The use of natural and artificial barriers to mitigate pesticide drift from agricultural and forest applications is discussed. This technique has been considered as an alternative to current methods at a time when environmental concerns are under great public scrutiny. There has been a variety of research experiments on this subject from New Zealand to The Netherlands which have documented reductions in spray drift of up to 80-90%. However, there are still enormous data gaps to utilize this method accurately. The aerodynamic factors of wind barriers and shelter effects on crop growth and yield have been well investigated. In contrast, some of the important aspects of drift mitigation, e.g. porosity and turbulence, have been difficult to obtain and no standard methodologies are currently available to evaluate and classify windbreaks and shelterbelts or to determine their efficiency in reducing drift. Thus there is a significant opportunity to incorporate windbreaks into the tool set of drift mitigation tactics. Government policies, initiatives, legislation, etc, which currently address water quality, BMP, stewardship, buffers, etc, are issues which so far have not included windbreaks as a valuable drift mitigation strategy.

No abstract

FLUENT, a computational fluid dynamics program, was used to investigate flow movements in sprayer tanks with hydraulic jet agitators. Two-and three-dimensional simulations were carried out utilizing single-phase (liquid phase only) and multiphase (solids particles in liquid) models. Earlier experimental studies of agitation effectiveness identified important factors affecting agitation effectiveness. This study was initiated to evaluate simulation as a tool in sprayer agitation system design. Interpretations of the flow field predictions supported previous measurements that determined system pressure to be the most influential factor on agitation effectiveness due to the direct relationship between pressure and jet velocity. Multiphase predictions of particle deposit amounts at the tank bottom were not feasible due to the computational demand of the model, which was an attempt to simulate three-dimensional turbulent flows with solid-liquid mixtures. Quantitative verification of single-phase simulations was accomplished by velocity measurements using hot-film sensors in a sprayer tank. Velocities were measured at 9 locations within the sprayer tank, and 12 jet agitation simulations were used. There were 118 of the 144 measured velocities within 50% of velocities predicted by FLUENT, and 120 of 144 measured velocities were within 0.2 m/s of predicted values. FLUENT-generated values tended to be greater than measured velocities near the top of the tank, and FLUENT velocities were always less than measured velocities at a position near the center of the tank.

A wind tunnel study was conducted to determine pesticide deposition on commonly used windbreak tree species used as spray drift barriers and associated exposure of honey bees. Although it has been known that windbreaks are effective in reducing chemical drift from agricultural applications, there is still an enormous information and data gap on details of the dependence of the mechanism on the biological materials of the barriers and on standardization of relevant assessment methods. Beneficial arthropods like honey bees are adversely affected by airborne drift of pesticides. A study was initiated by first establishing a wind tunnel to create a controlled environment for capture efficiency work. Suitable spray parameters were determined after a preliminary study to construct and develop a wind tunnel protocol. A tracer dye solution was sprayed onto the windbreak samples and honey bees located in the wind tunnel at various simulated wind speeds. Analysis of data from this work has shown that needle-like foliage of windbreak trees captures two to four times more spray than broad-leaves. In addition, it was determined that, at lower wind speeds, flying bees tend to capture slightly more spray than bees at rest.

No abstract