Biochar Alone Did Not Increase Microbial Activity in Soils from a Temperate Climate That Had Long-Term Acidity Stress

Reviewer 1 Report

Abstract

Lines 18-19. The sentence is not finished. It is advisable to indicate the time during which the improvement occurred рН.

Introduction

Lines 24-25 Add links confirming the effect of biochar on the stability of aggregates and the preservation of water in the soil. Please specify the phrase «the retention of soil».

Materials and methods

Lines 61. Bring to uniformity: Experimental site ore experimental plots.

Lines 64. It is likely that the experience was laid in 2016. Please specify the start date and end date of the experience here, not below.

Lines 66-67. Specify the type of soil according to the international classification.

Lines 70. Probably this item should be numbered 2.2. I suggest calling it «Lines Soil analysis». If this section refers to 2.1, move the paragraph above the table.

Lines 79. Remove unnecessary spaces in mg / kg.

Lines 94. Specify the source of wood chips. What size of bio-coal fractions did you use? How did you bring the biochar to a depth of 20 cm? After applying biochar, what methods of tillage were used until the moment of soil sampling?

Table 2. Have you used Optical Emission Inductively Coupled Plasma Spectroscopy method to determine the N, C, H, S and O?

If yes, then it is better to give uniform units of measurement in the table for the content of biochar (mg/g) in the sample, and below give hm% for the same elements. If you add up all the indicators, for example, in %, you get more than 100%. Please check the data. Also use a single number of decimal places.

Write how you expected hm%: percent humic mass? How was determined humic mass?

ISO 10390:2005 is applicable to all types of air-dried soil samples, for example pretreated in accordance with ISO 11464. This is for soil not biochar. This standard has been revised by ISO 10390:2021. Why is this method used in the table for the C/N?

Usually, to characterize the quality of the biochar structure, the following ratios are used H/C and O/C. The lower the oxygen and hydrogen content, the stronger the bond of the carbon rings of the biochar, respectively, the lower the ratio values, the higher the quality of the product, which has a direct relationship with the rate of its decomposition (Spokas, K. A. Review of the stability of biochar in soils: predictability of O:C molar ratios // Carbon Manage. – 2010. – Vol.1. –  P. 289-303).

Lines 102-16. Specify exactly that the samples were taken only in 2020.

Lines 126-128. Specify in more detail the dates of measurements of soil respiration. What formula was used to calculate soil respiration? Specify the size of the camera that was used. Also specify the repeatability of the experiment and the soil respiration measurement device. Soil respiration is a dynamic process. You are probably getting discrete points, which is not soil respiration. You measure emissions/fluxes/emissions of gases, but not soil respiration.

It is better to briefly describe all the methods of determination, and not just refer to the authors of the method. The journal is international, sorry, but not everyone uses these techniques.

Results

Lines 150. Correct 3.1 to Table 3.

Lines 151-152. Has the total biomass of rapeseed been determined? Why would such a crop rotation be chosen? Was rapeseed planted as a siderate to improve fertility?

Discussions

Lines 185. Change the item name and numbering 3.2.

Lines 185-189. The arguments given are not related to the discussion in lines 190-193.

Таблица 7. Use one number of decimal places.

Lines 260. Again, paragraph 3.2.

Review the Discussion section. Some parts of the section lose the logic of reasoning, so the discussions are difficult to understand. Please make the section easier to read and understand.

Conclusion

Review the conclusion. You should not repeat the results of the study several times.

Lines 335-337. In conclusion, a reference to the research of other authors is not appropriate.

Lines 339 – 347. It is better to remove this paragraph from the manuscript, since you should not focus on the lack of data. If you have data only for 2020, specify this exactly in the Abstract, Materials and Methods. Do not write that the data is missing. Of course, it is desirable to show the data (soil properties at the beginning of the experiment) so that the manuscript has a comparative characteristic. Also, in the Abstract, agricultural crops that grew in 2017, 2018, 2019 should not be indicated. It is better to say this in the methods.

Links

Lines 414-417. Identical links.

Final comment

From the Abstract of the manuscript, it can be found out that biochar significantly inhibits microbial activity in the soil. Below, the authors indicate the content of substances in biochar that inhibit the activity of microorganisms. A question arises. Why was biochar containing dangerous substances used in the study? From lines 253 – 256, it can be learned that the concentration of these substances is dangerous for the vital activity of mice and rats and probably for humans. Probably, the grown products using such a bio-coal will be dangerous for human health. Does rapeseed contain these substances? It is not clear how such an amount of substance can be contained in wood biomass? The source of the wood used for the production of bio-coal is also unclear.

In general, the manuscript has an interesting scientific result, but the way they are presented should be improved. The Abstract, Materials and Methods, Discussions and Conclusions should be substantially reworked. The Materials and Methods sections of the Discussions should be given special attention. The materials and methods section requires clarification of some conditions for conducting the experiment. The Discussion section should be more clearly and logically stated. In all sections of the text, it is necessary to specify the start time of the experiment, the end time of the experiment, the sampling time.

Author Response

Dear opponent, I have allowed to insert the answers in a separate file.

Best regards,

Dvořáčková Helena

Author Response File: Author Response.pdf

Reviewer 2 Report

The manuscript entitled "Biochar alone did not increase microbial activity in soils from a temperate climate that had long-term acidity stress" is an interesting investigation of filed application of biochars. A limited long term studies are present on this topic therefore this investigation has this novel aspect of application of biochar on acidic soils and its associated factors. The manuscript needs following minor revisions such as

1. the English of the manuscript need comprehensive revision as there are several language and grammatical mistakes issues of spacing between words is present.

2. Abstract is not clearly describing clear cut findings of the study and authors are not able to summerize main finding

3. Introduction : Some paragraphs are too short for example line 38-41 and literature is not up to date therefore author need to add some recent literature relevant to topic, in last paragraph of the introduction use of long sentences make aims of the studies confusing. Avoid this and use short sentences.

4. Material and methods this section is well written but issues of spacing between words is common. Please  check for proper citation of the methods described.

5. Results and discussion section need moderate revision what i see in result section seems to be written in haste and is very short some of the data for example pre and post soil analysis is not mentioned. Comparative analysis of parameter is missing for example table six is not giving any information as i don't see any parameter compared with control. The author must discuss their findings incomparison of statistical controls. What information the readers can extract from table 7 ? is this relevant to study?

Similar is the case of discussion section author must first discuss their own findings and then compare them with literature studies to synchronize the write up and understanding.

Author Response

Dear opponent, I have allowed to insert the answers in a separate file.

Best regards,

Dvořáčková Helena

Author Response File: Author Response.pdf