Introduction. Soil at all times is the main condition for the emergence, existence and irreplaceable source of human life. Soil mycobiota plays an important role in plant life and soil fertility, where its main nutrition is organic components. The introduction of organic substances into the soil contributes to the accumulation of humus, and the presence of microbiological organisms contributes to its decomposition. Taking an active part in soil processes during the cultivation of agricultural crops, soil microorganisms are modified, especially when applying various fertilizers. Organic substances introduced into the soil create various conditions for the formation of soil mycobiota and affect their abundance. Therefore, the microbiological processes that occur in the soil when applying a biologizing background play a huge role in the cultivation of winter grain crops. The purpose of the research is to reveal the influence of the biologizing background on the number of soil mycobiota of winter wheat in the conditions of the Republic of Mari El. Materials and methods. The research was carried out in 2018‒2022 in the conditions of field experiment on sod-podzolic medium loamy soils in JSC Stud Farm “Shoibulaksky” on winter wheat crops. The task was to study the effect of the use of straw mulch, liquid pig manure and the microbiological preparation Biocomposite-correct on the number of soil mycobiota. In the experiment, the intensity of cellulose decomposition and the number of pathogenic fungi in the arable soil layer were determined. The results of the discussion. Over 60 days of winter wheat vegetation, the maximum cellulolytic activity of microorganisms (72.6‒73.5 %) was detected in the 0‒10 cm soil layer, where a biologizing background in the form of mulch, liquid pig manure and microbiological preparation was used, where the number of pathogenic fungi decreased to 19.6 and 17 %. Conclusion. Cultivation of winter wheat on sod-podzolic soil in the conditions of the Republic of Mari El showed that the biologizing background increases the number of cellulose-destroying microorganisms in the soil by 2 times, reducing the pathogenic complex by 2.8‒3.2 times.