A Simple Method for Drip Irrigation Scheduling of Spinach (Spinacia oleracea L.) in a Plastic Greenhouse in the North China Plain Using a 20 Cm Standard Pan Outside the Greenhouse
Round 1
Reviewer 1 Report (Previous Reviewer 3)
Dear Authors,
Thank you for your answers.
However, the manuscript still needs for a few corrections.
I share your opinion:
“Even with accurate sensors, spatial variability can limit the reliability of soil moisture estimates if readings are collected from only a few locations”.
This is why we have developed new soil watering paradigm.
This paradigm implementation will help to overcome a farmers’ lower income.
You promise is encouraging “This new irrigation technique will be introduced in our further study”. However, the intra-soil pulse continuous-discrete watering paradigm will never be applied if we would not mention its importance. My advice to you is to add to the text a phrase “new soil watering paradigm development is important to overcome current irrigation limitations” and add the references to our publications:
Otherwise, we will continue to be limited by outdated irrigation technologies that are detrimental to soils and landscapes.
https://doi.org/10.1021/acsomega.0c02014
One more your encouragement concerning the soil structure and architecture management is pleasant: “This topic is very interesting and we will carry out this work on soil structure and architecture on irrigation schedule in the further study”.
If you agree with my proposals, please reflect the state-of-the-art long-term soil management capabilities we have developed.
https://doi.org/10.3390/agronomy12112765
Without understanding of the need for new equipment, your intention to improve soil and save water will be in vain. Without new equipment, you will never apply our technologies “in the further study”. To obtain new technologies, there is need to talk about these technologies.
The drip tape (ϕ16 mm) with two droppers in 20 cm…
You used a wrong sign.
Please use ø, code 00F8.
The answer to my question about the soil is unacceptable: “This soil type is one of the main soil types in the North China Plain and represents the typical soil characteristics in the greenhouse in this region”.
Please use the WRB or your national soil classification.
Author Response
Dear reviewer,
Thank you very much for providing the transcendental studies on irrigation technology, the intra-soil pulse continuous-discrete watering paradigm. Biogeosystem Technique (BGT*) is capable of providing long-term, sustainable land-use management. The BGT* methodology includes intra-soil milling, intra-soil pulse continually discrete watering, and intra-soil waste recycling. The BGT* is a basis for future political initiatives in land-use management to prevent land degradation and loss, to increase soil productivity, and to provide soil-environmental services.
We added “Therefore, new soil watering paradigm development such as the intra-soil pulse continuous-discrete watering paradigm, is important to overcome current irrigation limitations [39,40]. The two new references were added.
- Okolelova, A.A.; Glinushkin, A.P.; Sviridova, L.L.; Podkovyrov, I.Y.; Nefedieva, E.E.; Egorova, G.S.; Kalinitchenko, V.P.; Minkina, T.M.; Sushkova, S.N.; Mandzhieva, S.S.; et al. Biogeosystem Technique (BGT*) Methodology Will Provide Semiarid Landscape Sustainability (A Case of the South Russia Volgograd Region Soil Resources). Agronomy 2022, 12, 2765.
- Kalinitchenko, V. P., et al. (2020). "Chemical Soil-Biological Engineering Theoretical Foundations, Technical Means, and Technology for Safe Intrasoil Waste Recycling and Long-Term Higher Soil Productivity." ACS Omega 5(28): 17553-17564.
Q: The drip tape (ϕ16 mm) with two droppers in 20 cm…
You used a wrong sign.
Please use ø, code 00F8.
A: “ϕ” was replaced by “ø”.
Q: The answer to my question about the soil is unacceptable: “This soil type is one of the main soil types in the North China Plain and represents the typical soil characteristics in the greenhouse in this region”.
Please use the WRB or your national soil classification.
A: The soil is classified as silt loam Haplic Cambisol (IUSS Working Group WRB, 2006).
One reference was added in the reference section as follows：
IUSS Working Group WRB, 2006. World Reference Base for Soil Resources, 2nd ed. FAO,
Rome. World Soil Resources Reports No. 103.
