Under the conditions of a 24-day model experiment on soil samples of ordinary chernozem (Corg=3.6%, pH=7.4), the effect of biopreparations on the biological activity and on the dynamics of the content of two forms of soil organic matter (Chwl and Corg) was evaluated. Based on the results of theeffectof the used biopreparations on the intensity of substrate-induced soil respiration, they can be classified as means of biological activation of soil. The biological activity of the soil increased in the Rizoplan-Sporex-Bisolbi-Trichosan-Baktofit series when the biopreparations were applied to the soil before sowing, varying in the range of 57–156.7 µl CO2/h/g of soil, while the indicator in the reference variant was 28.6 µl CO 2 /h /g soil. The bioactivation agents show a pronounced ability to destroy soil organic matter, which is expressed in a reduction of the gross carbon content. The fraction of organic carbon extracted by hot water is negatively correlated with plant biomass (r = –0.845), which may indicate the involvement of this fraction in the direct formation of biomassat the early stage of barley plant development. At the same time, the carbon of the microbial biomass is characterized by a weak correlation with the plant biomass (r=0.298) in the period studied.