Improvement of Active Organic Carbon Distribution and Soil Quality with the Combination of Deep Tillage and No-Tillage Straw Returning Mode

1. Summary

Dear Reviewer, thank you for your valuable comments which made my article better. We have reorganised the article to accentuate the sections that are novel and would like and kindly request you to reconsider our article as we believe that this study is scientifically important. All changes in the article are highlighted in red font and my point-by-point response is provided below.

2. Point-by-point response to Comments and Suggestions for Authors

Comments 1: Improving the distribution of active organic carbon and soil quality is a topic that is very current and quite often discussed in scientific research. This is a global topic, so a big plus for the fact that it was taken up by the authors. The authors state that in China, the government has gradually promoted the application of nature conservation principles of farming techniques in the relevant regions of Northeast China. However, the Northeast has a variety of climatic conditions and guidelines for this are still lacking straw return techniques for specific soil and climatic conditions, which, according to the authors, would improve the distribution of organic carbon. Maize is the main crop grown in this area conducted a three-year experiment to address the lack of straw return techniques and blind fertilization in current agricultural production. The experiment adopted a rotational cultivation mode combining two years of no-till straw coverage with one-year deep loosening and burying of straw (NPT) and traditional rotational cultivation burial mode (RT) as a control and analyzed the characteristics of changes in soil organic matter carbon and its active components at different levels of nitrogen application, evaluating differences in soil organic carbon and soil quality in the short term. They say it's a study can provide a reference value for the early state of soil fertility and straw return modes in a grain production area model in the southern part of the Northeast Plain. Why only for this region? setting such a goal, it can be assumed that this assumption may have a chance of success in similar soil and climatic conditions.

Response 1: Firstly, we would like to express our sincere appreciation for your highly positive evaluation of our research. We strongly agree with your statement. The selection of the southern corn-producing region in the Northeast Plain is primarily based on our field investigation, which revealed a lack of proper straw returning methods in this area. Furthermore, the soil and climate types in this region are representative to a certain extent. Therefore, our study can provide valuable references for the impact of straw returning on soil organic carbon under warm-temperate continental climates and brown soil conditions. This part was mentioned already in lines 9-11 (Abstract) and 94-96 (Introduction) of the manuscript.

Comments 2: The description of the experimental material lacks information and where the information about environmental data, e.g. rainfall, temperature and soil data, comes from.

Response 2: Agree. I added this section and modified Figure 1, and marked it in red on lines 123-127 of the manuscript.

Comments 3: Since the experiments are planned in a split-block system, the plot size should be given, e.g. 15m2.

Response 3: Agree. In the experimental design section of the manuscript, I have given the total number of plots as well as the plot size. They are marked in red on the fourth page of the manuscript, lines 137-138. If you think this expression is inappropriate here, please be sure to mention it!

Comments 4: There is practically no statistical analysis - only ANOVA, there are only calculations, and this makes it difficult to draw correct conclusions.

Response 4: I greatly agree with your suggestion that although most of our research content is based on analysis of variance, the trend of change between the data analyzed through the results in this article is obvious and more significant differences (e.g., Figure 2). As well as each treatment was compared using 3 replications followed by averaging, statistical analysis was performed through the internationally widely recognized statistical analysis software SPSS 23.0 from IBM. And our experiment is a long-term orientation experiment, we will do more intensive and detailed in the future research.

Comments 5: The Excel package is also not very scientific.

Response 5: Thank you dearly for your reminder, I agree with your valuable comments, for the application of Excel software I just use it for the calculation and organization of the experimental data, it may be that the data analysis part of my manuscript (page 6, lines 231-238) is not clearly expressed, I have rewritten this part.

Comments 6: The presentation of the results in the form of graphs is difficult to read.

Response 6: I agree with your valuable comments, in addition to the graphical representation of my data results, we have also put in the supplemental file a data table representation to illustrate the data results, and in order to make it easier for you to review, as well as the aesthetics of the article layout required by the journals, we are going to include a tabular representation in the results section (e.g., Figure 2, Table S3). The results of the modifications have been highlighted in red.

Comments 7: Chart 2 needs improvement, is illegible and may be misleading.

Response 7: Sorry English is not my first language, by "chart 2" do you mean "figure 2" in the article, whether it is "figure 2" or not I have modified figure 2 to make it more recognizable. If it is Table 2, I have also modified it to make it more complete.

Comments 8: Presenting the results in tables with only the level of significance is not sufficient in my opinion. It would be good to supplement it with the share of variance components.

Response 8: Thank you very much for reviewing this section, we strongly agree and we have changed the presentation of Tables 1 and 2 as you requested and have also revised the presentation related to this section. Although the content of lines 264-268 on page 7 has been revised, it does not affect the overall content of the whole text or other contents.

Comments 9: In the conclusions, I lack justification for the innovativeness of this study, emphasizing the contribution to the development of the discipline.

Response 9: I agree with your comments, and I have changed and improved the conclusion section by adding a statement on innovativeness and on discipline development. Changes are marked in red on page 14, lines 527-532.

