The Influence of Newly Developed Spray Drift Reduction Agents on Drift Mitigation by Means of Wind Tunnel and Field Evaluation Methods

Round 1

Reviewer 1 Report

Reviewer A (Remarks to the Authors)

This manuscript reports the influence of newly developed spray drift reduction agents (three newly developed agents, four commercial ones, and a water solution) on drift mitigation. This study was carried out experimentally by means of a wind tunnel and in-field evaluation methods. Two nozzles (an air-injector flat spray nozzle and a standard flat spray nozzle) were tested at the fixed injection pressure of 4 bar and volume flow rate of 1.82 LPM (liter per minute), and two types of spray drift (ground spray drift and airborne spray drift) were evaluated in a wind tunnel and in-field conditions. The results reported the impact of wind speed, nozzle type, and drift reduction agent (DRA) on spray drift mitigation. In my opinion, the manuscript is currently not suitable for publication in Agriculture as it is. The authors should address the following comments and questions:

 

1. In the whole manuscript, the terms used in this manuscript must be unified. Using various terms with the same meaning leads to confusion for readers. For example, a flat spray nozzle(page 12, line 425, etc.) and a standard nozzle(page 4, line 100, etc.) should be unified to a standard flat spray nozzle, and an air injector(page 1, line 21, etc.) should be unified to an air-injector flat spray nozzle.

2. On page 2, Line 87-89: Two sentences with the same meaning are being repeated. Please revise it in one sentence.

3. On page 5, Table 1: In Table 1, the physical properties of the four commercial DRAs, three newly developed DRAs, and water used in this study are introduced. The highlight of this study is the influence of the DRAs on the drift mitigation of the spray. In addition, the variables that have the greatest influence on spray drift are the droplet size and distribution of the spray. From this point of view, the density of DRAs and the average droplet size (VMD), if possible including the size distribution, when sprayed using two nozzles should be added in Table 1. Please complement this.

4. On page 6, Line 256: The test nozzle was installed at 50 cm above the surface of the liquid collection flasks (i.e., above the corrugated tin). This distance is important to distinguish between ground spray drift and airborne spray drift. Please describe the reason for using 50 cm in detail.

5. On page 6, Line 259-261: Two test nozzles with the same spray angle and flow rate of 120 deg. and 1.82 LPM, an air-injector flat spray nozzle (Lechler IDK 120-04, Lechler GmbH, Germany) and a standard flat spray nozzle (Lechler LU 120-04, Lechler GmbH, Germany), were introduced. Since the spray angle and flow rate described herein are provided by the manufacturer, especially the flow rate is expected to change according to the DRAs presented in Table 1, which is important in evaluating the amount of spray drift. Please add the results of the flow rate measurement according to the DRAs.

6. On page 6, Line 262-263: It is not clear what “The nozzle sprayed the liquid in both directions, in the longitudinal direction of the tunnel, at a distance of 85 cm, i.e., a spray area of 170 cm (at an air velocity of 0 m s^-1)” means. Please explain further.

7. On page 8, Fig.3: Too many terms are being used in relation to the direction of the wind. (For instance, lateral air velocity, longitudinal direction, vertical direction, both direction, wind direction, side wind speed, adjacent lateral air velocities, etc.) Please add the coordinates system in x, y, z to Fig. 3 and describe the direction of the wind according to the coordinates system. In particular, the direction of the wind that acts on the flat-fan spay is not clear. After indicating the spray structure, please clearly indicate the direction of the wind.

8. On page 8, Fig.3: Please add the distance between the ground and the chamber (where the wind comes out) connected to the fan.

9. On page 9, Line 341: In Fig. 6, the side wind velocity was changed to 2, 4, 6, 8, and 10 m/s. However, Line 341 specifies only 6-10m/s. It seems to be referring to something that is not a common case that is higher than those recommended for spraying agricultural crops. Please revise this part clearly.

10. In page 10, Fig. 6: Please change “Vanduo” to “water”.

11. In page 10, Line 381-383 and Fig. 6a: The amount of spray drift according to the DRAS is associated with droplet size due to the change in physical properties of the DRAS. However, the authors' explanations are only cited for reference results. Please explain the drift amount according to the DRAs in connection with the properties of the DRAs described in Table 1. And the numerical value shown above the bar chart is the value for the case of the injection flow rate of 30 ml. Therefore, it should be shown first that the flow rate of all DRAs is the same 30 ml at 4 bar.

