Nitrogen Split Application Can Improve the Stalk Lodging Resistance of Maize Planted at High Density

Round 1

Reviewer 1 Report

Comments

SUMMARY

The paper addresses the research area related to “Crop Production” of the MDPI Agriculture journal. I believe that the target journal is an appropriate forum for this article. The paper aims to evaluate the effects of nitrogen application rate on the stalk lodging resistance of maize under different planting densities with integrated watering and fertilization using drip irrigation.

BROAD COMMENTS

The Introduction section is well done. The methodology is well written and detailed. I appreciate the fact that the authors did two years (seasons) trials in the study. This help to capture the variability and minimizing the experimental errors. However, the weakness of this study is that the authors failed to include detail about the ANOVA test performed in the study. Besides, the authors failed to put the conclusion of the study in a big picture; it is too specific to the study area and the experiment. Please do include more implications of the results of the study in the conclusion section.

SPECIFIC COMMENTS

Lines 15-42: The abstract is too long. I suggest the author reduce it.

Lines 105-117: The authors used 3 different plant densities in 2017 and 5 in 2018. The fact that 9.0 and 12.0 x 10⁴ plant densities were only applied in 2018, may be seen a limitation of the study because of a lack of validation. I suggest the authors mention this cleary as a limitation of the study.

 Line 170, 193, 207, 215, 227: The results presented in Figures 1-5 imply that the authors conducted ANOVA before doing the means separations using Duncan’s multiple. Since ANOVA is a parametric test, some pre-requisite tests should be conducted before it (e.g., ‘normality and homogeneity of variance). I suggest the authors include in the manuscript the detail about the statistical tests they performed on the data before doing the ANOVA.

Line 334: Author Contributions section did not inform us about what each author did in this study. Please revise this section to include the missing information.

Lines 1-439: This study lacks some pictures of the field during the experiment. I suggest the author include them in the manuscript if it is possible.

 

 

Author Response

Dear reviewer,

Thanks for the comments on our manuscript “Nitrogen split application can improve the stalk lodging resistance of maize planted at high density” (ID: agriculture-877918).

We appreciate and accept the modification suggestions and have revised the manuscript accordingly. The revised parts are shown in the red text and track changes mode in the original manuscript. The detailed responses to the reviewers’ comments are presented as follows:

SUMMARY

The paper addresses the research area related to “Crop Production” of the MDPI Agriculture journal. I believe that the target journal is an appropriate forum for this article. The paper aims to evaluate the effects of nitrogen application rate on the stalk lodging resistance of maize under different planting densities with integrated watering and fertilization using drip irrigation.

1. BROAD COMMENTS

The Introduction section is well done. The methodology is well written and detailed. I appreciate the fact that the authors did two years (seasons) trials in the study. This help to capture the variability and minimizing the experimental errors. However, (1) the weakness of this study is that the authors failed to include detail about the ANOVA test performed in the study. (2) Besides, the authors failed to put the conclusion of the study in a big picture; it is too specific to the study area and the experiment. Please do include more implications of the results of the study in the conclusion section.

Responses: Thank you very much for all useful advices.

(1) According to your suggestion, we have added more detail about the ANOVA test performed in the study. The detailed corrections are shown in Line 174-179.

(2) According to your suggestion, we have revised the conclusion of this study make it in a big picture. The detailed corrections are shown in Line 357-362.

2. SPECIFIC COMMENTS

• Lines 15-42: The abstract is too long. I suggest the author reduce it.

Responses: Yes. According to your suggestion, we have revised the abstract. The detailed corrections are shown in Line 14-32.

(2) Lines 105-117: The authors used 3 different plant densities in 2017 and 5 in 2018. The fact that 9.0 and 12.0 x 10⁴ plant densities were only applied in 2018, may be seen a limitation of the study because of a lack of validation. I suggest the authors mention this cleary as a limitation of the study.

Responses: Thank you very much. We used three different plant densities in 2017 and find some trends in these plant densities, so we reduce the density gradient from 3.0×10⁴ plants ha^-1 to 1.5×10⁴ plants ha^-1 in 2018. Five planting densities were used in 2018, namely 7.5, 9.0, 10.5, 12.0, and 13.5 × 10⁴ plants ha^-1. The planting density used by local farmers was 9.0×10⁴ plants ha^-1, and the highest grain yield were obtained at 12.0×10⁴ plants ha^-1. We have added this information in Line 111-114.

(3) Line 170, 193, 207, 215, 227: The results presented in Figures 1-5 imply that the authors conducted ANOVA before doing the means separations using Duncan’s multiple. Since ANOVA is a parametric test, some pre-requisite tests should be conducted before it (e.g., ‘normality and homogeneity of variance). I suggest the authors include in the manuscript the detail about the statistical tests they performed on the data before doing the ANOVA.

