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United States Department of Agriculture

Agricultural Research Service

Research Project: Pesticide Application Technologies for Spray-drift Management, Maximizing In-field Deposition, and Targeted Spraying

Location: Crop Production Systems Research

2010 Annual Report

1a. Objectives (from AD-416)
Objectives are: 1) Control off-target drift and enhance penetration of active ingredients, such as fungicides and biological control agents, into crop canopies; and 2) Develop remote sensing methods, utilize and evaluate Global Positioning Systems (GPS), develop methods amenable to rapid image processing, and evaluate flow control systems to support variable rate aerial application.

1b. Approach (from AD-416)
This project seeks to advance application technology through improvements in 1) drift management technology, 2) technologies for improved within-canopy deposition, 3) use of low-altitude remote sensing to identify stressed plants, and 4) performance of variable rate aerial application systems. While drift management is a concern for all pesticide applications, it is of particular concern for aerial applications. The potential for drift is greater for aerial application due to higher altitudes of spray release and greater air turbulence in the wake of the aircraft. Determination of optimal spray release height will be a goal, as the effect of this variable on within-canopy deposition and off-target drift has not been considered adequately. Experiments for both drift and deposition will attempt to reduce confounding of treatment data with environmental effects, preserving statistical precision of the experiments. Penetration of sprayed material to the lower portions of the canopy is critical for control of fungal spore diseases like Asian Soybean Rust (ASR). Studies will compare nozzle types paired with carefully selected formulations and tank mixes for spray penetration. The deleterious effects of off-target herbicide drift to cotton will be detected using hyperspectral, multispectral, and thermal remote sensing techniques. Evaluation of variable rate aerial application systems will be continued and improvements will be made through interaction with system component manufacturers. Experiments are also proposed to demonstrate the validity of techniques developed.

3. Progress Report
Experiments were conducted to determine the effects of formulation, relative humidity (RH), ambient temperature, and droplet volume on the size of droplet stains applied to water sensitive paper (WSP) used in spray drift and deposition studies. This experiment was conducted to improve spread factor equations for more accurate representation of droplet diameter. An experimental protocol was designed to permit manual placement of droplets onto WSP placed in an environmental chamber using micropipettes so that the effects of these variables could be modeled. Preliminary model results indicated a 0.5% increase in droplet stain area per 1% increase in RH. A field experiment was conducted to compare the ability of rotary atomizers and flat fan nozzles to deposit aerially applied spray into a soybean canopy. The experiment was expanded to include ground spraying treatments with two spray tips to match treatments in an experiment by cooperative study with the USDA, ARS, ATRU in Wooster OH. Results from both studies are being analyzed. A study was conducted to characterize injury due to off target drift of Glyphosate herbicide from aerial application. Four replications of soybeans, corn, and cotton were planted in strips, and spray sampling lines were placed in a “star” pattern to allow for wind shifts before the single application of glyphosate by air. Samplers were collected and the fields were flown at 7, 14, and 21 days after application with a multispectral camera to characterize damage patterns. Concentrations of Glyphosate on drift samplers were inferred by analysis of a Rubidium Chloride tracer placed in the spray mix. Correlations were made between concentration of RbCl on samplers and damage extent from vegetation indices derived from remote sensing images. Analysis was extended further using geostatistical methods in collaboration with Auburn University. Data have been analyzed from an experiment to evaluate a variable-rate aerial application system and to improve response time of the flow controller to step changes in flow. The system manufacturer was a participant in the study and re-programmed the algorithms. A journal article was published in FY 2010 to document these improvements.

4. Accomplishments
1. Automatically Triggered Multispectral Field Imaging System. An aerial multispectral imaging system was successfully employed on agricultural aircraft by ARS researchers at Stoneville, MS, to determine areas of herbicide-induced crop injury after application of glyphosate. The imaging system is pilot-friendly because it allows hands-free operation; field locations to image can be pre-programmed. This multispectral platform shows promise as a new tool for operators of agricultural aircraft because imaging runs can be scheduled more frequently than conventional aerial remote sensing services. Frequent scheduling is particularly important when crop stress is being monitored. Convenience of this system could greatly increase the possibility of acceptance of remote sensing as a management tool by the agricultural community where agricultural aircraft are prevalent.

2. Laser-based Spray Altitude Determination. ARS researchers at Stoneville, MS, developed a new laser-based system for agricultural aircraft to determine the height of spray release from agricultural aircraft, a variable that has previously been difficult to quantify accurately. Determination of spray release height is very critical as it influences the propensity for off-target drift from aerial application.

3. Effects of Application Altitude on Deposition from a Flat-fan Spray Nozzle. Tests with a flat fan nozzle by ARS researchers at Stoneville, MS, showed that higher aerial application altitude increased the tendency for drift, but that height of application did not appreciably affect spray deposition within the swath (over the target crop). The latter is an important finding because it indicates that this nozzle type may be insensitive to changes in application height and thus be just as effective in applying chemical to the target within a range of application altitudes.

4. Modeled Impact of Factors that Affect Off-target Drift. A methodological study was conducted ARS researchers at Stoneville, MS, in collaboration with Texas A&M University to provide valuable information on the level of the impact from factors that affect drift using simulation software such as the Agricultural Dispersal Model (AGDISP). The new method can be used to search for the optimal spray conditions, which would be valuable to generate guidelines for aerial applicators to achieve an optimal spray result.

Review Publications
Huang, Y., Lan, Y., Thomson, S.J., Fang, A., Hoffmann, W.C., Lacey, R. 2010. Development of Soft Computing and Applications in Agricultural and Biological Engineering. Computers and Electronics in Agriculture. 71:107-127.

Huang, Y., Thomson, S.J., Lan, Y., Maas, S.J. 2010. Multispectral Imaging Systems for Airborne Remote Sensing to Support Agricultural Production Management. International Journal of Agricultural and Biological Engineering. 3(1):50-62.

Thomson, S.J., Huang, Y., Hanks, J.E., Martin, D.E. 2010. Improving Flow Response of a Variable-rate Aerial Application System by Interactive Refinement. Computers and Electronics in Agriculture. 73(1):99-104.

Huang, Y., Zhan, W., Fritz, B.K., Thomson, S.J., Fang, A. 2010. Analysis of Impact of Various Factors on Downwind Deposition Using a Simulation Method. American Society for Testing and Materials 7(6):1-10.

Last Modified: 06/23/2017
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