A Fertilisation Strategy Combining Mineral Fertiliser and Biosolid Improves Long-Term Yield and Carbon Storage in a Calcareous Soil
, Xavier Portell 1, Rodrigo Antón 1,3, Iñigo Virto 1 and Luis Orcaray 2Round 1
Reviewer 1 Report
The authors have presented a potential use of biosolids produced from sewage treatment plants. sewage sludge do contain organic material, if properly used can be beneficial. However, in this case the observation of biosolid application is not supported well. Mainly, how did they remove the contaminants form the sludge, how long did the biosolid application was carried out in the 18 years period. what are the changes observed (except for the considered research time 2018). The comprehensive comparison of these components would firmly establish the observed results. But that is not the case here. So, I suggest a Major review.
Author Response
Dear Reviewer;
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
In this study, the author compared the combined fertilization(CF) technology of mineral nitrogen (Nmin) and biosolid (BS) from urban wastewater treatment plants to the soil. On the one hand, this technology can reduce the environmental damage caused by the excessive use of mineral nitrogen; On the other hand, factory waste can be handled properly, which favors the circular economy. Therefore, this combined fertilization technology is essential for sustainable agricultural development. The author also explored the response in soil total nitrogen and organic carbon content of different CF treatments and reasonably explained the impact of grain yield. The results are important references for soil ecologists and agronomists to understand further the underlying mechanism of CF. Overall, the experiment is well-designed, and the manuscript is composed correctly. I have several opinions as follows.
(1) In the preface, NFU should have a clear explanation, such as the conversion of NFU to Mg N ha-1. Recommended implanted crop 180 NFU should be converted into Mg N ha-1 representation (line158).
(2) The calculation of C:N, but the corresponding graphs of C:N for each treatment are not visible in the Results. In Figures 1, 2, and 3, the abscissa should be NFU Nmin, which can easily be mistaken for total NFU. Figure 3 is unlabeled letter.
(3) There is a typo in New Territories South Region; it should be TNS (line 288). There are two misspellings of UFN, which should be NFU (lines 247, 275). There is a typo in FC, it should be CF (lines 310, 450, 461). Three misspelled COS should be SOC (lines 314, 315, 411).
Author Response
Dear Reviewer;
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
The authors presented a research article on: IN SEARCH OF SUSTAINABLE AGRICULTURE. PARTIAL SUBSTITUTION OF CHEMICAL FERTILISERS BY BIO-SOLID TO OBTAIN SIMULTANEOUSLY MAXIMUM YIELDS AND ORGANIC CARBON STORAGE IN A CALCAREOUS AGRICULTURAL SOIL.
The topic could be useful as it presents the long-term effect of soil amendments. However, too many inconsistencies persist across the manuscript.
The topic is unnecessarily long and abnormal for a research topic, and not recommended. The title should be informative and brief as much as possible. It could simply read: “Partial substitution of chemical fertilizer with biosolids improves long-term yield and carbon storage in a calcareous soil”.
The treatments used are quite confusing. The treatment does not show a partial substitution. Rather, it shows mineral fertilizers and their combinations with BS at the same fertilizer rate. The scope of the study needs to be redesigned.
Generally, the results were poorly presented, comparisons should be between the treatments and with/without biosolids. Interactions were reported but not presented anywhere in the manuscript or the supplementary material.
Some results are contradictory. Why will there be a significant increase in grain yield and at the same time, a significantly low NUE? What is the initial N content of the soil and how can it influence NUE? Besides, no results on the availability of N were highlighted after soil amendment. This is important to explain NUE rather than tying it to SOC, which requires several parameters before it can be proven.
Particularly, CF and FC were used perhaps to refer to the same treatment (I am not sure about that). There is a need for consistency and clarity.
Also, too many references are used. References for this type of paper should not go beyond 100 (which is even too much). Too many citations do not necessarily add value to the work. The source of the citation and how they are systematically used in the relevant positions are more important. The introduction alone has over 100 citations. I think there is a need to cut down on excessive citations in this manuscript
The entire manuscript needs to be revisited and unnecessary explanations in the methods be removed to give clarity.
Additional comments:
The abstract is too shallow as regards the observations. There should be some reports on the proportion of changes observed. The statement presented as results are too general and cannot give any specific information or highlight the results obtained. Some presentation as found in the conclusion the regards to the proportion of changes observed should be highlighted in the abstract.
Line 22: applied every 3 years for 18 years while lines 121-122 state: …..observe the efficacy of the combined fertilization in obtaining maximum yields three years since the application of the BS.
Be consistent with the time reported. There is a very big difference in these periods reported.
Line 25-27: the statement in the first and second sentences looks contradictory.
Line 171: From the combination of both factors, 9 treatments were obtained plus the control,….what are the treatments? If Table 2 represents the treatments, then make reference to it in this section
Line 186: wastewaters have a high concentration of heavy metals which are also a source of environmental concern when they are applied to the soil even as biosolids (after treatment). It will be better to report the heavy metals composition of the applied BS.
Line 207: write the full meaning of all abbreviations used in the table as a footnote
Line 221: write 13.5m2 correctly
Line 224: write Mg ha-1 correctly
Line 233: use lower case for Carbon and Nitrogen at the beginning of the word
Line 255-256, 263-264: where is the result of the interaction?
Line 268: you can add additional information as a footnote of the figure. Eg, what the error bars stand for, number of replicates, p level, etc. do the same for all other figures where applicable
Line 272-273, 278-279: where is the result of the interaction?
Line 283: write the figure caption in sentence case.
Line 285: what do you mean by Total Nitrogen Soil?
Line 288: what does NTS stand for?
Line 287-288, 292: where is the result of the interaction?
Line 299-305: something must be wrong with the results or analysis. If ANCOVA showed an increase in NUE, why give an alternative explanation different from the observation? Besides, the efficient utilization of N at its time of need best explains NUE, contrary to your explanations. This must be revisited.
Line 337: There was no reference to NUE in the results section. Besides, how the NUE was calculated must be provided
Line 404: low SOC can also result from excessive CO2 emission from BS amendment. GHG emission has been a significant drawback to the use of BS in soils. The addition or removal of straw should not be the major reason since other treatments having the same management had an increase. Besides, there was a notable increase in SOC as shown in Fig 3. Where did the observation of a decreased SOC come from?
Conclusion:
Lines 455-460: the proportions given here are more or less imaginary. They were not presented anywhere in the manuscript. These should be part of the results and discussed accordingly.
Line 461: CF and FC are used. These are confusing. Too many abbreviations are used indiscriminately
Author Response
Dear Reviewer;
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The manuscript is revised sufficiently.
Author Response
Dear reviewer;
Please see the attachment
Author Response File: Author Response.pdf
Reviewer 3 Report
The author did a good job in addressing the comments raised, which has significantly improved the manuscript. However, these few minor comments should be addressed to further enhance it before publication.
For the interactions reported in your results, it will be ideal to at least show the statistics, in this case, the ANOVA table in your supplementary material. It helps to give a better evaluation for interested readers.
The subsections headings should be uniform: either italicized or normal fonts (check subsections 2.1-2.5, 3.1-3.4 and 4.1 etc)
Line 204: the R software version can be included.
Author Response
Dear reviewer;
Please see the attachment.
Author Response File: Author Response.pdf
