Dear Barthod et al.,
Thank you for your careful consideration and timely response to the reviewer comments on your SOIL Discussion manuscript “Can worms be used to produce amendments with reduced CO2 emissions during co-composting with clay and biochar and after their addition to soil?” I invite you to submit the revised manuscript so that I may review the full manuscript for publication. Overall the reviewers and I found the science sound, this is an opportunity to ensure the paper is clear to the readership of SOIL.

Dear Barthod et al.,
Thank you for your careful revision of the manuscript “The effects of worms, clay and biochar on CO2 emissions during production and soil application of co-composts.” Overall I find the revised manuscript improved. In consultation with the reviewers, I believe there are some additional revisions that could be made to improve the logical flow of the manuscript. Below I have made some suggestions for reorganizing the text to clarify the paper’s message and continuity.

The experimental design includes all the clay and biochar additives to compost, with and without earthworms. The data show that the clay and biochar additives had the greatest effect on the compost properties (Table 1) and CO2 production (Table 2). Adding earthworms generally increased CO2 production, but clay/biochar patterns remained mostly the same (Fig. 4, 5). This builds a story of a primary response to clay and biochar additives and a secondary response to earthworms. However, in the current organization of the manuscript, the earthworm response is presented first and with greatest emphasis. It would strengthen the flow of the paper to emphasize the response of the additives by presenting them first in the hypotheses, results, and discussion.

In the Introduction, it may be helpful to include some information to set-up alternatives to the expected outcomes, especially if worms did not enhance C stabilization, as the data show. Use the Introduction to set-up the message the data presents, layout a road map for the story the data will develop.

In the Discussion, I would suggest organizing by hypothesis, or independent variable, rather than response variable. For example, present a section discussing the addition of clay & biochar, and their effects on compost properties and CO2 production and a section on the effects of earthworms on compost CO2 production. Following the experimental design and retaining the final section dedicated to the response of compost added to soils is fine, but consider reorganizing within the section to maintain the message that clay/biochar enhanced compost produced a consistent response and worm additions produced a secondary increase in C mineralization. This will reinforce the data message and reduce confusion for the reader. I also recommend a reorganization of the Conclusion to reflect my suggestions above.

Dear Barthod et al,
Thank you for your revision of the manuscript “The effects of worms, clay and biochar on CO2 emissions during production and soil application of co-composts.” However, the revisions don’t address the underlying structural changes I suggested. For example, the Discussion is still presented as a list through the response variables (compost properties (4.1), C mineralization (4.2-4.4), C-balance (4.5)). I was looking for a more cohesive structure such as Effects of compost additives (4.1), Effects of worms (4.2), and Effects of co-(vermi) compost production (4.3), which would reflect the revised order of your hypotheses. This requires re-organizing sentences and paragraphs, not necessarily adding new text. In addition, the Introduction does not include any addition introduction of explanations if worms might increase C mineralization (which is what the data show). The logical flow problems reviewer 1 identified I believe primarily stem from the current organizational emphasis on each measurement rather than a synthesis of the responses to articulate overall effects of amendments, worms, and their interaction. The data are there, but the main take-home messages are not coming through clearly. Thank you for your dedication.

Dear Barthod et al,
I appreciate your continued work with this manuscript. I have consulted with the original reviewers and we feel the manuscript continues to lack clarity, as mentioned in the original reviews. Reviewer 1 has graciously offered this second round of comments to specify concerns and offer more concrete ways to improve the manuscript. I would recommend a strong re-working of Discussion to address these concerns, the Discussion continues to read as a list of results with some context and does not present the key take-home messages clearly. As authors you may address these changes as you see fit, but one option might be to restructure the Discussion with new sub-titles that focus on the key take-home messages, rather than the responses measured in the study. As such I am recommending a full revision rather than just a minor revision.

Reviewer 1 comments:
In summary, the data are interesting but they’re not yet presented in a way that a reader can take home a clear message, and sometimes that interferes with actual analysis of the data (see section 4.2.1 discussion below, for example).

Specific comments: 

all discussion section headers need revision to convey an idea instead of state a topic.  For example, headers like 

"4.2.1 Effect of worms on CO2 emissions during composting without additives” 

would be more useful to readers if, instead, it read something like 

“4.2.1 Worms alone did not lead to increased CO2 emissions”

That said, looking at section 4.2.1 it’s still pretty confusing in terms of content.  The first sentence in this section says that data show that worms don’t increase CO2 emissions during compositing, and then the text points the reader to figures 3 and 4.  But neither figure 3 or figure 4 compare composting with and without worms, which is what would be needed to make this point.  To back up this sentence the reader would have to look at figure 3, find the number for the compost-only data point on the y axis, then go to figure 4 and read the compost + worm data point, and decide if those two values are different.  Even doing this, there isn’t any way to compare the error bars because the two figures aren’t on the same graph, and the sentence doesn’t provide any information on whether or not these two values are statistically the same or different.

Section 4.2.2 is titled “effects of worms on carbon mineralization during composting with clay”.  This title needs to instead say something that conveys a conclusion: do worms increase or decrease carbon mineralization?  What is the role of clay in changing this? The section would be more useful to the reader if there were a main idea presented in the header.  

After resolving the header in this section, the text in this section needs revision to convey one idea clearly.  What do the authors want their reader to understand about worms, clay, and composting CO2 emissions?  There’s only one paragraph in this section.  It would help the reader understand the work if this one paragraph conveyed one idea.  What’s the idea here?

sections 4.2.3 and 4.3 need this kind of reassessment too.

Without this reassessment of the discussion section (what are the main points?) the conclusion has trouble conveying ideas clearly.

more comments: 
p. 18 line 434-435:  “Biochar/clay mixture showed synergistic effects.”  What does this mean?

Tables and figures:  There’s not enough text yet in the captions to fully interpret the information here:
Table 1: the abbreviations need definition (M, B, V).
Table 3: All that is said here is “Carbon balance. Data are presented as mean and standard error.”  Does this table show carbon released or carbon retained?  How do these data close a carbon balance - in other words, what is the input carbon?  How is “total carbon mineralized” calculated?

The figure quality also needs further attention.

For example, Figure 3: The font style and size varies throughout.  The complexity of the mesh background does not make the data clearer.  Figure 3 also looks like its aspect ratio has been altered (wider than tall, see shape of data points in the figure).  Figure 3 contains a title within the figure that is not informative (“compost”).  The legend has been cropped by the process of the conversion to pdf.

Dear Berthod et al.,
Thank you for your dedication to improving the manuscript The effects of worms, clay and biochar on CO2 emissions during production and soil application of co-composts submitted to SOIL. I have consulted with the original reviewers and we find this version greatly improved and appropriate for publication within SOIL. Below are a few minor technical errors to correct in the process of final publication. Congratulations!

Minor technical corrections:
move “neither” to “either” at line 227 and line 322.  
line 369 change dioxine to dioxin
line 393 change “evidenced” to “showed” 

Dear Dr Barthod,

Thank you for choosing SOIL, this is a very interesting contribution. Please note the three minor technical corrections suggested by the TE.

Kind regards,

Kristof Van Oost