Development of some soil properties under the influence of fertilization with composts and vermicomposts of tannery sludge

A pot experiment was carried out in 1996-1999 in which compost and vermicompost were prepared from a combination of untreated organic sludge from a mechanical and biological tannery sludge treatment plant with wheat straw and fruit tree leaves before proceeding to combine the untreated chemical sludge with these pre-prepared composts and vermicomposts and added wheat straw. Comparative fertilization was then applied with farmyard manure and mineral NPK. The organic materials applied for the treatment affected an increase in pH value and a decrease in hydrolytic acidity. The scale of the changes depended on the kind of used materials. Although composts and vermicomposts used for the treatment did not directly affect an increase in soil organic C content, it stabilised this feature value in a similar manner to farmyard manure treatment. Fertilization with untreated sludge lowered organic C content in a similar manner to the mineral treatment. Organic fertilization did not alter the total nitrogen content of the soil. The positive effects of tannery organic material application included an increased amount of phosphorus available to plants, whereas the treatment negatively affected the contents of assimilable forms of potassium.