Analysis of Relationship between Soybean Relative Maturity Group, Crop Heat Units and ≥10 °C Active Accumulated Temperature

Round 1

Reviewer 1 Report

This journal is an international journal, and terms, like ≥10C AAT, need to be well defined for the reading audience. 

The calculation of Crop Heat Units (CHU) is adequately described.

Relative Maturity Group (RMG) needs a definition.  Most of the discussion refers to maturity groups (MG), but the regression is on RMG.  The relationship between the two needs to be clear, especially how the “relative” is calculated.

The calculation of ≥10C AAT is not described.  At face value ≥10C AAT looks remarkably similar to GDD (growing degree days) which is very well documented in the literature.  If ≥10C AAT is actually a synonym for GDD, this needs to be stated clearly.  The regression models clearly show that the core information from CHU and ≥10C AAT are different measurements of the same phenomenon.  Without information about how ≥10C AAT is calculated it is impossible for the reader to comprehend the true value of this study.

It is improper to start a sentence with a number or symbol.  If it is necessary to start a sentence with ≥10C AAT, it should be abbreviated to, for instance, AAT; and that term then used in the text to refer to ≥10C AAT.

Author Response

Response to reviewer 1

Thank you very much for all the comments. The authors have revised the manuscript (agronomy-1707940) thoroughly according to your valuable suggestions. Our revisions (addition, deletion or replacement) are highlighted in yellow in the manuscript. We believe that the revised manuscript has been improved greatly and is in a much better shape.

1. This journal is an international journal, and terms, like ≥10C AAT, need to be well defined for the reading audience. 

Response: The authors agreed with reviewer’s valuable suggestion. In the introduction section, the authors have defined≥ 10℃ AAT as “≥ 10℃ active accumulated temperature (≥ 10℃ AAT) refers to the sum of daily active temperature (daily average temperature ≥ 10℃) in a certain period of time or a certain growing season of crops. The index is most widely used in main production region in China, including Heilongjiang, northeastern Inner Mongolia and other places. Breeders and farmers used ≥ 10℃ AAT to describe the heat requirement and determine the adaptation zone of each cultivar in these regions.” In the data and methods section, the formula for calculating AAT is given as “AAT was calculated from the daily average temperature in each of the of the 95 sites using the following formula [3]:

AAT =  (if ,  AAT = 0.0)                       (3)                                               

Where n is the number days for growth, Ti is the average temperature for the ith day, B is the base temperature for soybean growth which is 10℃ commonly. AAT value of each year was calculated as the sum of average daily AAT all through the year and the AAT value of each site in Northeast China is 30-year average..” 

2. The calculation of Crop Heat Units (CHU) is adequately described.

Response: Thanks for your valuable suggestions. The calculation of Crop Heat Units (CHU) is given in the data and methods section as “Average daily CHU was then computed from the daily temperature normals in each of the 95 sites using the following formula [1] and [2]:

where Ymax and Ymin are the contributions to CHU from average daily maximum (Tmax) and minimum (Tmin) air temperatures, respectively.

Then, average daily CHU = (Ymax + Ymin) / 2.0

CHU value of each year was calculated as the sum of average daily CHU all through the year and the CHU value of each site in Northeast China is 30-year average.”

3. Relative Maturity Group (RMG) needs a definition. Most of the discussion refers to maturity groups (MG), but the regression is on RMG.  The relationship between the two needs to be clear, especially how the “relative” is calculated.

Response: Thanks for your good suggestion. The authors have revised the explanation of RMG as “ The relative MG (RMG) is as graduations within a MG by being exact to one digit decimal of MG value. For the MG later than MG 0.0, RMG is as the precise MG by adding a decimal to MG value. For example, a cultivar with RMG of 5.6. For the MG prior to MG 0, for instance MG 00.5 is corresponding to RMG -0.5. In order to precisely quantify them, negative expressing of RMG values were used for the rating system. RMG of -1.1 to -2.0 , -0.1 to -1.0 were corresponding to MG 000.9-MG 000.0, MG 00.9- MG 00.1, respectively. RMG with continuously digitalized value is convenient for model construction and data analysis.”

