Plant Density Recommendations and Plant Nutrient Status for High Tunnel Tomatoes in Virginia
Round 1
Reviewer 1 Report
This article focuses on the effects of tomato in-row distance and the number of planting rows on plant height, number, and weight of marketable and unmarketable fruit under high tunnels on the Eastern Shore of Virginia and analyzes the limiting factors that have a decisive effect on tomato yield under high density planting conditions. This manuscript was of significance for high tunnel production. If used properly, it will be helpful to increase the overall yield and quality of the plants. In my opinion, this article provides more comparative and data analysis, which is very convincing, but there are some deficiencies in content and logic. I just have a few points that need to be addressed:
1. Line 16-21: It would be better if the sequential order of the two sentences “We evaluated ...... in a double row.” and “The experiment ...... experimental plots.” in this paragraph could be reversed.
2. Line 68: What do you mean by “the structures” in the text? Please provide a picture of the structures which may make this paragraph easier to understand.
3. Line 80-90: It would be better if the sequential order of the two sentences “Planting density treatments ...... in a double row.” and “The experiment ...... plots.” in this paragraph could be reversed.
4. Line 137-138: Please explain the division between marketable and unmarketable fruits.
5. Line 217: Please clarify what “Such stress” means.
6. Line 216: Please clearly explain the connection between “plant height” and “etiolation”.
7. Line 217-218: Please supplement how far-red light conditions lead to the etiolation in plants.
8.Line 248-251: Is the meaning of “Water creates ...... cell” and “When tomato ...... fruit remains high” repeated?
Author Response
I would like to extend my sincere gratitude to you and the esteemed reviewers for taking the time to review our manuscript. Your thoughtful and constructive feedback has been invaluable in shaping the final version of our work. The insights and suggestions provided have greatly improved the clarity and quality of the manuscript. Please find our comments below.
Comment 1. We rearranged the sentences according to the reviewer's suggestion.
Comment 2. We included a picture of the structures in the document to better showcase the design of the experiment, according to the reviewer's suggestion.
Comment 3. We rearranged the sentences according to the reviewer's suggestion.
Comment 4. Line 116. The following sentence was included in the materials and methods. "Fruits with visible blemishes, mechanical damage, or deformation, and/or smaller than the minimum requirement were considered unmarketable"
Comment 5. The sentence was changed to: "A common indicator of plant-to-plant shading or competition for solar radiation is the increase in plant height".
Comment 6. The following paragraph was added. "In optimal conditions, plants develop sturdy stems and leaves to support their overall growth and reproduction. Etiolation is a specific growth response to low light conditions. When a plant is grown in low light or complete darkness, it undergoes certain morphological changes to increase its chances of capturing available light. Etiolation is characterized by increased internode length leading to taller and spindly stems, as the plant reaches for available light, as well as reduced leaf expansion and apical dominance."
Comment 7. The following paragraph was added: "Far-red light conditions, detected by phytochromes, trigger a shade avoidance response in plants. This response includes elongation growth, enhanced apical dominance, and changes in leaf morphology, collectively leading to etiolation. Under normal light conditions, phytochromes are in a state where they are more sensitive to red light than to far-red light. This means that when a plant receives sufficient red light, the phytochromes signal to the plant that there is enough light available, and the plant will grow normally. However, if a plant receives more far-red light than red light, or if it receives very low levels of both red and far-red light, the phytochromes will signal to the plant that light is limited, and the plant will undergo etiolation [14-16]."
Comment 8. Both sentences were combined to: "Sufficient irrigation water helps maintain turgor pressure within the fruit cell, which in turn helps to preserve the structural integrity of the cell and prevent collapsing or shrinking [19,20]"
Thank you,
Reviewer 2 Report
I have had the pleasure of reviewing your manuscript titled " Plant density recommendations and plant nutrient status for high tunnel tomatoes in Virginia." I must commend your comprehensive and robust approach to this pertinent issue in the realm of agricultural science.
