Utilization of Inorganic Nanoparticles and Biochar as Additives of Agricultural Waste Composting: Effects of End-Products on Plant Growth, C and Nutrient Stock in Soils from a Mediterranean Region

Round 1

Reviewer 1 Report

This article, which deals with the influence of different combinations of compost on soil properties, nutrient management and Lolium perenne production in greenhouse conditions, is written at a good level. In terms of structure, the article meets all the criteria set out in the guidelines for authors. Despite the fact that enough attention has been paid to this issue in the past, the credibility of this article is increased mainly by the number of observed and evaluated variants with different residues, resp. additives.

Appropriate statistical methods as well as graphical representation were used to present the results. From the citations used in Article (67), it is clear that the authors have studied this issue in detail.

I have only a few formal comments on the article.

There are a few typos in the text that need to be corrected (f.e. line 172; 307; 311; 512). Also in Table 1, the term ammendments is grammatically incorrect.

In the results (3.1 Influence of factors in soil and plant growth), the authors refer to Table 1 when evaluating the results, in which, however, the given values ​​and conclusions do not occur (line 259).

I also believe that the tables should be listed as close as possible to the first link in the text. Therefore, I recommend moving Table 2. and Table 3. respectively, according to this methodology.

Author Response

Comments and Suggestions for Authors

This article, which deals with the influence of different combinations of compost on soil properties, nutrient management and Lolium perenne production in greenhouse conditions, is written at a good level. In terms of structure, the article meets all the criteria set out in the guidelines for authors. Despite the fact that enough attention has been paid to this issue in the past, the credibility of this article is increased mainly by the number of observed and evaluated variants with different residues, resp. additives.

Appropriate statistical methods as well as graphical representation were used to present the results. From the citations used in Article (67), it is clear that the authors have studied this issue in detail.

I have only a few formal comments on the article.

1. There are a few typos in the text that need to be corrected(f.e. line 172; 307; 311; 512). Also in Table 1, the term ammendments is grammatically incorrect.

R: We appreciate your observation. The proposed changes were performed.

2. In the results (3.1 Influence of factors in soil and plant growth), the authors refer to Table 1 when evaluating the results, in which, however, the given values ​​and conclusions do not occur (line 259).

R: Thanks for your valuable suggestion. This section was defined just to explain the results obtained by ANOVA and how every factor contributes to the variance. Changes were done to provide the results in an understandably way.

3. I also believe that the tables should be listed as close as possible to the first link in the text. Therefore, I recommend movingTable 2. and Table 3. respectively, according to this methodology.

R: Thank you again for your suggestion. Tables were moved as you suggested in order to be listed as close possible to the first link in the text. Now you can find the table in lines 343 and 344 below the corresponding section.

Reviewer 2 Report

The manuscript entitled "Utilization of inorganic nanoparticles and biochar as additives of agricultural waste composting: Effects of end-products on plant growth, C and nutrient stock in soils from a Mediterranean region" is a well-crafted manuscript, however before further perusal I suggest working on the below-appended comments and suggestions for the overall improvement of the manuscript--

1. Introduction- No major comment; Minor comment, Line 114- physic, I guess it may be physical

2. Materials and methods – Line no-157 to 158,- it's not clear why authors have used distilled water and for what adjustment. Since none of the experiments were performed with sterile conditions why distilled water is needed. Please provide justification -
3. Line no 163-165- Unclear what authors monitored as physicochemical properties and how it was done, how the greenhouse gases emissions were monitored please include explanations in the section—
4. Line no 175- corresponding to approximately 25 Mg organic carbon per ha to a depth of 5 cm please recheck, I guess there is some error –
5. Authors in section 2.3 wrote compost end products were applied to soil one week before the establishment of plants --- 5 plants were sown in each pot, what was the size of the pot, how much soil was there, 5 plants sown were either thinned or they were retained till the end, nothing is clear from this section—I strongly suggest please rewrite the whole section and make it clearer for the better understanding of the readers---
6. Results –Figure 3- the data is represented per pot or per plant nothing is clear –please work on this—
7. Also include the information in Y-axis regarding the data obtained or represented
8. Discussion – the subsections have the same numbering as 4.1—please check –
9. Conclusions- No comments

Author Response

Comments and Suggestions for Authors

The manuscript entitled "Utilization of inorganic nanoparticles and biochar as additives of agricultural waste composting: Effects of end-products on plant growth, C and nutrient stock in soils from a Mediterranean region" is a well-crafted manuscript, however before further perusal I suggest working on the below-appended comments and suggestions for the overall improvement of the manuscript

1. Introduction- No major comment; Minor comment, Line 114- physic, I guess it may be physical

R: The modification as you suggested was done. Please see line 114.

