## 3 Results and Discussion
### Initial Direct Effects of Biochar on Soil Characteristics  
Table 3 shows the characteristics of the soil and the soil added with biochar (soil + biochar) before crop development. Initially, the soil presented a pH that was slightly alkaline, with a sandy texture consistent with its bulk density, and with those characteristics present in arid and semi-arid soils [36; 39; 40]. Additionally, we found high Pav and exchangeable Ca, Mg, and K contents; very low content of OM, medium CEC, low concentrations of N\({}_{\text{inorg}}\) medium content of Mn, Zn, Fe, and Cu; and without problems of salinity or toxicity by metals in this soil. The abundance of Ca and Mg is common in calcareous soils [36; 41]. The high content of P and K, and the medium value of CEC could be due to the sheep droppings addition that was added to this soil for 20 years. However, the low OM (2%) content confirms that organic amendments are quickly mineralized in sandy soils [38]. In light of the above, biochar, thanks to its stability, is a better option than organic manure to increase the organic carbon content in this soil. \begin{table}
\begin{tabular}{c c} \hline \hline
**Characteristic** & **Value** \\ \hline pH & 5.9 \(\pm\) 0.11 \\ EC (\(\mu\)S\(\cdot\)m\({}^{-1}\)) & 20,800 \(\pm\) 875 \\ C\(\cdot\)N & 4.5 \(\pm\) 0.38 \\  & (mg\(\cdot\)L\({}^{-1}\)) \\ COD & 5723 \(\pm\) 125 \\ N\({}_{\text{T}}\) & 1277 \(\pm\) 35 \\ P\({}_{\text{T}}\) & 603 \(\pm\) 27 \\ Ca & 1241 \(\pm\) 142 \\ K & 5568 \(\pm\) 375 \\ Mg & 909 \(\pm\) 48 \\ Na & 74 \(\pm\) 8.9 \\ Cu & 0.091 \(\pm\) 0.004 \\ Fe & 2.58 \(\pm\) 0.002 \\ Zn & 0.910 \(\pm\) 0.005 \\ Auvins & 1158 \(\pm\) 12.7 \\ Gibberellins & 2.5 \(\pm\) 1.76 \\ \hline \hline \end{tabular} EC: electric conductivity, COD: chemical oxygen demand, N\({}_{\text{T}}\): total nitrogen, P\({}_{\text{T}}\): total phosphorus.  
\end{table} 
Table 2: Characteristics of the nopal-based biofertilized used in this study. Once biochar was added, some soil characteristics changed significantly (\(p<0.05\)), as shown in Table 3 and Figures 2-4. The bulk density diminished 21%, 1.16 times more than theoretically expected according to Formula (1), while WHC increased 6%, and pH decreased from slightly alkaline to neutral. The previous changes were beneficial for the soil quality, and the modified characteristics were similar to those required by the study crop, since _Physalis ixocarpa_ growths better in sandy loam and well-drained soils, with pH among 5.5 and 7.3. The improvement of the physical characteristics of the soil is explained by the porous structure of the added biochar, which causes a mixing or dilution effect that diminishes BD [7,28,30,33,37, 7, 33] and retains water in its pores [65,66]. In this case, the large difference in density between soil (1.33 g\(\cdot\)cm\({}^{-3}\)) and biochar (0.2 g\(\cdot\)cm\({}^{-3}\)) increases the dilution effect. However, since the amount of biochar applied was only 0.2%, the observed changes are also due to aggregation ability. Notwithstanding, the increase in WHC (6%) was not statistically significant; it was 12.4% higher than the theoretically expected value (49%). [PERSON] et al. [37] obtained higher increases than us in WHC (11% and 14%) in two arid soils using a much larger application rate of biochar (22 Mg\(\cdot\)ha\({}^{-1}\)) of biochar pyrolyzed at 700 \({}^{\circ}\)C. In contrast, [PERSON] et al. [36] achieved an initial increase in WHC of 10% with 8 Mg\(\cdot\)ha\({}^{-1}\) (equal to that applied in this study) of biochar pyrolyzed at 300 \({}^{\circ}\)C. The data from the previous studies demonstrate the importance of selecting the pyrolysis conditions to obtain good outcomes while making efficient use of resources. Figure 3: (**a**) Organic matter (OM) and (**b**) inorganic nitrogen (N\({}_{\text{inorg}}\)) of the studied soil (S), with biochar (S + B), and with different treatments: CT: soil + 100% chemical fertilization, BT20 and BT50: soil + biochar + 20, or 50% of chemical fertilization, respectively, and BBfT: soil + biochar + bioferilization.