Meteorological Effects on Deposition and Drift of Aerially Applied Sprays

Abstract

Drift from aerial application of crop protection materials is influenced by many factors such as ambient winds, temperature, relative humidity, and atmospheric stability. The applicator is responsible for making all possible efforts to reduce the potential for drift. Atmospheric conditions and stability must be considered and adjusted for on the basis of real-time observations and past experience. The objective of this research was to document the effects of atmospheric conditions and stability on the deposition and drift of aerially applied sprays. Two treatments, a fine spray 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. Results indicated increased downwind ground deposition resulting from increased wind speed, and increased airborne concentrations resulting from smaller droplet sprays and increased wind speed. Airborne concentration data demonstrated that increased atmospheric stability increased the time that smaller droplets remained suspended in the air, which could lead to increased downwind transport. However, these stable conditions are generally characterized by low wind speeds, which could potentially offset the increased suspension time. Overall, the results indicated that wind speed was the most dominant meteorological factor in the transport and fate of aerially applied sprays.