Composts from Grapevine and Hazelnut By-Products: A Sustainable Peat Partial Replacement for the Growth of Micropropagated Hazelnut and Raspberry in Containers

Round 1

Reviewer 1 Report

The manuscript horticulturae-2219054 “Composts from grapevine and hazelnut by-products: a sustainable peat partial replacement for the growth of micropropagated hazelnut and raspberry in containers” is an interesting article with some promising results. The investigation showed the performance of two different agricultural residues-based compost, in the design of nursery substrates for the replacement of peat. The article analyzed chemical and microbiological properties of both compost and their effects on yields and other biological responses of raspberry and hazelnut.

The article in general is well organized and showed an interesting experimental design for the trails, however, there are shortcomings that need to be improved for being attractive and clearer for the readers.

Despite the good results, the interpretation can be enhanced to avoid some wrong conclusions, therefore discussion need to be reviewed. Material and methods section and the presentation of the results is little confused, need to include the monitoring of composting process among others and tables and figures need to be modified in text (there are editing mistakes in legends). As I mentioned before, discussion section needs to be complemented avoiding some inconsistent statements and released the correct data of the research and under the described framework and methods.

Therefore, I suggest handling back the manuscript to the authors with major revisions. Some general comments as follow.

Introduction section:

Considering that the article is related to nursery substrates based on the peat replacement and compost is suggested as potential material for the peat replacement, therefore more details of the process of composting and compost should be given in the design of growing media.

In page 2; lines 49-50: Authors should include some aspects related to the process of composting and the mentioned phenolic substances as well as in discussion and the interpretation of results.

In page 2; line 63: Can the authors provide some potential percentages related to lignocellulosic components in the composition of both residues.

In page 2; line 92-95: Even though authors made some characterization as total metal contents, and IG test, I think there is not enough information to evaluate for example heavy metal toxicity which is more related to availability and chemical species. The same with the microbiological aspects, there is more information needed or some extra analyzes included. I suggest modifying the objective according to the results obtained. 

Material and methods section

Despite composting is the main technological approach suggested, the stabilization indexes are barely analyzed by the utilization of C/N ratio. Stability of compost is very important parameter because its implication on C and N dynamics. Authors must present additional information about compost stabilization.

In this section, authors should also include a characterization of feedstock.

In page 3, line 137: Please Include reference.

In page 4, line 150: Authors should briefly explain the process.

Including a table with the suggested treatments would be easy to read.

Please, also the authors should explain why Duncan test was selected as Post-Hoc analysis. Moreover, and according to the results, it is possible to include repeated measures Anova for a better interpretation of results?

Result and discussion section

There are several mistakes on figures, in all legends of raspberry and hazelnut figures authors refer to Compost A, please modify.

Authors must include some data related to the process of composting, as temperature profiles. This information is critical in composting process and can clarify the interpretation in terms of compost stability and microbiological conditions.

Is also hard to interpretate the different figures where time should also be considered as factor.

Figure 3 has the legend after a paragraph, please modify.

Mineralization and MRT of substrate should be also included.

In general terms, discussion need to be improved.

The utilization of digestates where manures were used should include in discussion potential aspects related to this material also, where even some emerging pollutants can also affect the responses in plants.

There are several results that need to be synthetized, and some possible relationships that can be occurring, provide multivariate analyses should be also a good way for improve the interpretation of results. Please consider including it.

Author Response

Answers to REVIEWER 1

R1: Considering that the article is related to nursery substrates based on the peat replacement and compost is suggested as potential material for the peat replacement, therefore more details of the process of composting and compost should be given in the design of growing media.

Authors: We added more information about composting in both the Material and Methods and Results sections. In particular, in section 2.1 Compost preparation and analysis we added a description of compost preparation: “The mass was thoroughly turned to achieve uniformity, then six subsamples were collected in different points and mixed to obtain a 3 kg homogenous sample from each compost. Physico-chemical analysis of the samples, which was then carried out by the external laboratory EST (Bergamo, Italy).”

