In the southern Black Forest magnesium deficiency symptoms have been observed in Picea abies as well as in Fagus sylvatica stands. Field and laboratory findings clearly indicate that Mg deficiency is a site specific problem which above all is related to the poor Mg availability from the substrate. The paper presents the results of fertilizer experiments with Mg sulfate ("Kieserit") in a Norway spruce plantation and a natural regeneration of European beech both suffering from extremely low Mg supply from the soil. Effects of different application rates on the development of nutrient contents in leaves and needles over a period of three vegetation periods are discussed.
