Phytotoxic Effects of Al on Root Growth Are Confounded in the Presence of Fulvic and Humic Acids
Round 1
Reviewer 1 Report
The manuscript describes the direct effects of fulvic and humic acids which confound the effect of Al toxicity on plant root growth.
The manuscript consists of abstract/keywords, introduction, materials and methods, results, discussion, conclusions, abbreviations, funding, authors' contributions, data availability, conflicts of interest, and references.
The summary is adequate.
The introduction supports the development of the discussions presented in the manuscript.
The materials and methods are suitable and it is possible to reproduce the experiments with the information presented.
The results and discussions are in accordance with the results obtained by the authors.
The conclusions are adequate to the obtained results.
Authors are suggested minor revisions/adaptations in editing the text:
Lines 60, 66 and 95:
((Besho and Bell 1992) (Hue and Amien 1989).;
At these high rates, ....((Chernikov et al. 1991) (Kögel et al. 1988) (Kononova and Alexandrova 1973);
(For example, (Dobbss et al. 2007; Hiradate et al. 2006).
These parts of the text have a lot of parentheses.
Comments for author File: 
Comments.pdf
Author Response
The response to reviewer 1 is in the attached word document.
Author Response File: Author Response.pdf
Reviewer 2 Report
1. A title should be concise and easy to understand. Therefore, the title in the current study should be rewritten.
2. Line 7: please correct the punctuation here. Is it “in acidic soils aluminum (Al) toxicity,” or “in acidic soils, aluminum (Al) toxicity”. The second sentence of background should reduce or delete
3. What was the plant used in the current study? It should have been mentioned firstly in the abstract.
4. The study focused on root growth, but in the abstract, there was no numeric data in this aspect. Moreover, there should have been a conclusion for what treatment performed best.
5. For the introduction, one paragraph for each idea (acidic soils, Al toxicity, organic matter, and FA-HA) is enough. Therefore, this section should be cut off. Moreover, it should have an explanation why leaves of eucalyptus and hay were used instead of other sources and a review about both of them? Format of citations are incorrect. Please add some sentences of microorganism that contribute to reduce Al toxicity. Lines 109-110 should remove
6. In my opinion, the fourth treatment should have been 20 FA and 20 HA instead, in order to keep the equal amount of organic acid applied.
7. When the name has been previously mentioned, it can appear in short, such as E. camaldulensis.
8. The statistical analysis should be separated into a subsection.
9. Line 130. why is “the Nil” here?
10. Some sentences should be shorter, clearer and more concise. Such as in line 162-165, the sentence here should be cut into 2 sentences, and rewritten at some points.
11. Punctuation should be carefully checked. Loads of mistakes in punctuation have been found, leading to lessen the readability of your article. For example, in line 179, there should be a coma right after the phrase “in the E-HA”. There should also be a coma after the phrase “In both the E- FA40HA40 and H-FA40HA40 treatments”.
12. Although relative root lengths have been provided, an absolute root length should be introduced once, such as the maximum or the minimum root length.
13. The discussion needs to be improved. Results should be limited in the discussion. More literatures should be added to compare with your data, to explain the mechanisms between FA, HA, Al, plants, and soils. In addition, please use more recent literatures if possible.
14. Lines 457, it should be “Schnitzer and Skinner (1963)”.
15. The conclusion should be shorter and more concise. The first paragraph of conclusion should delete. Other sentences should reduce the part of explanation
Moderate editing of English language
Author Response
The response to Reviewer 2s comments and suggestions is in the attached word document.
Author Response File: Author Response.pdf
Reviewer 3 Report
Review report of the manuscript “Direct Effects of Fulvic and Humic Acids Confound the Effect of Al toxicity on Plant Root Growth
The research issue undertaken by the Authors is not new but considers new aspects of Al-organic acids interactions in conditions that mimic soil solution.
I have decided to recommend to the Editor to reconsider the manuscript after major revision due to the following reasons:
- the topic of the paper is only related to the effects of studied factors (Al, HA, FA) on plant root growth, while Al-HA, AL-FA interactions are also widely described, therefore I strongly recommend changing the topic or changing the text of the paper;
- I recommend extending the Material and Methods chapter with a brief description of FA and HA isolation from Eucalyptus and Hay extracts. The way of analysis prescription suggests that extracts were only obtained by the extraction of Eucalypthus and Hay with the solution mentioned in the text. It is not true. The FA and HA isolation was much more sophisticated. Following the presented text, the readers will not understand how it was possible to prepare FA and HA solutions at accurate OA concentrations.
- my first methodological question concerns the solubility of HA. As the Authors mentioned in the text, the pH of the tested solution was 4.5. In such conditions, HA will precipitate because it can be only soluble at very high pH values. How did you evaluate the HA interactions with the Al ions? If the HA precipitation was expected it should be clarified to the readers and how it will influence the HA-AL interactions. The second question considers the diameter of the filter paper to prepare the solutions. Usually in the literature 0.45µm filter is recommended for DOC fraction filtration, while in the presented experiment 0.22 µm was applied. Was there a certain reason for such a choice?
- the Results chapter is very long, and too detailed and some repetitions occur. Therefore I suggest shortening it and making it more clear and better related to the manuscript’s topic.
Author Response
The response to Reviewer 3s comments and suggestions is in the attached Word file.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
I agree with authors. Please check errrors after accepted track changes
Minor editing of English language required
Reviewer 3 Report
Corrections implemented in the paper and explanations provided by the authors are sufficient to recommend accepting the article for publication in the Soil System research journal.
