## 3 Results and Discussion
### Metagenomic Analysis of Soil Samples with and Without Hydroinfiltrators
The use of biochar as a soil amendment induces phylum-level shifts in soil microbial communities. [PERSON] et al. (2011) [23], in a study on cucumbers grown with biochar in greenhouse conditions, observed that the dominant phyla were _Pseudomonadata_, _Bacteroidota_, _Actinomycetota_, and _Bacilotta_, both in control \begin{table}
\begin{tabular}{l c c c c} \hline \hline \multicolumn{5}{l}{(b) Whittaker Index (I\({}_{\text{W}}\))} \\ \hline  & SC20 & SH20 & **SC40** & **SH40** \\ \hline SC20 & 0.000 & 0.502 & 0.439 & 0.596 \\ SH20 & & 0.000 & 0.481 & 0.366 \\ SC40 & & & 0.000 & 0.495 \\ SH40 & & & 0.000 & 0.000 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: _Cont._  
Figure 5: Study of the bacterial community in soil samples. Phyla with an average relative abundance \(>\) 1%. soil and soil/biochar samples. However, these authors reported that biochar application increased the relative abundance of certain phyla, such as _Bacteroidota_ and _Actinomycetota_, while negatively affecting others, such as _Pseudomonada_. Similarly, [PERSON] et al. (2013) [24], in a soybean study, observed enrichment of _Acidobacteriota_, _Gematimanodota_, _Pseudomonada_ and _Actinomycetota_ after biochar application. In turn, [PERSON] et al. (2014) [25], in a study of forest soils in China, reported that _Pseudomonada_, _Actinomycetota_ and _Acidobacteriota_ were the predominant phyla in soils amended with biochar. In general, soil depth is a key factor in the structure of bacterial communities [26]. However, in our study, at the genus level, soil with the hydroinfiltrators did not show substantial shifts in populations across different depths (Figure 6 and Table S2), as corroborated by the beta diversity indices (Table 2). This finding will be discussed further below. At the genus level, the most abundant were _Bacillus_ (6.0%) and _Sphingomonas_ (4.7% based on the average relative abundance (Figure 6). Among the major genera, others such as _Blastococcus_, (1.8%) _Microvirga_ (1.7%) and _Skernamella_ (1.6%) were also found. Additionally, the presence of uncultured genera and others corresponding to unclassified environmental taxa was also noteworthy. The composition of the bacterial community at the genus level was clearly influenced by the use of hydrofiltrators in the soil (Figure 6). According to our results, _Bacillus_ (6.0%) and _Sphingomonas_ (4.7%) showed the greatest proportions in soils with hydrofiltrators. Other genera such as _Blastococcus_ (1.8%), _Microvirga_ (1.7%), and _Skernamella_ (1.6%) were also positively affected, although to a lesser extent. Other studies also reported a positive effect on bacterial populations after biochar application, including _Bacillus_[27; 28], _Sphingomonas_[29; 30], _Blastococcus_[31; 32] and _Microvirga_[33; 34; 35]. As previously stated, _Bacillus_ and _Sphingomonas_ were the dominant genera [33; 34] in soils with hydroinfiltrators (SH20 and SH40) (Figure 6), showing substantial differences  
Figure 6: Study of the bacterial community in soil samples. Genera with an average relative abundance \(>1\%\). in their abundance when compared to the control soils. Both genera were considered beneficial for plant growth, as will be discussed henceforth. _Bacillus_ is one of the most abundant genera in soil biota and plays multiple relevant functions in ecosystems [22; 36]. _Bacillus_ spp. actively participated in biogeochemical cycles and enhanced nutrient availability. Certain species possess the ability to fix atmospheric nitrogen (diazotrophs), producing NH\({}_{3}\) available for plants [37; 38; 39]. Others can solubilise P [40] and several nutrients such as potassium and zinc [41; 42; 43]. In addition, many species contribute to the production of plant phytohormones and act as plant-growth-promoting rhizobacteria (PGPR) [44; 45]. _Bacillus_ spp. also play a key role as a biocontrol agents and in the bioremediation of soils contaminated with heavy metals through the production of siderophores and other metabolites [46; 47].