Deficit Irrigation for Efficiency and Water Saving in Poplar Plantations

Round 1

Reviewer 1 Report

The manuscript was written on a relevant topic i.e., Drip Irrigation for Efficiency and Water Saving in Poplar Plantations. A clear hypothesis and objective are not given in the manuscript. The methodology followed is sound. The result section is written good but the discussion section is very poor. It is expected from the authors that the discussion section has in depth possible explanation/mechanism for the recorded observations which is absent in this MS. So, the discussion section must be re-written.   

After thoroughly reading the manuscript, I have found following correctios which might improve the manuscript further.

 

Specific comments:

·       Line 93: Change CO2 to CO₂

·       In Table 1, check the value of Saturation per cent, change PH to pH

·       Line 118: Change kg ha-1 to kg ha^-1

·       Line 122-123: The objective of the MS must not be given in material and methods section

·       Line 164-166: It will be better to add an equation of percent volume water content

·       Line 173-175: In Fig 1, Check the value in regression equation

·       Line 201-202: Add reference for equation 1.

·       Line 229: In Table 3, why in first year, the value of DM in Mg ha^-1 in T3 and T4, have standard deviations equal to their mean value i.e., 0.79±0.72, 0.59±0.58.

·       In Table 3, check the value of DBH in T3 during second year.

·       Line 273-276 and 280-289: These paragraphs are result part and should be given in the result section.

Author Response

Dear Reviewer,

the authors thank you for the valuable information and suggestions that have proved extremely useful for the improvement of the manuscript. We hope you find our answers to your questions satisfying. Here are the answers point-by-point.

Best regards.

The authors

Reviewer 1

Comments and Suggestions for Authors

The manuscript was written on a relevant topic i.e., Drip Irrigation for Efficiency and Water Saving in Poplar Plantations. A clear hypothesis and objective are not given in the manuscript. The methodology followed is sound. The result section is written good but the discussion section is very poor. It is expected from the authors that the discussion section has in depth possible explanation/mechanism for the recorded observations which is absent in this MS. So, the discussion section must be re-written.

After thoroughly reading the manuscript, I have found following correctios which might improve the manuscript further.

 Specific comments:

Line 93: Change CO2 to CO₂

Done

 

In Table 1, check the value of Saturation per cent, change PH to pH

Done

Line 118: Change kg ha-1 to kg ha^-1

Done

 

Line 122-123: The objective of the MS must not be given in material and methods section

The sentence was deleted.

 

Line 164-166: It will be better to add an equation of percent volume water content

Done. The sentence has been changed and the formula has been entered

 

Line 173-175: In Fig 1, Check the value in regression equation

Done.

 

Line 201-202: Add reference for equation 1.

Done. Added a new sentence with references (lines 265-269).

 

Line 229: In Table 3, why in first year, the value of DM in Mg ha^-1 in T3 and T4, have standard deviations equal to their mean value i.e., 0.79±0.72, 0.59±0.58.

Because, in the first year, biomass production is low and has a wide variability of values ranging from a minimum of 0.042 to a maximum of 2.49 Mg ha^-1 (respectively 0.02 and 1.19 Mg DM ha^-1). For this reason, SD is almost similar to the average.

 

In Table 3, check the value of DBH in T3 during second year.

Done.

 

Line 273-276 and 280-289: These paragraphs are result part and should be given in the result section.

Done. The paragraphs have been changed and moved to the results section, lines 324-332.

 

Reviewer 2 Report

Review & Comments for sustainability 1886869

General Comments

This study evaluates different levels of drip irrigation to support growth of a hybrid poplar plantation in southern Italy. The study is well-designed and executed. The manuscript is well-written, but there are a few words misspelled and a few other writing errors here and there.

This study is very applied in nature. Essentially, it is optimizing drip irrigation to achieve good growth of the desired crop (hybrid poplar trees) at a particular location. Since hybrid poplar is a widespread tree used for short-rotation forest plantations, the results are likely to be of interest to researchers and managers using or interested in this type of forestry system. However, the authors point out in the Discussion that there have been a number of studies of irrigation on hybrid poplar plantations already. The only information that may be considered novel is their comparison of several different levels of irrigation to maintain certain levels of soil water content. The Conclusion mentions that they plan to use the results of this study for a broader sustainability analysis of efficiency and sustainability (energy, economic) for these types of production systems. In my mind, this planned study is likely novel enough to be worth publication.