Responses: Yes. According to your suggestion, we had added more details about the statistical tests they performed on the data before doing the ANOVA. The detailed corrections are shown in Line 174-176.

(4) Line 334: Author Contributions section did not inform us about what each author did in this study. Please revise this section to include the missing information.

Responses: Yes. According to your suggestion, we had revised the Author Contributions section. The detailed corrections are shown in Line 364-368.

(5) Lines 1-439: This study lacks some pictures of the field during the experiment. I suggest the author include them in the manuscript if it is possible.

Responses: Yes. According to your suggestion, we had added some pictures of the field during the experiment. The detailed corrections are shown in Figure 1.

In addition, in previous study, we reported the joint planter applying drip tape, plastic film, punch holes and sowing by the article of “Zhang, G.Q.; Liu, C.W.; Xiao, C.H.; Xie, R.Z.; Ming, B.; Hou, P.; Liu, G.Z.; Xu, W.J.; Shen, D.P.; Wang, K.R.; Li, S.K. Optimizing water use efficiency and economic return of super high yield spring maize under drip irrigation and plastic mulching in arid areas of China, Field Crop Research. 2017, 211, 137–146.”

 

Reviewer 2 Report

The research topic undertaken by the authors is interesting and has practical application, however, the research methodology requires a number of corrections (given below and in the manuscript text). The results of the research show certain trends, but drawing conclusions is rather difficult, as these are only one-year or two-year results.

Introduction:

- The research hypothesis is unclear - what results did the authors expect in the case of applying extreme (+/-) doses of fertilization and sowing density (7.5 10⁴/13.5 10⁴/ha) in the context of integrated drip irrigation and fertilization?

Methods:

- "Experimental Design" needs to be improved and refined. In fact, these were 2 one-way experiments (this approach should be adopted throughout the work). In 2017, the following densities were used: 7.5, 10.5, 13.5 10⁴/ha, and in 2018, the densities were: 7.5, 9.0, 10.5, 12.0, 13.5 10⁴/ha. Therefore, in 2018, two additional densities were introduced (9.0 and 12.0 10⁴/ha). Please explain in the methodology the reason for this? This makes it impossible to interpret the statistical results on average over the years of research (or between the years of research). N fertilization was identical in the years of the study. The varied fertilization and density of maize plants were constant factors.

- Very high doses of N were used in the studies. Please explain in the methodology why such a dose range was adopted?

- There is a lack of information on the weather conditions in the research years. The authors provide only the long-term average, which in practice adds little to the discussion with the obtained research results. And yet the variability of weather conditions (especially the amount and distribution of rainfall at the dates of fertilizer application/irrigation) has a very large impact on the performance of fertilizers (regardless of irrigation).

- The mulch biomass also brings some nitrogen into the soil and this is available to the plants.

- There is a lack of information on plant protection products used in maize. Please complete this information.

- The methodology only briefly mentions the method of agrotechnics used in maize. One can only guess that it was a ploughless system. You should add these information.

- The results of the studies in the two years differ significantly and are not compared in these years. The third year of research would make it easier to draw conclusions and show the actual influence of experience factors on the characteristics studied. However, the one-year results should also be repeated to draw correct conclusions. This is a suggestion for future research.

Conclusions:

- This chapter needs to be improved. It should be clearly stated: which range of plant density and N fertilization turned out to be the most favorable in the research. Did it prove to be in line with the adopted hypothesis? For example, do a plant density of 12.0 10⁴/ha and a fertilization of N = 270 kg/ha promote the resistance of corn stalks? Or has some other combination of these factors proved to be beneficial?

- Then specify - up to which limit we can increase nitrogen fertilization and plant density with the use of integrated drip irrigation and fertilization technology. This is because in this way the effects of high N doses and high seeding densities can be mitigated. The above aspect is the point of this study and must be clearly emphasized.

Comments for author File: Comments.pdf

Author Response

Dear reviewer,

Thanks for the comments on our manuscript “Nitrogen split application can improve the stalk lodging resistance of maize planted at high density” (ID: agriculture-877918).

We appreciate and accept the modification suggestions and have revised the manuscript accordingly. The revised parts are shown in the red text and track changes mode in the original manuscript. The detailed responses to the reviewers’ comments are presented as follows:

1. The research topic undertaken by the authors is interesting and has practical application, however, the research methodology requires a number of corrections (given below and in the manuscript text).

Responses: Thank you very much. we have added more detail about methodology in the revised manuscript.

2. The results of the research show certain trends, but drawing conclusions is rather difficult, as these are only one-year or two-year results.

Responses: Thank you very much. Actually, soil foundation fertility in our test fields are poor, crop growth state is sensitive to fertilizer, so we can see a clear difference by set four different nitrogen fertilization rates. And we had referred to the relevant literature of previous researches, although just two-year results in this study, the trend of this study also makes sense. According to the comments of the reviewer, we’ll continue to pay attention to this issue in future studies.

