Straw Incorporation in Contaminated Soil Enhances Drought Tolerance but Simultaneously Increases the Accumulation of Heavy Metals in Rice
Round 1
Reviewer 1 Report
Since the industrial revolution, the contamination of agricultural soils with heavy metals has increasingly become a serious global environmental concern and poses a huge threat to human beings and natural ecosystems. Heavy metals negatively affect, not just plant physiology and biology and soil microorganisms but they also pose health risks for both humans and animals through food-chain bioaccumulation.
Diverse approaches such as chemical precipitation, thermal processes, and physical separation, have been developed and made available to clean up the contaminated environment. However, these techniques not only present several disadvantages, such as the destruction of particle structure and microbial activities in soils, as well as high cost, they also, in many cases, transfer the pollutant from one form to another. Phytoremediation, which uses metal hyperaccumulator plants to remove contaminants from soils, is another cost-efficient and environmentally friendly remediation technology.
Natural materials that are available in large quantity, such as straw, may have potential as inexpensive sorbents or immobilizers for both organic and inorganic pollutants. As a heterogeneous material, straw has been used as a biosorber to reduce heavy metals in aquatic environments and as a chelator source of inorganic pollutants in soil. Agricultural crop residues, besides from the basic constituents, usually contain extractives and diverse molecules composed of a variety of functional groups capable of binding heavy metal. The metals cations have a good affinity with the anionic matters present on the straw surfaces and can form stable complexes.
In the present study, heavy metals were used as models of pollutants to investigate the effect of straw on drought stress tolerance and heavy metal bioaccumulation, as well as their interaction. The authors conclude that straw incorporation enhances drought stress tolerance as well as heavy metals bioaccumulation in rice crop and really impressive experiment.
Some minor changes are suggested before it can be considered for publication:
The novelty of the MS must be highlighted in a better way during revision. Moreover, the literature is not robust and very recent, it must be updated e.g.
Wang, Y., Liang, H., Li, S., Zhang, Z., Liao, Y., Lu, Y., Zhou, G., Gao, S., Nie, J. and Cao, W., 2022. Co-utilizing milk vetch, rice straw, and lime reduces the Cd accumulation of rice grain in two paddy soils in south China. Science of The Total Environment, 806, p.150622.
Zong, Y., Chen, H., Malik, Z., Xiao, Q. and Lu, S., 2022. Comparative study on the potential risk of contaminated-rice straw, its derived biochar and phosphorus modified biochar as an amendment and their implication for environment. Environmental Pollution, 293, p.118515.
Su, Y., Kwong, R.W., Tang, W., Yang, Y. and Zhong, H., 2021. Straw return enhances the risks of metals in soil?. Ecotoxicology and Environmental Safety, 207, p.111201.
Shan, A., Pan, J., Kang, K.J., Pan, M., Wang, G., Wang, M., He, Z. and Yang, X., 2021. Effects of straw return with N fertilizer reduction on crop yield, plant diseases and pests and potential heavy metal risk in a Chinese rice paddy: A field study of 2 consecutive wheat-rice cycles. Environmental Pollution, 288, p.117741.
Mohamed, I., Bassouny, M.A., Abbas, M.H., Ming, Z., Cougui, C., Fahad, S., Saud, S., Khattak, J.Z.K., Ali, S., Salem, H.M. and Azab, A., 2021. Rice straw application with different water regimes stimulate enzymes activity and improve aggregates and their organic carbon contents in a paddy soil. Chemosphere, 274, p.129971.
Mention the type of straw which are used in the experiment
Line 135 “Mature and well-developed rice seeds” mention the variety used
Line 137 “then washing”, rephrase
Line 229-230 “Graphs pad prism and MS Excel” both version and country names are missing
While discussing the values of different parameters, the decimal points used should be uniform with respect to the parameter.
