Spray Droplet Size Standard S-572 Robert E. Wolf Extension Specialist Application Technology Biological and Agricultural Engineering

Efficacy and Drift Potential is Influenced by Size of the Spray Droplets - Volume Median Diameter (VMD) Droplet Spectrum (Range - big to small) % Volume in droplets less than 200 microns in size

One micron (  m ) =1/25,000 inch Relationship of Drift to Drop Size

Comparison of Micron Sizes for Various Items: (approximate values) pencil lead 2000 (  m ) paper clip 850 (  m ) staple 420 (  m ) toothbrush bristle 300 (  m ) sewing thread150 (  m ) human hair100 (  m ) 150

1/2 of spray volume = larger droplets VMD 1/2 of spray volume = smaller droplets

Cutting Droplet Size in Half Results in Eight Times the Number of Droplets 500 Microns 250 Microns 250 Microns 250 Microns 250 Microns 250 Microns 250 Microns 250 Microns 250 Microns

Important Droplet Statistics Operational Area

Evaporation of Droplets Wind High Relative Humidity Low Temperature Low Relative Humidity High Temperature Fall Distance

Example Reference Graph Cumulative Volume Fraction Drop Size (microns) very fine/ fine fine/medium medium/ coarse coarse/ very coarse very coarse/ extremely coarse VF F M C VC XC Guidance to Chemical Manufacturers Match the crop protection product to the target Adhere to label guidelines based on an industry standard ASAE S-572 Buffer Zones or No Spray Zones Maximize Efficacy Minimize Drift EPA Requested Changes Coming !?!?

ASAE S-572 Droplet Size Standard

Origin Of Standardized Spray Droplet Size Categories British Crop Protection Council (BCPC) Droplet size classifications, primarily designed to enhance efficacy. Uses the term SPRAY QUALITY for droplet size categories ASAE Standard S572 Droplet size classifications, primarily designed to control spray drift. Uses the term DROPLET SPECTRA CLASSIFICATION for droplet size categories.

Specifics of the Standard Based on spraying water through reference nozzles. Nozzle manufacturers can conduct the tests. Must use a set of reference tips and a laser- based instrument. Droplet Spectra measurements must be with the same: Instrument, measuring method, sampling technique, scanning technique, operator, and in a similar environmental condition.

Coverage Need knowledge of the product being used. Systemic Contact What is the target? Soil Grass Broadleaf (smooth, hairy, waxy) Leaf orientation – time of day

ASAE DSC and Volume Median Diameter (D V0.5 ) From PMS* Laser Spectrometer Very Fine (VF) < 182µm Fine (F) µm Medium (M) µm Coarse (C) µm Very Coarse (VC) µm Extremely Coarse (XC) >656µm *USDA ARS College Station, TX Droplet Spectra Classification (DSC) Droplet Size Range

Nozzle Technology? How to use?? Nozzles designed to reduce drift Improved drop size control Emphasis on ‘Spray Quality’

Spray Characteristics are Important to Understand: Demonstrates Turbo Flat vs TurboDrop-5 MPH Wind

Nozzles Types?

Extended Range Flat-fan: Tapered edge pattern 80 and 110 degree fan Requires overlap - 50 to 60% psi range

Extended Range Flat-fan: Tapered edge pattern 80 and 110 degree fan Requires overlap - 50 to 60% psi range 110° 80°

Demo

Nozzles Types?

Turbo Flat-fan: l Turbulence chamber as in the Turbo Flood l Tapered edge, wide angle flat pattern l Designed to work in flat-fan nozzle holder l Uniform spray distribution, 50-60% overlap l Wide pressure range, 15 – 90 psi l Large, drift resistant droplets l Plastic with superior wear characteristics

Turbo Flat-fan: l Turbulence chamber as in the Turbo Flood l Tapered edge, wide angle flat pattern l Designed to work in flat-fan nozzle holder l Uniform spray distribution, 50-60% overlap l Wide pressure range, 15 – 90 psi l Large, drift resistant droplets l Plastic with superior wear characteristics TT XR

Demo

Nozzles Types?

Air-Induction/Venturi Nozzles Where air is drawn into the nozzle cavity and exits with the fluid.

Air/Induction – Venturi Nozzle: Spraying Systems AI TeeJet Air intake venturi section Mixing Chamber - air and spray solution blended Exit orifice - Pattern tip - forms large air-bubble drops Better Penetration? Reduced run-off? Improved coverage? Adequate efficacy? Reduced drift? YES!!!

XR Flat-fan and Turbo Flat-fan compared to Venturi Style 5.0 MPH wind at 40 psi XR vs TurboDropTurbo Flat vs Turbo Drop

Demo

Driftable Droplets: Spraying Systems-2000 Nozzle Type (0.5 GPM Flow) Approximate % of Spray Volume < 200 Microns 15 PSI40 PSI XR %22% XR 80056%12% DG 11005N/A11% DG 8005N/A7% TT 11005<1%<6% TF-2.5<1% AI 11005N/A<1%

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Computer Models:

AgDRIFT® Program Map

Example of Model Use – Aerial Applicators Standard Operation

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