2,4-D (PC code 051505) MRID 49384801

 

2

 

Low Speed Wind Tunnel Droplet Size Spectrum Measurements

Report: MRID 49384801. Henry, R.S. Havens, P.L. Schleier III, J.J. and G.R. 

Kruger. 2014. Low Speed Wind Tunnel Droplet Size Spectrum 

Determinations with GF-2726. Unpublished study performed (Study # 

140720) by West Central Research and Extension Center, Univ. of NebraskaLincoln. 402 West State Farm Road, North Platte, NE. and submitted by the

Dow AgroSciences LLC, Indianapolis, IN 46268. Experiment initiation 

2/19/2014 and completion 07/01/2014 (p. 4). 

Havens, P.L. Low-Speed Wind Tunnel Droplet Spectrum Determinations 

with GF-2726, Supplemental Droplet Spectrum Information. Unpublished 

study performed (Study # 140989) by West Central Research and Extension 

Center, Univ. of Nebraska-Lincoln. 402 West State Farm Road, North Platte, 

NE. and submitted by the Dow AgroSciences LLC, Indianapolis, IN 46268. 

Experiment initiation 03/10/2014 and completion 08/06/2014 (p. 4).

Document No.: MRIDs 49384801 and Havens, P.L. 2014.

Guideline: Not applicable

Statements: This method was not conducted according USEPA GLP Standards. Signed 

and dated statements of Data Confidentiality, Quality Assurance Statement

and GLP were provided (pp. 2-5).

Classification: The Agency finds that the experiment meets the criteria for a scientifically valid 

study and provides acceptable information.

PC Code: 051505

Reviewer: [Faruque Khan, Senior Scientist, EFED, ERB1

Signature: Date: 09/03/2014
2,4-D (PC code 051505) MRID 49384801

 

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EXECUTIVE SUMMARY

A low speed wind tunnel study was conducted to evaluate droplet size spectra for 2.8% v/v 

mixture of Enlist Duo (GF-2726) herbicide using 37 nozzles representing a wide range of 

designs from several manufactures. The objective of this study was to evaluate the drop size 

distribution (DSD) produced with GF-2726 in a low speed wind tunnel with these nozzles and 

compare them to the results produced with an Air Induction Extended Range 11004 (AIXR

11004) nozzle at 40 psi, which also represents a nozzle used in a field study (MRID 48844001). 

The droplet size spectra of nozzles were measured using laser diffraction technique in the low 

speed wind tunnel facility at the University of Nebraska-Lincoln West Central Research and 

Extension Center in North Platte, Nebraska. The percent of driftable fines (≤141 μm) from the 

AIXR 11004 at 40 psi from wind tunnel study were used as the performance standard for drift 

reduction. Deposition curves for each tested nozzle and the operating pressure combination were 

also generated using AGDISP (v8.26) model. Based on a metric of % ≤141 μm and AGDISP 

(v8.26) modeling for near-field deposition, the following nozzle/pressure combinations (Table 1)

provided equivalent or reduced driftable fines as compared to the AIXR 11004 at 40 psi for 

ground application of GF-2726. In addition, the % driftable fines results were also found to be 

linearly related to the operating pressure for a given nozzle, but limited information related to 

DSD for nozzles hindered AGDISP modeling. Thus, the maximum operating pressure listed in 

Table 1 for each nozzle is based on nozzle/pressure combination tested in the low speed wind 

tunnel. 

Table 1. Specifications of Tested Nozzles with Maximum Operating Pressure

Manufacturer

Nozzle Model

Acceptable Maximum 

Operating Pressure

(psi)

ABJ Agri Products Air Bulle Jet

(AB)

11004 40

11006 30

AirMix

(AB)

11004 15

11006 15

Greenleaf Technologies TurboDrop XL

(TDXL)

11003 40

11004 45

11006 75

TurboDrop XL-D

(TDXL-D)

11003 90

11004 90

11006 100

11008 80

Hardi Ltd. ISO Minidrift

(MD)

11004 10

11005 10

Hypro (Pentair Ltd.) Guardian Air

(GA) 11005 15

Ultra Low Drift

(ULD)

120025 15

12004 70

12006 50

12008 15

Lechler, Inc. ID Air Induction

(ID)

11004 40

11005 60

TeeJet Technologies (Spraying 

Systems Inc.) Air Induction

(AI)

11004 60

11006 60

11008 70
2,4-D (PC code 051505) MRID 49384801

 

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Table 1. Specifications of Tested Nozzles with Maximum Operating Pressure

Manufacturer

Nozzle Model

Acceptable Maximum 

Operating Pressure

(psi)

Air Induction Extended 

Range

(AIXR)

110025 40

11003 30

11004 40

11006 40

Air Induction Turbo 

Twinjet

(AITTJ60)

11004 40

11006 40

Extended Range

(XR) 11006 15

Turbo Tee Air Induction

(TTI) 11004 85

Wilger Industries, Ltd. Combi-Jet MR

(MR)

11006 60

11108 60

A. BACKGROUND INFORMATION

The emission droplet size spectrum formed by the atomization of a pesticide is affected by many 

application conditions (nozzle type, pressure, etc.) and the physical properties of the tank mix 

(e.g. dynamic surface tension, viscosity etc.). Drift can be measured directly in field experiments, 

but a field scale study is labor-intensive and expensive and is thus prohibitive for testing large 

numbers of operational parameters. The characteristics of sprays in wind tunnels have been 

shown to correlate well with the potential of off-target drift (Fritz et. al., 2010). Existing ISO 

22856 (ISO, 2008), ASABE S572.1 (ASABE, 2012), ASTM E2798-11(ASTM, 2012) and the 

draft USEPA standard testing methods protocol titled “Generic Verification Protocol for Testing 

Pesticide Application Spray Drift Reduction Technologies for Row and Field Crops” (USEPA, 

2014) offer guidance on wind tunnel testing methodology. The current study was conducted to 

determine droplet size spectra for nozzles representing a wide range of design from several 

manufactures. The goal was to determine the droplet size distribution (DSD) produced by GF2726 (a 2.8% v/v mixture of Enlist Duo herbicide, 2,4-dichlorophenoxyacetic acid choline salt, 

PC Code 051505) in a low speed wind tunnel with a variety of nozzle tips and compared them to 

the DSD produced by the AIXR 11004 nozzle at 40 psi. Droplet size distribution is a critical 

input parameter for spray drift modeling programs such as AgDRIFT and AGDISP. These 

models can provide potential deposition curves using DSD and many other application 

parameters used in pesticide application. 

