Conquering Soil Acidification: The Synergistic Effects of Basalt Powder, Lime, and PAM

Zhang, Qianmei; Peng, Xiuhong; Zhu, Hongxia

doi:https://doi.org/10.5194/egusphere-2024-1870

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https://doi.org/10.5194/egusphere-2024-1870

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16 Jul 2024

| 16 Jul 2024

Conquering Soil Acidification: The Synergistic Effects of Basalt Powder, Lime, and PAM

Qianmei Zhang, Xiuhong Peng, and Hongxia Zhu

Abstract. Soil acidification poses a substantial threat to agricultural productivity by releasing salt ions, diminishing soil fertility, and increasing susceptibility to aluminum toxicity. The aim of the study was to investigate the potential improvement of acid yellow soil through the combined application of basalt powder, lime, and polyacrylamide (PAM). Herein, 0.1 g mixed basalt powder and CaO with various proportion were added to 10 g acidic yellow soil with an initial pH of 4.16 to explore the efficient of mixed soil amendments. X-ray fluorescence (XRF) analysis of basalt powder revealed its effectiveness in supplementing soil mineral nutrients. The optimal results of reduced acidification and ion leaching of soil were obtained when the addition proportion of basalt powder to lime was 8/2 and addition ratio of PAM was 0.0002 %. The addition of mixed amendments markedly increased the pH (by up to >2.0 units) and acid-damage capacity (20.3 mmol/kg) of soil, meanwhile decreased the leaching of K⁺(58.1 %), Na⁺(42.9 %), Mg²⁺(26.3 %), and Al³⁺ (below the detectable limit) as shown by the optimal tests. The basalt powder undergoes decomposition in the soil solution, resulting in the formation of some weak acids (i.e., H₂SiO₄), the release of OH^-, and an increase in soil pH. The study reveals the underlying mechanisms of soil remediation with mixed amendment, which has potential guidance for the application of mixed soil amendment and the environment risks prediction of contaminated soil.

Received: 26 Jun 2024 – Discussion started: 16 Jul 2024

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.

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Qianmei Zhang, Xiuhong Peng, and Hongxia Zhu

Status: final response (author comments only)

RC1:
'Comment on egusphere-2024-1870', Giuliano Marchi, 30 Jul 2024

I reviewed the manuscript entitled "Conquering Soil Acidification: The Synergistic Effects of Basalt Powder, Lime, and PAM".
There is really few points to be corrected. Most of them in the abstract. Most of them are related to unusual methods used in the experiments. One of them is the acid damage capacity. It should be shortly described before the use of the term.
The text is altogether very good. The acid damage is an interesting method, at the end, very informative of basalt-mixture resiliency to pH drop with the amount of acid added. The results are robust, and show the interactions occurring within the mixture in order to achieve the best buffer for soil pH.
I added a few suggestions directly in the MS text.

Citation: https://doi.org/10.5194/egusphere-2024-1870-RC1
- AC1: 'Reply on RC1', Xiuhong Peng, 02 Aug 2024
  
  First and foremost, I would like to extend our heartfelt gratitude for the insightful comments and constructive suggestions you have provided.
  You have rightly suggested the inclusion of the full chemical name of polyacrylamide in the title, and we wholeheartedly agree with your recommendation. Additionally, you have highlighted the necessity of specifying the addition ratio within the abstract. This paper delves into the optimal ratio of CaO to basalt powder. Regarding your query about whether we should enumerate several experimental ratios, we are giving it due consideration and will make a decision in the near future.
  Your third point raises a crucial question about the role of X-ray fluorescence (XRF) in demonstrating the effectiveness of basalt powders. XRF is instrumental in identifying the mineral composition and estimating the content of basalt powder, as detailed in the first paragraph of section 3.1 and further discussed in section 4.1. The basalt powders are rich in various nutrients, and their mineral makeup is indicative of their weathering propensity and, consequently, the rate of nutrient release. For instance, as elaborated in section 4.1, research has established that Mg-rich minerals within the lattice structure are more prone to weathering compared to Ga-rich minerals. Our XRF analysis reveals that the predominant mineral constituent is Mg-rich serpentine, suggesting that our powder will exhibit a more rapid weathering rate, which bodes well for its efficacy in soil nutrient enrichment.
  Once again, we are immensely thankful for your invaluable feedback.
  
  Citation: https://doi.org/10.5194/egusphere-2024-1870-AC1
CC1:
'Comment on egusphere-2024-1870', Xuan Gao, 30 Aug 2024

This study investigated the potential improvement of acid yellow soil through the combined application of basalt powder, lime, and polyacrylamide . This article conducted detailed experiments, and it is well written. However, the specific application scenarios should be mentioned.

