Low Plant Density Improves Fruit Quality without Affecting Yield of Cucumber in Different Cultivation Periods in Greenhouse
, Wenfeng Nie 2,†, Tingting Qian 1,*, Lizhong He 1, Hongmei Zhang 1, Haijun Jin 1, Jiawei Cui 1, Hong Wang 1, Qiang Zhou 1 and Jizhu Yu 1,*
Round 1
Reviewer 1 Report
The production of agricultural foods is very important to feed million people around the world using any approaches. The low plant density is NOT new approach, but several previous studies reported about that concerning the production of cucumber under greenhouse conditions like:
Ayala-Tafoya et al. (2019). Plant density and stem pruning in greenhouse cucumber production
I can notice that the precious article, authors used low plant density more than the current study (1.68 and 2.22 plants m-2)?? Why the author did not use lower rate like this?
It is very common to check first the plant density and sue below this level and higher as well!
On which base did you select these rates of density? Are from recommended or what?
So, there is NO novelty.
General comments
1- In abstract, author mentioned that:
“Hence, our study suggests that properly reduced plant density of cucumber could be a practicable approach for not only saving the labor and agricultural material inputs, but also improving fruits quality, thus receiving excellent economic benefit.”
Did you calculate and evaluate the economic evaluation, investment of this work? Clear that
2- Keywords: this all times, please avoid to use any word already mentioned in the title to increase the database of your work!!!
3- Introduction: statistical data of production needs to be update
4- Materials: a- Where the details about irrigation and fertilization of this work?
b- Where the soil, which use and its properties??
c- - did you measure the canopy???
d- Need a schematic diagram showing the shape and style Venlo- type glass greenhouse!!!
e- line 85, use of Deltastar RZ F1 hybrid of cucumber instead of cucumber variety
f- lines, 87-89: The words are opposite each other.. which are true?
g- lines 97 to 101: number of weeks are false. Week 14 -26 How? It should be from week 4 to week 17 and so on of the all, which need adjustment the weeks numers
h- transplant date change to be transplanting date
j- Fig. 1 not clear, you have to make 3 collected photos for each density and details for each photo in each group???
k- Where the marketable yield of cucumber?
l- Line 148, you mentioned that the content of chlorophyll.. which chlorophyll you mean, a, b, total …? And which formula used to calculate it? Clear!
m- Soluble sugar: how do you measured it and the references?
n- Why do you estimated the nitrate and nitrite content? Although you did not use nitrogen fertilization in the treatments or the factors? So clear the reason..
5- Results:
-Figs. 2 & 3 are not clear, please??
- line 217-220 and fig 3: there are no significant differences on total cucumber yield per square meter according to different densities. How? and the main target of your experiment did not do as your discussion in lines 272-273
- Fig 5 not clear?? Chang the style of columns or curves by another
This work is not complete to be published, so major revision is needed?
Author Response
Point 1: The production of agricultural foods is very important to feed million people around the world using any approaches. The low plant density is NOT new approach, but several previous studies reported about that concerning the production of cucumber under greenhouse conditions like:
Ayala-Tafoya et al. (2019). Plant density and stem pruning in greenhouse cucumber production
I can notice that the precious article, authors used low plant density more than the current study (1.68 and 2.22 plants m-2)?? Why the author did not use lower rate like this?
It is very common to check first the plant density and sue below this level and higher as well!
On which base did you select these rates of density? Are from recommended or what?
So, there is NO novelty.
