The Effect of Biochar Particle Size on the Leaching of Organic Molecules and Macro- and Microelements
Round 1
Reviewer 1 Report (Previous Reviewer 3)
Comments and Suggestions for AuthorsSome comments are listed to improve the manuscript:
1. Abstracts: since the title mentioned the effect of biochar particle size on elemental leaching, it should discuss the results about which particle size impact more on soil element leaching.
2. Introduction, Line 61-63: ‘i) action as the sorbent of various inorganic and organic molecules and 61 ionic compounds and as well as on ii) action as the source of various organic and mineral 62 molecules and ions,’ Here the inorganic and organic molecules, minerals should be added more details. Set some examples for these compounds.
3. Introduction: why did the study choose to measure the PAHs? The link between PAHs and leaching of microelements was not clearly introduced in the introduction.
4. Materials and Methods: what is the rule of selecting the particle sizes?
5. Materials and Methods: Please make it clear, what are the total inorganic elements measured in this section?
6. Results and Discussion, line 242-243: ‘The main aim of the research was to investigate the role of biochar particle size on the crucial characteristics important for possible agronomical utilization of biochar as a soil conditioner.’ This sentence is more like being in the introduction instead of Results and Discussion.
7. Results and Discussion, line 242-265: ‘The main aim of… as well as its optimal form and dosage’. Too much information was repeated in the introduction and materials sections, I do not think this part was necessary to be discussed in the section. Instead, please describe the results more directly and evolve discussion.
8. Results and Discussion, subtitles: the subtitles in this section ‘3.1. Physicochemical characteristics of the studied biochar samples, the effect of size fraction and cultivation in the model soil’, ‘3.2. Macroelement and microelement contents in the size-fractionated biochars and comparison with biochar samples from the cultivation experiments’ was too long.
9. Figure 4: The resolution of the figures should be improved. For figure 4, the small letters were not clearly matched with the bars from my perspective.
10. Results and Discussion: I suggest using the main results to replace the subtitle of ‘3.3 GC-MS analysis’.
11. Results and Discussion, line 715:’ the author of publication’ was a grammatic error.
12. Results and Discussion, Line 726-728: this sentence was too vague, what was the exact reason for this difference?
13. Conclusion: The most of the content in the conclusion should move to discussion part. The current content was well concluded.
Comments on the Quality of English LanguageSome English grammar errors were clearly seen in the manuscript, besides, the English writing should be more concise.
Author Response
Dear reviewer,
we would like to thank you for the time taken for precise reading and reviewing of our manuscript entitled (The effect of biochar particle size on the leaching of organic molecules and macro- and microelements). The authors appreciate the objectivity of your comments and suggestions.
Hereby, we can confirm that we have properly considered each point of the comments, and we have modified the manuscript accordingly. Here are the responses to the reviewer´s comments:
Point 1. Abstracts: since the title mentioned the effect of biochar particle size on elemental leaching, it should discuss the results about which particle size impact more on soil element leaching.
Response of authors:
We would like to thank the reviewer for this important comment. We have incorporated the crucial results describing the effect of biochar particle size on macronutrients and micronutrients leaching as well as the observed trends in detected PAHs contents in biochar (Lines: 24–29 and 32–33).
Point 2. Introduction, Line 61-63: ‘i) action as the sorbent of various inorganic and organic molecules and ionic compounds and as well as on ii) action as the source of various organic and mineral molecules and ions,’ Here the inorganic and organic molecules, minerals should be added more details. Set some examples for these compounds.
Response of authors:
Thank you for this comment. We have included examples of individual potential groups of mentioned molecules and moieties. The text on lines 67–71 was correspondingly modified in the following way:
…which is based on i) action as the sorbent of various inorganic (heavy metals, multivalent ions) and organic molecules (polycyclic aromatic compounds, substituted heterocycles) and ionic compounds and as well as on ii) action as the source of various organic (substituted aliphatic and aromatic moieties originating from decomposed biomass) and miner-al molecules and ions (mineral ions – K, Na, Mg, Ca), which can be leached to the surrounding soil [18,19].
Point 3. Introduction: why did the study choose to measure the PAHs? The link between PAHs and the leaching of microelements was not clearly introduced in the introduction.
Response of authors:
We would like to thank you for this point but the collective of authors has a different opinion. The main idea of the manuscript was to study the effect of particle size on the leaching of various molecules. Agronomically important are for sure mineral components such as macro and microelements. On the other hand, polyaromatic hydrocarbons and substituted heterocyclic compounds can be co-generated during biochar production. We wanted to emphasize also this aspect in the second part of the manuscript. We have observed that the contents in our studied biochar samples were far below defined EBC limits. This is definitely an important result, which underlines biochar non-toxicity (regarding its bound PAHs (which are strongly bound in biochar structure = immobilized). The author collective has an opinion, that the reason for incorporation of the release potential of PAHs and substituted heterocyclic compounds in our manuscript is adequately explained in the introduction section (lines 96–107):
Besides the mineral contents another important group of chemicals, which need to be monitored in biochars having the potential use in agriculture, are the polycyclic organic compounds. These toxic substances can be co-generated during biochar production as side products of biomass pyrolysis [26–29]. Probably the most important group of polycyclic aromatic compounds – polyaromatic hydrocarbons (PAHs) can be further divided according to the molecular weight of individual substances into low molecular weight (LMW) PAHs, containing 2–3 benzene nuclei, and high molecular (HMW) PAHS, containing 4–7 benzene rings in the structure of a molecule. HMW PAHs exhibit many times higher levels of toxicity than LHMW PAHs [27]. Despite the serious toxic effects of these compounds, their mobility is limited as they are strongly bound to the residual biochar matrix. Hale et al. [30] reported that the bioavailable fraction of PAHs in biochar is approximately 1 % of their total content.
Point 4. Materials and Methods: what is the rule of selecting the particle sizes?
Response of authors:
The selection of the particle sizes in a sieving analysis was done mainly concerning the actual distribution of particle sizes in the particular used biochar samples to have a more narrow distribution of particles for the subsequent analysis. Originally the main four fractions (below 0.5, 0.5–2, 2–4 and above 4) were planned to be analysed for all the studied samples. Unfortunately, in the case of BCH-CZ sample, the distribution was different, there was a dominant fine fraction and there were also bigger residual aggregates. However, the middle fractions (approximately 1-4 mm) were limited. Unfortunately, we cannot influence the particle size distribution of these samples as they were all commercial products, which were purchased for our research. For this reason, we decided to separate this sample only into two size fractions.
Point 5. Materials and Methods: Please make it clear, what are the total inorganic elements measured in this section?
