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25 April 2023

What type of wooden posts are suitable for protection systems?

What type of wooden posts are suitable for protection systems?

In fruit growing, wooden posts are widely used. Especially for supporting fruit trees. Fruit trees, such as apple trees, pear trees and cherry trees, frequently need support to guide their branches and fruit to protect them from wind damage. Wooden poles are used as vertical support to keep fruit trees upright and guide them as they grow. Different types of wooden posts are used in fruit growing, depending on the size of the fruit trees, the desired height, the growing conditions and the type of fruit. Wooden posts are available in different types, treated or untreated. Only which wooden posts are suitable for a protecting system?

Wooden posts for fruit canopies

A hail protection system or a rain protection system is a system and as long as it stays up, it's good right? But why is it that every year reports reach us that many hectares of protection systems are going down? The climate is changing. Hailstorms and rainstorms are becoming more frequent and increasingly severe and grim. How prepared are you? Are you sure your system is strong enough? The strength of a fruit system depends on many different factors. The right distances between posts, the right anchor spacing and using the right materials are some of those factors. Therefore, in this article, we write which type of wooden posts are best to use in your orchard.

We have already written an article once about the difference between wooden posts and concrete posts. Click here to read it. 

hail nets on wooden poles

What is important when it comes to wooden posts?

In any case, it is important that wooden posts last longer than one cultivation round. This is what is needed with hail nets, rain caps and support. Important aspects with a wooden post are: Pressure force, Torsion (rotate), Bending/elasticity and the lifespan. And of course, there are suppliers who can offer guarantees on their wooden posts.

At have compared wooden posts from different suppliers for this blog on:

  • Mechanical resistance;
  • Penetration;
  • Retention.

Below in the table you can see the differences between the wooden posts. The C1 to C6 are the Carmo wooden posts. It is important to note that the Carmo wooden posts are always tested at their thinnest end and the other wooden posts at their thickest end.

testen van houten palen voor fruitoverkapping

Mechanical resistance wooden posts

Mechanical resistance in wooden posts refers to the ability of the wood to withstand external loads, forces or stresses without breaking, deforming or collapsing. This is a very important property of wooden posts as the wooden posts are used in a fruit canopy construction. The wooden posts must be able to cope with different loads and stresses.

The table below shows the tests done with wooden posts with 10 cm.

Results: In the mechanical resistance tests for diameters between 7.5 centimetres and 10 centimetres, Carmo's wooden posts averaged 30% more mechanical resistance!

The table below shows the tests done with posts from 10 cm upwards.

Results: In the mechanical resistance tests for diameters between 10 centimetres and 12 centimetres, Carmo's wooden posts averaged 46% more mechanical resistance!

Conclusion mechanical resistance wooden posts

If you want wooden posts in your orchard that can strongly withstand external loads, forces and stresses, it is best to choose Carmo wooden posts.

Penetration wooden poles

Penetration in wooden posts is, simply put, the treatment of wooden posts. Why is treatment of wooden posts necessary? Wood is biodegradable, which means food for insects, termites and fungi. Insects, termites and fungi that feed on the nutrients in the wooden post. The penetration or treatment extends the life cycle of the wooden post. The treatment also changes the wooden posts from non-durable to durable wood. Contact of the wooden post with the soil leads to faster infestation, especially in the critical/embedded zone (see photo below).

This zone is conducive to mould development due to: oxygen, humidity and temperature. You probably recognise it with old wooden posts breaking off at the soil line. This is why it is important that wooden posts are treated. In the tests, all piles were cut into discs (samples) and injected with Chrome Azurol. By injecting, the copper in wooden poles gets a blue colour reaction (see photo below).

Results: The Carmo wooden posts have much greater penetration. The inside turned much bluer after testing. The bluer the disc the better the treatment succeeded.

Additional comments/critical factors

In samples 1,2,5,6 and 7, it can be observed that the sapwood is not fully impregnated. And even cracks were observed in samples 2,5 6 and 7. Cracks are due to the wrong raw material, removal of bark during production and sanding correction to make the posts beautiful. By these things, you promote the entry and attack of woody insects resulting in premature infestation.

Conclusion penetration wooden posts

If you want wooden posts in your orchard that have been properly impregnated, it is best to choose Carmo wooden posts. Other wooden posts are not treated properly and thus may rot or break off prematurely.

Retention wooden posts

For wooden posts, there are different risk classes:

  • Risk class 1: Sheltered application of wood, protected from wind and weather and not exposed to moisture.
  • Risk class 2: Protected application of wood, protected from weather and wind, but with occasional high humidity that may lead to exposure to moisture.
  • Risk class 3: Unprotected application of wood, without ground contact. The timber is either permanently exposed to wind and weather or is protected against weather and wind but is regularly exposed to moisture.
  • Risk class 4: Application of wood in contact with soil or fresh water and therefore permanently exposed to moisture.
  • Risk class 5: Application of wood in permanent contact with salt water.

For fruit protecting systems, it is important that wooden posts are at risk class 4. This is because wooden posts in orchards are in contact with soil, fresh water and are permanently exposed to moisture.  It is therefore recommended that the minimum retention for risk class 4SP is 22.5 kg/m3.

Below you can see how the suppliers' wooden posts compare to risk class 4SP:

Conclusion retention wooden posts

Carmo houten palen (niet hier boven in het overzicht) hebben een gemiddelde retentie van 35 kg/m3. Dit ligt ver boven het aanbevolen niveau. De een hoge retentie van houten palen is dus een belangrijke factoor voor de duurzaamheid en levensduur van de houten palen/

So what type of wooden posts are suitable for fruit systems?

From all tests, Carmo wooden poles emerged as the best. Our advice is therefore to use Carmo wooden posts for hail netting, rain covers and fruit support. An additional advantage of Carmo wooden posts is the 20-year full warranty. There is often no guarantee on wooden posts, only Carmo can give a guarantee on its wooden posts. The warranty includes: A total replacement of the product due to rot in the first 20 years. Carmo wooden posts can be recognised by a nail in the head with the production date.

Curious about the story of Carmo wooden posts? Then read the blog series on our website. In that blog series, Carmo's entire production process is reviewed.

Rick Mudde - English

Rick Mudde

Product specialist fruit canopies

My mission is to help as many fruit growers as possible get a good harvest.

So that fruit damage can be prevented, no delivery problems occur, and fruit growers can harvest successfully!