The issue of Plant density in high tunnel production is indeed a pressing one, and your research not only highlights the problem but provides a tangible and innovative solution. Your study design is appropriately rigorous, enabling a holistic understanding of the variables at play. Your focus mainly on vegetative growth characteristics and productivity is highly commendable. However, there are some crucial amendments required as follow:
Point 1: My first comment pertains to line 59-62 where you illustrated the main objective of the study. The hypothesis of your work needs to be more justified. Please justify.
Point 2: in Line 84 you stated that “tomato plants were transplanted at the experimental site on July 12, 2023” and measurements collected such as plant height and tissue samples for foliar nutrient concentration analysis at 4, 8, and 12 weeks after transplant (WAT). There appears to be an error in the transplanting date. Please rectify the date accordingly.
Point 3: Regarding the measurements conducted, I would like to highlight the focus on growth and yield characteristics, as well as the nutrient status of the plants. However, it might be beneficial to consider incorporating additional physiological measurements, particularly those related to the photosynthetic efficiency of the cultivated plants. This could offer a more comprehensive understanding of the outcomes obtained, especially when considering different plant densities.
Point 4: Another aspect of your manuscript pertains to address the need for error values in your data tables. Providing error values alongside the mean values in your tables is necessary to give an accurate representation of your data's variability and precision. The inclusion of error values, such as standard deviations, standard errors, or confidence intervals, helps to convey the spread and reliability of your data.
Author Response
I would like to extend my sincere gratitude to you and the esteemed reviewers for taking the time to review our manuscript. Your thoughtful and constructive feedback has been invaluable in shaping the final version of our work. The insights and suggestions provided by the reviewers have greatly improved the clarity and quality of the manuscript. Please find our response to your comments below.
Comment 1. We included the following paragraph in the document: " There are plenty of recommendations for tomato planting density in open fields and under greenhouse conditions across most producing areas of the U.S., ranging from 3.6 to 1.1 plants per square meter. However, there are no plant density recommendations for the mid-Atlantic U.S. for high tunnel conditions, as most farmers have simply adopted open-field recommendations for this system. There is a tendency to increase plant population under protected structures as fertilization and water management are more strictly managed and farmers face a relatively high initial investment compared to open-field production, enhancing the need to maximize yield per unit area. Our hypothesis is that tomato plants under high tunnels could be planted at a higher density than open field systems given the higher frequency of application of water and fertilizer applied. Hence, the objective of this study was to identify the effect of high planting density on tomato plant nutrient status under high tunnels in the Eastern Shore of Virginia."
Comment 2. Thank you. Indeed, there was a mistake. The date was corrected to July 12, 2021.
Comment 3. Your suggestion to expand the measurements is insightful. While our focus has been on growth, yield, and nutrient status, integrating physiological assessments, such as photosynthetic efficiency, would undoubtedly enrich our findings. This inclusion could enhance our understanding of the effects of varying plant densities on the overall performance of the cultivated plants. Thank you for this valuable input. We will definitely prioritize this suggestion for future evaluations of plant density considerations, as we believe studies of this nature should be conducted for many other crop species in interaction with fertilization rates and irrigation regimens under high tunnels.
Comment 4. We added standard error values to all tables in the document, please see the attachment.
Author Response File: 
Author Response.docx
Reviewer 3 Report
This study is not of scientific value and only proves what has already been studied previously about limiting factors. At the same time, the indication of units of measurement not in the international format is unacceptable and shows disrespect for the reader. The literature review of articles on a similar topic is poorly presented, so the authors felt that their study was unique. There are no references to the methods that were used when setting up the experiment. Although the figures, for example, for fertilizers, the authors did not invent themselves, but took them from literary sources. This study should not be published in a high-ranking journal.
Author Response
I would like to extend my sincere gratitude to the reviewer for taking the time to read our manuscript. I regret that our views do not align regarding the validity of this work, and we will gladly work towards improving the readability of the manuscript to showcase its importance. To simplify our response, we decided to address each sentence from the reviewer's comment individually.
- This study is not of scientific value and only proves what has already been studied previously about limiting factors.
