A comparative research on the impact of organic amendments on the soil characteristic and uptake of heavy metals, micro and macroelements of Odontarrhena chalcidica has been carried out. Experiments have been implemented in controlled conditions. The serpentine soil used in this experiment was sampled from the vicinity of the village Kazak, Bulgaria. The pot experiment was a randomized complete block design containing 9 treatments and three replications (27 pots). The treatments consisted of a control (no organic meliorants), and compost, vermicompost, biochar and activated carbon (added at 2.5% and 5.0%, respectively, recalculated based on dry soil weight). The application of organic additives to the soil influences the physicochemical properties and leads to an increase in organic matter and the content of macroelements (P, K, Ca and Mg) and trace elements (Fe, Mn, Zn) in the soil. The application of organic additives to the soil affects the uptake of Ni, micro and macroelements by Odontarrhena chalcidica. Plant biomass increased significantly, and there was a clear correlation between the amount of supplement applied and the increase in biomass. Organic additives had a positive effect on yield, influenced by the type of additive and dose. Ni yield was 3 times higher in the variants with 5% compost and 2.5% vermicompost input. The application of biochar resulted in a twofold decrease in Ni yield, while the application of activated carbon resulted in a marginal increase.
Keywords: phytomining, activated carbon, biochar, compost, vermicompost, serpentine soils, O. chalcidica