R1: In page 2; lines 49-50: Authors should include some aspects related to the process of composting and the mentioned phenolic substances as well as in discussion and the interpretation of results.

Authors: Additional information and consideration concerning the presence of phenolic compounds, composting process and results were added to both the Introduction and Discussion sections. 

R1: In page 2; line 63: Can the authors provide some potential percentages related to lignocellulosic components in the composition of both residues. 

Authors: we introduced estimates of the percentage of lignocellulosic components of hazelnut shells and vine pruning to the Introduction section.

R1: In page 2; line 92-95: Even though authors made some characterization as total metal contents, and IG test, I think there is not enough information to evaluate for example heavy metal toxicity which is more related to availability and chemical species. The same with the microbiological aspects, there is more information needed or some extra analyzes included. I suggest modifying the objective according to the results obtained.

Authors: the produced compost showed values of heavy metal that allow its commercialization in the European Community, according to the European Regulation CE 2003/2003. The external lab only detected the parameters to allow the commercialization in the European Community. The temperature recorded during the composting process allowed a complete disinfection of the compost hence no more microbiological analyses were carried out. However  we have modified the objectives at the end of the Introduction section, removing references to the investigation of toxicity and making them more in line with the purposes of the research. We thank the reviewer for this suggestion, and will implement further analysis in our future works.

Material and methods section

R1: Despite composting is the main technological approach suggested, the stabilization indexes are barely analyzed by the utilization of C/N ratio. Stability of compost is very important parameter because its implication on C and N dynamics. Authors must present additional information about compost stabilization. 

Authors: Concerning the composting conditions, we commented on the temperatures of the composting process in section 2.1. Composts preparation and analysis. Regarding the compost stability, we added considerations on the C.E.C. values used as an index of compost maturity followed by the related bibliographic reference to the Results section > 3.1 Compost characteristics.

R1: In this section, authors should also include a characterization of feedstock. 

Authors: Chemical characteristics of each component of the feedstock (maize, triticale, silage, cow slurry, grape stalks and winter pruning wood, shells and skins of toasted nuts) likely vary depending on variety, agronomic practices, seasonality, and will impact the chemical characteristics of the produced compost  accordingly. Nonetheless, the aim of this study was not to analyze the fluctuations in chemical composition of the compost depending on the chemical variability of the input material. As such we considered that a characterization of the feedstock in terms of quantities of individual components and a chemical characterization of the substrate used for the trial would be sufficient for this work, and we did not perform additional chemical characterizations.

R1: In page 3, line 137: Please Include reference.

Authors: Reference 28 was added. 

R1: In page 4, line 150: Authors should briefly explain the process. 

Authors: We added a brief description of the process used for pathogen inoculations and the damping off assessment by Pane et al. (cited as reference 30) to the section 2.3 Microbiological and Suppressiveness Characterizations of Materials and Methods.

R1: Including a table with the suggested treatments would be easy to read.

Authors: A table summarizing the treatments in comparison was inserted to clarify the differences between compost and species in section 2.4 Plant Materials and Nursery Trial of Materials and Methods.

R1: Please, also the authors should explain why Duncan test was selected as Post-Hoc analysis. Moreover, and according to the results, it is possible to include repeated measures Anova for a better interpretation of results?

Authors: The aim of the anova applied in this work is to detect possible negative impacts of the use of compost replacement in the substrate. As such we preferred using a Post-Hoc test with a lower chance to incur in false negative (Type II) errors, and a higher chance to make false positive (Type I) ones, such as Duncan. 

Concerning the repeated anova, this can be used when the entities measured at different times are exactly the same. In the presented trial the physiological indexes were measured on the last completely developed leaf at different dates, meaning on different leaves during the season. Concerning the height of the plants, in order to be able to replace the single plant in case of death, representative plants were sampled at every date from a larger plant population, so that individuals were not necessarily the same at every date. In conclusion, a repeated measure Anova is not applicable to this trial.

