Effects of Planting Density and Nitrogen Management on Light and Nitrogen Resource Utilization Efficiency and Yield of Summer Maize in the Sichuan Hilly Region
and Jichao Yuan 1,2,3,*Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsDear Editor and authors, initially when I read the file I had the impression that it was very regional. I understand the importance of the research carried out, but its nature is very regional and should be published in a local magazine, or even in a technical bulletin. I see few new elements that justify its publication, this is evident because there is no basis in the introduction, I suggest that the authors redo the introduction, making clear more specific points that provide a basis for the variables analyzed, such as the data observed in figure 5. But What makes the article most difficult to accept is its simple and very regional nature, given Agronomy's high impact factor. Below are some other suggestions for improving the article.
Introduction
The introduction needs to be restructured and redone according to the initial comment
Material and Methods
Line 97: Mention the methodologies used to determine nutrient availability to ensure reproducibility
Results
The figures are not self-explanatory, as there are no elements such as the year it was evaluated, I suggest inserting this information in the figure and putting it in the caption, because as I understand that there is the same variable analyzed in 3 parts of a figure, each part must be a specific year .
Another point is that the interactions and their significance of the evaluated treatments are shown, however the letters inserted in the test and the approach taken go in the opposite way, because when there is an interaction of factors the CORRECT approach is to unfold the comparison of a factor within the levels of the other, The article is wrong in this approach, So the authors need to redo the statistical analyzes carried out. I understand that it will be a rework, the comparisons will change and consequently the results section but it is the only correct approach to take
Change Correlative analysis to correlation analysis in the text
Discussion
The discussion needs to be better structured by creating a sequence (telling a story according to the data), and be careful with various inferences from the nitrogen fertilizer management observed, because the same only applies to crop conditions similar to the one developed.
Author Response
Response:
Thank you for your kind comments.
This study was conducted in the Sichuan Hilly Region which is the main ecotype of the southwest maize region. The southwest maize region is one of the three major maize areas in China. Although the study sites are somewhat localized, they are still representative of an important ecological type of maize in China. The results of the study provide a reference for similar ecological regions and have also been analyzed in some comparisons with light-rich regions such as northern China. Therefore, this study still has some theoretical and practical significance. In fact, most of the studies were site-specific, and only a few conducted joint experimental studies at multiple ecological areas.
There is actually a lot of research on maize planting density and nitrogen rate, however, (1) This study focuses on the interaction and synergy between the two in terms of RUE and NUE, and specifically discusses whether more or less nitrogen needs to be applied after densification (previous studies with contradictory results). We point out that nitrogen can be moderately reduced at low and medium planting densities in areas (plots) with excessive nitrogen rate, but excessive nitrogen reduction should not be applied after densification in order to avoid yield losses due to nitrogen deficiency as well as excessive exhaustion of nitrogen in the soil, which is not beneficial for sustainable development. (2) In this study, we not only investigated the effects of planting density and nitrogen rate on the light distribution, absorption, and utilization as well as yield of maize populations, but also quantified their relationships, especially the quantitative relationships between light distribution with RUE (Fig. 5 et al.) and yield, and the quantitative relationships between the amount of nitrogen rate with nitrogen utilization efficiency. (3) Densification is an effective method to increase maize yield, this study not only explores the possibility and potential of maize densification in this region, but also points out that densification should be based on the local sunlight and other resources. Poor sunlight areas should not be overly dense to avoid poor field ventilation and light penetration resulting in stem and leaf growth, collapse of the field, and thus yield loss. Therefore, there are still some new ideas and progress in this article, and I hope you will partially agree with it!
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Comments 1: The introduction needs to be restructured and redone according to the initial comment.
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Response 1: Thank you for your suggestion, we have made the necessary modifications. Our idea of writing is: it is very important to improve maize yield. Densification can improve maize yield by increasing RUE, and there is still some space in this aspect in our country. However, the appropriate density in different ecological regions and environmental conditions needs to be further investigated. Nitrogen fertilization can also improve maize yield, but there is currently an excessive use of nitrogen fertilizer problems. So it is necessary to reduce the nitrogen rate and improve nitrogen utilization efficiency. Some studies have shown that densification can be combined with nitrogen reduction, but others believe that densification should be coupled with nitrogen increase, so optimize the nitrogen-densification management strategy need further research. Sichuan Hill Region is an important maize production area, in order to adapt to the demands of the new circumstances, maize production from spring maize to summer maize, however, the research on its nitrogen-densification management strategy is very limited. Therefore, a 3-year field experiment was conducted with the prospect of achieving three objectives.