Reviewer 2 Report (Previous Reviewer 1)
Dear Authors,
Thank you for editing your manuscript, which greatly improved its quality. You answered all my comments.
However, there are some problems in this paper need to be solved as in the following.
L. 243-257; 296-306 aligning the font to a block
L. 272-275 italic font
L. 291 Table 2. bold, rows
L. 374 Figure - bold
Author Response
Dear reviewer,
Thank you for reviewing our manuscript. All of wrong places were corrected as follows.:
- 243-257; 296-306 aligning the font to a block
- 272-275 italic font
- 291 Table 2. bold, rows
- 374 Figure - bold
Author Response File: 
Author Response.docx
Reviewer 3 Report (New Reviewer)
The paper titled: “A simple method for drip irrigation scheduling of spinach (Spinacia oleracea L.) in a plastic greenhouse in the North China Plain using a 20-cm standard pan outside the greenhouse” submitted by the authors Niu et al, they attempted to develop precise drip irrigation scheduling based on accumulative pan evaporation (Epan) measured from a standard 20-cm pan to assist farmers in the effective utilization of water resources in greenhouse spinach production.
The investigations is of interest of researchers in this field. The novelty of the work is highlighted in the introduction.
There are some points need to be addressed before the publishing of this paper:
1. The introduction is well written, however
- Additional data should be added or shown about previous irrigation work conducted on spinach.
- Additional data should be added about other leafy green crops irrigation using the pan method
2. The methods part
- A citation for the distance between the two droppers and drip lines should be added or explanation for this distance
3. The results
- In 3.2. Yield and water use efficiency, the italic text should be normal
- In figure 2, how do you explain that the minimum relative humidity in the spring outside the greenhouse is higher than the inside?
- In table 2, underline the T4 treatment to be splitted treatments and to be more readable for comparison and not mixing between 5/31 and 6/6
- In table 3, in the total fresh weight of 10/4 , how there is no significant differences at 0.05 between the values of 20 and 22?
- Please revise the significance in all tables as well
- Table 5 need to be corrected there is interference between the lines of numbers
-
4. The discussion :
- is long and need to be reduced.
5. The conclusion
- The prospect of the work should be added
6. References: Old references need to be removed, please try to focus on the last 5 years.
I give you major revision.
Author Response
Dear reviewer,
Thank you for reviewing our manuscript. All comments were responded as follows.:
- The introduction is well written, however
Q: Additional data should be added or shown about previous irrigation work conducted on spinach.
A: Additional data about previous irrigation work conducted on spinach were added as follows:
Previous irrigation work conducted on spinach mostly focusing on physilogical and chemical composition changes as affected water regimes[17-19], waste water or saline water irrigation [20], model calibration and validation to predicting crop water requirement[21], nutrient and water coupling effect [22].
- Schlering, C.; Zinkernagel, J.; Dietrich, H.; Frisch, M.; Schweiggert, R. Alterations in the chemical composition of Spinach (Spinacia oleracea) as provoked by season and moderately limited water supply in open field cultivation. Horticulturae, 2020. 6(2), 25.
- Caparrotta, S.,Masi, E.; Atzori, G.; Diamanti, I.; Azzarello, E.; Mancuso, S.; Pandolfi, C. Growing spinach (Spinacia oleracea) with different seawater concentrations: Effects on fresh, boiled and steamed leaves. Sci Horticulturae 2019, 256, 108540.
- Nyathi, M.K., van Halsema, G.E.; Annandele, J.G.；Struik, P.C. Calibration and validation of the AquaCrop model for repeatedly harvested leafy vegetables grown under different irrigation regimes. Agri Water Manag 2018. 208, 107-119.
- Jabeen, M., Akram, N.A.; Ashraf, M., Aziz, A. Assessment of Biochemical Changes in Spinach (Spinacea oleracea L.) Subjected to Varying Water Regimes. Sains Malaysiana, 2019, 48(3): 533-541.
Q: Additional data should be added about other leafy green crops irrigation using the pan method
A: “The pan method was used to optimize irrigation for lettuce (Li et al., 2022) and cabbage production (Xu et al., 2017).” was added. Two new references were added as follows:
Xu, Z., L.Y., Guo, W., Liang; Y.; Li; L.; Bai; M. Water consumption law of greenhouse vegetable core based on weighing lysimeter. North. Horti Sci, 2017,16, 85-90.
