You are being redirected because this document is part of your ASTM Compass® subscription.
    This document is part of your ASTM Compass® subscription.


    The Effect of Adjuvants at High Spray Pressures for Aerial Applications

    Published: 2016

      Format Pages Price  
    PDF (152K) 16 $25   ADD TO CART
    Complete Source PDF (23M) 224 $77   ADD TO CART

    Cite this document

    X Add email address send
      .RIS For RefWorks, EndNote, ProCite, Reference Manager, Zoteo, and many others.   .DOCX For Microsoft Word


    Controlling droplet size is a critical part of making any successful agrochemical spray application. This is particularly true for higher-speed aerial applications where secondary atomization from air shear becomes the most dominant factor driving spray droplet size. Previous research has shown that higher spray pressures can result in larger droplet-sized sprays by increasing the exit velocity of the spray liquid from the nozzles, which in turn decreases the differential velocity between the spray liquid and surrounding airstream, reducing secondary breakup. This work explores the effects of higher-than-normal spray pressures on two typical aerial application nozzles in the presence of a formulated herbicide spray solution, with and without additional adjuvants. Generally, the spray solution effects followed trends seen in previous studies, with crop oil-containing adjuvants resulting in the largest droplet-sized sprays and the silicones and polymers the smallest. Increasing spray pressure increased droplet size across all combinations of nozzle, airspeed, and spray solution, without exception. The most promising results from this work showed that for typical high-end application airspeeds, increasing spray pressure from the lowest to highest pressures tested generally resulted in spray classifications increasing at least one size coarser. The results from this work demonstrate that larger, faster-flying agricultural aircraft can adopt current methods, with potentially minor equipment adjustments, to generate medium and larger spray qualities and to allow for more efficient applications while meeting agrochemical product label requirements.


    aerial application, droplet size, droplet size model, adjuvants, spray pressure

    Author Information:

    Fritz, Bradley K.
    U.S. Department of Agriculture, Agricultural Research Service, College Station, TX

    Hoffmann, W. Clint
    U.S. Department of Agriculture, Agricultural Research Service, College Station, TX

    Henry, Ryan S.
    University of Nebraska, Pesticide Application Technology Research and Extension Lab, North Platte, NE

    Committee/Subcommittee: E35.22

    DOI: 10.1520/STP159520150086