Optimising Legume Integration, Nitrogen Fertilisation, and Irrigation in Semi-Arid Forage Systems

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript is well-written, presenting a thorough analysis and discussion. However, there are noticeable redundancies in the Results and Discussion sections that could be significantly condensed. Figures in the Results section may be combined, retaining only those that directly support the hypothesis and objectives of the study.

Line 76–80: To better highlight the economic benefits, consider discussing the land equivalent ratio (LER) and the advantage of multiple crop harvests in intercropping systems compared to sole cropping. This could help illustrate how intercropping offsets production costs.

Line 93–96: Since the study does not utilize remote sensing techniques for evaluating water management efficiency, this content is not relevant to the scope of the study and can be removed from the Introduction.

Line 132: Please specify the fertilizer product used as the nitrogen source and indicate the timing of nitrogen top dressing. Additionally, for the P₂O₅ and K₂O applications mentioned in line 146, clearly state the fertilizer types used. Also, explain the rationale or basis for the selected fertilizer rates.

Line 144: Indicate the seed rate used, e.g., in kg/ha, and specify the quantity applied in the experimental plots.

Line 169–172: Clearly define the calculation methods for NUPE, NUE, and NNI, as these are central metrics in the study. Consider including this information in Table 2 as well for clarity.

Line 306: This line can be deleted as the information is already provided in the caption for Figure 3. Similar redundancies should be reviewed and removed from other figure descriptions as well.

Author Response

Mr. Luís Silva

lmr.silva@campus.fct.unl.pt

01^st June 2025

Dear Editor Ms. Cheryl Han,

Nitrogen

 

Please find attached the revised version of the manuscript entitled “Balancing Legume Integration, Nitrogen Fertilisation, and Irrigation for Productivity and Profitability in Semi-Arid Forage Systems”. First of all, suggested by the Reviewer 2, and agree by we, the authors, the title of the manuscript was improved to “Optimizing Legume Integration, Nitrogen Fertilisation, and Irrigation in Semi-Arid Forage Systems”

All modifications were made in accordance to the reviewers consideration and the responses to their comments and suggestions are also attached. We would like to thanks for the reviewers effort and dedicated time to evaluate our manuscript. In our opinion, significant modifications were carried out across the manuscript allowing us to improve considerably our work.

All the document has been revised and make it more correct and readable.

Thanks for your attention!

 

Yours sincerely,

Mr. Luís Silva

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

REVIEW COMMENTS

Balancing Legume Integration, Nitrogen Fertilisation, and Irrigation for Productivity and Profitability in Semi-Arid Forage Systems ----AJ364671

Note: Some lines are highlighted in red or blue or with upper-case letters to emphasize certain recommendations or suggestions for article improvement.

GENERAL COMMENTS:

This manuscript tackles a relevant and timely topic in sustainable forage production under semi-arid conditions. The focus on integrating legumes, nitrogen fertilization, and irrigation is well-justified, and the inclusion of an economic analysis enhances its practical value. However, to meet Agronomy Journal standards, significant improvements are needed in clarity, methodological detail, structural organization, and statistical rigor. Notably, previous studies have questioned the rationale of applying nitrogen to forage or cover crops, which are traditionally intended to scavenge residual soil nitrogen. Research exploring alternative nitrogen inputs in forage systems, such as biological fixation through legumes, is essential for advancing sustainable and economically viable forage management. Please see the recommendations provided below to improve your research results.

 

LINE-BY-LINE COMMENTS:

• Lines 2–4: The title is informative but overly long. Consider simplifying to:
  “Optimizing Legume Integration, Nitrogen Fertilization, and Irrigation in Semi-Arid Forage Systems”
  This maintains clarity while improving conciseness, although the article talks about productivity and profitability, these are not part of the key input strategies investigated

 

Abstract:

• Lines 29–44: We suggest that authors can include specific values for yield improvement, nitrogen use efficiency (NUE), and profitability, as these are key to their study mentioned both in the tittle and in the key words. Additionally, the authors can state explicitly where statistical significance was observed not generalizing numbers.
• Line 36: "Moderate N doses (120 kg ha⁻¹) were more efficient..." This is vague especially when there are NO SOIL test results (Pre-plant) presented in the paper. How can you convince the readers that the response was due to applied nitrogen?
• We suggest that authors specify how efficiency was assessed (e.g., NUE, yield per kg of N, or economic return).
• Lines 39–40: “...no significant differences were observed between crops.” Which parameters showed no significant difference—yield, NUE, or profitability?
• Management and environment are too broad and should not be used in the study that was conducted in a specific location for 137 days.
• Additionally, the “genotype” which genotypes were evaluated by the study? The authors need to revise the whole paper and revisit this option. I suggest that they remove it, as it is misleading.

