Understanding spray drift
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Understanding Spray Drift. Robert E. Wolf Extension Specialist Application Technology. Biological and Agricultural Engineering. Why Interest in Drift?. Spotty pest control Wasted chemicals Off-target damage More high value specialty crops Urban sprawl and..... Less tolerant neighbors

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Understanding spray drift l.jpg

Understanding Spray Drift

Robert E. Wolf

Extension Specialist Application Technology

Biological and Agricultural Engineering


Why interest in drift l.jpg
Why Interest in Drift?

  • Spotty pest control

  • Wasted chemicals

  • Off-target damage

  • More high value specialty crops

  • Urban sprawl and.....

  • Less tolerant neighbors

  • Litigious Society

  • More wind?? (Timing)

  • Environmental impact

    • Water and Air Quality

  • Public more aware of pesticide

    concerns! (Negative) (Perceptions)

  • Result-higher costs-$$$


Slide3 l.jpg

Productivity

The application

triangle

Off-site protection

Efficacy



Definition of drift l.jpg
Definition of Drift

Movement of spray particlesand vaporsoff-target causing less effective control and possible injury to susceptible vegetation, wildlife, and people.

Adapted from National Coalition on Drift Minimization 1997 as adopted from the AAPCO Pesticide Drift Enforcement Policy - March 1991


Types of drift l.jpg
Types of Drift

Vapor Drift - associated with volatilization (gas, fumes)

Particle Drift - movement of spray particles during or after the spray application


Factors affecting drift l.jpg
Factors Affecting Drift

  • Equipment & Application

    • nozzle type

    • nozzle size

    • nozzle pressure

    • height of release

  • Weather

    • air movement (direction and velocity)

    • temperature and humidity

    • air stability/inversions

    • topography

Spray Characteristics

  • chemical

  • formulation

  • drop size

  • evaporation


Wind direction l.jpg
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.


However drift potential may be high at low wind speeds l.jpg
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.



Wind speeds gradients l.jpg

30

20

10

6

2

0

11 mph

10 mph

8 mph

Height Above Crop Canopy, Feet

7 mph

5 mph

Wind Speeds Gradients

Wind Speed

The relation between height above the canopy of a crop like cotton or soybean and the speed of wind.


Wind current effects l.jpg
Wind Current Effects

  • Wind currents can drastically affect spray droplet deposition

  • Structures drastically affect wind currents

    • Wind breaks

    • Tree lines and orchards

    • Houses and barns

    • Hills and valleys


Wind patterns near shelterbelts l.jpg

3

2

Height

5 0 5 10 15

Wind Patterns Near Shelterbelts

Distance from shelterbelt (tree heights)

Generalized pattern of wind in the neighborhood of a shelterbelt.


Wind patterns near treelines l.jpg
Wind Patterns Near Treelines

Adapted from Survey of Climatology:

Griffiths and Driscoll,

Texas A&M University, 1982


Wind patterns around buildings l.jpg
Wind Patterns Around Buildings

Ground

Diagram of wind around a building.

Adapted from Farm Structures*

* H.J. Barre and L.L. Sammet, Farm Structures (Wiley, 1959)


Slide16 l.jpg

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 2002 Master Catalog

**Plastimo Airguide Inc., 1110 Lake Cook Road, Buffalo Grove, IL 60089(708-215-7888)


Inversions l.jpg

Normal Temperature Profile

Cooler

Temperature decreases

with height

Altitude

Warmer

Increasing Temperature

Inversions

Under normal conditions air tends to rise and mix with the air above. Droplets will disperse and will usually not cause problems.


Temperature inversions l.jpg

Temperature Inversion

Warm Air

Temperature increases

with height

Altitude

Cool Air

Increasing Temperature

Temperature Inversions

Under these conditions

the temperature increases as you move upward. This prevents air from mixing with the air above it. This causes small suspended droplets to form a concentrated cloud which can move in unpredictable directions.


Recognizing inversions l.jpg
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.



Precautions for inversions l.jpg
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.