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Comments 2: Line 97: Mention the methodologies used to determine nutrient availability to ensure reproducibility |
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Response 2: Thank you for pointing this out. We have added correlative article to support it.
Comments 3: The figures are not self-explanatory, as there are no elements such as the year it was evaluated, I suggest inserting this information in the figure and putting it in the caption, because as I understand that there is the same variable analyzed in 3 parts of a figure, each part must be a specific year .
Response 3: Thank you for pointing this out. We have made the necessary modifications to the relevant figures as suggested by you.
Comments 4: Another point is that the interactions and their significance of the evaluated treatments are shown, however the letters inserted in the test and the approach taken go in the opposite way, because when there is an interaction of factors the CORRECT approach is to unfold the comparison of a factor within the levels of the other, The article is wrong in this approach, So the authors need to redo the statistical analyzes carried out. I understand that it will be a rework, the comparisons will change and consequently the results section but it is the only correct approach to take.
Response 4: We agree with this comment. In this article, a split-plot experimental design was used, with the main plot being planting density and the secondary plot being nitrogen rate, and the analysis of variance (ANOVA) was also performed according to this experimental method (model). Planting density was used for multiple comparisons with means, and all differences between nitrogen rate treatments were t-tested for significance at different densities (different lowercase letters are significant at the 5% level).
Comments 5: The discussion needs to be better structured by creating a sequence (telling a story according to the data), and be careful with various inferences from the nitrogen fertilizer management observed, because the same only applies to crop conditions similar to the one developed.
Response 5: We agree with this comment. We have modified the discussion. |
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsGeneral comments
Many interesting results are presented in the manuscript. The study have been carried out correctly. The results were correctly analyzed. However the way of results presentation and description should be improved.
Detail comments
Title of the manuscript
The title is in accordance with the content of the manuscript.
Abstract
- Lines 19-21: “For every 100 kg/hm2 increase in nitrogen fertilizer, RUE increases by 0.16%, NUE decreased by 25.0 kg/kg and soil apparent nitrogen loss quantity increased by 67.84 kg/hm2, respectively.”
In my opinion this is an over interpretation of the results. The increases of RUE and NUE values are not constant for each 100 kg increase of N rate. It may be true only to a specific range of N rates.
Introduction
- Lines 34-35: “the increase of maize yield has to be achieved by increasing the yield per unit area which has become the main way to increase maize yield” ?? Do you thinm maybe about increase maize production ??
Materials and methods
- Figure 1. - In my opinion, this drawing is too small and does not make it possible to get acquainted with the weather conditions of the research
- Line 110: Chen [31] – it should be Chen et al. [31]
- Line 117: “V13 stage”?? - this is unclear. Please add references.
- Line 132: “𝑆𝑜𝑙𝑎𝑟 𝑟𝑎𝑑𝑖𝑎𝑡𝑖𝑜𝑛 𝑖𝑛𝑡𝑒𝑟𝑐𝑒𝑝𝑡𝑖𝑜𝑛 𝑟𝑎𝑡𝑒 (𝑅𝑆𝐼)” ?? – why not SRI ??
- Line 173: “ears” ?? and lines 176 and 177: “grains per panicle” ?? – grains in maize plants are formed in cobs
Results
- Line 184: “Effects of density and nitrogen rate ….” I suggest “Effects of planting density and nitrogen rate…”
- Lines 186-188: “As planting density and nitrogen rate increased, the population extinction coefficient (K) and solar radiation interception (SRI) increased, light transmission (LT) decreased.”??
This statement is true only for the N dose. It does not follow from Fig. 2 that planting density significantly affect LT (no appropriate designations for this factor).
- Line 202: “Vertical bars represent the mean ± standard error” ??? - There are no vertical bars on figure 2.
- Line 205: “Effects of density and nitrogen rate on yield and its components in summer maize” – maybe beter: “Effects of planting density and nitrogen rate on summer maize grain yield and its components” – the same concerns titles of another parts and some figures.
Lines 209-211: “Reducing ni-209 trogen rate decreased yields by declining the number of grains per panicle and the 100-210 grain weight, and this effect increased with the planting density increase” ??
The description is imprecise. Not every reduction in N dose resulted in a significant reduction in yield and its components.