Response of authors:
The collective of the authors would like to point out that the list of total measured elements in the ICP-OES analysis is listed on lines 198–200 in the manuscript. It is common for both the determination of aqueous-extractable inorganic elements (section 2.5.1) as well as for the total content of inorganic elements (section 2.5.2). To make it clear lines 229–232 of the manuscript were modified in the following way:
The following elements were detected – macroelements (Na, Ca, Mg, K, P), microelements (Al, Fe, Zn, Mn, Cu, Cr, Ni) and heavy metals (Cd, Co, As, Pb) in both used experimental approaches (section 2.5.1 and 2.5.2).
Point 6. Results and Discussion, line 242-243: ‘The main aim of the research was to investigate the role of biochar particle size on the crucial characteristics important for possible agronomical utilization of biochar as a soil conditioner.’ This sentence is more like being in the introduction instead of Results and Discussion.
Response of authors:
The collective of the authors considered this suggestion and decided to modify the first paragraph of the Results and Discussion section in the following way:
“The effect of biochar particle size on the crucial characteristics important for its possible agronomical utilization is discussed in the present study from three different aspects. Firstly, the variation in the physicochemical characteristics of biochar (section 3.1.) is assessed. Secondly, the effect on a leaching of mineral contents of biochar (section 3.2) is investigated. Thirdly, the effect on the availability of polyaromatic organic molecules and substituted heterocyclic compounds (section 3.3) is also taken into account.” (lines 274-280).
Point 7. Results and Discussion, line 242-265: ‘The main aim of… as well as its optimal form and dosage’. Too much information was repeated in the introduction and materials sections, I do not think this part was necessary to be discussed in the section. Instead, please describe the results more directly and evolve discussion.
Response of authors:
We agree with this reviewer's comment and for this reason, we decided to correct this part of the manuscript in the following way (lines 274-302):
„The effect of biochar particle size on the crucial characteristics important for its possible agronomical utilization is discussed in the present study from three different aspects. Firstly, the variation in the physicochemical characteristics of biochar (section 3.1.) is assessed. Secondly, the effect on leaching of mineral contents of biochar (section 3.2) is investigated. Thirdly, the effect on the availability of polyaromatic organic molecules and substituted heterocyclic compounds (section 3.3) is also taken into account. To be able to discuss these agronomically crucial characteristics of biochar consistently in real conditions in the soil (2 years in total). The obtained results were correlated with data from leaching experiments applied to the individual size fractions of the studied biochar samples. These findings together with previously published data could represent crucial knowledge necessary for the further assessment of biochar as the soil conditioner and help to determine its agronomical potential as well as its optimal form and dosage.“
Point 8. Results and Discussion, subtitles: the subtitles in this section ‘3.1. Physicochemical characteristics of the studied biochar samples, the effect of size fraction and cultivation in the model soil’, ‘3.2. Macroelement and microelement contents in the size-fractionated biochars and comparison with biochar samples from the cultivation experiments’ was too long.
Response of authors:
The collective of the authors of the manuscripts agree with this reviewer´s comments. For this reason, we modified the titles of these two particular sections in the following way:
„3.1 Physicochemical characteristics“ (Line: 303) and „3.2 Total and aqueous extractable macroelements and microelements content“ (Line: 468)
Point 9. Figure 4: The resolution of the figures should be improved. For Figure 4, the small letters were not clearly matched with the bars from my perspective.
Response of authors:
The collective of the authors would like to thank for pointing out this mistake. We have correspondingly corrected both Figures 4 (line: 722) a 5 (line: 763) to increase the quality and better matching of bars with small letters describing the significance difference according to the Tukey test.
Point 10. Results and Discussion: I suggest using the main results to replace the subtitle of ‘3.3 GC-MS analysis’.
Response of authors:
We agree with this comment. It would be clearer for a reader to replace our original general title with a title, which more reflects the performer analysis in that particular section of the manuscript. For this reason, the title of section 3.3 was modified to „Extractable contents PAHs and substituted heterocyclic compounds“ (Line: 711).
Point 11. Results and Discussion, line 715:’ the author of publication’ was a grammatic error.
Response of authors:
Thank you for your comment. The text was corrected according to your suggestion (Line: 769).
Point 12. Results and Discussion, Line 726-728: this sentence was too vague, what was the exact reason for this difference?
Response of authors:
We agree with this comment. The text in that part of the manuscript was extended to provide a more detailed description of the observed phenomenon (Lines: 781-788 and 792-794).
Point 13. Conclusion: The most of the content in the conclusion should move to discussion part. The current content was well concluded.
Response of authors:
We agree with this reviewer's comment that the original Conclusion of the manuscript was too long. We have modified its text to be shorter but to maintain the crucial ideas and results of the work, which we would like to transfer to the readers (Lines: 867, 871-876, 880-883, 885-895, 907).
Comments on the Quality of English Language
Some English grammar errors were clearly seen in the manuscript, besides, the English writing should be more concise.
Response of authors:
The collective of authors would like to point out that the language of the manuscript was corrected by a professional native-speaker scientific proofreader, which can be verified by the certification enclosed in this response to the reviewer's comments as well as to the manuscript draft.
Author Response File: 
Author Response.pdf
Reviewer 2 Report (New Reviewer)
Comments and Suggestions for AuthorsThe authors performed an excellent piece of work, which is of great interest to society, though I suggest some modifications
1. Introduction - Highlight the uniqueness and significance of investigating particle size in real-world scenarios.
2. Keywords - Refrain from utilizing duplicate phrases that are already included in the title.
3. GPS coordinates may be accurate up to three decimal places. Restrict the number of decimal places to a maximum of three. (Lines 141-144).
4. The ash percentages of each sample are essential for quantifying the quantity of metal ions present in it. Integrate the ash percentages into Table 3.
5. The comparison of biochar is inaccurate due to the use of two different pyrolysis settings. Please provide an explanation of the rationale for using various pyrolysis conditions.
6. Explain the disparity in biochar pH between H2O and CaCl2 mediums.
7. Establish a correlation between ash% and conductivity - This kind of graph would provide readers with valuable insight into the direct relationship between ash percentage and conductivities.
8. The mineral composition of biochar is influenced by the soil conditions under which it was produced. Examine this component by referencing relevant literature research.
9. Figure 3 can be split into two graphs and then merged– This way would be easy to read the data.
10. Improve the quality of figure 6.
Author Response
Dear reviewer,
we would like to thank you for the time taken for precise reading and reviewing of our manuscript entitled (The effect of biochar particle size on the leaching of organic molecules and macro- and microelements). The authors appreciate the objectivity of your comments and suggestions.
Hereby, we can confirm that we have properly considered each point of the comments, and we have modified the manuscript accordingly. Here are the responses to the reviewer´s comments:
The authors performed an excellent piece of work, which is of great interest to society, though I suggest some modifications.
Point 1. Introduction - Highlight the uniqueness and significance of investigating particle size in real-world scenarios.
