Effects of Two Types of Straw Biochar on the Mineralization of Soil Organic Carbon in Farmland

Round 1

Reviewer 1 Report

General comment: The authors reported the effect of banana and cassava straw biochar on soil carbon composition and transformation. The authors did a thorough investigation. The data analysis and discussion were appropriate. However, the method section lacks detail and some of the data are missing (e.g., Tables 6 and 7). Moreover, the manuscript is very lengthy. The authors should consider condensing it and only report the key findings. Additional suggestions and comments can be found in my specific comments.

 

Specific comments:

Line 17: The 2 in CO2 should be in subscript.

Line 18: Superscript “-1”.

Line 26: Define SOC.

Line 26: What does “It” refer to?

Line 124: Define the abbreviations in the Table. Report the values as mean ± standard deviation.

Line 126: Provide the name, manufacturer, and model of the equipment used for pyrolysis.

Lines 133-134: Why were these abbreviations selected? The abbreviations should be more reader friendly.

Line 136: Table 2 is unnecessary and should be removed.

Line 146: Change “ml” to “mL” throughout the manuscript.

Line 146: What was the concentration of sodium hydroxide?

Line 149: Provide references for all the analytical methods.

Line 153: Define “TOC”.

Line 181: Which post-hoc test was used?

Line 185: No method was provided for FTIR.

Lines 188-192: Provide wavenumber and references for the functional groups.

Line 209: Use “α=0.05” or “p>0.05”.

Line 232: The figures have a poor resolution. Why were there no error bars for some figures? It is also not appropriate to use a line chart for this figure since there is no continuity between the different treatments. A bar chart would be more appropriate. If the authors would like to use a line chart, then the x axis should be days and the different treatments should be differentiated by colors.

Line 287: It is unclear what the unit of catalase activity mean since it was not specified in the method.

Line 360: What is the BoxLucas in the figure? The caption should read “Accumulation of C…”. Why were there no error bars in the figures?

Line 399: Table 6 is missing.

Line 403: Do not use “highly significant” or “very significant”. Just provide the p values. Make changes throughout this section.

Line 417: Table 7 is missing.

Lien 424: What were their treatments?

Line 571: The conclusions section is too long. Please summarize the key findings in a paragraph or two.

Author Response

Manuscript ID:sustainability-1016320 Major Revise

Manuscript Title: Effects of Two Types of Straw Biochar on the Mineralization of Soil Organic Carbon in Farmland

Authors: Lening Hu, Shuangli Li, Ke Li, Haiyan Huang, Wenxin Wan, Qiuhua Huang, Qiuyan Li, Yafen Li, Hua Deng*, Tieguang He*

Dear Editors and Reviewers:

Thank you for your letter and for the reviewers’ commemts concerning our manuscript. Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have made correction which we hope meet with approval. Revised portion are marked in yellow in the paper. The main corrections in the paper and the responds to the reviewer’s comments are as flowing:

Reviewer #1:

1. The 2 in CO2 should be in subscript and Superscript “-1”

Reply: Thank you for your suggestion, we have revised this in the manuscript.

• The supplementary content are marked on manuscript, Lines 22-23

The results showed that the cumulative CO₂ emissions from cassava straw were 15.82 (1% addition ratio) and 28.14 μg·kg^-1 (2%)

2. Define SOC and What does “It” refer to?

Reply: Thank you for your suggestion, we have revised this in the manuscript.

• The supplementary content are marked on manuscript, Lines 20 and Lines 30

SOC is defined on line 18 : total organic carbon （TOC）, soluble organic carbon (SOC)

“It” refers to catalase and urease activity

3. Define the abbreviations in the Table. Report the values as mean ± standard deviation.

Reply: Thank you for your suggestion, we have revised this in the manuscript.

• The supplementary content are marked on manuscript, Lines 145, Table 1

Table.1 Basic physical and chemical properties of soil

pH	Ec（us·cm-1）	Olsen-P（mg·kg-1）	TOC（g·kg-1）	CEC（cmol·kg-1）
5.56±0.01	40.50±3.17	8.71±0.16	5.31±0.01	38.46±0.25

Table 1 has been modified to mean ± standard deviation

4. Provide the name, manufacturer, and model of the equipment used for pyrolysis.

Reply: Thank you for your suggestion, we have revised this in the manuscript.