Response 1: Appropriate density is very important for cucumber production, while the different regions have different favorable density, which depend on the climatic conditions, especially for the local radiation. We invited a Dutch grower as the consultant in our greenhouse, and he advise the normal density of cucumber in Shanghai, China was about 3.0 plants m-2. We have used the cucumber density of 3.0 plants m-2 for about three years in cucumber production, and we attempt to optimize the density and consulted some cucumber experts, and finally we decided the three densities of 2.25, 3.0, and 3.75 plants m-2, which can all be used in cucumber cultivation practice in Shanghai, China. We downloaded the article of “Ayala-Tafoya et al. (2019). Plant density and stem pruning in greenhouse cucumber production”. In this article the authors made an adequate density treatment and the result clarified the influence of plant density on cucumber growth and yield. However, our study paid more attention to the effect of plant density on dry matter distribution, yield and quality of cucumber. Considering that too high density will weaken the growth of cucumber due to nutrient competition, it will also bring about the harm of pests and diseases, and will affect the growth of other density treatments in the greenhouse, so we did not choose a higher density.
Point 2: General comments
1- In abstract, author mentioned that:
“Hence, our study suggests that properly reduced plant density of cucumber could be a practicable approach for not only saving the labor and agricultural material inputs, but also improving fruits quality, thus receiving excellent economic benefit.”
Did you calculate and evaluate the economic evaluation, investment of this work? Clear that
Response 2: At low density, hanging hooks, planting, twisting, pruning, leaf cutting, lowering, all of which can be significantly saved, while less seeds, seedling rockwool blocks, and chemical pesticide at low planting densities will also reduce material inputs. But it is not easy to calculate the accurate cost in our experiments, for lacking labor cost and sales income. So we did not calculate and evaluate the economic evaluation. We have changed the sentence to “Hence, our study suggests that properly reduced cucumber plant density to 2.25 plants m-2 could be a practicable approach in greenhouse in Shanghai” (lines 32-33). We also deleted the related sentence in conclusions (lines 400-402).
Point 3: 2- Keywords: this all times, please avoid to use any word already mentioned in the title to increase the database of your work!!!
Response 3: We thank the reviewers' suggestion. We have changed the keywords to avoid words in the title (lines 34-35).
Point 4: 3- Introduction: statistical data of production needs to be update
Response 4: The 2020 cucumber production data is the latest data from the FAOSTAT website (https://www.fao.org/faostat/en/#data/QCL) (line 41).
Point 5: 4- Materials: a- Where the details about irrigation and fertilization of this work?
Response 5: The details about irrigation and fertilization were illustrated in the new manuscript. Cucumber plants were irrigated by drip fertigation which controlled by computer. The drain nutrient solution was about 20-30% of the applied after transplanting. The original mother nutrient solutions (A and B) were based on Hoagland’s solution with modifications and the mother nutrient concentrations were listed in Table 1. The mother nutrient solutions were revised following the advice of Eurofins (branch company of Suzhou, China) by regular nutrient solution testing. EC of 2.0-2.5 dS m−1 and pH of 5-6 were maintained before cucumber harvest. Once harvesting started, EC of 2.5-3.0 dS m−1 and pH of 5-6 were maintained (lines 102-111).
Point 6: b- Where the soil, which use and its properties??
Response 6: We used rockwool as substrate for soilless cultivation. Cucumber seeds were sown in Grodan blocks (10 cm × 10 cm × 6.5 cm) for seedling growth in the seedling greenhouse in which the climate can be controlled well. In each cultivation period, cucumber seedlings were planted on rockwool slabs (100 cm×20 cm×7.5 cm) in greenhouse and irrigated by drip fertigation (lines 128-132).
Point 7: c- - did you measure the canopy???
Response 7: No, we did not measure the canopy photosynthesis. The photosynthesis we measured on the leaves which are selected from the upper canopy and are fully expanded.
Point 8: d- Need a schematic diagram showing the shape and style Venlo- type glass greenhouse!!!
Response 8: The picture of Venlo- type glass greenhouse was added in the MS (figure 1, A. Line 138).
Point 9: e- line 85, use of Deltastar RZ F1 hybrid of cucumber instead of cucumber variety
Response 9: We thank the reviewers' suggestion. We changed the Deltastar to Deltastar RZ F1 hybrid cucumber in lines 96-97.
Point 10: f- lines, 87-89: The words are opposite each other. which are true?
