COMPARISON OF DROP SIZE DATA FROM GROUND AND AERIAL APPLICATION NOZZLES AT THREE TESTING LABORATORIES

Spray drop size is a critical factor in the performance of any agrochemical solution and is a function of spray solution, nozzle selection, and nozzle operation. Applicators generally select a particular nozzle based on the drop size reported by manufacturers and researchers. Like most population sampling methods, the accurate measurement of spray drop sizing is a function of sampling methodology, accuracy of the measurement, and inferences about a total population from a subset. Studies were conducted to determine the repeatability and accuracy of spray drop size from a standardized set of spray nozzles at three different application technology research laboratories (USDA-ARS in College Station, Texas; University of Nebraska-Lincoln in North Platte, Nebraska; and University of Queensland, Gatton in Gatton, Australia). To minimize differences in drop size measurements between laboratories, the same set of nozzles was used at each location. The three laboratory measurements of drop size varied by less than 5% except for the measurement of the very largest drops in a spray plume. Day-to-day differences in drop size measurements within each lab were also found to be around 5%. This work shows that through careful monitoring of spray pressure, air speed, and measurement distance, very close agreement in drop size measurements can be obtained between different facilities.