Effect of a Soil Water Balance Controlled Irrigation on the Cultivation of Acer pseudoplatanus Forest Tree Liners Under Non-Limiting and Limiting Soil Water Conditions

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

General comments

This paper is generally well written and the application of SWB has certain practical value. Several issues should be illustrated and modified before the it could be further handled.

Specific comments

[1] The author wrote down the multiplication sign ‘·’ as ‘.’, like 120L.h^-1 in line201.

[2] ET_a was simply estimated by single crop coefficient method in this study, however, since there was low moisture condition in soil and the E from soil could not be that potential, dual crop coefficient method was more suitable.

[3] Is there any basis or reference for Kc 0.3-1.1? If so, please list it. Kc should be estimated by lysimeter in the actual field.

[4] There were no detailed describe of CR and deep percolation estimate method, they should be properly improved and compared between rainfed and irrigated treatments, because they are all important factors in SWB. Also, Meteorological parameters used in ETo calculations were poorly described in terms of source and quality.

[5] The results and conclusion were quite plain. Irrigation certainly makes plants grow better, but there was too much discussion about the obvious conclusion. The focus of the article should be on how to make future water demand prediction and irrigation decisions based on SWB. The depth of the article in this aspect is not satisfactory.

Author Response

Dear reviewer,

We revised your remarks and comments as good as possible. Below our answers to your comments.

 

Comments 1: The author wrote down the multiplication sign ‘·’ as ‘.’, like 120L.h^-1 in line201.

Answer 1: We changed throughout the entire manuscript and appendices.

 

Comments 2: ET_a was simply estimated by single crop coefficient method in this study, however, since there was low moisture condition in soil and the E from soil could not be that potential, dual crop coefficient method was more suitable.

Answer 2: We understand this remark. We have clarified our approach in the new manuscript. We indeed consider a higher evaporation after a wetting event and the original Figure 2 was a bit misleading. The new Figure 2 shows how we adjusted Kc according to high evaporation after soil wetting. The exact calculation procedure is described in the Annex.

 

Comments 3: Is there any basis or reference for Kc 0.3-1.1? If so, please list it. Kc should be estimated by lysimeter in the actual field.

Answer 3: We agree that we do not have exact data to justify our assumption for the chosen Kc values. We did not had the opportunity to use a lysimeter or other instrumentation to do this. We can only base our self on the evolving canopy cover. The SWB however was well validated with aid of the soil sensor data, soil samples and water retention characteristics. In Figure 4 we document the quality of our SWB calculation. In the new MS we have now indicated that the chosen Kc values are based on an assumption due to the lack of good reference values in literature. In the discussion section we added that uncertainty about the underlying processes is inherent to the use of a SWB.

 

Comments 4: There were no detailed describe of CR and deep percolation estimate method, they should be properly improved and compared between rainfed and irrigated treatments, because they are all important factors in SWB. Also, Meteorological parameters used in ETo calculations were poorly described in terms of source and quality.

Answer 4: We agree that we did not foresee information about the different fluxes of the SWB. We have now elaborated our MS to do so. There is a new Figure (Figure 5) that fills this gap. We also elaborated this in the results and discussion section.

With respect to the ETo calculation, we added extra information about the origin of the data (collected at the Semmerzake weather station) as well of the rainfall data. By checking this information we noticed that in the previous version of the paper ETo in 2022 was calculated from a weather station in Deurne, we have in the recent paper chanced this all to Semmerzake. This resulted in small changes in the figures in Table 3.

 

Comments 5: The results and conclusion were quite plain. Irrigation certainly makes plants grow better, but there was too much discussion about the obvious conclusion. The focus of the article should be on how to make future water demand prediction and irrigation decisions based on SWB.The depth of the article in this aspect is not satisfactory.

Answer 5: We extended the discussion and focus also about the different fluxes of the SWB. We pay now attention to the relation between irrigation and water percolation out the root zone and benchmark the water stress thresholds to experiments in fruit crops, since we could not find any similar experiment on open field grown ornamental trees in literature.

For each particular plant parameter measured, the discussion was supplemented with possibilities for growers towards irrigation control, so that the practical significance of the research is also more highlighted. Often the conclusion is that we will perform further research on how growers can implement a certain parameter in irrigation control in practice. 

The conclusion was rewritten with focus on both the SWB and plant growth.

 

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript provides a detailed assessment of the effect of irrigation, based on soil water balance calculation, on the soil and plant water status, tree growth and commercial quality of Acer pseudoplatanus forest tree liners grown under two different water supply levels. I think this definition of the study is more precise than the one given by the authors (“in optimal and suboptimal soil conditions”).

The title of the manuscript is quite expressive, though I miss the concrete suggestions how to refine the irrigation practice(s) applied in young tree plantations.

The abstract is too general, I recommend revising the last sentence of it to provide more quantitative results (see my comment in the file attached).