Introduction:

The introduction is clear stating the hypotheses at the end of the introduction, outlining the expected effects of legumes, N fertilization, and irrigation. I have no comment on it, it can go from there except few double spaces which are unnecessary like on line 83, and the use of words like “the findings “may” contribute” this suggest that the authors are not sure of the contributions of the study findings. This language is all through the paper and needs to be revised.

MATERIALS AND METHODS:

Experimental design

• The authors mention that the study has three nitrogen levels N0, N1, and N2) in the whole plot (Main plot/main block), whatever term on line 132. However, on line 113, different numbers are indicated.
• The design mentions. The main block 131 had three doses of N topdressing (N0, N1, and N2 with 0, 120, and 200 kg ha−1 of fertiliser with 132 27% N, respectively). The sub-blocks had two different forage crops, and the sub-sub- 133 blocks had two irrigation management scenarios (rainfed vs. irrigated) between lines 131 to 134. This is supposed to be split-split plot, rather than the split-plot simply mentioned in the article.
• Line 114 mentions the “Varrying genotypes” this is misleading as no genotypes were involved in the study and therefore not a credible work to discuss G by E, I therefore recommend that the authors revisit the paper to remove this and re-write the sections in which it was mentioned.
• Again, on line 114… talks of simulation…… is this a simulation study? How many data points were involved in this study? Forty-eight plots over the duration of the study???
• Line 117–118: The method for drying and sieving is briefly mentioned but lacks details on the mesh size or duration of drying.
• Line 119: “All agronomic variables...” lacks definitions at this point.
• Line 126…. “...explained in [23]” again relies too heavily on a prior publication. Describe the method in detail and put the reference rather than the reference for the readers to look it up.
• Line 131–133): N doses are described here as 0, 120, and 200 kg ha⁻¹, which conflicts with earlier values of 32.4 and 54 kg ha⁻¹ (Line 112). Reconcile or clarify whether these are cumulative doses including the basal application.
• Line 133 list the treatments in each level (e.g., whole plot, N0, 120, ……, SUB-PLOT…. Etc
• Line 135 lists the clear growth stages of the crops.
• SOIL TEST RESULTS Pre-plant and after termination of the study needed for the paper such as this that discus the nutrient application, uptake, and tissue concentrations of nutrients.
• Line 137 was their randomization within the whole plot, sub-plots, and sub-sub-plots? Line 137 “Replicated 4 times, totalling 48 plots” …… plot allocation method and randomisation process are not explained.
• Line 138----- Plots were set up on flat location……was the split-split the best approach for this site?
• The authors mentioned that irrigation was applied at field capacity. Which soil type, what was the plant rooting depth, what was the soil field capacity? How was soil FC determined?
• How were the irrigation requirements determined? How much water (inches, mm, ha, meters) etc was applied in the irrigated (IRRGATION + SEASON PRECIPITAION) = Total season moisture (gross), this information is needed.
• Line 145–147: “Sufficient doses of phosphorus... potassium... and a dose of N (27.6 kg N ha-1)” are applied uniformly. Although these are not part of major trts the authors need to clarify whether this basal dose is included in the N treatment totals since the sources of N may include additional P and K. The wording currently implies it is not.
• Line 166… Equation (1) is cited but not labeled/formatted correctly. Follow AJ journal guidelines for equations (numbered, centered, and in appropriate format).
• Line 175–177 Land cost of €173 ha-1 is cited but the rationale is not discussed. Indicate whether this is a rental cost, opportunity cost, or derived from market value. Do farmers rent land or is this an important consideration for a broad recommendation?
• Line 180–185… Harvesting and basal fertiliser costs were excluded… was this intended or it does not contribute to the costs of forage production?
• Line 229–231…although the spearman’s correlation matrix is a strong analytical tool for traits response relationships, the measured parameters and the conditions of the study described in here in the paper, I do not think they warrant this type of analysis! Additionally, the method of testing significance (e.g., p-values, multiple comparison correction is not described. Authors need to justify the choice of the method used.
• Line 237–239: Sensitivity analysis levels of ±10% and ±20% are used but lack justification. The authors need to explain how these percentages were selected; do they reflect realistic variability in market conditions or operational costs?
• Line 243): Use of “coefficient of variation, standard deviation, and interquartile analysis…………………these descriptive statistics were they for outlier removal or distribution checking???? This should be clarified.