Efficacy and drift potential is influenced by l.jpg
Efficacy and Drift Potential is Influenced by

  • Size of the Spray Droplets -

    Volume Median Diameter (VMD)

  • Droplet Spectrum (Range - big to small)

% Volume in droplets less than

200 microns in size


Relationship of drift to drop size l.jpg
Relationship of Drift to Drop Size

One micron (m) =1/25,000 inch


Comparison of micron sizes for various items approximate values l.jpg

pencil lead 2000 (m)

paper clip 850 (m)

staple 420 (m)

toothbrush bristle 300 (m)

sewing thread 150 (m)

human hair 100 (m)

Comparison of Micron Sizes for Various Items: (approximate values)

150


Slide26 l.jpg

1/2 of spray volume = smaller droplets

VMD

1/2 of spray volume = larger droplets


Cutting droplet size in half results in eight times the number of droplets l.jpg
Cutting Droplet Size in HalfResults in Eight Times the Number of Droplets

250

Microns

250

Microns

500

Microns

250

Microns

250

Microns

250

Microns

250

Microns

250

Microns

250

Microns


Important droplet statistics l.jpg
Important Droplet Statistics

VMD

(50%)

Operational Area

VD0.1

(10%)

VD0.9

(90%)


Evaporation of droplets l.jpg
Evaporation of Droplets

High Relative Humidity

Low Temperature

Low Relative Humidity

High Temperature

Fall Distance

Wind


Spray characteristics are important to understand l.jpg
Spray Characteristics are Important to Understand

Demonstrates Turbo Flat vs TurboDrop-5 MPH Wind



Coverage l.jpg
Coverage

  • Need knowledge of the product being used.

    • Systemic

    • Contact

  • What is the target?

    • Soil

    • Grass

    • Broadleaf (smooth, hairy, waxy)

    • Leaf orientation – time of day


Asae dsc and volume median diameter d v0 5 from pms laser spectrometer l.jpg
ASAE DSC and Volume Median Diameter (DV0.5) From PMS* Laser Spectrometer

Droplet Spectra

Classification (DSC)

Droplet Size

Range

  • Very Fine (VF) < 182µm

  • Fine (F) 183-280µm

  • Medium (M) 281-429µm

  • Coarse (C) 430-531µm

  • Very Coarse (VC) 532-655µm

  • Extremely Coarse (XC) >656µm

*USDA ARS College Station, TX




Example of model use aerial applicators standard operation l.jpg
Example of Model Use – Aerial Applicators Standard Operation


Strategies to reduce drift l.jpg
Strategies to Reduce Drift:

  • Select nozzle to increase drop size

  • Increase flow rates - higher application volumes

  • Use lower pressures

  • Use lower spray (boom) heights

  • Avoid high application speeds/rapid speed changes

  • Avoid adverse weather conditions

    • High winds, light & variable winds, calm air

  • Consider using buffer zones

  • Consider using new technologies:

    • drift reduction nozzles

    • drift reduction additives

    • shields, electrostatics, air-assist


Drift reduction additives l.jpg
Drift Reduction Additives:

  • Many available!

  • Not EPA regulated

  • Long chain polymers

  • New-soluble powders

  • 50 - 80% reduction in off-target movement

  • Pump shear problems

  • Effect on the pattern?


Goodland drift project l.jpg
Goodland Drift Project

  • 8 Companies

  • 19 Drift Reduction/Deposition Aids

  • Water

  • X-77 @ .25%

  • 2 Airplanes

    • AT 502 - Hawkeye – Bill and Dave

    • Cessna Ag Husky w/wing tips – Cary

  • 3 reps with the drift tower

  • 1 pass over a canopy – top and bottom

  • 260 flight passes each

  • 4600 cards


Participants in the study l.jpg

41-A

Formula One

AMS 20/10

Border EG 250

Control

INT VWZ

Inplace

Garco Exp-3

INT YAR

Border XTRA 8L

HM2005-C

HM0226

Liberate

Target LC

HM2052

INT HLA

HM 0230

Valid

Double Down

Participants in the Study:

Companies

Products

  • United Suppliers

  • Helena Chemical

  • Garco

  • Loveland

  • Wilber-Ellis

  • Rosen’s

  • Precison Labs

  • SanAg


Some other things to keep in mind when planning a spray application l.jpg
Some Other Things to Keep in Mind when Planning a Spray Application

Allow enough time for:

  • Scheduling and planning the application

  • Obtaining the products

  • Setting up the application date

  • Weather delays or maintenance problems, if necessary.

Try not to 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.


In conclusion l.jpg
In Conclusion Application

Minimizing spray drift is in the best interests of everyone. Do your part to keep applications on target.


Slide44 l.jpg

Thank You Application


For more information contact l.jpg
For more information contact: Application

[email protected]

www.bae.ksu.edu/rewolf/


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