Chemical and Biological Response of Four Soil Types to Lime Application: An Incubation Study

Round 1

Reviewer 1 Report

This study examines the effect of a liming agent on four soil types under citrus orchards in China, examining both chemical and biological changes. This was done under controlled incubation conditions. While the results provide interesting insight into the response of these soils to lime (in particular the biological aspects), the results and outcomes tend to be rather more confirmatory of existing knowledge, though are useful for regional understanding. As such the work is relevant and useful, but several aspects need improvement to improve clarity and also relevance to a wider audience.

In the introduction it was indicated the intent was to explore practical solutions to deal with acidity for citrus orchard soils. In this regard the study has not really achieved the objective as it has shown the effect of lime additions under laboratory and controlled condition on various soil properties, but without relating these back to practical relevance or use in orchards. The outcomes of these findings need to be better contextualized to citrus orchard conditions and the benefit or risk to orchard crops. Some suggestions to improve on this include:

Presenting the lime rates as an equivalent/approximate field level applications ate would give more practical insight into likely rates needed. 

Also consider that the study was as an incubation at a constant moisture and temperature, using milled soils and lime, with through mixing, thus likely represents an exaggeration of field responses. Under field conditions applying agricultural grade limes (at the rates used here) and  incorporating into whole soil (ploughing/discing) would likely not provide the same magnitude or rate of response observed here. Thus relating these results back to real-world conditions should be considered if the practical relevance is to be considered. Also keep in mind that in orchards, after establishment it is  difficult to incorporate lime under tree driplines (usually due to potential root damage), so often lime is only topdressed - this further reduces the effectiveness of lime application. As such how would the incubation results relate to real-world application?

I also feel an opportunity to better examine/discuss the responses in the different soils was not fully utilised. Given that soils respond differently to amendments, more detail on soil types/properties would provide insight into practical management across different site types.  

Other concerns noted (with several annotated comments in the PDF manuscript) include:

Methods section requires considerably more detail. This includes more information on soils used, experimental design and some laboratory methods and also the calculations and analysis sections.

Results and discussion sections could be improved by considering the responses in relation to the soil types used in the incubation

Conclusions can be improve by better relating findings to practical application given that it is unlikely real-world response will reflect those of a incubation study.

Figures and tables - some captions can be improved so that detail in figure or table is easier to understand without needing to refer back to text sections. Captions should provide enough detail so that the table or figure can stand alone. Some suggestions to improve selected items is given in annotated PDF.

Grammar - While generally good, there are opportunities to improve using an editorial service or competent English first language speaker.

References - some formatting inconsistencies noted.

Comments for author File: Comments.pdf

Author Response

Point 1: Presenting the lime rates as an equivalent/approximate field level applications ate would give more practical insight into likely rates needed.

Response 1: We have added the corresponding field application rates in the manuscript. (Line 109~110)

Point 2: Also consider that the study was as an incubation at a constant moisture and temperature, using milled soils and lime, with through mixing, thus likely represents an exaggeration of field responses. Under field conditions applying agricultural grade limes (at the rates used here) and  incorporating into whole soil (ploughing/discing) would likely not provide the same magnitude or rate of response observed here. Thus relating these results back to real-world conditions should be considered if the practical relevance is to be considered. Also keep in mind that in orchards, after establishment it is  difficult to incorporate lime under tree driplines (usually due to potential root damage), so often lime is only topdressed - this further reduces the effectiveness of lime application. As such how would the incubation results relate to real-world application?

Response 2: Thanks to the reviewer for pointing this out. We think that the actual amount of lime can be calculated based on the local soil capacity and the depth of the soil planned to be improved, combined with the lime dosage recommended in this paper. However, considering the different conditions between field and culture experiment, long-term field trials are still needed to examine the effects of liming on soil fertility, soil microbial community and citrus yield and quality, and this is what we intend to do next.

Point 3: I also feel an opportunity to better examine/discuss the responses in the different soils was not fully utilised. Given that soils respond differently to amendments, more detail on soil types/properties would provide insight into practical management across different site types. 

Response 3: According to this suggestion, we have made appropriate modification in the discussion section of the manuscript, discussed the differences in the response of different soils to lime amendment. (Line 405~406, 416~418)

Point 4: Methods section requires considerably more detail. This includes more information on soils used, experimental design and some laboratory methods and also the calculations and analysis sections.

Response 4: We have modified the unclear expression of the material section, re-explained the calculation method of soil integrated fertility index (IFI) (Line 149~153), and added information on soil type and clay content (Table 1).

Point 5: Results and discussion sections could be improved by considering the responses in relation to the soil types used in the incubation

Response 5: We have made modefications in revelent section. (Line 405~406, 416~418)

Point 6: Conclusions can be improve by better relating findings to practical application given that it is unlikely real-world response will reflect those of a incubation study.

