How much oil does an olive tree produce?

In our case and with the data we have from the last 10 years, the amount of oil produced by an olive tree is around 5 to 10 liters.

So when you pass through a landscape of olive groves you quickly get an idea of how each olive tree produces on average one and a half of the typical 5-liter bottles that you see in the stores.

What does the amount of oil produced by an olive tree depend on?

An olive tree produces more or less oil based on the following parameters:

• age and size of the tree crown
• whether the olive tree is rain-fed or irrigated
• the weather conditions during the year
• the cyclical yield
• agronomic care: fertilizers, treatments and pruning

Let's detail them a little.

Age and size of the crown of an olive tree (for example in traditional or intensive olive groves)

When an olive tree is planted, it does not begin to produce fruit immediately. Olive seedlings usually have a height of one meter when bought in the garden center, just enough so that they can be attached to a stake and a protector can be attached to prevent rabbits from gnawing the trunk.

Obviously, this plant does not produce olives. You have to wait until the tree is 4 or 5 years old for it to produce olives. The farmer harvests the olives, even if in these years it is uneconomical, since leaving them on the tree would slow down its growth.

In these years, the farmer aims for the trunk to reach a free height without branches of at least 1 meter, so that in the future it can be accessed with a vibrating clamp for harvesting and to create three main branches from which to develop the crown of the olive tree.

An olive tree in a traditional or intensive frame can reach its maximum level of production between 15 and 20 years, depending on the availability of water, the absence of diseases and severe frost, and the correct and sufficient administration of fertilizer.

Regarding the size of the crown, it is limitated by the available space, which depends on the planting pattern.

In traditional olive groves, with a density of less than 200 trees per hectare, the olive trees are more widely spaced, and are usually larger trees, and therefore the amount of oil that each olive tree can generate increases with respect to whether it is an intensive or super-intensive olive grove.

In these traditional olive groves, the limiting factor was not, or isn't, space, but rather the availability of water, especially in dry land.

In intensive olive groves, with densities between 300 and 400 trees per hectare, the development of the crowns is limited by the neighboring olive trees, so the amount of oil generated per tree is less than that of a traditional olive tree.

Another issue is the production of oil per hectare. In all cases, intensive olive groves usually produce more oil than traditional ones.

Irrigated or rain-fed olive trees

Although the olive grove has traditionally been a rain-fed crop, and the olive grove produces fruit in conditions without excessive drought, the irrigation of an olive grove produces an increase in the amount of oil that an olive tree generates.

In order to maximize the effect of irrigation on the harvest in the traditional way, it has been considered to let irrigation replace the lack of spring and autumn rain in dry years and extend the rainy season in those years when the rain otherwise falls sufficiently. That is, extend the spring to May and June.

Extending the rainy season in the fall would not have much effect because it is harvest season and could be counterproductive. This is because in October the veraison of the olive begins, the transition from green to purple color. When this process begins, the generation of oil inside the olive (lipogenesis) stops, so any supply of water to the olive tree results in an increase in water in the fruit. This aspect can make it difficult to extract the oil in the oil mill.

Weather conditions

In this case the conditions are varied. Apart from the contribution of water, either by irrigation or rain, the main conditions are the following:

• The absence of severe frost in winter and especially late spring frost. The latter is the most harmful to production because the new stems, responsible for future harvests, have already been developed and a late frost easily damages them.
• The temperature during flowering. The olive tree is in bloom in mid-May. Too high temperatures cause the flowers to wither, thus significantly reducing the number of future olives.

Cyclical yield

The cyclical yield is a very typical phenomenon in the cultivation of the olive grove. The Spanish term "vecería" refers to the break that an olive tree naturally takes after a large fruit production. That is, a large olive harvest one year is usually followed by a low production the next because the olive tree is exhausted.

As such, "vecería" can be translated into cyclical yield, where the harvest is good one year, and not the next.

We have always thought that the alternate bearing was due to traditional forms of agriculture, in which the harvest was delayed to achieve the highest fat yield, and that this delay meant that the olive tree could not recover in time. This coupled with a deficit of nutrients for the formation of the fruit, especially phosphorus.

However, we began to think that the cyclical yield, although attenuated with modern agricultural management, is inherent to the crop.

Agronomic care

In this section, we look at proper use of fertilizers and treatments.

However, it deserves a special remark about controversial and strange pruning.

Olive pruning is always an interesting topic to discuss among farmers because it is so subjective.

There are many types of pruning, crown pruning, maintenance pruning, rejuvenation pruning and basically any adjective you can think of.

Pruning is essential to optimize all the resources contributed to the olive grove in the production of olives.

The overall objective of pruning is the creation of an orderly, ventilated tree crown that receives sufficient sunlight for the correct development of the largest number of fruits.

The strategies and ways to achieve this goal are found in any teacher booklet, although criteria and visions are gradually reconciled.