B. MATERIALS and METHODS

The experiment was performed in the low-speed wind tunnel facility at the West Central 

Research and Extension Center, University of Nebraska-Lincoln, North Platte, Nebraska 

(UNL:WCREC). The droplet spectra were analyzed using a Sympatec Helos/Vario KR laser 

diffraction system with the R7 lens (Sympatec Inc., Clausthal, Germany) that was capable of 

detecting droplets in a range from 18 to 3750 μm. The spray plume was traversed through the 

laser beam by means of a linear actuator and the laser was positioned at 30.5 cm (12 inches) 
2,4-D (PC code 051505) MRID 49384801

 

5

 

downwind of the nozzle tip. All measurements were replicated to provide three measurements 

per treatment, with average data being reported for each application. Ambient temperature 

(±1°C) and relatively humidity (±3%) were continuously monitored and recorded. The air 

velocity in the tunnel was monitored in a plane just downwind of the nozzle body with a hot-wire 

anemometer. Readings (±0.2 m/s) were taken for 30 seconds (the acquisition frequency was 0.8 

seconds) at the centerline and at 80% of the distance from the center-line to the walls to the left, 

right, above and below the centerline. As a confirmation of nozzle performance, each of the 

tested nozzles was checked for nominal flow rate by setting the sprayer pressure to 40 psi and 

collecting duplicate 15-second volumes into a graduated cylinder. The collected volumes (mL) 

were averaged and converted to gallons per minute for comparison to the nozzle specifications.

Thirty-seven commercially-available nozzles were tested, each over a range of operating

pressures (Table 2). Each tested nozzle was randomly selected from a lot of ten. Pressures were 

“centered” about 40 psi, with the intent of spanning various spray qualities as defined by the 

manufacturers. The nozzles included the nozzles (XR11004, TTI1004 and AIXR11004) tested in 

the field experiment with GF-2726 (MRID 48844001). For testing, spray solution of 2.8% v/v 

GF-2726 in tap water were made in 5-and 10-gallon batches for the experiment. Enlist Duo has 

a density of 1.171 kg/L and contains 24.42 % (w/w) of 2,4-D choline salt (16.65% (w/w) 2,4-D 

acid equivalent) and 22.17% (w/w) glyphosate dimethylammonium salt to represent nominal rate 

of 2,4-D choline.

Table 2. Specifications of tested nozzles

Manufacturer Nozzle Model Pressure Tested

(psi)

ABJ Agri Products

Air Bubble Jet

(AB)

11004

30

40

75

11006

30

40

75

AirMix (AM)

11004

15

40

55

11006

15

40

65

Greenleaf Technologies

TurboDrop XL

(TDXL)

11003

30

40

60

11004

30

40

45

60

70

11006

30

40

65

75

TurboDrop XL-D

(TDXL-D) 11003 30

40
2,4-D (PC code 051505) MRID 49384801

 

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Table 2. Specifications of tested nozzles

Manufacturer Nozzle Model Pressure Tested

(psi)

90

11004

30

40

90

11006

30

40

100

11008

30

40

80

Hardi Ltd.

ISO Minidrift

(MD)

11004

10

40

55

11005

10

40

55

Hypro (Pentair Ltd.)

Guardian Air

(GA)

11004

15

40

55

11005 15

40

Ultra Low Drift

(ULD)

120025

15

40

65

12003

30

40

50

12004

15

40

60

70

95

12006

15

40

50

65

12008

15

40

55

Lechler, Inc.

ID Air Induction

(ID)

11004

30

40

55

95

11005

30

40

60

100

TeeJet Technologies (Spraying 

Systems Inc.) Air Induction

(AI) 11004

30

40

60
2,4-D (PC code 051505) MRID 49384801

 

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Table 2. Specifications of tested nozzles

Manufacturer Nozzle Model Pressure Tested

(psi)

100

11006

30

40

60

100

11008

30

40

60

70

80

Air Induction Extended 

Range

(AIXR)

110025 30

40

11003 30

40

11004

15

40

70

11006

15

40

70

Air Induction Turbo 

Twinjet

(AITTJ60)

11004

20

40

55

11006

20

40

65

Extended Range

(XR)

11004

15

40

45

11006

15

40

60

Turbo Tee Air Induction

(TTI) 11004

15

40

85

Wilger Industries, Ltd.

Combi-Jet MR

(MR)

11004

30

40

45

11006

30

40

60

80

11008

30

40

50

60

80
2,4-D (PC code 051505) MRID 49384801

 

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Statistical Analysis

Statistical analyses were performed by comparing means (3 replications) of volume percent fines 

by a Dunnett’s test, cited in the SAS Manual (SAS Institute Inc, 2012) with the control being the 

mean from the AIXR11004 nozzle at 40 psi. In order for the Dunnett’s test to be consider 

reliable, a test of the unequal variances was used, employing a Levene’s test (SAS Institute Inc, 

2012). In some cases, the variances were found to be statistically equal, which led to the 

exclusion of some tests (sets exhibiting abnormally high or low standard deviations) until the 

unequal variance test was satisfied. These excluded tests were not included in the mean 

comparisons and thus could not be classified as to their compatibility of the standard. Statistical 

tests were performed in the SAS JMP Pro software (SAS Institute, Inc., Cary, NC).

