Enhancing Soil Nitrogen Retention Capacity by Biochar Incorporation in the Acidic Soil of Pomelo Orchards: The Crucial Role of pH

Round 1

Reviewer 1 Report

Dear Editor,

I have recently had the opportunity to review the manuscript entitled "Enhancing soil nitrogen retention capacity by biochar incorporation: the crucial role of pH”. This manuscript explores an intriguing topic; however, there are several key areas that require attention and revision before it can be considered for publication.

Firstly, the title of the manuscript, although descriptive of the work undertaken, could benefit from a higher degree of specificity. The title should ideally encapsulate the primary findings or the unique approach of the study in a more detailed manner to differentiate it from other similar works in the field.

Upon reviewing the body of the manuscript, I found several instances where further clarification and elaboration would be beneficial. Specific comments are provided inline throughout the manuscript, and I strongly encourage the authors to address these for improved clarity and comprehensibility of their work.

The Introduction section of the manuscript needs substantial improvement. As it currently stands, there is insufficient background information related to the hypothesis tested. This deficiency makes it difficult for readers to understand the context and significance of the study. Therefore, I urge the authors to provide more detailed background and properly set the context for their research.

Furthermore, the novelty of the study is not explicitly justified. The general concept that biochar can enhance soil pH and thus improve the efficiency of soil nitrogen related processes is not new. The authors need to differentiate their study from the existing body of knowledge in the field, perhaps by explaining the unique approach, technique or perspective that they have taken. This justification should ideally be included in the revised Introduction.

The changes suggested for the Introduction will naturally necessitate an adjustment in the Discussion section. The Discussion should closely follow the contents of the Introduction and reflect upon the issues and hypotheses raised there.

One significant oversight in the manuscript is the lack of clarity regarding the type of soil used in the study until the Methodology section. This information is vital for the reader's understanding of the research and should be explicitly stated earlier on, preferably in the Introduction.

Based on these considerations, I recommend that the authors thoroughly revise their manuscript to address these points and resubmit it. This work has the potential to contribute significantly to the field, but it needs substantial refinement to meet the publication standard.

Comments for author File: Comments.pdf

Generally good, just a few minor corrections here and there. 

Author Response

Reviewer 1

Author Response File: Author Response.docx

Reviewer 2 Report

The paper is very relative and time demanding for the relationship between nitrogen and biochar interaction in soil. A few corrections and updated references should be included, some mentioned in the attached file.

Comments for author File: Comments.pdf

Some of the sentences are confusing in the abstract and introduction section, ple rewrite the sentences for better understanding.

Author Response

Reviewer 2

Author Response File: Author Response.docx

Reviewer 3 Report

This manuscript discusses a topic of interest, the effect on pH on soil nitrogen retention  by biochar incorporation. it is not extraordinarily novel but well-structured and appropriate. The use of 15N labeling is valued as a novelty. The experiments with samples enriched with 15N are complex and have been carried out correctly, making them of great interest.

However, some improvements and clarifications are recommended before its acceptance for publication in the Agronomy journal. Some phrases in the abstract and introduction are too general and need to be improved. For example, it is stated that biochar is currently mainly used to improve acidic soil and reduce nitrogen loss, but this may not be entirely accurate or clear in the introduction. The application of 0% and 1% biochar should not be considered as two doses of biochar; instead, it should be referred to as 1% biochar and a control without biochar. The introduction should also specify the type of biochar, as the results vary significantly depending on the biomass nature and pyrolysis conditions.

In the introduction, some relevant issues are missing, such as biochar stability. It is recommended to consider articles by Knicker et al., for example, on this topic, which discuss biochars and pyrogenic materials labeled with 15N. A more extensive explanation of nitrogen use efficiency is requested.

In the materials and methods section, please specify the type of reactor and pyrolysis residence time, as well as the type and texture of the soil. Use the same units for organic carbon content (preferably g kg-1).

Regarding the dosage, explain why the decision was made to use a 1% dose.

Line 127, what moisture levels were maintained?

Regarding laboratory analyses, specify the sensitivity of the instruments, measurement error, and used standards.

The value of Figure 1 in the results is significant, although the number of data points (samples) is limited.

In the results and discussion section, besides pH, there may be other factors playing an important role in soil nitrogen retention, such as specific surface area and soil porosity.

The conclusions (lines 377-379) are sometimes contradictory to what is discussed. It is necessary to provide a better explanation of what is meant by nitrogen mineralization. Based on the obtained results, can you make predictions about the effects on alkaline soils to which alkaline biochar is added?"

Minor revision. A final quick review of the text is recommended

Author Response

Reviewer 3

Author Response File: Author Response.docx