It was once believed that the olive tree suited poor, dry soils and could yield where other tree crops struggled. That is only partly true. The olive tree gives stable, high yields for many decades on fertile soils with adequate moisture, and sound nutrition is what supports those yields.
Check the soil before fertilizing
Before any fertilization program, the soil's physical properties and fertility are assessed, as they govern nutrient uptake. Two key parameters are pH and calcium content, because both affect the absorption of several elements. The optimum pH for the olive is around 6.5, although the tree performs well in soils with pH from 5.5 to 8. In acidic soils, adding lime before planting raises the pH, but only after analysis and in consultation with an agronomist. Nutrients the olive tree needs
From leaf analysis, indicative lower sufficiency limits are about 1.5% for nitrogen, 0.1% for phosphorus, and 0.5% for potassium. Nitrogen is the most important element for both oil and table olives, as it supports vegetation and production. Its deficiency shows as short annual growth and small, pale leaves that fail to turn deep green. Whenever a deficiency is diagnosed, the fertilization program is drawn up with an agronomist.
A season-by-season program
In practice, fertilization follows three phases. Base fertilization is applied in the winter months, from December to February, with a compound fertilizer such as 11-15-15 or similar, ideally just before rainfall so it is incorporated into the soil. As common practice, roughly 2 to 5 kg are applied per adult tree, depending on age, size and soil analysis, within a radius of about 60 to 90 cm from the trunk and never against it. In spring, where needed, a surface nitrogen application supports flowering and fruit set. Rates are also adjusted to alternate bearing, the difference between productive and off years, so the tree is not overloaded.
The role of organic matter
Organic matter, especially as humus, improves soil structure and texture, buffers pH, retains moisture, activates soil microorganisms, and increases nutrient uptake. Organic fertilizers, therefore, often form the basis of a rational program. In autumn, manure can be incorporated into the soil. In non-irrigated groves, many growers add about 10 to 20 tons of manure per hectare every two years, while in irrigated groves this is spaced out to every 3 to 4 years. Here, too, each field differs, and soil management is adjusted after analysis.
Calcium, magnesium and boron
In the calcareous soils that dominate the olive-growing Mediterranean, calcium deficiency is rare. Chlorosis in such soils is more often caused by limited iron availability at high pH than by a shortage of calcium. Any calcium or iron correction is made only after soil analysis and with an agronomist, so that an existing iron deficiency is not made worse.
Magnesium and boron are also important for fruit development. Magnesium is the central component of the chlorophyll molecule, while boron plays a decisive role in fruit set and in the transport of sugars. When a deficiency is found, foliar fertilizers are applied, with boron usually given before flowering.
All of the above are general guidelines and common practices. Every grove is different, so the fertilization program is built on soil and leaf analysis and in consultation with a licensed agronomist.
1.) Olive Tree Information & Uses
3.) Are Olive Farms profitable?
4.) Olive Tree Alternate Bearing
5.) Olive Tree Propagation & Pollination
6.) Olive Tree Climate - Temperature Requirements
7.) Olive Tree Soil Requirements
9.) Olive Tree Fertilizer Requirements
10.) Olive Tree Water Requirements
13.) Olive Trees Diseases and Pests
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