Nutrient Solution from Aqueous Extracts as an Alternative to Fertigation in Hydroponic

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This MS evaluated the nutrient content variation in the hydroponics cultivation system and the response of lettuce crop’s yield and quality to three nutrient solution treatments. Result in this study is interesting that aqueous extracts is a better nutrient solution for soilless crop cultivation with high yield and good quality and good to environment. However, the experiment was carried out just one season, and some conclusions are conflict to the results in published paper. Therefore, this reviewer strongly suggests resubmit it after adding more experimental data.

Some comment and suggestions:

(1)   In section 2, present the thickness of the thin nutrient solution and if this solution depth enough for root development and nutrient uptake (Line 108).  

(2)   If possible, some pictures can be presented to show the NFT system.

(3)   the experimental area for each treatment should be described, and if there were treatment replications?

(4)   How long time the solution in the system will be refreshed. If the solution in the system was continuously operated. the solution in the root should be the same to the solution tank. In this case, it is nonsensical to compare the nutrient content in the solution among the three treatments in section 3.1.

(5)   The values of nitrate for the three treatment may be misplaced on Fig.1. Ckeck it. 

(6)   In section Dry material (Line 422), The result of higher dry matter content in T0 than other two treatments was not in agreement with other researches. therefore, one or two more crop seasons experiment should be carried out to confirm the present conclusion. 

(7)   Line 437, How to define the commercial production and fresh weight of the aerial part.

Author Response

First of all, thank you for the in-depth review of the manuscript. Below we detail each of the comments. We have also sent the manuscript for English review (certificate included). The manuscript is with visible changes. We have also uploaded the modified manuscript.
(1)    In section 2, present the thickness of the thin nutrient solution and if this solution depth enough for root development and nutrient uptake (Line 108).  
Line 90 to 105 (line 108 in manuscript before review): In response to Reviewer 1's comment, we have expanded the system description (line 90 to 105, formerly line 108) and included a descriptive outline (Figure 1). Although the thickness of the nutrient solution in the NFT system is very thin, its continuous renewal allows it to meet the nutritional needs of the crop. The NFT system has been designed since the 1960s, and has demonstrated its ability to produce low-growing horticultural crops such as lettuce and even long-cycle crops such as tomatoes.
(2)    If possible, some pictures can be presented to show the NFT system.
Line 107: Thank you for your comments. We have included a diagram of the cultivation system used in the trial (Figure 1).
Line 126: We have also included photographs of the experiment where we can see how the aqueous extracts were prepared and handled in the field (Figure 2).
(3)    the experimental area for each treatment should be described, and if there were treatment replications? 
Line 176-194: Thank you for the in-depth review of the manuscript, we have included a description of the experiment with respect to the surface, repetitions and number of plants.
(4)   How long time the solution in the system will be refreshed. If the solution in the system was continuously operated. the solution in the root should be the same to the solution tank. In this case, it is nonsensical to compare the nutrient content in the solution among the three treatments in section 3.1. 
Linea 213-222: Thanks for the comment. We have proceeded to expand the description of the management of the nutrient solution during cultivation. The initial composition of the nutrient solution for each treatments (T0 and T1=T2) is shown in Table 1. And it is also the composition of the nutrient solution used to fill the tank and supply the plants' consumption. This operation was carried out every 1 or 2 days, not allowing it to go below 50L. The water consumption that occurs throughout the crop is replaced, but since it is a short cycle it is not necessary to make a complete change. The water consumption of each treatment is different and therefore the changes in concentration in the irrigation solution according to treatments are included.
 (5)   The values of nitrate for the three treatment may be misplaced on Fig.1. Ckeck it. 
Figure 1 (line 259 in manuscript before review), which has been eliminated, corresponded to the average value of NO3 and NH4 in the nutrient solution of the recirculation tank throughout the crop. We have eliminated it, since the values per fortnight included in Table 2 are sufficient to explain the evolution of the nutrient solution in the crop cycle.
(6)   In section Dry material (Line 422). The result of higher dry matter content in T0 than other two treatments was not in agreement with other researches. therefore, one or two more crop seasons experiment should be carried out to confirm the present conclusion. 
Line 500-506: The dry matter values (Table 4) correspond to the average of 3 repetitions and 3 plants per repetition, so we believe that they are sufficient to consider the values in the analysis of the work. Although it does not match the reference mentioned in the work. We appreciate your suggestions but it is not possible to repeat the experiment. 
(7)   Line 437, How to define the commercial production and fresh weight of the aerial part.
Line 273-278: The description of the production calculation has been expanded. Commercial production (Figure 3 Line 529) was calculated by multiplying the planting density by the average fresh weight of the aerial part of the plants per repetition. We have eliminated the figure (Figure 2 in manuscript before review Line 418) in which the average weight of the aerial part appeared since it could lead to confusion.

Kind regards

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Line 99,100:  solution. And obtain correct this dot. 

In the introduction i suggest citing this work:https://doi.org/10.1016/j.scienta.2023.112178 

Line 108 to 111: This NFT description should be placed into the Introduction or deleted. It is not needed in the MM section.

Figure 2: please edit the data labels. Now they cover the SE marks.

Please provide a more deatiled description of the nitrate analysis. Not just reference.

Please provide more detalies, what excatly does the airation of the extract does, so it becomes better.

