Comprehensive Assessment of Plant and Water Productivity Responses in Negative Pressure Irrigation Technology: A Meta-Analysis
, Renlian Zhang 1, Xueping Wu 1, Huaiyu Long 1, Zhimei Sun 2 and Shuxiang Zhang 1,*
Round 1
Reviewer 1 Report
Attached you will find the .pdf file enriched with my comments. The discussion part should be improved.
Comments for author File: 
Comments.pdf
Author Response
Reviewer #1:
- Line 61 and line 304: "e.g.," amended to italic.
Response: Thank you, we have made the corrections as requested.
- Line 109: Sentence modification.
Response: It has been amended to "A schematic diagram of the negative pressure irrigation system designed by the Chinese Academy of Agricultural Sciences is shown in Figure 1a.
- Line 142: Please control the format, "ln At" should be "lnAt" in bold.
Response: Thank you, we have made the corrections as requested.
- Line 161: Please rephrase "metafor R package".
Response: Thanks for your comment. We have amended it as required.
- Please specify in the caption what TN is. It is the first time it appears. Same in Figure 3
Response: We have amended it as required, please see Figure 2 and 3 for details
- Please uniform caption text format. Also in Figure 3 and 4 captions.
Response: Thank you, we have made the corrections as requested.
- Two consideration for this sentence (line 160):
- 1) it is a discussion sentence, maybe should be moved in the appropriate paragraph
- 2) I wonder what it means "relatively reliable". It's a tricky concept. It could be reliable for you and not for me? Or? It should be better explained.
Response: 1) We believe that publication bias tests are not a major part of the article and do not fit into the discussion section, as is often seen in other Meta-analysis literatures.
2) The "relative reliability" here is compared to the unpublished bias test. Our presentation was indeed inaccurate and has been revised, thank you.
- This sentence is highly unclear, I suggest to check it and rephrase (lines192-195).
Response: Thanks for this question. We have re-phrased the content in response to the reviewers' comments.
- Vc = volatile compounds? Please, add definition in brackets (line 220).
Response: Vc stands for vitamin C in our article and has been marked in the revised version.
- Anyway, I think it’s a discussion sentence to be moved there. (lines 247)
Response: Thank you, we have moved the sentence.
- Lines 263, Please clarify and rephrase.
Response: Thanks for this question. We have re-phrased the content in response to the reviewers' comments.
- It’s very difficult to understand this data not having access to this study. (Line 284)
Response: 0 kPa is the negative pressure value of the water supply, which proved that when the negative pressure of -5 kPa can increase the WUE.
- Lines 275-284, It’s difficult to catch the point.
Response: Thanks for this question. We have re-phrased the content in response to the reviewers' comments.
- This sentence is too long, please, rephrase it (lines 288-289).
Response: Thank you, we have revised this long sentence into three short sentences.
- This sentence is not clear, please rephrase. (lines 321-323).
Response: Thank you, we have revised the sentence.
- This sentence is not clear, please rephrase. (lines 334-339).
Response: Thank you, we have revised the sentence.
- We have removed duplicate content in line 361 (soluble sugar).
- "Figure5" modified to "Figure 5" in line 452.
- Other modifications are detailed in the blue and red font sections of the revised version.
Author Response File: Author Response.pdf
Reviewer 2 Report
In the field of advanced water saving technologies for greenhouse crops, the authors in this manuscript, using metaanalysis, carried out an interesting study on how NPI technology can generate a stable water supply, help the soil water content to remain within a stable range and ensure that crops absorb water according to their physiological needs. The authors, using published articles related to NPI, the method of metaanalysis was used to systematically analyze the advantages of NPI over conventional irrigation. In fact, the authors considered various parameters including nutrient concentration, soil nature and vegetation type, providing a theoretical basis for the development of NPI technology and concluded that NPI significantly promotes crop yield, indicating negative pressure ranges of -2~-5 kPa as the best indicators of crop yield, moreover the yield increases of leafy vegetables were significantly higher than those of fruit and vegetables, and overall, there was a predominance of sandy loam on clay soils and alkalescent soils on neutral soils in NPI conditions.
The experimentation was well performed and the methods adopted are reliable and effective.
The results provided by the authors are particularly useful for the knowledge, development and application of NPI technology.
The manuscript can be accepted.