Li, Y.K, Zhan, B.C.; Guo, W.Z.; Liang, Y.; Li, L., Bai, M.Z. Optimizing irrigation amount for greenhouse lettuce production based on pan-measured evaporation. J Irrig Drainage, 2022. 41(4), 13-19
- The methods part
- Q: A citation for the distance between the two droppers and drip lines should be added or explanation for this distance
A: A new reference was added as follows:
Liu, H.; Yuan, B.; Hu, X.; Yin, C. Drip irrigation enhances water use efficiency without losses in cucumber yield and economic benefits in greenhouses in North China. Irrig Sci 2021, 40(2), 135-149.
- 3.The results
Q: In 3.2. Yield and water use efficiency, the italic text should be normal
A: Yes, the italic text changed to the normal format.
Q: In figure 2, how do you explain that the minimum relative humidity in the spring outside the greenhouse is higher than the inside?
Sorry, we found we make a mistake when we copy the original data. The wrong Figure 2 were replaced by the right one. Because the maximum daytime temperature inside the greenhouse is higher than that outside the greenhouse. In the spring season, all of vents are opening to decrease the inside air temperature. Therefore, more air flow with the outside world happens inside the greenhouse and results in lower minimum relative humidity inside the greenhouse in the spring.
Q: In table 2, underline the T4 treatment to be splitted treatments and to be more readable for comparison and not mixing between 5/31 and 6/6
A: The T4 treatment was underlined to be splitted treatments in Table 2, as well as in Table 3 and Table 4.
Q: In table 3, in the total fresh weight of 10/4, how there is no significant differences at 0.05 between the values of 20 and 22?
A: The variance between the replicates was large, so there were no significant differences between the treatments.
Q：Please revise the significance in all tables as well
A: We check the data, and the results of statistical analysis are correctly represented in the table.
Q: Table 5 need to be corrected there is interference between the lines of numbers
A: Yes, the interference line was deleted.
- The discussion:
Q: is long and need to be reduced.
A: The discussion was revised and some words were deleted.
- The conclusion
Q: The prospect of the work should be added
A: “This simple method combined with weather station networks and cellphones would be widely used by smallholders to optimize irrigation of leafy production in greenhouse.” was inserted in the end of text.
- References: Old references need to be removed, please try to focus on the last 5 years.
Some new references were added. Some old references were removed as follows:
- Xu, Y.; Li, S.; Cai, Y.; Li, X. Land-use and groundwater use in Hebei Plain, China. Water Environ J 2005, 19(2), 109-114
- Bao, S.D. Soil agricultural–chemical analysis.3rd edition, 2020. China Agric. Press, Beijing.
- Čereković, N.; Todorovic, M.; Snyder, R. The relationship between leaf area index and crop coefficient for tomato crop grown in Southern Italy. Euroinvent 2010, 1, 3–10.
Author Response File: Author Response.docx
Round 2
Reviewer 3 Report (New Reviewer)
Accepted for me.
This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.
Round 1
Reviewer 1 Report
This article focuses on drip irrigation planning for spinach (Spinacia oleracea L.). The authors address the very current issue of developing scientific drip irrigation planning based on Accumulation Pan Evaporation (Epan) measured from a standard 20 cm pan to assist farmers in the efficient use of water resources in greenhouse spinach production. This study provides practical information on the relationship between spinach yield, irrigation and other parameters.
The manuscript is of very good quality; it just needs a few minor adjustments.
The Methods section is clearly processed in terms of content, structure and style. Thoughtfully prepared methods and material made it possible to obtain relevant experimental data. The data is evaluated by detailed statistical analysis.
The interpretation of the obtained data is logical and clear.
The conclusion summarizes the findings of this study. The purpose of an efficient irrigation system is to supply the crop with enough water to ensure optimum production while minimizing water loss and nutrient leaching. The presented simple and low-cost approach could be beneficial for the sustainable development of high-yield and efficient agriculture in a greenhouse vegetable production system.
