Debunking Sprayer Myths

Tom Wolf

AgriMetrix Research and Training

Saskatoon, SK

agrimetrix@gmail.com

@Nozzle_Guy

Challenge:

Controlling pests without

harming your neighbours’

crops or the environment

Trends for 2014

more fungicides

more stainless steel

wider booms

faster speed capability

bigger tanks

more pulse width modulation

more auto boom height

more complex monitors

twin fan nozzles

Myth #1

“More pressure forces spray

into canopy”

Pressure affects:

Flow rate

Spray quality

Pattern uniformity

Droplet velocity

Droplet Velocity Distributions

0

2

4

6

8

10

12

14

16

18

0 200 400 600 800 1000 1200

Ve

loc

ity

(m

/s)

Droplet diameter (µm)

Low

Pressure

High Pressure

Droplet Speed

At tip:

all droplets: 70 km/h

• 50 cm below tip:

– Large droplets: 28 km/h

– Small droplets: 7 km/h

Droplet Direction

Large droplets:

combination of nozzle and

travel direction

e.g. 30 km/h , 10 km/h

• Small droplets:

– whichever way the wind is blowing

Velocity rapidly dissipates with height

Myth #2

“Higher water volumes lead

to runoff”

y = 0.0023x + 0.2689

R² = 0.9452

0

1

2

3

4

5

6

0 500 1000 1500 2000 2500

Fo

xta

il s

pra

y r

ete

ntio

n

(µ

L/g

dw

)

Water volume (L/ha)

Spray Retention on Foxtail

Myth #3

“Spray drift is no issue for

fungicides & insecticides”

New Buffer Zone Label Language

Untreated (Buffer Zone)

20 m Conventional application

15 m Low-drift application

untreated

5 m Very low-drift application

untreated

Aquatic Organisms are Sensitive

“Do not apply with spray droplets smaller than ASAE medium classification”

“…When using a shroud, BZ can be reduced by 70%...”

Typical Herbicide Buffer Statements

Caramba

Astound

Prosaro

Lorsban

Myth #4

“Faster travel speed saves

time and boosts productivity”

Areas of unequal pressure create

vortices which remove small

droplets from the spray cloud

Vortices become more

pronounced at faster travel

speeds

Scenario 1

800 gal tank

80’ boom

12 mph

10 gpa

50 gpm fill

84 acres/h

Productivity (not counting turns)

Scenario 2

800 gal tank

80’ boom

18 mph

10 gpa

50 gpm fill

110 acres/h

Drive Faster

Scenario 3

800 gal tank

80’ boom

12 mph

10 gpa

300 gpm fill

110 acres/h

Fill Faster

Scenario 4

800 gal tank

120’ boom

12 mph

10 gpa

50 gpm fill

111 acres/h

Spray Wider

Fill Efficiency

Myth #5

“Double nozzles produce

more droplets and improve

coverage.”

Droplet Number

0

5000

10000

15000

20000

25000

30000

35000

40000

45000

50000

Dro

ple

t N

um

be

rER11006, 40 psi

SR11006, 40 psi

MR11006, 40 psi

DR11006, 40 psi

Myth #6

“Calm early mornings have

the lowest drift risk”

Daily Wind Pattern

Time of day (h)

Win

d s

pe

ed

at

1 m

he

igh

t (m

/s)

0

1

2

3

4

5

6

7

8

0 4 8 12 16 20 24

Thermal Turbulence

Unstable (Desirable normal daytime conditions)

Stable (inversion)

Spray cloud

disperses, moving

upward and

downwind

Spray cloud

hangs over

treated area in high

concentration

Warm Soil

Cold soil

Cold air - dense, still

Warm, still air

Inversion Conditions

Dispersion

Heig

ht

Temperature H

eig

ht

Temperature

Unstable Stable

(Inversion)

3 pm 11 pm

Sunset 10 pm

3 am 5 am

Sunrise 5 am

7 am 8 am 9 am 3 pm

Temperature

Heig

ht

Inverted layer

No dispersion Inversion cap

3 pm 11 pm

Sunset 10 pm

3 am 5 am

Sunrise 5 am

7 am 8 am 9 am 3 pm

Myth #7

“A rate controller calibrates

the sprayer”

Best Practices – Sprayer Setup

Metering /

Calibrating

Pressure Drop

Screens

Myth #8

“If I mess up agronomic

decisions, I can correct that

with a good spray application”

Effect of Time of Removal

0

500

1000

1500

2000

2500

Untreated XR 8001

(Fine) Air Mix

(Coarse) TurboDrop XL/TT

(Extr. Coarse)

Gra

in Y

ield

(k

g/h

a)

7 days

17 days

3 bu/acre

Myth #9

“Ammonia is a good general

purpose tank cleaner”

Myth #10

“There is an optimal nozzle

that does it all”

Grassy Targets, Contact Products

Droplet Size

Wee

d C

on

tro

l Medium Coarse Extra Coarse Very Coarse

Broadleaf Targets, Systemic Products

Droplet Size

Pes

t C

on

tro

l Medium Coarse Extra Coarse Very Coarse

Water Volume and Canopies

Win some, Lose some

Nozzle %<200 %>600 % 200 - 600

Conv. 37 6 57

LD-1 17 12 71

LD-2 8 27 65

LD-3 5 37 58

Drift Rebound Most Useful

Spray Quality

Spray Quality Volume Median

Droplet Diameter Min. Volume Comments

Extremely Coarse >550 µm 15 gpa Not usually recommended

Very Coarse

450 – 550 µm 10 gpa Broadleaf plants only

Coarse 350 – 450 µm 5-7 gpa Grasses and broadleaves

Medium 250 – 350 µm 3-5 gpa Grasses and broadleaves

Fine 150 – 250 µm 3 gpa Not recommended

Very Fine

<150 µm 3 gpa Not recommended

Summary

Use a Coarse spray

Calibrate all nozzles

Operate in middle of pressure range

Keep booms and travel speed low if possible

Fill faster

Add water to improve canopy penetration

Spray on time

Understand inversions and avoid them

Respect buffer zones

Be thorough when cleaning sprayer