Influence of treated sewage sludge applications on total and available heavy metal concentration of sandy clay soil

The objective of this study is to determine influence of treated sewage sludge (TSS) rates on total and available heavy metal concentrations in a sandy clay soil. The experiment was conducted in the experimental fields of Ege Agricultural Research Institute in Menemen, Izmir, Turkey. The field study was conducted in 20 parcels in a randomized-block design with four repetitions and five different applications including control, mineral fertilizer, TSS 12.5 t ha(-1), 25.0 t ha(-1), 37.5 t ha(-1) as dry matter. The parcels dimensions were 3 m x 3 m. Corn (Zea mays) was planted as the first crop and wheat (Triticum durum) was planted as the second crop. Increasing TSS applications to this soil resulted in significantly increased concentrations of total Cr and Zn in soil as average of five sampling periods. However, concentrations of total Cu, Cd, Ni and Pb in soil did not significantly change. Total heavy metal concentrations in soil were found under threshold values. Increasing TSS applications to this soil resulted in significantly increased available (diethylenetriaminepentaacetate-DTPA-extractable) concentrations of Cu, Cr, Ni and Zn in soil. However, available Cd and Pb concentrations in soil did not change significantly.