Effect of Cultivated Species and Planting Pattern on Plant Growth, Soil Properties, and Soil Metabolites in a Rain-Fed Orchard in Gansu, China

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

In the revised manuscript, the authors present the results of an in situ field study on the effect of species and planting pattern on plant growth, with reference to shoot length, root length, belowground biomass dry weight and overall root activity, as well as on some soil chemical properties (total nitrogen, total phosphorus and potassium, available phosphorus and potassium) and some metabolites in the soil rhizosphere, in an apple orchard planted with Vulpia myuros, Vicia villosa, Orychophragmus violaceus and Brassica campestris in two patterns: inter-rows and tree-disk. The results obtained may contribute to the development of the scientific background on the role of the so-called cover crops in the sustainable development of apple orchards and the improvement of environmental quality under conditions similar to those in Gansu province.

I believe that the topic addressed is of interest for Gansu province, given the large area of cultivation of apple orchards in the classical system, with unfavorable effects on the soil in the long term, even if it is not an absolutely new topic regarding the role of cover crops in fruit tree plantations, but it certainly brings important practical contributions for farmers.

Given the content of the manuscript, I believe that the title of the paper should be adjusted to be consistent with the results presented: only the chemical properties of the soil, and the term grass is used especially for species from the Gramineae family, meadow species, perhaps it would be more appropriate, given the four species used in the study, to use the expression cultivated species.

In the abstract, in lines l24-l26 the species Orychophragmus violaceus and Vulpia myuros are recommended, but without any information about Orychophragmus violaceus being highlighted in the content of the abstract. I believe that the abstract should be completed with results about Orychophragmus violaceus.

The research methodology is correct, appropriate to the parameters studied, the presentation of the results and the statistical interpretation are those usually used in determinations of this type.

In order to have better clarity on the working methodology, I believe that some additional information would be necessary:

L Chapter 2.1, Study area: in order to have a much clearer perception of the climatic conditions of the area, I believe that information on the average monthly temperatures and the dynamics of monthly precipitation would be useful, considering that the study was carried out under non-irrigated conditions.

In chapter 2.2, Experimental design, the following should be presented:

1. a sketch of the experiment followed with the dimensions of the study variants;
2. information should be added regarding the quantities/number of seeds per square meter for the cultivated species and the sowing date;
3. there should be details regarding the volume of topsoil harvested for analysis samples;
4. there should be details regarding the soil content in total nitrogen, total and available phosphorus, total and available potassium before the cultivation of the four species of cover crops, very important in order to more clearly highlight the effect of the cultivated plants on the chemical parameters of the soil monitored in the study.

The results obtained are correctly interpreted, with clear expression, highlighting the effect that the cultivated species and the planting pattern have on some plant growth characteristics and some chemical parameters of the soil, in correlation with some research previously carried out by different authors.

To substantiate the study, 37 references appropriate to the issues addressed were selected and used, although there are other important articles on this topic.

The table and figures presented in the manuscript are correctly developed and well framed in the text.

The conclusions drawn by the authors are consistent with the results obtained, but I believe that the effect of the studied factors on the metabolites in the soil rhizosphere and their role in plant growth should be better highlighted.

In conclusion, with the clarifications requested above, with the adjustment of the title and conclusions, I believe that the manuscript can follow the next editorial stages. It would be useful for agricultural practice in the area for the studies to be repeated after other periods of time, in two-year cycles, to follow up the experiment.

Comments for author File: Comments.pdf

Comments on the Quality of English Language

The quality of the English language allows understanding of the text, but it can be improved.

Author Response

Dear Reviewers:

On behalf of my co-authors, we are very grateful to you for giving us an opportunity to revise our manuscript again. We have studied reviewers’ comments carefully and tried our best to revise our manuscript according to the comments. Based on the instructions provided in your letter, we uploaded the file of the revised manuscript, and all the changes highlighted by using red-colored text. We appreciate you very much for your positive and constructive comments and suggestions on our manuscript. The following are the responses and revisions I have made in response to the reviewers' questions and suggestions on an item-by-item basis.

Comment 1: Given the content of the manuscript, I believe that the title of the paper should be adjusted to be consistent with the results presented: only the chemical properties of the soil, and the term grass is used especially for species from the Gramineae family, meadow species, perhaps it would be more appropriate, given the four species used in the study, to use the expression cultivated species.

Response: Thank you for your comments and suggestions to our manuscript. Based on your comments, we have revised the nouns that appear throughout the text. The corrections are in the revised manuscript and using red-colored text.

Comment 2: In Chapter 2.1, Study area: in order to have a much clearer perception of the climatic conditions of the area, I believe that information on the average monthly temperatures and the dynamics of monthly precipitation would be useful, considering that the study was carried out under nonirrigated conditions.

