Soil enzyme activity indicates potential of the soil to sustain biochemical processes, which are essential for the maintenance of soil fertility. Dehydrogenase activity reflects total oxidative activity of soil micro flora, catalase activity is responsible for the decomposition of H₂O₂. Redox potential (Eh) is an index of the soil aeration status. Effects of soil temperature and water content on Eh, soil dehydrogenase activity and catalase activity in an Eutric Histosol at three different fields planted with Populus nigra, Salix americana, and grasses (with Alopecurus pratensis, Phalaris arrmdinacea, Festuca pratensis as dominating species) were studied at the depths of 10, 30, 50, 70 cm. Enzyme activity and redox potential showed seasonal fluctuations following natural changes of soil water content and temperature. Dehydrogenase activity was significantly correlated with soil temperature and water content (r = 0.37** and r = 0.27***, respectively). Redox potential showed a significant correlation with soil water content (r = 0.32***). Catalase activity did nut exhibit any correlation with the tested parameters. The type of plantation influenced enzyme activities; tree cover was characterised by higher dehydrogenase and catalase activities than meadow soils.