Effects on growth and nutrition of sewage sludge application in acid pine forests (Pinus sylvestris, L.) in a temperature gradient in Sweden

摘要

Sewage sludge (20% dw) was applied to acid pine forests (Pinus sylvestris, L.) on sandy soils in a temperature gradient in Sweden, in order to investigate the effects on soil nitrogen mineralization, leaching and plant uptake of nitrogen, balance of base cations between soil and vegetation, accumulation and uptake of heavy metals and the effects on tree productivity. In a pilot study a comparison was made between liquid (4% dw) and dewatered sludge (20% dw). The effects of different doses were also investigated. Soil and vegetation samples were investigated over an eleven year period with special emphasis on the macro nutrients N, P, Na, K, Ca and Mg, as well as the heavy metals Cd, Cr, Cu, Ni, Mn, Pb and Zn. Measurements of tree productivity were performed 5 years after sludge application. Sewage sludge application increased pH and the concentrations of inorganic nitrogen and other major nutrients in the soil during the first years following the application, while a decrease in C/N ratio was significant still 11 years after sludge treatment. The effects were correlated to the dose of applied sludge. Liquid sludge caused a more pronounced transport of inorganic nitrogen to deeper soil profiles, compared to dewatered sludge. Application of sewage sludge increased the long-term accumulation of Cr and Cu in the moor layer, and in the northern sites also of Pb and Zn. The concentrations of most heavy metals in the vegetation were unaffected by the sludge application. However, a small increase was found for Cu and Ni in leaves of Vaccinium vitis-idaea. The highest productivity response of sludge application was found in pine forests in Central Sweden, with initially low soil nutrient concentrations, and with nitrogen as a supposed limiting factor. Also in Northern Sweden, above the Arctic Circle a positive production response was found. 55 refs