Influence of Spray Droplet Size on Paraquat and Glyphosate Efficacy

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Influence of Spray Droplet Size on Paraquat and
Glyphosate Efficacy

• Robert Wolf
• Biological and Agricultural Engineering Dept.
• Cathy Minihan and Dallas Peterson
• Department of Agronomy

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Nozzle is still an important part of the
application process!

• Determines the application rate
• Determines the uniformity
• Determines the coverage
• Determines the drift potential

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Determines coverage

• Need knowledge of the product being used.
• Systemic
• Contact
• What is the target?
• Soil or canopy?
• Grass or broadleaf (smooth, hairy, waxy)?
• Orientation and time of day?

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Whats new in nozzle technology?

• Nozzles designed to reduce drift
• Improved drop size control

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XR Flat-fan and Turbo Flat-fan compared to
Venturi Style Nozzle5.0 MPH wind at 40 psi
XR vs TurboDrop
Turbo Flat vs Turbo Drop
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1/2 of spray volume smaller droplets
VMD
1/2 of spray volume larger droplets
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Objective of this study

• Field measure the spray droplet characteristics
  of a venturi flat-fan nozzle compared to extended
  range and turbo flat-fan nozzles.

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Materials and Methods

• Experiments Exp. 1 and 2 Early and Late
  Postemergence Grass
• Exp. 3 and 4 Early and Late Postemergence
  Broadleaves
• Location Manhattan, KS
• Exp. Design 2 x 3 x 3 factorial with 4 reps
• Plot Size 3 x 9 m with 1.5 m buffer
• Crop Oats Don(Exp. 1 and 2)
• Weeds Velvetleaf, pigweed, and morning glory
  (Exp. 3 and 4)
• Visual Ratings 1, 2, and 4 weeks after treatment
• Herbicides (2) Paraquat, 0.14 kg/ha
• Glyphosate, 0.23 kg/ha
• Application Conditions
• Exp. 1 Exp. 2 Exp. 3 Exp. 4
• Date April 19, 2000 May 5, 2000 Aug. 18,
  2000 Sept. 1, 2000
• Oat/weed Size 15 cm 51 cm 10 cm 21 cm
• Temperature 20 C 25 C 21 C 24C
• R. H. 50 56 75 71

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Materials and Methods cont.

• Spray Tips (3) Extended Range Flat-fan (XR)
• Turbo Flat-fan (TT)
• Air Induction Flat-fan (AI)
• Spray Volumes (3) 19 L/ha (110015 orifice tips)
• 38 L/ha (11003 orifice tips)
• 76 L/ha (11006 orifice tips)
• Application Ground Speed 10 km/h
• Spray Pressure 276 kPa
• Spray Tip Spacing 76 cm
• Canopy Boom Height 51 cm

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DropletScan? used to analyze droplets
Water Sensitive Paper
Software lock-key
Color Scanner
Portable computer
Color Printer
System Components
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What is DropletScan? ?

• A software program that will allow accurate and
  rapid measure of spray droplet impressions on
  water-sensitive paper.
• Developed at K-State by Devore Systems - modeled
  after Crumbscan, a software program to
  determine hole sizes in slices of bread.

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Important Droplet Statistics

• Dv0.1 (µm) - 10 of the spray volume in drops lt
  number reported
• Dv0.5 (µm) - 50 of the spray volume in drops lt
  number reported
• (also is VMD- volume median diameter)
• Dv0.9 (µm) - 90 of the spray volume in drops lt
  number reported
• Number of droplets under 200 microns

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Important Droplet Statistics
VMD (50)
Operational Area
VD0.9 (90)
VD0.1 (10)
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Collection Procedure
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Sample cards
TT
XR
AI
38 L/ha
XR
TT
AI
19 L/ha
TT
XR
AI
76 L/ha
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Results and Discussion
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All Studies - Dv0.5 (µm) (VMD) Means
19
38
76
110015
11003
11006
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All Studies Dv0.1 (µm) Means
110015
11003
11006
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All Studies Number of Droplets Below 200 Microns
110015
11006
11003
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Results for Efficacy Studies
Early Post (Oats Only)
Late Post (Oats Only)
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Summary of findings Dv0.5 (µm) (VMD)

• In general as the spray volume increased the
  Dv0.5 (µm) (VMD) also increased.
• The venturi flat-fan tips produced larger
  droplets than the turbo flat-fans which produced
  droplets larger than the extended range flat-fan
  tips.

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Summary of findings Dv0.1 (µm)

• The extended range flat-fan had the lowest micron
  size across all volumes with the 19 L/ha being
  the smallest.
• The turbo flat-fans were the next smallest.
• The venturi flat-fans had the largest micron size
  for this category.

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Summary of Findings - Droplet Count under 200
microns

• At 19 L/ha the extended range flat-fans nearly
  tripled the venturi flat-fans for number of
  droplets created under 200 microns.
• At 38 L/ha the extended range flat-fans more than
  doubled both the turbo and venturi flat-fans for
  number of droplets created under 200 microns.

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Summary of findings for the Efficacy (oats)
Studies

• Efficacy data collected indicates that the
  venturi and turbo flat-fan tips performed equally
  well or better than the extended range flat-fan
  tips regardless of herbicide and timing.
• Spray volume did not affect control of oats at
  early postemergence, but control was better with
  19 and 38 L/ha than 76 L/ha at late postemergence
  regardless of herbicide.

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Take Away Message

• Pesticide applicators can achieve good weed
  control while minimizing water requirements by
  utilizing low spray volumes using venturi and
  turbo flat-fan tips risking less chance for drift.

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Thanks