Decomposition Rate of Organic Residues and Soil Organisms’ Abundance in a Subtropical Pyrus pyrifolia Field

Round 1

Reviewer 1 Report

This work is not new, since it is a topic that has been working on for many years. The authors of the article have important errors of approach, since the importance that they highlight in the title is the rate of decomposition organic C, however, what is most shown in the development of the text is related to the presence and action of the macroorganisms.
Repeatedly mention is made of the Biota of the soil, considering only macro-organisms. Soil biota are micro and macro-organisms plus herbs and plants, which have highly hierarchical action processes, which not only occurs in macro-organisms, of which they make a large list with the different families found. They refer to Forstall, et al, 2020, for example, but these authors clearly indicate that their study population was the soil macroarthropod community and they do not refer to the soil biota, as in this article.

It is required to relate the title with the objectives, statistical analysis and conclusions of the work.

As a formal comment, it seems to me that it is important that the authors write their article in the third person. In addition, it is important that at the beginning of the article they describe the meaning of some acronyms.

Author Response

Reviewer #1: Article aims to assess the effect of mulching, composting and their combination on the dynamics of soil organic matter, plant rootability and the affecting on soil biota. The research was carried out to answer the following questions: can organic residue management affect the rate of decomposition? Is it possible to find differences in the rate of decomposition of organic residues due to the influence of soil organisms? How can the use of organic residues improve the structure of soil biota? The study was conducted in a 16-year P. pyrifolia field in Brazil. The strength of this work is the experimental design: a sufficient number of replicates and the duration of the experiment allow showing significant differences in the factors studied. The use of not only chemical, physical, but also biological indicators (soil biota) in assessing the results of the experiment demonstrates the complexity of the work performed and additionally confirms its results. However, some parts of the work can be significantly improved. It can be seen that a large and very thorough field work has been carried out, but it is not sufficiently transparently described, which may interfere with its reproduction. Therefore, in addition to other wishes listed below for the correction, the authors should focus on a simple and transparent description of the field experiment.

Abstract

line 20: Please provide a transcript of the OR at the first mention

We have adjusted it accordingly. See L20-21.

line 26: Hereinafter check superscript

We have adjusted it accordingly. See L26, and L28.

line 27: At the first mention, it is completely incomprehensible what the "k" and "priming effect" is. Please add explanations to the abstract (maybe in brackets).

Agreed. We have given explanation on L21.

Introduction

line 44-46: "However, field studies considering the effects of the continuous use of organic residues as compost and mulching on organic residues decomposition modulated by the soil biota activity are rare." -This statement must be backed up citing references

Agreed. See L48.

line 50: "Decomposition of organic residues is controlled by their quantity (C-rich) and quality 50 (N-rich) along with soil biota community [10]." - Decomposition of organic matter, as is known, also can be controlled by many other factors, for example: fractional composition of organic matter, temperature, moisture. Therefore, the above statement is not entirely complete, it must be reformulated and show that the quantity and quality of organic matter are not all factors of organic decomposition.

We have revised this statement. See L51-54.

line 65: "However, it remains unclear the role of soil biota community on organic residues decomposition in a 16-year P. pyrifolia field." - Of course, in a particular 16-year-old field, which was considered in the framework of this work, the role of soil biota may be unclear. However, this is too narrow a formulation, which does not explain the choice of this particular object and methods. Why exactly a 16 year old field? and why exactly P. pyrifolia? Why is such a facility important for the tropical region and for Brazil? It is necessary to more smoothly lead the reader to the choice of the object of research. Here's a great article on scientific writing skills.: Mensh B, Kording K (2017) Ten simple rules for structuring papers. PLoS Comput Biol 13(9): e1005619. https://doi.org/10.1371/journal.pcbi.1005619

We have chosen Pyrus pyrifolia because it is one of the fourth most important tree species into the Brazilian fruticulture in which pearl fruits have been shown to be important social-economic impact in the southern Brazil. See L68-70.

line 67, 70, 73, also 79: The use of the hypothesis of soft speech ("may") in the formulation is not correct. The hypothesis could be formulated unambiguously.

We have adjusted accordingly. See L72-78.

Materials and Methods

line 85-87: first sentence should be moved to Introduction; and its very good for improving text on line 65.

