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The authors have made the minor revision requested. This manuscript is now acceptable for publication.
[# PeerJ Staff Note - this decision was reviewed and approved by Paula Soares, a PeerJ Section Editor covering this Section #]
Reviewer 2 raises several important points that need to be addressed. The others are satisfied with work, but note that there are still outstanding language issues that detract from the paper.
**PeerJ Staff Note:** Please ensure that all review and editorial comments are addressed in a response letter and that any edits or clarifications mentioned in the letter are also inserted into the revised manuscript where appropriate.
**Language Note:** The review process has identified that the English language must be improved. PeerJ can provide language editing services - please contact us at [email protected] for pricing (be sure to provide your manuscript number and title). Alternatively, you should make your own arrangements to improve the language quality and provide details in your response letter. – PeerJ Staff
The manuscript contains sufficient introduction and background. It follows profession structure of an article.
However, English language editing is still needed for clarity. For example, Line 18-24: A very long and unclear sentence. Please rewrite and follow the grammatical rules
This is well done
Conclusions are well stated, linked to original research question & limited to supporting results.
The authors need to edit the sentence and grammatical structure for clarity
Title & Abstract
In this revised version, the revisions are not highlighted using tracked changes or colored text, making it a bit difficult to check whether the authors have appropriately addressed the comments. A “response to reviewers” file, if presented, can help understanding of the rationale behind the changes. I nonetheless provide comments on the revised manuscript.
Currently, the Abstract lacks a discussion on the specific recommendations for management strategies stemming from the results, particularly on phosphorus fractionation. Some of this is discussed in the Discussion section (e.g., L 291-301) but other paragraphs seem to be rather brief and need further elaboration (e.g., L 302-305). I would also like to see more specific recommendations suited for each of the study sites (Sademo, Holeta, and Damotu, please see my comments on the post hoc test below). Since “management” is in the title, concise information on the implications for agronomy from the phosphorus fractionation results is expected in the Abstract.
Introduction
My suggestion to include the optimum phosphorus for barley growth has been addressed and a relevant reference has been provided. However, the introduction is still somewhat brief (at one and a half pages) due to the lack of detailed introduction on previous work and introduction to soil phosphorus management.
Although some effort was made to provide the background research on lime and phosphorus fractionation work in Ethiopia (e.g., L 68 and also in the results in L 255), a detailed description of the work is not provided. The lines from L 58-66 are introductory to the usefulness of determining the phosphorus constituents in the soil for agriculture, but do not go into further detail. In the previous review, I recommended a few related studies that were conducted by the authors. I am confused about why this previous work was only barely referenced in the current paper (e.g., in L 324), particularly in the introduction section. This is important because it would allow readers to understand the significance of the findings.
In terms of soil phosphorus management in agriculture, a review by Roberts and Johnston (2015) may be useful for the introduction, particularly in reference to specific best management practices (e.g., the principle of “4Rs”—the right nutrient source, the right rate, the right time, and in the right place). This introduction to soil phosphorus management is critical for understanding the aim of the phosphorus characterization done in this study.
Figures & Tables
Table 1 caption: Specify what P-values the number of asterisks correspond to.
Table 2 caption: Specify which locations are relevant to the contents of the table.
Figure 3: The label for the y-axis is missing. If applicable, please add error bars.
Material and Methods
In the revisions, the authors explained that the sites were selected to represent the range of soil characteristics present in the nitisols of Ethiopia that have potential for barley agriculture and some soil physico-chemical properties were provided. The additional details, including in the statistical methods, provide the much-needed clarity. I also appreciate the extra information in the Annex. The ANOVA is followed by a post hoc LSD test. There are a few details that will help enhance the methods:
Since the rate of lime is described later in the section (L 121-123), add “specific to each site, as described below” to the end of L 112 for clarity.
The source of the phosphorus fertilizer and compost (e.g., manufacturer) is missing. In addition, the source of the BH-1307 barley seeds should be provided. Please include this information to enable the replication of the experiment.
L 176: “The” is missing in front of “saturated NaCl solution” because this refers to the same solution in L 169.
L 206: Here and subsequently just “HI” is fine. This term is already defined earlier in L 198.
