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A three-year experimental study has been conducted in apple orchards of Southern Piedmont to assess the quality of spray deposition on the canopy, the incidence of ground losses and of drift effects according to the sprayer adjustments. A conventional air-assisted sprayer, fitted with an axial fan (900 mm in diameter) and hollow cone nozzles, has been used for the trials. Four different volume application rates (300, 500, 700 and 1000 l/ha) were compared, operating at 6.0 km/h forward speed and with an air flow rate equal to 30000 m3/h. To assess the coverage of the canopy, in three different growth stages of the crop, samples of leaves picked up from different parts of the plants treated with the test liquid (a solution of water and yellow dye Tartrazine E102) were analyzed, while ground losses were determined by means of Petri dishes disposed on the ground in the treated area. To evaluate the incidence of drift, samplers (filter papers) were fixed on poles above the top of vegetation in the middle of the treated area so to detect the amount of spray dispersed in the atmosphere and susceptible to drifting away from the orchard.

Results pointed out that the application of reduced volumes (300-500 l/ha), calibrated according to the growth stage of the plants, allowed to obtain a better coverage of the target and to reduce ground losses, while increasing drift risks were registered when fine droplets were sprayed.