The Influence of Aerial Hyperspectral Image Processing Workflow on Nitrogen Uptake Prediction Accuracy in Maize

Round 1

Reviewer 1 Report

The paper is very interesting and presents original results of innovative research.

The manuscript is well prepared but requires a couple of improvements. Particular attention should be paid to necessary clarifications in the Methodology chapter and additions in the Discussion chapter.

Specific suggestions and comments:

Introduction:  If "nitrogen uptake" appears in the title it seems reasonable to also mention in the "Introduction" chapter why prediction of N uptake is important.

line 110: „southern Minnesota”. Specify the country.

Line 112 : Explains the abbreviation “MN”.

Line 116: Clarify the term “conventional”, i.e. conventional according to? Clarify the term sidedress'.

Line 123-132: Specify references to the method for calculating nitrogen uptake (NU) ” as the product of the aboveground biomass and total nitrogen concentration”.

Clarify term "above ground biomass". Biomass weight, biomass area? “aboveground biomass or “aboveground dry biomass”?

Clarify differences between “nitrogen concentration”, and "total nitrogen concentration".

Tissue sample preparation: why 60 degrees, why 1 mm sieve? .  Add reference.

line 128: Two methods of N determination were used, Kjeldahl and Dumas (dry combustion). Why two, not one? Could the difference in error between the reference methods (manual and automated) affect the conclusions of the study? If so refer to this in the results and discussion.

Line 136 : „ Reso- 135 non, Inc., Bozeman, Montana, USA) … (Ronin-MX, 136 DJI, Inc., Shenzhen, China)”. Use abbreviations of country names or full names. If China then United States, but if USA then CHN.  Use ISO country code.

Line 165: “Figure 1:” change to “Figure 1.”. Applicable also to Table 1 Figure 2 and others.

Line 336:. Equation 1: “defined as follows.” Change to “defined as follows:”. Equations 3: Requires correction.

Lin 356: “Eq 1-3” . Correct the citation. As required by the publisher.

Line 392: “Resonon, Inc., Bozeman, Montana”  Add country.

Line 395: “(GDAL/OGR-contributors, 2021) “ change to “[36]”

Line 402: Add link to reference

Line 489: Use the names of phenological phases commonly used in biology and agriculture. V are used only in the US. In biological, life and agricultural sciences the standard is the BBCH scale.

If it is not possible to convert V into BBCH efficiently (e.g. in graphics). Please indicate how the value of V corresponds to BBCH. Applies to the entire manuscript, starting with the introduction.

10.1046/j.1365-3180.1997.d01-70.x

10.5073/20180906-074619

Line: 567 and  586: Figure 7 and 8: The values in the graphics are not visible, the font is too small.

Line 693:  Between Nigon et al. (2020)”. Correct the citation form.

Chapters 4.1.1; 4.1.2.; 4.1.3.; 4.1.4; 4.1.5. 4.2; 4.4, in the Discussion, do not contain references to papers by other authors.

Line 855 and 858: Citation 50 is not valid for this paragraph. The work does not concern these issues.

Line 894: “(ReSe Applications…” . Add closing brackets.

Line 947: Author Contributions: Use the publisher's requirements i.e. initials.

Line 953-957: Funding: “Minnesota Department of Agriculture” - Specify the country of the funding institution. In the case of the University of Minnesota this is stated in the affiliations, in the others it is not.

The manuscript lacks a declaration: Data Availability Statement.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

The research work is interesting and falls within the scope of the journal. There is well consistency between the title and the results of the manuscript. The write-up of the manuscript is also good. However, improvements like sentence structure and short sentences would make the manuscript more effective. The manuscript dataset certainly contains constructive information for the scientific community.
The following points may be addressed by the authors to enhance the worth of the manuscript.
Introduction:
The introduction part is well written.
Materials and Methods: 
The materials and methods are well presented. However, some points should be considered. 
I) Authors have not discussed recommended dose of nitrogen for the maize crop. Discuss recommended dose of nitrogen and cite a proper reference.
II) Write one paragraph on or briefly explain developmental stages of maize as authors have mentioned only codes of developmental stages of maize crop.
Results:
The description of the results has been done correctly.
Discussion: 
The presented discussion is correct based on the objectives of the present research study.
Conclusion:
The conclusion is also correct. However, it is too long. Reconcile it for a better understanding of the manuscript.
Specific Comments:
Line 39- Give space between reference (1-5) and necessary to derive quality image data.
Line 59- Remove the repeated references (12-15).
Line 105- Replace we also discuss the implications of findings by we also discussed the implications of findings.
Line 111- Replace The Wells experiment (43.85437, -73.72977) was conducted near Wells by The Wells experiment (43.85, -93.73) was conducted near Wells.
Line 112-What is MN and write the full abbreviations of MN?
Line 112-113- Replace Agroecology Research Farm (44.063635, -93.540281) by Agroecology Research Farm (44.06, -93.54).
Line 120-Write about V8 development stage of the maize crop.
Line 121-Also write the recommended dose of Nitrogen for maize crop.

Author Response

Please see attached.

Author Response File: Author Response.pdf

Reviewer 3 Report

The manuscript is well written. I have minor fixes only:
- line 26: subscript the -1;
- remove topics from the Introduction and make the text flowing. It is necessary to make it more dynamic;
- narrow down the conclusions. They seem more like a demonstration of results than conclusions per se.

Author Response

Comments and Suggestions for Authors

The manuscript is well written. I have minor fixes only:

- line 26: subscript the -1;

I think the reviewer meant to superscript (^-1); also, this appears ~line 30 in the current version.

- remove topics from the Introduction and make the text flowing. It is necessary to make it more dynamic;

Without more detail on what is meant exactly here, it is difficult to make the appropriate changes. Furthermore, other reviewers had positive feedback on the introduction and that it is well written.

- narrow down the conclusions. They seem more like a demonstration of results than conclusions per se.

Thanks for the feedback. Many changes were made to shorten and to make more concise (got it down from 3 paragraphs to 2).

Round 2

Reviewer 1 Report

The authors made all relevant changes to the manuscript or justified their statement convincingly.