CONTENT AND REMOVAL OF Cu AND Zn WITH HARVESTED CROPS GROWN ON SOIL FERTILIZED WITH COMPOSTED MUNICIPAL SEWAGE SLUDGE

The purpose of the study has been to determine the direct and residual effect of farmyard manure and composts made from sewage sludge on the content and uptake of copper and zinc by crops growing in a four-field crop rotation system. In 2004-2007, a field experiment was established on proper grey-brown podzolic soil, originating from light boulder clay, rich in P, moderately abundant in K and low in Mg, whose reaction was pH = 5.04. The experiment involved a four-field crop rotation cycle with the following crops: potato, spring barley, winter oilseed rape and winter wheat. The design of the experiment, set up according to the random block method, consisted of 8 object (2 x 4): 1) FYM 2) composted sewage sludge, 3) compost (sewage sludge + straw), 4) dried and granulated sewage sludge. The composts and farmyard manure were applied once in the rotation system (under potato) at a rate of 10 t d.m. ha(-1) or twice, each time 5 t d.m. ha(-1) (under potato and under winter oilseed rape). In the objects fertilized with organic fertilizers and manure, nitrogen was balanced to 150 kg.ha(-1) (under potato) and to 120 kg.ha(-1) (under oilseed rape) depending on their total content of nitrogen. Spring barley and winter wheat received only mineral fertilizers. Before the experiment was set up, samples of soil, manure and composts had been collected for determination of Cu and Zn in 1 mol HCl dm(-3) by atomic absorption spectrophotometry. The content of zinc and copper in the crops was modified by the form of sewage sludge and sewage sludge composts to a greater extent than by the way these fertilizers were applied in the crop rotation system. Soil fertilization with dried and granulated sewage sludge or composted sludge increased the content of copper and its removal with harvested potato and winter rape, but the analogous values were higher when the cereals were grown on FYM fertilized soil. The strongest influence on the content and removal of zinc was exerted by soil fertilization with dried and granulated sewage sludge. The index of copper and zinc uptake was to a greater degree conditioned by the species of a crop than by the type of fertilizers or their application method. Municipal sewage sludge and sewage sludge composts can be used as a substitute of manure in farms which do not keep farm animals.