Water Dynamics and Hydraulic Functions in Sandy Soils: Limitations to Sugarcane Cultivation in Southern Brazil
, Jorge Luiz Moretti de Souza 2, André Carlos Auler 2, Ricardo Augusto de Oliveira 3, Renã Moreira Araújo 3, Aaron Kinyu Hoshide 1,4, Daniel Carneiro de Abreu 1,5 and Wininton Mendes da Silva 6
Round 1
Reviewer 1 Report
The principal goal of this paper is to document the physical characteristics of soils planted to sugarcane in a well-drained sandy Oxisol of Brazil. In light of these measured characteristics, the authors hoped to provide land-use considerations that improve the continued cultivation of this species.
The methods used in this study consisted of measuring the saturated hydraulic conductivity, unsaturated hydraulic conductivity, and porosity of samples that were evaluated. It was not clear how many samples were evaluated, but several statistical tests were performed on the datasets to evaluate similarity of results at different depths. The authors present a series of methods used to calculate available water contents and easily available water contents. The parameter symbology adopted for these expressions can be difficult to follow at times, making the analytical techniques somewhat difficult to evaluate. Many of the equations that were presented could be easily referenced in a supplement to the manuscript, if desired.
Overall, I think the paper has a lot of good content and provides data necessary to understand the sustainability of sugarcane cultivation for the soil of interest. The study provides quantitative metrics that can be used for evaluating best practices for sugarcane cultivation locally. In general, the manuscript is well-structured but requires a bit of effort before it is ready for publication.
There are two general items that require minimal effort to fix throughout the text. First, the authors have a tendency to continue redefining their acronyms and units, especially for trivial abbreviations of length (e.g., m), mass (e.g., kg), etc. Please ensure that these are not explained beyond their first usage, if necessary. Additionally, the authors incorrectly use significant figures throughout the manuscript, both in tables and in-line text. I have included specific examples in my detailed comments document so that the authors can correct this issue.
The authors present and discuss their results in terms of variability in soil loss at the site. However, they never mention soil loss and compaction explicitly as motivating factors of the study. I recommend that the authors either present this information in a dedicated background section or in a dedicated paragraph of the introduction to ensure that the message of the paper is fully realized from the beginning to end of the manuscript.
Comments for author File: 
Comments.pdf
Author Response
Comments and Suggestions for Authors
The principal goal of this paper is to document the physical characteristics of soils planted to sugarcane in a well-drained sandy Oxisol of Brazil. In light of these measured characteristics, the authors hoped to provide land-use considerations that improve the continued cultivation of this species.
The methods used in this study consisted of measuring the saturated hydraulic conductivity, unsaturated hydraulic conductivity, and porosity of samples that were evaluated. It was not clear how many samples were evaluated, but several statistical tests were performed on the datasets to evaluate similarity of results at different depths. The authors present a series of methods used to calculate available water contents and easily available water contents. The parameter symbology adopted for these expressions can be difficult to follow at times, making the analytical techniques somewhat difficult to evaluate. Many of the equations that were presented could be easily referenced in a supplement to the manuscript, if desired.
Overall, I think the paper has a lot of good content and provides data necessary to understand the sustainability of sugarcane cultivation for the soil of interest. The study provides quantitative metrics that can be used for evaluating best practices for sugarcane cultivation locally. In general, the manuscript is well-structured but requires a bit of effort before it is ready for publication.
There are two general items that require minimal effort to fix throughout the text. First, the authors have a tendency to continue redefining their acronyms and units, especially for trivial abbreviations of length (e.g., m), mass (e.g., kg), etc. Please ensure that these are not explained beyond their first usage, if necessary. Additionally, the authors incorrectly use significant figures throughout the manuscript, both in tables and in-line text. I have included specific examples in my detailed comments document so that the authors can correct this issue.
The authors present and discuss their results in terms of variability in soil loss at the site. However, they never mention soil loss and compaction explicitly as motivating factors of the study. I recommend that the authors either present this information in a dedicated background section or in a dedicated paragraph of the introduction to ensure that the message of the paper is fully realized from the beginning to end of the manuscript.
Corrections were made to the manuscript.
Soil porosity (TP, macro and micro) were determined from soil water retention curve.
The pore distribution curve was also calculated from the soil water retention curve according to Silva et al. (2018) [3] (https://doi.org/10.1590/18069657rbcs20180058)
In order to estimate the actual volumetric moisture and matric potential at field capacity, we assumed this condition is reached when the drainage rate (?) is a percentage (p) of the saturated hydraulic conductivity (KS) based on Prevedello (1999) [21]. “this condition” is the condition for field capacity according to Prevedello. The values of p were also based on Prevedello's article.