Response 10: We did not use a CO2 creator or CO2 pump to increase the CO2 concentration. But Air Treatment Unit (ATU) brings more air in greenhouse, increasing the air pressure inside the greenhouse, which in turn enrich the CO2 concentration in the greenhouse. To avoid the contradiction between these two sentences, we have deleted “and there was no supplemental CO2 enrichment in the experimental greenhouses” in lines 98-99.
Point 11: g- lines 97 to 101: number of weeks are false. Week 14 -26 How? It should be from week 4 to week 17 and so on of the all, which need adjustment the weeks numers
Response 11: Week numbers are counted from the first week of 2017, not from the sowing date, as shown in figure 2 (line 222).
Point 12: h- transplant date change to be transplanting date
Response 12: We thank the reviewers' suggestion. We have modified this mistake in lines 120, 123 and 126.
Point 13: j- Fig. 1 not clear, you have to make 3 collected photos for each density and details for each photo in each group???
Response 13: We thank the reviewers' suggestion. The fig 1 (B) has been replaced with a new clear figure in line 138.
Point 14: k-Where the marketable yield of cucumber?
Response 14: The yield we measured was marketable yield. Cucumbers that did not meet the harvesting standards were not included in the yield.
Point 15: l- Line 148, you mentioned that the content of chlorophyll. which chlorophyll you mean, a, b, total …? And which formula used to calculate it? Clear!
Response 15: Chlorophyll in the manuscript was total chlorophyll content. We have written it clear in new manuscript in lines 184-188.
Point 16: m- Soluble sugar: how do you measured it and the references?
Response 16: We have added the reference in line 191.
Point 17: n-Why do you estimated the nitrate and nitrite content? Although you did not use nitrogen fertilization in the treatments or the factors? So clear the reason.
Response 17: The nitrate ions in cucumber fruits always have negative effects on human health especially in nutrient solution irrigation mode. Therefore, this study determined nitrate and nitrite content for two purposes, one was to study whether reducing planting density would increase or decrease nitrate and nitrite accumulation in fruit; second, whether reducing planting density will improve fruit nutrition while improving food safety.
Point 18: 5- Results:
-Figs. 2 & 3 are not clear, please??
Response 18: The fig 2 and 3 have been replaced with new figures (lines 222, 241).
Point 19: - line 217-220 and fig 3: there are no significant differences on total cucumber yield per square meter according to different densities. How? and the main target of your experiment did not do as your discussion in lines 272-273
Response 19: There are no significant differences on total cucumber yield per square meter because low density treatment has fewer plants per square meter but higher yield per plant while high density treatment has more plants per square meter but lower yield per plant (figure 4). Therefore, there are no significant differences on total cucumber yield per square meter among the three density treatments. The main target of our experiment was to indicate that yield per unit area is not exactly positively correlated with density. Furthermore, low density treatment increased the contents of soluble sugar, total phenolic, flavonoid, soluble protein, Vc, chlorophyll, and carotenoid content in fruits, which improved fruits quality. Therefore, the main target of our experiment was to explain that cultivation method with properly reduced plant density improves fruit quality without affecting yield of cucumbers in greenhouse.
Point 20: - Fig 5 not clear?? Chang the style of columns or curves by another
This work is not complete to be published, so major revision is needed?
Response 20: We thank the reviewers' suggestion. The fig 5 has been replaced with a new figure (line 276).
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Hallo,
the scientific aim and novelty is low. Many paper exist about the optimum plant density for cucumber, but the results confime existing paper quite well.
- figure 2 to much results in one graph (scaling!)
- figure 3 and 5 is hard to read or to see differences (scaling)
Author Response
Point 1:the scientific aim and novelty is low. Many paper exist about the optimum plant density for cucumber, but the results confime existing paper quite well.
- figure 2 to much results in one graph (scaling!)
