Assessment of the Agronomic Value of Manure-Based Fertilizers
Round 1
Reviewer 1 Report
All comments are listed in the attached document and article with comments
Comments for author File: Comments.zip
Author Response
Reviewer #1
- It is a very interesting research and a lot of work has been done, it is my respect for the authors of publication, but when reading the introduction to the publication, it is not clear, why it is necessary to mix manures of different composition, It is easier to regulate the N:P ratio by adding only mineral fertilizers. Is it linked to manure management technologies? Are there any manure management cents in Portugal that would be interesting for the practical application of this research? To make the publication better, I would suggest improving the introduction to emphasize the connection to manure management technologies with the possibility of producing manure-based fertilizers and obtaining agriculture-advanced solutions. The publication does not emphasize whether the use of manure mixtures improves their homogenization process, which is very important especially when using poultry manure. The technical solution of these processes is very important, researchers should deepen their research in this direction, maybe it would be a progressive solution both in handling manure in livestock farms, and in crop production with a more homogenized and defined composition of manure.
Response: We agree with the reviewer and we have tried to answer to the questions along the introduction. Alterations to the introduction were conducted to better suit the research and introduce the theme properly to the reader.
- Some notes on the methodological part
A broader description of the manure should be given in the publication, because I would say poultry manure is atypical because it has a rather high percentage of dry matter - about 76%, when it is usually 40-60% and a relatively low concentration of phosphorus. Atypical cattle slurry , where the dry matter concentration is about 15%, when the slurry concentration is about 5%, maybe it should be called liquid manure.
Response: The manures used in the experiments are within the normal composition range found in Portugal and in other methodologies consulted. Still, we recognize that the cattle slurry used in this experiment contained a great amount of straw material increasing the dry matter concentration. We added information relative to the farms of origin to better help the reader to understand the background of the manures.
- The NPK fertilizers used in the study were not characterized, and it is very strange that nitrate nitrogen was not found in their composition.
Response: Initially we did not differentiate the mineral N forms in the mineral fertilizers. However, in the reviewed manuscript it was added information relative to the mineral fertilizers’ composition, as well as, alterations to Table 1. Please see the reviewed manuscript.
- The calculation of available nitrogen according to Portugal's recommendations is debatable because nitrogen mineralization largely depends on the soil and climatic conditions, so what may be correctly determined and suitable for Portugal, I think is less suitable for the northern countries of Europe. Maybe it would be worth taking the ratio of total nitrogen to total phosphorus. Then the obtained data would gain wider applicability, the local climate zone would not be defined.
Response: We agree, that is why we emphasized the fact that it was according to the Portuguese legislation, which considers the fact that not all N will be mineralized only part of the N will be available, it can be adjusted to the crop, the fertilization plan and other factores. We decided to use the mean value for Portugal, since it is the methodology applied. Since this is a country specific feature, we felt the need to have it described in the methodology section more extensively, as we presented in the submitted manuscript.
- By the way, I want to pay attention to whether phosphorus is presented as P2O5 in all the presented calculations, or maybe somewhere as elemental P, let's not forget that it is numerically different by 2.3 times. Please review this before publishing the data, as there may be a serious deviation in the presentation of the experimental data.
Response: We agreed, and that was analysed by the authors carefully, and the information relative to the form P is presented in the material and Methods and is reinforced in the tables and figures legends.
- Manure should be added to the soil at least a month before, and mineral fertilizers a week before. A methodical fertilization mistake was made.
Response: The crop used in this study is a winter crop, oat, and due to our Mediterranean climate, if the manure was applied a month before the sow, the risks of nitrate and phosphorus leaching would be exponential due to the precipitation associated with the winter season in this region.
- The descriptions of the chemical analysis should be supplemented, as the very small values of the standard deviations given raise doubts about the analytical uncertainty and error calculations. In Table 1, part of the data is presented with 3 decimal places and the other part with 2 decimal places. It is understandable, that the analysis of manure cannot be as accurate as that of mineral substances due to its heterogeneity, so it is more realistic to present data in percentages or more rounded numbers.
Response: The manures were stirred before sampling, to decrease the heterogeneity problems, reason why the standard deviations are small. The number of decimals were corrected, please see the reviewed Table 1. We preferred to present the analytical values with less decimal number, instead of percentage, to facilitate the reading.
- The multivariate nature greatly complicates the description of the experiment. The authors' desire to conduct research in three agrochemicals different soils is understandable. Less understandable tis calculation: “ Five lines per pot with 10 seeds each were sowed. After germination, five plants per line were kept (a total of 20 plants per pot.” ?? Maybe 25 plants per pot?
Response: Sorry for the mistake and thank you for correction. The proper number of plants per pot were now provided. Please see the reviewed manuscript.
- In my opinion, the authors did not pay enough attention to the conclusions and generalization of the research result, maybe due to lack of time, but clearer conclusions about the possibilities of mixing different types of manure could be formulated. Does it make sense to mix manure with mineral fertilizers and apply it to the soil with a very short period before sowing (less than a week)?
Response: The conclusions were developed to address the reviewer’s concerns (please, see the revised manuscript with track changes). As referred, the period between application and sowing which was used corresponds to the normal practice in Portugal, due to Mediterranean weather, with all the rain concentrated in the winter.
