The role of biochar-microbe interaction in alleviating heavy metal toxicity in Hordeum vulgare L. grown in highly polluted soils

Abstract

The influence of heavy metal-tolerant bacteria, biochar, and their joint application on Hordeum vulgare L., grown in highly polluted soils was analysed for the first time. The high concentrations of heavy metals (HMs) (Zn, Mn, Cr, Cu, Pb, Ni, Cd) were determined in the polluted soil (Spolic Technosol) obtained from the Lake Atamanskoe. The effects of these HMs led to marked differences in H. vulgare L. growth. HMs toxicity slows down the development of the plant by changing morphometric parameters. Application of biochar and microbes reduced the HMs accumulation and enhanced H. vulgare L. growth compared with plants grown in polluted soil without amendments. However, all treatments showed high accumulation of HMs in above- and underground tissues as compared with plants grown in unpolluted soil. The application of biochar and HM-tolerant bacteria decreased the HM content 1.78–9.23 fold and 1.79–5.30 fold, respectively, while the addition of both bacteria and biochar has led to a 3.11–17 fold decrease in HMs content and was the most effective to decrease the translocation of all the studied metals. The metal-tolerant bacteria influenced the plant growth to a large extent. The most prominent impact of biochar + bacteria application was observed for leaves length and dry weight of plants: the parameters were significantly higher and reached those of unpolluted control. However, all of the tested amendments improved the growth performance of plants in polluted soil. The alleviation of metal toxicity by the addition of biochar may be beneficial for the introduced bacteria and increase their activity.