Estimation of Maize Yield and Protein Content under Different Density and N Rate Conditions Based on UAV Multi-Spectral Images
Round 1
Reviewer 1 Report
Manuscript entitled „Estimation of Maize Yield and Protein Content Under Different Density and N Rate Conditions Based on UAV Multispectral Im-Ages” presents interesting study on UAV-based monitoring of maize for in-season prediction of grain yield and its quality. The manuscript is quite well prepared however contains some drawbacks.
1) Please write “-1” in superscript in all the manuscript, e.g. line 78
2) Line 88-89: The main aim of the experiment is evaluation of the effect of nitrogen fertilization. It would be good if content of mineral nitrogen (NH4+ and NO3- ions) were presented, not only total nitrogen. Please provide more details about methods of extraction of phosphorus and potassium.
3) Line 92: Please provide more details about the genotypes of maize used in the experiment, ie. Zhengdan 958 and Suyu 41. For example FAO number or other parameters which present length of vegetation of these genotypes. Moreover some characteristics of the plants should be presented, e.g. height of plants, cob size, etc.
4) Line 103: What was average grain moisture during harvest?
5) Please provide some information about weather conditions for study area (e.g. monthly average temperature and sum of precipitation).
6) Please provide basic information about agronomic practices in the experiment, including sowing and harvest date, plant protection, forecrop.
7) What coefficient was used for calculation of protein content based on N concentration (it was multiplied by 6.25 or other value?).
8) Please provide more details about flight parameters, e.g. altitude, front and side overlap, solar angle during flights, pixel size (at ground level).
9) Table 1: Please provide range of wavelengths together with central wavelengths.
10) Figure 1: Size of the charts is very small. I suggest to change 3 columns x 2 rows to 2 columns x 3 rows to increase size of the charts. The same comment is for Fig. 2, 3 and 4.
11) Figure 5: Please add title of vertical axis in the charts because it is not very clear what is presented in the figure. The same comment is for fig. 6 and 7.
12) It would be good if the results of PCA were presented in graphical form as biplots. It would allow to evaluate relationships between studied variables as well multivariate variability of the studied treatments.
13) Table 6: ANOVA was performed for each year separately. It would be good if the combined ANOVA was performed for both years together (year as a factor) and the mean results for both years were presented.
14) Table 7 and 8: Regression models were evaluated separately for two cultivars. Please compare the results between genotypes. It would be good if more general model was constructed which is independent on the specific cultivar.
15) Conclusions should be rewritten because should be more specific with the aim of the study. It is quite obvious that many vegetation indices are strongly correlated. I recommend to summarize in Conclusions following topics: most important vegetation index (probably NDVI?), differences between cultivars and years (it is possible to develop one model for both cultivars and both years?).
Author Response
Dear Reviewer:
Thanks for your letter and the reviewers' constructive comments concerning our manuscript entitled. Those comments are all valuable and very helpful for revising and improving our manuscript, and significantly guide our research. We have studied these comments carefully and made modifications which we hope meet with your approval. Revised portions are marked red in the manuscript. The main corrections in the manuscript and the responses to the reviewers' comments are listed below.
Comment: 1) Please write “-1” in superscript in all the manuscript, e.g. line 78
Response: We are very sorry for our careless mistake and it was rectified in the manuscript.
Comment: 2) Line 88-89: The main aim of the experiment is evaluation of the effect of nitrogen fertilization. It would be good if content of mineral nitrogen (NH4+ and NO3- ions) were presented, not only total nitrogen. Please provide more details about methods of extraction of phosphorus and potassium.
Response: Thank you very much for your suggestion. The details of P and K determination are supplemented in the text. However, because the previous experiment did not determine the content of mineral nitrogen (NH4+ and NO3- ions) and the existing conditions could not do this supplementary experiment, so the data in this aspect was not supplemented in the paper.
Comment: 3) Line 92: Please provide more details about the genotypes of maize used in the experiment, ie. Zhengdan 958 and Suyu 41. For example FAO number or other parameters which present length of vegetation of these genotypes. Moreover some characteristics of the plants should be presented, e.g. height of plants, cob size, etc.
Response: Relevant details about maize genotypes are supplemented in article Line 115-118.
Comment: 4) Line 103: What was average grain moisture during harvest?
Response: In the article, Line 124 adds relevant content.
Comment: 5) Please provide some information about weather conditions for study area (e.g. monthly average temperature and sum of precipitation).
