摘要：The aim of this study was to determine the content of organic carbon, nitrogen, phosphorus, potassium and total nickel and its fractions, separated by the BCR procedure in selected natural fertilizers. Swine, bovine and chicken (from broilers and layers) manures, from selected individual farms from the districts of Siedlce, Sokolow and Losice in Mazowieckie province, were analyzed. The organic carbon was determined by the oxidation-titration method and total nitrogen content by the Kjeldahl method. Total phosphorus, potassium and nickel content was determined by inductively coupled plasma atomic emission spectrometry (ICP-AES). Sequential fractionation of nickel was made using the analytical procedure, in accordance with the methodology proposed by the European Community Bureau of Reference, abbreviated as a BCR method. The results were analyzed statistically using the STATISTICA 12PL (StatSoft, Tulsa, USA). Analyzed organic materials were varied both in terms of content macroelements and nickel. The highest content of organic carbon and total nitrogen contained was found in swine manure, phosphorus and potassium in manure from layers, while manure from broilers contained the largest quantities of nickel. Distribution of nickel in the analyzed fractions depend on the origin of organic fertilizer. The swine, bovineand manure from layers contained the most oxidizable fraction, therefore formsof nickel associated with organic matter and sulfides, while the least reducible fraction. Differently, this fraction was dominated in the manure from broilers. In this organic material the smallest percentage accounted for exchangeable and easily soluble in an acidic environment forms.
