Optimum Nitrogen and Density Allocation for Trade−Off Between Yield and Lodging Resistance of Winter Wheat

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The paper is well-written, providing a detailed review of the effects of planting density and fertilization on wheat lodging resistance and yield. While there may be an abundance of data presented in tables and figures, this is largely due to the extensive scope of the research. I believe the paper can be accepted after minor revisions. Comments are provided below.

 

Abstract

L12-14: The objective is not entirely clear. You compared the varieties SN23 and SN16 under three fertilization levels and four planting densities, with a focus on the N2D2 combination (240 kg N and 225 plants per m²). This should be reformulated for clarity. Additionally, express fertilization levels as 120, 240, and 360 kg N/ha instead of using the format "1.20 x 10²," which is confusing. Similarly, describe planting densities as "225 plants per m²" for consistency.

L15: Add a sentence specifying the duration of the experiment, its location, and the traits measured.

At the end of the abstract, summarize the key findings in a logical order (e.g., physical changes → biochemical changes → yield) and conclude with a strong statement emphasizing the practical implications of the research.

 

Introduction

The introduction is too brief.

Include a few sentences discussing the interaction between nitrogen application and planting density.

The objective stated at the end of the introduction is unclear and should be clarified.

In addition to the effects on lignin and hemicellulose, emphasize the impact on yield components more explicitly.

 

Materials and Methods

Specify the the sowing and harvest dates.

Provide a clear explanation of Figure 1.

L145-146: Check and correct the English for better clarity.

 

Results

All results are presented in detail and are relevant to the study objectives.

 

Discussion

The discussion is clear and logically structured.

Did climatic factors influence lodging resistance? This aspect could be elaborated further.

While there is a significant amount of data in the tables and figures, this reflects the comprehensive nature of the research and is acceptable after minor revisions.

 

Final Remarks

The study provides a thorough analysis of wheat lodging resistance and yield under varying planting densities and fertilization levels. Minor revisions for clarity and consistency are recommended before publication.

 

Author Response

Comments 1: Abstract: L12-14: The objective is not entirely clear. You compared the varieties SN23 and SN16 under three fertilization levels and four planting densities, with a focus on the N2D2 combination (240 kg N and 225 plants per m²). This should be reformulated for clarity. Additionally, express fertilization levels as 120, 240, and 360 kg N/ha instead of using the format "1.20 x 10²," which is confusing. Similarly, describe planting densities as "225 plants per m²" for consistency.

Response 1: Thank you for highlighting the areas where we could improve. The following is the purpose of the modification: increasing nitrogen and planting density can enhance crop yield, but it can reduce lodging resistance due to decreased lignin content. There is an urgent need to find feasible measures to balance these conflicting factors (Lines: 12-13). The presentation of fertilisation levels and planting densities has been completely revised, including the main text, supplementary material, etc.

Comments 2: Abstract: L15: Add a sentence specifying the duration of the experiment, its location, and the traits measured

Response 2: Thank you for pointing out the shortcomings of the article, here is a revised version of this section (Lines: 13-17): We conducted a two-year field experiment in Tai'an, Shandong Province, China, evaluated SN23 (lodging resistant) and SN16 (lodging sensitive), under three nitrogen applications (120 kg/ha, N1; 240 kg/ha, N2; 360 kg/ha, N3) and four planting densities (75 plants/m2, D1; 225 plants/m2, D2; 375 plants/m2, D3; 525 plants/m2, D4), with N2D2 as the control, and measured lodging resistance re-lated indexes and yield.

Comments 3: Abstract: At the end of the abstract, summarize the key findings in a logical order (e.g., physical changes → biochemical changes → yield) and conclude with a strong statement emphasizing the practical implications of the research.

Response 3: Thank you for bringing up our shortcomings, we have made the changes you requested (Lines: 17-24): N2D3 (SN23) increased internode length by 0.40 cm, reduced fresh weight by 0.09 g, resulting in a bending moment reduction of 0.39 g/cm. Lignin, cellulose, and hemicellulose decreased by 18.27, 16.48, and 16.22 mg/g DW, while S and G lignin subunits decreased by 118.09 and 127.34 μg/g DW, and H subunit increased by 23.59 μg/g DW, Eventually, the breaking strength was reduced by 1.74 g/cm. resulting in a reduction of 0.09 in the Lodging resistance index. The yield reached 10.17 t/ha due to an increase in spike number by 100.33 plants/m², achieving an optimal balance between yield and lodging resistance in this experiment. Provides a viable solution for balancing lodging resistance and yield in winter wheat.

