the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 30 Aug 2024
Soil conditioner mixtures as an agricultural management alternative to mitigate drought impacts
Abstract. Agricultural activities in the northeastern German plains are at risk due to climate change. Soil amendment with conditioners that improve water storage is a plausible alternative to mitigate such risks. While single conditioner additions to soil can be positive, doubts regarding their individual scalability have been raised. An unexplored alternative is to apply multiple conditioners as mixtures, thus reducing individual application rates while harnessing possible complementarities derived from the interaction of diverse conditioner types. Here we report evidence suggesting that the addition of conditioner blends leads to significant improvements in soil properties not observed with single conditioner additions.
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Status: final response (author comments only)
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CC1: 'Comment on egusphere-2024-2566', Jaedson Mota, 21 Sep 2024
RC:
Abstract, Lines 7-12: It is important that the main results are included in the abstract.
Citation: https://doi.org/10.5194/egusphere-2024-2566-CC1 -
AC1: 'Reply on CC1', Juan F. Dueñas, 27 Sep 2024
Dear Jadson,
Thanks for your comment. We will make sure to include more details of our main results in a newer version of the abstract.
Best Regards,
Juan F Dueñas on behalf of the coauthors.
Citation: https://doi.org/10.5194/egusphere-2024-2566-AC1
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AC1: 'Reply on CC1', Juan F. Dueñas, 27 Sep 2024
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RC1: 'Comment on egusphere-2024-2566', Anonymous Referee #1, 30 Sep 2024
MS No.: egusphere-2024-2566
Reviewer
The article " Soil conditioner mixtures as an agricultural management alternative to mitigate drought impacts" is well presented and addresses a subject of environmental relevance and interest to the scientific community. The experimental procedures adopted are aligned with the precepts of the scientific method. The results are well discussed, and the conclusions are coherent.
Lines 60-61: Why was the duration of the experiment three weeks? What is the rationale for this trial period?
Lines 166-173: The mixture of conditioners promoted what we call “emergent processes or properties” – when several components compete to enhance attributes that were not expressed in the presence of just one of them. What role does each conditioner play in this tangle of beneficial effects on the soil? Of the conditioners evaluated, is it possible to establish the sequence of importance of each of them?
Lines 247-248: “For instance, biochar or silicon persist in soil for a significantly longer period of time than straw (Wahdan et al., 2023)”. Given the possibility of longer residence time in the soil, researchers consider the possibility of obstruction of soil pores by both materials. If this risk exists, the authors can suggest how to manage the application of conditioners?
Citation: https://doi.org/10.5194/egusphere-2024-2566-RC1 -
AC2: 'Reply on RC1', Juan F. Dueñas, 22 Oct 2024
The article " Soil conditioner mixtures as an agricultural management alternative to mitigate drought impacts" is well presented and addresses a subject of environmental relevance and interest to the scientific community. The experimental procedures adopted are aligned with the precepts of the scientific method. The results are well discussed, and the conclusions are coherent.
We would like to thank the reviewer for these positive comments.
Lines 60-61: Why was the duration of the experiment three weeks? What is the rationale for this trial period?
Thanks for your question. We designed this experiment to be an initial proof-of-concept. In that spirit we selected a simple microcosm system, which is attractive as it is easier to control and allows us to focus on soil processes and microbial organisms without having to consider the nuances introduced by the presence of a plant. Since it is reasonable to think that at the scale of this experiment, changes in soil processes and microbial taxa occur in a matter of hours to days, we considered the three week trial period as suitable to assess treatment effects, hence showing the potential of our concept. On the other hand, as the experiment seeked to simulate a moderate drought period, we considered that a drought that takes place for more than three weeks would not fall within this category, at least for the area of Berlin-Brandenburg. We intend to include this reasoning to justify the duration of the experiment in a new version of the manuscript.
Lines 166-173: The mixture of conditioners promoted what we call “emergent processes or properties” – when several components compete to enhance attributes that were not expressed in the presence of just one of them. What role does each conditioner play in this tangle of beneficial effects on the soil? Of the conditioners evaluated, is it possible to establish the sequence of importance of each of them?
