Review Reports - Can Biochar Alleviate Machinery-Induced Soil Compaction? A Field Study in a Tuscan Vineyard

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Thank you for the opportunity to review your manuscript. I found it to be an informative and well-structured study that engages a relevant topic in soil science. Your transparent approach, thoughtful interpretation of findings, and effective use of visual aids made for an engaging read. That said, I believe the manuscript could be strengthened through revisions in the following areas:

The abstract effectively summarizes the key components of your work. However, it is somewhat lengthy. Consider condensing it by focusing on the most essential points—particularly in the middle section—while retaining the clear articulation of your findings and conclusions.

The introduction is strong and demonstrates a good command of the literature. Your selection of references is well-considered and supports the narrative convincingly. That said, the last paragraph, where you describe the purpose and aim of the study, could benefit from greater clarity and conciseness. This paragraph is crucial, as it sets the direction for the reader—consider making the research questions and objectives more explicit.

The Materials and Methods section is generally well-presented. However, I suggest that you expand the rainfall data provided. While you cite the total annual rainfall, it would significantly enhance the context to include seasonal or monthly rainfall distribution, especially given the known impact of precipitation timing on soil moisture and compaction behavior.

Regarding sampling frequency, three sampling events over the study period may be on the low side, especially for dynamic field conditions. If increasing the sampling frequency is not feasible, consider providing a rationale for the chosen schedule. The statistical analysis is appropriately designed and appears robust, lending credibility to your interpretations.

Your use of the Proctor test is understandable given its standardization and ease of comparison. However, I encourage you to acknowledge its limitations more explicitly. This method, while valid in controlled settings, may not fully capture the in-situ compaction dynamics, particularly in stony soils. Including a brief discussion of field-based alternatives such as cone index measurements at different soil depths would demonstrate methodological awareness and could guide future research.

The results are clearly organized and well-supported by the tables and figures. I appreciate the level of detail, which allows the reader to follow the progression of the findings. The discussion is thoughtful and refreshingly candid. I particularly valued your acknowledgment of the limitations posed by the stony nature of the tested soils—this enhances the credibility of your interpretations.

One surprising result is the lack of significant impact of slope on soil compaction. This warrants more in-depth consideration. You suggest that the stoniness may explain this, which is plausible, but the explanation would benefit from elaboration or citation of similar findings in comparable contexts.

Your conclusions are well-supported by the data and appropriately cautious in tone. I especially appreciate your avoidance of overgeneralization. The alignment between your findings and final statements is strong, and your transparency regarding methodological constraints is a strength of the paper.

While the scientific content is sound, at times the tone and style feel closer to an extension bulletin or farmers' journal than a peer-reviewed research article. This is especially true of the title and a few sections of the text. I encourage you to revise for a more academic tone, especially in how results are presented and in transitions between sections.

This is a solid and honest piece of research. With relatively minor revisions, it has the potential to make a valuable contribution to the literature. I encourage you to sharpen the articulation of your objectives, expand methodological context (particularly rainfall and compaction testing), and consider slight shifts in tone for academic alignment.

Author Response

Reviewer 1:

Comments 1: Thank you for the opportunity to review your manuscript. I found it to be an informative and well-structured study that engages a relevant topic in soil science. Your transparent approach, thoughtful interpretation of findings, and effective use of visual aids made for an engaging read. That said, I believe the manuscript could be strengthened through revisions in the following areas:

Response 1: Thank you for your comments. The abstract underwent a comprehensive re-evaluation and was condensed across all its sections. In the following, reviewers’ comments are followed by our comments in italics.

Comments 2: The introduction is strong and demonstrates a good command of the literature. Your selection of references is well-considered and supports the narrative convincingly. That said, the last paragraph, where you describe the purpose and aim of the study, could benefit from greater clarity and conciseness. This paragraph is crucial, as it sets the direction for the reader—consider making the research questions and objectives more explicit.

Response 2: Thank you for your comment. The 'Aim of the Study' section has been refined for improved clarity and conciseness, with the research questions and objectives now explicitly stated (L102-110).

Comments 3: The Materials and Methods section is generally well-presented. However, I suggest that you expand the rainfall data provided. While you cite the total annual rainfall, it would significantly enhance the context to include seasonal or monthly rainfall distribution, especially given the known impact of precipitation timing on soil moisture and compaction behaviour.

Response 3: We added a description of seasonal rainfall distribution in the text (L119-120).