The description of the parameters of equations 5 through 12 are right after equation 12. Since most of the parameters of these equations are repeated, the authors will decide to describe them all at the end.
The same happens in the sequence of equations 14 through 18.
Estimation of the "Θ" function was performed in a routine developed in the R statistical program. A script (routine) was made in the R language to estimate the "Θ" function.
The observed discrepant values were removed. Used 6 repetitions.
peer-review-26995729.v1.pdf
Submission Date
31 January 2023
Date of this review
10 Feb 2023 19:48:24
Reviewer 2 Report
Dear Authors
I found some inconsistencies in Table 1 that affected the resulst. Please see that attached pdf
Regards
Tammo
Comments for author File: Comments.pdf
Author Response
Comments and Suggestions for Authors
Dear Authors
I found some inconsistencies in Table 1 that affected the resulst. Please see that attached pdf
Regards
Tammo
For the 0-20 cm depth, the coarse, fine silt and clay weight (i.e., 769.7, 120.7, 67.6, 94.8), I obtain a total of 1052 grams/100o gram. This is greater than the total of 837.6 grams. Moreover, the total should not be more than 1000 grams.
Yes, two samples were used. The first was performed the separation of the sand, silt and clay fractions (837.6, 67.6, 94.8 = 1000). Due to the importance of sand fractionation, the separation of coarse and fine sand fractions was performed.
This 0.41 cm3 cm-3 is different than the porosity of 0.33 cm3 cm-3 cited for the 0-20 cm depth in the same table.
Yes, different methods were used. The determination of the particle density was with the volumetric flask method in deformed samples. The porosity was obtained with the soil water retention curve in undeformed samples.
This needs to be improved before this article can be reviewed. Moreover, I do not understand why soil physical measurement should be published in a journal that deals with sustainability. Finally, the authors should justify why the soil physical properties of a sandy soil in Brazil are of interest to a worldwide audience.
In light of the increasing demand for food and biofuels, as well as climate change that interferes with water availability for both human consumption and agriculture. Understanding the physical water attributes of soils is critical for the adoption of sustainable management practices that can promote food security and biofuel availability. We have clarified the sustainability implications and global relevance at the end of the Conclusion section.
peer-review-26995745.v2.pdf
Submission Date
31 January 2023
Date of this review
08 Feb 2023 19:45:01
Reviewer 3 Report
After careful reading, I consider that the structure, logical flow, literature review and statistics used in this manuscript need to improve further.
Authors made frequent mistakes throughout the MS. The authors would do well to refer to other peer-reviewed publications for guidelines on what is most appropriate in tables, results, and figures, and what is better placed in an appendix.
Although I am aware that there is a great effort behind the manuscript, there still are several difficult parts for publication.
My details comments are in attached zip file.
Comments for author File: Comments.zip
Author Response
Comments for ‘Water Dynamics and Hydraulic Functions in Sandy Soils: Limitations to Sugarcane Cultivation in Southern Brazil’
All suggested corrections were made to the manuscript.