 

Comments 4: Introduction: The introduction is too brief.

Response 4: Thank you for pointing out our shortcomings, we have revised the introduction as follows (Lines: 27-72):

Wheat (Triticum aestivum L.) contributes a fifth of the calories consumed in the global human diet and also supplies substantial amounts of protein, minerals, vitamins, and dietary fiber, and serves as a cornerstone for human and ani-mal survival [1,2]. But lodging causes yield losses of 7%–80%, limiting yield potential [3,4,5]. Current strategies to boost yield rely on higher nitrogen inputs and increased planting density [6,7]. Unfortunately, these strategies can exacerbate lodging, ultimately reducing yields [3]. A discrepancy occurs between the resistance to lodging and the steady increase in yield [8]. There is an urgent need to investigate new strategies for nitrogen application combined with planting den-sity to balance lodging resistance and yield.

Nitrogen application is crucial for boosting yield [9]. Nitrogen deficiency hampers growth and development, leading to reduced productivity [10,11,12]. Conversely, exces-sive nitrogen application results in elongated and enlarged cells, weakening structural in-tegrity. This can lead to increased hollowness in thick and thin-walled tissues, longer stems, a higher center of gravity, smaller stem diameters, and thinner stem walls [13,14,15,16,17]. During early stem development, high nitrogen downregulates genes (PAL, CoMT) related to lignin (reduced S and G subunits and increased H subunits), cellulose, and hemicellulose biosynthesis, leading to a decrease in mechanical strength [18,19,20,21,22]. Optimizing nitrogen application is essential for maximizing yield and lodging resistance.

Optimizing plant density serves as the primary approach to boosting crop yields [23]. Low planting density causes inefficient use of resources, ultimately reducing productivity [24]. High planting density limits light penetration through the canopy, disrupts carbon distribution, and decreases cellulose production [25,26]. It also inhibits the activity of cru-cial genes, such as PAL and COMT, which are essential for lignin synthesis, resulting in fewer S and G lignin subunits [20,27,28,29,30]. This raises the likelihood of plants lodging and results in an additional decrease in yield.

Nitrogen fertilization and planting density are pivotal for boosting crop yield, as they modify the population structure, which in turn alters the light interception rate and radia-tion use efficiency, ultimately influencing lodging resistance and yield [31,32]. Elevating the nitrogen application and plant density can enhance plant growth, leading to an in-crease in green leaf surface area and the interception of photosynthetically active radiation (IPAR), which is a crucial prerequisite for the production of dry matter [33,34,35]. When nitrogen application is fixed, increasing planting density is often adopted as a strategy to augment the plant density per unit area, thereby compensating for deficiencies in produc-tivity [15].

Nitrogen application exhibited a positive correlation with the number of spikes and thousand-kernel weight, while no significant association was observed with the number of grains [36]. Conversely, planting density positively correlated with the spike number and yield, but negatively correlated with the number of grains number per spike and 1000-grain weight [37]. Yield composition must be regulated by selecting the optimum planting density in conjunction with appropriate nitrogen fertiliser application to achieve maximum yield [38,39].

This necessitates a trade-off between lodging resistance and yield formation. The present study aims to identify optimal strategies for stable yield and lodging resistance by quantifying relevant lodging resistance and yield.

Comments 5: Introduction: Include a few sentences discussing the interaction between nitrogen application and planting density.

Response 5: We apologise for this shortfall and the following was added about the interplay between nitrogen fertiliser and planting density (Lines: 54-62): Nitrogen fertilization and planting density are pivotal for boosting crop yield, as they modify the population structure, which in turn alters the light interception rate and radia-tion use efficiency, ultimately influencing lodging resistance and yield [31,32]. Elevating the nitrogen application and plant density can enhance plant growth, leading to an in-crease in green leaf surface area and the interception of photosynthetically active radiation (IPAR), which is a crucial prerequisite for the production of dry matter [33,34,35]. When nitrogen application is fixed, increasing planting density is often adopted as a strategy to augment the plant density per unit area, thereby compensating for deficiencies in produc-tivity [15].

 

Comments 6: Introduction: The objective stated at the end of the introduction is unclear and should be clarified.

Response 6: We apologise for this and thank you for pointing it out. We have amended this paragraph to clarify (Lines: 70-72): this necessitates a trade-off between lodging resistance and yield formation. The present study aims to identify optimal strategies for stable yield and lodging resistance by quantifying relevant lodging resistance and yield.

