the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
The effect of Static Chamber's Base on N2O Flux in Drip Irrigation
Abstract. Static chambers are commonly used to provide in-situ quantification of N2O fluxes. Despite their benefits, when left in the field, the physicochemical conditions inside the chamber's base may differ from the ambient, especially in drip-irrigated systems. This research aimed to study the effects of static chambers' bases on water and N-forms distribution and the impact it has on N2O measurements in drip irrigation. N2O emissions were measured in a drip-irrigated avocado orchard for two years, using bases with a dripper at their center (In) and bases installed adjacent to the dripper (adjacent). During the irrigation/fertigation season, the measured N2OIn fluxes were greater than the N2OAdjecent fluxes (0.82 ± 0.15 vs. 0.36 ± 0.05 ng cm-2 sec-1). In contrast, during the winter, when the orchard is not irrigated or fertilized, insignificant differences were observed between the measured N2OAdjecent and N2OIn fluxes. Three dimentional simulations of water flow and N-forms transport and transformations showed two opposing phenomena (a) increased water contents, N concentrations, and downward flushing when the dripper is placed inside the base, and (b) hampering of the lateral distribution of water and solutes into the most bio-active part of the soil inside the base when the base is placed adjacent to the dripper. It also showed that both "In" and "adjacent" practices underestimate the "true" cumulative flux from a dripper with no base by ~25 % and ~50 %, respectively. A nomogram in a non-dimensional form corresponding to all soil textures, emitter spacings and discharge rates, was developed to determine the optimal diameter of an equivalent cylindrical base to be used along a single dripline.
-
Notice on discussion status
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
-
Preprint
(1517 KB)
-
Supplement
(600 KB)
-
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(1517 KB) - Metadata XML
-
Supplement
(600 KB) - BibTeX
- EndNote
- Final revised paper
Journal article(s) based on this preprint
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2022-141', Anonymous Referee #1, 10 Jun 2022
Please see pdf for typos/suggested edits.
This manuscript was a pleasure to read and is very well presented.
Besides minor typos and suggestions as per the marked pdf:
- consider expressing fluxes in units more familiar to readers e.g g/m2/d even as a one off comparison.
- L236 check text and caption for Fig. 3 align
L266-267 Add text to indicae why higher WFPS or higher N concentrations favour higher N2O. See pdf.
L319-333 is this results? Shift to results section.
P10 alot of this text reads as results or methods. Suggest some is shifted to appropriate sections and discussion revised.
For the conclusion suggest "...we concluded that static chamber methodology, which requires the insertion of bases into the soil, underestimates N2O emissions when used in drip irrigation........This effect can be mitigated through optimising chamber design. A nomogram is proposed..."
-
AC1: 'Reply on RC1', Shahar Baram, 16 Jun 2022
Reply to comments made by reviewer 1:
We wish to thank the reviewer for his kind word and insightful comments.
Comment 1: Please correct minor typos as marked on the attached pdf.
Reply: Thank you for noticing the typos. All were corrected.
Comment 2: Consider expressing fluxes in units more familiar to readers e.g g/m2/d even as a one off comparison.
Reply: The units were changed to g m-2 d-1 in all the graphs and text as suggested.
Comment 3: - L236 check text and caption for Fig. 3 align
Reply: Indeed the caption had a typo where NO3 and NH4 were mixed. It was corrected.
Comment 4: L266-267 Add text to indicae why higher WFPS or higher N concentrations favour higher N2O. See pdf.
Reply: As requested, an explanation was added to the text “Suggests N2OIn results from conditions more conducive to denitrification (e.g., higher WFPS) or nitrification (e.g., higher NH4+ concentrations) (Lines 313-314 in the revised text).
Comment 5: L319-333 is this in the results? Shift to results section.
Reply: As suggested, some of the text was transferred to the results section. The revised section now reads ”Comparison of cumulative N2O emission measured in 2018, 2019, and 2020 and the simulated cumulative emissions (over 60 days) showed the N2OIn flux to be 40% – 70% higher than the N2OAdjecent (Fig. 7B)”.
Comment 6: P10 a lot of this text reads as results or methods. Suggest some is shifted to appropriate sections and discussion revised.
Reply: As suggested the text on page 10 was modified. A substantial portion of the text was moved to the Methods section, under a new subsection titled “2.2.4 Recommendation on the diameter of the chamber's base” . Another part was moved to the results section.
