land is not economically exploited.
Olive trees are preferred to have a trunk of normal height to facilitate the necessary cultivation care and normal ventilation. The most suitable varieties for organic farming are considered to be those that are resistant to pests and diseases and are adapted to the soil-climatic conditions of each region.
Varieties grafted on wild olives show resistance to soil diseases and develop a large root system. The olive varieties 'Koroneiki', 'Ladoelia' and secondarily 'Picual' show considerable resistance to enemies and diseases.
Nutritional requirements of olive trees:
Significant amounts of the main nutrients of nitrogen, phosphorus and potassium are removed from the olive grove every year due to the needs of the plant for vegetative growth and production. It is natural that when the quantities removed are greater than those available there will be a reduction in production unless these elements are supplemented.
The amount of elements to be added to the soil of each olive grove depends on the type of soil, the available stocks, the cultivation practice followed (pruning, irrigation, etc.) and the production of the year. Consequently, it is not possible for anyone to come up with an ideal fertilisation strategy that applies to all conditions, but it can single out some general guidelines. The most important parameter is always the nutritional requirements of the crop, in this case the olive.
The first concern is to replenish at least the nutrients removed by harvesting and pruning. It has been found that on average 100 kg of olives remove from the soil: 0.9 kg Nitrogen (N), 0.2 kg Phosphorus (P), 1.0 kg Potassium (K) and 0.4 kg Calcium (Ca).
An amount of nutrients that are trapped in the soil, in non-digestible form (mainly in Phosphorus and Potassium) or even lost by rinsing to the lower layers of the soil, mainly in Nitrogen, must be taken into account. Fertilization methods The fertilization of the organic olive grove aims at the improvement of the soil productivity and the strategy that ensures long-term improvement of the texture and structure of the soil along with the increase of its fertility.
Olive fertilization should be based on a program to maintain and rejuvenate the soil of the olive groves. This program is mainly based on the application of the method of green fertilization with legumes, grasses or mixtures, the addition of compost from organic materials, as well as the addition of animal manure, which necessarily comes from animals primarily organic or even extensive breeding.
Organic fertilization: An economical and practical way of fertilizing the organic olive grove is the preparation of compote using the plant residues of the olive grove with manure from organically or extensively farmed animals.
One way to make organic compote is to use olive leaves from olive mills along with about 10-20% of sheep and goat manure. The construction of this type of organic compote costs money, so it is usually used in the first 3-4 years of conversion of the olive grove into organic. In the following years, olive leaves and other plant residues can be used together with 20-40% oil extracts from the tanks of the oil mills.
It is well known that mill waste has a good content of various nutrients, organic matter and microorganisms. The best time to place the compote is immediately after harvest. For every tenth, an average of 2 cubic meters of compost is recommended. The fertilization is supplemented with the integration of the natural vegetation of the olive grove, with the integration of the leaves and branches up to 5 cm thick that are crushed by the cultivation, with the use of special mechanical tools-crushers, as well as with the use of the effluents of the olive mills.
Part of this article can be found on gargalianoionline.gr (News from Messinia on time)