## 2 Materials and Methods  
### Trial Location and Spraying Equipment  
The laboratory trial was carried out in the facilities of the Department of Agricultural, Forest and Food Sciences (DiSAFA) of the University of Turin located in Grugliasco (Turin, Italy). A test bench was used to simulate the working conditions of the pneumatic sprayer. This test bench consisted of both pneumatic and hydraulic circuits mounted over three different spaces, as shown with detail in [PERSON] et al. [55]. These spaces included a spraying area, a droplet size measurement area and a control and data acquisition room.  
The test bench liquid circuit simulated those mounted in real pneumatic sprayers, including a water tank, a membrane pump AR 202 (Annovi Reverberi S.p.a, Modena, Italy) driven by an electric engine equipped with pressure regulation valves, and a manometer characterized by 0.02 MPa resolution to precisely control the liquid pressure. The test bench ended up in the liquid hose inserted in the air spout of the pneumatic circuit. The liquid flow rate was controlled through a plastic disc with calibrated holes in its perimeter. The air assistance to achieve the spray in the test bench consisted of a centrifugal fan 500 mm diameter (CIMA S.p.a., Pavia, Italy) controlled by a central unit, in which the electric intensity flowing to the driving electric engine, and proportionally the rotary speed of the fan, could be manually adjusted. This control box could set the rotary speed (rev min-1) of the electric engine, measured by a laser tachometer integrated in the system. Thus, even when the control parameter was the amperage, the rotary speed was the indicator to manually regulate the system. As it was previously mentioned, both circuits merged in the air spout, in which the liquid was released through the liquid hose at constant pressure. The air spouts tested included two different types: a cannon-type spout and a hand-type spout (Figure 1a) generally installed on the spray head TC.2M2C.50P (Cima S.p.a., Pavia, Italy). These two kinds of spouts are usually simultaneously employed in the commercial pneumatic sprayers operating in vineyards, as shown in Figure 1b.  
These spouts were conveniently modified to alter the insertion position of the liquid hose, as it showed to have a major importance in the generated droplet size in cannon spouts [55]. The insertion position was, consequently, established as the main variable of the study, and it was called \"hose position\" (HP). It presented four possible levels in each spout type, called \"conventional position\" (CP), \"alternative position\" (AP), \"out position\" (OP) and \"extreme position\" (XP), as shown in Figure 2a. The CP position corresponds to that established by the manufacturer for the commercial equipment (Figure 2b,c). The other hose positions, namely AP, OP and XP, varied according to the spout type, as shown in Figure 2b for the cannon and in Figure 2c for the hand spouts. In particular, in both spout-types, the AP corresponds with the one in which the outermost part of the hose is placed coincident with the border of the air spout (Figure 2b,c), and the XP was experimentally set as the maximum distance in which a uniform liquid atomization could be achieved. This distance value was experimentally found by moving the liquid hose out of the air spout along its longitudinal axle  
Figure 1: (**a**) Cannon-type and hand-type spouts mounted on the spray head TC.2M2C.50P for (**b**) multiple-row spray application in a vineyard.  
through a rail in steps of 5 mm and the droplet size spectra measured in each position. Once this maximum distance was exceeded, the spray cloud changed drastically, appearing as extremely coarse droplets and losing the normal distribution. The OP was set at an intermediate distance between the AP and the XP (Figure 2b,c).