Forestry established on peat soils or cutaway bog will often need subsequent applications of fertilizer in order to close canopy and reach maturity. The most common nutrient deficiencies on peat soils is phosphorus and nitrogen. If your trees are not growing in height and dis-colouration is occurring on the leaves or needles this most often is a nutrient deficiency, however high water table and disease can also cause dis-colouring and stunted growth so it is important to have your local co-op forester assess your site and advise you.
If a nutrient deficiency is evident a foliar analysis can be undertaken (during December and January when the tree is dormant and nutrient levels are stable) which involves removing foliage from a sample of trees and sending to a recognised laboratory to analyse the nutrient concentrations in the foliage. The results of this test will enable your co-op forester to recommend what fertiliser needs to be applied and when.
Depending on the size of your forest, it may be more cost effective for this re-fertilisation to completed by helicopter. Please note aerial fertilisation of forest plantations can only be undertaken after an aerial fertilisation licence has issued from the Forest Service. This is required under S.I. No. 592 of 2006 and S.I. No. 790 of 2007, European Communities (Aerial Fertilisation) (Forestry)(Amendment) Regulations 2007. It is an offence to carry out aerial fertilisation of a forest without a valid licence. Your local co-op forester can advise you on whether this is necessary and the process involved.