Effects of sewage sludge treatments on plant nutrients, heavy metals and tall fescue (Festuca arundinacea Schreb.)

This study was conducted to investigate the effects of anaerobically stabilized sewage sludge (SS) converted into 90% dryness granules at different doses of control, 3% SS, 6% SS, and 9% SS on elemental composition of Festuca arundinacea Schreb. and physicochemical properties of soil. Color measurements were made with the CIE L* a* b* method unit; the highest color (4.10) and the highest coating score (5.7) were calculated for the 6% SS treatment. The highest biomass (9.11 g) was obtained from the 3% SS and the lowest (7.67 g) from the 9% SS dose. Plant height measurements were listed as follows: 3% SS (9.5 cm) > 6% SS (8.8 cm) > control (8.7 cm) > 9% SS (8.1 cm). Average bioaccumulation factor for the present heavy metals were ordered as: Cd (0.542) > Hg (0.452) > Cr (0.448) > Ni (0.246) > Pb (0.076). The lowest geoaccumulation index (I-geo) was obtained in Cr (-1.35) and the highest value in Cd (1.69). Available P, K, Ca, Mg were analyzed with ammonium acetate extraction method, and Fe, Zn, Cu, and Mn in the soil extracted with DTPA were determined. In the soil samples, total N (0.180%) and available elements (mg kg-1) P (101.393), Ca (6502.570), Mg (609.433), Na (259.44), Fe (13.61), Cu (4.05), Zn (17.76), and B (1.00) were determined at high values in the 9% SS application. Heavy metals (mg kg-1) were extracted with aqua regia. Nickel (48.87), Pb (26.83), Cd (0.97), and Hg (153.12 mu g kg-1) were determined at high values in the 9% SS application. Plant nutrients in the plant samples were extracted from acid digestion, and N (3.93%), P (0.51%), Mg (0.59%), Ca (1.77%), Zn (127 mg kg(-1)), and B (15 mg kg(-1)) were determined at high values in the 9% SS application. Heavy metals' (Ni, Cd, Cr, Pb, and Hg) content toxic effects were not observed in the plants.