3. Introduction:

- The research hypothesis is unclear - what results did the authors expect in the case of applying extreme (+/-) doses of fertilization and sowing density (7.5 10⁴/13.5 10⁴/ha) in the context of integrated drip irrigation and fertilization?

Responses: Thank you very much. We applying extreme doses of fertilization and sowing density in the context of integrated drip irrigation and fertilization expect to cover all treatments that may be used in actual production, in order to increase the scope of application of our results. We have added the hypothesis in Line 80-83, and added the more information in Line 116-118.

4. Methods:

(1) "Experimental Design" needs to be improved and refined. In fact, these were 2 one-way experiments (this approach should be adopted throughout the work). In 2017, the following densities were used: 7.5, 10.5, 13.5 10⁴/ha, and in 2018, the densities were: 7.5, 9.0, 10.5, 12.0, 13.5 10⁴/ha. Therefore, in 2018, two additional densities were introduced (9.0 and 12.0 10⁴/ha). Please explain in the methodology the reason for this? This makes it impossible to interpret the statistical results on average over the years of research (or between the years of research). N fertilization was identical in the years of the study. The varied fertilization and density of maize plants were constant factors.

Responses: Yes, you are right. We used 3 different plant densities in 2017 and find some trends in these plant densities, so we reduce the density gradient from 3.0× 10⁴ to 1.5×10⁴ plants ha^-1 in 2018. We have explained this in revised manuscript. The detailed corrections are shown in Line 113-116.

What’s more, we have added more information about the data analysis for planting density, nitrogen application rate, and their interaction effect. The detailed corrections are shown in Line 178-181.

(2) Very high doses of N were used in the studies. Please explain in the methodology why such a dose range was adopted?

Responses: Yes. At different regions, the nitrogen application rate is related to soil fertility, tillage patterns, fertilization techniques, and so on. Additionally, the N application rate is closely related to maize yield level. Our research area is located in the irrigated spring-maize area of Northwest China. In this area, the rainfall is scarce, the soil is barren, and the light resources are sufficient. In one season a year, the growth period of spring maize is as long as 160 days. The highest yield that we obtained corresponds to a planting density (12 plants m^-2), grain yield (21.55 t ha^-1), and nitrogen partial factor productivity (59.9 kg kg^-1). Populations with a high planting density require more nitrogen fertilizer to meet their growth needs. Our experimental fields using the water fertilizer integrated phase fertilization technology of drip irrigation in Xinjiang, even local farmers’ nitrogen application rate is about 300 kg ha^-1. In the studies, we adopted higher dose range in order to explore the trend of stalk lodging resistance of maize under the treatments of high nitrogen application. We have added this information in Line 117-118, and Line 120.

(3) There is a lack of information on the weather conditions in the research years. The authors provide only the long-term average, which in practice adds little to the discussion with the obtained research results. And yet the variability of weather conditions (especially the amount and distribution of rainfall at the dates of fertilizer application/irrigation) has a very large impact on the performance of fertilizers (regardless of irrigation).

Responses: Yes. According to your suggestion, we have added the precipitation and air temperature during the 2017 and 2018 growing seasons. And compared the weather conditions with historical averages. The detailed corrections are shown in Table 1.

What’s more, rainfall is little in Xinjiang, and we never fertilize and irrigate on rainy days, so there is no case mentioned by the reviewer.

(4) The mulch biomass also brings some nitrogen into the soil and this is available to the plants.

Responses: Maybe there were some misunderstand of “mulch” to reviewer. In our study, mulch refer to plastic film, not the biomass mulch. We have revised this information in the revision manuscript. The detailed corrections are shown in Line 121.

(5) There is a lack of information on plant protection products used in maize. Please complete this information.

Responses: Yes. According to your suggestion, we have added the information about plant protection products used in maize. The detailed corrections are shown in Line 135-140.

(6) The methodology only briefly mentions the method of agrotechnics used in maize. One can only guess that it was a ploughless system. You should add these information.

Responses: Yes. According to your suggestion, we have added the information about the seeding method in this study. The detailed corrections are shown in Line123-127, and Figure 1.

(7) The results of the studies in the two years differ significantly and are not compared in these years.

Responses: Thank you very much for this useful advice. Because there were only two years’ research, and the treatments of 9.0 and 12.0 x 10⁴ plants ha^-1 just in 2018, we failed to compare in these years. But the trends of two years experiments were same, there is no doubt that results were correct. 

(8) The third year of research would make it easier to draw conclusions and show the actual influence of experience factors on the characteristics studied. However, the one-year results should also be repeated to draw correct conclusions. This is a suggestion for future research.

Responses: Yes, you are right. The more researches be carried out, the more credible results for study. And we’ll pay attention to the effect of nitrogen application on the development of maize root system and lodging resistance in future research. Thank you for again for your useful advice.

