Die Wirkung von ausgefaultem Klärschlamm auf den Stoffwechsel 3jähriger Fichten und Kiefern

Effect of digested sewage sludge on the metabolism of three year old spruce and pine trees. Three year old Norway spruce and Scots pine trees were grown in mixtures of sand and sewage sludge. The mixtures used were composed of 5 litres of sand and 1.25 or 1.67 litres of digested sewage sludges from municipal waste water treatment plants. A mixture of 5 litres of sand and 1.67 litres of peat was used as a control. In all cases sewage sludge depressed growth as measured by height and the yields of fresh material. The contents of N, Ca, Mg, Zn in the needle dry matter were higher than in control. The P content was only increased in the newly formed needles in the high sewage sludge treatments. However, the corresponding Mn contents were depressed, also the K contents in spruce. The higher rate of nitrogen assimilation, in the sewage sludge treatments especially in spruce, lead to a greater accumulation of the amino acid arginine and also to a reduction in the content of organic acids and polyphenols. These effects do not explain why some plants died. For spruce a lethal factor appears to be the depression of water uptake combined with high transpiration. The ratio of K/Ca in the needles was extremly low, which indicated a possibility of both potassium deficiency and calcium toxicity. The observed enrichment of proline is also associated with water stress. Scot pine was more sensitive than spruce to treatment with sewage sludge. In all treatments with sludge some Scot pine trees died, especially when municipal wastewater sewage sludge was used.