Effect of Soil Configuration on Alfalfa Growth under Drought Stress
Round 1
Reviewer 1 Report (Previous Reviewer 2)
Thank you to the authors for revising their response letter and manuscript as much as possible. Below are outstanding comments for the authors to improve their paper.
- Most of the line numbers referred to in the response letter did not correspond where the actual corrections were in the revised manuscript which made it difficult to follow the revisions but I appreciate your attempt.
- There seem to be fundamental misunderstanding of the use of the van Genuchten model in this manuscript. The van Genuchten model can be used to estimate soil water content ( θ), soil water potential (h), hydraulic conductivity (K). The van Genuchten. I still do not know how diffusion rates were calculated using the van Genuchten equation. I suggest the authors add an appendix where they explain those calculations where the van Genuchten model was used to calculate diffusion rates.
- According to the response of the authors to my comment below, they explained how diffusion rates were calculated, but I still do not see where that explanation was given in the manuscript. This is where the authors should have copied the section where the explanation was given here so I can directly verify but that was not done:
“Point 35: Line 252: How were soil diffusion rates measured? Was this the same as the soil hydraulic conductivity values calculated using the van Genuchten model?
Response 35: It was also calculated using the van Genuchten model. We added a explanations to this in the position where the equation was firstly mentioned.”
Is the sentence below where the authors refer to as the explanation given? If yes, then I don’t think that is adequate explanation since non of the variables or parameters defined by the authors in the paper refer to diffusion rates.
” The equation[22] is as follows, and soil diffusion rates discussed in this paper was also measured using this equation.”
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report (Previous Reviewer 1)
The manuscript has been improved. However, the authors stated in their response letter 'Dear editor and reviewers, these are all the corrections we can finish within the given time. We’re afraid we can't correct all. Hope these will not affect the acceptance of the paper. We will continue checking and improving, but it might take longer time', I believe the authors would need more time to revise the manuscript to address the major concerns (under 'general comments', the authors skipped those comments in their response letter) from me and the other reviewer in order to meet the standard of publication at Sustainability.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report (Previous Reviewer 1)
I appreciate the efforts that the authors made to improve the manuscript. The manuscript has been greatly improved. Be mindful of some formatting issues (for example, L30 should have a blank space after 'cm', L212 should have a blank space between 'can' and 'attribute', L260 has repeated periods, and L266 has redundant blank space). In addition, I suggest that the authors add a footnote to explain why some values are missing and what A-J means in Table 3.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.
Round 1
Reviewer 1 Report
General comments:
The manuscript “Effect of Soil Configuration on Alfalfa Growth Under Drought Stress” investigated the impact of different topsoil reclamation strategies on alfalfa growth through a pot experiment. The topic investigated is meaningful and would be of general interest to the audience of Sustainability. However, I think this work lacks a proper research background setup as well as an in-depth discussion associated with the results. Therefore, it provided limited insights into the current stage and future perspectives regarding the application. Moreover, the writing is hard to follow because of grammar issues and fragmented sentences. My suggestion is rejection, but I think the paper might meet publication standards after extensive revisions.
Specific comments:
L15. Awkward sentence.
L23. Avoid using ‘treatment I and J’ in the abstract because readers would want to know what those refer to.
L25-28. Please emphasize the novelty of this work. It is not clear whether such findings have been reported by others in the past.
L36. Fix the grammar problem.
L40. Try using different texts in the abstract and intro.
L51-62. Try shortening this section. Lots of texts here are associated with well-known theories that did not need to be explained in great detail.
L68. There is a large gap between the intro and the objectives. The objectives need to be better justified. For example, why is alfalfa used as a test subject? What does ‘configuration’ mean in this context, and how did the authors decide on the specific configurations?
L164. Label the treatments in the caption.
L231. Is this the matric potential for soil or leaf? The caption did not match the text on the Y-axis.
L237. Fix the grammar error.
L289-297. How much of this has been known? What were the findings from previous work, and how did those compare with your study? In-depth discussion should be added as well as future work. For example, what research gap did this study try to fill? How far are we from moving a pot study like this to actual reclamation applications?