 

Comments 7: Introduction: In addition to the effects on lignin and hemicellulose, emphasize the impact on yield components more explicistly.

Response 7: Thank you for your feedback, we have revised our content accordingly. Here is the updated version (Lines: 63-69): Nitrogen application exhibited a positive correlation with the number of spikes and thousand-kernel weight, while no significant association was observed with the number of grains [36]. Conversely, planting density positively correlated with the spike number and yield, but negatively correlated with the number of grains number per spike and 1000-grain weight [37]. Yield composition must be regulated by selecting the optimum planting density in conjunction with appropriate nitrogen fertiliser application to achieve maximum yield [38,39].

 

Comments 8: Materials and Methods: Specify the the sowing and harvest dates.

Response 8: We apologise for the lack of sowing and harvesting dates. The sowing and harvesting dates have been written of the countermodification (Lines: 95-96): sowed on 12 October 2019 and 2020 and harvested on 11 June 2020 and 2021.

 

Comments 9: Materials and Methods: Provide a clear explanation of Figure 1.

Response 9: We apologize for not explaining Figure 1 clearly enough initially. To address this, we have enhanced the figure notes for Figure 1 with a clearer and more detailed explanation (Lines: 84-87): The rainfall and temperature patterns observed during the period encompassing the initial planting of winter wheat in October 2019 through to its harvest in June 2021, across the second cropping season, exhibited a consistent trend of initial decline, followed by an increase, a sub-sequent decrease, and ultimately a sustained rise. No standard deviation has been added to this figure.

 

Comments 10: Materials and Methods: L145-146: Check and correct the English for better clarity.

Response 10: We apologise for our lack of clarity and have made a correction in the revised manuscript: the grain yield (t/ha) was measured at a moisture content of 14% in winter wheat (Lines: 169-170).

 

Comments 11: Discussion: Did climatic factors influence lodging resistance? This aspect could be elaborated further.

Response 11: Thank you for pointing out our deficiencies. Wind is the main environmental factor that exacerbates lodging, so the effects of wind are primarily discussed (Lines: 445-449): additionally, wind is a major environmental factor contributing to crop stalk lodging. When the wind force acting on the plants exceeds the maximum tolerance of the stalks prior to their breaking, stalk lodging occurs [44]. Therefore, the increased wind force and rainfall during the later stages of growth (Figure 1) may exacerbate the risk of lodging [51,52].

 

Thank you deeply for reviewing our manuscript. Your insightful comments were invaluable. We apologize for any shortcomings and have thoroughly revised the paper based on your feedback. Your dedication to advancing science is greatly appreciated.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The Authors have evaluated the optimal nitrogen dose and density distribution for balancing productivity and lodging resistance in winter wheat.

The topic is pertinent and in line with the journal scope.

The manuscript has a robust structure and is well described supported by a strong statistical analysis.

Minor revisions are required to improve the overall quality of the manuscript.

Abstract:

-        In this section it would be better to add some details describing the field contest city and country where the experiment took place.

Introduction:

-        In this section it would be better to emphasise the vital importance of wheat for human and animal nutrition citing some recent articles relevant for this research.

 

Material and methods

-        Line 82. Add city and country where the instrument (electronic balance) was produced.

Results

-        Sometimes the quality of the figures is poor (i.e. Figure S2, Figure S3, Figure S4, Figure S5, Figure S7, Figure 7, Figure 8, Figure 9, Figure 11).

Where possible try to enhance the quality of the figures.

 

-        Line 335: Add the figure number.

 

-        ALL Tables and Figures. The authors should specify if they add standard deviation or standard error afert the mean value in all figures and tables.

 

Additional comments:

The study aims to identify the ideal nitrogen application and planting density for winter wheat types to optimise yield and lodging resistance.

 

The topic in this research article is pertinent to agronomy and food production, as lodging is a major yield-reducing factor for wheat (Triticum aestivum L.) production. This work addresses a particular gap in comprehending the relationship between nitrogen and planting density concerning lodging resistance, a relatively underexplored aspect of winter wheat.

 

This study offers a comprehensive valuation of two distinct winter wheat types (lodging-resistant and lodging-sensitive) under different nitrogen levels and planting densities, presenting practical recommendations for enhancing yield and minimising lodging risk.

 

The conclusions correspond with the supplied data, unequivocally illustrating how the optimal treatment (N2D3) enhances yield and lodging resistance, so addressing the principal study topic. The results are supported by comprehensive statistical analysis and yield-related characteristics.

 

The references seem suitable and pertinent to nitrogen application, planting density, and lodging conditions.

