Effects of Wood, Peat and Coal Ash Fertili- zation on Scots Pine Foliar Nutrient Concentrations and Growth on Afforested Former Agricultural Peat Soils

The effects of ash and commercial fertilizers on the foliar nutrient concentrations and stand growth of Scots pine were studied in four fi eld experiments established on former cultivated peat soils. The aims were to compare ash types (wood, peat and coal ash), study the effects of ash treatment (pelletization), compare ash fertilization with commercial fertilizers, and to study the interaction between ash fertilization and weed control. Foliar samples were collected 1–3 years and 7–8 years after fertilization. In the unfertilized plots, the foliar nitrogen and phosphorus concentrations were fairly high, while those of potassium were low in all the experiments. The boron levels were low in three out of the four experiments. Application of either loose or pelletized wood ash, as well as of commercial fertilizers, increased foliar potassium and boron concentrations, and thus successfully remedied the existing nutrient imbalances and defi ciencies. Since phosphorus defi ciencies are rarely encountered on fi eld afforestation sites, poorquality wood ash with low phosphorus concentration could be used. Peat ash containing phosphorus, but only small amounts of potassium and boron, was not found to be very suitable for soil amelioration in connection with fi eld afforestation. Coal ash, containing only small amounts of potassium, was a good source of boron for pine even when used in small amounts, and thus it can be used in cases where boron defi ciencies alone are encountered. Wood ash signifi cantly increased the height growth of Scots pines in two of the experiments, but peat ash and coal ash had no statistically signifi cant effect. Wood ash increased the number of healthy seedlings. Vegetation control decreased seedling mortality by 24%, increased the growth of pine and decreased the proportion of trees damaged by elk and by deciduous trees.