Submitted to: American Society of Agricultural Engineers Meetings Papers
Publication Type: Other
Publication Acceptance Date: 8/3/2004
Publication Date: 8/3/2004
Citation: Fritz, B.K. 2004. Role of atmospheric stability in drift and deposition of aerially applied sprays - preliminary results. American Society of Agricultural Engineers Meetings Papers, August 1-4, 2004, Ottawa, Canada. Paper No. 04-1031.
Interpretive Summary: Drift from aerial application and crop protection materials is influenced by controllable factors, such as nozzle type and spray pressure, and uncontrollable factors, such as wind speed and atmospheric stability. Applicators are responsible for considering atmospheric conditions and adjusting operational factors to maximize on-target deposition and minimize the potential for drift. Generally, greater drift potential has been demonstrated to be associated with greater atmospheric stability. Field trials were conducted over the course of several mornings with the objective of assessing the degree of ground deposition and downwind drift of aerially applied spray treatments under various atmospheric stability conditions. Initial results indicated increased deposition on the ground at farther downwind distances under unstable conditions and greater spray drift under unstable conditions as a result of high wind speeds. These results will help applicators make informed decisions resulting in application of crop protection materials with maximum on-target deposition and minimal off-site drift.
Technical Abstract: Drift from aerial application of crop protection materials is influenced by many factors, including atmospheric stability. The applicator is responsible for insuring that all factors are considered and that all possible efforts are made to reduce the potential for drift. Atmospheric conditions must be considered and adjustments made based on real time observations and past experience. Many studies have indicated that a more stable atmosphere increases the potential for drift. It is therefore important to have an understanding of atmospheric stability and how it can impact the deposition and drift of aerially applied sprays. The objective of this research was to document the effects of atmospheric stability, especially under very stable to stable conditions, on the deposition and drift of aerially applied sprays. Two treatments, a FIME and a MEDIUM spray, were used. Ground deposition and airborne concentrations of spray were sampled at multiple downwind locations using mylar cards and monofilament line, respectively. Tests were performed beginning at first light and continued for approximately two hours. Sampling during these times gave a high probability that stable and very stable conditions would be encountered. Statistical and graphical analyses indicated that there were no significant differences between treatments, but that stability had a significant effect on ground deposition in the near-field and on airborne concentrations in the far-field. Regression analysis indicated that wind speed was a significant factor for both ground deposition and airborne concentrations in both the near-field and the far-field. These results tend to support previous findings. Several difficulties that turned up in the analysis are discussed, including lack of sufficient samples during stable and ver stable conditions and a need for additional sampling heights. Solutions being implemented in the next set of field studies, i.e. additional sampling heights at each downwind distance location and methodology to increase the number of replications, are also discussed.