Comment 7: For the conclusion suggest "...we concluded that static chamber methodology, which requires the insertion of bases into the soil, underestimates N2O emissions when used in drip irrigation........This effect can be mitigated through optimizing chamber design. A nomogram is proposed..."
Reply: We adopted the suggested edits to the text and modified it to “ … we concluded that static chamber methodology, which requires the insertion of bases into the soil, underestimates N2O emissions when used in drip irrigation. “These effects can be mitigated through optimizing the chamber design. A nomogram is proposed…” .
Citation: https://doi.org/10.5194/egusphere-2022-141-AC1
-
AC1: 'Reply on RC1', Shahar Baram, 16 Jun 2022
-
RC2: 'Comment on egusphere-2022-141', Anonymous Referee #2, 16 Jun 2022
Review for Baram et al.,
In general, the manuscript is well and clearly written. In the manuscript authors aiming to resolve spatial variability issue in static-chamber based measurements of soil N2O emissions from drip-irrigated systems.
The study is comparing in situ measured soil emissions of N2O from two different positions of chambers, adjanct to the dripper and dripper inside of the chamber. Then authors using numerical modeling to explain observed differences between the two positions and to estimate “true” flux.
- Calculating cumulative emissions – why don’t you use linear interpolation? I do not think that your results will change, but I think that use of arbitrary Q10 is not any better than to estimate cumulative/daily flux using linear interpolation. Calculation of daily emissions can be done by dividing annual accumulative emissions by number of included in cumulative flux estimation days.
Hoben, J. P., Gehl, R. J., Millar, N., Grace, P. R., & Robertson, G. P. (2011). Nonlinear nitrous oxide (N2O) response to nitrogen fertilizer in on-farm corn crops of the US Midwest. Global Change Biology, 17(2), 1140–1152. http://dx.doi.org/10.1111/j.1365-2486.2010.02349.x
- Why do you think that your modeled emissions are better than observed? I think that for real answer if static chamber methods under- or overestimate real fluxes a comparison between static chambers and eddy-covariance based measurements is needed.
- You are using 3D flow model and some simple assumptions, you may model the water flow well, but I doubt that you can model N2O emissions. At least DayCent model, after ~30 years of development can not.
Lutz, F., Del Grosso, S., Ogle, S., Williams, S., Minoli, S., Rolinski, S., Heinke, J., Stoorvogel, J. J., & Müller, C. (2020). The importance of management information and soil moisture representation for simulating tillage effects on N2O emissions in LPJmL5.0-tillage. Geoscientific Model Development, 13(9), 3905–3923. https://doi.org/10.5194/gmd-13-3905-2020
I think that the manuscript of acceptable quality and importance and rising very important question of how to scale-up field-based measurements of soil gaseous emissions.
a) with all problems of using static chambers they provide good information on treatment differences and b) models today not ready to provide good estimation of field emissions. Therefore, static chambers will be used in the near future.
I am wondering if your proposed method to calculate optimal chamber (base) size for field measurements of soil N2O emissions (monogram) will provide better flux estimation. I think that few weeks of additional measurements comparing the proposed “optimal base size” with bases used to acquire data for the manuscript under discussion will improve the manuscript. If you are claiming that using modeled flow of water and nutrients, you can determine the optimal chamber – prove it.
Citation: https://doi.org/10.5194/egusphere-2022-141-RC2 -
AC2: 'Reply on RC2', Shahar Baram, 17 Jun 2022
Reply to comments made by Reviewer #2
We thank the reviewer for the comments and concerns.
Please find below our detailed replies to all the comments.
Comment 1: Calculating cumulative emissions – why don’t you use linear interpolation? I do not think that your results will change, but I think that use of arbitrary Q10 is not any better than to estimate cumulative/daily flux using linear interpolation. Calculation of daily emissions can be done by dividing annual accumulative emissions by number of included in cumulative flux estimation days.
Reply: We thank the reviewer for raising this point. All calculations were modified as suggested using linear interpolation and numerical integration between sampling times. The text was modified accordingly: “…by linear interpolation and numerical integration between sampling times. Cumulative N2O flux estimates for N2OIn and N2OAdjacent were taken as the average of the cumulative fluxes of the 12 individual chambers, each”.
Comment 2: Why do you think that your modeled emissions are better than observed? I think that for real answer if static chamber methods under- or overestimate real fluxes a comparison between static chambers and eddy-covariance based measurements is needed. And, Comment 3: You are using 3D flow model and some simple assumptions, you may model the water flow well, but I doubt that you can model N2O emissions. At least DayCent model, after ~30 years of development cannot.You are using 3D flow modeld and some simple assumptions, you may model the water flow well, but I doubt that you can model N2O emissions. At least DayCent model, after ~30 years of development cannot.
