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Peer-Review Record

Carbon Sequestration and Contribution of CO2, CH4 and N2O Fluxes to Global Warming Potential from Paddy-Fallow Fields on Mineral Soil Beneath Peat in Central Hokkaido, Japan

Reviewer 1: Anonymous
Reviewer 2: Anonymous
Received: 18 November 2019 / Accepted: 23 December 2019 / Published: 27 December 2019
(This article belongs to the Special Issue Greenhouse Gas Emissions in Agroecosystems)

Round 1

Reviewer 1 Report

The authors covered most of my comments.

I still find several issues with English, but this remains on the authors and the journal to solve.

Thank you. 

Reviewer 2 Report

The authors have addressed the comments and explained areas of concern in my view. I have no further comments.

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

The paper was a resubmission and it was improved significantly. However, I would like to ask the authors to make a read proof by an English native speaker before providing us the final version, as in some cases it requires more time to understand the phrasing than the content. Especially, the discussion part is very complex and in many cases it redirects the reader. I would like to ask the authors to change this part thoroughly aiming to discuss separately specific results (what was the result in your study, what is the scientific reason that occurred, what other have done concerning this results and how they are connected between them). if necessary, use different paragraphs for each result.

For the rest of my specific comment, go through the PDF file uploaded.

Thank you.

Comments for author File: Comments.pdf

Author Response

Resubmission ROUND -3

Reviewer -1

 

Ref: Manuscript ID- agriculture- 608054 ‘Carbon sequestration and contribution of CO2, CH4 and N2O fluxes to global warming potential from paddy-fallow fields on mineral soil beneath peat in central Hokkaido, Japan’.

We would like to express our heartfelt gratitude to the reviewer for his/her kind consideration.

Our responses to the reviewers’ comments (reviewer-1)

General comments:

The paper was a resubmission and it was improved significantly. However, I would like to ask the authors to make a read proof by an English native speaker before providing us the final version, as in some cases it requires more time to understand the phrasing than the content. Especially, the discussion part is very complex and in many cases it redirects the reader. I would like to ask the authors to change this part thoroughly aiming to discuss separately specific results (what was the result in your study, what is the scientific reason that occurred, what other have done concerning this results and how they are connected between them) if necessary, use different paragraphs for each result.

Answer: We would like to express our heartfelt gratitude to the reviewer for his/her nice comments.

The English language of this manuscript has been checked by an American University graduate. Hopefully the language is quite better now than before.

We tried our best to discuss by avoiding complexity in the discussion section elsewhere.

Comments: For the rest of my specific comment, go through the PDF file uploaded.

Modification highlighted by yellow colour in the manuscript.

 

Comments and Suggestions for Authors

Specific Comments

 

Comments: Please remove previous L-48 to 49.

Answer: Removed.

Comments:  Line 59 - leads.

Answer: leads replaced by will lead. (Now L-61)

 

Comments: Line 61-add “,”

Answer: Added “,”. (Now Line 63)

 

Comments: Line 62-63: Could you please define some studies saying that?

Answer: We already added couple of references (Bruce et al., 1999; Liou et al, 2003; Zou et al., 2003and Tang et al., 2016)  those studies said this. (Now Line 66)

 

Comments: Line 63 delete “the”

Answer: Deleted the.

 

Comments: Line 73 - replace "they did not use" with "not"

Answer: Modified as  with "not" (Now Line -78).

 

Comments: Line 79: delete "s"

Answer: Deleted (Now Line 85).

 

Comments: Line 97: fields

Answer: we added “s”. (Now Line 102)

 

 Comments: Line 97- Delete ",through measured from paddy field"

Answer: Deleted.

 

Comments: Line 101: eavluate

Answer: We modified as evaluate. (Now Line 107)

 

Comments: Line 109 - Please explain why you selected 2 multiple drainage and 1 single. Since you change the soil dressing from 20 to 29 cm in the first case, why you do not do it in the second too?

Answer: We selected farmer’s field and emphasized on actual management conditions which farmers usually have been done, we did not change or modified anything. The frequency of drainage depended on management, field conditions and farmers’ judgment. That is why the selection of multiple and single drainage was done unintentionally. As we stated in our manuscript, in the 1960s, the peat soils were drained, top dressed with about 30 cm of mineral soil, and turned into productive crop fields. Because of farming for many years, the thickness of mineral soils has been changed irregularly fields to fields due to plowing for crop cultivation. 

