Transcript Kansas Turfgrass Conference
Understanding Spray Drift
Robert E. Wolf Extension Specialist Application Technology
Why Interest in Drift?
Spotty pest control Wasted chemicals Off-target damage Litigious Society ????
Result - higher costs - $$$ Windy?? (Timing) Environmental impact (Water and Air Quality)
Misapplication Facts:
2% 33% 8% 24% Equipment Drift Tank Mix Wrong Field Off Label 33%
Facts about drift:
23% 13% 26% Nozzle Applicator Physical Other 38%
Why is the Nozzle Important?
Amount of spray applied Uniformity of the spray Coverage on the target
Amount of off-target drift
Technical Aspects of Spray Drift
Definition of Drift:
Movement of vapors people .
spray particles and off-target causing less effective control and possible injury to susceptible vegetation, wildlife, and 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 chemical formulation drop size evaporation Equipment & Application nozzle type nozzle size nozzle pressure Weather height of release 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.
Wind Meters and Compass Name Features Dwyer Floating Ball Wind Wizard Turbo Meter Mechanical Wind speed - knots, feet/min, meters/sec, mph Cost* 15.50
39.50
135.00
Kestrel 1000 Kestrel 2000 Kestrel 3000 Plastimo Iris 50** Maximum, average, current wind speed - knots, feet/min, meters/sec, mph Maximum, average, current wind speed, temp, wind chill- knots, feet/min, meters/sec, mph All wind speed features plus temp, wind chill, dew point, heat index, relative humidity Compass 89.00
119.00
159.00
89.00
*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)
Inversions:
Under normal conditions air tends to rise and mix with the air above. Droplets will disperse and will usually not cause problems.
Altitude 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.
Altitude Temperature Inversion Temperature increases with height Warm Air Cool Air Increasing Temperature
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.
Cloud of 5-25 u oil droplets generated under unstable conditions 105 foot temperature monitoring tower 105’ 38°F 64’ 40°F 32’ 40°F 16’ 41°F 8’ 41°F
Cloud is dispersing
2.5 mph wind 105’ 38°F 64’ 38°F 32’ 37°F 16’ 36°F 8’ 33°F .5 mph wind Shallow surface inversion STABLE conditions up to 64’ NEUTRAL conditions at 105’
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 .
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)
Spray Droplet Size
Drift & Dropsize Relationship:
Particle drift will result from the smaller drops created during the spray process. The size of the droplets created is critical.
Dropsizes are measured in microns using laser beams.
Dropsize Facts:
One micron = 1/25,000 inch Expressed as (VMD) Volume Median Diameter Example - VMD = 500 microns
Comparison of Micron Sizes for Various Items: (approximate values) pencil lead paper clip
150
staple toothbrush bristle sewing thread human hair 2000
(
m
)
850
(
m
)
420
(
m
)
300
(
m
)
150
(
m
)
100
(
m
)
Raindrop compared to a Turbo Turf Flood
5.0 MPH wind at 40 psi Turbo Turf Flood Raindrop Drop
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 500 Microns 250 Microns 250 Microns 250 Microns 250 Microns 250 Microns 250 Microns 250 Microns
Important Droplet Statistics:
Operational Area
Evaporation of Droplets
High Relative Humidity Low Temperature Low Relative Humidity High Temperature Wind
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 adverse weather conditions Consider using buffer zones Consider using new technologies: • drift reduction nozzles • • drift reduction additives shields
Drift Reduction Additives: Many available!
Not EPA regulated Long chain polymers New-soluble powders 50 - 80% reduction in off-target movement Pump shear problems
EPA Requested Changes Coming!!!!
New Label language Comments Public ‘Listening Sessions’ planned Sometime in 2003??
Match the crop protection product to Adhere to label guidelines based on an industry standard • ASAE S-572 900 800 700 600 500 400 300 200
E e f e a Example Reference Graph
v / n fine/medium a y a coarse/ very coarse e e very coarse/ extremely coarse XC VC C C M M F F VF Spray Zones Maximize Efficacy Minimize Drift 100 0 0 0.1
0.5
u a o e c Cumulative Volume Fraction 0.9