Reply: Our field measurements show that the measured N2O flux is highly affected by the location of the chamber’s base relative to the drip line. We agree that eddy-covariance based measurements may provide a good tool to validate our field measurement on a larger scale. Nevertheless, in the discussed emitter-spacing scale eddy-covariance could not be used.
Please note, that we do not think that our modeled emissions are better than the measured/observed emissions. Further, we do not think that the simple assumptions used by us to model N2O fluxes accurately capture the “true” N2O flux, as rightfully commented by the reviewer. Yet, our results raise a question as to what is the “correct” or the most representative way to capture the true ambient N2O emissions around a single dripper, part of a drip line, when using static chambers.
N2O fluxes are mainly driven by N availability and form (i.e., nitrate vs. ammonium), oxygen availability, and soil water content [readily expressed as the ratio between the volumetric water content and the porosity (WFPS)]. Thus, we decided to use a robust 3D flow model to study the effect that a chamber base may have on water and N distribution in the top soil. The main assumption for both the 3D flow model and the DIDAS model simulations/computations was that the ambient N2O emissions (i.e., not affected by the base) will be those emitted from a location with minimal perturbation by the base. That is, places where the N-form concentrations and distributions, and the water content are not affected by the base.
With this assumption in mind, the model was used to:
- Evaluate the impact of the dripper location relative to a base (i.e., inside, adjacent, few cm away, etc.);
- Find the optimal base diameter;
Comment 4: I am wondering if your proposed method to calculate optimal chamber (base) size for field measurements of soil N2O emissions (monogram) will provide better flux estimation. I think that few weeks of additional measurements comparing the proposed “optimal base size” with bases used to acquire data for the manuscript under discussion will improve the manuscript. If you are claiming that using modeled flow of water and nutrients, you can determine the optimal chamber – prove it.
Reply: In continuation to the reply to comments 2 and 3, to date, the standard method for static chambers calls for the use of basses. Hence, there is no way to get the “true” ambient N2O emissions from a single dripper. With that in mind and the model’s limitation in predicting N2O emissions (simplified assumptions), we do not see how few weeks of additional measurements comparing the proposed “optimal base size” with bases used to acquire data will benefit the manuscript.
Our intention was to merely raise the problem of the systematic, 3D heterogeneities around a dripper, to present relevant, simulated results, and to propose relevant methodologies assisting in deciding regarding the size and placement of the base. It will take many users in many conditions (soil types, wetting patterns, variable N carbon (C) and O regimes), rather than a single study, to tell whether these methodologies are constructive or not.
Citation: https://doi.org/10.5194/egusphere-2022-141-AC2
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2022-141', Anonymous Referee #1, 10 Jun 2022
Please see pdf for typos/suggested edits.
This manuscript was a pleasure to read and is very well presented.
Besides minor typos and suggestions as per the marked pdf:
- consider expressing fluxes in units more familiar to readers e.g g/m2/d even as a one off comparison.
- L236 check text and caption for Fig. 3 align
L266-267 Add text to indicae why higher WFPS or higher N concentrations favour higher N2O. See pdf.
L319-333 is this results? Shift to results section.
P10 alot of this text reads as results or methods. Suggest some is shifted to appropriate sections and discussion revised.
For the conclusion suggest "...we concluded that static chamber methodology, which requires the insertion of bases into the soil, underestimates N2O emissions when used in drip irrigation........This effect can be mitigated through optimising chamber design. A nomogram is proposed..."
-
AC1: 'Reply on RC1', Shahar Baram, 16 Jun 2022
Reply to comments made by reviewer 1:
We wish to thank the reviewer for his kind word and insightful comments.
Comment 1: Please correct minor typos as marked on the attached pdf.
Reply: Thank you for noticing the typos. All were corrected.
Comment 2: Consider expressing fluxes in units more familiar to readers e.g g/m2/d even as a one off comparison.
Reply: The units were changed to g m-2 d-1 in all the graphs and text as suggested.
Comment 3: - L236 check text and caption for Fig. 3 align
Reply: Indeed the caption had a typo where NO3 and NH4 were mixed. It was corrected.
Comment 4: L266-267 Add text to indicae why higher WFPS or higher N concentrations favour higher N2O. See pdf.