Abstract

The authors state that all irrigation levels tested resulted in greater plant growth than the control (no irrigation), but that there was no significant difference between the 3 irrigation levels themselves (maintenance of 20, 30, 40, and 50% soil water content). Given this, I do not understand their recommendation of 40% soil water content as the recommended irrigation level. If the goal is water conservation, it appears that 20% soil water content is sufficient. In looking at the Results, there is some merit in their conclusion in the abstract, but their summary of the results in the abstract does not support that conclusion.

Introduction

The Introduction includes a lot about what is meant by precision agriculture and the contribution of using woody crops for energy to meet sustainability goals. What is missing is much introduction of the science behind the actual study: growth of the trees themselves, the importance of soil water availability, and justification for yet another study of irrigation of hybrid poplar. I recommend the authors rewrite this section to focus on the science behind their actual study and a stronger justification for their objectives and approach.

Materials and Methods

The authors describe the climate and seasonal weather conditions of the site. A figure illustrating this would be useful.

The authors provide copious information about the soil type, which is good, but they never provide the taxonomy of the soil. That would help the reader understand a little more about the soil.

Table 1 contains a lot of summary information about the soil, but the authors do not indicate what depth range they sampled to measure these characteristics. 

Some of these characteristics are likely unnecessary for the purposes of this study, but there is no problem with their inclusion. What is missing, however, is a measure of the soil water retention curve, i.e. the relationship between gravimetric water content and soil water potential. This is important to understand plant water availability and thus to interpret their results of plant growth response to irrigation levels. Since this soil has a texture class of silty-clay, one could use typical soil water release curves for this texture class to predict the optimal soil gravimetric water content (30-40%). The results support this prediction. In reality, it is soil water potential that controls plant water availability, so that is key information for achieving optimal irrigation. I recommend the authors include this for the study.

The description of the field design of this study is not clear to me. I recommend the authors include a figure to illustrate the characteristic arrangement of blocks, treatments, and seedlings. Also, in Lines 115 and 116, the authors claim they adopted a completely randomized design. If treatments are arrayed in blocks, then it is a randomized block design.

The treatment levels are fine, but T1 is not technically a control, since it was scheduled for irrigation at 20% soil water content. In that regard, there is not an unirrigated control for this study, which is not a problem.

The authors do not describe their statistical analyses in this section, instead placing it in the Discussion. It should be placed in the Materials and Methods section. The authors need to clarify the experimental design they used for the analysis. They need to specify what response variables are being compared. They also need to identify what multiple comparison test they used. There are several that are compatible with the Kruskall-Wallis non-parametric test.

Discussion

The description of the statistical analyses should be placed in the Materials and Methods section.

The authors do not adequately explain the purpose of including the hypsometric curves relating DBH to height. It’s a valid observation, but what is important about knowing this? Also, this relationship and the procedure for calculating the curves are not described in the Materials and Methods section. They should be. The parameters for the curves are also not statistically compared, which I expect they can be. That choice is up to the authors.

This section also does not interpret or evaluate these results in the context of the climate and soil in which the trees grew. This is important to be able to generalize these results beyond the particular location and time period in which the study took place. The authors provide detailed information about the soil type and the climate and weather patterns in the Materials and Methods section, but those characteristics and conditions are largely ignored in the Discussion. 

Tables

 

There are a few instances in which the authors use a comma (“,”) instead of a period (“.”) in their numerical data.

 

Author Response

Dear Reviewer,

the authors thank you for the valuable information and suggestions that have proved extremely useful for the improvement of the manuscript. We hope you find our answers to your questions satisfying. Here are the answers point-by-point.

Best regards.

The authors

Reviewer 2

 

General Comments

This study evaluates different levels of drip irrigation to support growth of a hybrid poplar plantation in southern Italy. The study is well-designed and executed. The manuscript is well-written, but there are a few words misspelled and a few other writing errors here and there.

