Residual Effect of Bentonite-Humic Acid Amendment on Soil Health and Crop Performance 4–5 Years after Initial Application in a Dryland Ecosystem
, Yangmei Bao 1,†, Baoluo Ma 2, Neil B. McLaughlin 2, Ming Li 1 and Jinghui Liu 3,*Round 1
Reviewer 1 Report
The manuscript ,,Residual effect of bentonite-humic acid amendment on soil health and crop performance 4-5 years after initial application in a dryland ecosystem,, solves an interesting topic. However, the manuscript needs to be improved.
I have the following comments, questions and comments.
The language of the manuscript should be improved.
The abstract should be factual, but should include background, results and conclusions.
Line 39: How much montmorillonite should bentonite contain to be satisfactory?
Line 41: This could be useful and mentioned here. https://www.mdpi.com/1996-1944/15/3/1083
Line 51: What form is considered, calcium or sodium form of bentonite?
Line 90: What percentage of clay should it be?
Line 115: Did you manage to achieve all the set goals?
Line 124: GPS coordinates should be performed better.
Line 182: Improve the notation of equations with explanations throughout the manuscript.
Line 186: Indicate the purity of all chemicals used in the experiments.
Line 230: The manuscript contains a large number of abbreviations, so a list of the most important ones should be given at the beginning of the manuscript so that the manuscript can be better oriented.
Line 249: Figure 1 should be improved and also added additional numbers on the y-axis to better identify the values of the curves.
Line 258: List all standard deviations in Table 1.
Line 269 and 299: The same as case 249.
Line 436: Please, indicate the possible risks of such research. Add your recommendations for future research.
Line 471: Make sure the references are added correctly according to the journal's instructions.
Author Response
Reviewer 1, Agronomy Dear reviewer, Re: Agronomy Manuscript 1635535 Title: Residual effect of bentonite-humic acid amendment on soil health and crop performance 4-5 years after initial application in a dryland ecosystem Authors: Bin Ma, Yangmei Bao, Bao-Luo Ma, Neil B. McLaughlin, Ming Li, Jinghui Liu. Date: March 25, 2022
Please see our revised manuscript on Bentonite-Humic Acid (BHA) soil amendment as detailed above. We would like to thank you very much for the meticulous and constructive comments in improving the quality of our manuscript. We have taken into consideration all the comments and suggestions and have made extensive changes to the text and provided explanations in our following item-by-item responses to the comments. The modified phrases and text in the revised manuscript are in red font color.
We hope the changes made to the manuscript and the explanations in the response letter are adequate and clear, and that this manuscript will now be acceptable for publication in Agronomy. We will remain fully cooperative with regard to any further comments and suggestions you may have. Thanks again.
Sincerely yours,
Dr. Bin Ma and Jinghui Liu, Corresponding author
Professor of Agronomy
Below are our point-by-point responses to the editor's and referees' comments: The reviewer and editor’s comments are given in blue font, our responses in black font, and any sections pasted from the revision are given in black italics font.
Referees' Comments to Author:
Reviewer #1:
Comment 1: The manuscript ,,Residual effect of bentonite-humic acid amendment on soil health and crop performance 4-5 years after initial application in a dryland ecosystem,, solves an interesting topic. However, the manuscript needs to be improved.
Response 1: Thanks for your encouraging comments and compliments.
Comment 2: The language of the manuscript should be improved.
Response 2: Good suggestion. Dr. McLaughlin is a native English speaking scientist, and he has reviewed the manuscript for proper English usage an grammar, and made appropriate revisions.
Comment 3: The abstract should be factual, but should include background, results and conclusions.
Response 3: Good suggestion. We revised the ABSTRACT section as follows:
Lines14-32: Degraded soils (including salinized, eroded and low organic matter) resulting from natural and human affects are universal in arid and semi-arid regions all over the world. Bentonite and humic acid (BHA) are increasingly being tested to remediate these degraded lands with potential bene-fits on crop production and soil health. A field study was conducted to quantify the effects of BHA application at six rates (0, 6, 12, 18, 24 and 30 Mg ha−1) on (i) dynamic changes in soil properties, and (ii) oat crop productivity parameters, in a dryland farming ecosystem. The specific objective of this paper was to determine the residual effects four to five years after a one-time BHA application on soil health and crop performance. The findings demonstrated that with the increasing rates of one-time BHA application, soil profile water storage displayed a piecewise linear plus plateau increase, whereas soil electrical conductivity, pH and bulk density were all reduced significantly (P < 0.05) in the 0-20 cm and 20-60 cm layers. The improved soil environments gave rise to an increased activity of soil enzymes urease, invertase and catalase that respectively reached the peak values of 97%, 37% and 32% of the control at the rates of 18 to 24 Mg BHA ha-1. In turn, these boosted soil nutrient turnover, leading to a 40% higher soil available P. Compared with the control treatment, application of BHA at the estimated optimum rate (roughly 24 Mg ha-1) increased grain yield by 20%, protein yield by 62%, water use efficiency by 41%, and partial factor productivity of N by 20%. Results of this study indicated for the first time that a one-time BHA application would be a new and effective strategy to combat land degradation, drought, and promote a sustainable soil micro-ecological environment in dryland agroecosystem under a varying climate scenario.
