Comprehensive Growth Index (CGI): A Comprehensive Indicator from UAV-Observed Data for Winter Wheat Growth Status Monitoring

Round 1

Reviewer 1 Report

This paper introduces the comprehensive methods for predicting winter wheat growth monitoring data using UAV multispectral imagery. They discuss the three zones as Elongation, Booting, and Flowering stages, where the Elongation stage with the MSR model was the best, the Booting stage was with GPR, and the Flowering stage was SVR model, respectively.

The paper was presented well and was useful to agronomy. By using the tool indicator crop monitoring, these comprehensive methods would be challenging for the developer and researcher to study.  

The comments to the authors have some words as below,

1. Table 7, please rewrite the word in columns "Modeling set" and "Modeling set" or Validation..?

2. The experimental setup of UAV in section 2.2.1 should indicate how to measure and collect the dataset in the field, for the better, show the picture of wheat plants in section 2.2.2  

3. The author should add the flowchart of methods and how to evaluate them to make the paper readable and easily understood.

4. Please recheck and follow the reference style of MDPI. 

5. Introduction section, please show the main contribution of the paper by comparing it with the previous references or any other.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

The study focused on drone-acquired remotely sensed indices that are a proxy for wheat growth. The authors created CGI (which I am not sure what the actual name is) in two varieties: CGIavg and CGIcv, to model plant growth status. The study has good merits and was conducted with scientific rigour. However, the presentation of the results is very confusing and is difficult to follow due to a lot of errors in terminology, grammar, and language. It is with regret that I do not find the current form of the paper to be suitable for publication. Extensive English editing is necessary and the structure of the paper needs an overhaul. My comments are detailed below:

L2: Title does not make sense. Need to spell out CGI first and what does "from UAV-observed for" mean?

Abstract: needs English editing

L25 - CGIcv not defined in text

L32 - double semi-colon between UAV images and machine learning

L38 - avoid using "my country". Best to use China or full name of PRC, whichever is suitable.

L42-L55 - what are examples of comprehensive growth indicators? Are leaf length, chlorophyll content, etc examples? Spell these out and include references. No references were included in the paragraph/

L57-80 - be consistent when using abbreviations. You mention CGI several times in its spelled out form, you should use CGI instead. Also check the placement of references i.e. L75. For other abbereviations, these need to be spelled out i.e. PLSR, NDVI, VTCI.

L82-83 - this is a weak closing paragraph for the introduction in that it does not provide a satisfying rationale for the study and also spells out only the main objective. You should deconstruct this into the other specific objectives aimed by your study (i.e. derive optimal combination of parameters, test whcih algorithm is most suitable, etc).

L95 - observe proper molecular notation with subscripts i.e. P2O5, K2O etc.

L136 - check formatting of headers

L145 - spell out SPAD here (for all abbervaitions spell them out in the first usage in the text)

L166 - For table 1 spell out the name of the index. Please define in the text your process of normalizing the optical bands, this is mentioned in the caption but not in the text.

L169 - please differentiate color index from vegetation index, not clear in the text

Table 2 - please use correct notation format for the equations, avoid inline.

L255-L261- this section looks to be best put in the methods or introduction.

L277 - inconsistent growth stage names, in earlier sections elongation was referred to jointing stage.

Fig 2-4. Is it possible to put in error bars here?

L278 - no need to specify single asterisk as it wasn't used. (don't use *0.05, just use one asterisk and set that at 0.01).

L284 - no need to mention all the indices one by one, just mention if there are exceptions which are insignificant, or say all indices were significant

L317-318 - please use the same term to refer to equations (Equation or Formula?)

Fig 5 and Fig 9 are difficult to know the difference of. Likewise to other charts on correlation. It will be better to either do a comparison side-by-side of CGIavg vs CGIcv rather than the current presentation that makes it difficult to appreciate the differences of the two methods.

Fig 10-15 the plot is formally called a 'Scatterplot with a 1:1 reference line'. correct this please.

Discussion

The discussion lacks substance to analyze and synthesize the results in view of related studies. There is no mention if their study improves upon other methods and what are the current limitations of their study and how these were handled. Current content in the discussion is better suited to the introduction. To improve this section, please include comparisons of your current method with previous studies and what are the current areas of improvement.

Conclusions

Similarly, the conclusions are just a rehash of the results and does not provide a satisfying synthesis of the study. It is better to re-structure the objectives statements in the introduction and use the conclusions to discuss if the objectives were answered and how the results of this study can be used in further research.

I strongly recommend this be proofread professionally.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

Report Reviewer

Title: CGI: a comprehensive indicator from UAV-observed for winter 2 wheat growth status monitoring

Summary brief

The work proposes a method to construct new comprehensive growth indicators based on images acquired from drones and ground data. The experiment was carried out using three different varieties, fertilization levels, and seeding densities.

General concept comments

The abstract needs to be rewritten to better describe the study's objectives and methods. While the introduction provides a good overview of the state of knowledge and research developments, it is unclear what specific issues the present work aims to address. The materials and methods section are explained but requires some modifications for clarity. Additionally, information about image analysis, the software used, and the techniques employed for data extrapolation is missing. It is not clear how the Comprehensive Growth Index (CGI) is derived, and it appears that ground measurements are used. Therefore, the approach to estimating growth conditions from a remote platform does not seem efficient. Furthermore, the data representations in figures 3, 4, and 5 are somewhat superficial and lack scientific detail. I recommend using fewer indices to improve the overall understanding of the article. The English language was used correctly and need only few corrections.

