comparison of venturi spray tips and spray pressure on glyphosate and paraquat efficacy

Kansas State University Biological and Agricultural Engineering Department

Comparison of Venturi Spray Tips and Spray Pressure on Glyphosate and

Paraquat Efficacy

Robert Wolf Biological and Agricultural Engineering Dept.

Cathy Minihan and Dallas Peterson Department of Agronomy


Objective of this study:

Compare the efficacy and spray droplet characteristics of three venturi flat-fan nozzles against the turbo flat-fan tip at 207, 345, and 482 kPa (30, 50, and 70 psi).


Materials and Methods:Experiments: Location: Ashland Bottoms, Manhattan, KSExp. Design: 2 x 3 x 4 split-split plot with 3 reps (24 treatments)Drop Collectors: Placed in 2 reps with 2 cards per rep (96 cards)Plot Size: 3 x 9 m with 1.5 m bufferWeeds Velvetleaf, common sunflower, sorghum, cornVisual Ratings: 1, 2, and 4 weeks after treatment

Herbicides (2): Paraquat, 0.487 lb ae/a (1.3pt/a), NIS @ .25% v/vGlyphosate, 0.28lb ae/a (12 oz/a), AMSU @17 lb/100

gal

Application Conditions: Date: July 09, 2002 Weed Size: Vele - 15 cm, Cosf - 20 cm, Sorg – 25 cm, Corn – 13 cm Temperature: 37 C R. H.: 20% Wind: S-SW@ 4-5 km/h


Spray Tips (4):Turbo Flat-fan (TT)Air Induction Flat-fan (AI)Ultra lo-drift (ULD)Air Mix (AM)

Spray Volume: 94 L/ha (11002 orifice tips)Application Ground Speed: 5.5, 7.1, and 8.4 km/hSpray Pressure: 207, 345, and 482 kPaSpray Tip Spacing: 76 cm, tilted 15 degreesCanopy Boom Height: 51 cm

Materials and Methods cont.:


Collection Procedure:


DropletScan used to analyze droplets:

System ComponentsSystem Components


Results and Discussion


Volume Medium Diameter:

549*

625*

571* 582

500

520

540

560

580

600

620

640

Mic

ron

s

TT AI AM ULD

VMD (50%)

*Significant .05


Control: Tip / Pressure

50

60

70

80

90

100

% C

ontr

ol

Velvetleaf Sunflower Sorghum Corn

Tip - 14 DAT

TT AI AM ULD

*

0

20

40

60

80

100

% C

ontr

ol

Velvetleaf Sunflower Sorghum Corn

Pressure - 14 DAT

30 psi 50 psi 70 psi

*Significant


Tip and pressure interactions:

50

60

70

80

90

100

% C

ontr

ol

TT AI AM ULD

Tip * Pressure - Velvetleaf - 14 DAT

30 50 70

50

60

70

80

90

100

% C

ontr

ol

TT AI AM ULD

Tip * Pressure - Common Sunflower - 14 DAT

30 50 70

50

60

70

80

90

100

% C

ontr

ol

TT AI AM ULD

Tip * Pressure - Sorghum - 14 DAT

30 50 70

50

60

70

80

90

100

% C

ontr

ol

TT AI AM ULD

Tip * Pressure - Corn - 14 DAT

30 50 70


% Area coverage - water sensitive paper:

Gramoxone-Tip-Pressure Interaction

0.0

10.0

20.0

30.0

40.0

50.0%

Are

a C

ov

era

ge

Touchdown-Tip-Pressure Interaction

0.0

10.0

20.0

30.0

40.0

50.0

% A

re

a C

ov

era

ge

LSD 11.5%

LSD 11.5%


Summary of findings Dv0.5 (µm) (VMD):

Venturi tips produced larger droplet VMD’s than the turbo flat-fan.

The AI produced significantly larger droplet VMD’s than the Air Mix and turbo flat-fan, but not the ULD.


Summary of Findings: %Area Coverage

Significant differences were measured for percent area coverage among chemical, tip, and pressure interactions.

Means for Percent area coverage ranged from 47 to 20 percent with means separated by at least 11.5% considered significant.


Summary of findings: Efficacy

Very few significant efficacy interactions were measured among herbicide, tip, and pressure variables.

Paraquat provided better velvetleaf control.

Glyphosate gave better sorghum and corn control.

Common sunflower control was simmilar with each product.


Summary of findings: Efficacy cont. Only minor differences in control were

measured among tips and pressures. The turbo flat-fan tended to be slightly

lower (<10%) in control than the venturi tips.

AI and Airmix tips tended to give lightly better (no significance) control than the ULD.

No significant differences were found in weed control among the three pressures.


Final thoughts:

Why reduced control with turbo flat-fan?– high temperature, low humidity resulting in

smaller drops (evaporation) that were quicker drying.

Venturi tips performed well regardless of whether a systemic or contact herbicide was used.

Performance over a wide range of pressure is also possible.

Venturi tips appear to be a viable option to minimize spray drift potential while maximizing performance.


Thanks

comparison of venturi spray tips and spray pressure on glyphosate and paraquat efficacy

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