An air-assisted system was used with a Micromax III speed spinning disc nozzle and assess its effects on spray penetration, deposition and reduction of drift in an artificial canopy representing cotton plants. The effects of air-assist velocities (10, 15, 25 m s(-1)) to carry droplets and application volumes (20 and 401 ha(-1)) and two droplet sizes obtained by changing disc speed on spray deposition and drift potential were investigated with different cross-wind velocities (1.5, 2.5, 3.5 m s(-1)) in a wind tunnel. Deposition data produced by the spinning disc nozzle with and without air assistance were compared using a fluorometric method. Spray pattern displacement (SPD) was also determined using a spray patternator in the wind tunnel. Wind velocity, air assistance, application volume, droplet diameter and their interactions significantly affected deposition on plants. The highest deposit on plants was obtained with the combination of no cross-wind, spray volurne of 201 ha(-1), an air-assist velocity of 25 m s(-1) and droplet diameter of 210 gm. Downwind drift was partly controlled at an air-assist velocity of 25 m s(-1) when drift potential could be reduced up to 39%. (c) 2005 Elsevier Ltd. All rights reserved.