Author Response
The reviewer declares that the article is acceptable, thank you for your review.
Reviewer 3 Report
The article is very interesting and performs a thorough review of the state of the art of irrigation application with negative pressures, however it should clarify the following aspects:
1- One of the advantages of irrigation with negative pressure cited in the literature is that it maintains the water content in the soil in a stable range. At the same time this fact can be a limiting factor since the soil texture influences the infiltration rate and therefore the water balance in such a way that the higher the clay content the more suitable the soil is for the application of the NPI technique. This circumstance is described in lines 177 and 233-235, however it does not mention the appropriate moisture content or moisture range for this type of irrigation.
2- In figure 1 you describe three images a, b, and c. You should indicate the source of origin of these images.
3- It is understood that the meta-analysis technique used applies to the 44 studies that appear as references in the bibliography and are the basis of the primary studies used, and in section 2 Data analysis describes having used Egger's test to the results of the publications with respect to 5 variables: crop yield, water use efficiency, crop quality, nutrient content and nutrient concentration. It is necessary to provide the graphical representation by funnel plot of these measured effects to evaluate the publication bias study.
4- Figures 2, 3, and 4 describe the representation of the box or whisker diagrams and the distributions obtained in the analyzed results, which are symmetrical; however, the express indication of the numerical value of the same in the center of each of the boxes is missing to facilitate its reading and comprehension.
5- The study shows that the characteristics or effects analyzed for the variables studied are:
(a) Crop yield: applied NPI, crop types, soil texture, pH, organic matter, assimilable P and TN (total nitrogen in soil). In Figure 2
b) Water use efficiency: NPI applied, crop types, soil texture, pH, organic matter, assimilable P and TN (total nitrogen in soil). In Figure 3
c) Crop quality: soluble sugar, Vitamin C (Vc), and soluble proteins. In Figure 4.
d) Nutrient content; N content, P content and K content. In Figure 4
e) Nutrient uptake: N concentration, P concentration, and K concentration. In Figure 4.
To evaluate the representativeness of the results obtained, it is necessary to provide a graphic representation of Egger's test for each of the effects studied.
Author Response
Reviewer #3:
- The paper not mention the appropriate moisture content or moisture range for NPI.
Response: Thanks for reviewer’s comment. Added discussion of soil moisture content on lines 252-254.
- In figure 1 you describe three images a, b, and c. You should indicate the source of origin of these images.
Response: The NPI installation was designed by the Chinese Academy of Agricultural Sciences and the schematic was drawn by us (Figure a), Figure b and c show photos of our previous greenhouse growing trials, and added the corresponding references [3,5,9,25].
- It is necessary to provide the graphical representation by funnel plot of these measured effects to evaluate the publication bias study.
Response: Publication bias tests are extremely important for meta-analysis. However, our study is not suitable for publication bias testing using funnel plots because of the small difference in sample size between all studies (basically 3 to 6). Egger's test is also a test for publication bias, with high test efficacy and more easily understood results. Details can be found in the literature (Sterne, J. A. C.; Sutton, A. J.; Ioannidis, J. P. A.et al. (2011). Recommendations for examining and interpreting funnel plot asymmetry in meta-analyses of randomized controlled trials. BMJ, 343(jul221), d4002–d4002. doi:10.1136/bmj.d4002).
- Figures 2, 3, and 4 describe the representation of the box or whisker diagrams and the distributions obtained in the analyzed results, which are symmetrical; however, the express indication of the numerical value of the same in the center of each of the boxes is missing to facilitate its reading and comprehension.
Response: Thanks for your comment. All the effect sizes in the Figures 2, 3, and 4 are available from the corresponding author or provide as supplementary material.
- To evaluate the representativeness of the results obtained, it is necessary to provide a graphic representation of Egger's test for each of the effects studied.
Response: Thanks for your comment. I would like to use the results of the crop yield in Figure 2 as an example to express my point of view. Negative pressure values, crop types and soil texture, etc. as subgroups for crop yield results, there is data crossover in crop yields between subgroups. Therefore, there is no need to perform publication bias tests for each subgroup as it would be a repetitive exercise. Our current approach is consistent with much of the published meta-analysis literature. We use the p-value of the Egger's test to represent the results, rather than a graphic representation because the Egger's test graphs do not show the results as clearly as the p-value.
Author Response File: Author Response.pdf