Author Response File: 
Author Response.docx
Reviewer 2 Report
The manuscript "Assessment of the agronomic value of manure-based fertilizers” assessed the agronomic value of manure-based fertilizers. The content of the article is okay, but it requires some reorganizations that would improve its quality and make it appropriate for readers. Here are some major comments recommended for the authors
1. Please modify the abstract with more significant data. The significance of the study should be mentioned clearly in the abstract section.
2. Provide significant words which are more relevant to the work in logical sequence as ‘keywords’.
3. The introduction does not provide sufficient background and does not include all relevant references. It needs the addition of some recent new research progress in this field. Justify the novelty/originality of the present paper and its difference with other papers published in this field.
4. Line no 80-81; why authors selected pig slurry, cattle slurry, cattle manure and poultry manure, any background information?
5. Provide a better explanation for your data. Avoid only comparing your results to previous studies. Interpret and discuss the meaning of your results more deeply. Discussions need to be supported by the latest references and need to be explained in depth. The authors should highlight the reason of their result findings in the light of available literature.
6. It is strongly recommended to add a subsection, 'practical implications of this study,' outlining the challenges in the current research, future work, and recommendations, before the conclusion.
7. Conclusions are mainly based on suppositions and not on the empirical results or literature evidence. All conclusions must be convincing statements on what was found to be novel, impactful based on strong support of the data/results/discussion.
8. The manuscript contains some typos, stylistic issues, and some grammatical errors. The manuscript should be checked once for any grammatical as well as typological errors like somewhere spaces and comma (,), if not given, which need to be addressed before its final publication.
Author Response
Reviewer #2:
The manuscript "Assessment of the agronomic value of manure-based fertilizers” assessed the agronomic value of manure-based fertilizers. The content of the article is okay, but it requires some reorganizations that would improve its quality and make it appropriate for readers. Here are some major comments recommended for the authors
- Please modify the abstract with more significant data. The significance of the study should be mentioned clearly in the abstract section.
Response: The abstract was rewritten providing more significant data. Please see the “revised manuscript with changes marked”.
- Provide significant words which are more relevant to the work in logical sequence as ‘keywords’.
Response: The keywords were reviewed, please see the new manuscript.
- The introduction does not provide sufficient background and does not include all relevant references. It needs the addition of some recent new research progress in this field. Justify the novelty/originality of the present paper and its difference with other papers published in this field.
Response: We understood and agreed with the reviewer. The introduction was rewritten, please see the reviewed manuscript.
- Line no 80-81; why authors selected pig slurry, cattle slurry, cattle manure and poultry manure, any background information?
Response: These manures were selected according to the Portuguese reality and a previous scooping of manures in Portugal was conducted by the authors in a previous work. This information was added to the manuscript.
- Provide a better explanation for your data. Avoid only comparing your results to previous studies. Interpret and discuss the meaning of your results more deeply. Discussions need to be supported by the latest references and need to be explained in depth. The authors should highlight the reason of their result findings in the light of available literature.
Response: The MBFs analysed in this study were tested in first hand, therefore the literature about the production of bio-based fertilizers is scarce, or they were produced using different technologies, often more technological demanding, which was not our case. We felt the need to compare the results with the few available updated references but keeping them as a base of discussion to the results obtained in this study. Nonetheless, by analysing the discussion, we understood what the reviewer meant and tried to explore more the data obtained in this study. Thank you for your remark.
- It is strongly recommended to add a subsection, 'practical implications of this study,' outlining the challenges in the current research, future work, and recommendations, before the conclusion.
Response: In the original manuscript, we did not feel able to start thinking about the practical implications of applying MBFs. Mainly because some of the implications were not objectively evaluated in this manuscript. However, we have accepted the reviewer’s suggestion, and added the section about 'practical implications of this study'. We believe that it has increased the reader’s comprehension about the thematic of MBFs production and use. Please see this new section on the revised manuscript.
- Conclusions are mainly based on suppositions and not on the empirical results or literature evidence. All conclusions must be convincing statements on what was found to be novel, impactful based on strong support of the data/results/discussion.
Response: By reviewing the conclusion, we understand how we did not have straight forward conclusions. The conclusion was reviewed, please see the “revised manuscript with changes marked”.
- The manuscript contains some typos, stylistic issues, and some grammatical errors. The manuscript should be checked once for any grammatical as well as typological errors like somewhere spaces and comma (,), if not given, which need to be addressed before its final publication.
Response: The manuscript was reviewed by the authors, please see the “revised manuscript with changes marked”.
Round 2
Reviewer 1 Report
I want to draw attention to the remaining smalls mistake in the text, that need to be corrected.
Comments for author File: 
Comments.pdf
Author Response
We thank the reviewer for the new suggestions. We addressed the subjects that still needed to be improved. Please see the new manuscript in the lines 78-80, 196-198, 216-226 and 684, to see the modifications made.
Reviewer 2 Report
The authors addressed all of my queries, therefore the manuscript may be accepted in the present form.
Author Response
Thank you for the last comments, they enriched the manuscript.