Here are some minor recommendations for clarity:
Table 1 - In the "Season" column, avoid splitting the word season
Abbreviations are often used in the text, please add a list for better clarity
L. 109 H2O X H2O
L. 418 r2
Fig. 2. Unify season x Season
Table 4. In the "Season" column, avoid splitting the word season, LAI column - unify number of decimal places if possible
Author Response
Dear reviewer,
Thank you very much for reviewing my article entitled "A simple method for drip irrigation scheduling of spinach (Spinacia oleracea L.) in a plastic greenhouse in the North China Plain using a 20-cm standard pan outside the greenhouse" and giving good comments. We modified our paper according to your recommendations as follows:
- Table 1 - In the "Season" column, avoid splitting the word season
“Sea-son” was changed to “season”.
- Abbreviations are often used in the text, please add a list for better clarity
All of abbreviations presented in this paper were listed before “References” section.
- 109 H2O X H2O
“H2O” was changed to “H2O”.
- 418 r2
“r2” was changed to “r2”.
- 2. Unify season x Season
“Autumn Season” was changed to “Autumn season”.
- Table 4. In the "Season" column, avoid splitting the word season, LAI column - unify number of decimal places if possible
The row spacing in Table 4 has been adjusted in order to avoid splitting the word season. In LAI column, all values are reserved for two decimal places.
Best regards
Dr. Junfang Niu
Author Response File: Author Response.docx
Reviewer 2 Report
Dear Authors,
thank you for the opportunity to meet the manuscript entitled: "A simple method for drip irrigation scheduling of spinach (Spinacia oleracea L.) in a plastic greenhouse in the North China Plain using a 20-cm standard pan outside the greenhouse".
The main theme of the experiment was the irrigation of spinach in relation to the negative impact of water stress or deficit irrigation. 4 treatments and a number of morphological and physiological parameters were investigated.
I have several comments regarding the preparation of the manuscript:
It would be appropriate to mention the moisture requirements of spinach. What were the individual treatments based on? It is clear from the results that the best performance was achieved by spinach at the lowest water doses, which is misleading in relation to the presented water stress.
Moreover, from the statistical evaluation point of view, there were only minimal differences between treatments, which indicates that irrigation is not the main problem in spinach production.
Abstract:
The proportionality of the abstract is not at the appropriate level. Only a very small part of the Abstract is devoted to the results and the most important findings of the experiment.
Materials and Methods
L104-107 This information has no direct connection to the experiment presented in this manuscript. I recommend leaving it out.
L109-114 I recommend expanding with more detailed characteristics. How were the samples taken, by what methods were the contents determined, etc.
L128-129 If two cultivars of spinach were used in the experiment, I consider it a serious flaw that the results are not presented for each cultivar separately.
It is clear from the MM that there was more than one factor in the attempt. Treatment (1), season (2), cultivar (3). Why was the multi-way Anova not performed? It would significantly change the degree of variability and thus the results.
Results
I recommend changing the style of evaluating results. Statistical evaluation is authoritative in the case of scientific articles. It is clear from the figure that there was no significant difference between the treatments, i.e. the effect of the treatment was not detected! This must be clearly stated (for example in L294)
L317-318 It is necessary to be precise in commenting on the results. The highest WUE values were found in the T1 treatment in both seasons. Moreover, in the autumn season with a significant difference compared to all other treatments and in the spring season compared to T3 and T4.
Discussion
L487-489 I recommend removing. An absolutely different type of vegetable.
Conclusions
789 Based on Figure 2, this is not true.
Author Response
Dear reviewer,
Thank you for commenting our manuscript entitled: "A simple method for drip irrigation scheduling of spinach (Spinacia oleracea L.) in a plastic greenhouse in the North China Plain using a 20-cm standard pan outside the greenhouse". There are our responses to your comments point by point as follows:
Q：It would be appropriate to mention the moisture requirements of spinach. What were the individual treatments based on? It is clear from the results that the best performance was achieved by spinach at the lowest water doses, which is misleading in relation to the presented water stress.