1. Summary

Dear Reviewer, thank you for your valuable comments which made my article better. We have reorganised the article to accentuate the sections that are novel and would like and kindly request you to reconsider our article as we believe that this study is scientifically important. All changes in the article are highlighted in red font and my point-by-point response is provided below.

2. Point-by-point response to Comments and Suggestions for Authors

Comments 1: Abstract: objectives are missing.

Response 1: Dear reviewers, the objective of our study focused on the issues of backward straw return technology and blind fertilization in the southern part of the maize-producing area in the Northeast Plain of China (Page 1, lines 9-11 of the text). And to explore the optimal return mode based on two straw return modes combined with three nitrogen application rates under the premise of ensuring carbon sequestration and increasing corn yield (Page 1, lines 17-18 of the text).

Comments 2: L115: soil background information sampling depth should be the same as following treatment depth (40 cm).

Response 2: Dear reviewers, thank you for asking us this question. At the first experiment, the nutrient content of the 20-40 cm soil layer was not measured, but this issue does not have an impact on the results of this study. Moreover, rotary tillage (RT mode) of the soil has been the main tillage method in the area before the experiment in our study, and the effect of organic carbon in the 0-40 cm soil layer of RT mode has been discussed in depth in this paper.

Comments 3: L148: will be -> was.

Response 3: Changes have been made as you requested and are highlighted in red on page 5, line 157 of the text.

Comments 4: for the RT mode, since the straw was almost completed cleared from the soil surface, why no-till planter was used? Please clarify.

Response 4: Dear reviewer, thank you for your question, for the RT model we did not remove the straw completely, but crushed it and retained it on the surface, and then the combined rotary tiller turned it into the soil. Maybe my narration was not clear enough to mislead you, I have made a refinement to that part (page 5, lines 158-159). The no-till planter is equally applicable to the RT model and was used to maintain the same experimental conditions as the other tillage models.

Comments 5: Results: please rearrange the text and figures so that the figures will appear after the paragraph first mentions it.

Response 5: I agree with you, I've rearranged the text and figure (Page 9, part 3 of the results).

Comments 6: Statistical analysis: please clarify if different soil layers were compared together among treatments.

Response 6: It is highly agreeable to you and we have changed the data analysis section and marked it in red on page 6, lines 231-238.

Comments 7: Table 1: please explain why there are so many significant interaction between tillage and fertilization treatments.

Response 7: I strongly agree with your comments and thank you for your valuable comments. I have re-analysed the content of Table 1 and corrected the significance issue in the table, which is mainly in lines 264-268 (in red) in the article, but it does not affect the content of the article as a whole and the content of the analysis section afterwards.

3. Response to Comments on the Quality of English Language

Dear reviewer, thank you for your proposal, which will be a better article for me. We apologise for the poor language of the manuscript. We spent a long time on the manuscript, repeatedly adding and deleting sentences and sections apparently resulting in poor readability. We hope that this revision will further improve the readability and grammar of the article. If there are still problems, please mention them so that we can revise them!

1. Summary

Dear Reviewer, thank you for your valuable comments which made my article better. We have reorganised the article to accentuate the sections that are novel and would like and kindly request you to reconsider our article as we believe that this study is scientifically important. All changes in the article are highlighted in red font and my point-by-point response is provided below.

2. Point-by-point response to Comments and Suggestions for Authors

Comments 1: L10 line: southern part of Northeast Plain?

Response 1: Dear reviewers, the Northeast China Plain is the largest plain in China, and because of the diversity of soil and climatic conditions in this large area (mentioned in lines 94-95, page 3 of the text), we therefore use the term " southern part of Northeast Plain " to describe the location of our study, which is mentioned in the section on Materials and Methods (mentioned in lines 113-114, page 3 of the text).

Comments 2: L13 line: how would two return modes both work as control?

Response 2: I strongly agree with your comments and thank you for your valuable comments. I have changed this part of the text and highlighted it in red on page 1, line 13 in the text.

Comments 3: L117: NH4+NO3?

Response 3: Thank you for the reminder that the indicator is soil alkali-hydrolyzable nitrogen, I have revised that section (page 4, line 121).

Comments 4: L122: Change the x-axis from number to month.

Response 4: I agree with you, and have corrected Figure 1 and added temperature data for 2018-2020 (page 4, lines 126-127).

Comments 5: L124: add a diagram of your experiment design with main plot, subplot, and replications included.

Response 5: I agree with your proposal and I have added the schematic diagrams on the experimental design for the main plot, subplot, and replications (lines 144-146 on page 4).

Comments 6: L154: Add a corresponding citation.

Response 6: I have understood your suggestion that the "five-point sampling method" is just what we are customary to use, but it is statistically correct, and I have re-described the sentence (page 5, lines 164-165).

Comments 7: L221: Add more details to this section, such as, the model, the treatments you compared, the normality and homogeneity tests you have ran. Put as much details as you can.

Response 7: It is highly agreeable to you and we have changed the data analysis section and marked it in red on page 6, lines 231-238.

Comments 8: L229: Make the soil readable.

Response 8: I agree with you and I have changed this part of the description (lines 242-246 on page 7).