This study is very applied in nature. Essentially, it is optimizing drip irrigation to achieve good growth of the desired crop (hybrid poplar trees) at a particular location. Since hybrid poplar is a widespread tree used for short-rotation forest plantations, the results are likely to be of interest to researchers and managers using or interested in this type of forestry system. However, the authors point out in the Discussion that there have been a number of studies of irrigation on hybrid poplar plantations already. The only information that may be considered novel is their comparison of several different levels of irrigation to maintain certain levels of soil water content. The Conclusion mentions that they plan to use the results of this study for a broader sustainability analysis of efficiency and sustainability (energy, economic) for these types of production systems. In my mind, this planned study is likely novel enough to be worth publication.

 

Abstract

 

The authors state that all irrigation levels tested resulted in greater plant growth than the control (no irrigation), but that there was no significant difference between the 3 irrigation levels themselves (maintenance of 20, 30, 40, and 50% soil water content). Given this, I do not understand their recommendation of 40% soil water content as the recommended irrigation level. If the goal is water conservation, it appears that 20% soil water content is sufficient. In looking at the Results, there is some merit in their conclusion in the abstract, but their summary of the results in the abstract does not support that conclusion.

The sentence in the abstract relating to the correct observation of the reviewer has been revised and implemented with the addition of a new text (lines 22-28).

 

Introduction

 

The Introduction includes a lot about what is meant by precision agriculture and the contribution of using woody crops for energy to meet sustainability goals. What is missing is much introduction of the science behind the actual study: growth of the trees themselves, the importance of soil water availability, and justification for yet another study of irrigation of hybrid poplar. I recommend the authors rewrite this section to focus on the science behind their actual study and a stronger justification for their objectives and approach.

The introduction has been extended to the suggested topics and new text has been added to lines 92-110 and 116-125.

 

Materials and Methods

 

The authors describe the climate and seasonal weather conditions of the site. A figure illustrating this would be useful.

Added figure 1 showing the poplar plantation and the experimental design adopted (row 148).

 

The authors provide copious information about the soil type, which is good, but they never provide the taxonomy of the soil. That would help the reader understand a little more about the soil.

Added new test to lines 128-133 and 138-142

 

Table 1 contains a lot of summary information about the soil, but the authors do not indicate what depth range they sampled to measure these characteristics.

Added clarification in the text to line 142.

 

Some of these characteristics are likely unnecessary for the purposes of this study, but there is no problem with their inclusion. What is missing, however, is a measure of the soil water retention curve, i.e. the relationship between gravimetric water content and soil water potential. This is important to understand plant water availability and thus to interpret their results of plant growth response to irrigation levels. Since this soil has a texture class of silty-clay, one could use typical soil water release curves for this texture class to predict the optimal soil gravimetric water content (30-40%). The results support this prediction. In reality, it is soil water potential that controls plant water availability, so that is key information for achieving optimal irrigation. I recommend the authors include this for the study.

The present work focused mainly on the technological use of sensors and the irrigation system. The percentage of water in the soil was considered as a fixed parameter established for the activation of the irrigation system according to the four irrigation treatments considered. The observation is however correct and the suggestion to insert the soil water retention curve is precious. The graph representing the soil water retention curve was then added to the side of Figure 2, which becomes Figure 2a and 2b.

New explanatory and clarifying sentences were added to lines 209-213 and 215-232.

 

The description of the field design of this study is not clear to me. I recommend the authors include a figure to illustrate the characteristic arrangement of blocks, treatments, and seedlings. Also, in Lines 115 and 116, the authors claim they adopted a completely randomized design. If treatments are arrayed in blocks, then it is a randomized block design.

Figure 1 (line 148) with the scheme of completely randomized experimental design has been inserted. This design was obtained by random attribution of the experimental treatment, not considering its position. It is not a randomized block design.

 

The treatment levels are fine, but T1 is not technically a control, since it was scheduled for irrigation at 20% soil water content. In that regard, there is not an unirrigated control for this study, which is not a problem.

