عنوان مقاله [English]
Although sewage sludge as a cheap source with a high content of both organic matter and nutrients has a positive effect on plant growth, the accumulation of some heavy metals following its application, limits the use of this material in agriculture. In present study, an experiment was designed according to a completely randomized factorial design experiment. Treatments consisted of three levels of sewage sludge (0, 50 and 100 g Kg-1), four level of biochar/residue (control, biochar, crop residues and biochar + crop residues) with three replications. Results indicated that sewage sludge has a positive and significant effect on dry matter yield of bean (12.6 %). The addition of this material also increased the uptake and concentration of Zn, Cu, Fe and Mn (measured by atomic absorption spectrophotometer) in bean shoot demonstrating the applicability of this substance in the supply of cationic trace elements for plants. The addition of a mix of rice husk biochar and crop residues to sewage sludge treated soil had a positive effect on the growth of bean, in such a way the maximum dry matter yield was obtained in the interaction of this treatment with the application of sewage sludge at 100 g Kg-1 level that had a growth rate 40.4 % as compared to the control treatment. Generally, the use of rice husk biochar and crop residues significantly decreased mean Zn and Mn concentrations in bean shoots as compared to the control. But the addition of rice crop residues and a mix of rice husk biochar and crop residues caused a significant decrease in mean Cu concentration in bean shoots.