Norway spruce stands at eleven sites in Finland, Norway and Sweden have been studied under various climates, atmospheric deposition of N and S and fertilisation regimes. Nitrogen was growth restricting at eight inland sites, while P was growth restricting at three coastal sites. Liming and N fertilisation caused serious B deficiency on some of the inland sites. It is likely that liming affects uptake of B, whereas N fertilisation causes a dilution due to increased growth. Application of S combined with N probably caused K deficiency at one of the sites. The reliability of foliar analyses as a method to diagnose nutrient status and the likely changes after nutrient input to spruce forests in the Nordic countries, are discussed. The CR- and the DOP-method are evaluated for diagnostic purposes. Both methods seem to give reliable conclusions even if the CR-method often produces more specific results. Interpretation based on both current and one year old foliage improved the diagnostic prognoses. The accuracy of diagnosis also relies on knowledge and ability of the interpreter. Based on the results it is reason to be cautious about recommendations of single element fertilisations, e.g. with N alone, because the demand of other elements beyond available pools frequently occurs. Forest trees in the boreal region are probably well adapted to N deficiency, which means that they can handle the physiological consequences rather well, while deficiencies of other elements usually are more detrimental to growth vigour and stress related diseases.
