The effect of organic fertilisers on distribution of heavy metals among fractions in soil

The investigations aimed at determination of the main forms in which lead, copper, chromium and cadmium occur in soil after the application of various organic fertilisers. The experiment, including nine plots, was set up using randomised blocks method. Mixed farmyard manure was the comparative fertiliser. It was applied in two doses. The doses of peat compost and raw organic sludge were calculated according to the amount of nitrogen in the applied FYM dose. Phosphorus on the plots with manure and raw organic sludge was supplemented with superphosphate to the amount applied in the peat compost, while potassium was supplemented up to its amount in manure doses as 60% potassium salt. Feat compost had been prepared from sludge supplied by sewage treatment plant with an addition of 10% of dry mass of garden peat in relation to dry sludge mass. After four years of the experiment the contents of heavy metals (Pb, Cu, Cr and Cdf were determined using Zeien and Brummer sequential chemical extraction method. Applied organic fertilisers did not cause an increase in total Ph, Cu and Cd contents in comparison to the soil from the control (untreated). Application of sewage sludge and its compost with pear caused an increase in total forms of chromium. The greatest amounts of lead and copper were detected in the fractions attached to soil organic matter and amorphic iron oxides. The least amounts of ph, Cu and Cr were found in the mobile and exchangeable fractions. Cadmium was characterised by high mobility in soil which confirms its big share (over 50%) in the mobile fraction and the trace amounts of this element bound in the residual fraction.