Fe(II)-OM Complexes Formed by Straw Returning Combined with Optimized Nitrogen Fertilizer Could Be Beneficial to Nitrogen Storage in Saline-Alkaline Paddy Soils
Round 1
Reviewer 1 Report
The research is interesting and properly performed. Some hints for a better comprehension of the important work that you did, mainly regarding the presentation of the used methodology.
1) In the title and conclusions you specify that data were collected from saline-alkalin soils; however in the methods there is no information on the salinity and Na content of the experimental soil.
2) In the title it is specified that data regards paddy rice; however in the methods there is no indication about the agronomic practices that certainly influenced the obtained results. For instance the depth of ploughing or even wether the soil was ploughed each year, when? When was the straw precisely buried? Before or after ploughing?
3) In the paper there is an interesting table which describes the community of organism classes that were found.But neither in the legend nor in the caption the explanation of the different colors can be found. Moreover, in the methods it is not reported how did you obtain the data.
4) The graphs of NH3-N and FeIi have no figure label and caption.
5) in line 236 you state that SOC content was increased by 5-years straw application, without any reference to N; instead in table 1 the interaction between N level and straw burial was significant (as you say). By the way, the increment that you found (according to your data the initial SOC more than doubled in certain plots in only 5-yrs of straw application) appears very quick in comparison with the increase rate of other experiments. Which was the C/N ratio of the used straw? In line 291 you did speak about the importance of C/N ratio of the the sediment (however it is not so clear which sediment are you talking of. I presume it is the rice straw; is it not?
Author Response
Reviewer #1: The research is interesting and properly performed. Some hints for a better comprehension of the important work that you did, mainly regarding the presentation of the used methodology.
1. In the title and conclusions you specify that data were collected from saline-alkalin soils; however in the methods there is no information on the salinity and Na content of the experimental soil.
Answer: Thank you for your suggestion. We have add it to “The physicochemical properties of soil (0-20 cm) before the experiment were as follows: 0.29% salt content, pH 8.1, SOC 4.87 g kg-1, total nitrogen (TN) 1.12 g kg-1, available phosphorus (AP) 14.4 mg kg-1, and available potassium (AK) 229 mg kg-1.”.
In the title it is specified that data regards paddy rice; however in the methods there is no indication about the agronomic practices that certainly influenced the obtained results. For instance the depth of ploughing or even wether the soil was ploughed each year, when? When was the straw precisely buried? Before or after ploughing?
Answer: Thank you for your suggestion. We have revised it to “The experimental plots were ploughed manually in early June each year to a depth of 20 cm. Rice straw (40% C) was cut into 5-8 cm long and applied into the plot before plowing”.
In the paper there is an interesting table which describes the community of organism classes that were found.But neither in the legend nor in the caption the explanation of the different colors can be found. Moreover, in the methods it is not reported how did you obtain the data.
Answer: Thank you for your suggestion. We have revised it to “Figure 4. Relative abundance of different bacterial communities at the class levels across all the treatments. The bubble chart indicts the relative abundance of significant enriched class, where red represents higher relative abundance and blue represents lower relative abundance”. In the methods, we have add it to “Flash software was used to combine and reads to obtain the complete V3eV4 hypervariable region. Classification of OTUs were using the Ribosomal Database Project classifier. Chao1, Shannon and Simpson abundance-based indices were used to estimate the α-microbial biodiversity of the samples”.
- The graphs of NO3--N and FeIi have no figure label and caption.
Answer: Thank you for your suggestion. Content of NO3--N (a), Fe(II) (b) and relationships between NO3--N and Fe(II)aq (c) after inputting straw incorporation and N fertilization application rates in saline-alkaline paddy soils were all Figure 1.
- In line 236 you state that SOC content was increased by 5-years straw application, without any reference to N; instead in table 1 the interaction between N level and straw burial was significant (as you say). By the way, the increment that you found (according to your data the initial SOC more than doubled in certain plots in only 5-yrs of straw application) appears very quick in comparison with the increase rate of other experiments. Which was the C/N ratio of the used straw? In line 291 you did speak about the importance of C/N ratio of the the sediment (however it is not so clear which sediment are you talking of. I presume it is the rice straw; is it not?
Answer: Thank you for your suggestion. We have revised it to “Previous studies have found that N fertilizer could promote SOC accumulation by inhibiting soil respiration and decomposing stability carbon [25]. In this study, 5 years of N fertilizer application increased the content of SOC”. The C/N ratio of the used straw was 58/1.
Author Response File: 
Author Response.docx
Reviewer 2 Report
This paper describes an experiment on nitrogen application and returning straw to rice fields. This is an interesting topic, but also one that has been studied extensively already. It should be clearer explained what new this paper introduces. Thorough English language revision is also recommended. This reviewer does not feel competent to fully review the molecular data, but my impression is that the occurrence of genes is seen as a cause, independent of the treatment, but I think it is also an effect of treatments? A lot of data/results are presented, but the discussion of them is not very clear or understandable.
Author Response
Reviewer #2: This paper describes an experiment on nitrogen application and returning straw to rice fields. This is an interesting topic, but also one that has been studied extensively already. It should be clearer explained what new this paper introduces. Thorough English language revision is also recommended. This reviewer does not feel competent to fully review the molecular data, but my impression is that the occurrence of genes is seen as a cause, independent of the treatment, but I think it is also an effect of treatments? A lot of data/results are presented, but the discussion of them is not very clear or understandable.
Answer: I am very grateful to your comments for the manuscript. Although the effect of carbon input on NDFO process have been extensively studied, but straw returning affects the process in saline-alkaline paddy soils remains unclear. Therefore, the changes of soil aggregates, NO3--N and Fe(II) under the condition of straw returning were investigated to perform the effect mechanism of straw returning on nitrogen storage in saline-alkaline paddy soils. The abundance of bacteria with nirK genes, as well as their community composition, have been reported to vary in response to different fertilization regimes. Therefore, in this study, we believe that nirK gene could be affected by different treatments. The manuscript has been revised by Native English Speaker. The discussion section of the manuscript has been supplemented.
Author Response File: Author Response.docx