Response 1: We thank the reviewers' suggestion. Our research did more work about the effect of plant density on dry matter distribution, yield and quality of cucumber. We demonstrated that cultivation method with properly reduced plant density improves fruit quality without affecting yield of cucumbers in greenhouse. Climate parameters would influence the cucumber growth and yield, we exhibited one year data that to explain the different growth and yield in different cultivation period. The fig 2 has been replaced with a new figure, we think it looks better now (line 222).
Point 2: - figure 3 and 5 is hard to read or to see differences (scaling)
Response 2: We thank the reviewers' suggestion. The fig 3 and 5 have also been replaced with new figures (lines 241, 276).
Author Response File: Author Response.pdf
Reviewer 3 Report
Dear authors:
I have read the manuscript, Low plant density improve fruit quality without affecting yield of cucumber in greenhouse.
Title:
· The title of the manuscript must be modified by adding what is related to planting dates (for example: different seasonal environmental conditions or cultivation periods)
· improve correct to improves
Abstract:
Line 27: remove nitrate
Keywords:
add sowing date
Introduction:
Line 50 - 58: What does this paragraph have to do with the manuscript?
Materials and Methods:
Line 91-92:
Authors mentioned: outside temperature, radiation sum, air temperature in the greenhouse were monitored and controlled automatically, How (controlled automatically in the greenhouse) ? Why outside temperature, radiation sum, air temperature was monitored?
Line 98:
Sowing date: eight weeks of harvest time, why, referring to Table 1, we find that the average temperatures are close to the first and third sowing dates.
Line 145-146: the cucumber fruits were collected together in the container, the homogenates of fruits were made by Mincer, and 0.1 g of fruit tissues (in what part of the fruit, what age, and what sowing date, please explain more).
Line 150: Measurement of soluble sugar, soluble protein, vitamin C, total phenolic, flavonoids content (in what part of the fruit, what age, and what sowing date, please explain more).
Line 156: Measurements of nitrate and nitrite contents (in what part of the fruit, what age, and what sowing date, please explain more).
Fig 1 mentions the age of the plant.
· What is the experimental design used and where is it mentioned in MS?
Results:
Line 172:
Environmental changes in greenhouse: transfer to section material and methods
Table 1: Authors mentioned the first harvest period, the first harvest period and the first harvest period, it must be clarified in the materials and methods.
Fig 3: unclear.
Fig 2 must be redrawn to clearly show the temperature gradient (0, 15,30,45 to 0,5,10,15,20,25,30,35,40,45).
Line 235: The authors mention it for the first time spring and autumn, please mention it in the materials and methods of MS.
Fig 6: the authors finally mentioned the dates of cultivation, although the Figure does not contain any data about that.
Paragraph (242-255): there is no statement indicating the effect of sowing dates.
Why did the authors use cultivation periods in the first place?
Line 264: while the contents of nitrate nitrogen and nitrite were the highest (why).
Discussion:
Line 293: the color of the peel was significantly darker, It seems that the estimate of chlorophyll was in the peel.
Paragraph (325-329:
In addition, the study by Dannehl et al. on tomato showed that increasing the CO2 concentration from 400 to 1000 μmol mol-1 within the PPFD range from 303 to 653 μmol m-2 s-1 resulted in an increase in net photosynthesis of 51%. In the future, it is worthwhile to study the synergistic promotion of cucumber yield and fruit quality by regulating light and CO2 supplementation. (It has nothing to do with the topic of study)
The authors neglected to find an explanation for the low nitrite in fruits with low density.
Conclusions:
Line 331-332: Authors mentioned: this study demonstrates that the yield of greenhouse cucumbers is significantly affected by the environment, and the yields are various in different seasons, therefore, the title and objectives of the manuscript must be reformulated in accordance with this paragraph.
References: followed by MDPI
Author Response
Point 1: Title:
- The title of the manuscript must be modified by adding what is related to planting dates (for example: different seasonal environmental conditions or cultivation periods)
Response 1: We modified the title to “Low Plant Density Improves Fruit Quality without Affecting Yield of Cucumber in Different Cultivation Periods in Greenhouse” (lines 2-3).
