Project No.:              05-RS-01      

Project Leader:       Richard Stoltz, ADAP Analyst, California Agricultural Aircraft Assn. (CAAA), Clovis, CA

Cooperating Personnel:   C. Del Carlo (Chairman, CAAA)

For the race track pattern, all tested aircraft met or exceeded the minimum coefficient variation parameters.  The back and forth parameters were met or exceeded by four of the planes and four planes had patterns that were marginally acceptable.  The helicopter had patterns that were excellent for both types of flight patterns.  Most planes use a racetrack pattern while helicopters typically use a back and forth pattern.

All aircraft tested quite well for percent of spray volume below 200 microns, minimum Vd 0.1 (200 microns or larger) and overall droplet spectrum.  The percent coverage for those droplet cards placed on the orchard floor in 2005 was 1.7.  Coverage for cards placed on the berm was 2.3%.  The crop canopy was heavier along the berm due to the 18ft tree spacing versus 24 foot row spacing and thus more material was intercepted by the canopy than was intercepted on the orchard floor.  In the March 2004 trial, coverage was 5.8% on the berm and 8.2% on the orchard floor.  This drop in coverage from 2004 to 2005 was a direct result of full canopy versus the trees having just leafed out.

Horizontal drift is a concern.  This year’s results indicate the further away the cards are from the center of the spray swath, the less the percent coverage.  While horizontal drift was mostly reduced to some degree, it does not appear that full crop canopy had much effect when compared to a just leafed out canopy.  Vertical drift was quite low. As was the case of horizontal drift, full crop canopy versus a young canopy did not appear to have much effect on vertical drift.

Researcher Richard Stoltz discusses research results at 2005 conference

A drift study was also conducted in an open ground setting. Vertical and horizontal drift were measured.  The coverage’s, for both horizontal and vertical drift, were greater when compared to the crop canopy study.

From the aircraft studied, the potential for drift is minimal and the likelihood of a good, efficacious application is present.  Also, these aircraft, as configured, are not likely to create a drift problem during application as long as other drift mitigating measures are employed.  These measures would include applying when wind speed and direction are favorable and avoiding applying during low level inversion conditions.