Results
The addition of mean values for treatment groups enhances the understanding of the overall results. The ANOVA results for grain yield are now presented in Table 1, which include important information such as the df, SS, and MS. However, the ANOVA results for the other metrics (dry biomass, HI, and TSW) should also be presented.
The ANOVA results shown in Table 1 identified significant differences among locations (“LON”) and also a significant interaction effect between lime and location for grain yield. Without the complete post hoc results, the relationships are not clear and could not be interpreted. The caption in Table 2 does not specify from which locations the barley yield components were derived from. The LSD results should include locations since it had significant effects on the metrics.
Discussion
The first paragraphs of the discussion focuses on the effects of lime and phosphorus treatments, as well as their combined effects. However, this section should include the new information yielded from the post hoc tests on the metrics on yield, after the authors have evaluated those results (rather than simply stating that there were significant location and interaction effects in L 224-228). Discuss why some locations might be more affected by the lime treatment in the context of the post hoc results.
Conclusion
The concluding paragraphs are strong in providing specific recommendations for managing the growth of barley in acidic soils. It also identifies the limitations of the current study and highlights avenues for research, including the use of soil microbiota that plays a critical role in phosphorus uptake in plants. I have no further comments on the conclusion.
NA
All the comments have been addressed; however, the key words are missing.
Line 52: change Without to without (capitalized word)
Line 64-65: types. (Fife, 1962; Peterson & Corey, 1966; 65 Williams et al., 1967; Smillie & Syers, 1972). Make it one sentence by removing the full stop.
Comments on the objectives have been addressed.
References
While the citation inconsistencies within the text have been corrected, the reference list still contains formatting issues. The authors should revise the references to ensure they are complete, accurate and consistently formatted according to the journal’s style. Addressing these issues is essential prior to publication as a properly formatted reference list will significantly enhance the clarity and professionalism of the manuscript.
e.g.
1. Batjes, N.H. (2011)
Bremner JM. 1960
2. Kamprath E. J., F. Adams. (1984)Crop response (Line 471)
Katrina A. Macintosh, Brooke K. Mayer, Richard W. McDowell, Stephen M. Powers,
Lawrence A. Baker, Treavor H. Boyer, and Bruce E. Rittmann. (2018). Managing
No comment
No comment
The science presented in this paper is sound and I don;t believe it neds to go back to the reviewers; however, it suffers from numerous minor grammatical and spelling errors, as well as poor writing clarity, which detracts from its acceptability. There are many run-on sentences, subject-verb agreement issues, articles missing and verb tenses. Examples of mistakes include "money (many) studies, metrological (meteorological) station, baches (batches) of extraction, etc. The numerous inconsistencies are widespread enough that a native English reader (or an AI grammar and spell-checking tool) should be used to correct the document before resubmission.
**Language Note:** The Academic Editor has identified that the English language must be improved. PeerJ can provide language editing services - please contact us at [email protected] for pricing (be sure to provide your manuscript number and title). Alternatively, you should make your own arrangements to improve the language quality and provide details in your response letter. – PeerJ Staff
The submitted manuscript presents original and relevant research on phosphorus fractionation in Ethiopian Nitisols and its implications for barley growth, addressing a crucial agricultural challenge in acidic soils. All three reviewers agree that the study is valuable and methodologically sound in its conception, with well-defined aims and potentially meaningful contributions to soil nutrient management. However, substantial major revisions are required across all sections to ensure clarity, rigour, and alignment with publication standards.
In terms of basic reporting, the reviewers highlight significant issues with grammar, sentence structure, and consistency, recommending professional language editing. The title and abstract do not fully reflect the study’s core focus, and the objectives are overly broad. The introduction should better establish the work's novelty by incorporating additional Ethiopian and international studies, particularly on phosphorus fractionation, barley response to lime and phosphorus, and the minimum nutrient requirements for barley yields. References and citations are inconsistent and need to conform to PeerJ formatting guidelines, including style, completeness, and DOIs.
The reviewers all agree that methods are generally thorough but that critical details are missing, including site histories, compost composition, lime application rates, experimental layout, treatment structure, and the duration of experiments. The statistical analysis is deemed inadequate—two-way ANOVA, MANOVA, and assumption checks are necessary, with post hoc tests to validate interactions. A clearer description of fractionation methods and restructuring detailed protocols into supplementary materials is also advised.