The observation is correct, the T1 thesis is improperly considered a control as a minimum irrigation treatment is carried out, but it is still considered a reference treatment for comparison with all the other theses.

 

The authors do not describe their statistical analyses in this section, instead placing it in the Discussion. It should be placed in the Materials and Methods section. The authors need to clarify the experimental design they used for the analysis. They need to specify what response variables are being compared. They also need to identify what multiple comparison test they used. There are several that are compatible with the Kruskall-Wallis non-parametric test.

Done. Sentences concerning the statistical tests carried out have been inserted in this section (lines 284-289).

 

Discussion

 

The description of the statistical analyses should be placed in the Materials and Methods section.

Done.

 

The authors do not adequately explain the purpose of including the hypsometric curves relating DBH to height. It’s a valid observation, but what is important about knowing this? Also, this relationship and the procedure for calculating the curves are not described in the Materials and Methods section. They should be. The parameters for the curves are also not statistically compared, which I expect they can be. That choice is up to the authors.

Explanation text has been added in Materials and Methods section regarding hypsometric curves (lines 248-255).

 

This section also does not interpret or evaluate these results in the context of the climate and soil in which the trees grew. This is important to be able to generalize these results beyond the particular location and time period in which the study took place. The authors provide detailed information about the soil type and the climate and weather patterns in the Materials and Methods section, but those characteristics and conditions are largely ignored in the Discussion.

Suggestion accepted; new clarification text added on lines 402-412.

 

Tables

 

There are a few instances in which the authors use a comma (“,”) instead of a period (“.”) in their numerical data.

Revised and corrected tables.

 

Reviewer 3 Report

1. TITLE

The title could not reflect the core content and innovation of this paper.

2. ABSTRACT

There was too much background description and too little quantitative summary of the key results.

3. KEY WORDS

The choice of key words was repeated with the title.

4. Introduction

Without in-depth analysis of the research progress of drip irrigation poplar, the innovation of this paper cannot be seen from the current introduction.

5. Mothods

The test protocol should be described in more detail, such as how to control moisture for each treatment, rather than focusing on the rate determination of soil moisture sensor.

6.Results

As an irrigation experiment, soil moisture change data should first be presented. And the data presented were too simplistic.

7. Discussion

No in-depth discussion was conducted to clarify the important contribution of this study

Author Response

Dear Reviewer,

the authors thank you for the valuable information and suggestions that have proved extremely useful for the improvement of the manuscript. We hope you find our answers to your questions satisfying. Here are the answers point-by-point.

Best regards.

The authors

Reviewer 3

 

1. Title

The title could not reflect the core content and innovation of this paper.

Changed title.

 

2. Abstract

There was too much background description and too little quantitative summary of the key results.

Revised abstract

 

3. Key words

The choice of key words was repeated with the title.

Revised and changed keywords

 

4. Introduction

Without in-depth analysis of the research progress of drip irrigation poplar, the innovation of this paper cannot be seen from the current introduction.

Revised introduction and implemented text

 

5. Methods

The test protocol should be described in more detail, such as how to control moisture for each treatment, rather than focusing on the rate determination of soil moisture sensor.

Added in-depth text on the irrigation control mode using soil moisture sensors (lines 234-242).

 

6.Results

As an irrigation experiment, soil moisture change data should first be presented. And the data presented were too simplistic.

Inserted new clarification text (209-216 and 393-402).

 

7. Discussion

No in-depth discussion was conducted to clarify the important contribution of this study

Added new text on the topic to the lines 485-490.

Reviewer 4 Report

Dear Authors,

Please find my comments in the attached PDF file.

Respectfully

Comments for author File: Comments.pdf

Author Response

Dear Reviewer,

the authors thank you for the valuable information and suggestions that have proved extremely useful for the improvement of the manuscript. We hope you find our answers to your questions satisfying. Here are the answers point-by-point.

Best regards.