This is an insightful remark and we thank the reviewer for the questions it raises. In our previous research with multiple stressors on soil, we have not been able to conclusively establish what role each of the individual components in a mixture is playing when it comes to the expression of a certain result. We have been able to establish that over a certain number of components, the system appears to be ‘steered’ in either a positive or negative trend. There are certain statistical methods that allow us to estimate whether the interaction of two factors is additive, multiplicative or antagonistic. However, there are no such methods available for interactions that include more than three factors. Latest research in our lab shows that the similarity in the mode of action and nature of individual components is a promising predictor of the magnitude and direction of the effect when present together in a mixture.
In summary, more research is needed to establish the role each individual factor plays when present in a mixture. At this point we can only propose which mechanism could be at play, which we believe we did in the discussion section (L189-L226). But in the absence of a good method to untangle the contribution of individual amendments, we prefer to use a more tentative language and leave the discussion as is.
Lines 247-248: “For instance, biochar or silicon persist in soil for a significantly longer period of time than straw (Wahdan et al., 2023)”. Given the possibility of longer residence time in the soil, researchers consider the possibility of obstruction of soil pores by both materials. If this risk exists, the authors can suggest how to manage the application of conditioners?
Thanks for another insightful comment and question. As far as we are aware, biochar can be incorporated into soil aggregates and is a porous material. Therefore, we do not think that pore obstruction is a major risk in that particular case. Having said this, there are still major gaps in our knowledge of the long term effects of biochar in soils, particularly regarding capture or release of heavy metals, emission of greenhouse gasses, and possibly residual liming effects. Regarding silica, we have very little data to determine whether the risk of pore obstruction exists. A conceivable risk arising from the longer residence time of amorphous silica could be that this material promotes soil disaggregation. Amorphous silica's most common industrial application is as an anti-caking agent. Hence, interference with soil aggregation could be considered risky as this can potentially lead to modification of the soil pore structure but also other important soil processes such as carbon fixation. We could include a couple of lines in the discussion section highlighting these potential risks.
Citation: https://doi.org/10.5194/egusphere-2024-2566-AC2
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AC2: 'Reply on RC1', Juan F. Dueñas, 22 Oct 2024
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RC2: 'Comment on egusphere-2024-2566', Anonymous Referee #2, 04 Oct 2024
The article is written in an understandable language an it is very interesting, I have almost no comments regarding the editing. But:
a) The authors only evaluated water retention capacity. For a stronger statement, other parameters should have been presented, such as soil porosity, hydraulic conductivity, among others. It is weak point of it;
b) In my opinion, the methods should be described in more details, as well as the choice of soil conditioners and the treatments (amendment mixtures) evaluated;c) When using Soil conditioner mixtures, changes in soil electrical conductivity may affect plant growth. This could be further explored;
d) The economic costs are crucial to the viability of the proposed scheme. Further discussion is recommended;
e) The researchers acknowledge the limitations of the research due to the short observation time and the scale on which the experiment was conducted. However, to conclude on the suitability of the conditioners tested based solely on the analysis of the parameters presented is a major oversimplification.
My detailed comments are below:
Abstract: I recommend rewriting the abstract with a brief description of the methodology, results and conclusion. The introduction should be shorter;
The text in lines 65 and 66 could be placed after the description of the soil collection in line 63;
The results of the soil chemistry analysis (lines 62-65) could be presented in a table;
Line 68: Why was the number of repetitions for the treatments of single amendments lower (n=8)?
Citation: https://doi.org/10.5194/egusphere-2024-2566-RC2 -
AC3: 'Reply on RC2', Juan F. Dueñas, 22 Oct 2024
The article is written in an understandable language an it is very interesting, I have almost no comments regarding the editing.
We thank the reviewer for the positive comments.
But:
a) The authors only evaluated water retention capacity. For a stronger statement, other parameters should have been presented, such as soil porosity, hydraulic conductivity, among others. It is weak point of it;We thank the reviewer for this observation, with which we agree. We deliberately chose a fast, yet least accurate method to determine water retention capacity because the scope of the paper was to create a proof-of-concept trial and given the amount of soil in our experimental units was rather small (35 g each, L68). We generally agree that the parameters that the reviewer is suggesting can serve to build a much stronger case to support the potential of our proposed drought adaptation strategy. However, as the reviewer might be well aware, to obtain such parameters would demand greater amounts of soil which we unfortunately did not envision for this particular experiment. We agree that our approach is therefore limited in the level of generalization it allows, yet we believe we have not hidden this limitation to the readers. In fact we make these and other limitations clear in the discussion section (L172-173) and at the introduction section (L49-58). We are open to add a statement in the introduction that better clarifies the scope of the experiment and we would be happy to include the suggestions of the reviewer as possible parameters to measure in future experiments at the discussion section.
