# Effect of Precision Nitrogen Fertilization of Grassland on Soil Microbial Structure
## 3 Results and Discussion
### Quantitative and Qualitative Characteristics of Actinomycetes in the Soil Profile
For _Streptomyces venezuelae_ at a depth of 0.25 m in the soil profile, the highest abundance, falling within the range of 4.545 to 4.988 CFU/g of soil, was characterized by an area occupying 1.8%. This area was also located in the northwestern part of the field (Figure 12d). The area characterized by the lowest abundance of this species (range 1.001 to 1.444 CFU/g of soil) included an area (6.3%) consolidated in the central and northeastern parts of the field. A significant abundance was primarily located in the central part of the field (27.5%). Figure 11: Spatial variation of occurrence of _Streptomyces albidoflawus_ in the soil profile; (**a**) at a depth of 0.05 m; (**b**) at a depth of 0.15 m; (**c**) at a depth of 0.25 m; (**d**) at a depth of 0.35 m.  
The analysis of data regarding the abundance of actinomycetes in the soil profile offers valuable insights into the diversity of these organisms in the study area. The results reveal significant variations in the average number of actinomycetes depending on soil depth. The average abundance was lowest at a depth of 0.35 m, with only 46.9 CFU/g of soil, while it peaked at 0.05 m, reaching as high as 1075.6 CFU/g of soil. Interestingly, the areas with the highest and lowest actinomycete abundance accounted for just 0.9% and 5.8% of the field area, respectively. Similar findings were reported by [PERSON] [71] and [PERSON] [72]. Notably, the presence of _Streptomyces albidoflavus_ and _Streptomycesenezulae_ strains across all depths of the soil profile suggests their widespread distribution in the study area. [PERSON] et al. [73] and [PERSON] et al. [74] highlighted an important observation regarding microbial distribution in soil: they found that the topsoil layer (0-5 cm) harbored a higher number of microorganisms (including actinomycetes) compared to the deeper layer (5-15 cm). This difference is likely due to the higher density of roots in the topsoil, which provides essential nutrients. The supply of water-soluble compounds makes microbial activity in the root zone particularly dynamic. Moreover, actinomycetes were observed to be the second most abundant group of microorganisms in the soil, regardless of the intensity of grassland use. [PERSON] et al. [75] noted the significant influence of agricultural  
Figure 12: Spatial variation of occurrence of _Streptomycesenezulae_ in the soil profile; (**a**) at a depth of 0.05 m; (**b**) at a depth of 0.15 m; (**c**) at a depth of 0.25 m; (**d**) at a depth of 0.35 m.  
practices and atmospheric conditions on soil microbial composition. They found that actinomycetes responded most markedly to vegetation management practices. For instance, higher populations of actinomycetes were recorded in moved areas, especially during the last moving cycle, when their numbers reached 102.4 CFU/g dry mass of soil in moved meadows, compared to 43.9 CFU/g dry mass of soil in pastures. Additionally, a high abundance of actinomycetes was observed during dry periods. The authors also emphasized that actinomycetes significantly influence the inorganic nitrogen content of the soil, irrespective of agricultural practices, underscoring the importance of this group of microorganisms in the soil nitrogen cycle.