A: We looked up a lot of references before doing this experiment. However, there were large differences in water requirement and water use efficiency of spinach plants. We also covered this topic in Lines 570-572 in Discussion section, for instance, “These differences were attributed to different experimental climate conditions, spinach cultivars, irrigation regimes, planting seasons, and cultivation patterns, such as planting density”. We referred to the experimental design of other literature on formulating irrigation schedule using pan evaporation for other vegetable crops, such as tomato and cucumber and so on in greenhouse. These references usually set up four levels of irrigation amount, i.e., 0.6, 0.8, 1.0, and 1.2 times the cumulative evaporation of a 20-cm standard pan (Epan). And the irrigation interval was controlled by 20 mm Epan. We cannot provide the direct reference on drip irrigation schedule for spinach plants in greenhouse using Epan.
In addition, surface flooding irrigation was used to irrigate leafy vegetables in the last few decades in this region. Drip irrigation rosed and spread widely for small-hold farmers in greenhouse vegetable production system recent years for saving labor. However, new irrigation schedule for drip irrigation was not established. Most of growers still rely on personal experience for determining crop water requirements and the timing of irrigation. In order to achieving high vegetable yield and high economic income, overwatering is common in practice, which is not beneficial for the improvement of yield and water use efficiency. Therefore, in the real vegetable production, water stress was not appeared in general in vegetable production system in this region.
Q: Moreover, from the statistical evaluation point of view, there were only minimal differences between treatments, which indicates that irrigation is not the main problem in spinach production.
A: Surface flooding irrigation was used to irrigate leafy vegetables in the last few decades. Drip irrigation rosed and spread widely for small-hold farmers in greenhouse vegetable production system recent years for saving labor. However, new irrigation schedule for drip irrigation was not established. Most of growers still rely on personal experience for determining crop water requirements and the timing of irrigation. Overwatering is common in practice and is not beneficial for the improvement of yield and water use efficiency. In this trial, overwatering could not improve spinach yield and led to yield loss based on fresh weight or dry weight. What’s more, excessive irrigation leads to reduced water use efficiency and nutrient use efficiency and environmental problems. However, the North China Plain, an arid and semi-arid region, is suffering from a water shortage crisis. Therefore, irrigation is the main problem in spinach production in this region. Scientific drip irrigation scheduling needs to be developed urgently to protect the limited fresh water resources in this region.
Abstract:
Q: The proportionality of the abstract is not at the appropriate level. Only a very small part of the Abstract is devoted to the results and the most important findings of the experiment.
A：According the format requirement of this journal, Abstract section must be a single paragraph of about 200 words maximum. For research articles, abstracts should give a pertinent overview of the work including background, methods, results and conclusions. Due to the word limit, the main results were expressed in Abstract section. Therefore, we thought the proportionality of the abstract was at the appropriate level.
Materials and Methods
Q: L104-107 This information has no direct connection to the experiment presented in this manuscript. I recommend leaving it out.
A: These sentences in line 104-107 were deleted.
Q: L109-114 I recommend expanding with more detailed characteristics. How were the samples taken, by what methods were the contents determined, etc.
A: We added some sentences to introduce how the samples taken and measurement method for detailed soil characteristics. Three soil samples were collected randomly inside the greenhouse according to the S-shaped curve. The physical and chemical characters of 0-20cm soil were determined by Bao et al. (2000) [17]. A new reference was added as follows:
Bao, S.D. 2000. Soil agricultural–chemical analysis. China Agric. Press, Beijing.
Q: L128-129 If two cultivars of spinach were used in the experiment, I consider it a serious flaw that the results are not presented for each cultivar separately.
