Effect of Chinese Milk Vetch (Astragalus sinicus L.) and Rice Straw Incorporated in Paddy Soil on Greenhouse Gas Emission and Soil Properties
Round 1
Reviewer 1 Report
First of all, I apologize with the authors for the delay of my report.
The work is entitled “Effect of Chinese milk vetch (Astragalus sinicus L.) and rice straw incorporated in paddy soil on correlations between greenhouse gases and soil properties”. This title is not so appropriate for the work. The effect of CMV incorporation on the correlation between GHG and soil properties was not really analyzed, and it was poorly discussed. Nevertheless, the work is very interesting to me. The objective is clear and well stated. The experiment seems well done, even if some further details is needed, in particular data analysis is poor compared with the potential of the dataset. Results of soil gas fluxes (CO2, CH4 and NO2) are clear about the potential contribution of CMV as green manure and its reduced impact in terms of NO2 emission when incorporated together with rice straw compared also with the control. It is also clear that CMV did not increased the emission of CH4, while it increased the mineralization rate when incorporated with straw, in agreement with other studies. However, on my view, a comparison with straw alone and with straw plus a chemical fertilizer would be more suited to assess the actual potential of green manure practice in mitigating GHG emissions from rice cultivation.
The key point is that effect of CMV on the correlation between GHG emissions and soil properties was not really analyzed. Firstly, it is not clear how the analysis of correlation was made, and secondly the correlations were made on the pooled dataset, while a discrimination among treatments, or a ANOVA for analyzing the difference of soil properties would be more appropriate to fit with the title of the work (see my comments below).
My suggestion is to improve the statistics, adding further results for feeding the discussion, and/or (?) to change the title, for example “Effect of Chinese milk vetch (Astragalus sinicus L.) and rice straw incorporated in paddy soil on greenhouse gases emission and soil properties”.
In detail
Materials and methods
Line 64 – Did you maintained the dark condition for the entire experiment duration or only during the pre-incubation stage?
Lines 66-67 – It would be of interest to know the rationale by which you calculated the doses of CMV and rice straw. Did you mimic the in field condition, or did you have a target in terms of C or C:N?
Line 81 – “rapidly” is generic and not properly scientific, please provide a maximum or mean rage of time within which you analyzed your samples. For example within 7 days
Line 82 – Description of equipment is not clear. Did you mean electronic or electron capture device? Did you use FID for both CO2 and CH4? Which device for NO2? Please provide further details. It is an important step of your research and this information is in needed by other researchers.
Line 85 – “(Arrange gas production time according to the change of gases emission)”: statement not clear. What did you really mean? Maybe that you arranged the frequency of gas collection according to the change of gases emission?
Line 89 – Just a curiosity: did you not take any measurement of P (pressure) in your incubator?
Line 91 – in “produced during he chamber was sealed”, please correct he with the.
Line 93 – Soil sampling and analysis. Did you sample and analyze all parameters in days 3, 9, 34, and 52 or only nitrate nitrogen and ammonium nitrogen?
Overall, in M&M, statistical analyses are poorly described. In particular, analyses of correlation are not clear. I mean, it is difficult to understand I you checked only Ftotal of day 52 against the value of soil parameters in day 52, or if you pooled together Ftotal of days 3, 9, 34 and 52 against the value of soil parameters in the same days.
Line 105 – in “Soil microbial biomass carbon and nitrogen were determined by chloroform fumigation and K2SO4 extraction, respectively” please provide also acronyms used in results section.
Results
Line 143 – in section 3.4 “Correlation between greenhouse gas emissions and soil factors” you did not mention AK. Did you not observe any correlations with cumulative fluxes? Why did you measured AK in soil? Is it a control parameter? In case you cannot explain maybe it is better to remove AK measurement from M&M.
Moreover, did you check for correlations among soil parameters? I’m also wondering why did you not use ANOVA for analyzing the effect of treatments on soil properties to the light of the title and the discussion? I believe soil data were not fully exploited.
Figure 4 – do empty boxes mean that the correlation was not significant? Please explain it in the caption.
Discussion
Section “4.2 Correlations between greenhouse gases and soil factors”, the discussion is very little, considering that this aspect should be the key of the work, maybe it depends also by the little data analysis you made.
Author Response
Dear Reviewer 1，
We are thankful to your valuable comments to improve the quality of our manuscript.
Please see the attachment.
Author Response File: 
Author Response.docx
Reviewer 2 Report
The article presents the results of an experiment in pots consisting in continuously measuring emissions of the three main greenhouse gases from a paddy soil with and without the incorporation of rice straw and / or Astragalus sinicus.
This theme corresponds to the aims and scope of the journal. The results are original and interesting. The style is precise. The methodology is described with great precision as recommended.
However, we suggest to the authors, if they have to revise their text, to eliminate the expression "about" (for example lines 130, 132, 134) for data worded with precision or if they consider that these are approximate not to put two digits after the decimal point.
Author Response
Dear Reviewer 2,
We are thankful to your valuable comments to improve the quality of our manuscript.
Point 1: We suggest to the authors, if they have to revise their text, to eliminate the expression "about" (for example lines 130, 132, 134) for data worded with precision or if they consider that these are approximate not to put two digits after the decimal point.
Response 1: The word "about" has been eliminated.
