The nutrient status of three Norway spruce (Picea abies L. Karst.) plantations in southwestern Quebec were studied through foliar analysis. At all locations low N and K and marginal Mg foliar concentrations were identified. / Diagnostic fertilization resulted in significantly improved foliar K, N, Ca/K molar ratio and in some cases Mg. The foliage of the treated trees has an improved dark green colour as compared with the controls. From this research it is evident that nutrient deficiencies of N, and K in particular, are showing up in spruce stands in the areas where atmospheric pollution is relatively severe. The use of foliar nutrient concentrations along with evaluation of visual decline symptoms give the best results in assessment of the trees' current nutrient status. Proper diagnostic fertilization, using KNO$ sb3$ and (K,Mg)SO$ sb4$, helped to correct the nutrient disturbances on the calcareous soils of the region, impoverished by former agricultural use. In these soils the balance of Ca with K and Mg is crucial for their proper uptake. The base cations addition enlarged the available P pool, as a result of the improved organic matter decomposition. (Abstract shortened by UMI.)

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