Performance of Drift-Reducing Nozzles in Controlling Small Weed Seedlings with Contact Herbicides

Round 1

Reviewer 1 Report

Comments for author File: Comments.docx

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

The subject of the paper is consistent with the scope of the journal. The paper presents a study about the effect of pressure and drift reducing nozzle type on spray deposition, and droplet characteristics and on the efficacy of two types of contact herbicides on two growth stages of two weed species. The work is really interesting because the obtained results are very useful to take decisions about how to apply these herbicides in an efficient way. The experimental design is very well planned and is very complete. Furthermore, the paper is well written and organized. For all these reasons in my opinion the paper can be published considering the comments/changes described below:  

 

INTRODUCTION

Lines 103-105: Change for: Are spray coverage on horizontal water sensitive papers and spray droplet characteristics good predictors of efficiency of contact herbicides?

 

MATERIALS AND METHODS

Lines 134-137. Please add the data of the spray distribution measurement for each nozzle/pressure with a horizontal distribution test bench as a supplementary material.

 

Table 2. How did you decide the herbicide doses for bentazon? For Phenmedipham is clear but not for bentazon.

 

Table 2. Why do you use triglyceride oil for bentazon and not for phenmedipham? The addition of the oil affects the spray coverage and droplets characteristics and maybe the efficacy.

 

Table 3. What hours do you consider day and night? Add the information. I suggest to change the table for a graphic with the evolution of the weather conditions per day indicating the different periods.

 

Lines 175-177. Droplet size was measured using pure water. However, the herbicide formulations probably affect these measurements. Therefore, I suggest to do the measurements also with the two herbicides used in the study.

 

Lines 197. Syngenta is written in a bigger size letter

 

Lines 196-198. Spray coverage characteristics were measured using pure water. However, the herbicide formulations probably affect these measurements. Therefore, I suggest to do the measurements also with the two herbicides used in the study.

 

Lines 207-208. Explain how do you calculate foliage dry biomass. Did you check that after 16h at 75ºC the biomass was dry?? It is normal to check that the weight of biomass is constant in consecutive measures.

 

Section 2.5 Data analysis. In general, this section should be described in more detail.  What was the level of confidence in the different test used? Explain the data analysis for droplet characteristics and for spray coverage. Add more details for the biomass data analysis, what test did you use for mean separation? Add more detail about the regresions. Why quadratic? In the results in some occasions, you use the exponential regression, please explain step by step what you did, indicate all the functions you tested and justify your election. What data did you use for the regressions? The mean values? Why did not you consider the data of all repetitions?? I suggest to use all the data. Show also the p-value for each regression not only the R2.

 

 

RESULTS

 

Change “droplet number density” for “impact number density”

 

Lines 260-261. Change for: Doubling the spray pressure increased the impact number density of the  air induction nozzles with about 40%, up to about 80 droplets cm-2 at higher forward speed advance to maintain the spray volume of 200 L/ha.

 

Figure 2. What do the letters mean? What statistical analysis was done? Change Droplet number density for impact number density.

 

Figure 3 and Figure 4. Add the data of selectivity indices and p-values as a supplementary material. Check the letters, for example in figure 3A the AVI at 2.5 the letters are "abce" and I think they should be "abcde".

 

DISCUSSION

 

Lines 484-485.  Droplet rebound and runoff is written in a bigger size letter.

Author Response

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Author Response File: Author Response.docx