Comments 4: Regarding sampling frequency, three sampling events over the study period may be on the low side, especially for dynamic field conditions. If increasing the sampling frequency is not feasible, consider providing a rationale for the chosen schedule. The statistical analysis is appropriately designed and appears robust, lending credibility to your interpretations.

Response 4: The rationale of the sampling frequency now is more explicit in the last part of the introduction, that has been improved (L102-110).

Comments 5: Your use of the Proctor test is understandable given its standardization and ease of comparison. However, I encourage you to acknowledge its limitations more explicitly. This method, while valid in controlled settings, may not fully capture the in-situ compaction dynamics, particularly in stony soils. Including a brief discussion of field-based alternatives such as cone index measurements at different soil depths would demonstrate methodological awareness and could guide future research.

Response 5: Actually, our work is based on a field study, and we did not use the Proctor test.

Comments 6: The results are clearly organized and well-supported by the tables and figures. I appreciate the level of detail, which allows the reader to follow the progression of the findings. The discussion is thoughtful and refreshingly candid. I particularly valued your acknowledgment of the limitations posed by the stony nature of the tested soils—this enhances the credibility of your interpretations.

Response 6: Actually, we did not explain the lack of significant impact of slope on soil compaction by the stone content of soil. We just stated that several studies reported that slopes increase BD upon soil compaction compared to flat conditions. Nonetheless, in the current version of the manuscript we added an additional reference, bringing the total to three, to studies that found an exception to the slope effect, and we also expanded the discussion about that point (L382-386).

Comments 7: Your conclusions are well-supported by the data and appropriately cautious in tone. I especially appreciate your avoidance of overgeneralization. The alignment between your findings and final statements is strong, and your transparency regarding methodological constraints is a strength of the paper.

Response 7: Thank you for your comments. We revised the whole text and the title according to your comments

Comments 8: This is a solid and honest piece of research. With relatively minor revisions, it has the potential to make a valuable contribution to the literature. I encourage you to sharpen the articulation of your objectives, expand methodological context (particularly rainfall and compaction testing), and consider slight shifts in tone for academic alignment.

Response 8: Thank you for your comments. We made the suggested improvement, and we think that the current version is improved compared to the previous one.

Reviewer 2 Report

Comments and Suggestions for Authors

The research presents an important approach to the deposition of biochar to protect the soil from compaction, however some points could be improved to make the manuscript clearer and more concise:
a) The Introduction is complete and covers all the topics necessary for the work, however more references to the use of biochar in vineyards could be explored. In addition, the conditions of interaction between machines and tires with the soil could have been explored more in the review.
b) In the methodology, more topics could be included. I suggest subdividing and reorganizing the sequence. First describe the location, then the forms of biochar deposition and finally the tests and analyses. For example, in L110-190, only the experimental site is the topic. This could be divided.
c) An explanatory figure with the steps of the experiment would be interesting in the methodology. I suggest including a figure or flowchart to facilitate understanding of the experimental conduct.
d) In the statistical analyses, better describe the data treatment and exclusion of outliers. Indicate the amount of data that was excluded and provide quantitative data. e) In the methodology, I believe it is not necessary to describe the days of the operations, but rather the period or month of collection. It is more important to describe these collections directly in relation to the period of crop management and machine input. I suggest reorganizing these topics. A figure would also help to clarify the temporality of collections and mechanized operations.
f) The outliers described in lines 264-266 can be moved to the methodology.
g) Improve the resolution of Figure 2. I also suggest colored images and labels on the graphs. This Figure is very important for the research and could be better explored.
h) In the discussion, more references could be explored and the relationship between soil density and the effect of uncontrolled factors in the research could be highlighted. In the discussions, the real differences and applicability of biochar in real crop conditions should be highlighted.
i) The conclusions can be summarized in smaller topics or paragraphs. For example, in Lines 427-435, it seems to me that it is a discussion topic? As a conclusion of the work, these ideas need to be synthesized and direct.

Comments for author File: Comments.pdf

Comments on the Quality of English Language

The language is good, but could be revised for clarity. Long paragraphs with many ideas. The text could be more succinct.

Author Response

Reviewer 2:

Comments 1: The research presents an important approach to the deposition of biochar to protect the soil from compaction, however some points could be improved to make the manuscript clearer and more concise:
a) The Introduction is complete and covers all the topics necessary for the work, however more references to the use of biochar in vineyards could be explored. In addition, the conditions of interaction between machines and tires with the soil could have been explored more in the review.