L301. Add a blank space between ‘alfalfa’ and ‘and’.
Reviewer 2 Report
Comments for authors
This study examined the impact of adding montmorillonite-enriched sandstone to sandy soil in restoring vegetation through soil column experiments. Alfalfa was grown in the soil columns and the water retention and hydraulic conductivity of the soils were measured coupled with water potential measurement of the leaves of the alfalfa. Overall, the paper addresses important questions for improving soil’s ability to support plant growth, especially in degraded soils. I commend the effort made by the authors to measure different parameters in the soil columns and for attempting to connect their data to a recommendation of the mixture of soil types that can support the growth of alfalfa.
However, there are several critical methodological issues that must be addressed to improve the understanding and replicability of the methodology. The introduction should also be expanded to discuss previous similar studies and the research gap that led to this study. Results of similar studies in the literature should also be compared in the discussion section. I suggest thorough proofreading for some grammatical errors.
Below are specific comments in the various sections of the paper that the authors need to address.
Abstract
1. Line 23: I suggest describing what the letters I and J mean in the abstract so a reader can understand the abstract as a standalone document.
2. Line 25: "It" should be specified
3. Line 26: Please specify what you mean by other high-moisture soil materials .
4. Line 27: Please replace the word "formula" with a suitable word.
Introduction
1. The introduction needs to be broken into separate paragraphs where each paragraph talks about a main topic. Currently, there are only two paragraphs with the first paragraph running more than 30 lines. Please break your intro section into at least 4-paragraphs.
In addition, the authors should discuss previous studies involving the use of composite soils to investigate how that affects plant water uptake and survival in plants. The introduction currently lacks adequate consideration of previous related studies.
2. Lines 44-47: Please break this sentence into two.
3. Line 50: What do the authors mean by the "root content". Should it be "root length density"?
4. Line 67: A connecting paragraph before the last paragraph stating the objectives is required. This connecting paragraph should highlight the novelty of the study and provide concluding remarks on the rationale of the study, and how they lead up to the objectives of the study.
5. Line 68: Please specify which region you are referring to.
6. Line 69: What is the definition or meaning of "soil configuration"?
7. Line 68-74: This sentence is too long. Please break it down into shorter sentences that clearly state the objectives of the study.
Methods
1. Line 80: Please clarify why alfalfa was chosen as the testing species?
2. Line 81: The mechanical composition of what?
3. Line 80: Can the authors elaborate on how a cutting ring was used to determine soil water characteristics?
4. Line 84: Are 1.40 g/cm3 and 1.65 g/cm3 the bulk densities of the soil? If so, please specify.
5. Line 85: Please specify numerically what you mean by " a certain amount".
6. Line 86: How were the samples filled into the cutting ring? Were they compacted to a specific density?
7. What was the diameter of the cutting ring?
8. Were the samples wetted? How much water was used to wet them?
9. Line 87: Please elaborate on what the high-speed centrifuge was used to measure in the samples.
10. Line 88: So many details are left out here. How was data for the soil water retention measured? Please elaborate.
11. Line 89: This equation is the van Genuchten model for describing the water content as a function of the soil water pressure head for the range from saturation to the permanent wilting point. Please include those details and cite the original paper shown below:
Van Genuchten, M. T. (1980). A closed-form equation for predicting the hydraulic conductivity of unsaturated soils 1. Soil Sci. Soc. Am. J., 44(5), 892-898.
12. Table 1: Put all the units of measurement in parentheses. E.g. Sand (%)
13. Line 94: Ks (cm/h) should be the saturated hydraulic conductivity.
14. Line 109: From Figure 1, it looks like the 20 cm layer of sandy soil was only for G, H, I, and J but your statement is not clear on which columns had the 20 cm sandy layers.
15. Please consider adding an actual image of the experimental design to complement the schematic diagram shown in Figure 1.
