Effect of Interaction Between Nozzle Orientation and Crop Canopy Architecture Upon Distribution of Charged and Uncharged Spray Droplets

Abstract

The distribution of spray deposits, applied with an experimental air-atomizing nozzle (ENS, Parker Hannifin Corp.) was examined on cabbage, corn, soybean, and chrysanthemum plants. Very small droplets (Dv0.5∼20 um), of a water + surfactant + fluorescent tracer mixture, were produced by the nozzle which could operate in either an electrostatically charged or an uncharged mode. A fluorometric method was developed to analyze adaxial and abaxial deposits separately with a fluorometer. Comparing microscopic and image analysis counts of fluorescent spots (“droplets”) revealed that the latter technique detected less than 1/3 of the droplets present, while the quantitative fluorometer measurements showed no correlation with qualitative data on droplet density. Charging the spray produced consistently greater deposits than in the corresponding uncharged treatments. Penetration through the foliage was excellent on all crops. Abaxial deposits were much greater on corn than on the other crops with “horizontal” foliage. In some experiments, considerable “rebound” of the air-flow was observed and droplets carried upwards were possibly responsible for the higher abaxial deposits on cabbage and soybean compared to chrysanthemum where the greater foliar density dissipated the air movement and reduced the potential drift hazard.