Intermountain Forest Tree Nutrition Cooperative - Six Year Fertilizer Response of Managed Second-Growth Douglas-fir Stands in the Inland Northwest

Growth data collected from 94 Douglas-fir sites in six geographic regions of the Intermountain Northwest were used to determine six-year growth response of managed Douglas-fir stands to two rates of nitrogen fertilizer. Fertilizer rates were 200 and 400 pounds nitrogen per acre in the form of urea. An analysis of covariance model was used to estimate treatment effects and differences in growth among regions, adjusting for site differences in initial basal area per acre.In 1980, 1981 and 1982 the Intermountain Forest Tree Nutrition Cooperative (IFTNC) established large scale fertilization study trials to study the effects of nitrogen fertilization on forest nutrition, growth and survival of second-growth, even-aged Rocky Mountain Douglas-fir. The purpose of this paper is to summarize the Douglas-fir study trial data results presented in the 1988 IFTNC workshop