4. The calculation of ≥10C AAT is not described. At face value ≥10C AAT looks remarkably similar to GDD (growing degree days) which is very well documented in the literature.  If ≥10C AAT is actually a synonym for GDD, this needs to be stated clearly.  The regression models clearly show that the core information from CHU and ≥10C AAT are different measurements of the same phenomenon.  Without information about how ≥10C AAT is calculated it is impossible for the reader to comprehend the true value of this study.

Response: The reviewer has a great point. The authors have added the calculation formula of ≥10C AATin the data and methods section as “AAT was calculated from the daily average temperature in each of the of the 95 sites using the following formula [3]:

AAT =  ((if ,  AAT = 0.0)                       (3)                                               

Where n is the number days for growth, Ti is the average temperature for the ith day, B is the base temperature for soybean growth which is 10℃ commonly. AAT value of each year was calculated as the sum of average daily AAT all through the year and the AAT value of each site in Northeast China is 30-year average..” 

 AAT is different from GDD (growing degree days). AAT is the sum of daily average temperature ≥ 10℃during the growth period., whereas GDD is the sum of daily average temperature minus base temperature during the growth period. The formula of GDD is as follows, 

GDD=  (if ,  GDD = 0.0)  

Where n is the number days for growth, Ti is the average temperature for the ith day, B is the base temperature for soybean growth.

5. It is improper to start a sentence with a number or symbol. If it is necessary to start a sentence with ≥10C AAT, it should be abbreviated to, for instance, AAT; and that term then used in the text to refer to ≥10C AAT.

Response: Thanks for your valuable suggestions. The authors have replaced ≥10C AAT with AAT throughout the manuscript.   

Author Response File: Author Response.docx

Reviewer 2 Report

In this MS the authors carried out an analysis of different indexes related to soybean development in a variety of environments. In my opinion, those indicators are all related to temperature which is just a part of the environmental requirements of soybean. However, because those indexes are used in different parts of the world, it is interesting the approach to comparing varieties worldwide. The MS is well written but maybe a better description of each parameter is necessary. Moreover, I have some comments, questions and suggestions which are listed afterwards:

• Lines 43-46: I do not understand the sentence. How is it related whith the text before?
• Lines 57-59: It sounds as if this work was in Canada. Maybe you can mention that as an example or complete the sentence with something like "and could be important in other regions".
• Line 83: I don't understand why the author uses the word "experiment". No experiments are described afterwards, only the extraction of data from a database.
• Lines 85-88: Please combine these two sentences in only one.
• Lines 102-104: How did the authors calculated the CHU?
• Line 112 – Figure 1: The size of the region of interest should be higher. Moreover, it is not necessary such long arrow.
• Lines 115-119: I suggest to include this section before the description of the "experiments".
• Lines 147-149: The same information is found in the text and table 1, it must appear only once.
• Lines 157-159: This sentence is unnecessary
• Lines 159-161: revise the wording.
• Lines 166-168: Isn't that an obvious result since the CHU is calculated from the temperatures just like the >10°C AAT?
• Lines 190-206: This information must be in the introduction section because it is necessary to understand why the authors calculated all those indexes.
• Lines 212-213: Were these parameters included in the CHU calculation? Why did the authors mention these variables at this point for the first time?
• Lines 259-260: There are 3 supplementary tables but only one is described here.

Author Response

Response to reviewer 2

Thank you very much for all the comments. The authors have revised the manuscript (agronomy-1707940) thoroughly according to your valuable suggestions. The detailed changes from the original manuscript are shown in italics and documented below. Our revisions (addition, deletion or replacement) are highlighted in yellow in the manuscript. We believe that the revised manuscript has been improved greatly and is in a much better shape for publication.

In this MS the authors carried out an analysis of different indexes related to soybean development in a variety of environments. In my opinion, those indicators are all related to temperature which is just a part of the environmental requirements of soybean. However, because those indexes are used in different parts of the world, it is interesting the approach to comparing varieties worldwide. The MS is well written but maybe a better description of each parameter is necessary. Moreover, I have some comments, questions and suggestions which are listed afterwards:

1. Lines 43-46: I do not understand the sentence. How is it related whith the text before?

Response: Thanks for your valuable suggestions. In line 43-46, the definition and application range of ≥ 10℃ active accumulated temperature (≥ 10℃ AAT) are described. Since in the text before illustrated the Northeast China occupies a large proportion of soybean planting area and play an important role in soybean production, and due to the climate condition, relatively low average temperature and short frost-free period in the Northeast China, heat is the limit factor for soybean growth in this area. The authors have revised the sentence and clarified the connection of these sentences as “Heilongjiang and northeastern Inner Mongolia have relatively low average temperature and short frost-free period compared with other soybean producing region and therefore heat is the limiting factor for soybean adaptation, growth and yielding in these regions [4], therefore an index for evaluating the heat condition of location and heat requirement of variety is of necessity, and it facilitates to determine the suitable adaptation area of each cultivar. ≥ 10℃ active accumulated temperature (≥ 10℃ AAT), is most widely used in main production region in China, including Heilongjiang, northeastern Inner Mongolia and other places, refers to the sum of daily active temperature (daily average temperature ≥ 10℃) in a certain period of time or a certain growing season of crops [1, 5, 6]. Breeders and farmers used ≥ 10℃AAT to describe the heat requirement and determine the adaptation zone of each cultivar in these regions.”

2. Lines 57-59: It sounds as if this work was in Canada. Maybe you can mention that as an example or complete the sentence with something like "and could be important in other regions".

Response: The reviewer has a great point. The authors have revised the sentence as “CHU is an important index to evaluate the suitability of soybean varieties for production in various regions of Canada and could be important in other regions [11].”  

3. Line 83: I don't understand why the author uses the word "experiment". No experiments are described afterwards, only the extraction of data from a database.

Response: This is a very valuable suggestion. The authors have revised it to data 1 and data2 in the text, and revised “experimental design and data collection” to “data collection”.

4. Lines 85-88: Please combine these two sentences in only one.

Response: Thanks for your good suggestion. The authors have combined these two sentences in only one, “ The RMGs of 395 soybean varieties were identified in our previous study, which included varieties from Heilongjiang, Jilin, Liaoning and Northeast Inner Mongolia [17, 13], and 181, 120, 60, and 34 varieties were originated in Heilongjiang, Jilin, Liaoning, and northeastern Inner Mongolia respectively.”

5. Lines 102-104: How did the authors calculated the CHU?

Response: Thanks for your valuable suggestions. CHU is the average of the contributions to CHU from average daily maximum air temperatures (Ymax) and minimum air temperatures (Ymin).In terms of Ymax, if average daily maximum air temperature (Tmax) <= 10.0, Ymax = 0.0; If Tmax> 10.0, Ymax = 3.33 (Tmax – 10.0) – 0.084 (Tmax – 10.0)² ;In terms of Ymin, if average daily minimum air temperatures Tmin < =4.44, Ymin = 0.0; if Tmin> 4.44, Ymin = 1.8 (Tmin – 4.44).

6. Line 112 – Figure 1: The size of the region of interest should be higher. Moreover, it is not necessary such long arrow.

Response: Thanks for your valuable suggestions. The authors have revised Figure 1.

7. Lines 115-119: I suggest to include this section before the description of the "experiments".

Response: The reviewer has a great point. The authors have included this section as claculation before the description of the "experiments".

8. Lines 147-149: The same information is found in the text and table 1, it must appear only once.

Response: Thanks for your comments. The authors have deleted it in the text, and revised it as “The ≥ 10℃ AAT for MG 000-00, MG 0, MG I, MG II and MG III were listed in Table 1.” 

9. Lines 157-159: This sentence is unnecessary

Response: The reviewer has a great point. The authors have deleted this sentence.

10. Lines 159-161: revise the wording.

Response: The reviewer has a great point. The authors have revised “Annual ≥ 10℃ AAT ranged from about 1646℃ to 3736℃, and that for CHU were from 2293 to 4763 (Supplementary Table S3). Negative relationships between CHU and latitude, between ≥ 10℃ AAT and latitude were found, and R2 were 62.06% and 53.51%, respectively.” 

11. Lines 166-168: Isn't that an obvious result since the CHU is calculated from the temperatures just like the >10°C AAT?

Response: Thanks for your comments. The authors agreed that both CHU and AAT are calculated with temperature. Temperature are higher in lower latitude and temperature shared a negative relationship with latitude, therefore CHU and AAT have negative relationships with latitude of sites. The authors have added “This attributed to the temperature have a negative relationship with latitude of sites.”      

12. Lines 190-206: This information must be in the introduction section because it is necessary to understand why the authors calculated all those indexes.