This work originated from a gap in knowledge regarding planting density recommendations for high tunnels in the U.S. Many publications are available regarding plant density for open-field tomato production (although outdated), and greenhouse production. However, high tunnel production has been neglected in terms of applied research in the Mid-Atlantic, and many extension publications simply assign open-field recommendations to the high tunnel system. This is an incorrect approach as conditions inside the tunnel might promote different plant responses compared to an open field, and recommendations might vary. In fact, our results directly contradict recommendations from Cornell University, the University of Kentucky, and the University of Missouri.
Please see the following links:
chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://extension.missouri.edu/media/wysiwyg/Extensiondata/Pub/pdf/manuals/m00170.pdf
chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://www.uky.edu/ccd/sites/www.uky.edu.ccd/files/hightunneltomatoes.pdf
chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://rvpadmin.cce.cornell.edu/uploads/doc_360.pdf
Our thought process was based on the existing tendency to increase plant population under protected structures compared to open fields, as fertilization and water management are more strictly managed and farmers face a relatively high initial investment, enhancing the need to maximize yield per unit area. Our hypothesis was that tomato plants under high tunnels could be planted at a higher density than open field systems given the higher frequency of application of water and fertilizer applied.
We think this was a valid reasoning, given that, compared to open fields, under high tunnels plants are exposed to lower levels of abiotic stressors and higher frequencies and lower volumes per application of water and fertilizer, making the system more efficient than its open field counterpart. Hence, potentially a higher density of plants could have been maintained. On the other hand, it was also plausible that the planting density recommendations from greenhouses were not suitable either, as many of the trellising, pruning practices, and growth habit selection differ from high tunnels, hence, we hypothesized that the correct answer was somewhat in the middle.
We also conducted an extensive search for literature on the topic, with minimum applicable results to the conditions of our study. The most interesting component of our research was that the traditional limiting factor assigned to the regulation of plant density (light availability) did not apply to our study, as plants did not show signs of limited biomass production, etiolation, or differences in the concentration of nutrients of foliar samples. To our eyes, this opened several questions about current production recommendations. If all plant tissue samples were within acceptable levels, then:
- Did we over-fertilize? If so, the current recommendation of 200 lb per acre (224 kg/ha of N) presented in the Mid-Atlantic Commercial Vegetable Production Handbook (chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://njaes.rutgers.edu/pubs/commercial-veg-rec/tomatoes.pdf) must be revised.
- If light and fertilizer were not limiting factors? What was it?
- If fertilizer was the limiting factor, then the acceptable levels of nutrients in plant tissues must be revised.
We think that, given the importance of all these questions, this information was easily applicable to the international scientific community, hence our decision to send the manuscript for publication.
2. At the same time, the indication of units of measurement not in the international format is unacceptable and shows disrespect for the reader.
We decided to go with the original units used during the study, but we could easily modify them to simplify the document for international readers.
3. The literature review of articles on a similar topic is poorly presented, so the authors felt that their study was unique.
Our manuscript cited 29 sources to showcase the current consensus for planting densities under high tunnel systems, but we would gladly go deeper into the literature to reinforce our manuscript.
4. There are no references to the methods that were used when setting up the experiment. Although the figures, for example, for fertilizers, the authors did not invent themselves, but took them from literary sources.
I apologize, but I fail to understand this comment or suggestion. We followed standard procedures for the establishment of the experiment. We selected a Randomized Complete Block Design to minimize potential errors related to field gradients in the experimental area. We selected data collection dates that match generally accepted vegetative transitions for solanaceous crops, as well as selecting dependent variables that serve to validate our hypothesis at that moment of the conception of the experiment. Regarding the fertilization plan, we did not intend to define fertilizer recommendations for tomatoes at that moment, so we followed the regionally approved recommendation for tomato planting. We did not deem it necessary at that moment to include the source of the production practices recommendations, we could easily add them to the manuscript if necessary.
5. This study should not be published in a high-ranking journal.
We hope our responses help to shed some light on any doubts about the approach we followed and the validity of our data. If there is anything else we can do to clarify our position or improve the manuscript, please let us know. Although valid in the round of science, we hope the reviewer can reconsider this position, as it has been an outlier across all the reviewing processes of the manuscript.
Reviewer 4 Report
The manuscript horticulturae-2575898 discusses the plant density recommendations and plant nutrient status for high tunnel tomatoes in Virginia.
