The decline of soil organic matter is the most common soil degradation process in arable lands. On sloping terrains, it is intensified by the flow of water erosion. A three-year experiment was conducted on Calcic chernozem on sloping terrain, with the application of conservation and traditional soil treatments. Two tillage systems on winter wheat—maize rotation where tested—conventional technology and conservation technology, including minimum tillage (no ploughing) and a cover crop between two main crops. The activity of peroxidase, polyphenol oxidase, alkaline phosphatase, protease, ß glucosidase, urease, as well as the content of labile carbon fractions, were measured twice in a year (in spring and autumn). Applied erosion control practices have a positive effect on soil organic matter, labile organic fractions and enzyme activity. The highest degree of correlation of the amount of total organic carbon and microbial biomass carbon was found by polyphenol oxidase activity (r =  +0.55 and r =  +0.47, p < 0.0001) and available potassium forms (r =  +0.52 and r =  +0.50, p < 0.0001). Minimum tillage for growing wheat and maize on sloping terrain, with the inclusion of a cover crop in the rotation, is an appropriate practice for improving soil biochemical indicators.