In conclusion section, in line number 453 “A higher accumulation of was heavy metals found in the root” rearrange it
In figure no 2, 3 and 4, the unit is not clear, modify it to make it visible
The treatment number in each treatment in Figure may be made subscript if possible
Under each Figure, there is a statement, “Different letter indicates significance difference in treatments at p ≤ 0.05”. It should be removed from Figure 5 as there are no letters added. Also, replace “different letter” with “different letters” in the rest of the Figures
Author Response
Since the industrial revolution, the contamination of agricultural soils with heavy metals has increasingly become a serious global environmental concern and poses a huge threat to human beings and natural ecosystems. Heavy metals negatively affect, not just plant physiology and biology and soil microorganisms but they also pose health risks for both humans and animals through food-chain bioaccumulation. Diverse approaches such as chemical precipitation, thermal processes, and physical separation, have been developed and made available to clean up the contaminated environment. However, these techniques not only present several disadvantages, such as the destruction of particle structure and microbial activities in soils, as well as high cost, they also, in many cases, transfer the pollutant from one form to another. Phytoremediation, which uses metal hyperaccumulator plants to remove contaminants from soils, is another cost-efficient and environmentally friendly remediation technology. Natural materials that are available in large quantity, such as straw, may have potential as inexpensive sorbents or immobilizers for both organic and inorganic pollutants. As a heterogeneous material, straw has been used as a biosorber to reduce heavy metals in aquatic environments and as a chelator source of inorganic pollutants in soil. Agricultural crop residues, besides from the basic constituents, usually contain extractives and diverse molecules composed of a variety of functional groups capable of binding heavy metal. The metals cations have a good affinity with the anionic matters present on the straw surfaces and can form stable complexes. In the present study, heavy metals were used as models of pollutants to investigate the effect of straw on drought stress tolerance and heavy metal bioaccumulation, as well as their interaction. The authors conclude that straw incorporation enhances drought stress tolerance as well as heavy metals bioaccumulation in rice crop and really impressive experiment.
Response: Thanks for a comprehensive evaluation and appreciation
Some minor changes are suggested before it can be considered for publication:
The novelty of the MS must be highlighted in a better way during revision. Moreover, the literature is not robust and very recent, it must be updated e.g.
Wang, Y., Liang, H., Li, S., Zhang, Z., Liao, Y., Lu, Y., Zhou, G., Gao, S., Nie, J. and Cao, W., 2022. Co-utilizing milk vetch, rice straw, and lime reduces the Cd accumulation of rice grain in two paddy soils in south China. Science of The Total Environment, 806, p.150622.
Zong, Y., Chen, H., Malik, Z., Xiao, Q. and Lu, S., 2022. Comparative study on the potential risk of contaminated-rice straw, its derived biochar and phosphorus modified biochar as an amendment and their implication for environment. Environmental Pollution, 293, p.118515.
Su, Y., Kwong, R.W., Tang, W., Yang, Y. and Zhong, H., 2021. Straw return enhances the risks of metals in soil?. Ecotoxicology and Environmental Safety, 207, p.111201.
Shan, A., Pan, J., Kang, K.J., Pan, M., Wang, G., Wang, M., He, Z. and Yang, X., 2021. Effects of straw return with N fertilizer reduction on crop yield, plant diseases and pests and potential heavy metal risk in a Chinese rice paddy: A field study of 2 consecutive wheat-rice cycles. Environmental Pollution, 288, p.117741.
Mohamed, I., Bassouny, M.A., Abbas, M.H., Ming, Z., Cougui, C., Fahad, S., Saud, S., Khattak, J.Z.K., Ali, S., Salem, H.M. and Azab, A., 2021. Rice straw application with different water regimes stimulate enzymes activity and improve aggregates and their organic carbon contents in a paddy soil. Chemosphere, 274, p.129971.
