The Impact of Different Winter Cover Crops on Weed Suppression and Corn Yield under Different Tillage Systems

Round 1

Reviewer 1 Report

Comments to the Author

I have reviewed with interest your manuscript entitled „The impact of different winter cover crops on weed suppression and corn yield under different tillage systems”.

Authors in their study evaluated the potential of white clover and ryegrass to inhibit the 15 growth of weeds and the effect of their residue return to the field on subsequent crops in a cover 16 crop-corn rotation system. Results constitute evidence that the incorporation of WC and RG into the soil by RT could be a feasible practice to reduce the reliance on synthetic herbicides in the corn-based cropping systems. Statistical method of ANOVA was used.

In my opinion the current version of your manuscript is suitable for publication in Agronomy, but after revisions. The quality of the presentation should be improved-e.g., the introduction is not written in an appropriate manner. In general, manuscript needs improvement. I suggest a reorganization of the results and discussion, focusing on the most relevant aspects.

There are same grammar mistakes and awkward sentences, that make the text difficult to follow at some points.

The article suffers from a number of small mistakes, ranging from misspellings to incorrectly phrased sentences.

Some adjustments are suggested to qualify the paper:

Issues include:

The Abstract should not exceed 200 words.

General comment to the Introduction section: The content of the literature review chapter is related to the research topic. Up-to-date literature references are presented in the manuscript by the author(s), but critical analysis has not been carried out with a high degree of accuracy.

In the chapter "Materials and Methods", the methodology is adequate, but there is a lack of information in some aspects. Some more information should be explained in the text. Please provide soil texture, chemical parameters, and references on the methods used to provide the soil properties.

In the chapter "Results", the results are displayed correctly.

The “Discussion” is informative. Moreover, the Authors attempt to discuss their important results and the rest is a quotation of literature. Please try to discuss your results in depth and link them with the appropriate literature throughout the whole section. In my opinion, the Discussion seems to be review of literature.

Other specific suggestions:

1. Lines 21-23: Proved the sentence, please.
2. Line 26: ‘Results’ of pot experiment……… add, please.
3. Line 28: Pot experiment recommended…?
4. Line 29: RG showed…” Please, correct the sentence.
5. Line 72: ‘in the corn period’..?
6. Line 136: active substance add, please.
7. Line 221: RG showed…? Proved the sentence, please.
8. Line 223-224: maybe change on: ‘100 days’ instead of: ‘one hounded days’.
9. Line 444: change ‘wise’ on other word, please.

I hope that these comments help you to make an improved version of the manuscript.

Author Response

We would like to thank you for your careful reading, helpful comments, and constructive suggestions, which have significantly improved the presentation of our manuscript.

We have carefully considered all comments from the reviewers and revised our manuscript accordingly. The manuscript has also been double-checked, and the typos and grammar errors we found have been corrected. In the following section, we summarize our responses to each comment from the reviewers. We believe that our responses have well addressed all concerns from the reviewers. We hope our revised manuscript can be accepted for publication.

• Comments from reviewer 1:
• • The Abstractshould not exceed 200 words.

  We gratefully appreciate your valuable suggestion. We have adjusted the word count of the abstract so that it is under 200 words.

  • General comment to the Introduction section: The content of the literature review chapter is related to the research topic. Up-to-date literature references are presented in the manuscript by the author(s), but critical analysis has not been carried out with a high degree of accuracy. 

  Thank you so much for your careful check. I have discussed it in more depth in the revised version of the manuscript based on the article topic.

  • In the chapter "Materials and Methods", the methodology is adequate, but there is a lack of information in some aspects. Some more information should be explained in the text. Please provide soil texture, chemical parameters, and references on the methods used to provide the soil properties.

  Thank you for your comments. I have added the reference to the soil classification in the revised version of the manuscript.

  • The “Discussion” is informative. Moreover, the Authors attempt to discuss their important results and the rest is a quotation of literature. Please try to discuss your results in depth and link them with the appropriate literature throughout the whole section. In my opinion, the Discussion seems to be review of literature.

  Thank you so much for your careful check. I have discussed it in more depth in the revised version of the manuscript based on the article topic and results in “Discussion” section.

  • Lines 21-23: Proved the sentence, please

  Thank you for your comments. This part of the conclusion has been removed due to the word limit.

  • Line 26: ‘Results’ of pot experiment……… add, please.

  Thank you for your comments, we add the results of the pot experiment in the revised manuscript.

  • Line 28: Pot experiment recommended…?

  My expression is wrong, I have corrected it in the revised manuscript.

