Influence of Water Erosion on Soil Aggregates and Organic Matter in Arable Chernozems: Case Study

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Dear Authors,

The submitted manuscript entitled Influence of water erosion on organic matter and soil aggregates of arable Chernozems: case study in the Central Russia Upland is an interesting topic taking into account the soil science and the potential for the soil protection and agriculture support. However, due to many uncertainties, low quality elements and debatable novelty it cannot be accepted in the present form, hence I suggest the major review.

First issue is the title. You have inluded Central Russia Upland as your research area, but the studies present only very limited local scale. Your case stusy is in this case soil transect.

Second issue is the quality of the figures. The readability of them is limited and the PCA plot is very hard for the interpretation. I suggest to perform Kruskall-Wallis test to check whether the data is appropriate for this type of analyses. Moreover, in the text it is written that the statistics were perform in R Software. According to my experience and the appearence of plots, they are not original plots from this software. Please write exactly which packages were used to calculate all your statistics.

Third issue. Due to the very local and limited soil samples, I cannot see any impact for the international studies on soil science. The number of samples should be increased, otherwise the article shoud be submitted to the national journal that focus on the local soil problems.

All the other detailed comments were included in the attached document.

Comments for author File: Comments.pdf

Comments on the Quality of English Language

No significant issues found. The manuscript is well written in terms of English.

Author Response

Dear Reviewer!

We sincerely thank you for the great work you have done in reviewing our article! We have tried to make the most of the corrections that you recommended. We also changed the title of the article, improved the quality of the figures.

As for the problem of locality of our research, which you mentioned in the review, we would like to emphasize that the soil we study is widespread in many regions of the world. Soils that can be identified as a Chernozem or its analogues in various classifications are widespread on the territory of the Eurasian and North American continents. In addition, since we chose Haplic Chernozem as the object of research exactly, this makes the results of our work potentially extrapolable to a wide range of soils with similar properties.

As for the volume of our samples, for the most part we tried to conduct studies with such a sample size that we could show the significance of the differences between the studied indicators. For this purpose, samples for most of our studies were selected from two soil catena (2 soil pits for each degree of water erosion, for a total of 6 soil pits). Unfortunately, we could not carry out the sampling and preparation of more soil thin sections, since the micromorphological method is extremely labour-intensive and is mainly used without repetitions. However, in our future work, we plan to improve this and focus on sampling more micromonolites and making more soil thin sections, respectively.

We would like to thank the reviewer for their offer on the improvement of figures quality. During our statistical analysis, we used the following statistical packages: dplyr, stats, ggplot2, and FSA, which allowed us to process primary data for statistical analysis and data visualization. PCA was the main method used to analyze pyrolytic data and is widely used by researchers to assess differences in SOM structure [1-3] (Buurman et al., 2007, Campo et al., 2011, Dinno, 2015). The results of PCA were not only necessary to assess differences in SOM structure, but also for a deeper understanding of the features of pyrolysis and the study of potential precursors among SOM components [4] (Vuppaladadiyam et al., 2023). When identifying groups of pyrolyzates, we relied not only on literature data but also on experimental results. After analyzing PCA, we examined the statistical significance of selected pyrolyzate groups using the Kraskal-Wallis test, followed by Dunn's post-hoc analysis. We would like to thank the reviewer for their recommendation. These tests are more suitable for our data than the classical analysis of variance (ANOVA).

We would like to respond in detail to some of your comments in order to clarify all the inaccuracies.

It should be clarified that black soils is a generally accepted term used for soils united by the presence of a black horizon with a high content of organic matter [1]. The majority of black soils would correspond to Chernozems, Kastanozems and Phaeozems, some other groups such as Vertisols, Fluvisols, Cambisols and Anthrosols may also fit the definition of black soils [2]. In the United States of America and Argentina, black soils correspond to the Mollisols Great Order according to the United States of America Soil Taxonomy [3]. For this reason, we added the term black soils to the list of keywords, because we believe that then more interested colleagues will be able to read our article.