Response: We have highlighted the novelty (Please see lines 98-116) and consulted and cited the mentioned papers to update the introduction and discussion sections (Highlighted as yellow in the reference section)
Mention the type of straw which are used in the experiment
Response: We have mentioned the type of straw (Please see line 21)
Line 135 “Mature and well-developed rice seeds” mention the variety used
Response: We have mentioned the used variety as per the suggestion of the reviewer
Line 137 “then washing”, rephrase
Response: Rephrased (Please see line 143)
Line 229-230 “Graphs pad prism and MS Excel” both version and country names are missing
Response: We have added both the version and country names for Graphs pad prism and MS Excel used during the present study (Please see lines 238-240)
While discussing the values of different parameters, the decimal points used should be uniform with respect to the parameter.
Response: We have made the values uniform as per the suggestion of the reviewer and highlighted
In conclusion section, in line number 453 “A higher accumulation of was heavy metals found in the root” rearrange it
Response: Modified as per the suggestion of the reviewer (Please see lines 477-478)
In figure no 2, 3 and 4, the unit is not clear, modify it to make it visible
Response: The units in mentioned Figures are already looking visible and correct
The treatment number in each treatment in Figure may be made subscript if possible
Response: We have modified the treatment number as per the suggestion of the reviewer
Under each Figure, there is a statement, “Different letter indicates significance difference in treatments at p ≤ 0.05”. It should be removed from Figure 5 as there are no letters added. Also, replace “different letter” with “different letters” in the rest of the Figures
Response: We have removed the mentioned statements from the caption of Figure 5
Author Response File: 
Author Response.docx
Reviewer 2 Report
These are my main comments on the manuscript entitled “Straw incorporation enhances drought stress tolerance but at the same time increases bioaccumulation of heavy metals under contaminated soil in Oryza sativa L.” The authors examined the impacts of straw incorporation in soil on Cd, Cu, Pb, and Fe availability, accumulation, and drought stress tolerance in rice grown in glasshouse conditions.
Overall the manuscript is clear, organized, and presented well-structured. The introduction was well written and covered the recent literature review and gave a good background of the main idea of the study. Results are well-designed and statistically analyzed. However, the manuscript needs some improvements. Following substantial revisions should be incorporated into the manuscript before acceptance.
avoiding repeating the results and strengthening with more explanation of the results based on evidence and comparing the finding with previous or relevant studies showing the importance of these studies and how the finding contributes to the scientific community.
Specific comments
Title: The title in the present form is incorrect. (“under” is incorrect in this context; furthermore use simultaneously instead of “at the same time”). Please rewrite. Here is my suggestion, but the authors feel free to create a new title.
“The examination of the impacts of straw mulching on rice’s drought tolerance and heavy metals uptake grown in contaminated soil”
Keywords: Please arrange the keywords in alphabetical order.
Introduction:
Please explain why the selected four heavy metals (Fe, Cd, Pb, and Cu) only were examined.
Materials and methods:
Did you analyze the straw’s parameter? e.g. element contents? Please add the results to the Materials and methods.
Line 127: Please correct: Different physicochemical parameters such as pH, e
Line 131: Please delete “respectively”.
Line 131: What was the normality of the acid (or %)? What kind of acid was used? The methods of digestion and protocol of determining of heavy metals content of soil are unclear. Please add more information.
Line 132: A concentration is an amount of any type per volume of liquid or gas system, whereas content is an amount of any type per mass of liquid or gas or solid system. The authors used mg kg-1 unit which is mass. The authors determined the element content and NOT the element concentration. Please correct it throughout the whole manuscript.
Line 132: Please specify the equipment, producer, type, etc.
Line 135: Please add the hybrid name of the test plant.
Line 150: Do you have information related to photon flux? Please add this information.
Line 177. Please replace the determination of carotenoids here. Use carotenoids (plural).
2.6. Estimation of carotenoidS content in leaves
2.7. Estimation of proline in leaves
Line 178: Please rewrite, the sentence is incorrect.
