Effects of Different Nitrogen Applications and Field Return Depth on the Diversity and Function of Bacteria in Returned Straw in Cold Paddy Fields
Round 1
Reviewer 1 Report
The submitted manuscript entitled “Effects of different nitrogen applications and field return depth on the diversity and function of bacteria in returned straw in cold rice areas” by Lin et al. reports rice straw degradation kinetics and variation in bacterial community structure under different levels of nitrogen application and depths of return in the Jilin Province of China.
Overall, the study is interesting and exhaustive. Usage of statistical parameters further strengthens the observations. Microbial population dynamics and enzyme characteristics have been properly studied and explained. The study is supposed to be useful for readers. However, I have certain concerns regarding current version of the manuscript which I have enlisted as Major and Minor comments below –
Major comments:
1. Pg 3, lines 101- 103: “13.75 g of rice straw….. was weighed into a nylon mesh bag……. to produce straw bales.”
It would have been helpful to understand the setup if the images were shown as Supplementary material. Also further it has been mentioned that the straw bales were buried at 450 angles to ensure uniform distribution and maximum soil contact. How 450 angle would help? Wouldn’t burying horizontally would have the same effect?
2. Fig. 3: The only component that appears to have degraded is the soluble fraction and that too, within the initial 20 days of incubation. There is no significant utilization of other components throughout the experiment. Please explain this.
3. Pg. 10, line 312: “Straw decomposing bacteria were significantly affected by different depths of return”
It is known fact that microbial diversity changes with increasing soil depth (Hao et al., 2020). But surprisingly, Fig. 6C doesn’t say so (if I assume that the color codes are uniform in both the bar graphs). Rather there isn’t much variation in microbial diversity till 30 cm. Does this explains why there hasn’t been significant difference in the degradation rates at both the depths (Fig. 2)? If so, then authors might focus on this aspect in the discussion part. Else, if my interpretation is wrong (as observed from Fig. 7), then probably the figure (color codes) in Fig. 6C need to be modified.
Ref. -
Hao J, Chai YN, Lopes LD, Ordóñez RA, Wright EE, Archontoulis S, Schachtman DP (2020). The Effects of Soil Depth on the Structure of Microbial Communities in Agricultural Soils in Iowa, USA. Appl Environ Microbiol. 87:e02673-20.
Minor comments:
1. Title: “cold rice areas” à The term looks bit unusual. Authors might rethink about its usage. Something like “cold paddy fields” or “paddy fields in cold areas” might fit better.
2. Abstract, Pg 1, line 11: “depths of return (0–15 cm, 15–30 cm) of 1-mature-winter tillage…..” à rewrite as “depths (0–15 cm, 15–30 cm) of return of 1-mature-winter tillage…”
3. Abstract, Pg 1, line 19: Define the acronyms - αG, βG, βX, and CBH when they first appear in the abstract
4. Pg 2, line 56: “nitrogen fertilizer” à “nitrogenous fertilizer”
5. Pg 2, line 90: “annual active temperature of approximately 2650 ℃” à Please rectify
6. Under “Materials and Methods”, heading of section 2.2 seems to be wrongly copied from that of section 2.1
7. Pg 3, line 101: “drying weight” à “dry weight”
8. Pg 3, line 121: “Dried straw sample fractions were determined….”
Please rephrase the sentence
9. Pg 3, line 118: “Partially dried samples were used for degradation rate and composition fraction determination”
while in line 122: “The straw degradation rate was determined via the weighing method."
Is weighing partially dried samples an accurate parameter for degradation study?
10. Pg 3, line 125: “samples to be tested were melted on ice” à Please explain. Did the authors mean thawing?
11. Fig. 4, 5 & 6: Please increase the font size for better visibility.
12. Pg 19, line 483: “activity of leucoaminopeptidase in the early and middle stages of straw decomposition had been” à Please complete the sentence
13. Pg 21, line 562: “cooled areas” à Cold areas
Author Response
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Author Response File: 
Author Response.docx
Reviewer 2 Report
In this paper, the author investigated the effects of nitrogen application and depth on the decomposition rate and material composition of returned straw, the structural characteristics and representative enzyme activities of the bacterial community in returned straw, the multifunctionality of the soil from the perspective of biodegradation and the impact of soil multifunctionality. Providing novel insights into the optimization of straw return strategy and fertilization in single-season rice cropping systems in cool regions. My detailed comments provided below：
1. The format of the author 's name is incorrect.
2. Line43: References with more than 2 consecutive references need abbreviations. The correct format is [7,8].
3. Line98: Description of the study site?
4.Line262:hm-2
5. Fig 3 and Fig 8 lacks a description of abcd
6. Figure 5 is not clear.
7. Line547: Where is Reference 66?
8. More than half of the citations are out of date, which are not helpful for identifying the research gaps. A latest review, International Journal of Agricultural & Biological Engineering;2020;Vol.13;No.6;P207-214, is suggested for your reference.
9. The reference needs to be added to the doi at the end.
10. It is also recommended to seek help from a professional to improve the English of the manuscript.
Author Response
Please check the attachment
Author Response File: Author Response.docx
