ZINC AND CADMIUM ACCUMULATION IN MAIZE (ZEA MAYS L.) AND THE CONCENTRATION OF MOBILE FORMS OF THESE METALS IN SOIL AFTER APPLICATION OF FARMYARD MANURE AND SEWAGE SLUDGE

The total content of heavy metals in soil does not indicate bioavailability of these elements after introduction of sewage sludge to soil. Determination of the rate of heavy metal mobilization from sewage sludge after its application to soil is very important for agricultural practice since it allows us to asses the rate at which these elements pass into the soil solution, which conditions their uptake by plants. This research has been conducted to assess the effect of farmyard manure and sewage sludge fertilization on the amounts of zinc and cadmium absorbed by maize and the content of their mobile forms in soil. The research consisted of a three-year pot experiment. Farmyard manure and sewage sludge fertilization resulted in larger total yields of maize biomass (for the 3-year period of the investigations) than harvested from the treatments where only mineral compounds were used as fertilizers. Irrespectively of the fertilizer dose, the total (for 3 years) amounts of zinc and cadmium absorbed by maize were the highest in the treatments where only mineral salts were added and Zn and Cd quantities taken up by maize in the first year of the experiment contributed to this result. Fertilization with farmyard manure and sewage sludge did not cause any significant mobilization of mobile zinc and cadmium forms in soil after the first year of the research. As a result of organic matter mineralization and progressing soil acidification, in the second and third year of the research, the content of mobile forms of the elements in soil increased, although to a lesser degree than under the influence of exclusively mineral treatment.