• The supplementary content are marked on manuscript, Lines 200

Using banana straw and cassava straw as raw materials, biochar was prepared by slow pyrolysis in a box-type resistance furnace (model: 4-10 company: Shanghai Dongxing Building Materials Test Equipment Co., Ltd.) under the condition of 500 ℃, 2 h and oxygen restriction.

5. Why were these abbreviations selected? The abbreviations should be more reader friendly.

Reply: Thank you for your suggestion, we have revised this in the manuscript.

• The supplementary content are marked on manuscript, Lines 174

In XSB, X is the initials of banana pinyin, and SB is the acronym of straw biochar in English. In MSB, M is the initials of cassava pinyin, and SB is the acronym of straw biochar in English.

6. Table 2 is unnecessary and should be removed.

Reply: Thank you for your suggestion, we have revised this in the manuscript.

• The supplementary content are marked on manuscript, Lines 175

Table 2 has been delete

Table.2 Experimental Design

Handling code	CK	1%XSB	2%XSB	5%XSB	1%MSB	2%MSB	5%MSB
Cassava straw biochar addition /%	0	0	0	0	1	2	5
Banana straw biochar addition/%	0	1	2	5	0	0	0

7. Change “ml” to “mL” throughout the manuscript.

Reply: Thank you for your suggestion, we have revised this in the manuscript.

• The supplementary content are marked on manuscript, Lines 184 and Lines 408~412

Modify the corresponding position in the text

A 10 mL beaker filled with a certain concentration of sodium hydroxide solution was placed in a white polyethylene bottle, and carbon dioxide emissions were analysed on days 1, 3, 5, 7, 10, 15, 20, 25 and 30.

The catalase activity of the 5% XSB biochar treatment was the highest in the third week of culture, 40.17 mL·g^-1, and the catalase activity of the 2% XSB biochar treatment was the highest in the fifth week of culture, 43.73 mL·g^-1. CK, 1% MSB, 2% MSB and 5% MSB showed significant differences at different stages. The catalase activity in the 5% MSB and 2% MSB treatments reached the highest level in the third week of culture, 33.30 mL·g^-1 and 27.67 mL·g^-1, respectively.

8. What was the concentration of sodium hydroxide?

Reply: Thank you for your suggestion, we have revised this in the manuscript.

• The supplementary content are marked on manuscript, Lines 184

The sodium hydroxide concentration of 0.1 mol·L^-1 has been indicated herein

9. Provide references for all the analytical methods.

Reply: Thank you for your suggestion, we have revised this in the manuscript. The reference document method has been marked in this section, such as the yellow mark part.

• The supplementary content are marked on manuscript, Lines 188-195

Total organic carbon (TOC) in the soil was determined by potassium dichromate oxidation spectrophotometry (Jing et al., 2020). The pH (Yadav et al., 2019) value was determined by a pH meter at a ratio of soil to water of 1:2.5. Soil was extracted by deionized water, and soluble organic carbon (DOC) (Zimmerman et al., 2011) was determined by a TOC analyser after centrifugation. Available phosphorus was determined by NaHCO₃ extraction-molybdenum antimony colorimetry (Jing et al., 2020). Catalase activity (Li et al., 2019)was determined by potassium permanganate titration, Its calculation formula is as follows:

 

 

10. Define “TOC”.

Reply: Thank you for your suggestion, we have revised this in the manuscript.

• The supplementary content are marked on manuscript, Lines 188

The TOC is total organic carbon. Soil was extracted by deionized water, and soluble organic carbon (DOC) was determined by a total organic carbon (TOC) analyser after centrifugation.

11. Which post-hoc test was used?

Reply: Thank you for your suggestion, we have revised this in the manuscript.

• The supplementary content are marked on manuscript, Lines 244

The post-event test used is Duncan multiple-range test. A description has been added on line 194, as follows:

The average value and standard deviation were calculated using the standard method in Excel 2016. One-way ANOVA was used to study the effects of biochar treatment on soil organic carbon, available phosphorus and enzyme activities. The Duncan multiple-range test was used for post-test All statistical tests were carried out using SPSS 24.0, and the mapping was completed using Origin 9.1 mapping software.

 

12. No method was provided for FTIR.

Reply: Thank you for your suggestion, we have revised this in the manuscript.

• The supplementary content are marked on manuscript, Lines 146-148

FTIR adsorption spectra was recorded from wavelengths 4000 to 400 cm^-1 at the resolution was 0.09 cm^-1 (Bruker Tensor 27, Ettlingen, Germany). A small amount of biochar samples passed through 100 mesh sieve were mixed with KBr for FTIR analysis.

