Assessment of Agro-Ecological Apple Replant Disease (ARD) Management Strategies: Organic Fertilisation and Inoculation with Mycorrhizal Fungi and Bacteria

Round 1

Reviewer 1 Report

The authors evaluate two management strategies: AMFbac and MDK for overcoming the economic losses encountered with ARD.   

The manuscript is well written, clear and easy to understand. It definitely makes a good read and conveys the message in an objective manner. The authors have clearly mentioned the benefits and drawbacks of their techniques as well as provided comments about its potential use.  

Minor questions/comments  

1) Line 307: Why was a different composition of AMFbac used in the field test?

2) The title of the manuscript is a little confusing and wordy, I would suggest the authors to rephrase the title to make it clear and succinct.

I would recommend that the manuscript be ok with minor edits.

Author Response

We sincerely thank the reviewers for their attention and work in reviewing our manuscript, particularly for helpful comments and thoughts as input to our manuscript but also for minor corrective remarks. According to the helpful comments of the reviewers we have carefully but considerably revised the manuscript.

We carefully revised the English language of the manuscript. However, the given time of 10 days was too short for our regular English editing service to check and edit the manuscript for additional language errors. If the reviewers or editors consider a language check necessary, we would be grateful to do this by a professional editing service after review.

Comment 1:  Line 307: Why was a different composition of AMFbac used in the field test?

Response 1: Thank you for this question. In Pot Experiment A and Pot Experiment B we used a different product of arbuscular mycorrhizal strains, as well as a different product of bacterial strains than in field test. It was our objective to analyse for a more general effect of the biological amendment of arbuscular mycorrhiza in combination with bacterial strains, rather than to show an inoculate-specific effect of one selected commercial product.

We slightly revised the description of the method when first mentioned in line 114ff: A composite of biological soil amendment products containing arbuscular mycorrhiza species (AMF) and bacterial strains (bac), hereinafter named AMFbac after its principal components.

Additionally, we added a half-sentence in the methods to further clarify (line 200): For the field test, we used a different product for the same principal composition of AMFbac […]

Comment 2: The title of the manuscript is a little confusing and wordy, I would suggest the authors to rephrase the title to make it clear and succinct.

Response 2: Thank you for your note. We edited the title. The title now reads “Assessment of agro-ecological Apple Replant Disease (ARD) management strategies: organic fertilization and inoculation with mycorrhizal fungi and bacteria” (line 2-5).

Reviewer 2 Report

Title:

• Needs rewriting for English – suggest replace ‘at the example of’ with a colon

Abstract:

• It is not clear what “Müncheberger Dammkultur” and AMFbac’ refer to – are these brand names?
• “Both treatments 21 showed an effect, which could in both cases be linked to avoidance strategies in the plant.” Is vague – need to see actual results/values
• Lines 21-24 make claims without presenting actual results
• Needs substantial re-writing

Introduction:

• Sound background
• Not sure yet what “pre-trial experiment’ actually refers to? On reading the methods I see that this study involves replicated pot/field trials so needs to make this clear as this is appropriate to the complex issue of ARD.

Methods:

• Tree vigour rating is very simplistic of CSA only?
• Root morphology a subjective ranking of 1 to 3

Results:

• Lines 233-243 are methods
• Lines 249-252 – treatment with MDK had lower CSA and growth rate than replant only soil??
• Lines 255-271 include interpretation which needs to be confined to the discussion section
• Table 8 missing root ratings?
• Lines 291-316 are methods not results
•  

Discussion

• Lines 397-409 introductory material – instead perhaps give an overview of the key findings of the study for ease of reading?
• Lines 411-416 is intro material
• Ok so line 417 the discussion starts! But what are the growth responses – be specific
• Will concentrating roots into the mulch decrease the tree’s ability to mine for water? Or other issues such as more susceptible to wind throw?
• Line 442 – what exactly is ‘soil exchange’?
• Lines 474-483 – good to see the inconsistency clearly acknowledged – is this emphasized in the abstract?
• “Accordingly, the AMFbac treatment has no significant effect on root colonisa-502 tion, but raises tree vigour in general, for example by improving the unlocking of nutrients 503 for the plant.” Is vague in the extreme and should be rewritten/omitted

Conclusion

• I don’t think “thereby indicating a positive effect on tree vigour by an influ-554 ence on the nutrition cycle of the plant” can be included as written given there was no assessment of tree nutrition
• Otherwise a well written section

References

Some in german, some personal communication – check appropriateness/correctness of referencing

Author Response

We sincerely thank the reviewers for their attention and work in reviewing our manuscript, particularly for helpful comments and thoughts as input to our manuscript but also for minor corrective remarks.

