Review Reports - Low Nitrogen Availability in Organic Fertilizers Limited Organic Watermelon Transplant Growth

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Dear Editor-in-Chief,

Thank you for giving me the opportunity to review the manuscript entitled “Nitrogen Availability in Organic Fertilizers Limited Organic 2 Watermelon Transplant Growth “

The study investigates the effects of organic fertilizers on watermelon transplants, emphasizing nitrogen (N) availability and its role in growth. While previous studies have explored organic fertilizers, few have specifically addressed the nitrogen content's effects on watermelon transplant development under organic farming systems, adding a unique perspective.The data presented is original, obtained from controlled greenhouse experiments.

1- The research quality is high, with a solid experimental design and appropriate statistical analyses. However, expanding on the interactions between various fertilizers might have enriched the analysis. The choice to focus primarily on N availability is justified, but a brief exploration of potential interactive effects between N, P, and K could provide a more comprehensive view of plant nutrient dynamics.

2- The introduction provides an adequate background on organic fertilizer use in transplant production, though it is lengthy and repetitive in some areas (lines 27-67). The length and coherence are generally suitable for establishing the study’s context, yet some conciseness could improve clarity.

3- The experimental design is appropriate, with 12 treatment groups that include four organic fertilizers, one conventional fertilizer, and seven blends, offering comprehensive insight into organic fertilizer effects:

a) Fertilizer preparation, transplant sowing, and growth conditions are well-documented. However, it would be beneficial to include more information on the microbial activity in the substrate, as this could affect nutrient mineralization rates (p. 6).

b) Key growth parameters are measured accurately and reflect the study’s objectives. However, incorporating soil microbiota assessments could have provided a more in-depth understanding of the organic fertilizer dynamics.

c) The use of one-way ANOVA is suitable for this experiment, but a two-way ANOVA might have captured interactions between fertilizer type and nutrient concentration more effectively.

4- The graphs and Tables are well-designed, effectively supporting the text. Specifically, the correlation graphs in Figure 3 clearly depict the relationships between nutrient availability and growth parameters. However, the presentation of some data, such as in Table 2, could be improved by highlighting key findings.

5- The results are precise and well-structured, with statistical significance noted. However, results on soil microbial activity, if available, would further enhance understanding of the organic fertilizers' long-term impacts.

6- The discussion provides a thorough interpretation of the results in the context of nitrogen availability, correlating findings with prior research. However, the discussion could expand on why specific fertilizers performed better or worse, potentially linking it to the substrates' microbiological composition. Mechanisms for nitrogen mineralization in organic fertilizers are discussed, but specific microbial interactions that might influence this process could add depth (p. 18, lines 590-603).

7- While the paper addresses N's role effectively, more detail on the impacts of P and K deficiencies on root structure could be beneficial, as roots are critical for transplant establishment.

8- The language is generally clear and scientific, though there are minor grammatical issues and repetitive phrasing that could be improved:

a) Repetitive phrases, such as "N availability," are frequent and could be varied for readability.

b) There are occasional inconsistencies in the citation format, and some figures (e.g., Table 2) could benefit from clearer labeling for quick reference.

c) Some sentences are overly complex and could be simplified for clarity. For instance, the sentence on p. 19, lines 601-603, could be split for readability.

Comments on the Quality of English Language

The language is generally clear and scientific, though there are minor grammatical issues and repetitive phrasing that could be improved

Author Response

Thank you for giving me the opportunity to review the manuscript entitled “Nitrogen Availability in Organic Fertilizers Limited Organic 2 Watermelon Transplant Growth “

The study investigates the effects of organic fertilizers on watermelon transplants, emphasizing nitrogen (N) availability and its role in growth. While previous studies have explored organic fertilizers, few have specifically addressed the nitrogen content's effects on watermelon transplant development under organic farming systems, adding a unique perspective. The data presented is original, obtained from controlled greenhouse experiments.

We thank the reviewer for their positive review, and we really appreciate your suggestions that help us to improve our manuscript.

We thank the reviewer for this comment. We added a paragraph in the Introduction (Line 84-95) to discuss the effect of P and K. Since P and K in our fertilizers did not tend to be limiting or strongly affecting transplant growth, we did not add more discussion regarding P and K. We thank the reviewer again for this constructive comment.

We appreciate the reviewer's feedback and have removed redundant sentences in the Introduction.

We thank the reviewer for their input. We actually discussed this among the authors and we plan to include this in future studies. Unfortunately, we could not include it in this study since we don’t have any more substrate samples. We added some discussion in 4.4 Limitations and future directions (Line 629-645) to address the effect of microbial activity.

c) The use of one-way ANOVA is suitable for this experiment, but a two-way ANOVA might have captured interactions between fertilizer type and nutrient concentration more effectively.