Response of authors:
The collective of the authors agree with this comment. For this reason, the introduction section has been supplemented by the following text, which underlines the importance of the particle size of biochar:
(Lines 75–87) …. Thomas et al. [23] and Akhtar et al. [24,25] have strengthened the importance of biochar particle size. Smaller biochar particles have a more significant effect on soil sorption capacity—and thus plant growth especially under salt stress. This effect can be explained by improved soil-biochar contact between particles [26]. There may be an optimal biochar particle size for enhancing plant growth responses as far as large biochar particles may reduce particle mixing and accessible surface area for sorption. On the other hand, very small biochar particles can have reduced effects on soil water holding capacity and their application can lead to increased soil conductivity and pH [27]. Recent literature presents an optimal biochar particle size in the range of 0.5–1.0 mm [23]. The optimal particle size of biochar is crucial also from the agronomical point of view concerning its application on the field during the tillage or using mechanical spreaders, where depending on the spreader construction the optimal particle size can be in the range of 1-5 mm [28]….
Point 2.Keywords - Refrain from utilizing duplicate phrases that are already included in the title.
Response of authors:
Thank you for this comment. We have modified the list of keywords to agriculture, biochar; fraction size; mineral and organic content; polyaromatic hydrocarbons; soil conditioner.
Point 3. GPS coordinates may be accurate up to three decimal places. Restrict the number of decimal places to a maximum of three. (Lines 141-144).
Response of authors:
We would like to thank the reviewer for this comment. We absolutely agree. GPS coordinates were modified according to the reviewer's comment (lines 171-175)
Point 4. The ash percentages of each sample are essential for quantifying the quantity of metal ions present in it. Integrate the ash percentages into Table 3.
Response of authors:
The contents of inorganic ash (mineral content) for the studied samples – WMIN were according to the reviewer´s comment incorporated into Table 3. The adequate text (….and inorganic mineral ash (WMIN)….) was also added to the materials and method section (Line: 202).
Point 5. The comparison of biochar is inaccurate due to the use of two different pyrolysis settings. Please provide an explanation of the rationale for using various pyrolysis conditions.
Response of authors:
The main aim of our work was to compare the agronomical potential of commercial biochar samples, which are available in the markets near the Czech Republic and might be for this reason accessible to the farmers from the Czech Republic. These samples belonged to the sample database of one of our projects and were selected as the promising representatives having the highest agronomical potential. Unfortunately, in some cases, the production parameters were not accessible during the purchase and we obtained them later after email contact and verification of our research purposes. For this reason, we couldn´t influence these producers' dependent aspects of biochar.
Point 6. Explain the disparity in biochar pH between H2O and CaCl2 mediums.
Response of authors:
The explanation of this difference is connected with ionic strength and partial cation exchange between CaCl2 solution and biochar. Soil pH is generally measured in a soil-aqueous suspension. However, the presence of soluble salts in a soil sample may affect pH, and for this reason, some prefer to measure it in a suspension of soil in a solution of 1 M KCl or 0.01 M CaCl2. The presence of salts in these solutions masks the effect of varying soluble salt concentrations in individual samples. The pH measured in 1 M KCl or 0.01 M CaCl2 solution is typically lower than the pH of the same soil measured in water due to the higher concentration of H+ in the resultant suspension from the cation exchange phenomenon. Addequatelly modified text was incorporated in a manuscript (Lines 383-387).
Point 7. Establish a correlation between ash% and conductivity - This kind of graph would provide readers with valuable insight into the direct relationship between ash percentage and conductivities.
Response of authors:
Thank you for the important comment, which in our opinion improved the level of the manuscript. We have decided to incorporate the suggested graphical dependence of conductivity and ash content into the supplementary materials of the manuscript (Figure S2). The reason is straightforward, the manuscript already contains 6 figures and 5 tables, which is in our opinion already a high number and for these reasons, we have decided to include the suggested graphical illustration in the supplementary materials of the manuscript. Moreover, the discussion in the manuscript text was adequately extended by using the outcomes coming from Figure S2 (Lines: 371–378):
…. Figure S2 (Supplementary materials) indicate a dependence of the conductivities of studied biochar samples on their mineral ash content (WMIN). There is a visual separation of individual studied biochar samples, which is significant proof of the importance of biochar mineral content on this parameter and this has a direct connection to the production conditions and source biomass feedstock…
Point 8. The mineral composition of biochar is influenced by the soil conditions under which it was produced. Examine this component by referencing relevant literature research.
Response of authors:
The author collective does not understand the meaning of this reviewer's comment. If it is connected with the production conditions of biochar, we believe the information is already mentioned throughout the manuscript. We have also incorporated some additional discussion in the manuscript text (Lines: 373-378). If not and the meaning of this comment is different, please specify.
Point 9. Figure 3 can be split into 2 graphs and then merged–This way would be easy to read the data.
Response of authors:
We thank the reviewer for this suggestion. We have separated Figure 3 into two particular parts, which are merged into one figure (Line: 685). Correspondingly, the data for fractions of biochar samples BCH-N and BCH-S are shown in Figure 3A and data for remaining biochar BCH-CZ are shown in Figure 3B. We have pointed out, that this modification significantly improved the visibility and resolution of shown data in this figure.
Point 10. Improve the quality of figure 6.
Response of authors:
We agree, that the resolution of Figure 6 was a little bit lower. We have adequately increased the resolution of Figure 6 (Line: 835).
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
Comments and Suggestions for AuthorsDear authors,
Although the topic of your article is very interesting and of great interest for agriculture and environment, unfortunately results that are presented in the article are not sufficient to describe how particle size and texture influence agronomical potential of biochar.
I have inserted many comments in the text of the paper but the main deficiencies of your paper are following:
1. Some of the data that you present in the paper are already published
3. You do not analyze the influence of particle size on measured properties (micronutrients and organics) although the title is indicating that tis the main topic of the paper.
3. And finally, the biggest drawback of your paper is missing data from the pot experiment that you described in materials and methods and which is quite interesting in design and could give valuable results and explanations on relationship between biochar particle size and its agronomic potential. There are no results presented although these results should be the core of the paper.
I would strongly recommend you to rewrite the paper and to present result from the pot test and than to submit the paper again.
Comments for author File: Comments.pdf
Author Response
Dear reviewer,
we would like to thank you for the time taken for precise reading and reviewing of our manuscript entitled The effect of biochar particle size and texture on the leaching of organic molecules and macro- and microelements (title modified according to the suggestion of a reviewer, original name: Biochar particle size and texture – parameters affecting its agronomical potential through the effect on the leaching of organic molecules and macro- and microelements). The authors appreciate the objectivity of your comments and suggestions.
At the beginning of the author's response to the reviewer´s comments, we have to explain the way how the manuscript was modified/corrected. Firstly, the original uploaded version of the manuscript was due to our mistake and swapping of the Word files not the final version of the document. Unfortunately, the uploaded version of the manuscript missed some crucial sections in the results and discussion dealing with the characterization of biochar samples obtained after the termination of cultivation experiments in selected soil samples (cultivation for 2 years in four different soils in the presence of Zea mays as the model plant). We believe that without these missing parts, the original idea of the manuscript would be not complete, and the information transferred to the readers would be not clear. For these reasons, we included the missing parts of the text in the revised version of the manuscript and highlighted them in the text by red colour. Secondly, all the other corrections made according to the notes and suggestions of the individual reviewers are highlighted by the green colour of the text.
