Effects of sewage sludge used as fertilizer on the yield and chemical contents of common vetch (Vicia sativa L.) and soil

This study was conducted to determine the effects of sewage sludge (SS) used as fertilizer at different concentrations [Control, 20 kg ha^–1 nitrogen (N), 30 ton ha^–1 SS (S1), 60 ton ha^–1 SS (S2) and 90 ton ha^–1 SS (S3), 20 kg ha^–1 N + 30 ton ha¹ SS (N + S1), 20 kg ha^–1 N + 60 ton ha^–1 SS (N + S2) and 20 kg ha^–1 N + 90 ton ha^–1 SS (N + S3)] on common vetch yields and chemical features. For this purpose, an increasing level of SS was applied to the soil samples. The residuals of some heavy metal (Hg, Cr, Fe, Ni, Zn, Mn, Cd, Pb, Cu, Co, and Se) and macro element (K, Ca, Na, Mg, C, and S) concentrations were measured in leafs, seeds and soils. According to the results of this study, SS, when applied to soil in increasing amounts, raised the mineral matter contents of the plants, which favorably affected plant growth. Accordingly, it affected the herbage yield, increasing the yield in parallel with the increasing SS concentrations. Applying N with the SS positively influenced the heavy metal contents on leafs and seeds of common vetch and residue in the soil. Besides, the heavy metal contents were found at below critical levels in the soil, leaf and seeds. Therefore, SS application as fertilizer used in appropriate concentrations did not pollute the soil very much, but did lead to an increase in plant products.