ARS | Publication request: Evaporation and deposition coverage of single droplets on various waxy surfaces

Submitted to: International Crop Protection Compendium
Publication Type: Abstract Only
Publication Acceptance Date: May 20, 2008
Publication Date: September 28, 2008
Citation: Zhu, H., Yu, Y., Ozkan, H.E., Derksen, R.C., Krause, C.R. 2008. Evaporation and deposition coverage of single droplets on various waxy surfaces. International Crop Protection Compendium.73(4):711-718

Technical Abstract: The droplet evaporation and residual coverage area on surfaces with various waxy conditions was investigated to improve the foliar spray application efficiency. The investigation was conducted with an environmental-controlled chamber under controlled laboratory conditions. A stereoscope and a high definition digital camera was used to record the droplet evaporation process. Variables for the investigation were: three different target surfaces (hydrophilic slide, hydrophobic slide, and crabapple leaf), five droplet sizes (246, 343, 575, 762, and 886 µm). The spray mixtures used to form droplets included different combinations of water, an alkyl polyoxyethylene surfactant, and two insecticides. Adding the surfactant into spray mixtures resulted in a great decrease in droplet evaporation time and a great increase in maximal droplet coverage area while adding drift retardant into the spray mixtures resulted in a slight increase in droplet evaporation time but did not change the maximal coverage area. The evaporation time of 343 µm droplets containing insecticides at 60% RH on the hydrophilic surface increased from 70 to 91 s after drift retardant was added into spray mixtures, and decreased from 70 to 50 s after surfactant was added. Among the three target surfaces, the droplets had the longest evaporation time and smallest coverage area on the hydrophobic surface, while droplets had the shortest evaporation time on crabapple leaf surfaces, and largest coverage area on the hydrophilic surface.