If the tested mean was equivalent or significantly less than the control, it was classified meeting 

the standard. Means statistically greater than the control were classified as not meeting the 

standard. For sets not meeting the unequal variance standard, means were noted and if a higher 

pressure set met the standard, it was also flagged as likely to be acceptable.

AGDISP Modeling Procedure

Deposition curves for each tested nozzle and pressure combination were generated using 

AGDISP (v8.26) model. The key inputs and example AGDISP model output were included in 

the Appendix A. All inputs, except for the droplet spectra and operating pressure, were kept 

constant for all of the simulations. Deposition curves were provided in the MRID 49384801. 

C. QUALITY CONTROL FOR SAMPLING

To measure the reproducibility of the test system over the duration of the testing, nozzles 

specified by ANSI/ASAE Standard S572.1 (1; 13) (reference nozzles) were tested with water 

sprays. Droplet size spectra of these standard nozzles were performed at the beginning of each 

testing day, as well as at the conclusion of testing. Test data was processed to give Dv0.1, Dv0.5 

and Dv0.9 (Descriptors in Table 3) for comparison across treatment sets. Standard nozzles were 

consistent over three days of testing period (Table 3 in MRID 49384801). The standard 

deviations of the DSD averaged 2.4% of the means of six reference nozzles (very fine to fine, 

fine to medium, medium to coarse, coarse to very coarse, very coarse to extremely coarse and 

extremely coarse to ultra-coarse), with a maximum variability of 5.3%, suggesting that minimal 

deviation occurred during the course of the study. 

Table 3. The following descriptors were used to indicate the droplet size for each 

treatment.

Droplet Size Description

Dv0.1 10% of the volume of the spray is contained in droplets smaller than this diameter

Dv0.5 50% of the volume of the spray is contained in droplets smaller than this diameter. 

(This value is commonly called the Volume Median Diameter (VMD)

Dv0.9 90% of the volume of the spray is contained in droplets smaller than this diameter

Although this study was not carried out in under FIFRA GLP standards, the work was performed 

following the appropriate quality control, personnel, auditing and archiving procedures that have

been implemented at the UNL:WCREC wind tunnel facility. A copy of the “UNL-WCREC 
2,4-D (PC code 051505) MRID 49384801

 

9

 

Standard Operating Procedures” (SOP UNL 1.4) was provided in Appendix A of the submitted 

study. Raw data worksheets, logged environmental data, electronic data files and statistical 

analysis of this study are archived in the archive facility of Dow AgroSciences LLC, 9330 

Zionsville Road, Indianapolis, IN, USA.

D. RESULTS AND DISCUSSION

Air Speed

Air speed measurements were taken over the off-center points over the face of the wind tunnel at 

a range of airspeeds from 16.0 to 16.3 miles per hour (mph), indicating a reduction in speed 

away from the centerline of about 4%, within the acceptable range of 10% stated in SOP UNL 

1.4. The mean measured airspeed at the four off-center points was 16.18 mph, with a maximum

variation of < 1%, indicating that consistent flow was present in the working section of the wind

tunnel. However, the measured airspeed at the centerline was 16.7 mph, slightly higher than the 

nominal speed of 15 mph.

Nozzle Flow Rate Measurement 

The results of the nozzle flow rate measurements are shown in Table A-1 in the Appendix A. 

Average variation from nominal flow for all nozzles was 5.2%, or, on an absolute basis, 0.094 

L/min (range -0.01 to 0.2 L/min). An analysis of variance indicated no significant different of the 

% variation with nozzle orifice size (α = 0.05). Analysis of variance of the absolute variations 

indicates a slightly higher and statistically significant increase of the variation at the largest 

orifice sizes. However, since the overall analysis of the % fines metric is on a comparative basis 

only, the relative variation in flow is a more compelling indicator that the flow rates were 

statistically consistent. Analysis of variance results were provided in the Appendix B of MRID 

49384801.

Measurement of Percent of Fines (≤141 μm) Fraction

The complete data set, including graphical representation and a tabular summary of the entire 

spray output distribution for each of the spray nozzle and pressure combinations, with statistical 

analysis of replicates can be obtained from the submitted MRIDs (49384801 and Havens, 2014). 

An example of graphical representation of droplet size spectrum and a tabular summary of AIXR 

11004 at 40 psi were included in Appendix B. The AIXR 11004 nozzles, operated at 40 psi, 

yielded % fines results of 1.77% (standard deviation 0.04) at ≤141 μm. These are the values that 

defined whether nozzle and pressure combinations “meet the standard” for drift potential of 

additional nozzles. Additional percent fines of ≤150 μm fractions for tested nozzles were also 

reported. However, the statistical outcome was the same for either metric (<141 μm or 150 μm. 

Table 4 summarizes the finding for all of the tested nozzles. The percent of mean fine fraction 

(1.77% of ≤141 μm) for the AIXR 11004 nozzle at an operating pressure 40 psi was used in 

evaluating the statistical differences from tested nozzles at a confidence level of α = 0.05. 

Complete output of the unequal variance (Levene’s test) and means comparisons (Dunnett’s test) 

were included in the Appendix B of MRID 49384801. Statistical results with “equivalent” and 

“less” (Table 4, Column 6) are considered acceptable nozzles that have potential to reduced 
2,4-D (PC code 051505) MRID 49384801

 

10

 

driftable fines. In some cases there was insufficient variance to allow a statistical comparison for 

several nozzles; for these nozzles, a designation of “N/A” (not applicable) was reported in the 

Table 4. For these nozzles, if a higher pressure set met the statistical “equivalent” or “less” 

designation, it was considered likely to reduce driftable fines. 

Extrapolation of Operating Pressure

In many cases the maximum tested passing pressure yielded % of fines well below the standard

nozzle (Table 4). The relationship of % fines with pressure was explored by the study authors 

and the results suggest that there is a linear relationship between these variables (Figure 1). 

Detailed statistics were presented in Appendix C in the MRID 49384801.

