Abstract
The development and testing of drift reduction technologies (DRTs) have come to the forefront of application research in the past few years in the United States. DRTs can be spray nozzles, sprayer modifications, spray delivery assistance, spray property modifiers (adjuvants), and/or landscape modifications. A protocol for testing DRTs in high speed wind tunnels has been previously reported and was expanded to test spray nozzles. This manuscript reports on the initial implementation of the DRT program for conducting DRT evaluations of three spray nozzles under high speed conditions (i.e.,45–65 m/s (100–140 mph)), which are relevant to the aerial application of crop production and protection materials. The spray nozzles were evaluated in the USDA-Agriculture Research Service High Speed Wind Tunnel facility. The droplet size of each of the nozzles with different airspeeds, spray pressures, and orientation was measured with a Sympatec Helos laser diffraction instrument. The droplet size spectra for each test were input in a spray dispersion model (AGDISP), which calculates the downwind drift expected from a typical aerial application scenario. As compared to the reference nozzle, the three spray nozzles reduced spray drift by 70–84 % as compared to the reference nozzle. The nozzles generated spray droplets with volume median diameters 60–80 μm larger than the reference nozzle. One of the aerial application industry’s best management practices (BMPs) is to not spray directly on the downwind edge of a field. The spray swath near this edge is moved upwind (i.e., offset) by 1/2 to 1 swath width. When this BMP was combined with the drift reductions from the spray nozzles, the amount of drift reduction was slightly increased; however, application efficiencies increased to 93–96 %. These results demonstrate the possibility of combining multiple drift reduction techniques and technologies to greatly reduce spray drift.
