Appropriate Water and Nitrogen Regulation Promotes Soybean Yield Formation and Improves Water–Nitrogen Use Efficiency

Response to Reviewer 2 Comments

1. Summary

Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisions/corrections highlighted/in track changes in the re-submitted files.

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

 Comments 1: Abstract: should revise again and summarize with important information.

Response 1: We thank reviewer 2 for his scientific advice. The authors have reworked the abstract of the manuscript, including elements such as the summary of important information and the overall sentence structure. (Lines 10-38)

Comments 2: Keywords: should rewrite with alphapitically order.

Response 2: We thank reviewer 2 for his scientific advice. The authors have corrected the keywords in the manuscript. (Lines 39-41)

Comments 3: Introduction: should revise again with more cleare.

Response 3: We thank reviewer 2 for his scientific advice here. Corrections have been made by the authors in the manuscript, as shown in detail in the manuscript. (Lines 95-98)

Comments 4: Figure 1: mension the source of map

Response 4: We thank reviewer 2 for his questions. The maps involved in the authors' manuscript were drawn by themselves using ArcGIS software, and there is no academic misconduct such as reusing images or stealing images from other authors.

Comments 5: Figure 2: mension the source of weather data

Response 5: We thank reviewer 2 for his scientific advice. The authors have added notes on the sources of meteorological data covered in the manuscript. (Lines 109-110)

Comments 6: (2.2. Experimental design): it is the best to add flowchart representing the exprimental design with one replicate

Response 6: We thank reviewer 2 for his professional advice. While the authors strongly agree with the suggestions made by the reviewers, the authors have expressed the layout of the experiment and the initial design plan of the experiment through textual descriptions in the manuscript as a way of demonstrating the completeness of this study in the hope of obtaining the approval of the reviewers.

Comments 7: (The experimental layout is shown in Figure 3): it is not satisfyed, should cleare one replicate included all treatments used in the present study

Response 7: Reviewer 2 is thanked for his scientific advice. Figure 3 shows information on the spacing of rows and film spacing of soybeans planted in the experiments of this study, as well as the planting method of soybeans (drip irrigation under film, flat crop, one drip irrigation tape controlling two rows of soybeans), and the authors of the text describe how replicates of each treatment are represented in this issue. (Lines 128-136)

Comments 8: (a portable photosynthesis tester (LI-6400XT)): add the version, compony, country for this instrument

Response 8: We thank reviewer 2 for his scientific advice. The authors have added versions, companies and countries to the two software involved in the manuscript. (Lines 156-157)

Comments 9: (Water-Nitrogen Use Efficiency): add refrence

Response 9: We thank reviewer 2 for his scientific advice. The authors have added references to those covered in the manuscript. (Line 191)

Comments 10: (IBM SPSS Statistics 26 software):write as: Statistical Package for Social Sciences (SPSS v. 26, IBM Corporation, Armonk, New York, USA)

Response 10: Thanks to reviewer 2 for more correct corrections here, which the authors have made in the manuscript. (Lines 210-222)

Comments 11: (Microsoft PowerPoint 2016 and Origin 2021.): add the version, compony, country

Response 11: We thank reviewer 2 for his scientific advice. The authors have added versions, companies and countries to the two software involved in the manuscript. (Lines 224-227)

Comments 12: Should add Standered error with all mean value for all data in table 2.

Response 12: We thank reviewer 2 for his scientific advice. The authors need to explain that in the manuscript, the data presented within Table 2 are the two factors involved in this study (moisture and nitrogen fertiliser) and whether or not there is a significance in the interaction between the two factors, as well as the F-values after ANOVA. Therefore, the authors preferred no standard error added.

Comments 13: Should add Standered error with all mean value for all data in table 4.

Response 13: We thank reviewer 2 for his scientific advice. The authors have added standard errors to all means of all data in Table 4 for those covered in the manuscript (Table 4). (Line 299-210)

Comments 14: (Figure 9): change to "Heatmap plot correlation ..........

Response 14: Thanks to reviewer 2 for more correct corrections here, which the authors have made in the manuscript. (Line 444)

Comments 15: (Discussion):  the discussion section is good, but need to more several studis with more explanation regarding all results reported in the current study.

Response 15: We thank reviewer 2 for his scientific advice. The authors have added a partial explanation of the results in the Discussion section. (Lines 480-536)

Comments 16: Should add the limations of the current study after the discussion section.

Response 16: We thank reviewer 2 for his scientific advice. The authors have added limitations of the current study in the Discussion section. (Lines 480-536)

Comments 17: (Conclusions): it is a good written, but need to summarize with more important results

also, should add a reccomandations

Response 17: We thank reviewer 2 for suggesting revisions that would have made it better here. The authors have revised the conclusion section of the manuscript accordingly. (Lines 564-569)

Response to Reviewer 3 Comments

1. Summary

Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisions/corrections highlighted/in track changes in the re-submitted files.

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

 Comments 1: Title: It does not follow the guidelines as the initial words should be capitalized. The title is also lengthy and confusing, needing modification! I suggest simplifying it to avoid repeating words.

