Assessment of Acidic Biochar on the Growth, Physiology and Nutrients Uptake of Maize (Zea mays L.) Seedlings under Salinity Stress

Round 1

Reviewer 1 Report

The article brings new knowledge to science, it is clarity and logical coherence and generally good written. I have some comments that will improve the quality of the manuscript:
lines 68-70: instead of strange looking i. ii. iii. insert 1. 2. and 3.
Table 1. should be just after the 2.1. chapter, below line 84.
Figure 4. and 5: Data on FW and DW should not be presented in one graph as there are different ranges of values. Alternatively, you can combine FW root and FW shoot and analogously DW root and DW shoot. However, in the case of the one-way Anova analysis, the homogeneous groups in this case should be marked with different letters.
Table 3., 4. and 5.: The abbreviations (TN, TP, TK, EC) should be expanded in the table footer

Author Response

Note: The line number mention by editor in the comments are kept same which is according to the manuscript, whereas the line number mention in the response for the corresponding comments line is the new line number of modified version of manuscript.

 

The article brings new knowledge to science, it is clarity and logical coherence and generally good written. I have some comments that will improve the quality of the manuscript:

Comment:
lines 68-70: instead of strange looking i. ii. iii. insert 1. 2. and 3.

Response:

Lines 68-71: We have changed the letters to numbers as suggested.

Comment:
Table 1. should be just after the 2.1. chapter, below line 84.

Response:

Line 84-85: The Table 1 has been moved to the suggested location.

Comment:
Figure 4. and 5: Data on FW and DW should not be presented in one graph as there are different ranges of values. Alternatively, you can combine FW root and FW shoot and analogously DW root and DW shoot. However, in the case of the one-way Anova analysis, the homogeneous groups in this case should be marked with different letters.

Response:

Lines 177-200: We have redrawn the Figure 4 and 5 and we combined root and shoot FW in Figure 4 and analogously root and shoot DW in Figure 5.

Comment:
Table 3., 4. and 5.: The abbreviations (TN, TP, TK, EC) should be expanded in the table footer

Response:

Lines 251-252, 275-276, 297-298, and 308-311: The abbreviations (TN, TP, TK, EC) were now defined in the footer of Table 2, 3, 4, and 5.

 

Author Response File: Author Response.pdf

Reviewer 2 Report

1. The years of the investigations are not indicated.

2. Relationships between different indicators could have been calculated.

3. The conclusions must be more detailed.

4. Unclear sentence „ For root, the highest TN, TP, TK and Na were found under B₀S₁, B₀S₁, B₄₅S₁ and B₀S₁ respectively“ (21-22 lines).

Author Response

Note: The line number mention by editor in the comments are kept same which is according to the manuscript, whereas the line number mention in the response for the corresponding comments line is the new line number of modified version of manuscript.

Comment:

1. The years of the investigations are not indicated.

Response:

Line 96: The year of the experiment is added in the M&M section.

Comment:

2. Relationships between different indicators could have been calculated.

Response:

Lines 143-145 and 300-311: Relationships between plant growth parameters and root and shoot Na content have been calculated and the correlation method was detailed in M&M section.

Comment:

3. The conclusions must be more detailed.

Response:

Lines 433-441: The conclusion has been detailed and we suggested further studies on acidic biochar in alleviating the adverse effects of salinity on maize seedling.

Comment:

4. Unclear sentence „ For root, the highest TN, TP, TK and Na were found under B0S1, B0S1, B45S1 and B0S1 respectively“ (21-22 lines).

Response:

Lines 21-22: the sentence is now revised as follow: The highest concentrations of TN, TP, TK and Na in root were obtained with the treatments B₀S₁, B₀S₁, B₄₅S₁ and B₀S₁ respectively.

 

Author Response File: Author Response.pdf

Reviewer 3 Report

The manuscript assesses the effect of biochar on maize growth and physiology when subjected to salinity stress. Insight into how to cope with salinity stress through biochar may better help in crop management when salinity stress is a problem. Hence, the subject of the paper is interesting, the statistical design and analysis commendable. Unfortunately, many false statements are actually reported in the result section since non-consistent with what show the corresponding Figures and Tables. In addition, the result section focusses a lot on non-significant results, which may overshadow the significant results more interesting for the study.

Please find in the following other general and more specific comments.