Reply: As requested, an explanation was added to the text “Suggests N2OIn results from conditions more conducive to denitrification (e.g., higher WFPS) or nitrification (e.g., higher NH4+ concentrations) (Lines 313-314 in the revised text).
Comment 5: L319-333 is this in the results? Shift to results section.
Reply: As suggested, some of the text was transferred to the results section. The revised section now reads ”Comparison of cumulative N2O emission measured in 2018, 2019, and 2020 and the simulated cumulative emissions (over 60 days) showed the N2OIn flux to be 40% – 70% higher than the N2OAdjecent (Fig. 7B)”.
Comment 6: P10 a lot of this text reads as results or methods. Suggest some is shifted to appropriate sections and discussion revised.
Reply: As suggested the text on page 10 was modified. A substantial portion of the text was moved to the Methods section, under a new subsection titled “2.2.4 Recommendation on the diameter of the chamber's base” . Another part was moved to the results section.
Comment 7: For the conclusion suggest "...we concluded that static chamber methodology, which requires the insertion of bases into the soil, underestimates N2O emissions when used in drip irrigation........This effect can be mitigated through optimizing chamber design. A nomogram is proposed..."
Reply: We adopted the suggested edits to the text and modified it to “ … we concluded that static chamber methodology, which requires the insertion of bases into the soil, underestimates N2O emissions when used in drip irrigation. “These effects can be mitigated through optimizing the chamber design. A nomogram is proposed…” .
Citation: https://doi.org/10.5194/egusphere-2022-141-AC1
-
AC1: 'Reply on RC1', Shahar Baram, 16 Jun 2022
-
RC2: 'Comment on egusphere-2022-141', Anonymous Referee #2, 16 Jun 2022
Review for Baram et al.,
In general, the manuscript is well and clearly written. In the manuscript authors aiming to resolve spatial variability issue in static-chamber based measurements of soil N2O emissions from drip-irrigated systems.
The study is comparing in situ measured soil emissions of N2O from two different positions of chambers, adjanct to the dripper and dripper inside of the chamber. Then authors using numerical modeling to explain observed differences between the two positions and to estimate “true” flux.
- Calculating cumulative emissions – why don’t you use linear interpolation? I do not think that your results will change, but I think that use of arbitrary Q10 is not any better than to estimate cumulative/daily flux using linear interpolation. Calculation of daily emissions can be done by dividing annual accumulative emissions by number of included in cumulative flux estimation days.
Hoben, J. P., Gehl, R. J., Millar, N., Grace, P. R., & Robertson, G. P. (2011). Nonlinear nitrous oxide (N2O) response to nitrogen fertilizer in on-farm corn crops of the US Midwest. Global Change Biology, 17(2), 1140–1152. http://dx.doi.org/10.1111/j.1365-2486.2010.02349.x
- Why do you think that your modeled emissions are better than observed? I think that for real answer if static chamber methods under- or overestimate real fluxes a comparison between static chambers and eddy-covariance based measurements is needed.
- You are using 3D flow model and some simple assumptions, you may model the water flow well, but I doubt that you can model N2O emissions. At least DayCent model, after ~30 years of development can not.
Lutz, F., Del Grosso, S., Ogle, S., Williams, S., Minoli, S., Rolinski, S., Heinke, J., Stoorvogel, J. J., & Müller, C. (2020). The importance of management information and soil moisture representation for simulating tillage effects on N2O emissions in LPJmL5.0-tillage. Geoscientific Model Development, 13(9), 3905–3923. https://doi.org/10.5194/gmd-13-3905-2020
I think that the manuscript of acceptable quality and importance and rising very important question of how to scale-up field-based measurements of soil gaseous emissions.
a) with all problems of using static chambers they provide good information on treatment differences and b) models today not ready to provide good estimation of field emissions. Therefore, static chambers will be used in the near future.
I am wondering if your proposed method to calculate optimal chamber (base) size for field measurements of soil N2O emissions (monogram) will provide better flux estimation. I think that few weeks of additional measurements comparing the proposed “optimal base size” with bases used to acquire data for the manuscript under discussion will improve the manuscript. If you are claiming that using modeled flow of water and nutrients, you can determine the optimal chamber – prove it.
Citation: https://doi.org/10.5194/egusphere-2022-141-RC2 -
AC2: 'Reply on RC2', Shahar Baram, 17 Jun 2022
Reply to comments made by Reviewer #2
We thank the reviewer for the comments and concerns.
Please find below our detailed replies to all the comments.