Response 1: The suggestions made by reviewer 3 are much appreciated, and the authors have revised the title of the manuscript, including problems with initial capitalisation and lengthy content.

Comments 2: Abstract: The abstract has many issues and must be redone. It is outside the journal's guidelines as it exceeds the 200-word limit (see the instructions to authors provided by Agronomy - MDPI). I believe the first sentence is controversial and not supported by the literature, so I suggest eliminating it. Use a maximum of two sentences in the introduction of the abstract to convincingly justify your research. The objective must be added clearly. A methodology section should be added, as there are only treatment details. Results should be summarized, but specific important metrics or quantitative results of the study's findings should be incorporated into the new version. A general conclusion should also be provided. A graphical abstract should also be prepared to improve the study's understanding.

Response 2: The scientific issues raised by reviewer 3 are greatly appreciated. The authors agree with the reviewer's suggestion and have adjusted the relevant content in the abstract by deleting the first sentence of the abstract. Secondly, in the Methods section, the authors described the experiment as ‘Water and nitrogen regulation by drip irrigation under membrane for two consecutive growing seasons’.

Comments 3: Keywords: Do not repeat words already present in the title.

Response 3: Many thanks to reviewer 3 for raising this critical issue. The authors have revised the keywords. (Lines 44-67)

Comments 4: Introduction: The introduction does not contribute to the understanding of the work. It seems to me that studying irrigation levels and nitrogen fertilization does not bring any new information, so it is very important that the authors take care of this section. As it stands, the justification does not provide a foundation to convince the reader that the research is relevant. The problem is not presented clearly, making it difficult to understand the importance and relevance of this work. In short, the introduction is insufficient to understand the study's objective, although the objective is also not clear. The hypothesis was not presented, making it impossible to analyze whether the objectives meet the proposal. Thus, I suggest the authors add arguments to the introduction, focusing on the most relevant and important information for the study's context. Organize the introduction to follow a clear logical progression: general context, specific problem, importance of the problem, gaps in current knowledge, hypothesis, and study objectives. Paragraphs serve to divide subjects, so use shorter paragraphs and clear topics to facilitate reading. I also believe the last paragraph of the introduction should be rewritten, as what the work proposes should be informed in the objectives, and how the study was conducted should be informed in the materials and methods section. Thus, I suggest using the last paragraph to present the hypothesis (clearly) and the study's objectives (also clearly).

Response 4: Many thanks to reviewer 3 for suggesting revisions. The authors have revised the introductory section of the manuscript. (Lines 44-97)

Comments 5: Materials and Methods: The methodology is incomplete and needs further clarification of the proposed procedures. Many basic pieces of information are missing, and as presented, the reader would not be able to replicate the experiment. In fact, I think it is even difficult to understand if the methodology meets the study's objectives. More specific details about soil, climate, plant, water, and irrigation system would be useful. Characterize the material used in soybean sowing. Present physical parameters related to irrigation water. Characterize the irrigation system (material, pressure, flow rate, spacing, application intensity, irrigation efficiency, etc.). How was the water management of the irrigation carried out? This information is necessary, as well as graphs showing crop evapotranspiration, total and effective rainfall, soil moisture, etc. Provide information on soil preparation, such as acidity correction, fertility, and compaction. Here are other considerations:

Response 5: Many thanks to reviewer 3 for raising this critical issue. The authors describe the physico-chemical properties of the soils in the study area and specific indicators of climatic conditions in the Materials and Methods section of the manuscript (Lines 100-112). Also, the characteristics of the materials used for soybean sowing are mentioned in the Materials and Methods section, including details of irrigation and fertiliser application methods, equipment, and materials (Lines 118-127). In addition, irrigation water management was done by pump pressurisation using drip irrigation under membrane. Finally, there are deficiencies in soil compaction and other indicators, but the ploughed land will be deeply tilled before sowing, which will have less impact on seed germination and later root growth.

Comments 6: Line 100: Present the retention curve and values of field capacity and permanent wilting point. Physical soil data such as granulometry should also be presented. This is important for a study involving irrigation. The complete chemical analysis of the soil should also be presented for both soybean growing cycles. This is basic for a study that worked with soil fertility.

Response 6: Many thanks to reviewer 3 for raising this key issue. The research indicators involved in the Materials and Methods section of this study describe the physicochemical properties of the soil in the experimental field (e.g., information such as bulkiness, acidity and alkalinity), including growth indicator measurements, light and indicator measurements, yields, and water and nitrogen use efficiencies, etc. The direction of the soil physicochemical properties is not involved in the discussion in the manuscript, and the authors plan to delve deeper in their future research to explore the complete soil chemical changes in the growth cycle of the two soybeans.

Comments 7: Line 104: Provide daily information on solar radiation, maximum and minimum air temperatures, maximum and minimum relative air humidity, reference evapotranspiration (PM-FAO56). Remember that the study is about irrigation, and this information is fundamental for crop water management.

Response 7: Many thanks to reviewer 3 for raising this critical issue. In manuscript Figure 2, the average daily temperature and average daily rainfall for the two growing seasons of soybean are included; this meteorological data was provided by the local meteorological department, and there may be non-disclosability for data such as solar radiation; therefore, this study replaces some of the meteorological data by assigning latitude and longitude of the specific study area.

