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Herbicide Drift Management

Herbicide Drift Management. John Boyd University of Arkansas. What is drift?. Movement of spray particles and/or vapors off-target. Types of Drift. Vapor Drift - associated with volatilization, gases and fumes. Particle Drift - movement of spray particles. Misapplication Facts. 2%.

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Herbicide Drift Management

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  1. Herbicide Drift Management John Boyd University of Arkansas

  2. What is drift? Movement of spray particles and/or vapors off-target.

  3. Types of Drift • Vapor Drift - associated with volatilization, gases and fumes. • Particle Drift - movement of spray particles.

  4. Misapplication Facts 2% 8% Equipment 33% Drift Tank Mix 24% Wrong Field Off Label 33% Source: Farmland Insurance 1996

  5. Contributions to Drift

  6. Factors Affecting Drift

  7. Weather & other Factors Affecting Drift • Temperature & humidity • Wind (direction and velocity) • Air stability/inversions • Topography

  8. Drift Potential Depends on • The percentage of small droplets in the droplet size range. • Droplet size is measured in microns. • The key factor is the percentage of the spray droplets less than 200 microns in diameter.

  9. Droplet Size • Spray drift droplets are measured in microns and expressed as Volume Median Diameter or VMD • One micron = 1/25,000th inch

  10. Comparison of Micron Sizes

  11. 1/2 of spray volume = smaller droplets VMD 1/2 of spray volume = larger droplets

  12. Cutting Droplet Size in Half Results in Eight Times the Number of Droplets = 250 Microns 500 Microns 2 more droplets fill in the sphere

  13. Important Droplet Statistics: VMD (50%) Operational Area VD0.9 (90%) VD0.1 (10%)

  14. Evaporation and Deceleration of Various Size Droplets* Droplet Terminal Final Drop Time to Deceleration Diameter Velocity diameter evaporate distance (microns) (ft/sec) (microns) (sec) (in) 20 .04 7 0.3 <1 50 .25 17 1.8 3 100 .91 33 7 9 150 1.7 50 16 16 200 2.4 67 29 25 *Conditions assumed: 90 F, 36% R.H., 25 psi., 3.75% pesticide solution

  15. Size Very Fine Medium Coarse Very Fine Coarse Dv0.1 <55* 55-94 95-164 165-225 >225 Dv0.5 <119 119-216 217-353 354-464 >464 Dv0.9 <204 204-369 370-598 599-789 >789 %<141 57.2 20.2-57.2 5.7-20.1 2.9-5.6 <2.9 *Numbers listed are in Microns Nozzle Drop Size ClassificationBritish Crop Protection Council (BCPC)

  16. Drop Size Classification & Use • Very Fine • Fine • Medium • Coarse • Very Coarse • <119 m • 119-216 m • 217-353 m • 354-464 m • >464 m Insecticides and Fungicides Herbicides and Postemergence Soil Applications of Herbicides

  17. Software for estimating droplet size distribution is available on the web. http://apmru.usda.gov/downloads/downloads.htm

  18. Evaporation of Droplets High Relative Humidity Low Temperature Low Relative Humidity High Temperature Fall Distance Wind

  19. Wind • Do not spray at any wind speed if it is blowing towards sensitive areas - all nozzles can drift. • Spray when breeze is gentle, steady, and blowing away from sensitive areas. • Spraying in dead calm conditions is never recommended.

  20. Drift Potential May be High at Low Wind Speeds • Because: • Light winds (0-3 mph) tend to be unpredictable and variable in direction. • Calm and low wind conditions may indicate presence of a temperature inversion. • Drift potential is lowest at wind speeds between 3 and 10 mph (gentle but steady breeze) blowing in a safe direction.

  21. Conditions • Where are what are the adjacent crops? • Are there houses, a town or other sensitive areas near the site?

  22. Buffer Zone • A buffer zone means an area where pesticide is not directly applied thereby providing protection to a defined area. • Buffer zones may depend on: • state regulations • pesticide product labels • prevailing weather conditions • sensitive/protected area(s)

  23. Product Selection • You may have several options on products. • Understand the product chemistry! • Consider the effect this product may have on homes and gardens near the application site. • Consider environmental and wildlife safety.

  24. Equipment Selection and Setup • Select equipment to produce the largest droplet size possible and still provide adequate coverage. • Be aware that some products require relatively smaller droplets to ensure good coverage.

  25. When Planning a Spray Application • Allow enough time for planning and executing the operation. Including weather and equipment delays. • Do not fall into the trap of declaring “I need to spray right now!”. Forcing a job under poor conditions almost always leads to drift or other errors.

  26. Wind Direction • Wind direction is very important • Know the location of sensitive areas - consider safe buffer zones. • Do not spray at any wind speed if it is blowing towards sensitive areas - all nozzles can drift. • Spray when breeze is gentle, steady, and blowing away from sensitive areas. • “Dead calm” conditions arenever recommended.

  27. However, Drift Potential May be High at Low Wind Speeds • Because: • Light winds (0-3 mph) tend to be unpredictable and variable in direction. • Calm and low wind conditions may indicate presence of a temperature inversion. • Drift potential is lowest at wind speeds between 3 and 10 mph (gentle but steady breeze) blowing in a safe direction.

  28. Name Features Cost* Dwyer Floating Ball 15.50 Wind Wizard Mechanical 39.50 Turbo Meter Wind speed - knots, feet/min, meters/sec, mph 135.00 Kestrel 1000 Maximum, average, current wind speed - knots, feet/min, meters/sec, mph 89.00 Kestrel 2000 Maximum, average, current wind speed, temp, wind chill- knots, feet/min, meters/sec, mph 119.00 Kestrel 3000 All wind speed features plus temp, wind chill, dew point, heat index, relative humidity 159.00 Plastimo Iris 50** Compass 89.00 Wind Meters and Compass *Prices for Wind Meters taken from Gempler’s 2000 Master Catalog **Plastimo Airguide Inc., 1110 Lake Cook Road, Buffalo Grove, IL 60089(708-215-7888)

  29. Recognizing Inversions: • Under clear to partly cloudy skies and light winds, a surface inversion can form as the sun sets. • Under these conditions, a surface inversion will continue into the morning until the sun begins to heat the ground.

  30. Precautions for Inversions • Surface inversions are common . • Be especially careful near sunset and an hour or so after sunrise, unless… • There is low heavy cloud cover • The wind speed is greater than 5-6 mph at ground level • 5 degree temp rise after sun-up • Use of a smoke bomb or smoke generator is recommended to identify inversion conditions.

  31. Nozzles are important • Control the amount – GPA. • Determine uniformity of application. • Affects the coverage. • Influences the drift potential.

  32. Spray Characteristics are Important to Understand Demonstrates Turbo Flat vs TurboDrop-5 MPH Wind

  33. XR Flat-fan @20, 40, 80 PSI Turbodrop XL @20, 40, 80 PSI Boom Drift

  34. Strategies to Reduce Drift • Increased drop size. • Higher application volumes. • Lower pressure. • Avoid adverse weather conditions.

  35. Strategies to Reduce Drift • Buffer zones. • Drift reduction nozzles • Drift reduction additives • Consider using new technologies: • drift reduction nozzles

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