The authors

Reviewer 4

 

Reviewer’s Comments & Queries:

Through the manuscript, the authors attempt to evaluate the effect of supply of different volumes of irrigation water on poplar growth in Italy. While this is an interesting topic, in my humble opinion the paper still needs some major improvements. You can kindly find my comments both in general and in more detailed and technical aspects of the investigation, as below:

 

General Comments:

1. First and foremost, please replace “drip irrigation” with “deficit irrigation” in the title. This study is about the effect of different levels of deficit irrigation on the biomass, not the effect of drip irrigation on the biomass. In this study, drip irrigation was just a tool to deliver water to the plant. The authors did not investigate irrigation evaluation indices like water use efficiency, irrigation application efficiency and etc. Therefore, it is better to emphasize on the deficit irrigation rather than the drip irrigation.

Title changed according to the suggestion.

 

2. the introduction is not in line with the scope of the paper. This study is about the effect of deficit irrigation on the poplar growth and biomass, however, authors mostly dealt with the importance of poplar plantation. Please consider adding some information regarding the deficit irrigation and mention some of the recent investigations in this area.

Added a new clarification text to lines 93-125.

 

3. Please clearly mention the research gap and novelty of the work in the introduction section. What is/are the main difference/s between this study and other studies?

Text added to lines 116-125.

 

4. Based on what criteria the authors selected the theses? Why 20%, 30%, 40%, and 50%?

Added a new clarification text to lines 224-232.

 

5. In the materials and methods section, the authors did not clearly explain when the irrigation starts and ends. Please add it to the manuscript.

Text revised and added for further clarification on lines 234-242.

 

6. Although the automated irrigation system developed and used in this study is impressive, there is no need to mention the details regarding it. I suggest deleting some of the extra information regarding

it, for example lines 137 – 144 and lines 182 – 186.

In the opinion of the authors, the text is useful for understanding the operation of the automated irrigation system. On the contrary, it was requested to specify this aspect better by other reviewers.

 

7. The result section is very short. I suggest either reporting the results in more details or combining the results and discussion sections.

The suggestion was accepted by combining Results and Discussions in a single section.

 

8. The authors defined the statistical analyses in the discussion section. Please consider moving them to the materials and methods section and only present the results derived from them in the discussion section.

Done.

 

9. There are some paragraphs that are long and hard to follow. The paragraphs should be no more than 200 words. Please break long paragraphs.

The manuscript has been revised to that effect.

 

10. There are so many editorial mistakes in the References section. Please check.

References verified and correct.

 

Detailed Comments:

Line 47 – 48: Please place this sentence on the line 54, before the sentence starting with “This system, which is …”. Precision irrigation is a more general concept than drip irrigation. So, it is better to start the paragraph with a short description of precision irrigation and continue with the description of drip irrigation as an example of precision irrigation.

Done.

 

Line 107: Please replace “clay - silt” with “silty clay”

Done.

 

Table 1: Please replace “97,00” with “97.00”, and replace “PH” with “pH”.

Done.

 

Line 122 - 123: I suggest authors not to mention the purpose of the study in the Materials and Methods section. 3

Done.

 

Line 188: What does a “common irrigation program” mean? Please clarify. Also, I suggest using the word “irrigation schedule” instead of using “irrigation program”.

Done.

 

Line 229: What do “dry periods” and “critical period” mean? Please clarify.

Added new text for clarification to lines 293-296.

 

Figure 2: Please do not use abbreviations like T and R. If want, please explain them in the figure script.

Done.

 

Line 250 – 255: Please briefly present the information of each table and figure rather than just explaining the title of them.

Specifications inserted in the caption of Figure 2.

 

Line 266: Differences in what? Please clarify.

Modified sentence, however the statistical differences refer to the quantitative variables examined (diameters, heights, and quantity of aboveground biomass).

 

Line 277: What does “substantial statistical equality” means? What kind of variables? Please clarify.

Right observation: the sentence has been changed and "substantial" has been deleted. The variables are those reported in the previous point.

 

Line 292: Based on what investigation authors claim that “The equations that best interpret the data are polynomial”? Did authors investigate other equations? If yes, please provide a short description of it. Otherwise, please mention some studies to support this statement.

Yes, we have considered the power, linear and logarithmic equations, all with a lower coefficient of determination than the polynomial equation. However, further clarification was provided by adding new text to lines 251-255.

