Optimizing Sulfur Fertilization for Enhanced Physiological Performance, Grain Filling Characteristics, and Grain Yield of High-Yielding Winter Wheat Under Drip Irrigation

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The research contributes to understanding the physical aspects and agricultural significance of sulphur application for winter wheat under drip irrigation systems. The experimental design is adequate, and the findings are useful and relevant at present due to the growing interest in the sustainable use of nutrients. The study has merit and can be suitable for publication after considerable improvement regarding clarity, novelty, emphasis, and a more detailed discussion of wider implications. Below are my comments on the Manuscript.

1. Add at the end of the abstract one or two brief statements on the most novel results and their implications.

 

2. Materials and Methods:

Comment 1: It is proposed to present a diagram or table of the treatment groups for better understanding.

Comment 2: Justify the decision to apply sulfur only at the jointing stage. Is there any  benefit to yield from other timings, e.g., tillering?

Comment 3: Is there variation in initial soil sulfur content between plots, and if so, how was it controlled?

 

3. Results: This section needs substantial improvement.

Comment 1: The SPAD, photosynthesis, and antioxidant activity figures (e.g. Figs. 2–8) are useful but could be made easier to understand with brief in-figure captions.

Comment 2: In tables, indicate the optimal treatment per parameter (e.g. bold or asterisk) to facilitate the reader's understanding.

Comment 3: Discuss varietal differences in response to sulfur application, especially in relation to grain filling strategies  (duration versus rate focus).

 

4. Discussion:

Comment 1: The majority of the discussion aims to validate previous studies. It is important to highlight the new aspects of the study, such as the cultivar-specific recommendations for drip fertigation.

Comment 2: Elaborate on the possible sulphur-nitrogen interactions and the possible implications for fertilizer management.

Comment 3: Please discuss the cost-effectiveness or cost-benefit of sulphur application for farmers.

5. Long-term soil sulfur monitoring or integration with precision farming tools could be useful as future research directions to include in the conclusion.

 

Other comments:

- Please check the Manuscript for minor typos and redundancies (e.g., in methods sections, similar phrases are used).

 - Shorten long sentences in the Introduction and Discussion for better ease of reading.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The paper is very interesting, but it needs some corrections and adjustments. See Below:

Abstract:

- In the abstract make clear the source of sulphur used in the study.

- Line 22- 23 – “yield increased by 6.57–16.65% for YN999 and 16.96–18.26% for JM20” Including percentage gains is valuable, but absolute yield values (kg/ha) would enhance the practical relevance and facilitate interpretation.

- Line 24 - "region-specific sulfur application rates of 30–45 kg/ha..." This recommendation should be qualified by specifying that it applies under the conditions of the North China Plain and within drip fertigation systems, to prevent overgeneralization.

Introduction:

- Lines 56–59: “predominantly rely on excessive nitrogen fertilization… disrupting sulfur-nutrient balance…” This is a valuable practical observation. However, reference to data on S/N imbalances in local soils would reinforce this argument.

- Lines 66–67: “specific physiological mechanisms through which sulfur influences wheat grain filling remain a critical knowledge gap.” This is an appropriate justification for the study, but a clear, hypothesis-driven research question is lacking and should be explicitly stated.

Material and Methods:

Lines 89–90: “completely randomized block design with three replications.” The statistical design is appropriate, but the number of plant or sample units per replicate, and whether analyses were duplicated or triplicated, should be specified for reproducibility.

Lines 97-98: Make it clear which sulphur source was used in the study. If it was elemental sulphur, emphasize that.

Lines 104–105: “applied via a drip fertigation system...”  Well-justified approach. However, details on the volume of water used during fertigation are missing and are relevant for interpreting sulfur mobility and uptake.

Lines 132–134:  “The number of days after anthesis t was used as the independent variable…” The application of the Richards equation is technically sound, but its mathematical complexity warrants a schematic or graphical explanation to aid reader comprehension.  

Results and Discussion:

Line 223: “JM20, however, displayed shifted trends: S3 replaced S2 as the optimal treatment…”
This shift in cultivar response between years is interesting and should be followed by a physiological rationale for the temporal and genotypic variability.

Lines 265–267:  “The grain growth dynamics consistently exhibited a 'slow-fast-slow' pattern...” This is expected and typical. However, the inclusion of statistical comparisons of the fitting models (e.g., AIC) would increase analytical depth.

Line 307: “The year, cultivar, and treatment have significant effects on MG2, MG3, RGC2, and RGC3.”  The main effects are described, but the text does not explore potential interactions (e.g., Year × Cultivar). Consider emphasizing whether sulfur response was consistent across environments and genotypes.

