Spectroscopic Investigation on the Effects of Biochar and Soluble Phosphorus on Grass Clipping Vermicomposting

Round 1

Reviewer 1 Report

The research paper "Biochar Reduces the Deleterious Effect of Acidity and Salinity Induced by Single Superphosphate Fertilizer and Alters Phosphorous Speciation in Vermicomposted Grass Clippings" is interesting and contains some new findings. However, major points need improve .

The authors have to address the following points:

• Abstract need more quantitative information.
  Keywords should consider NMR is not main content in this paper.
• The authors should introduce biochar in more details: Bulletin of Environmental Contamination and Toxicology volume 108, pages616–628 (2022)
• The characterization should add more details.
• Why did the authors use PCA among different multivariate analysis methods. Discussion on PC effect is not clear.
• Discussion is not comprehensive. More comparison should be added
• Conclusions should emphasize new findings in this work.

Author Response

Dear Reviewer, we deeply appreciate all the comments and suggestions highlighted that help us to improve the manuscript. After thoroughly reading the comments, we decided to accept almost all the proposed suggestions pointed out. Responses, explanations, and some disagreements to all comments are described below.

 

Abstract need more quantitative information.

Done.

 

Keywords should consider NMR is not main content in this paper.

With all due respect to the reviewer, we disagree. Analyzing the MS quantitatively, the results section has 1104 words, of which 684 were related to the results obtained by NMR. In addition, of the 5 figures, 3 were obtained from NMR data, that is, more than 60% of the results obtained are related to NMR. Furthermore, this technique was a differential of the work, providing information that made it possible to infer the processes involved, otherwise, it would be a mere empirical study whose conclusions would be speculative or limited. Keywords are the authors' choice and aim to facilitate the search for MS, as NMR is not included in the title, we chose to include it in the keywords to increase the findability of the MS. For example, someone working with compost and NMR would easily find our work by searching for "compost AND NMR", and our MS could assist them in discussing their own results or even confirm or refute our findings.

 

The authors should introduce biochar in more details: Bulletin of Environmental Contamination and Toxicology volume 108, pages616–628 (2022)

We added “Novotny, E.H., Maia, C.M.B.F., Carvalho, M.T.M., Madari, B.E., 2015. Biochar: Pyrogenic carbon for agricultural use - A critical review. Rev. Bras. Cienc. Solo, 39, 321-344. http://dx.doi.org/10.1590/S1415-43662012000700009” as a reference for biochar conceptualization.

 

The characterization should add more details.

Unfortunately, we don´t have conditions to make new analysis with the samples of this experiment. The experiment and the project were concluded in 2018 and we have no samples to reanalyze.

 

Why did the authors use PCA among different multivariate analysis methods? Discussion on PC effect is not clear.

We chose PCA because it is a powerful mathematical tool that systematically organises and facilitates the interpretation of multivariate data. It is a technique widely used and known by the scientific community. As it is a projection method, and not a statistical one, it dispenses with the assumptions of statistical methods (such as PLS, PLS-DA etc), such as homoscedasticity, normality and independence of residuals. As it is a longitudinal study, this last premise is violated, if we used the PLS(-DA) model, for example. This could be solved with a more complex model, but we believe it to be unnecessary. Furthermore, due to the high cost of NMR analyses, the database was limited, and as we do not have the mathematical guarantee that the estimators obtained are unbiased, any validation method would be extremely temerarious. We could have used MCR, however, since the PCA, which provides a unique solution, showed in a simple and clear way the driving forces of the phenomena under study, with the advantage of orthogonality, we opted for the simplest solution, namely, the ordinary PCA having based on the Occam's razor principle.

The discussion of the PCs was improved.

 

Discussion is not comprehensive. More comparison should be added

We rephrased part of the discussion to turn it more comprehensive

 

Conclusions should emphasize new findings in this work.

Done.

 

Reviewer 2 Report

The current study entitled “Biochar Reduces the Deleterious Effect of Acidity and Salinity Induced by Single Superphosphate Fertilizer and Alters Phosphorous Speciation in Vermicomposted Grass Clippings ” is good. For a better understanding in-depth, it is a need time to work on this topic. Furthermore, the achievement of potential benefits by using current technology is also dependent on the extensive research work for more exploration. Although the experiment is well organized, I suggest a major revision due to the following deficiencies.

Abstract

1. Make the title a simple statement.
2. Give the problem statement in a single line.
3. Give a reason for the selection of the current technique biochar while it is well established that biochar increase soil salinity by releasing its own structural nutrients.
4. Quantitative data is also important to support your conclusion. Would you please provide some quantitative data in terms of percentage significant increase or decrease in the abstract?
5. Please provide a conclusive conclusion with is withdrawn through research in a single line.
6. Give future prospective in a single line.
7. As per standard suggestions, please avoid using title words as keywords.

