Fertiliser addition is important for tree growth on cut-over peatlands in eastern Canada

Fertilisation is considered essential for tree growth on cut-over peatlands. However, little research has been carried out on these managed ecosystems in North America. Two experiments were conducted on peatlands planted with black spruce (Picea mariana (Mill B.S.P.) and tamarack (Larix laricina (Du Roi) K. Koch). The first experiment compared the efficiency of six different localised and soil-incorporated fertilisers, applied at planting time, in promoting the growth and survival of seedlings. A second experiment evaluated the nutritional needs of previously established black spruce and tamarack plantations that exhibited stagnating growth. Growth and survival of black spruce seedlings were best improved with the commercial Forest PakTM fertiliser (2N-0.5P-0.7K g per plant), whilst for tamarack the optimum was reached with an experimental formulation fertiliser (7N-3P-5K g per plant). Spot fertilisation with granulated PK fertiliser (0N-3.1P-5.7K g per plant) led to lower success for both species. For re-fertilisation, the shortage of phosphorus was the most growth-limiting factor for both tree species. Tamarack showed a beneficial response to a complementary application of potassium, whereas for black spruce the application of nitrogen and potassium in addition to phosphorous induced an additional growth increase.