The study was carried out in the year 2007 on biological properties of the soil in which two varieties of amaranth (Amaranthus cruentus L.) - Rawa and Aztec - were cultivated. In order to observe the changes in the number of soil microflora and its enzymatic activity, soil samples were collected from the same spots late in spring (June) and in autumn (October). It was noticed that higher number of bacteria and Actinomycetes colonies, and activity of dehydrogenase and catalase, were found in the soil where Amaranthus cruentus L. Aztec was cultivated, as compared to Rawa. Soil environment where Amaranthus cruentus L. Rawa was cultivated had higher number of fungal colonies. No matter where the soil samples had been collected, higher biological activity was observed in the soil samples collected in autumn, as compared to the soil samples collected in spring. The statistical analysis that was carried out revealed that the number of microorganisms and activity of the investigated enzymes (dehydrogenase and catalase) were positively correlated with the contents of organic matter, sorptive capacity and reaction of the soils. Equally significant positive correlations were observed between enzymatic activity and number of fungi colonies, bacteria colonies, and Actinomycetes colonies.