13. Provide wavenumber and references for the functional groups.

Reply: Thank you for your suggestion, we have revised this in the manuscript.

• The supplementary content are marked on manuscript, Lines 254

The wave numbers of the infrared functional groups are indicated in FIG. 1

Figure. 1. FTIR Spectra of XSB and MSB

14. Use “α=0.05” or “p>0.05”.

Reply: Thank you for your suggestion, we have revised this in the manuscript.

• The supplementary content are marked on manuscript, Lines 273

Note: The mean value ± standard deviation of soil pH in different time (n=3), the same letter

indicates that the effect of biochar addition on soil is not significant (α=0. 05)

15. The figures have a poor resolution. Why were there no error bars for some figures? It is also not appropriate to use a line chart for this figure since there is no continuity between the different treatments. A bar chart would be more appropriate. If the authors would like to use a line chart, then the x axis should be days and the different treatments should be differentiated by colors.

Reply: Thank you for your suggestion, we have revised this in the manuscript.

• The supplementary content are marked on manuscript, Lines 301

Some numbers do not have error bars because the error is small, so they cannot be shown in the figure. I have modified the line chart in Figure 2 to a bar chart, as follows：

16. It is unclear what the unit of catalase activity mean since it was not specified in the method.

Reply: Thank you for your suggestion, we have revised this in the manuscript.

• The supplementary content are marked on manuscript, Lines 194、198

Catalase activity was determined by potassium permanganate titration, Its calculation formula is as follows:

                            (1)

Urease activity was determined by indophenol blue colorimetry and was expressed as the amount of urea converted into NH₃-N per gram of soil per hour, Its calculation formula is as follows:.

     (2)

The calculation of catalase activity and urease activity has been supplemented in lines 194 and 198 of the experimental method section. The method refers to Li Zhengao's book "Soil and Environmental Microorganism Research Method"

17. What is the BoxLucas in the figure? The caption should read “Accumulation of C…”. Why were there no error bars in the figures?

Reply: Thank you for your suggestion, we have revised this in the manuscript.

• The supplementary content are marked on manuscript, Lines 471

BoxLucas is automatically generated during linear fitting. It has been deleted and error bars have been added in the figure, as shown in the following figure：

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

18. Table 6 is missing.

Reply: Thank you for your suggestion, we have revised this in the manuscript.

• The supplementary content are marked on manuscript, Lines 529

Since a table has been deleted, Table 6 becomes Table 5 and has been added to the text, Table 5 is as follow:

Table 5 Correlation of physical and chemical properties, organic carbon and enzyme activities of soil treated with two kinds of straw biochar

Banana straw biochar

Cassava straw biochar

Indicators

Olsen-P

pH

Catalase

Urease

SOC

DOC

Olsen-P

pH

Catalase

Urease

SOC

DOC

Olsen-P

1

.868**

-.864**

-.477**

.955**

.635**

1

.772**

-.806**

.807**

.936**

-.821**

pH

1

-.926**

-0.139

.855**

.301*

1

-.497**

.430**

.888**

-.811**

Catalase

1

0.113

-.859**

-.289*

1

-.719**

-.732**

.637**

Urease

1

-.377**

-.734**

1

.688**

-.624**

SOC

1

.492**

1

-.842**

DOC

1

1

 

19. Do not use “highly significant” or “very significant”. Just provide the p values. Make changes throughout this section.

Reply: Thank you for your suggestion, we have revised this in the manuscript.

• The supplementary content are marked on manuscript, Lines 525

This section is a description of correlation. The correlation values are in Table 5, which has been added in this section. The correlation has significant correlation and extremely significant correlation. In this section, highly significant and very significant indicate the degree of correlation, so highly significant and very significant are used.

20. Table 7 is missing.

Reply: Thank you for your suggestion, we have revised this in the manuscript.

• The supplementary content are marked on manuscript, Lines 546

Since a table has been deleted, Table 7 becomes Table 6 and has been added to the text, Table 6 is as follow:

Table 6 Correlation between Soil CO₂ Emission and Enzyme Activity

	Banana straw biochar				Cassava straw biochar
	Urease	Catalase		CO2 emissions		Urease	Catalase	CO2 emissions
CO2 emissions	0.442	0.515*	1		0.751**		0.732**	1
Catalase	0.113	1			-.719**		1
Urease	1				1

21. What were their treatments?

Reply: Thank you for your suggestion, we have revised this in the manuscript.

