EFFECT OF NITROGEN, PHOSPHORUS AND MAGNESIUM FERTILIZERS ON GROWTH OFA SEMIMATURE JACK PINE FOREST, NORTHWESTERN ONTARIO

In the spring of 1969, an experiment to test response (mean DBH, BA, B A%, and total and merchantable volume increments) to nitrogen (N), pho sphorus (P) and magnesium (Mg) fertilizers, singly and in combination, was established in a semimature jack pine (Pinus banksiana Lamb.) for est on a Site Class IIl sandy site in the Dryden-Sioux Lookout area of northwestern Ontario, Canada. Analysis of variance of 10-year increme nts revealed highly significant (P = 0.01) responses of mean DBH incre ment, BA and percent BA increments, and total and merchantable volume increments to N, but no response to either P or Mg. An interaction bet ween N and P was noted, however, in relation to BA and to total and me rchantable volume increments. The best treatment in terms of total vol ume increment over that of the control was 151 kg N ha(-1) plus 62 kg Mg ha(-1), which produced ca. 16 m(3) ha(-1) of extra wood over 10 yea rs.