Agricultural practices with high traffic and with low input of organic material into the soil result in the deterioration of soil structure leading to soil compaction. It is accompanied by the reduction of gas exchange and by limited colonizable habitats. The changes in microbial biomass and its activity cannot be readily explained by interactions of altered gas and water exchange. In order to explain the differences in biological activity of compacted and uncompacted soils, the soil structure related microbial turnover was observed. The content and the availability of soil organic carbon, microbial biomass and respiration activity in micro- (