## 3 Results and Discussion
### Dominant Classes and Orders of Soil Bacteria Under Horse Beans Cultivated in Different Systems
The relative OTU numbers belonging to these classes in sample \"0\" was always statistically significant (\(p<0.05\)) greater than in the other experimental treatments. The comparison with sample \"0\" (plantless, fallow buffer zone of the field experiment) revealed the highest relative difference (10.63%) for _Actinobacteria_ in the strip-till system (ST vs. FA). The greatest decrease in OTUs was observed for _Alphaproteobacteriaia_ in the same cultivation system (Figure 5). Moreover, statistically significant differences were observed for _Betaproteobacteriaia_, _Clostridia_, _Delaproteobacteriaia_, _Plantomycinetia_, and _Thermoophilia_ between CT and FA; for _Bacillus_, _Betaproteobacteriaia_, _Clostridia_, and _Delaproteobacteriaia_ between RT and FA; for _Betaproteobacteriaia_, _Clostridia_, _Delaproteobacteriaia_, and _Sphingobacteria_ between ST and FA; as well as for _Bacillus_, _Betaproteobacteriaia_, _Clostridia_, _Delaproteobacteriaia_, _Gemmaprotebacteri_, _Sphingobacteria_, and _Thermoophilia_ between NT and FA (Figure 5). The first two principal coordinates explained 95.18% of the variance in the cultivation systems based on the percentages of operational taxonomic units' dominant classes of bacteria (Figure 3B). The cultivation systems formed three groups. One of them was FA  
Figure 5: Relative OTU numbers of 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; “red” means negative difference; “green” means positive difference). \({}^{\star}\)\(p<0.05\); ns—not significant. and CT, another was RT and NT, and the other was ST, which was clearly different from the others (Figure 3B). The share of OTUs of unclassified bacterial orders ranged from 7.18% to 9.49%, depending on the cultivation system. The dominant orders were _Actinomycetes_, followed by _Bacillus_ and _Rhizobiales_ (Figure 6). According to [PERSON] et al. [53], there are 16 orders in the Actinobacteria class. These are _Actinomycetes_, _Actinomycetes_, _Bifidobacteriales_, _Catenulisporales_, _Corynebacteriales_, _Frankiales_, _Glycomycetales_, _Jiangellales_, _Kineosporiales_, _Micrococcales_, _Micromonosporales_, _Propinionucleariales_, _Pseudonocardiales_, _Streptomycesetales_, _Streptomycesetales_, and _Incertae sedis_. In our study, _Actinomycetes_ was the only order whose percentage of OTUs exceeded 1%. The highest relative share of OTUs of this order, i.e., 44.21%, was found in treatment 4 (strip-till cultivation); whereas, the lowest share, i.e., 33.62% was found in sample \"0\" (plantless, fallow buffer zone of the field experiment) (Figure 6). The results of our study are in line with the findings of the research conducted by [PERSON] et al. [33], who observed the dominance of this group of bacteria, especially in less fertile soils with the inflow of additional organic matter. According to [PERSON] et al. [54], the dominance (numbers and distribution) of _Actinomycetes_, which play an important role in the decomposition of organic matter, may indicate good soil fertility. Apart from the _Actinomycetes_ order, there was also a large percentage of OTUs of the _Bacillus_ order, which belongs to the _Firmicutes_ phylum. The dominance of this group  
Figure 6: The percentages of operational taxonomic units (OTUs) of the dominant orders 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). of bacteria depends on the source of carbon rather than the pH of the soil environment due to their ability to produce spores. In our study, the largest numbers of OTUs of this order were found in treatments RT, ST, and NT, in which reduced tillage technologies (reduced tillage, strip tillage, and direct drilling) were used (Figure 6).