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United States Department of Agriculture

Agricultural Research Service

Related Topics


Location: Soil, Water & Air Resources Research

2013 Annual Report

1a. Objectives (from AD-416):
1. Measure the movement of simulated spray drift using a combination of lidar and micrometeorological methods over a range of atmospheric conditions. 2. Evaluate the movement of spray droplets under different atmospheric conditions to determine the likelihood of offsite movement from a field. 3. Estimate the probability of interception of spray drift by a simulated buffer placed at the edge of a field to determine the potential for the use of bioenergy buffers as methods for the capture of spray drift. 4. Develop a decision tool to apply spray applications to reduce the potential for spray drift.

1b. Approach (from AD-416):
Studies will be conducted using a combination of micrometeorological equipment (sonic anemometers, air temperature, windspeed, relative humidity, and surface temperature) with lidar to measure the movement of spray droplets as they are released from a ground-based application unit. These studies will be conducted in a commercial field using simulated spray conditions by applying water with surfactants and not pesticides. This will allow for repeated applications over the same path without having to move the equipment to obtain observations over a range of atmospheric conditions of stability, surface wetness, and windspeed. Once the data are collected from these observations an analysis will be made of the change in the spray droplet concentration with distance and time from the application unit as a function of the atmospheric conditions. These data will be assembled into a mathematical representation of the surface in order to estimate the movement of the droplet plume with time and distance across the field and allow for the development of a model to represent the movement patterns throughout a day. Once this is complete then the observations will be evaluated to determine the potential for offsite movement along with the interception by a simulated bioenergy buffer placed at the edge of the field. These initial observations will provide a base for the development of a decision support tool to predict when spray drift would occur from a field and evaluate when applications need to be made to reduce potential spray drift from applications to row crops.

3. Progress Report:
The purpose of this experiment was to evaluate the movement of spray drift from the application of pesticides onto soybean using a ground-based application unit. Experiments were conducted on a soybean field in 2011 using a combination of micrometeorological equipment to quantify atmospheric stability and a lidar system to quantify the movement patterns of spray drift. In this experiment, water droplets with a surfactant were used to simulate the release of a pesticide into the atmosphere. It was found that the wake created by the movement of the spray rig created turbulence which enhanced the upward movement of the spray droplets. When these droplets were lifted into the atmosphere there was greater downwind movement induced by the unstable air over a partial ground cover of soybean. These results have been used to refine spray drift models for use with ground-based application units. The movement patterns of the spray droplets are governed by a number of factors and understanding these interactions will help devise guidelines to reduce spray drift.

4. Accomplishments

Last Modified: 2/23/2016
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