the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 05 Jun 2024
Assessment of the Effect of Soil Amendments and A Three Phase Soil Water Retention Model
Abstract. Nowadays, using soil amendments to improve physical hydrological properties is popularly employed in agricultural engineering. This paper at first reports an experiment to compare the effect of two different soil amendments for their effect on soil water retention capacity. They two agents are the natural clay and a conditioning soil retainer. Soil water retention curve (SWRC) has been selected to quantify their effect on a benchmark pure sand soil in full range of water saturation, i.e. from fully saturated to nearly dry. Both the classic van Genuchten model and a novel three phase soil water retention model have been adopted to characterize the effect of the two soil amending agents on soil water retention capacity. The research results demonstrate that the clay has a significant enhancement on soil water retention at low content of clay and high soil water content range, however its effect reduces considerable with increasing clay content. Meanwhile the conditioning water retainer shows little effect at high soil water content range but has significant effect on soil water retention at low soil water content range. The results indicate the conditioning water retainer can help the reduction of the surface water evaporation and the water reservation underneath. The modelling has shown that the three-phase model is able to effectively represent the soil water retention curve in full range of soil water content, which provides a convenient tool to efficiently characterise the effect of conditioning water retainer. In addition, the three-phase model also provides the functional analysis and help understand the working mechanisms of the agents.
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Status: open (until 31 Jul 2024)
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RC1: 'Comment on hess-2024-161', Anonymous Referee #1, 21 Jun 2024
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Review report for: "Assessment of the Effect of Soil Amendments and A Three Phase Soil Water Retention Model"
In this paper the authors present a duel method retention curve evaluation procedure to evaluate the retention curve on a wide range of saturation degrees, and suggest a unified empirical model to evaluate the retention curve in the entire saturation spectrum. In addition, this paper presents an evaluation of adding a surface tension amendment to different soil mixtures with different fraction of clay to sand.
Here are my thoughts about this manuscript:
Readability: the paper is well organized and easy to follow. However, the paper includes some typos and many grammatical issues that are mostly annoying. In some cases, these errors reduce the intelligibility of the text. The reference list is not well organized (not uniform, duplicate entries, not all references are cited, etc.).
The importance of this study draws, according to the authors, from agricultural engineering in climatic unstable conditions. However, it eludes me how suction tension of more than 100MPa and saturation degrees below 10-3 are relevant for agricultural practices. Moreover, "improving" the retention curve according to this paper means more water in the soil, it remains unclear how unextractable high water content aids plants. The feasibility of adding clay and homogenization the soil mixture at any relevant agricultural scale is also not clear.
The scientific quality and methods are inadequate. The experiments are conducted without repetitions. The different methods used to evaluate the retention curves at the different ranges directly affect the treatment (leaching vs evaporation affect the polymer concentration), but this is not discussed at all in the method section and partly mentioned in the results. The type of clay mineral used is not mentioned. The porosity values of the different soil mixtures and the surface tension of the different polymer concentration are not reported. The model, is composed of a superposition of pressure elements of different process. It is based on a large number of strictly empirical constants. It is not mentioned how the parameters are fitted. The paper states that the model help understand the working mechanisms of the agents, this is not the case. The parameters are not discussed at all, and there is no attempt to correlate the parameters to the different soil properties while very week and non-monotonic effect of the amendment is presented. Despite the many parameters (9!), the model fails to satisfy the basic physical conditions at fully saturated and dry media.
Finally, the analysis of the results is very limited. There are no recommendations on if/how to use the polymer. The usability of the model is unclear, how do the authors expect a practitioner to evaluate the different parameters? There is no physical discussion on the parameters or the results. For example, what is the meaning of the alpha=beta observation? why all the fitting parameters have negative values? The fitted absolute large values of the parameters suggests very unstable and sensitive model which is unlikely to work for transient numerical schemes. Additional aspects that are not in the scope of this paper are not mentioned, such as the expected effects on the water flow and its distribution due to changes in the capillary forces.
Therefore, I suggest not to publish this work in HESS.
For future publication attempts, I attach some specific comments:
- Check typos and grammatical errors (for example):
- "They" instead of "The" in line 21
- "farce" in line 284
- Line 44 – Lemos et al. 2021 is not a good citation for this claim; I suggest you look for a relevant review.
- Line 47—Spitalaniak et al., 2019—also looked for the matric potential (i.e., a water availability indicator).
- Line 47 – Xerdiman et al., 2022 – investigated the construction of artificial soil on rocky slopes – not sure how this is related to this work.
- Lines 178-179 – 3 times increase compared to what?
- Line 180: "However, when the clay content is over 30%, the effect on soil water content increment becomes much less." It is not clear what you mean.
- Line 182: the difference in the saturation degrees is larger in high suction values, but the trend is more pronounced in the intermediate values (as expected).
- Line 183: The volume of surface film water is very small (what is the width of the film you are considering?). you don't need it. The reduction of pore sizes can explain this observation.
- What are the porosity values of the different soil mixtures?
- 2a – can you explain the non-monotonic behavior in clayey sand B for the high-suction? Using repetitions might help understand if this is an artifact or not.
- Line 190: I don't see this effect. In Fig.3a, clayey sand A, the saturation of the different treatments 3%>0%>5% for almost the entire suction spectrum, and in clayey sand B (Fig. 3b) 5%>0%>3% (up to the suction anomaly). Maybe if you use a linear axis, you will be more convincing. Also, repetitions and statistical evaluation may help.
- Line 216 – What do "inaccessible pores" mean? if they can be saturated, then why not drained?
- 4b is not mentioned in the main text. The proportionality of the residual "water" saturation to the initial WR concentration may suggest that the WR precipitated as a solid.
- 2: Remove one of the three equations (I think it is better to remove 2b).
- is Ss different than one? If not, it is redundant. Just put 1 in the equations.
- Line 259: is pb different from pv in Fig. 6? Please clarify
- Line 261: what are empty pore surfaces? The vapor-filled ones?
- 9, please clarify how the physical bounds at dry and saturated media are reached
- 7: the fitting procedure of the models is not explained. What are the values of the different constants, how do they relate to the clay and sand content and to the WR concentration?
- 8. It would be helpful if you kept the same colors as in previous figures for the different treatments. At the very least, keep the same colors for the different treatments in the plot (e.g., why do yellow markers confirm to the purple line and so on?)
- Line 352: The word "predicted" is used loosely. Have you forward estimated the fitting parameters?
- 10: What is the physical interpretation of the negative capillary suction values near saturation?
- 12: what about g?
- References: please revise the reference list. For example:
- You have two papers with the same authors and title that were written in the same year and published in the same journal on different pages (see Wang et al., 2008).
- Sometimes, you use a comma after the year and sometimes a dot.
- Not consistent italics for journal names.
- Not consistent "and" between authors (e.g., line 493)
- What is West Lebanon, NH (line 504)?
- Mikhail et al., 1968 not referenced.
- Monnier et al., 2010 not referenced.
- Also, in the text, you cite, for example, Wang et al., 2022 (in lines 55 and 57), but it is not clear to which entry in the reference list you are referring.
Citation: https://doi.org/10.5194/hess-2024-161-RC1 - Check typos and grammatical errors (for example):
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