Water Infiltration in Different Soil Covers and Management in the Cerrado–Amazon Ecotone, Brazil

Round 1

Reviewer 1 Report

The manuscript presents an interesting field experimental study on infiltration on ywo sub-basins of the Amazon River watershed, Brazil, comparing the effects of soil, land useand location within the sub-basin on infiltration rates determined in the field using a rainfall simulador. As well explained in the Introduction, the infiltration is a key process of the water cycle and its appraisal is, therefore, a key element for catchment response studies. As also stressed by the authors, the study area represents na important case for addressing catchment hydrological response to rainfalls due to its actual land use and prospected changes. All elements considered, the data presented in the paper is a significant contribution for improving actual knowledgement about catchment infiltration in that area of the Globe, encompassing sensitive biomes as the Amazonia and the Cerrado.

The pape ris well structured, well grounded in literature and the objectives are clearly stated. Discussion and Conclusions are well elaborated sections.

Some improvements are, nevertheless require either in the methodology description or in results presentation, besides a necessary review of the English language, where special attention should be paid to scientificaly common  terminology.

Some major issues should be considered during the revision of the actual version of the manuscript:They concern statistics as related to the experimental design and to the comparisons and and conclusions that can be extracted from data analysis, namely by statistical inference. Results presented are not clear to this respect and authors should consider the comments included in the pdf version of the manuscript. Another nuclear issue is that concerning the criteria used to selecte the rainfall simulation sites, which requires some more information to be added to the presente formo f the manuscript. Thirdly, authors do not actually address or discuss  the issue of transferring point measurment data, as those of outcoming from rainfall simulations, to the catchment scale, which is the geographical unit selected a priori, certainly not by chance.

Somewhat surprisingly, the main issue that apparently drove the selection of the study area, which regards the transitional zone between two biomes and its change trends and threats to the water cycle of the Amazon watershed, is entirely waived out of the discussion. For the sake of coherence, authors could also consider this issue in their revision exercise of the manuscript.

The manuscript is recommended for publication after major revision and the commented pdf, together with the above stated comments, should be a basis for generating revised version, which is strongly encouraged.

Comments for author File: Comments.pdf

Author Response

Author’s Reply to the Review Report (Reviewer 1)

Comments and Suggestions for Authors

The changes were made and together with the suggestions of the other reviewers, they significantly improved the quality of the article. Thank you for your comments and suggestions.

PDF File

- Line 73: principal. Correct along the text

Response: The term “main” was replaced by “principal”

- Line 101: Design

Response: The term “organization” was replaced by “design”

- Line 118: It is not clear how the selection of the rainfall simulation rainfall runs was performed.

Authors should give more details on the selection criteria, considering not only the broad location (based on basin section of the basin and land use) but also on the site-specific characterisitics that might, might not, allow comparison between rainfall simulation sites.

Response: the characteristic of the simulated rain is presented in the following paragraph (PI = 75 mm h^-1, during 42 min). The rain application locations were defined in order to represent the characteristics of each use and land cover, in the different regions of the two sub-basins.

- Line 120: What does this mean?

Response: The text has been changed for better understanding

- Line 128: water height. Correct in all paragraph and text where applicable.

Response: The text was changed to “surface runoff depth”, which is more commonly used.

- Line 145: The other symbols in equations should be identified also. At least some of them have a common name in literature. It should be included, besides providing a physical interpretation when applicable. Also, what is R in the equations? Units should also be added.

Response: The text was changed and all variables were identified.

- Line 148: square

Response: The term “Quadratic” has been replaced by “square”

- Line 169 (Table 1): The sequence of particle size ranges should be from lowest to highest or vice-versa. Correct the position of collumns accordingly.

Response: The change was made as suggested. Thanks.

- Line 172: This is certainly not correct. Correct or clarify.

Response: The term “line” was replaced by “column”.

Line 181: These are not the symbols presented earlier. Correct

Response: The terms were replaced by “Rio and Rif”

Line 183: The comparison is was made between the 3 treatments for the entire set of data, meaning the entire column, by basin or by basin x land use.? The same question applies in the case of comparisons in line. Clarify in the footnote.

The comparisons in line should be between comparable results either Rif or Ri0, between sections of the basins. Comparing statistically the two rates is meaningless as for the experimental conditions described, and the common ones in similar studies, the two rates are sharply different.

The analysis should be able to reply to questions it does not reply in what regards their infiltration characteristis:

- Are the basins different? - Are their sections different? Is there an effect of land use that is different from basin to basin or section to section? One-way approaches like this one, with a design that assumes three-way analysis, are not appropriate.

