Using Cover Crops as Means of Controlling Weeds and Reducing the Applied Quantity of Glyphosate-Based Herbicide in No-Till Glyphosate Tolerant Soybean and Corn

Round 1

Reviewer 1 Report

See my comments to the author in the Word file attached.

Comments for author File: Comments.pdf

There are grammatical errors throughout, and sentences that need to be paraphrased to make it more clear.  

Author Response

Dear REVIEWER 1

Abstract

Q01: Please add any conclusion or recommendation from the findings of this study to the abstract.

Answer01: We added a conclusion from the findings of this study to the abstract (last sentence)

Materials and methods

Q02: Experimental design for this study has not been explained or mentioned clearly. Was there any blocking? Was it a CRD or RCBD design? How were the treatments randomized?

Answer02: We added details about the design in the text. We also added a figure of the experimental site (Figure 1) for clarification.

Q03: What was the width of the corn and soybean rows?

Answer03: We added the width of the corn and soybean rows in the text.

Q04: In soybean, the first weed cover was estimated before first pre-emergence herbicide application, which means there were cover crops present along with the weeds. How confident the author is in their visual estimation of weed cover when there were cover crops present along with the weeds.

Answer04: Apart from winter wheat, the other CCs were not present at that time. Winter wheat was easily identifiable and distinguishable from weeds in the plots.

Q05: Line 129: How was the height of the corn and soybean measured? Was it measured from ground to the extended leaf tip in case of corn? What about soybeans?

Answer05: The measure was executed from ground to the extended leaf tip for both crops. We added this information in the text.

Q06: For grain yield, was the center two rows harvested?

Answer06: Yes, we harvested the center rows in order to avoid bias with the edge of the plots. We explained this in the text.

Statistical analysis:

Q07: Need more clarification as to how the statistical analysis was performed.

Answer07: We added details in the Statistical analyses section in the text. For example, we clarified the way we determined the normal distribution of our data.

Q08: What software was used for ANOVA analysis?

Answer08: We used JMP16 software. We added this information in the text.

Q09: What were the fixed and random factors in the ANOVA analysis.

Answer09: The fixed factor was the Crop management and the random factors were the years and the crop rotation.

Q10: Where is the ANOVA table for main effects and interactions.

Answer10: We added a table (Table 2) that includes the results of the main effects on the different studied parameters.

Q11: Was Year treated as fixed or random effect? Was there any interaction of year with treatment?

Answer11: Year was treated as a random effect. We added this information in the text.

Results

Tables and figures:

Q12: Figure 1: Data for this figure is presented as Treatment and year interaction without providing p-values for main effects and interaction. Was treatment and year interaction significant?

Answer12: We changed the figure in order to clarify the observed results (Figure 2). The interaction between crop management and year is not significative in both crops, that’s why we added different histograms for each year.

Q13: Table 1: It seems data in this table is presented from three-way ANOVA for Crop Rotation, Crop Management and Years but this has not been mentioned in the statistical section. I would suggest presenting a separate ANOVA table to clarify what analysis was done and the author chose to present data in the current form based on the main and interaction effects.

Answer13: The table intended to show the results obtained after a one-way ANOVA. We modified this table (Table 3) in order to give more details regarding  our approach.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments for author File: Comments.pdf

Author Response

Dear REVIEWER 2,

Abstract

Q01: “However, weeds had a large impact on water content which reflected on plant parameters and yields in plots with only 0.84 L ha-1 of GBH applied”.

This sentence is not clear, please paraphrase so that its clear to the readers

Answer01: We modified this sentence following reviewer's comment.

Introduction.

Q02: “In counterpart, the intensive use of herbicides with these mechanisms of action has 39 contributed significantly to the actual 500 cases of herbicide resistance globally [11] and 40 this problem may increase with the impact of climate change”.

Please use the updated data her, number of herbicide resistant weeds currently is more than 500.

Answer02: We updated the data following reviewer's comment. We also added the most recent reference on the subject.

Q03: Line 42, direct seedling (DS) – Is it direct seeding or direct seedling?

Answer03: The right way to write it is seeding. We made the correction following the reviewer's comment.

Q04: Line 48 - N-(phos-48 phonomethyl)glycine) – Please confirm the bracket use here.

Answer04: We confirm the bracket but this long word can be removed if necessary.

Q05: Line 50 – Give full form of GR.

Answer05: We made the correction following reviewer's comment. We change GR for GT as previously announced in the text.

Q06: “combining the use of GBH with other herbicides with different mechanisms of action or increasing to mechanical tillage”

Check for grammatical issue in this sentence.

