## 2 Materials and Methods
### Droplet Size Spectra and Airflow Speed Measurements  
The droplet size spectra were measured with a Malvern Spraytec(r) laser diffraction system STP5342 (Malvern Instruments Ltd., Worcestershire, UK) (Figure 3a). The instrument has a maximum measurement frequency of 10 kHz and a measurement range of 0 to 2000 \(\upmu\)m. The instrument includes software (SprayTec Software v3.30, Malvern) for managing the data acquisition and charting. This software directly acquired the droplet size parameters D50 (or Volumetric Mean Diameter, VMD), D10 and D90. It also calculated V100, the fraction of the spray with droplets below 100 \(\upmu\)m in diameter, which easily can be blown away by the wind according to different authors [56; 57]. The droplet homogeneity could also be drawn from the aforementioned droplet size parameters, if expressed as the RSPAN Factor (RSF), which can be calculated as shown in Equation (1) [12; 59].  
\[RSF=\frac{D90\,-\,D10}{D50} \tag{1}\]  
where RSF is dimensionless, and D90, D10 and D50 are expressed in \(\upmu\)m.  
Figure 2: (**a**) Liquid hose positions from the inner to the outer part of spouts (green arrow): conventional position (CP) (0 cm reference) passing through alternative position (AP), out position (OP) and extreme position (XP). Distances (cm) from the reference position were different for (**b**) the cannon-type and (**c**) the hand-type spouts.  
The conventional hydraulic hollow cone nozzle Albuz(r) ATR lilac and the air-induction Albuz(r) TVI 8001 (CoorsTek Inc., Eveerux, France) both operated at 0.7 MPa pressure, were selected as reference conventional spray technology for the comparison with the droplet size spectra investigated using the modified pneumatic spouts. In particular, the ATR lilac nozzle is well known to produce very fine (VF) spray quality, likewise the TVI 8001 nozzle is well known as a drift-reducing nozzle for the ultra-coarse (UC) spray quality generated [43]. Furthermore, the Albuz(r) ATR lilac was studied by other authors, and it is widely used by farmers with conventional hydraulic air-assisted sprayers both in vineyards and orchards [60]. The droplet size spectra generated by the reference nozzle were measured using the same laser diffraction system device described above and the methodology usually applied for the measurements of droplet size spectra generated by hydraulic nozzles, fully detailed in [PERSON] et al. [25].  
The measurement of the airflow speed was performed with a Pitot-tube-based anemometer Testo 400 (Testo SE & Co. KGaA, Lenzkirch, Germany) (Figure 3b) at 1 Hz frequency with a measurement resolution of \(\pm\)0.01 hPa, a differential pressure corresponding to 1.28 m s\({}^{-1}\), and a measurement range of up to +2000 hPa (571.43 m s\({}^{-1}\)). The instrument was fixed to an ad hoc support developed by the researchers with some modifications to properly adapt it to the experiment [55]. The main advantage of this support was the possibility to keep the air speed measurement instrument in the center of the air spout (Figure 3b), avoiding errors that could deeply affect the measurements when holding it manually. The modifications in the instrument were essentially aimed at an enlargement of the holding tube to measure speed in the outermost position of the liquid hose (XP). Thus, the airflow speeds were measured along the central axis in six positions, corresponding to 0, 5, 10, 16, 22 and 28 cm to the CP for the cannon-type spout and in five positions, corresponding to 0, 2.5, 5.0, 9.5 and 12.5 cm in a single spout for the hand-type nozzle. Preliminary trials were conducted to ensure the airflows generated individually by the four spouts that composed the hand-type nozzle were comparable. In each sampling position, the data were recorded for 60 s per each of the three replicates performed.