The Effect of Cultivation Techniques on the Antioxidant Properties and Phenolic Acid Content in the Roots of Five Sweet Potato (Ipomoea batatas L.) Cultivars Grown Under the Climatic and Soil Conditions of Southeastern Poland

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Dear authors,

I appreciate level of prepared article, including introduction, description of methods and discussion to obtained results. Conclusions are also clearly prepared. I have notes for revision, mostly to Method chapter:

Methods

L 174-188 / Agronomic practices:

- why just information about harvest 2023 is mentioned? please, add exact date for harvest

- please, add exact date for planting of seedlings to the field

- you can combine these dates to the separate table or just to the text

- please, add information about way of seedling planting to the field

- did you use hillock system or flat soil for experiment?

- there would be perfect to add some photo from experiment

- what about irrigation?

Results and discussion

I understand that probably quantitative parameters (yield or tuber weight) have been used for previous published article. In all experiments, relationship of quantity and quality is corresponding. Mostly for grower, quantity is determining, quality less-determining. For this reason, if it is possible, I would give yield data to the correlation with quality of sweet potato cultivars; if these data has been published, I would use it by the way of used reference. Please, re-think it.

 

 

Author Response

Response to Reviewer 1 Comments

Manuscript ID: Agronomy- 4252825

Title: The effect of cultivation techniques on the antioxidant properties and phenolic acid content in the tubers of five sweet potato (Ipomoea batatas L.) cultivars grown under the climatic and soil conditions of southeastern Poland

Dear Reviewer 1,

We are very grateful for the insightful review of our manuscript. The comments and suggestions of reviewer 1, which have been incorporated into the text, will greatly enhance its scientific value. The text has been corrected in accordance with the reviewer's comments. The corrections have been marked in blue in the ‘track changes’ mode, and comments on the corrected version are provided below. We hope that the manuscript in its current form meets the requirements of the journal ‘Agronomy’.

Point 1: Methods L 174-188 / Agronomic practices: - why just information about harvest 2023 is mentioned? please, add exact date for harvest

Response 1: Thank you very much for this valid comment. This was an oversight on our part. The missing harvest dates for 2021 and 2022 have been added to the manuscript. ,,Harwest ocurred in mid October (18 October 2021, 16 October 2022, 12 October 2023)’’

Point 2: please, add exact date for planting of seedlings to the field

Response 2: Thank you very much for this comment. The missing information has been added to the manuscript.,, Sweet potatoes seedlings were manually transplanted to the field in May (14 May,2021, 16 May 2022, 13, May 2023) with a spacing of 40x75 cm on ridges’’.

Point 3. Please provide information on how the seedlings were planted in the field.

Response 3: Thank you very much for this comment. The manuscript has been revised accordingly.

,,Sweet potatoes seedlings were manually transplanted to the field’’

Point 4. Ideally, a photo from the experiment would be included.

Response 4: Thank you for this suggestion; however, we do not have photographs from the plantation establishment.

Point 5. did you use hillock system or flat soil for experiment?

Response 5: Thank you for this comment. The manuscript has been revised accordingly.

,,with a spacing of 40x75 cm on ridges’’.

 Point 6. What about irrigation?

Response 6: We kindly inform that no irrigation system was used in this experiment.

 

Point 7. Ideally, a photo from the experiment would be included. Response 7:  Thank you for this suggestion; however, we do not have photographs from the plantation establishment.

Point 8. ,, I understand that probably quantitative parameters (yield or tuber weight) have been used for previous published article. In all experiments, relationship of quantity and quality is corresponding. Mostly for grower, quantity is determining, quality less-determining. For this reason, if it is possible, I would give yield data to the correlation with quality of sweet potato cultivars; if these data has been published, I would use it by the way of used reference. Please, re-think it.’’

Response 8: Thank you for this valuable comment. The manuscript has been appropriately revised. The relationship between yield, cultivation technology, genotype, and weather conditions has been clarified and supported with relevant literature references, while avoiding duplication of previously published results.

The following sentence has been added to the manuscript:

,,The relationship regarding the effect of cover application on yield and tuber quality of sweet potato cultivars grown under Polish agro-climatic conditions has been presented in previous publications by Krochmal-Marczak et al. [2,6] and is cited here to support the interpretation of the relationship between yield and tuber quality traits.”

