Intermountain Forest Tree Nutrition Cooperative - 14th Annual Meeting Presentations

Forest fertilization for enhancing tree growth and improving the value of harvested timber has been an effective silvicultural practice in the Inland Northwest forests. Early large scale study trials were installed in 1980, 1981 and 1982 to study the effects of nitrogen fertilization on forest nutrition, growth and survival of second-growth, even-aged Rocky Mountain Douglas-fir. A total of 98 research sites located across six ecologically diverse geographic regions throughout the Intermountain Northwest were respectively monitored for twelve, fourteen and sixteen years after establishment. Subsequent evidence from the Douglas-fir trials suggested that elements other than nitrogen, particularly potassium, may be limiting on some forest site types and may have significant influence on forest health. In response, a subset of the original trials was retreated in 1987 and 1988 with nitrogen and/or nitrogen plus potassium treatments. Technical and refereed documents include initial establishment and growth responses. Additional documentation is also presented for the 1987 and 1988 retreatment