Response: We feel great thanks for your professional review work on our article. The monthly variations of precipitation and temperature in the experimental site have been added to the revised manuscript by using red-colored text.

Comment 3: In chapter 2.2, Experimental design, the following should be presented.

Response: Thank you for pointing this out. The seeding rate for the cultivated species and sowing date, soil sampling methods, and basic physicochemical properties of the soils have been added to the revised manuscript by using red-colored text.

Comment 4: To substantiate the study, 37 references appropriate to the issues addressed were selected and used, although there are other important articles on this topic.

Response: We sincerely appreciate the valuable comments. We have updated the literature based on the revised manuscript and cited new references that are relevant to this topic.

Comment 5: The conclusions drawn by the authors are consistent with the results obtained, but I believe that the effect of the studied factors on the metabolites in the soil rhizosphere and their role in plant growth should be better highlighted.

Response: After careful discussion, we have revised the third paragraph of the Discussion, and we have added discussions between soil metabolites, plant growth, and soil physicochemical properties. The detailed corrections are in the revised manuscript and using red-colored text.

Thank you very much for your attention and time. Look forward to hearing from you.

Sincerely,

Corresponding author:

Qi Li, Ph. D.

College of Pastoral Agricultural Science and Technology, Lanzhou University

Lanzhou 730020, Gansu, China

Email address: liqi@lzu.edu.cn

Reviewer 2 Report

Comments and Suggestions for Authors

Dear All,

The manuscript entitled “Effect of grass species and planting pattern on plant growth, soil properties, and soil metabolites in a rain-fed orchard in Gansu, China” presents a two-year field experiment evaluating the influence of four orchard grass species (Vulpia myuros, Vicia villosa, Orychophragmus violaceus, and Brassica campestris) under two planting configurations (tree-disk and inter-row) on plant performance, soil nutrients, and rhizosphere soil metabolomics.

This topic is important and timely, especially given the global push for low-input, sustainable orchard systems. The study is generally well-structured and includes comprehensive biochemical and morphological data. However, the rationale and central hypothesis require clarification, and some methodological and interpretive sections need substantial strengthening. The manuscript would benefit from deeper analytical framing, stronger linkage between metabolomic and ecological processes, and attention to soil classification and diagnostic interpretation of nutrient values.

Strong Points

Relevant subject and location: Study addresses soil restoration and fertility enhancement in rain-fed systems, a key concern in semi-arid regions like Gansu.
• Comprehensive dataset: The integration of plant growth metrics, soil nutrients, and metabolite profiling presents a multifactorial approach.
• Practical application: Results are directly relevant for orchard management and suggest species-specific recommendations.
• Experimental replication: Five replicates per treatment provide statistical validity.
• Appropriate analytical techniques: GC-MS for metabolite identification and redundancy analysis (RDA) enhance the study’s methodological robustness.

Weaker Aspects

• Lack of a clearly articulated mechanistic hypothesis: The rationale for choosing specific species and planting patterns needs more scientific underpinning.
• Omission of soil taxonomy: The classification of soil types (e.g., FAO/WRB or USDA) is missing and should be explicitly stated.
• No diagnostic reference for soil fertility: Nutrient levels are not interpreted using national or regional guidelines, leaving ambiguity on adequacy.
• Superficial interpretation of metabolites: The role of several metabolites is listed but lacks physiological linkage to soil microbiota or stress signaling.
• Inconsistent English phrasing: Numerous awkward or vague phrases throughout the manuscript reduce clarity and precision.

So, I have annotated below (and along the manuscript) an attempt to clarify certain ideas, but the authors should examine my suggested wording changes carefully to be sure that I have not misinterpreted what they wanted to say.

Clarify Hypothesis and Objectives

NOTICE – Issue: The introduction does not explicitly present a testable, mechanistic hypothesis nor explain why these specific four species and patterns were chosen.
– Action Required: Conclude the Introduction with a hypothesis such as: “We hypothesize that different grass species and their spatial planting patterns differentially influence root development and soil nutrient partitioning due to their physiological and rhizospheric traits.”

Soil Taxonomy and Diagnostic Context

NOTICE – Issue: The manuscript lacks any reference to the soil classification system (e.g., FAO, USDA).
– Action Required: Include a clear classification in Section 2.1 and discuss whether the soil type presents constraints on nutrient availability or water retention.

Nutrient Status Interpretation

NOTICE – Issue: No official or research-based interpretation of measured nutrient levels (e.g., TP, NH₄⁺, NO₃⁻) is provided.
– Action Required: Insert a paragraph summarizing nutrient ranges using regional or FAO soil fertility guidelines, and categorize observed values as low, adequate, or high.

Biological Replication Transparency

NOTICE – Issue: Although five replicates are stated, it's not always clear whether these were biological (plot-level) replicates or technical repetitions.
– Action Required: Clarify whether each replicate represents an independent plot under the same treatment (biological), especially for metabolite analysis.

