Ten-year Growth Response to Fertilizer of a 90-year-old Black Spruce Stand in Northwestern Ontario

Abstract

A fertilizer experiment with three levels of urea, two of triple superphosphate and two of muriate of potash was established in a 90-year-old black spruce (Picea mariana [Mill.] B.S.P.) stand on a moist-to-wet site in northwestern Ontario. Response variables estimated or measured at 6 and 10 years after fertilization were mean DBH increment, BA increment (per cent and absolute), and total and merchantable volume increment. Analysis of variance and Duncan's New Multiple Range Test were carried out. Results indicated significant growth response only for one combination of N and P, and only in relation to mean DBH increment. No interactions were significant. Inspection of data revealed trends suggesting that response, which was limited, was generally to P and to a smaller degree to N. Compared with literature values, volume growth responses were generally low, about 9 m3/ha estimated total volume increment over controls in 10 years. Possible reasons for low response, including nutrient loss (particularly of N) from the root zone and low application rates are discussed.