Agreed. See L68-70.

line 94: "var. Housui." - check term.

We have checked it. See L90.

line 100: It would be great to compare temperature and precipitation with long-term mean values (usually over a 30-year period) in order to understand the weather context of the study. The term "thermal amplitude" is not entirely clear - is it daily temperature fluctuations from day to night or fluctuations during the month?

We understand the reviewer point-of-view. Of course, it would be great to compare temperature and precipitation with long-term scales. However, it is out of our questions: can organic residue management affect the rate of decomposition? Is it possible to find differences in the rate of decomposition of organic residues due to the influence of soil organisms? How can the use of organic residues improve the structure of soil biota? In a further manuscript, we will consider his/her suggestion. Finally, thermal amplitude was the monthly fluctuations from maximum and minimum temperature.

line 109-110 (figure 2): This figure can be one of the key factors in better understanding experimental design:

1. In the legend of the picture there are a lot of the same designations (black border) - you may not need to repeat them.
2. The marks of the places where the samples were laid should be made brighter, for example, black - now they are poorly visible.
3. Are mesh bags of both sizes buried in the place where each tag is installed? Their number can be shown in the figure in numbers.
4. The part of the figure that shows the borders of Brazil, the region and the city where the research took place now occupies more than half of the figure: this is not the most important information, it can be placed in the box and the key part of the figure (the second line of the figure, the outer two parts on the right are the tree and the field diagram) could be bigger. It is necessary to redo the drawing in such a way that it is clearly visible from it where and in what quantity the samples were located. It is also necessary to indicate how the samples for mulching, control and compost were located relative to each other.
5. line 170: "...was used to sample soil organisms." - in Figure 2, it is necessary to show where the traps were installed, their number is also unclear.

Agreed. We have adjusted all figure 2.

line 119: "...cow manure (1: 2: 1 ratio)." - why were these proportions chosen?

We followed the regional organic farmers’ recommendation.

line 129 (table 1): The error of values is necessary. n = 20 is it for each item of the table separately or in total?

We have added the standard deviation values, and n = 20 is it for each item of the table separately. See L130.

line 138-139: "Available phosphorous was measured by Mehlich-1 and determined using colorimetry. The" - more detailed information about the instrument and the number of replicates is needed to be able to repeat the analysis.

Agreed. See L143-145.

line 144 (table 2): Information on errors and number of replicates is needed. is the content of substances shown per cubic decimeter of original soil or dried soil?

We have added the standard deviation values. The content is showed per cubic decimeter of dried soil passed through a 2-mm size sieve. See L139.

line 154-155: "We placed hundred forty-four litterbags per plot that were distributed in the central portion of each." - that is, 36 on each field? it is necessary to spell it out more clearly

Agreed. We placed hundred forty-four litterbags per plot (sixteen bags around each central plant). See L161-162.

line 159: "...oven-dry weight." - What scales were weighed on and how?

Litterbags were harvested and placed in individual paper bags. In the lab, the organic residues sampled in each litterbag were oven-dried at 60 °C until constant weight for 72 h, and then organic residues samples were weighed. See L165-169.

line 160: "X/X0= e(-kt)." - check the dimension of the quantity: if "k" is years, and "t" is months, then x is expressed in -months/year, which is probably incorrect

Thanks for this important comment. In fact, “t” is years. We have corrected it in the text. See L169.

line 163: "hd = (ln(1-0.5)/ln(e)) x (1/-k)" - ln(e)=1, must be removed, since it is equal to one. Has the model been tested for robustness?

Agreed. We have removed hd and td equation. Yes, we have tested both models for robustness.

line 174: "...neutral detergent and 15 mL of 70% alcohol. " - what kind of detergent?

I have used neutral liquid detergent.

"We did not find any nest in our study plots during the soil biota collection." - there is no need to write about what was not found.

Agreed. We have removed this statement.

line 184: "...(“shapiro.test” function)" - here you can give information about which program the specified functions were used in, for example: "...(“shapiro.test” function; here and below in R 3.4.0, R Core Team 2018)"

We described it accordingly. See L200-201.

Results

line 210: "Mean values (n = 2304) followed..." - for each sample or all together? should be specified for each sample, possibly in a extra table column

All together. Each plot had “n” equal to 144 that it the number of bags per plot.

