Spatial Variability Analysis of Wheat Nitrogen Yield Response: A Case Study of Henan Province, China

Round 1

Reviewer 1 Report

Dear Authors,

The manuscript submitted is based on the secondary data and was fitted to different ML methods and finally concluded the finding. The actual field experiment is missing. I hope the manuscript won't meet the requirement of the journal.  Thanks

Author Response

Dear Reviewer:

We thank the Reviewer for the comments. We have tried our best to revise our manuscript after reading the Reviewer’s reports. The actual field experiment (include “3414” field experiment and “three-zone demonstration” experiment) were conducted by Henan Provincial Station of Soil and Fertilizer, and we have participated in experiments design, data collect, and analyze. We also use an English editing service from MDPI for manuscripts.  

Wheat is an important grain crop in China, and understanding the spatial variation of wheat nitrogen yield is of great reference value for wheat production in China. Spatial analysis refers to the evaluation of nitrogen productivity during wheat growth at a regional scale. It involves studying how the wheat yield is influenced by the soil nitrogen content, nitrogen fertilizer application, nitrogen deposition, and soil nitrogen supply capacity. This analysis provides insights into the spatial patterns of nitrogen productivity’s influence on wheat yields, allowing for a better understanding of the factors that affect wheat yields.

The study of machine learning and map-comparison also provides new methods for analyzing the spatial distribution of wheat nitrogen yield and recommending nitrogen fertilizer usage. The results showed that the wheat nitrogen yield response was mainly concentrated around 1300-2400 kg/ha in Henan Province, with the highest values observed in the southern and eastern regions. We determined that the soil nitrogen supply capacity was pivotal in influencing the nitrogen yield response. The eastern region showed low nitrogen levels but high yields, suggesting the necessity to supplement nitrogen fertilizer based on the soil nitrogen supply capacity to maintain the soil fertility balance, which was about 120-150 kg/ha. The southern region exhibited high nitrogen levels but low yields, indicating the need to reduce nitrogen fertilizer application based on wheat nitrogen uptake and regulate soil moisture to improve the soil nitrogen mineralization rate. Thus, we suggest reducing nitrogen fertilization application by 50 kg/ha in the paddy soil region. As a result, nitrogen fertilizer management should prioritize the soil nitrogen supply capacity and wheat nitrogen uptake rather than solely relying on the soil nitrogen content during the wheat growth stage.

Once again, thank you for the suggestions to my research.

Author Response File: Author Response.pdf

Reviewer 2 Report

 Please consider the following

What are the varieties or cultivars of wheat exploited in the current study for each tested district?

How the author measure wheat productivity?, what is the harvested wheat samples per unit area were used?

There are several measures represent significant tools to measure the importance of nitrogen application such as nitrogen use efficiency, nitrogen agronomic efficiency, nitrogen utilization efficiency, nitrogen uptake. Why the author did not use one or more of them in the current study?. These parameters are useful to be compare with and validate the parameter “soil nitrogen supply capacity”

Support the introduction section and Discussion section by the importance of nitrogen for plant growth and productivity, and the importance of nitrogen rationalization. You can use the following references:

1.          https://doi.org/10.1080/00103624.2020.1744631

2.           https://doi.org/10.1080/00103624.2018.1510949

Author Response

Dear Reviewer:

Thank you very much for giving us an opportunity to revise our manuscript, and  we have studied comments carefully and conscientiously answer questions after reading the requirements. We thank the your constructive criticism that has helped us to improve our manuscript. Thank you very much again for all your help.

1. What are the varieties or cultivars of wheat exploited in the current study for each tested district?

Response: We thank the Reviewer for the constructive comment. Wheat is the main food crop in Henan Province, and the main wheat cultivars are Bainong aikang (58), Yumai (70) and Zhengmai (366) in tested district. We have added the sentence in the “Materials and Methods” section, and marked in red.

2. How the author measure wheat productivity? What is the harvested wheat samples per unit area were used?

Response: Thanks for the Reviewer’s careful comment. During the wheat’s mature period, a square meter (1m×1m) were collected to estimate spike number m^-2, grain number per spike m^-2, 1000-grain weight, and grain yield ha^-1. The calculation formula is as follows:

Wheat yield (kg/ha)= spike number×grain number per spike×1000-grain weight

We used 10 quadrats (1m×1m) to estimate wheat production per unit area (667 m²). The soil and plant samples were collected in each quadrat, separately. The plant samples included stem leaves and grains. The calculation formula was added in the “Materials and Methods” section, and marked in red.