• The supplementary content are marked on manuscript, Lines 551-557

The processing method has been added to the 4.1 CO₂ emissions section as follows:

Ameloot et al. reported, biochar was prepared from willow wood (Salix dasyclados) and swine manure digestion material at 350 ℃ and 700 ℃ respectively, When the four treatments of blank, DS350, DS700, WS350 and WS700 were applied to agricultural soil, the C mineralization in all treatments increased rapidly in the early stage, and then the CO₂ emission continued to increase at a much slower rate, which is similar to our results. This may be due to the rapid degradation of unstable or volatile components in the soil and the slow degradation of stable components in the soil.

22. The conclusions section is too long. Please summarize the key findings in a paragraph or two.

Reply: Thank you for your suggestion, we have revised this in the manuscript.

• The supplementary content are marked on manuscript, Lines 741-752

The conclusion part is modified as follows：The cumulative CO₂ emission from cassava straw biochar was 15.82 g • kg-1 (1% addition ratio), 28.14 g • kg-1 (2% addition ratio) was lower than that from banana straw biochar (46.77 g • kg-1 (1% addition ratio), and 59.26 g • kg-1 (2% addition ratio) showed that cassava straw biochar had certain emission reduction effect than banana straw biochar. The content of organic carbon in each treatment was higher than CK (blank control), indicating that the two kinds of biomass char were beneficial to the promotion of organic carbon, and the content of organic carbon in cassava straw biochar was higher than that in banana straw biochar. The mineralization trend of soil organic carbon is basically the same when the two kinds of straw biochar are applied. The application of biochar increases the mineralization rate and accumulated mineralization amount of soil organic carbon. Different straw biochar has different effects on soil organic carbon mineralization. Banana straw biochar has stronger mineralization effect on soil organic carbon than cassava straw biochar.

Reviewer #2:

1. Although the subject of the manuscript is very important, the authors were not able to use its potential. The discussed topic was poorly presented and the cited literature is extremely scarce. The only thing I can advise is a thorough re-editing of the entire text. Collecting many important and new literature items and re-writing the entire manuscript based on them.

Reply: Thank you for your suggestion, we have revised this in the manuscript.

• The supplementary content are marked on manuscript, Lines 46-47

Therefore, reducing greenhouse gases in farmland soil is of great significance to mitigate global temperature rise. [2]

• Lines 49

straw returning to the field is a common soil fertilization method in the early stage of rural China. [3]

• Lines 110-113

Phosphorus is important for plant metabolic substances such as nucleotides, nucleic acids and enzymes, as well as for energy transfer. In the soil, phosphorus is a rather immobile element  which bonds with common soil constituents such as calcium (Ca), aluminium (Al), and iron (Fe).[20]

• Lines 551-557

Ameloot et al. reported, biochar was prepared from willow wood (Salix dasyclados) and swine manure digestion material at 350 ℃ and 700 ℃ respectively, When the four treatments of blank, DS350, DS700, WS350 and WS700 were applied to agricultural soil, the C mineralization in all treatments increased rapidly in the early stage, and then the CO₂ emission continued to increase at a much slower rate, which is similar to our results. This may be due to the rapid degradation of unstable or volatile components in the soil and the slow degradation of stable components in the soil.

• Lines 646-647

According to the research results of the interaction and influence between enzyme activity and soil microbial activity,[47]

• Lines 659-660

The activity of catalase increased with the addition of the two kinds of biochar, which may be due to the adsorption performance of biochar and the easy storage of the porous structure of biochar, thus improving the activity of catalase. [49]

• Lines 731-733

moreover, the change of CO₂ concentration will cause the change of pH value, which will indirectly affect the activity of soil enzymes. [55]

• Lines 735

may be related to different organic carbon components and different enzyme performance differences. [56].

2. My next complaint is the poor level of English used in the manuscript. The text should be checked by a professional translator

Reply: Thank you for your suggestion. Regarding English grammar and other issues, I have resubmitted the polishing company for polishing. I polished it once before submitting it to the periodical. The following is my first polishing certificate.

 

 

3. I do not understand why the authors did not use the ready template that is available on the journal website? Please format the text according to the template provided by the journal.

Reply: Thank you for your suggestion, we have revised this in the manuscript.

