A New Idea to Improve the Test Method of Soil Aggregate Stability for Soils with a Texture Gradient

Round 1

Reviewer 1 Report

Comments for author File: Comments.pdf

Author Response

Response to Reviewer comments

Reviewer #1

The submitted MS is focused on aggregate stability mechanisms, and the potentially staged experiments and the results obtained look worthy of publication in the journal. However, at this point it is difficult to assess the real value of the manuscript due to several major shortcomings: poor structure in the article (results and discussion contain parts that should be given in methods and results, respectively); the methods lack the necessary information about the measurement parameters or references; the design of the experiment is not clearly described; hypotheses need clarification; much of the discussion is devoted to discussing the phenomena in general instead of mainly describing the contribution of the results to the existing understanding of hydrophobic phenomena. The discussion should therefore be shortened or restructured, starting with a discussion of your findings.

Response: Thank you for your constructive comments. We tried our best to improve the manuscript according to your comments.

 

Question 1: add line numbering.

Response: Thank you so much for your suggestion. We have added line numbering in the revised manuscript.

 

Question 2: figure 6 and table 5 should be placed and described within results part firstly.

Response: Thank you very much. Because the purpose of section 4.2 was to discuss the contribution of clay and cation exchange capacity to the aggregate breakdown index and its limitations, it became an important part to analyze the correlation between clay percentage and cation exchange capacity and aggregate breakdown index. Based on this, to better explain the significant negative correlation between clay percentage and aggregate breakdown index, it is also an effective means to explore the micromorphology characteristics of soils with a texture gradient. Therefore, we think the Figure 6 and Table 5 should not be placed and described within results part.

 

Question 3: try to reduce the amount of vague language, e.g.:.

Response: Thank you very much for your comments. We have replaced the “e.g.” with “such as”.

 

Question 4: Fig. 2 separate it to two distinct figures, first–with ethanol and hexane dispersion) and 2nd with hexane and deionized water dispersion.

>> immersion time (a and b)

which time?

>> F 2-0.25 mm indicates that initial aggregates are crushed to a grain size of 2- 0.25 mm. F < 0.25 mm indicates that initial aggregates are crushed to a grain size of < 0.25 mm.

not clear. does it mean, that after the aggregate stability test during time “a” aggregates had size less <2 mm, and after time b < less than 0.25 mm? clarify it within the results, if so.

Response: Thank you very much for your constructive comments. We have separated the Figure 2 to two distinct figures, namely Figure 2 and Figure 3 in the revised manuscript, and revised the corresponding descriptions about F 2-0.25 mm and F < 0.25 mm (Lines 227-231).

 

Question 5: Fig. 3 add a significant difference.

Response: Thank you very much for your comments. We have added a significant difference in the revised manuscript (Figure 4).

 

Question 6: Bot sure if Figure 4 is necessary, it doesn't seem to add anything compared to Table 3. Besides, you have the same dimensions of the indicator, but completely different values. apparently, figure 4 shows the percentage variability of the indicator, which is already expressed as a percentage -- hard to understand.

Response: Thank you very much for your detailed comments. The table 3 was mainly used to indicate the difference among the treatments, while the Figure 4 was mainly used to show the changing trend of aggregate breakdown index with increasing immersion time. To avoid redundancy, the table 3 was placed in Appendix (Table A3).

 

Question 7: Table 2 add the coordinated of soil sites.

Response: Thank you very much for your suggestion. We have added latitude and longitude of corresponding sampling points (Table 2).

 

Question 8: This indicates that the hydrophilic groups (-OH) contained in ethanol can act on the surface of soil particles.

“can act on the surface”—clarify.

Response: Thank you very much for your detailed comments. Soil particles contain both hydrophilic and hydrophobic surfaces. When ethanol contacts soil aggregates, not only ethanol can fill the pores of aggregates, but also the hydrophilic groups (-OH) contained in ethanol can be arranged on the surface of particles. This process causes swelling of soil aggregate (Shao and Chen, 1980; Xiong and Chen, 1990). Therefore, we describe that the hydrophilic groups (-OH) contained in ethanol can act on the surface of soil particles. However, because the “act on” is not easy to understand, we believe that it is appropriate to change the “act on” to “interact with”. Therefore, this sentence can be described as the “hydrophilic groups (-OH) contained in ethanol interacted with the hydrophilic surface of soil particles” (Lines 29-30).

