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Independent.ie

Sunday 21 October 2018

Winter checks vital for long term prospects of your trees

Bad weather can take a toll on stocking density which in turn could affect grant payments, writes Steven Meyen

Severe phosphorus deficiency in Sitka spruce can also lead to low nitrogen availability in soils. Nutritional deficiencies can reduce stocking density. Photo: Teagasc
Severe phosphorus deficiency in Sitka spruce can also lead to low nitrogen availability in soils. Nutritional deficiencies can reduce stocking density. Photo: Teagasc
Steven Meyen

Steven Meyen

If your trees are only a few years old, go for a walk through your plantation now to check if any trees need replacing.

Trees may have died off for a variety of reasons. It is important to replace any failures during the current planting season to ensure the forest develops evenly and to avoid unnecessary maintenance later on.

Ideally, tree stocking density should be maintained as close to 100pc as possible to optimise future tree selection and quality timber production.

To receive the Forest Service (DAFM) second instalment grant after four years, at least 90pc of the trees should have developed well and be growing vigorously.

If the stocking density is too low, the Forest Service may delay or refuse the second instalment grant. Premium payments could also be affected.

Tree stocking density can be estimated using circular plots. A handy little trick is to place a stake in the ground and tie an eight-metre tape or string to the stake. Tighten the tape and walk around in a circle, while counting all live trees within this circle.

Checking tree stocking density in a young forest. Photo: Teagasc
Checking tree stocking density in a young forest. Photo: Teagasc

Count the number of trees within this eight metre radius circle, and multiply the result by 50 to estimate the stocking density on a per hectare basis.

Repeat this process in a few different locations to get an accurate, representative assessment.

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As an example; the required stocking density for a Sitka spruce plantation is 2,500 trees per hectare. This means that for a Sitka spruce plantation you should count 50 live trees in the eight-metre circle to have a tree stocking density of 2,500: 50 x 50 = 2,500.

If you have an oak woodland, then you need a stocking density of 3,300 trees per hectare. In this case, you need to count 66 live trees within the eight-metre circle: 66 x 50 = 3,300.

Review insurance requirements

I believe it is really important to insure your forest crop. Do you have an appropriate level of protection in place?

There are a number of good-quality, effective insurance policies on offer. Shop around for the most suitable and effective policy.

Policies may cover loss of timber value and/or cost of replanting, fire brigade charges, public liability and employer's liability.

Nutrient requirements

The most important nutrients in forestry are phosphorus, nitrogen and potassium. Phosphorus is of fundamental importance from an early stage for good root development. Both nitrogen and potassium are important for photosynthesis.

The nutrient requirements of trees have to be satisfied throughout the rotation in order to achieve healthy trees, good growth rates and high yields. These requirements depend on the soil type and tree species planted.

Trees growing on infertile, peaty or mineral soils may begin to lose vigour and display symptoms of nutrient deficiency in the years after planting. These deficiencies can occur despite correct fertiliser application at planting time.

I know I sound like a broken record but once again, go for regular walks through your forest so that you get to know your trees. This will allow you to identify potential nutrient deficiencies early on.

Mind you, other factors such as poor drainage, lack of adequate vegetation control, exposure, frost and disease may sometimes produce deficiency-like symptoms. Therefore it is vital to find the source of any possible growth problem before attempting to rectify it.

It is also important to control competing weeds prior to application of fertiliser to young trees. This will ensure that the trees rather than the weeds benefit from the nutrient application!

Where symptoms occur, foliar analysis is recommended to determine the nature and the extent of a possible nutrient problem.

All evergreen conifers should be sampled ideally in December but if necessary this can be extended to the end of February at the latest. Broadleaves and larches are sampled in August.

How to take foliar samples

  • Collect needle samples from mid November to mid February (approximately 10 cm long) from side branches from the top half of the tree.
  • Collect one side branch per tree from 25-30 different trees that are representative of the area to be fertilised. Do not mix different species (do not mix Norway spruce with Sitka spruce for instance).
  • Put all 25-30 branches in a clean plastic bag punctured with several small holes for aeration.
  • Clearly label the bag with date, location and surname and keep the samples cool (at bottom of fridge) and make a note for yourself where samples were taken.
  • Fill in a foliar sampling form available from your local Teagasc forestry adviser. They can also assist with completing the form. Test needle samples for N, P, and K.
  • Place needle samples, completed sampling form and cheque in a strong envelope.
  • Send off immediately to a suitable laboratory such as www.southernscientificireland.com, 066 9763588 or www.forestry.gov.uk/fr/aliceholt. Avoid holidays and weekends.
  • If the same area needs to be resampled, use the same laboratory

Steven Meyen is a Teagasc firestry advisor email: Steven.Meyen@teagasc.ie


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