Effect of nitrogen, phosphorus and magnesium fertilizers on growth of a semimature jack pine forest, northwestern Ontario

Abstract

In the spring of 1969, an experiment to test response (mean DBH, BA, BA%, and total and merchantable volume increments) to nitrogen (N), phosphorus (P) and magnesium (Mg) fertilizers, singly and in combination, was established in a semimature jack pine (Pinus banksiana Lamb.) forest on a Site Class III sandy site in the Dryden-Sioux Lookout area of northwestern Ontario, Canada. Analysis of variance of 10-year increments revealed highly significant (P = 0.01) responses of mean DBH increment, BA and percent BA increments, and total and merchantable volume increments to N, but no response to either P or Mg. An interaction between N and P was noted, however, in relation to BA and to total and merchantable volume increments. The best treatment in terms of total volume increment over that of the control was 151 kg N ha−1 plus 62 kg Mg ha−1, which produced ca. 16 m3 ha−1 of extra wood over 10 years. Key words: forest fertilization, nitrogen, phosphorus, magnesium fertilizers, jack pine growth response