Hereby, we can confirm that we have properly considered each point of the comments and we have modified the manuscript accordingly. Here are the responses to the reviewer´s comments:
Point 1: Some of the data that you present in the paper are already published
We would like to thank you for this point. Actually, this issue is also explained at the beginning of the results and discussion section (Lines: 326-344). We explained in that part of the text, that this work continues on our previous published work (Kalina et al., 2022, Agronomy, doi: 10.3390/agronomy12081768). Also, all the data, which were published in our previous manuscript and are used in the current manuscript, are properly cited. The reason, why we included some of our previous data in the current manuscript is to introduce the topic of our present work in broader consequences, to define the basics of the problem by the results obtained by the physicochemical and morphological characteristics of studied biochar samples. These aspects were further studied in more detail either from the view of particle size effect on leaching and potential to leach the mineral contents of biochar as well as the organic contents with special attention to the group of polycyclic aromatic compounds as these groups of molecules can be co-generated during biochar production and according to the EBC should be monitored.
Point 2: You do not analyze the influence of particle size on measured properties (micronutrients and organics) although the title is indicating that tis the main topic of the paper.
Thank you, but we think that all the aspects described in the manuscript are properly analysed and discussed. The only minor exception might be in the case of biochar fraction size effects on micronutrient contents, as the concentrations of micronutrients were extremely low (almost meeting the limits of the method (ICP-OES)). We don’t agree with the reviewer that the effect of particle size on the organic content of biochar is not analysed in the manuscript. This topic is addressed either from the point of view of total organic matter content (lines: 350–405) but also from the view of specific groups of organic components – polycyclic aromatic compounds (lines: 763-863), which are discussed in the last part of the discussion section and these aspects are also statistically evaluated by the calculation of Pearson correlation coefficients.
Point 3: And finally, the biggest drawback of your paper is missing data from the pot experiment that you described in materials and methods and which is quite interesting in design and could give valuable results and explanations on relationship between biochar particle size and its agronomic potential. There are no results presented although these results should be the core of the paper.
Ok, we agree with this comment of the reviewer. Unfortunately, the data obtained from the analysis of biochar samples after the cultivation in the particular soils were missing in the previously uploaded version of the manuscript due to a mistake made during the uploading of the manuscript. We have explained this issue at the beginning of the authors' response to the reviewers’ comments. We added all the missing parts of the text into the current revised version of the manuscript (these originally missed parts of the text are highlighted in the current revised version of the manuscript by the red colour of the text; the revisions made according to the comments of the reviewers are highlighted by the green colour of the text).
Besides these described modifications, we have also performed the English style and spell-check corrections, which were suggested by one of the reviewers. This step was realized by a native professional proofreader. We believe that these corrections considerably enhanced the quality of the manuscript. Please, kindly find the modified manuscript enclosed.
Moreover here are some of the authors' comments to the notes and revisions made by the reviewer directly to the text of the manuscript (some of the comments were not clear or probably written in another language)
Point 1: Line 178 (in the revised version of the manuscript) – Does the biochar from Biouhel.cz s.r.o company have the EBC certification
Response: No it doesn´t. It is described in the text, that EBC certifications have only the first two mentioned biochar samples. The last one was the biochar produced by the domestic producer in the Czech Republic, which produces the material for use in agriculture (but without EBC certification)
Point 2: Table 1 (line 179 in the revised version of the manuscript) – Why there are only 2 fractions of biochar BCH-CZ
Response: This material was much more fine in its structure, it was not possible to provide more particular size fractions
Point 3: Line 202–203 – Why did we select the soil sample in the work?
Response: These soil samples are the most abundant soil types in the Czech Republic. This sentence was added to the text (lines 202-203).
Point 4: Line 215–238 – Pot cultivation experiments should be written in more detail.
Response: This paragraph was supplemented by a more detailed description of the experiment (lines 218–219, 230–231).
Point 5: Line 293 – Why did you use hydromatrix?
Response: We used this setup of GC-MS because it was optimized for this kind of analysis and it provided us with the best results.
Point 6: lines: 535-537 – But you have a higher pH for BCH-N than BCH-Cz and BCH-S and BCH-N sample has lower K content.
Response: This issue is also connected with the used biomass feedstock and the pyrolysis conditions, which has also an effect on the residual (not pyrolyzed) content of organic matter, which in the case of BCH-CZ was different (lower pyrolysis temperature) and resulted in lower pH of this material. More details on this topic are discussed in our previously published manuscripts (doi: 10.3390/ma15248855 and doi: 10.3390/agronomy12081768).
Point 7: Lines 541 and 544 – reference?
Response: The reference is not needed, these values are actual measured data, which are also shown in the manuscript (in Figure 2A).
Point 8: Line 590–593 – The results shown in Figure 3A do not this statement.
Response: We don’t agree with the reviewer. Generally said, Mg and Na are in the case of the studied biochar samples beside K other significant macroelements, which were detected (plus P in the case of BCH-S sample). This statement is further explained in the text.
Point 9: Lines 597-600 – be careful with an explanation like this about the pH
Response: The text describing the observed trend was modified according to the suggestion of the reviewer.
Point 10: Lines 680-707 – description of direct and indirect correlation obtained by Pearson correlation analysis
Response: We don’t agree with the suggested modification of indirect correlation to the negative and direct correlation to the positive. The terms used in our manuscript are generally used in statistical analyses
Point 11: Line 686 – Please specify the statistical significance of the test
Response: The statistical significance was according to the suggestion added to the data showing results of the Pearson correlation analysis in Table 7 (line 698) and Table 8 (848) as well as to the text describing the Pearson correlation analysis of K content in the particular fractions of biochar (lines 550 and 553).
Point 12: Line 717-718 – Ni and Cr are not micronutrients, delete them
Response: Ni and Cr are listed in some sources between micronutrients, but they are not common. For this reason, we have decided to delete these two elements from the text (lines 717-718)
Point 13: Line 718 – I would rather say their bioavailability is limited
Response: The statement was modified according to the suggestion of the reviewer (line 718)
Point 14: Line 801 – The decrease is not general, BCH-N does not follow the trend
Response: We agree with the point, the sentence was modified according to the suggestion of the reviewer.
We hope that the provided modifications and offered explanations will meet Your requirements.
Best regards,
The authors collective
Author Response File: Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for Authors« Biochar particle size and texture… » paper by Sovova et al. Is a nicely written paper of importance to Agronomy and to researchers interested in biochar and its diverse applications.
It asks important questions relevant to the elements or molecules left in the biochar after carbonization and their extraction from samples with controlled texture and particle size.
It could be published after consideration of the comments noted below.