 

MISSING INFORMATION THAT MUST BE SUPPLIED

• The paper is such as this that looking at forage production in semi-arid environments, nitrogen management, nutrient uptake and irrigation, the following information must be provided.
  1. Soil test data for pre-plant and post termination
  2. Weather data (rainfall, temperature, Evaporation, and evapotranspiration), and GDD
  3. Irrigation method used description, how water was applied, how much was determined, how controls was ensured to avoid leaching, how soil water holding capacity was determined, how much water was applied etc.
  4. Tissue nutrient testing, at in-season and at the end of the season preferably

GENERAL STATEMENT

1. Attention to details! Table one “Table 1. This is a table. Tables should be placed in the main text near to the first time they are cited…… Line 152. This is not a minor error.
2. Repeated table and figure labels. Follow the AJ journal to edit all figures and tables.
3. The figure and tables must be complete and clear following the AJ standards. None of the figures in this article are complete. Re-draw all the figures to label clearly the x- and Y – axis, the figure label goes after the figure, clearly stating what is about the figure and if there are any used acronyms must be explained.
4. The table label ….do the same, use the AJ template to learn more about table formatting.

RESULTS

General observations: Presentation of results is most of the time vague. The choice of results presentation method matters especially to the target audience. All these box plots are not clear, poorly labeled, faint with poor visual impressions. The alternative method, e.g., tables, should be chosen.

• Line 260–261----Outliers were removed using the interquartile method, but no details are provided on thresholds (e.g., 1.5× IQR). Authors need to specify the criterion for outlier exclusion and how many data points were excluded. This affects the integrity and reproducibility of the results. For example, table 6 shows sample size ranging from 29 to 45, which is true?
• This brings another question. The study had 48 plots = 48 observation units at plot level over the 137 days!! WAS THIS STUDY REPEATED OR NOT? Was the analysis conducted on the combined data or separate data?
• Again, the author mentioned on line 137-138 that the flat location…. Was chosen to avoid errors. What was the cause of the outliers that were treated? Was this sampling error or experimental error?
• Line 266–273…Table 6 some variables show extreme coefficients of variation (e.g., NUE: 295.1%, NUpE: 190.6%.... Such high variability may indicate skewed data or poor treatment response. This warrants further explanation or transformation.
• Table 6 is presented without indicating if values shown are pre- or post-outlier removal.
• Table 7 (Line 285): It is unclear how many observations were tested per variable in the Shapiro–Wilk test. Authors need to report sample size (n) for each variable tested, especially since some variables had fewer than 45 observations (e.g., NUE: n = 29). This is too small a sample from which to make conclusions.
• The abbreviation “Nt” for nitrogen treatment is inconsistently used. In other places, N0/N1/N2 is used without definition here.
• Line 295: The sentence is overly vague ("...variables that showed the most significance...”) …. This can benefit from re-writing.
• Table 8, some interactions such as N0.MIX AND N2.MIX among others are useless and do not have any agronomic significance.

GENERAL COMMENTS

1. Re-write the results in a format that can be clear and understandable.
2. Choose the format that can show the data clearly not these faint and unclear boxplots!
3. The single study single year with forty-eight rows of data with some removed cannot be used to make such huge recommendations.
4. These calculations from a very narrow sample are misleading and should not be used to make any significant agronomic recommendations.
5. Figures and tables need to be re-worked.
6. Additional data is needed if any recommendations are to be made from this study.
7. Weather data and soil information are key to such study and must be also included.
8. The small sample small observations skewed with large outliers cannot be used to make a sound agronomic recommendation. Do an additional study and provide additional data to prove your results.

