Zur Verfügbarkeit und Freisetzung von Nährstoffen in einer intensiv bewirtschafteten Moorwiese nach einer gewässerbaulichen Maßnahme

Abstract

A bog meadow at the Augraben (Altmark, Saxony-Anhalt) as well as the waters of the drainage systems and bordering ditches were investigated for their total contents and soluble concentrations of carbon, nitrogen, phosphorus, sulphur, potassium, calcium, magnesium, iron, aluminium, manganese, chloride, ammonium, nitrate, sulfate and phosphate. In addition natural isotope variations of carbon (13C/12C) and nitrogen (15N/14N) in the soil were assessed. Intensive grassland use and changes in the groundwater levels, as well as a soil pH-value of 7.2, led to an increased mineralization of the organic substance. Accordingly, particularly high levels of sulphate (0.13 mg S/g dry weight, nitrate (0.1 mg N/g dry weight), and calcium (0.73 mg/g dry weight) ions were found in the top soil. In contrast the level of however phosphate (< 0.003 mg P/g dry weight) remained low. The data indicate that nitrate and sulphate are leaching from the soil into the bordering ditches via the draining systems, but phosphate is presumably bound in form of calcium sulphate. In this process may also iron-(III)-hydroxide/oxide hydrates play an important role in the immobilization of phosphate.Key words: bog meadow, intensive grassland use, soil, surface water, nutrients