Answer06: We corrected this grammatical issue.

Q07: Also, despite the current criticism and debate surrounding the use and impact of GBH and his impact on human and environmental health, a ban on its use does not seem feasible without significant economic and environmental repercussions.

Please replace the word “his” with other appropriate word.

Answer07: We changed the word ‘’his’’ for ‘’its’’.

Q08: Furthermore, many producers believe that CC represent more labor and can compete with crops of interest, which is question their adoption. – Please correct the grammar here.

Answer08: We made the correction following the reviewer’s recommendation.

Materials and method

The entire methodology section should be written with greater clarification.

Answer: We modified several sentences of the Materials and Method section

Q09: In the methodology, please mention the design of experiment, is it RCBD?

Answer09: We put the information in the text and added a figure of the experimental design

Q10: In DSCC plot: 2019: Wheat was planted: wheat (Hoffman HRF: May 8th 2019), and cover crops were planted May 12th and 27th., If wheat and cover crops were co-planted in the plots please mention how? Density of cover crops should also be mentioned. Were the cover crops and wheat growing together in the plots or cover crops were terminated at some point? These things should be mentioned in the procedure for clarification. Same question goes for corn and soybean too.

Answer10: We have clarified in the text how the CCs have been sown and terminated. We also added some details about the seedling for each CCs mix in the table 1.

Reviewer 3 Report

Dear authors, the subject of the manuscript and the ideia of the work are interesting, but I found the text very difficult to understand the text, mostly at the material and methods section.  You have to improve the sequence of treatments done, the cover crops used, the analysis that you did (their presentations in the text). One example, what statistical program they used? The data had a normal distribution? Why not to join both years in one analysis? A improvement should be done for acceptance.

Author Response

Dear REVIEWER 3,

Materials and method

Dear authors, the subject of the manuscript and the idea of the work are interesting, but I found the text very difficult to understand the text, mostly at the material and methods section.

An improvement should be done for acceptance.

Q01: You have to improve the sequence of treatments done, the cover crops used, the analysis that you did (their presentations in the text).

Answer01: We thoroughly improved the material and method section. We added a new figure of the experimental design to clarify the text.

Q02: One example, what statistical program they used?

Answer 02: We added the information in the Statistical analyses section in the text.

Q03: The data had a normal distribution?

Answer03: We added the way we determined the normal distribution of our data. Other details about our statistical approach have now been added.

Q04: Why not to join both years in one analysis?

Answer 04: In order to have a main effect test, we used a Chi squared analysis that combined both years in one analysis.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

I highly appreciate that the authors have made an extensive effort to my previous comments and have made significant improvements to the manuscript. However, I still have some questions/concerns regarding the details provided in the M&M section. There are also some typos throughout the manuscript which need to be carefully checked.  Please refer to the Word file attached for my additional comments.

Comments for author File: Comments.pdf

Author Response

DEAR REVIEWER 1 (RESPONSE FOR ROUND 2)

Materials & Methods:

General comment: The plot design is still very confusing and not well explained in the M&M section. If there were three crop rotations with and without cover crop and three rates of herbicide then there should be in total 18 treatments (3 x 2 x 3) instead of 8 as mentioned in the M&M.

Q01: Author needs to explain clearly what are the eight treatments they are evaluating.

Answer01: Only 8 of weed managements (or treatments) were considered in the study. Those 8 weed managements were T5 (corn DS 3.3), T6 (corn DSCC 0.84) , T7 (corn DSCC 1.67), T8 (corn DSCC 3.3), T9 (soybean DS 3.3), T10 (soybean DSCC 0.84), T11 (soybean DSCC 1.67), T12 (soybean DSCC 3.3) for 2019 and T1 (corn DS 3.3), T2 (corn DSCC 0.84), T3 (corn DSCC 1.67), T4 (corn DSCC 3.3), T5 (soybean DS 3.3), T6 (soybean DSCC 0.84), T7 (soybean DSCC 1.67), T8 (soybean DS 3.3) for 2020. We added a new figure illustrating the complete design clarifying the information on weed management considered in the text.

Q02: It has been mentioned in the abstract that only the highest rate of 3.3 L ha^-1 GBH was used for the DS plots with no CC but this information is not provided anywhere in the M&M section.

Answer02: The mentioned plots in the abstract were the DS 3.3 described in the Materials and Methods section. We added the clarification in the text.

Q03: I would highly recommend authors to clearly explain the plot layout and treatments in the M&M section. Information provided in the abstract should come from the rest of the manuscript and not the other way around.

Answer03: We made sure that the information in the abstract indeed comes from the rest of the manuscript.

