Long-term leaching of nutrients from drained peatland after ash fertilisation

Sirpa Piirainen, Timo Domisch, Mika Nieminen and Mikko Moilanen

After Wise Use – The Future of Peatlands, Proceedings of the 13th International Peat Congress: Chemical, Physical and Biological Characteristics of Peat

drainage-water, heavy-metals, nitrogen, phosphorus

Piirainen et al. 2008: Long-term leaching of nutrients from drained peatland


The increased use of forest-based biofuels for energy production stresses also the utilisation of wood ash as a forest fertiliser. Wood ash contains considerable amounts of mineral nutrients, especially phosphorus (P) and potassium (K) that are usable by the ground vegetation and tree stands. On the other hand, wood ash does not contain any nitrogen (N). Therefore, N rich and simultaneously P and K poor drained peatlands are the best suitable sites for ash fertilisation. However, the concern about element leaching to watercourses has prevented any large-scale fertilisation. The objective of this study was to determine the leaching of nutrients and heavy metals from drained peatland catchments over a 10-year period following wood and peat ash applications. Both loose and granulated ashes were used. After 10 years, the concentrations of sulphur compounds accompanied by B, K, Cl, Ca, and Mg in drainage water were still slightly higher at wood ash treatments compared to the control. No increased leaching of P or N compounds was observed during the entire study period. The leaching of heavy metals was very low and not affected by ash treatments.