2. Krochmal-Marczak, B.; Sawicka, B.; Słupski, J.; Cebulak, T.; Paradowska, K. Nutritional value of sweet potato (Ipomoea batatas (L.) Lam.) cultivated under south-eastern Polish conditions. J. Agric. Res. 2014, 4, 169–178.
3. Krochmal-Marczak, B.; Sawicka, B.; Tobiasz-Salach, R. Impact of cultivation technology on the yield of sweet potato (Ipomoea batatas) tubers. Emir. J. Food Agric. 2018, 30, 978–983. https://doi.org/10.9755/ejfa.2018.v30.i11.1863.

 

 

 

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

Dear Authors,

The manuscript is on high level, but some recommendations are in the document. 

Thank You

 

Comments for author File: Comments.pdf

Author Response

Response to Reviewer 2 Comments

Manuscript ID: Agronomy- 4252825

Title: The effect of cultivation techniques on the antioxidant properties and phenolic acid content in the tubers of five sweet potato (Ipomoea batatas L.) cultivars grown under the climatic and soil conditions of southeastern Poland

Dear Reviewer 2,

We are very grateful for the insightful review of our manuscript. The comments and suggestions of reviewer 2, which have been incorporated into the text, will greatly enhance its scientific value. The text has been corrected in accordance with the reviewer's comments. The corrections have been marked in blue in the ‘track changes’ mode, and comments on the corrected version are provided below. We hope that the manuscript in its current form meets the requirements of the journal ‘Agronomy’.

 

Response to the comments that were marked in the manuscript text

 

Point 1. I miss numerical values. Achieved results in values are the best way to description and for future citation value.

Response 1. We thank Reviewer 2 for this important comment. We have revised the abstract in accordance with the reviewer’s suggestion. The corrected abstract is provided below.

,,The study confirmed that cultivation technologies, cultivar, and meteorological conditions significantly influenced the contents of ascorbic acid, total polyphenols, and phenolic acids in sweet potato tubers. Ascorbic acid content ranged from 27.22 to 111.9 mg·100 g⁻¹ DW, with the highest values recorded in the traditional cultivation system (TC), reaching 111.9 mg·100 g⁻¹ DW in ‘Carmen Rubin’ and 111.4 mg·100 g⁻¹ DW in ‘Beauregard’. In contrast, in the ‘Satsumo Imo’ cultivar grown under nonwoven fabric, ascorbic acid content decreased to 49–58% of the values obtained in TC. Genetic factors strongly differentiated the contents of bioactive compounds. The ‘Purple’ cultivar showed the highest contents of total polyphenols (up to 963.5 mg·100 g⁻¹ DW) and phenolic acids (17067.42 mg·100 g⁻¹ DW), whereas the lowest values were recorded in ‘Satsumo Imo’ (858.82–1225.89 mg·100 g⁻¹ DW). Cultivation under polyethylene film increased and stabilized phenolic compounds. The ‘Carmen Rubin’ cultivar also exhibited high phenolic acid content (5332.04–5447.60 mg·100 g⁻¹ DW), while ‘Beauregard’ was characterized by high stability of this trait (1535.93–1581.46 mg·100 g⁻¹ DW). From a practical perspective, the results highlight the importance of appropriate cultivar selection and cultivation technology for obtaining raw material with high functional value. These findings may serve as a basis for developing agrotechnical recommendations aimed at producing sweet potatoes with enhanced nutritional and health-promoting quality under the climatic and soil conditions of Poland.’’

 

Point 2. On what basis or according to what were the fertilizer doses determined?
Calculation of nutrients in terms of crop nutrient requirements or another method? It is enough to explain or define in one or two sentences.

Response 2. Thank you for this comment. We have supplemented the text.

,,Fertilizer doses were calculated based on the results of soil analyses carried out by the District Chemical-Agricultural Station in Rzeszów, (Poland) and adjusted to the nutrient requirements of sweet potato, in accordance with standard agronomic recommendations for this crop under temperate climate conditions (Table 3)’’.

Point 3. The same recommendation about numerical values of results.

