Incorporation of organic amendments is one of the most eco-friendly and economic strategies for the restoration of contaminated soils through diminishing mobility and bioavailability of heavy metals in these soils. This study was carried out under field conditions during the summer season of 2017 on a clay loam soil naturally polluted with Cd (7.61 mg kg-1) due to successive irrigations with wastewater. The main goal of this study was to evaluate the influence of sugarcane bagasse-derived biochar (SBDB) at different rates on fractionation of Cd in soil and its implications on the growth of soybean and concentrations of Cd within the different plant parts. Incorporation of SBDB into the chosen contaminated soil caused noticeable changes in soil pH, electrical conductivity and organic matter, especially with increasing the rate of application. Immobilization of Cd in the used soil was highly influenced by soil properties. According to the sequential extraction procedure, application of SBDB had an efficient role in reducing the soluble/exchangeable fraction. Moreover, it declined both the reducible and oxidizable forms of Cd. The dry weight of soybean organs (roots, seeds, and straw) improved significantly with SBDB additions. The highest dry weight values of straw and seeds for soybean plants were recorded when the soil was treated with SBDB at rates of 15 and 30 t ha-1. Concentrations of Cd in straw and seeds of soybean were markedly affected by its availability in the soil. They decreased from 2.77, 0.96, and 0.62 mg kg-1 at the control treatment (CK) to 1.75, 0.47, and 0.20 mg kg-1 at B4 treatment (30 t SBDB) ha-1 in roots, straw, and seeds of soybean, respectively. In conclusion, the use of SBDB showed high efficiency in the amelioration of Cd-polluted soils and in decreasing Cd toxicity on soybean plants.
Keywords: Bagasse biochar; Cadmium; Contaminated soil; Fractionation; Soybean; Toxicity.