I have changed the full-text format to the format of Sustainability Periodicals. The following are some screenshots.

4. The authors did not attempt to perform microbiological analyzes. Microorganisms play a very important role in the context of the use of biochar. The authors emphasize it in the text, but it is a pity that they themselves did not attempt to perform this type of analysis of the microbiocenotic composition of the microbial population

Reply: Thank you for your suggestion. It gave me a lot of inspiration. We will refer to your opinions for microbial analysis in further research, such as microbial biomass carbon, soil high throughput determination, etc.

Reviewer 2 Report

Dear Authors,

Although the subject of the manuscript is very important, the authors were not able to use its potential. The discussed topic was poorly presented and the cited literature is extremely scarce. The only thing I can advise is a thorough re-editing of the entire text. Collecting many important and new literature items and re-writing the entire manuscript based on them.

 

My next complaint is the poor level of English used in the manuscript. The text should be checked by a professional translator

 

I do not understand why the authors did not use the ready template that is available on the journal website? Please format the text according to the template provided by the journal.

 

The authors did not attempt to perform microbiological analyzes. Microorganisms play a very important role in the context of the use of biochar. The authors emphasize it in the text, but it is a pity that they themselves did not attempt to perform this type of analysis of the microbiocenotic composition of the microbial population.

 

 

Author Response

Manuscript ID:sustainability-1016320 Major Revise

Manuscript Title: Effects of Two Types of Straw Biochar on the Mineralization of Soil Organic Carbon in Farmland

Authors: Lening Hu, Shuangli Li, Ke Li, Haiyan Huang, Wenxin Wan, Qiuhua Huang, Qiuyan Li, Yafen Li, Hua Deng*, Tieguang He*

Dear Editors and Reviewers:

Thank you for your letter and for the reviewers’ commemts concerning our manuscript. Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have made correction which we hope meet with approval. Revised portion are marked in yellow in the paper. The main corrections in the paper and the responds to the reviewer’s comments are as flowing:

Reviewer #2:

1. Although the subject of the manuscript is very important, the authors were not able to use its potential. The discussed topic was poorly presented and the cited literature is extremely scarce. The only thing I can advise is a thorough re-editing of the entire text. Collecting many important and new literature items and re-writing the entire manuscript based on them.

Reply: Thank you for your suggestion, we have revised this in the manuscript.

• The supplementary content are marked on manuscript, Lines 46-47

Therefore, reducing greenhouse gases in farmland soil is of great significance to mitigate global temperature rise. [2]

• Lines 49

straw returning to the field is a common soil fertilization method in the early stage of rural China. [3]

• Lines 110-113

Phosphorus is important for plant metabolic substances such as nucleotides, nucleic acids and enzymes, as well as for energy transfer. In the soil, phosphorus is a rather immobile element  which bonds with common soil constituents such as calcium (Ca), aluminium (Al), and iron (Fe).[20]

• Lines 551-557

Ameloot et al. reported, biochar was prepared from willow wood (Salix dasyclados) and swine manure digestion material at 350 ℃ and 700 ℃ respectively, When the four treatments of blank, DS350, DS700, WS350 and WS700 were applied to agricultural soil, the C mineralization in all treatments increased rapidly in the early stage, and then the CO₂ emission continued to increase at a much slower rate, which is similar to our results. This may be due to the rapid degradation of unstable or volatile components in the soil and the slow degradation of stable components in the soil.

• Lines 646-647

According to the research results of the interaction and influence between enzyme activity and soil microbial activity,[47]

• Lines 659-660

The activity of catalase increased with the addition of the two kinds of biochar, which may be due to the adsorption performance of biochar and the easy storage of the porous structure of biochar, thus improving the activity of catalase. [49]

• Lines 731-733

moreover, the change of CO₂ concentration will cause the change of pH value, which will indirectly affect the activity of soil enzymes. [55]

• Lines 735

may be related to different organic carbon components and different enzyme performance differences. [56].

2. My next complaint is the poor level of English used in the manuscript. The text should be checked by a professional translator

Reply: Thank you for your suggestion. Regarding English grammar and other issues, I have resubmitted the polishing company for polishing. I polished it once before submitting it to the periodical. The following is my first polishing certificate.

 

 

3. I do not understand why the authors did not use the ready template that is available on the journal website? Please format the text according to the template provided by the journal.

Reply: Thank you for your suggestion, we have revised this in the manuscript.

