THE INFLUENCE OF LONG-TERM FERTILIZATION WITH SLURRY, MANURE AND NPK ON THE SOIL CONTENT OF TRACE ELEMENTS

Long-term application of fertilizers can change the chemical composition of the soil environment. Our objective has been to determine total amounts of trace elements (Cu, Mn, Zn, Cd and Pb) in the top layer of soil after 34 years of annual applications of organic and mineral fertilizers. The first experiment was set up in 1972 on lessive soil, while the second one was started in 1973 on brown soil. The same crops were grown in both experiments. Bovine manure and slurry were applied in the first experiment, while the other one involved the application of swine manure and slurry. Slurry was applied at two different doses. One dose of slurry was applied together with manure and mineral fertilization in amounts balanced according to nitrogen. The other dose of slurry was determined so that it brought to soil the same amount of organic carbon as introduced with a manure dose. Manure and slurry were also applied in combination with phosphorus and potassium fertilizers in amounts equal half the content of these components used delivered through exclusive mineral fertilization. The total metal content was assessed using the atomic absorption spectrometry method, with prior mineralization in a 1:1 mixture of nitric and chloric acid. The application of fertilizers over many years increased the content of trace elements. The actual effect varied between the analyzed soil types, depending also on the type of fertilizer and the dose of slurry. The average content of Cu, Cd and Pb was 13.8% higher in lessive than in brown soil, while the amount Mn was lower by as much as 32.7%. Among the doses balanced with respect to nitrogen, the effect of manure caused an increase in the Mn, Zn and Ni content in lessive soil, as well as Cu and Pb in brown soil compared to the application of the slurry dose balanced with manure according toorganic carbon. Mineral fertilizers did not increase the content of the analyzed metals as much as manure, with the exception of Cu and Pb in lessive soil and Ni in brown soil. Compared to manure, the application of slurry in the second dose balanced with manure using organic carbon resulted in increased concentrations of Cu and Pb in lessive soil as well as Mn, Zn, Cd and Ni in brown soil. Additional fertilization with phosphorus and potassium (PK) had various effects on the content of trace elements.