Abstract :
Fertilizer (18:40:0, N:P:K) was applied by two methods, each at different levels, following establishment of a hybrid poplar (Populus trichocarpa Torr. & Gray × Populus deltoides Bartr. ex Marsh.) plantation, containing four clones, on central Vancouver Island. Nitrogen and P were supplied at 0, 100, and 200 kg·ha-1 by banding, and at 0, 25 and 50 kg·ha-1 by placing in holes adjacent to cuttings. After one season, response to placed treatments (mean height 182 cm) was greater than to banded treatments (mean height 149 cm). The 50 kg·ha-1 placed treatment increased stem volume 4.3-fold above control, and the 200 kg·ha-1 banded treatment increased stem volume 2.4-fold above control. Uptake of N and P was about 10-fold greater per kilogram of fertilizer nutrient for placed than banded treatments. Fertilizer increased leaf N concentration, but concentrations of most other nutrients declined despite increased uptake. Significant increases in stem volume occurred when leaf N concentration was about 29 g·kg-1 in clone 1, but 23-25 g·kg-1 in the other clones. Clone 2 tolerated foliage P concentrations below 1.4 g·kg-1 at the greatest growth rates. Stem volume was positively correlated with soil total N% and organic C% in the 16-30 cm horizon.
