Do Fallow Season Cover Crops Increase N2O or CH4 Emission from Paddy Soils in the Mono-Rice Cropping System?
Round 1
Reviewer 1 Report
The present paper deals with an interesting and up-to-date topic and should be of interest for readers of Agronomy Journal.
One limitation of the study is the fact that it was performed for only one year that might be considered as a specific case.
But the main issue is related with the set-up of GHG measurement: Why did you measure GHG emissions only during the rice growing season and subsequent fallow period? Why did you not measure GHG emissions during cover crop growth? This way it is not possible to assess the global impact of cover crop on GHG emissions since significant emissions should have occurred during the cover crop growth.
Considering this issue, the objective of the study is not attend: you cannot assess the impact of cover crop on GHG during rice growth, but only assess the impact of cover crop on the subsequent fallow period.
The authors should revised the whole manuscript attending this point. Even if not so interesting, this new objective might also be of interest since cover crops cannot be grow every year.
Other issues:
L92-93: Before incorporation, the ryegrass, Chinese milk vetch and rice residue were weighed and cut into 2- to 3-cm pieces: Why did you do such treatment? I strongly influence the degradation of residues and consequently all the results presented here
L117-118: Please clarify the fluxes calculation mode: what are the units of C ?
Author Response
Comments: The present paper deals with an interesting and up-to-date topic and should be of interest for readers of Agronomy Journal. One limitation of the study is the fact that it was performed for only one year that might be considered as a specific case. But the main issue is related with the set-up of GHG measurement: Why did you measure GHG emissions only during the rice growing season and subsequent fallow period? Why did you not measure GHG emissions during cover crop growth? This way it is not possible to assess the global impact of cover crop on GHG emissions since significant emissions should have occurred during the cover crop growth.
Considering this issue, the objective of the study is not attend: you cannot assess the impact of cover crop on GHG during rice growth, but only assess the impact of cover crop on the subsequent fallow period.
The authors should revised the whole manuscript attending this point. Even if not so interesting, this new objective might also be of interest since cover crops cannot be grow every year
Response: Thanks for your positive comments and raising this point. We are sorry for the unclear presentation. We actually planted cover crops in winter fallow period and measured GHG emissions during both of the rice growing season and cover crop period, as indicated in Figure 1 in the manuscript. To clarify the meaning, we have modified “winter fallow period” to “cover crop period” in the revised manuscript (Line 14, 76, 122, 167, 191, 294 in the revised manuscript). Yes, we agree with the reviewer that a longer study would provide more comprehensive information about long term effects. Therefore, we are still running the experiment including more treatments and we hope that we could find something new and submit our second manuscript to the journal.
Comments: L92-93: Before incorporation, the ryegrass, Chinese milk vetch and rice residue were weighed and cut into 2- to 3-cm pieces: Why did you do such treatment? I strongly influence the degradation of residues and consequently all the results presented here.
Response: Thank you for your helpful comments. Field management was consistent with local practices. Before incorporation, the ryegrass, Chinese milk vetch and rice residue were weighed to control the residues application amount. According to the local field management, cover crop residue need to be cut into 2- to 3-cm pieces for easy incorporation.
Comments: L117-118: Please clarify the fluxes calculation mode: what are the units of C?
Response: Thank you for the suggestion. The irrelevant wording has been deleted.
Author Response File: 
Author Response.doc
Reviewer 2 Report
The submitted manuscript is well prepared, interesting, and within the scope of the Agronomy journal. The research focuses on the emission of greenhouse gasses from the soil under different management systems and the results of the study shown some interesting environmentally friendly solutions supporting rice productivity.
However, some minor corrections and the addition of some results should be taken into consideration by the authors.
#1 The Latin names of rice and cover crops are missing in the abstract and the text.
#2 Lines 9 - 11 Authors in abstract wrote, "Cover crop management during the fallow season may play a relevant role in improving crop productivity and soil quality by increasing nitrogen (N) and soil organic carbon (SOC) accumulation ...". But the results of the evaluation of soil N and C after the harvest are not presented even in paragraph "2.4. Soil sampling & measurement" adequate procedure are described. Also, the results of the mentioned analyses are not described and discussed.
#3 Some discussion of the relationships between nitrogen (N) and soil organic carbon accumulation and the emission of greenhouse gasses from the soil will noticeably improve the quality of the paper as well as conclusions.
#4 Line 11 Authors in abstract wrote, "(GHG) emissions in soil" should be "(GHG) emissions from the soil"
#5 Line 289 Space should be added "summary.Paris,"
#6 Line 291 is "CH4 and N2O" should be "CH4 and N2O"
#7 Line 338 is "(astragalussinicus L.) should be (Astragalus sinicus L.)
Author Response
Comments: The submitted manuscript is well prepared, interesting, and within the scope of the Agronomy journal. The research focuses on the emission of greenhouse gasses from the soil under different management systems and the results of the study shown some interesting environmentally friendly solutions supporting rice productivity.
However, some minor corrections and the addition of some results should be taken into consideration by the authors.
#1 The Latin names of rice and cover crops are missing in the abstract and the text.
Response: Thank you for the comments, the Latin names of rice and cover crops have been included in the abstract and the text (Line 15-19, 93-95 in the revised manuscript).
Comments: #2 Lines 9 - 11 Authors in abstract wrote, "Cover crop management during the fallow season may play a relevant role in improving crop productivity and soil quality by increasing nitrogen (N) and soil organic carbon (SOC) accumulation ...". But the results of the evaluation of soil N and C after the harvest are not presented even in paragraph "2.4. Soil sampling & measurement" adequate procedure are described. Also, the results of the mentioned analyses are not described and discussed.
Response: Thank you for your helpful comments. We fully agree that nitrogen and soil organic carbon are important factors that should be considered in the present study. The relevant information has been included in the revised manuscript (Line 20-21, 29-31, 196-198, 240-242, 303-308 in the revised manuscript). The experiment is still running to evaluate the long-term effects of cover crops on SOC sequestration and N accumulation.
Comments: #3 Some discussion of the relationships between nitrogen (N) and soil organic carbon accumulation and the emission of greenhouse gasses from the soil will noticeably improve the quality of the paper as well as conclusions.
Response: Yes, we fully agree your comments, relevant results and discussion have been included in the revised manuscript (Line 20-21, 29-31, 196-198, 240-242, 303-308 in the revised manuscript).
Comments: #4 Line 11 Authors in abstract wrote, "(GHG) emissions in soil" should be "(GHG) emissions from the soil"
Response: Thank you for the suggestion, the wording has been modified (Line 11 in the revised manuscript).
Comments: #5 Line 289 Space should be added "summary. Paris,"
Response: Thanks, changed accordingly (Line 321 in the revised manuscript).
Comments: #6 Line 291 is "CH4 and N2O" should be "CH4 and N2O"
Response: The wording has been changed (Line 323 in the revised manuscript).
Comments: #7 Line 338 is "(astragalussinicus L.) should be (Astragalus sinicus L.)
Response: Change accordingly (Line 370-372 in the revised manuscript).
Author Response File: Author Response.doc
