Simulated Climate Change Impacts on Corn and Soybean Yields in Buchanan County, Iowa

Round 1

Reviewer 1 Report (New Reviewer)

The paper is good and may provide the readers with novel information concerning climate change influences on cropping systems.

There are some points where the manuscript should be improved in favour of better understanding.

I suggest the authors to change the title inserting some words or expressions that may précise the topic - namely climate change impacts are estimated, predicted, forecasted etc - since a single study doesn't provide enough basis for determining an impact.

Regarding the crops and the cropping systems I would advise the authors to insert  Latin names of the crops, since avaerage readers may be anywhere in the world belonging to the international agric community, consequently the word "corn" would not mean the maize crop for all of them. Also, there are more species within Glycine genus in production.

The introduction of the paper is good, however it would make a benefit to give a better literature review of the problem, especially in the field of scenarios and modelling giving information on relevant IPCC results and FAO communications.

Concerning the materials and methods a much shorter and at the same time a more detailed description of the model should be presented for better understanding.

The reader is confused sometimes reading the abundant information in the results chapter. It is quite clear  that 12 scenarios from which three was chosen to be the basis for yield projections need detailed description, however these parts are to be condensed a bit focusing on the results obtained.

The conclusions are good and acceptable, however apart from climate change impacts there may be agronomic uncertainities in the future as well that may influence the predicted trends (future use of agrochemicals, technical applications, environmental concerns etc). So I suggest to indicate the uncertainity of these factors - jaust as a sort of additional information.

Finally, a thorough grammatical review would make the paper better and more edible.

Author Response

RESPONSES TO REVIEWERS’ COMMENTS

Dear Editor:

Please find below, a summary of how we addressed all reviewer comments. Our responses are in bold typeface while reviewer comments are italicized. The revised manuscript is also being submitted. We were sure to retain all our modifications in track changes mode.

Sincerely,

Authors.

Responses to Comments by Reviewer 1:

Comment 1 by Reviewer 1:

I suggest the authors to change the title inserting some words or expressions that may précise the topic - namely climate change impacts are estimated, predicted, forecasted etc - since a single study doesn't provide enough basis for determining an impact.

Response:

We appreciate the reviewers input and we have edited the title accordingly by inserting the word “Simulated” before the rest of the title.

Comment 2 by Reviewer 1:

Regarding the crops and the cropping systems I would advise the authors to insert  Latin names of the crops, since avaerage readers may be anywhere in the world belonging to the international agric community, consequently the word "corn" would not mean the maize crop for all of them. Also, there are more species within Glycine genus in production.

Response:

Very much appreciated. We have included the Latin names of the two crops.

Comment 3 by Reviewer 1:

The introduction of the paper is good, however it would make a benefit to give a better literature review of the problem, especially in the field of scenarios and modelling giving information on relevant IPCC results and FAO communications.

Response:

Thanks. We have expanded the literature review accordingly and included several IPCC and FAO citations.

Comment 4 by Reviewer 1:

Concerning the materials and methods a much shorter and at the same time a more detailed description of the model should be presented for better understanding.

Response:

Thanks. We have provided more detailed description of the APEX model, and also trimmed several other sections of the Methods section to reduce the length.

Comment 5 by Reviewer 1:

The reader is confused sometimes reading the abundant information in the results chapter. It is quite clear  that 12 scenarios from which three was chosen to be the basis for yield projections need detailed description, however these parts are to be condensed a bit focusing on the results obtained.

Response:

Thanks. We realized that the results section was a bit hard to read. It actually consists of three sections and we used section numbers to clearly distinguish between the sections in order to make it more readable. We did attempt to reduce the length of the results and discussion section. However, it appears all the material we left in there is vital to an understanding of the results. So we do not think we succeeded in reducing the length much at all. However, we can say that it is much easier to read now, since it is divided into three subsections. The description of the scenarios is also much clearer.

Comment 6 by Reviewer 1:

The conclusions are good and acceptable, however apart from climate change impacts there may be agronomic uncertainities in the future as well that may influence the predicted trends (future use of agrochemicals, technical applications, environmental concerns etc). So I suggest to indicate the uncertainity of these factors - jaust as a sort of additional information.

Response:

Thanks. We have included the appropriate language to indicate the limitations and/or caveats due to unpredictable future use of these and other inputs.

Comment 7 by Reviewer 1:

Finally, a thorough grammatical review would make the paper better and more edible.

Response:

Thanks. We went through the manuscript and did a thorough grammatical check. I believe we caught and resolved all outstanding grammar errors.

Reviewer 2 Report (New Reviewer)

The scientific article is very interesting and concerns the current research topic of the impact of climate change on the agriculture of the future. It concerns economically important crops in the state of Iowa. The state is among the largest in corn and soybean production.

In general, the obtained results are clearly presented but are of a very hypothetical nature. It is not known whether breeding and agrotechnical progress will result in a further linear increase in yields in the years 2021-2095. It is also not known whether the climate forecasts will come true and what the scenario will be.

The article has two problems:

1/ in the chapter results and discussion there are no elements of a scientific discussion consisting in confronting your own results with the literature

2/ simulations of yield changes caused only by climate change in future scenarios 2021-45, 2046-2070 and 2071-2095 are not fully explained. The authors refer to the APEX model. Not a single weather-yield relationship is given as an example.

