# 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  
The lowest mean value of actinomycete abundance was obtained at a depth of 0.35 m, while the highest was recorded at 0.05 m. These values were 46.9 CFU/g of soil and 1075.6 CFU/g of soil, respectively, with coefficients of variation of 46% and 6%. The observed values of actinomycete abundance were significantly different at different depths of the soil profile. Figure 6 illustrates the abundance of actinomycetes at various levels of the soil profile. The area of the field characterized by the highest abundance of actinomycetes in the soil at a depth of 0.05 m (ranging from 1168.855 to 1189.955 CFU/g of soil) accounted for only 0.9% of the total area. An area comprising 5.8% of the tested area had the lowest abundance of actinomycetes, with values ranging from 1000.044 to 1021.145 CFU/g of soil. In an area covering as much as 39.9% of the field, actinomycete values were observed to fall within the range of 1042.247 to 1063.348 CFU/g of soil, corresponding to the central part of the study area (Figure 7a). Regarding the abundance of actinomycetes in the soil at a depth of 0.15 m, the highest abundance was recorded in an area occupying 3.4% (ranging from 744.441 to 799.987 CFU/g of soil). The same area (3.4%) was also occupied by regions with the lowest abundance of actinomycetes. An area of 26.2% was occupied by regions located in the central part of the field (Figure 7b), where the abundance of actinomycetes fell within the range of 621.159 to 646.705 CFU/g of soil. In the lower parts of the soil profile at a depth of 0.25 m, the highest abundance of actinomycetes was recorded in an area located mainly at the southwestern end of the field, covering 0.9% of the total area. The lowest abundance was recorded at the eastern end and in the central part of the field, accounting for 6%. An area covering 26.2% of the field had an abundance of actinomycetes falling within the range of 227.238 to 248.336 CFU/g of soil (Figure 7c). At a depth of 0.35 m, the highest abundance of actinomycetes, ranging from 82.215 to 89.99 CFU/g of soil, was recorded in an area occupying 2.2% of the field. The lowest abundance of actinomycetes, with values ranging from 20.002 to 27.778 CFU/g of soil, was found in a plot covering 8.8% of the field. A significant abundance of microbes was characterized by an area occupying as much as 23.7% of the field, located in the eastern and central parts (Figure 7d). Two strains were selected for identification: _Streptomyces albidoflavus_ (Figure 9) and _Streptomyces venezuelae_ (Figure 10). The number of ray species in each layer of the soil profile is shown in Figure 8. The presence of _Streptomyces albidoflavus_ and _Streptomyces venezuelae_ strains was recorded at all depths within the analyzed interval (0.05-0.35 m). It can be observed that the abundance of both species decreased with depth. In the topsoil layer, the average abundance of _Streptomyces albidoflavus_ and _Streptomyces venezuelae_ was 538 CFU/g of soil for each species. However, in the layer at a depth of 0.15 m, the abundance of _Streptomyces venezuelae_ exceeded that of _Streptomyces albidoflavus_ by an average of 131 CFU/g of soil. In the deeper soil layers (0.25-0.35 m), the abundance of  
Figure 8: Average amount of individual strains of actinomycetes in the soil profile. The obtained mass spectra were compared with the mass spectra exhibiting the highest similarity index found in [PERSON]'s MALDI Biotyper database (Figures 9a and 10a). In the soil profile at a depth of 0.05 m, two species of actinomycetes were identified: _Streptomyces albidoflavus_ and _Streptomycesenezulae_. In the case of _Streptomyces albidoflavus_, the highest abundance was found within the range of 584.196 to 594.712 CFU/g of soil in an area occupying 1.5% of the total field. This area was located in the northeastern and southwestern parts of the field (Figure 11a).