Response 1: We added a part referring to the use of biochar in vineyard, and another to the interaction between tires and soil, citing the issues related to rutting formation and soil displacement (L38-40 and L79-82)

Comments 2: b) In the methodology, more topics could be included. I suggest subdividing and reorganizing the sequence. First describe the location, then the forms of biochar deposition and finally the tests and analyses. For example, in L110-190, only the experimental site is the topic. This could be divided.

Response 2: We agree with the reviewer. In the current version of the manuscript, an additional section has been added (Experimental design and soil management) (L149)

Comments 3: c) An explanatory figure with the steps of the experiment would be interesting in the methodology. I suggest including a figure or flowchart to facilitate understanding of the experimental conduct.
Response 3: An explanatory Illustration has been added as supplementary material: the illustration shows the timeline of the field campaign and the tractor trafficking interactions. An additional illustration schematises the experimental design of our study. Last, three pictures have been added showing the field status at the time of first (before and after soil compaction) and second Field campaign.

Comments 4: d) In the statistical analyses, better describe the data treatment and exclusion of outliers. Indicate the amount of data that was excluded and provide quantitative data.

Response 4: We added this information, moving a part of the text here from the results section (L249-253).

Comments 5: e) In the methodology, I believe it is not necessary to describe the days of the operations, but rather the period or month of collection. It is more important to describe these collections directly in relation to the period of crop management and machine input. I suggest reorganizing these topics. A figure would also help to clarify the temporality of collections and mechanized operations.
Response 5: We did not fully understand this comment, meaning that indicating the specific day include the information about the period or the month of soil sample collection. Anyway, the collection of soil samples was carried out independently, not coinciding with typical vineyard management practices. For the first year of the study, samples were collected immediately before and after a simulated compaction event, following a designated period after biochar application. The second sampling point occurred one year later. The illustration of the timeline of the field campaign and the tractor trafficking periods, added as supplementary material, should help to clarify the interactions between the two.

Comments 6: f) The outliers described in lines 264-266 can be moved to the methodology.

Response 6: We moved this part in the “Statistical analysis” section (L249-253).

Comments 7: g) Improve the resolution of Figure 2. I also suggest colored images and labels on the graphs. This Figure is very important for the research and could be better explored.

Response 7: We improved this picture according to the suggestions of the reviewer.

Comments 8: h) In the discussion, more references could be explored and the relationship between soil density and the effect of uncontrolled factors in the research could be highlighted.

Response 8: We added some additional references in different parts of the discussion, and we added a part specifically addressing the issue of the uncontrolled factors in the soil compaction field studies (L366-369)

Comments 9: In the discussions, the real differences and applicability of biochar in real crop conditions should be highlighted.
Response 9: Field experiments with biochar are essential to understanding how it affects soil health and crop yields in real-world conditions. These experiments help researchers assess the potential of biochar to improve soil properties, such as water retention and nutrient availability, and reduce pollutants. Long-term studies are especially important to assess the persistence and long-lasting impact of biochar on soil and plant health. Our experiment allowed us to assess the limitations of laboratory experiments and evaluate the real-world effects of biochar on soil compaction.
We added a sentence about this concept in the discussions (L363.366)

Comments 10: i) The conclusions can be summarized in smaller topics or paragraphs. For example, in Lines 427-435, it seems to me that it is a discussion topic? As a conclusion of the work, these ideas need to be synthesized and direct.

Response 10: We reorganised the conclusion section according to the reviewer suggestions. Now the text is clearer and direct.

Reviewer 3 Report

Comments and Suggestions for Authors

Why are the keywords "pyrogenic carbon" and the title and text use the term "biochar"?
"Biochar, a carbon-rich byproduct derived from biomass pyrolysis or gasification, is increasingly recognized as a promising soil amendment due to its environmental benefits, including carbon sequestration, resistance to microbial breakdown, the capacity to trap environmental contaminants (e.g., anti-biotics, heavy metals) and many other beneficial aspects [30–33]."

I do not agree that biochar, which can be effectively used as a soil fertilizer, can be obtained by gasification. Usually, to preserve the porous structure and high content of macronutrients, it is recommended to use slow low-temperature pyrolysis, and not gasification. In fact, the study used biochar obtained using slow pyrolysis technology.