The results and discussion are credible but still incomplete. The reviewers request full ANOVA tables, integration of phosphorus fractions with yield outcomes, and a more straightforward presentation of figures and tables with complete captions, consistent terminology, and explanation of abbreviations. The discussion is overly descriptive rather than mechanistic, requiring deeper interpretation of phosphorus dynamics, lime-phosphorus interactions, limitations of the study, and practical management implications. Future directions and agricultural applications should be expanded.
In summary, the reviewers stress that major revisions are required, and the manuscript must be addressed carefully, reviewing each comment line by line, to achieve publishable quality. We look forward to receiving the revised manuscript.
**PeerJ Staff Note:** Please ensure that all review, editorial, and staff comments are addressed in a response letter and that any edits or clarifications mentioned in the letter are also inserted into the revised manuscript where appropriate.
**PeerJ Staff Note:** It is PeerJ policy that additional references suggested during the peer-review process should only be included if the authors agree that they are relevant and useful.
Ambiguous and unclear in most parts. For example:
Line 22: Change 'immediately' to 'readily'
Line 69: delete 'nutrient'
Lines 108-111: needs to be rewritten
Line 111: change 'expressed' to 'determined'
Line 114: should be 'Walkley and Black (1954) method.'
Lines 168-171: not necessary
Lines 257-260: Please rewrite and don't forget to use punctuation for clarity
Lines 262-263: Remove the initials from the in-text citation to be consistent
Lines 276-277: Please rewrite
Lines 292-294: Please rewrite
Line 299: Again, inconsistent with other in-text citations
Original primary research within the Aims and Scope of the journal.
Research question well defined, relevant & meaningful. It is stated how research fills an identified knowledge gap.
Impact and novelty not assessed.
Most of the discussion is not mechanistic. At the moment, it is mostly about being consistent with one study or the other.
Table 2: state what the bold numbers represent
Figure 3: What was the number of replicates? Add error bars
Title & Abstract
The title is related to the manuscript, but in my opinion, it misses the mark on the core focus of the study. Rather than focusing on “soil nutrient management strategies,” this study analyzed the phosphorus fractionation in agricultural soil for barley growth. I suggest editing the title to something similar to “Analysis of phosphorus fractionation in Nitisols of the central Ethiopian highlands and recommendations for barley growth.”
The abstract is strong and sets out the aim of the study, which is to evaluate the inorganic P fractions in Nitisols in central Ethiopia and the effects of lime treatments on barley growing on acidic soils. The relevance of the results on the different forms of P found in acidic (and strongly acidic) soils for soil nutrient management is also highlighted. However, it is missing the test results on the growth of barley across lime and phosphorus input treatments. The relevance of these different forms of phosphorus to their availability to plants (e.g., phosphorus sorption) should be discussed. The last sentence of the abstract should relate to the control of barley growth via soil management.
The grammar is strong and the manuscript reads well, although there are some minor errors throughout, particularly in the Discussion.
Introduction
The introduction section highlights soil degradation (particularly phosphorus limitation) as a major problem for agriculture, and the importance of research on phosphorus fractionation for enhancing phosphorus availability for plants. In addition, the problems with phosphorus availability in acidic soils in the study region are highlighted. The aims of the study are also expressed well. However, since one of the study aims is to help managers optimize phosphorus fertilizer addition, I would incorporate some info on the minimum phosphorus levels required for yielding barley crop in the area or optimal rate of addition (see Agegnehu and Lakew 2013).
While some references are provided for the effects of enhancing phosphorus availability in the acidic soils in Ethiopia (L 60 - 62), a few other studies examined the effect of the addition of lime and phosphorus on barley production in nitisols (Dejene et al. 2021, 2023). Moreover, there is no discussion of previous work on the fractionation and availability of phosphorus already done in Ethiopia (e.g., Kiflu et al. 2017)
I think that a better case for the novelty of the study, which I believe is the combined approach with fractionation and barley growth, can be argued after the contributions of these studies to barley are acknowledged and discussed.
