Assessment of spray deposition and recycling rate in the vineyard from a new type of air-assisted tunnel sprayer

A new, two-row, air-assisted tunnel sprayer was tested in the vineyard in comparison to a conventional, broadcast sprayer. The tunnel was fitted with external axial flow fans (airflow rate: 2.23 m3 s1 per row) and lamellate separating panels, designed to filter the excess spray and recover its liquid fraction for recycling, while discharging the air to the outside. Two field tests were performed, at end of flowering and beginning of ripening. Mean deposits on the leaves and on leaf undersides at twelve canopy locations (three height ranges, two depths and the two sides of the row) were assessed using a soluble colour dye (Tartrazine) as a tracer. Mean foliar deposition from the tunnel sprayer and the reference sprayerwas not statistically different at either growth stage. The tunnel sprayer gave increased deposit variability on leaf undersides in the first test, associated with uneven deposition over the canopy heights and significant differences between the two sides of the row. Thiswas corrected bya different adjustment of the nozzles and air outlets in the second test when, as a whole, the overall performances of both sprayers could be considered comparable. Penetration into the canopy was similar despite smaller airflow rate of the tunnel sprayer, and coverage of undersides was also comparable and in line with previous tests performed with air-assisted vineyard sprayers. The recycling rate of the tunnel sprayer was 50.1% of spray volume applied in the first experiment, and 34.0% in the second experiment. This confirmed the potential of this technique for substantial spray saving and reduction in chemical input, without compromising deposition.