spray coverage vs. droplet sizenotill.okstate.edu/presentations/2012-no-till-oklahoma... · 2017....

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