Therefore, the study authors posit that it should be possible to extrapolate or interpolate to a 

maximum pressure that meets the standard (1.77% of ≤141 μm). The pressure was rounded to 

the nearest 5 psi below the extrapolated maximum. A summary showing the maximum 

extrapolated pressure was included in Table 6 of the MRID 49384801. However, the 

applicability of such data for use in modeling exercises will be limited. 

Figure 1. Analyses of Percent Fines Versus Operating Pressure
2,4-D (PC code 051505) MRID 49384801

 

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Table 4. Comparisons of Driftable Fine and AGDISP Deposition Curves for Tested Nozzles with AIXR 11004 at 

Operating Pressure of 40 psi to Determine Acceptability of Additional Nozzle for GF2726 formulation of 2,4-D.

Manufacturer Nozzle Model

Pressure 

Tested

(psi)

Mean % of 

Fine

(≤141μm)

Fraction

(driftable Fines)

Significantly 

Exceeded the 

Standard1 

Compatibility of 

AGDISP Curves 

of tested nozzles 

to AIXR 11004 

@ 40psi 

Nozzles Met 

Acceptable Matric of 

% ≤141μm and 

AGDISP Deposition 

ABJ Agri Products

Air Bubble Jet

(AB)

11004

30 1.16 No Below Yes

40 1.79 Equivalent Overlap Yes

75 4.47 N/A Above No

11006

30 1.68 No Overlap Yes

40 2.75 Yes Above No

75 6.40 Yes Above No

AirMix

(AM)

11004

15 0.38 No Below Yes

40 2.09 Yes Above No

55 3.69 Yes Above No

11006

15 0.47 No Below Yes

40 2.64 Yes Above No

65 5.48 Yes Above No

Greenleaf 

Technologies

TurboDrop XL

(TDXL)

11003

30 0.66 No Below Yes

40 1.07 No Below Yes

60 2.16 Yes Above No

11004

30 0.45 No Below Yes

40 0.77 No Below Yes

45 0.94 No Below Yes

60 2.16 N/A** Below No

70 1.97 Yes Below No

11006

30 0.29 No Below Yes

40 0.52 No Below Yes

65 1.40 No Below Yes

75 1.64 No Below Yes

TurboDrop XL-D

(TDXL-D)

11003

30 0.17 No Below Yes

40 0.34 No Below Yes

90 1.53 No Below Yes

11004

30 0.23 No Below Yes

40 0.25 No Below Yes

90 1.65 Equivalent Below Yes

11006 30 0.05 N/A* Below Yes
2,4-D (PC code 051505) MRID 49384801

 

12

 

Table 4. Comparisons of Driftable Fine and AGDISP Deposition Curves for Tested Nozzles with AIXR 11004 at 

Operating Pressure of 40 psi to Determine Acceptability of Additional Nozzle for GF2726 formulation of 2,4-D.

Manufacturer Nozzle Model

Pressure 

Tested

(psi)

Mean % of 

Fine

(≤141μm)

Fraction

(driftable Fines)

Significantly 

Exceeded the 

Standard1 

Compatibility of 

AGDISP Curves 

of tested nozzles 

to AIXR 11004 

@ 40psi 

Nozzles Met 

Acceptable Matric of 

% ≤141μm and 

AGDISP Deposition 

40 0.21 No Below Yes

100 1.34 No Below Yes

11008

30 0.32 N/A* Below Yes

40 0.35 N/A* Below Yes

80 1.04 No Below Yes

Hardi Ltd. ISO Minidrift

(MD)

11004

10 0.29 No Below Yes

40 2.88 N/A** Above No

55 4.08 Yes Above No

11005

10 0.16 No Below Yes

40 2.29 Yes Above No

55 3.06 Yes Above No

Hypro (Pentair Ltd.)

Guardian Air

(GA)

11004

15 0.29 No Below No2

40 1.97 Yes Above No

55 3.40 Yes Above No

11005 15 0.44 No Below Yes

40 2.06 Yes Above No

Ultra Low Drift

(ULD)

120025

15 0.40 No Below Yes

40 2.78 N/A** Above No

65 5.97 N/A** Above No

12003

30 1.65 N/A** Above No

40 2.81 N/A** Above No

50 4.00 Yes Above No

12004

15 0.05 No Below Yes

40 0.69 No Below Yes

60 1.30 No Below Yes

70 1.73 Equivalent Below Yes

95 3.37 N/A** Crossover No

12006

15 0.18 No Below Yes

40 1.12 No Below Yes

50 1.59 No Below Yes

65 2.43 Yes Crossover No
2,4-D (PC code 051505) MRID 49384801

 

13

 

Table 4. Comparisons of Driftable Fine and AGDISP Deposition Curves for Tested Nozzles with AIXR 11004 at 

Operating Pressure of 40 psi to Determine Acceptability of Additional Nozzle for GF2726 formulation of 2,4-D.

Manufacturer Nozzle Model

Pressure 

Tested

(psi)

Mean % of 

Fine

(≤141μm)

Fraction

(driftable Fines)

Significantly 

Exceeded the 

Standard1 

Compatibility of 

AGDISP Curves 

of tested nozzles 

to AIXR 11004 

@ 40psi 

Nozzles Met 

Acceptable Matric of 

% ≤141μm and 

AGDISP Deposition 

12008

15 0.45 No Below Yes

40 3.00 Yes Above No

55 4.61 N/A** Above No

Lechler, Inc. ID Air Induction

(ID)

11004

30 0.45 No Below Yes

40 0.87 No Below Yes

55 1.57 No Below Yes

95 3.97 N/A Crossover No

11005

30 0.41 No Below Yes

40 0.43 No Below Yes

60 0.73 No Below Yes

100 3.56 Yes Crossover No

TeeJet Technologies 

(Spraying Systems 

Inc.)