I have changed the full-text format to the format of Sustainability Periodicals. The following are some screenshots.

4. The authors did not attempt to perform microbiological analyzes. Microorganisms play a very important role in the context of the use of biochar. The authors emphasize it in the text, but it is a pity that they themselves did not attempt to perform this type of analysis of the microbiocenotic composition of the microbial population

Reply: Thank you for your suggestion. It gave me a lot of inspiration. We will refer to your opinions for microbial analysis in further research, such as microbial biomass carbon, soil high throughput determination, etc.

 

Round 2

Reviewer 1 Report

General comment: The authors have addressed some of my comments. However, there are still some errors that need to be fixed. More details are provided in my specific comments.

 

Specific comments:

Line 17: The graphical abstract is very confusing. For example, it is difficult to tell if the decrease in CO2 a result of 1%, 2%, and 5% biochar because there are so many boxes and arrows. I also do not see the need of using the facial expressions.

Line 17: I still think the abbreviations should be changed. Since Sustainability is an English language journal, it does not make sense to use pinyin as abbreviations. Why not change MSB to CSB for cassava straw biochar, and XSB to BSB for banana straw biochar?

Line 168: The line number is mixed with the formula.

Line 175: “post-hoc test”.

Line 177: The method used for correlation analysis should also be provided.

Line 329: In the method section, the authors mentioned that Duncan multiple-range test was used for post-hoc test, while Tukey’s test is mentioned here. Which one was used?

Line 405: Change “ug” to “μg” throughout the manuscript.

Line 415: The full table was not displayed. Consider splitting it into two tables.

Line 430: The numbers did not align with the column heads.

Lines 435-437: Awkward sentence and wrong punctuations.

Line 437: What do these abbreviations mean?

Lines 571-573: No need to report specific numbers in the conclusion.

Author Response

Manuscript ID:sustainability-1016320 Minor Revise

Manuscript Title: Effects of Two Types of Straw Biochar on the Mineralization of Soil Organic Carbon in Farmland

Authors: Lening Hu, Shuangli Li, Ke Li, Haiyan Huang, Wenxin Wan, Qiuhua Huang, Qiuyan Li, Yafen Li, Hua Deng*, Tieguang He*

Dear Editors and Reviewers:

Thank you for your letter and for the reviewers’ commemts concerning our manuscript. Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have made correction which we hope meet with approval. Revised portion are marked in yellow in the paper. The main corrections in the paper and the responds to the reviewer’s comments are as flowing:

Reviewer #1:

1. The graphical abstract is very confusing. For example, it is difficult to tell if the decrease in CO2 a result of 1%, 2%, and 5% biochar because there are so many boxes and arrows. I also do not see the need of using the facial expressions.

Reply: Thank you for your suggestion, we have revised this in the manuscript.

• The supplementary content are marked on manuscript, Lines 16

The graphic summary has been modified, as shown in the following figure:

2. I still think the abbreviations should be changed. Since Sustainability is an English language journal, it does not make sense to use pinyin as abbreviations. Why not change MSB to CSB for cassava straw biochar, and XSB to BSB for banana straw biochar?

Reply: Thank you for your suggestion, we have revised this in the manuscript.

I have replace all that abbreviations of XSB and MSB in this text with BSB and CSB, as follow：

1% BSB, 2% BSB, 1% CSB, 2% CSB and 5% CSB, respectively. All treatments were performed in triplicate.

3. The line number is mixed with the formula.

Reply: Thank you for your suggestion, we have revised this in the manuscript.

All line numbers have been checked and modified

4. “post-hoc test”.

Reply: Thank you for your suggestion, we have revised this in the manuscript.

• The supplementary content are marked on manuscript, Lines 175

The post-event test used is Duncan multiple-range test. The following is a screenshot of the software used:

Duncan multiple-range test

5. The method used for correlation analysis should also be provided.

Reply: Thank you for your suggestion, we have revised this in the manuscript.

• The supplementary content are marked on manuscript

Pearson's method was use for correlation analysis

6. In the method section, the authors mentioned that Duncan multiple-range test was used for post-hoc test, while Tukey’s test is mentioned here. Which one was used?

Reply: Thank you for your suggestion, we have revised this in the manuscript.