3. There are several measures represent significant tools to measure the importance of nitrogen application such as nitrogen use efficiency, nitrogen agronomic efficiency, nitrogen utilization efficiency, nitrogen uptake. Why the author did not use one or more of them in the current study?These parameters are useful to be compare with and validate the parameter“soil nitrogen supply capacity”

Response: According to the Reviewer's good instruction, we have added the parameter “wheat nitrogen uptake” in the "Results" section and marked in red. The spatial distribution of the soil nitrogen supply capacity and wheat nitrogen uptake under the recommended nitrogen fertilization had the same trend (Fig. 11 ). The highest value was observed in the eastern region, and the lowest was in southern region. The soil nitrogen supply capacity and wheat nitrogen uptake mainly concentrated around 105-150 kg N/ha and 2.2-2.6 kg/100kg, respectively.  

Figure 11. Spatial distribution characteristics of soil nitrogen supply capacity and wheat nitrogen uptake.

Note: a: soil nitrogen supply capacity; b: wheat nitrogen uptake.

4. 4. Support the introduction section and Discussion section by the importance of nitrogen for plant growth and productivity, and the importance of nitrogen rationalization. You can use the following references:(1) https://doi.org/10.1080/00103624.2020.1744631,(2) https://doi.org/10.1080/00103624.2018.1510949.

Response: Thanks for the Reviewer’s constructive comment. We have read the two references, which showed the importance of nitrogen for plant growth and productivity, and the importance of nitrogen fertilization rational application. The references can explain our results in a deeper way, so we cited the references in the “Introduction” and “Discussion” section. They are better for our manuscripts, thank you a lot.

In the “Introduction” section, Saudy et al. (2020) showed that nitrogen use rationalization significantly enhanced wheat yield and its components for production by 2-year field experiment. Lower nitrogen application promotes soil mineralization and nitrogen use efficiency for crop growth (Saudy et al. 2018), which is directly related to the soil nitrogen supply capacity. Saudy et al. (2020) showed that reducing applied nitrogen fertilizer by 25% could enhance nitrogen use efficiency to about 60%, so it is crucial to implement nitrogen fertilizer reduction and efficiency enhancement technologies in Henan Province.

In the “Discussion” section, we should adapt nitrogen fertilization amounts to soil factors and wheat demand, which would not only improve nitrogen fertilizer use efficiency but also reduce nitrogen environmental pollution (Saudy et al. 2018).  

Once again, thank you very much for your comments and suggestions.

Author Response File: Author Response.docx

Reviewer 3 Report

Please refer to the track changes in the manuscript

Comments for author File: Comments.pdf

Minor corrections required

Author Response

Dear Reviewer:

Thank you very much for giving us an opportunity to revise our manuscript, and  we have studied comments carefully and conscientiously answer questions after reading the requirements. We also use an English editing service from MDPI. We thank the your constructive criticism that has helped us to improve our manuscript. Thank you very much again for all your help.

1. 1. Predominant factor ……..(controlling wheat grain production) . Please complete.

Response: Thanks for the Reviewer’s constructive comment. We have completed the sentence and marked in red. Upon comparing the spatial distribution of soil nitrogen content, nitrogen fertilizer, and nitrogen deposition, we found that soil nitrogen supply capacity emerged as the predominant factor for controlling wheat grain production.

2. 2. Could you please define the N supply capacity?

Response: We are sorry that we did not show clearly about N supply capacity. We have defined the N supply capacity in the “Introduction” section and marked in red. The soil nitrogen supply capacity refers to the inherent ability of the soil to provide a sustainable supply of nitrogen to crops, which can be expressed by the crop’s nitrogen uptake without nitrogen fertilization.

3. 3. “valuable information” is too generic. Please be specific about the information that you intend to generate through this study.

Response: Thanks for the Reviewer’s constructive comment. We have added the specific information through this study. The aim of this investigation is to reduce the application of nitrogen fertilization to save input costs and enhance the nitrogen use efficiency without negatively affecting grain yields, as well as reduce adverse environmental impacts.

4. 4. Kindly explain the “ value of nitrogen fertilizer management” What is it?

Response: We are sorry that we did not express clearly. The nitrogen fertilizer management was an experiment ("three-zone demonstration" experiment), which was carried out in 2010 in Henan Province. This experiment can predict the nitrogen fertilizer application and wheat nitrogen uptake more accurately due to the amounts of experiment sites (n=2277). According to the Reviewer's good instruction, we have revised the “ value of nitrogen fertilizer management” into “ value of nitrogen fertilizer application” in the “Materials and Methods” section and marked in red.