Air Induction

(AI)

11004

30 0.50 No Below Yes

40 0.89 No Below Yes

60 1.68 No Below Yes

100 3.61 Yes Above No

11006

30 0.41 N/A* Below Yes

40 0.77 No Below Yes

60 1.14 N/A* Below Yes

100 2.59 Yes Above No

11008

30 0.47 No Below Yes

40 0.89 No Below Yes

60 1.48 No Below Yes

70 1.90 Equivalent Below Yes

80 2.36 Yes Overlaps No

Air Induction 

Extended Range

(AIXR)

110025 30 1.14 No Below Yes

40 1.85 Equivalent Overlap Yes

11003 30 1.40 No Below Yes

40 2.09 N/A** Above No

11004

15 0.28 N/A* Below Yes

40 1.77 Standard1-- ---

70 4.05 Yes Above No
2,4-D (PC code 051505) MRID 49384801

 

14

 

Table 4. Comparisons of Driftable Fine and AGDISP Deposition Curves for Tested Nozzles with AIXR 11004 at 

Operating Pressure of 40 psi to Determine Acceptability of Additional Nozzle for GF2726 formulation of 2,4-D.

Manufacturer Nozzle Model

Pressure 

Tested

(psi)

Mean % of 

Fine

(≤141μm)

Fraction

(driftable Fines)

Significantly 

Exceeded the 

Standard1 

Compatibility of 

AGDISP Curves 

of tested nozzles 

to AIXR 11004 

@ 40psi 

Nozzles Met 

Acceptable Matric of 

% ≤141μm and 

AGDISP Deposition 

11006

15 0.27 No Below Yes

40 1.76 Equivalent Overlap Yes

70 3.34 N/A** Above No

Air Induction 

Turbo Twinjet

(AITTJ60)

11004

20 0.39 No Below Yes

40 1.75 Equivalent Overlap Yes

55 3.08 Yes Above No

11006

20 0.27 No Below Yes

40 1.74 Equivalent Overlap Yes

65 3.69 Yes Above No

Extended Range

(XR)

11004

15 2.63 Yes Above No

40 8.20 Yes Above No

45 9.19 N/A** Above No

11006

15 1.40 No Below Yes

40 7.18 N/A** Above No

60 10.29 Yes Above No

Turbo Tee Air 

Induction

(TTI)

11004

15 0.09 No Below Yes

40 0.38 No Below Yes

85 1.70 Equivalent Below Yes

Wilger Industries, 

Ltd.

Combi-Jet MR

(MR)

11004

30 1.79 N/A Above No

40 2.22 Yes Above No

45 2.84 N/A** Above No

11006

30 0.59 No Below Yes

40 0.99 No Below Yes

60 1.66 Equivalent Below Yes

80 2.43 Yes Below No

11008

30 0.73 No Below Yes

40 1.00 No Below Yes

50 1.31 No Below Yes

60 1.75 Equivalent Below Yes

80 3.61 N/A** Crossover No
2,4-D (PC code 051505) MRID 49384801

 

15

 

Table 4. Comparisons of Driftable Fine and AGDISP Deposition Curves for Tested Nozzles with AIXR 11004 at 

Operating Pressure of 40 psi to Determine Acceptability of Additional Nozzle for GF2726 formulation of 2,4-D.

Manufacturer Nozzle Model

Pressure 

Tested

(psi)

Mean % of 

Fine

(≤141μm)

Fraction

(driftable Fines)

Significantly 

Exceeded the 

Standard1 

Compatibility of 

AGDISP Curves 

of tested nozzles 

to AIXR 11004 

@ 40psi 

Nozzles Met 

Acceptable Matric of 

% ≤141μm and 

AGDISP Deposition 

1 Percent of mean fine fraction (1.77%; ≤141μm) of AIXR 11004 nozzle @ 40 psi with GF 2726 herbicide was used in evaluating the statistical 

differences at confidence level of α = 0.05. Statistical results with equivalent and less are considered acceptable nozzles and pressure combination.

2 Rejected due to non-equal variance ground by study authors 

N/A*-Insufficient variance to allow statistical comparison of means. Since at a higher pressure the same nozzle did not exceed the acceptability 

threshold, the nozzle at the defined operating pressure was considered to have met the standard. 

N/A** - Insufficient variance to allow statistical comparison of means. Since at a higher pressure the same nozzle exceeded the acceptability threshold, 

the nozzle at the defined operating pressure was considered to have failed. 
2,4-D (PC code 051505) MRID 49384801

 

16

 

Figure 1. Example of Linear fits of % fines wih nozzle pressure

AGDISP Modeled Deposition Curves

AGDISP (v8.26) model was used in generating near field deposition using the droplet spectra 

and operating pressure of the tested nozzles. An example of a deposition curve for the AIXR 

11004 at various pressures is depicted in Figure 2. If the placement of a curve is overlapped or 

below the standard curve (i.e. AIXR 11004 @ 40 psi), it was designated as an acceptable nozzle 

for the defined pressure. Any curve laying above or crossing over the standard curve was 

designated as incompatible nozzle. The complete results of the deposition curves analysis were 

provided in the Appendix C of MRID 49384801. The qualitative deposition curves comparison 

on near-field deposition confirmed the conclusions reached by the % of fines analysis for the 

majority of nozzles (Table 4). One additional nozzle, the GA11004, yielded lower modeled 

deposition than the standard at an operating pressure of 15 psi. The same nozzle also yielded 

very low fines at the same pressure, but the nozzle was rejected due to statistical criteria by the 

authors of the study.

Figure 2. Example of a Deposition Curves for AIXR 11004 Nozzle at Various Pressure 

using AGDISP Model. 

D. ACCEPTABILITY/DEFICIENCIES/CLARIFICATIONS

Graphical analytical data for tested nozzles were submitted, so reviewers were able to confirm 

the reported drop size distribution and statistical analysis. However, raw analytical data for each 

replication were not submitted. There is no major deficiency except the lack of the raw analytical 

data observed in the submitted study. The following inconsistencies were also noted. 

