Comparative Study on Aquaponic and Hydroponic Systems for Sustainable Hemp Production in a Controlled Environment
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThis manuscript focuses on understanding the impact of light on fiber hemp leaves grown as a salad crop under aquaponic and hydroponic systems. The study is novel in terms of its objective; however, minor revisions are needed in a few sections of the paper. The introduction places considerable emphasis on CBD and THC, while it would benefit from discussing the broader applications of fiber hemp—particularly the use of hemp leaves as a salad. Since the primary focus of the study is on hemp as a salad crop, information on the nutritional value and taste of hemp leaves should be included. The life cycle assessment section is thorough and well-articulated. However, the interaction plots for leaf area and plant length could be improved visually, ensuring consistency in Y-axis scaling.
Author Response
Comment 1: The introduction places considerable emphasis on CBD and THC, while it would benefit from discussing the broader applications of fiber hemp—particularly the use of hemp leaves as a salad. Since the primary focus of the study is on hemp as a salad crop, information on the nutritional value and taste of hemp leaves should be included.
>> Thank you for your suggestion. We have added a description of the hemp application as fiber, salad and microgreen in Line 84 to 89.
The focus of our study was to evaluate the performance of two soilless systems under different light conditions during the early vegetative stage of hemp growth,and the environmental impact of these systems. We didn’t conduct the experiment on the nutrition value and taste of hemp leaves since it’s already been done by Mi et al. (2020) and Pannico et al. (2022). I added a brief description of this in Line 85 to 86.
Comment 2: The life cycle assessment section is thorough and well-articulated. However, the interaction plots for leaf area and plant length could be improved visually, ensuring consistency in Y-axis scaling.
>> Thanks, we have updated all interaction plot graphs.
Reviewer 2 Report
Comments and Suggestions for AuthorsThis manuscript explores the effects of different light intensity treatments on the growth and environmental impacts of industrial hemp in hydroponic and aquaponic systems, and employs a cradle-to-gate life cycle assessment (LCA) to evaluate the environmental performance of both systems. The research topic is innovative and of practical importance, particularly in the areas of sustainable agriculture and efficient resource utilization. Overall, the manuscript is well-structured, effectively integrating traditional cultivation techniques with modern controlled environment agriculture (CEA).However, there are still several details that need further improvement to enhance the transparency of the experimental methods and the quality of the article. Detailed comments are listed as follows:
- It is recommended to strengthen the introduction by highlighting the role of light intensity in optimizing plant growth and sustainability in CEA.
- Line161-162: Source of fingerlings: Where did the fingerlings come from? Were they all the same age and size to start?
Line164-166:Although it was mentioned that a lower stocking density was chosen based on research, the reasons for selecting Butterfly Koi as the experimental fish were not fully explained. Relevant evidence such as its advantages in aquaculture and fish vegetable symbiosis systems can be supplemented. - Line173-174:The author state the N-P-K ratio, but what was the concentration of the FLORAGRO® solution? How much FLORAGRO® was added to the water?
- Line184-186:Why did the author choose those light intensities?
- Did the authors conduct repeated or parallel experimental setups?
- In the Results and Discussion section, although multiple percentage changes are mentioned in the article, there is a lack of statistical significance analysis (such as whether to verify the significance of differences through t-tests, ANOVA, etc.).Suggest adding relevant statistical indicators (such as p-value, confidence interval CI) to make the results more scientifically convincing.
8. Line278-288: The description of THC testing is detailed, but it appears to be too informative and off topic in the "Results and Discussion" section. It is recommended to compress it into 1-2 sentences and move it to "Materials and Methods" or "Appendix" for more appropriate information. - The title for Section 3.2 is missing.
Author Response
Comment 1: It is recommended to strengthen the introduction by highlighting the role of light intensity in optimizing plant growth and sustainability in CEA.
>> Added, please check line 92 to 96.
Comment 2: Line161-162: Source of fingerlings: Where did the fingerlings come from? Were they all the same age and size to start?
>> Fish are transported by Toledo Goldfish. All fish were 14 months old when we started the experiment.
Comment 3: Line164-166: Although it was mentioned that a lower stocking density was chosen based on research, the reasons for selecting Butterfly Koi as the experimental fish were not fully explained. Relevant evidence such as its advantages in aquaculture and fish vegetable symbiosis systems can be supplemented.
>> We selected Butterfly Koi due to their adaptability and ability to survive in variable water conditions, making them suitable for controlled-environment systems (Watson et al., 2004). Additionally, Koi are known to produce a steady waste output, which helps maintain a consistent nutrient flow to plants (Hussain et al., 2015).
Works Cited:
Watson, C. A., Hill, J. E., & Pouder, D. B. (2004). Species profile: Koi and goldfish (p. 6). Stoneville, MS, USA: Southern Regional Aquaculture Center.