The relevant references are listed as follow:

1. Xiong, Y., Chen, J.F., 1990. Properties of soil colloid. China Science Press, Beijing (in Chinese).
2. Shao, Z.C., Chen, J.F., 1980. A primary study on the soil hydrophilicity. Acta Pedologica Sinica. 17, 267-274 (in Chinese).

 

Question 9: To prevent interference between different breakdown mechanisms.

Please, add some comments about this difference–not all researches will correctly guess what you mean.

Response: Thank you very much for your suggestion. We have added corresponding descriptions about distinguishing different breakdown mechanism (Lines 68-72).

 

Question 10: However ethanol is.

Very complicated sentence. Try to simplify this part.

Response: Thank you very much for your comments. We have simplified it in the revised manuscript (Lines 72-78).

 

Question 11: Both of these liquids.

It’s better to write clearly “Both water (?) and ethanol (?) act on..”

Also try to use strict description of action instead “act on”

Response: Thank you very much for your suggestion. We have modified relevant descriptions in the revised manuscript (Lines 78-79).

 

Question 12: it may not be appropriate to

approtiate to select for what? maybe to distinguish of ?? from ?? by ethanol

Response: Thank you very much. In this study, to verify the speculate that it may not be appropriate to select ethanol and water solutions as raindrop materials to distinguish mechanical impact caused by raindrops and slaking caused by soil hydrophilicity in previous studies during rainfall, we compared the aggregate breakdown index of soil undergoing ethanol and hexane dispersion. Our results showed that hydrophilic groups (-OH) contained in ethanol can interact with the hydrophilic surface of soil particles. Therefore, we believe it is appropriate to select hexane solution instead of ethanol to prevent interference between different breakdown mechanisms. Meanwhile, we have modified corresponding description of this paragraph to ensure it more logical in the introduction section (Lines 68-84).

 

Question 13: the above four

not clear

it becomes especially unclear about the 4 types when you use three active liquids below

Response: Thank you very much for your suggestion. We have modified it and adjusted the position of the relevant description according to your comments (Lines 54-57).

 

Question 14: have different mechanisms for soil aggregates fraction

describe more strictly four mechanisms of soil interactions with different liquids. maybe the simply figure describing these mechanisms can help. but if you have not time on it, try to clearly distinguish them in text.

Response: Thank you very much for your suggestion. We have added the descriptions about different aggregate breakdown mechanisms in the revised manuscript according to your comments (Lines 51-57).

 

Question 15: from “Natural soil…” to “percent and CEC.”

These paragraphs will be more logical if will be placed before the description of the difference of liquids.

Response: Thank you very much for your suggestion. We have adjusted the position of the relevant descriptions according to your comments.

 

Question 16: On the basis of two polar liquids (deionized water and ethanol), to determine whether the hydrophilic groups contained in ethanol can act on hydrophilic parts of soil particle surface, Finish the first sentence here. a nonpolar solution with a hydrophobic group was also selected as another soaking solution.

And describe why you used nonpolar.

Response: Thank you very much. The main purpose of this study is to verify whether the hydrophilic groups contained in ethanol can interact with hydrophilic parts of soil particle surface. Therefore, it is necessary to select an absolutely hydrophobic liquid to compare with ethanol, namely nonpolar liquid.

 

Question 17: After we comprehensively analysed the boiling point, density, surface tension, polarity, volatility and other factors of various non- polar solutions,

may be deleted – do not help.

Response: Thank you very much for your suggestion. We have deleted it.

 

Question 18: To verify our theoretical speculation that ethanol with hydrophilic group can act on hydrophilic parts of soil particle surface;

not a clear hypothesis -- it is impossible to disprove it with this wording.