 This report does not provide a summary of the entire spray output distribution for 

reference nozzles with statistical analysis of replicates tested in the wind tunnel. In 

addition, graphical outputs of Sympatec Helos laser diffraction particle size analyzer for 

0.0010

0.0100

0.1000

1.0000

0 10 20 30 40 50

Fraction of Applied

Distance (ft)

AXIR 11004

AXIR11004-40

AXIR11004-15

AXIR11004-70
2,4-D (PC code 051505) MRID 49384801

 

17

 

reference nozzles were not included in this report. These are critical information for 

reviewer.

 The report is inconsistent in some areas of data reporting. For example, 

Treatment=ID11004-95 in page 59 (Study ID 140989) does not match those reported

values in page 152 of MRID 49384801.

 Information for some nozzles were provided twice in pages 15 and 16. 

E. CONCLUSIONS

A wind tunnel study was conducted to evaluate droplet size spectra for GF-2726 using 37 

nozzles including AIXR 11004 representing a wide range of design from several manufactures.

The % fines results were found to be linearly related to the operating pressure for a given nozzle 

and thus maximum pressures that would meet the % fines specification were defined for each 

nozzle. Thirty two of 36 tested nozzles (excluding AIXR 11004 @ 40psi), operated within their 

rated pressure ranges, yielded % fines measurements equal to or less than the field-tested 

standard nozzle AIXR 11004 operated at 40 psi. Additional near-field deposition modeling with 

AGDISP also confirmed these results majority of tested nozzles. A total of 75 nozzle/pressure 

combinations were found to be compatible to nozzle AIXR 11004 @ 40 psi. 

F. REFERENCES

ASABE. (2012). ANSI/ASAE S572.1 MAR2009 Spray Nozzle Classification by Droplet

Spectra. St. Joseph, MI: American Society of Agricultural and Biological Engineers.

ASTM. (2012). ASTM Standard E2798-11: Standard Test Method for Characterization of

Performance of Pesticide Spray Drift Reduction Adjuvants for Ground Application. West

Conshocken, PA: ASTM International.

Fritz, B. K., Hoffmann, W. C., Birchfield, N. B., Ellenberger, J., Khan, F., Bagley, W., Hewitt, 

A. (2010). Evaluation of Spray Drift Using Low-Speed Wind Tunnel Measurements and 

Dispersion Modeling. Journal of ASTM International, 7(6). doi: 10.1520/JAI102775.

Havens, P.L. 2014. P.L. Low-Speed Wind Tunnel Droplet Spectrum Determinations with GF2726, Supplemental Droplet Spectrum Information. Unpublished study performed (Study # 

140989), submitted by the Dow AgroSciences LLC, Indianapolis, IN 46268. Experiment 

initiation 03/10/2014 and completion 08/06/2014 (p. 4).

ISO. (2008). Standard 22856: Equipment for crop protection, methods for laboratory 

measurement of spray drift - Wind tunnels. Geneva, Switzerland: International Standards

Organization. 

USEPA. (2014). U.S. EPA Generic Verification Protocol for the Testing Pesticide Spray Drift

Reduction Technologies for Row and Field Crops (Final ed.). Washington, DC.
2,4-D (PC code 051505) MRID 49384801

 

18

 

Appendix A.

Table A-1. Flow rate Results. 

Nozzle

Collected 15-sec volumes (mL) 

mL/min gal/min

Variation 

from

nominal (%)

Variation 

from 

nominal 

L/min 

1st collection 2nd collection mean

AIXR110025 245 240 242.5 970 0.256 2.5% 0.024 

ULD120-025 250 245 247.5 990 0.262 4.6% 0.044 

AIXR11003 300 300 300 1200 0.317 5.7% 0.065 

TDXL11003 320 310 315 1260 0.333 11.0% 0.125 

TDXL-D11003 305 310 307.5 1230 0.325 8.3% 0.095 

ULD120-03 290 300 295 1180 0.312 3.9% 0.045 

AB11004 390 395 392.5 1570 0.415 3.7% 0.056 

AI11004 375 375 375 1500 0.396 -0.9% -0.014 

AITTJ6011004 400 405 402.5 1610 0.425 6.3% 0.096 

AIXR11004 390 390 390 1560 0.412 3.0% 0.046 

AM11004 400 410 405 1620 0.428 7.0% 0.106 

GA11004 405 405 405 1620 0.428 7.0% 0.106 

ID11004 380 380 380 1520 0.402 0.4% 0.006 

MD11004 405 400 402.5 1610 0.425 6.3% 0.096 

MR11004 390 400 395 1580 0.417 4.4% 0.066 

TDXL11004 400 400 400 1600 0.423 5.7% 0.086 

TDXL-D11004 410 420 415 1660 0.439 9.6% 0.146 

TTI11004 405 400 402.5 1610 0.425 6.3% 0.096 

XR11004 410 400 405 1620 0.428 7.0% 0.106 

ULD120-04 410 400 405 1620 0.428 7.0% 0.106 

AB11005 500 500 500 2000 0.528 5.7% 0.108 

GA11005 490 500 495 1980 0.523 4.6% 0.088 

ID11005 510 530 520 2080 0.550 9.9% 0.188 

MD11005 500 500 500 2000 0.528 5.7% 0.108 

AB11006 600 600 600 2400 0.634 5.7% 0.129 

AI11006 590 590 590 2360 0.624 3.9% 0.089 

AITTJ6011006 590 580 585 2340 0.618 3.0% 0.069 

AIXR11006 580 580 580 2320 0.613 2.2% 0.049 

AM11006 580 580 580 2320 0.613 2.2% 0.049 

MR11006 590 600 595 2380 0.629 4.8% 0.109 

TDXL11006 600 600 600 2400 0.634 5.7% 0.129 

TDXL-D11006 600 605 602.5 2410 0.637 6.1% 0.139 

XR11006 590 610 600 2400 0.634 5.7% 0.129 

ULD120-06 590 600 595 2380 0.629 4.8% 0.109 
2,4-D (PC code 051505) MRID 49384801

 

19

 

Nozzle

Collected 15-sec volumes (mL) 

mL/min gal/min

Variation 

from

nominal (%)

Variation 

from 

nominal 

L/min 

1st collection 2nd collection mean

AI11008 760 790 775 3100 0.819 2.4% 0.072 

MR11008 780 800 790 3160 0.835 4.4% 0.132 

TDXL-D11008 800 820 810 3240 0.856 7.0% 0.212 

ULD120-08 790 800 795 3180 0.840 5.0% 0.152 
2,4-D (PC code 051505) MRID 49384801

 

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Appendix B.

