Evaluation of SPAD Index for Estimating Nitrogen and Magnesium Contents in Three Blueberry Varieties (Vaccinium corymbosum L.) on the Andean Tropics

Round 1

Reviewer 1 Report

·        This manuscript describes an interesting investigation that provides new data to estimate variations in SPAD readings between blueberry varieties and to determine whether chlorophyll index (SPAD) values are associated with nitrogen and magnesium content in blueberries in the vegetative phase.

·        The purpose of this paper is clearly stated and the literature review has been properly addressed. Thus, the reasons for approaching this research topic have been well revealed.

·        The paper is well presented and the methodology is well and sufficiently detailed. The results, clearly presented in 8 figures and 1 table, are well reported and discussed.

·            The references cited are relevant for this research topic.

·        The issues addressed are relevant in the field and aim to fill some of the existing gaps regarding the correlation between the total chlorophyll index (SPAD) and the concentration of nitrogen and magnesium quantified in leaves of blueberry varieties in the vegetative phase under conditions found in Paipa-Boyacá.

·        The originality is well emphasized, the reported results recommend the SPAD method for non-destructive determination of nitrogen and magnesium content in different blueberry varieties under field conditions.

·          This study has great potential for application, since it is an easy, fast and accessible method for producers.

·        Although there are no scientific shortcomings in this paper, the conclusion could be extended for a better overview of the findings highlighted.

·        A careful check of the full manuscript is necessary to correct any grammatical or syntax errors.

Comments for author File: Comments.pdf

Author Response

The authors thank you for your important concept about our manuscript and for the important suggestions, which were taken into account and have improved the quality of our document.

Reviewer 1.

• 
  This manuscript describes an interesting investigation that provides new data to estimate variations in SPAD readings between blueberry varieties and to determine whether chlorophyll index (SPAD) values are associated with nitrogen and magnesium content in blueberries in the vegetative phase.
• The purpose of this paper is clearly stated and the literature review has been properly addressed. Thus, the reasons for approaching this research topic have been well revealed.
• The paper is well presented and the methodology is well and sufficiently detailed. The results, clearly presented in 8 figures and 1 table, are well reported and discussed.
• The references cited are relevant for this research topic.
• The issues addressed are relevant in the field and aim to fill some of the existing gaps regarding the correlation between the total chlorophyll index (SPAD) and the concentration of nitrogen and magnesium quantified in leaves of blueberry varieties in the vegetative phase under conditions found in Paipa-Boyacá.
• The originality is well emphasized, the reported results recommend the SPAD method for nondestructive determination of nitrogen and magnesium content in different blueberry varieties under field conditions.
• This study has great potential for application, since it is an easy, fast and accessible method for producers.
• Although there are no scientific shortcomings in this paper, the conclusion could be extended for a better overview of the findings highlighted.

Response: the conclusion was improved

• A careful check of the full manuscript is necessary to correct any grammatical or syntax errors.

Response: correction was made

Author Response File: Author Response.pdf

Reviewer 2 Report

General comments

In my opinion, the article is quite interesting; however, there are some parts that need to be improved.

The article has a serious problem. The study should be repeated for at least one more year to eliminate environmental influence.

Specific comments:

Materials and Methods:

2.1. Localization

“geographic coordinates 5°45'N and 73°45'W”. The geographic coordinates must be exact, representing the center of the farm.

2.3. Crop mamagement

“The mineral nutrition plan was managed according to the requirements proposed by [27] carrying out two fertigation pulses per week. “.

Mineral nutrition should be explained in detail.

2.4. Measurement of SPAD, Nitrogen y Magnesium values

Germination. Is a mistake?

2.6. Statistical Analysis

“The data analysis was done with (29).” The sentence must be finished. Then put the reference

Bibliography and references in text should be checked.

Author Response

The authors thank you for your important concept about our manuscript and for the important suggestions, which were taken into account and have improved the quality of our document.

Reviewer 2.

General comments

In my opinion, the article is quite interesting; however, there are some parts that need to be improved.

The article has a serious problem. The study should be repeated for at least one more year to eliminate environmental influence.

Response: In relation to the adjustment of the data through the replication of the test, the observation being valid, it can be indicated that theoretical references were followed against the measurement methodology of the non-destructive SPAD method that allowed guaranteeing low influence of environmental factors in relation to the data obtained, this could be evidenced by obtaining mathematical models with very good adjustments and little variability, as well as the non-existence of an outlayer evidenced in the Box plot graphs and compliance with the assumptions of analysis of variance with p-values > 0.05.

Specific comments:

Materials and Methods:

2.1. Localization

“geographic coordinates 5°45'N and 73°45'W”. The geographic coordinates must be exact, representing the center of the farm.

Response: correction was made

2.3. Crop management

“The mineral nutrition plan was managed according to the requirements proposed by [27] carrying out two fertigation pulses per week. “.

Mineral nutrition should be explained in detail.

Response: correction was made

2.4. Measurement of SPAD, Nitrogen y Magnesium values

Germination. Is a mistake?

Response: correction was made

2.6. Statistical Analysis

“The data analysis was done with (29).” The sentence must be finished. Then put the reference

 Response: correction was made

Bibliography and references in text should be checked.

Response: Bibliography and references were checked and some corrected.

Author Response File: Author Response.pdf

Reviewer 3 Report

The research topic is of great scientific interest.

The design and conduct of the experiment was carried out at a sufficient scientific level.