 

Line 294 – 295: Why did T2 and T3 show a similar trend, while T4 show a stronger height response than the others, especially for larger diameters? Please discuss and mention probable reasons.

Done. A clarification sentence was added to lines 365-371.

 

Line 301: Please replace “calculated” with “estimated”.

Done.

 

Figure 5: Please discuss why for lower DBH values (lower than 8 cm), the descending trend of height is T2, T3, T4, and T1 but for larger DBH, the trend changes. In other words, why T4 has a steeper slope than other theses?

See lines 365-371.

 

Line 327 – 370: This is a very long and hard-to-follow paragraph (43 lines). Please split the paragraph into a few paragraphs.

Revised paragraphs.

 

Line 372: Please start the conclusion section with a brief description of the aim of the study.

Done.

 

Round 2

Reviewer 1 Report

 

The authors have satisfactorily did corrections/improvements as suggested. Therefore, the manuscript might be considered for publication.  

Author Response

Dear Reviewer,

we renew our thanks for the positive opinion expressed on the manuscript.

Best regards.

The authors

 

Comments and Suggestions for Authors

The authors have satisfactorily did corrections/improvements as suggested. Therefore, the manuscript might be considered for publication.

 

Reviewer 2 Report

The revised manuscript has adequately addressed my concerns. It is suitable for publication.

Author Response

Dear Reviewer,

we renew our thanks for the positive opinion expressed on the manuscript.

Best regards.

The authors

 

Comments and Suggestions for Authors

The revised manuscript has adequately addressed my concerns. It is suitable for publication.

Reviewer 3 Report

Although the author changed the title to the impact of deficit irrigation, this topic was not analyzed in detail in the paper.

1. From the introduction, it was still not possible to find the research progress on deficit irrigation of poplar and the scientific problems proposed in this paper. Also, if the author wants to highlight the development of automated drip irrigation systems, then the introduction also needs to add research progress on such systems.

2. As a paper on the effect analysis of water-saving irrigation, descriptions specific to irrigation systems should be simple and repeatable. However, the existing description of the irrigation automatic irrigation system was too much, and the specific operation of irrigation treatment was lack of description, such as the start time of irrigation, etc.

3. What's more, for deficit irrigation, the level range of different treatments (irrigation amount ranging from 20 to 1366L tree -1) cannot be scientifically confirmed.

4. The location and rationality of soil observation points were not explained. In addition, because there were no datas on the varitions of soil moisture in the paper, it was impossible to judge whether different treatments are really controlled in the corresponding soil moisture range.

5. The article lines 242-243 do not specify what irrigation treatments were carried out in 2019.

6. From the discussion, it was not clear what was (1) the generalization value of the research results in this paper, (2) the difference in the distinction of predecessors, and (3) the reason for the results.

Author Response

Dear Reviewer,

We thank you again for the further valuable information and suggestions for revising the manuscript, which has been further implemented. Here are our point-by-point answers with the hope that they will be satisfactory for you.

Best regards.

The authors

 

Comments and Suggestions for Authors

Although the author changed the title to the impact of deficit irrigation, this topic was not analyzed in detail in the paper.

 

1. From the introduction, it was still not possible to find the research progress on deficit irrigation of poplar and the scientific problems proposed in this paper. Also, if the author wants to highlight the development of automated drip irrigation systems, then the introduction also needs to add research progress on such systems.

Added new text on lines 91-107.

 

2. As a paper on the effect analysis of water-saving irrigation, descriptions specific to irrigation systems should be simple and repeatable. However, the existing description of the irrigation automatic irrigation system was too much, and the specific operation of irrigation treatment was lack of description, such as the start time of irrigation, etc.

The description of the irrigation treatments, with the addition of further specifications, is given in lines 261-266.

 

3. What's more, for deficit irrigation, the level range of different treatments (irrigation amount ranging from 20 to 1366L tree -1) cannot be scientifically confirmed.

The average quantity of water per tree was calculated on the basis of the volume of water distributed for each thesis, recorded by the system control unit and verified by mechanical meters placed on each line. The amount of water reported in the text is therefore that actually administered.