Unfortunately, each fertilizer type had its unique nutrient concentration in our study, which made it impossible to use 2-way ANOVA to test for their interactive effect on watermelon transplant. This was discussed in Discussion 4.4. Limitations and future direction (Line 596-609).

We thank the reviewer for their suggestion. We added color scale in Table 2 to highlight the difference in EC, nitrate-N and nitrite-N concentration accordingly.

We thank the reviewer for their positive comment. Discussion regarding microbial activity was added to Line 629-645.

Discussion regarding microbial activity was added to Line 629-645.

7- While the paper addresses N's role effectively, more detail on the impacts of P and K deficiencies on root structure could be beneficial, as roots are critical for transplant establishment.

We thank the reviewer for their comment, and we agreed. Background information on P and K effect on root growth was added to Introduction (Line 84-95). Our results indicated that P and K tended to be excessive among our fertilizer treatments, therefore we skipped the details on P and K deficiency in the Discussion section.

8- The language is generally clear and scientific, though there are minor grammatical issues and repetitive phrasing that could be improved:

a) Repetitive phrases, such as "N availability," are frequent and could be varied for readability.

We thank the reviewer for their suggestion. We have replaced some of the phrase 'N availability' with other variances.

b) There are occasional inconsistencies in the citation format, and some figures (e.g., Table 2) could benefit from clearer labeling for quick reference.

We thank the reviewer for pointing these out. The citation format has been updated, and we have deleted column 3-5 for clarity.

c) Some sentences are overly complex and could be simplified for clarity. For instance, the sentence on p. 19, lines 601-603, could be split for readability.

We thank the reviewer for their suggestion. The sentence was rewritten and the term 'multicollinearity' was defined to increase clarity.

Reviewer 2 Report

Comments and Suggestions for Authors

Major comments

1) as column 2 in Table 1 of Material and Methods section is a repetition of columns 3-5 I propose to substitute it to the characteristics of the main organic sources (corn steep liquor, hydrolyzed soy protein, etc). that will make easier to understand the scheme of the experiment

2) Table 2- add statistics- the significance of differences

3) the viability of transplants greatly depends on their antioxidant status. In this respect is was highly desirable to evaluate at least the antioxidant activity of shoot and root extracts and the content of polyphenols and/or proline. Furthermore, in this respect the complexity of investigation and the possibility of other than N, P, K factors effecting the transplant growth should be mentioned not only in the Conclusion section, but also in Introduction

Minor comments:

1)revise the reference list according to the authors guidelines

2)Figure 3A- are you sure that nitrite N slope= - 108.1????

Author Response

Major comments

We thank the reviewer for pointing it out. We actually received a similar comment from the other reviewer as well. The columns 3-5 were deleted and the fertilizer information was updated in Supplemental Tables 1 and 2. We did not add that information to Table 2 because the list of ingredients is too long. Adding that info to Table 2 would create a formatting issue for both us and editors and affect the readability of Table 2.

2) Table 2- add statistics- the significance of differences

We thank the reviewer for their comment. We did not run statistics since we sampled each fertilizer type directly from the bags or bottles and the chemical properties were not expected to change over time. We did, however, track the EC and pH of fertilizer solutions right before applying, as shown in Supplemental figure 2. We hope this makes sense.

We thank the reviewer for their constructive comment. We added a paragraph in the Discussion (Line 621-628) to discuss the possible changes in antioxidant.

Furthermore, in this respect the complexity of investigation and the possibility of other than N, P, K factors effecting the transplant growth should be mentioned not only in the Conclusion section, but also in Introduction

We thank the reviewer for their constructive comment. Would the reviewer mind expand this comment a bit further? The main objective of this study was to correlate N, P and K content and availability and N:P:K ratios of different organic fertilizers with watermelon transplant growth. In the Discussion, we focused on N, and to a lesser extent, P and K. We did not really explore other possibility because we did not quantify more parameters, other than EC and pH. But even EC and pH did not significantly affect transplant growth in our study. We added more background information on the effect of P and K on crop growth in Introduction (Line 84-95), would this address your concern? Thank you so much!

Minor comments:

1)revise the reference list according to the authors guidelines

We thank the reviewer for pointing these out. The citation format has been updated.

2)Figure 3A- are you sure that nitrite N slope= - 108.1????

That number was correct unfortunately... The nitrite concentration was very low (note the scale of x-axis for nitrite) which made the slope large. We added a sentence in Result (Line 324-325) to point out the small nitrite-N concentration range. And that was really why we added Discussion 4.2.2. Shoot growth and nitrite toxicity, just to discuss that nitrite toxicity was unlikely the cause for the reduced shoot biomass.