Response: Thanks for your comments. The authors have moved this paragraph to the introduction section and integrated the content in the introduction in the revised manuscript.

13. Lines 212-213: Were these parameters included in the CHU calculation? Why did the authors mention these variables at this point for the first time?

Response: Thanks for your comments. These parameters were not included in the CHU calculation. It is because in the discussion section, we discussed factors influenced CHU, in the result section, we found latitude has an effect on CHU, besides that, other variables such as elevation and distance to ocean also influenced CHU as reported by other studies.

14. Lines 259-260: There are 3 supplementary tables but only one is described here.

Response: The reviewer has a great point. The authors have added the other 2 supplementary tables Citation in the revised manuscript.

Author Response File: Author Response.docx

Reviewer 3 Report

Dear authors,

You manuscript provides useful insight into the relationship between different methods for quantifying the effects of temperatures on soybean development. The results should be beneficial for soybean researchers and breeders, but there are some minor oversights that need to be addressed, and these are included as comments in the attached file. However, I'm not certain that this manuscript is good enough for A1Q1 journal, but that is the decision for the editor.

Best of luck!

Comments for author File: Comments.pdf

Author Response

Response to Reviewer 3

Thank you very much for all the comments. The authors have revised the manuscript (agronomy-1707940) thoroughly according to your valuable suggestions. The detailed changes from the original manuscript are shown in italics and documented below. Our revisions (addition, deletion or replacement) are highlighted in yellow in the manuscript. We believe that the revised manuscript has been improved greatly and is in a much better shape for publication.

1. Line 92: This is already written in the previous sentence.

Response: Thanks for your valuable suggestion. The authors have deleted this sentence in the revised manuscript.  

2. Line 145: Later in the manuscript R squared is expressed in %, please unify it through the text.

Response: Thanks for your comment. The authors have revised this throughout the manuscript.  

3. Line 163: This part is repetition, you have already written it in the previous sentence.

Response: Thanks for your comment. The authors have deleted this sentence in the revised manuscript.

4. Line 164: This belongs in the Discussion.

Response: Thanks for your comment. The authors have moved this sentence to the discussion section in the revised manuscript.

5. Line 174: Please specify what are those unknown places.

Response: This is a valuable question. The authors have revised the methods of geographical distribution mapping as” Geographical distribution map of annual AAT and CHU in Northeast China were constructed with ArcGIS 10.1 using ordinary kriging interpolation.”, and deleted the unknown places part.  

6. Line 177: This is incorrect, a region cannot have lower heat requirement. Higher latitude regions have less available heat, so cultivars with lower heat requirements (shorter vegetation) should be favoured. Please rephrase.

Response: The reviewer has a great point. The authors have revised the sentence as “Also the decrease of ≥ 10℃ AAT and CHU was observed with the increase of latitude in the northeastern China, suggesting that higher latitude region has lower available heat, cultivars with lower heat requirement should be favored with these regions. It provides an important reference for the selection of soybean varieties in these regions.” 

7. Line 212: Please provide a reference for this statement.

Response: Thanks for your comment. The reference is the citation No. 30 in the manuscript. The authors revised this sentence as “In addition, elevation and distance to lake or ocean also have influence on CHU [30].” 

8. Line 238: Where is this data presented? Please include it in the results.

Response: This is a valuable question. The relationship between CHU and MG identified in the current study were added in Table 1.  

9. Line 241: This explanation for the difference in CHU/MG between this study and values determined in Ontario is a bit vague...Why are early-sowing and late-harvest recommended for high yields in NE China? Does it have to do with some other limiting factors? Which ones? Or if you prefer, why do the same MG soybean cultivars have longer vegetation in NE China than in Ontario? Please elaborate.

Response: Thanks for your comment. The authors have elaborated the explanation why early-sowing and late-harvest is recommended for high yields in NE China. It is because in Northeastern China, average temperature is relatively low and short frost-free period is short, temperature is the limited factor influencing soybean yield formation. In order to adequately take advantage of active accumulated temperature, soybean is sown early in April when the temperature is low and harvested after frost. Since the sowing time is early, the emergence and growth are slow, which takes longer time for completing the growth cycle. This is the reason why the same MG soybean cultivars have longer vegetation in NE China than in Ontario. The authors deleted the second reason of photoperiod sensitivity in the original manuscript.