Result and discussion section

R1: There are several mistakes on figures, in all legends of raspberry and hazelnut figures authors refer to Compost A, please modify.  

Authors: We corrected the legends, indicating compost A for legends concerning raspberry, and compost B for legends concerning hazelnuts.

R1: Authors must include some data related to the process of composting, as temperature profiles. This information is critical in composting process and can clarify the interpretation in terms of compost stability and microbiological conditions. 

Authors: Composting temperature was recorded through a PT100 thermal sensor (Gandolfi, Parma, Italy). Fifty-five days of thermophilic phase were followed by a further 2-month curing period. 

R1: Is also hard to interpretate the different figures where time should also be considered as factor. Authors: The aim of the figures and anova analysis for all of the considered plant parameters was to identify possible differences depending on treatment at any of the considered growth stages. Conversely, authors did not aim at deriving a temporal analysis which, by adding another factor to the anova model, would also lower its statistical power. The representation with barplots and boxplots were chosen to highlight the differences occurring in single dates.

R1: Figure 3 has the legend after a paragraph, please modify. 

Authors: The caption of figure 3 was mistakenly reported some lines below, within the text. We apologize. Now it is returned to the right position.

R1: Mineralization and MRT of substrate should be also included. 

Authors: We thank you for the right suggestion, but we don't have mineralization analysis and MRT. We will include these analyses in our next experiments.

R1: In general terms, discussion need to be improved. The utilization of digestates where manures were used should include in discussion potential aspects related to this material also, where even some emerging pollutants can also affect the responses in plants. 

Authors: The quality and safety of composts are indeed extremely important. As far as digestates are concerned, currently biogas plants do not accept livestock waste with heavy metals beyond the legal limits as well as emerging pollutants, both because they would produce problems to the anaerobic digestion and because the use of the produced digestates would be impeded. We supplemented the section 3.1 Compost characteristics of the Discussion with a comment on this important issue.

R1: There are several results that need to be synthetized, and some possible relationships that can be occurring, provide multivariate analyses should be also a good way for improve the interpretation of results. Please consider including it.

Authors: We agree that a multivariate analysis may shed some further light on the overall response of the plants to the treatments. Nonetheless, this technique would only be partially applicable to our dataset. Plant responses were acquired in a different number of non-synchronous times depending on the considered parameter. Using a multivariate analysis in these conditions, would imply treating all responses as happening in a single moment. However, plant responses showed to be time dependent and not to occur without distinction across the whole season. In conclusion, we consider the use of a multivariate analysis applied to the whole dataset as not appropriate. Possibly a multivariate analysis focusing on a single date would provide a synthesis for the plant responses measured at that time. In our experiment, the need to measure several variables across multiple dates, treatments and species, imposed an optimization of the experiment via changing the number of replicates, which end up not to be equal, depending on the considered parameter. A multivariate analysis would use, as input, only the replicates for which all variables were measured. This number would be reduced to n = 5 for some variables (e.g. leaf chlorophyll estimation), which we consider too small for a satisfactory application of a multivariate analysis. As a conclusion we will consider including a multivariate analysis in further experiments focusing on fewer dates but with a more even number of replicates.

Author Response File: Author Response.docx

Reviewer 2 Report

The manuscript with the theme Composts from grapevine and hazelnut by-products: a sustainable peat partial replacement for the growth of micropropagated hazelnut and raspberry in containers addresses a topical issue, at least from the perspective of the use of by-products in agriculture.

The composting of wood residues from vineyards and the skin of hazelnuts and the use of organic matter as a partial substitute for peat in nurseries represents a sustainable solution for reducing the consumption of peat and at the same time for the superior utilization of agricultural by-products.

The authors carry out a logical and persistent analysis, based on current bibliographic sources and using appropriate research methods.

The material is well structured, the results and discussions being correctly presented. The conclusions chapter should be developed.

I suggest the authors to present the limitations of the study.

Author Response

Answers to REVIEWER 2

R2: The material is well structured, the results and discussions being correctly presented. The conclusions chapter should be developed.
Authors: The conclusions were integrated with further considerations.