  • Line 29: RG showed…” Please, correct the sentence.

  My expression is wrong, I have corrected it in the revised manuscript.

  • Line 72: ‘in the corn period’..?

  My expression is wrong, it’s “during the maize growing period”. I have corrected it in the revised manuscript.

  • Line 136: active substance add, please.

  Thank you for your comments, I have added the active substance composition of Atrazine in the revised manuscript.

  • Line 221: RG showed…? Proved the sentence, please.

  Thank you for your comment. Due to the lack of data to support this conclusion, I have amended it to "RG has better coverage in early growth".

  • Line 223-224: maybe change on: ‘100 days’ instead of: ‘one hundred days.

  Thank you for your suggestion. I have changed “one hundred days” into “100 d”

  • Line 444: change ‘wise’ on other word, please.

  Thank you for pointing out this problem in the manuscript. I have changed “wise” into “appropriative”

Author Response File: Author Response.docx

Reviewer 2 Report

GENERAL COMMENTS

The manuscript entitled “The impact of different winter cover crops on weed suppression and corn yield under different tillage systems” is a two-year field experiment aiming at evaluating the impact of green manuring from two winter cover crops (white clover and ryegrass), combined with two soil tillage, on weed suppression and corn yield. The topic is of high importance and interest in the view of sustainability. The subject of the manuscript falls with the general scope of the Journal and provides interesting data for the scientific community.

However, the paper shows some weaknesses, especially:

• the level of English language which need to be improved. Please check the manuscript with the help of a mother-tongue proofreader.
• M&Ms lack of several information, while other ones are not clear
• in particular, authors should clarify better that this research involves a field experiment and a pot experiment, each one with different aims
• the absence of a weed floristic composition analysis is an important gap
• references need to be improved

TITLE: could be improved with a more attractive title.

ABSTRACT: It properly summarise the manuscript, although the background could be improved, since no information is provided about the combination of green manuring and tillage, which is the topic of this research. In addition, the main results need to be better highlighted, for example by adding values in brackets. Below some comments:

• line 13: please write “white” without capital letter
• line 21: please add values in brackets
• line 22: please add the mean value (in brackets) of RG
• lines 24-25: please add values in brackets
• lines 27-28: too generic, please report the specific variable under study and values

INTRODUCTION: the overall organization of this section is good.

• I suggest starting the introduction with a brief section about the need of sustainable agronomic practices such as cover cropping
• lines 36: please add a definition or explanation of rotation tillage
• line 42: “Furthermore” is a repetition with line 41
• lines 43-46: this is not true, because the weed suppressive ability of cover crops is not only related to competition (i.e. physical interference). Allelopathic mechanisms (root exudates from living mulches or chemicals leached from plant residues) are also of key importance in this process. I suggest this recent review (“Crop Allelopathy for Sustainable Weed Management in Agroecosystems: Knowing the Present with a View to the Future”, Agronomy 2021, 11(11), 2104; https://doi.org/10.3390/agronomy11112104) to implement the phytotoxic activity of cover crops, here and/or in the discussion
• line 46: what is NT? Please spell out an acronym the first time is used
• lines 47-53: in my opinion these references are not relevant and off topic for this research. In this manuscript, you did not evaluated the effect of cover crop extracts. Therefore, please change them with field experiments about weed suppression of cover cropping. The literature shows a wide number of examples, such as Restuccia et al. 2020 (https://doi.org/10.3390/plants9111506)
• line 57: please change “interplanting” with “intercropping”
• lines 56-66:
• this section could be improved by adding more information about the chemistry of cover crop allelochemicals, whith specific reference to the species under study or at least to the botanical family
• line 67: what is WC? Please spell out an acronym the first time is used
• lines 68-71: sentences not clear, please rephrase
• the aims need to be better explained

M&M: In some parts, this section is incomplete and imprecise. See specific comments:

