Abstract

This study was conducted to determine the effects of sewage sludge using fertilizer at different doses (3, 6, and 9 ton da^-1) on birds’ foot trefoil yields and chemical features. Residual of some heavy metal (Cd, Pb, Cu and Co) and macro element (K, Ca, Na, S, C and Mg,) concentrations were measured in soils and plants. According to the results of the study, sewage sludge, when applied to the soil with increasing amounts, raised the mineral matter content of plant, which affected the growth of plant favorably. Consequently, it affected the high herbage yield and increased the yield in parallellism with increasing doses of sewage sludge. Heavy metal contents were found under the critical levels in soil and plant. So, sewage sludge application as fertilizer used in appropriate doses did not pollute the soil that much, but leads to an increase in plant products.  

Key words: Sewage sludge, macro elements, heavy metals, birds foot trefoil, and fertilization.