## 3 Results and Discussion
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Parameter**} & \multirow{2}{*}{**Source of Variation**} & \multicolumn{2}{c}{**Airflow Velocity (m s\({}^{-1}\))**} \\ \cline{3-4}  & & **Fan Drive in First Gear** & **Fan Drive in Second Gear** \\ \hline \multirow{6}{*}{Diffuser height (cm)—A} & 10 & 19.36 \(\pm\) 6.45 \({}^{\text{a}}\) & 22.59 \(\pm\) 7.14 \({}^{\text{a}}\) \\  & 20 & 14.80 \(\pm\) 3.71 \({}^{\text{b}}\) & 17.14 \(\pm\) 4.73 \({}^{\text{b}}\) \\  & 30 & 11.67 \(\pm\) 2.40 \({}^{\text{c}}\) & 13.13 \(\pm\) 2.97 \({}^{\text{c}}\) \\  & 40 & 9.06 \(\pm\) 1.61 \({}^{\text{d}}\) & 10.98 \(\pm\) 1.86 \({}^{\text{c}}\) \\  & 50 & 8.06 \(\pm\) 1.47 \({}^{\text{d}}\) & 10.06 \(\pm\) 1.80 \({}^{\text{c}}\) \\ \cline{2-4}  & \(p\)-Value & \(<\)0.001 & \(<\)0.001 \\ \hline \multirow{6}{*}{Position of diffuser relative to the sprayer’s axis of symmetry—B} & 10 & 14.63 \(\pm\) 5.59 \({}^{\text{a}}\) & 17.08 \(\pm\) 6.18 \({}^{\text{a}}\) \\  & 20 & 12.71 \(\pm\) 4.77 \({}^{\text{a}}\) & 15.50 \(\pm\) 5.99 \({}^{\text{ab}}\) \\ \cline{1-1}  & 30 & 11.25 \(\pm\) 7.18 \({}^{\text{a}}\) & 12.42 \(\pm\) 7.51 \({}^{\text{ab}}\) \\ \cline{1-1}  & 40 & 12.41 \(\pm\) 4.19 \({}^{\text{a}}\) & 14.82 \(\pm\) 5.12 \({}^{\text{ab}}\) \\ \cline{1-1}  & 50 & 11.61 \(\pm\) 4.45 \({}^{\text{a}}\) & 13.71 \(\pm\) 4.91 \({}^{\text{b}}\) \\ \cline{1-1} \cline{2-4}  & \(p\)-Value & 0.151 & 0.048 \\ \hline \multirow{6}{*}{Side of the sprayer boom—C} & data & 11.24 \(\pm\) 4.82 \({}^{\text{b}}\) & 13.24 \(\pm\) 5.83 \({}^{\text{b}}\) \\  & data & 13.96 \(\pm\) 5.75 \({}^{\text{a}}\) & 16.32 \(\pm\) 6.25 \({}^{\text{a}}\) \\ \cline{1-1} \cline{2-4}  & \(p\)-Value & 0.011 & 0.003 \\ \hline A \(\times\) B & \(p\)-Value & 0.848 & 0.796 \\ A \(\times\) C & \(p\)-Value & 0.002 & 0.020 \\ B \(\times\) C & \(p\)-Value & 0.003 & 0.002 \\ A \(\times\) B \(\times\) C & \(p\)-Value & \(<\)0.001 & \(<\)0.001 \\ \hline \hline \end{tabular}  
* Means followed by different letters were significantly different for each parameter (\(p\)-values are shown in the table).  
\end{table} 
Table 1: The influence of the over-row sprayer’s operating parameters on airflow velocity (mean values \(\pm\) standard deviations). The registered airflow velocities significantly differed on both sides of the boom and partly when the diffusers were positioned along the sprayer's longitudinal axis (when the fan was operated in second gear). These results pointed to a design error in the central plenum: the air generated by the radial fan was not evenly distributed across the diffusers. This error prevented the uniform distribution of the spray liquid along the horizontal plane; this should be eliminated in the next version of the prototype sprayer. The airflow velocity values were not significantly influenced by the interaction effect between the diffuser height and the diffuser's position relative to the sprayer's axis of symmetry, whereas the interaction effects of other the experimental factors significantly affected the airflow velocity. The airflow velocities at both fan-speed settings at a diffuser height of 20 cm are compared in Figure 5. Their distribution was not symmetrical relative to the sprayer's longitudinal axis or the axis of each individual diffuser. This observation could partly be attributed to the same design error in the central plenum as well as the fact that the diffusers were not precisely installed on the boom, so their axes of symmetry were not always perpendicular to the sprayed surface. In the next stage of the study, the airflow velocity was measured when the diffusers were positioned at different heights and at different intervals. The results of these measurements are presented in Table 2. The greatest variations in the airflow velocity were noted at the lowest diffuser height (10 cm), regardless of the diffuser spacing. On average, the airflow velocity at the most distant measurement points was 187% (minimal diffuser spacing) or even 1160% (maximal diffuser spacing) lower than that noted along the diffuser axis.