R2: I suggest the authors to present the limitations of the study.
Authors: The limitations of the research were incorporated into the discussion and conclusions

Author Response File: Author Response.docx

Reviewer 3 Report

Dear authors: the manuscript presents relevant data to be used in plant production. However, some improvements should be done. As a general comment, paragraphs should not exceed 4-5 sentences, with no more than four lines each. Avoid one-sentence paragraphs.

Please find specific suggestions in the attached pdf document. Some minor errors are highlighted in yellow.

Best regards

Comments for author File: Comments.pdf

Author Response

Answers to REVIEWER 3  

Comments and suggestions

R3: paragraphs should not exceed 4-5 sentences, with no more than four lines each. Avoid one-sentence paragraphs.

Authors: we appreciate the suggestion and modified the organization of the paragraphs to improve readability. 

Answers to the specific suggestions in the attached pdf document

R3: Line 37 :Italy is included in “worldwide” term.
Authors: the redundant words "in Italy" was deleted.

R3: Line 61 -Unify units: tons are expressed differently.  
Authors: the unit of measurement has been standardized in the text, using 'tons'.

R3: Line 114- Reference of the technique
Authors: Composting was performed following the protocol adopted in previous published experiments; references are now reported.

R3: Line 120 - What was the experimental design? Repetitions?
Authors: We did not replicate these measurements, but extreme attention was paid to the uniformity of the compost, both in the composting phase and in the preparation of the sample, which was analyzed by an accredited laboratory. A more detailed description of the process was added to the text.

R3: Line 131 - References of the technique?
Authors: The method used is reported in reference 27, that is mentioned a few lines above. We also repeated it below. 

R3: Line 136 - References of the technique?
Authors: We added a brief description of the process used for pathogen inoculations and damping off assessment by Pane et al. in the cited references (30).

R3: Line 153 - It is not clear the proportion of compost. Compost A and B were used combined or separately?
Authors: The two composts were used separately: compost A + commercial peat for raspberry; compost B + commercial peat for hazelnut. We changed the description to clarify this difference.

R3: Line 153 - What experimental design did you use?
Authors: The completely randomized design used of this trial is reported some lines below (in line 182)

R3: Line 153 - Please, provide scientific name of the species used, at least at first naming.
Authors: We reported them in the Introduction and at first naming in Material and Methods.

R3: Line 184 - What is the meaning of DOY?
Authors: We added the meaning of the abbreviation DOY in line 184.

R3: Line 196 – I suggest expressing as previously, dates may be confusing, it should be better to indicate them as DOY . 

Authors: We replaced dates with DOY in figures.

R3: Line 209 – Did you check ANOVA assumptions compliments?
Authors: The mean species responses to the different treatments were compared by means of one-way analysis of variance (ANOVA), after confirmation of the homogeneity of variance and normality assumptions, followed by Post-Hoc Duncan test (at p < 0.05) using the R statistical software (R Core Team, 2022).

R3: Line 230 - Please, indicate dispersion values-
Authors: The analyzes were carried out by an external laboratory on a single sample per compost type (they were not repeated). However, they were carried out on a sub-sample taken from a homogeneous composite sample of 3 kg. A detailed description of the procedure was added to the 2.1. Composts preparation and analysis section of Materials and Methods.

R3: Line 233 - What is the meaning of ‘germination for shoots’.
Authors: We changed the sentence, which did not clearly express the results.

R3: Figure 1 - Possibly is better to show as number of days
Authors: We replaced dates by DOY.

R3: Line 264 - You should not repeat information in Tables and Figures
Authors: We could omit the Tables, but the data are reported in the supplementary files. This is not a real repetition, as the tables can be consulted optionally in order to easily view the exact numbers.

R3: Below the line 284 - Is figure 3?   The caption of figure 3 was mistakenly reported some lines below, within the text.
Authors: We apologize. Now it is returned to the right position.

Author Response File: Author Response.docx