Effect of zeolite, biochar, and mycorrhiza on phytoremediation potential of forage Amaranth (Amaranthus caudatus L.) in lead contaminated soil

High absorption and accumulation of lead in the cultivated Amaranthus caudatus L. make this plant suitable for the purpose of phytoremediation of lead-contaminated soils. The present factorial experiment was carried out based on a completely randomized design with three replications in the Greenhouse of the Faculty of Agriculture, Lorestan University, during 2019. The factors considered in the study included zeolite (0, 5 and 10℅), biochar (0, 7.5 and 15℅), and mycorrhizal fungi (no mycorrhiza and use of mycorrhiza). The highest plant height (1.93 m) and root dry weight (2.55 g) were obtained in the combined treatment of not using zeolite, biochar 15% by weight, and mycorrhiza. Also, the highest biological yield (54.05 g) and accumulated lead in roots (20.05 mg/kg) were obtained in the combined treatment of zeolite 5%, biochar 15%, and no mycorrhiza. Moreover, the highest number of sub-branches (26.67) was recorded in the combined treatment of zeolite 10% + no biochar + no mycorrhiza (Z2B0M0). Furthermore, the highest concentrations of lead in the soil around roots (49.92 mg/kg) were observed in the treatment consisting of zeolite 5% + biochar 7.5% + mycorrhiza. Findings also showed the highest activities of catalase, peroxidase, and superoxide dismutase enzymes in the combined treatment of the plants with zeolite 10% + biochar 15% + no mycorrhiza were obtained. On the other hand, the highest activities of ascorbate peroxidase and glutathione reductase were recorded in the combined treatments of zeolite 5% + biochar 7.5% + no use of mycorrhiza and zeolite 10% + biochar 15% + the use of mycorrhiza, respectively. The highest concentration of lead in leaves (17.71 mg/kg) was obtained in none zeolite + none mycorrhiza + biochar 15%, which was among the best treatments of the study resulting in a high biological performance of the plants (41.55 g). Finally, the most favorable treatment with the highest biological yield (54.05 g) and maximum lead contents of the roots (20.05 mg/kg) was obtained by zeolite 5% + biochar 15% + none mycorrhiza. The maximum biological yield of the plant (54.05 g) and the highest concentration of lead in roots (20.05 mg/kg) were observed in the combined treatment of zeolite 5%, biochar 15%, and no mycorrhiza (Z1B2M0). This is the best treatment for phytoremediation, in which the plants absorb the highest concentration of lead. On the other hand, the highest accumulation of lead in leaves (17.71 mg/kg) was obtained in the treatment with no zeolite and mycorrhiza + using biochar 15% (Z0B2M0). In view of the high biological performance of Amaranthus caudatus L. in this treatment (41.55 g), it is considered one of the most effective plants in bioaccumulation.