You mentioned that “the agricultural use influence the increase in bulk density, and thus the presence of bigger aggregates. Especially in so called carbon rich, fertile soils, such as Chernozems, Phaeozems...” But in this case we should respectfully disagree. It is well known, that soil compaction occurs in land with unsustainable use. In Russian soil science, there are standards for the health of the soil structure that agricultural producers must adhere to [5]. This is achieved by introducing into agricultural practice not only annual plowing, but also cultivation, harrowing, turn-under of crop debris and other procedures depending on soil conditions in the farm. Many of these procedures are included into the cropping system on the Experimental field, where we did our research. This information we also added in the part “Materials and methods”.

Unfortunately, in paragraph 4.3. we were unable to expand the number of examples from the literature data, since the study of Сhernozems by the micromorphological method is carried out more often either to establish their genesis under different vegetation and cultivation systems and on deposits of different ages [6-9], or to establish the consequences of ancient erosion events and their influence on the genesis of Сhernozems or Сhernozem-like soils [10-12]. To our deep regret, micromorphological works, in which attention is paid specifically to modern eroded chernozems, remain scarce [13].

We express our heartfelt appreciation to you for your careful work on the review of our article. We have tried to make all the corrections you suggested and clarify all the inaccuracies you encountered in our manuscript. We sincerely hope that after the changes made, our article will be suitable for publication in the respected journal Agronomy.

 

1. Buurman P., Peterse F., Almendros Martin G. Soil organic matter chemistry in allophanic soils: a pyrolysis-GC/MS study of a Costa Rican Andosol catena // European Journal of Soil Science. ‒ 2007. ‒ T. 58, № 6. ‒ C. 1330-1347.
2. Campo J., Nierop K. G. J., Cammeraat E., Andreu V., Rubio J. L. Application of pyrolysis-gas chromatography/mass spectrometry to study changes in the organic matter of macro- and microaggregates of a Mediterranean soil upon heating // Journal of Chromatography A. ‒ 2011. ‒ T. 1218, № 30. ‒ C. 4817-4827.
3. Dinno A. Nonparametric pairwise multiple comparisons in independent groups using Dunn's test // The Stata Journal. ‒ 2015. ‒ T. 15, № 1. ‒ C. 292-300.
4. Vuppaladadiyam A. K., Varsha Vuppaladadiyam S. S., Sikarwar V. S., Ahmad E., Pant K. K., S M., Pandey A., Bhattacharya S., Sarmah A., Leu S.-Y. A critical review on biomass pyrolysis: Reaction mechanisms, process modeling and potential challenges // Journal of the Energy Institute. ‒ 2023. ‒ T. 108. ‒ C. 101236.
5. 2022. Global status of black soils. Rome. https://doi.org/10.4060/cc3124en
6. IUSS Working Group WRB. 2015. World Reference Base for Soil Resources 2014, update 2015 International soil classification system for naming soils and creating legends for soil maps. World Soil Resources Reports No. 106. FAO, Rome.
7. Soil Survey Staff. 2014. Keys to Soil Taxonomy, 12^th USDA-Natural Resources Conservation Service, Washington, DC.
8. Shein E.V. Course of soil physics. Moscow: Publishing house of MSU, 2005. 432 p.
9. Chendev, Y. G., Khokhlova, O. S., & Alexandrovskiy, A. L. (2017). Agrogenic evolution of automorphic chernozems in the forest-steppe zone (Belgorod oblast). Eurasian Soil Science, 50(5), 499–514. doi:10.1134/s1064229317050040
10. Nørnberg, P., Dalsgaard, K., & Skammelsen, E. (1985). Morphology and composition of three mollisol profiles over chalk, Denmark. Geoderma, 36(3-4), 317–342. doi:10.1016/0016-7061(85)90011-4
11. Dultz, S., & Kühn, P. (2005). Occurrence, formation, and micromorphology of gypsum in soils from the Central-German Chernozem region. Geoderma, 129(3-4), 230–250. doi:10.1016/j.geoderma.2005.01
12. Bedrna, Z. (1972). Soil Micromorphology of the piedmont zonality in central Europe. Zeszyty Problemowe Postępów Nauk Rolniczych, 123.F
13. Von Suchodoletz, H., Tinapp, C., Lauer, T., Glaser, B., Stäuble, H., Kühn, P., & Zielhofer, C. (2017). Distribution of Chernozems and Phaeozems in Central Germany during the Neolithic period. Quaternary International. doi:10.1016/j.quaint.2017.10.041
14. Ajami M., Khormali F. (2012). Pedogenic and micromorphological evidences of land degradation on deforested loess-derived soils in eastern Golestan province. Journal of Science and Technology of Agriculture and Natural Resources, Vol. 16, No. 61(B), 141-155 ref. 29.
15. Jogmans A.G., Bruins H.J. (2012). Micromorphology of ancient agricultural Terraces in the Negev Desert, Horvat Haluqim (Israel), Proceedings of the 14th International Working Meeting on Soil Micromorphology
16. Drewnik M., Żyła M. (2019). Properties and classification of heavily eroded post-chernozem soils in Proszowice Plateau (southern Poland), Soil Science Annual 70(3):225-233 doi:10.2478/ssa-2019-0020