5. 5. Explain hm²is it Per m²?

Response: Thanks for the Reviewer’s comment. During the wheat’s mature period, a square meter (1m×1m) were collected to estimate spike number m^-2, grain number per spike m^-2, 1000-grain weight, and grain yield ha^-1. The calculation formula is as follows:

Wheat yield (kg/ha)= spike number×grain number per spike×1000-grain weight

1ha=10000 m²

6. 6. Plant N content ? if so the stage of growth and how it was measured.

Response: Thanks for the Reviewer’s comment. We have revised this sentence and marked in red. The wheat nitrogen uptake was measured by stem leaf and grain nitrogen content during wheat’s mature period under no nitrogen fertilization and recommended nitrogen fertilization. Soil nitrogen capacity refers to the wheat nitrogen uptake during wheat’s mature period under no nitrogen fertilization.

7. 7. Better say three yield field levels and define the three levels.

Response: We thank the Reviewer for the constructive comment. We have defined the three levels in the “Results” section and marked in the red. There was no significant correlation between wheat nitrogen yield response and wheat yields under low, medium, and high yield levels, respectively.  Note: a: low yield fields (wheat yield≤ 5250 kg/ha); b: medium yield fields (5250 kg/ha

8. 8. Please explain weather all the 729 data points were used (mean N yield response) or only the minimum and maximum data points were used to derive wheat N yield response.

Response: Thanks for the Reviewer’s careful comment. We used all the 729 data points to derive wheat nitrogen yield response. The average nitrogen yield response was 1662 kg/ha, and the standard error was 37.

9. 9. Please enlarge the font in legends. They are hardly visible. You may need to include the specific legend for the Fig 6 (a). Fig 6 (a) does not contain three highest value ranges shown in the legend.

Response: Thanks for the Reviewer’s constructive comment. We have enlarged the font in legends, and we made the specific legend for Fig 6 (a).

Figure 6. Spatial distribution characteristics of wheat yield and wheat nitrogen yield response.

Note: a: wheat yield under none-nitrogen fertilization; b: wheat yield under recommended fertilization; c: wheat nitrogen yield response.

10. 10. Please set the texts in legends more visible.

Response: Thanks for the Reviewer’s constructive comment. We have enlarged the font in legends for the Fig 7.

Figure 7. Spatial distribution characteristics of soil nitrogen content.

Note: a: TN in 1980; b: TN in 2010; c: TN change from 1980 to 2010. TN: soil total nitrogen.

11. 11. Please make the legend texts visible.

Response: Thanks for the Reviewer’s constructive comment. We have enlarged the font in legends for the Fig 9.

Figure 9. Spatial distribution characteristics of nitrogen fertilization.

12 and 13. Could you please provide the number of observations for the two variables.

Response: We thank the Reviewer for the constructive comment. The number of observations sites for wet and dry nitrogen deposition was 1807 and 43, respectively. (Zhu et al. 2015; Jia et al. 2016). We have added this sentence in the “Materials and Methods” section and marked in red.

14. 14. Varied?

Response: According to the other Reviewer's suggestion, we have deleted this sentence.

15. 15. This statement seems supported only by Fig 11. Fig 12talks about the variation among soil types.

Response: We thank the Reviewer for the constructive comment. We have revised the statement by Fig 11. The spatial distribution of the soil nitrogen supply capacity and wheat nitrogen uptake under the recommended nitrogen fertilization had the same trend (Fig. 11 ). The highest value was observed in the eastern region, and the lowest was in southern region. The soil nitrogen supply capacity and wheat nitrogen uptake mainly concentrated around 105-150 kg N/ha and 2.2-2.6 kg/100kg, respectively. We have deleted Fig. 12 in this section.

16. 16. Kindly provide the reference from text for this number.

Response: We thank the Reviewer for the constructive comment. This number of wheat nitrogen uptake was calculated combine Fig11(b) and Table 3. The average of wheat nitrogen uptake was  165 kg/ha (2.4 kg/100kg×6881 kg/ha) in 2010, and the soil nitrogen content increased by 345 kg/ha.

17. 17. Is regulating the temperature is feasible?

Response: According to the Reviewer's good instruction, we have deleted the “temperature” in the sentence. Therefore, we could improve the soil nitrogen mineralization rate by regulating soil moisture under different soil types.