Minor Comments and Technical Corrections

1. Page 1, Line 20
   Issue: Long and awkward sentence: “tree-disk pattern promoted root development and increased…”
   Fix: Split into two clearer sentences: “The tree-disk pattern promoted root development. This increase in below-ground biomass contributed to changes in soil nutrient dynamics.”

2. Page 1, Abstract
   Issue: Hypothesis is missing from the abstract.
   Fix: Add one line at the end: “We hypothesized that different grass species and planting patterns would differently affect root growth and soil biochemistry.”

3. Page 2, Line 84
   Issue: “five topsoil samples” lacks clarity about mixing or replication.
   Fix: Clarify: “Five independent topsoil samples were collected per treatment and analyzed separately to assess biological variation.”

4. Page 2, Line 92
   Issue: No soil classification is provided.

5. Page 2, Line 102
   Issue: Vague sentence: “rhizosphere soil was collected.”
   Fix: Specify: “Rhizosphere soil was defined as soil adhering to roots after gentle shaking.”

6. Page 3, Line 142
   Issue: Excessive precision: “2746.11 g·m⁻²”
   Fix: Round: “2750 g·m⁻²” (or use ± SD if appropriate)

7. Page 4, Line 171
   Issue: Redundancy in listing all species repeatedly.
   Fix: Use abbreviations after first full mention.

8. Page 4, Line 199–202 (Figure 3)
   Issue: Axis labels lack full unit clarity.
   Fix: Use: “Available P (mg·kg⁻¹)” instead of “P content”

9. Page 5, Line 232
   Issue: “The results showed that…” overused.
   Fix: Rephrase: “Vicia villosa significantly increased soil total N compared to other treatments.”

10. Page 5, Line 245
    Issue: Term “significantly” is used without statistics.
    Fix: Add p-values or test name: “(p < 0.05, ANOVA, Tukey’s HSD)”

11. Page 6, Line 275
    Issue: Overinterpretation: “negatively correlated with root biomass.”
    Fix: Clarify whether correlation is statistically significant and biologically meaningful.

12. Page 7, Line 300
    Issue: Mechanism of action for metabolites not discussed.
    Fix: Add explanation: “Phthalates may act as microbial inhibitors, potentially altering rhizosphere activity.”

13. Page 8, Line 335
    Issue: Ambiguity in “soil metabolite patterns were complex.”
    Fix: Specify key trends or examples.

14. Page 8, Line 350
    Issue: “Suggests O. violaceus had a stronger impact” lacks data link.
    Fix: Add reference to a figure or statistical outcome.

15. Page 9, Line 377
    Issue: Lack of conclusion section.
    Fix: Add final paragraph: “In conclusion, Vicia villosa and tree-disk planting enhanced soil nutrient status and metabolite diversity, supporting their potential for sustainable orchard management.”

16. Throughout manuscript
    Issue: Inconsistent use of NH₄⁺ and NO₃⁻
    Fix: Standardize chemical notation per journal guidelines.

17. Throughout manuscript
    Issue: Use of the phrase “plant growth was promoted” without quantification.
    Fix: Replace with: “Plant height increased by X% relative (compared) to the control.”

18. Throughout figures
    Issue: Error bars are missing or not explained.
    Fix: Add: “Error bars represent ± standard deviation (n = 5).”

19. References section
    Issue: Underrepresentation of international literature on orchard cover crops.
    Fix: Include foundational global references (e.g., from Agriculture, Ecosystems & Environment, Plant and Soil).

20. General language
    Issue: Phrasing like “the soil was good” or “nutrients were improved” is vague.
    Fix: Use precise scientific terminology (e.g., “soil C:N ratio decreased by X%”).

Comments for author File: Comments.pdf

Comments on the Quality of English Language

The manuscript is generally understandable; however, the English language requires moderate revision to improve clarity and precision. Several sentences are awkwardly phrased or overly complex, which may obscure key scientific messages. Particular attention should be given to terminology consistency, sentence structure, and verb tenses. It is recommended that the authors seek assistance from a professional scientific editor or a native English speaker with expertise in agronomy or soil science to polish the language before publication.

Author Response

Dear Reviewers:

On behalf of my co-authors, we are very grateful to you for giving us an opportunity to revise our manuscript again. We have studied reviewers’ comments carefully and tried our best to revise our manuscript according to the comments. Based on the instructions provided in your letter, we uploaded the file of the revised manuscript, and all the changes highlighted by using red-colored text. We appreciate you very much for your positive and constructive comments and suggestions on our manuscript. The following are the responses and revisions I have made in response to the reviewers' questions and suggestions on an item-by-item basis.

Comment 1: Lack of a clearly articulated mechanistic hypothesis: The rationale for choosing specific species and planting patterns needs more scientific underpinning.