 

Sometimes the quality of the figures is poor (i.e. Figure S2, Figure S3, Figure S4, Figure S5, Figure S7, Figure 7, Figure 8, Figure 9, Figure 11).

Where possible try to enhance the quality of the figures.

 

In all Tables and Figures, the authors should specify if they add standard deviation or standard error after the mean value in all figures and tables.

Comments for author File: Comments.pdf

Author Response

Comments 1: Abstract: In this section it would be better to add some details describing the field contest city and country where the experiment took place.

Response 1: In the revised manuscript, on lines 13-14, we have added the information regarding the city and country where the experimental site is located: we conducted a field experiment in Tai'an, Shandong Province, China.   Comments 2: Introduction: In this section it would be better to emphasise the vital importance of wheat for human and animal nutrition citing some recent articles relevant for this research. Response 2: We are honoured by your pointing out our shortcomings and here is what we have revised (Lines: 28-30): Wheat (Triticum aestivum L.) contributes a fifth of the calories consumed in the global human diet and also supplies substantial amounts of protein, minerals, vitamins, and dietary fiber, and serves as a cornerstone for human and ani-mal survival [1,2].

Comments 3: Material and methods: Line 82. Add city and country where the instrument (electronic balance) was produced.

Response 3: In lines 106-107 of the revised manuscript, we made the change: the electronic balance we used was supplied by Sartorius, Beijing, China.

 

Comments 4: Results: Sometimes the quality of the figures is poor (i.e. Figure S2, Figure S3, Figure S4, Figure S5, Figure S7, Figure 7, Figure 8, Figure 9, Figure 11). Where possible try to enhance the quality of the figures.

Response 4: We sincerely apologize for any inconvenience caused by the low dpi of our figures. In response, we have resubmitted all figures in higher dpi for your review. We offer our heartfelt apologies once again and express our profound gratitude.

Comments 5: Results: Line 335: Add the figure number.

Response 5: We apologise for the omission of the figure number and thank you for pointing it out: this figure is Figure S6. Effect of nitrogen application and planting density on lignin in five internodes of SN23 and SN16 on milk stage, and dough stage (Lines: 368-369).

Comments 6: Results: ALL Tables and Figures. The authors should specify if they add standard deviation or standard error afert the mean value in all figures and tables.

Response 6: Thank you for pointing out our shortcomings, which we have corrected in our revised manuscript.

 

Thank you immensely for your thorough review and constructive suggestions. We've revised our manuscript accordingly. Your dedication to enhancing research quality is deeply admired. Your input has been invaluable.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The research topic is relevant, and the findings provide valuable insights into optimizing nitrogen application and planting density for winter wheat. The results of this study are highly significant for improving the efficiency of nitrogen use and optimizing planting density, which are critical factors for sustainable agricultural practices. The manuscript presents a comprehensive study with well-detailed materials and methods, clear results, and a well-articulated discussion. Overall, the manuscript demonstrates the quality required for publication.

 However, there are a few minor comments and suggestions that could enhance the clarity and readability of the manuscript:

1.-The variable "Stem breaking strength (g cm, N)" is currently denoted as "(N)," which could lead to confusion with the nitrogen treatments also labeled as "(N).

2.-The representation in Figure 2 is unclear. Specifically, the meaning of the 12 bars for each internode in each variety is not evident.

Conclusion

These minor revisions will improve the manuscript's clarity and help readers better understand the study's results and implications. The manuscript is otherwise well-prepared and suitable for publication following these adjustments.

 

Author Response

Comments 1: The variable "Stem breaking strength (g cm, N)" is currently denoted as "(N)," which could lead to confusion with the nitrogen treatments also labeled as "(N).

Response 1: We apologise for the inconvenience caused by our oversight, and for this reason we have amended (g cm, N) to (g cm, R), and made the corresponding changes in the figure and in the revised manuscript.   Comments 2: The representation in Figure 2 is unclear. Specifically, the meaning of the 12 bars for each internode in each variety is not evident. Response 2: We deeply regret the oversight in not including the necessary note in the illustration. Please find the note we have now added below. We sincerely hope you will accept our apologies: the meaning of the 12 bars for each internode in left to right is N1D1, N1D2, N1D3, N1D4, N2D1, N2D2, N2D3, N2D4, N3D1, N3D2, N3D3, N3D4 (Lines: 195-196, 203-205). We are immensely grateful to you meticulous evaluation and valuable feedback. Your insights have greatly enhanced the quality of our work. Thank you for your time and dedication.

Author Response File: Author Response.pdf