Continuous Phytoremediation Potential Comparison of Cd Contaminated Soil by Hyperaccumulator Solanum Nigrum L. Under Two Planting Modes

Solanum nigrum L. has been described as a Cd hyperaccumulator, but the potential for continuous remediation, long-term effects of different planting methods, or chemical chelating agents have not been fully characterized. The potential for continuous phytoremediation of Cd-contaminated farmland soil (2.08 mg kg -1 Cd) by 2 planting methods (flowering harvest twice a year and maturity harvest once a year) and the continuous promoting effect of EDTA were studied in a 3-year pot experiment. The results showed that the Cd accumulation capacity by S. nigrum decreased with remediation times, which was mainly caused by the reduction of extractable Cd concentration in soil. The biomass of S. nigrum in treatments with two harvests a year at the flowering stage was significantly greater than that in treatments with harvest once a year at the maturity stage. This resulted in a significantly higher Cd accumulation in the former method than the latter, making it more suitable for practical application. The addition of EDTA improved Cd availability to plants in soil, and the promoting effect did not change with remediation times. The study results have demonstrated that the planting mode of two harvests a year at the flowering stage with the addition of EDTA seems to be a viable option to apply for rapid phytoremediation of Cd contaminated farmland soil