|Thank you for your careful revisions of the manuscript. I have two main points, followed by line edits for minor revision.|
The hypothesis does not require the analysis of microbial indicators (PLFA) or C composition data (FTIR): “We hypothesized that 170 significant increases in subsoil carbon stocks were associated with the combination of high concentrations of soluble C and nutrients from compost and increased hydraulic transport associated with cover crops.” Please include each of these within the hypotheses, objectives, or research questions, otherwise these methods are not justified to be included in the manuscript. Ideally the hypotheses can link the main metrics (C composition, microbial indicators, hydraulic conductivity, nutrient and C at depth within an interactive mechanism or overarching theory - like cascade theory).
The first half of the discussion needs to integrate paragraphs summarizing the literature (more fit for an introduction) with the paragraphs on the current findings. Specific lines within the discussion are indicated below for these edits.
133 Define SOM - first use in the main text here.
150 - I don’t think you necessarily need the cover crop type listed in the intro, merely when you make direct comparisons within the discussion.
185-193 - Experimental design can be above the hypothesis in the introduction.
190 - You can add climate warming “and subsequent soil C losses” to tie this final sentence into the experiment tightly.
233 - Insert space for “2 m”.
246 - Merely a suggestion - this information could go into a table to improve accessibility, but is fine as is.
273 - Define EOC the first time it is mentioned.
305 - Add “For each sample 6g of soil” so that the sentence does not start with a number.
317 - Again, start with “The” before 2018 carbon and nutrient stocks...
317 - Previously ‘C’ and ‘N’ are used for carbon and nitrogen, stay consistent.
325 - Is there a need to account for microaggregate-sized sand? (Simply by rinsing a subset of the microaggregate sample through the 250 sieve completely and weighing before and after dry mass.)
328 Delete second “PLFA analysis” in the last part of the sentence
330 Subscript on N2
334 Lowercase S on PLFAs
353 Ensure there is a citation for R here too.
373 Stay consistent with “carbon” vs “C” - check throughout
390 The first paragraph of the results section is repeated twice.
420 These graphs look much better! As a suggestion, generally gray-scale is preferred for accessibility and for readers who may print B+W only. I don’t think the treatments (OG, CONV, CONV+WCC require colors).
431 - Typically the alpha level is set prior to the analysis (eg, p = 0.05 or 0.1), this allows for consistent interpretation of the results. Here the ~3Mg ha “increase” is not significant at that level, so it should not be reported as an increase unless the p-value is set to above 0.26. Essentially, there was not high enough power to detect if the observed difference is real.
455 Recommendation: Flip the y axis for Fig. 4 so the soil ‘surface’ 0 cm is at the top of the graph to make it more intuitive.
465 Is that averaged across dates?
Fig 9 a-d is separated by depth rather than date - Is it possible to present the nutrient data in the same way (Fig 6) - by depth rather than date? It seems the nutrient analysis was not repeated measures, but analyzed as an average over time (L 464). To me, it makes more sense for Fig. 6 to also just be an average over the growing season and presented at different depths. The depth patterns are set up as the most important for hypothesis testing in the introduction, and seasonal dynamics were not as important. Alternatively, you could also add an interesting hypothesis about seasonal dynamics.
Fig 7 B - This is Mineral N, not total N. Please correct throughout the manuscript.
573-583 - Delete this paragraph or integrate it within the context of your results, rather than summarizing the literature as if for an introduction.
583 - Fig. 4 is the depth of moisture, not moisture content. If the volumetric moisture content is the important variable, then present that in the text, and put the water depth into supplemental.
656 - SOC vs soil organic carbon - stay consistent
636-649: Cascade theory was introduced already in the introduction, so you can remove those lines here. Also this whole paragraph does not mention findings of this study. Please start the discussion with the present experimental findings and then bring in supporting information from the literature to help create a seamless discussion.
703 From Fig. 7B it looks like ORG subsoils did not have significantly different mineral N, so please explain how it was a ‘higher value in ORG subsoils’. Also, how are you distinguishing higher movement of nutrients at depth from merely lower crop uptake?
730 - Rather than “we attribute” perhaps “we observed/found evidence that the SOC...”
735 Again, I would change the hypothesis to include something about temporal dynamics, or simply aggregate data across the four dates. Can you explicitly link the seasonal data to the objectives of the experiment?
739 - In the response to the review, you stated there were no irrigation events during this study, but here state that nutrient transport depends on irrigation water. Can you please explain the time frame you are referring to here in the discussion?
741 The growing season stoichiometry is more suitable than what? Than off-season stoichiometry? Please reword the sentence.
757 I would shift away from emphasizing microbial activity (in the first half of the sentence) to reflect the factor that changed during this study “This shift in irrigation and decrease in water inputs potentially increased...”
761 This is the first mention of tillage within this experiment. Please list in the methods/experimental design.
764 “In turn, higher transport led to increased C stocks and reduced levels of microbial stress” This was supported by results, but also needs to be part of the hypothesis and objectives of the study to justify the methods used and inclusion of this as a main concluding point.