Variation of Spray Deposit and Loss with Air-jet Directions applied in Orchards

Axial fans with a radial air flow have been most commonly used in fruit growing areas. These generate a large radial plume which is poorly targeted for modern intensive orchards. A highvolume directed air-jet system (HVDAS) sprayer, based on a standard axial fan has been developed to determine the influence of the air jet direction generated by the sprayer on the incanopy spray deposit and off-target loss in orchards of different tree row volumes. Three sprayers with axial fans but with different air discharge systems were compared (conventional, cross-flow, HVDAS with the air spouts directed at 20 and at 40° upwards). The treatments were carried out in dwarf and semi-dwarf orchards. In modern orchards, the HVDAS sprayer with air spouts set 20° upwards produced a higher in-canopy deposit and a lower off-target loss than the conventional and cross-flow sprayers. Further raising of the air spouts directing the air-jets at 40° upwards, increased the spray loss and enhanced the risk of airborne drift without any influence on spray deposit.