• lines 86-87: for inorganic nitrogen do you mean the sum of nitric and ammoniacal nitrogen? If yes, please specify. In addition, please add the percentage of the textural classes
• line 90: please explain the mechanical tillage adopted and the herbicides used during the past 20 years
• please improve the description of the climatic trend during the 2 years
• Figure 1: What temperature refer to? (average, minimum or maximum air temperature? Please specify)
• Figure 1: the left y axis is not clear concerning the variables and the units of measurement
• lines 97-98: it is a repetition of line 84
• line 102: please add the area of each plot
• line 103: what is the area of each subplot? Description of the experimental design is not very clear. Please add a Figure the scheme of the treatments, highlighting main plots and subplot, with dimensions
• line 105: How the fresh aerial biomass of WC and RG were collected? Please explain the sampling methodology
• line 109: please add the binomial name of milk vetch and indicate its dry weight yield in kg ha^-1
• lines 111-116: it is not clear, please rephrase
• lines 111-120: it is another experiment, but it is very difficult to understand for readers. Please add a new paragraph about this pot experiment, why and how it was carried
• lines 122-124: please use the hectar (ha) as surface unit measurement
• lines 122-124: which variety of WC and RC? Besides, add specific information about the variety of cover crops and corn, together with comments related to their growth cycle
• line 125: at which soil depth?
• line 133: which fertilizers? Add specific information
• line 135: herbicide at which dose?
• No irrigation was provided? Please specify
• line 138: please rephrase the title
• line 145-146: if I well understand, weeds were collected by just a 0.5 m × 0.5 m quadrat per plot. It is an insufficient surface sampling area. Moreover, how the quadrat was located within the plot?
• lines 147-148: what are Graminae? Likely you intend Poaceae. Anyway, this classification of weeds is not valid. Please classify according to the botanical family or life cycle (annual, biennial, perennial) or ecophysiological group (terophytes, hemicriptophytes, etc.).
• statistical analysis is also not clear. How season was considered? Looking at results, it seems that you considered it as a random factor, since results are reported for each season. If yes, please specify

RESULTS:

• starting results directly with a table is quite inappropriate
• Figure 3: as above-stated, this classification of weeds is inappropriate. I strongly encourage authors integrating a table with the floristic composition of weeds (list of weeds detected during the 2 years with their scientific name, botanical family, life cycle, ecophysiological group and frequency or density
• lines 286-287: please check the paragraph title
• Figure 6: in order to better visualize white clover and ryegrass, you could use two different colours
• Figure 7: I suggest adding two bold sub-titles within the figures to clearly indicate white clover (A,B,C,D) and ryegrass (E,F,G,H)
• Figure 7 and 8: instead of asterisks, please use statistical letters or include the LSD value for P<0.05

DISCUSSION: overall good. However, this section lacks of appropriate references with similar works in the literature. In detail, the authors should compare their results with other ones on the same species. Therefore, I suggest:

• integrating into the text similar researches carried out on clovers. For instance, see:
• “Trifolium subterraneum cover cropping enhances soil fertility and weed seedbank dynamics in a Mediterranean apricot orchard”. Agron. Sustain. Dev. 41, 70 (2021). https://doi.org/10.1007/s13593-021-00721-z
• “Improving soil health, weed management and nitrogen dynamics by Trifolium subterraneum cover cropping”. Sustain. Dev. 40, 18 (2020). https://doi.org/10.1007/s13593-020-00621-8
• including other works involving the use of ryegrass in field conditions

Author Response

We would like to thank you for your careful reading, helpful comments, and constructive suggestions, which have significantly improved the presentation of our manuscript.

We have carefully considered all comments from the reviewers and revised our manuscript accordingly. The manuscript has also been double-checked, and the typos and grammar errors we found have been corrected. In the following section, we summarize our responses to each comment from the reviewers. We believe that our responses have well addressed all concerns from the reviewers. We hope our revised manuscript can be accepted for publication.

• Comments from reviewer 2:

• line 13: please write “white” without capital letter.

We gratefully appreciate your careful check. We have corrected this mistake in revised manuscript.

• line 21: please add values in brackets. 

Thank you so much for your suggestion. I have added the values in this sentence.

• line 22: please add the mean value (in brackets) of RG.

Thank you for your comments. I have added the mean value of RG in the revised version of the manuscript.

• lines 24-25: please add values in brackets.

Thank you so much for your suggestion. I have added the values in this sentence.

• lines 27-28: too generic, please report the specific variable under study and values

Thank you for your comments. This part of the conclusion has been removed due to the word limit.

• I suggest starting the introduction with a brief section about the need of sustainable agronomic practices such as cover cropping.

Thank you for your comments, we added a reference about sustainable agronomic practices this part in the revised manuscript.

• lines 36: please add a definition or explanation of rotation tillage

Thank you for your comments, we added a definition of rotation tillage in the revised manuscript.

• line 42: “Furthermore” is a repetition with line 41.

Thank you for your comments, we have adjusted the sentence in the correct way.

• lines 43-46: this is not true, because the weed suppressive ability of cover crops is not only related to competition (i.e. physical interference). Allelopathic mechanisms (root exudates from living mulches or chemicals leached from plant residues) are also of key importance in this process.

