Orange cultivation.

»Orange tree plantation

·When are orange trees planted?

The best time of the year to plant orange trees is in spring, when there is no risk of sudden frosts, usually between April and June.

·How are orange trees planted?

Currently, the most commonly used planting frame for this type of tree is 6×3, which allows the fruit to be harvested using specialised machinery and facilitates pruning.

Edaphoclimatic requirements

·Soil

Orange trees prefer soils of medium consistency (sandy or sandy loam texture), well drained, deep and fertile, with a pH between 6 and 7.

It is important to note that a proportion of more than 50 % clay in soils significantly affects root growth. In addition, they do not tolerate salinity.

·Climate

The orange tree is a subtropical species and therefore does not tolerate frost. It is not very cold hardy and does not require chilling hours for flowering. In addition, during the summer it needs warm temperatures for the correct ripening of the fruits.

Besides, it is a tree that requires a lot of rainfall, which must be supplemented by irrigation in the event of insufficient rainfall.

• Orientation on the plot

The orange tree should be planted facing the sun and sheltered from the wind. It is a tree that requires a lot of light for the flowering and fruiting processes and is very sensitive to wind, and may suffer fruit loss due to vibration transmission.

»Care requirements for the orange tree

·Soil preparation for orange tree cultivation

Soil preparation for orange trees consists in:

• Eliminating weeds
• Aerating topsoil
• Incorporating fertilisers or organic matter
• Increasing water retention capacity
• Preparing for flood irrigation.

The soil is tilled 3-4 times a year, between March and September. The rest of the year, the soil is maintained with a vegetation cover.

·Orange tree irrigation

Orange trees need a lot of water between spring and autumn. Generally, watering is done every 3-5 days if localised irrigation is used or every 15-20 days if flood irrigation is used.

Nowadays, in-ground drip irrigation is commonly used, which optimises irrigation and improves the efficiency of nitrogen fertilisation. In addition, this irrigation system reduces the evapotranspiration of the crop.

• Orange tree pruning

The orange tree has a ball-forming habit and production on the periphery. For this reason, they are pruned in order to lobulate the shapes (make them protruding) to improve the light reaching the surface and thus increase production.

However, training pruning is very controversial. As an evergreen species, orange trees accumulate reserves in the branches, shoots and leaves, and when pruning is carried out, the harvest decreases proportionally.

Some authors recommend pruning every year while others recommend pruning every 3-4 years to clean the centre of the tree.

» Necessary nutrients for the cultivation of orange trees

The main nutrients that orange trees need are:

Macronutrients

• Nitrogen: It’s an essential element for growth, flowering, productivity and fruit quality.

• Phosphorus: It’s involved in the metabolism of sugars and nucleic acids and in the plant’s energy processes.

• Potassium: It’s essential as a coenzyme and in protein synthesis, photosynthesis and carbohydrate metabolism.

• Magnesium: It’s constituent of the central atom of the chlorophyll molecule.

• Calcium: Most of its activity is due to its coordination capacity, as it is able to establish stable and at the same time reversible bonds between molecules.

• Sulphur: It’s a key in protein synthesis as it is an important component of some amino acids and coenzyme A.

Micronutrients

• Iron: It’s essential for photosynthesis and respiration.
• Zinc: It’s involved in various enzymes.
• Manganese: It’s involved in the activation of numerous enzymes.
• Copper: It enables enzyme bonds in redox reactions.
• Molybdenum: It’s involved in atmospheric nitrogen fixation and nitrate reduction.

The deficiency or insufficiency of any of these mineral elements can negatively affect the development and productivity.

Fertiliser for orange trees

• What fertilisers does the orange tree need in its cultivation?

As we have already seen in the previous section, the main components that orange tree fertiliser should contain are nitrogen, potassium and phosphorus.

Citrus trees generally require large amounts of fertiliser, which accounts for a large part of the costs. In addition, orange trees often suffer from deficiencies, especially magnesium and zinc.

For the organic cultivation of orange trees, organic fertilizers will be applied, such as manure, compost or earthworm humus, as well as those formulated based on algae, minerals or other natural elements.

Some of the fertilizers recommended for growing orange trees in Fervalle are Calbomix, Siapvalle or Missvalle.

Calbomix is a formulation rich in nitrogen, calcium, magnesium and enriched with micronutrients with a high greening power in the crop. Its advantages include:

• It favours the correct development and fattening of the oranges
• It increases production
• It increases the post-harvest preservation of fruits
• It’s an excellent corrector of micronutrient deficiencies
• It participates in cell division, strengthening the cell wall, during the fruit formation process

Siapvalle is a bio-stimulant rich in L-amino acids of animal origin Its functions include:

• It provides energy to trees
• It increases the production, caliber and homogenization of the harvest
• It chelates soil nutrients and transports them from the roots to the most apical areas

Missvalle is a blend of essential microelements (magnesium, manganese, molybdenum and zinc). Its benefits include:

• It supports nitrogen uptake and chlorophyll synthesis
• Synthesis of phytohormones
• It provides necessary nutrients
• It promotes sprouting
• It improves flowering, fruit set and fruit development

»Orange harvesting

Harvesting oranges is usually done manually with the help of pliers. It is done when the oranges present:

• Soluble solids/acidity ratio of 8 or more and yellow-orange color on at least 25% of the fruit surface
• Soluble solids/acidity ratio of 10 or more and green-yellow color on at least 25% of the fruit surface