Heavy metals are present naturally in soil but because of human activities, are added to the soil. Addition of heavy metals in soil through the application of soil amendments such sewage sludge creates soil pollution. An alternative in decreasing soil pollution risk is converting the organic amendments into biochar via pyrolysis. Biochar has large surface area, high stability against degradation and high power ion absorption compared to other forms of organic matter in the soil. The objective of this study was to determine the effect of sewage sludge and its biochar on uptake of heavy metals. This greenhouse experiment was carried out in a completely randomized design in factorial arrangement with three replications in greenhouse in Isfahan University. The treatments were biochar (0 and 10 t ha -1 ), sewage sludge (0, 10 t ha -1 ) and three levels of cadmium (0, 5 and 10 mg kg -1 ) and using spinach and corn. Shoot and root biomass of corn and spinach were significantly increased with the application of sewage sludge and biochar. Cadmium uptake by the plants increased as Cd concentration increased in the soil. The greatest Cd concentration was observed in pot with 10 mg/kg Cd and without sewage or biochar addition in spinach plants. Sewage sludge and biochar application decreased the uptake of Cd by both plants. Based on our results biochar can be used to immobilize Cd in soil and thus reduce its uptake by plants.