The text is well-written; some points are raised below.
1. Ls.66-82: Provide a drawing to illustrate the field experiment.
2. L. 70: “polythene”?
3. Ls. 75-9: Please, replace mil with mm.
4. Ls. 90-6: Should be clarified if irrigation and fertilizers are for the 2-ft in-row cultivation.
5. Ls.99-101: Same as previous.
6. Table 4: not clear the 4-, 8-, 12-WAT results “for all treatments”.
7. Ls. 194-5: Not clear in Table 4.
8. Ls. 198-205: Also, not clear in Table 4.
9. Discussion: What other factor besides the water could be responsible?
Author Response
I would like to extend my sincere gratitude to you as a reviewer for taking the time to read our manuscript. Your constructive feedback has been invaluable in shaping the final version of our work. Please see our responses to your suggestions below. Also, please see attached document for the most recent version of the manuscript.
1- We included a diagram of the treatment distribution and overall setting of the experiment. Additionally, per suggestion of another reviewer, we included a picture of the tunnels where the study was conducted.
2- We corrected the word to ‘Polyethylene.’
3- We changed all references to plastic thickness from mil to mm. Line 83. 6 mil to 0.1524 mm. Line 88, 1.25 mil to 0.0317 mm, Line 92, 15 mil to 0.381 mm.
4-5-. In Line 125. We included the following sentence: “All irrigation and fertilization practices were in accordance with the commercial standard for tomatoes planted at 2 ft of in-row spacing in single row, based on the recommendation of the Mid-Atlantic Commercial Vegetable Production Recommendation Handbook. “
6- We included the following footnote under Table 4: “Means for sampling dates represent the average across all treatments for each sampling date.“
7- . Lines 194 to 205 do not refer to Table 4, but rather to an interaction between in-row distance and sampling date, which p-value is shown in Table 4. We described the results of such interaction including the data points in the text but did not consider necessary the inclusion of a table. If required, we can easily create a table and include it in the manuscript.
8- We included the following paragraph to the discussion section:
Alternately, high planting densities could have limited the ability of plants to correctly pollinate. Tomato plants are typically self-pollinating plants, which means they have flowers with both male and female reproductive structures and can often achieve pollination with minimal interference of external pollinators like insects or wind. However, tomatoes can benefit from vibration producing bee species and wind-induced movement of the flower cluster to elicit full pollen release. Cooley and Vellejo-Marin (2021) [21] showed that both supplemental pollination by buzz-pollinating bees and open pollination by assemblages of bees, which include buzz pollinators, significantly increase tomato fruit weight compared to a no-pollination control. Correct pollination is a key factor related to seed production and sizes which in turn is highly correlated to fruit weight [22-24]. Under greenhouse conditions, it is common for farmers to introduce pollinators to the structure to maximize the potential yield of their system. However, it is plausible that the high-density treatments under the high tunnel limited the reach of natural pollinators to the flower clusters, as flowers could have been produced within the dense foliage of the treatment, resulting in a reduced yield per plant.
Reviewer 5 Report
Thank you for submitting your research work to Horticulturae Journal.
Please find some comments below.
1) Provide soil analysis information previous to your work.
2) provide information on soil physical properties like bulk density, PWP and Field capacity.
3) line 109 fix Magnesium must be (Mg)
4) must provide information on the methodology used to determine each nutrient concentration (leaf tissue analysis)
5) fix X axis in figure 1, there is a symbol I can not define after each month. In addition, improve the quality and visualization of the plot.
6) must fix the format of every table. Check other papers to see how some tables are presented deleting lines between rows and columns. Check this paper to improve format https://www.mdpi.com/2072-4292/13/3/396
7) Table must change tomato plant into "tomatoes plants´ height", or are you referring to a single tomato plant?
8) line 148, not sure why you are adding the "z" footnote, however, should be 1 inch = 2.54 cm
9) line 175 says "plant tissue analysis" did you analyze the whole plant? please explain which part of the plant was used for this analysis and the methodology.
10) line 177, remove "tissue" before concentrations
11) lines 236 to 241. Whatever the nutrient concentration, that must be clarified if was determined on the whole plant, leaflet, or petiole level, there is no information regarding soil analysis. Therefore, there is a risk of over-fertilization affecting the ROI of the grower and with the involved potential environmental consequences. Discuss and explain this point.