According to the helpful comments of the reviewers we have carefully but considerably revised the manuscript.

We carefully revised the English language of the manuscript. However, the given time of 10 days was too short for our regular English editing service to check and edit the manuscript for additional language errors. If the reviewers or editors consider a language check necessary, we would be grateful to do this by a professional editing service after review.

Comment 1: Needs rewriting for English – suggest replace ‘at the example of’ with a colon

Response 1: Thank you for your note. We edited the title. The title now reads “Assessment of agro-ecological Apple Replant Disease (ARD) management strategies: organic fertilization and inoculation with mycorrhizal fungi and bacteria” (line 2-5)

Comment 2: It is not clear what “Müncheberger Dammkultur” and AMFbac’ refer to – are these brand names?

Response 2: Thank you for this question. “Müncheberger Dammkultur” as well as “AMFbac” are no brand names. The “Müncheberger Dammkultur” is a specific mulch composition in the form of ridge planting. It is named after the location of its emergence at the Müncheberger Field Station for Fruit Genetic Resources. The biological soil amendment “AMFbac” is named after abbreviations of its components: arbuscular mycorrhiza species (AMF) and bacterial strains (bac). We added the information of designation the treatments in our manuscript (line 103-117).

Comment 3: “Both treatments 21 showed an effect, which could in both cases be linked to avoidance strategies in the plant.” Is vague – need to see actual results/values

Comment 4: Lines 21-24 make claims without presenting actual results

Response 3 and 4: Thank you for your comments. We supplemented the value of treatments’ potential to mitigate ARD effects on plant vigour and omitted our statement that effect of treatments could be linked to avoidance strategies in the plant.

Comment 5: Needs substantial re-writing

Response 5: Thank you for your advice to revise the abstract. We carefully revised the abstract under particular consideration of comment 2 to 4.

Comment 6: Sound background

Response 6: Thank you.

Comment 7: Not sure yet what “pre-trial experiment’ actually refers to? On reading the methods I see that this study involves replicated pot/field trials so needs to make this clear as this is appropriate to the complex issue of ARD.

Response 7: Thank you for your advice. We titled our experimental approach as ‘pre-trial’, because they were scaled to the pot experiments and fields tests as would be done in an experiment for preselection of viable elements of a strategy or product, which would then be further validated by further retries. However, we think our methodology is already well explained throughout the introduction, and to avoid confusion, we deleted the sentence referring to a ‘pre-trial’.

Comment 8: Tree vigour rating is very simplistic of CSA only?

Response 8: The trunk cross-sectional area (CSA) is employed as a sensitive plant physiological parameter and is found to be a practical and robust parameter representing below-ground and above-ground tree performance (Cavael et al., 2020).

Comment 9: Root morphology a subjective ranking of 1 to 3

Response 9: We agree that the root morphology ranking is subjective. The root morphology ranking is simplistic but yet very practical and with 0 (= no adventitious roots) over 1 (= small and thin adventitious roots of an herbaceous habitus) to 2 (= strong and pronounced adventitious roots) explicit and sufficiently accurate for our observations and communication with the farmer. In further investigations a weight out of adventitious roots can be used as a more detailed method to quantify the extent of adventitious roots.  

Response 8 and 9: We agree the reviewer that the CSA is a simplistic measure of tree vigour and that root morphology ranking of 0 to 2 is subjective. However, both measures are comprehensible and are applicable (also by non-scientific experts and farmers) in field observation.

Comment 10: Lines 291-316 are methods not results

Comment 11: Lines 233-243 are methods

Comment 15: Lines 291-316 are methods not results

Response 10, 11 and 15: Paragraphs concerning formalisation of the 'Müncheberger Dammkultur' (MDK), as well as the AMFbac treatment have been removed from results section and integrated into methods section (line 131-146 and line 182-211).

