Combined Foliar Zinc and Nitrogen Application in Broccoli (Brassica oleracea var. italica L.): Effects on Growth, Nutrient Bioaccumulation, and Bioactive Compounds

Round 1

Reviewer 1 Report

The topic of this research is very actual. It is necessary to know nutritional composition of consumed vegetables or crops in generally, especially in recented period when people are exposed to higher risk of various serious dieases.

The nitrogen and zinc are very important  nutrients in plant nutrition. The nitrogen belongs to basic nutrients influencing on the production of phytomass and zinc is very important factor influencing on the quality of produced crops. The range of analysed qualitative parameters is excellent and it contributes to complex view on solved theme.

I am also very satisfied with level of english grammar.

Author Response

All authors would like to thank the kind comments of the reviewer.

Reviewer 2 Report

The paper is well organized and strutured.

The abstract has a clear aims and presents the sum of the work developed by the authors.

The introduction furnishes a nice scientific background.

Materials and methods are clearly described, allowing reproduction of the experiments and giving a clear perspective of accuracy / precision of the authors data. results seem robust and support the discussion the main conclusion, although synthetic.

Author Response

We would like to thank the nice comments of the reviewer. Regarding discussion and conclusions, the paper  has been improved in order to accomplish of the reviewers 3 and 4.

Reviewer 3 Report

The manuscript agronomy-1132875 has been reviewed. I think that the authors conducted appropriate experiment and analyses, but the conclusions derived from them were accumulation of circumstantial evidence, and new findings have a small impact. There are nominal descriptions that make it difficult to judge whether the content of the discussion is logically described and thus should be revised substantially. I suggest major revision before its consideration for publication.

1. Title , Combined zinc and nitrogen application in broccoli and not (of broccoli)
2. Rephrase Zinc with zinc and Nitrogen with nitrogen in title
3. Line 11, remove if
4. Line 13, what do you mean by one foliar and two foliar Zn application? Rephrase?
5. Line 36-38, provide a suitable reference, preferably a review article
6. Introduction is too short to provide enough details on the subject matter. There should be a gap statement describing the need for this study, the novelty and how this research is different from many others in this field.
7. Authors should better develop a hypothesis
8. Line 58, section 2.1 remove (.)
9. Same for the section 2.2. in fact for all the sections and sub-sections
10. How water holding capacity was maintained and was it the constant throughout the experiment?
11. Line 92, what do you mean by commercial maturity, rephrase it
12. Line 104, how phytate was measured? Provide a suitable reference instead
13. How the authors checked the significance of the data? I suggest authors to go for this especially for the data presented in figures.
14. The discussion needs a strong improvement. The discussion of mechanisms should be improved further
15. Why 0.25 N+0.25 N performed best in the present experiment? What could be the possible synergies between the applied treatments at varying ratios? This aspect could further add in the value of the manuscript and should be considered for interpretation in the discussion.
16. The conclusion is fine and supported by the results obtained however, general hypothetical statements should be removed.

Author Response

Please see attachment

Author Response File: Author Response.docx

Reviewer 4 Report

Comments on agronomy-1132875

Title

The title may be modified as “Combined foliar application of Zinc and Nitrogen in broccoli (Brassica oleracea var. italica L.): Effects on growth, nutrient bioaccumulation, and bioactive compounds”

Abstract

The results need quantitative presentation in the abstract

Line 15-20, very long sentence, split this sentence

Line 22-23, “However, as the 0.25+0.25 treatment obtained good results in the florets as regards antioxidant activity and total phenol …” rephrase this sentence in order to make it meaningful.

There is a lack of clear conclusions. State clearly, what was found ultimately

Introduction

Line 28, “In the last few years, crops of the Brassica genus have become a key part of the human diet ...” the word “crops” may not be suitable here. Replace with “species”

A clear hypothesis and objectives need to be added in the last section

Materials and Methods

Line 78, the abbreviation of calcium ammonium nitrate is “CAN” not “NAC”. Cross-check throughout the manuscript

Tables

In Table 2, the values of Fisher’s protected LSD test look wrong, these need recheck

Figures

Add lettering based on LSD values in Figure 1-3

Also, it is very difficult to differentiate between the bars of LSD p and LSD Zn. Instead, give the actual values for both in each Figure

