## 3 Results and Discussion
### Wheat Yield  
Grain and straw yields of the five varieties for each tillage type are presented in Tables 9 and 10 under the three nitrogen doses. Globally, ANOVA results (Table 11) show that only variety has a very highly significant effect on grain and straw yields (F values = 14.62 and 6.41, respectively, and \(p\)-value \(<\) 0.001), whereas there were no significant differences between the two tillage types (F values = 4.40 and 1.20 and \(p\)-values = 0.171 and 0.388, respectively) and the three nitrogen doses (F values = 3.95 and 2.06 and \(p\)-values = 0.064 and 0.190, respectively). None of the interactions was significant. [PERSON]'s post hoc test showed that the Louiza variety had the lowest grain yield (3.18 t ha\({}^{-1}\)), followed by I.C and M.G with intermediate grain yields (4.05 and 3.72 t ha\({}^{-1}\), respectively) and finally Faraj and Nachit with the highest grain yield (4.13 and 4.46 t ha\({}^{-1}\)) (Table 9). A comparison of the values presented in Table 9 with those presented in Table 1 shows that grain yields for the three varieties correspond to considerably increased yields in semi-arid areas, although the study site is in a favorable area. In addition, the observed yield values are much lower than those corresponding to the yield potential that can be reached if all crop conditions (soil, climate, and crop management practices) are optimal. These low grain yield values are mostly the consequence of water stress that occurred for the last three years. A slightly higher grain yield was attained under NT (4.07 t ha\({}^{-1}\)) \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Nitrogen (kg N ha\({}^{-1}\))** & **Tillage/Depth (cm)** & **0-5** & **5-10** & **10-20** & **20-40** & **40–60** & **Mean** & **Mean** \\ \hline
20 & NT & 5.5 (0.7) & 12.2 (1.2) & 8.7 (0.9) & 5.2 (0.9) & 5.2 (1.2) & 7.4 (2.4) & 8.4 (3.1) \\  & CT & 6.9 (0.8) & 6.1 (0.8) & 10.8 (1.0) & 10.4 (0.6) & 12.6 (4.0) & 9.4 (3.2) & \\ \hline
40 & NT & 6.9 (1.0) & 13.0 (1.8) & 8.7 (1.1) & 13.4 (1.3) & 15.1 (2.9) & 11.4 (2.8) & 13.9 (3.8) \\  & CT & 17.8 (1.8) & 14.7 (1.9) & 19.9 (1.3) & 12.1 (0.9) & 17.8 (1.9) & 16.5 (2.8) & 15.8 (3.9) \\ \hline
60 & NT & 11.2 (0.8) & 19.5 (3.7) & 19.9(4.3) & 19.0 (5.0) & 10.4 (0.9) & 16.0 (4.2) & \\  & CT & 10.8 (0.5) & 16.0 (2.3) & 19.5 (2.1) & 14.7 (2.9) & 17.3 (4.5) & 15.7 (3.6) & 15.8 (3.9) \\ \hline \hline \multirow{2}{*}{Mean} & NT & 7.9 (2.4) & 14.9 (3.4) & 12.4 (4.9) & 12.5 (4.6) & 10.2 (3.3) & 11.6 (4.1) & \\  & CT & 11.8 (3.9) & 12.3 (4.7) & 16.7 (4.4) & 12.4 (2.4) & 15.9 (3.3) & 13.8 (4.0) & \\ \hline \hline \end{tabular}
\begin{tabular}{c c c c c c c} \hline \hline
**Mean** & & 9.9 (3.7) & 13.6 (4.0) A & 14.6 (5.0) & 12.5 (3.7) A & 13.1 (4.4) A & 12.7 (4.3) \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Nitrate content (mg kg\({}^{-1}\)) measured at the end of the experiment for each nitrogen dose (kg N ha\({}^{-1}\)), tillage type, and soil depth (cm). Means (\(n\) = 3) with standard deviations followed by the same letter are not statistically different at the 0.05 significance level according to [PERSON]’s post hoc test. NT= no tillage, CT= conventional tillage. compared to CT (3.75 t ha\({}^{-1}\)). The effect of tillage type on yield was not significant, although there were significant differences in soil properties (especially OC, CEC, ammonium, and nitrates) corresponding to the two tillage types, which could also be explained by water stress that prevented these varieties from using all available nitrogen. With respect to nitrogen doses, mean grain yields were 4.09, 3.92, and 3.72 t ha\({}^{-1}\) under 20, 40, and 60 kg N ha\({}^{-1}\), respectively. Water stress is likely the cause of the absence of nitrogen dose effect, reducing nitrogen use efficiency.