-The title is a little bit long and should have around 10 words
-Limit to 6 keywords ; for example pH or conductivity are not attractive keywords for a biochar paper.
-The literature survey is not up to date. The authors should cite relevant papers dated 2023-2024.
-With references 14-20 the authors could consider citing https://doi.org/10.1007/s42247-023-00603-y
-Between lines 102 and 103 (« …1 % of their total content. » and « Due to the above-summarized findings, we focused… ») the authors should add a short paragraph to indicate what is lacking in the literature and worth to be reported. In other words, the novelty statement of the paper should be provided. The reader cannot see the gap filled by this interesting paper.
-There is no obvious justification for the choice of the biochar samples. They are not from the same biomass, pyrolysis conditions are different, they are produced in three different countries which induces issues related to energy required to ship specimens. This reviewer is aware that this is a fundamental work but sustainability should be considered.
-Justify the drying at 45 °C for 48h. This gives extra cost to the whole process. Do the authors believe that farmers will dry biochar prior to use ? samples without any drying should have been tested.
-The following statement in lines 301-303« which results in the increased content of relatively temperature-stable alkaline inorganic salts (salts of alkaline metals and alkaline earth metals e.g., K, Na, Mg and Ca)… » could be supported by the work of Bayoka et al https://doi.org/10.1016/j.jaap.2023.106069 (see Figure 2, the increase of K/C with pyrolysis temperature (Figures 2g-i), and the decrease of N/K with temperature (Figure 3).
-The paper will be strengthen with SEM images of the three types of biochars.
-The ICP study of the extractable elements is certainly interesting but does it correlate with specific surface area (SSA). BSH-S samples have highest SSA, does leach elements more easily ?
Author Response
Dear reviewer,
we would like to thank you for the time taken for precise reading and reviewing of our manuscript entitled The effect of biochar particle size and texture on the leaching of organic molecules and macro- and microelements (title modified according to your suggestion, original name: Biochar particle size and texture – parameters affecting its agronomical potential through the effect on the leaching of organic molecules and macro- and microelements). The authors appreciate the objectivity of your comments and suggestions.
At the beginning of the author's response to the reviewer´s comments, we have to explain the way how the manuscript was modified/corrected. Firstly, the original uploaded version of the manuscript was due to our mistake and swapping of the Word files not the final version of the document. Unfortunately, the uploaded version of the manuscript missed some crucial sections in results and discussion dealing with the characterization of biochar samples obtained after the termination of cultivation experiments in selected soil samples (cultivation for 2 years in four different soils in the presence of Zea mays as the model plant). We believe that without these missing parts, the original idea of the manuscript would be not complete, and the information transferred to the readers would be not clear. For these reasons, we included the missing parts of the text in the revised version of the manuscript and highlighted them in the text by red colour. Secondly, all the other corrections made according to the notes and suggestions of the individual reviewers are highlighted by the green colour of the text.
Hereby, we can confirm that we have properly considered each point of the comments and we have modified the manuscript accordingly. Here are the responses to the reviewer´s comments:
Point 1: The title is a little bit long and should have around 10 words
We would like to thank you for this point. The original title was selected to point out the fact, that the present manuscript is the second part of our complex in-depth research of selected commercial biochar samples. The first part was published in Agronomy in 2022 (doi: 10.3390/agronomy12081768). On the other hand, we understand that the original manuscript title was too long and complicated and the idea of separation of our work according to the particular topics between two individual manuscripts issued in different years could be not clear to the readers. For these reasons, we have decided to modify the title according to your suggestion to “The effect of biochar particle size and texture on the leaching of organic molecules and macro- and microelements”.
Point 2: Limit to 6 keywords; for example pH or conductivity are not attractive keywords for a biochar paper.
Thank you for this point. We agree, the updated list of keywords is following:
agriculture, biochar, macro- and microelements, particle size, polyaromatic hydrocarbons, soil conditioner
Point 3: The literature survey is not up to date. The authors should cite relevant papers dated 2023-2024.
Thank you for this point. We have included up-to-date references in the modified version of the introduction section (ref. no. 9 - doi:10.1016/j.jaap.2023.105858; 10 – doi:10.1007/s11814-023-1465-4; ref. no. 18 – doi:10.3390/agronomy13051394; ref. no. 19 – doi:10.3389/fenvs.2023.1114728; ref. no. 28 – doi:10.1016/j.ecoenv.2023.115589 and ref. no. 29 – doi:10.1021/acssuschemeng.2c00952) (lines: 50, 71 and 123). We believe the added up-to-date references have strengthened the theoretical background of the work described in the introduction section.
Point 4: With references 14-20 the authors could consider citing https://doi.org/10.1007/s42247-023-00603-y.
Thank you for your suggestion. We included this reference to that part of the text (Line: 50, reference no: 8). We believe the suggested reference fits to the ideas described in the paragraph and it scientifically strengthens that part of the text.
Point 5: Between lines 102 and 103 (« …1 % of their total content. » and « Due to the above-summarized findings, we focused… ») the authors should add a short paragraph to indicate what is lacking in the literature and worth to be reported. In other words, the novelty statement of the paper should be provided. The reader cannot see the gap filled by this interesting paper.
Thank you for this important comment. We agree that the motivation of the work was from the original introduction section not clear. For these purposes, we have significantly rewritten the concluding part of the introduction section (Lines: 131–171) to point out the main motivation of the manuscript, which is the research on the particular effect of biochar fraction size and texture on the corresponding mineral and organic matter contents of biochar. These aspects were studied from the analysis of aqueous-extractable contents of these compounds in combination with their total detected content in biochar structure. This comparison gave us an idea about the potential long-term release of these particular groups of compounds from biochar structure to the soil. Moreover, to be able to discuss these results with respect to the real conditions in the soil, these data were compared to the analysis performed on the biochar samples obtained after the termination of long-term cultivation experiments in four different soil types. The obtained set of biochar complex characteristics represented by the content and potential availability of mineral nutrients, organic molecules and polycyclic aromatic compounds and the connection of these characteristics to the corresponding texture of material (particle size, specific surface area) can provide the necessary insights, which could help in further assessment of the optimal application conditions of biochar in agriculture, where it could serve as a promising soil supplement.
Point 6: There is no obvious justification for the choice of the biochar samples. They are not from the same biomass, pyrolysis conditions are different, they are produced in three different countries which induces issues related to energy required to ship specimens. This reviewer is aware that this is a fundamental work but sustainability should be considered.
We fully understand your comment about the variability of selected biochar samples in the work. Originally, the selection of the biochar sample database in our work consisted of commercial materials, which possess the EBC (European Biochar Certificate) for use in agriculture as the soil conditioner. We have collected in our database several other commercial biochar samples possessing the EBC certification (from Germany, Serbia, Italy...). In the end, we understood that it is not possible to realize all the analyses on the whole sample database and to perform the long-term cultivation test due to the capacity issues of people and also our cultivation boxes. For these reasons, we have focused on the nearest producers to the Czech Republic – Germany (Novocarbo GmbH) and Austria (Sonnenerde GmbH). Additionally, we also added one product of a local producer from the Czech Republic (Biouhel.cz company), which provides a commercial product for agriculture to the Czech market. We wanted to have a comparison of this product with the data for producers having the EBC certification.