Response: Thank you for the in-depth analysis of the statistics developed. We understand the notes and improve the identification score of the statistics performed. The main explanations were inserted in the table notes.

Line 198 (Table 3): See comment in a table above. Display the meaning of asteriscs in the footnote

Response: The change was made as per the suggestion and the asterisk was added to the footer of the table.

Line 240: Root mean square error. coefficient

Response: The change was made but the term “efficiency” was maintained as it had already been defined in the methodology.

Line 386: Summary explanations for the different responses of the two basins and the basins sections should be presented also in the conclusions

Response: The text was changed.

Once again, we thank you for your evaluation of the article and your important contribution to its improvement.

Reviewer 2 Report

The article addresses the important issue of water infiltration in different soils and under different forms of use. This parameter has a decisive influence on the flow of water in the soil. Reading the article gave me a few comments:

1) Lines 88-90: please provide soil classifications according to the current WRB classification.

2) Line 135: hydraulic conductivity: saturated or unsaturated ? please add this infromation

3) Lines 141-143 please provide an explanation of all symbols in equations 1, 2 and 3

4) Line 175 The initial (Tio) and final (Tif) infiltration rate or (Rio) and (Rif) ? please check these symbols with the title of Table 2 and its contents

5) Lines 372-385: conclusions: conclusions and inferences too general please give more detailed conclusions about the amount of infiltration depending on the type of soil and the form of its use based on Table 2

The research in the article was designed and carried out correctly, the results of the research and their interpretation are not objectionable, quite an extensive discussion was made comparing the results obtained in the paper with the results of other authors, the paper is suitable for publication after taking into account the above corrections in the MDPI journal Soil Systems.

Author Response

Author’s Reply to the Review Report (Reviewer 2)

The article addresses the important issue of water infiltration in different soils and under different forms of use. This parameter has a decisive influence on the flow of water in the soil.

Thank you for your comments and suggestion

Lines 88-90: please provide soil classifications according to the current WRB classification.

Response: In addition to the Brazilian Soil Classification System, the WRB classification was inserted.

Line 135: hydraulic conductivity: saturated or unsaturated ? please add this information

Response: the term “saturated” was added.

Lines 141-143: please provide an explanation of all symbols in equations 1, 2 and 3.

Response: Done

Line 175: The initial (Tio) and final (Tif) infiltration rate or (Rio) and (Rif)? please check these symbols with the title of Table 2 and its contents.

Response: The change has been made. Thanks.

Lines 372-385: conclusions: conclusions and inferences too general please give more detailed conclusions about the amount of infiltration depending on the type of soil and the form of its use based on Table 2

Response: The text was changed. Thanks

The research in the article was designed and carried out correctly, the results of the research and their interpretation are not objectionable, quite an extensive discussion was made comparing the results obtained in the paper with the results of other authors, the paper is suitable for publication after taking into account the above corrections in the MDPI journal Soil Systems.

Response: Once again, we thank you for your evaluation of the article and your important contribution to its improvement.

Reviewer 3 Report

Review of Soilsystem-1697423-submission:

In this article, water infiltration, surface runoff, and erosion in the sub-catchments of two smaller rivers of Teles Pires River in Brasilia and their agricultural areas with different vegetation cover are investigated using artificial sprinkler equipment at the top, middle, and bottom of the slopes. Authors analyzed the contribution of tillage, soil cover and properties on water infiltration and surface runoff generated by simulated rainfalls. The evolution of the infiltration rate of the studied areas depending on land use and soil properties was evaluated. Both the Horton and Philip infiltration models were found to be suitable for estimating infiltration rates in the Renato and Caiabi River sub-regions regardless of land use and land cover.

Main commands:

1.       The methods of determining either of the soil characteristics and plant mass values ​​listed in Table 1 are not given. There is only a reference in Brazilian language.

2.       Neither determination of the infiltration rate of the applied rain intensity of 75 mm/hour nor the method of measuring the surface runoff is described, for which the reference literature number 14 is not sufficient.

Minor commands:

Line nr

60: Concentric ring method in the European literature is called as double-ring method.

66: “occupations” is a not definite term for land cover or land use in the Amazon/Cerrado ecotone. Even the ecotone term is not well known for non-ecologist readers, so it worth to explain it. 

107 and 110: Neither V7 and V4 vegetative stage was not defined earlier, so reader doesn’t know their meaning.

111: The plant species name (Latin and Englis) of Brachiaria genus is not given. It would be important since different species have different heights and rooting depths.

113: Instead of soil without cover, better to use non vegetated soil, or non-covered soil or soil without coverage.

