Transcript Coalition on Drift Minimization

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
Litigious Society
More wind?? (Timing)
Environmental impact
• Water and Air Quality
 Public more aware of pesticide
concerns! (Negative) (Perceptions)
 Result-higher costs-$$$
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Productivity
The application
triangle
Off-site protection
Efficacy
Technical Aspects of Spray Drift
Definition of Drift
Movement of spray particles and
vapors off-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
Vapor Drift - associated with
volatilization (gas, fumes)
Particle Drift - movement of spray
particles during or after the spray
application
Factors Affecting Drift
Spray Characteristics Equipment & Application
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chemical
formulation
drop size
evaporation
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nozzle type
nozzle size
nozzle pressure
height of release
Weather
 air
movement (direction and velocity)
 temperature and humidity
 air stability/inversions
 topography
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 are never
recommended.
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.
Spray Droplet Movement with
Various Wind Speeds
Droplet
Sizes
(microns)
5 mph
Wind
10 mph
Wind
15 mph
Wind
20
mph
Wind
100
24 ft.
48 ft.
72 ft.
96 ft.
200
9
18
26
35
400
5
9
14
18
500
4
7
10
14
600
3
6
9
12
Boom height: 3 feet
Wind Speeds Gradients
Height Above Crop Canopy, Feet
30
20
10
6
2
11 mph
10 mph
8 mph
7 mph
Wind Speed
5 mph
0
The relation between height above the canopy of a
crop like cotton or soybean and the speed of wind.
Wind Current Effects
 Wind currents can drastically affect spray
droplet deposition
 Structures drastically affect wind
currents
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Wind breaks
Tree lines and orchards
Houses and barns
Hills and valleys
Height
Wind Patterns Near Shelterbelts
5
0
5
10
15
Distance from shelterbelt (tree heights)
Generalized pattern of wind in the neighborhood of a shelterbelt.
Wind Patterns Near Treelines
Adapted from Survey of Climatology:
Griffiths and Driscoll,
Texas A&M University, 1982
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)
Wind Meters and Compass
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
*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
Under normal
conditions air
tends to rise and
mix with the air
above. Droplets Altitude
will disperse and
will usually not
cause problems.
Normal Temperature Profile
Cooler
Temperature decreases
with height
Warmer
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.
Temperature Inversion
Temperature increases
with height
Altitude
Cool Air
Increasing Temperature
Warm Air
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.
105 foot temperature monitoring tower
105’ 38°F
Cloud of 5-25 u oil
droplets generated under
unstable conditions
64’
40°F
32’
40°F
16’
41°F
8’
41°F
Cloud is dispersing
2.5 mph wind
105’ 38°F
.5 mph wind
64’
32’
16’
8’
38°F
37°F
36°F
33°F
Shallow surface inversion
STABLE conditions up to 64’
NEUTRAL conditions at 105’
Courtesy – George Ramsay, Dupont
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.
Spray Droplet Size
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
One micron (m) =1/25,000 inch
Comparison of Micron Sizes for Various
Items: (approximate values)
2000 (m)
pencil lead
paper clip
150
staple
850 (m)
420 (m)
toothbrush bristle
sewing thread
300 (m)
150 (m)
human hair
100 (m)
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
250
Microns
250
Microns
500
Microns
250
Microns
250
Microns
250
250
250
250
Microns Microns Microns Microns
Important Droplet Statistics
Operational
Area
Evaporation of Droplets
High Relative Humidity
Low Temperature
Wind
Low Relative Humidity
High Temperature
Spray Characteristics are
Important to Understand
Demonstrates Turbo Flat vs TurboDrop-5 MPH Wind
ASAE S-572 Droplet
Size Standard
Coverage
Need knowledge of the product being used.
• Systemic
• Contact
What is the target?