L 48: The “source-sink dynamics of applied phosphorus” requires elaboration.
L 53-54: Provide some info on what the fractionation method involves.
L 56-57: This sentence has an error.
See references:
- Agegnehu G, Lakew B. 2013. Soil test phosphorus calibration for malting barley (Hordeum vulgare L.) production on Nitisols of Ethiopian highlands. Tropical Agriculture. 90(4), 177.
- Dejene M, Abera G, Desalegn T. 2021. Response of food barley (Hordeum vulgare L.) with combined uses of lime and varied phosphorus sources on acidic nitisols of Wolmera District. Journal of Soil Science and Environmental Management. 12(3):115-31.
- Dejene M, Abera G, Desalegn T. 2023. The effect of phosphorus fertilizer sources and lime on acidic soil properties of mollic rhodic nitisol in Welmera District, Central Ethiopia. Applied and Environmental Soil Science. 2023(1):7002816.
- Kiflu A, Beyene S, Jeff S. 2017. Fractionation and availability of phosphorus in acid soils of Hagereselam, Southern Ethiopia, under different rates of lime. Chemical and Biological Technologies in Agriculture. 4;4(1):21.
Figures & Tables
The figures are generally clear and legible, although Figure 3 could be improved (see below).
Table 1 caption: Explain the meaning of (1) the bold font, (2) capital letters next to means, and (3) the abbreviations in the first row.
Table 2 caption: What is the unit of measurement for all of these values? See my comment on Table 1 regarding font and abbreviations.
Fig. 2 caption: Please insert the abbreviations (SDM, HC, and DM) into this caption.
Fig. 3: Explain the abbreviations in the caption. Consider recreating this figure on R for clarity. Alternatively, providing summary figures on the statistically significant differences (e.g., lime x phosphorus) on growth parameters would be helpful.
Material and Methods
The methods are very clear, and the authors have provided an adequate level of detail to enable a basic replication of the study. The details appear to be complete, describing the field experiment and soil phosphorus fractionation procedure. However, there are some areas for improvement in clarification before the study can be fully replicated.
Site information:
I feel that more information can be provided on each of the three sites (Damotu, Holeta, and Sademo). Can the authors provide reasons why these three sites were chosen? I am also curious about the agricultural history of these sites and whether there are differences in their previous management. Is there any data on the soil chemical properties?
The replicate number of 3 is relatively low, but it is typical in such studies, and there should be sufficient statistical power to observe meaningful results. My suggestions for improvements and clarifications are listed below:
L 75: Specify whether these min/max temperatures are monthly, yearly, or daily.
L 76: Provide the range of pH values.
L 77: Growth experiment details – Specify where the barley was obtained. What was the duration of the growth experiment? Mention the start and end dates. What was the watering regime?
L 79-80: For clarity, please specify the whole experimental design: 3 phosphorus 3 lime * 3 replicates = 27 plants.
L 81: References missing for the “recommended phosphorus rate.” (alternatively, in L 96-105).
L 82: Clarify the P2 treatment. What does this mean in terms of the P2O5 per hectare?
L 85-86: Provide the exact quantities of lime used, as it was already done in L 81 for the phosphorus.
L 96: Provide the manufacturer or source of the TSP.
L 105: Again, where are these “standard” recommendations from?
L 108: Correct to "samples". In this case, the three phases should be referred to using (1), (2), and (3) rather than 1st, 2nd, and 3rd.
L 112-113: Both the Kjeldahl and Bray methods should be cited (e.g., Bremner 1960).
L 139: Provide the citation for Method II, as done for Method I in Line 127. In addition, provide at least some details on this method.
L 140 and 150: Concentrations of NaCl are missing.
L 154-158: When were these traits measured after the start of growth?
L 163: Inappropriate phrasing–Delete “ensuring robust and reproducible results.”
The calculation of the harvest index (HI, L 191) needs to be provided in the methods. Also, please explain the purpose of this metric.
Statistical analysis
L160: What exactly are the “key dependent variables”?
