The Objectives of Pruning
By Marcelo Berlanda, Agronomist & Consultant for The Olive Centre
“It is a fact that to produce fruit, olive trees need to grow and produce new branches each year”
Training helps give the tree the optimal shape to allow for efficient harvest as well as achieving early crops.
Once the trees have reached their optimum canopy volume for the environmental conditions of the area, it is likely that the yields could start declining. This is due to the fact that the inner part of the canopy does not receive sufficient sunlight, which causes defoliation, resulting in a low Leaf to Wood Ratio.
If the tree grows above its optimum size, it creates serious issues for the harvester machines. The tree becomes too high and too wide for the machines, it has thick branches which can cause damage on the picking heads and also reduces removal efficiency of the machine as well as slows down the overall harvesting speed.
It is a fact that to produce fruit, Olive trees need to grow and produce new branches each year; therefore the trees need to grow every year. It is here where pruning becomes a very useful management tool.
Pruning helps increase Fruit Size, Oil Yield, Light Interception, and Leaf to Wood ratio, it promotes new growth and reduces water and fertiliser requirements.
1- Tree Training
Objectives: Achieve early start of production with higher yields, an increased number of production years, higher fruit quality, prepare the trees for the type of harvester that is going to be used on the grove.
Timing: training takes place during the first 3 years of tree life.
During the first year minimum pruning is required (provided the trees come with a suitable shape from the nursery), lower and vigorous branches competing with the leader should be removed. The aim is to encourage a straight vertical trunk with horizontal branches coming out. Water shoots must be removed to stop competition for water and nutrients.
On the second and third year the aim is to remove lower branches below 600-700-800-1000mm (must be done gradually)
There must be a balance between what is taken out and what is left on. If we remove too much canopy, we have a negative effect on the tree, because we are removing photosynthetic area setting the tree back for a while until it starts growing again.
Light pruning is a process by which we only take a small amount of foliage (a couple of small branches), therefore we are not affecting tree balance. That is why it can be done from August until the end of May.
Heavier pruning in this process we take large amounts of foliage therefore we are promoting a stronger reaction from the tree, this makes it susceptible to frost damage. That is why we should be delaying it until the end of September unless the weather is warmer. If that is the case we could start at the beginning of September.
Tree training not only involves light and heavy pruning but also tree tying and skirting.
This type of pruning is performed on mature trees once they have reached full size. It has the aim of balancing the tree to obtain uniform and constant production every year.
As we know when trees are young there is a larger number of non-productive branches and that is because those branches are actively growing, but once they have reached their potential, they stop growing and start producing fruits, after a while, those branches are exhausted and they stop producing, therefore they should be removed, to encourage new growth and renew the tree.
If bloom is light, pruning can be confined to non-productive parts of the tree, preserving as much bloom and potential crop as possible. In years of heave bloom, pruning can be more severe without excessive crop removal.
Time of pruning: bud break until early December.
3- After Harvest (Cleaning)
The aim is to clean up the large broken branches that are left after the harvesters have gone through the grove. We could avoid it by spraying the trees with copper after harvest and wait until spring to take the damaged wood out.