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Soil
Grass
Broadleaf (smooth, hairy, waxy)
Leaf orientation – time of day
ASAE DSC and Volume Median Diameter
(DV0.5) From PMS* Laser Spectrometer
Droplet Spectra
Classification (DSC)
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Very Fine (VF)
Fine (F)
Medium (M)
Coarse (C)
Very Coarse (VC)
Extremely Coarse (XC)
Droplet Size
Range
< 182µm
183-280µm
281-429µm
430-531µm
532-655µm
>656µm
*USDA ARS
College Station, TX
Computer Models:
AgDRIFT® Program Map
Example of Model Use –
Aerial Applicators Standard Operation
CP STRAIGHT STREAM NOZZLE
FOR USE ON FIXED-WING AIRCRAFT
AERIAL APPLICATORS SPRAY NOZZLE HANDBOOK
USDA ARS AGRICULTURAL HANDBOOK NO. XXX
The author is I. W. Kirk, Agricultural Engineer, Areawide Pest M anagement Research Unit,
F
I X E D - W I N G
Southern Plains Agricultural Research Center, Agricultural Research Service, U. S. Department of Agriculture, 2771 F&B Road, College Station, TX 77845-4966, USA.
Directions: Enter CP STRAIGHT STREAM nozzle settings, pressure, and airspeed in the cells highlighted below.
(Atomization parameters are valid only with nozzle and operational settings specified in the Acceptable Range.)
Orifice Size,
Deflector Angle,
Pressure,
Airspeed,
inches
degrees
psi
mph
Acceptable Range: .061 to .171
0 to 30
20 to 60
100 to 160
0.125
5
30
130
Application parameters are displayed in the box below.
CAUTION: Do not enter or clear data in the cells in this box!
DV0.5 =
330 µm
= Volume median diameter
RS =
1.33
= Relative Span
%V<100µm =
4.26 %
= Percentage of spray volume in droplets smaller than 100 µm diameter.
%V<200µm = 13.52 %
= Percentage of spray volume in droplets smaller than 200 µm diameter.
DSC = MEDIUM
= ASAE S572 AUG99 Droplet Spectra Classification
Values and classifications reported here are least-squares best-estimate predictions from experimental data collected in a w ind tunnel.
Values reported from other laboratories may not yield the exact same values, but similar trends w ould be expected.
The droplet spectra classification category is based on droplet sizes in the mid-80% of the spectrum and not a single data point.
Trade names are mentioned solely for the purpose of providing specific information. M ention of a trade name does not constitute a guarantee or warranty of the product by the
U. S. Department of Agriculture, and does not imply endorsement of the product over other products not mentioned.
Strategies to Reduce Drift:
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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:
Many available!
Not EPA regulated
Long chain polymers
New-soluble powders
50 - 80% reduction in offtarget movement
 Pump shear problems
 Effect on the pattern?
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Goodland Drift Project
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8 Companies
19 Drift Reduction/Deposition Aids
Water
X-77 @ .25%
2 Airplanes
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3 reps with the drift tower
1 pass over a canopy – top and bottom
260 flight passes each
4600 cards
• AT 502 - Hawkeye – Bill and Dave
• Cessna Ag Husky w/wing tips – Cary
Participants in the Study:
 United
Suppliers
 Helena Chemical
 Garco
 Loveland
 Wilber-Ellis
 Rosen’s
 Precison Labs
 SanAg
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10.
41-A
11.
Formula One
12.
AMS 20/10
13.
Border EG 250 14.
Control
15.
INT VWZ
16.
Inplace
17.
Garco Exp-3
18.
INT YAR
19.
Border XTRA 8L
HM2005-C
HM0226
Liberate
Target LC
HM2052
INT HLA
HM 0230
Valid
Double Down
Some Other Things to Keep in Mind
when Planning a Spray Application
Allow enough time for:
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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
Minimizing spray drift is in
the best interests of
everyone. Do your part to
keep applications on target.
For more information contact:
[email protected]
www.bae.ksu.edu/rewolf/