Response: In the article, Line 106-109 adds weather related content.
Comment: 6) Please provide basic information about agronomic practices in the experiment, including sowing and harvest date, plant protection, forecrop.
Response: In the articles Line121-127 and Line129-130, the relevant contents of agricultural practice are supplemented.
Comment: 7) What coefficient was used for calculation of protein content based on N concentration (it was multiplied by 6.25 or other value?).
Response: It was multiplied by 6.25, and we added relevant content in Line 140-141 of the article.
Comment: 8) Please provide more details about flight parameters, e.g. altitude, front and side overlap, solar angle during flights, pixel size (at ground level).
Response: The relevant contents of UAV flight are supplemented in Line 146-148.
Comment: 9) Table 1: Please provide range of wavelengths together with central wavelengths.
Response: The wavelength range is 400-900nm, and the central wavelength is shown in Table 1.
Comment: 10) Figure 1: Size of the charts is very small. I suggest to change 3 columns x 2 rows to 2 columns x 3 rows to increase size of the charts. The same comment is for Fig. 2, 3 and 4.
Response: Thank you for your suggestion, and the figure is modified to ensure its resolution.
Comment: 11) Figure 5: Please add title of vertical axis in the charts because it is not very clear what is presented in the figure. The same comment is for fig. 6 and 7.
Response: Thank you for your suggestion，and the figure is modified in the article.
Comment: 12) It would be good if the results of PCA were presented in graphical form as biplots. It would allow to evaluate relationships between studied variables as well multivariate variability of the studied treatments.
Response: Thank you for your suggestion. We tried to convert PCA into the form of graph, but there are many indicators in the graph, which are relatively messy, so we finally chose the form of table.
Comment: 13) Table 6: ANOVA was performed for each year separately. It would be good if the combined ANOVA was performed for both years together (year as a factor) and the mean results for both years were presented.
Response: Thank you very much for your suggestion. According to your suggestion, we will modify Table 6 to achieve a better performance.
Comment: 14) Table 7 and 8: Regression models were evaluated separately for two cultivars. Please compare the results between genotypes. It would be good if more general model was constructed which is independent on the specific cultivar.
Response: Thank you very much for your suggestion. The comparison of the two varieties prediction models is supplemented in Line 274 and 285. At the same time, we also tried to build a general model independent of a specific variety, but the R2 of the model obtained was low.
Comment: 15) Conclusions should be rewritten because should be more specific with the aim of the study. It is quite obvious that many vegetation indices are strongly correlated. I recommend to summarize in Conclusions following topics: most important vegetation index (probably NDVI?), differences between cultivars and years (it is possible to develop one model for both cultivars and both years?).
Response: Thank you very much for your suggestion. We have made changes to the inclusion in the article, but the prediction model established by integrating the year and variety is not very effective, so it is not reflected in the article.
We would like to take this opportunity to thank you for all your time involved and this great opportunity for us to improve the manuscript. We hope you will find this revised version satisfactory.
Sincerely,
The Authors
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Manuscript, entitled (Estimation of Maize Yield and Protein Content Under Different Density and N Rate Conditions Based on UAV Multispectral Im-Ages) reported that Based on the correlation analysis, the NDVI, RVI, DVI, PPR can be used to establish the prediction model of yield and the NDVI, DVI,RVI and PSRI were effective canopy vegetation indices to predict kernel protein content. The best prediction periods for grain yield and kernel protein were physiological maturity and 35 days after silking, respectively. There are several shortcomings that should be included in order to enhance the final manuscript for the readers.
Abstract
· Line 12. Please do not use pronouns in scientific writing such as (We) in all manuscript· Line 15. Change ha-1 to ·ha-1.
· Please write the full name of spectral indices such as NDVI, RVI …. Which was presented as first time?
· Iine 17 and line 18. This sentence is not clear (The results showed that NDVI, RVI and PSRI could reflect the difference of maize growth under different treatments). Please give more details.
· In abstract, please give information about the R2 of the relationships between spectral indices and measured parameter. The abstract is more description and does not support by digital results.
· What is conclusion of the abstract?
Introduction
· More citations need to add to the sentence from line 49 to 54.
· The introduction lack of the previous studies which include the relationships between different spectral indices and grain yield and protein content. There are several studies can be used to supported this point.
· Also the authors should give the basic for using the spectral bands in Visible and near infrared region for estimate these parameters.
