Field evaluation of a calibration method for air-assisted sprayers involving a vertical patternator

Vertical spray patternators are used in Europe for the inspection and calibration of orchard and vineyard sprayers. However, little information is available about their reliability, particularly when used for crop-specific calibration, involving the adjustment of nozzle position and orientation according to canopy size and geometry. A method, based on the use of a lamellate patternator, was evaluated for adjusting the nozzle orientation of a conventional, axial-fan sprayer. The treatments included: (a) keeping the nozzle orientation as determined by the manufacturer (no calibration); (b) adjusting the nozzle orientation in the field, following visual observation (in-field calibration); and (c) adjusting the nozzles in order to obtain, on the lamellate patternator, a vertical spray pattern reflecting the canopy outline of the vineyard (patternator calibration). The above treatments were applied in a hedgerow vineyard, at beginning of flowering and at fruit set, and spray deposits on the canopy determined by colorimetry, using a water-soluble dye (Tartrazine) as a tracer. No calibration gave the most uniform deposit distribution in the first experiment, whereas in-field calibration was best in the second experiment. In both experiments, Patternator calibration gave the largest differences between deposits at different heights on the canopy, related to low collecting efficiency of the patternator, particularly at the middle and top canopy locations. (C) 2003 Elsevier Ltd. All rights reserved.