LSD p denotes “same broccoli fraction” is not a good abbreviation. Replace it with a suitable one

Overall, the introduction and discussion sections need attention and improvement. The following papers may be considered for improvement of introduction and discussion sections

Hussain A., Z. A. Zahir, A. Ditta, M. U. Tahir, M. Ahmad, M. Z. Mumtaz, K. Hayat, S. Hussain. 2020. Production and implication of bio-activated organic fertilizer enriched with zinc-solubilizing bacteria to boost up maize (Zea mays L.) production and biofortification under two cropping seasons. MDPI-Agronomy 10(1):39 https://doi.org/10.3390/agronomy10010039

Zeb H., A. Hussain, M. Naveed, A. Ditta, S. Ahmad, M.U. Jamshaid, H.T. Ahmad, B. Hussain, R. Aziz, M.S. Haider. 2018. Compost enriched with ZnO and Zn-solubilizing bacteria improves yield and Zn-fortification in flooded rice. Italian Journal of Agronomy 13(4): 310-316. http://dx.doi.org/10.4081/ija.2018.1295

Conclusion

The authors should only discuss the findings and avoid speculation.

Line 297, “both causing an accumulation of up to 50 mg Zn kg-1 in the floret with excellent bioavailability”. Have the authors investigated bioavailability?

Also, it should be written past tense as the study has already been performed

Author Response

Please see the attachment

Author Response File: Author Response.docx

Round 2

Reviewer 3 Report

The authors have nicely incorporated all of the comments and suggestions. However, the references are not well updated. There are only3-4 references from the last 5 years. I suggest authors supplement and enrich references with the latest studies. Some of the related are provided herewith.

https://doi.org/10.1007/978-981-15-6953-1_7

doi: 10.1016/S2095-3119(18)62095-7

Agronomy 2020, 10, 1344; doi:10.3390/agronomy10091344

DOI: http://dx.doi.org/10.15666/aeer/1803_38733885

Author Response

Thank you for your comments. I have include the following references in order to update the used references and I have correct the references along the paper accordingly

1. Aziz, M.Z.; Yaseen, M.; Abbas, T.; Naveed, M.; Adnan Mustafa, A.; Hamid, Y.; Saeed, Q.; Ming-gang, X. Foliar application of micronutrients enhances crop stand, yield and the biofortification essential for human health of different wheat cultivars. J Integr Agric,  2019, 18(6), 1369–137                   in "Previous studies have shown that agronomic biofortification through foliar application increases total Zn concentrations in the edible fractions of broccoli, in both deficient and adequate Zn-containing soils [2-3, 18-20]
2. Umar W.; Ayub, M.A.; Rehman, M.Z.; Ahmad, H.R.; Farooqi, Z.U.; Shahzad, A.; Rehman, U.; Mustafa, A.; Nadeem, M. Nitrogen and Phosphorus Use Efficiency in Agroecosystems. In: Kumar S., Meena R.S., Jhariya M.K. (eds) Resources Use Efficiency in Agriculture. 2020. Springer, Singapore.            in the following sentence "However, information regarding the combined application of Zn with nitrogen (N), which is perhaps the major agricultural practice in crop production, has not been practically studied, despite of Zn is needed to accomplish various essential processes including the metabolism of N "

Reviewer 4 Report

The authors have improved the manuscript as per comments/issues raised.

The authors are suggested to add the final conclusion at the end of  the abstract and conclusion section

The letters added in the Figures should be revised as small letters

Author Response

Thank you for your comments.

The abstract now include the sentence "Therefore, 0.25+0.25 and 0.25N+0.25N applications have been confirmed as the applications that improve more both growth and accumulation of Zn and biocompounds in broccoli"

And in conclussion "It had a high efficiency for agronomic biofortification with Zn, with the 0.25+0.25 treatment and especially the 0.25 N+0.25 N treatment (giving rise to the synergistic effect of N on Zn) standing out in terms of both plant and floret growth, and both causing an accumulation of up to 50 mg Zn kg^-1 in the floret, as well as a higher total phenol content and without impaired any of the glucosinolates, being therefore, the recommended treatments." in the conclusions" 

Letters have been changed by small letters in all the figures