Effect of Nitrogen Supply on Growth and Nitrogen Utilization in Hemp (Cannabis sativa L.)

Round 1

Reviewer 1 Report

Manuscript is written in a well - structured manner and interesting to read. The aim of the paper was to investigate nitrogen accumulation, assimilation and utilization in hemp, as well as the growth and physiological response of hemp to nitrogen concentrations. Those aims were well covered by the results, and gives us more precise answers about hemp responses to nitrogen in controlled conditions, which could serve for field recommendations of nitrogen for hemp production in the future. About 50 percent of the references are within last 5 years, which is satisfactory. References with the number 1, 23, 28, and 43 don't have the correct doi, so the authors should correct them (I found the correct doi for references by the number 1 and 23, and they are given in the comments within the document attached). There is no abnormal number of self-citations. Manuscript is written in a scientific manner, and the experimental design matches the specific objectives that authors wanted to investigate. In the section Materials and Methods, suggestion for the authors is to define for how long have you applied nutrient solution, besides the given information about the start of the application (3 weeks after sowing) and the frequency of application (every 3 days). Even better would be to define the vegetative stages of the hemp, in which stage did the application of nutrient solution started, when it ended, and also in which stage were all the growth related indexes and other parameters measured. Also, suggestion is to write when did you measure stem volume (probably after measuring stem dry weight), which should be noted as well, so the results could be reproducible as much as they can. In the Results section, one statement in the line 150 wasn't correct and should be looked at, about linear correlation between Chl content and N level, because there are no correlations presented in this manuscript. In the line 110, there is a mistake in abbreviation (SSD should be SMD), and in the descriptions of table 1 there is a mistake for the p-value (p=0.5, but should be p=0.05). Besides this, everything else in the Results section is well presented. In the Conclusion section, you mention the growth rate, however, the manuscript don't contain any information on the growth rate of the hemp. To obtain information about the growth rate, one should do repeated measurements on chosen growth index over a period of time. Please consider to correct this. 

Comments for author File: Comments.pdf

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

In its current form, your paper remains difficult to read.  My suggestion is to have someone who is preferably a scientist and a native English speaker, go through your paper and edit for clarity.  In order to give your work a fair chance of being accepted, we have to make every effort possible to secure reader understanding.   If we don’t get the English right, the value of the work diminishes.  
I presently recommend that this paper be released. 

The results might be rewritten, and the English revised. These comments should be considered for all manuscript.

It would be best for a reader to know the general behaviour in the abstract and then read in the exact results and their discussion.

The introduction and discussion section are too short. I invite the authors to do more synthesis and to be more precise and direct in presenting the hypothesis, methodology and comparison to other findings in the literature.

Author Response

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Reviewer 3 Report

Dear authors,

Thank you for the opportunity to review this Manuscript (Effect of nitrogen supply on growth and nitrogen utilization in hemp (Cannabis sativa L.)). A pot experiment was conducted 10 using four main hemp cultivars in China. Nitrogen concentration was set as 1.5, 3.0, 6.0, 12.0, 24.0 11 mmol/L NO3-Nin the nutrient solution. The results were expected that exogenous N supply improved the plant growth, dry matter accumulation, and nitrogen accumulation in hemp during the vegetative growth period, but N supply should not exceed 6.0 mmol/L. The study tested N rates but did not use the Regression test to demonstrate the optimal rate. For example, the rate of 6.0 mmol/L was found and indicated as the optimal rate, however, it was not demonstrated in the model (quadratic or linear). Also, the authors have great results about the physiological indicators, but with poor demonstrating.

 

Abstract: The authors could explore more details in the abstract.

Introduction:

The authors could explore more details about the N fertilization for Hemp with studies demonstrating the better N sources and rates. Another idea is that the authors could explore the hem cultivation in the field and greenhouse.

 Material and methods:

I did not understand, the seeds were fertilized with total N, total P, total K, hydrolysable N, 68 Olsen-phosphorus, available potassium was 5.46, 0.37, 1.04, 0.14, 0.14, and 0.42 g kg−1, 69 respectively. Why? While, in the Hoagland formula, there was no N.

All indicator equations should present as Equations in the manuscript.

 

Results and Conclusion

Figures with rates must be present as line graphs with the model to explain the better rate.  Figures 1, 2, 3, and 4 should be edited. Please, demonstrate a better model to explain the data.

Topic 3.1: Table 1 should present as Figure. Probably, a linear model will explain the N rates on Plant height and stem diameter of hemp cultivars. Which cultivar was more responsive to N rates?

Again, in Figure 1, there were different results. Looks that WM1 and YM1 present a linear response to N rates, while the BM and YM7 there was a quadratic response. The authors should test this idea with regression analysis.

In general, the results are not adequately explored.

The NUE, it is known that the increase of N rates reduces the NUE. Perfect. The authors should demonstrate how many reduce, and which cultivar was more responsive.

The results of physiological indicators are very interesting. However, there were not adequately explored. The authors should test the regression test for each cultivar to explain the better response.

Based on editions recommended the Discussion and Conclusion should be modified.

This rate of 6.0 mmol/L should be found with a regression test.

Author Response

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Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

all modifications are done 

Author Response

Dear Reviewer:

Thank you for the review of our manuscript in "Agronomy". We have now improved whole manuscript, please see revised annx.

Author Response File: Author Response.docx

Reviewer 3 Report

I suggest the publication of paper.

 

Author Response

Dear reviewer :

        thank you for the review of our manuscript in "Agronomy".  We hanve employed a scientist and a native English speaker editing the manuscript,and now improved language throughout the manuscript, please see revised annx. 

Regards

Author Response File: Author Response.docx