## 2 Materials and Methods
### Spray Deposition
#### 2.3.2 Spray Deposition Assessment  
Plastic collectors (dimension 70 mm \(\times\) 30 mm, thickness 0.3 mm; ITW Formex, Carol Stream, IL, USA) were used to assess the canopy deposition and ground losses (Figure 2c). On full-grown carrots, the collectors were placed in the canopy with either a horizontal or vertical position to evaluate the canopy deposition, and horizontally on the ground, preferably under the leaves, to evaluate the ground losses. Six collectors were placed per zone (ground or canopy) and per bin, corresponding to 72 collectors per spray experiment (2 zones \(\times\) 6 collectors \(\times\) 6 bins). The collectors on the ground were placed in between the lines to avoid a shielding effect from the edges. As the top of the canopy was higher than the edges, this was not done for the collectors in the canopy. With the early-stage  
Figure 2: Plantation scheme in bin. Full development stage (**a**), early growth stage (**b**), deposition collectors in the vegetation (**c**).  
carrots, it was not possible to sample the spray losses to the ground under the canopy due to the low crop height. Therefore, only four collectors were placed in the canopy per bin, corresponding to 12 collectors per spray experiment (1 zone \(\times\) 4 collectors \(\times\) 3 bins). Collectors were placed randomly but 0.3 m away from the bin edges to avoid border effects.  
Before placing the new collectors, the canopy was allowed to dry completely (the drying time depended on the temperature and the wind). Since all trials were performed on the same plots, the risk of cross contamination from one trial to another was evaluated. For this purpose, a set of blank collectors was placed in the canopy between two consecutive experiments for some time (10 min). After analysis, these collectors showed no measurable contamination.  
Spray mixture of E102 Tartrazine yellow food dye 85% _w/w_ (Alpasud, France) with water, at a concentration of 5 g L\({}^{-1}\), were used in the spray deposition experiments. A volume of about 50 mL of spray mixture was systematically sampled at a nozzle outlet before each spray application to determine the mixture concentration. After each repetition, the collectors from the same bin and the same zone (canopy or ground) were placed into a small container of 100 mL, washed with 20 mL of deionised water for the canopy collectors or 10 mL for the ground collectors. A sample of each washing solution was placed in a 4 mL cuvette. The Tartrazine concentration of every sample was determined by measuring the absorbance of the washing solution with a spectrometer set at a wavelength of 427 nm (Secomam, Uviline 9100, Champigny sur Marne, France) and by comparing the results against the calibration curve. In case the concentration of the dye was too high, samples were diluted. Deionised water was used as a blank to calibrate the spectrometer. Spray mix samples were used to draw the calibration curves considering successive dilutions up to the upper detection limit of quantification of the spectrometer. Three sub-diluted samples were measured to draw the calibration curve. The absolute spray depositions were calculated using Equation (1) according to ISO22401 (2015):  
\[D_{i}=\frac{(\rho_{s}-\rho_{b})\times V_{all}}{\rho_{spray}\times n_{coll} \times A_{coll}} \tag{1}\]  
where \(D_{i}\) is the absolute spray deposition per sample (mL cm\({}^{-2}\)), \(\rho_{s}\) is the absorbance value of the sample (adim.), \(\rho_{b}\) is the absorbance value of the blank (adim.), \(V_{all}\) is the volume of the dilution liquid (deionised water) added per sample to extract the tracer deposition (ml), \(\rho_{spray}\) is the estimated absorbance value of the spray mix concentration applied during the test and sampled at the nozzle outlet (adim.), \(n_{coll}\) is the number of collectors per sample (adim.), \(A_{coll}\) is the surface area of one side of the collector (cm\({}^{2}\)).