Potential of Pine Bark to Replace Perlite in Coir-Based Substrates: Effects on Nutrient Uptake, Growth, and Phytochemicals in Lettuce Under Two Salinity Levels

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This study investigates the use of pine bark as an alternative material to perlite and is considered an important study from the perspective of environmental impact. However, the experimental design was not appropriate for evaluating “substitutability,” and the results lacked consistency.

1. Instead of setting up EC treatment zones, we believe that experimental zones with varying ratios of perlite and pine bark should have been established to evaluate substitutability. With only an 8% mixture, there is a high likelihood that other substrates or EC influences would significantly affect the results, making it difficult to reach a conclusive discussion. In particular, if substitutability is claimed based on the lack of significant differences in lettuce growth, this point should be evaluated more cautiously.
2. Tables 2, 4, 5, and 6
It appears that results for four treatment zones were obtained for the Mix×EC combination, but it is unclear what each represents. I feel that the results for each treatment should be recorded as in Figures 1–3, followed by statistical analysis.

Author Response

Thank you for your comments

Comment 1 - This study investigates the use of pine bark as an alternative material to perlite and is considered an important study from the perspective of environmental impact. However, the experimental design was not appropriate for evaluating “substitutability,” and the results lacked consistency. Instead of setting up EC treatment zones, we believe that experimental zones with varying ratios of perlite and pine bark should have been established to evaluate substitutability.

Response

Electrical conductivity (EC) levels were included as a relevant variable because the concentration of the nutrient solution is known to interact with substrate properties and can influence plant responses. Our aim was to determine whether any potential limitations from the partial substitution of perlite with pine bark would become more evident under different EC conditions.

Regarding the expression “evaluate substitutability,” we agree with your suggestion and have replaced it with “the potential to replace” throughout the manuscript, including the title, which has been revised to:

"Potential of Pine Bark to Replace Perlite in Coir-Based Substrates: Effects on Nutrient Uptake, Growth, and Phytochemicals in Lettuce under Two Salinity Levels”.

Comment 2- "With only an 8% mixture, there is a high likelihood that other substrates or EC influences would significantly affect the results, making it difficult to reach a conclusive discussion. In particular, if substitutability is claimed based on the lack of significant differences in lettuce growth, this point should be evaluated more cautiously.

 

Response 

We are grateful for this thoughtful and constructive comment, which highlights an important consideration in evaluating our results. Although 8% may appear to be a low proportion, it was deliberately chosen based on our previous experience to avoid extremes—very high or very low amounts of perlite can negatively affect key physical properties of the substrate, such as aeration and water retention. Moreover, in our modest opinion even modest changes in substrate composition can influence water dynamics, nutrient availability, and plant growth, making this proportion meaningful for detecting potential effects. Nevertheless, your point is highly relevant, and we have added the following sentence to the manuscript to acknowledge the need for further investigation:

“However, further studies are needed to analyze how different proportions of pine bark in the mixture affect lettuce growth and quality, and to evaluate whether this substitution remains suitable for crops with longer vegetative cycles.”

 

2. Tables 2, 4, 5, and 6
   It appears that results for four treatment zones were obtained for the Mix×EC combination, but it is unclear what each represents. I feel that the results for each treatment should be recorded as in Figures 1–3, followed by statistical analysis.

Response

 

We appreciate your observation and agree that an alternative presentation could potentially provide more detail. Accordingly, Table 2 has been transformed into a figure for clearer visualization. However, for Tables 4, 5, and 6, we chose to retain the tabular format because the interaction between Mix × EC, as well as the individual effects of Mix or EC, did not significantly affect the measured parameters. In our view, presenting the tables in this case is more appropriate, as the interaction results are important for showing that the effect of EC is not influenced by the mix.

Reviewer 2 Report

Comments and Suggestions for Authors

Dear Authors, The work is interesting and presented very well. A few comments are noted in the text in the attached PDF. The main problem concerns the quality of the Figures and the supplementary Conclusion. In the conclusion, I would include a sentence to emphasize the novelty of the study and the eco-friendly approach that demonstrates the potential to replace Perlite—with its drawbacks mentioned in the Introduction—with locally sourced pine bark. This replacement has no effect on the quality and nutritional value of the final product (lettuce).    

Comments for author File: Comments.pdf

Author Response

Thank you for your comments

Comment 1 – A few comments are noted in the text in the attached PDF.

Response – The comments made in the attached PDF were taken into consideration.

Comment 2 – The main problem concerns the quality of the figures and the supplementary horizontal axis. Explain the abbreviation DAP (also in Fig. 2). Poor resolution of the graphics applies to all figures.

Response – The figures have been improved, and the abbreviation DAP has been explained in the relevant figure captions.

Comment 3 – I would include a sentence to emphasize the novelty of the study and the eco-friendly approach that demonstrates the potential to replace perlite—with its drawbacks mentioned in the Introduction—with locally sourced pine bark. This replacement has no effect on the quality and nutritional value of the final product (lettuce).
Response – As suggested, we added the following sentence to the Conclusions section:

“This study shows that pine bark, an eco-friendly alternative, has the potential to replace perlite—a material with environmental and economic drawbacks—in coir-based substrates for lettuce cultivation, without affecting the yield and quality of lettuce.”

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Thank you very much for your revisions. I understand that you have taken our comments into consideration as much as possible.
However, I was unable to confirm any new experimental results or changes to the experimental design that would overturn the rejection decision. Therefore, I regret to inform you that we must once again reject your submission.

Sorry.

Author Response

Thank you for your review and comments. While we note your concern regarding the lack of new experimental results, we believe the current study presents original and relevant findings that contribute meaningfully to addressing the urgent need for more sustainable substrates. These insights, in our view, support an important and timely direction for the field.