Author(s): Manfred Sager
In Austria, farm animals are estimated to produce about 20×106 ton of excrements annually. In order to predict possible changes of the inorganic compositions of the target soils from various organic fertilizers, mean compositions of excrements, composts and sewage sludges have been compiled on a dry weight basis. Although the high amounts of K and P were beneficial, there were some high concentrations of Na in biogas residues and pig manures. Intense additions of Cu, Zn, and Se are reflected in high loads in the respective excrements, and these amounts in some instances exceeded the threshold limits for soil contamination. Selenium addition to arable soils can be regarded as beneficial, however, as Austria is a low Se area. Composts and sewage sludges were higher in Al and lithophilic trace elements than were the excrements. Factor analysis traced phosphates as the main source of Cd. Cr in processed matrices was significantly higher, and abrasion from tools should be considered in future investigations. Other unwanted trace elements, like Ni, Pb, As and Hg, were found at a rather low concentration.