Impact of capillary rise and recirculation on simulated crop yields

Kroes, Joop; Supit, Iwan; van Dam, Jos; van Walsum, Paul; Mulder, Martin

doi:https://doi.org/10.5194/hess-22-2937-2018

Articles | Volume 22, issue 5

https://doi.org/10.5194/hess-22-2937-2018

© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 3.0 License.

https://doi.org/10.5194/hess-22-2937-2018

© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 22, issue 5

Research article

|

17 May 2018

Research article |

| 17 May 2018

Impact of capillary rise and recirculation on simulated crop yields

Joop Kroes, Iwan Supit, Jos van Dam, Paul van Walsum, and Martin Mulder

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Final revised paper (published on 17 May 2018)
Supplement to the final revised paper
Preprint (discussion started on 20 Apr 2017)
Supplement to the preprint

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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- Supplement

RC1: 'Review of hess-2017-223', Anonymous Referee #1, 24 Apr 2017
- AC1: 'Response to Referee #1 (reviewer1_hess-2017-223-RC1.pdf)', Joop G. Kroes, 05 Jul 2017
  - AC2: 'Additional Response to Referee #1 (reviewer1_hess-2017-223-RC1.pdf)', Joop G. Kroes, 30 Aug 2017
RC2: 'Referee comments on "Impact of capillary rise and recirculation on crop yields"', Anonymous Referee #2, 30 Jul 2017
- AC3: 'Response_Reviewer2_hess-2017-223-RC2.docx', Joop G. Kroes, 30 Aug 2017
RC3: 'Evaluation', Piotr Kowalik, 09 Aug 2017
- AC4: 'Response_Reviewer3_hess-2017-223-RC3', Joop G. Kroes, 30 Aug 2017

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

ED: Publish subject to revisions (further review by Editor and Referees) (03 Sep 2017) by Nunzio Romano

AR by Joop G. Kroes on behalf of the Authors (13 Oct 2017) Author's response Manuscript

ED: Referee Nomination & Report Request started (29 Oct 2017) by Nunzio Romano

RR by Anonymous Referee #2 (16 Dec 2017)

Suggestions for revision or reasons for rejection

I went through the comments of the referees and replies of the authors (it is unfortunate that the authors did not centralize the complete comments with the respective replies).

While minor comments were appropriately dealt with, most of the major points raised by the referees were incompletely addressed.

As reported by referees #1 in his/her general comments, “the authors should recognize that quantitative work was done on the relation between capillary rise and crop yield”. To this remark, I would add that the authors should extensively discuss their results in comparison to the existing literature. The referee #1 specifically referred to such studies and pointed at misleading sentences suggesting that there were no such studies. Yet, these misleading sentences are mostly left unchanged in the manuscript, for instance in the conclusions “We think that the quantification of upward flow on yield is a novelty” and “Another aspect which cannot be found in the referenced studies is the lack of a quantification of the impact of capillary rise and recirculation on crop yields”.

The second general comment of referee #1 points out that the illustrations of hydrological conditions in Figure 2 are unclear, particularly the first two conditions. Yet, the figure was left unchanged. Please clarify the figure, and note that the red horizontal bars can be easily removed by setting the Powerpoint to full screen before pushing on the PrintScreen button.

The first major comment of referee #2 highlights that the methods presented in the study are not adequate to reach its objective (i.e. demonstrating that, in place of the common “bucket approach”, recirculation should be implemented in crop models in order for them to be more accurate). A comparison of simulated results obtained with both assumptions is proposed. The comparison does not demonstrate that recirculation makes the crop model more accurate, but only that Swap is sensitive to recirculation. In their reply, the authors explain that the data available is not sufficient to validate that Swap with recirculation is more accurate than “bucket” Swap, and stick with the sensitivity analysis. Their hypothesis thus cannot be demonstrated.

The second major comment of referee #2 regards the level of detail of the material and methods, which has since been improved.

The third major concern of referee #2 addresses the validity of lessons drawn from the simulated results, given that the accuracy of the model with recirculation, compared to measured yield, is so low. Switching recirculation on or off generates deviations of the predicted yield that are all smaller than the standard error of the model. The authors reply that the poor quality of the input data might explain the poor accuracy of the model, and insist on the point that they know *by experience* that recirculation is important in crop models. They might be right but the problem is that the results shown in the manuscript do not support the validity of the model *in the considered conditions*, and support even less so the validity of lesson taken from the model in conditions where it appears not to be accurate. It seems that the authors take predictions of the model for granted, as if they were real observations.

Referee #3 points out that allowing percolation while blocking upward flow is not a realistic condition. I agree with the reply of the authors, that the point is not to make the boundary condition realistic, but to make the modified model representative of a bucket model. However, the quality of two models cannot be compared by using the parametrization of only of them. Bucket models may be quite effective in reproducing observed yields, despite their lack of physical basis, when using their own parametrization. In this paper the authors try to discredit the bucket approach in a way that is not scientifically sound.

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RR by Anonymous Referee #4 (26 Jan 2018)

Suggestions for revision or reasons for rejection

General: This is an interesting manuscript contrasting simulated results for drainage, recirculated, and capillary rise from the water table, and the effect on crop yield. The revisions so far were good. The conclusions are supported by the study. Now the main concerns are the Abstract, quality of some of the Figures, and some verb tense issues.

Specific

Abstract: Start with a justification statement (why the research is needed). Then include a hypothesis, objective, or proposed outcome statement (separate from methods statements).
"Upward soil water flow is a vital supply of water to crops. The purpose of this study was to determine if upward flow and recirculated percolation water can be quantified separately, and to determine the contribution of capillary rise and recirculated water to crop yield and groundwater recharge." Other parts of the abstract may then need to be shortened.

Introduction: okay

Methods: Present your methods in past tense.

Results:
Figure 4: Either remove the caption on the lower plot (since it is the same as for the upper plot) or enlarge it.

Present your results in past tense.

Supplemental Figures S4-S18 needs axes, tick labels, data points, plot captions, etc. to be greatly enlarged because they are undecipherable.

L. 377-379: This sentence is awkward, perhaps "The shallow groundwater in Dutch conditions often do not have deep leaching because excess precipitation or upward seepage is discharged via drainage systems." (Possibly add a citation.)

Discussion: good
Present discussion of your results in past tense.

Conclusions: good
Present conclusions from your study in past tense.

(Only already published data get to be given in present tense.)

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ED: Publish subject to revisions (further review by editor and referees) (06 Feb 2018) by Nunzio Romano

AR by Joop G. Kroes on behalf of the Authors (07 Mar 2018) Author's response Manuscript

ED: Referee Nomination & Report Request started (24 Mar 2018) by Nunzio Romano

RR by Sally Logsdon (26 Mar 2018)

ED: Reconsider after major revisions (further review by editor and referees) (26 Mar 2018) by Nunzio Romano

AR by Joop G. Kroes on behalf of the Authors (17 Apr 2018) Author's response Manuscript

ED: Publish as is (22 Apr 2018) by Nunzio Romano

AR by Joop G. Kroes on behalf of the Authors (26 Apr 2018)

Short summary

Impact of upward flow by capillary rise and recirculation on crop yields is often neglected or underestimated. Case studies and model experiments are used to illustrate the impact of this upward flow in the Dutch delta. Neglecting upward flow results in yield reductions for grassland, maize and potatoes. Half of the withheld water behind these yield effects comes from recirculated percolation water as occurs in free-drainage conditions; the other half from increased upward capillary rise.