Submitted to: American Society Agricultural Engineers/National Aerial Applicators Assoc
Publication Type: Proceedings
Publication Acceptance Date: December 3, 2001
Publication Date: N/A
Interpretive Summary: Spray drift is a matter of concern because spray materials that move outside of the intended target area are lost for their intended purpose and can have adverse effects on non-target areas, bodies, or objects. The agricultural chemical industry, regulatory and research agencies, and other interested companies and organizations have devoted considerable effort in recent years to better understand the sources and causes of spray drift. For aerial applications, spray droplet size has been identified as the major factor that operations can influence to reduce spray drift. Aerial spray nozzle models provide a means for applicators to estimate spray droplet size and other spray properties that influence spray drift. This study was conducted to determine whether other spray properties estimated from the models could aid applicators in selecting operational conditions to reduce spray drift. Study results confirm that maximizing droplet size or maximizing droplet size coupled with minimizing the driftable fine droplet content of the spray provide the best guidelines for aerial spray applicators to minimize spray drift.
Technical Abstract: Spray droplet spectra classification data are available for the spray nozzles in common use in the aerial application industry. Various additional droplet spectra parameters for these nozzles are also available. Emphasis has been placed on volume median diameter as an indicator of spray drift potential. But it is common knowledge that the small droplet content of the spray is the part of the droplet spectrum that is most prone to drift. Field measurements of spray drift with different formulations of glyphosate were correlated with wind tunnel measurements of spray droplet parameters of the same formulations. Maximizing any of the droplet size parameters ? DV0.1, DC0.5, DV0.9, D10, D30, or D32 ? or minimizing any of the small droplet content parameters ? relative span, percent spray volume less than 100 um diameter, or percent spray volume less than 200 um diameter ? will reduce spray drift. The combination of increasing DV0.5, and reducing either the percent spray volume less than 100 um or the percent spray volume less than 200 um provides the best multi-factor assessment for reducing spray drift. This information will provide guidance to aerial operators in mitigating spray drift based on physical properties of sprays from their nozzles and operation conditions.