ARS | Publication request: An overview of spray drift reduction testing of spray nozzles

Submitted to: National Agricultural Aviation Association Meeting
Publication Type: Proceedings
Publication Acceptance Date: December 7, 2009
Publication Date: December 7, 2009
Citation: Fritz, B.K., Hoffmann, W.C., Thornburg, J.W., Bagley, W.E., Birchfield, N., Ellenberger, J. 2009. An overview of spray drift reduction testing of spray nozzles. National Agricultural Aviation Association Meeting. Paper No. AA09-002.

Interpretive Summary: Concerns exist about possible detrimental effects to the environment and other nearby crops caused by drift associated with the spray application of crop production and protection products. To address this problem, an increasing number of drift-reducing technologies are being developed and marketed for use with agricultural chemicals. As the market for drift-reducing technologies continues to grow, there is a need to scientifically quantify and rate the effectiveness of these products. Cooperative studies with the Environmental Protection Agency were conducted to determine the applicability and feasibility of evaluation protocols for drift-reducing technologies and a drift rating system. As a result of this work, improved testing and rating methodologies were suggested in order to provide a science-based program that appropriately credits applicators for reduced drift with the use of effective technologies.

Technical Abstract: The importance of the development and testing of drift reduction technologies (DRTs) is increasing. Common spray drift reduction technologies include spray nozzles and spray adjuvants. Following draft procedures developed for a DRT program, three spray nozzles were tested under high air speed conditions (i.e. 45-64 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 produced by each of the nozzles with different airspeeds, spray pressures, and orientation were measured with a Sympatec Helos laser diffraction instrument. The measured droplet size spectra for each test was input in a spray dispersion model (AGDISP) to calculate the downwind drift expected from a typical aerial application scenario. The three spray nozzles reduced spray drift by 70-84 percent as compared to a reference nozzle. The nozzles generated spray droplets with volume median diameters 60-80 um larger than the reference nozzle. One of the aerial application industry’s Best Management Practices (BMP) is the use of a swath offset at the downwind most edge of a spray block. 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 to 96-96 percent. These results demonstrate the possibility of combining multiple drift reduction techniques and technologies to greatly reduce spray drift.