Example of Sympatec Laser particle Size Analyzer Reports for AIXR 11004 @40 psi
2,4-D (PC code 051505) MRID 49384801

 

21

 

Table C-1. Spray Droplet Distribution Analysis Results for selected AIXR Nozzles and 

Pressure. 

summary metrics, 

um 

AIXR11003-40 AIXR11004-

15 

AIXR11004-

40 

AIXR11004-70 AIXR11006-

15 

AIXR11006-

40 

AIXR11006-70 

Dv10 227.0 341.4 245.3 193.1 387.1 250.5 209.3 

VMD 424.3 620.9 467.7 385.9 692.7 477.8 418.3 

Dv90 654.0 883.1 718.7 607.4 1020.6 742.6 678.7 

RS 1.0 0.9 1.0 1.1 0.9 1.0 1.1 

droplet size, um 

18 0.000 0.000 0.000 0.000 0.000 0.000 0.000 

22 0.000 0.000 0.000 0.000 0.000 0.000 0.000 

26 0.000 0.000 0.000 0.000 0.000 0.000 0.000 

30 0.000 0.000 0.000 0.000 0.000 0.000 0.000 

36 0.000 0.000 0.000 0.000 0.000 0.000 0.000 

44 0.000 0.000 0.000 0.000 0.000 0.000 0.000 

52 0.000 0.000 0.000 0.043 0.000 0.000 0.020 

62 0.000 0.000 0.000 0.153 0.000 0.000 0.120 

74 0.077 0.000 0.080 0.377 0.000 0.073 0.307 

86 0.203 0.000 0.197 0.710 0.000 0.197 0.593 

100 0.480 0.000 0.447 1.267 0.023 0.447 1.063 

120 1.087 0.077 0.957 2.367 0.107 0.960 1.977 

150 2.523 0.367 2.113 4.780 0.337 2.103 3.930 

180 4.730 0.893 3.873 8.147 0.717 3.787 6.627 

210 7.757 1.737 6.277 12.410 1.273 6.027 10.067 

250 13.077 3.397 10.500 19.353 2.350 9.933 15.780 

300 21.780 6.443 17.430 29.787 4.327 16.397 24.667 

360 34.707 11.617 27.920 43.867 7.810 26.417 37.200 

410 49.000 18.403 40.020 58.087 12.667 38.157 50.380 

500 67.457 29.633 56.743 74.943 21.333 54.543 66.870 

600 85.080 46.293 75.343 89.497 35.247 73.037 82.743 

720 95.983 67.660 90.330 97.643 54.383 88.617 93.813 

860 99.903 88.413 97.810 99.820 75.040 97.160 98.727 

1020 100.000 98.943 99.953 100.000 90.920 99.937 99.973 

1220 100.000 98.973 100.000 100.000 98.863 100.000 100.000 

1460 100.000 98.973 100.000 100.000 99.990 100.000 100.000 

1740 100.000 98.977 100.000 100.000 100.000 100.000 100.000 

2060 100.000 100.000 100.000 100.000 100.000 100.000 100.000 

2460 100.000 100.000 100.000 100.000 100.000 100.000 100.000 

2940 100.000 100.000 100.000 100.000 100.000 100.000 100.000 

3500 100.000 100.000 100.000 100.000 100.000 100.000 100.000 
2,4-D (PC code 051505) MRID 49384801

 

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Appendix C

Table D-1. Selected input parameter of AGDISP Modeling

Parameter Value comments 

Application method section 

Method Ground 

Nozzle type Flat fan Although many of the nozzles 

tested are of the air induction 

type, the direct use of the DSD 

overrides the use of “air 

induction” as the nozzle type. 

If air induction were chosen, 

the adjustment of the spectrum 

by the model would “double 

count” the air induction effect 

Boom pressure Set to each tested value Has effect on the driving 

speed of the application, so 

will change the deposition. 

Release height 3 ft Default 

Spray lines 20 Default 

Meteorology section 

Wind type Single height Default 

Wind speed 15 mph Under bound from label 

Wind direction -90 deg Worst-case and default 

Temperature 65 F Default 

Relative humidity 50% Default 

Surface section 

Angles 0 Default 

Canopy None Default 

Surface roughness 0.12 ft Mean of “crops” cover type 

Application technique section 

Nozzles 54, even spacing Standard boom setup 

DSD From wind tunnel results, 

imported in library 

Atmospheric stability Strong Default 

Swath section 

Swath width 90 ft Standard boom 

Swath displacement 0 ft Worst-case 

Spray material section 

Spray volume rate 15 gal/acre From Enlist Duo label 
2,4-D (PC code 051505) MRID 49384801

 

23

 

Table D-1. Selected input parameter of AGDISP Modeling

Volatile/nonvolatile 

fraction 

Enlist Duo at 2.8% v/v See calculation below1

1The tested mixture was 2.8% (v/v) Enlist Duo in water. Enlist Duo has a density of 1.171 kg/L

and contains 24.42 % (w/w) of 2,4-D choline salt (16.65% (w/w) 2,4-D acid equivalent) and

22.17% (w/w) glyphosate dimethylammonium salt.