12. On page 12, Fig. 7: Figures 6 and 7 show a difference in drift amount between the two nozzles. However, the authors' explanations are limited to citations of references. Air-induction nozzles are known to produce droplets two to three times larger than standard flat fan nozzles. Please explain the description of Fig 7 in connection with the nozzle characteristics.

13. On page 13, Line 455-459: As shown in Table 2, the wind speed at which the test was carried out is 2, 3, 4, 5, 6, 8 m/s. However, the wind speed described in Lines 455-459 is not clear. This needs to be supplemented.

14. On page 13, Line 470: What does PCS mean? If it is a unit like pieces, please fill it out exactly.

15. On page 13, Table 2: What does the height (h) used in Table 2 mean? Please describe in detail using Fig. 2 or Fig. 3. In addition, Why did you measure the water-sensitive paper coverage at 4 m away from the nozzle?

16. On page 15, Line 475: There is a typo. “the flats pray nozzle” should be changed to “the flat spray nozzle”.

17. On page 15, Line 490: In the highest leaf coverage, what does leaf coverage ratio mean? In this study, water-sensitive papers were used to evaluate the coverage ratio. Therefore, modify the term (leaf coverage ratio) so that it is not confused with mock or real plant experiments. Like this, please unify the leaflet coverage term used (on page 17, line 499).

 

18. On page 19, 4. Conclusion: In this manuscript, it is concluded that the newly developed DRA7e and air-injector flat spray nozzle are the most advantageous for drift mitigation. However, there is not enough logical explanation connected with the DRAs and the nozzle types as to why both conditions are advantageous for drift mitigation. The conclusion must be substantially revised. 

Author Response

Dear Reviewer,

First of all, we would like to thank you for reviewing our manuscript. We appreciate your comments, suggestions, and recommendations to improve the quality of the manuscript. All comments were taken into account and the manuscript was revised. All corrections are highlighted in the text. Responses to comments are provided below:

This manuscript reports the influence of newly developed spray drift reduction agents (three newly developed agents, four commercial ones, and a water solution) on drift mitigation. This study was carried out experimentally by means of a wind tunnel and in-field evaluation methods. Two nozzles (an air-injector flat spray nozzle and a standard flat spray nozzle) were tested at the fixed injection pressure of 4 bar and volume flow rate of 1.82 LPM (liter per minute), and two types of spray drift (ground spray drift and airborne spray drift) were evaluated in a wind tunnel and in-field conditions. The results reported the impact of wind speed, nozzle type, and drift reduction agent (DRA) on spray drift mitigation. In my opinion, the manuscript is currently not suitable for publication in Agriculture as it is. The authors should address the following comments and questions:

1. In the whole manuscript, the terms used in this manuscript must be unified. Using various terms with the same meaning leads to confusion for readers. For example, a flat spray nozzle(page 12, line 425, etc.) and a standard nozzle(page 4, line 100, etc.) should be unified to a standard flat spray nozzle, and an air injector(page 1, line 21, etc.) should be unified to an air-injector flat spray nozzle.

According to a reviewer's comment, the terms used in the manuscript were unified. Used terms are "standard flat spray nozzle", and "air-injector flat spray nozzle".

2. On page 2, Line 87-89: Two sentences with the same meaning are being repeated. Please revise it in one sentence.

Taking into account the reviewer's comment, the sentence “Sprayed droplet diameter is strongly affected by nozzle type and operating pressure” was removed. In the manuscript, we left the sentence “The diameter of the sprayed droplets is strongly influenced by the type of nozzle and the operating pressure”.

3. On page 5, Table 1: In Table 1, the physical properties of the four commercial DRAs, three newly developed DRAs, and water used in this study are introduced. The highlight of this study is the influence of the DRAs on the drift mitigation of the spray. In addition, the variables that have the greatest influence on spray drift are the droplet size and distribution of the spray. From this point of view, the density of DRAs and the average droplet size (VMD), if possible including the size distribution, when sprayed using two nozzles should be added in Table 1. Please complement this.

The reviewer's comment was accepted. Table 1 was improved by adding the density of 100% solution. Moreover, was added Figure 9 ("Droplets size parameter Dv₁₀, Dv_50, and Dv₉₀ as a function from a distance of target zone of sprayer L when spraying DRA7e with a sprayer with 5 air-injector flat spray nozzles (lateral wind velocity v=10 m s^-1)") and Figure 10 ("Relative span RS of droplets as a function from a distance of target zone of sprayer L when spraying DRA7e with a sprayer with 5 air-injector flat spray nozzles (lateral wind velocity v=10 m s^-1)") in manuscript page 18.

