Biochar alleviates phytotoxicity in Ficus elastica grown in Zn-contaminated soil

Zinc (Zn) immobilization by two distinct biochars in soil, together with concomitant alleviation of phytotoxic responses in Ficus elastica Roxb. ex Hornem., were examined. Rooted cuttings of F. elastica were grown in 880 mg kg^{− 1} Zn-spiked sandy soil amended with grain husk (GH) or cattle manure (CM) biochar at 0, 10, 30 and 50 g kg^{− 1} soil for a period of 6 months. Addition of both GH and CM biochars had significant positive impacts on physiological parameters such as plant growth, leaf relative water content, photosynthetic pigments and leaf gas exchange characteristics. The responses to addition of CM biochar were significantly better than to GH biochar. Lipid peroxidation declined in leaves of plants grown in Zn-contaminated, biochar-amended soil. This was confirmed by luminescence and Fourier transform infrared analysis of the leaf material. Biochar significantly reduced the availability of soil Zn, as evidenced by lower concentrations of Zn in leaves and leachates of biochar treated plants relative to control plants. These findings show that biochar can effectively immobilize soil Zn, and as a result, alleviate Zn phytotoxicity by reducing its uptake and accumulation in the plant. Adding biochar to soils contaminated with metals thus holds promise as a means of restoring blighted lands.