Response: Thank you very much for your suggestion. We have modified it in the revised manuscript (Lines 109-110).

 

Question 19: This study provides guidance for determining the stability of soil aggregate in the future.

oddly sentence, and redundant in the intro part. maybe can placed in abs or/and conclusions after correction.

Response: Thank you very much for your suggestion. We have deleted it.

 

Question 20: respectively

nothing to match

Response: Thank you very much for your suggestion. We have deleted it.

 

Question 21: X-ray diffraction revealed that the clay mineral of the test soils was mainly illite/smectite mixed-layer and illite.

reference to published data on these objects or other proof.

Response: Thank you very much for your suggestion. We reference to published data.

The relevant references are listed as follow:

Li, J., Zhong, S., Han, Z., Gao, P., Wei, C., 2022. The relative contributions of soil hydrophilicity and raindrop impact to soil aggregate breakdown for a series of textured soils. International Soil and Water Conservation Research. 10, 433-444.

 

Question 22: The particle size distribution (PSD) was measured by Laser diffraction particle size analyzer.

add the parameters of analysis and description of pretreatment, or the reference, where described method details.

Response: Thank you very much. According to your comments, we have added the specifying sample preparations and optical parameters (Lines 120-125).

 

Question 23: SEM

the same according to which it was performed (ref), which parameters where determined.

Response: Thank you very much for your suggestion. According to your comments, we have added the specifying parameters (Lines 125-127).

 

Question 24: 2.2. Soil sample treatments

Soil aggregate fractionation

Response: Thank you very much for your suggestion. We have changed “Soil sample treatments” to “Soil aggregate fractionation” (Line 131).

 

Question 25: by static disintegration method

reference needed

Response: Thank you very much for your suggestion. We have added reference in the revised manuscript (Line 140).

 

Question 26: Before the experiments, to ensure a constant matric potential, the test soil aggregates were oven dried at 40°C (24 h)

to the 2.2 part.

Response: Thank you very much for your suggestion. We have transferred “Before the experiments, to ensure a constant matric potential, the test soil aggregates were oven dried at 40°C (24 h)” to the section 2.2 (Lines 134-136).

 

Question 27: six soil aggregates // 50 g soil

not clear what quantity of soils was really used

Response: Thank you very much. We have modified it for a better understanding (Lines 140-146 and Lines 157-158).

 

Question 28: As shown in Table A1, there was no significant difference in the aggregate stability index (ASI) after 100 min. // As shown in Table A2, there was little change in ASI among the various soaking times when ethanol and hexane were used as the soaking solutions.

not clear, is the first part about experiment with water? Clarify.

Response: Thank you very much for your suggestion. We have supplemented it (Lines 142-143).

 

Question 29: ASI and ABI

please, decode, and the references, if these indices are introduced before

Response: Thank you very much for your suggestion. We have added references in the revised manuscript (Lines 173-174).

The relevant references are listed as follows:

1. Li, J., Zhong, S., Han, Z., Gao, P., Wei, C., 2022. The relative contributions of soil hydrophilicity and raindrop impact to soil aggregate breakdown for a series of textured soils. International Soil and Water Conservation Research. 10, 433-444.
2. Hou, T.Y., Berry, T.D., Singh, S., Hughes, M.N., Tong, Y.N., Papanicolaou, A.N.T., Wacha, K.M., Wilson, C.G., Chaubey, I., Filley, T.R., 2018. Control of tillage disturbance on the chemistry and proportion of raindrop-liberated particles from soil aggregates. Geoderma, 330, 19-29.

 

Question 30: The contribution of soil hydrophilicity (hydration) (CSH).

to methods part.

Response: Thank you very much for your suggestion. We have transferred the calculated method of the contribution of soil hydrophilicity (hydration) to section 2.3 (Lines 192-196).