Comment 12: Lines 249-252 – treatment with MDK had lower CSA and growth rate than replant only soil??

Response 12: Thank you for your note. There was a mistake in our table (Table 7), that has been corrected now. The treatment with MDK had a stronger CSA and growth rate than replant soil.

Comment 13: Lines 255-271 include interpretation which needs to be confined to the discussion section

Response 13: Thank you for this comment. We have carefully revised this section to represent the results only. Interpretations of growth rates and tree vigour should now be confined to the discussion section (line 327-337).

Comment 14: Table 8 missing root ratings?

Response 14: Missing root ratings for trees on no-replant soil are because uprooting of trees by the cyclone in October 2017 happened on the replant soil location, but not on no-replant soil. We added this information in section Materials and Methods (line 179) and in table caption (Table 3). The uprooting was considered unrelated to the replant, determined only by the weather event, respectively.

Comment 16: Lines 397-409 introductory material – instead perhaps give an overview of the key findings of the study for ease of reading?

Response 16: Thank you for your advice. We moved this paragraph to the introductory section of the manuscript (line 72-78).

Comment 17: Lines 411-416 is intro material

Response 17: We omitted this paragraph.

Comment 18: Ok so line 417 the discussion starts! But what are the growth responses – be specific

Response 18: Thank you for your comment. We supplemented the value of treatment’s potential to mitigate ARD effects on plant vigour (line 483-490).

Comment 19: Will concentrating roots into the mulch decrease the tree’s ability to mine for water? Or other issues such as more susceptible to wind throw?

Response 19: The MDK was formalised to imitate natural biological metabolic processes that take place in mixed woodlands in Central Europe. We tested the MDK on an orchard in Central Europe. In general, here, it is not necessary to pay increased attention to environmental impacts such as water shortage or wind throw on orchards. However, fruit growers and experts reported that during periods of high temperatures along with little rainfall an additional irrigation of trees treated with MDK may have a favourable impact on tree performance. It was also reported that strong rainfalls that lead to strong water runoff on the soil surface may wah away the MDK treatment that is applied as an additional groundcover on natural topsoil. However, in this study we did not collected data for such environmental circumstances. Thus, before implementation of the MDK treatment in regions affected by extreme environmental impacts (such as water shortage, strong rainfall or wind throw) the MDK treatment needs to be tested for their suitability and maybe needs to be local-specific adapted in their formalisation. We added this information in an additional sentence to the discussion section (line 523-526).

Comment 20: Line 442 – what exactly is ‘soil exchange’?

Response 20: Thank you for your further inquiry. ‘Soil exchange’, respectively ‘soil replacement’ involves excavating replant soil that is contaminated (or with a high risk of ARD) and replacing it by no-replant soil to improve orchards' fertility. We added an explanation in our manuscript (line 510-513).

Comment 21: Lines 474-483 – good to see the inconsistency clearly acknowledged – is this emphasized in the abstract?

Response 21: We took care in the revision of this manuscript to clearly highlight the inconsistency of the effect in the abstract and conclusion sections.

Comment 22: “Accordingly, the AMFbac treatment has no significant effect on root colonisa-502 tion, but raises tree vigour in general, for example by improving the unlocking of nutrients 503 for the plant.” Is vague in the extreme and should be rewritten/omitted

Response 22: Thank you for your comment. We omitted this sentence.

Comment 23: I don’t think “thereby indicating a positive effect on tree vigour by an influ-554 ence on the nutrition cycle of the plant” can be included as written given there was no assessment of tree nutrition

Response 23: Thank you for your comment. We omitted this sentence.

Comment 24: Otherwise a well written section

Response 24: Thank you.

Comment 25: Some in german, some personal communication – check appropriateness/correctness of referencing

Response 25:

Reference [21] and [22] are databases that are entitled in German. Both databases are also presented in English version.  We complemented the reference in the reference section by adding ‘available in German and English

Reference [24] is a technical literature that is published only in German. We complemented the reference in the reference section by adding ‘available in German and English.

Reference [48] Günzel, L. Management practices. Personal communication, 2016 was substituted by a contribution of co-author H. Schwärzel.

References

Cavael, U.; Diehl, K.; Lentzsch, P. Assessment of growth suppression in apple production with replant soils. Ecol Indic 2020, 109, 105846.