Discussion

line 363: "...rootability improvement" - this parameter has not been part of the experiment. It is impossible to draw an unambiguous conclusion how it changed under the influence of mulching or compost.

Agreed. We have removed it.

Conclusions

line 407:  "...positive effects on soil organic matter dynamics" - what is the positive effect? acceleration of organic decomposition? it is necessary to use more stringent wording. what is meant by soil organic matter? It is clear from the study that the experiment evaluated the rate of decomposition of organic matter not in the soil, but in compost and mulch, in fields that are processed with compost and mulch. If so, this statement should be expressed explicitly in the description of the experiment, and also not to replace the term "organic matter of soil" with the term "organic matter of compost / mulch".

We have adjusted it accordingly. See L421-423.

It is also necessary to correct the title: "Increased soil organic C decomposition rate and soil biota abundance by organic residues management in a Subtropical Pyrus pyrifolia field" - after all, it is not the decomposition of soil organic matter that is accelerated, but mulch or compost. A name like this might be suitable: "Increased decomposition rate of mulch and compost organic residues management and soil biota abundance in a Subtropical Pyrus pyrifolia field"

Agreed. Thanks for this suggestion. See L 1-4.

Also, please check the term soil biota - in fact, only soil mesofauna was investigated, in particular insects. It is wrong to draw a conclusion about the entire soil biota only on the basis of the results of such a study. Indeed, this term also includes the soil microbiological community, which plays an extremely important role in the rate of decomposition of organic matter.

In fact, we identified both macro- and mesofauna individuals. To avoid misunderstanding, we used organisms instead biota. 

Good luck!

Thank you!

Author Response File: Author Response.docx

Reviewer 2 Report

Article aims to assess the effect of mulching, composting and their combination on the dynamics of soil organic matter, plant rootability and the affecting on soil biota. The research was carried out to answer the following questions: can organic residue management affect the rate of decomposition? Is it possible to find differences in the rate of decomposition of organic residues due to the influence of soil organisms? How can the use of organic residues improve the structure of soil biota? The study was conducted in a 16-year P. pyrifolia field in Brazil. The strength of this work is the experimental design: a sufficient number of replicates and the duration of the experiment allow showing significant differences in the factors studied. The use of not only chemical, physical, but also biological indicators (soil biota) in assessing the results of the experiment demonstrates the complexity of the work performed and additionally confirms its results.

However, some parts of the work can be significantly improved. It can be seen that a large and very thorough field work has been carried out, but it is not sufficiently transparently described, which may interfere with its reproduction. Therefore, in addition to other wishes listed below for the correction, the authors should focus on a simple and transparent description of the field experiment.

Abstract

line 20: Please provide a transcript of the OR at the first mention

line 26: Hereinafter check superscript

line 27: At the first mention, it is completely incomprehensible what the "k" and "priming effect" is. Please add explanations to the abstract (maybe in brackets).

Introduction

line 44-46: "However, field studies considering the effects of the continuous use of organic residues as compost and mulching on organic residues decomposition modulated by the soil biota activity are rare." - This statement must be backed up citing references

line 50: "Decomposition of organic residues is controlled by their quantity (C-rich) and quality 50 (N-rich) along with soil biota community [10]." - Decomposition of organic matter, as is known, also can be controlled by many other factors, for example: fractional composition of organic matter, temperature, moisture. Therefore, the above statement is not entirely complete, it must be reformulated and show that the quantity and quality of organic matter are not all factors of organic decomposition.

line 65: "However, it remains unclear the role of soil biota community on organic residues decomposition in a 16-year P. pyrifolia field." - Of course, in a particular 16-year-old field, which was considered in the framework of this work, the role of soil biota may be unclear. However, this is too narrow a formulation, which does not explain the choice of this particular object and methods. Why exactly a 16 year old field? and why exactly P. pyrifolia? Why is such a facility important for the tropical region and for Brazil? It is necessary to more smoothly lead the reader to the choice of the object of research. Here's a great article on scientific writing skills.: Mensh B, Kording K (2017) Ten simple
rules for structuring papers. PLoS Comput Biol
13(9): e1005619. https://doi.org/10.1371/journal.
pcbi.1005619

line 67, 70, 73, also 79: The use of the hypothesis of soft speech ("may") in the formulation is not correct. The hypothesis could be formulated unambiguously.