Line 346: “sulfur primarily increased TGW, and thus yield, by altering these grain filling parameters.” This is a key finding. However, the possibility that TGW increases may have occurred at the expense of spike number or grains per spike is not addressed.

Conclusion:

Lines 411–414:  “under a control yield of 8000 kg/ha, 30 kg/ha sulfur achieves the optimal yield…” The dose-yield relationship is promising and offers practical value. Nevertheless, the conclusion would benefit from referencing the statistical basis (e.g., response surface or interaction analysis) used to define the "optimal" dose.

Lines 420–421:  “helping to reverse the farmers' ‘nitrogen-focused, sulfur-neglected’ fertilization practices…” This is a strong practical implication. It could be further strengthened by recommending extension strategies or the development of region-specific fertilization guidelines.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Dear Authors,

Review of the article “Optimization of sulfur fertilization to enhance physiological performance, grain filling characteristics, and grain yield of high-yielding winter wheat under drip irrigation.”

General comments

1. Introduction – Well written and professionally structured, effectively introducing the research topic.
2. Materials and methods – Detailed and providing sufficient information for experimental replication.
3. Methodology (line 99) – The authors discuss reducing nitrogen (N) application in agriculture but apply 210 kg N/ha. Explain how this is consistent with sustainable N management practices.
4. Timing of urea application – While urea is highly soluble and enzymatically hydrolysable (→ NH₃ → NH₄⁺ → NO₃⁻), late N application in wheat is unconventional. Justify this approach with relevant literature.
5. Results section – Needs significant improvement. Current descriptions lack depth – key findings should be clearly highlighted and discussed.
6. Discussion – well conducted, with appropriate links to existing literature.
7. Conclusions – should be reworded to provide clear, evidence-based conclusions rather than rehashing results. Given the two-year duration of the study, overly general statements should be avoided. Results are primarily relevant to drip fertigation systems and may not be broadly applicable to conventional agriculture.

Specific Comments

1. Grain Yield Reporting – Report wheat grain yields in t ha⁻¹ (not just %) for better agronomic validity.
2. Tables 1–3 – improve descriptions by clearly indicating statistical significance (ANOVA, letters a, b, c…).
3. Explain differences between sulfur treatments and wheat varieties.
4. Figures 2, 7, and 8 – Add annotations with ANOVA significance markers to distinguish treatment/variety effects.
5. Figures 3–6 – Improve clarity – Current graphs do not show visible variation in photosynthetic parameters by sulfur rates or varieties. Consider re-plotting with adjusted significance scales or indicators.

Additional Suggestions

1. Farmer Applicability – Since drip fertigation is not widely used, moderate conclusions to avoid overestimating practical significance.
2. Statistical Rigor – Ensure that post hoc tests (e.g., Tukey HSD) are used where needed to support comparisons.
3. Key Improvements: Conciseness and Precision – Removed unnecessary language and strengthened scientific tone.
4. Structural Clarity – Separated general/specific notes for better readability.
5. Practical feedback – Direct requests for corrections (e.g., yield units, ANOVA designations).

 

 

Comments on the Quality of English Language

I have no complaints about the English language

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

This study tested the sulfur effects on wheat in the North China Plain. The topic fits the journal’s scope. The whole test is well-structured with a clear aim. However, revision is suggested to better shape this manuscript. Comments are as follows:

L10-11: Should be “The North China Plain is one of the major wheat cultivation regions.  As a cornerstone of global food security, wheat makes the enhancement of its yield critically important.”

L57-L59: The author claimed most Chinese farmers “rely on excessive nitrogen fertilization to achieve yield gains, yet this approach depletes soil nutrients and disrupts sulfur-nutrient balance”, then why did the author not set up nitrogen fertilization treatments? Please write the limitations of this study before the conclusion.

L66-67: Are you sure “the specific physiological mechanisms through which sulfur influences wheat grain filling remain a critical knowledge gap”? Critical knowledge gap means no one did it before.

Figure 1: It’s uncommon to see “total” value points in a time series plot. Please delete those two points and present the two total annual precipitation values in section 2.1.

L140-141: Maybe I miss it, but I do not find the abbreviation of grain filling rate (G) in the main text.

L188-193: More SPAD variability results should be presented for each treatment, not on variety and time. i.e. Ranking the SPAD as what the author did for photosynthetic characteristics.

L248: Format error.

L272: “ultimate growth quantity (A)” increased. Which “A” increased? A of S0? Compared with whose A? Please specify.

L278-279: Again, compared with whose R0? It is important to specify the treatment, or it’s not convincing for S2 and S3 to be the optimal treatments.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

All my concerns were addressed accordingly. I have no further comments on this version of the manuscript. 

Reviewer 4 Report

Comments and Suggestions for Authors

I have no more comments.