Comments 8: Line 106: I have a strong concern about this item. I see that two levels of irrigation were used to evaluate the impact of water restriction, and three levels of nitrogen fertilization were analyzed. It is crucial to understand the interaction between these management practices and the efficiency of water and fertilizer use. However, I see that each combination of irrigation and nitrogen levels was treated as an isolated treatment. I disagree with this approach, as the variance analysis should include the interaction between the two factors, providing valuable insights into how these combined treatments affect the variables of interest. Interaction analysis is crucial to better understanding the synergistic or antagonistic effects between irrigation and nitrogen fertilization, which are not evident when analyzing the factors separately. The absence of this analysis can lead to an incomplete interpretation of the results and make it difficult to understand how the treatments interact in agricultural practice. For farmers and resource managers, understanding these interactions is essential to making informed decisions about crop management practices. Therefore, I strongly recommend that the authors reanalyze the data, including the interaction between irrigation and nitrogen fertilization in the ANOVA. This will not only provide a more comprehensive understanding of the combined effects of the treatments but also result in more robust and applicable recommendations for agricultural management. But of course, besides the interaction, the control should be considered in the ANOVA, and an appropriate mean test should be performed.

Response 8: Many thanks to reviewer 3 for his suggestions. The authors also strongly agree with the view articulated by the reviewers that ANOVA should include the interaction between the two factors, providing valuable insights into how these combined treatments affect the variables of interest. Interaction analyses are critical to better understand the synergistic or antagonistic effects between irrigation and nitrogen fertilization that are not evident when the two factors are analyzed separately. Therefore, when the authors analysed the manuscript study, the significance analyses between treatments are presented as plots, as in Figures 4-Figures 8. For the significance analyses between water and nitrogen fertiliser and water-nitrogen interaction effects are presented through tables, as shown in Tables 2 and 3.

Comments 9: Line 178: This is not water use efficiency (WUE)! Water use efficiency is a physiological characteristic, usually carbon (CO2) assimilation by water transpiration. This equation deals with an agronomic characteristic, which in this case would be water productivity (WP). I also have doubts about what would be the numerator of this equation 3, whether it is dry or fresh mass. Regarding the denominator, is it ETo or ETc??? Or is it net or gross irrigation depth? Or is it the total water volume considering also rainfall? Regarding precipitation, is it total or effective precipitation?

Response 9: Many thanks to reviewer 3 for his suggestion. In the yield calculation of soybean, we usually use its dry weight as the final measure, so the numerator of formula 3 is the dry mass. Meanwhile, the denominator of formula 3 is ET, which represents the amount of water consumed over the full life span of the soybean. regarding precipitation, it is the total rainfall.

Comments 10: Results: The results section will change with the new statistical analyses, and I will make a new evaluation of the new version presented by the authors. However, I see that the current version presents several flaws, including lack of clarity and organization of the text, making the interpretation of the data confusing and disorganized. The descriptions of the results are inadequate, with a lack of quantitative details and specific statistical analyses, hindering the understanding of the differences observed between treatments. The interpretation of the graphs is superficial, and the figures are mentioned out of order, suggesting that all figures should be consolidated into a single section to facilitate reading. Problems of coherence and cohesion, besides the absence of justifications for the methods and analyses used, compromise the study's credibility.

Response 10: First of all, I would like to thank you for your careful review and valuable comments on our paper. We fully understand the concerns you raised about the results section, especially regarding the importance of clarity, organisation, data interpretation, quantitative details and statistical analysis. The authors have reorganised the structure of the results section to ensure that the descriptions are clearer and more organised and to avoid confusion in data interpretation. In addition, the authors further scrutinised the full text to ensure coherence and consistency across all sections to avoid compromising the overall quality of the study.

Comments 11: Discussion: The manuscript's discussion has critical flaws, including repetition of information and lack of cohesive structure. There are insufficient references, which undermines the text's credibility. The discussion lacks a critical and detailed analysis of the results, does not adequately address comparisons with previous studies, and fails to explore the implications of the findings. The statements are generalized and lack specific data to support them.

Response 11: The suggestions made by reviewer 3 are greatly appreciated. The authors have corrected the discussion of the manuscript, including the completeness of information, number of references, critical analysis, and limitations of the study, and the results of the corrections are presented in the manuscript. (Lines 480-543)

Comments 12: Conclusion: The conclusion of the manuscript needs improvement, as it should answer the objectives, which, in turn, should be provided at the end of the introduction clearly. The conclusion also lacks a critical and deep analysis of the implications of the results, not adequately discussing the potential impacts of the tested treatments.

Response 12: Many thanks to reviewer 3 for his suggestions. The authors have corrected the results of the manuscript and the revisions are presented in the manuscript. (Lines 545-562)

Comments 13: References: They are insufficient for the content of the manuscript.

Response 13: Many thanks to reviewer 3 for his suggestions. The relevant literature has been corrected and the revisions are presented in the manuscript. (Lines 577-668)