Study of the increase in phytoremediation efficiency in a nickel polluted soil by the usage of native bacteria: Bacillus safensis FO.036b and Micrococcus roseus M2

Nickel (Ni) is a heavy metal and soil pollutant but existence of small amount of it as a metallic part of urease enzyme in the plants is necessary. Remediation of spots contaminated with heavy metals is particularly challenging. Phytoremediation, the use of plants for environmental restoration, is a novel clean up technology. In this study, five levels of nickel [control (Ni0), Ni125, Ni250, Ni500 and Ni1000 (mg kg-١ )] as nickel chloride (NiCl2.6H2O) and three levels of bacterial inoculants [control (B0), Bacillus safensis FO.036b (B1) and Micrococcus roseus M2 (B2)] were used in sunflower (Helianthus annus), amaranthus (Amaranthus retroflexus) and alfalfa (Medicago sativa) for phytoextraction of nickel. A factorial experiment with a randomized complete block design (RCBD) with three replications was used. Results demonstrated that by increasing the nickel concentration in soil, its absorption by the plants has increased significantly. The highest concentration of nickel was found in shoot of amaranthus (176.83 mg kg-1) and in the root of plants, in alfalfa (462.73 mg kg-1) by usage of inoculant (P