# Effect of Precision Nitrogen Fertilization of Grassland on Soil Microbial Structure
## 3 Results and Discussion  
### Determination of Nitrate Content  
As the depth of the soil profile increased, there was a decrease in nitrate content. In the soil layers at 0.15 m and 0.25 m, the decrease in nitrate values was 7.83 mg NO\({}_{3}\)\({}^{-}\)/100 g of soil, with low coefficients of variation of 17% (0.15 m) and 15% (0.25 m). In contrast, a much lower decrease in nitrate content was observed in the deeper soil layers (between 0.25 m and 0.35 m)--only 0.68 mg NO\({}_{3}\)\({}^{-}\)/100 g of soil. The largest variation (12.02 mg NO\({}_{3}\)\({}^{-}\)/100 g) in nitrate content was recorded at depths between 0.05 m and 0.35 m, with a coefficient of variation of no more than 13%. A graphical display of the nitrate content in the soil at a specific point is shown in Figure 4. To determine the spatial distribution of nitrate content in the soil at all analyzed depths, their spatial variation was mapped (Figures 5-8). Figure 4: Nitrate content in the soil profile. Figure 5: Spatial variation of soil nitrate content and its percentage structure in the field; (**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 field area with the highest soil nitrate content at a depth of 0.05 m (ranging from 25.762 to 26.668 mg/100 g of soil) accounted for 3.6% of the total area (Figure 5a). A small portion, about 1.5% of the total investigated area, depicted a zone of lowest soil nitrate content (18.501 to 19.408 mg NO3\({}^{-}\)/100 g). In an area covering 21% of the field, soil nitrate content was observed to be in the range of 20.317 to 21.223 mg NO3\({}^{-}\)/100 g of soil. This area was located in the western and northeastern parts of the field. For soil nitrate content recorded at a depth of 0.15 m, the highest nitrate content was within the range of 21.583 to 22.581 mg NO3\({}^{-}\)/100 g of soil, occupying 1.5% of the area (Figure 5b). Soil nitrate content in the range of 17.59 to 18.587 mg NO3\({}^{-}\)/100 g of soil characterized an area accounting for as much as 30.4%. This area included the western and eastern parts of the field. The field area with the highest soil nitrate content at a depth of 0.25 m (ranging from 12.653 to 13.2 mg NO3\({}^{-}\)/100 g of soil) accounted for 3% of the total area (Figure 5c). The areas with the lowest soil nitrate content, ranging from 8.276 to 8.823 mg/100 g of soil, accounted for twice the size of the aforementioned area. This region included the western and northeastern parts of the field. Similarly, in an area covering about 24% of the tested field at the same depth of 0.25 m, the nitrate content of the soil was observed to be in the range of 11.012 to 11.558 mg NO3\({}^{-}\)/100 g of soil. For soil nitrate content recorded at a depth of 0.35 m, the highest nitrate content ranged between 11.989 and 12.485 mg NO3\({}^{-}\)/100 g of soil (Figure 5d). Based on the collected data, there is a clear downward trend in soil nitrate content as the depth of the soil profile increases. The decrease is particularly significant in the shallower soil layers (0.15 m and 0.25 m), where it reached an average reduction of 7.83 mg NO3\({}^{-}\)/100 g of soil, with low coefficients of variation of 17% and 15%, respectively. In contrast, a smaller decrease of only 0.68 mg NO3\({}^{-}\)/100 g of soil was observed in the deeper soil layers (0.25 m and 0.35 m). The results also highlight the spatial variation of soil nitrate content across different layers of the soil profile. In all layers, the area with the lowest nitrogen content occupied up to 1.5% of the study area, while the area with the highest nitrogen content comprised up to 3.6%. This aligns with observations by [PERSON] et al. [66], who noted a similar trend for both conventional and reduced tillage. However, exceptions to the general downward trend were identified by [PERSON] et al. [67].