12) Conclusion section: Add a few sentences explaining what was your objective. Add some sentences on further research needed and if there were any limitations that need to be considered next time.
13) Must add economic analysis of the results.
Mainly based on comments for Table 1.
Author Response
I would like to extend my sincere gratitude to you for taking the time to review our manuscript. Your thoughtful and constructive feedback has been invaluable in shaping the final version of our work. The insights and suggestions provided have greatly improved the clarity and quality of the manuscript. Please find our comments below.
Comment 1 and 2. The following statement was included:
Line 85- Soil samples were collected at the experimental site at 8 inches (20.3 cm) depth and sent to the laboratory before the establishment of the experiment. The soil under the structures presented an average pH of 6.7 and soluble salt content of 0.18 mmho/cm. Additionally, soil samples contained 10.9 ppm of nitrate-N, 3.8 ppm of ammonium-N, 169 ppm of phosphorus, 70 ppm of potassium, 44 ppm of magnesium, and 315 ppm of calcium. The soil was composed of 57% sand, 30% silt, and 13% clay, with a field capacity of 25.8% at 6 kPa and a permanent wilting point of 4.7% at 1500 kPa.
Comment 3. Corrected.
Comment 4. The following statement was added:
Line 142- Total nitrogen was determined by oxygen combustion gas chromatography with subsequent quantification by a thermal conductivity detector. Total P, K, Ca, Mg, and S concentrations were determined with Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES), after closed-vessel nitric acid (HNO3) digestion in a microwave digestion system.
Comment 5. We updated the figure and attached it to the manuscript as a modifiable object, in case the size of the font needs to be increased.
Comment 6. All tables were corrected to the suggested format, please see the attached document.
Comment 7. The value refers to the average height of one tomato plant, calculated from the average of 5 tomato plants per plot.
Comment 8. Footnotes from all tables were corrected, please attached document.
Comment 9. Line 140- The following sentence was included: “Tissue samples were composed of five true leaves per plot, collected from the middle of the plant and avoiding apical leaves, damaged leaves, and leaves showing signs of senescence.”
Comment 10. Corrected.
Comment 11. Line 298 – The following sentence was included in the manuscript: “Additionally, the soil analysis at the experimental site was considered low in N, K, Ca, and Mg, supporting the hypothesis that the crop consumed mostly the nutrients provided throughout the fertilization program and was not overfertilized.”
Comments 12 and 13. Line 332 – The following paragraph was included in the manuscript. “Greenhouse recommendations have not been traditionally applied to high tunnel conditions, as it is a common belief among farmers and agricultural professionals that high tunnels closer resemble open field conditions than other protective or controlled structure systems. However, farming under high tunnels requires a higher initial investment than open field conditions and provides partial protection to the plants allowing better control of fertilizer and water applications, application of pruning and training practices, and installation of trellising systems. Hence, it is necessary to develop a specific production system for high tunnels designed to maximize the potential profitability of the farmer. The objectives of this study were to identify planting density recommendations for tomatoes under high tunnel conditions and to evaluate their chances in plant nutrient status. Our results demonstrated that farmers should not seek to increase tomato plant density under high tunnel conditions under the current production system, as it will not result in increased yield per area. Furthermore, a simple economic estimation of the cost of implementation of high densities under high tunnels suggests that increasing the plant density from 4,256 (standard recommendation) to 11,616 plants per acre requires an additional investment of approximately $5,971 per acre, after accounting for seeds, trays, and stakes for trellising. This estimation does not account for the additional labor cost required for transplanting and maintenance of the plants.”
Author Response File: Author Response.docx
Round 2
Reviewer 3 Report
Thanks to the authors for updating their manuscript. A good adjustment has been made. However, it is still worth noting controversial points:
1. Analysis of 29 (finally 33) literary sources is still not enough. If you carefully analyze the list of references, then most of the analyzed studies were made in the USA. However, this journal is international, and research in the USA may not be relevant to the scientific community of the world. In other countries, similar studies were carried out (China, India, Poland, and others), but the authors do not refer to the experience of other researchers and countries. If you do not take into account the experience of other countries, it may seem that your study is unique. This analysis is lacking. I hope the authors understand what I mean. Otherwise, such a study should be published only in scientific journals in the United States.
