The performance of an air-assisted sprayer operating in vines

The performance of a sprayer fitted with two vertical adjustable air outlets has been studied in vineyards investigating the effects of changing the fan speeds (1400, 2000 and 2500/min) and the direction of the air-jet (90 and 120° backward angle of the outlet side deflectors in relation to the treated row). Laboratory measurements were made before the field trials in order to define the operating characteristics of the sprayer. The sampling methodology in the vineyard was based on a framework and a system of intersecting nylon threads dividing the canopy into elementary volumetric zones. The spray flux entering and leaving the canopy, and the losses to the ground and to the air were measured. The spray coverage on the leaves at different heights and depths in the canopy has been also quantified. In all the tests, the air outlets were adjusted to localize the spray application to the appropriate heights determined by the growth of canopy. Considering the spray deposit and the environmental losses, the best results were observed with the 120° backward angle of the outlet side deflectors and the low and medium fan speeds. The effect of the fan speed compared with that of the direction of the air stream appeared more evident. The spray losses doubled by increasing the fan speed and frequently these losses were not limited to the treatment area but drifted outside. The degree and the uniformity of the spray coverage were strongly influenced by the high fan speed. © 2000 Silsoe Research Institute.