Crop Management
Establishment of the
Plantation
Before deciding to grow avocados, it is necessary to take into account certain parameters and to carry out certain suitability checks on the plot of land.
The research nature of the Project lies in the production of a unique Greek Provencal Avocado Plantation, for the production of certified propagation material for distribution to nursery companies, with the final recipients being the producers.
- Topographic suitability of the plot
- Check for lower winter and spring temperatures from nearby weather stations. Frequent winter or spring frosts mean an unsuitable plot of land.
- Check for a permanent source of moisture within the field, or for the presence of pathogens from a previous crop. In these cases, the field must be cleared and left fallow for at least one growing season.
- Soil and irrigation analysis, and verification of results by an experienced agronomist.
- Selection of varieties and rootstocks suitable for the field, based on previous test and analysis results.
- Selection of planting distances depending on the intensity of cultivation, the producer's capabilities and the machinery available. The selection of planting distances is a decision of the producer, but it has been proven that denser plantings produce greater quantities of fruit. An efficient production unit consists of at least 50 plants/acre (4x5 m spacing).
- Choice of planting shape (squares or rectangles)
- Ground preparation including
- Removal of weeds with pre-emergence herbicides or mechanical means, and removal of previous crop residues
- Light plowing up to 30-40 cm of soil. We avoid deeper plowing, because it inverts the soil, which is usually less fertile.
- Addition of organic matter, especially in case of low concentration, depending on the results of the soil analysis.
- Milling to incorporate organic matter, leveling and compacting large lumps
- Creating "embankments", especially in fields with drainage problems, for better aeration of the root system
- Installation of an irrigation system and immediate irrigation after planting
Επιλογή Κατάλληλων Υποκειμένων & Ποικιλιών
Choosing the right rootstocks and varieties is a critical step in successful avocado cultivation, as it affects yield, disease resistance, and growing conditions. Rootstocks are selected based on their soil adaptability, resistance to soil pathogens and their efficiency in nutrient uptake. There are many choices between seedling & clonal rootstocks.
After many years of research, rootstocks with specific characteristics have now been created, suitable for adapting to different requirements, such as tolerance or resistance to cold, diseases, salinity, the creation of low trees, etc. The selection must be made carefully, based on the needs of each producer, the microclimate of the installation area and the conditions of the plot.
The maintenance of these characteristics in rootstocks is carried out exclusively by vegetative propagation, so they are referred to as Clonal rootstocks (Figure 1), in contrast to Seedlings, which may also be resistant to conditions such as cold. Any use of seeds (seeds) for the creation of seedlings will lead to variation and differentiated characteristics, compared to the mother plant. In Greece, bacon and zutano are used as seedling rootstocks. Clonal rootstocks are currently supplied by nurseries abroad.
The most common varieties are Hass, which dominates the market due to its high quality, Fuerte, with a balanced flavor and early production, and Zutano, which is preferred for its resistance to colder climates. The selection is made based on the region's climate, soil type and market demand, thus ensuring the maximum possible productivity and fruit quality.
Διαχείριση Άρδευσης & Λίπανσης
Water management during flowering can be critical for fruit production, as there is an increased demand for water. Also, the rapid fruit development phase is the second critical period for irrigation. During this period, effective irrigation management reduces fruit drop and increases final fruit size. At this stage of development, it is also recommended that irrigation intervals be shortened, especially in summer, to ensure maximum fruit size.
In general, when watering avocados, we should keep in mind that:
- No more water should be applied than is necessary to keep the soil in the root zone moist (avoiding root asphyxiation problems, with the development of fungal diseases, especially in areas with poor drainage)
- Applying too much water can lead to increased rates of water and nutrient leaching below the root system.
- In cases of shallow soil with poor drainage, the amount of water in each watering should be small, as major damage may occur, even drying out of the trees.
- In spring, if the soil still has enough moisture, watering should not begin early, so that the soil warms up more easily, so that there is no delay in the start of root activity.
- In soils that have slightly more salts than normal, and have good drainage, each watering should be done with more water to flush out the salts.
