Measuring and modeling the movement of spray dropletsinto off-target areas

摘要

Spray drift can cause significant environmental harm and is a problem for the agricultural chemical application industry. Models help predict the distance of smaller, drift-prone droplet travel from wind tunnel studies, but field testing is required to validate predicted drift from these models. The purpose of this research was to investigate spray drift from three different spray quality nozzles into an off-target area up to 30 m from the end of the spray boom with varying cross-boom wind velocities. Field tests were carried out using a UTV-mounted boom sprayer driving perpendicular to the wind direction. Using pink spray dye, off-target droplets were collected on white Kromekote droplet collection cards spaced on 2 m intervals to 30 m downwind. Tests were done during four days with differing wind speeds less than 15 mi/h. Three different spray quality nozzles were used: fine, medium and very coarse. Each individual card was scanned with a flatbed scanner. The resulting images were analyzed with DepositScan software which found the number, area and diameter of the droplets on each card. The number of droplets collected on cards, decreased with distance from the boom to a low, but non-zero number of droplets were found on cards out to 30 m. Usinga statistical model, there was a clear extension of off-target application rates into the 2 to 10 m distance away from the boom depending on droplet size and a low probability of substantial off-target application rates in the 10 m to 30 m region.