The introduction omits the aspect of the influence of soil compaction on the functioning of the soil microbiota, which determines soil fertility and, accordingly, plant productivity. And also the effect of biochar on soil microbiota. Soil is considered as a non-living substrate, but this is not the case.
Figure 2 and Figure 4 – it would be desirable to make the labels on the axes clearer
Figures 3 and 4: in what units are the moisture data given? In % or in m3/m3? What soil moisture was estimated6 volumetric or weight? This is also not clear from the methodology. Why are the BD data given with a relief gradation (slope/flat), but the moisture data are given without this factor?
P11 L364 “e.g. [54,59].” It is probably worth expanding the description of exceptions.
How do the authors initially estimate the possibility of changing the bulk density? For simplicity, let's take the fertile soil layer of 30 cm (initial BD = 1.39 Mg/m3), into which about 1% biochar by weight was added (even with BD = 0.4 Mg/m3). Is it worthwhile to look for an effect from such a small dose?

Author Response

Reviewer 3

Comments 1: Why are the keywords "pyrogenic carbon" and the title and text use the term "biochar"?

Response 1: Keywords are useful for effective database searching. Therefore, it is generally unproductive to list terms already present in the title or abstract, as these fields are typically included in standard searches. In this case, we used pyrogenic carbon because it is a broader scientific term that refers to all carbonaceous materials formed by the incomplete combustion or thermal decomposition (pyrolysis) of organic matter. This includes a continuum of materials ranging from soot and black carbon from wildfires, to charcoal, and specifically to biochar.

Comments 2: Biochar, a carbon-rich byproduct derived from biomass pyrolysis or gasification, is increasingly recognized as a promising soil amendment due to its environmental benefits, including carbon sequestration, resistance to microbial breakdown, the capacity to trap environmental contaminants (e.g., anti-biotics, heavy metals) and many other beneficial aspects [30–33]."

Response 2: We do not agree with the reviewer that biochar, which can be effectively used as a soil fertilizer, cannot be obtained through gasification. While it is true that slow, low-temperature pyrolysis is often preferred to preserve the porous structure and retain higher levels of macronutrients, this does not mean that gasification cannot produce biochar suitable for soil applications. IBI (International Biochar Initiative), also, define “Biochar is made by high-heat, low-oxygen processes, i.e. pyrolysis or gasification”. https://biochar-international.org/why-biochar/

Gasification is primarily aimed at producing syngas, but it also yields a solid carbon-rich residue (char). In fact, several studies in the scientific literature (Trozzo et al., 2025; Garcia-Jaramillo et al., 2021 Hansen et al., 2017 and 2015 etc..) have shown that biochar derived from gasification can be used successfully in agricultural settings, although it may have lower yields and somewhat different physical or chemical properties compared to biochar from slow pyrolysis. Therefore, while the specific study mentioned used biochar produced via slow pyrolysis, it is not accurate to categorically rule out gasification as a viable method for producing agronomically useful biochar.

References cited:

Trozzo, L., D’Ottavio, P., Kishimoto-Mo, A. W., & Francioni, M. (2025). Wood gasification biochar enhances soil carbon sequestration without affecting greenhouse gas fluxes or wheat yield in sub-alkaline soil. Soil and Tillage Research, 251, 106556.

Garcia-Jaramillo, M., Meyer, K. M., Phillips, C. L., Acosta-Martinez, V., Osborne, J., Levin, A. D., & Trippe, K. M. (2021). Biochar addition to vineyard soils: effects on soil functions, grape yield and wine quality. Biochar, 3(4), 565-577.

Hansen, V., Müller-Stöver, D., Imparato, V., Krogh, P. H., Jensen, L. S., Dolmer, A., & Hauggaard-Nielsen, H. (2017). The effects of straw or straw-derived gasification biochar applications on soil quality and crop productivity: A farm case study. Journal of Environmental Management, 186, 88-95.

Hansen, V., Müller-Stöver, D., Ahrenfeldt, J., Holm, J. K., Henriksen, U. B., & Hauggaard-Nielsen, H. (2015). Gasification biochar as a valuable by-product for carbon sequestration and soil amendment. Biomass and Bioenergy, 72, 300-308.

Comments 3: The introduction omits the aspect of the influence of soil compaction on the functioning of the soil microbiota, which determines soil fertility and, accordingly, plant productivity. And also the effect of biochar on soil microbiota. Soil is considered as a non-living substrate, but this is not the case.

Response 3: Thank you for this comment. We added two parts in the introduction referring to soil microbiota with reference to soil compaction and biochar addition (L40-42 and L77-79)

Comments 4: Figure 2 and Figure 4 – it would be desirable to make the labels on the axes clearer

Response 4: We improve the readability of the two figures.

Comments 5: Figures 3 and 4: in what units are the moisture data given? In % or in m3/m3? What soil moisture was estimated6 volumetric or weight? This is also not clear from the methodology. Why are the BD data given with a relief gradation (slope/flat), but the moisture data are given without this factor?