Resposnse 6: The conclusions were improved based on this recommendation. We discussed the relationship between our findings and practical appliations and analyzed how our results can be applied to actual citrus production. (Line 463~469)

Point 7: Figures and tables - some captions can be improved so that detail in figure or table is easier to understand without needing to refer back to text sections. Captions should provide enough detail so that the table or figure can stand alone. Some suggestions to improve selected items is given in annotated PDF.

Resposnse 7: Appropriate modifications were made in the figures and captions.

Point 8: References - some formatting inconsistencies noted.

Response 8: Citations with irregular format were modified according to the formatting rules.

Thanks for your criticism and suggestions on this article.

Author Response File: Author Response.docx

Reviewer 2 Report

Citing too many Chinese journals! ‘How to identify and adopt cleaner strategies to improve the continuous acidification in orchard soils?’ in Volume 330, Journal of Cleaner Production, and ‘Reducing aluminum is the key nutrient management strategy for ameliorating soil acidification and improving root growth in an acidic citrus orchard’ in Land Degradation and Development, may be more suitable as your research background.

Line 58-59. Note that, liming is not a good method of long-term soil improvement. It can only be used as a short-term emergency measure. Because long-term application of lime will lead to the imbalance of soil nutrient ratio and change the physical structure of soil, and the improvement effect of lime is also unstable, re-acidification often occurs and it can only affect small areas of the soil. Therefore, I don't think this literature is an appropriate citation, nor is it new findings.

We know that the application of lime in orchards is impossible to broadcast, so I hope that the recommended amount of lime you give in the abstract and conclusion can be converted into kg/ha or kg/tree according to the thickness of the soil layer and soil bulk density.

What do the four pictures in Figure 1 and Figure 2 mean? Diagrams need to be self-explanatory. The dots are so large that no error bars can be seen.

What does the red point in Figure 3 mean?

What does the legend in Figure 4 mean?

I feel that you are very casual in making figures and tables, without a scientific and rigorous attitude. This attitude does not match your school.

From the introduction, materials and methods, result analysis, and discussion, I have not seen anything new and insightful. Do you think that by measuring some microorganisms and doing some statistical analysis, the article will be worthy of being published? What is the innovation of the draft? Lines 71-73 are fabrications, and there have been many studies related to orchard acidification.

Author Response

Point 1: Citing too many Chinese journals! ‘How to identify and adopt cleaner strategies to improve the continuous acidification in orchard soils?’ in Volume 330, Journal of Cleaner Production, and ‘Reducing aluminum is the key nutrient management strategy for ameliorating soil acidification and improving root growth in an acidic citrus orchard’ in Land Degradation and Development, may be more suitable as your research background.

Response 1: Thank you for your suggestion and we have incorporated the suggested literature as Refs.

Point 2: Line 58-59. Note that, liming is not a good method of long-term soil improvement. It can only be used as a short-term emergency measure. Because long-term application of lime will lead to the imbalance of soil nutrient ratio and change the physical structure of soil, and the improvement effect of lime is also unstable, re-acidification often occurs and it can only affect small areas of the soil. Therefore, I don't think this literature is an appropriate citation, nor is it new findings.

Response 2: We apologize for the inappropriate expression. We have revisited this document and corrected inappropriate statement in the manuscript (Line 62~63).

Point 3: We know that the application of lime in orchards is impossible to broadcast, so I hope that the recommended amount of lime you give in the abstract and conclusion can be converted into kg/ha or kg/tree according to the thickness of the soil layer and soil bulk density.

Response 3: Thank you for this advice. We have added the corresponding field application rates in the manuscript (Line 109~110). In the conclusion section, we discussed how the experimental results can be applied in real production and analyzed the shortcomings of this study (Line 463~469).

Point 4: What do the four pictures in Figure 1 and Figure 2 mean? Diagrams need to be self-explanatory. The dots are so large that no error bars can be seen. What does the red point in Figure 3 mean? What does the legend in Figure 4 mean?

Response 4: We have made appropriate modifications in the figures and captions.

Point 5: From the introduction, materials and methods, result analysis, and discussion, I have not seen anything new and insightful. Do you think that by measuring some microorganisms and doing some statistical analysis, the article will be worthy of being published? What is the innovation of the draft? 

Response 5: In our early investigation, the average pH value of 26 orange orchard soils collected in western Zhejiang was only 4.38. Soil acidification is still a serious problem. Lime has the advantages of low price, easy to obtain and obvious acidification improvement effect. Therefore, we intend to find out the amount of lime that can improve soil acidity without damaging soil fertility and soil health. However, considering the different conditions between field and incubation experiment, long-term field trials are still needed to examine the effects of liming on soil fertility, soil microbial community and citrus yield and quality.
We have modified the inappropriate statement (Line 77~78).

Thanks for your criticism and suggestions on this article.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

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