## 3 Results and Discussion
### Dominant Phyla of Soil Bacteria Under Horse Beans Cultivated in Different Systems  
The 16S rRNA metagenomic analysis of the soil metabolome revealed the dominance of three phyla of bacteria: _Actinobacteria_, _Firmicutes_, and _Proteobacteria_, which were found in all experimental treatments. There were similar findings presented in publications on arable soils [30; 31; 32]. The metagenomic analyses showed that, among all bacterial phyla identified in sample \"0\" and in the soil samples collected from the horse bean plantation, _Actinobacteria_ were predominant. The percentage of OTUs was as follows: sample \"0\" collected before the experiment--41.19% (treatment 1), traditional tillage (treatment 2)--39.57%, reduced tillage (treatment 3)--43.10%, strip tillage (treatment 4)--50.72%, and direct drilling (treatment 5)--40.04% (Figure 1). The reads of _Actinobacteria_ were particularly abundant from soil DNA, where the strip tillage system was applied (treatment 4) (Figure 1). Apart from the assessment and identification of the dominant phyla in the soil samples, differences in the number of OTUs between the soil samples collected from the horse beans grown in different cultivation systems and the control soil were analyzed: CT vs. FA, RT vs. FA, ST vs. FA, and NT vs. FA. They are shown in Figure 2.  
All four comparisons showed that, in the experimental treatments, the _Acidobacteria_ and _Gemmatimonadetes_ phyla were more abundant than in sample \"0\" collected from the fallow buffer zone of the experiment. An inverse relationship was observed for the _Verrucomicrobia_ phylum. The percentage of OTUs in sample \"0\" was always greater than in the soils cultivated in different systems. The largest positive difference in the number of OTUs (9.54%) in relation to sample \"0\" was observed for the _Actinobacteria_ phylum in the strip-till treatment. In the same cultivation system, the largest negative difference (\(-\)7.39%) was observed for the _Proteobacteria_ phylum (Figure 2). As observed by [PERSON] and [PERSON] [11], _Actinobacteria_ are a approphytic group of microorganisms which adapt and proliferate intensively in an environment with high availability of organic matter. This effect could be seen in the strip tillage system, as well as in the soil under a horse bean plantation. [PERSON] et al. [33] also observed the dominance of _Actinobacteria_, especially in less fertile soils with a supply of additional organic matter (rice straw). The researchers indicated the important eco-physiological role of these microorganisms. _Actinobacteria_ communities broadly adapt to the decomposition of plant residues. They are of potential significance for the decomposition of these residues and carbon sequestration in the soil. This phylum mineralizes organic material. Similarly to oligotrophic microorganisms, it spares carbon in the soil, which additionally proves its ecological role in the pedon [34; 35]. It is important to note that _Actinobacteria_ can quickly adapt to unfavorable environmental conditions, such as drought by producing conidia. This is why they are capable of decomposing organic matter even at low soil moisture. Our  
Figure 1: The percentages of operational taxonomic units (OTUs) of dominant phyla 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). study confirmed this fact, as evidenced by the weather conditions during the experiment (Table 1). _Proteobacteria_ was another dominant phylum in our study. Its relative OTU numbers ranged from 24.60% in the strip-till treatment to 35.67% in the reduced tillage system (Figure 1). The study by [PERSON] et al. [36] also showed that Proteobacteria was the dominant phylum in agricultural soils. [PERSON] et al.