Point 7: Justify the drying at 45 °C for 48h. This gives extra cost to the whole process. Do the authors believe that farmers will dry biochar prior to use? samples without any drying should have been tested. We agree that the drying process could significantly increase the costs. But have to explain this procedure, which was mentioned in the manuscript. Unfortunately, the text in the method section of the manuscript was not clear. We have dried only those samples, which were subsequently sieved on individual fractions (a drying step was added to increase the efficiency of sieve analysis). The samples used for cultivation experiments (which simulate the practical application by the farmers on a laboratory scale) were used without the drying step. For these reasons the text (Lines: 181–185) was modified in the following way to increase clarity: ”Biochar samples used for the cultivation experiments were utilized in the forms as were obtained from the producers without any further pre-treatment. The samples used for the study on the particular effects of the fraction size of biochar were initially air-dried at 45 °C for 48 hours to remove the absorbed moisture (its presence might complicate the fractionation of biochar during the sieve analysis)”.
Point 8: The following statement in lines 301-303« which results in the increased content of relatively temperature-stable alkaline inorganic salts (salts of alkaline metals and alkaline earth metals e.g., K, Na, Mg and Ca)… » could be supported by the work of Bayoka et al https://doi.org/10.1016/j.jaap.2023.106069 (see Figure 2, the increase of K/C with pyrolysis temperature (Figures 2g-i), and the decrease of N/K with temperature (Figure 3).
We agree with the reviewer that the suggested reference can scientifically support the ideas written in that part of the manuscript. For this reason, we included the mentioned reference in a text (line: 423–426, reference no. 41).
Point 9: The paper will be strengthen with SEM images of the three types of biochars.
We agree with this suggestion. The visualization of the internal porous structure and morphology of used biochar samples obtained by SEM helped to create the complex idea of used biochar samples and the corresponding characteristics studied in the manuscript. We have included SEM images of used biochar samples in Figure 1 (line: 198). Moreover, the information about the SEM analysis and its correlation with corresponding SSA was included in the text in the Materials and Methods section (lines: 193-194) and also in the Result and Discussion section (Lines: 482–493).
Point 10: The ICP study of the extractable elements is certainly interesting but does it correlate with specific surface area (SSA). BSH-S samples have highest SSA, does leach elements more easily ?
We agree with your suggestion. The SSA should be in direct connection with the potential to leach the inorganic elements from the material when it comes in contact with an aqueous solution. This can be explained by the increased surface area between solid material and solvent in the case of particles with higher SSA. The discussion in the text of the manuscript was extended in this suggested way (Lines: 526-532, 596-606 and 823-826).
Besides these described modifications, we have also performed the English style and spell-check corrections, which were suggested by one of the reviewers. This step was realized by a native professional proofreader. We believe that these corrections considerably enhanced the quality of the manuscript. Please, kindly find the modified manuscript enclosed.
We hope that the provided modifications and explanations of our opinions on the particular comments will meet Your requirements.
Best regards,
The authors collective
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsSome comments are listed to improve the manuscript:
1. The main issue of the current version of manuscript is to clearly explain the reason why this manuscript including two parts, the content of elements and PAHs in both total and aqueous extractable, what is the link between these two parts?
2. Keywords: the number of keywords is way too many, reduce them into 5 to 6 words.
3. Line 96: what is PHAs?
4. Introduction section: There are too many ‘authors’ in the introduction, which impacts the flurence of the context. I suggest more directly introduce the current background of the biochar effects on soil physiochemical properties.
5. Introduction: the main research questions are not clear, please summarize them in the introduction.
6. Results, line 271-273: ‘The higher capability of the finest biochar particle to release inorganic ions has a direct effect on the physicochemical properties’. It is not available to get these results from Table 4.
7. Figure 1: the label of y-axis is too long, as ‘total and aqueous’ has been mentioned in the legend of the figure.
8. Results: It is lack of significant difference presented in the figures, therefore, the comparison of concentrations was not convinced.
9. Results, line 345-349: Here it shows the Pearson correlation coefficient, however, the significance needs to be presented.
10. The discussion part was missing in the manuscript, since the Results section contained a certain amount of discussion, I suggest change the section name of ‘Results’ into ‘Results and Discussion’.
11. Conclusion: The current version of conclusion is not clear and concise, it is more like a summary instead of conclusion, please rewrite this section.
Author Response
Dear reviewer,
we would like to thank you for the time taken for precise reading and reviewing of our manuscript entitled The effect of biochar particle size and texture on the leaching of organic molecules and macro- and microelements (title modified according to the suggestion of a reviewer, original name: Biochar particle size and texture – parameters affecting its agronomical potential through the effect on the leaching of organic molecules and macro- and microelements). The authors appreciate the objectivity of your comments and suggestions.
At the beginning of the author's response to the reviewer´s comments, we have to explain the way how the manuscript was modified/corrected. Firstly, the original uploaded version of the manuscript was due to our mistake and swapping of the Word files not the final version of the document. Unfortunately, the uploaded version of the manuscript missed some crucial sections in results and discussion dealing with the characterization of biochar samples obtained after the termination of cultivation experiments in selected soil samples (cultivation for 2 years in four different soils in the presence of Zea mays as the model plant). We believe that without these missing parts, the original idea of the manuscript would be not complete, and the information transferred to the readers would be not clear. For these reasons, we included the missing parts of the text in the revised version of the manuscript and highlighted them in the text by red colour. Secondly, all the other corrections made according to the notes and suggestions of the individual reviewers are highlighted by the green colour of the text.
Hereby, we can confirm that we have properly considered each point of the comments and we have modified the manuscript accordingly. Here are the responses to the reviewer´s comments:
Point 1: The main issue of the current version of manuscript is to clearly explain the reason why this manuscript including two parts, the content of elements and PAHs in both total and aqueous extractable, what is the link between these two parts?
The authors´ collective of the manuscript agree that the separation of the discussion section into two parts might be a little bit confusing. The overall idea of the manuscript was to study the particular effects of biochar fraction size and texture on the corresponding mineral and organic matter contents of biochar. These aspects were investigated by the analysis of aqueous-extractable contents of these compounds in combination with their total detected content in biochar structure. Firstly, our previous manuscript was dealing with the particular effects of biochar fraction size on the overall organic matter content in biochar and the physicochemical properties of biochar (these characteristics are in more detail discussed in our previous publication – Kalina, M. et al., Agronomy 2022, 12, doi: 10.3390/agronomy12081768). The results of our previous work brought us to the idea of providing a complex view on the effect of biochar fraction size and texture and the mineral and organic contents of biochar and the availability of these types of structures. According to the EBC certification, there is a specific group of polycyclic aromatic organic compounds, which needs to be also monitored (substituted PAHs, nitrogen and sulfur heterocycles and substituted naphthalenes). To be able to provide complex information on the effect of biochar fraction size on the content and availability of these particular mineral and organic components, we decided to include the availability of polycyclic aromatic compounds as the concluding chapter of the present manuscript.
