Growth-enhancing fertilisation is usually the choice for the fertilisation for mineral soils. This means applying nitrogen fertiliser, because the supply of nitrogen is usually the factor restricting tree growth on mineral soils. Meanwhile, peatlands usually contain plenty of nitrogen, but other nutrients may be in short supply or poorly balanced, which is why corrective fertilisation is used in such environments.
Fertilisation stimulates growth
Nutrient deficiency can often be determined visually, based on the look of the trees. Our forest specialists can help you assess nutrient deficiencies. After fertilisation, the needles recover, and enhanced photosynthesis improves tree growth. In moorlands, growth-enhancing fertilisation can boost growth by as much as 30 per cent, while in peatlands, corrective fertilisation can double or even triple tree growth.
The result of fertilisation depends on the location of the forest, the fertility of the soil and the condition of the trees. Where growth-enhancing fertilisation is concerned, forest owners can expect to see overall growth of 13–25 cubic metres per hectare over the duration of the fertilisation’s effect. Fertilisation is also a profitable investment from a financial perspective. Depending on the site, it can offer forest owners profits of 10–20 per cent.
More logs and shorter rotation with growth-enhancing fertilisation
Growth-enhancing fertilisation is most beneficial in thinned forests that are in good condition. After thinning, the crowns and roots should be given two to three years to grow stronger before fertilisation. The best sites for growth-enhancing fertilisation are mature pine-dominated sub-xeric heath forests and commercial mesic heath forests dominated by spruce and pine. In pine forests, most of the growth-enhancing impact of fertilisation is achieved in an average of six years, and in spruce forests, in approximately eight years.
Fertilisation increases growth and accelerates the conversion of pulpwood into log wood. Final felling then results in more wood of greater value. Moreover, in a fertilised forest, the following felling can be carried out up to six years earlier than in an unfertilised forest.
Ash fertilisation suits peatlands
In drained peatlands, tree growth is often restricted by the lack of potassium and phosphorus. The best fertiliser for nutrient-poor peatlands is high-quality wood ash, which usually contains all the nutrients in the right proportion trees require. Ash fertilisation helps rectify tree growth far into the future, for as long as 50 years. Forest owners can apply for subsidies for the costs of corrective fertilisation of peatlands under the Sustainable Forestry Financing Act.
Ash fertilisation is well suited to wooded, nitrogen-rich thick peatlands.
Previously, drainage repair was often carried out in peatlands in connection with corrective fertilisation, but based on current knowledge, drainage is not particularly useful for tree growth if the water surface is already more than 30 centimetres below ground level. Fertilisation spurs forest growth. Since a forest that is in good condition and grows well evaporates more water and keeps soil moisture well balanced, drainage repair is not always necessary. Unnecessary drainage repair results in more carbon being released due to the decomposition of peat. It also poses a risk of increased impacts on waterways.
Waterways and groundwater taken into account in fertilisation
Fertilisation is carried out with forestry tractors, making use of previous tracks, or from a helicopter. Growth-enhancing fertilisation is carried out throughout the growing season. Ash fertilisation can also be carried out in the winter in connection with thinning.
Fertilisation projects are carried out carefully, with respect for the environment. Buffer zones 20 to 50 metres wide are left along waterways, and habitats important to the biodiversity of forest nature are excluded from fertilisation. Wood ashes are the only type of fertiliser used in groundwater areas that play an important role for water supply. Recreational forest use, such as berry and mushroom picking, is not prevented by fertilisation.
You can place an order for the fertilisation of a forest estate in Finland with one of our forest specialists. The information on this page only applies to conditions in Finland.