2. The Materials part has been improved very well. Of course, it is worth inserting a part with recommendations approved at the regional level for planting tomatoes. I remind you that this magazine is international and the requirements in different countries may differ. The reader should be able to familiarize himself with all the conditions of the experiment. That is why it is imperative to indicate international units of calculation, since they are used by most countries of the world.
3. Undoubtedly, this study is interesting, but this scientific journal is international, so be sure to take into account again other countries. Therefore, the required corrections will increase the scientific significance of your work for other researchers. I hope you will correct this manuscript.
Author Response
I would like to extend my sincere gratitude to you for taking the time to review our manuscript. Your thoughtful and constructive feedback has been invaluable in shaping the final version of our work. The insights and suggestions provided have greatly improved the clarity and quality of the manuscript. Please find our comments below.
As all three comments from the reviewer are similar in nature we decided to provide a summary of the improvements made to the manuscript in relation to the comments.
We conducted an extensive search through multiple sources of peer-reviewed manuscripts databases, including Google Scholar, JSTOR, PubMed, Research Rabbit, DOAJ, and Research Gate among others, and using several keywords including 'high' 'tunnel' 'high-tunnel' 'tomato' 'tomatoes' 'density' 'spacing' 'distance' 'row' 'rows' among others. We were able to expand our literature review and provide a better understanding of the body of literature related to our research focus. It is important to note that we excluded any study that was not conducted under a tunnel structure, as the whole premise of the manuscript is that open field and greenhouse systems (and any of its variations) are different from tunnel production systems.
The following section was added to the discussion of the manuscript (please see the document attached).
Line 368- Similar work has been conducted in different locations around the globe with results varying with locations, cultivars, and cofounding factors under evaluation. Zahid et al. (2020) [34] evaluated in-row spacings of 45, 60, and 75 cm in a single row in combination with two irrigation regimens [standard and deficit irrigation] for tomatoes under high tunnels in Rachna Doab, Pakistan. Their data indicated that the highest yield per unit area was obtained with 45 cm of in-row spacing (equivalent to 1.5 ft), with no interaction with the irrigation regimen. The authors hypothesized that low levels of potassium in the soil lead to a reduction in yield in the high-density treatments. Reid et al. (2023) [35], evaluated grafted tomatoes under high tunnels in three in-row spacings in single rows [40, 50, and 60 cm]. Tomato plants produced the highest yield at 60 (equivalent to 2 ft) and 50 cm (equivalent to 1.64 ft), compared to 40 cm, while grafted tomatoes overperformed compared to engrafted ones. Wells (1994) [36], compared in-row spacings of 30 cm, 45 cm, and 60 cm with 1 m between planting rows, in combination with different levels of removal of side shoots. They identified that the highest yield per area was at 12 inches (equivalent to 1 ft) with no side shots, while the lowest yield per area was at 24 inches (2ft) and one side shot. Another study in Turkey evaluated 15 cm, 25 cm, and 35 cm of in-row distance in a single row in combination with different treatments of truss pruning (3, 4, 5, and 6 trusses per plant). The authors found that 35 cm (equivalent to 1.14 ft) of in-row distance produced more fruits per plant and heavier individual fruit weight than the rest of the treatments, although yield per unit area was increased the closer spacing [37]. Conversely, Rashid et al. (2016) [38], investigated the interaction between three in-row spacings [60, 90, and 120 cm] and four N rates [0, 60, 100, 140 kg/ha] for tomatoes under high tunnels. Researchers concluded that tomato plants under high tunnels produced the highest yield with a combination of 90 cm (equivalent to 2.95 ft) of in-row spacing and 100 kg/ha of N. Overall, the variation across results in the literature suggest that in-row spacing recommendations should not be generalized across production regions and system, and moreover, should be based on locally generated research data.
Reviewer 5 Report
Thank you for improving your work.
Author Response
Thank you so much for the suggestions.
