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Title: Spray drift reduction evaluations of spray nozzles using a standardized testing protocol

item Hoffmann, Wesley
item Fritz, Bradley - Brad
item THORNBURG, J - Rti International, Usa
item BAGLEY, WILLIAM - Wilbur-Ellis Company
item BIRCHFIELD, NORM - Environmental Protection Agency (EPA)
item ELLENBERGER, J - Environmental Protection Agency (EPA)

Submitted to: Journal of ASTM International
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/8/2010
Publication Date: 7/30/2010
Citation: Hoffmann, W.C., Fritz, B.K., Thornburg, J.W., Bagley, W.E., Birchfield, N.B., Ellenberger, J. 2010. Spray drift reduction evaluations of spray nozzles using a standardized testing protocol. Journal of ASTM International. 7(6):JAI102820.

Interpretive Summary: Mitigation of drift associated with spray application of crop production and protection products is a continual concern for the spray application industry. As such, an increasing number of drift-reducing technologies are being developed and marketed for use with agricultural chemicals in aerial application treatments. We conducted studies to scientifically quantify and rate the effectiveness of these products in order to inform end users. By properly selecting spray nozzles and adopting established Best Management Practices, we determined that aerial applicators can reduce spray drift by 70-84% and ensure that between 93-96% of the sprayed product deposits in the field. The implementation of these results will result in improved applications and encourage rapid adoption of drift reducing technologies.

Technical Abstract: The development and testing of drift reduction technologies has come to the forefront of application research in the past few years in the United States. Drift reduction technologies (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/sec (100-140 mph)), which are relevant to the aerial application of crop production and protection materials. The spray nozzles were evaluated in the USDA-ARS High Speed Wind Tunnel facility. Droplet size of each of the nozzles with different airspeeds, spray pressures, and orientation were measured with a Sympatec Helos laser diffraction instrument. The droplet size spectra for each test was 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 those by the reference nozzle. One of the aerial application industry’s Best Management Practices (BMP) 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 ½ 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.