Other formal matters:

1/ the work lacks chapter number 2

2/ line 256 and 402 - citation of literature

3/ table 1 and 2 - why provide the same information in both columns, if they differ only in 2 cases?

Author Response

Responses to Comments by Reviewer 2:

In general, the obtained results are clearly presented but are of a very hypothetical nature. It is not known whether breeding and agrotechnical progress will result in a further linear increase in yields in the years 2021-2095. It is also not known whether the climate forecasts will come true and what the scenario will be.

The article has two problems:

Comment 1 by Reviewer 2:

1/ in the chapter results and discussion there are no elements of a scientific discussion consisting in confronting your own results with the literature.

Response:

Thanks. We included several discussions that related our results specifically to existing literature to indicate how ours compares with what has already been published on this particular subject.

Comment 2 by Reviewer 2:

2/ simulations of yield changes caused only by climate change in future scenarios 2021-45, 2046-2070 and 2071-2095 are not fully explained. The authors refer to the APEX model. Not a single weather-yield relationship is given as an example.

Response:

Thanks. We appreciate the reviewer’s input and have included more careful discussion of the impacts of climate on yields while discussing Figure 4 - 6.

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

Dear authors,

I have reviewed your manuscript “Climate change impacts on corn and soybean yields in Buchanan County, Iowa” for possible publication in Agriculture. I found it very interesting, but the logic of the method part is confusing. I'm not sure why you want to analyze trends in temperature and precipitation (Fig. 1-3), which seems to have little to do with your final results, or is there a correlation that you didn't mention in your discussion. In addition, the whole article is wordy and takes away from the point of your research. I suggest you rearrange the structure of your manuscript.

Author Response

Responses to Comments by Reviewer 1:

Comment 1 by Reviewer 1:

I have reviewed your manuscript “Climate change impacts on corn and soybean yields in Buchanan County, Iowa” for possible publication in Agriculture. I found it very interesting, but the logic of the method part is confusing.

Response:

We appreciate the reviewers input and we have edited the methods section to make it more readable.

Comment 2 by Reviewer 1:

I'm not sure why you want to analyze trends in temperature and precipitation (Fig. 1-3), which seems to have little to do with your final results, or is there a correlation that you didn't mention in your discussion.

Response:

We now more clearly motivate the reason why such analysis of trends in temperature and precipitation are relevant in his context. We also cite several articles that do essentially the same thing in order to provide appropriate context for readers to understand the results.

Comment 3 by Reviewer 1:

In addition, the whole article is wordy and takes away from the point of your research. I suggest you rearrange the structure of your manuscript.

Response:

We agree that there was some repetitive content. We have reviewed the manuscript and removed redundancies. We did find some redundant text and duplicative material in the methods section and addressed them accordingly.

Author Response File: Author Response.docx

Reviewer 2 Report

This study evaluated the climate change impacts on corn and soybean yields in Buchanan County, Iowa, using the APEX model. The study is important and significant, but some revisions need to be done before the manuscript can be accepted.

General comments:

1. Section 2 Background, better move it to the introduction section. In addition, simplify the content, please.

2. What is the parameters for the calibrated APEX model, the authors could show them using a table or other means. The parameters are of interest for readers.

3. May be a discussion section should be added to the manuscript.

Specific comments:

1. Table 3, meanings of the symbols of “X” and “-” in the table should be described in the table title?

2. Figure 1, the vertical coordinate ranges of the five subplots should be consistent. Additionally, it is difficult to read the values of the dots for comparing each time period. Check all the figures as well, please.

3. Why not use the new climate projections of SSPs instead of RCPs?

4. The references are old and lack some published in recent three years.

Author Response

Responses to Comments by Reviewer 2:

Comment 1 by Reviewer 2:

This study evaluated the climate change impacts on corn and soybean yields in Buchanan County, Iowa, using the APEX model. The study is important and significant, but some revisions need to be done before the manuscript can be accepted.

Response:

Thanks. We appreciate the reviewer’s inputs.

General comments:

Comment 2 by Reviewer 2:

1. Section 2 Background, better move it to the introduction section. In addition, simplify the content, please.

Response:

We appreciate the reviewer’s input and have merged the Background material into the Introduction section.

Comment 3 by Reviewer 2:

2. What is the parameters for the calibrated APEX model, the authors could show them using a table or other means. The parameters are of interest for readers.

Response:

Again, we appreciate the reviewer’s comments and have included key APEX parameters in the new Table 6.

Comment 4 by Reviewer 2:

3. May be a discussion section should be added to the manuscript.

 Response:

We agree. We renamed the Results section Results and Discussion and provided some discussion of the results.

Specific comments:

Comment 5 by Reviewer 2:

1. Table 3, meanings of the symbols of “X” and “-” in the table should be described in the table title?

Response:

Agreed. We explained those symbols that appear in the table.

Comment 6 by Reviewer 2:

2. Figure 1, the vertical coordinate ranges of the five subplots should be consistent. Additionally, it is difficult to read the values of the dots for comparing each time period. Check all the figures as well, please.

Response:

We enlarged the figures and made them more consistent and readable.

Comment 7 by Reviewer 2:

3. Why not use the new climate projections of SSPs instead of RCPs?

Response:

The most widely available climate projections we had access to are what we used. Most studies on climate change that we are aware of used the RCPs.

Comment 8 by Reviewer 2:

4. The references are old and lack some published in recent three years.

Response:

We agree. We added at least a dozen new references that tare within the past two years, and quite a few more that are within the past three to four years.