## 3 Results and Discussion
### Soil
#### 3.1.2 Chemical Properties  
Mean values of organic carbon (OC), potassium, phosphorus, and cationic exchange capacity (CEC) for the two tillage types and at the five depths are presented in Table 3.  
With respect to organic carbon (OC) contents, ANOVA (Table 4) showed a highly significant difference (F value = 143.06 and \(p\)-value = 0.007) between NT and CT, with a slightly higher mean value for NT (8.8 g kg\({}^{-1}\)) compared to CT (8.4 g kg\({}^{-1}\)). There was also a very highly significant difference between depths (F value = 71.42 and \(p\)-value < 0.001), with the highest mean values at the soil surface (11.1 and 10.5 g kg\({}^{-1}\) at the 0-5 and 5-10 cm depths, respectively), as opposed to the 40-60 cm depth (6.0 g kg\({}^{-1}\)). [PERSON]'s post hoc test showed that only the 10-20 and 20-40 cm depths did not differ significantly, with mean OC values of 7.9 and 7.5 g kg\({}^{-1}\), respectively. This result is in agreement with research on organic matter stocks in conservation systems, which are higher at the surface than in ploughed systems [19; 20; 21], with small differences at deeper horizons [22]. Other studies have shown that OC levels in conservation systems are generally higher in the top 10 cm \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Wheat Variety** & **Faraj** & **Nachit** & **Louiza** \\ \hline Year of official inscription & 2007 & 2018 & 2011 \\ \hline Quality & Protein (\%) & 15.3 & 15.0 & 14.8 \\ Yellow index & 29 & 27 & 33 \\ \hline \multirow{3}{*}{Yield (t ha\({}^{-1}\))} & Favorable areas & 5.9 & 5.9 & 5.5 \\  & Semi-arid areas & 3.8 & 4.1 & 3.1 \\ \cline{1-1}  & Potential & 6.8 & 7.1 & 6.0 \\ \hline \end{tabular} Source: INRA. (2022). Nouvelles obtentions variétales INRA. INRA editions: Rabat, Morocco.  
\end{table} 
Table 1: Main characteristics of the three varieties. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & \multicolumn{5}{c}{**Texture**} \\ \cline{2-5}  & **Clay (\%)** & **Fine Silt (\%)** & **Coarse Silt (\%)** & **Fine Sand (\%)** & **Coarse Sand (\%)** & **CoCO\({}_{3}\) (\%)** \\ \hline NT & 46.6 & 6.4 & 36.2 & 6.8 & 3.7 & 0.3 \\ \hline CT & 46.5 & 5.6 & 37.2 & 6.3 & 4.0 & 0.4 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Soil texture measured before the start of the experiment for no tillage (NT) and conventional tillage (CT) at a 15 cm depth. of soil compared to tilled soil, decreasing sharply in the underlying horizons [23]. There was no significant interaction between the two factors (F value = 2.36 and \(p\)-value = 0.060), indicating that the ranking of tillage types in terms of OC content was the same for the five depths and higher for NT than CT.  
ANOVA (Table 4) showed no significant differences between NT and CT in terms of available phosphorus (F value = 12.57 and \(p\)-value = 0.071), with mean values of 115 mg kg\({}^{-1}\) for NT and 113 mg kg\({}^{-1}\) for CT. This qualifies the soil as rich in P\({}_{2}\)O\({}_{5}\) according to the interpretation standards. Phosphorus levels decrease significantly with depth for both NT and CT (F value = 536.17 and \(p\)-value < 0.001), with the highest content at the soil surface (177 mg kg\({}^{-1}\) at the 0-5 cm depth) and the lowest content in the deepest layer (50 mg kg\({}^{-1}\) at the 40-60 cm depth). There was a very highly significant interaction between the two factors (F value = 48.87 and \(p\)-value < 0.001), indicating that the ranking of tillage types changed with depths; for example, at the 0-5 cm depth, NT content (196 mg kg\({}^{-1}\)) was higher than CT content (161 mg kg\({}^{-1}\)), whereas at the 20-40 cm depth, the trend was reversed (57 mg kg\({}^{-1}\) for NT vs. 93 mg kg\({}^{-1}\) for CT). According to ANOVA, exchangeable potassium content was not significantly different between NT and CT (F value = 11.66 and \(p\)-value = 0.076), with a slightly higher mean value for NT (92 mg kg\({}^{-1}\)) compared to CT (84 mg kg\({}^{-1}\)). These values show that the soil is moderately rich in potassium according to the standards.