Integrated Cover Crop and Fertilization Strategies for Sustainable Organic Zucchini Production in Mediterranean Climate

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This manuscript covers the investigation of the combination of different cover crop managements and organic fertilization strategies to optimize sustainable organic zucchini production and improve soil organic carbon (SOC) under Mediterranean conditions.

1. The figures presenting the results do not meet the quality or stylistic standards of a scientific article, both in terms of design and how the information is displayed (e.g., exposed grid lines, etc.). The authors should improve each figure to show greater attention to detail and meet the standards expected by the journal.
2. Still regarding the results, without the tables and figures attached to the excerpt, it is difficult to assess the clarity of visual data presentation and verify whether the letters indicating statistical significance in figures/tables (as mentioned for Table 2 and Figure 2) are correctly applied. The absence of figures, such as Figure 1 showing the C×F interactions, limits full understanding of some results.
3. Honestly, I did not understand why zucchini is only mentioned in the title and at the very end of the introduction—and is not even cited in the abstract. From the abstract onwards, the manuscript could better contextualize the importance of the plant species and the relevance of zucchini research to readers.
4. The abstract is too short in length; the mention of "residual effect of fertilization on SOC showed a smaller reduction in T3 and T4" is somewhat ambiguous without specifying what the reduction is compared to (e.g., compared to T1 and T2, or to SOC levels during fertilization years). This is just one example of how the abstract fails to clarify important points from the manuscript. Specifying the basis of comparison for the “smaller reduction” in SOC under the residual effect, among other details, would help improve the abstract.
5. In the introduction, there is an attempt to establish a conceptual basis for the importance and potential of integrated agroecological practices in the Mediterranean context and under climate change, but the empirical results later in the same article reveal challenges and complexities (such as the lack of significant effect of cover crops on SOC in this study, the dominance of year/climate factor on yield, and the differences in SOC persistence between types of fertilizer), which temper the initial expectations and show that the implementation and results of these practices in the field can be significantly influenced by site- and year-specific factors. However, these aspects are not addressed in depth or with full coherence in the introduction section, and the authors could improve and revise it to better meet the expectations created for readers when approaching the text.
6. Regarding methods, the description of climatic conditions only refers to Figure 1; a brief interpretation of the main climatic differences in the text of the methods section, before the discussion, could be useful. Similarly, Figures S1 (TOC of fertilizers) and 4 (Heavy Metals) are referenced, but a brief description of their content in the methods section would be beneficial before presenting them in the results.
7. I did not understand why Figure S1 is in the main text and not in the supplementary material files.
8. Although some statistical effects are listed, the magnitude of the differences in heavy metal levels for the significant factors (Year for Pb and Ni, Cover Crop for Cr) is not explicitly quantified in the text. Referring to Figure 4 helps to some extent, but quantifying the largest differences in the text would be useful.
9. The discussion could perhaps explore a bit more the significant interaction between Cover Crop and Fertilization for aboveground biomass, since the yield discussion focuses mainly on the main effect of cover crop management. A deeper explanation of how the specific combination of cover management and fertilizer types influenced biomass could also enrich this section.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

This manuscript reports on a two-year field study to evaluate the effect of a cover crop rotation, management of the cover crop, and the use of organic amendments on the soil carbon dynamics and yield of zucchini. The study was overall well conducted, and the results are well presented and discussed in the manuscript.

I suggest that the authors provide additional details on the methodology, to improve the reproducibility of the study, and to better understand some of the results obtained. It is unclear if some of the materials and amendments used are allowed under EU organic certification standards, and this should be clarified.

The authors chose to focus the results, with respect to some variables, only on Year 1, due to a drought and poor crop performance on Year 2. However, it may be helpful to briefly discuss whether any of the treatments (such as the cover crop used as a surface mulch), resulted in any benefits relative to other treatments, such as improved soil moisture conservation, during the year of drought. On year 2, there was considerable rain prior to planting, and it would be interesting to see if any of the treatments were able to better conserve some of this early residual moisture relative to other treatments.

Because zucchini is a short-season crop, it may be relevant for the authors to discuss the pattern and effects of nutrient mineralization from the cover crops and amendments, on such a short-season crop; with respect to the synchronization of rates of nutrient mineralization with the periods of high crop uptake demand. However, as suggested below, it would be helpful to have a good idea of the general fertility of the soil, prior to starting the experiment, to better understand the nutrient dynamics of the system.

Additional comments on the text include,

L 53, Citation for Erana?

L 104, Please indicate what was the original soil pH and fertility of the experimental site, based on soil nutrient analysis, and what would be the fertilizer recommendations based on the soil analysis for zucchini production in this region. Perhaps it would be helpful to include a table indicating the soil nutrient analysis (inc. pH and SOC), before and after experiment completion. Was the soil deficient in any particular nutrients prior to starting the experiment?

L 106, Is there a cultivar name for the cover crop, and source?

L 111, Were the plots arranged in a Completely Randomized Design?

L 117, Please indicate the distance between plots, to prevent amendment contamination between treatments

L 118, Are coal mining wastes allowed for organic farming in Europe?

L 119, Are municipal solid wastes or sewage sludge allowed in organic farming in Europe?

L 118-120, Would it be possible to include a table describing the composition (by weight or percentage) of each of the two organic amendments used in the experiment (municipal waste & composts).

L 120, Is urea allowed for organic farming in Europe?

L 123, Please describe the type of crop residues used (from the cover crop?)

L 125-130, What was the source of fertilizer applied to the CT treatment? Was the same fertilizer applied to all treatments? Please provide a justification as to why fertilizer was supplied as part of the treatments (in addition to the experimental treatments). Perhaps include a table, indicating the amount of fertilizers plus compost/organic/GM materials applied on each treatment along with the estimated amount of nutrients (NPK in Kg/Ha) present in the compost/organic GM materials for each of the treatments. It would help to provide the estimated amount of NPK provided by each of the amendments (mine waste, compost, green manure, and grass clippings) used in the experiment, for each treatment.

L 136, It would help to describe the planting arrangement within each plot. How many rows of zucchini per plot, and was harvest data collected only from the inner rows, to prevent border effects?

L 143, Did you determine the cover crop biomass at termination?

L 181, Please clarify if this was a rainfed experiment or if there was irrigation and if so, describe the irrigation system and schedule. Irrigation is mentioned in the Discussion (L 443), but it is not mentioned elsewhere. If irrigation was indeed used, then you need to reevaluate your discussion on the crop performance during the 2nd year of the experiment (apparently due to low rainfall, re L 409).  If irrigation was NOT used, then please rephrase L 443, to clarify this.

L 187, Were soil samples for nutrient analysis collected both before and after experiment completion? This is mentioned in the Results, but perhaps should be also mentioned in the M&Ms.

L 193, Was the municipal solid waste also tested for potential toxic chemical contamination?

L 511, 532, Double check that references are properly cited.

Minor editorial suggestions are included in the attached copy of the manuscript

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Comments for author File: Comments.pdf

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The authors present an interesting study, and the paper is well written. However, the methodology should be fully supported with appropriate citations, ensuring a strong foundation for the research. Additionally, the repetition of results in both tables and figures should be avoided to enhance clarity and conciseness. I also recommend improving the abstract, results, and discussion sections by incorporating a more comprehensive literature review to provide better context and support for their findings. Hence, I recommend major revisions.

Comments on the Quality of English Language

Can be improved to increase the readability. 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript has been improved an thus I have no more comments.

Reviewer 3 Report

Comments and Suggestions for Authors

No further comments.