Response: Thank you for your comments and suggestions to our manuscript. Based on your comments, we have added the mechanistic hypothesis. The corrections are in the revised manuscript and using red-colored text.

Comment 2: Omission of soil taxonomy: The classification of soil types (e.g., FAO/WRB or USDA) is missing and should be explicitly stated.

Response: Thank you for your suggestions to our manuscript. We have been added the classification of soil types by using red-colored text (Page 2, Line 85).

Comment 3: No diagnostic reference for soil fertility: Nutrient levels are not interpreted using national or regional guidelines, leaving ambiguity on adequacy.

Response: Thank you for pointing this out. The basic physicochemical properties of the soils have been added to the revised manuscript by using red-colored text.

Comment 4: Superficial interpretation of metabolites: The role of several metabolites is listed but lacks physiological linkage to soil microbiota or stress signaling.

Response: After careful discussion, we have revised the third paragraph of the Discussion, and we have added discussions between soil metabolites, plant growth, and soil physicochemical properties. The detailed corrections are in the revised manuscript and using red-colored text.

Comment 5: Inconsistent English phrasing: Numerous awkward or vague phrases throughout the manuscript reduce clarity and precision.

Response: Thank you again for pointing this out. We have used English language editing services to improve our manuscript. If there are still parts that need improvement, please point them out. We will further seek language editing services to improve our manuscript.

In addition, according to the other comments from the reviewers, we have revised the original text. The detailed corrections are in the revised manuscript and using red-colored text.

Sincerely,

Corresponding author:

Qi Li, Ph. D.

College of Pastoral Agricultural Science and Technology, Lanzhou University

Lanzhou 730020, Gansu, China

Email address: liqi@lzu.edu.cn

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

Dear All,

The authors have addressed the primary scientific concerns raised during the first review round and have implemented substantial revisions. The addition of a mechanistic hypothesis, soil taxonomy classification, and a refined discussion of metabolite-soil-plant interactions significantly improves the manuscript’s scientific foundation and interpretability. 

Strengths of the Revised Manuscript

1. Mechanistic Hypothesis: The authors have clearly articulated a functional hypothesis linking grass species/planting patterns to soil and plant physiological processes.

2. Soil Classification & Fertility Diagnostics: The use of a formal soil taxonomy system (USDA/FAO) and the addition of regional nutrient adequacy guidelines strengthen the interpretation of soil fertility impacts.

3. Metabolite Interpretation: The revised discussion now links metabolites more clearly to plant-soil signaling, especially under semi-arid orchard management conditions.

4. Language Quality: English grammar and clarity have notably improved. However, a final language polishing (especially sentence transitions and article usage) is advised.

Minor Points for Improvement

• Table Formatting: Please standardize table captions and ensure uniform alignment and unit presentation across all tables.

• Soil Taxonomy Citation: Include a citation (e.g., FAO/WRB or USDA reference) for the soil classification methodology to reinforce reproducibility.

• Metabolite Function Clarity: While the revised discussion adds interpretation, specific biochemical pathways or microbial processes associated with the detected metabolites (e.g., flavonoids or organic acids) could still benefit from 1–2 literature-based clarifications.

Author Response

Dear Reviewers:

On behalf of my co-authors, we are very grateful to you for giving us an opportunity to revise our manuscript again. We have studied reviewers’ comments carefully and tried our best to revise our manuscript according to the comments. Based on the instructions provided in your letter, we uploaded the file of the revised manuscript, and all the changes highlighted by using red-colored text. We appreciate you very much for your positive and constructive comments and suggestions on our manuscript. The following are the responses and revisions I have made in response to the reviewers' questions and suggestions on an item-by-item basis.

Comment 1: Table Formatting: Please standardize table captions and ensure uniform alignment and unit presentation across all tables.

Response: Thank you for pointing this out. The tables have been standardized and added to the revised manuscript by using red-colored text.

Comment 2: Soil Taxonomy Citation: Include a citation (e.g., FAO/WRB or USDA reference) for the soil classification methodology to reinforce reproducibility.

Response: We feel great thanks for your professional review work on our article. The reference “Kovacevic, M.S.; Juric-Kacunic, D.; Libric, L.; Ivos, G. Engineering soil classification according to EN ISO 14688-2:2018. Gradevinar 2018, 70(10), 873-879.” have been added to the revised manuscript by using red-colored text.

Comment 3: Metabolite Function Clarity: While the revised discussion adds interpretation, specific biochemical pathways or microbial processes associated with the detected metabolites (e.g., flavonoids or organic acids) could still benefit from 1–2 literature-based clarifications.

Response: Thank you for your comments and suggestions to our manuscript. After careful discussion, we have revised the third paragraph of the Discussion, and we have added discussions of soil metabolites by organic acids. The detailed corrections are in the revised manuscript and using red-colored text.