Line 181. I think, the authors used 300ml supernatant and NOT 300 liter. Please correct it.
Line 187: Delete wavelength.
Line 194: Use “calculated” instead of measured. Specific wavelengths were used to measure….and the formula was used for calculation.
Line 211-212. See my previous comment. (line 194)
Line 220: Please indicate the % or normality of acids.
Results:
Table 1. Please calculate significant differences between normal and contaminated soil.
Why did the authors measure only these four heavy metals? Did not they detect any others?
Although, Al is not heavy metal but its physiological impacts as the same as heavy metals.
Figure 1: Please present biomass results in g plant-1.
Line 255: Please correct and check the whole manuscript: Different letterS indicate significance…
Line 260, 285, 300, etc.: The title of this chapter is RESULTS, which means the authors present only their results. Please do not use literature references in this chapter. Delete these sentences.
Table 2. Please reanalyze again and use the following table template.
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Chl-a |
Chl-b |
Chl a+b |
Car |
FW |
DW |
Proline |
RWC |
Cd |
Cu |
Fe |
Pb |
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Chl-a |
1 |
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Chl-b |
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1 |
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Chl a+b |
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1 |
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Car |
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1 |
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FW |
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1 |
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DW |
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1 |
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Proline |
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1 |
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RWC |
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1 |
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Cd |
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1 |
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Cu |
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1 |
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Fe |
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1 |
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Pb |
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I am not a native English speaker but the manuscript needs an English check and improvement.
I can suggest publishing this paper after a major revision.
Author Response
These are my main comments on the manuscript entitled “Straw incorporation enhances drought stress tolerance but at the same time increases bioaccumulation of heavy metals under contaminated soil in Oryza sativa L.” The authors examined the impacts of straw incorporation in soil on Cd, Cu, Pb, and Fe availability, accumulation, and drought stress tolerance in rice grown in glasshouse conditions. Overall the manuscript is clear, organized, and presented well-structured. The introduction was well written and covered the recent literature review and gave a good background of the main idea of the study. Results are well-designed and statistically analyzed. However, the manuscript needs some improvements. Following substantial revisions should be incorporated into the manuscript before acceptance.
Response: Thanks for your appreciation and recommendation
avoiding repeating the results and strengthening with more explanation of the results based on evidence and comparing the finding with previous or relevant studies showing the importance of these studies and how the finding contributes to the scientific community.
Response: We have modified the manuscript as per the suggestion of the reviewer by avoiding the repetition of the results and strengthening with more explanation of the results based on evidence and comparing the finding with previous or relevant studies
Specific comments
Title: The title in the present form is incorrect. (“under” is incorrect in this context; furthermore use simultaneously instead of “at the same time”). Please rewrite. Here is my suggestion, but the authors feel free to create a new title. “The examination of the impacts of straw mulching on rice’s drought tolerance and heavy metals uptake grown in contaminated soil”
Response: We have modified the title as “Straw incorporation in contaminated soil enhances drought tolerance but simultaneously increases the accumulation of heavy metals in rice”
Keywords: Please arrange the keywords in alphabetical order.
Response: We have arranged the keywords as per the suggestion of the reviewer
Introduction:
Please explain why the selected four heavy metals (Fe, Cd, Pb, and Cu) only were examined.
Response: The selection of four heavy metals (Fe, Cd, Pb, and Cu) was based fact that these are the most commonly found metals in most contaminated soils as clear from the recent literature (Please see lines 53-56)
Materials and methods:
Did you analyze the straw’s parameter? e.g. element contents? Please add the results to the Materials and methods.
Response: As we have mentioned that we collected the rice straw from non-contaminated soil. To nullify this impact, we have included a control with the straw application under normal and contaminated soils both
Line 127: Please correct: Different physicochemical parameters such as pH, e
Response: Corrected (Please see line 131)
Line 131: Please delete “respectively”.