 

Comments: Line 109 - rephrase "were mineral soil dressed peat"... Do you mean "mineral soil dressed peatland"?

Answer: We modified as per suggestion. (Now Line 115) Comments: Line 109 - delete "of soil-dressed peatland fields"Answer: Deleted 

Comments: Line 114 - Delete "in the winter-fallow period"

Answer: Deleted Comments: Line 116-117 - Why you refer to this again. It was mentioned in line 113-114.Answer: Deleted this sentence. Comments: Line 133  - change ", no other weeds or/if any it was very small and negligible" to "; no weeds were grown and if any negligible in size and volume".Answer: Changed as no weeds were grown and if any negligible in size and volume. (Now Line 138) Comments: Line 134 - delete yr-1.Answer: Deleted. 

Comments: Line 142  - what do you mean by "might"?? you selected the fields out of luck?

Answer: Modified this sentence.  

Comments: Line 142  - have been directed

Answer: Modified as per suggestion.

 

Comments: Line 144  - Please define the amount per ha or if not available provide a qualitative comparison and a ranking between the 3 fields.

Answer: Field D1-M, D2-M and D3-S received 5.21, 5.58 and 7.51 t ha-1, respectively of leftover rice straw from previous year’s rice crop. (Now Line 151).

 

Comments: Line 147  - stop the sentence here and start over.

Answer: Modified as per suggestion.

 

Comments: Line 147  - possibly

Answer: Changes have been made. (Now Line 156)

 

Comments: Line 150-152-  The presence of cracks and the increase in the amplitude result in a significantly higher penetration rate [24], resulting in water and nutrients deficiency in the shallow roots [25] and percolation rate increases due to water productivity decreases [26].

Answer: Modified as per suggestion. (Now Line 159-161)

 

Comments: Line 154-  Connect this table with my question on ranking the fields above.

Answer: Modified as per suggestion.

 

Comments: Line 158- Is fact that D3-S has a sandy soil connected to the drainage pattern used?

Answer: Yes that's a reason too.(Now Line 156)

 

Comments: Line 159- fix the table style. not only here!

Answer: Modified as per suggestion. (Now Line 167-168)

 

Comments: Line 162 -Depending

Answer: Modified as per suggestion. (Now Line 170).

 

Comments: Line 163- Delete this sentence and keep the (three chambers per field) in the end of the previous sentence.

Answer: Modified as per suggestion. (Now Line 171)

 

Comments: Line 165- Transplanting

Answer: Modified as per suggestion. (Now Line 172) 

Comments: Line 168- Bases

Answer: Modified as per suggestion. (Now Line 175)

 

Comments: Line 169- change to "to sample CH4 and N2O gases."

Answer: Changed as "to sample CH4 and N2O gases." (Now Line 176)

 

Comments: Line 171- is more than 20 cm deep and ...

Answer: Modified as per suggestion (Now Line 178).

 

Comments: Line 172- delete distance and put wide.

Answer: Modified as wide. (Now Line 179)

 

Comments: Line 172- transplanting

Answer: Modified as per suggestion. (Now Line 179)

Comments: Line 181-I would add a picture of the structure. it will be a lot more understandable for the reader.

Answer: We already added Figure 1. Chamber placement and boardwalks construction picture. (Now Line 190).

 

Comments: Line 185- put “a”

Answer: Modified as per suggestion. (Now Line 194)

 

Comments: Line 188- combine the description with a picture of your apparatus.

Answer: In figure 1. we described.

 

Comments: Line 188- delete electronic

Answer: Deleted.

 

Comments: Line 194- change paragraph

Answer: We made a separate paragraph. (Now Line 205)

 

Comments: Line 197- “,”

Answer: Changes have been made. (Now Line 207).

 

Comments: Line 200- put this into brackets like with the GC.

Answer: modified as per suggestion. (Now Line 2010)

 

Comments: Line 203- do not repeat that N2 is the carrier.

Answer: Changes have been made. (Now Line 2013)

 

Comments: Line 210- each...

Answer: Changes have been made. (Now Line 220) 

Comments: Line 211- again I would propose that you use an accompanying picture.

Answer:  Have already been added picture.

 

Comments: Line 214- ‘the”

Answer: Changes have been made. (Now Line 223)

 

Comments: Line 211-‘into’

Answer: Changes have been made. (Now Line 224)

 

Comments: Line 227- was this assumption used in previous studies? Please provide refs.