4. On page 6, Line 256: The test nozzle was installed at 50 cm above the surface of the liquid collection flasks (i.e., above the corrugated tin). This distance is important to distinguish between ground spray drift and airborne spray drift. Please describe the reason for using 50 cm in detail.

Following a reviewer's comment, we described the reason for using a nozzle 50 cm above the surface of the liquid collection flasks (i.e., above the corrugated tin). The reason was added in the 257 and 258 lines.

5. On page 6, Line 259-261: Two test nozzles with the same spray angle and flow rate of 120 deg. and 1.82 LPM, an air-injector flat spray nozzle (Lechler IDK 120-04, Lechler GmbH, Germany) and a standard flat spray nozzle (Lechler LU 120-04, Lechler GmbH, Germany), were introduced. Since the spray angle and flow rate described herein are provided by the manufacturer, especially the flow rate is expected to change according to the DRAs presented in Table 1, which is important in evaluating the amount of spray drift. Please add the results of the flow rate measurement according to the DRAs.

According to a reviewer's comment, we added the flow rate measurement according to the DRAs. It was added in the 262–264 lines.

6. On page 6, Line 262-263: It is not clear what “The nozzle sprayed the liquid in both directions, in the longitudinal direction of the tunnel, at a distance of 85 cm, i.e., a spray area of 170 cm (at an air velocity of 0 m s^-1)” means. Please explain further.

The reviewer's comment was taken into account. We explained the sentence "The nozzle sprayed the liquid in both directions, in the longitudinal direction of the tunnel, at a distance of 85 cm, i.e., a spray area of 170 cm (at an air velocity of 0 m s^-1)" in more detail in the 266–270 lines. Moreover, we have improved Figure 1 by adding x,y,z coordinate system.

7. On page 8, Fig.3: Too many terms are being used in relation to the direction of the wind. (For instance, lateral air velocity, longitudinal direction, vertical direction, both direction, wind direction, side wind speed, adjacent lateral air velocities, etc.) Please add the coordinates system in x, y, z to Fig. 3 and describe the direction of the wind according to the coordinates system. In particular, the direction of the wind that acts on the flat-fan spay is not clear. After indicating the spray structure, please clearly indicate the direction of the wind.

According to a reviewer's comment, we improved Figure 3, and we described the direction of the wind according to the coordinates system, also we described the direction of the wind that acts on the flat-fan spay. We added descriptions in the 313, 314, and 328 lines.

8. On page 8, Fig.3: Please added the distance between the ground and the chamber (where the wind comes out) connected to the fan.

Following a reviewer's comment, we added distance between the ground and the chamber connected to the fan to Figure 3.

9. On page 9, Line 341: In Fig. 6, the side wind velocity was changed to 2, 4, 6, 8, and 10 m/s. However, Line 341 specifies only 6-10m/s. It seems to be referring to something that is not a common case that is higher than those recommended for spraying agricultural crops. Please revise this part clearly.

We are taking into account the reviewer's comment and we revised and supplemented lines 355–359.

10. In page 10, Fig. 6: Please change “Vanduo” to “water”.

Taking account of the reviewer's comment, we changed “Vanduo” to ”H₂O”.

11. In page 10, Line 381-383 and Fig. 6a: The amount of spray drift according to the DRAS is associated with droplet size due to the change in physical properties of the DRAS. However, the authors' explanations are only cited for reference results. Please explain the drift amount according to the DRAs in connection with the properties of the DRAs described in Table 1. And the numerical value shown above the bar chart is the value for the case of the injection flow rate of 30 ml. Therefore, it should be shown first that the flow rate of all DRAs is the same 30 ml at 4 bar.

The reviewer's comment was accepted. We supplemented lines 401–405 and explained the drift amount according to the DRAs in connection with the properties of the DRAs described in Table 1. By the way, we supplemented Method section lines 262–264 by adding information about flow rate: “The flow rate when spraying water and DRA1–DRA4 differs slightly and amounts 1.82±0.03 l min^–1 at a pressure of 4.0 bar. By using DRA5–DRA7 the flow rate was 1–2% lower”.

12. On page 12, Fig. 7: Figures 6 and 7 show a difference in drift amount between the two nozzles. However, the authors' explanations are limited to citations of references. Air-induction nozzles are known to produce droplets two to three times larger than standard flat fan nozzles. Please explain the description of Fig 7 in connection with the nozzle characteristics.

The reviewer's comment was taken into account and lines 450–452 explained the difference in drift amount between the two nozzles was in connection with the nozzle characteristics.