Comment 4: Line 39: How much montmorillonite should bentonite contain to be satisfactory?
Response 4: The main mineral component of bentonite is montmorillonite, with a content of 85-90%; this figure was mentioned in line 95 of the revision. We did not address the question of the minimum montmorillonite content to be satisfactory. However, given that montmorillonite is the ‘active ingredient’, it would seem reasonable to expect that a bentonite from a different source with lower (or higher) montmorillonite content could achieve the same effect at a higher (or lower) bulk application rate so that the same rate of montmorillonite was applied. This bulk rate could easily be calculated by multiplying our application rate by the ratio of the montmorillonite content of the two bentonite sources.
Line49: Bentonite, an aluminum phyllosilicate clay consisting 85-90% of montmorillonite, can be used as a natural and non-toxic water absorbing soil amendment [3].
Comment 4: Line 41: This could be useful and mentioned here. https://www.mdpi.com/1996-1944/15/3/1083
Response 4: Good suggestion. We have now cited this as an additional reference.
Lines50-54: Bentonite has been widely used as a lubricant in drilling mud and boreholes, as an agent for stabilization of soil structure in construction sites [4,5], for improvement of soil rheological or sealing properties in geo-environmental applications, and for absorption and fixation of heavy metals in waste water treatment [6].
Reference:
[5] Wang, Q., Slaný, M., Gu, X., et al. Lubricity and rheological properties of highly dispersed graphite in clay-water-based drilling fluids[J]. Materials, 2022, 15:1083.
Comment 5: Line 51: What form is considered, calcium or sodium form of bentonite?
Response 5: Sodium. This was specified in the revision as suggested.
Lines64-67: Application of a combination the sodium form of bentonite with humic acid (BHA) has been evaluated as a new water saving and ecological restoration strategy on soils with low clay and organic matter in the arid and semi-arid region of northern China [7].
Comment 6: Line 90: What percentage of clay should it be?
Response 6: It contains 59%-60% clay. In the revision, we reworded this section and so the percentage clay does not fit.
Comment 7: Line 115: Did you manage to achieve all the set goals?
Response 7: Yes, all of the goals were achieved, we quantified the effect of all BHA on all of the soil and crop parameters listed in the objectives. The improvements measured four to five years after the initial application were linear with the BHA application rates, and many, but not all, response parameters reached a plateau or saturation point at approximately 24 Mg ha-1. Obviously, more work needs to be done. In particular, the 24 Mg ha-1 appears to be optimum for some parameters, but for other parameters, a plateau or saturation rate was not evident even at 30 Mg ha-1 implying that the optimum rate had not yet been reached.
Comment 8: Line 124: GPS coordinates should be performed better.
Response 8: Revised as suggested. GPS coordinates were 111.7° E longitude, 39.5° N latitude (Line135).
Comment 9: Line 182: Improve the notation of equations with explanations throughout the manuscript.
Response 9: Revised as suggested.
Comment 10: Line 186: Indicate the purity of all chemicals used in the experiments.
Response 10: Revised as suggested. Lines205-207: All of the reagent chemicals had a purity≥99% and were purchased from Tang-Shan SanYou Co., Ltd., Hebei, China.
Comment 11: Line 230: The manuscript contains a large number of abbreviations, so a list of the most important ones should be given at the beginning of the manuscript so that the manuscript can be better oriented.
Response 11: Revised as suggested, we added a sentence to give the abbreviations at the beginning of the manuscript.
Lines35-40: Abbreviations: Soil water storage (SWS); Soil water content (SWC); Soil bulk density (SBD); Soil electrical conductivity (SEC); Soil available phosphorus (AP); Soil alkaline nitrogen (AN); Soil available potassium (AK); Soil organic matter (SOM); Zadoks’ scale Growth Stage (GS); Grain protein (GP); Evapotranspiration (ET); Water use efficiency (WUE); Partial factor productivity of nitrogen (PFPN); Total grain protein yield (TGP); Grain yield (GY); Biomass yield (BY).