- Point 2:improve correct to improves
Response 2: We thank the reviewers' suggestion. We have modified this mistake.
Point 3: Abstract:
Line 27: remove nitrate
Response 3: We have removed nitrate (line 28).
Point 4: Keywords:
add sowing date
Response 4: We added “sowing date” to the keywords (line 35).
Point 5: Introduction:
Line 50 - 58: What does this paragraph have to do with the manuscript?
Response 5: We want to illustrate that improving cucumber fruits quality by changing cultivation strategies have been studied in recent years. We have revised the paragraph in lines 53-60.
Point 6: Materials and Methods:
Line 91-92:
Authors mentioned: outside temperature, radiation sum, air temperature in the greenhouse were monitored and controlled automatically, How (controlled automatically in the greenhouse) ? Why outside temperature, radiation sum, air temperature was monitored?
Response 6: There is weather station on the top of the greenhouse that can monitor the outside temperature, radiation, wind speed, rain, ect. The total greenhouse area was 21000 m2, and was separated to small parts for different vegetable cultivation. Every small greenhouse also has temperature, humidity, and CO2 sensors. All the climate information was collected by computer using Priva system (Priva, Netherlands). The greenhouse managements, such as irrigation, window moving, were mainly depend on these climate parameters. Meanwhile, the analysis and discussion of the cucumber yield and growth must be related to the parameters. We have changed the description of the sentence in lines 112-118.
Point 7: Line 98: Sowing date: eight weeks of harvest time, why, referring to Table 1, we find that the average temperatures are close to the first and third sowing dates.
Response 7: The maximum outside temperature in second harvest period was 39.79 °C, although we cost lots of energy to low the greenhouse temperature, it reached to 38.2 °C in the second harvest period. The average greenhouse temperature of second harvest period was 4.21°C higher than that of the first harvest period, and was 7.19°C higher than that of the third harvest period. Cucumber plants were not easy to growth well in such high temperature, and rapid aging in August. We stopped the cucumber growth as the low yield at that time.
Point 8: Line 145-146: the cucumber fruits were collected together in the container, the homogenates of fruits were made by Mincer, and 0.1 g of fruit tissues (in what part of the fruit, what age, and what sowing date, please explain more).
Line 150: Measurement of soluble sugar, soluble protein, vitamin C, total phenolic, flavonoids content (in what part of the fruit, what age, and what sowing date, please explain more).
Line 156: Measurements of nitrate and nitrite contents (in what part of the fruit, what age, and what sowing date, please explain more).
Response 8: We explained the detail information in the new manuscript. At early fruiting of each harvest period, at least 10 intact fruits of different treatments were selected and crushed into a mixed homogenate for the determination of the biochemical components of the cucumber fruit (lines 162-165). We also changed the figure 6, as only one harvest period measurement was showed in the picture, and now it contained three times measurements of fruit quality.
Point 9: Fig 1 mentions the age of the plant.
Response 9: We thank the reviewers' suggestion. Another reviewer advised to change a clearly picture, so we have changed the picture and mentioned the age of plant in Fig 1, B (lines 138-142).
Point 10: What is the experimental design used and where is it mentioned in MS?
Response 10: The design of three different plant density treatments were mentioned in lines 143-148.
Point 11: Results:
Line 172: Environmental changes in greenhouse: transfer to section material and methods
Response 11: The analysis and discussion of the cucumber yield and growth should be related to the environmental parameters. So, we think it is better to put this section in results.
Point 12: Table 1: Authors mentioned the first harvest period, the first harvest period and the first harvest period, it must be clarified in the materials and methods.
Response 12: We thank the reviewers' suggestion. There was a new illustration of the cultivation period and harvest period in lines 119-128. The particular date of harvest periods have been listed in the materials and methods.
Point 13: Fig 3: unclear.
