Soil Cd Contamination and Evaluation of It's Effects on Soil Biological Quality and Plant Growth

Recently the concept of soil quality has been widely emphasized than that of water or air quality. The maintenance of soil quality is critical for ensuring the sustainability of the environment and biosphere. Cadmium (Cd) as one of heavy metals (HM) which has toxic effects on activity and compound of soil biota. Phytoremediation which refers to the use of plants and helper microorganisms for remediation of contaminated soils is an effective and low cost method for reclamation of heavy metals polluted soils. Soil biological parameters can be used for evaluating the quality of contaminated soils. Arbuscular mycorrhizal fungi (AMF) and plant growth-promoting rhizobacteria (PGPR) are known to enhance plant growth and survive in HM-contaminated soils through different mechanisms. This study was conducted to evaluate the efficiency of phytoremediation and the effect of AMF and PGPR in reducing adverse effects of Cd to Hyoscyamus plant. This experiment were performed at greenhouse condition with three replicates in a factorial plot, including two factors; cadmium levels (0, 10, 30 and 100 mg kg-1 soil), and microbial inoculation treatments (control, PGPR and AMF inoculation). The results showed increasing soil Cd caused increased shoot Cd concentration and microbial metabolic quotient (qCO2). Furthermore, Cd significantly decreased plant shoot yield, microbial biomass carbon (MBC), microbial respiration, substrate-induced respiration (SIR), mycorrhizal symbiosis percent as well as bacterial population. Microbial inoculation effectively decreased inhibitory effects of Cd on biological parameters. It is conclude that in soils contaminated with Cd, using plant growth-promoting microorganisms can decline adverse effects of Cd on growth and microbial indices of soil quality.