Reaction of micromycetes of leached chernozem on the application of different forms of nitrogen fertilizers

Application of nitrogen fertilizers did not significantly affect the number of micromycetes. The restructuring of the species structure of the mycobiome did not exceed the adaptive zone of “stress” – a change in the frequency of occurrence of typical species. Typical types of leached chernozem micromycetes include deuteromycetes of the genera Aspergillus, Penicillium, Trichoderma, Gliocladium, Humicola, Fusarium, zygomycetes (genus Rhizopus), ascomycetes (genera Thalaromyces, Chaetomium). On average, the density of dominant species of micromycetes increased by 20 %, which indicates the development of the “dominance concentration” of typical species and a decrease in the share of rare and random species of fungi in the mycocomplex. In the experiment variants, the density of Penicillium daleae, P. funiculosum, Fusarium solani, and Aspergillus ustus species increased compared to control. These types of micromycetes are toxigenic and synthesize broad-spectrum mycotoxins (fungicidal, antibiotic, and phytotoxic). As a result, the phytotoxic activity of the soil increased to 7 and 20 % (native soil) and to 19-34 % (initiated microbial community). More pronounced changes were observed in the variant with ammonium sulfate. Thus, nitrogen fertilizers at a dose of N90 cause a “stress” reaction of the mycobiome, an increase in the share of toxigenic species and phytotoxic activity of leached chernozem. With long-term systematic use of nitrogen fertilizers, even in medium doses, it is possible to reduce the potential fertility of chernozems.