Short-Term Effect of Different Inputs of Organic Amendments from Olive Oil Industry By-Products on Soil Organic Carbon and Physical Properties

Round 1

Reviewer 1 Report

First of all, this paper is very interesting and could be very helpful to academia and farmers. Here are some of my questions.

Title -> I would avoid saying "some physical properties", either You mention which are they or just generalize with physical properties

Line 24: could this sentence be written more scientifically?

Line 75: I don't see the point of this sentence, since You didn't investigate nematodes In your work, you better focus on the implications of your research

Line 99: how did You determine the quantity to replace nitrogen fertilization, this needs to be mentioned

Could You also provide a graph for climate properties for those two years of investigation?

Table 1: where are the values of Zn and Cu for OMF?

In the statistical analysis, since You had a 2-year experiment, why didn't You perform a 2-way ANOVA, the results would be interesting.

Author Response

Reviewer 1

Comments and Suggestions for Authors

First of all, this paper is very interesting and could be very helpful to academia and farmers. Here are some of my questions.

We thank the reviewer for appreciating our paper.

Title -> I would avoid saying "some physical properties", either You mention which are they or just generalize with physical properties

1. R. Ok, as suggested we modified the title in “Short term effect of different input of organic amendments from olive oil industry by-products on soil organic carbon and physical properties”

 

Line 24: could this sentence be written more scientifically?

R Ok, the sentence has been modified in “CP1 induced the largest increase in soil TOC, TEC and HC content and a significant improvement in aggregate stability; the addition of a large quantity of organic carbon (CP2) did not determine a proportional increase in soil organic matter content”.

 

Line 75: I don't see the point of this sentence, since You didn't investigate nematodes in your work, you better focus on the implications of your research.

1. Ok, the sentence has been deleted.

 

Line 99: how did You determine the quantity to replace nitrogen fertilization, this needs to be mentioned.

1. Ok, it has been added: “The quantity of applied OMW was equal to the maximum allowed by the Italian law (80 m³ ha^-1), while the amount of CP1 and OMF was quantified on the basis of the average annual quantity of nitrogen removed by the olive trees [46]”.

Nevertheless, we preferred to insert this information in the Materials and Methods section rather than in the Introduction.

 

Could You also provide a graph for climate properties for those two years of investigation?

1. We provided this graph in Supplementary materials (figure S1).

Figure S1. Ombrothermic diagrams [76] of the study site showing rainfall (P, mm) and temperatures (T, °C) during the two experimental years.

 

Table 1: where are the values of Zn and Cu for OMF?

1. The Zn and Cu content of the commercial OMF was not determined by the manufacturer.

 

In the statistical analysis, since You had a 2-year experiment, why didn't You perform a 2-way ANOVA, the results would be interesting.

1. 2-way ANOVA can be performed only for TOC and Ist, for all the other parameters we have only the results related to the soil sampling made at the end of the experiment. Anyway, we tried to perform the statistical analysis as you suggested, but the obtained results did not provide different information. (See the table below with the statistical results).

Summary of the effects of Treatment (T) and Year (Y) on TOC measured in September, aggregate stability after 1 minute (Ist1), after 10 minutes (Ist10), and after 100 minutes (Ist100) of shaking and their interaction (two-way ANOVA).

	TOC	Ist1	Ist10	Ist100
Main effects
Treatment	***	***	***	***
Year	***	***	ns	***
Interaction
TxY	ns	*	ns	ns

*P<0.05; ** P<0.01; *** P<0.005; ns, not significant.

Treatment and Year are always significant except for Ist10, where only the Treatment significantly affects the results. Also, in the one-way ANOVA Ist10 results appear quite distinct between the treatments regardless of the year considered. Moreover, in the same analysis, the Year effect is however appreciable for all the other parameters.

For clearness of exposition, we think it is better to adopt the same statistical approach for all the considered soil characteristics, also because the large part of interactions is not significant.

 

Author Response File: Author Response.docx

Reviewer 2 Report

While the manuscript falls within the scope of the journal and the manuscript's theme is very interesting, I believe that it needs some revision.

-There are so many studies like this. What was the novelty of your study?

-Abstract: It would be helpful if you provided some more statistical results in the abstract.

-Key words: It is not acceptable at all to use these key words! Replace them with some more appropriate ones.

-Introduction line 46: What year/years?

-Introduction lines 78-84: These lines are not necessary for the introduction.

-Table 1: Is there any information available on the pH of olive mill wastewater?

- Section 2.2. Soil Sampling and Analyses: Could you provide us with any information about the history of the field selected for sampling?

- Materials and Methods lines 144-145: give appropriate references to this procedure.

- Materials and Methods lines 179-225: Long and wordy! Provide a summary of the physical analysis methodology.

Fair enough.

Author Response

Reviewer 2

Comments and Suggestions for Authors

While the manuscript falls within the scope of the journal and the manuscript's theme is very interesting, I believe that it needs some revisions. There are so many studies like this. What was the novelty of your study?

1. We modified the introduction with the aim of highlighting the novelty aspects of this study:

Although several authors carried out research on the effects of organic amendments derived from olive oil industry by-products on crop productivity [36,37,38] or on soil chemical properties [39], few studies investigated and compared the impact of composted olive oil industry by-products respect to the raw ones on SOC dynamics [35], soil structure characteristics and related hydrological properties. In this regard some authors studied the impact of either olive mill wastewater alone [24,40,41] or of composted OP [33,42,43], and, in the latter case, only on a limited set of soil physical characteristics. To help fill this gap, the effects of raw and composted olive mill residual products on soil organic C and on a wide set of physical properties were tested by a field trial carried out in a hilly, clay loam soil under olive.