- Line 216: “Grain number per panicle” – the same like in lines 176-177
- Figures 3 and 5. - In my opinion, this figures are too small and does not make it possible to get acquainted with such great number of results
- Lines 274-276: “For every 100 kg/hm2 increase in nitrogen rate, NDMPE, NUE and PFP increased by 5.3 kg/kg , 25.0 kg/kg and 6.5% respectively.” ?? – similar problem like in lines 19-21. The same concerns statements in lines: 289-290; 335-337 and 344-346
- Line 268: “Effects on nitrogen utilization efficiency” ?? It should be: “Effects of planting density and nitrogen …..” or simple “Nitrogen utilization efficiency” (the same concerns titles of parts 3.4.1 and 3.4.3
- Line 286: “and rate (ANLR) decreased (Fig. 8).” ?? – there is no ANLR on figure 8
Discussion
- Lines 304-305: “In this study, for each 1% increase in RUE, the 304 yield increased by 2762.3 kg/hm2(R2=0.931**).” ?? - I did not find such calculations in the manuscript.
- Lines 318-319: “SRI raised (Fig. 318 2),” ?? - I did not find SRI on Fig.2
- Line 325: “a poor sunlight area (11.2 MJ/m2) (Table 1),” ?? there is no sunlight area in table 1
Conclusion
- Lines 387-389: “The appropriate nitrogen-density combination under the experimental condition was planting density of 67,500 plants/hm2 with nitrogen rate of 180 kg/hm2.” ?? This is an overinterpretation. The study did not determined the optimal combination of plant density and N rate. It was only stated that the combination “67,500 plants/hm2 with nitrogen rate of 180 kg/hm2” was better than the other combinations tested.
Author Response
- Lines 19-21: “For every 100 kg/hm2 increase in nitrogen fertilizer, RUE increases by 0.16%, NUE decreased by 25.0 kg/kg and soil apparent nitrogen loss quantity increased by 67.84 kg/hm2, respectively.”
In my opinion this is an over interpretation of the results. The increases of RUE and NUE values are not constant for each 100 kg increase of N rate. It may be true only to a specific range of N rates.
Response: Thank you for your kind comments. This result was found for the range of nitrogen rates used in this experiment, and in addition, this range essentially includes the nitrogen rates generally used in actual production.
Introduction
- Lines 34-35: “the increase of maize yield has to be achieved by increasing the yield per unit area which has become the main way to increase maize yield” ?? Do you thinm maybe about increase maize production ??
Response: Thank you for your kind comments. What we mean is that in the limited area of arable land, the total grain yield of maize can be increased by increasing the grain yield per unit area to ensure food security in our country.
Materials and methods
- Figure 1. - In my opinion, this drawing is too small and does not make it possible to get acquainted with the weather conditions of the research
Response: Thank you for your kind comments. We have made the necessary modifications.
- Line 110: Chen [31] – it should be Chen et al. [31]
Response: Thank you for your kind comments. We have revised it.
- Line 117: “V13 stage”?? - this is unclear. Please add references.
Response: Thank you for your kind comments. V13 is the stage when the 13th leaf unfolds, which is the internationally recognized Iowa System expression. It roughly corresponds to the trumpet stage.
- Line 132: “????? ????????? ???????????? ???? (???)” ?? – why not SRI ??
Response: Thank you for your kind comments. We have made the necessary modifications.
- Line 173: “ears” ?? and lines 176 and 177: “grains per panicle” ?? – grains in maize plants are formed in cobs
Response: Thank you for your kind comments. We have standardized the change from “panicle” to “ear”, which include the cobs and the grains above it.
Results
- Line 184: “Effects of density and nitrogen rate ….” I suggest “Effects of planting density and nitrogen rate…”
Response: Thank you for your kind comments. We have made the necessary modifications.
- Lines 186-188: “As planting density and nitrogen rate increased, the population extinction coefficient (K) and solar radiation interception (SRI) increased, light transmission (LT) decreased.”??
This statement is true only for the N dose. It does not follow from Fig. 2 that planting density significantly affect LT (no appropriate designations for this factor).
Response: Thank you for your kind comments. Overall, the statement is also correct for planting density, which is what the experimental data show. It is just not intuitively obvious due to the smaller Figure 2 and the larger range of light transmission (0-100%). As the planting density increases, more plants increase the leaf area, the extinction coefficient increases, and the light transmittance decreases.
Line 202: “Vertical bars represent the mean ± standard error” ??? - There are no vertical bars on figure 2.
Response: Thank you for your kind comments. We deleted irrelevant information.