Comment 12: Line 249: Figure 1 should be improved and also added additional numbers on the y-axis to better identify the values of the curves.
Response 12: Thanks for the comment. We disagree that more numbers on the y-axis should be used. Many authors use too many numbers on the axes which adds clutter and necessitates too small font size to be legible. We think the optimum number for the y-axis is five with an acceptable range of four to six, or at the very most, seven. For the scale of the dependent variable, four numbers were the logical choice to utilize the 1, 2, 5 or 10 intervals. With this scaling, it is easy to interpolate between the numbers to determine intermediate values on the axis. We did rescale the last panel (catalase) from the original three numbers to the present six numbers; this should help in determining the numerical values of the traces.
Comment 13: Line 258: List all standard deviations in Table 1.
Response 13: Revised as suggested.
Comment 14: Line 269 and 299: The same as case 249.
Response 14: Thanks for the comment. The same captions were used for all three figures with appropriate adjustments for the different dependent variables as suggested.
Comment 15: Line 436: Please, indicate the possible risks of such research. Add your recommendations for future research.
Response 15: Thanks for the comment. We have added the possible risks of such research and our recommendations for future research in the Discussion and Conclusions sections. The corresponding revision is given as follows:
Lines436-439. However, it has been noted that too much BHA would likely be detrimental as demonstrated in an earlier study [49], where failure of plant growth was found with large amounts of bentonite application in mining areas.
Lines477-484. Our study implies that one-time BHA application may serve as a new sustainable strategy to improve soil health and crop productivity in arid and semi-arid regions. However, it should be pointed out that a successful strategy for drought abatement in one crop, soil and site-specific agroecosystem may have little effect in other soils and ecosystems; this aspect needs further study. Further research at higher application rates is also required to better define the optimum application rate, to measure the degrada-tion and long-term stability of the BHA amendment, and to determine the economics under variable weather conditions.
Comment 16: Line 471: Make sure the references are added correctly according to the journal's instructions.
Response 16: Revised as suggested for all reference citations.
Reviewer 2 Report
The manuscript is devoted to the assessment of the introduction of humic-bentonite mixture in a long-term field experiment on a wide range of soil indicators reflecting soil fertility. In addition, an assessment of the effect of this mixture on the yield and quality of oat products was carried out. The manuscript corresponds to the profile of the journal and will be of interest to a wide range of readers. The absolute advantages of the work are not only a well-staged experiment, but also competent processing of the results and their in-depth discussion.
Author Response
Response to Reviewer 2 Comments
Comment 1: The manuscript is devoted to the assessment of the introduction of humic-bentonite mixture in a long-term field experiment on a wide range of soil indicators reflecting soil fertility. In addition, an assessment of the effect of this mixture on the yield and quality of oat products was carried out. The manuscript corresponds to the profile of the journal and will be of interest to a wide range of readers. The absolute advantages of the work are not only a well-staged experiment, but also competent processing of the results and their in-depth discussion.
Response 1: Thanks for your encouraging comments.
Reviewer 3 Report
The paper presents a thoroughly developed interaction of bentonite mixture with humic acid in relation to soil properties and enzymatic activity. The local interest of the obtained data should be emphasized due to the product used in the experiment, as well as soil and climatic conditions. The publication contains a lot of information supported by a statistical analysis. The paper is well prepared, although the authors did not avoid some imperfections that hinder the reception and interpretation of data. Below, I present my comments and thoughts related to it, as a proposal to be included in the new version of the paper.
1. Abstract should be supplemented with a part related to the experiment and methods used in the work
2. The first sentence in the abstract is quite confusing, because the degradation processes occur everywhere on Earth, regardless of the region, the more so as the authors do not indicate what type of degradation is being discussed.
3. The first sentence in Introduction contains old and outdated data and source - this should be changed with current data. Again, there is no information about what type of soil degradation we are talking about. It can be suspected that it is about the problems of desertification and exposure to erosive processes, but it has never resounded anywhere, the more so that in the introduction this problem is very enigamatic and is not referred to further in the work. These elements should be clarified.
4. The introduction is too long and eclectic, not very coherent. It is necessary to shorten and edit it so that it creates a logical whole.
5. There is no chemical analysis of samples from before the experiment, presented in table form and even briefly discussed. I know that there is control in the experiment, but the data obtained for the control soil relate to the time of the experiment and this is not sufficient information in the context of the real impact on the tested parameters of the product used.
6. Please enter the tables with the statistics values ​​for the ANOVA performed
7. Due to the better reception of the work, I suggest replacing the present subsection 3.2 with 3.1, and the current 3.1 will be 3.2. This will be more logical due to the content contained in the table and the figure.