 

In conclusion, the novelty aspects of the paper are:

• The study of the effects of composted OP on SOC dynamics and, at the same time, on a set of physical properties (bulk density, aggregate stability, soil macroporosity, penetration resistance and water retention) related to soil structure conditions.
• The comparison between composted and raw olive industry by-products.

 

Despite the greater difficulty in interpreting the results, the choice of carrying out a field trial allows to get more representative and readily usable information compared to that obtainable by lab, mesocosm or pot experiments.

 

-Abstract: It would be helpful if you provided some more statistical results in the abstract.

1. Ok, trying, as much as possible, to keep the journal's required size of around 200 words, we have added more information about the results.

 

-Key words: It is not acceptable at all to use these key words! Replace them with some more appropriate ones.

1. Ok, we modified the list of the keywords.

 

-Introduction line 46: What year/years?

1. Ok, the time range has been indicated.

 

-Introduction lines 78-84: These lines are not necessary for the introduction.

1. Ok, the lines have been partially eliminated; we preferred to keep the sentence “For these reasons, soil structure characterization and evaluation provide useful information about soil health”, as we think this is useful to underline the role of soil structure in providing information on the soil health status.

 

-Table 1: Is there any information available on the pH of olive mill wastewater?

1. Yes, the pH value of the OMW Is reported in Table 1 and it falls in the typical range for this by-product

 

- Section 2.2. Soil Sampling and Analyses: Could you provide us with any information about the history of the field selected for sampling?

1. Ok, it was added.

 

-Materials and Methods lines 144-145: give appropriate references to this procedure.

1. The appropriate reference is Yeomans and Bremner (1988); we have modified the sentence and inserted this reference.

 

- Materials and Methods lines 179-225: Long and wordy! Provide a summary of the physical analysis methodology.

2. Ok, we shortened the 2.2.3. section “Physical analyses”, eliminating some information deemed non-essential; about the method for determining the aggregate stability (turbidimetric technique), however, we believe that it cannot be abbreviated further without jeopardizing the possibility of its possible use by other soil scientists.

 

Comments on the Quality of English Language

Fair enough.

Author Response File: Author Response.docx

Reviewer 3 Report

Dear authors,

The article needs to be rewritten from the ground up. It would be advisable to combine the Results and Discussion sections for an easier understanding of the issue and the obtained results. It doesn't have to be surprising that when you add a higher amount of organic fertilizer, you will measure less TOC in the soil after a certain time. As you mentioned, the results could be affected by different microbial activity in the different treatments. The activity of the edaphon in connection with the delivered organic matter is the key factor that affects the soil properties (in my opinion). You should pay more attention to this in the Discussion. Overall, it is possible to make a good article from your data. However, it is necessary to interpret the data more clearly and professionally.

Comments for author File: Comments.pdf

Author Response

Reviewer 3

Comments and Suggestions for Authors

Dear authors,

The article needs to be rewritten from the ground up.

1. We cannot accept this suggestion, first because the motivation is not sufficiently substantiated; moreover, the manuscript has been reviewed by two other referees who have not expressed such a drastic opinion. However, we have modified the paper according to the suggestions of all three reviewers and to the editor's recommendations.

 

It would be advisable to combine the Results and Discussion sections for an easier understanding of the issue and the obtained results.

1. Following the Journal instructions we have kept the Results and Discussion sections separate, we think that this option improves the clarity of exposition of the manuscript.

 

It doesn't have to be surprising that when you add a higher amount of organic fertilizer, you will measure less TOC in the soil after a certain time. As you mentioned, the results could be affected by different microbial activity in the different treatments. The activity of the edaphon in connection with the delivered organic matter is the key factor that affects the soil properties (in my opinion). You should pay more attention to this in the Discussion.

1. R. In the Discussion section we have tried to explain the obtained results as best as possible, comparing them with those present in the literature and advancing some hypotheses based on the data available to us. We can agree with you that "the activity of edaphon in connection with the delivered organic matter is the key factor that affects the soil properties"; in fact we have referred to this aspect and cited some scientific papers that support this thesis, but not having measured data the best we can do is substantiate this hypothesis through data (e.g., total macroporosity and regular macropores increase) functionally related to soil biological activity.

 

Overall, it is possible to make a good article from your data. However, it is necessary to interpret the data more clearly and professionally.

1. Thank you so much for your comments, we hope that after the revision the manuscript has been improved.

 

Replies to comments in the attached pdf file:

Page 3: In table 1, the information relating to pH measurement has been entered and the meaning of all the abbreviations explained.

Page 4: At the beginning of the 2.2.1 Chemical analyses paragraph, there's a comment in an unknown language. Sorry, we do not understand this comment.

Page 5, row 219: the space after the bracket has been inserted.

Page 9: regarding the comment inserted on page 9 about the opportunity not to insert figures in the discussion, we take the liberty of not agreeing. In many scientific articles published in the most various journals, in the discussion paragraph there are figures that have the precise purpose of facilitating the discussion of the results.

Author Response File: Author Response.docx

Round 2

Reviewer 3 Report

The article has been suitably improved and is ready for publication. Congratulations.