Author Response

First of all, thank you for the in-depth review of the manuscript. Below we detail each of the comments. We have also sent the manuscript for English review (certificate included). The manuscript is with visible changes. We have also uploaded the modified manuscript.
Line 99,100:  solution. And obtain correct this dot. 
Line: 113-117. Thanks for your review. We have revised and expanded the wording of the objective of the work.
Line 108 to 111: This NFT description should be placed into the Introduction or deleted. It is not needed in the MM section.
Line 91-105: The description of the system has been moved and expanded to the Introduction section between lines 91-105, and a schematic figure (Figure 1 Line 107) of the NFT system and another figure (Figure 2 Line 175) with photographs of the experiment have been included to help better explain the system and the test.
Figure 2: please edit the data labels. Now they cover the SE marks.
Line 500: According to the reviewers' comments, we have decided to eliminate the figure, since they asked that we simplify the results included in the work. The fresh and dry weight have been included in Table 4 (Line 500).
Please provide a more deatiled description of the nitrate analysis. Not just reference.
Line 262-266 It has been expanded in the text with a brief description of the referenced method.
Please provide more detalies, what excatly does the airation of the extract does, so it becomes better.
Line 125-194. We have expanded the requested description

Kind regards

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

This paper describes the test of vermi-tea as fertiliser in hydroponics with and without extra aeration. The paper requires shortening, language editing and full revision before it can be considered for publication. Particularly results should be summarised much more, only important results need to be shown, other results can be put in supplementary material. The aeration process appears to mainly induce nitrification, if there are other changes they should be highlighted, but is not necessary to list all elements for all solutions at all times. Plant growth should be reported as dry weight (only), Any difference in dry matter % can then be reported as well. To show fresh weight and dry matter content as is done here is confusing. It is not very surprising that nitrate content in leaves are higher in solutions with higher nitrate content, shorten this part.

Comments on the Quality of English Language

There are many minor mistakes, it is still possible to understand, but extensive editing is required.

Author Response

Thank you very much for your comments. We have tried to thoroughly review the manuscript, both the content and the English. We have sent it to the translation service (we attach the certificate). The manuscript is with visible changes. We have also uploaded the modified manuscript.
The Introduction and Material and methods section has been expanded and corrected according to the reviewers' suggestions, including two figures that explain in depth the operation of the hydroponic system used (NFT).
Regarding the content, we have eliminated part of the data that it suggests and left those results that we believe are important to be able to manage the aqueous extracts.
We have also decided to leave all the analyzed ions in the nutrient solution, since the excess of some of them can act in competition with other nutrients, and the limitation of the concentration (EC) forces us to assume limitations in some nutrients. We have also left the pH since it influences microbial activity and it is not possible to acidify as recommended in hydroponic crops.

Kind regards

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Most of the comments and suggestions are well responded. However, the different results on plant dry mater with inorganic nutrition and organic fertilizer in this study is not coincide with Masarirambi et al. (38). Authors should discuss the reason that made the difference in the two studies.

Author Response

Dear Reviewer,
First of all we thank you for your review. 
The paragraph is between lines 475 and 491. We trust that it will be useful to justify the differences between both manuscripts.
“The difference between the two manuscripts may be produced by the type of organic matter used and its richness in nutrients. In our experiment, the aqueous extracts (T1 and T2) present low concentrations of P (Table 2), which justifies that the dry matter of the organic treatments is lower, even with aeration, as it does not reach the recommended values for lettuce (T0). The dry weight of the root and aerial part of the T0 treatment are significantly greater than those quantified in the organic treatments (T1 and T2). This increase of more than 4% and 10% in the dry matter of the aerial part and root, respectively, may be caused by the increase in the assimilation, translocation and utilization of phosphorus as a consequence of the higher concentration of H2PO4 (Table 2) in the T0 (P concentration in T0, is 6 times higher than in T1 and T2), which is corroborated by the highest concentration of P in sap (Table 3). Phosphorus is essential for the processes of photosynthesis and respiration. In this regard, Russo and Pappelis (1995) report that phosphorus promotes greater elongation and production of root hairs that lead to an increase in the dry weight of the plant.
Russo, V.; Pappelis, A. Senescence in sweet corn as influenced by phosphorous nutrition. Plant nutr. 1995, 18(4), 707-717.
The document has been edited in English by MDPI, reviewed for correct use of grammar and common technical terms, and edited to a level suitable for reporting research in an academic journal. We have included the justification.

Green text has been added to this document.

Kind regards

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The authors have addresed all my comments.

Author Response

Dear Reviewer

First of all, thank you for reviewing the manuscript. We have re-reviewed the content of the document following the instructions.
The document has been edited in English by MDPI, reviewed for correct use of grammar and common technical terms, and edited to a level suitable for reporting research in an academic journal. We have included the justification.

Green text has been added to this document.

Kind regards

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

I still don't think it is suitable for publication. Nost of the ppoints raised in my previous assessment have not been addressed adquately, and I don't think the pictures/figures that have been put in add much.

Shorten manuscript, in particular the very detailed discussion on how the solution changes, instead give more explanation for important trends and results.

Comments on the Quality of English Language

N/A

Author Response

Dear Reviewer

First of all, thank you for reviewing the manuscript. We have re-reviewed the content of the document following the instructions.
The document has been edited in English by MDPI, reviewed for correct use of grammar and common technical terms, and edited to a level suitable for reporting research in an academic journal. We have included the justification.

Green text has been added to this document.

Kind regards