Disposal of post-harvest residues from agro-ecosystem remains one of the urgent issues of today for agricultural producers. Burning straw and stubble is an extremely radical and destructive method for biogeocenosis, because during combustion between straw and the soil layer due to water vapor, conditions are created that the burning temperature exceeds 600°С. As a result of such actions, microorganisms, worms, insects, small vertebrates die and the fertile layer of humus is destroyed. Modern biological preparations, which contain a complex of living agronomically useful microorganisms, help to solve the issue of postharvest residues. By accelerating the destruction of organic masses in the soil, the C:N ratio is equalized, organic substances are supplied in a form available to plants, the development of phytopathogens is inhibited, moisture is retained, and humus accumulation processes are active. Field studies were conducted to determine the effectiveness of the new biological preparation BioSistem POWER KS (BioSistem POWER, SC), which contains active bacterial strains of the genera Paenabacillus, Azotobacter, Enterobacter and micromycetes of the genus Trichoderma. Selection of soil samples was carried out 90 days after processing, laboratory tests were carried out in accordance with generally accepted microbiological methods. It was established that the use of BioSistem POWER KS biological preparation (BioSistem POWER, SC) compared to the control increases the level of carbon dioxide emission of the soil of the experimental variants by 2 times, the level of cellulolytic activity by 23–34% depending on the rate of use, the antifungal activity of the soil by 2.5-3 times. Therefore, the biopreparation BioSistem POWER KS (BioSistem POWER, SC) at the rate of 0.3 and 5 l/ha can be recommended to agricultural producers for use in the autumn-spring period to accelerate the decomposition of post-harvest residues.