spray coverage vs. droplet sizenotill.okstate.edu/presentations/2012-no-till-oklahoma... · 2017....
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Spray Coverage vs. Droplet Size
Joe Armstrong Weed Science Extension Specialist
Randy Taylor Ag Machinery Extension Specialist
1 micron = 1/25,000 inch
Optimum droplet size varies by application
Contact insect., fung.
Systemic insect., fung.
Contact herbicide
Systemic herbicide
Soil-applied herbicide
Soil-incorp. herbicide
Very fine
Fine Medium Coarse
V Coarse X Coarse
Two types of herbicide activity
Contact Systemic Liberty / Ignite glyphosate
Sharpen 2,4-D
Cobra dicamba
Ultra Blazer Select Max (clethodim)
Reflex / Flexstar Finesse
paraquat atrazine
15 GPA w/ MEDIUM droplets
Product Label recommended:
droplet size GPA
Liberty Medium
(250 – 350 microns) 15
Aim 450 microns 10
Roundup PowerMAX
“Large droplets” 3 – 15
Finesse “Large”
(>150 – 200 microns) At least 3
Headline Medium to Fine 15 (soybean rust)
Warrior Medium or coarser --
Why does droplet size matter?
Driftable particles Driftable particles
Contact herbicides Contact herbicides
Systemic/soil applied herbicides
Systemic/soil applied herbicides
Why does droplet size matter?
500 microns =
1 droplet
250 microns =
8 droplets
125 microns =
64 droplets
Why does droplet size matter?
15 GPA 5 GPA
Carrier volume adjustment made with change in nozzle orifice size
Why does droplet size matter?
North Dakota State University
Application parameters Nozzle orifice
↑ size = More volume per acre Larger droplets
↓ size = Less volume per acre Smaller droplets
Sprayer speed
↑ speed = Less volume per acre Less droplets per acre
↓ speed = More volume per acre More droplets per acre
Pressure ↑ pressure =
More volume per acre Smaller droplets
↓ pressure = Less volume per acre Larger droplets
Coverage Experiment With field-scale application parameters, can I increase spray volume to increase coverage and minimize drift?
5, 10, 15 GPA
glyphosate, Liberty
XR, Extended Range FF TT, Turbo Tee AIXR, Air Induction XR
5
110° flat fan 02, 04, 06 nozzles Operated at 40 psi, 12 mph
10
15
GPA
1 inch
XR, Extended Range FF TT, Turbo Tee AIXR, Air Induction XR
5
110° flat fan 02, 04, 06 nozzles Operated at 40 psi, 12 mph
10
15
GPA
1 inch
Nozzle type and size affects droplet number
407
544
997
798
939 861
382 434
858
0
200
400
600
800
1000
1200
AIXR TT XR
# o
f d
rop
lets
02 04 065 GPA 10 GPA 15 GPA
Reference point for droplet size
Volume Median Diameter VMD
VMD (microns)
50% of spray volume 50% of spray volume
Nozzle type and size affects droplet size
474 431
369
616 587
464
718
645 622
0
100
200
300
400
500
600
700
800
AIXR TT XR
VM
D
02 04 065 GPA 10 GPA 15 GPA
Carrier volume affects coverage
15 15 17
28 31
25
45
29*
41
0
10
20
30
40
50
AIXR TT XR
% C
ove
rage
02 04 065 GPA 10 GPA 15 GPA
?
Droplet size, carrier volume effect on weed control?
Droplet size, carrier volume effect on weed control?
All nozzle / GPA combinations performed
equally in terms of efficacy for glyphosate and Liberty
Minimum drift
Maximum coverage
Minimum coverage
Many small
droplets
Many small
droplets
Poor droplet retention on leaf surface
High probability for driftable particles
High probability for driftable particles
Insufficient coverage of leaf surface
Few small
droplets
Few small
droplets
Many large
droplets
Many large
droplets
Few large
droplets
Few large
droplets
Maximum drift
Minimum drift
Maximum coverage
Minimum coverage
Many small
droplets
Many small
droplets
Poor droplet retention on leaf surface
High probability for driftable particles
High probability for driftable particles
Insufficient coverage of leaf surface
For most applications, this will be the
optimum combination of drift reduction and
coverage
For most applications, this will be the
optimum combination of drift reduction and
coverage
Few small
droplets
Few small
droplets
Many large
droplets
Many large
droplets
Few large
droplets
Few large
droplets
Maximum drift
GPA, coverage, droplet size Application parameters must be chosen based on:
Pesticide applied
Target pest
Environmental conditions
Drift minimization