General comment

Please, when revising the paper, carefully consider the following:

• In the result section, when a decrease or increase for a given parameter is reported, it is not worth mentioning when the decrease/increase is not statistically significant. At least you may briefly report it if further necessary for the discussion. You may be more focusing on patterns showing significant differences.
• The result section should be carefully worked again, avoid conflicting statement with what show Figures and Tables.
• In the discussion section, many results have been wrongly reported as significantly affected by biochar application. Please revise thoroughly the discussion section by distinguishing significant and non-significant responses. Explain the reasons of the significant response. Non-significant responses may also be discussed based on the literature.

Specific comment

L38. Please omit “to”.

L67. Your hypothesis assumes that saline soils are alkaline. You may add a few lines between soil salinity and alkalinity in the first chapter of the introduction i.e. in L30-44.

L97-98. Please replace 30/25 ºC with 25/30 ºC.

L97-98. Please rephrase.

L 122 This is not actually the leaf area. This is rather an approximation. Worth mentioning it.

L139-142 Please provide additional information about what you are testing i.e. the independent and dependent variables. For the multiple comparisons of means, are you comparing control vs treatments, and also different level of treatment between them?

L146-148 It is not true that biochar affects the overall parameters tested. For example, in Fig. 2 B₃₀S₁ and B₄₅S₁ do not significantly differ with B₀S₁. Also, in Fig 5, there is no difference between B₃₀S₁ and B₀S₁ for root dry/fresh weight. Please check carefully the Figures and rephrase the statement.

L148-149 Here again, number of leaves in Fig. 2 does not show any significant difference between B₃₀S₁ / B₄₅S₁ and the control, Shoot FW and DW do not differ between B₃₀S₁ and the control (Fig. 4), and root FW/DW do not significantly differ between B₄₅S₁ B₃₀S_1.5 B₄₅S_1.5 in one hand and the control in the other hand (Fig 5).

L150-153 What reported in the statement is conflicting with what shown in the corresponding Figures. For example:

• For plant height: Fig 1 clearly shows a higher increase in B₄₅S₅ vs B₄₅S₁ when compared to control.
• A similar pattern (B₄₅S₅ > B₄₅S₁ when compared to control) is also shown for number of leaves, leaf area, shoot/root FW/DW.

Is it a problem of phrasing?

L262 Add in the Fig title or footnote the meaning of TN, TP, and TK since they are not standard abbreviations.

L243-244 But the difference is not significant for TN, TP and Na. I even wonder if it is worth mentioning.

L244 I assume N is for TN. Please be consistent throughout the paper with abbreviations/symbols used for readability purpose.

L250-253 But the effect is not significant, which means no effect at all.

L260-261 However, Na decrease is not significant.

L287-289 What do you mean by statistically. In addition, the statement is not clear.

L299-301 Table 4 rather shows not significant effect of biochar for EC, TK and Na.

Reviewer 4 Report

The manuscript of Sustainability 1112079 from Soothar al., applied acidic biochar and exogenous NaCl on one cultivar of Maize and wanted to answer if application of acidic biochar could alleviate salt stress and promote plant growth. Authors collected a wide range of physiological growth factors and nutrient changes of maize seedlings with and without salinity stress after acidic biochar cotreatment. Although authors found that the use of acidic biochar can reduce the adverse effect of salt in root zone and that the nutrients content in the soil was improved after the addition of acidic biochar, the experimental design was not supportive. I believe this manuscript need further efforts to meet the standard of Sustainability, if authors could address some concerns as listed below.

Major concerns:

1. Salinity stress is not quantitative. Although physico-chemical properties of soil were sown in Table 1, the quantitative amount of NaCl in soil and treatment is not clear. Based on Table 1, the amount of Na in soil could be enough for salinity stress. The experimental aim might be shifted.
2. No quantitative description of how many plants were treated and counted in all of experiments. All data is from one time/year experiment, there is no biological significance.
3. Authors need to show representative pictures of plants holding different properties along with analytical data. It could be more promising.

Major concerns:

1) Line 111: what do Fv and Fm stand for?

2) Figure 2 and 4: The scale mark of y-axis is missing.

2) Line 202: What is 2.40.7%?

3) Line 224: The increasement of chlorophyll content were 36.9 and 4.6%. Is that right?

4) Table 4: Inconsistent font sizes.

Author Response

Note: The line number mention by editor in the comments are kept same which is according to the manuscript, whereas the line number mention in the response for the corresponding comments line is the new line number of modified version of manuscript.

The manuscript of Sustainability 1112079 from Soothar et al., applied acidic biochar and exogenous NaCl on one cultivar of Maize and wanted to answer if application of acidic biochar could alleviate salt stress and promote plant growth. Authors collected a wide range of physiological growth factors and nutrient changes of maize seedlings with and without salinity stress after acidic biochar co-treatment. Although authors found that the use of acidic biochar can reduce the adverse effect of salt in root zone and that the nutrients content in the soil was improved after the addition of acidic biochar, the experimental design was not supportive. I believe this manuscript need further efforts to meet the standard of Sustainability, if authors could address some concerns as listed below.

