Abstract
A single-factor field experiment was carried out at the Cultivar Evaluation Station in Szczecin-Dabie in 2008-2010. The soil on which this experiment was set up is formed from light loamy sand (lls). In respect of granulometric composition, it is classified to the category of light soils, of soil quality class IV b and good rye complex. In the experiment, compost produced with municipal sewage sludge by the GWDA method was used. This compost contained clearly more nitrogen and phosphorus in relation to potassium. The content of heavy metals (Cd, Cu, Mn, Ni, Pb and Zn) in composts did not exceed standards of the Regulation of the Minister of Agriculture and Rural Development (Official Journal of Laws No. 165, item 765 of 2008) referring to organic fertilisers. In the study design, the following fertilisation treatments were applied: I - carbonate lime (CaCO3) at a dose of 1.5 Mg CaO · ha-1, II - high-calcium brown coal ash at a dose of 1.5 Mg CaO · ha-1, III - municipal sewage sludge compost at a dose of 250 kg N·ha-1, IV - municipal sewage sludge compost at a dose of 250 kg N · ha-1 + high-calcium brown coal ash at a dose of 1.5 Mg CaO · ha-1 (1st year of study), V - high-calcium brown coal ash at a dose of 1.5 Mg CaO · ha-1 (1st year of study), and 0.75 Mg CaO · ha-1 in following study years each, VI - municipal sewage sludge compost at a dose of 250 kg N · ha-1 + high-calcium brown coal ash at a dose of 1.5 Mg CaO · ha-1 (1st year of study), and 0.75 Mg CaO · ha-1 in following study years each. In addition, mineral fertilisation was applied annually in the form of multi-component fertiliser Polifoska 20, complex fertiliser Polimag S and ammonium nitrate. A test plant was perennial grass - Amur silver grass (Miscanthus sachariflorus). The obtained results show that Amur silver grass biomass contained on average the most nitrogen, ie 6.87 g·kg-1 d.m., in 2008, while the most phosphorus (0.39 g P·kg-1 d.m.), potassium (7.82 g K·kg-1 d.m.), magnesium (0.98 g Mg·kg-1 d.m.) and sulphur (1.19 g S·kg-1 d.m.) in 2010, whereas the most calcium ie 4.13 g Ca kg-1 d.m., in 2009. Significantly more nitrogen, calcium and sulphur was contained by Amur silver grass biomass from the objects where municipal sewage sludge compost had been applied without and with addition of high-calcium brown coal ash when compared to calcium carbonate or high-calcium brown coal ash being applied at a dose of 1.5 Mg CaO · ha-1. Differences in average phosphorus, potassium and magnesium contents in test plant biomass from particular fertilisation objects were not significant. The biomass of Amur silver grass contained significantly more cadmium, nickel, lead and zinc as affected by organic fertilisation without and with addition of high-calcium brown coal ash when compared with the objects where solely calcium carbonate or high-calcium brown coal ash had been introduced into soil. Differences in the average content of cadmium, nickel and zinc in test plant biomass from the objects fertilised with municipal sewage sludge compost without and with addition of high-calcium brown coal ash were not significant. The uptake of heavy metals by Amur silver grass biomass, ie its mean value of three harvest during three years of its cultivation, can be arranged in the following descending order of values: Zn > Mn > Pb > Cu > Ni > Cd. The degree of cadmium, copper, manganese, nickel, lead and zinc bioaccumulation in test plant biomass differed, depending on the fertilisation applied. The average degree of cadmium, nickel, lead and zinc accumulation after three study years was intense for all fertilisation objects, whereas average for copper and manganese.
Soil enzymes as indicators of long-term sewage sludge compost application
