Frost hardiness of Thujaplicata and Pseudotsugamenziesii seedlings when nutrient supply varies with season

Seedlings of coastal Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) and western redcedar (Thujaplicata Donn ex D. Don) were subject to three nutrient treatments varying the rate of application of nitrogen (N) and phosphorus (P) over the growing season. A control treatment provided seedlings with a constant supply of N and P. A high–low treatment reduced the rate of N and P supply after mid-July. A low–high treatment initially supplied seedlings with low amounts of N and P, and then increased the rate of supply after mid-July. Foliar nutrient concentration of seedlings of each species from each nutrient treatment was measured in September and the following April. Cold tolerance of seedlings was assessed five times over the winter season by freeze-induced electrolyte leakage and twice by differential scanning calorimetry (DSC). Nutrient treatment did not significantly affect foliar nutrient concentration in either species. Height of Douglas-fir seedlings was also unaffected by nutrient treatment, but western redcedar seedlings in the control treatment were 6.3 cm taller than those in the high–low treatment. Interpolated damage at −13 °C from freeze-induced electrolyte leakage indicated that Douglas-fir seedlings from the control treatment had 19.8% less damage than high–low seedlings in October, 18% less damage in November, and 1.6% less damage in December. The same trend was evident, although not always significant, in western redcedar. Differential scanning calorimetry analyses of Douglas-fir in October and November showed freezing and melting curve onset and peak temperatures to be, on average, 2.3 °C and 0.4 °C warmer, respectively, in control seedlings than in high–low plants.

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.

Effects of Soil pH on Four Field-Grown Nursery Crops

Four woody nursery crops were grown for 3 years (1981–1983) in plots with varying pH levels. Greater growth of ‘Compacta’ Japanese holly and Foster's holly occurred in 1981 and 1982 at lower pH levels (4.1–5.8). However, Mn phytotoxic symptoms appeared on ‘Compacta’ Japanese holly dunng the fall of 1982. Foliar Mn levels of all 4 species exceeded 2500 ppm when grown at the lowest pH level, with the exception of Foster's holly in 1983. Growth of ‘Nellie R. Stevens’ holly was not affected by pH, while Taxus growth was enhanced in 1983 at the higher pH levels (4.7–5.9). Foliar nutrient concentration trends were similar among the 4 crops.