Scilight Press

The aim of this work was to compare the contribution of heavy metal contamination (Cd, mobile form, 6.4±0.5 mg/kg), short-term drought (25 days) and pH decrease (4.8 pHKCl units versus 6.6 pHKCl units in control) to toxicological and microbial status of the experimental soil to conclude on the agricultural suitability on similar soils. Each functional load was modelled separately in a microfield experiment. It was shown that increased soil acidity led to maximum differences in toxicity indices from those of the control soil compared with the action of other unfavourable factors: 36.4% in the test for Paramecium caudatum and 56.8% in the test for Escherichia coli to control. The results of laboratory bioassays were consistent with the reaction of soil enzymes: the decrease in the urease activity in acidic soil reached 39.09%, the decrease in the catalase was 25.23% compared to the soil without load. At the same time, the community of soil microflora was subjected to restructuring under all types of load with the dominance of oligotrophic microflora, which was uncharacteristic for natural soil. Consequently, the degree of change in ecological, toxicological and microbiological characteristics of the soil decreased under the influence of factors in the following series: soil acidity > drought ≈ contamination.