L160-161: ANOVA test whether the effects of treatments (as well as their interactive effects) on growth parameters are significant. Since both lime and phosphorus treatments were used, a two-way ANOVA is the most appropriate analysis. Was this analysis used? Two-way ANOVA should be followed by a post-hoc Tukey's HSD test to evaluate the statistical relationships among all treatment groups.
It is also recommended to run MANOVA when there are multiple dependent variables and they are likely not independent from each other to account for their correlations. Moreover, the assumptions of ANOVA (e.g., homoscedasticity) should be checked using Levene's and Shapiro-Wilk tests. If the assumptions are violated, the log-transform of the data or non-parametric tests should be considered.
Reference:
Bremner JM. 1960. Determination of nitrogen in soil by the Kjeldahl method. The Journal of Agricultural Science. 55(1):11-33.
Results
The study makes a valuable contribution to the field by providing new information on the link between phosphorus forms existing in acidic soils and barley growth. The results reported agree with barley growth under phosphorus and lime additions, and the replication is sufficient for confidence in the credibility of the data.
I have some suggestions for improving the information on the results. In particular, the full ANOVA results (with MS and degrees of freedom) should be presented in a table or supplementary table. The results on the differences in phosphorus fractionations across different treatments could also be statistically tested (e.g., using ANOVA) to enhance the contribution of the paper.
L 177-178: Provide the means for these groups.
L 184-187: Either provide the complete mean grain yield values or cite the relevant Table or Figure.
Discussion
The findings described are in agreement with the results presented, and they align with the two objectives stated in the introduction. The discussion section is sound, detailing the response of the barley to lime and phosphorus treatments and recommending management strategies most likely useful for soils with different acidity levels. The authors note that the lime treatment had minimal effects on growth because of the relatively low acidity of the soil at the site. Of course, the results on growth should be reevaluated following the implementation of appropriate two-way ANOVA and post hoc tests. I suggest further discussion on a few topics.
The relevance of the results on HI (or reproductive efficiency) for agricultural management needs some explanation.
Discuss the interaction between lime and phosphorus according to the results from the two-way ANOVA (or other non-parametric two-factor test).
Limitations of the study
Discuss any potential limitations of the study, such as limitations in sites, treatments, or cultivars.
Future directions
Although these are mentioned in the conclusions, the discussion section allows for a more detailed evaluation of each topic, such as the findings of previous studies (with a focus on barley), leading up to the state of knowledge today. Various avenues for future research can be discussed, such as soil pre-treatment (e.g., with composting or manure) and the effect of the timing of soil application on plant growth. Moreover, the potential for microbial treatments for mildly acidic soils should be discussed in more detail–For example, including information on specific endophyte treatments that may be most suitable for barley. Murphy et al. (2014) may be useful for this:
Murphy BR, Doohan FM, Hodkinson TR. 2014. Fungal endophytes of barley roots. The Journal of Agricultural Science 152(4):602-615.
Recommendations for management
Discuss the practicality of these insights for agriculture in practice. Do the authors see any challenges in implementing resilient nutrient management practices (e.g., for policy or land managers such as farmers)?
Other comments
L 257: Is this subscripted Pi the same as without the subscript found elsewhere? Please check.
L 269: “Like study” does not make sense. Do you mean “A similar study indicated”?
L 273: A comma is missing.
Conclusion
The conclusion section is sound and provides an overview of the results and future directions. However, the structure of the section needs to be improved. The sentences should read as a paragraph or two, rather than 5 disjoint sentences (L 343-357). I recommend a numbered list within a sentence rather than using bullet points. The last sentence of the conclusions rounds off the study well.
The paper was done well, but addressing the following will improve it.
General:
The manuscript would benefit from thorough English language editing to improve grammar, sentence structure, unclear phrasing which reduce clarity and overall readability...replace the words in in lines 216 (pulled), 234 (Ai-bonded), 254 (from), 258 (reviled), 261 (which a lines with money studies), 263 (Some amendments like liming and organic inputs can improve), 269 (Like study indicate), 277 (pattern), 309 (reducing environments). I recommend that the authors carefully revise the text or seek professional language editing support to ensure clarity, conciseness, and proper scientific expression throughout the manuscript.