 

Question 31: Lines 206-208: When soil aggregates were crushed to a grain size of 2-0.25 mm, from S1 to S6, the average contribution of hydration on aggregate breakdown is 99.83%, 99.80%, 99.59%, 98.67%, 97.56% and 96.78%, respectively (Fig. 3).When initial soil aggregates were crushed to a grain size of 2-0.25 mm.

I can't understand from your article what is meant here. according to the methods, you worked with one fraction of aggregates 2-0.25 mm. there may be nothing wrong with the methods, but you should present the results differently.

Response: Thank you very much for your suggestion. The 2-5 mm soil aggregate were selected as test materials instead of 2-0.25 mm aggregates in this study. Meanwhile, we have revised corresponding descriptions about “When soil aggregates were crushed to a grain size of 2-0.25 mm, from S1 to S6, the average contribution of hydration on aggregate breakdown is 99.83%, 99.80%, 99.59%, 98.67%, 97.56% and 96.78%, respectively” (Line 217 and Line 220).

Question 32: The enrich ratio (ER)

methods

Response: Thank you very much for your suggestion. We have transferred the calculated method of the enrich ratio (ER) to section 2.3 (Lines 197-201).

 

 

We would like to give special thanks to you for your constructive comments. All of your suggestions were very insightful and have provided significance guidance for our manuscript and future research. We tried our best to improve the manuscript and have made changes accordingly. If you have any further questions or concerns, please let us know.

Author Response File: Author Response.docx

Reviewer 2 Report

Pay attention to the rules of the English language

Author Response

Response to Reviewer comments

Reviewer #2:

Pay attention to the rules of the English language.

Response: Thank you for your constructive comments. The English writing of the manuscript has been carefully edited by native English-speaking editors at AJE Language Editing Services.

We would like to give special thanks to you for your constructive comment. We have studied your comment carefully and have revised English language of the paper as suggested. If you have any further questions or concerns, please let us know.

Author Response File: Author Response.docx

Reviewer 3 Report

The paper presents interesting methodological investigation on stability of aggregates of soils with different texture with an emphasis on the role of hydration on aggregates breakdown. There are some aspects which need clarifications and are marked in the attached file. The main one concerns the estimation of the factors influencing the ABI (section 3.2 and discussion)  as it is not pointed out which soaking solution was considered for ABI data.

There are some questions and suggestions for editing the text provided in the attached file.  What do you mean for "effective particles" in Eq. 6?

Comments for author File: Comments.pdf

Author Response

Response to Reviewer comments

Reviewer #3:

The paper presents interesting methodological investigation on stability of aggregates of soils with different texture with an emphasis on the role of hydration on aggregates breakdown. There are some aspects which need clarifications and are marked in the attached file. The main one concerns the estimation of the factors influencing the ABI (section 3.2 and discussion) as it is not pointed out which soaking solution was considered for ABI data.

Response: Thank you for your constructive comments. We have made relevant modifications according to your comments.

 

Question 1: Line 21: Needs revision.

Response: Thank you so much for your comments. We have modified it in the revised manuscript (Line 21).

 

Question 2: Lines 53-58: Can be explained better.

Response: Thank you so much for your comments. We tried our best to improve it in the revised manuscript (Lines 73-78).

 

Question 3: Line 62: Needs clarification.

Response: Thank you so much for your comments. We have modified it to ensure more logical in this paragraph (Lines 54-57).

 

Question 4: Lines 89-90: Needs revision.

Response: Thank you so much for your comments. According to the comments, we have modified it in the revised manuscript (Lines 98-100).

 

Question 5: Table 2: Is it SOM or SOC? pH in H2O?

