ИСТИНА

In this study, we analyzed the heavy metal(HM) contaminated soils with different humus content before and after adding of biochar (5%) and lignohumate (0.05%). Phytotesting, biotesting using organisms of main’s trophic levels organisms, microbial structure community as well as microbial functional activities using chromatographic methods were performed with different soil types - agrosodpodzolic, chernozem and , agrozem (Moscow region, Ural and Kalmykia, Russian Federation ). The addition of HM in poor-humus soil was more toxic and led to the complete death of test plants, while the plants in rich-humus soil continued to develop until flowering. The basal respiration and other indicators of microbial metabolic activity also changed to a greater extent in poor-humus soil. A decrease in the toxic phytoeffect of heavy metals during the remediation activity of biochar was observed in samples with a high humus content, while the addition of the tested dose of biochar did not affect plant development in poor-humus soils. The efficiency of biochar increased in some variants of humus-poor soils with the addition of lignohumate (0.05%) Key words: metalpolluted soil, organic carbon, microbial biodiversity, remediation, biotest Acknowledgement. This research was funded by the Russian Foundation of Basic Research (grant #18-04-01218a)