|
Line number |
Comment |
|
22 |
Check grammar errors |
|
22 |
Need to be more scientific in writing Ex: don’t use ‘we’ |
|
24 |
Since ‘m’ is a SI unit, no need to explain the symbol, |
|
25-28 |
No need to give much attention for analyzing parameters in the abstract. Instead of that, try to explain more findings and conclusions. |
|
|
Better to rewrite the abstract section |
|
41 |
Its variability….. |
|
42 |
What is meant by “Influencing aeration” |
|
50 |
Give SI unit symbols |
|
50-51 |
Is 58.7 of AWC for pineapple cultivated soils? For sandy soils |
|
56 |
Give SI unit symbols |
|
58 |
Variations in practical size distribution |
|
64 |
Give SI unit symbols |
|
91 |
Symbol is enough |
|
99 |
Need to be more scientific in writing Ex: don’t use ‘we’ |
|
106, 107, 111, 124, 134, 137, 168, 273, 280, 323, 310, 305,339, 340, 363, 371 |
Symbol is enough |
|
137, 142, 220 |
Check whether those tension values are really negative Yes, because it is the matric potential of water in the soil. |
|
173 |
Keep a distance after stopping a sentence |
|
273 |
Quantify the value; higher or lower |
|
274 |
Rewrite the sentence, meaning is not clear |
|
281 |
….. with increasing the sand fraction…. |
|
284 |
Rewrite it, check with the data |
|
297 |
…. With increasing depth… Cite the figure correctly |
|
Figure 1 a |
Cite this figure in your text |
|
Table 2 |
Better to center the data; otherwise, readers may confuse. Ex: 95% confidant interval column |
|
Figure 2 |
Reduce the font size of figure titles and keep in same font as the text |
|
Table 4, Table 5, Table 6 |
Maintain the uniformity in data presenting. In some depth you have mentioned significance symbol in upper case, but in some depths it is not. Please check |
|
Figure 3 |
Keep in same font as the text |
|
364 |
Why italic? |
|
Figure 4 |
Try to avoid overlapping the content Reduce the font size of axes titles Keep same font style as text |
|
Table 1, Table 6, Table 7 |
Check the table titles; some words are italic in some point. |
|
421, 425, 433 |
Keep citation at the end of the sentence |
|
443 |
Don’t use ‘we’ |
|
370, 373 |
Why P>0.05 |
|
597 |
Is it Mt or t? symbol and units are not matching metric tons per hectares (t/ha) |
|
|
Give few points about future research potential on this field |
Round 2
Reviewer 1 Report
There are still a few areas that could be improved with minor edits. I've tracked those in the uploaded document.
Comments for author File: Comments.pdf
Author Response
Comments and Suggestions for Authors
There are still a few areas that could be improved with minor edits. I've tracked those in the uploaded document. peer-review-27690516.v1.pdf
We have made requested minor edits from the pdf file including:
- We added a paragraph on the geomorphology of the experimental site. The Latossolos are at the top, the predominant pedogenic processes are associated with vertical subsurface soil water movement (Thomaz; Fidalski, 2020). The Caiuá Aquifer is an important water source for the northwest region of the state of Paraná, with an outcrop area of approximately 30,000 km². This aquifer is characterized by being free and porous, with bicarbonated calcic to calcium-magnesian waters. The aquifer is composed of aeolian sandstones from the Caiuá Group, which were deposited in the Upper Cretaceous over a paleodepression formed by the basaltic flows of the Serra Geral Formation (Pereira, 2016).
Added References:
Pereira, Thomaz Yanca Zulpo. Avaliação da vulnerabilidade e fontes de contaminações. Difusas e pontuais do aquífero Caiuá. Universidade Federal do Paraná. Setor de Ciências da Terra. Curso de Geologia Curitiba, 2016.
Thomaz, E. L.; Fidalski, J. Interrill erodibility of different sandy soils increase along a catena in the Paranavaí Alloformation. REVISTA BRASILEIRA DE CIENCIA DO SOLO, v. 44, p. 1-13, 2020.
- We have changed so are not using the adjectives ”deformed” and “undeformed” when describing soil samples.
- Clarification of separation into grain fractions followed by weighing of grain fractions.
- We changed the x-axis title in Figure 1a to “Depth interval (m)” by adding (m).
- The error bars in Figure 1a are in cm/hour and not in one or two standard deviations (sigmas). We have clarified this in the caption for Figure 1.
- We have changed to just using m and not meter in the legend for Figure 4.
- We have clarified the writing as requested to read:
“The variables fine sand, clay, microporosity, volumetric soil moisture at the permanent wilting point, volumetric soil moisture at the inflection point, soil density, and available soil water capacity (–6 kPa) were higher and had more expressive physical-hydric attributes in the soil layers at depths of 0.2 to 0.4 m and 0.4 to 0.6 m (Figure 4).”
- We have edited the manuscript to not imply “accumulation” of clay content in the lower soil layers at the beginning of the Results section and at the start of the Discussion section. We have removed the first sentence at the start of the Discussion section regarding the “pedogenetic process of clay loss.”
Additional responses to comments are as follows:
Still unclear. do you mean that it is defined this way? If so, then say so. If this is the case, the sentence is still misleading... You state that field capacity is conditional upon drainage rate being an arbitrary percentage of Ks. The drainage rate is always some percentage of Ks, so how can field capacity be determined in this way?? I think this just needs some rewording and clarification. The authors must explicitly state what "this condition" refers to. Unclear as written.
We have clarified this in the writing. The estimated moisture at field capacity occurs when the drainage rate is considered negligible. With the KS equations and the soil water retention curve, it is possible to perform an iterative process (programming). Equation 6 is simplified by considering that the field capacity condition is reached when the drainage rate reduces to a given percentage (p) of saturated hydraulic conductivity.
