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United States Department of Agriculture

Agricultural Research Service


item Smith, Lowrey
item Thomson, Steven

Submitted to: American Society of Agricultural Engineers Meetings Papers
Publication Type: Proceedings
Publication Acceptance Date: 12/6/2004
Publication Date: 12/6/2004
Citation: Smith, L.A., Thomson, S.J. 2004. Effect of cp-nozzle setup on spray distribution and swath width. American Society of Agricultural Engineers Meetings Papers. Paper No. AA04-002. p. 15.

Interpretive Summary: Spray deposit uniformity following the application of agricultural chemicals is important to both the applicator and to the environment. Uniform spray deposits across the swath enhance the effectiveness of the application's performance and can allow application rates to be reduced without reducing effectiveness. Aerial applications are less uniform than applications with ground-based sprayers and must be evaluated to determine the width of swath being effectively treated with sufficient spray. This effective swath is then used by the operator to control the distance between successive spray passes. Effective swath width associated with aerial applications is affected by air turbulence caused by the aircraft, height of spray release, wind speed, wind direction, boom width, type of nozzle and nozzle setup. Experienced operators have determined for their airplane what release height, boom width, and wind characteristics give the best results, but they may not be aware of slight modifications in effective swath width that occur due to using different nozzle setups to achieve different requirements of the spray job. This study evaluated four nozzle setups that included two orifice diameters combined with two deflectors. The effects of these setups were compared in terms of spray distribution uniformity and effective swath width. Deposits on 13-cm square Mylar collectors (spaced at 1-m intervals) were quantified by measuring the concentration of Rubidium tracer in a 20-ml volume of wash solution with an atomic absorption spectrometer. Results showed that the use of nozzles that sprayed a solid jet of spray mix without secondary deflectors to assist with atomization reduced deposit uniformity significantly and reduced effective swath widths by one or two meters compared to that achieved with the use of five degree deflectors. Nozzle deflectors did not significantly affect spray deposit amounts for a particular application rate. For the conditions of this study, the coefficient of variation value associated with effective swath widths ranged from 27 to 29-%.

Technical Abstract: An Air Tractor 402B, equipped with a standard drop-boom kit, an AutoCal II automatic flow control, and CP-Straight Stream nozzles, was used to evaluate the effect of nozzle settings on spray distribution and swath width. Treatments consisted of two nozzle orifice diameters (0.198 cm (0.078 in); 0.157 cm (0.062 in)) and two deflectors (0 degree, 5 degree). A sampling line, consisting of 38 horizontal fallout sheets at one-meter intervals, was established perpendicular to and centered on the flight line. The samplers were loaded with 12.7 cm (5 in) square Mylar sheets that were collected in leak-proof zip-lock bags after each application pass. Results indicated that orifice diameter had a significant effect on spray deposit from a single application pass but that single-pass deposits associated with deflector settings were similar. The coefficient of variation (CV) associated with single-pass spray deposits was significantly affected by nozzle deflector angle but orifice diameter did not affect CV significantly. Field applications were simulated by overlapping three single-pass patterns and spacing them apart by a distance equal to the swath width being evaluated. Analysis of the simulated field application revealed that the minimum acceptable CV for the conditions of this study ranged from 26.5% to 29.2% with an average of 28.3%. Use of the straight stream (0 degree) deflector reduced effective swath width by 1 or 2 meters compared to the 5 degree deflector.

Last Modified: 08/18/2017
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