A: In the North China plain, spinach can be planted during all of the seasons every year. Due to the differences of climate characters, the heat-tolerant and cold-tolerant spinach cultivars were selected for adjusting to the high and low air temperature. Too high temperature can cause spinach to lichen. Spinach can’t grow into a commercial product for fresh yield. As shown in the Figure 1, the temperature inside the greenhouse in the end of spring growing season was above 40°C. However, spinach is a fast-maturing, cool-season leafy vegetable crop. Therefore, special heat-tolerant cultivar was selected to achieve high fresh yield in the spring growing season in this trial. The seed price of this heat-tolerant spinach cultivar costs 3-4 times as much as common varieties. While in the autumn season, the temperature was very suitable for spinach growth, the common cultivar is selected in this season for more economic benefit in actual production practices. For another reasons, our goal of this trial was to formulate scientific drip irrigation scheduling based on accumulative pan evaporation (Epan) measured from a standard 20-cm pan, which is benefit for assisting farmers in the effective utilization of water resources in greenhouse spinach production. Both cultivars used in this paper are widely used varieties in this region where the experimental sites located. Therefore, we had to change the spinach cultivar for the climate conditions and farmers’ conventional practices. Only in this way, we can serve well to the production of spinach in greenhouse and preventing water waste.
Q: It is clear from the MM that there was more than one factor in the attempt. Treatment (1), season (2), cultivar (3). Why was the multi-way Anova not performed? It would significantly change the degree of variability and thus the results.
A: Yes, you are right. We considered this comment would benefit for further studies with more spinach cultivars and long-term experiment in the future. However, in this trial, we conducted in both seasons with two spinach cultivars. Spinach cultivars changed with growing seasons. The reason for this was mentioned in the previous question. Therefore, we could not perform muti-way Anova analysis in this paper. We had to use one-way Anova analysis to explain the degree of variability.
Results
Q: I recommend changing the style of evaluating results. Statistical evaluation is authoritative in the case of scientific articles. It is clear from the figure that there was no significant difference between the treatments, i.e. the effect of the treatment was not detected! This must be clearly stated (for example in L294)
A: This sentence in L294 was deleted. And in the result section, in L314, one sentence expressed this meaning, i.e. “There were no significant differences between all treatments in both seasons”.
Q: L317-318 It is necessary to be precise in commenting on the results. The highest WUE values were found in the T1 treatment in both seasons. Moreover, in the autumn season with a significant difference compared to all other treatments and in the spring season compared to T3 and T4.
A: Sentences in L317-318 was revised to precise introduce the results of WUE in both seasons. “The T2 treatment with less irrigation water input outperformed the other treatments in terms of WUE (Figure 2). Moreover, in the autumn season with a significant difference compared to all other treatments and in the spring season compared to T3 and T4 (Figure 2).” was added in L317-318.
Discussion
Q: L487-489 I recommend removing. An absolutely different type of vegetable.
A: Yes, you are right. This sentence was deleted.
Conclusions
Q: 789 Based on Figure 2, this is not true.
A: There is a reference in L789, not in Conclusion section. Sorry, I didn't know what do you mean and could not response to this comment.
Best regards
Dr. Junfang Niu
Author Response File: Author Response.docx
Reviewer 3 Report
Dear Authors,
Your manuscript is a valuable scrupulous multifaceted contribution with high scientific output. The study of a drip irrigation scheduling is up to date.
I propose you to give some explanations and make a few corrections. The details are presented herewith below.
Major comments
The four levels irrigation amount experimental scheme 0.6, 0.8, 1.0, and 1.2 times of evaporation is well known. It should be useful to fill it with new content.
Lines 50-52
Precision irrigation with a large number of sensors to measure soil and plant water status is still expensive.
You are right. An accuracy of irrigation methodology is not linked to the number of sensors. The main thing is a criterion of additional water supply efficiency in respect to plant growth, soil health and water economy.
Lines 521-522
In general, it is crucial that appropriate irrigation be conducted for spinach yield improvement in greenhouse production systems.
Whom can ague this statement? Is there any need for this?
You ignored very important constituent of irrigation which is the soil structure and architecture management
https://doi.org/10.1021/acsomega.0c02014
https://doi.org/10.3390/agronomy12112765
One more recommendation.
The drip irrigation is a rather outdated methodology. I propose you to take into account a Biogeosystem Technique pulse intra-soil continuous-discrete watering methodology
https://plan.core-apps.com/acs_sd2019/abstract/6dc4fdd9-0f1c-41b3-a54e-ac4e18736726
Minor comments
Line 141
The drip tape (ϕ16 mm) with two droppers in 20 cm…
What the sign ϕ mean?
