Some aspects of boron, copper and iron nutrition of lodgepole pine and Douglas-fir

This thesis reports the findings of two complementary investigations on boron, copper and iron nutrition of lodgepole pine and Douglas-fir. The primary aim of the first study was to determine the critical levels of boron, copper, total iron and "active" iron for lodgepole pine grown under controlled conditions in the greenhouse. The second study, conducted at five different field locations in interior British Columbia, involved foliar application of copper sulphate, ferrous sulphate and urea to lodgepole pine; and ferrous sulphate and urea to Douglas-fir. The main objective of the field study was to assess tree growth and foliar nutrient responses to foliar-applied nutrients. Both studies involved the application of nitrogen to investigate its significance for the micronutrients. The findings from the greenhouse experiments indicated that for lodgepole pine, the critical range, expressed as concentration is 7 to 16 ppm for boron and 2 to 3 ppm for copper. The lower value in each case is the critical value. For "active" and total iron, the critical values are 32 and 44 ppm, respectively. Concentrations at or below the critical value, in each case, may be associated with acute deficiency of the nutrient element. Concentrations above the critical value imply that the nutrient is at a level sufficient for optimum or near-optimum growth. Results from the field experiments with lodgepole pine indicated fairly comparable values to those from the greenhouse. The critical value for copper was found to be 4 ppm for copper and 29 ppm for active iron. It was also suggested that copper toxicity in lodgepole pine might occur whenever foliar copper concentration exceeds 17 ppm. Foliar nutrient application proved to be a quick and effective means of raising copper and iron concentrations to adequate levels in lodgepole pine foliage; and iron in Douglas-fir foliage where these nutrients were deficient. Foliar application of urea was effective in raising foliar nitrogen concentration in lodgepole pine, but not in Douglas-fir. Combined nutrient applications were more effective than individual nutrient application. However, these effects on foliar nutrients were only temporary and did not last beyond the year of application, except in Douglas-fir which seemed able to retain more applied iron in the foliage than did lodgepole pine, during the second year of growth. Shoot growth and blomass production in both species responded greatly to treatments only during the second growing season following fertilization. Lodgepole pine needle length at one of the sites also showed a significant positive response to treatments in the second year of growth. The highest response was obtained from treatments that caused minimal foliar scorching. No significant positive tree growth response was detected during the year of fertilizer application. The safe application dosage (where no foliar injury was evident) of copper sulphate and ferrous sulphate to lodgepole pine was 0.1 and 2 percent, respectively. No foliar injury was observed with 4 percent ferrous sulphate applied to Douglas-fir. Nitrogen applied at 2 percent urea did not cause any foliar burn in either species. The application of 1 percent copper sulphate was extremely toxic to lodgepole pine; 4 percent ferrous sulphate caused moderate foliar burn. Nitrogen absorbed by the root system (greenhouse experiment) appeared to have an antagonistic effect on foliar boron, copper, total and active iron in lodgepole pine. The concentration and content of these micronutrients in the foliage decreased as foliar nitrogen increased as a result of increasing the nitrogen supply. Foliar feeding of urea (field experiment), on the other hand, did not seem to have any physiological interaction with foliar copper. In fact, there was a synergistic effect of urea on foliar iron. The level of total and active forms of iron in the foliage was increased as a result of urea application.Land and Food Systems, Faculty ofGraduat