Response 5: Units are in % and are calculated as volumetric water content of soil. We added this info to the M&M section (L236). In the methodology, both the methods (by wight and volume) are described as we calculated soil humidity by weight on the collected soil samples and we monitored soil humidity, but just in the year after first compaction event (L225-239).
Last, in the current version of the manuscript, we changed Fig 3 giving the values for both the slope conditions. As the differences were not that high, and that information was not relevant for our scope, we did not change figure 4, providing data averaged across both flat and sloped plots. These info were added to the text and to the fig 3 and 4 captions (L310)

Comments 6: P11 L364 “e.g. [54,59].” It is probably worth expanding the description of exceptions.

Response 6: We expanded the discussion, adding also an additional reference (L382-386).

Comments 7: How do the authors initially estimate the possibility of changing the bulk density? For simplicity, let's take the fertile soil layer of 30 cm (initial BD = 1.39 Mg/m3), into which about 1% biochar by weight was added (even with BD = 0.4 Mg/m3). Is it worthwhile to look for an effect from such a small dose?

Response 7: The data are: Soil BD = 1.39 Mg/m³, Biochar BD = 0.4 Mg/m³, Application rate = 1% by weight (i.e., for every 100 g of soil, 1 g of biochar). Crucially, as biochar is significantly less dense than the mineral soil, replacing 1% of the soil mass with biochar means that the biochar occupies a substantially larger volume than the soil mass it effectively displaces. This increased volume of the less dense material directly contributes to a reduction in the overall bulk density of the soil-biochar mixture.

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

Due to the changes made to the manuscript, the quality of presentation has improved, but some points still require minor revisions:
a) standardize the paragraphs for greater clarity and fluidity in the text. Very short paragraphs such as L169-173 can be unified with L174 and 176 in a single paragraph.
b) Figures and Tables should be shown and discussed next. Figure 2 and Table 4, for example, are in sequence, with separate discussion text. I suggest exploring the results separately in sequence. Bring greater contribution from the literature and citations to complement the results on these points. The exploration is superficial.
c) Explore more references in the area of compaction and relate the effect of biochar on the soil to reduce compaction. Base it on research and articles. Make the discussions more robust.
d) The conclusions should be summarized in topics, this helps to increase the clarity and relevance of the findings of this research.

Comments on the Quality of English Language

The language is clear, but the uniformity of the text and paragraph pattern needs to be reviewed.

Author Response

Review Report Form

Comment 1: Due to the changes made to the manuscript, the quality of presentation has improved, but some points still require minor revisions:
a) standardize the paragraphs for greater clarity and fluidity in the text. Very short paragraphs such as L169-173 can be unified with L174 and 176 in a single paragraph.
Response 1: We agree with the reviewer. We revised the manuscript accordingly, unifying four paragraphs (L142, L172).

Comment 2: b) Figures and Tables should be shown and discussed next. Figure 2 and Table 4, for example, are in sequence, with separate discussion text. I suggest exploring the results separately in sequence. Bring greater contribution from the literature and citations to complement the results on these points. The exploration is superficial.

Response 2: We believe there may be a misunderstanding in this comment. Figure 2 presents the data whose statistical analysis is reported in Table 4; for this reason, these two elements are consistently referenced together throughout the manuscript. As required by the journal Soil Systems, we have structured the paper with separate “Results” and “Discussion” sections, which explains the delayed discussion of the data showed in the table and picture.

Regarding the literature contribution and citation count, we respectfully disagree with the reviewer’s assessment. The manuscript includes a substantial number of references (80), which is quite comprehensive for an original research article. However, in the current version of the paper wea added three more references to studies in relation to the comment below (ref 61, 62 and 65). We believe the manuscript now includes all key studies relevant to the topic (biochar and compaction)

Comment 3: c) Explore more references in the area of compaction and relate the effect of biochar on the soil to reduce compaction. Base it on research and articles. Make the discussions more robust.
Response 3: We added more references (ref 61, 62 and 65) to studies relating to studies investigating compaction behavior of soils with biochar amendment, expanding the discussion with three additional parts (L345-350; L355-358; L427-430). We believe the discussion is more robust and comprehensive.

Comment 4: d) The conclusions should be summarized in topics, this helps to increase the clarity and relevance of the findings of this research.

Response 4: In the current version of the paper, we clearly summarized the conclusions by topic, also including the main findings in bullet points. It should now be very clear and explicit.