Effects of long-term fertilisation and growth on micronutrient status in Norway spruce trees

Stockfors, J., Linder, S., & Aronsson, A. 1997. Effects of stand age, long-term fertilisation and growth on micronutrient status in Norway spruce trees. Studia Forestalia Suecica 202. 15 pp. ISSN 0039-3150. ISBN 91-576-5399-2. Effects of fertilisation treatments (amounts and composition) on needle concentrations of micronutrients (boron, copper, iron, manganese and zinc), were studied in a long-term fertilisation experiment with young Norway spruce (Picea abies (L.) Karst.) in Central Sweden. Stored current-year’s needles (1967-1989), and material from a biomass sampling in 1989, were used to determine changes in micronutrient status with stand development, and to estimate total amounts of micronutrients, in all aboveground organs for a wide range of nutrient regimes and stand productivities. Different combinations of nitrogen, phosphorus, potassium, calcium, magnesium and micronutrients were applied. Fertilisation resulted in a wide range of growth rates: the most optimal treatments grew more than three times as fast as the control stands. When micronutrients were included among the elements supplied, internal concentrations of boron, manganese and zinc increased. Needle concentrations of copper and iron were, however, not affected by fertiliser treatment or by differences in growth rate. While copper concentrations in all aboveground organs were similar between treatments, large amounts of iron were stored in the branches. With increasing growth rates the increased amount of iron incorporated into needle biomass was balanced by a decrease in concentration and amount of iron in the branches. Boron concentrations in needles from fertilised trees were occasionally close to deficiency levels when trees were not supplied with boron. Boron appeared to be retranslocated from older needles to current developing shoots, thereby reducing the ‘dilution effect’ caused by increased biomass production.