Biochar-Improved Growth and Physiology of Ehretia asperula under Water-Deficit Condition

Round 1

Reviewer 1 Report

Looking for the effective methods for water retention in soil is very topical and important issue in the plant production. It results from the increase of global temperature which causes the increased transpiration and decreasing the amount and uneven distribution of rainfall during vegetation. Showed in the manuscript the method to retention of considerable amount of water available for plants by use of biochar is the interested and badly needed action. Therefore undertaken issue of study is needed and justified although is partly known in cultivation of other plant species. The novelty in these studies is mainly the evaluation of the effect of biochar on Ehretia asperula, because the other issues were mostly a subject of the study in experiments with other plant species.

My comments:

1. In the Abstract is wrote that „ Water stress considerable decreased the growth and photosynthesis efficiency of Ehretia asperula. From the Material and methods results that it was measured only Fv/Fm values. As we know to measure of photosynthesis are used special devices.
2. In which way the biochar doses in the pot experiments were determined? How was counted a dose from t/ha on kg/pot?
3. What mean this value: the surface area of WB was 270.76 m2 g−1?
4. The characteristics of the biochar should be provided, in spite of such information given in the other paper (Rajapaksha et al. [22]).
5. How much water were the plants watered (how was a field water capacity of this soil?). Whether the plants were not watered at all during the drought by period of 10 days –was it possible?
6. In how many repetitions this experiment was established? Why in the experiment was until 240 pots when the first factor were 5 biochar doses and the second – irrigation and lack of irrigation (2 levels of soil moisture) what gives 10 objects.
7. It should be uniform of x axis description (on the fig. 4 is: 0, 5, 10, 15, 20, and on the fig. 5 is: 0 ton of biochar; 5 tons of biochar …. .
8. Figures 2 and 3 are hardly legible. Reading of „Vertical bars represent mean  SD” is impossible, so their posting in manuscript is unnecessary.
9. Obtained results in effect of biochar use seem too optimistic. For instance: using of biochar in a dose 15t/ha caused the increase of Ehretia asperula leaves area by 60% - it is possible? (tab.1.)
10. In Discussion Authors did not make an attempt for explanation some dependencies - why the use of biochar had such positive effect on some measured parameters, but they limited themselves to compare the own results with these obtained by other scientists.
11. Conclusions should be limited because they are too detailed and are the summary description of results. There is also lack of information at which soil moisture conditions the use of biochar gives better effects.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

The article was written based on very valuable research material that is worth publishing. However, the aim of the research needs to be clarified, the research hypothesis needs to be set, and the description of the methodology, as well as the analysis of the results, leaves much to be desired. The methodological information should be supplemented and systematized. The description of the results needs to be deepened, especially the analysis of the factor which was named by the authors as the main one (the amount of biochar) and the importance of the interaction of factors should be better displayed. I strongly insist on this improvement. The data collected is very rich, but it should be presented in such a way that the differences between the objects being compared are visible. The introduction of different letters to indicate statistically different values is a recognized and clear way. 

Some detailed comments are included in the manuscript.

Since I consider the presented material to be of great value, after making the suggested major changes, I would be pleased to recommend the manuscript for publication in Applied Sciences.

Comments for author File: Comments.pdf

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Please find the notes in the attached pdf.

Anyway, in my opinion the manuscript is enteresting althought there is not a lot of novelty. No information about how the Biochar interacts with the soil and the plants roots are reported.

The paragraph 2.2 has to be rewrite in order to be more clear to readers.

Analisys of the soil used ti fill the pots are needed.

Comments for author File: Comments.pdf

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

I would like to inform that Authors improved the manuscript according to my suggestions to a sufficient degree. At the moment I have no comments other than this that results obtained in effect of use of WB have big values in compare to control. For instance at 0 t WB /ha the leaf number is 21,8 and at 15 t WB /ha is 34,0 (tab.3). In opinion of some scientists, the effect of WB use can’t be too large in the first year of research and the better results can be expected in the next years. I am giving this suggestion for editorial consideration.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

The manuscript was improved, however, some important issues were omitted.

I insist that in formulating the objective of the study, all the characteristics that were adopted as measures of the effect of BW on the growth and physiology of Ehretia asperula are listed.

I also suggest that after presenting the objective of the study, the null and alternative hypotheses should be presented. Was it expected that the application of WB would alleviate the negative effects of water stress on plants and this beneficial effect of WB would increase as the WB dose increased?

I have a concern about soil moisture, which is included as a Physiological Attribute in the Materials and Methods chapter. This still needs to be corrected in the manuscript (also properly included in the study objective).

The following paragraph from the Materials and Methods chapter is still unclear: “The percentage of wilted plants under drought stress was recorded from the fifth day to the tenth day of withholding water. The percentage of wilted plants was calculated when 75% of leaves per seedling withered.” Do you mean that a seedling was considered wilted only when 75% of its leaves were withered?

Finally, in my opinion, too little attention was still paid to the analysis of BW doses (the main experimental factor). Only the most favorable variant was indicated, ignoring the fact that in many cases even the lowest dose gave positive effects in relation to the control. I suggest that this issue be further developed in the manuscript.

I hope that the above suggestions will help the authors refine the manuscript before publication.

Author Response

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Reviewer 3 Report

Dear Authors,

the required revisions have been done and now, in my opinion, the manuscript can be published on Applied Sciences.

Author Response

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