8. There is a lot of data in the paper, but they are described in a marginal and residual manner. The description of the results should be expanded.
9. Discussion of the results largely based on speculation, supported only by literature. Data cannot be interpreted in this way. See lines 371-373 for examples of this type; 385-386.
How do you explain the observed changes that the authors talk about in a general way on lines 377-378? When interpreting the obtained data, such general statements should be avoided, because they do not break anything and are common knowledge.
10. In Conclusions, in line 446 - 447, authors write again about changes that they did not analysed. This needs to be redrafted.
11. In some workplaces I have noticed minor linguistic errors that need to be consulted with a native speaker translator.
Author Response
Reviewer 3, Agronomy Dear reviewer, Re: Agronomy Manuscript 1635535 Title: Residual effect of bentonite-humic acid amendment on soil health and crop performance 4-5 years after initial application in a dryland ecosystem Authors: Bin Ma, Yangmei Bao, Bao-Luo Ma, Neil B. McLaughlin, Ming Li, Jinghui Liu. Date: March 25, 2022
Please see our revised manuscript on Bentonite-Humic Acid (BHA) soil amendment as detailed above. We would like to thank you very much for the meticulous and constructive comments in improving the quality of our manuscript. We have taken into consideration all the comments and suggestions and have made extensive changes to the text and provided explanations in our following item-by-item responses to the comments. The modified phrases and text in the revised manuscript are in red font color.
We hope the changes made to the manuscript and the explanations in the response letter are adequate and clear, and that this manuscript will now be acceptable for publication in Agronomy. We will remain fully cooperative with regard to any further comments and suggestions you may have. Thanks again.
Sincerely yours,
Dr. Bin Ma and Jinghui Liu, Corresponding author
Professor of Agronomy
Below are our point-by-point responses to the editor's and referees' comments: The reviewer and editor’s comments are given in blue font, our responses in black font, and any sections pasted from the revision are given in black italics font.
Referees' Comments to Author:
Reviewer #3:
Comment 1: The paper presents a thoroughly developed interaction of bentonite mixture with humic acid in relation to soil properties and enzymatic activity. The local interest of the obtained data should be emphasized due to the product used in the experiment, as well as soil and climatic conditions. The publication contains a lot of information supported by a statistical analysis. The paper is well prepared, although the authors did not avoid some imperfections that hinder the reception and interpretation of data. Below, I present my comments and thoughts related to it, as a proposal to be included in the new version of the paper.
Response 1: Thanks for your encouraging comments and compliments.
Comment 2: 1. Abstract should be supplemented with a part related to the experiment and methods used in the work
Response 2: Good suggestion. We revised the ABSTRACT section as follows:
Lines14-32: Degraded soils (including salinized, eroded and low organic matter) resulting from natural and human affects are universal in arid and semi-arid regions all over the world. Bentonite and humic acid (BHA) are increasingly being tested to remediate these degraded lands with potential bene-fits on crop production and soil health. A field study was conducted to quantify the effects of BHA application at six rates (0, 6, 12, 18, 24 and 30 Mg ha−1) on (i) dynamic changes in soil properties, and (ii) oat crop productivity parameters, in a dryland farming ecosystem. The specific objective of this paper was to determine the residual effects four to five years after a one-time BHA application on soil health and crop performance. The findings demonstrated that with the increasing rates of one-time BHA application, soil profile water storage displayed a piecewise linear plus plateau increase, whereas soil electrical conductivity, pH and bulk density were all reduced significantly (P < 0.05) in the 0-20 cm and 20-60 cm layers. The improved soil environments gave rise to an increased activity of soil enzymes urease, invertase and catalase that respectively reached the peak values of 97%, 37% and 32% of the control at the rates of 18 to 24 Mg BHA ha-1. In turn, these boosted soil nutrient turnover, leading to a 40% higher soil available P. Compared with the control treatment, application of BHA at the estimated optimum rate (roughly 24 Mg ha-1) increased grain yield by 20%, protein yield by 62%, water use efficiency by 41%, and partial factor productivity of N by 20%. Results of this study indicated for the first time that a one-time BHA application would be a new and effective strategy to combat land degradation, drought, and promote a sustainable soil micro-ecological environment in dryland agroecosystem under a varying climate scenario.
Comment 3: 2. The first sentence in the abstract is quite confusing, because the degradation processes occur everywhere on Earth, regardless of the region, the more so as the authors do not indicate what type of degradation is being discussed.
Response 3: Thanks for the suggestion. We have revised the abstract and clarified the type of degradation prevalent in the area that we are addressing.
