The application of sewage sludge (50 t ha−1) had highly significant (P < 0.01) positive effects on cation exchange capacity and organic matter, total nitrogen, phosphorus, iron and manganese diethylenetetramine-penta-aceticacid-extractable in soil, and nitrogen, phosphorus, iron and manganese in plant. Also, compost application (50 t ha−1) increased significantly (P < 0.01) the electrical conductivity in soil and potassium in soil and plant. Dry biomass increased significantly (P < 0.01) from 7.7 to 28.7 g per pot with sewage sludge application (50 t ha−1).Conclusions
Application of biosolid as fertilizer sources has become a common practice in Iran, especially in the agricultural lands. The reuse of these nutrients had some beneficial effects on soil fertility, such as increased cation exchange capacity, pH, organic matter, total nitrogen, phosphorous, iron and manganese. However, these benefits were limited by the presence of some potentially toxic trace metals in biosolid.