Nitrogen fertilization requirements of Douglas-fir container seedlings vary by seed source
1995
Thompson, G.
Growth of container Douglas-fir (Pseudotsuga menzesii (Mirb.) Franco) from different seed sources from western Washington to western Montana was evaluated following application of 100, 150, or 200 ppm nitrogen (N) during the rapid growth phase. The optimal level of N varied between seed sources for height, caliper, and bud growth, as well as for shoot-to-root ratio. Target seedling specifications were met adequately for the westernmost sources at 100 and 150 ppm N, whereas eastern sources required 150 or 200 ppm. Nitrogen levels should thus be tailored to individual Douglas-fir seed sources to maximize the number of shippable seedlings per lot.
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