A System to Evaluate Shear Effects on Spray Drift Retardant Performance

A laboratory system was developed to simulate shear on mixtures of water and drift retardants due to their recirculation in sprayer tanks. Three significantly different drift retardants (AgRHO DR-2000, Nalco-Trol and Nalco-Trol II) were evaluated in both a Myers A36 orchard airblast sprayer and the laboratory system. Droplet size distributions of sprayed samples from the sprayer and the laboratory system were measured with an Aerometric Phase/Doppler Particle Analyzer. Droplet size distributions of sprayed samples with drift retardants sheared with the laboratory system had similar trends to those of samples sheared with the airblast sprayer as the number of recirculations increased. When the number of recirculations through the system increased from 0 to 11.4, DV0.5 of sprayed samples of the 0.1% DR-2000 mixture did not change significantly from the initial value of 587 mm, but DV0.5 of sprayed samples with 0.0547% Nalco-Trol and the 0.0547% Nalco-Trol II mixtures decreased from 592 to 422 mm and from 505 to 366 mm, respectively. Also, the percent spray volume < 200 mm for mixtures with DR-2000 and Nalco-Trol taken after 11.4 recirculations was 72.8 and 34.1% less than that of a water spray. A possible test system for an ASAE standard is presented.