EFFECTS OF PLANTING SPACING AND REFERTILIZATION ON GROWTH AND NUTRITION OF BLACK SPRUCE (PICEA-MARIANA (MILL) BSP) PLANTED ON A MINEROTROPHIC PEATLAND IN NEWFOUNDLAND, CANADA

In 1973, a black spruce (Picea mariana (Mill.) B.S.P.) plantation was established in central Newfoundland on a minerotrophic, open peatland that had been ditched at 1.8 m spacings. The seedlings were planted at spacings of 1.2, 1.8, and 2.4 m and spot fertilized with a mixture of 71 g urea, 99 g ground rock phosphate, and 41 g potassium sulfate. In 1985, 12 years after establishment, concentrations of N (0.90%), P (0 .10%), and K (0.28%) suggested that nutrient deficiencies were limitin g growth. Consequently, P, P-K, and N-P-K were applied in the amounts of 60 kg/ha P, 100 kg/ha K, and 200 kg/ha N. Controls (no refertilizat ion) were also included in the experiment, although these plots had be en spot fertilized in 1973. Between 1985 and 1991, height growth, need le weight, and needle nutrients were not significantly different among planting-spacing treatments. Height growth was greatest in the P-K tr eatment, whereas needle weights were greatest in the N-P-K treatment i n 1987. Uptake of N was significantly improved by application of P-K a s well as by application of N-P-K. Concentrations of N, P, and K incre ased to levels of 2.43, 0.25, and 0.60%, respectively, following appli cation of fertilizers containing those elements. However, by 1991, con centrations had decreased to 1.10, 0.14 and 0.43%, respectively. The e ffects of refertilization on uptake of Ca, Mg, and Cu were mainly nons ignificant.