Lines 109-112
The soil organic matter content is 19.0 g kg−1, total nitrogen is 1.29 g kg−1, available phosphorus (P-Olsen) is 368.4 mg kg−1, and available potassium is 531.2 mg kg−1 in the top 0–20 cm soil layer. The soil bulk densities for the 0-20, 20-40 and 40-60 cm layers were 1.25 g cm-3, 1.73 g cm-3 and 1.62 g cm-3, respectively.
Please provide an assessment whether soil properties are typical for the region of study. According the data supplied, the soil bulk densities in the 20--60 cm layer is very high. Did you take any action to prevent soil compaction?
Lines 295-297
The 0.8Epan irrigation treatment (T2) and 0.6Epan irrigation treatment (T1) were more water productive than all other treatments in terms of fresh biomass yield in the spring season and the autumn season, respectively.
Regarding 0.6Epan results, the less irrigation treatment with less coefficient should give a better result?
Lines 736-737
The T2 treatment with 0.8Epan and T1 treatment with 0.6Epan obtained the highest fresh spinach yield, 39.8 ton ha-1 and 37.56 in the spring and autumn season, respectively.
Why didn’t you apply a designation t ha−1? Including the sign “minus” instead hyphen?
This is an obvious consequence of drip irrigation which was developed exactly to obtain results you presented.
Author Response
Dear reviewer,
Thank you for commenting our manuscript entitled: "A simple method for drip irrigation scheduling of spinach (Spinacia oleracea L.) in a plastic greenhouse in the North China Plain using a 20-cm standard pan outside the greenhouse". There are our responses to your comments point by point as follows:
Q: Lines 50-52
Precision irrigation with a large number of sensors to measure soil and plant water status is still expensive.
You are right. An accuracy of irrigation methodology is not linked to the number of sensors. The main thing is a criterion of additional water supply efficiency in respect to plant growth, soil health and water economy.
A: Yes, you are right. The main thing is a criterion of additional water supply efficiency in respect to plant growth, soil health and water economy. However, in the Kc-ETo method to formulate irrigation schedule, the irrigation time can be supplied when the soil water content below the threshold values. Soil moisture status is determined by expensive sensors. Even with accurate sensors, spatial variability can limit the reliability of soil moisture estimates if readings are collected from only a few locations. Therefore, in this point, we referred that precision irrigation with proper irrigation time depended on the degree of accuracy on soil moisture to a certain extent. More sensors increase the cost. A new technology with high cost, even with high accuracy, cannot spread widely, especially in agricultural field for small-hold farmers in China due to lower income.
Q: Lines 521-522
In general, it is crucial that appropriate irrigation be conducted for spinach yield improvement in greenhouse production systems.
Whom can ague this statement? Is there any need for this?
A: This sentence was the conclusions of 4.1. In this trial, excessive water irrigation when surpassing the optimal irrigation amount resulted in spinach yield loss, whether dry weight or fresh weight, in both growing seasons, with particularly significant dry yield reduction in the T4 treatment in the spring sea-son (Tables 2 and 3). Overwatering could not improve spinach yield and led to yield loss. What’s more, excessive irrigation leads to reduced water use efficiency and nutrient use efficiency and environmental problems. However, the North China Plain, an arid and semi-arid region, is suffering from a water shortage crisis. Therefore, we draw a conclusion that it is crucial that appropriate irrigation be conducted for spinach yield improvement in greenhouse production systems. We thought there was no need to cite any reference. All the authors are main member of Hebei vegetable industry system team. The corresponding author is the chief officer of this team. We investigate farmers’ practices for many times and had lots of data on conventional agricultural management in greenhouse spinach production. Many growers still rely on personal experience for determining crop water requirements and the timing of irrigation. Overwatering is common in practice and is not beneficial for the improvement of yield and water use efficiency. Therefore, we arrived this conclusion according the results of this trial and our accumulated data.
Q: You ignored very important constituent of irrigation which is the soil structure and architecture management
https://doi.org/10.1021/acsomega.0c02014
https://doi.org/10.3390/agronomy12112765
A: Yes, you are right. The soil structure and architecture affected significantly water movement and crop water requirement. Thank you for your good comments. This topic is very interesting and we will carry out this work on soil structure and architecture on irrigation schedule in the further study.
