Response of thinned White fir stands to fertilization with nitrogen plus sulphur.

Abstract

A single application of 200 pounds nitrogen (N) plus 33 pounds of sulphur (S) per acre to white fir (Abies concolor (Gord. & Glen.) Lindl.) increased periodic annual increments of basal area and volume by 1.7 ft²acre^-1year^-1 and 43 to 68 ft³acre^-1-year^-1 respectively over 4- or 5-year periods. The stands become infested with budworms (Choristoneura occidental is Freeman and C. retiniana (Walsingham)) after fertilization thereby causing increased variability in height growth. The influence of fertilization on height growth therefore was statistically significant in only one of the two stands studied. Evidence in these and other studies suggest that thinned white fir and grand fir (Abies grandis (Dougl. ex D. Don) Lindl.) respond well to N plus S on pumice and ash soils and to N on many other soils. Rates of N application higher than 200 pounds per acre are not recommended.

Citation

Cochran, P.H. 1991. Response of thinned White fir stands to fertilization with nitrogen plus sulphur. Res. Note PNW-RN-501. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 20 p