Materials and Methods

line 85-87: first sentence should be moved to Introduction; and its very good for improving text on line 65.

line 94: "var. Housui." - check term. 

line 100: It would be great to compare temperature and precipitation with long-term mean values (usually over a 30-year period) in order to understand the weather context of the study.  The term "thermal amplitude" is not entirely clear - is it daily temperature fluctuations from day to night or fluctuations during the month?

line 109-110 (figure 2): This figure can be one of the key factors in better understanding experimental design:

-In the legend of the picture there are a lot of the same designations (black border) - you may not need to repeat them.

-The marks of the places where the samples were laid should be made brighter, for example, black - now they are poorly visible.

-Are mesh bags of both sizes buried in the place where each tag is installed? Their number can be shown in the figure in numbers.

-The part of the figure that shows the borders of Brazil, the region and the city where the research took place now occupies more than half of the figure: this is not the most important information, it can be placed in the box and the key part of the figure (the second line of the figure, the outer two parts on the right are the tree and the field diagram ) could be bigger. It is necessary to redo the drawing in such a way that it is clearly visible from it where and in what quantity the samples were located. It is also necessary to indicate how the samples for mulching, control and compost were located relative to each other.

line 119: "...cow manure (1: 2: 1 ratio)." - why were these proportions chosen?

line 129 (table 1): The error of values is necessary. n = 20 is it for each item of the table separately or in total?

line 138-139: "Available phosphorous was measured by Mehlich-1 and 138 determined using colorimetry. The" - more detailed information about the instrument and the number of replicates is needed to be able to repeat the analysis.

line 144 (table 2): Information on errors and number of replicates is needed. is the content of substances shown per cubic decimeter of original soil or dried soil?

line 154-155: "We placed hundred forty-four litterbags 154 per plot that were distributed in the central portion of each." - that is, 36 on each field? it is necessary to spell it out more clearly

line 159: "...oven-dry weight." - What scales were weighed on and how?

line 160: "X/X0= e(-kt)." - check the dimension of the quantity: if "k" is years, and "t" is months, then x is expressed in -months/year, which is probably incorrect

line 163: "hd = (ln(1-0.5)/ln(e)) x (1/-k)" - ln(e)=1, must be removed, since it is equal to one. Has the model been tested for robustness?

line 170: "...was used to sample soil organisms." - in Figure 2, it is necessary to show where the traps were installed, their number is also unclear.

line 174: "...neutral detergent and 15 mL of 70% alcohol. " - what kind of detergent? 

"We did not find any nest in our study plots during the soil biota collection." - there is no need to write about what was not found.

line 184: "...(“shapiro.test” function)" - here you can give information about which program the specified functions were used in, for example: "...(“shapiro.test” function; here and below in R 3.4.0, R Core Team 2018)"

Results

line 210: "Mean values (n = 2304) followed..." - for each sample or all together? should be specified for each sample, possibly in a extra table column

Discussion

line 363: "...rootability improvement" - this parameter has not been part of the experiment. It is impossible to draw an unambiguous conclusion how it changed under the influence of mulching or compost. 

Conclusions

line 407:  "...positive effects on soil organic matter dynamics" - what is the positive effect? acceleration of organic decomposition? it is necessary to use more stringent wording. what is meant by soil organic matter? It is clear from the study that the experiment evaluated the rate of decomposition of organic matter not in the soil, but in compost and mulch, in fields that are processed with compost and mulch. If so, this statement should be expressed explicitly in the description of the experiment, and also not to replace the term "organic matter of soil" with the term "organic matter of compost / mulch". 

It is also necessary to correct the title: "Increased soil organic C decomposition rate and soil biota abundance by organic residues management in a Subtropical Pyrus pyrifolia field" - after all, it is not the decomposition of soil organic matter that is accelerated, but mulch or compost. A name like this might be suitable: "Increased decomposition rate of mulch and compost organic residues management and soil biota abundance in a Subtropical Pyrus pyrifolia field"

Also, please check the term soil biota - in fact, only soil mesofauna was investigated, in particular insects. It is wrong to draw a conclusion about the entire soil biota only on the basis of the results of such a study. Indeed, this term also includes the soil microbiological community, which plays an extremely important role in the rate of decomposition of organic matter.