16. Line 114: Please clarify what you mean by reducing interference from the external environment.
17. Line 115: Please clarify what you mean by the calculated fertilizer and why you are adding fertilizer to the soil columns. Secondly, what were these calculated values?
18. Line 120: Was the gravel added to all soil columns or just one soil column? Please clarify.
19. Line 121: Is there a reason why the soil columns were left to settle for 60 days?
20. Line 123: You can replace " until no water came out of the small hole at the bottom" with " until drainage stopped"
21. Line 124: Is this the 20 cm layer of sand you referred to in line 109? And which treatment had this top sandy layer? Please clarify.
22. Line 127: How were these holes dug in the soil columns and with what equipment? Please clarify.
23. Line 130: Please clarify what nutrients were provided to the plants.
24. Line 131: Please elaborate on how leaf water potential was measured and with what instrument.
25. Line 131-133: What was the above and below biomass from the dead treatments used for after drying?
26. Line 141: Please give details in your statistical analysis. What were the independent and dependent variables for the one-way and two-way ANOVA analysis? Were there any interaction factors for the two-way ANOVA? Did you test for the two key assumptions of ANOVA (normality and equal variance) before running ANOVA? Please give details.
27. What do you mean by "significance between treatments was compared using Tukeys' t-test "?
28. Line 143: You mention that ANOVA was used for the analysis and then here you mention Tukey's t-test. Please clarify.
Results
1. Line 147: From Figure 2, it appears the biomass quantity starts high at day 45 and then decreases up to day 65, but you report a gradual increase. Please clarify.
2. Figure 2: Even though you mention what A-J means in the methods section but I suggest you still define what the letters A-J mean in the figure caption so a reader can quickly interpret the figure without having to dig through the paper.
3. Line 153: Be consistent in how you refer to figures. Somewhere above you use "Figure 2" but here you use "Fig. 3"
4. Line 157: What equipment was this?
5. Table 2: The unit of water holding capacity is either volume per volume or weight/weight. Please clarify.
6. Line 197: Did you mean Table 1 here?
7. Table 3: should be moved below the paragraph it is first mentioned i.e. after line 216
8. Line 204: Why is there "Figure 1" in this line?
9. Lines 220-222: From Figure 4, It appears all treatments experienced a decreasing leaf water potential which was expected with time with drying, not just A,E, and F. Therefore, I disagree with the phrase "indicating that treatment I was the more suitable soil reconstruction module"
10. Line 222-224: The authors never mentioned that they measured chlorophyll and fluorescence ratios anywhere in the methods section, so where is this statement coming from?
11. Line 229: How was diffusivity measured or calculated? This was not mentioned in the methods section.
12. Figure: Please include a legend that describes what the symbols mean. Also, elaborate on Figure 4 caption. "Variation in leaf water potential" is not descriptive enough.
Discussion
1. Line 237: Should be "died" not "dying."
2. Line 252: How were soil diffusion rates measured? Was this the same as the soil hydraulic conductivity values calculated using the van Genuchten model?
3. Line 254: It is generally known that sandy soils have the highest soil hydraulic conductivity/ soil water diffusivity in saturated conditions but also have the lowest water retention. This seems to contradict your statement that "owing to the fact that sandy soil induces drought stress response in plants through low soil water conductivity and acts as a water retainer ". Please revise or clarify.
4. Line 251-256: Please break this sentence into two/three sentences and clarify why the soil diffusion rates were different in the treatments. I cannot see the connection between a high soil water conductivity in the sandy soil and how that enhances water retention. Please clarify.
5. Line 288-290: From your results, the following sentence may not be entirely accurate as the resprouting was seen in only some of the treatments and thus was dependent on the soil configurations in the columns. Please specify in your explanation: "This means that alfalfa can effectively prevent water losses by regulating its own growth characteristics and is able to sprout quickly when water conditions improve. "
Conclusion
Line 299: The use of the term diffusivity should be clarified in this paper. Diffusivity usually refers to the movement of solutes and water vapor but in this paper, it seems you were only dealing with the movement of water (hydraulic conductivity). I would suggest you keep your terminologies consistent with literature.