Introduction

1. Please follow the title and rewrite the introduction in the following sequence as i.e., Biochar, Deleterious Effect of Acidity and Salinity, Single Superphosphate Fertilizer and Vermicomposted Grass Clippings, problem statement, aims of study and hypothesis.
2. Also, provide a novelty statement at the end. What new things authors have done or correlated in this research compared to old ones?
3. Would you please give a single line about the knowledge gap which your research has covered along with the hypothesis statement?

Material and methods:

1. Give GPS location of the experiment.
2. Please provide a reference for statistical analysis.

Results and Discussion.

1. Very descriptive. Please give only significant results. Also, give mechanistic discussion. It is not a correct way to discuss results based on other scientists' findings. Please elaborate on specified mechanisms which are regulating and result. Please rewrite the results and discussion again

Conclusion

1. Add the targeted beneficiary audience who will get benefits from this research.
2. Also, give clear-cut recommendations while describing the best treatment.

Author Response

Dear Reviewer, we deeply appreciate all the comments and suggestions highlighted that help us to improve the manuscript. After thoroughly reading the comments, we decided to accept all the proposed suggestions pointed out.

The current study entitled “Biochar Reduces the Deleterious Effect of Acidity and Salinity Induced by Single Superphosphate Fertilizer and Alters Phosphorous Speciation in Vermicomposted Grass Clippings ” is good. For a better understanding in-depth, it is a need time to work on this topic. Furthermore, the achievement of potential benefits by using current technology is also dependent on the extensive research work for more exploration. Although the experiment is well organized, I suggest a major revision due to the following deficiencies.

Abstract

1. Make the title a simple statement. Done.
2. Give the problem statement in a single line. A single line was added to the text.
3. Give a reason for the selection of the current technique biochar while it is well established that biochar increase soil salinity by releasing its own structural nutrients. ok.
4. Quantitative data is also important to support your conclusion. Would you please provide some quantitative data in terms of percentage significant increase or decrease in the abstract? Done.
5. Please provide a conclusive conclusion with is withdrawn through research in a single line. Done.
6. Give future prospective in a single line. ok.
7. As per standard suggestions, please avoid using title words as keywords. checked

Introduction

1. Please follow the title and rewrite the introduction in the following sequence as i.e., Biochar, Deleterious Effect of Acidity and Salinity, Single Superphosphate Fertilizer and Vermicomposted Grass Clippings, problem statement, aims of study and hypothesis.
2. Also, provide a novelty statement at the end. What new things authors have done or correlated in this research compared to old ones?
3. Would you please give a single line about the knowledge gap which your research has covered along with the hypothesis statement?

We try to meet all the requirement above.

Material and methods:

1. Give GPS location of the experiment. Done
2. Please provide a reference for statistical analysis. Done

Results and Discussion.

1. Very descriptive. Please give only significant results. Also, give mechanistic discussion. It is not a correct way to discuss results based on other scientists' findings. Please elaborate on specified mechanisms which are regulating and result. Please rewrite the results and discussion again. We try to improve both results and discussion.

Conclusion

1. Add the targeted beneficiary audience who will get benefits from this research. Done.
2. Also, give clear-cut recommendations while describing the best treatment. Done.

We introduce two sentence to considering the review´s comments.

Reviewer 3 Report

The paper is scientifically rigorous and well written. However, the experimental design is a bit confusing and complicated.  Would it better fit a split plot design with main plots as vermicomposting and sub-plots as the 4 different composting treatments?  Also, why are the replications combined prior to vermi-composting?  These point appear to need some clarification.

Comments for author File: Comments.pdf

Author Response

Dear Reviewer, explanations and some disagreements to the comments are described below.

The paper is scientifically rigorous and well written. However, the experimental design is a bit confusing and complicated.  Would it better fit a split plot design with main plots as vermicomposting and sub-plots as the 4 different composting treatments?

This experiment is not characterized as a split plot experiment once there is no sub parcels. Different treatments are compared with and without vermicomposting and so, vermicomposting is a factor of variance in the factorial arrangement.

  Also, why are the replications combined prior to vermi-composting?  These point appear to need some clarification.

It is a detail of the composting process which was performed before the vermicomposting experiment and does not influence the experimental results. In the way to clarify the paper we did the changes on the text.