Answer: We have provided reference. (Now Line 238)

Comments: Line 235- transplanting

Answer: Changes have been made. (Now Line 242) 

Comments: Line 239- delete "immediately" and change to "just"

Answer: Changes have been made. (N L 246)

 

Comments: Line 242- not clear which section you are referring to.

Answer: We have changed that sentence and described details about C analysis. (N L 248-250)

 

Comments: Line 258- the abbreviation was already used in the text before.Answer: Yes and we modified as GWP 

Comments: Line 261- The two previous sentences should be combined in one and give ONE definition for GWP. However, it shouldn't be here (maybe in the intro that you refer to this for the first time, as it it the M&M section and the term is well known.

Answer: Two sentences already been combined and GWP definition transfer from materials and method to introduction section. (N L 252)

 Comments: Line 274-‘.’Answer: Modified as per suggestion. Comments: Line 286- is this right?Answer: Yes right. (N L 295) Comments: Line 291- delete "were"Answer: Deleted. 

Comments: Line 309- there was no significant difference in N2O fluxes.

Answer: Changes have been made. (N L 320)

 

Comments: Line 322- you should use CS after the first time you use the abbreviation.

Answer: Changes have been made.

 

Comments: Line 324- the same

Answer: Changes have been made.

 

Comments: Line 327- the same

Answer: Changes have been made.

 

Comments: Line 365- this sentence is not clear. D3-S has 5016, D2-M has 3990 and D1-M has 3823 g CO2eq/m2/yr. So, the annual GWP from D3-S is 25.7% higher than D2-M and 31.2% higher than D1-M.

Answer: Changes have been made as “the net annual GWP from D3-S field was 31.2% and 25.7% higher than D1-M and D2-M field, respectively.” (N L 385-386).

 

Comments: Line 384- repetition.

Answer:  Repetition has been omitted.

 

Comments: Line 389- who

Answer: Changes have been made. (N L 410)

 

Comments: Line 391- nice to show different work on the same subject, but you do not really discuss the reasons that the results were different. What was the climatic, soil, residue or management reasons for this difference?

Answer:  The reason for the difference between their results and our study could possibly be due to different climatic conditions (subtropical climate with the mean temperature was about 25°C during growing season in Shanghai, China), soil (organic matter content 18.8 g kg-1 and total N 1.24 g kg-1 with high pH 7.9 to 8.0) and management practices (direct seeding and continued flooding until October 2 with intermittent irrigation from July 15 to August 2).  (N L 412-417).

 

Comments: Line 396-delete ‘there by’

Answer:  Deleted.

 

Comments: Line 397-wasn't it mentioned in the previous sentence?

Answer:  Changes have been made.

 

Comments: Line 402-‘_’ delete

Answer:  Deleted

 

Comments: Line 410- fellow to ‘Fallow’

Answer:  Changes have been made. (N L 435)

 

Comments: Line 412- delete :would like to say that our findings" and say "provide".

Answer:  Changes have been made. (N L 437)

 

Comments: Line 413- delete "which will" and say "to"

Answer:  Changes have been made. (N L 437)

 

Comments: Line 416- the question remains. Why all the rest were using another method and you chose to use this? what are the advantages that led you there? this should be provided in the M&M.

Answer: We have summarized this explanation as “We calculated soil C sequestration using the C budget method” and moved it to materials and method section. (N L 252)

 

 Comments: Line 420- that was between

Answer:  Changes have been made. (N L 448)

 

Comments: Line 427- perhaps due to the rate

Answer:  Changes have been made. (N L 454)

 

Comments: Line 430- showing

Answer:  Changes have been made. (N L 457)

 

Comments: Line 434- management

Answer:  Changes have been made. (N L 462)

 

Comments: Line 440-this phrase provide contradictory results. please rephrase.

Answer:  Have been rephrasing as “we presume that the differences in soil microbial activity occurred mostly during the drainage as a result of change from anoxic soil in the submerged conditions to the aerated soil during drainage period.” (N L 462-469)

 

Comments: Line 443- Please rephrase. Do you mean that the annual cumulative CH4 emissions were about 52% higher than D1-S and D2-M?

Answer:  Have been rephrase as “comparing D3-S with D1-M and D2-M fields, the annual cumulative CH4 emissions were approximately 52% higher in D3-S due to differences in crop residues and drainage effects. (N L 471-473)

 

Comments: Line 444- Wasn't that mentioned before?

Answer:  Changes have been made.

 

Comments: Line 446- What does "maximum efficiency" means in this phrase?

