Effect of Biochar on Cadmium Fractions in Some Polluted Saline and Sodic Soils

Soil contamination by heavy metals is becoming a serious environmental problem especially in saline and sodic soils and information on different fractions of metals is useful to predict their mobility and availability in soil. Addition of organic amendments, as an important technique to remediation of metals has been considered recently. Therefore, the effect of sugarcane bagasse-derived biochar on cadmium (Cd) fractions in saline, sodic, saline-sodic and normal soils were evaluated through an incubation experiment using sequential extraction. Treatments included biochar (0, 2, and 4 wt %) of sugarcane bagasse and 50 mg Cd kg⁻¹ with three replications. In all studied soils with 2 and 4% biochar application, the organic matter fraction was the dominant form of Cd. Biochar had no significant influence on exchangeable Cd in normal and sodic soils. Whereas, application of 2 and 4% biochar increased exchangeable Cd concentration in saline and saline-sodic soils probably due to high capacity of biochar to sorb salts that mitigate the negative effects of salts in soil solution. The mobility factor (MF) of Cd in studied soils was high (20–50%). The MF value decreased with the increase of biochar dosage. According to reduced partition index, Cd was partitioned in all fractions. Based on these results, biochar can mitigate the effect of Cd pollution in these soils.