Hussain, T., Verma, A. K., Tiwari, V. K., Prakash, C., Rathore, G., Shete, A. P., & Saharan, N. (2015). Effect of water flow rates on growth of Cyprinus carpio var. koi (Cyprinus carpio L., 1758) and spinach plant in aquaponic system. Aquaculture international, 23, 369-384.
Comment 4: Line173-174:The author state the N-P-K ratio, but what was the concentration of the FLORAGRO® solution? How much FLORAGRO® was added to the water?
>> 34 mL nutrients added to all the replicates in the hydroponic system. Please Check Lines 192 to 193.
Comment 5: Line184-186:Why did the author choose those light intensities?
>> The light intensities were selected based on a review of previous studies. A recent study by Roman et al. (2024), although not conducted in hydroponic or aquaponic systems, found that low light intensities ranging from 30 to 180 µmol/m²/s effectively supported plant morphological responses. In contrast, Moher et al. (2022) reported that light intensities around 600 to 900 µmol/m²/s produced robust plants during the vegetative stage of indoor Cannabis sativa, which is comparable to our study. Additionally, Eaves et al. (2020) found that hemp yield increased linearly with light intensity up to at least 1500 µmol/m²/s. Based on these findings, we selected a high light intensity of >752 µmol/m²/s and a low light intensity of <141 µmol/m²/s for our experiment.
Please Check Lines 198 to 203.
Comment 6: Did the authors conduct repeated or parallel experimental setups?
>> We used three replicates for each system configuration, and the experiment was conducted in a parallel setup. Please Check Lines 172 to 173.
Comment 7: In the Results and Discussion section, although multiple percentage changes are mentioned in the article, there is a lack of statistical significance analysis (such as whether to verify the significance of differences through t-tests, ANOVA, etc.).Suggest adding relevant statistical indicators (such as p-value, confidence interval CI) to make the results more scientifically convincing.
>> Thanks for the suggestion. We have added a mixed model ANOVA table for both light intensity impact on plant growth.
Please check Table 2 and 3.
Comment 8: Line 278-288: The description of THC testing is detailed, but it appears to be too informative and off topic in the "Results and Discussion" section. It is recommended to compress it into 1-2 sentences and move it to "Materials and Methods" or "Appendix" for more appropriate information.
>> Thanks, the details of THC testing is moved to Materials and Methods under section 2.2. Please Check Lines 174 to 178.
Comment 9: The title for Section 3.2 is missing.
>> Thanks. We have corrected it.
Reviewer 3 Report
Comments and Suggestions for AuthorsI have reviewed the paper “Comparative Study on Aquaponic and Hydroponic Systems for Sustainable Hemp Production in a Controlled Environment”, edited by Zarin Subah and colleagues. Below authors can find some suggestions for improving their manuscript.
Line 12- Cannabis sativa in italics. Please check the entire manuscript for this.
Lines 105-109: at the end of the Introduction chapter it is necessary to more clearly state the purpose of the paper and the justification for the design of this experimental system.
Lines 139-144: please specify where these analyses were performed.
Lines 178-179: please explain why these light intensities were chosen in the experimental design (752 µmol/m²/ and 141 µmol/m²/s)? The difference between them is significant, and the results obtained are somewhat to be expected - the larger dimensions of the plant grown under intense light conditions. The large difference in intensity between the 2 variants does not allow us to detect an optimal value for plant growth processes.
Lines 200-201: it is not clear what is meant by plant length and leaf area gain being measured “regularly” - the fish-related parameters were measured once every two weeks. In this context, what does “regularly” mean?
Lines 355-404: a more credible justification (if any) is needed of the potential impact that hemp cultivation can have on human health and global warming. However, we are talking about a species for which the cultivated areas are limited or very limited.
Line 557- Please justify the need for the table in Appendix A.1. Is it possible that hemp cultivation can have an effect on global warming? However, the cultivation of the species is carried out on small areas.
I suggest the authors to also consult the following papers, with studies on hydroponic hemp culture:
https://doi.org/10.3389/fpls.2020.01169
DOI: 10.1055/s-0030-1251772
The bibliographic references are written completely inconsistently with the Instructions for Authors. They should be rewritten individually and rewritten correctly and completely.
Author Response
Comment 1: Line 12- Cannabis sativa in italics. Please check the entire manuscript for this.
>> Corrected it.
Comment 2: Lines 105-109: at the end of the Introduction chapter it is necessary to more clearly state the purpose of the paper and the justification for the design of this experimental system.
>> Added. Please check Lines 115 to 120.
Comment 3:Lines 139-144: please specify where these analyses were performed.