18. 18. Should incorporate this table into the discussion part?

Response: We thank the Reviewer for the constructive comment. We have put Table 4 in the “Results” section, which reflects the correlation coefficient between soil nitrogen supply capacity and environmental factors in eastern region (high yield fields). As seen in Table 4, precipitation and temperature had a notable positive correlation with the soil nitrogen supply capacity.

Once again, thank you very much for your comments and suggestions.

Author Response File: Author Response.pdf

Reviewer 4 Report

 Excessive application of nitrogen fertilizer and low utilization efficiency of nitrogen fertilizer have always been problems in agricultural production in China.Wheat is an important grain crop in China, and understanding the spatial variation of wheat nitrogen yield is of great reference value for wheat production in China.Henan Province is the main wheat producing area in China, and it has been selected as the research object, which is quite representative.This study uses machine learning methods to analyze the spatial variation of nitrogen yield in wheat in Henan Province, and analyzes the influencing factors on nitrogen yield in wheat production, providing a reference for the scientific application of nitrogen fertilizer.The study of machine learning and graph comparison methods also provides new methods for analyzing the spatial distribution of wheat nitrogen yield and recommending nitrogen fertilizer usage.

My suggestion is:

When studying the spatial variation of nitrogen yield in wheat, variety factors are included.

My suggestion is that the manuscript is suitable for publication.

 Excessive application of nitrogen fertilizer and low utilization efficiency of nitrogen fertilizer have always been problems in agricultural production in China.Wheat is an important grain crop in China, and understanding the spatial variation of wheat nitrogen yield is of great reference value for wheat production in China.Henan Province is the main wheat producing area in China, and it has been selected as the research object, which is quite representative.This study uses machine learning methods to analyze the spatial variation of nitrogen yield in wheat in Henan Province, and analyzes the influencing factors on nitrogen yield in wheat production, providing a reference for the scientific application of nitrogen fertilizer.The study of machine learning and graph comparison methods also provides new methods for analyzing the spatial distribution of wheat nitrogen yield and recommending nitrogen fertilizer usage.

My suggestion is:

When studying the spatial variation of nitrogen yield in wheat, variety factors are included.

My suggestion is that the manuscript is suitable for publication.

Author Response

Dear Reviewer:

We thank the Reviewer for the very positive comments. We also use an English editing service from MDPI. According to the Reviewer's good instruction, we have added the information of wheat cultivars in the “Materials and Methods” section and marked in red. Wheat is the main food crop in Henan Province, and the main wheat cultivars are Bainong aikang (58), Yumai (70) and Zhengmai (366).

In Henan Province, the amount of fertilizer applied reached 935 kg/ha in 2011, far exceeding the internationally recognized safe limit of 225 kg/ha, and nitrogen use efficiency is as low as 30% in some areas. Therefore, in the initial study, we discussed the main influence factors nitrogen fertilization application and soil nitrogen supply capacity to wheat yield with the spatial patterns, but neglected the discussion of wheat cultivars. According to the Reviewer's good instruction, we will combine wheat cultivars and nitrogen fertilization application in different yield regions next step, and show the nitrogen fertilization application suggestions for all the wheat cultivars in Henan Province.

Once again, thank you very much for your affirmation.

Author Response File: Author Response.pdf

Reviewer 5 Report

Comments for author File: Comments.pdf

Author Response

Dear Reviewer:

Thank you very much for giving us an opportunity to revise our manuscript, and  we have studied comments carefully and conscientiously answer questions after reading the requirements. We thank the your constructive criticism that has helped us to improve our manuscript. Thank you very much again for all your help.

1. 1. Line 39-40. This sentence is not clear. Is talking about total or mineralized nitrogen? What do you mean by derivative?

Response: We are sorry that we did not express clearly. We are talking about the source of plant total nitrogen, and we have revised the sentence in Line 39-40. According to Ju et al. (2002), approximately 45% of wheat nitrogen uptake came from nitrogen fertilizer while the other 55% of from soil nitrogen mineralization during mature period. However, soil nitrogen mineralization is also affected by the quantity of nitrogen fertilizer applied throughout wheat growth.

2. 2. Does this annual nitrogen deposition include dry and wet deposition?

Response: Thanks for the Reviewer’s careful comment. This annual nitrogen deposition include dry and wet deposition. Additionally, several studies have demonstrated that atmospheric deposition (dry and wet) contributes 80-90 kg N/ha per year in North-Central China, which also influences wheat production.