Citation: https://doi.org/10.5194/egusphere-2024-1870-CC1
- AC2: 'Reply on CC1', Xiuhong Peng, 30 Aug 2024
  
  We greatly appreciate your insightful feedback. Our research suggests that the composite soil amendments possess significant potential for the comprehensive rehabilitation of acidic soils across diverse regions. Common challenges faced by acidic soils include low pH levels, nutrient scarcity, and the detrimental release of aluminum ions. The application of basalt powder, lime, and polyacrylamide has demonstrated efficacy in addressing these issues. Nevertheless, when implementing these amendments, it is crucial to consider adjusting the ratio of basalt powder to lime based on the specific acidity levels of the soil to avoid excessively increasing the pH post-amendment.
  
  Citation: https://doi.org/10.5194/egusphere-2024-1870-AC2
CC2:
'Comment on egusphere-2024-1870', Weiwei Wang, 30 Aug 2024

This work introduced a low-cost and high efficiency soil amendment, which had potential guidance for the soil remediation. The materials utilized in research were in solid form, but PAM was introduced as dissolved solution. Please elaborate the application methods of the amendment in actual agricultural practices.

Citation: https://doi.org/10.5194/egusphere-2024-1870-CC2
- AC3: 'Reply on CC2', Xiuhong Peng, 01 Sep 2024
  
  感谢您的垂询。在实际应用中，我们已经考虑了应用的方法，尽管论文中没有明确详细说明。首先，将碎玄武岩粉和生石灰按特定比例混合，并在土壤耕作过程中施用。聚丙烯酰胺由于添加量低，可以按质量比与水粗略混合，然后在浇水时均匀地铺布在翻动的土壤表面。
  
  Citation: https://doi.org/10.5194/egusphere-2024-1870-AC3
- AC4: 'Reply on CC2', Xiuhong Peng, 01 Sep 2024
  
  Thank you for your inquiry. In practical applications, we have taken into account the method of application, although it is not explicitly detailed in the paper. Firstly, the crushed basalt powder and quicklime are mixed in a specific ratio and applied during soil tilling. Polyacrylamide, due to its low addition rate, can be roughly mixed with water according to a mass ratio and then uniformly spread over the surface of the turned soil when watering.
  
  Citation: https://doi.org/10.5194/egusphere-2024-1870-AC4
RC2:
'Comment on egusphere-2024-1870', Mario Reichenbach, 11 Sep 2024

General comments
This manuscript addresses the combined effect of basalt powder, lime and polyacrylamide as soil amendments on soil acidification. Based on lab experiments covering soil pH buffer curves, acid damage capacities and leaching and adsorption experiments, the authors show that those amendments improve soil acidity issues by raising soil pH and reducing nutrient leaching. This topic is relevant for establishing best practices for soil management and preserving soil health. However, the manuscript contains many flaws and weaknesses in the methodology and in the interpretation of the data. While the authors are using well-established wet-chemistry methods, the description of the experimental design is not clear. The main issue is the lack of any statistical analysis of the data. The observed trends are not statistically back-upped thus there is not much confidence in the conclusions drawn from the data. Another main problem is the lack of theory-driven research questions and testable hypothesis. As such, the manuscript does not have a clear storyline and the discussion is not tied back to hypothesis. Since no hypothesis are formulated, it is difficult to decide, which results and display items are important to focus on for delivering the key message of the manuscript. Thus, the discussion lacks direction and contains many speculative and over-simplified parts, which are not supported by the results. Another issue is that there is not much information where the soil samples were taken from and how representative they are. Even the sample size is nowhere mentioned in the manuscript. If I understood it right, only one soil sample was taken and then splitted to seven aliquots without any replicates. This may explain the absence of any statistical analysis with such a small sample size. Moreover, it is a purely lab-based study with no connection to a specific study area. Thus, in how far the results and conclusion can be upscaled or applied to other soil systems remains unclear. Lastly, the wording needs to be improved. Some parts of the manuscript sound like an AI-generated text. I regret to say that the quality of the manuscript is not suitable for publication in SOIL and suggest rejection. Please see my comments below for more details.

Below are the edits and comments on the manuscript
Title
I suggest revising the title. It sounds a bit AI-generated. Also, please don´t use abbreviation in the title.

