AbstractA field study on mineral nutrition of 12 year old Norway spruce (Picea abies(L.) Karst.) was carried out on a Lower Triassic region in the Eifel mountains in a plantation where the juvenile trees exhibited marked visual differences on adjacent plots, thus indicating a patchy pattern concerning the fertility status of the soil. This was confirmed by geological, pedological and chemical analyses, including X‐ray diffraction analyses of the clay minerals and soil water as well as needle element analyses. A combined K and N deficiency was diagnosed for those trees, which exhibited growth retardation and small, rigid, and yellowish‐green needles. Chlorophyll and protein content and glutamine synthetase activity were reduced while triphenyltetrazoliumchloride (TTC) reduction was enhanced in the sick trees as compared to adjacent healthy looking trees of the same age and provenance. A diagnostic fertilization treatment with K and Mo, respectively, yielded the following results. One year after administration of Mo a marked increase in total N content of the needles was observed, due to an increase of the storage pools for soluble (nonprotein) nitrogen, namely the basic amino acids arginine, histidine and lysine and also of ornithine. Yet, no visual recovery of the trees was observed. On the other hand, K fertilization caused an improvement of all biochemical parameters, except protein content and soluble N storage pools. The relationships between Mo dependent nitrate reduction, potassium content and nitrogen metabolism are discus
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