3. 3. Line 48-49. What about biological nitrogen fixation? Have estimates been made?

Response: Thanks for the Reviewer’s constructive comment. We added biological nitrogen fixation in Line 48-49 and marked in red. Li et al. (2020) showed soil biological nitrogen fixation of about 63 kg N/ha per year in Henan Province, but the value was less than nitrogen deposition. We can also think of biological nitrogen fixation as a part of soil nitrogen supply capacity, when the value is equal to the actual nitrogen by wheat uptake. Thus, we used nitrogen fertilizer, soil nitrogen content, soil nitrogen supply capacity, and nitrogen deposition to determine the main factor affecting wheat production.

4. 4. Line 54-56. If one of the justifications is the importance of making an efficient application of

nitrogen, it is important to give an idea of how inefficient the application is currently, and how

efficient can it be.

Response: According to the Reviewer's good instruction, we have added the sentence in Line 54-56. The amount of fertilizer applied reached 935 kg/ha in 2011, far exceeding the internationally recognized safe limit of 225 kg/ha, and nitrogen use efficiency is as low as 30% in some areas. Saudy et al. (2020) showed that reducing applied nitrogen fertilizer by 25% could enhance nitrogen use efficiency to about 60%, so it is crucial to implement nitrogen fertilizer reduction and efficiency enhancement technologies in Henan Province.

5. 5. Line 60. Other related factors, like which ones?

Response: Thanks for the Reviewer’s constructive comment. It involves studying how the wheat yield is influenced by the soil nitrogen content, nitrogen fertilizer application, nitrogen deposition, and soil nitrogen supply capacity.

6. 6. Line 63-65. The objective of the work should go beyond just providing valuable information for

nitrogen management. It provides too much information, to leave the objective there.

Response: Thanks for the Reviewer’s constructive comment. The aim of this investigation is to reduce the application of nitrogen fertilization to save input costs and enhance the nitrogen use efficiency without negatively affecting grain yields, as well as reduce adverse environmental impacts.

7. 7. Line 73-75. I suggest that in addition to the local soil classification, the main soil groups according to the WRB classification to which they correspond be included. Or do all these soil types correspond to Vertisols? At least mention that the fluvo-aquic soil, which is the most dominant soil, is a Vertisiol (if so), and include some estimated percentage of its distribution.

Response: Thanks for the Reviewer’s constructive comment. We have added the WRB classification in Line 73-75 and marked in red. The dominant soil types are fluvo-aquic soil, cinnamon soil, red clay, yellow cinnamon soil, yellow-brown soil, lime concretion black soil, and paddy soil. According to WRB classification, they are categorized as Cambisols, Luvisols, and Anthrosols. The most widely distributed is fluvo-aquic soil (Cambisols), which accounts for 32% of Henan Province, and fluvo-aquic soil is mainly distributed in eastern region of Henan Province.

8. 8. Line 76. Please try to the size of the map legend (Figure 1)?

Response: Thanks for the Reviewer’s constructive comment. We have enlarged the font in legends for the Fig 1.

Figure 1. Study area.

9. 9. Line 104. Please verify “envEnvironmental”.

Response: Thanks for the Reviewer’s careful comment. We have revised “environmental” in the sentence.

10. 10. Line 229-231. Try to increase the size of the map legend (Figure 6).

Response: Thanks for the Reviewer’s constructive comment. We have enlarged the font in legends for the Fig 6.

Figure 6. Spatial distribution characteristics of wheat yield and wheat nitrogen yield response.

Note: a: wheat yield under no nitrogen fertilization; b: wheat yield under recommended fertilization; c: wheat nitrogen yield response.

11. 11. Line 243-245. Try to increase the size of the map legend (Figure 7).

Response: Thanks for the Reviewer’s constructive comment. We have enlarged the font in legends for the Fig 7.

Figure 7. Spatial distribution characteristics of soil nitrogen content.

Note: a: TN in 1980; b: TN in 2010; c: TN change from 1980 to 2010. TN: soil total nitrogen.

12. 12. Line "Wet and dry nitrogen deposition changed obviously..." Why is it obvious?

Response: We are sorry that we did not express clearly. We have revised the sentence in Line 258. Fig. 10 shows the spatial distribution characteristics of wet and dry nitrogen deposition in Henan Province. The highest values of wet and dry nitrogen deposition were observed in the northern region, and the lowest values were observed in the southwestern and southern regions.