>> The water analysis was done by Veolia Municipal Water Division, Boise, Idaho 83709. Please check Line 150.
Comment 4:Lines 178-179: please explain why these light intensities were chosen in the experimental design (752 µmol/m²/ and 141 µmol/m²/s)? The difference between them is significant, and the results obtained are somewhat to be expected - the larger dimensions of the plant grown under intense light conditions. The large difference in intensity between the 2 variants does not allow us to detect an optimal value for plant growth processes.
>> The purpose of incorporating light intensity in this study was not to determine an optimal light level or only compare the light intensity's impact on plant growth. Instead, we aimed to evaluate the performance of two soilless systems under different light conditions during hemp growth, in order to examine the interaction among light intensity, system type, and plant response.
The selected light intensities were based on a review of previous studies. Roman et al. (2024), although not conducted in hydroponic or aquaponic systems, found that low light intensities ranging from 30 to 180 µmol/m²/s effectively supported plant morphological responses. In contrast, Moher et al. (2022) reported that light intensities around 600 to 900 µmol/m²/s produced robust plants during the vegetative stage of indoor Cannabis sativa, which aligns with the goals of our study. Additionally, Eaves et al. (2020) found that hemp yield increased linearly with light intensity up to at least 1500 µmol/m²/s. Based on these findings, we selected a high light intensity of >752 µmol/m²/s and a low light intensity of <141 µmol/m²/s for our experiment. Please check Line 198 to 203 in the manuscript.
As shown in Results Section 3.1, under the same high light intensity (752 µmol/m²/s), the hydroponic system produced greater hemp leaf area, while under the low light intensity (141 µmol/m²/s), the aquaponic system showed better performance. Our focus was not on comparing different light intensities, but rather on assessing the performance of each system under its respective light treatment.
Works Cited:
Eaves, J., S. Eaves, C. Morphy and C. Murray. "The relationship between light intensity, cannabis yields, and profitability." Agronomy Journal 112 (2020): 1466-70.
Moher, M., D. Llewellyn, M. Jones and Y. Zheng. "Light intensity can be used to modify the growth and morphological characteristics of cannabis during the vegetative stage of indoor production." Industrial Crops and Products 183 (2022): 114909.
Roman, M., M. Li, J. Yuan, M. Rehman and L. Liu. "Dynamics of industrial hemp vegetative growth and metabolite accumulation in response to light intensity." South African Journal of Botany 169 (2024): 82-94.
Comment 5: Lines 200-201: it is not clear what is meant by plant length and leaf area gain being measured “regularly” - the fish-related parameters were measured once every two weeks. In this context, what does “regularly” mean?
>> Regularly means “Daily” except weekends. Edited it. Please check Line 232.
Comment 6:Lines 355-404: a more credible justification (if any) is needed of the potential impact that hemp cultivation can have on human health and global warming. However, we are talking about a species for which the cultivated areas are limited or very limited.
>> While the current cultivation area of industrial hemp remains limited, assessing the environmental implications of its production per kilogram is crucial, particularly in controlled environment agriculture systems such as aquaponics and hydroponics. The LCA results presented in this study provide a comparative, model-based estimate of potential environmental burdens, including global warming potential and human health impacts, per unit of hemp produced in each system. This allows stakeholders to assess the sustainability of different production systems (aquaponics, hydroponics, or conventional) and make informed decisions as cultivation scales in response to regulatory and market trends.
Comment 7:Line 557- Please justify the need for the table in Appendix A.1. Is it possible that hemp cultivation can have an effect on global warming? However, the cultivation of the species is carried out on small areas.
>> Deleted Appendix A table.
As hemp cultivation continues to expand, assessing the environmental impact per kilogram of hemp produced in aquaponic and hydroponic systems will support producers in making sustainable decisions.
Comment 8:I suggest the authors to also consult the following papers, with studies on hydroponic hemp culture:
https://doi.org/10.3389/fpls.2020.01169
DOI: 10.1055/s-0030-1251772
>> Thank you for the suggestion.
Comment 9:The bibliographic references are written completely inconsistently with the Instructions for Authors. They should be rewritten individually and rewritten correctly and completely.
>> We followed the 'Instructions for Authors' section, which states that references must be numbered in the order of appearance in the text. We used EndNote software with the MDPI Chicago style.
Round 2
Reviewer 2 Report
Comments and Suggestions for AuthorsAll prior concerns have been adequately addressed.The revised manuscript is scientifically sound, well-structured, and contributes meaningfully to the field.Recommended for acceptance after minor formatting revisions.
Author Response
Thank you.
Reviewer 3 Report
Comments and Suggestions for AuthorsThe authors have made the suggested changes to improve their manuscript. In my opinion, the paper can now be accepted for publication.
Author Response
Thank you.