For these above-mentioned reasons, the concluding part of the introduction section and the initial paragraphs of the discussion section were rewritten to point out the main motivations of the work and the reason, why the discussion section was separated into two separate chapters (Lines: 131–170, 333–341).
Point 2: Keywords: the number of keywords is way too many, reduce them into 5 to 6 words.
Thank you, we agree with your suggestion. The updated list of keywords is following:
agriculture, biochar, macro- and microelements, particle size, polyaromatic hydrocarbons, soil conditioner
Point 3: Line 96: what is PHAs?
We would like to thank the reviewer for pointing out this mistake. This is a spell-check mistake. There should be PAHs. This mistake was corrected in a revised version of the manuscript (Line: 124).
Point 4: Introduction section: There are too many ‘authors’ in the introduction, which impacts the flurence of the context. I suggest more directly introduce the current background of the biochar effects on soil physiochemical properties.
Thank you, we understand your point. We have rewritten the significant parts of the introduction section to provide more focused information on the main topics addressed in the following parts of the manuscript (Lines: 46–72, 74–76, 80–81, 84–119). According to the suggestion, the total number of cited references of the authors has also decreased.
Point 5: Introduction: the main research questions are not clear, please summarize them in the introduction.
We would like to thank the reviewer for this important comment. We agree that the motivation of the work was from the original introduction section not clear. For these purposes, we have significantly rewritten the concluding part of the introduction section (Lines: 131-170) to point out the main motivation of the manuscript, which is the research on the particular effect of biochar fraction size and texture on the corresponding mineral and organic matter contents of biochar and mainly their availability to the soil (after biochar application as the soil conditioner).
Point 6: Results, line 271-273: ‘The higher capability of the finest biochar particle to release inorganic ions has a direct effect on the physicochemical properties’. It is not available to get these results from Table 4.
We agree that mainly in the case of pH, the effect was not statistically significant and there were also mentioned some characteristics, which were not shown in that table. For this reason, we modified the text (lines: 409–411) to discuss the only data shown in the table (currently Table 5, because one table – Table 2 was added to the manuscript during the revision process).
Point 7: Figure 1: the label of y-axis is too long, as ‘total and aqueous’ has been mentioned in the legend of the figure.
We agree with this reviewer's point and for this reason the label of the y-axis of Figure 2 (originally Figure 1, but one more figure (figure 1) was added to the manuscript according to the suggestion of one reviewer, who suggested showing SEM image of used biochar samples was added to the manuscript). The modified label of the y-axis of Figure 2A is: “K content in dry biochar (mg/g)”.
Point 8: Results: It is lack of significant difference presented in the figures, therefore, the comparison of concentrations was not convinced.
We understand that some of the results were not of a significant difference, but the main idea of the manuscript was the correlation of various characteristics of biochar (organic content, the content of polycyclic organic compounds, macro and microelements contents etc.) with the fraction size of biochar. It was not possible to get statistically significant differences in all the studied aspects. Nevertheless, we believe that the results of our work have shown several significant aspects which can be influenced by the particle size of used biochar. This is an important result taking into account the possible utilization as a soil conditioner in agriculture.
Point 9: Results, line 345-349: Here it shows the Pearson correlation coefficient, however, the significance needs to be presented.
This is an important point, and we agree with your suggestion. The text (lines 548 and 551-552) was supplemented by a significance level indication. Also, the remaining Pearson correlation analysis coefficients in the manuscript were supplemented by missing information about the significance level (Table 7, line: 696 and Table 9, line: 846).
Point 10: The discussion part was missing in the manuscript, since the Results section contained a certain amount of discussion, I suggest change the section name of ‘Results’ into ‘Results and Discussion’.
Thank you for this point. We agree with the suggested modification of the section title. Originally, the section “Result” should have been named “Results and Discussion”. The title of this section was corrected according to your point (line: 267).
Point 11: Conclusion: The current version of conclusion is not clear and concise, it is more like a summary instead of conclusion, please rewrite this section.
We would like to thank the reviewer for pointing out the issue. We have modified the conclusion section (lines: 898-907, 910-913, 916-921, 929-930, 950-952) to provide a more concise and clearer take-home message of the main outcomes of the work. In our opinion, the suggested modification helped in providing a clear message of the main outcomes of the research.
Besides these described modifications, we have also performed the English style and spell-check corrections, which were suggested by one of the reviewers. This step was realized by a native professional proofreader. We believe that these corrections considerably enhanced the quality of the manuscript. Please, kindly find the modified manuscript enclosed.
We hope that the provided modifications and explanations of our opinions on the particular comments will meet Your requirements.
Best regards,
The authors collective
Author Response File: Author Response.pdf
Reviewer 4 Report
Comments and Suggestions for AuthorsThis valuable contribution on the mechanisms of biochar as a soil amendment can be improved by extensive editing:
1. Remove the "we..." orientation in much of the text; e.g., delete "These aspects were addressed in our study." (Line 15). Lines 109-110 could be "Our research primarily focused..." Line 114 could start with "The obtained set of basic..." In Line 436, "Statistical" and "was performed also to" could be removed if "show" is changed to "showed". Editing of Lines 659-660 could include replacing "We believe the results summarized in our work will" with "These results".
2. Several sentences start with numbers.
3. The last sentences of Sections 2.4, 2.5.1, and 2.5.2 are not needed given the opening sentence of 2.7, which would suffice by deleting "the results" and replacing "in the manuscript are shown in the form of" with "as".
4. Section 3 should be "Results and Discussion"
5. The literature citations are oddly placed in many cases.
6. The Worg column in Table 4 would be better placed at the far right.
7. Add significance indicators to Tables 6, 7, and 8 if there is significance.
8. Table 8 is not cited in the text.
9. References are not consistently formatted.
10. Add et al. coauthors to Reference 3.
Comments on the Quality of English LanguageEditing needed.
Author Response
Dear reviewer,
we would like to thank you for the time taken for precise reading and reviewing of our manuscript entitled The effect of biochar particle size and texture on the leaching of organic molecules and macro- and microelements (title modified according to the suggestion of a reviewer, original name: Biochar particle size and texture – parameters affecting its agronomical potential through the effect on the leaching of organic molecules and macro- and microelements). The authors appreciate the objectivity of your comments and suggestions.
