Immediate effects of the application of various fungal strains with urea fertiliser on microbiome structure and functions and their relationships with the physicochemical parameters of two different soil types

Abstract The incessant increase in the demand for food from the world population, which is occurring due to its continuous growth has, as a consequence, led to an increase in the use of fertilisers. Our work aims to analyse the application effect of various fungal strains with urea fertiliser on the structure and functions of bacterial communities, including ammonia-oxidising microorganisms (AOM) in different soil types. By analysing the abundance of ammonia-oxidising archaea (AOA) and bacteria (AOB), we observed that the application of urea fertiliser (UC) changed the soil microbial community, causing a disturbance in soil microorganisms diversity, whereas the addition of fungal strains to urea fertiliser (UA100; UA60) did not have a disordering effect compared to the Control soil (C). This indicates that the addition of fungal strains mitigated the adverse effects of urea on the soil environment. A similar effect was observed for the genes involved in the carbon cycle (bacterial carbon fixation, chitinase, and methanotrophic pathway genes). It was observed that the addition of fungi to the urea fertiliser had a positive effect, as the abundance of functional genes recorded in these treatments was the same as in the Control soil. From the diversity point of view, it is worth emphasizing that the diversity index changed after fungal organisms' addition. We may also observe that the addition of fungal strains to urea protected or even improved the state of the soil macropores which are important for microbial communication in the soil environment. Furthermore, it may be concluded that to avoid a strong negative effect from the application of urea and the mitigation of its influence by fungal strains, we must consider the soil texture, pH, total carbon content, and soil organic matter including humic and fulvic acids.