Grasslands are the most carbon-rich of all agricultural ecosystems, but are also the most endangered. The global area of grassland decreased during the 20th century, mainly due to conversion to arable land, improper management, and abandonment. Due to ongoing climate change, maintenance of an adequate level of soil organic matter is of primary importance, not only to maintain the productive function of the soils, but also to ensure their role as carbon stores. The main aim of this study was to assess the linkages between selected chemical and biochemical soil properties in alluvial grassland soils, characterized by a low water table. The area under study was located in the Koło Basin, central Poland. Soil parameters, such as total organic carbon, total nitrogen, pH, phosphorus, magnesium, and potassium contents, as well as enzymatic activity and soil microbial structure were studied. Positive correlations were observed between total organic carbon content and the following enzymatic activities: dehydrogenase (r = 0.63), acid phosphatase (r = 0.69), and alkaline phosphatase (r = 0.86). There was a significant correlation between fungi abundance and phosphorus and potassium contents, and between actinobacteria abundance and total organic carbon content.