Immobilization of cadmium (Cd) through adding organic amendments is considered as a good and an economic in-situ remediation way to diminish its mobility and bio-availability in contaminated soils. This experiment was conducted under natural conditions in the greenhouse of Soils and Water Department, Faculty of Agriculture, Benha University Egypt. The aim of this study was to evaluate the effect of cattle slurry (CS), green manure (GM) and their combination (CG) on the growth of forage maize, Cd accumulation in its different tissues and Cd fractionation in a clay loamy soil polluted with heavy metals due to using waste and industrial water in the irrigation. The bio-accumulation and translocation of Cd by maize were also evaluated. Incorporation of CS, GM and CG residues into the chosen contaminated soil increased soil pH and improved both soil organic matter (SOM) and available phosphors contents. Application of CS, GM and CG significantly decreased the concentration of exchangeable Cd but amounts of organic-bound and precipitated Cd were strongly affected and increased by them. In the present study, concentrations of exchangeable Cd decreased by 1.21-3.26 times, 1.46-9.54 times and 2.18-6.53 times after 45 days and by 1.29-4.44 times, 1.88-17.14 times and 2.79-10 times after 70 days due to incorporation of CS, GM and CG amendments, respectively. Immobilization of Cd in the used soil was highly influenced by soil properties. The growth of forage maize, which was expressed by the dry weights of its shoots and roots significantly improved due the application of CS, GM and CG. The highest dry weights of maize shoots and roots were obtained when the soil was treated with highest rates of CS, GM and CG. In this study, GM was the most efficient amendment in decreasing Cd accumulation in shoots and roots of maize. Results of sequential extraction of Cd confirmed that addition of CS, GM and CG amendments had marked role in decreasing soluble/exchangeable Cd through converting it into more stable and un-available forms, and this could cause strong reductions in its bio-availability to forage maize. Compared to the control treatment, amounts of Cd in shoots and roots of maize were reduced by 72.69-43.59%, 88.87-75.97% and 83.10-65.58% after 45 days, and by 86.67-73.59%, 96.32-88.32% and 91.03-85.89% after 70 days in response to the highest rates of CS, GM and CG, respectively. Concentrations of Cd in maize shoots and roots were highly depended on its availability in the soil. Both of CS, GM and CG amendments could be effectively applied and recommended for immobilization of Cd with high improvements for soil properties and large decreasing for Cd risk on maize plants grown on the used contaminated soil. |