Response 3. We thank Reviewer 2 for this important comment. We have revised the conclusions in accordance with the reviewer’s suggestion. The corrected text is provided below:

 

,,The study confirmed that cultivation technologies, cultivar, and meteorological conditions significantly influenced the contents of ascorbic acid, total polyphenols, and phenolic acids in sweet potato tubers. Ascorbic acid content ranged from 27.22 to 111.9 mg·100 g⁻¹ DW, with the highest values recorded under the traditional cultivation system (TC) in ‘Carmen Rubin’ (111.9 mg·100 g⁻¹ DW) and ‘Beauregard’ (111.4 mg·100 g⁻¹ DW). In contrast, in ‘Satsumo Imo’ grown under nonwoven fabric (FW), ascorbic acid decreased to 49–58% of TC values. Genotypic effects strongly differentiated bioactive compound accumulation. ‘Purple’ exhibited the highest contents of total polyphenols (up to 963.5 mg·100 g⁻¹ DW) and phenolic acids (17067.42 mg·100 g⁻¹ DW), whereas the lowest values were recorded in ‘Satsumo Imo’ (858.82–1225.89 mg·100 g⁻¹ DW). Cultivation under polyethylene film (FC) increased and stabilized phenolic compound levels in comparison with TC and FW systems. The highest phenolic responses to FC were observed in ‘Purple’ and ‘Carmen Rubin’, while ‘Beauregard’ showed high stability across all cultivation systems. In contrast, ‘Satsumo Imo’ exhibited strong sensitivity to environmental variation. Additionally, ‘White Triumph’ achieved the highest phenolic compound levels under FC, whereas FW increased interannual variability of secondary metabolites. Overall, the results highlight that appropriate cultivar selection combined with FC cultivation is an effective strategy for enhancing the functional quality of sweet potato tubers under temperate climate conditions. These findings may serve as a basis for developing agrotechnical recommendations for producing sweet potatoes with improved nutritional and health-promoting value in Poland.’’

 

 

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Reviewer

1. Powers

• Powerful Experiment: Investigation for 3 years.
• Multidisciplinary Approach: Combines agronomy with biochemistry.

Advanced statistical methods: Split-plot design, Principal Component Analysis, cluster analysis, and heatmaps, examination of connections among cultivars, years, and cropping systems.

This study is both regionally and relevant because it addresses the adaptation of the tropical crop in Poland's temperate climate.

2. Weaknesses and Uncertainties

The manuscript's header and copyright license, both of which reference 2026, present an anachronism. Furthermore, Reference 15 indicates access on "January 9, 2026." Given that the data concludes in 2023, this discrepancy raises questions regarding the document's temporal relevance and whether it constitutes a future simulation or a preliminary draft.

• Inconsistency in Terminology: In the initial text (Abstract/Introduction), the nonwoven covering is referred to as FW (nonwoven fabric). In the Materials and Methods section, the abbreviation changes to WC. In the PCA results, the abbreviations vary by cultivar (SW, WW, CW, PW), which hinders smooth reading.

The "polypropylene-wool" error needs to be fixed. The text incorrectly describes something as "polypropylene-wool fabric-covered." Later on, the material is correctly identified as "polypropylene (PP) nonwoven." The word "wool" should not be there; it is technically wrong and could easily be confused with real wool.

The discussion could benefit from a more thorough examination of the effects of exceptionally dry months, such as June 2022, which recorded only 6.5 mm of precipitation, on tuber physiology, given the precipitation and temperature data presented in Table 2. This would help clarify the observed reductions in nutrient levels.

3. Redundancies and Writing

The descriptions of PCA results for the five cultivars are quite similar, often using the same phrases (e.g., "PC1 separates the systems... PC2 reflects annual variability"). To avoid the impression of using a "standard text" repeatedly, it is better to combine these observations into a comparative analysis.

4. Citation and Reference Verification

Formatting Errors in Tables: Table 4 presents several values marred by odd symbols (like 104~0+0~57a,c). This likely points to a character conversion issue or a typing mistake, both of which require correction to maintain data integrity.

Final Review:

1. Cultivar Name: The text currently spells it "Satsumo Imo."

The more widely accepted spelling internationally is "Satsuma-Imo."

2. Units of Measurement: Verify that the use of mg 100 g-1 d.w. is consistent across all tables, as variations between fresh and dry mass can drastically alter the interpretation of vitamin C results.
3. Climate x Treatment Interaction: The article mentions that plastic covering increased phenols in the "warmest year of 2021". However, thermal coverings tend to have greater benefit in cold years; this biological contradiction deserves careful review in the discussion.