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

 

The manuscript tested and analyzed the effect of water erosion on soil organic matter and aggregates of arable Chernozemsin in the Central Russia by collecting soil samples from different locations on a slope (representing different water erosion degree). The paper obtained some interesting results. The paper as a whole is clearly written, but the materials and methods section is not clearly and needs to be revised.

 

The authors collected soil samples from different locations on a slope representing different levels of erosion. Therefore, a detailed descript of the slope is needed, such as the history or years of reclamation and planting, the cropping system, the tillage method, as well as the length of the slope, the direction of plough, and an explanation is needed as to explain why the different sampling sites represent different erosion degree.

Many of the conclusions in the manuscript are based on statistical tests, and these statistical results (e.g., whether the differences are significant or not) need to be labeled alongside the data results in the appropriate tables

 

Specific questions:

1. L12，is “mean weighted aggregate diameter (MWD)” “ mean weight diameter of aggregate”？

2. L13，organic carbon content (SOC). However, there are no results about SOC in the main text, only SOM.

3. L87, slope steepness 0.5-5.1°.  However, the unit of slope in Figure 1 is %. Please use consistent slope units throughout the text.

4. Fig.1.，The degree of erosion at different sites needs to be labeled on the graph. In the slope, which site is （1）laid down，which site is（2）weakly，which site is（3）moderately eroded？In addition, the length of the slope and the distance between each sampling location need to be labeled.

5. L118， what is JC content？

6. L171-173，“In moderately ……higher than in moderately……”. The sentence does not make sense and contains errors.

7. Fig.2.，Missing coordinate names, missing units for vertical coordinates

8. L192，0.38,0.18 and 0.23. The results of these statistical tests should be presented in Table 1.

L197，0.04, 0.81 and 0.09. The results of these statistical tests should be presented in Table 1.

L200，p=0.82, 0.31 and 0.31. The results of these statistical tests should be presented in Table 1.

All the statistics in the latter section need to be labeled in the corresponding tables.

9. Table 1. How “coefficient of structurality” and “efficient of water resistance” be measured and calculated? All this needs to be stated in Materials and Methods. The results of the significance test need to be presented in the table.

10. Soil bulk density data are available in Table 2, but L216-222 does not address the soil bulk density results.

11. Table 2. The results of the significance test need to be presented in the table.

12. L239-240，The sentence does not make sense and contains errors.

13. Figure 4. It needs to be stated what optical orientation characteristics of carbonates have and how they can be recognized.

14. L266 and L276， what is Bk horizon and what is Ap horizon?

15. Table 3, Why is the value of lowermost greater than that of uppermost instead?

16. Figure 5, What is POPs?

Author Response

Dear esteemed Reviewer!

We are deeply grateful to have read your review of our article and made as many corrections as you indicated. All statistical differences were transferred from the text to the tables. We added the history of land use in the study area to the " Materials and Methods" section, and added formulas for calculating soil structure indicators. We have improved figures according to your comments. We have added a clarification that the soil horizon indices are given in accordance with the FAO soil description guidelines and reference to how carbonates can be recognized on the microlevel.

Additionally, we would like to note that the different sampling sites are represent different erosion degree because of length of the slope (distance from the sensor to the sampling site). At the paragraph 4.2. we have added an explanation on the dependence of the formation of flows with critical rates on the length of the slope. It is the critical rates of water flow that lead to soil washout and the formation of eroded soils.

