Effect of wood ash mulch on growth of Scots pine seedlings after transplanting into peat soil: A pilot study

Abstract

Wood ash production from power plants and the use of recycled ash for earthworks and forest peatland fertilization have increased markedly in Finland in recent decades. In this study, effects of wood-based ash on potted Scots pine seedlings were tested in a greenhouse. Seedlings were grown for one to two growing periods in peat with ash mulch thicknesses 0–8 cm. Seedlings grew well in ash thicknesses 0–4 cm during the first growing period. Seedling mortality (60%) occurred with the thickest ash mulch. Soluble nutrients in press water extracts were high compared with the control treatment. N and P levels were suboptimal also with ash mulch. During the second growing period, seedling mortality occurred (17%) already with the thinnest ash mulch. The results suggest that ash mulch around seedlings in quantities of less than 0.5 cm (or 7 kg·m<sup>–2</sup>) is feasible and is not detrimental to Scots pine seedlings. The results provide foundation for further field research on the longer-term impacts of wood ash mulch on planted seedlings on boreal forest sites and on the feasibility testing of the mulch as a supplement to or substitute for the soil preparation for seedling planting.