Abstract
In general, the abstract contains parts which are not clear. It does not do a good job to in presenting the relevance and novelty of the study and shows only a very generic conclusion. See details below.
Line 32 – 33: How can you say something about the effectiveness? The XRF-analysis gives you data about the mineralogical composition but no information about relationships.
Line 40: Does the formation of acids due to basalt powder weathering counteract the pH buffering effects in your sample?
Line 41: Your data and analysis do not allow you to state something about mechanistic processes. Your results are purely descriptive and your sample size is very small to draw conclusion about specific processes.
Line 39 – 41: The basalt powder “decomposes” because of the added acid but does not produce acid during weathering.
Line 41– 43: This is a very generic conclusion of the study.

Introduction
The introduction contains unclear statements which are too general. The statements need to be more precise and more specific. Thus, it is hard to fully comprehend the knowledge gap and the novelty of the study. Specifically, the introduction lacks clear and theory-driven research questions. It also missing testable hypothesis and a rationale which should be linked with the research gaps. After reading the introduction, the reader should be able to fully comprehend the research aim and hypothesis. However, this is not the case here. Also, the study objective is very vague. See details below.
Line 46 – 47: The first sentence sounds weird and reads like a AI-generated text. Please revise. Please explain the link of soil degradation and human productivity.
Line 46 – 65: This section is very general and unspecific. What is the key message and how is it related to your study?
Line 72: What about the other two amendments you mentioned earlier (mixed and composite amendments)? Why are there not explained in more detail here?
Line 73 – 77: What are the main results from the cited studies and how do they relate to your study? Can there a knowledge gap derived from those studies? Also, please revise wording.
Line 87 – 89: Does this mean that the effect are known but not the mechanistic process behind?
Line 90 – 92: What has the data scarcity to do with the weathering rate? Hard to follow the train of thoughts. Please provide more details about the different factors (climate, mineralogy, topography, microbial activity etc.) which can impact the weathering rate.
Line 95: What do you mean with “environmental sustainability” in this context?
Line 97 – 98: Please revise wording.
Line 98 – 99: Please explain “principles of environmental sustainability”.
Line 99 – 100: What is PAM? More details needed.
Line 100 – 107: This section is too general and unspecific. Thus, it is not much informative.
Line 108 – 109: Be more specific. This sentence is just a filler with no informative value.
Line 113 – 116: Needs references.

Material and methods
The experimental design is not descripted very clear and needs revision. The overall sample size and the sample size of the test groups are not mentioned. There are no statistical analysis described at all. Based on your data, simple ANOVA and/ or Random fixed models would be suitable to back up your conclusions. See details below.
Line 120: What soil classification system are you using? What exactly is yellow loam?
Line 124: What do you mean with “> 98% lime powder” and why is the molecular weight of the PAM important?
Line 125 – 126: More explanation needed on the preliminary experiments.
Line 126: What do you mean with “original basalt samples”?
Line 127: Be more precise. What do you mean with “were pulverized to a particle size”?
Line 128 – 131: Hard to understand.
Line 132: Please provide more details for the XRF analysis. A more detailed description of the working steps is needed.
Line 136 – 139: I do not understand this. Please revise.
Line 140 – 142: Study aims belongs more to the introduction section.
Line 145: More details about the additive proportions. Be specific.
Line 145 – 148: Please revise wording.
Line 153: Why is the suspension left for 2 days?
Line 154: More information needed about the test groups.
Line 156 – 160: Is this the same for all soil and crop types?
Line 161: Unnecessary filler sentence. Delete it.
Line 164: How was the soil pH measured?
Line 165 – 168: Was this done for all samples and amendments? More explanation needed.
Line 170: Filler sentence. Delete it.
Line 173 – 174: Why was the suspension settled for 2 days and then agitated again?
Line 176: How was the predetermined acid quantity calculated?
Line 177 – 178: More explanation needed.

