Transcript Keys to Drift Management - Biological and Agricultural Engineering

Keys to Spray Drift Management
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-$$$









Documentation – Recordkeeping:
 All certified applicators are required to
maintain records of federally restricted
use pesticide (RUP) applications.
Pesticide Recordkeeping Requirements:
 Optional information ??????
•
•
•
•
Target pest(s)
Size/density of pest
Adjuvants
Application method
 Aerial, ground, chemigation, incorporation
• Special equipment details
 Boom/nozzle, airplane, helicopter, banding
 Droplet size, pressure
• Reentry time/date
• Environmental conditions – Actual
 Wind speed, direction, temperature, humidity, time
Why am I keeping all of this information?
Refresh your memory
Safety
Better performance
Demonstrate care and concern
Stay ahead of the competition
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




chemical
formulation
drop size
evaporation




nozzle type
nozzle size
nozzle pressure
height of release
Weather
 air
movement (direction and velocity)
 temperature and humidity
 air stability/inversions
 topography
Weather factors of concern:
 air movement
(direction and velocity)
• Topography, etc.
 temperature and humidity
 air stability/inversions
Courtesy – George Ramsay, Dupont
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.
Determining wind direction:
 Compass
• Provide magnetic description
• Direction blowing from
• Into your face!
Drift Potential: 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: Spray Droplet Movement
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
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
•
•
•
•
Wind breaks
Tree lines and orchards
Houses and barns
Hills and valleys
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 Patterns Around Buildings:
Overhead
View
Wind
Diagram of Wind Around a Building
Adapted From Farm Structures*
* H.J. Barre and L.L. Sammet, Farm Structures (Wiley, 1959)
Handheld windmeters:
www.ambientweather.com
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
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
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:
 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.
Evaporation of Droplets:
High Relative Humidity
Low Temperature
Wind
Low Relative Humidity
High Temperature
Efficacy and Drift Mitigation:
Size of the Spray Droplets - Microns
Volume Median Diameter (VMD)
Droplet Spectrum (Range - big to small)
% Volume in droplets less than
200 microns in size
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
Improving Coverage?
Important Droplet Statistics:
Operational
Area
EPA Requested Changes Coming!?!?
 Buffer Zones or No
Spray Zones
 Maximize Efficacy
 Minimize Drift
9
0
0
900
8
0
0
800
7
0
0
700
e
r
y
f
i
n
e
/
f
i
n
e
veryv
fine/
fine
f
i
n
e
/
m
e
d
i
u
m
fine/medium
m
e
d
i
u
m
/
c
o
a
r
s
e
medium/
coarse
c
o
a
r
s
e
/
v
e
r
y
c
o
a
r
s
e
coarse/
very
coarse
e
r
y
c
o
a
r
s
e
/
e
x
t
r
e
m
e
l
y
c
o
a
r
s
e
veryv
coarse/
extremely
coarse
6
0
0
600
5
0
0
500
C
XCX
CC
C
VCV
4
0
0
400
Drop Size (microns)
• ASABE S-572
E
x
a
m
p
l
e
R
e
f
e
r
e
n
c
e
G
r
a
p
h
Example
Reference
Graph
DropSize(microns)
 Guidance to Chemical
Manufacturers
 Match the crop
protection product to
the target
 Adhere to label
guidelines based on
an industry standard
3
0
0
300
MM
2
0
0
200
FF
1
0
0
100
F
VFV
00
.
1
0.10
.
5
0.50
C
u
m
u
l
a
t
i
v
e
V
o
l
u
m
e
F
r
a
c
t
i
o
n
Cumulative
Volume
Fraction
.
9
0.90
ASAE S-572 Droplet
Size Standard
>150
151250
251350
351450
451550
>551
Source: Crop Life – July 2002
What is the ‘Real’ difference ?
……Medium droplet at 225 microns
……Coarse droplet at 300 microns
How much heavier? Or is it???
300 = 1.33
225
1.33 bigger
1.333 = 1.33 * 1.33 * 1.33 = 2.35
2.35 * 100 = 235% heavier
Nozzle Technology…….
 Nozzles designed to reduce drift
 Improved drop size control
 Emphasis on ‘Spray Quality’
tr8
tr1 004
10
x r 04
8
m 00 4
c i1
x r .87 5
11
00
tk 4
dg vs 2
11
tt1 004
10
04
ra
4
tfv
p2
tfv
ab s2
11
dr 004
am 8011 04
004
av
i11 rf4
0
td ai -04
04 11
-x 00
r1
10 4
td ru 08
04 -4
-tt cp
ul 11 0
d1 08
20
-0
4
ttj
04
Percent Area Coverage
Wind Tunnel Drift Results:
Coverage on WSP at 1 Meter Dow nw ind
100.0
90.0
80.0
70.0
60.0
50.0
40.0
30.0
20.0
10.0
0.0
LSD = 12.7
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
In Conclusion:
Minimizing spray drift is in
the best interests of
everyone. Do your part to
keep applications on target.
Disclaimer:
Brand names appearing in this
presentation are for identification and
illustration purposes only.
No endorsement is intended, nor is
criticism implied of similar products not
mentioned.
For more information contact:
[email protected]
www.bae.ksu.edu/faculty/wolf/