Effects of fertilization on the nutrition and growth of a slow-growing Engelmann spruce plantation in south central British Columbia
A study was undertaken to investigate the effects of ground and foliar fertilizer applications on the growth of a 15-year-old Engelmann spruce (Piceaengelmannii Parry) plantation in the south central interior of British Columbia. The site had been broadcast burned prior to plantation establishment, and poor growth performance and pretreatment foliar analyses indicated that multiple nutrient deficiencies were likely growth limiting. Fertilization has had a very strong positive influence on height increment and branch elongation. Although growth responses were minimal in the 1st year after treatment, cumulative increases in height increment over the next 2 years averaged 41 cm (range 28–48 cm) greater than those recorded in unfertilized trees. In relative terms, these responses averaged 102% (range 90–120%). Improvements in branch increment over this 2-year period also averaged 102% (range 85–115%). Results indicate that the majority of the growth response has been due to improved nitrogen nutrition. Combined ground applications of nitrogen and a "complete mix" fertilizer were no better than nitrogen alone in stimulating tree growth. The effectiveness of 2% ferrous sulphate and sodium sulphate sprays was probably adversely affected by foliar scorching following spray application. However, despite foliar burning, results indicate that trees may respond favourably to iron applications if accompanied by ground applications of nitrogen and other deficient nutrients (likely sulphur). Because the study design did not allow distinction of cause and effect, with respect to the consequences of the prior broadcast burn, it cannot be stated conclusively that burning is responsible for inadequate stand nutrition and poor tree growth on this site. However, when combined with evidence of impaired nutrition following slash burning from other studies, it may be safely inferred that burning will exacerbate existing nutritional problems and that fertilization under these conditions may at least temporarily improve plantation performance.