Thank you for your comments. I have corrected it in the revised manuscript.

• I suggest this recent review (“Crop Allelopathy for Sustainable Weed Management in Agroecosystems: Knowing the Present with a View to the Future”, Agronomy 2021, 11(11), 2104; https://doi.org/10.3390/agronomy11112104) to implement the phytotoxic activity of cover crops, here and/or in the discussion.

Thank you for your kind suggestion. I have added this reference here in the revised manuscript.

• line 46: what is NT? Please spell out an acronym the first time is used

Thank you for your comment. It is no-tillage, I have corrected it in the revised manuscript.

• lines 47-53: in my opinion these references are not relevant and off topic for this research. In this manuscript, you did not evaluated the effect of cover crop extracts. Therefore, please change them with field experiments about weed suppression of cover cropping. The literature shows a wide number of examples, such as Restuccia et al. 2020 (https://doi.org/10.3390/plants9111506)

Thank you for your kind suggestion. I have replaced those cover crop extraction-related articles with this reference in the revised manuscript.

• line 57: please change “interplanting” with “intercropping”

Thank you for your suggestion. I have changed “interplanting” into “intercropping”

• lines 56-66:this section could be improved by adding more information about the chemistry of cover crop allelochemicals, with specific reference to the species under study or at least to the botanical family

Thank you for your suggestion. I have added some related references in this section.

• line 67: what is WC? Please spell out an acronym the first time is used

Thank you for pointing out this problem in the manuscript. I have corrected it in the revised manuscript.

• lines 68-71: sentences not clear, please rephrase the aims need to be better explained

Thank you for pointing out this problem in the manuscript. I have corrected it in the revised manuscript.

• lines 86-87: for inorganic nitrogen do you mean the sum of nitric and ammoniacal nitrogen? If yes, please specify. In addition, please add the percentage of the textural classes.

Thank you for pointing out this problem in the manuscript. inorganic nitrogen is the sum of nitric and ammoniacal nitrogen, and we add the classification reference of soil.

• line 90: please explain the mechanical tillage adopted and the herbicides used during the past 20 years

Thank you for your comment, we have added the explanations in revised manuscript.

• please improve the description of the climatic trend during the 2 years

Thank you for your comment, we have improved the climatic tend in revised manuscript

• Figure 1: What temperature refer to? (average, minimum or maximum air temperature? Please specify), and the left y axis is not clear concerning the variables and the units of measurement

Thank you for your comment, it is average temperature, we have specified the units and adjusted the Fig. 1 in revised manuscript.

• lines 97-98: it is a repetition of line 84

Thank you for pointing out this problem in the manuscript. We have deleted this repetition section.

• line 102: please add the area of each plot

Thank you for your comment, we added the area of each plot and subplot in revised manuscript.

• line 103: what is the area of each subplot? Description of the experimental design is not very clear. Please add a Figure the scheme of the treatments, highlighting main plots and subplot, with dimensions

Thank you for your comment, we reorganized the sentence in order to be more clear.

• line 105: How the fresh aerial biomass of WC and RG were collected? Please explain the sampling methodology

Thank you for your comment, the aerial biomass of WC and RG were given in Table 1. Due to the large variation in green manure yield in two years, we selected a possible yield as the basis for the design of the pot experiment. As we mentioned in the manuscript, the amount of cover crops returned to the field can be adjusted through external inputs, therefore, the setting of the proportion of cover crop and soil for pot experiments is not the focus of this study.

• line 109: please add the binomial name of milk vetch and indicate its dry weight yield in kg ha^-1

Thank you for pointing out this problem in the manuscript. We have corrected it in the revised manuscript.

• lines 111-116: it is not clear, please rephrase

Thank you for pointing out this problem in the manuscript. We have rephrased it in the revised manuscript

• lines 111-120: it is another experiment, but it is very difficult to understand for readers. Please add a new paragraph about this pot experiment, why and how it was carried

Thank you for your suggestion. We have rephrased it in the revised manuscript based on your suggestion.

• lines 122-124: please use the hectar (ha) as surface unit measurement

Thank you for pointing out this problem in the manuscript. We have corrected it in the revised manuscript.

• lines 122-124: which variety of WC and RC? Besides, add specific information about the variety of cover crops and corn, together with comments related to their growth cycle

Thank you for your comment, seeds for experiments are not validated varieties, but common names are given in revised manuscript. We have added the purchase channels of the cover crop and rephrased the sentence order so that the reader can easier to understand their growth cycle.

