The research involved the use of a variety of organic waste materials, fresh and composted, including: sludge from two sewage treatment plants, from Siedlce and Łuków, and broiler droppings. A total content of phosphorus was determined using the ICP-AES method following a dry mineralization of materials in muffle oven at 450^oC. The fractions of phosphorus were separated using the Chang-Jackson sequential analysis with further modifications. The total phosphorus content depended on the origin of organic material. The highest content was determined in the sludge 85% of which was municipal waste and 15% – industrial waste and the lowest – broiler droppings. The sum of extracted phosphorus in respective fractions accounted for a higher percentage share than the amount not exposed to extraction.

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