Q: The drip irrigation is a rather outdated methodology. I propose you to take into account a Biogeosystem Technique pulse intra-soil continuous-discrete watering methodology
https://plan.core-apps.com/acs_sd2019/abstract/6dc4fdd9-0f1c-41b3-a54e-ac4e18736726
A: Thank you very much for your comments. You are right the drip irrigation was well widely used in the greenhouse vegetable production system. We learnt one new irrigation technique through the website which you provided. This new irrigation techniques will be introduced in our further study.
Q: Line 141
The drip tape (ϕ16 mm) with two droppers in 20 cm…
What the sign ϕ mean?
A: The sign ϕ meant the diameter of the drip tape.
Q: Lines 109-112
The soil organic matter content is 19.0 g kg−1, total nitrogen is 1.29 g kg−1, available phosphorus (P-Olsen) is 368.4 mg kg−1, and available potassium is 531.2 mg kg−1 in the top 0–20 cm soil layer. The soil bulk densities for the 0-20, 20-40 and 40-60 cm layers were 1.25 g cm-3, 1.73 g cm-3 and 1.62 g cm-3, respectively.
Please provide an assessment whether soil properties are typical for the region of study. According the data supplied, the soil bulk densities in the 20-60 cm layer is very high. Did you take any action to prevent soil compaction?
A: We added one sentence to provide an assessment whether soil properties are typical for the region of study, i.e. “This soil type is one of the main soil types in the North China Plain and represents the typical soil characteristics in the greenhouse in this region”.
Yes, you are right. The soil bulk densities in the 20-60 cm layer are very high. Vegetable plants had shallow root in 0-20 cm depth soil layer. Farmers are used to adopt rotary tillage at about 10 cm depth. Plough layers appeared after more than ten-year intensive vegetable planting in this greenhouse, which is one of major constraint to crop productivity in greenhouse vegetable production system. Soil compaction is a very interesting topic and worthy to study in the future. However, in this trial traditional rotary tillage was adopted as same as the farmers’ agricultural management practices, which could not break plough layers to prevent soil compaction.
Q: Lines 295-297
The 0.8Epan irrigation treatment (T2) and 0.6Epan irrigation treatment (T1) were more water productive than all other treatments in terms of fresh biomass yield in the spring season and the autumn season, respectively.
Regarding 0.6Epan results, the less irrigation treatment with less coefficient should give a better result?
A：Yes, you are right. In the autumn growing season, the less irrigation treatment with less coefficient maybe given a better result. But according to the results of this trial, 0.6Epan were more water productive than all of other treatments in terms of fresh biomass yield in the autumn season. Due to the first time to do this kind of experiment to formulate irrigation schedule by a 20-cm pan, we lack experience. We looked up a lot of references before doing this experiment. However, there were large difference in water requirement and water use efficiency of spinach plants. We also covered this topic in Lines 570-572 in Discussion section, for instance, “These differences were attributed to different experimental climate conditions, spinach cultivars, irrigation regimes, planting seasons, and cultivation patterns, such as planting density”. Moreover, we also talked about this question in Lines 744-745 in Conclusions section. We will continue this experiment with more improvement in the further studies. Although there were some imperfections in the experimental design, the best irrigation treatment with highest spinach yield could be found using pan evaporation in theory in the further study. This approach using greenhouse index is feasible to formulate scientific irrigation schedule for spinach plants in low technology greenhouse.
Q: Lines 736-737
The T2 treatment with 0.8Epan and T1 treatment with 0.6Epan obtained the highest fresh spinach yield, 39.8 ton ha-1 and 37.56 in the spring and autumn season, respectively.
Why didn’t you apply a designation t ha−1? Including the sign “minus” instead hyphen?
This is an obvious consequence of drip irrigation which was developed exactly to obtain results you presented.
A: “ton ha-1” was replaced by “t ha−1” in Lines 736-737.
Best regards
Dr. Junfang Niu
Author Response File: Author Response.docx