Reviewer 4 Report

Dear Authors,  the aim of the experiment described in the manuscript is an impact of different additives to the grass residues on the establishment and development of the E. fetida.  The paper is very interesting but I feel unsatisfied reading the Introduction due to the lack of clear information why soluble phosphate and charcoal were added to the composting biomass? Should it somehow improve  composting process or the final product? Biochar significantly increases C content in the initial material. The chemical composition of the grass residue points that the biomass is characterized by rather high C/N ratio (47), so what is the purpose to increase it even more? If there are reasons for that - it should be presented. The same - concerning using soluble phosphate to the composting biomass. What is the purpose? The aim of the composting process should be to obtain the final product of a high quality that can be succesfully applied to the soil improvings its properties. I would like you to improve the Introduction section and explain what are benefits of using the mentioned additives or just move the text from  lines 327-334 to the Introduction.

Second comment: I need more information about  process of composting, whether the temperature and moisture content wre controlled during the process? How the quality of the compost was estimated? If the quality of the final product was low, we cannot be sure that it didn't affect the earthworm population. pH of the compost with soluble phosphate was below 5 - in these conditions heavy metals are easy mobilized from the organo-mineral complexes, so again we cannot be sure that the population decrease of the earthworm was a consequence of phosphorus or e.g. Cd release - it could be helpful to receive more information about other parameters of the compost.

Third comment: speaking about humification it would be necessary to present changes in humic substances during the process; content of humic and fulvic acids.

The title is too long in my opinion - I would shortened it to e.g.: Effect of biochar and soluble phosphorus addition on vermicomposted grass clippings. 

One more detailed comment: line 70 - term "atomic ratio" shouldn't be used when speaking of initial biomass non homogeneous; better use just C/N ratio.

Kind regards

 

 

Author Response

Dear Reviewer, we deeply appreciate all the comments and suggestions highlighted that help us to improve the manuscript. After thoroughly reading the comments, we decided to accept almost all the proposed suggestions pointed out. Responses, explanations, and some disagreements to all comments are described below.

 

Dear Authors,  the aim of the experiment described in the manuscript is an impact of different additives to the grass residues on the establishment and development of the E. fetida.  The paper is very interesting but I feel unsatisfied reading the Introduction due to the lack of clear information why soluble phosphate and charcoal were added to the composting biomass? Should it somehow improve  composting process or the final product? Biochar significantly increases C content in the initial material. The chemical composition of the grass residue points that the biomass is characterized by rather high C/N ratio (47), so what is the purpose to increase it even more? If there are reasons for that - it should be presented. The same - concerning using soluble phosphate to the composting biomass. What is the purpose? The aim of the composting process should be to obtain the final product of a high quality that can be succesfully applied to the soil improvings its properties. I would like you to improve the Introduction section and explain what are benefits of using the mentioned additives or just move the text from  lines 327-334 to the Introduction.

The biochar used in this experiment is composed by charcoal small fragments which helps the composting process to increase the piles porosity, facilitating the gas flux. It is not expected that this charcoal react during composting and it is considered an inert material. Other effects, such as physical protection for microorganisms and water and organic compounds absorption, are also expected and it is described in lines 327-334. We added this information at the introduction to clarify this point.    

Second comment: I need more information about  process of composting, whether the temperature and moisture content wre controlled during the process? How the quality of the compost was estimated? If the quality of the final product was low, we cannot be sure that it didn't affect the earthworm population. pH of the compost with soluble phosphate was below 5 - in these conditions heavy metals are easy mobilized from the organo-mineral complexes, so again we cannot be sure that the population decrease of the earthworm was a consequence of phosphorus or e.g. Cd release - it could be helpful to receive more information about other parameters of the compost.

The composting process is described in Benites et al, 2004. Temperature and moisture were monitored daily. The composting piles passed thru a thermophilic phase for the first 20 days and after them were stabilized during a mesophilic phase. Composting was not complete once plant fragments are still present in the final compost. But extractable humic substances increased after composting compared with original material. Other parameters then pH, CE were not measured and we don’t have this information.    

Third comment: speaking about humification it would be necessary to present changes in humic substances during the process; content of humic and fulvic acids.

The humification process was evaluated by spectroscopy and humic substances extraction was not performed.

The title is too long in my opinion - I would shortened it to e.g.: Effect of biochar and soluble phosphorus addition on vermicomposted grass clippings. 

We altered the title following your suggestion

One more detailed comment: line 70 - term "atomic ratio" shouldn't be used when speaking of initial biomass non homogeneous; better use just C/N ratio.

We completely agree. Thank you.

Round 2

Reviewer 1 Report

The authors have addressed all the comments.

Reviewer 2 Report

Dear Authors

I am satisfied with the responses.