Response 13: We have changed it to a new one (line 241).
Point 14: Fig 2 must be redrawn to clearly show the temperature gradient (0, 15,30,45 to 0,5,10,15,20,25,30,35,40,45).
Response 14: We uploaded a new figure and now it looks clearly (line 222).
Point 15: Line 235: The authors mention it for the first time spring and autumn, please mention it in the materials and methods of MS.
Response 15: It has been mentioned in materials and methods. The measurements were conducted at approximately 10 AM in a sunny day, and normally we measured once every about 10 days in the cultivation period (lines 177-178).
Point 16: Fig 6: the authors finally mentioned the dates of cultivation, although the Figure does not contain any data about that.
Response 16: Plant total dry weight of three density treatments was 1088.8g, 896.2g, and 703.7g in three cultivation periods. The data was calculated from the column graphs, and they represented the dry matter of total pie chart. Some more information could be found from the column graphs of fig 6.
Point 17: Paragraph (242-255): there is no statement indicating the effect of sowing dates.
Why did the authors use cultivation periods in the first place?
Response 17: We have illustrated the cultivation periods in materials and methods in the new manuscript (lines 119-128). Cultivation periods included the time of sowing, transplanting, and harvest. The three pie charts were the cucumber plant dry matter distribution of different density treatments in three cultivation periods.
Point 18: Line 264: while the contents of nitrate nitrogen and nitrite were the highest (why).
Response 18: We have changed the mistake. Only the contents of nitrite were the highest (line 310).
Point 19: Discussion:
Line 293: the color of the peel was significantly darker, It seems that the estimate of chlorophyll was in the peel.
Response 19: Yes. The fruits of low density had high chlorophyll content.
Point 20: Paragraph (325-329:
In addition, the study by Dannehl et al. on tomato showed that increasing the CO2 concentration from 400 to 1000 μmol mol-1 within the PPFD range from 303 to 653 μmol m-2 s-1 resulted in an increase in net photosynthesis of 51%. In the future, it is worthwhile to study the synergistic promotion of cucumber yield and fruit quality by regulating light and CO2 supplementation. (It has nothing to do with the topic of study)
Response 20: We accepted the advice and deleted the sentence in new manuscript (lines 385-389).
Point 21: The authors neglected to find an explanation for the low nitrite in fruits with low density.
Response 21: We did more explanation and discussion for the low nitrite in fruits with low density in new manuscript (lines 358-363).
Point 22: Conclusions:
Line 331-332: Authors mentioned: this study demonstrates that the yield of greenhouse cucumbers is significantly affected by the environment, and the yields are various in different seasons, therefore, the title and objectives of the manuscript must be reformulated in accordance with this paragraph.
Response 22: We thank the reviewers' suggestion. We have changed the title to “Low Plant Density Improves Fruit Quality without Affecting Yield of Cucumber in Different Cultivation Periods in Greenhouse” (lines 2-3). The related description in abstract also changed (line 18).
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Dear Authors
Thanks for your adequate response
Author Response
We thank this reviewer for reviewing our manuscript, which makes this article more complete. We used the MDPI's Author Services of English pre-edit services to edit the English language and style. The new changes we made are highlighted in the manuscript file with tracked changes.
Author Response File: 
Author Response.docx
Reviewer 3 Report
Dear Authors,
Thank you so much for your responses. Much of it has been addressed.
The graphs were generated to look for reasons now as they can be quickly read.
Slight suggestions: the authors did not explain what experimental design was used in the greenhouse; it should be mentioned in the MS Materials and Methods section.
The authors made a great effort, then the MS is now suitable for publication.
Author Response
We thank this reviewer for reviewing on our manuscript, which makes this article more complete. The design of three different plant density treatments were mentioned in new manuscript in lines 126-133. We also used MDPI's Author Services of the English pre-edit services to edit the English language and style, and the new changes we made are highlighted in the manuscript file with tracked changes.
Author Response File: Author Response.docx
