| Abstract: | A survey investigation of the relationship between nutritional factors and the decline of Picea omorika growth Soil and needle samples were collected from 193 sites of Picea omorika (mostly in private gardens) in Northern Germany ranging from normal to seriously damaged plants. The needles were analysed for N, P, K, Ca, Mg, Cu, Zn, Mn, Fe, B, Cl and Na. In the soil samples pH, P, K and Mg were determined. - 1 In 54 cases (= 30,3% of the 178 sites with injured trees) the cause of the damage could not be established. In a few cases only (12 sites = 6,7%) Mg deficiency seemed to have caused the injuries. But in a large number of cases the needles showed high Cl contents, hence Cl toxicity was the most important cause (103 sites = 57,9%) of the damage.
- 2 The critical content of needles sampled in autumn is 0,27 % C1. Above this value CI-toxicity is highly probable and between 0,22 and 0,27 % CI it is possible.
- 3 High Cl-content is associated with mottled chlorosis and in many cases also with a brown discoloration beginning at the tip of the needle. The symptoms are usually stronger at the tips of branches than in central or basal parts.
- 4 Susceptibility to Cl-toxicity is similar for Picea omorika and Picea abies.
- 5 C1-toxicity may be caused by high application of deicing salt and Cl-containing fertilizers. Some of the fertilizers specially developed for the nutrition of conifers even contain too much Cl.
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