- Line 205: “Effects of density and nitrogen rate on yield and its components in summer maize” – maybe beter: “Effects of planting density and nitrogen rate on summer maize grain yield and its components” – the same concerns titles of another parts and some figures.
Response: Thank you for your kind comments. We have made the necessary modifications.
Lines 209-211: “Reducing ni-209 trogen rate decreased yields by declining the number of grains per panicle and the 100-210 grain weight, and this effect increased with the planting density increase” ??
The description is imprecise. Not every reduction in N dose resulted in a significant reduction in yield and its components.
Response: Thanks for your kind comments. In general, this is the trend that can be seen in Figure 3, and is further illustrated by the extent of the reduction in the last sentence. To be more accurate, we have added the phrase "in general" at the beginning of the sentence.
- Line 216: “Grain number per panicle” – the same like in lines 176-177
Response: Thank you for your kind comments. We have standardized the change from “panicle” to “ear”.
- Figures 3 and 5. - In my opinion, this figures are too small and does not make it possible to get acquainted with such great number of results
Response: Thank you for pointing this out. We have made the necessary modifications to the relevant figures as suggested by you.
- Lines 274-276: “For every 100 kg/hm2 increase in nitrogen rate, NDMPE, NUE and PFP increased by 5.3 kg/kg , 25.0 kg/kg and 6.5% respectively.” ?? – similar problem like in lines 19-21. The same concerns statements in lines: 289-290; 335-337 and 344-346
Response: Thank you for your kind comments. This result was found for the range of nitrogen rates used in this experiment. We wanted to quantify the relationship between the nitrogen rate and the relevant traits under the experimental conditions rather than simply describing that the nitrogen rate had an effect on the traits of interest.
- Line 268: “Effects on nitrogen utilization efficiency” ?? It should be: “Effects of planting density and nitrogen …..” or simple “Nitrogen utilization efficiency” (the same concerns titles of parts 3.4.1 and 3.4.3
Response: Thank you for pointing this out. We have made the necessary modifications on the titles.
- Line 286: “and rate (ANLR) decreased (Fig. 8).” ?? – there is no ANLR on figure 8
Response: Thank you for pointing this out. The ANLR is the percent in the figure, and we present it in the figure interpretation.
Discussion
- Lines 304-305: “In this study, for each 1% increase in RUE, the 304 yield increased by 2762.3 kg/hm2(R2=0.931**).” ?? - I did not find such calculations in the manuscript.
Response: Thank you for pointing this out. This is the result of a regression analysis using yield and RUE data, which was not included in the results section to avoid too much repetition, and was included in the discussion to highlight this quantitative relationship. If you think it is necessary, we can also add it to section 3.3.
- Lines 318-319: “SRI raised (Fig. 318 2),” ?? - I did not find SRI on Fig.2
Response: Thank you for pointing this out. SRI is calculated from “1- Light transmittance”, while Light transmittance data is already available in Fig. 2, and SRI is not provided to avoid duplication of data.
- Line 325: “a poor sunlight area (11.2 MJ/m2) (Table 1),” ?? there is no sunlight area in table 1
Response: Thank you for pointing this out. It was an error on our part. We have deleted it.
Conclusion
- Lines 387-389: “The appropriate nitrogen-density combination under the experimental condition was planting density of 67,500 plants/hm2 with nitrogen rate of 180 kg/hm2.” ?? This is an overinterpretation. The study did not determined the optimal combination of plant density and N rate. It was only stated that the combination “67,500 plants/hm2 with nitrogen rate of 180 kg/hm2” was better than the other combinations tested.
Response: Thank you for your kind comments. The result in the conclusion was shown to be the best combinations under the conditions of this experiment.
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsDear Authors, optimising the planting density of one of most widely grown crops as maize is very important from scientific as practical aspects. Your attempts described in the manuscript in my opinion can be treated as significant step to achieve this goal. Your manuscript is based on results of field trial which was performed in a standard way - all methods applied are standard ones and they can help answering the problems mentioned in lines 79-84. Result are presented in a clear way and drawings are of high quality. Conclusions (Section 5) are supported by obtained results.
Please consider adding four publications to your literature resources cited. In my opinion at least new article by Shao et al. could be mentioned in Discussion Section.
Djaman K., Allen S., Djaman D.S., Koudahe K., Irmak S., Puppala N., Murali K., Darapuneni M.K, Angadi S.V. Planting date and plant density effects on maize growth, yield and water use efficiency. 2022, Environmental Challenges, 6, 100417, https://doi.org/10.1016/j.envc.2021.100417.
