## 3 Results and Discussion
### Dielectric Properties Measurement Results at Different Flow Rates  
Figure 6 presents the dielectric properties of plasma-treated water at flow rates of 0.5, 1, and 2 L/min, compared with nitrate-mixed water (NO\({}_{3}\) + RO) and untreated RO water. Starting with the dielectric constant (\(\epsilon^{\prime}\)) shown in Figure 6a, it is observed that the dielectric constant decreases as the frequency increases across all flow rates. At the lowest flow rate (0.5 L/min), the water samples exhibit the highest dielectric constant over the frequency range, indicating a greater electrical energy storage capacity. Furthermore, the dielectric loss factor (\(\epsilon^{\prime\prime}\)) increases with frequency at all flow rates, with particularly high values observed at higher flow rates, indicating increased energy loss in the form of heat, as shown in Figure 6b. This analysis highlights the importance of controlling the flow rate during the plasma treatment process to modify the dielectric properties of water. A lower flow rate significantly enhances the efficiency of nitrate fertilizer production by increasing electrical energy storage capacity and reducing energy loss. Therefore, optimizing water flow rate management and control in the plasma process is crucial for improving production efficiency and energy use in the agricultural industry. Table 1 shows the dielectric properties of pure water samples treated with plasma for nitrate production at different flow rates. The data reveal significant differences in the dielectric constant (\(\epsilon^{\prime}\)) and dielectric loss factor (\(\epsilon^{\prime\prime}\)) under various conditions, including nitrate-mixed water (NO\({}_{3}\) 10 g), reverse osmosis filtered water (RO water), and plasma-activated water (PAW) at flow rates of 1.0, 2.0, and 3.0 L/min. When comparing NO\({}_{3}\) + RO, RO water, and PAW samples, the nitrate-mixed water (NO\({}_{3}\) + RO) consistently exhibited the highest dielectric constant (\(\epsilon^{\prime}\)) values across all frequencies due to the direct addition of nitrate ions. This was followed by plasma-activated water (PAW) and then RO water, indicating that the increase in \(\epsilon^{\prime}\) and \(\epsilon^{\prime\prime}\) correlates with a higher electrical energy storage capacity. The trend suggests that the polarizability of the material in an electric field is enhanced by the presence of nitrate ions. Notably, the dielectric constant decreases with increasing frequency, which is typical behavior for dielectric materials as their dipole alignment ability diminishes at higher frequencies. The dielectric loss factor (\(\epsilon^{\prime\prime}\)), which represents energy loss as heat, was higher in the nitrate-mixed water (NO\({}_{3}\) + RO 10g) sample compared to plasma-activated water (PAW) and RO water, particularly at higher frequencies. This indicates that the presence of nitrate ions contributes to increased dielectric losses, while plasma treatment introduces additional conductive pathways or reactive substances that also affect these properties. Figure 6: Measurement results of (**a**) dielectric constant (\(\epsilon^{\prime}\)) and (**b**) dielectric loss factor (\(\epsilon^{\prime\prime}\)) at flow rates of 0.5, 1.0, and 2.0 L/min. The flow rate significantly impacts the dielectric properties of the PAW sample. At a flow rate of 0.5 L/min, the PAW sample showed the highest dielectric properties compared to flow rates of 1.0 and 2.0 L/min, with elevated values of both \(\epsilon^{\prime}\) and \(\epsilon^{\prime\prime}\). This suggests efficient energy storage with increased losses, similar to those observed in nitrate-mixed water (NO\({}_{3}\) + RO). Additionally, the data indicates that \(\epsilon^{\prime\prime}\) values generally increase as the flow rate decreases across all frequency ranges, implying greater energy losses due to longer interaction times between plasma and water molecules at lower flow rates.