Q04: Also mention in the M&M if only the corn and soybean phases of the corn-wheat & soybean-wheat rotation was used for data collection

Q05: The plot sizes mentioned by the author does not add up. If the individual plot size was 9m X 20m and the corn was planted in 30 inches row then there should be 12 rows of corn instead of 4 rows as mentioned by the author.

Answer05: Sorry for the confusion. Corn was sown at a distance of 76 cm (30 inches) in the corn plots. The 4 rows mentioned before represent 4 replicates of the 12 treatments present on the site as illustrated in the new figure 1.

Q06: If soybean rows were planted 7 inches apart (as mentioned by the author) then there should be way too many soybean rows per plot than just 4.

Answer06: Answer similar to Q05. Soybeans were sown at a distance of 19 cm (7.5 inches) apart in the soybean plots. The 4 rows mentioned represent 4 replicates of the 12 treatments present on the site as illustrated in the new figure 1.

Q07: Also how come the rows were spaced 12m apart (mentioned by author in the next sentence). What about the wheat row spacing?

Answer07: The distance between rows is 12 m. (distance between row #1 and row #2, between row #2 and row #3 and between row #3 and row #4) illustrated on figure 1. Wheat was sown at a distance of 19 cm (7.5 inches) apart in the wheat plots.

Q08: Soybean row spacing (7 inches) as mentioned by the author seems too narrow to me. Is that common in Canada?

Answer08: We specified 7.5" rather than 7". In fact, soybeans were sown at small intervals to stimulate the growth of large plants as recommended by agronomists from the Quebec Ministry of Agriculture (MAPAQ).

Q09: Also, I would suggest adding the list of all the 8 treatments (T1-T8) in the M&M section to make it more clear as to what treatment correspond to corn, soybean or wheat plots.

Answer09: We added a figure illustrating all weed management (treatments) and we specified which of these have been considered for sampling in 2019 and 2020 in the Material and Methods section in the text.

Q10: It is kind of hard to grasp if there was any herbicide treatment applied to the wheat phase of the rotation? No agronomic management is mentioned about the wheat phase of the rotation in the M&M.

Answer10: We added the clarification in the text.

Q11: Why was different rate of N was applied in both years and why was N split applied to corn in 2020?

Answer11: The different fertilization rates were suggested by the project's agronomists according to the growing conditions.

Q12: line 110: There is a typo ‘Three’ instead of ‘Tthree’.

Answer12: We have made the necessary corrections. We wrote three instead of “Tthree”

Q13: Authors mention fertilization in corn and soybean but no information is provided on any fertilization in wheat plots

Q14: Line 116-117: Information provided here about the previous year crop residue is for 2019 or 2020? I believe for each year the previous year crop residue would change for each rotation. Please clarify this.

Answer14: Yes, the type of residue will change within the same plot depending on the year. Since the crop sequence in each rotation is the same, corn always comes after wheat, soybean always come after corn and wheat always comes after soybean as shown in Figure 1 (As such, plots in T5 weed management were seeded on previous wheat residues in 2019 and on previous corn residues in 2020).

Q15: Line 124: Did rye cover crop survive the winter at all? Was it a winter cereal or rye grass? Winter cereal rye is winter hardy and has the ability to survive winter.

Answer15: Yes, similar to autumn wheat, autumn rye is a cereal with the ability to survive winter.

Q16: Line 136-145: Weed cover were estimated from corn and soybean plots only? What about the wheat plots? Was any weed data collected from the wheat phase of the rotation?

Answer16: Yes, weed cover rates have also been estimated in wheat plots, but are not included in the article, which focuses mainly on soybean and corn plots.

Q17: Line 154: Mention how many rows were harvested for yield estimates.

Results:

Q18: Fig 2: Please correct chart title for fig 2 (c) and (d) as they are for corn and not for soybean.

Answer18: Good observation! It was an unintentional error. We made the necessary corrections to the figure.

Q19: Line 227: ……years in the e corn-soybean…..

Answer19: We made the necessary correction by removing the unwanted “e” in the text.

Q20: Table 3: I recommend adding the information to this table that data is presented for the corn and soybean phases of the three crop rotations in 2019 & 2020 respectively.

Answer20: We added the information in the Note section below the Table 3.

Conclusion:

Q21: Line 425-426: The word “catch” crop is used here in the conclusion out of nowhere. This word has never been used even once anywhere in the manuscript before it appeared here. I recommend explaining or providing some context somewhere in the manuscript if the author wants to use this word here in the conclusion.

Answer21: We made the clarification by replacing the confusing term in the text.

Author Response File: Author Response.pdf