13. On page 13, Line 455-459: As shown in Table 2, the wind speed at which the test was carried out is 2, 3, 4, 5, 6, 8 m/s. However, the wind speed described in Lines 455-459 is not clear. This needs to be supplemented.

According to a reviewer's comment, we supplemented lines 488–491 adding a more detail description.

14. On page 13, Line 470: What does PCS mean? If it is a unit like pieces, please fill it out exactly.

PCS means pieces, i.e. droplet marks on the water-sensitive paper (equal to the number of droplets deposited on the water-sensitive paper). PCS was removed from the manuscript.

15. On page 13, Table 2: What does the height (h) used in Table 2 mean? Please describe in detail using Fig. 2 or Fig. 3. In addition, Why did you measure the water-sensitive paper coverage at 4 m away from the nozzle?

Height means the distance measured vertically in direction of the y axis (Figure 1) from corrugated tin to the analysis area center point on a water-sensitive paper. The wind tunnel has a limited chamber length, therefore water-sensitive paper was placed at a 4 m distance from the nozzle.

16. On page 15, Line 475: There is a typo. “the flats pray nozzle” should be changed to “the flat spray nozzle”.

According to a reviewer's comment, typo “the flats pray nozzle” was changed to “the flat spray nozzle”.

17. On page 15, Line 490: In the highest leaf coverage, what does leaf coverage ratio mean? In this study, water-sensitive papers were used to evaluate the coverage ratio. Therefore, modify the term (leaf coverage ratio) so that it is not confused with mock or real plant experiments. Like this, please unify the leaflet coverage term used (on page 17, line 499).

We are taking into account the reviewer's comment and unify the leaflet coverage term. The term "leaf" changed to "water-sensitive papers".

18. On page 19, 4. Conclusion: In this manuscript, it is concluded that the newly developed DRA7e and air-injector flat spray nozzle are the most advantageous for drift mitigation. However, there is not enough logical explanation connected with the DRAs and the nozzle types as to why both conditions are advantageous for drift mitigation. The conclusion must be substantially revised. 

Following a reviewer's comment, the conclusion was improved by adding explanations.

Author Response File: Author Response.pdf

Reviewer 2 Report

This manuscript is well written and organized. It clearly shows the relationship between wind speed, nozzle height, and droplet drift distance. However, the effect of droplet size is not included, which is also very important to spray drift. Considering that this study is about drift reduction agent (DRA) characteristics, relative test and discussion cannot be ignored. I suggest this manuscript to be published after adding necessary measurement and discussion about droplet size of each case.

Author Response

Dear Reviewer,

First of all, we would like to thank you for reviewing our manuscript. We appreciate your comments, suggestions, and recommendations to improve the quality of the manuscript. All comments were taken into account and the manuscript was revised. All corrections are highlighted in the text. Responses to comments are provided below:

This manuscript is well written and organized. It clearly shows the relationship between wind speed, nozzle height, and droplet drift distance. However, the effect of droplet size is not included, which is also very important to spray drift. Considering that this study is about drift reduction agent (DRA) characteristics, relative test and discussion cannot be ignored. I suggest this manuscript to be published after adding necessary measurement and discussion about droplet size of each case.

The reviewer's comment was accepted. Table 1 was improved by adding the density of 100% solution. Moreover, was added Figure 9 ("Droplets size parameter Dv₁₀, Dv_50, and Dv₉₀ as a function from a distance of target zone of sprayer L when spraying DRA7e with a sprayer with 5 air-injector flat spray nozzles (lateral wind velocity v=10 m s^-1)") and Figure 10 ("Relative span RS of droplets as a function from a distance of target zone of sprayer L when spraying DRA7e with a sprayer with 5 air-injector flat spray nozzles (lateral wind velocity v=10 m s^-1)") in manuscript page 18.

Author Response File: Author Response.pdf

Reviewer 3 Report

Dear Authors,

I want to commend you on your manuscript titled "The influence of newly developed spray drift reduction agents on drift mitigation by means of wind tunnel and in the field evaluation methods".  I found this manuscript to be of great value for the scientific and especially the spray application technology community. I think your introduction and materials and methods are very thorough and add significant value to the paper. My biggest issue is with the discussion of the results. It is simply too dense. Before publication in Agriculture, I would like to see this whole section cleaned up and made a little easier to follow. The tables with the +/- are not easy to follow and need to be cleaned up. I appreciate the inclusion of that information, but that might be better suited to be shown as a box and whisker plot. Even the bar graphs are a little too compressed where it's not user friendly to try to follow. Also, in your bar graphs, you kept water in Lithuanian (vanduo) - please change that to say H20 or water. 