The statistical analysis is convincing.

The proposed scientific hypothesis is confirmed.

Authors are recommended to pay serious attention to the use of the cited literature.

In the sentence «They are perennial fruit shrubs with blue or purple fruits, with a high content of anthocyanins and other antioxidants that provide important benefits for human health, making them attractive to consumers [2–4]» – it is recommended to replace reference 2; Article 2 is devoted to the method (SPAD) and does not seem to inform about the nutritional value of the berry.

In the sentence «In Colombia, the largest producers are in the departments of Boyacá and Cundinamarca [8] which contain approximately 95% of domestic production.» reference 8 should be replaced. The article [8] assessed the content of chlorophylls a, b and in general obtained by spectrophotometry and determined the correlation with the non-destructive method (SPAD) in Biloxi, Legacy and Victoria blueberry plants (Vaccinium corymbosum L.) in the vegetative phase in the conditions of the municipality of Pipa Boyaca (Colombia).

Reference 9 is also questionable, here we are talking about the Effect of inoculation with Acaulospora and Glomus on the growth and nutrition of blueberries (Vaccinium corymbosum) with different fertilization levels, but not about the volume of blueberry production in Colombia..

A reference about the oil palm is given to the sentence " Nutrients are comparatively more important in crop production because their deficiency can affect qual ity characteristics such as firmness and fruit color and can cause postharvest losse". It is necessary to replace link 11 (Orjuela, R. Nutrición y fertilización con micronutrientes y su efecto en palma de aceite (Elaeis guineensis Jack.). Revisión. Cienc y Tecnol Agropecu. 2019, 4, 93–110).

It seems inappropriate to refer to works 12 and 13….

References 16-20 consider potatoes, spring corn, rice (crops with different types of photosynthesis). It would be more correct to provide data on plants close to blueberries.

After removing the shortcomings, the article can be published in the journal.

Author Response

The authors thank you for your important concept about our manuscript and for the important suggestions, which were taken into account and have improved the quality of our document.

Reviewer 3.

The research topic is of great scientific interest.

The design and conduct of the experiment was carried out at a sufficient scientific level.

The statistical analysis is convincing.

The proposed scientific hypothesis is confirmed.

Authors are recommended to pay serious attention to the use of the cited literature.

In the sentence «They are perennial fruit shrubs with blue or purple fruits, with a high content of anthocyanins and other antioxidants that provide important benefits for human health, making them attractive to consumers [2–4]» – it is recommended to replace reference 2; Article 2 is devoted to the method (SPAD) and does not seem to inform about the nutritional value of the berry.

Response: Article 2 was removed of this sentence

In the sentence «In Colombia, the largest producers are in the departments of Boyacá and Cundinamarca [8] which contain approximately 95% of domestic production.» reference 8 should be replaced. The article [8] assessed the content of chlorophylls a, b and in general obtained by spectrophotometry and determined the correlation with the non-destructive method (SPAD) in Biloxi, Legacy and Victoria blueberry plants (Vaccinium corymbosum L.) in the vegetative phase in the conditions of the municipality of Pipa Boyaca (Colombia).

Response: Article 8 was removed of this sentence.

Reference 9 is also questionable, here we are talking about the Effect of inoculation with Acaulospora and Glomus on the growth and nutrition of blueberries (Vaccinium corymbosum) with different fertilization levels, but not about the volume of blueberry production in Colombia..

Response: in abstract the authors mentioned “Colombia, thanks to its diversity, has a great opportunity to meet the blueberry demands of the global markets”, for this reason, we cite this article.

A reference about the oil palm is given to the sentence " Nutrients are comparatively more important in crop production because their deficiency can affect qual ity characteristics such as firmness and fruit color and can cause postharvest losse". It is necessary to replace link 11 (Orjuela, R. Nutrición y fertilización con micronutrientes y su efecto en palma de aceite (Elaeis guineensis Jack.). Revisión. Cienc y Tecnol Agropecu. 2019, 4, 93–110).

Response: Reference 11 was replace by “Srivastava, A.K and C. Hu (eds.). 2020: Fruit Crops - Diagnosis and Management of Nutrient Constraints. Elsevier”.

It seems inappropriate to refer to works 12 and 13….

Response: Reference 12 was accompanied by 11 to better support the statement .We consider that work 13 is appropriate because they support the phrases that we include there.

References 16-20 consider potatoes, spring corn, rice (crops with different types of photosynthesis). It would be more correct to provide data on plants close to blueberries.

Response: We did not find enough articles on blueberry or similar species for the discussion, therefore, we removed some of these references and we include another.

New references:

Srivastava, A.K; Hu, C. Fruit Crops - Diagnosis and Management of Nutrient Constraints. Elsevier. 2020. 776 p.

Prado, R.M.; Rozane, D.E. Chapter 11. Leaf analysis as diagnostic tool for balanced fertilization in tropical fruits (131-143). In: A.K. Srivastava, Chengxiao Hu (eds). Fruit Crops - Diagnosis and Management of Nutrient Constraints. Elsevier. 2020.

Nestbya, R.; Retamales, J.B. Chapter 40. Diagnosis and management of nutritional constraints in berries (pp. 567-582). In: A.K. Srivastava, Chengxiao Hu (eds). Fruit Crops - Diagnosis and Management of Nutrient Constraints. Elsevier. 2020.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Tha chances hace been done

Reviewer 3 Report