Major concerns:

Comment:

1. Salinity stress is not quantitative. Although physico-chemical properties of soil were sown in Table 1, the quantitative amount of NaCl in soil and treatment is not clear. Based on Table 1, the amount of Na in soil could be enough for salinity stress. The experimental aim might be shifted.

Response:

Lines 81-85: We have quantified the salinity stress based on the electrical conductivity (EC) value was ~17 dS m^-1 and added in the Table 1. There were mistakes in the units of Na and Cl. The unit is mg kg^-1 instead of g kg^-1. Therefore those values were revised in Table 1 as follow: Na (g kg^-1) = 0.018 and Cl (g kg^-1) = 0.0071.

Comment:

1. No quantitative description of how many plants were treated and counted in all of experiments. All data is from one time/year experiment, there is no biological significance.

Response:

Lines 105-106: A total number of 35 plants was used during the experiment, with 5 plants per treatment and three replicates were use per treatment for statistical analysis as shown in the statistical analysis section. Base on the literatures and our previous similar published works (1. Hamani, A.K.M.; Chen, J.; Soothar, M.K.; Wang, G.; Shen, X.; Gao, Y.; Qiu, R. Application of Exogenous Protectants Mitigates Salt-Induced Na+ Toxicity and Sustains Cotton (Gossypium hirsutum L.) Seedling Growth: Comparison of Glycine Betaine and Salicylic Acid. Plants 2021, 10, 380. https://doi.org/10.3390/plants10020380

 

2. Li, S.; Hamani, A.K.M.; Si, Z.; Liang, Y.; Gao, Y.; Duan, A. Leaf Gas Exchange of Tomato Depends on Abscisic Acid and Jasmonic Acid in Response to Neighboring Plants under Different Soil Nitrogen Regimes. Plants2020, 9, 1674. https://doi.org/10.3390/plants9121674
3. Hamani, A.K.M., Wang, G., Soothar, M.K. et al. Responses of leaf gas exchange attributes, photosynthetic pigments and antioxidant enzymes in NaCl-stressed cotton (Gossypium hirsutum L.) seedlings to exogenous glycine betaine and salicylic acid. BMC Plant Biol 20, 434 (2020). https://doi.org/10.1186/s12870-020-02624-9) we believe that one round experiment in a under controlled environment is enough for trustable results.

Comment:

1. Authors need to show representative pictures of plants holding different properties along with analytical data. It could be more promising.

Response:

Thank you for your suggestion. We tried to add the representative pictures of plants showing different treatment as suggested. But, unfortunately we do not have good quality and stage by stage photos that could respond to your request because the few number of pictures taken during the experiment were taken with mobile phone. It’s noted and we will keep your suggestion in consideration for our future experiments.

Major concerns:

Comment:

1) Line 111: what do Fv and Fm stand for?

Response:

Lines 111-118: Fv is variable fluorescence (the difference between Fm and Fo) and Fm maximal and minimal fluorescence of dark adopted leaves. The maximal photochemical efficiency ofphotosystem II (Fv/Fm) is the most used chlorophyll fluorescence measuring parameter in the world. We calculated it to tests whether or not plant stress affects photosystem II in a dark adapted state. More details were given in M&M section.

Comment:

2) Figure 2 and 4: The scale mark of y-axis is missing.

Response:

Lines 166-167 and 191: The scale mark of y-axis were in Figure 2 and 4

Comment:

2) Line 202: What is 2.40.7%?

Response:

Line 180: The percentage 2.40.7% was a typing mistake it was actually 2.41%. We revised it.

Comment:

3) Line 224: The increasement of chlorophyll content were 36.9 and 4.6%. Is that right?

Response:

We have cross checked and the values of increasement are correct. The exact values of chlorophyll content in those treatments are: B0S1 = 27.67 and B45S1 = 37.87; B0S1.5 = 36.63 and B45S1.5 = 38.33. You can refer to these values for checking.

Comment:

4) Table 4: Inconsistent font sizes.

Response:

Line 295: font sizes revised!

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

The authors carefully revised the manuscript which greatly improved. I’m therefore satisfied with the revision made to the paper.

Reviewer 4 Report

The revised one has some improvement. I am fine with current version except for the author order. I strongly recommend that two correspondence authors go to the last spots.