Municipal sewage sludge is an unavoidable byproduct of the contemporary live and business activities of people. Proper handling and utilization of sewage sludge continue to create serious problems in Poland although this waste product is a source of both organic carbon and macronutrients. The present study has been carried out in order to assess the influence of municipal sewage sludge on the content of available forms of Cu, Zn and Mn in soil. A microplot experiment set up according to the random sub-block method was conducted in 2005-2008. The experiment was established on anthropogenic, humic urban soil developed from loamy sand rich in phosphorus and magnesium, but poor in potassium, and alkaline in reaction. The design of the trials comprised 5 doses of municipal sewage sludge from the Łyna Municipal Wastewater Treatment Plant in Olsztyn: 0, 70, 140, 210 and 280 Mg ha–1 of fresh matter. The tests have demonstrated that a dose of sewage sludge had a significant effect on the content of available forms of Cu, Zn and Mn in soil. In alkaline soil, however, the observed increase in the content of available forms of Cu, Zn and Mn was not hazardous to the environment, but could improve the plant nutrition with these elements. It is highly probable that the availability of Cu may increase in the second and third year after the application of sewage sludge. The accumulation of soluble Zn in soil started to decrease in the second year, but did not become significantly limited until four years after sewage sludge application. Sewage sludge raised the amount of soluble manganese in soil during the first three years, but in the final year of the experiment the quantity of soluble Mn in soil did not undergo any significant fluctuations.

17.4.2012