13. 13. In Discussion section, the manuscript discussion focuses on the spatial variability of the nitrogen content.However, it is necessary to discuss (include) other variables that may influence such as the type of soil, precipitation, etc.There are two important samplings, please explore a little deeper into the temporal variability.

Response: Thanks for the Reviewer’s constructive comment. We have added the influence factors (soil types and precipitation) in the “Discussion” section and marked in red.

In the eastern region, the soil type was mainly fluvo-aquic soil, which was formed by Yellow River alluvium, and wheat yield and soil nitrogen supply capacity were mainly affected by precipitation and temperature. During wheat production, an increase in precipitation could promote water and nitrogen metabolism in wheat, which is conducive to the synthesis of nutrients and the accumulation of photosynthetic products in the grain, improving the wheat yield and protein content (Dogan et al. 2010). The nitrogen yield response was the highest in paddy soil with higher nitrogen fertilization management and soil nitrogen content, which indicated that the soil nitrogen supply capacity was low in paddy soil. Compared to fluvo-aquic soil and paddy soil, we found that the soil types also affected the nitrogen yield response, which might be related to different soil textures and nitrogen mineralization rates.

We also explore the temporal variability in the “Discussion” section and marked in red.

The level of soil nitrogen content increased significantly in the past 30 years, which indicated that there was a general enrichment in nitrogen on farmland. In Henan Province, the variation in soil nitrogen significantly differed among regions, with an obvious increase in the eastern, southwestern, and southern regions, especially in fluvo-aquic soil and paddy soil. Based on the spatial and temporal variation characteristics of soil nitrogen in Henan Province, it is recommended that different regions adopt tailored nitrogen fertilization-management practices. The strong mineralization rate of the fluvo-aquic soil region is an important basis for wheat nitrogen uptake for production, and the main driving factor is precipitation and temperature. Thus, the amount of nitrogen fertilizer application is equal to the soil nitrogen supply in this region, which is about 120-150 kg/ha. The weak mineralization rate capacity of paddy soil results in the accumulation of residual nitrogen in the topsoil layer, particularly when a substantial amount of nitrogen is applied in wheat production. Thus, the amount of nitrogen fertilizer application should equal the wheat nitrogen uptake, which is about 150 kg/ha. Based on the actual nitrogen fertilizer application (about 200 kg/ha), we suggest reducing nitrogen fertilization by 50 kg/ha in the paddy soil region.

14. 14. In Conclusions section, The conclusions are a bit short, and a bit ambiguous. "distinct patterns of wheat nitrogen" How many, which ones? "indicating the need to reduce nitrogen fertilizer application and enhance fertilization techniques to mitigate nitrogen loss" How much should be reduced (interval)? How can techniques be improved? "suggesting the necessity to supplement nitrogen fertilizer to maintain soil fertility balance" How much should be increased in this area?

Response: According to the Reviewer's good instruction, We have revised the “Conclusions” section and marked in red.

Using machine learning and map-comparison methods, we identified the influential factors of the wheat nitrogen yield response in Henan Province. The wheat nitrogen yield response was mainly concentrated around 1300-2400 kg/ha in Henan Province, with the highest values observed in the southern and eastern regions. We determined that the soil nitrogen supply capacity was pivotal in influencing the nitrogen yield response. The eastern region showed low nitrogen levels but high yields, suggesting the necessity to supplement nitrogen fertilizer based on the soil nitrogen supply capacity to maintain the soil fertility balance, which was about 120-150 kg/ha. The southern region exhibited high nitrogen levels but low yields, indicating the need to reduce nitrogen fertilizer application based on wheat nitrogen uptake and regulate soil moisture to improve the soil nitrogen mineralization rate. Thus, we suggest reducing nitrogen fertilization application by 50 kg/ha in the paddy soil region. As a result, nitrogen fertilizer management should prioritize the soil nitrogen supply capacity and wheat nitrogen uptake rather than solely relying on the soil nitrogen content during the wheat growth stage.

Once again, thank you very much for your comments and suggestions.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Dear Authors, 

I want to thank the authors who have revised their manuscripts quickly.  Henan Province is one of the major wheat-growing states in China and the spatial pattern of nitrogen productivity on wheat yield in Henan province help the policymakers to recommend nitrogen fertilizer management and its application.

The authors have improved the content of the manuscript as per the reviewer's suggestion.  Use of different machine learning software, the authors tried to validate their hypothesis. If such type of manuscript falls within the aim and scope of the journal, then I recommend accepting it in its present form. Thanks