Results
The main issue with the results are the missing statistical analysis. The observed trends are not back-upped by any statistics thus there is no confidence behind the conclusion. Thus, how can the authors be sure that the trends they see are significant and not just coincidence? See details below.
Line 190 – 192: This is just a filler and has no informative value. Delete it.
Line 195 – 196: This is interesting but not relevant for your study.
Line 197 – 198: Filler sentence. Delete it.
Line 198 – 200: This is no surprise since basalt is a silicate rock. Silicate oxides are the main component of every silicate rock.
Line 200 – 202: More details needed since too generic.
Line 204 – 211: Hard to follow. Please revise wording.
Line 207: There are no chemical formulas in Figure 2.
Line 208: Is the isomorphism relevant for your study?
Line 213: Please improve wording.
Line 219 – 220: Hard to follow. Revise.
Line 220 – 223: This belongs to the method section.
Line 224: What is the unit here?
In general, those code names for the test groups are not informative at all. I suggest coming up with more descriptive names for the groups.
Line 225 – 229: Since there are no statistics beyond the results, you cannot rule out other potential factors, which could impact those buffer curves. Why not using random fixed models for testing the significance? This section also contains already interpretations.
Line 237 – 243: This section lacks references and already contains interpretations, which do not belong to the result section.
Line 240 – 242: Isn´t this trivial? This is to be expected when you add acid to your samples. This is part of the method, no? And why is it a gradual decomposition? Wouldn´t it be more interesting to focus how many elements were retained from leaching due to amendments?
Line 244 – 255: Again, how much confidence do you have in your results and conclusions? You simply can´t know, if the trends you see a statistically relevant since no statistical analysis were done. In addition, the sample size is nowhere stated in the manuscript. How big is your sample size? How representative is your dataset? Is the dataset solid enough to draw meaningful conclusions out of it. Frankly, I doubt it.

Discussion
The discussion lacks a clear storyline. The authors should emphasize on what we have learned and how this connects with the hypothesis. However, the argumentation is hard to follow and contains many speculative and over-simplified parts. Many conclusions are not supported by the data. See details below.
Line 257: This section header doesn´t make any sense.
Line 258 – 260: This statement is supported by what data? And what would be the consequence?
Line 260 – 262: This is over-simplified. Weathering processes and their influencing factors a way more complicated than presented here.
Line 262: Do you mean experimental instead of statistical analysis?
Line 263 – 266: Al-containing silicate rocks could be literally everything. The diversity of silicate rocks in the upper crust is huge. This statement has no informative value.
Line 265 – 266: Over-simplified. There are many more factors driving weathering rates.
Line 268: These are not metallic bonds.
Line 269 – 271: References are missing.
Line 271 – 276: This is over-simplified again. Basaltic rocks are highly diverse in their geochemical composition thus elemental composition based on their geo-tectonical settings in which they have formed.
Line 277 – 278: Bad wording and typos. Please revise.
Line 279 – 287: How are those statements related to your study? What is the take-home-message here. What can the reader learn from this?
Line 289: Basalt contain also a large amount of Ca-rich feldspars.
Line 288 – 292: This statement is based on what data? Also revise wording. Minerals undergo weathering but do not actively drive weathering processes. This part also contains speculative parts.
Line 292 – 294: Too simple. You don´t provide solid data for that statement.
Line 303 – 305: However, Figure 5 show that leaching still occurs. So how meaningful is this 300 % increase in acid damage capacity? How is the acid damage capacity calculated anyway? It is not described in detail in the methodology.
Line 306 – 307: This is quite a blunt statement. You simply claim positive correlations are present in your data without having done any correlation analysis or any other statistical analysis in your study at all. Figure 3 does not allow you to make any statements about correlations since it is not a scatter plot but a bar chart. You could do ANOVAS here.
Line 311 – 313: Where is the data for this statement?
Line 314 – 319: Hard to follow. Revise wording.
Line 321 – 324: This belongs to the appendix then.
Line 325 – 373: I suggest re-writing the discussion part. Many part a hard to follow, missing references and contain speculation. Try to focus on what the reader can learn from your data. What is the key message of your study?

Conclusion
This is a summary but not a conclusion.

Author contribution
I´m curious. Since all authors did supervision, were there other potential co-authors involved in the study (PhD students for example)?

Figures and tables
In general, the captions are not very informative to the reader. What is the key message of ach display item?
Table 1: Revise table. What is the difference of the upper and the lower part of the table? Is there an error with the column headers?
Table 2: What is the sample size? What about replicates?
Table 3: The codes are not informative. I suggest more descriptive names for the groups.
Figure 1: Unnecessary. What would be the key message or guidance for the reader here?
Figure 3: How was the acid damage capacity calculated? What´s the sample size?
Figure 5: Why are only two test groups presented? How do you explain that less elements are leached when adding acid?
Figure 6: This figure is based on what testing groups? There are three groups with PAM addition. How was the adsorption rate calculated? This figure is not described in the results.
Figure 7: What was the soil pH here? Please explain “neutral acidic conditions”. I mean, the pH changes anyway by adding the acid, no? This item is also not described in the result section.

