## 2 Materials and Methods
### Measurement of Droplet Size Spectra  
The nozzle model used in the study tests was the Universal Flat Fan Nozzle AP 120-03 from Agroplast Marcin Lopag (Sawin, Poland). According to the manufacturer's catalogue, the flow rate for this nozzle is 1.20 L/min at a spray pressure of 3 \(\times\) 10\({}^{-5}\) Pa. The droplet classification for this type of nozzle at 3 \(\times\) 10\({}^{-5}\) Pa pressure is a fine droplet. The spray solution was pressurized using compressed air in the spray tank; the pressure was kept at 3 \(\times\) 10\({}^{-5}\) Pa during the test with the help of a pressure regulator and pressure gauge. The spraying system components are shown in Figure 1.  
Figure 1: Components of the spraying system: 1—Air compressor, 2—Air pressure gauge, 3—Air pressure regulator, 4—Spray solution tank, 5—Spray pressure gauge, 6—Spray pressure regulator, 7—Nozzle holder rail, 8—Nozzle (with solenoid valve) and nozzle holder, 9—Measurement zone, 10—Laser diffraction device, 11—Spray plume. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Water Source** & **Density (kg/m3)** & **Viscosity (Pa-s *)** & **pH** &
\begin{tabular}{c} **Hardness mg** \\ **CaCO\({}_{3}\)/L (ppm)** \\ \end{tabular} & **Abbreviation** \\ \hline Sosnowka village & 0.9992 & 831 \(\times\) 10\({}^{-6}\) & 8.44 & Medium hard (225) & WS \\ \hline Laboratory of the & & & & & \\ University of Life & 0.9998 & 889 \(\times\) 10\({}^{-6}\) & 7.42 & Hard (518) & WUP \\ Sciences in Lublin & & & & & \\ \hline \hline \end{tabular}  
* Water temperature 21.5 \({}^{\circ}\)C, ppm—particles per million.  
\end{table} 
Table 3: The properties of water types used in the tests. A Sympatec GmbH-HELOS-VARIO/KR device (Sympatec GmbH, Clausthal-Zellerfeld, Germany) was employed to measure the droplet size characteristics and droplet size distribution of the spray plume. The device follows the physical principles of Laser Diffraction (LD), and the core of the measuring device contains a HELOS/R LD sensor. The device was positioned below the nozzle tip. The distance between the nozzle tip and the measurement zone was kept at 50 cm during the entire test, and the cross-sectional area of the spray plume at this position was analyzed. When the nozzle spray reaches the measurement zone, measuring began by means of the software (WINDOX 5.10) of the laser diffraction device. The nozzle was mounted inside a nozzle holder, and moved horizontally alongside its rail (right and left movement) by means of a DC servomotor. This was controlled through dedicated software with simple interface. Spraying the solution during sampling was controlled through a solenoid valve, which was managed by the same software that enabled nozzle movement. The following parameters [29] were measured for the adjuvants at the determined concentrations and for both types of water: (1) \(\mathrm{D}_{\mathrm{v0.1}}\), \(\mathrm{D}_{\mathrm{v0.5}}\), or volume median diameter (VMD), and \(\mathrm{D}_{\mathrm{v0.9}}\)--these refer to the droplet size at which 10, 50, and 90% of the spray volume is comprised of droplets of smaller or equal size, respectively. (2) Sauter mean diameter (SMD)--this parameter describes the spray fineness with regard to surface area. It is defined by the droplet diameter, which has the same ratio between volume and surface area as the entire volume of all droplets to the complete surface area of all the droplets. (3) Relative span (RS) of the spray--as a non-dimensional parameter representing the homogeneity of the spray spectrum. Values of RS close to zero imply a more uniform spray spectrum.