· what is new in your work that makes a difference in the body of knowledge? What has been done that goes beyond the existing research?
Materials and methods · Location map of this area should be added. · There was no data bout the physical, and mechanical of the soil. Please present this data in table. · Line 89. Please change kg−1 to kg−1. Please check this error in all manuscript. · Title of table 2 should be modified to include all information in the table. This table is not including only Equations of the vegetation. · What are the references of the spectral indices from A to S in table?. Or these indices are new. In this case, you can write (This work). Results · The resolutions of all figures should be improved. We cannot follow the data at the figures. Please improve them. · The title of Figures 1, 2 and 3 must be modified. This is the correlation matrix between all parameters at different growth stages. · Section 3.1. Change of vegetation index is poor written. Since the data presented in figures, the authors must present more the digital results from figure 1 to 7. · The sentence from Line 181 to line 183 must to put in discussion section. · Section 3.4. There is no information about the model was used in this study. What is calibration datasets and what is the validation datasets? Who many samples was used in calibration and for validation. Please more information need to add. · I suggest to authors to use machine learning model in this study. Discussions
· The discussion is not cover enough by previous studies. More citations should be added.
· As well as, PCA and subordinate function analysis are not cover good in discussion
· Please, write the practical applications of your work in a separate section, before the conclusions and provide your good perspectives?
Conclusions· Please write about the limitations of this work in details in conclusion section?
Author Response
Dear Reviewer:
Thanks for your letter and the reviewers' constructive comments concerning our manuscript entitled. Those comments are all valuable and very helpful for revising and improving our manuscript, and significantly guide our research. We have studied these comments carefully and made modifications which we hope meet with your approval. Revised portions are marked red in the manuscript. The main corrections in the manuscript and the responses to the reviewers' comments are listed below.
Comment: Line 12. Please do not use pronouns in scientific writing such as (We) in all manuscript. Line 15. Change ha-1 to·ha-1.
Response: We are very sorry for our careless mistake and it was rectified in the manuscript.
Comment: Please write the full name of spectral indices such as NDVI, RVI …. Which was presented as first time?
Response: Thank you very much for pointing out our mistakes and adding them in the article.
Comment: Iine 17 and line 18. This sentence is not clear (The results showed that NDVI, RVI and PSRI could reflect the difference of maize growth under different treatments). Please give more details.
Response: Line 16-20 supplements this part in the article.
Comment: In abstract, please give information about the R2 of the relationships between spectral indices and measured parameter. The abstract is more description and does not support by digital results.
Response: Thank you very much for your suggestion. We have revised and supplemented the content of abstract.
Comment: What is conclusion of the abstract?
Response: It is multi-period and multi-vegetation index can better monitor crop growth and help agricultural field management.
Comment: More citations need to add to the sentence from line 49 to 54.
Response: In the article, Line 61-70 supplements the relevant literature.
Comment: The introduction lack of the previous studies which include the relationships between different spectral indices and grain yield and protein content. There are several studies can be used to supported this point.
Response: Relevant supplements are made in line 67-70 of the article.
Comment: Also the authors should give the basic for using the spectral bands in Visible and near infrared region for estimate these parameters.
Response: Thank you very much for your suggestion Line 45-51 supplements this part in the article。
Comment: what is new in your work that makes a difference in the body of knowledge? What has been done that goes beyond the existing research?
Response: We link the change of vegetation index with the treatment to further prove the relationship between vegetation index and crop growth. A new method for evaluating crop growth is proposed by integrating multiple vegetation indexes. The prediction model of multi-period and multi-vegetation index is established to improve the prediction effect.Expand the application scope and improve the precision of UAV monitoring crop growth. Create a practical model for predicting the grain yield and protein content of summer corn.
Comment: Location map of this area should be added.
Response: The experimental location map is supplemented in the paper.
Comment: There was no data bout the physical, and mechanical of the soil. Please present this data in table.
Response: In the article, Line 106-107 supplements the relevant content.
Comment: Line 89. Please change kg−1 to kg−1. Please check this error in all manuscript.
Response: We are very sorry for our careless mistake and it was rectified in the manuscript.
Comment: Title of table 2 should be modified to include all information in the table. This table is not including only Equations of the vegetation.
Response: We have revised the table title in the article.
Comment: What are the references of the spectral indices from A to S in table?. Or these indices are new. In this case, you can write (This work).
Response: We have added in the table.