At the beginning of the author's response to the reviewer´s comments, we have to explain the way how the manuscript was modified/corrected. Firstly, the original uploaded version of the manuscript was due to our mistake and swapping of the Word files not the final version of the document. Unfortunately, the uploaded version of the manuscript missed some crucial sections in results and discussion dealing with the characterization of biochar samples obtained after the termination of cultivation experiments in selected soil samples (cultivation for 2 years in four different soils in the presence of Zea mays as the model plant). We believe that without these missing parts, the original idea of the manuscript would be not complete, and the information transferred to the readers would be not clear. For these reasons, we included the missing parts of the text in the revised version of the manuscript and highlighted them in the text by red colour. Secondly, all the other corrections made according to the notes and suggestions of the individual reviewers are highlighted by the green colour of the text.
Hereby, we can confirm that we have properly considered each point of the comments and we have modified the manuscript accordingly. Here are the responses to the reviewer´s comments:
Point 1: Remove the "we..." orientation in much of the text; e.g., delete "These aspects were addressed in our study." (Line 15). Lines 109-110 could be "Our research primarily focused..." Line 114 could start with "The obtained set of basic..." In Line 436, "Statistical" and "was performed also to" could be removed if "show" is changed to "showed". Editing of Lines 659-660 could include replacing "We believe the results summarized in our work will" with "These results".
We would like to thank you for this important point. We have corrected the text according to your suggested way. The text was modified on the following lines (e.g. l20, 30, 131-132, 326, 350, 816, 819, 841, 891-892, 932, 942-943).
Point 2: Several sentences start with numbers.
Thank you for this point. We have corrected these issues (Lines: 257, 272, 280, 291).
Point 3: The last sentences of Sections 2.4, 2.5.1, and 2.5.2 are not needed given the opening sentence of 2.7, which would suffice by deleting "the results" and replacing "in the manuscript are shown in the form of" with "as".
We would like to thank you for this point. We have corrected the text according to your suggestions (Lines: 259-261, 275-277, 284-286, and 298-300). Moreover, the same was done in section 2.6, where the sentence: “These samples were prepared in three independent replicates. The results are presented in the manuscript in the form of average value ± SD.” was also deleted (lines: 306–308).
Point 4: Section 3 should be "Results and Discussion"
The name of section 3 was corrected to “Results and Discussion”.
Point 5: The literature citations are oddly placed in many cases.
We would like to thank you for this point. We understand, that there were several places in the text, where the references were oddly placed. The collective of authors of the manuscript did their best to revise and correct the positions, where the citation of the individual references are shown in the text.
Point 6: The Worg column in Table 4 would be better placed at the far right.
We would like to thank the reviewer for the suggestion, but we have decided to leave the current format of Table 5. The reason is straightforward, we believe it is better this way for comparison of the total content of organic matter (Worg) and total organic carbon (as the main component of biochar organic matter), which are in a present form first two columns. The movement of Worg column to the right would bring more difficulties for comparison of these two important biochar characteristics.
Point 7: Add significance indicators to Tables 6, 7, and 8 if there is significance.
We agree with this suggestion. The missing significance was added to the titles of Tables 7, 8 and 9 (the numbers are +1 because one additional table (Table 2) was added to the manuscript).
Point 8: Table 8 is not cited in the text.
Thank you for this point, the citation of Table 8 was missing in the text. We have included this citation in the text, where the data from the table are discussed (Line: 738).
Point 9: References are not consistently formatted.
Thank you, we agree that some references had different formats. This mistake was corrected according to your suggestion.
Point 10: Add et al. coauthors to Reference 3.
Thank you for this comment. This reference was deleted from the reference list due to the corrections performed in the introduction section.
Besides these described modifications, we have also according to your suggestion performed the English style and spell-check correction of manuscript text by a native professional proofreader. We believe that these corrections considerably enhanced the quality of the manuscript. Please, kindly find the modified manuscript enclosed.
We hope that the provided modifications and explanations of our opinions on the particular comments will meet Your requirements.
Best regards,
The authors collective
Author Response File: Author Response.pdf
Round 2
Reviewer 3 Report
Comments and Suggestions for AuthorsComments：
1. It is important to include statistical analysis in the scientific work, here in the manuscript, I still did not see any significant labels in all the figures to see if the results are significant different or not.
2.There are too many Tables and figures presented in the main manuscript, I suggest moving at least three of tables to the supplementary materials. For the figures, some of them can be combined to one figure.
3. In section 3.3, It is lack of summarization and deep discussion after the PCA and RDA analysis, please try to answer the questions about what kind of biochar provides more organic molecules and macro-elements during the leaching.
Author Response
Dear reviewer,
we would like to thank you for the time taken for precise reading and reviewing of our manuscript entitled The effect of biochar particle size and texture on the leaching of organic molecules and macro- and microelements (title modified according to the suggestion of a reviewer, original name: Biochar particle size and texture – parameters affecting its agronomical potential through the effect on the leaching of organic molecules and macro- and microelements). The authors appreciate the objectivity of your comments and suggestions.
The present revisions made according to the comments of a reviewer are made in the text using the revision mode available in MS Word. We would like to confirm that we have properly considered each point of the comments and we have modified the manuscript accordingly. Here are the responses to the reviewer´s comments:
Point 1: It is important to include statistical analysis in the scientific work, here in the manuscript, I still did not see any significant labels in all the figures to see if the results are significant different or not.
The authors´ collective has decided according to the suggestion of a reviewer to include the statistical analysis by using Tukey test (identification of significant differences in shown data) into Figures 1–5. The following text explaining the use of the indexes indicating the significant differences in the data was added in a title Figure 1-5: “different letter indexes above columns indicate significant differences according to Tukey test on significance level 0.05.
Point 2: There are too many Tables and figures presented in the main manuscript, I suggest moving at least three of tables to the supplementary materials. For the figures, some of them can be combined to one figure.
Thank you for this suggestion. We agree that the previous version of the manuscript contained too many tables. We have transferred three tables (Table 3 => Table S1 (settings of ICP-OES analysis), Table 4 => Table S2 (settings of GC-MS analysis) and Table 8 => Table S3 (Al, Fe, Zn aqueous and total extractable contents in fractions of biochar) and one Figure (Figure 1 => Figure S1 showing SEM visualization of used biochar samples) in Supplementary materials.
Point 3: In section 3.3, It is lack of summarization and deep discussion after the PCA and RDA analysis, please try to answer the questions about what kind of biochar provides more organic molecules and macro-elements during the leaching.
We would like to thank the reviewer for this comment. We understand that the discussion in this section was originally simpler and more concise. All the observed trends in data were already discussed in the Results and Discussion section. However, we agree with a reviewer that the information about the mutual comparison between producers in respect to their organic/mineral content was not mentioned. We have included this information in section 3.4 (lines: 885–895) according to the suggestion of the reviewer (the numbering of this section was corrected, because we have found out, that there were two sections labelled 3.3 in the last version of the manuscript).
We hope that the provided modifications and explanations of our opinions on the particular comments will meet Your requirements.
Best regards,
The authors collective
Author Response File: Author Response.pdf