The Introduction section contains a sufficient number of relevant national and international references, highlights the topic in a broader context but does not provide the justification of the study in harmony with the title of the paper. Nevertheless, the first paragraph of the Discussion section could be connected to the main goal in a coherent way as the justification of the study is not only from scientific but also practical points of view.

The Materials and Methods section is logically structured and very detailed, including all the necessary information on the experimental site, the studied materials, setup, analyses, and calculations. Maybe the technical terms determining the different growing conditions should be revised.

The Results section provides a lot of information arranged in logical subchapters dedicated to the studied parameters. The tables and the illustrative figures are self-explanatory and aid the understanding of the results very well.

The Discussion section is very detailed, referring to other studies on the topic of the study, though it contains plenty of general statements beyond the concrete, quantified results.

The Conclusions section is laconic, and it is in conjunction with the results, but it should contain some implications, e.g., how and to what extent the results could be interpreted to other areas and conditions beyond the investigated ones.

In my opinion, the topic is important, but it should highlight more practical significance. The study is based on an extensive survey supported by up-to-date methodology.

I indicated some remarks in sticky notes in the manuscript.

Comments for author File: Comments.pdf

Author Response

Dear author,

We revised your remarks and comments as good as possible. Below you can find our answers on your comments.

 

Comments 1: The manuscript provides a detailed assessment of the effect of irrigation, based on soil water balance calculation, on the soil and plant water status, tree growth and commercial quality of Acer pseudoplatanus forest tree liners grown under two different water supply levels. I think this definition of the study is more precise than the one given by the authors (“in optimal and suboptimal soil conditions”).

Answer 1: We indeed tested 2 irrigation doses (rain-fed treatment versus irrigation according to the model) relative to each other, but noticed during the study that a gradient in soil quality was present in the test field where both irrigation treatments were located. Hence, we switched treatments from one location to another in 2023 (from the front to back zone and the other way around). We investigated the difference in soil quality between the front and back zone of the field with different analyses, along in the Materials and Methods section 2.2. Soil characteristics. Perhaps we better speak of optimal soil quality conditions and suboptimal soil quality conditions to make it clearer. This was changed throughout the manuscript.

 

Comments 2: The title of the manuscript is quite expressive, though I miss the concrete suggestions how to refine the irrigation practice(s) applied in young tree plantations.

Answer 2: We agree on this, so we changed the title to ‘Effect of a soil water balance controlled irrigation on the cultivation of Acer pseudoplatanus forest tree liners under non-limiting and limiting soil water conditions’.

 

Comments 3: The abstract is too general, I recommend revising the last sentence of it to provide more quantitative results (see my comment in the file attached).

Answer 3: We also agree on this comment. The sentences about the results were adjusted by adding the quantitative results.

 

Comments 4: The Introduction section contains a sufficient number of relevant national and international references, highlights the topic in a broader context but does not provide the justification of the study in harmony with the title of the paper. Nevertheless, the first paragraph of the Discussion section could be connected to the main goal in a coherent way as the justification of the study is not only from scientific but also practical points of view.

Answer 4: The title is changed, so now more in line with the referred literature and referred results. The first paragraph of the discussion is integrated into the Introduction section as proposed. The description of the goal at the end of the Introduction section is changed to highlight the novelty of this study (irrigation based on SWB calculation and the theoretical plant need) compared to older studies, but also to stress the practical point of view of this study, the importance for the growers in our region.

 

Comments 5: The Materials and Methods section is logically structured and very detailed, including all the necessary information on the experimental site, the studied materials, setup, analyses, and calculations. Maybe the technical terms determining the different growing conditions should be revised.

Answer 5: We agree. The technical terms about the different growing conditions, more specifically the technical terms on the soil scan, has been rewritten.

 

Comments 6: The Results section provides a lot of information arranged in logical subchapters dedicated to the studied parameters. The tables and the illustrative figures are self-explanatory and aid the understanding of the results very well.

Answer 6: Thank you for this comments. The figures on the soil (figures 2-5) changed a bit according to the remarks of reviewer 1, but are still clear.

 

Comments 7: The Discussion section is very detailed, referring to other studies on the topic of the study, though it contains plenty of general statements beyond the concrete, quantified results.

Answer 7: For each particular plant parameter measured, the discussion was supplemented with possibilities for growers towards irrigation control, so that the practical significance of the research is also more highlighted. Often the conclusion is that we will perform further research on how growers can implement a certain parameter in irrigation control in practice.

 

Comments 8:  The Conclusions section is laconic, and it is in conjunction with the results, but it should contain some implications, e.g., how and to what extent the results could be interpreted to other areas and conditions beyond the investigated ones.

Answer 8: We agree on this, so we rewrote the conclusion with more focus on practical implementation of the SWB and the effect of irrigation on tree growth.

 

Thank you.

 

 

 

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors made improvements as far as possible according to my suggestions, and also explained and discussed the limitations of some problems caused by data constraints. The current version is satisfactory enough to me，and wish you a good career.