For example, a 100-liter batch would contain the following:

Enlist Duo 2.8% * 100 L = 2.8L; 2.8L * 1.171 kg/L = 3.279 kg

Water: 100 -2.8 L = 97.2 L = 97.2 kg

Total weight: 3.279+97.2 = 100.497 kg

Active ingredient fraction: 3.279 kg * 16.65 % (a.e.) = 0.546 kg; 0.546 kg/100.497 kg = 0.0054 (dimensionless)

Non-volatile fraction: 3.279 kg* (24.42 % + 22.17%) = 1.528 kg; 1.528 kg/100.497 kg = 0.0152 (dimensionless)

AGDISP Model Input Data Summary

Title: AIXR 11004-40

Notes: 

Calculations Done: Yes

Run ID: AGDISP AIXR11004_40.ag 8.26 08-25-2014 15:26:30

--APPLICATION METHOD-- ----------------------------

Method Ground

--Ground Sprayer-- ----------------------------

Nozzle Type Flat Fan

Boom Pressure (psig) 40

--Spray Lines-- ----------------------------

Release Height (ft) 3

Spray Lines 20

Optimize Spray Reps No

Spray Line Reps # Reps

 1 1

2 1

3 1

4 1

5 1

6 1

7 1

8 1

9 1

 10 1

 11 1

12 1

 13 1

 14 1

15 1

16 1

17 1

18 1

19 1

20 1
2,4-D (PC code 051505) MRID 49384801

 

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--APPLICATION TECHNIQUE-- ----------------------------

Application Technique Liquid

--Nozzles-- ----------------------------

Boom Length (%) 98.34

Nozzle Locations # Hor(ft) Ver(ft) Fwd(ft)

 1 -44.26 0 0

 2 -42.59 0 0

3 -40.91 0 0

 4 -39.25 0 0

 5 -37.58 0 0

6 -35.91 0 0

 7 -34.23 0 0

 8 -32.57 0 0

9 -30.9 0 0

 10 -29.23 0 0

11 -27.56 0 0

12 -25.89 0 0

 13 -24.22 0 0

 14 -22.55 0 0

15 -20.88 0 0

 16 -19.21 0 0

 17 -17.54 0 0

18 -15.87 0 0

19 -14.2 0 0

20 -12.53 0 0

21 -10.86 0 0

22 -9.19 0 0

 23 -7.51 0 0

24 -5.84 0 0

25 -4.17 0 0

26 -2.5 0 0

27 -0.835 0 0

28 0.835 0 0

 29 2.51 0 0

 30 4.18 0 0

31 5.85 0 0

 32 7.52 0 0

 33 9.19 0 0

34 10.86 0 0

35 12.53 0 0

36 14.2 0 0

37 15.87 0 0

38 17.54 0 0

39 19.21 0 0

40 20.88 0 0

41 22.55 0 0

42 24.22 0 0

43 25.89 0 0

44 27.56 0 0

 45 29.23 0 0

 46 30.9 0 0

47 32.57 0 0

 48 34.23 0 0

 49 35.91 0 0

50 37.58 0 0
2,4-D (PC code 051505) MRID 49384801

 

25

 

 51 39.25 0 0

52 40.91 0 0

53 42.59 0 0

54 44.26 0 0

--Drop Size Distribution-- ----------------------------

Name AIXR11004-40

Type User-defined

Drop Categories # Diam (um) Frac

 1 18.00 0.0000

2 22.00 0.0000

 3 26.00 0.0000

 4 30.00 0.0000

5 36.00 0.0000

 6 44.00 0.0000

 7 52.00 0.0000

8 62.00 0.0000

9 74.00 0.0008

 10 86.00 0.0012

11 100.00 0.0025

 12 120.00 0.0051

 13 150.00 0.0116

14 180.00 0.0176

 15 210.00 0.0240

 16 250.00 0.0422

17 300.00 0.0693

18 360.00 0.1049

19 410.00 0.1210

20 500.00 0.1672

21 600.00 0.1860

22 720.00 0.1499

23 860.00 0.0748

24 1020.00 0.0214

25 1220.00 0.0005

26 1460.00 0.0000

27 1740.00 0.0000

 28 2060.00 0.0000

 29 2460.00 0.0000

30 2940.00 0.0000

 31 3500.00 0.0000

--SWATH-- ----------------------------

Swath Width 90 ft

Swath Displacement 0 ft

--METEOROLOGY-- ----------------------------

Wind Speed (mph) 15

Wind Direction (deg) -90

Temperature (deg F) 65

Relative Humidity (%) 50

--SPRAY MATERIAL-- ----------------------------

Name Enlist Duo

Spray Material Evaporates Yes

Spray Volume Rate (gal/ac) 15

Active Fraction 0.0054
2,4-D (PC code 051505) MRID 49384801

 

26

 

Nonvolatile Fraction 0.0152

Active Fraction of Tank Mix 0.0054

Fraction of Active Solution that is Nonvolatile 1

Additive Fraction of Tank Mix 0.0153

Fraction of Additive Solution that is Nonvolatile 0.64

--ATMOSPHERIC STABILITY-- ----------------------------

Atmospheric Stability Strong

--SURFACE-- ----------------------------

Upslope Angle (deg) 0

Sideslope Angle (deg) 0

--Canopy-- ----------------------------

Type None

Surface Roughness (ft) 0.12

--TRANSPORT-- ----------------------------

Flux Plane Distance (ft) 0

--ADVANCED SETTINGS-- ----------------------------

Wind Speed Height (ft) 6.56

Max Compute Time (sec) 600

Max Downwind Dist (ft) 2608.24

Vortex Decay Rate (OGE) (mph) 0.3355

Vortex Decay Rate (IGE) (mph) 1.25

Aircraft Drag Coeff 0.1

Propeller Efficiency 0.8

Ambient Pressure (in hg) 29.91

Ground Reference (ft) 0

Save Trajectory Files No

Half Boom No

Default Swath Offset 0 Swath

Specific Gravity (Carrier) 1

Specific Gravity (Active/Additive) 1.17

Evaporation Rate (μm2/deg C/sec) 84.76