The Effect of Air Flow Rate on Spray Deposition in a Guyot-trained Vineyard

The objective of this study was to analyse the effects of different air flow rates on spray deposition in a Guyot-trained vineyard (2.0 m row spacing) using a commercial air-assisted sprayer. Two experiments were performed at growth stages 17 (inflorescences fully developed) and 33 (beginning of berry touch; Eichorn and Lorenz scale). The air flow rate treatments included: zero (fan off), 3.17 m3/s, 4.19 m3/s, and 5.33 m3/s, with six replicates on randomised blocks. Spray deposits were measured on both the upper and under side of leaves, and on bunches, using a water-soluble dye (Tartrazine) as a tracer. At growth stage 17, the reduction of the air flow rate from 5.33 m3/s to 3.17 m3/s significantly increased overall mean deposition (+37%). The effect was mainly owing to an increase in deposits on the leaf upper side (+67%); on the under side, however, deposits were similar, while less variable for the high air flow rate (C.V. = 44% versus 63%). At growth stage 33, no significant differences were observed on either the leaves or the bunches. Total deposition on the canopy was in any case best for the low air flow rate (3.17 m3/s) treatment (47% and 57%, respectively, at the first and second growth stages). The results showed the potential for reducing air flow rates in this type of vineyard in order to reduce spray drift and power consumption.