114: Does soil disturbance in 0-10 cm depth mean shallow tillage or minimum tillage cultivation? Please, use a more definite term.

114-115: The sentence here doesn’t have a clear message. Which depth was adopted to what plot size and how that affected the collection of surface runoff isn’t clear. 

116: Instead of the reference please give what rain duration and intensity was applied as well as the time sequence.

117-118: The reason why the non-covered soils were manually turned over is not given.

120-121: Meaning of areas with medium slopes of 3rd is unclear.

121: The IDF relationship should be defined because giving its literature source is not enough.

123: Why 42 numbers occur twice?

125: How pre-wetting could standardize the soil moisture condition in a variable moisture content soil region? Please, define the pre-wetting process in details.

127-129: How was taken into account dependence of the wetting layer thickness on the amount of precipitation in case of different texture soils?

133-134: Why don’t you use texture or particle-size distribution terms instead of granulometry? Why do you use soil density instead of soil bulk density? The reference for the determination of soil properties is in Brazilian, so please briefly describe them in English.

145: The definition of R is missing from here.

147: Maybe maximizing the R²?

178: How the empty state of the subsurface layer was determined? Was it only an estimation regarding to moisture content or infiltration data?

208: Fig. 2 Analysis of main principal components ….

232: Even though the title of the chapter refers to infiltration models, infiltration models should be written in the sentence as well.

251-253: The sentence message is not clear. Please, write it more concretely regarding the meaning of the mean to which crop are lower, plus what does it mean that pasture area follow the same behavior as the spring and the mouth?

273: …the initial and final infiltration rates …

277: There is no Ds values in Table 1.

310: It is not clear how the simulated rainfall broke the soil surface layer. The rainfall generally compress the surface of soil formulating a crust on it. Please explain your statement.

313: What does it mean that surface runoff is more concentrated?

315: What is physical-water quality mean?

345: Is cover or coverage the right term?

348: …soil bulk density …

354: Here instead of both crops please write that corn and soybean.

357: Please explain why the total sand content shows positive correlation while other soil properties and the stable infiltration rate correlated negatively?

378: …clay content or amount …

Please, find them in the minor commands of the review.

Author Response

Author's Reply to the Review Report (Reviewer 3)

In this article, water infiltration, surface runoff, and erosion in the sub-catchments of two smaller rivers of Teles Pires River in Brasilia and their agricultural areas with different vegetation cover are investigated using artificial sprinkler equipment at the top, middle, and bottom of the slopes. Authors analyzed the contribution of tillage, soil cover and properties on water infiltration and surface runoff generated by simulated rainfalls. The evolution of the infiltration rate of the studied areas depending on land use and soil properties was evaluated. Both the Horton and Philip infiltration models were found to be suitable for estimating infiltration rates in the Renato and Caiabi River sub-regions regardless of land use and land cover.

Thank you for your comments and suggestion

- The methods of determining either of the soil characteristics and plant mass values ​​listed in Table 1 are not given. There is only a reference in Brazilian language.

Response: text was changed in lines 138-153.

- Neither determination of the infiltration rate of the applied rain intensity of 75 mm/hour nor the method of measuring the surface runoff is described, for which the reference literature number 14 is not sufficient.

Response: the precipitation intensity of 75 mm h^-1 was calculated using the IDF relations for the study region, considering a return period of 10 years and an average rainfall duration of 42 min (lines 124-126). The procedure for determining the infiltration rate is described in the following paragraph (lines 127-132).

Line 60: Concentric ring method in the European literature is called as double-ring method.

Response: the term was changed. Thanks

Line 66: “occupations” is a not definite term for land cover or land use in the Amazon/Cerrado ecotone. Even the ecotone term is not well known for non-ecologist readers, so it worth to explain it. 

Response: the word “occupations” was changed to “cover”. The term “ecotone” refers to a transition area between 2 biomes. It has been added to the text. Thanks

Lines 107 and 110: Neither V7 and V4 vegetative stage was not defined earlier, so reader doesn’t know their meaning.

Response: definitions of V7 and V4 have been added to the text.

Line 111: The plant species name (Latin and Englis) of Brachiaria genus is not given. It would be important since different species have different heights and rooting depths.

Response: Brachiaria ruziziensis. Information inserted in the text.

Line 113: Instead of soil without cover, better to use non vegetated soil, or non-covered soil or soil without coverage.

Response: To be in line with other reviewers, we adopted the terminology “without coverage soil”.

Line 114: Does soil disturbance in 0-10 cm depth mean shallow tillage or minimum tillage cultivation? Please, use a more definite term.

