The research was carried out on soil from the long-term static field experiments in Osiny near Puławy. The field experiment consisted of two cultivation systems: ‘conventional’ with mineral fertilizers and ‘ecological’ with organic fertilizers. Microbiological and physicochemical measurements were carried out. The number of microorganisms was presented by standard methods. Soil acidity, organic carbon, specific surface area and water vapour adsorption isotherms were determined. The authors found changes in basic microbiological and physicochemical properties of the soil under cultivation with mineral and organic fertilization of winter wheat. The results of measurements of the number of microorganisms were influenced by: fertilization, vegetation stage of the plant and the content of organic carbon. There was a stimulating influence of organic fertilization on a number of the microorganisms. Soil samples taken from the ‘con- ventional’ cultivation system were characterised by lower values of the structural parameters. Samples from the soil organic fertili- zed tended to have a higher content of organic carbon and posses- sed a more pronounced microporous structure. The specific surface areas of soil samples from organic farming were slightly higher than of those originating from the ‘conventional’ soil system.