The uptake and translocation of fertilizer N15 in young trees of Scots pine and Norway spruce

The uptake and translocation of labelled fertilizer nitrogen was investigated in 11-year-old and 12-year-old trees of Scots pine and Norway spruce growing in different self-sown stands. The fertilizer was applied as a topdressing to the soil 0-80 cm around the stem. The experiment area with Scots pine was situated at Vifors in the province of Gästrikland, and that with Norway spruce at Dalkarlsnäs, S.W. of Säter, in the province of Dalarna. The pine plants received 10 g of nitrogen in the form of either calcium nitrate. Ammonium sulphate or calcium cyanamide during the summer of 1962. The nitrogen materials added had been enriched with the isotope N15. The spruce plants mere fertilized with isotope-labelled ammonium sulphate in a dose corresponding to 20 g of nitrogen per tree. In the autumns of the years 1962, 1963 and 1964, samples mere taken of needles and of corresponding defoliated twigs from the issues of different years and were investigated in respect of their total content of nitrogen and of NI5. Some trees which were felled in the autumn of 1963 were analysed to determine the total recovery of added labelled nitrogen in the above-ground portion of the tree. The distribution of the atomic percentage of N15 was investigated in the bark and wood from annual rings of different years by the use of stem segments