Comment: The resolutions of all figures should be improved. We cannot follow the data at the figures. Please improve them.
Response: We have adjusted the size of the image in the article to improve its resolution.
Comment: The title of Figures 1, 2 and 3 must be modified. This is the correlation matrix between all parameters at different growth stages.
Response: Modify the title of the figure in the article.
Comment: Section 3.1. Change of vegetation index is poor written. Since the data presented in figures, the authors must present more the digital results from figure 1 to 7.
Response: The content of vegetation index change is supplemented in Line 192-203.
Comment: The sentence from Line 181 to line 183 must to put in discussion section.
Response: Thank you very much for your suggestion. Modifications have been made.
Comment: Section 3.4. There is no information about the model was used in this study. What is calibration datasets and what is the validation datasets? Who many samples was used in calibration and for validation. Please more information need to add. I suggest to authors to use machine learning model in this study.
Response: Thank you very much for your suggestion. In the article, Line 264-274 supplements the content of the prediction model. However, because we lack knowledge of machine learning, we can not use machine learning to model.
Comment: The discussion is not cover enough by previous studies. More citations should be added.
Response: We supplement the references in the discussion section of the article.
Comment: As well as, PCA and subordinate function analysis are not cover good in discussion.
Response: Thank you very much for your suggestion. We will adjust and supplement the discussion of PCA and subordinate function analysis.
Comment: Please, write the practical applications of your work in a separate section, before the conclusions and provide your good perspectives?
Response: Line350-358 adds relevant content in the article.
Comment: Please write about the limitations of this work in details in conclusion section?
Response: Thank you very much for your suggestion, and we have added to the conclusion section in the article.
We would like to take this opportunity to thank you for all your time involved and this great opportunity for us to improve the manuscript. We hope you will find this revised version satisfactory.
Sincerely,
The Authors
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The manuscript was corrected according almost all my comments. It is strange that authors replied in Chinese language, not in English, but I have translated their replies. The manuscript still requires minor corrections, ie. references are not formated according guidelines for authors.
Author Response
Dear Reviewer:
Thanks for your letter and the reviewers' constructive comments concerning our manuscript entitled. I'm very sorry that the reply provided to you earlier is in Chinese. Revised portions are marked red in the manuscript. The main corrections in the manuscript and the responses to the reviewers' comments are listed below.
Comment: The manuscript still requires minor corrections, ie. references are not formated according guidelines for authors.
Response: Thank you very much for pointing out our mistakes and we have revised the format of the references in the article.
We would like to take this opportunity to thank you for all your time involved and this great opportunity for us to improve the manuscript. We hope you will find this revised version satisfactory.
Sincerely,
The Authors
Author Response File: Author Response.pdf
Reviewer 2 Report
1- The introduction is still lack of the previous studies which include the relationships between different spectral indices and grain yield and protein content. The authors did not cover this point as it is.
2- The resolution of location map in figure 1 of this area should be improved.
3- The authors are not covering this point. There was no data bout the physical, and mechanical of the soil. Please present this data in table.
4- Table 2. Should be (Vegetation indices, formulas, and references used in this study).
Author Response
Dear Reviewer:
Thanks for your letter and your constructive comments concerning our manuscript entitled. Those comments are all valuable and very helpful for revising and improving our manuscript, and significantly guide our research. We have studied these comments carefully and made modifications which we hope meet with your approval. Revised portions are marked red in the manuscript. The main corrections in the manuscript and the responses to the reviewers' comments are listed below.
Comment: The introduction is still lack of the previous studies which include the relationships between different spectral indices and grain yield and protein content. The authors did not cover this point as it is.
Response: Thank you very much for your suggestion. In Line 67-73, we add the relevant content of previous studies on the relationship between vegetation index and yield and protein content.
Comment: The resolution of location map in figure 1 of this area should be improved.
Response: We are very sorry for our careless mistake and modified image resolution.
Comment: The authors are not covering this point. There was no data bout the physical, and mechanical of the soil. Please present this data in table.
Response: We added relevant content in Line 109-110.
Comment: Table 2. Should be (Vegetation indices, formulas, and references used in this study).
Response: Thank you very much for your suggestion and we are interested in Table 2 The title of has been revised.
We would like to take this opportunity to thank you for all your time involved and this great opportunity for us to improve the manuscript. We hope you will find this revised version satisfactory.
Sincerely,
The Authors
Author Response File: Author Response.pdf