Answer:  Maximum efficiency of the CH4 production define as “straw’s efficiency on CH4 production = total CH4 emission (g C m−2)/total dry matter of crop residue (g m−2) leftover)], which resulted in the large CH4 emissions under the single drainage system compared to double drainage (D1-M and D2-M) fields. (N L 475-478)

 

Comments: Line 448- that might be due to relatively lower soil temperature...

Answer:  Changes have been made. (N L 479)

 

Comments: Line 486- delete ‘has large’

Answer:  Changes have been made.

Author Response File: Author Response.pdf

Reviewer 2 Report

Dear authors,

This is a good study to investigate the annual net GHG balance in the paddy field and also the contribution from the growing and fallow period.

I have some important concerns with the paper especially the C budget calculation.

1, Could you explain why the three soils you used in this study varied so largely regarding the C, N content?

2, According to your description, the soil microbial respiration (Rm) looks more like soil heterotrophic respiration.

3, I doubt whether you consider litter and Rhizadeposit when you calculate the NPP in your work, as the NPP you showed was three times lower than other studies.

4, Consider the C budget, the straw should not be regarded as C loss as you returned to the soil.

5, The management effect on net GHG balance was not discussed.

6, Some of the discussions are not well explained. Such as the NPP, the N2O fluxes differences between growing and fallow periods. 

Besides, some of the tables need to improve, such as table 2.

Although the English have been checked, there is still some content unclear. For example, lines 22-24.

 

 

Author Response

Resubmission ROUND -3

Reviewer -2

 

Ref: Manuscript ID- agriculture- 608054 ‘Carbon sequestration and contribution of CO2, CH4 and N2O fluxes to global warming potential from paddy-fallow fields on mineral soil beneath peat in central Hokkaido, Japan’.

We would like to express our heartfelt gratitude to the reviewer for his/her kind consideration.

Our responses to the reviewers’ comments (reviewer-2)

General comments:

This is a good study to investigate the annual net GHG balance in the paddy field and also the contribution from the growing and fallow period.

Answer: We would like to express our heartfelt gratitude to the reviewer for his/her nice comments

Comments and Suggestions for Authors

 

Modification highlighted by bright green colour in the manuscript.

 

Specific Comments

 

Comments: “I have some important concerns with the paper especially the C budget calculation”.

 

Comments 1. Could you explain why the three soils you used in this study varied so largely regarding the C, N content?

Answer: We selected farmer’s field and emphasized on actual management conditions which farmers usually have been done, we did not change or modified anything. As we stated in our manuscript, in the 1960s, the peat soils were drained, top dressed with about 30 cm of mineral soil, and turned into productive crop fields. Farming for many years, the thickness of mineral soils has been changed irregularly fields to fields due to plowing for crop cultivation. Due to plowing, higher C and N content peat moves from the bottom to the top and mixed-up with mineral soil. Because of this, might be large difference in the amount of C and N in the three soils.

Comments 2. According to your description, the soil microbial respiration (Rm) looks more like soil heterotrophic respiration.

Answer: Yes, looks like.

Comments 3. I doubt whether you consider litter and Rhizadeposit when you calculate the NPP in your work, as the NPP you showed was three times lower than other studies.

Answer: We estimated the NPP above (grain, straw included litter) and below the ground (root) biomass of the rice plant.   (N L 444-446)

Comments 4. Consider the C budget; the straw should not be regarded as C loss as you returned to the soil.

Answer: We did not consider rice straw as C loss. Combine harvesters were used for rice grain harvest. Farmers left all rice straw in the field and collected only rice grain. Therefore, leftover all harvested straw in the field considered as “straw harvest = 0” in our C budget calculation.

Comments 5. The management effect on net GHG balance was not discussed.

Answer: As per suggestion we have discussed the management effect on net GHG balance under the section 4.2. Greenhouse gas fluxes (Rm, CH4 and N2O), New Line 507 to 512.

Comments 6. Some of the discussions are not well explained. Such as the NPP, the N2O fluxes differences between growing and fallow periods. 

Answer: We tried our best to improved discussion on NPP and N2O fluxes differences between growing and fallow periods. Those are included in the new lines 440 to 445 and 489 to 492, respectively.

Comments 7. Besides, some of the tables need to improve, such as table 2.

Answer: Tables already have been improved.

Comments 8. Although the English have been checked, there is still some content unclear. For example, lines 22-24.

Answer: Changes have been made.

Author Response File: Author Response.pdf

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