Evaluating the nutrient status and fertilization response potential of planted spruce in the interior of British Columbia

Factorial combinations of nitrogen (0, 100, and 200 kg/ha) and a "complete" fertilizer (0 and 1170 kg/ha) were applied to 10 spruce (Piceaglauca (Moench) Voss and hybrids) plantations in the central interior of British Columbia. Postfertilization patterns of foliar nutrient concentration and needle weight were used to evaluate the nutrient status and fertilization response potential of treated stands. When applied alone, N and the complete fertilizer generally had little effect on the weight of needles produced in the first year after treatment. Combined applications, however, often resulted in large responses. In 8 of the 10 installations, combined applications of N + complete fertilizer were significantly more effective than N alone in stimulating first-year needle weight. Which nutrient in the complete fertilizer is responsible for the increased needle-weight response cannot be stated conclusively. However, examination of foliar nutrient concentration data, combined with graphical analyses of relative differences in needle weight and nutrient concentration of added and nonadded nutrients, indicate that sulphur (and possibly potassium) may have a strong controlling influence on the N fertilization response potential of these stands. Systematic testing must be undertaken to verify these tentative diagnoses.