Below are details of some of the suggestions:

Rows 38: “my country” is not a scientific representation of the location.

Row 41-42: there are two-time monitoring in a single sentence.

Row 64: What is the acronym VTCI?

Row 77: What is the acronym PLSR?

Row 90-92: Are you sure that the unit of measurement are right? Generally, it is indicated in %.

Row 96-100: Also in this case, the unit of measurement is not correct.

Row 107: The drone is the Phantom 4 or Genie 4RTK or Matrice 600?

Row 116: Why did you make a flight with an altitude very low?

Row 118: the time of flight is very soon, generally it’s made near 12:00am.

Row 122: Missing the hyperspectral camera description in details.

Report Reviewer

Title: CGI: a comprehensive indicator from UAV-observed for winter 2 wheat growth status monitoring

Summary brief

The work proposes a method to construct new comprehensive growth indicators based on images acquired from drones and ground data. The experiment was carried out using three different varieties, fertilization levels, and seeding densities.

General concept comments

The abstract needs to be rewritten to better describe the study's objectives and methods. While the introduction provides a good overview of the state of knowledge and research developments, it is unclear what specific issues the present work aims to address. The materials and methods section are explained but requires some modifications for clarity. Additionally, information about image analysis, the software used, and the techniques employed for data extrapolation is missing. It is not clear how the Comprehensive Growth Index (CGI) is derived, and it appears that ground measurements are used. Therefore, the approach to estimating growth conditions from a remote platform does not seem efficient. Furthermore, the data representations in figures 3, 4, and 5 are somewhat superficial and lack scientific detail. I recommend using fewer indices to improve the overall understanding of the article. The English language was used correctly and need only few corrections.

Below are details of some of the suggestions:

Rows 38: “my country” is not a scientific representation of the location.

Row 41-42: there are two-time monitoring in a single sentence.

Row 64: What is the acronym VTCI?

Row 77: What is the acronym PLSR?

Row 90-92: Are you sure that the unit of measurement are right? Generally, it is indicated in %.

Row 96-100: Also in this case, the unit of measurement is not correct.

Row 107: The drone is the Phantom 4 or Genie 4RTK or Matrice 600?

Row 116: Why did you make a flight with an altitude very low?

Row 118: the time of flight is very soon, generally it’s made near 12:00am.

Row 122: Missing the hyperspectral camera description in details.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Thanks for promptly considering all comments and for the extensive edits you have put into this paper. I am satisfied with the changes done and recommend this to be published.

Author Response

Thank you very much for scrutinizing my article and providing your valuable comments. I am happy to know that you are satisfied with my work. Your professional advice means a lot to me and I will seriously consider it and improve it in my future endeavors.

Thank you again for your patience and support and I look forward to the opportunity to work with you again in the future.

Reviewer 3 Report

Report Reviewer

Several corrections have been made to the article and I think it has been heavily revised. However, this review revealed further corrections that can be made to improve the quality of the manuscript.  Below are some suggestions:

-          Line 101-104: The unit of measurement of the plant’s density are not correct. In this case, it should be indicated in number of plants/m².

-          In the first review process I wrote: Why did you fly at a very low altitude? The answer was not satisfactory. The low acquisition altitude is not a practice that can be done on a large scale. So, these data are probably not replicable and/or reliable.

-          The response on the flight time was also unsatisfactory. Perhaps it would be better to include other work that carried out and evaluated the effect of flight time and altitude.

-          The technical characteristics of the rooms must be included in the text.

Report Reviewer

Several corrections have been made to the article and I think it has been heavily revised. However, this review revealed further corrections that can be made to improve the quality of the manuscript.  Below are some suggestions:

-          Line 101-104: The unit of measurement of the plant’s density are not correct. In this case, it should be indicated in number of plants/m².

-          In the first review process I wrote: Why did you fly at a very low altitude? The answer was not satisfactory. The low acquisition altitude is not a practice that can be done on a large scale. So, these data are probably not replicable and/or reliable.

-          The response on the flight time was also unsatisfactory. Perhaps it would be better to include other work that carried out and evaluated the effect of flight time and altitude.

-          The technical characteristics of the rooms must be included in the text.

Author Response

Dear Editor and Reviewers

I am submitting here a manuscript entitled “CGI: a comprehensive indicator from UAV-observed for winter 2 wheat growth status monitoring”. Three reviewers gave us good suggestions. First, we would like to thank the reviewers for their constructive and helpful suggestions and improvements to our manuscript (agronomy-2692600). We revised the manuscript by following the suggestions of the reviewers. Our response to each suggestion or comment are given one by one in the following Pages of this letter. For details, please refer to the responses as follows (Reviewer comments are in black font, responses are in blue or red font. The location marked in the response indicated in the version of manuscript with track.

Thanks too much.

Looking forward to your favorable decision,

With best regards

Author Response File: Author Response.pdf