5. Conclusions:

• This chapter needs to be improved. It should be clearly stated: which range of plant density and N fertilization turned out to be the most favorable in the research. Did it prove to be in line with the adopted hypothesis? For example, do a plant density of 12.0 10⁴/ha and a fertilization of N = 270 kg/ha promote the resistance of corn stalks? Or has some other combination of these factors proved to be beneficial?

Responses: In this study, nitrogen split application can improve the stalk lodging resistance of maize planted at high density, so we couldn’t clear which range of plant density and N fertilization turned out to be the most favorable in the research. Because the stalk breaking force decreased as planting density increased, increase the nitrogen application rate in high density can improve the lodging resistance. Combined with recent research by our team, populations with a high planting density require more nitrogen fertilizer to meet their growth needs. In the article of “Zhang, G.Q.; Shen, D.P.; Xie, R.Z.; Ming B.; Xue J.; Li R.F.; Chen J.L.; Wang K.R.; Li S.K. Optimizing planting density to improve nitrogen use of super high-yield maize. Agronomy Journal. 2020, 1-12.”, our optimal nitrogen application rate of 360 kg ha^-1, and we increased the planting density, significantly increased maize yield, economic benefits and nitrogen fertilizer utilization, effectively reduced the amount of nitrogen fertilizer, and reduced the risk of nitrogen fertilizer pollution. Additionally, we applied fertilizer multiple times according to the maize growth period through the integrated system of water and fertilizer under drip irrigation under the film. And it proves to be in line with the adopted hypothesis that nitrogen application during the filling stage can reduce the adverse effects of the reduction of the stalks' resistance due to the transport of stalks to grain.

（2）Then specify - up to which limit we can increase nitrogen fertilization and plant density with the use of integrated drip irrigation and fertilization technology. This is because in this way the effects of high N doses and high seeding densities can be mitigated. The above aspect is the point of this study and must be clearly emphasized.

Responses: Yes. According to your suggestion, we have added this information in conclusion section. The detailed corrections are shown in Line 362-364.

Comments in the attachment

1. Order the keywords.

Responses: Yes. According to your suggestion, we have updated the order of keywords. The detailed corrections are shown in Line 33.

2. Weather conditions should be given for the years of study and compared with the long-term period.

Responses: Yes. According to your suggestion, we have added the precipitation and air temperature during the 2017 and 2018 growing seasons. And compared the weather conditions with historical averages. The detailed corrections are shown in Table 1.

3. Why were these?

Responses: Thanks for your comment, we are very sorry that we do not reserve samples in 2017. Therefore, we performed the analyzes only in 2018.

4. Deleted the “signification”

Responses: Yes. According to your suggestion, we have deleted the “signification” in Line 226 and Line 250.

5. Line 222-223, which is quite obvious

Responses: Yes. According to your suggestion, we have deleted this sentence. The detailed corrections are shown in Line 253-254.

 

Reviewer 3 Report

Work well written and very detailed. 

M&M are better investigated. In fact, there is no characterization of the site in terms of pre and post fertilization soil analysis. 

The soil described in this study is poor in organic matter, it is necessary to evaluate the soil characteristics and the effects of the amount to high doses of nitrogen. 

Many authors on other crops have shown that the increase in nitrogen fertilization improves the performance of the plant but over time this fertilization scheduling causes a declining plant activity and water pollution. 

It could be included in the work that these yield maximization techniques can be utilized in turnover with more sustainable techniques that improve soil fertility. 

In the study we talk about drip irrigation but the irrigation volumes is not described as well as the assessment of irrigation.  

In Table 1, the unit of the organic matter is wrong, it’s normally expressed in g kg-1. However the content is scarce. 

How were the factors in Table 1 determined? The method of analysis should be described. 

In the section data analysis it is not necessary to talk about how the data was collected. 

The content of Table 2 is not very innovative, this type of representation can only be mentioned in the text. 

Author Response

Please see the attachment

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

I have undertaken a review of the manuscript (revised) as well as the attached author responses to the initial review where I recommended major revisions. I am satisfied with the revisions made by the authors as they have addressed most, if not all, of my initial comments. Therefore, I do believe that the manuscript has been significantly improved.

Author Response

We are grateful to your valuable comments and suggestions in our paper. Those comments are very valuable and helpful for revising and improving our paper, as well as the important guiding significance to our following works.

Reviewer 2 Report

After analyzing and checking the authors' responses, I conclude that the manuscript has been improved in line with the comments. It is completed and correctly reworded and thus better understood. The authors' answers are sufficient.

Author Response

We are very pleasure to have your help in the revision of the paper. Those comments are very valuable and helpful for revising and improving our paper, as well as the important guiding significance to our following works. We hope to continue to get your guidance in our future work.