Soil and Tissue Analysis: Tools for Maintaining Soil Fertility

Abstract

Systematic monitoring through soil and plant analysis is essential for understanding and managing soil systems in forest nurseries. Analysis services are offered by Oregon State University, University of Idaho, and seven commercial laboratories in the U.S. Northwest, as well as the British Columbia Ministry of Forests. Suggested target fertility levels for raising Douglas-fir in Northwest nurseries are: pH of 5.0 to 6.0, total nitrogen (N) of 0.18 to 0.23%, available phosphorus (P) of 25 to 50 ppm, available potassium (K) of 80 to 120 ppm, exchangeable calcium (Ca) of 2 to 4 meq 1100 g, and exchangeable magnesium (Mg) of 1 to 2 meq 1100 g. Suggested ranges in macronutrient concentrations in Douglas-fir needle tissue are: 1.2 to 2% N, 0.1 to 0.2% P, 0.3 to 0.8% K, 0.2 to 0.5% Ca, 0.10 to 0.15% Mg, and 0.1 to 0.2% sulfur (S). The lower levels indicate deficiencies and the higher levels adequacy. Success of the fertility monitoring program depends on careful sampling and handling, consistency in laboratory servces used,and meticulous recordkeeping.