 

Comments for author File: Comments.pdf

Author Response

 

Response to Reviewer 3 Comments

Manuscript ID: Agronomy- 4252825

Title: The effect of cultivation techniques on the antioxidant properties and phenolic acid content in the tubers of five sweet potato (Ipomoea batatas L.) cultivars grown under the climatic and soil conditions of southeastern Poland

Dear Reviewer 2,

We are very grateful for the insightful review of our manuscript. The comments and suggestions of reviewer 3, which have been incorporated into the text, will greatly enhance its scientific value. The text has been corrected in accordance with the reviewer's comments. The corrections have been marked in blue in the ‘track changes’ mode, and comments on the corrected version are provided below. We hope that the manuscript in its current form meets the requirements of the journal ‘Agronomy’.

 

Point 1. he manuscript's header and copyright license, both of which reference 2026, present an anachronism. Furthermore, Reference 15 indicates access on "January 9, 2026." Given that the data concludes in 2023, this discrepancy raises questions regarding the document's temporal relevance and whether it constitutes a future simulation or a preliminary draft.

Response 1. We thank the reviewer for this comment and clarify this statement.

The access date of January 9, 2026, refers only to the verification of the availability of data on the cited website of the Statistical Office. The data themselves were retrieved in 2024 and pertain to the period from 2021 to 2023.

Point 2. Inconsistency in Terminology: In the initial text (Abstract/Introduction), the nonwoven covering is referred to as FW (nonwoven fabric). In the Materials and Methods section, the abbreviation changes to WC. In the PCA results, the abbreviations vary by cultivar (SW, WW, CW, PW), which hinders smooth reading.

Response 2. Thank you for this valid comment. We have standardized the inconsistent terminology throughout the text.

Point 3. The "polypropylene-wool" error needs to be fixed. The text incorrectly describes something as "polypropylene-wool fabric-covered." Later on, the material is correctly identified as "polypropylene (PP) nonwoven." The word "wool" should not be there; it is technically wrong and could easily be confused with real wool.

Response 3. Thank you for this comment. We have removed the incorrect expression from the manuscript text.

Point 4. The discussion could benefit from a more thorough examination of the effects of exceptionally dry months, such as June 2022, which recorded only 6.5 mm of precipitation, on tuber physiology, given the precipitation and temperature data presented in Table 2. This would help clarify the observed reductions in nutrient levels.

Response 4. We thank the Reviewer for this valid comment. We agree that a more detailed discussion of the impact of exceptionally dry months (e.g. June 2022 with 6.5 mm of precipitation) on tuber physiology, in light of the precipitation and temperature data presented in Table 2, could help explain the observed reductions in nutrient levels. However, in our study, weather conditions were considered as basic information describing the experimental environment and were not included as an experimental factor. Therefore, a detailed causal analysis of specific monthly precipitation events was beyond the scope of this work.

Redundancies and Writing

Point 5. The descriptions of PCA results for the five cultivars are quite similar, often using the same phrases (e.g., "PC1 separates the systems... PC2 reflects annual variability"). To avoid the impression of using a "standard text" repeatedly, it is better to combine these observations into a comparative analysis.

Response 5. We thank the Reviewer for this comment. We have addressed the reviewer’s suggestion and revised the manuscript accordingly.

,,Comparative analysis of phenolic acid profiles based on PCAPrincipal Component Analysis of Phenolic Acid ProfilesThe application of principal component analysis (PCA) enabled not only dimensionality reduction of the dataset, but primarily a comparative assessment of the effects of cultivation technology and growing season on phenolic acid profiles among sweet potato cultivars (Figure 4). The analysis revealed both shared structural features of phenolic profiles and clear cultivar-dependent differences, resulting from distinct metabolic strategies and variable responses to microclimate modification. PCA explained a high proportion of the total variance in phenolic acid profiles, with the first two principal components (PC1 and PC2) jointly accounting for 75.71% to 96.14% of the variability, depending on the cultivar (Figure 4). This enabled a quantitative evaluation of the relative contribution of cultivation technology (PC1) and growing season (PC2) to phenolic profile differentiation. Comparison of cultivar responses to cultivation technologies (PC1)In all examined cultivars, the first principal component (PC1) was the dominant axis, explaining between 41.20% and 77.22% of the total variance. Such a broad range indicates substantial cultivar-specific differences in the strength of the cultivation system effect. The highest PC1 contribution was observed in ‘Beauregard’ (77.22%), followed by ‘Carmen Rubin’ (66.59%), indicating that in these cultivars more than two-thirds of the total variability in phenolic profiles was directly associated with the cultivation system. In both cases, traditional cultivation (T) and cultivation under nonwoven fabric (W) occupied opposite positions along PC1, while polyethylene film (F) was located intermediately, indicating a gradual rather than abrupt response to microclimate modification. In the case of ‘White Triumph’, PC1 also explained 66.59% of the variance, but sample distribution along this axis was more dispersed, particularly for the film-covered treatment, suggesting moderate stability of the phenolic profile combined with susceptibility to protective cultivation techniques. Significantly lower PC1 contributions were recorded for ‘Satsumo Imo’ (47.20%) and ‘Purple’ (41.20%), indicating that less than half of the total variability in these profiles was related to cultivation technology. This pattern suggests greater internal metabolic variability and a relatively’’