In conclusion, we would like to cordially thank you for your patient work on the review of our article and your felicitous remark. We hope that after making the changes you have indicated, our article will be suitable for publication in the respected journal Agronomy.

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

Soil erosion is a serious environmental problem worldwide, whether it occurs in natural ecosystems or in human modified ecosystems. This manuscript takes the central highlands of Russia as an example to study the effects of soil erosion on organic matter and soil aggregates in cultivated black calcareous soil. The overall content of the paper is complete, with detailed data, and its research results have important reference significance for protecting black calcareous soil. In my opinion, this manuscript can be considered for publication. However, the following suggestions are made for the manuscript.

1. In the introduction, the manuscript should provide a clear explanation of the specificity and typicality of the research conducted in the selected region, in order to provide readers with universal insights. Especially, in present, there is a lack of research on OM conversion at the molecular level, as briefly mentioned in the last paragraph of the original introduction. Therefore, in the introduction, it is recommended to strengthen the combination of typical features of the selected region and molecular level OM transformation throughout the entire paper.

2. It is recommended to annotate the vertical axis of Figure 2 to make its meaning more complete.

3. From lines 171 to 172, "....higher than moderly erode..." Please check this sentence.

4. It is suggested that in the conclusion section, the author provide special explanations for the new findings of this study. Especially combining the selected regional features with the obtained conclusions.

5.In the results of Figures 4 and 5, the differences in the types of organic matter compounds at different sites are shown, especially the significant differences in nitrogen and lipid compounds. It should be conducted in-depth discussions on the occurrence of this phenomenon based on the selected plant species in the region and the distribution characteristics of the affected plant tissues. According to the possible sources of insoluble nitrogen and lipids, whether these compounds are related to oil and protein containing plant seeds (if there are phosphorus content measurements represented by phytic acid, it may be helpful to determine this), phenols and carbohydrates are related to plant leaves. The reason for only providing the explanation in lines 470-472 is actually still the result and seems unrelated to the total organic matter category.

6. It is recommended to include the significant differences related data from lines 190-192, 194-198, and 199-202 in the corresponding tables for readers to understand.

Author Response

Dear esteemed Reviewer!

We have made all the changes recommended. We have added to Introduction more specific information about some features of organic matter transformation on the molecular level. We have improved the quality of figures and corrected all the incorrect wording. Also we rewrote Conclusion and improved our tables according to your comments.

Thanks to the reviewer for their recommendation about the results of Figures 4 and 5. The study was conducted on a single agricultural land located on a slope. The slope areas under study were equally affected by the type of land use, including crop rotation, fertilizer systems, and cultivation methods. The slope was traditionally treated to a depth of 20 centimeters, which led to the homogenization of soil properties and a reduction in the heterogeneity of soil organic matter (SOM) composition under the influence of plant residues. Therefore, the study aimed to isolate the impact of slope erosion on physical and chemical soil properties. We assumed that plant residues influenced the results of pyrolysis, but this effect was also linked to erosion, which contributed to the washing away of light fractions of SOM. Accumulation of carbohydrates and polyphenols has been a trend in the accumulation of soil carbon in stable forms of SOM [1-3]. We assume that this phenomenon is less dependent on crop rotation and more dependent on the biochemical characteristics of soil organic matter stabilization.

We express our deep and sincere gratitude to you for the work you have done to review our manuscript. We hope that after the corrections have been made, our article will be suitable for publication in the respected journal Agronomy.

1. Gleixner G., Bol R., Balesdent J. Molecular insight into soil carbon turnover // Rapid Communications in Mass Spectrometry. ‒ 1999. ‒ T. 13, № 13. ‒ C. 1278-1283.
2. Derrien D., Marol C., Balabane M., Balesdent J. The turnover of carbohydrate carbon in a cultivated soil estimated by 13C natural abundances // European Journal of Soil Science. ‒ 2006. ‒ T. 57, № 4. ‒ C. 547-557.
3. Gerke J. Carbon Accumulation in Arable Soils: Mechanisms and the Effect of Cultivation Practices and Organic Fertilizers // Agronomy. ‒ 2021. ‒ T. 11, № 6. ‒ C. 1079.

Author Response File: Author Response.docx