2. Materials and methods – Line no-157 to 158,- it's not clear why authors have used distilled water and for what adjustment. Since none of the experiments were performed with sterile conditions why distilled water is needed. Please provide justification

R: Thank you for your valuable comment. We agree with you, actually under the experimental conditions (both in composting and greenhouse experiment) it could not be necessary. In a composting experiment as the developed previously, in order to provide the favorable conditions for the microbial community and all the metabolic pathways, the reactors or experimental units were adjusted at 65% which is a value widely described on literature for a regular composting system (justification and details are explained in other manuscript which is in progress). Both experiments were performed under laboratory scale and the initial experimental design for composting considered the inoculation of some microorganisms in order to improve the process and analyze several microbiologic parameters as well. Therefore, initially we used semi sterile conditions, however, as the experiment progress we finally declined with this objective and replicate the experiment for analyzing microbiological parameters in sterile conditions. We modified it in the final proof in order to avoid confusion for the readers, you can see at line 161.

3. Line no 163-165- Unclear what authors monitored as physicochemical properties and how it was done, how the greenhouse gases emissions were monitored please include explanations in the section—

R: As we previously commented, we firstly performed a composting study, and all the related results of this composting characterization and monitoring were included in other independent manuscript. On this composting study, promptly to be submitted, we analyzed several parameters that include Temp, pH, EC, OM%, C/N, water holding capacity, CIC, NH₄/NO₃, and also some microscopic and spectroscopic properties of the organic matter that include molecular structure by NMR among others. Biochar was also characterized. Nevertheless, considering that the mentioned parameters are included in the other independent manuscript, we decided to avoid presenting or given major details related to these parameters in this article. Under the same context, we can mention that we performed the analysis of GHG by the utilization of static closed chambers (Sánchez-Monedero et al., 2010) where the collected gas samples were analyzed by gas chromatography according to the methods described by the authors. In conclusion, we did not show these properties on the present manuscript because the extension of the section and the draft, and also because the results were not analyzed for this article. Therefore, we appreciate your comment, but the results just include some limited details in the text. However, we mentioned the evaluated parameters in the corrected proof (lines 168-169) and we are available if some of these properties are considered and asked to be included in this draft.

4. Line no 175- corresponding to approximately 25 Mg organic carbon per ha to a depth of 5 cm please recheck, I guess there is some error –

R: According to several scientific articles (e.g., Chodwhury et al., 2016) and technical reports (INN, 2004) there are different levels of compost and organic C to be applied into the soils according to the type of soils, conservation and crops. In this sense, for extensive crops and pastures, some of these reports suggest the utilization between 10 to 30 tons or Mg per Ha of C. Therefore, and taking into consideration these values we stablish the dose of compost addition to soil. We appreciate your observation.

5. Authors in section 2.3 wrote compost end products were applied to soil one week before the establishment of plants --- 5 plants were sown in each pot, what was the size of the pot, how much soil was there, 5 plants sown were either thinned or they were retained till the end, nothing is clear from this section—I strongly suggest please rewrite the whole section and make it clearer for the better understanding of the readers---

R: We agree with your observation. New details were included in order to improve the final manuscript where the content of soil, compost and grass seeds are now detailed as well as the volume of pots and design. All the new details are included in the same section in lines from 178 to 184. Thank you for your comment.

6. Results –Figure 3- the data is represented per pot or per plant nothing is clear –please work on this—

R: Thank you for your observation, the values represented on this figure are gram per pot. It was modified and included in the corrected figure (line 380).

7. Also include the information in Y-axis regarding the data obtained or represented

  R: It was also revised; we appreciate your comment. We include some extra description in figure 4 (lines 413 and 414).

8. Discussion – the subsections have the same numbering as 4.1—please check –

    R: It was corrected, thank you for your observation.

9. Conclusions- No comments.

Sánchez-Monedero, M.A., Serramiá, N., Civantos, C.G.O., Fernández-Hernández, A., Roig, A., 2010. Greenhouse gas emissions during composting of two-phase olive mill wastes with different agroindustrial by-products. Chemosphere 81, 18–25.

Chowdhury, S.; Bolan, N.S.; Seshadri, B.; Kunhikrishnan, A.; Wijesekara, H.; Xu, Y.; Yang, J.; Kim, G.H.; Sparks, D.; Rumpel, C. Co-composting solid biowastes with alkaline materials to enhance carbon stabilization and revegetation potential. Environmental Science and Pollution Research 2016, 23, 7099–7110, doi:10.1007/s11356-015-5411-9.

SAG, 2017. Pauta técnica para la aplicación de compost. Programa SIRSD-S. Servicio Agrícola Ganadero, Región de Atacama. Chile.