DISCUSSION:

• Line 396: “Yield shows a median of 3133.8 kg ha-1...” ……. This is purely descriptive, if no clear results were observed, a clear mention can be made. Discussion should focus on interpreting biological relevance and linking to literature.
• All from line 397 through………. line 486, the outcomes presented are barely descriptive. Not sure if the authors observed anything from which to make recommendations??
• Line 407- 410): “NUpE and NUE... even showed negative values...” …. This result is important but is only briefly mentioned. Authors should explain biologically how negative NUE could occur (e.g., high N application with low biomass response) and discuss the agronomic implications. Moreover, this is a study with no background soil information, no weather data etc.
• Line 412–414: The phrase “significant losses through volatilization, leaching and other processes” is speculative without data, especially when the authors mentioned that they selected the flat location to avoid errors.
• Line 419: “NNI... varied between 0.5 and 1.4...” ………………These ranges are presented without interpretation. Tell the readers how these values align with nutritional sufficiency standards in forage crops used in the study.
• Line 432–435): Statistical significance (e.g., Table 9, Figure 2) is cited but without corresponding values or effect sizes. Again, the tables and figures should clearly tell the outcomes of the study without the authors explaining.
• Line 480–486: A mention by the authors that …. “Triple interaction” having “limited effect” are vague…… What interactions on forty-five rows of data. Either remove this statement if uninformative or describe the effect observed in CPy, NUp, etc., even if it was minor.
• Line 525–527): “...cheaper to manage per unit produced...” …………. Ambiguous phrasing. Specify units e.g., “...lower cost per kg of dry matter produced,” and relate this to the current production costs and the yield of forage!
• Line 554–556: Statements like “intermediate dose of fertilisation made it possible to achieve the highest net revenue” should be supported with values.
• Line 613–617): Strong correlations are cited (e.g., r² = 0.9) but not referenced back to the practical implications.

Overall observations

1. The paper lacks evidence to make any recommendations.
2. The observations are insufficient.
3. Study lacks reproducibility.
4. The study was not repeated and therefore not a good one to make such observations.
5. The numbers are empty but descriptive status.
6. Additional data and supporting information can strengthen the work, but the observations and conclusions are overstated.

Conclusion:

• “Improves the effectiveness of these strategies” is vague.
• . reinforcing the importance of diversified cropping practices and the potential of integrated grass-legume systems.” …….. Not supported by data
• …The moderate nitrogen fertilisation rate of 120 kg N ha-1 emerges as an effective strategy for balancing yield and sustainability...” …… not supported by data, no soil tests (pre and post), no weather data, very few data rows, not repeated study, etc.
• Again, crucial point, but not clearly supported by a cost-benefit metric.
• Additionally, the analysis of profitability metrics and their correlation with agronomic variables...” …. No numbers, correlation does is /was wrongly used here to make conclusions.
• Too abstract, e.g., the …."Profitability metrics" and "agronomic variables" are generic terms.
• “...demonstrated that yield and crude protein yield were the strongest predictors of net profitability, with REVnet showing a strong positive correlation with CPy (r = 0.89).” ………………. CORRELATION ANALYSIS was wrongly applied. Clear numbers of tons or kg of forage harvested and sold based on the price and cost of production should be the ones based on making conclusions NOT Correlations

Good luck authors.

Comments for author File: Comments.pdf

Author Response

Mr. Luís Silva

lmr.silva@campus.fct.unl.pt

01^st June 2025

Dear Editor Ms. Cheryl Han,

Nitrogen

 

Please find attached the revised version of the manuscript entitled “Balancing Legume Integration, Nitrogen Fertilisation, and Irrigation for Productivity and Profitability in Semi-Arid Forage Systems”. First of all, suggested by the Reviewer 2, and agree by we, the authors, the title of the manuscript was improved to “Optimizing Legume Integration, Nitrogen Fertilisation, and Irrigation in Semi-Arid Forage Systems”

All modifications were made in accordance to the reviewers consideration and the responses to their comments and suggestions are also attached. We would like to thanks for the reviewers effort and dedicated time to evaluate our manuscript. In our opinion, significant modifications were carried out across the manuscript allowing us to improve considerably our work.

All the document has been revised and make it more correct and readable.

Thanks for your attention!

 

Yours sincerely,

Mr. Luís Silva

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have addressed all the comments in the revised manuscript. 

Comments on the Quality of English Language

I don't feel qualified to comment on the English language quality

Reviewer 2 Report

Comments and Suggestions for Authors

I am okay with the current draft