Growth of Pinus sylvestris after the application of wood ash or P and K fertilizer to a peatland in southern Sweden

Abstract

The effects of the application of wood ash and of fertilizer regimes including phosphorus (P) and potassium (K), with and without simultaneous addition of nitrogen (N), were investigated on a stand of Scots pine (Pinus sylvestris L.) saplings growing on a drained oligotrophic peatland site in southern Sweden. A randomized block design was used. Tree growth and concentrations of various elements in the needles were measured. The addition of similar doses of P (approx. 40 kg P ha) from different sources resulted in similar growth responses, amounting to 1.6–1.9 m ha yr of stem wood over the 26-year study. The P source was either wood ash (2500 kg d.w. ha) or PK-fertilizer (raw phosphate and potassium chloride). In response to several treatments there were both increased numbers of trees and increased growth of individual trees. The high PK-dose (40 kg P ha and 80 kg K ha) appeared to result in a larger growth increase than the low dose (20 kg P ha and 40 kg K ha). The N treatment had no additional effect on growth. In the control plots, tree growth was more or less negligible (0.04 m ha yr). After almost 26 years, concentrations of P and K in the needles of treated plants were still higher than in the untreated control plants. Nevertheless, in spite of the elevated P concentration, P appears to limit the growth of Scots pine. In conclusion, after sufficient drainage of this type of peatland site, it is possible for a forest stand to develop to the pole stage if wood ash or PK-fertilizer is applied.–13–1–1–1–1–1–1–13–1–1