Understanding the Priming Effect and the Routes and Stocks of C in Incubated Soil with Residue Inputs
Round 1
Reviewer 1 Report
In the manuscript, the priming effect and routes and stocks of C in the soil with residue inputs was studied by an incubation test. The topic is in traditional, but also of general interesting. The research objectives are clear. The manuscript is good organized. As we know that soil humus forms very slowly. The transformation from residues to soil humus need a long time even the decomposition of low-C:N residues is fast in soil. But the results showed that after incubation the final stocks of humin increased (31%) but decreased humic (54%) and fulvic acid (42%). Although there was a positive priming effect and a C stabilization route concentrated from C mic to humic substances with the addition of low-C:N. But the high transformation rates of humin, humic and fulvic acid just after 50-day incubation test are unbelievable. Please explain the reason of these final stocks researched. The decomposition of organic residues might increase the soil organic carbon and nitrogen. But it’s strange that the addition of residues with high and low C:N in the soil increases the stocks of humin and decreases humic and fulvic acid, but the total organic carbon and nitrogen in the soil are not changed after 50-day incubation test. More evidences are needed to support the results and routes of C stocks.Author Response
Reviewer#1: In the manuscript, the priming effect and routes and stocks of C in the soil with residue inputs was studied by an incubation test. The topic is in traditional, but also of general interesting. The research objectives are clear. The manuscript is good organized. As we know that soil humus forms very slowly. The transformation from residues to soil humus need a long time even the decomposition of low-C:N residues is fast in soil. But the results showed that after incubation the final stocks of humin increased (31%) but decreased humic (54%) and fulvic acid (42%). Although there was a positive priming effect and a C stabilization route concentrated from C mic to humic substances with the addition of low-C:N. But the high transformation rates of humin, humic and fulvic acid just after 50-day incubation test are unbelievable. Please explain the reason of these final stocks researched. The decomposition of organic residues might increase the soil organic carbon and nitrogen. But it’s strange that the addition of residues with high and low C:N in the soil increases the stocks of humin and decreases humic and fulvic acid, but the total organic carbon and nitrogen in the soil are not changed after 50-day incubation test. More evidences are needed to support the results and routes of C stocks.
Author: Dear Reviewer, thank you for your comments. The manuscript brings a perspective about the C dynamic in the humic substances. The results of C routes were intense because the study was ran in control conditions with loam soil and adequate conditions of water, oxygen, and temperature. A hypothesis is that the C presents in loam soil presents a low protection and the C routes maybe is higher. We added that information in the Conclusion to our readers. Thank you for the feedback.
Reviewer 2 Report
The review of the paper Understanding the priming effect and routes and stocks of C in 2 the soil with residue inputs.
The changes in the content and the quality of SOM are under high scientific interest due to the need of understanding the processes influencing the C mineralization and sequestration in soils. The paper in the presented form needs thorough revision by the author. I recommend reconsidering the manuscript after major revision.
Some comments
The English language needs correction.
Some sentences are not understandable e.g. Line 18, therefore I strongly suggest an overview of the text.
The most problematic part of the manuscript is the Materials and Methods chapter. It is very hard to understand the scheme of soil collection. Was it collected from fields cultivated with plants listed in the publication or the residues of these plants were added. There is no information whether sugarcane and brachiaria’s resides were added separately or mixed. The author has mentioned that the soils were incubated in the column and in the other part that the pots were weighted to keep a certain level of soil moisture. There is no information whether samples were transported to the laboratory as undisturbed or the soil structure was destroyed throughout mixing and other operations. Explaining these two over-mentioned parts would have a significant influence on results interpretation.
Chapter Results I advise changing the title of table 1. The daily mean suggests that the rate of degradation has been measured. In fact, the results show the mean value as results from the t-Student test. Please, explain what does the Ns symbol means. Figure 1 the Y-axis is not described. Moreover, the presented data are not adequate to the description in the Material and Method chapter. There is no evidence that soil parameters were determined on day 10 but on day 11, so the defined periods differ from one to another.
In figure 4 there is no information on the period in which the balance was quantified.
Author Response
Reviewer#2: The review of the paper Understanding the priming effect and routes and stocks of C in the soil with residue inputs. The changes in the content and the quality of SOM are under high scientific interest due to the need of understanding the processes influencing the C mineralization and sequestration in soils. The paper in the presented form needs thorough revision by the author. I recommend reconsidering the manuscript after major revision.
Author: Dear Reviewer, thank you for your comments. The editions were added in MS, following your suggestions.
Reviewer#2: The English language needs correction. Some sentences are not understandable e.g. Line 18, therefore I strongly suggest an overview of the text.
Author: Dear Reviewer, thank you for your comments. All manuscript was edited to English edition.
Reviewer#2: The most problematic part of the manuscript is the Materials and Methods chapter. It is very hard to understand the scheme of soil collection. Was it collected from fields cultivated with plants listed in the publication or the residues of these plants were added. There is no information whether sugarcane and brachiaria’s resides were added separately or mixed. The author has mentioned that the soils were incubated in the column and in the other part that the pots were weighted to keep a certain level of soil moisture. There is no information whether samples were transported to the laboratory as undisturbed or the soil structure was destroyed throughout mixing and other operations.
Author: Soil and residues were collected from fields cultivated, and residues were incubated separately. All suggestions were added in the M&M. Thank you for the suggestions.
Reviewer#2: Explaining these two over-mentioned parts would have a significant influence on results interpretation. Chapter Results I advise changing the title of table 1. The daily mean suggests that the rate of degradation has been measured. In fact, the results show the mean value as results from the t-Student test. Please, explain what does the Ns symbol means.
Author: Thank you the editions were made.
Reviewer#2: Figure 1 the Y-axis is not described. Moreover, the presented data are not adequate to the description in the Material and Method chapter.
Author: We checked and the Y-axis described the variables. Sorry, we did not understand your suggestions.
Reviewer#2: There is no evidence that soil parameters were determined on day 10 but on day 11, so the defined periods differ from one to another.
Author: Dear Reviewer, the variables were monitored in the 1st, 3rd, 6th, 12th, and 50th day of incubation. We added that information in all Figures with temporal demonstration.
Reviewer#2: In figure 4 there is no information on the period in which the balance was quantified.
Author: The stock was calculated according to the difference of C contents in 50-day and soil initial C (0-day). We added that information in the Figure 4, to elucidate it to our readers. Thank you for the suggestions.
Round 2
Reviewer 1 Report
The manuscript is improved after the revision. It's better to revise the corresponding contents in the Results according to you hypothesis, no just added informations in the figures and table 1.
Author Response
Dear Reviwer, thank you for the comments and suggestions. The manuscript demosntrate the previosly variables in soil and residues to support the results of C fluxes and routes. We would like to keep the results of these previosly variables. A pragraph in the discussion was added commeting our hypothesis. Thank you for all suggestions. Best
Author Response File: 
Author Response.docx