Point 5. Citation and Reference Verification

Formatting Errors in Tables: Table 4 presents several values marred by odd symbols (like 104~0+0~57a,c). This likely points to a character conversion issue or a typing mistake, both of which require correction to maintain data integrity.

Response 5. We thank the Reviewer for this comment. We have checked the entire table text and standardized it to ensure correct formatting and consistency.

Point 6. Cultivar Name: The text currently spells it "Satsumo Imo."

Response 6. The more widely accepted spelling internationally is "Satsuma-Imo."

We thank the Reviewer for this comment. We are aware that the internationally accepted form of the cultivar name is “Satsumo-Imo”. However, in the present manuscript we retained the form “Satsumo Imo”, as this naming convention is used in the plant material documentation and in some of the cited sources and scientific publications.

1. Krochmal-Marczak, B.; Sawicka, B.; Krzysztofik, B.; Danilčenko, H.; Jariene, E. The Effects of Temperature on the Quality and Storage Stalibity of Sweet Potato (Ipomoea batatas [Lam]) Grown in Central Europe. Agronomy 2020, 10, 1665. https://doi.org/10.3390/agronomy10111665
2. Krochmal-Marczak, B.; Cebulak, T.; Kapusta, I.; Oszmiański, J.; Kaszuba, J.; Żurek, N. The Content of Phenolic Acids and Flavonols in the Leaves of Nine Varieties of Sweet Potatoes (Ipomoea batatas) Depending on Their Development, Grown in Central Europe. Molecules 2020, 25, 3473. https://doi.org/10.3390/molecules25153473
3. Krochmal-Marczak B., Kiełtyka-Dadasiewicz A., Sawicka B. Właściwości antyoksydacyjne naparów z liści słodkiego ziemniaka zależnie od temperatury i czasu parzenia. Journal of Central European Agriculture, 2019, 20(3), p.961-966.

 

Point 7. Units of Measurement: Verify that the use of mg 100 g^-1 d.w. is consistent across all tables, as variations between fresh and dry mass can drastically alter the interpretation of vitamin C results.

Response 7. We thank the Reviewer for this comment. We have checked the entire text and standardized the notation of units to ensure correct formatting (mg 100 g⁻¹ d.w.).

Point 8. Climate x Treatment Interaction: The article mentions that plastic covering increased phenols in the "warmest year of 2021". However, thermal coverings tend to have greater benefit in cold years; this biological contradiction deserves careful review in the discussion.

Response 8. We thank the Reviewer for this comment and provide the following clarification:

Although thermal covers are generally considered particularly beneficial under cooler conditions, their effect on plant secondary metabolism cannot be attributed solely to temperature moderation. In the present study, the strongest stimulation of phenolic acid accumulation under plastic covers was observed in the warmest year of the experiment (2021). This apparent inconsistency with expected biological responses may be explained by a complex interaction between temperature, water availability, and microclimatic stress.

The 2021 growing season was characterized by elevated temperatures combined with periods of reduced precipitation, which may have intensified abiotic stress. Under such conditions, plastic mulching could have modified soil moisture retention, radiation balance, and the root-zone microclimate, thereby enhancing rather than alleviating stress signals. It is well documented that phenolic compound biosynthesis is non-linearly regulated by environmental factors, and its induction may be stronger under warm but stressful conditions than in cooler and more stable environments.

Therefore, the increased phenolic content observed under covers in 2021 should be interpreted as the result of an interaction between climatic conditions and cultivation technology, in which protective covers modulated both the nature and duration of stress stimuli, rather than merely compensating for lower temperatures.

 

 

Author Response File: Author Response.pdf