Good luck!

Author Response

Reviewer #2:

This work is not new, since it is a topic that has been working on for many years. The authors of the article have important errors of approach, since the importance that they highlight in the title is the rate of decomposition organic C, however, what is most shown in the development of the text is related to the presence and action of the macroorganisms.

We appreciate the reviewer’ comment. Our work is testing real problems that the organic farmers are facing every single day in the Southern Brazil. There is a need to solve a simple question, e.g., Pyrus pyrifolia fields following an organic farming system are responsible to 22% of fruticulture production from Santa Catarina, and in most of the cases they are spending plenty of money buying organic residues (e.g., bovine, swine, and goat manures) to support their own fields. Our work provided to them scientific information based on a robust statistical analysis. To our knowledge, this work is the first field study examining: 1) the effects of organic residues management on decomposition rate of mulch and compost in a Subtropical Pyrus pyrifolia field; and 2) the influence of organic residues on the structure of soil biota. In the first part of our manuscript, we tried to use chemical, and physical traits in assessing the results of the experiment, while in the second part we tried to use biological indicators (soil biota) to demonstrate the complexity of the work performed and additionally confirms our results.

Repeatedly mention is made of the Biota of the soil, considering only macro-organisms. Soil biota are micro and macro-organisms plus herbs and plants, which have highly hierarchical action processes, which not only occurs in macro-organisms, of which they make a large list with the different families found. They refer to Forstall, et al, 2020, for example, but these authors clearly indicate that their study population was the soil macroarthropod community and they do not refer to the soil biota, as in this article.

Agreed. Soil biota comprises a wide range of soil organisms. In our study, we identified both macro- and mesofauna individuals. To avoid misunderstanding, we used the term “organisms” instead “biota” in the whole manuscript. 

It is required to relate the title with the objectives, statistical analysis and conclusions of the work.

We have revised all manuscript following the reviewers’ comments. Now, all text was improved to relate title, aims, statistical analysis, and the conclusions. We tried our best to avoid misunderstandings and to be as clear as possible.

As a formal comment, it seems to me that it is important that the authors write their article in the third person. In addition, it is important that at the beginning of the article they describe the meaning of some acronyms.

We understand his/her point-of-view. We have described all acronyms in the text at their first mention. Thanks.

Round 2

Reviewer 1 Report

I insist that this work is nothing new, since it is a topic that has been worked on for many years.

The summary is clear and they mention that there are no significant differences in some of the treatments, however, this is not observed in the conclusions.

Even though the authors of the article made modifications to the title and in methodology, there is still a lack of information to be able to make a complete analysis, for example, the distribution of bags in the plot is not clear.

The results and discussion are weak, a complete analysis is not carried out.

The stated objectives are questions, not objectives. And the conclusions to these questions do not agree with the results, since for example, in response to question a) can organic waste management (considering the plots) influence the decomposition of waste in a garbage bag trial using different mesh sizes?

The authors point out: The management of organic waste determined decomposition of organic matter, soil, abundance and richness of organisms in an Acrisol in the South of Brazil.

In the results, no significant differences are seen in any of the treatments for the Shannon diversity index - H, nor for the Simpson dominance index - Cn.

There is no relationship between the Shannon diversity index – H with the Richness – S.

the authors point to the following conclusion: “Our finding suggests that organic waste has positive effects on the decomposition rate of mulch and compost (for example, enhancing the acceleration of organic waste decomposition)”, however, this conclusion requires some analysis since there are differences in the decomposition of ORs as a function of time in the different bags. The best results could be in bags with compost in both mesh sizes, but not in Mulching.

It seems to me that the conclusions make assumptions that are not supported by the data obtained.

As a formal comment, I reiterate that I think it is important that the authors write their article in the third person.

According to the difficulties encountered when reading the document and performing an analysis that would allow a relationship between the stated objectives and the conclusions, I recommend requesting to complete the methodology, perform a review of the results, Discussion of results and conclusions.

Author Response

pdf attached. 

Author Response File: Author Response.pdf