b) In my opinion, the methods should be described in more details, as well as the choice of soil conditioners and the treatments (amendment mixtures) evaluated;We thank the reviewer for this comment. We believe the reviewer refers more specifically to certain procedures in the methods section in the specific comments below, each of which we will address individually. Regarding the amendment characteristics, we believe we provide plenty of information in both the introduction (L25-40) and method (table 1, L75-84) sections. We further provide a succinct statement of the rationale to select these amendments at the methods section (L67). We are unsure if the last part of the reviewer critique refers to how the treatments were analyzed (i.e. statistical procedures) or which treatments were included in the experiment. If the answer is the latter, then we believe we have explained this clearly in the methods section (L113-L119), which together with the main figure presented, should clarify to the reader which treatment effects were actually assessed.
c) When using Soil conditioner mixtures, changes in soil electrical conductivity may affect plant growth. This could be further explored;
This is a very insightful comment. We agree with the reviewer that this would be an interesting parameter to measure in an experiment that involves plants, hence we would be happy to include this as a recommendation in the discussion section.
d) The economic costs are crucial to the viability of the proposed scheme. Further discussion is recommended;
We thank the reviewer for this comment, with which we fully agree. One of the primary motivations for developing this procedure arose because of the doubts in the economic scalability of applying single amendments. We would be happy to say more about this in the discussion section (L242-243), but we fear that without actual data, further speculation will not add much to the current manuscript. If deemed necessary, we would be happy to provide a graph in the supplementing materials including an extrapolated estimate of how much each of these interventions would have cost had they been applied to a hectare of land. We however think that an economic viability study is outside the scope of this piece.
e) The researchers acknowledge the limitations of the research due to the short observation time and the scale on which the experiment was conducted. However, to conclude on the suitability of the conditioners tested based solely on the analysis of the parameters presented is a major oversimplification.
We thank the reviewer for this comment. We would like to clarify that nowhere in our manuscript do we present the observation time and scale of the procedure as a limitation. We simply recognize that, of the large arsenal of procedures available to an ecologist, microcosm experiments offer some advantages and present some obvious limitations. We further apologize if, by reading our manuscript, the reviewer got the impression we are concluding our procedure and the amendments we included to be ready for application at large scale. We would like to direct the attention of the reviewer to the lines 273-275 of the conclusion. We believe these lines emphasize the preliminary nature of this concept and agree with the critique of the reviewer. In other words, we are convinced that further testing is necessary to fully confirm the merits of the procedure. If deemed necessary we would be happy to include cautionary statements in other sections of the paper to make this clearer to the readership.
My detailed comments are below:
Abstract: I recommend rewriting the abstract with a brief description of the methodology, results and conclusion. The introduction should be shorter;
Thanks for the suggestions. We would certainly expand the abstract to include more details on the methodology and main results. We originally wrote this article as a short communication, which required the abstract to be limited to 100 words. Since the handling editor reclassified our manuscript as a research article, we will have more space to include the requested details. Regarding the introduction, we believe it contains essential details and is not long.
The text in lines 65 and 66 could be placed after the description of the soil collection in line 63;
We agree with this suggestion and we will implement it in a new version of the manuscript.
The results of the soil chemistry analysis (lines 62-65) could be presented in a table;
We agree with this suggestion and we will implement it in a new version of the manuscript.
Line 68: Why was the number of repetitions for the treatments of single amendments lower (n=8)?
A concise answer is to keep workload manageable during the experimental upkeep. Since the effects of single amendment addition had been thoroughly tested in the literature, and given the large number of experimental units that would have needed to be included due to: 1) the number of amendments in the panel (5), and 2) amendment combinations (please see L71-73), we found a compromise by reducing the number of replicates in the individual addition instances (from 50 to 40), and by only including random combinations of 3-way amendments. In other words, we monitored 80 instead of 180 possible experimental units without loss of statistical power. We would include a statement to clarify this rationale in the corresponding paragraph in the methods section.
Citation: https://doi.org/10.5194/egusphere-2024-2566-AC3
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AC3: 'Reply on RC2', Juan F. Dueñas, 22 Oct 2024
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