## 3 Results and Discussion
### Concentration of Chlorophyll A, Chlorophyll B, Chlorophyll A + B and Carotenoids in Stevia Leaves
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Treatment 1**} & \multicolumn{3}{c}{**Calcium**} & \multicolumn{3}{c}{**Potassium**} & \multicolumn{3}{c}{**Magnesium**} & \multicolumn{3}{c}{**Phosphorus**} & **Nitrates (NO\({}_{3}\)-)** \\ \cline{2-10}  & \multirow{2}{*}{**July**} & \multirow{2}{*}{**September**} & \multirow{2}{*}{**July**} & \multirow{2}{*}{**September**} & \multirow{2}{*}{**July**} & \multirow{2}{*}{**September**} & \multirow{2}{*}{**July**} & \multirow{2}{*}{**September**} & \multirow{2}{*}{**July**} & \multirow{2}{*}{**September**} \\ \cline{3-3} \cline{6-10}  & & & & & & & & & & \\ \hline \multirow{3}{*}{0 W} & 900.00 \(\pm\) & 769.17 \(\pm\) & 3316.67 \(\pm\) & 2584.72 \(\pm\) & 163.33 \(\pm\) & 133.33 \(\pm\) & 128.72 \(\pm\) & 143.78 \(\pm\) & 2742.93 \(\pm\) & 1662.17 \(\pm\) \\  & 180.28 \(\pm\) & 207.22 \(\pm\) & 549.15 \(\pm\) & 388.70 \(\pm\) & 50.31 \(\pm\) & 29.79 \(\pm\) & 14.09 \(\pm\) & 53.08 \(\pm\) & 906.75 \(\pm\) & 553.03 \(\pm\) \\ \multirow{3}{*}{NR} & 886.11 \(\pm\) & 805.56 \(\pm\) & 2813.98 \(\pm\) & 2519.44 \(\pm\) & 167.22 \(\pm\) & 157.88 \(\pm\) & 153.30 \(\pm\) & 116.54 \(\pm\) & 1496.34 \(\pm\) & 977.44 \(\pm\) \\  & 138.13 \(\pm\) & 199.42 \(\pm\) & 463.19 \(\pm\) & 163.35 \(\pm\) & 42.51 \(\pm\) & 37.84 \(\pm\) & 38.06 \(\pm\) & 29.30 \(\pm\) & 612.32 \(\pm\) & 387.47 \(\pm\) \\ \multirow{3}{*}{1 W} & 897.22 \(\pm\) & 825.00 \(\pm\) & 2926.39 \(\pm\) & 2700.00 \(\pm\) & 159.44 \(\pm\) & 150.56 \(\pm\) & 147.39 \(\pm\) & 127.66 \(\pm\) & 1548.66 \(\pm\) & 922.94 \(\pm\) \\  & 205.56 \(\pm\) & 203.49 \(\pm\) & 475.91 \(\pm\) & 241.17 \(\pm\) & 39.64 \(\pm\) & 36.52 \(\pm\) & 32.13 \(\pm\) & 35.02 \(\pm\) & 706.41 \(\pm\) & 238.69 \(\pm\) \\ \multirow{3}{*}{2 W} & 936.11 \(\pm\) & 894.44 \(\pm\) & 2945.83 \(\pm\) & 2237.50 \(\pm\) & 1733.33 \(\pm\) & 170.00 \(\pm\) & 130.03 \(\pm\) & 129.19 \(\pm\) & 1753.97 \(\pm\) & 829.46 \(\pm\) \\ \cline{1-1}  & 162.07 \(\pm\) & 173.56 \(\pm\) & 516.65 \(\pm\) & 309.55 \(\pm\) & 66.47 \(\pm\) & 35.44 \(\pm\) & 15.63 \(\pm\) & 30.54 \(\pm\) & 565.51 \(\pm\) & 285.17 \(\pm\) \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Influence of irrigation on the concentration of various elements and nitrates in leaves of stevia measured in the years 2014-2016.  
spite differences in the irrigation practice. Potassium content ranged from 2813.89 in NR to 3316.67 mg\(\cdot\)100 g\({}^{-1}\) in 0 W in July, while it was in the range of 2519.44-2737.50 mg\(\cdot\)100 g\({}^{-1}\) in September. The greatest loss of potassium in the time period between two of the analyses was determined for the sample 0 W. However, in comparison, stevia plants grown in various parts of Morocco with different annual rainfall levels have shown differences in the potassium content [41]. Stevia plants grown in semi-arid regions were characterised with the greatest concentration of potassium, while stevia plants grown in semi-humid conditions were characterised with lower content of this element. However, the stevia plants grown in arid conditions acquired the lowest concentration of potassium; therefore, it is difficult to determine whether different water levels in the stevia cultivation play a significant role in the potassium content in the stevia leaves [41]. The concentration of nitrates also changed between July and September, but differences between applications of different watering regimes could be detected only in September. In July, the concentration of nitrates was in the range of 1496.34-2742.93 mg\(\cdot\)100 g\({}^{-1}\), while in September, the highest concentration of these ions was determined in sample 0 W (1662.17 mg\(\cdot\)100 g\({}^{-1}\)) and the lowest in sample 2 W (829.46 mg\(\cdot\)100 g\({}^{-1}\)). Similar results were acquired in the study by [PERSON] and [PERSON] [42], in which stevia plants grown in the soil with lower moisture content were characterised, at harvest, with the lowest uptake of nitrogen and nitrates.