Response: simulate shallow cultivation conditions (soil scarification)

Lines 114-115: The sentence here doesn’t have a clear message. Which depth was adopted to what plot size and how that affected the collection of surface runoff isn’t clear. 

Response: This layer of disturbed soil (0.0-0.10 m) was adopted to avoid subsurface horizontal movement of water, since the collection portion (in steel) reaches a maximum installation depth of 0.20 m; therefore, disturbance depths greater than 0.10 m do not guarantee that water moves only vertically in the soil layer.

Line 116: Instead of the reference please give what rain duration and intensity was applied as well as the time sequence.

Response: the duration and intensity of the rain applied are presented in the following paragraph (lines 122-126). The rains were applied in sequence and in the same position, that is, coverage soil (with vegetation), without coverage soil (removal of plant biomass – crop or pasture) and soil with disturbance at 0.10 m in layer (lines 115-117).

Lines 117-118: The reason why the non-covered soils were manually turned over is not given.

Response: The reason for manual turnover is related to the size of the experimental plot and the fact that rain is applied in the same position, as per the previous answer. To avoid changes in the physical characteristics of the soil, the experimental plot was not removed between one rain and another, and therefore, the turnedover was carried out manually.

Lines 120-121: Meaning of areas with medium slopes of 3rd is unclear.

Response: This information has been corrected and we prefer to present the slope of the area in decimal form (0.05 m m^-1).

Line 121: The IDF relationship should be defined because giving its literature source is not enough.

Response: the article cited [27] is the only study carried out in the region and, therefore, provides relevant information for determining the maximum average precipitation intensity. The 4 closest stations to the study area are: Alta Floresta, Foz Jusante Peixoto, Porto dos Gaúchos and Paranatinga. We understand that it is not necessary to present the IDF relationships for each station, as the reader has access to this information by consulting the aforementioned article.

Line 123: Why 42 numbers occur twice?

Response: We delete to the text one number “42”.

Line 125: How pre-wetting could standardize the soil moisture condition in a variable moisture content soil region? Please, define the pre-wetting process in details.

Response:  this information has been added and the text has been changed on lines 128-132.

Lines 127-129: How was taken into account dependence of the wetting layer thickness on the amount of precipitation in case of different texture soils?

Response: in fact, the thickness of the moistened layer was not taken into account. The intensity and duration of simulated rainfall were fixed for all regions and sub-basins, regardless of soil texture.

Lines 133-134: Why don’t you use texture or particle-size distribution terms instead of granulometry? Why do you use soil density instead of soil bulk density? The reference for the determination of soil properties is in Brazilian, so please briefly describe them in English.

Response: We correct the term “soil density” by “bulk density” in all the work (lines: 29, 136, 208,214, 220, 232, 262 and 359).

Line 145: The definition of R is missing from here.

Response: the definition was inserted in the text

Line 147: Maybe maximizing the R²?

Response: Done.

Line 178: How the empty state of the subsurface layer was determined? Was it only an estimation regarding to moisture content or infiltration data?

Response: no measurement was carried out with respect. It is just an observation regarding the process of water infiltration into the soil.

Line 208: Fig. 2 Analysis of main principal components ….

Response: Done.

Line 232: Even though the title of the chapter refers to infiltration models, infiltration models should be written in the sentence as well.

Response: The term has been changed.

Lines 251-253: The sentence message is not clear. Please, write it more concretely regarding the meaning of the mean to which crop are lower, plus what does it mean that pasture area follow the same behavior as the spring and the mouth?

Response: The text was changed.

Line 273: …the initial and final infiltration rates

Response: The term has been changed.

Line 277: There is no Ds values in Table 1.

Response: The term has been changed.

Line 310: It is not clear how the simulated rainfall broke the soil surface layer. The rainfall generally compress the surface of soil formulating a crust on it. Please explain your statement.

Response: Thanks for the comment. The text is really unclear and has been changed.

Line 313: What does it mean that surface runoff is more concentrated?

Response: The idea was to inform that due to the lack of coverage the effect of runoff is more intense, promoting greater soil loss. The text has been changed.

Line 315: What is physical-water quality mean?

Response: The text is not clear. We would like to highlight the possible changes in the physical-water attributes of the soil in pasture areas.

Line 345: Is cover or coverage the right term?

Response: We correct the term “coverage” by “cover”.

Line 348: …soil bulk density …

Response: The term has been changed.

Line 354: Here instead of both crops please write that corn and soybean.

Response: Done

Line 378: …clay content or amount …

Response: we used clay content.

Once again, we thank you for your evaluation of the article and your important contribution to its improvement.