Zhang Z., Zonggui X., Jun L., Rui W. Optimum Planting Density Improves Resource Use Efficiency and Yield Stability of Rainfed Maize in Semiarid Climate 2021, Frontiers in Plant Science, 12 DOI 10.3389/fpls.2021.752606
Testa G., Reyneri A., Blandino M. Maize grain yield enhancement through high plant density cultivation with different inter-row and intra-row spacings,. 2016, European Journal of Agronomy, 72, 28-37, https://doi.org/10.1016/j.eja.2015.09.006.
Shao H., Wu X., Chi H., Zhu F., Liu J., Duan J., Shi W., Xu Y., Mi G. How does increasing planting density affect nitrogen use efficiency of maize: A global meta-analysis. 2024, Field Crops Research, 311, 109369, https://doi.org/10.1016/j.fcr.2024.109369.
Reviewer would like to mention some weaker points of your manuscript which do not significantly limit scientific value of the manuscript.
Many publications referring to the problem of plant density optimisation are focused on selecting the optimal cultivar under given agronomic conditions – in your manuscript you did not mention what cultivar you have selected and why did you make this choice.
Reviewer as non native English speaker cannot evaluate language level in details but in my opinion revision the text by native English speaker is necessary – for example in line 40 instead of “good” I would suggest “proper”; the following sentences have unclear meaning: in lines 196-198 as in lines 207-208; in lines 251-253 and 273-274.
Instead of “Correlative analysis” should stand “Correlation analysis”.
Formal issues: many readers are used to area unit hectare (abb. ha) and square hectometer (abbr. hm2) seems to be a little bit odd;
All units as kg/ha, mg/kg, plants/ha and mg N/kg should be written as kg ha-1, mg kg-1 plant ha-1 and mg N kg-1
There are some technical error:
Wrong usage of capital letters in lines 162 and 167 instead of “Plant” should stand “plant” or alternatively word "soil" in lines 158, 160, 162 and 165 should also be capitalized.
in References section – line 410, 465 there are some additional words or characters (%).
Author Response
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Comments 1: Please consider adding four publications to your literature resources cited. In my opinion at least new article by Shao et al. could be mentioned in Discussion Section.
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Response: We agree with this comment. Therefore, we have added four publications in discussion. Comments 2: Reviewer would like to mention some weaker points of your manuscript which do not significantly limit scientific value of the manuscript. Response: Thanks for your kind comments. |
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Comments 3: Many publications referring to the problem of plant density optimisation are focused on selecting the optimal cultivar under given agronomic conditions – in your manuscript you did not mention what cultivar you have selected and why did you make this choice. |
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Response: Thank you for pointing this out. This cultivar is widely grown in the actual production of the region (see 2.1) and is well represented to better illustrate the experimental phenomena.
Comments 4: Reviewer as non native English speaker cannot evaluate language level in details but in my opinion revision the text by native English speaker is necessary – for example in line 40 instead of “good” I would suggest “proper”; the following sentences have unclear meaning: in lines 196-198 as in lines 207-208; in lines 251-253 and 273-274.
Response: Thank you for pointing this out. We have modified these statements.
Comments 5: Instead of “Correlative analysis” should stand “Correlation analysis
Response: We agree with this comment.
Comments 6: Formal issues: many readers are used to area unit hectare (abb. ha) and square hectometer (abbr. hm2) seems to be a little bit odd; All units as kg/ha, mg/kg, plants/ha and mg N/kg should be written as kg ha-1, mg kg-1 plant ha-1 and mg N kg-1 Response: Thank you for pointing this out. We have modified these issues.
Comments 7: There are some technical error: Wrong usage of capital letters in lines 162 and 167 instead of “Plant” should stand “plant” or alternatively word "soil" in lines 158, 160, 162 and 165 should also be capitalized. in References section – line 410, 465 there are some additional words or characters (%). Response: Thank you for pointing this out. We have modified these statements. |
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsDear Editor and authors, I understand that the article was improved based on the suggested modifications and I understand the relevance of the manuscript, but despite this I also understand that despite the justifications given by the authors the manuscript is still very local, so I still recommend that the article is rejected, but if the editor considers the manuscript to be relevant, I understand and can support his decision to accept the article. So the authors' justifications were enough for me.
Author Response
Thanks to the reviewer for giving us kind comments! We have continued to refine the article in the hope of getting an opportunity to submit it to Agronomy.