• line 125: at which soil depth?

Thank you for your comment. We cut off the above-ground part of the cover crop with a mower, so the soil depth is around 1 cm.

• line 133: which fertilizers? Add specific information

Thank you for your comment. We added specific information in the revised manuscript.

• line 135: herbicide at which dose?

It is label dose (1.2 kg ha^-1).

• No irrigation was provided? Please specify

Thank you for your comment. We added specific information of irrigation in the revised manuscript.

• line 138: please rephrase the title

Thank you for your comment. We rephrased the title.

• line 145-146: if I well understand, weeds were collected by just a 0.5 m × 0.5 m quadrat per plot. It is an insufficient surface sampling area. Moreover, how the quadrat was located within the plot?

We fully understand the reviewers' concerns, A sampling area of 0.25 m² is more than adequate for cover crop and weed biomass determination, and that the four replicates have similar biomass. We refer to previous research methods(Wulanningtyas et al., 2021). We used a random sampling method with the sampling frame located anywhere in the middle subplot.

• lines 147-148: what are Gramineae? Likely you intend Poaceae. Anyway, this classification of weeds is not valid. Please classify according to the botanical family or life cycle (annual, biennial, perennial) or ecophysiological group (terophytes, hemicriptophytes, etc.).

Thank you for pointing out this problem in the manuscript. We refer to previous studies in which researchers classified weeds into three categories of weeds viz grasses, broadleaved and sedges (Teja et al., 2016; Mishra, 2019). We have corrected it in the revised manuscript.

• statistical analysis is also not clear. How season was considered? Looking at results, it seems that you considered it as a random factor, since results are reported for each season. If yes, please specify

Thank you for your comment. We conducted a data analysis after each crop rotation cycle, and the field trial used a split-plot experimental design, while the pot trial used a single-factor randomized experimental design

• starting results directly with a table is quite inappropriate

Thank you for your comment. We have adjusted the order in the revised manuscript.

• Figure 3: as above-stated, this classification of weeds is inappropriate. I strongly encourage authors integrating a table with the floristic composition of weeds (list of weeds detected during the 2 years with their scientific name, botanical family, life cycle, ecophysiological group and frequency or densit

Thank you for pointing out this problem in the manuscript. We fully understood the reviewers' concerns and handled this problem in revised manuscript, as mentioned in point 36).

• lines 286-287: please check the paragraph title

Thank you for pointing out this problem in the manuscript. We have rephrased the title in revised manurscript.

• Figure 6: in order to better visualize white clover and ryegrass, you could use two different colors

Thank you for your suggestion. We have changed the graph legend to a different color.

• Figure 7: I suggest adding two bold sub-titles within the figures to clearly indicate white clover (A,B,C,D) and ryegrass (E,F,G,H)

Thank you for your suggestion. We have added two bold figure legend within the figures.

• Figure 7 and 8: instead of asterisks, please use statistical letters or include the LSD value for P<0.05

Thank you for your comment. We have corrected this mistake in revised manuscript.

• I suggest: integrating into the text similar researches carried out on clovers.

Thank you for your suggestion. We have added several relative references in this section.

References:

Mishra, K. (2019). Effect of herbicide bensulfuron methyl plus pretilachlor in weed management of transplanted kharif rice (Oryza sativa L.). Journal of Pharmacognosy and Phytochemistry 8, 378-382.

Teja, K.C., Duary, B., Dash, S., Bhowmick, M.K., and Mallikarjun, M. (2016). Efficacy of imazethapyr and other herbicides on weed growth and yield of kharif blackgram. International Journal of Agriculture, Environment and Biotechnology 9, 967-971.

Wulanningtyas, H.S., Gong, Y., Li, P., Sakagami, N., and Nishiwaki, J., et al. (2021). A cover crop and no-tillage system for enhancing soil health by increasing soil organic matter in soybean cultivation. Soil & Tillage Research 205, 104749. doi:10.1016/j.still.2020.104749.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

Dear Dr. Mu, I congratulate with you for the efforts in addressing the reviewers comments and suggestions. I think that the constructive comments provided by reviewers have improved the overall quality of the manuscript, which is now ready for publication, in my opinion. King regards

Author Response

1）Dear Dr. Mu, I congratulate with you for the efforts in addressing the reviewers comments and suggestions. I think that the constructive comments provided by reviewers have improved the overall quality of the manuscript, which is now ready for publication, in my opinion. King regards

  Thank you very much for your valuable comments and evaluation！