As the plants begin to enter production, we gradually reduce the proportion of nitrogen (N), limit the application of phosphorus (P) and increase the application of potassium (K). The total amounts for each element are determined by the results of soil and leaf analyses, as well as the size and productivity of the trees. It is indicated that for the production of 1,000 kg of fruit, 4.5 kg of nitrogen, 0.8 kg of phosphorus and 6.5 kg of potassium are removed, which must be replenished. As a general rule, the ratio of application of the three elements to adult trees of high productivity, as suggested by the literature, is: N:P:K = 2:1:4. However, for trees with the usual productivity they have when cultivated in Crete, a more realistic N:K ratio is 1:1.5.
Οι παραγωγοί μπορούν να παρακολουθούν τις οδηγίες για άρδευση που ανακοινώνει η Περιφέρεια Κρήτης σε συνεργασία με το Ινστιτούτο Ελιάς Υποτροπικών Φυτών & Αμπέλου του ΕΛΓΟ-ΔΗΜΗΤΡΑ, μέσω των εβδομαδιαίων δελτίων.
Μια πρωτοποριακή online πλατφόρμα για την άρδευση ακριβείας, ελεύθερης πρόσβασης για τους παραγωγούς, δημιούργησε το Ινστιτούτο Ελιάς, Υποτροπικών Φυτών & Αμπέλου του ΕΛΓΟ ΔΗΜΗΤΡΑ σε συνεργασία με το Ινστιτούτο Μεσoγειακών Σπουδών, το Πολυτεχνείο Κρήτης και το Ελληνικό Μεσογειακό Πανεπιστήμιο.
Η online πλατφόρμα, η οποία είναι ήδη σε λειτουργία, δίνει πληροφορίες για κάθε αγροτεμάχιο σε όλη την Κρήτη (καλλιέργειες ελιάς, εσπεριδοειδών, αμπέλου και αβοκάντο). Συνδυάζει καινοτόμες τεχνολογίες, όπως, τεχνικές γεωφυσικής & δορυφορικής τηλεπισκόπησης, μετρήσεις πεδίου, μετεωρολογική πληροφορία, βάσεις δεδομένων αγροτεμαχίων του ΟΠΕΚΕΠE, καθώς και μοντέλο αρδευτικών αναγκών.
Pruning
Pruning seeks to create trees of moderate vigor and relatively low height, with the aim of facilitating cultivation operations and reducing their costs.
When pruning, certain rules must be applied. Dense, rubbing, weak and diseased shoots are removed. In long branches, a top should be made and all shoots touching the ground should be removed.
Fruit pruning is one of the biggest expenses in cultivation, but it is absolutely essential for maintaining healthy trees, increasing fruit size, preventing leaf loss and tree exhaustion, and controlling self-fertilization. It should be done every year and includes:
- Thinning of flower buds (early)
- Thinning inflorescences (spring)
- Fruit thinning (in small-fruited varieties)
Special attention is needed during severe pruning to avoid putting the tree at risk of sunburn, and in any case, it is recommended to apply a special paste to the cuts to prevent the development of diseases.
Έλεγχος Εχθρών & Ασθενειών
Avocado cultivation faces challenges from various animal pests and diseases, which can affect yield and quality of production.
Animal Enemies: Climate change and the movement of propagating material have led to the emergence of new enemies, such as the ‘Ambrosia’ fungal-insect complex. These enemies can cause serious damage to avocado trees, affecting their health and productivity. The lack of an organized system of sampling and warnings makes it difficult to deal with them in a timely and effective manner, often leading to irrational use of chemicals by producers.
Diseases: Avocado diseases in Crete include fungal, bacterial and viral infections that can affect various parts of the plant, such as the leaves, fruits and the root system.
The initial control of the crop for pests and diseases is carried out by the producer. If anything concerning is detected, he should inform scientists from the competent bodies (DAAK, ELGO DIMITRA, etc.).
Avocado Harvesting Criteria
The avocado fruit must meet certain criteria before it can be harvested. The ripening guide used so far is:
1. Regulation 831/1997 of the European Union as amended and in force by Regulation 387/2005 laying down the marketing standards applicable to avocados – which states as a minimum dry matter content to ensure the ripening process
- 21% for the Hass variety
- 20% for the Fuetre, Pinkerton, Reed and Edranol varieties
- 19% for other varieties except the Antilles which are allowed to have a lower dry matter content.
The oil content of the fruit, which, according to bibliographic sources, must exceed 8%.
Fruits harvested before reaching the limit of normal maturity cannot ripen normally post-harvest, do not acquire the desired organoleptic characteristics and do not satisfy consumers.