Response: Deleted (Please see line 135)
Line 131: What was the normality of the acid (or %)? What kind of acid was used? The methods of digestion and protocol of determining of heavy metals content of soil are unclear. Please add more information.
Response: We have explained the digestion method used for soil in the present study
Line 132: A concentration is an amount of any type per volume of liquid or gas system, whereas content is an amount of any type per mass of liquid or gas or solid system. The authors used mg kg-1 unit which is mass. The authors determined the element content and NOT the element concentration. Please correct it throughout the whole manuscript.
Response: We have modified the use of concentration when describing the contents of heavy metals in soil or plant samples and highlighted them as yellow
Line 132: Please specify the equipment, producer, type, etc.
Response: We have added the information regarding the manufacturer and model for the equipment used during this study (Please see lines 138, 172, 193, 200, and 234-235)
Line 135: Please add the hybrid name of the test plant.
Response: We have added the hybrid name of the tested plant (Please see line 140)
Line 150: Do you have information related to photon flux? Please add this information.
Response: Sorry, we could not get this information from our greenhouse manager
Line 177. Please replace the determination of carotenoids here. Use carotenoids (plural).
2.6. Estimation of carotenoidS content in leaves
2.7. Estimation of proline in leaves
Response: Replaced
Line 178: Please rewrite, the sentence is incorrect.
Response: We have modified the mentioned sentence (Please see lines 184-185)
Line 181. I think, the authors used 300ml supernatant and NOT 300 liter. Please correct it.
Response: Yes, we agree with the reviewer. It was a typo. We have corrected (Please see line 187)
Line 187: Delete wavelength.
Response: Deleted (Please see lines 193-194)
Line 194: Use “calculated” instead of measured. Specific wavelengths were used to measure….and the formula was used for calculation. Line 211-212. See my previous comment. (line 194)
Response: Corrected at both the places (Please see lines 175 and 201-202, 219-220)
Line 220: Please indicate the % or normality of acids.
Response: We have indicated the normality of the acids used (Please see lines 228-229)
Results:
Table 1. Please calculate significant differences between normal and contaminated soil.
Response: Calculated and added (Please see Table 1)
Why did the authors measure only these four heavy metals? Did not they detect any others? Although, Al is not heavy metal but its physiological impacts as the same as heavy metals.
Response: The selection of four heavy metals (Fe, Cd, Pb, and Cu) was based fact that these are the most commonly found metals in most contaminated soils as clear from the recent literature. Moreover, the inadequate supply of micronutrients such as Fe and Cu also disrupts various physiological and biochemical attributes of plants as well as humans. Regarding the detection of any other metals, our project was limited to these metals as per the earlier commitment made at the time of project acceptance and as per the objectives.
Figure 1: Please present biomass results in g plant-1.
Response: We have cross-checked and revisited our whole experimental data and found that the already presented biomass is per plant basis
Line 255: Please correct and check the whole manuscript: Different letterS indicate significance…
Response: Corrected
Line 260, 285, 300, etc.: The title of this chapter is RESULTS, which means the authors present only their results. Please do not use literature references in this chapter. Delete these sentences.
Response: We have deleted the reference citations in the Results section
Table 2. Please reanalyze again and use the following table template.
|
|
Chl-a |
Chl-b |
Chl a+b |
Car |
FW |
DW |
Proline |
RWC |
Cd |
Cu |
Fe |
Pb |
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Chl-a |
1 |
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Chl-b |
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1 |
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Chl a+b |
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Car |
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Proline |
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Response: We have revised Table 2 as per the suggestion of the reviewer
I am not a native English speaker but the manuscript needs an English check and improvement.
Response: We have gone through the whole manuscript and corrected any typos and grammatical mistakes found during proofread
I can suggest publishing this paper after a major revision.
Response: Thanks for your recommendation
Author Response File: Author Response.docx
Round 2
Reviewer 2 Report
Thanks for the authors' corrections.