Introduction
The introduction is well structured; it provides the relevant background and highlights key issues on phosphorus management in acidic soils of East Africa. However, the authors need to address the following:
Refine the introduction to clearly articulate the problem being addressed, the motivation for the study, the specific objectives or research questions, and coverage of recent specific P Fractionation studies. Provide sufficient background from the given literature.
The objectives are too broad and lack clarity. Lines 67-70 improve the objectives of the research.
Materials and Methods:
The Materials and Methods section is comprehensive and provides detailed experimental and analytical procedures. To strengthen the paper, the authors need to address the following.
The authors need to describe the design fully. The following key details are missing.
Plot size, total number of treatments, experimental layout, and replicate structure across the locations.
Lines 77-80. The paper will benefit if the authors address these missing details.
The lime quantities were not provided; however, the paper will benefit if the quantities of lime could be shown in lines 91-93.
Compost is used as treatment, but its chemical characteristics are not provided in lines 98-100. The authors need to provide the chemical characteristics of the compost.
The experiment duration is stated as 2022 to 2024 in line 72, but the data collection is only described for the 2022 season in lines 10-111. The authors need to clarify whether it is a multi-location single-season or multi-year study.
The paper will benefit if the step-by-step fractionation method is summarized, and the detailed procedures are moved to a supplementary section in lines 119 to 152.
Results and Discussions
The manuscript presents important findings on phosphorus dynamics and soil fertility in acidic Nitosols of Ethiopia. The following need to be addressed to improve the clarity of the manuscript:
Table 1 lacks important methodological and presentation details. The rates and chemical composition of lime and P sources are not provided, making replication difficult. Measurement units for TSW are missing, and statistical analysis details (for instance, main effects, interaction effects, and ANOVA assumptions) are not described. Treatment abbreviations should be expanded in the title, and the table should include an explanation of the lettering system.
Letters (A, B, C, etc.) are used for significance grouping, but no explanation is given in the table on what their meanings are.
Inconsistent use of Aluminium bonded phosphorus (line 257), with Aluminium bonded phosphorus (Table 2) and likewise to Iron bonded phosphorus (line 267) with Iron bonded phosphorus (Table 2) interchangeably. The manuscript will benefit from the consistent use of the same terms throughout the article.
The authors should provide a clearer integration of findings, linking specific P pools to yield variations among treatments. As it stands, crop yield and biomass are presented separately from P fractionation outcomes.
To make Table 2 clearer, the authors need to address the following:
Some rows and columns are misaligned. Redo the table and align the rows and columns.
The table mixes treatment results, LM1, LM2, LM3, with site baseline samples; Pio for SDM, HC, DM, without clearly separating them into sections or subsections.
The codes LM1, LM2, LM3, P1, P2, and P3 are not explained in the table; their meaning must be either in the caption or footnotes.
The use of + in 0.1M NaOH + 1.5MKMnO4 should be clarified, whether it is a step-by-step extraction or a combined reagent (Table 2).
The P values were reported for crop parameters, but no statistical summary for changes in P fractions between treatments and sites......line 198-216. Conducting this statistical analysis and discussing the results of the same. This will enhance the quality of the paper.
References
There is no consistency in the way references are written:
1. Bunemann, E.K., Oberson, A., and Frossard, E. (2011).......
2. Duflo E., Kremer M. and Robinson J. (2008)........
3. Wierzbowska J, Sienkiewicz S, Zalewska M, Żarczyński P, Krzebietke S. (2020).
The first author’s name with a comma and in other cases without. Others after the first author's name, it has a full stop and a comma, while others have a comma only. The consistency in the way references are written needs to conform to the PeerJ article publications.
No consistency in the way citations were done:
1. Amaizah et al., 2012
2. Antonangelo, J et al 2017.
The first author’s name and initial were cited, while in the first case, it was not. The consistency in the way citations are written needs to conform to the PeerJ article publications.
DOIs need to be added where it is missing, and journal titles need to follow a consistent style. In addition, while the cited works are relevant, they are largely region-specific. The paper would benefit if the global and African cross-country studies were used to capture a broader context.
Cross-check all the citations in the text with the references in the reference section and make sure that all references have a corresponding citation within the text and vice versa. I recommend that the authors align the referencing style with PeerJ format requirements.
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