## 3 Results and Discussion
### Dominant Classes and Orders of Soil Bacteria Under Horse Beans Cultivated in Different Systems  
The metagenomic analysis showed that the type of soil cultivation system used at the horse bean plantation affected the content of bacterial OTUs within classes and orders. Also, in this case, only the orders and classes with >1% are reported (Figure 4). _Actinobacteria_ and _Alphaproteobacteria_ were the dominant classes with percentages 6.09-7.05% (Figure 4). These differences were statistically significant (\(p<0.05\)). Figure 3: Principal coordinate analysis (PCoA) was performed to detect the percentages of operational taxonomic units (OTUs) between individual cultivation systems dominant: (**A**) phyla, (**B**) classes, (**C**) orders, and (**D**) species of bacteria. FA—plantless, follow buffer zone of the field experiment—sample “0”; CT—conventional tillage; RT—reduced tillage; ST—strip tillage; NT—no tillage. [PERSON] et al. [48] observed similar dependencies related to the use of different reduced cultivation technologies. The researchers found a large number of OTUs in the classes of _Actinobacteria_ and _Alphaproteobacteria_ in no-tillage (NT) and reduced tillage (RT) systems. They explained that the increased growth of _Actinobacteria_ was caused by their greater sensitivity to physical disturbances due to their hyphal structure. Deep ploughing disrupted their mycelium, which broke the hyphae of _Actinobacteria_. Although the diameter of _S. coelicolor_ cells is smaller than 1 \(\upmu\)m, it may reach 100 \(\upmu\)m due to the elongation of hyphae at the ends by the membrane vesicle transporter [49]. Our study showed that _Alphaproteobacteria_ was another class that was frequently isolated in the soils under horse beans grown in different cultivation systems. The percentages of (OTUs) of this class amounted to 18.34% in sample \"0\", 18.98% in the traditional cultivation treatment (ploughing), 20.41% in the reduced tillage treatment (stubble cultivator), 13.96% in the strip till treatment, and 20.43% in the treatment with direct drilling into stubble (Figure 4). _Alphaproteobacteria_ are classified as oligotrophs, as they use organic resources very sparingly. Apart from oligotrophic bacteria, this class also includes the bacteria of agricultural significance, capable of fixing nitrogen in symbiosis with plants [50; 51]. [PERSON] et al. [52] observed that many _Alphaproteobacteria_ interacted with higher eukaryotes. These interactions range from pericellular colonization, through facultative intracellular multiplication, to enforcing an intracellular lifestyle. This wide range of interactions has a common feature--the modulation of proliferation of host cells. This sometimes leads to the formation of structures known as nodules in which bacteria can grow. Figure 4: The percentages of operational taxonomic units (OTUs) of the dominant classes of bacteria. The classifications with less than 1% numbers are gathered into the category “Other” (FA—plantless, fallow buffer zone of the field experiment—sample “0”; CT—conventional tillage; RT—reduced tillage; ST—strip tillage; NT—no tillage). Apart from the assessment and indication of the dominant classes in the soil samples, relative differences in the number of OTUs between a specific soil treatment collected from under horse beans grown in different cultivation systems (traditional tillage, reduced tillage, strip tillage, and direct drilling), and the control soil sample were also analyzed (CT vs. FA, RT vs. FA, ST vs. FA, ST vs. FT vs. NT). The results are shown in Figure 5. In all four comparisons, the numbers of _Actinobacteria_ and _Gemmatimonadetes_ classes in the soils cultivated in different systems was significant (\(p<0.05\)) greater than in sample \"0\"--plantless, fallow buffer zone of the field experiment. There was an inverse relationship observed for the _Acidimicrobia_, _Brocadiae_, and _Clostridia_ classes.