Comment 4:3. The first sentence in Introduction contains old and outdated data and source - this should be changed with current data. Again, there is no information about what type of soil degradation we are talking about. It can be suspected that it is about the problems of desertification and exposure to erosive processes, but it has never resounded anywhere, the more so that in the introduction this problem is very enigamatic and is not referred to further in the work. These elements should be clarified.
Response 4: We have cited one relevant paper in the revision to address this concern as follows:
Lines42-45. Globally, soil degradation (including salinized, eroded, low organic matter) resulting from changing climate scenarios and poor farming practices affects more than 75% of earth’s land surface [1], reducing food production security and increasing irrigation demand in dryland farming regions [2].
Reference:
[1] Talukder, B., Ganguli, N., Matthew, R., vanLoon, G.W., Hipel, K.W., Orbinski, J. Climate change-triggered land degradation and planetary health: A review[J]. Land Degradation & Development, 2021, 32:4509-4522.
Comment 5: 4. The introduction is too long and eclectic, not very coherent. It is necessary to shorten and edit it so that it creates a logical whole.
Response 5: Thanks for the suggestion. We have now cut down the Introduction section and edited it to be more logical.
Comment 6: 5. There is no chemical analysis of samples from before the experiment, presented in table form and even briefly discussed. I know that there is control in the experiment, but the data obtained for the control soil relate to the time of the experiment and this is not sufficient information in the context of the real impact on the tested parameters of the product used.
Response 6: We have added the table in the revision to address this concern as follows:
Table 1 Selected soil chemical properties in the experimental site.
|
Property |
Value |
|
pH |
7.8 |
|
SOM (g kg-1) |
10.3 |
|
AN (mg kg-1) |
45.1 |
|
AP (mg kg-1) |
7.4 |
|
AK (mg kg-1) |
124 |
Comment 7: 6. Please enter the tables with the statistics values ​​for the ANOVA performed
Response 7: We have added two tables in the revision to address this concern.
Comment 8: 7. Due to the better reception of the work, I suggest replacing the present subsection 3.2 with 3.1, and the current 3.1 will be 3.2. This will be more logical due to the content contained in the table and the figure.
Response 8: Revised as suggested.
Comment 9: 8. There is a lot of data in the paper, but they are described in a marginal and residual manner. The description of the results should be expanded.
Response 9: Thanks for the suggestion. We have expanded the results to be more specific.
Lines302-311: Specifically, SEC of 24 Mg BHA ha-1 treatment was reduced, respectively by 0.107 and 0.133 mS cm-1 in 0-10 cm, 0.296 and 0.291 mS cm-1 in 10-20 cm, 0.194 and 0.161 mS cm-1 in 20-40 cm, and 0.137 and 0.123 mS cm-1 in 40-60 cm soil layers, compared with those of the no BHA treatment (Fig. 3A). Average soil pH was reduced by 0.2units in both 2014 and 2015 for treatments of BHA application compared to the no BHA treatment (Fig. 3B). SBD of 0-60 cm layer showed a consistent decreasing trend in 2014 and2015 with increasing the rates of BHA application (Fig. 3C). For example, in the 10-20 cm soil layer, SBD was significantly reduced by 0.01-0.09 g cm-3 in 2014 and 0.01-0.19 g cm-3 in 2015 for all BHA treatments, compared with the no BHA treatment.
Comment 10: 9. Discussion of the results largely based on speculation, supported only by literature. Data cannot be interpreted in this way. See lines 371-373 for examples of this type; 385-386.
How do you explain the observed changes that the authors talk about in a general way on lines 377-378? When interpreting the obtained data, such general statements should be avoided, because they do not break anything and are common knowledge.
Response 10: Thanks for the suggestion. We have now deleted much of the speculation and general statements in this manuscript in the Discussion section.
Comment 11: 10. In Conclusions, in line 446 - 447, authors write again about changes that they did not analysed. This needs to be redrafted.
Response 11: Revised as suggested. Our study implies that one-time BHA application may serve as a new sustainable strategy to improve soil health and crop productivity in arid and semi-arid regions. (Lines477-479).
Comment 12: 11. In some workplaces I have noticed minor linguistic errors that need to be consulted with a native speaker translator.
Response 12: Revised as suggested. Dr. McLaughlin is a native English speaking scientist, and he has reviewed the manuscript for proper English usage an grammar, and made appropriate revisions.
Round 2
Reviewer 1 Report
The mansucript ,,Residual effect of bentonite-humic acid amendment on soil health and crop performance 4-5 years after initial application in a dryland ecosystem,, has been improved and now can be accepted in its current form.
