Soil remediation mitigates hazards from contaminants but could deprive soils of initial biota and enzymes. Historically contaminated acidic soil from Arnoldstein (Austria) and calcareous soil from Meza (Slovenia) were washed with 30 and 100 mmol/kg ethylenediaminetetraacetate (EDTA) to remove 78 % and 60 % Pb, 20.5 % and 36 % Zn, 83 % and 61 % Cd. 2.5 %, 5.0% and 10.0% (w/w) of healthy, uncontaminated soil or compost were added to fertilized remediated Austrian and Slovenian soils. For control, we used original and remediated soil without additives. The soil was poured into plastic buckets and spinach (Spinacia oleracea L.) was sown in them. The experiment was conducted in three replicates per treatment and lasted 15 weeks. We measured the chemical properties of the soil, the enzymatic activity in the soil, the mass of spinach and its photosynthetic activity. Remediation of the austrian soil decreased urease activity and increased ß-glucosidase activity. The dehydrogenase activity was not significantly impeded compared to the original soil. Conversely, the use of a high dose of EDTA in the Meza soil, necessary for effective remediation of calcareous soils, resulted in pronouncedly decreased enzyme activities (3.2 times on average). Compost increased the dehydrogenase activity and biochar enhanced the ß-glucosidase activity of the austrian soil. Compost and soil inoculum returned the enzyme activities of the slovenian soil back to the baseline in the original soil. At measured photosynthetic parameters of spinach (chlorophyll fluorescence, gas exchange measurements and SPAD value) on the last day of the experiment, there were no significant differences among treatments.
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