Comment 1: Calculating cumulative emissions – why don’t you use linear interpolation? I do not think that your results will change, but I think that use of arbitrary Q10 is not any better than to estimate cumulative/daily flux using linear interpolation. Calculation of daily emissions can be done by dividing annual accumulative emissions by number of included in cumulative flux estimation days.
Reply: We thank the reviewer for raising this point. All calculations were modified as suggested using linear interpolation and numerical integration between sampling times. The text was modified accordingly: “…by linear interpolation and numerical integration between sampling times. Cumulative N2O flux estimates for N2OIn and N2OAdjacent were taken as the average of the cumulative fluxes of the 12 individual chambers, each”.
Comment 2: Why do you think that your modeled emissions are better than observed? I think that for real answer if static chamber methods under- or overestimate real fluxes a comparison between static chambers and eddy-covariance based measurements is needed. And, Comment 3: You are using 3D flow model and some simple assumptions, you may model the water flow well, but I doubt that you can model N2O emissions. At least DayCent model, after ~30 years of development cannot.You are using 3D flow modeld and some simple assumptions, you may model the water flow well, but I doubt that you can model N2O emissions. At least DayCent model, after ~30 years of development cannot.
Reply: Our field measurements show that the measured N2O flux is highly affected by the location of the chamber’s base relative to the drip line. We agree that eddy-covariance based measurements may provide a good tool to validate our field measurement on a larger scale. Nevertheless, in the discussed emitter-spacing scale eddy-covariance could not be used.
Please note, that we do not think that our modeled emissions are better than the measured/observed emissions. Further, we do not think that the simple assumptions used by us to model N2O fluxes accurately capture the “true” N2O flux, as rightfully commented by the reviewer. Yet, our results raise a question as to what is the “correct” or the most representative way to capture the true ambient N2O emissions around a single dripper, part of a drip line, when using static chambers.
N2O fluxes are mainly driven by N availability and form (i.e., nitrate vs. ammonium), oxygen availability, and soil water content [readily expressed as the ratio between the volumetric water content and the porosity (WFPS)]. Thus, we decided to use a robust 3D flow model to study the effect that a chamber base may have on water and N distribution in the top soil. The main assumption for both the 3D flow model and the DIDAS model simulations/computations was that the ambient N2O emissions (i.e., not affected by the base) will be those emitted from a location with minimal perturbation by the base. That is, places where the N-form concentrations and distributions, and the water content are not affected by the base.
With this assumption in mind, the model was used to:
- Evaluate the impact of the dripper location relative to a base (i.e., inside, adjacent, few cm away, etc.);
- Find the optimal base diameter;
Comment 4: I am wondering if your proposed method to calculate optimal chamber (base) size for field measurements of soil N2O emissions (monogram) will provide better flux estimation. I think that few weeks of additional measurements comparing the proposed “optimal base size” with bases used to acquire data for the manuscript under discussion will improve the manuscript. If you are claiming that using modeled flow of water and nutrients, you can determine the optimal chamber – prove it.
Reply: In continuation to the reply to comments 2 and 3, to date, the standard method for static chambers calls for the use of basses. Hence, there is no way to get the “true” ambient N2O emissions from a single dripper. With that in mind and the model’s limitation in predicting N2O emissions (simplified assumptions), we do not see how few weeks of additional measurements comparing the proposed “optimal base size” with bases used to acquire data will benefit the manuscript.
Our intention was to merely raise the problem of the systematic, 3D heterogeneities around a dripper, to present relevant, simulated results, and to propose relevant methodologies assisting in deciding regarding the size and placement of the base. It will take many users in many conditions (soil types, wetting patterns, variable N carbon (C) and O regimes), rather than a single study, to tell whether these methodologies are constructive or not.
Citation: https://doi.org/10.5194/egusphere-2022-141-AC2
Peer review completion
Journal article(s) based on this preprint
Viewed
HTML | XML | Total | Supplement | BibTeX | EndNote | |
---|---|---|---|---|---|---|
243 | 44 | 10 | 297 | 25 | 6 | 5 |
- HTML: 243
- PDF: 44
- XML: 10
- Total: 297
- Supplement: 25
- BibTeX: 6
- EndNote: 5
Viewed (geographical distribution)
Country | # | Views | % |
---|
Total: | 0 |
HTML: | 0 |
PDF: | 0 |
XML: | 0 |
- 1
Asher Bar-Tal
Alon Gal
Shmulik P. Friedman
David Russo
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(1517 KB) - Metadata XML
-
Supplement
(600 KB) - BibTeX
- EndNote
- Final revised paper