## 3 Results and Discussion
### Physicochemical and Biological Characterisation of Soils
In addition, these high levels of Na could hinder the access of microorganisms to OM, which would explain the high OM concentration in the soils and its slow decomposition [48]. A high Na concentration can affect the important WHC indicator by decreasing the amount of available micropores, \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Indicators**} & \multicolumn{8}{c}{**Soils**} & \multirow{2}{*}{\(p\)} \\ \cline{2-2} \cline{4-11}  & & **Ac1** & & **Ac2** & & **Ac3** & **Ac4** & **Ir1** & **Ir2** & **Ir3** & **Sa1** & **Sa2** & **Sa6** \\ \hline pH & **7.29a** & 6.27 cd & 6.07 de & **5.89e** & 6.97b & 6.29 cd & 6.96b & 6.40c & 6.91b & 6.17 dee & \textless{}0.01 \\ EC & 0.24a & 0.24a & **0.14a** & 0.22a & 0.18a & 0.21a & 0.24a & **0.32a** & 0.28a & 0.20a & ns \\ WHC & 89a & **72a** & **120a** & 81a & 82a & 77a & 75a & 92a & 96a & 101a & ns \\ Moisture & 20.1 de & 29.5 ab & **19.5e** & 23.7 de & 27.6 abc & **32.5a** & 26.2 bc & 25.6 bcd & 28.9 abc & 29.0 abc & \textless{}0.01 \\ TOC & 2.50 ab & 2.74 ab & 2.50 ab & 2.20b & 2.27b & **1.87b** & 2.96 ab & 2.49 ab & **3.68a** & 2.64 ab & \textless{}0.01 \\ TN & 0.161g & **0.159h** & **0.181a** & 0.171f & 0.177b & 0.17 ze & 0.173d & 0.176c & 0.176c & 0.17 ze & \textless{}0.01 \\ CEC & **6.00a** & 5.24 cd & 5.80 ab & 5.58 abc & 5.36 bc & 5.83 ab & **4.76d** & 5.18 cd & 5.82 ab & 5.40 bc & \textless{}0.01 \\ Na & **2.32a** & 1.74 cd & 1.19e & 2.11 ab & 2.21a & 1.66d & **0.93f** & 1.21e & 1.95 bc & 2.17 ab & \textless{}0.01 \\ K & 1.88a & 1.92a & **1.37b** & 1.99a & 2.02a & **2.07a** & 1.98a & 1.84a & 2.03a & 1.84a & ns \\ Ca & 0.27 cd & **0.24d** & 0.42b & 0.48a & 0.28 cd & 0.47 ab & **0.49a** & 0.30c & 0.29 cd & **0.49a** & \textless{}0.01 \\ Mg & 1.5d & 1.49d & **2.84a** & 1.11 & **0.99g** & 1.74c & 1.38e & 1.75c & 1.88b & 1.09f & \textless{}0.01 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: One-way ANOVA with subsequent Tukey’s mean test on results of physicochemical indicators of sampled soils from Bajio region of Guanajuato. thus limiting the ability of the soil to supply water to crops, which is consistent with the results observed for this indicator [45]. There were high K levels in all of the soils, probably as a result of excessive use of chemical fertilisers and a lack of pre-sowing soil analysis. K is crucial for enzyme activation, protein synthesis and photosynthesis. However, in high concentrations, it can cause salt stress [49]. All of the soils showed very low Ca levels, possibly due to the exchange of this element for Al and Na in the clay matrix, influenced by the acidic pH of the soil [41]. Low Ca concentrations affect soil structure, causing a decrease in aggregates and macro- and micropores, and preventing adequate water and air flow in the soil, which could affect OM mineralisation and general microbial activity. Furthermore, Ca plays a structural role in plants, as it is part of the plant cell wall [48]. A low Ca concentration causes poor structural development in crops, together with a significant effect on the plant's ability to carry out photosynthesis, as it is an important factor in the functioning of chlorophyll. On the other hand, all of the soils presented adequate concentrations of Mg. A deficiency of this element causes a loss of pigmentation in leaves, interfering with plant development by reducing photosynthesis [49]. Concerning the biological phase of the soil, the analysed indicators did not present well-defined limits that would allow for their classification, unlike the physicochemical indicators. In the case of the indicators MBN and MBC, high values indicate the enzymatic capacities of the microbial population in relation to the N and C cycling present in the OM [50]. The MBN indicator showed that the Ac4 soil had the highest microbial capacity for N utilisation, while the Ir1 soil had the lowest capacity (Table 4). This difference can be attributed to the N concentrations (TN indicator) in these soils, as the Ac4 soil had a lower concentration compared with the Ir1 soil.