Response: Thank you so much for your comments. In the hilly regions of the Sichuan Basin, China, the content of soil organic matter is usually around 1% (Zhong et al., 2019; Li et al., 2020; Li et al., 2022). Meanwhile, to avoid the interference of organic matter when exploring the influence of soil texture on the hydraulic stability soil aggregate, we select soils with low organic matter content. Besides, the pH was measured with a pH meter (soil:water = 1.0:2.5)

The relevant references are listed as follows:

1. Zhong, S., Han, Z., Du, J., Ci, E., Ni, J., Xie, D., & Wei, C., 2019. Relationships between the lithology of purple rocks and the pedogenesis of purple soils in the Sichuan Basin, China. Scientific Reports, 9(1), 13272.
2. Li, J., Han, Z., Zhong, S., Gao, P., & Wei, C., 2020. Pore size distribution and pore functional characteristics of soils as affected by rock fragments in the hilly regions of the Sichuan Basin, China. Canadian Journal of Soil Science, 101(1), 74-83.
3. Li, J., Zhong, S., Han, Z., Gao, P., Wei, C., 2022. The relative contributions of soil hydrophilicity and raindrop impact to soil aggregate breakdown for a series of textured soils. International Soil and Water Conservation Research. 10, 433-444.

 

Question 6: Line 126: Please explain what do you mean.

Response: Thank you so much for your comments. According to the comments, we have modified it in the revised manuscript to ensure better understanding (Lines 140-141).

 

Question 7: Line 132: set of two sieves with 2 and 0.25 mm openings.

Response: Thank you so much for your comments. According to the comments, we have modified it in the revised manuscript (Lines 145-146 and Lines 157-158).

 

Question 8: Line 134: What kind of fresh-keeping film was used?

Response: Thank you so much for your comments. polyvinylidene chloride fresh-keeping film was used in this study.

 

Question 9: Line 150: Why do you choose to dry the samples at 50°C instead of 105°C?

Response: Thank you so much for your comments. In order to not influence the subsequent determination of microaggregates and particle composition, we used low-temperature drying to obtain samples masses. Meanwhile, we referred to the temperature settings of previous related studies, and the final temperature was set to 50 °C.

The relevant references are listed as follows:

1. Pihlap, E., Steffens, M., & Kögel-Knabner, I., 2021. Initial soil aggregate formation and stabilisation in soils developed from calcareous loess. Geoderma, 385, 114854.
2. Hou, T., Berry, T. D., Singh, S., Hughes, M. N., Tong, Y., Papanicolaou, A. T., Filley, T. R., 2018. Control of tillage disturbance on the chemistry and proportion of raindrop-liberated particles from soil aggregates. Geoderma, 330, 19-29.
3. Xiao, H., Liu, G., Zhang, Q., Fenli, Z., Zhang, X., Liu, P., Abd Elbasit, M. A., 2018. Quantifying contributions of slaking and mechanical breakdown of soil aggregates to splash erosion for different soils from the Loess plateau of China. Soil and Tillage Research, 178, 150-158.

 

Question 10: Section 3.2: It is not clear in this section which solution was used for the presented ABI data. Maybe deionized water as pointed in the title of Table 5?

Response: Thank you so much for your comments. According to the comments, we have modified it in the revised manuscript (Line 241 and Lines 256-257).

 

Question 11: Line 340: ABI for which test solution?

Response: Thank you so much for your comments. The ABI mentioned in section 4.2 indicates the aggregate breakdown after soil aggregate immerse in water solution. We have modified it in the revised manuscript (Line 336).

 

Question 12: Line 343: Please define what do you mean for total ABI.

Response: Thank you so much for your comments. The total ABI is the ratio of the total mass of 2-0.25 mm broken aggregate fractions and < 0.25 mm broken aggregate fractions to the mass of the initial soil aggregates. We have defined it in Table 4 in the revised manuscript (Lines 370-372).

 

Question 13: What do you mean for "effective particles" in Eq. 6?

Response: Thank you so much for your comments. The effective particles are particles that have not undergone digestion (removal of organic matter and calcium carbonate) and dispersion pretreatment (chemical dispersion with sodium hexametaphosphate and physical dispersion with ultrasound).

                                                                                

 

 

We would like to give special thanks to you for your constructive comments. All of your suggestions were very insightful and have provided significance guidance for our manuscript and future research. We tried our best to improve the manuscript and have made changes accordingly. If you have any further questions or concerns, please let us know.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The authors have revised the MS well according to the comments. Therefore it can be accepted for publication in this form.