 

4. The location and rationality of soil observation points were not explained. In addition, because there were no data on the variations of soil moisture in the paper, it was impossible to judge whether different treatments are really controlled in the corresponding soil moisture range.

Added new text on lines 195-204.

 

5. The article lines 242-243 do not specify what irrigation treatments were carried out in 2019.

For further clarification, new text has been added to lines 267-275.

 

6. From the discussion, it was not clear what was (1) the generalization value of the research results in this paper, (2) the difference in the distinction of predecessors, and (3) the reason for the results.

Added new explanatory text to lines 497-502.

Reviewer 4 Report

The authors did a great job revising the manuscript and it can be considered for publication. However, it would be even better if they apply the following suggestions:

1. Although the authors revised the paragraph from lines 116 to 125, I still do not see a clear statement of the research gap and novelty of the work.
By research gap, I expect the authors to clearly mention what the research gaps were and what made them to conduct this research. What were the main questions that they tried to find an answer to? They should mention, for example, limited studies have been conducted to investigate X. Needless to say, this statement should be valid.
By novelty, I mean that the authors should clearly mention that the previous studies have not investigated X but we did. They should explicitly mention the contribution of their work to this area of science. 
If the effect of deficit irrigation on poplar biomass has been investigated before, they should emphasize the region where they conducted their research because case studies are still valuable.

2. in line 243, what does the "common irrigation program" mean? Please clarify. Also please use "irrigation schedule" instead of "irrigation program".

Regards.

Author Response

Dear Reviewer,

We thank you again for the further valuable information and suggestions for revising the manuscript, which has been further implemented. Here are our point-by-point answers with the hope that they will be satisfactory for you.

Best regards.

The authors

 

Comments and Suggestions for Authors

The authors did a great job revising the manuscript and it can be considered for publication. However, it would be even better if they apply the following suggestions:

 

1. Although the authors revised the paragraph from lines 116 to 125, I still do not see a clear statement of the research gap and novelty of the work.

By research gap, I expect the authors to clearly mention what the research gaps were and what made them to conduct this research. What were the main questions that they tried to find an answer to? They should mention, for example, limited studies have been conducted to investigate X. Needless to say, this statement should be valid.

By novelty, I mean that the authors should clearly mention that the previous studies have not investigated X but we did. They should explicitly mention the contribution of their work to this area of science. 
If the effect of deficit irrigation on poplar biomass has been investigated before, they should emphasize the region where they conducted their research because case studies are still valuable.

Added new explanatory text to lines 94-109 and 497-502.

 

2. in line 243, what does the "common irrigation program" mean? Please clarify. Also please use "irrigation schedule" instead of "irrigation program".

Added new explanatory text to lines 267-275.

Round 3

Reviewer 3 Report

1. The authors still did not provide relevant data on seasonal soil moisture variation, which is an important basis for judging whether the corresponding moisture range has been reached by different treatments.

2. If the automatic irrigation system was not developed by the authors, please delete the relevant content or summarize them in the form of pictures as an supplementary document. Then if the system was developed, you need add the relevant control chart and interface.

3. In addition to the existing data, are there any relevant above-ground to below-ground growth data to support the conclusion of this paper？

Author Response

1. The authors still did not provide relevant data on seasonal soil moisture variation, which is an important basis for judging whether the corresponding moisture range has been reached by different treatments.

Starting and stopping irrigation, as in the text described, is controlled by the humidity level set for each sensor. If this is set for example to 40%, the sensor commands the start of irrigation at 39% and stop at 41% to maintain the average value of 40%. This means that the soil moisture at a depth of 30 cm is maintained at that level for the duration of irrigation.

 

2. If the automatic irrigation system was not developed by the authors, please delete the relevant content or summarize them in the form of pictures as an supplementary document. Then if the system was developed, you need add the relevant control chart and interface.

We accepted his suggestion by removing most of the description of the irrigation system and summarizing it in a few words.

 

3. In addition to the existing data, are there any relevant above-ground to below-ground growth data to support the conclusion of this paper?

Data relating to below-ground biomass were not recorded.