Reviewer 1: again, equation 12 yields units of L/T (i.e., velocity). How do you pull the time out? pstill does not appear in eq 12. Am I missing something?
Using the analytical model of soil water redistribution, the unsaturated soil hydraulic conductivity equation was derived with respect to ? and equated to z/t. Knowing z, we were able to calculate t. The description of the parameters in equations 4 through 12 are right after the presentation of equation 12. This is why p appears after equation 12.
Submission Date
31 January 2023
Date of this review
03 Mar 2023 16:54:55
Reviewer 2 Report
Dear authors
My apologies, but I do not understand how this manuscript can contribute meaningfully to the sustainability of sugar cane production since the soil physical characteristics of one soil have been determined once. . It should be submitted to a soil or hydrology journal.
More detail is given in the attached file
Comments for author File: Comments.pdf
Author Response
Comments and Suggestions for Authors
Dear authors
My apologies, but I do not understand how this manuscript can contribute meaningfully to the sustainability of sugar cane production since the soil physical characteristics of one soil have been determined once. . It should be submitted to a soil or hydrology journal.
We agree that the manuscript as originally written and modified is focused solely on soil hydrology. We have added additional analysis taking a sugarcane model already published in this MDPI Sustainability Special Issue and simulating sugarcane yields at different values for AWC and EAW. We have changed the Discussion section to focus on the sustainability implications of this new analyses based on the experimental results.
More detail is given in the attached file: peer-review-27690509.v2.pdf
We have made requested minor edits from the pdf file including:
- We have clarified the label as “Sand classification” to avoid confusion.
- Porosity was calculated with the soil water retention curve in the paragraph at the bottom of page 3:
“Total porosity (TP), measured in cubic meters (m3) of air space per volume of soil (m3), was considered equal to the volumetric soil moisture at saturation (θs) which was also measured in m3 / m3 of soil. The microporosity measured in m3 / m3 of soil corresponded to the volumetric moisture of the soil sample submitted to a tension of −6 kilopascals (kPa). The macroporosity also measured in m3 / m3 of soil was obtained by taking the difference between the value for TP and the value for microporosity [14].”
- We appreciate the comments on the inability of our research to allow for conclusions on green harvesting since we did a one-time sampling. We have changed the focus of the Discussion and Conclusion on improving modeling of sugarcane yields given the sandy soils at the experimental site. This translates directly to improving the economic sustainability of Brazil’s sugarcane industry which has indirect positive environmental implications such as using sugarcane to replace degraded pasture.
- The static water level of the aquifer measured in deep tubular wells was between 5 and 50 meters deep, representing 99% of the aquifer (Pereira, 2016).
Added Reference:
Pereira, Thomaz Yanca Zulpo. Avaliação da vulnerabilidade e fontes de contaminações. Difusas e pontuais do aquífero Caiuá. Universidade Federal do Paraná. Setor de Ciências da Terra. Curso de Geologia Curitiba, 2016.
- We are keeping the number of significant figures for rounding to three so rounding to the thousandths place for Table 1 so this is consistent with other tables for double digits numbers that are close to each other that are being compared, single digit numbers, and numbers less than one.
- We have rounded data in both Table 4 and Table 5 to the thousandths place or to one to three significant figures to be consistent with rounding in other tables as explained in 5) above.
Submission Date
31 January 2023
Date of this review
06 Mar 2023 16:06:30
Round 3
Reviewer 2 Report
Dear authors
The content in the manuscript has been connected to the sustainability of high sugar cane yields in Brazil.
However, still, the data are reported with too many digits, Only the significant digits should be kept. Since this is the third time that I remark that there are too many digits, I have attached the pdf with the rules for rounding off to the significant digits.
Comments for author File: Comments.pdf
Author Response
Comments and Suggestions for Authors
Dear authors
The content in the manuscript has been connected to the sustainability of high sugar cane yields in Brazil.
However, still, the data are reported with too many digits, Only the significant digits should be kept. Since this is the third time that I remark that there are too many digits, I have attached the pdf with the rules for rounding off to the significant digits.
Thanks very much for this feedback! We have rounded off or specified all data presented in tables to 3 significant figures based on the accuracy of the data measurements that were made as well as clarity in distinguishing numbers that are statistically significantly different from each other.
peer-review-28640173.v1.pdf
Submission Date
31 January 2023
Date of this review
18 Apr 2023 18:54:28