I really think  this is an outstanding paper - but needs to be made a bit easier to follow in the results - arguably the most important section in the paper. 

Best Regards,

A. Reviewer

Author Response

Dear Reviewer,

First of all, we would like to thank you for reviewing our manuscript. We appreciate your comments, suggestions, and recommendations to improve the quality of the manuscript. All corrections are highlighted in the text. Responses to comments are provided below:

I want to commend you on your manuscript titled "The influence of newly developed spray drift reduction agents on drift mitigation by means of wind tunnel and in the field evaluation methods".  I found this manuscript to be of great value for the scientific and especially the spray application technology community. I think your introduction and materials and methods are very thorough and add significant value to the paper. My biggest issue is with the discussion of the results. It is simply too dense. Before publication in Agriculture, I would like to see this whole section cleaned up and made a little easier to follow. The tables with the +/- are not easy to follow and need to be cleaned up. I appreciate the inclusion of that information, but that might be better suited to be shown as a box and whisker plot. Even the bar graphs are a little too compressed where it's not user friendly to try to follow. Also, in your bar graphs, you kept water in Lithuanian (vanduo) - please change that to say H20 or water.

I really think this is an outstanding paper - but needs to be made a bit easier to follow in the results - arguably the most important section in the paper.

We agree with a reviewer's comment that it is not easy for the user to follow the results due to a large amount of data. However, in order to successfully introduce newly developed products to the market, our aim was to carry out the most detailed research that would reflect the more accurate and reliable information. You are right in stating that a lot of numbers provided in the tables it more difficult for the reader to understand. Taking into account, we have marked the numbers in the tables with different colors. We expect this helps the reader in analyzing the tables. In addition, when describing the data of tables, we did not expand, but focused on the most important aspects, so that the reader can understand the information presented in the tables as easily as possible. We certainly agree that removing the +/- values from the tables would make them easier to follow. However, a confidence interval is one way of making statistical conclusions, and we want the reader to be able to see information about the reliability of our data.

According to a reviewer's comment, we changed “vanduo” to “H₂O” in the bar graphs.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The authors faithfully revised the manuscript line by line to the reviewer's comments. In particular, it showed density in Table 1 and explained the effects of viscosity and surface tension in Line 401-405 and Line 535-536, respectively. In addition, the droplet size and the span factor are shown in Figs. 9 and 10.

 

The highlight of this manuscript is to reveal the correlation between the mean droplet size and its distribution and spray drifts according to the change of physical properties of spray drift reduction agents. In particular, the key is to clarify why DRA7e is suitable for drift mitigation among newly developed spray drift reduction agents. However, the authors present the conjecture as a conclusion, as described in lines 640-642. Such speculative conclusions can confuse readers. If possible, suggest the correlation between the physical properties of DRAs -Droplet size and its distribution-Spray drift characteristics of DRAs.

Comments for author File: Comments.pdf

Author Response

Dear Reviewer,

We fully agree and understand the reviewer's concern and suggestion that the last sentence of the conclusions (lines 640-642) may be confusing for readers. The main objective of this study was to develop and test more efficient DRAs for different wind speeds (2-10 m s^-1). Therefore, the statement in the conclusions „The reason for this is probably the optimal combination of physical parameters (of surface tension, density, and viscosity) of the solution DRA7e” deleted and added in lines 620-630:

"The static and dynamic surface tension and density of the droplets in DRA7e are very similar compared to DRA5e and DRA6e. Only the viscosity of the solutions at 0.1% concentration differs: while the viscosity of DRA7e is 0.7 mPa s, the viscosity of both DRA5e and DRA6e is about 3 times higher. It can be concluded that the last mentioned parameter had a decisive influence on the droplet drift. When comparing the number of droplets drifted over a given distance in a lateral wind of the same velocity, DRA7e was the one with the highest droplet drift reduction. For example, in a 10 m s^-1 wind, about 250 droplets of DRA5e, about 200 droplets of DRA6e and about 160 droplets of DRA7e were drifted over a distance of 2 m. Correspondingly, at a distance of 10 m, 40 droplets each of DRA5e and DRA6e and about 27 droplets of DRA7e were drifted, although the spray distribution parameters Dv₅₀ and RS did not differ significantly".

Author Response File: Author Response.pdf

Reviewer 2 Report

Agree to accept in present form.

Author Response

Dear Reviewer,

Thank you for your time. 

Best wishes