Citation: https://doi.org/10.5194/egusphere-2024-1870-RC2
- AC6: 'Reply on RC2', Xiuhong Peng, 29 Sep 2024
  
  We are delighted to receive your comments. You have meticulously pointed out the unreasonable parts of the manuscript, and your valuable and useful suggestions are a great honor for us. Thank you for taking your precious time to offer us advice. We apologize for the late response, as we wanted to carefully address your comments. The reply to your questions is attached in "Reply on RC2 .pdf". Please take a moment to review it. Based on your suggestions, we have made detailed revisions to the manuscript, and the revised manuscript should meet your satisfaction! Thank you again for your professional suggestions!!
  
  Citation: https://doi.org/10.5194/egusphere-2024-1870-AC6
RC3:
'Comment on egusphere-2024-1870', Rezaul Karim, 23 Sep 2024
Review: Conquering Soil Acidification The Synergistic Effects of Basalt Powder, Lime, and PAM.
General Comments
I enjoyed reading the manuscript ‘Conquering Soil Acidification The Synergistic Effects of Basalt Powder, Lime, and PAM’, studied in Jiangxi Province, China.
One important concern is the standard of writing of the manuscript. I could say poor structure of sentences through out the manuscript. It requires restructuring the sentences for easy to read, clear and concise of the meaning and keep the bonding among the sentences in a paragraph and also paragraphs to sections.
Abstract
The abstract is to be clear and concise aligning with the title of the manuscript. it could be improved keeping in mind the classical structure of a good abstract.
L26-27 introductory sentence -good start.
L28-29 – the objectives is not clear. Is it ‘to investigate the potential improvement of acid yellow soil’ or ‘ to investigate the combined application of basalt powder, lime, and polyacrylamide (PAM) for the improvement, ,, ,,, “
L30-31 - Do you mean CaO as Lime, then introduce it at earlier. Why these sentence is here? Is the methods to establish the objectives? Need to be linked with objectices?
L-32 data analysis – XRF is data analysis tool rewrite it.
L-33-41 Results – rearrange and rewrite the results to support the objectives, not only presenting the data.
L-41- 43 - Outcomes – rewrite it to be focused.
Introduction
L-46-49 – This sort of sentence structure is used all-around the manuscript. These are not easy to read and understand and free flow of the topic. Please rewrite these sentences to make it concise and clear meaning.
Uses of Meanwhile, consequently, Simultaneously, meanwhile ,,,, with thereby ‘ phrase does not make the text readers friendly for a human.
Paragraph structure- make a topic sentence followed by the relevant information.
Research gap – discuss the relevant topics in introduction and narrow down into the research gap. Link the research gap with the objectives of the present study.
Material and Methods
Soil - L120 reference?

Amendments – purchasing procedure is not good use in academic writing.

L124-134 - Make it simplified.
Results
In Results, the manuscript contains several concepts, which could be presented in Introduction to find the research gap and link the objectives with the gap. For example, L 190 196 is not results.
Statistical analysis is a good way to present the data ( L 30). There could be several combination of experiments, based on CaO with various proportion (L30). Present these comparative studies and suggest from these the effective combination to gain the outcome.
Discussion
In discussion, relate the results to establish the objectives. It could be referred or refuted arguments using other references.
Conclusion
As I understood, it was a comparative study among combination of basalt powder, CaO, and PAM mixed modifier on soil enhancement. Rewrite the conclusion that the objectives were achieved.
L 376 - It is not worthy to present a new concepts in conclusion without discussing in results and discussion. For example, ‘optimal pH’ Only one time used in the text. Is it your objectives or comparative tool?
L-378- 382 rewrite coherently with the text.
L 384 – 385 ????
Additional comments
The manuscript requires a major change/ restructuring in presenting the results. Keep in mind that the literature reviews will be presented in Introduction, to find a research gap, which could be the aims of manuscript. The aims will be achieved by several objectives. To gain the objectives, the appropriate methods will be followed. The data/ results will be presented to achieve each objectives, finally, the aims of the manuscripts.
Citation: https://doi.org/10.5194/egusphere-2024-1870-RC3
- AC5: 'Reply on RC3', Xiuhong Peng, 28 Sep 2024
  
  Thank you for your careful reading and comments！！ We have made careful revisions and replies and the details are in the uploaded attachment.
  
  Citation: https://doi.org/10.5194/egusphere-2024-1870-AC5

Qianmei Zhang, Xiuhong Peng, and Hongxia Zhu

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Short summary

Soil acidification is crucial in soil degradation, affecting plant and microbial growth, threatening human productivity. It involves decreased pH, loss of basic ions, physical deterioration, nutrient deficiency, and toxic aluminum release. This study shows basalt powder and lime, with polyacrylamide, raise pH, boost nutrients, and reduce aluminum toxicity to plants.


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