Fertilization experiments on forest mineral soils: A review of the Norwegian results

The paper gives a brief overview of the background, history and main results of forest N fertilization experiments on mineral soils in Norway. Positive results of initial phosphorus (P) fertilization on survival and growth of Norway and Sitka spruce have only been achieved in the coastal districts of western Norway. Other elements have seldom given any significant effect. In young and old stands of Norway spruce and Scots pine nitrogen (N) fertilization with 150 kg N ha(-1) usually gave increment increases in the range of 1-2 m(3) ha(-1) yr(-1), for a period of 6-8 yrs after application. Given individually, no other element has proved stimulating to stem growth in a similar way. In young Norway spruce stands P has often given additional growth response when given together with N. Liming has been shown to have no or negative effects on tree growth. Fertilization experiments have changed from being management orientated towards addressing the problems of possible nutrient imbalances.