• The supplementary content are marked on manuscript, Lines 329

The test method in this article uses Duncan multiple-range test, which has been modified in the corresponding part of the article as follows:

Fig. 3. Content of soil catalase & urease after application of two kinds of straw biochar, BSB is banana biochar CSB is cassava biochar Duncan multiple-range test shows that there is significant difference between different letters at the same time (p=0.05)

7. Change “ug” to “μg” throughout the manuscript.

Reply: Thank you for your suggestion, we have revised this in the manuscript.

• The supplementary content are marked on manuscript, Lines 405

" ug " has been replaced with "μg ", as shown in Table 4

Table 4 Ratio of CO₂ emission and TOC of two straw biochar in medium culture stage

	CO2 emissions（μg/g）		TOC content（g/kg）	CO2 / TOC（%）
CK		0.42	1.12	0.16
1%BSB		3.13	1.95	0.22
2%BSB		5.33	2.47	0.14
5%BSB		5.68	3.95	0.03
1%CSB		0.55	2.10	0.07
2%CSB		1.86	2.80	0.08
5%CSB		3.37	4.39	0.04

 

8. The full table was not displayed. Consider splitting it into two tables.

Reply: Thank you for your suggestion, we have revised this in the manuscript.

• The supplementary content are marked on manuscript, Lines 416

Table 5 has been split into two tables, as follows, Table 5-1 & 5-2

Banana straw biochar
Indicators	Olsen-P	pH	Catalase	Urease	SOC	DOC
Olsen-P	1	.868**	-.864**	-.477**	.955**	.635**
pH		1	-.926**	-0.139	.855**	.301*
Catalase			1	0.113	-.859**	-.289*
Urease				1	-.377**	-.734**
SOC					1	.492**
DOC						1
Cassava straw biochar
Indicators	Olsen-P	pH	Catalase	Urease	SOC	DOC
Olsen-P	1	.772**	-.806**	.807**	.936**	-.821**
pH		1	-.497**	.430**	.888**	-.811**
Catalase			1	-.719**	-.732**	.637**
Urease				1	.688**	-.624**
SOC					1	-.842**
DOC						1

 

9. The numbers did not align with the column heads.

Reply: Thank you for your suggestion, we have revised this in the manuscript.

• The supplementary content are marked on manuscript, Lines 434

The position of the number and L column header has been adjusted as follows：

Table 6 Correlation between Soil CO₂ Emission and Enzyme Activity

	Banana straw biochar				Cassava straw biochar
	Urease	Catalase		CO2 emissions	Urease		Catalase	CO2 emissions
CO2 emissions	0.442	0.515*	1			0.751**	0.732**	1
Catalase	0.113	1				-.719**	1
Urease	1					1

 

10. Awkward sentence and wrong punctuations.

Reply: Thank you for your suggestion, we have revised this in the manuscript.

• The supplementary content are marked on manuscript, Lines 439-441

The sentence has been revised to read as follows:

Biochar can seriously affect soil carbon dioxide emissions [35]. Ameloot et al [36] reported, biochar was prepared from willow wood (Salix dasyclados) and swine manure digestion material at 350 ℃ and 700 ℃ respectively, when the four treatments of blank, DS350, DS700, WS350 and WS700 were

11. What do these abbreviations mean?

Reply: Thank you for your suggestion, we have revised this in the manuscript.

• The supplementary content are marked on manuscript, Lines 441

The abbreviation here is that abbreviation in the cited literature, WS mean willow wood and DS mean swine manure digestion material

12. No need to report specific numbers in the conclusion.

Reply: Thank you for your suggestion, we have revised this in the manuscript.

• The supplementary content are marked on manuscript, Lines 575-577

The specific figures have been partially removed as follows：

The cumulative CO₂ emission of cassava straw biochar with 1% and 2% addition ratios is lower than that of banana straw biochar, which indicates that cassava straw biochar has certain emission reduction effect than banana straw biochar. The content of organic carbon in each treatment was higher than CK (blank control), indicating that the two kinds of biomass char were beneficial to the promotion of organic carbon, and the content of organic carbon in cassava straw biochar was higher than that in banana straw biochar. The mineralization trend of soil organic carbon is basically the same when the two kinds of straw biochar are applied. The application of biochar increases the mineralization rate and accumulated mineralization amount of soil organic carbon. Different straw biochar has different effects on soil organic carbon mineralization. Banana straw biochar has stronger mineralization effect on soil organic carbon than cassava straw biochar.

Reviewer 2 Report

My corrections have been incorporated.

Author Response

Thank you for your suggestion, which inspired me very much and greatly improved my paper.