Bedrock Fragment Induced by Intensive Tillage Effect on Hydrological Properties and Erosion Processes under Different Rainfall Patterns
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThe presented study aimed to study the impact of various simulated rainfall intensities and soil rock fragments content on selected hydrological characteristic. The study provides valuable results on how the different rainfall pattern influence the occurrence of runoff processes, however the study failed to clearly address, how are these processes influenced by the presence of rock fragments.
Regarding the manuscript, I have following comments:
L 31-33: "Among the variable rainfall patterns, the soils with bedrock in the decreasing rainfall pattern significantly increased sediment yield and also had a promoting effect on runoff generation. The soils with bedrock displayed better erosion resistance compared to the soils without bedrock under different rainfall patterns." – contradicting statement
L 55: few aggregates, low aggregation – the statement is repetitive
L 67: gravel content in %
L74: “This makes it prone to fragmentation by tillage equipment, enhancing the operability of compensatory cultivation practices” – the meaning of this sentence is unclear
L 113: The soil type should be described according to latest WRB classification
L 132: the picture of an experimental setup would be an asset
L 195: I the text, I suggest to use abbreviations for sample with and without bedrock
L 384-387: The statement in these sentences is contradictory. First, you state, that the presence of rock fragments promotes surface runoff, in next sentence you state, that presence of rock fragments enhances soil erosion resistance, thus reducing the soil loss.
L 387-388: It is obvious, that presence of bedrock fragments leads to increase of skeletal material. This statement is duplicative.
L 416-418: This statement is repetitive, the same was claimed also in L: 392-394
The first and main study objective was described as: how bedrock fragment affects the soil hydrodynamic parameters, but instead, the discussion section was focused more on impact of different rainfall pattern, while impact of rock fragments was poorly described, often with contradictory statements.
The third goal, application of WEPP model was not addressed by the study at all. I suggest to redefine the study objectives.
How are the simulated results transferable to field or catchment scale?
Comments on the Quality of English LanguageSome minor language revision required.
Author Response
Response to Reviewer 1 Comments
The presented study aimed to study the impact of various simulated rainfall intensities and soil rock fragments content on selected hydrological characteristic. The study provides valuable results on how the different rainfall pattern influence the occurrence of runoff processes, however the study failed to clearly address, how are these processes influenced by the presence of rock fragments.
Response: Thank you very much for your careful reading and constructive comments. We have added some sentences to describe the occurrence of runoff processes influenced by the presence of rock fragments. Some sentences was written to introduce that soil hydrological characteristic and erosion process was influenced by the presence of rock fragments (please see Lines 375-.389.
Regarding the manuscript, I have following comments:
L 31-33: "Among the variable rainfall patterns, the soils with bedrock in the decreasing rainfall pattern significantly increased sediment yield and also had a promoting effect on runoff generation. The soils with bedrock displayed better erosion resistance compared to the soils without bedrock under different rainfall patterns." – contradicting statement
Response: Your suggestion are very reasonable. We have rewritten the sentences to be more stated clearly.
E.g., Among the variable rainfall patterns, the WB significantly increased sediment yield and also had a promoting effect on runoff generation. However, the WB displayed better erosion resistance compared to the CK under constant rainfall patterns.
L 55: few aggregates, low aggregation – the statement is repetitive
Response: Yes, we have deleted “low aggregation”.
L 67: gravel content in %
Response: We have changed to gravel content in % according to your comment.
L74: “This makes it prone to fragmentation by tillage equipment, enhancing the operability of compensatory cultivation practices” – the meaning of this sentence is unclear
Response: Your suggestion are very reasonable. We have rewritten this sentence to be more clearly.
E.g., When the cultivated depths of the soil profiles is smaller than tillage depth applied by farmers, parent materials or mudstone bedrocks would be crushed by tillage operations to sustain retain a certain cultivated depth.
L 113: The soil type should be described according to latest WRB classification
Response: Your suggestion are very reasonable.
The soils in this area, formed from purple mudstone/shale of Jurassic age, and are classified as Eutric Regosol according to the FAO soil classification system. The soil texture is predominately loam (USDA classification) with 42.62% clay, 28.33% silt and 29.05% sand.
L 132: the picture of an experimental setup would be an asset
Response: Your suggestion are very reasonable. We have added a picture of an experimental setup (please see current Figure 1).
L 195: I the text, I suggest to use abbreviations for sample with and without bedrock
Response: Your suggestion are very reasonable. We have used WB and CK to represent with and without bedrock, respectively.
L 384-387: The statement in these sentences is contradictory. First, you state, that the presence of rock fragments promotes surface runoff, in next sentence you state, that presence of rock fragments enhances soil erosion resistance, thus reducing the soil loss.
Response: Your suggestion are very reasonable. We have deleted the sentence “Exposed bedrock obstruct surface runoff while forcing it to merge and concentrate around them” to be stated more clearly.
L 387-388: It is obvious, that presence of bedrock fragments leads to increase of skeletal material. This statement is duplicative.
Response: Your suggestion are very reasonable. We have revised this sentence to be more clearly.
L 416-418: This statement is repetitive, the same was claimed also in L: 392-394
Response: Thank you very much for your suggestion. We have deleted the sentences “Studies have shown that when these bedrock are distributed near the soil surface, they can reduce the cross-sectional area available for water flow, leading to water accumulation in the upper layers and increasing surface roughness”.
The first and main study objective was described as: how bedrock fragment affects the soil hydrodynamic parameters, but instead, the discussion section was focused more on impact of different rainfall pattern, while impact of rock fragments was poorly described, often with contradictory statements.
Response: Your suggestion are very reasonable. Some sentences have been added to describe the impact of rock fragments. We have carefully revised the discussion to avoid contradictory statements.
The third goal, application of WEPP model was not addressed by the study at all. I suggest to redefine the study objectives.
Response: Your suggestion are very reasonable. We have deleted the WEPP model, and revised this sentence to be stated more clearly.
How are the simulated results transferable to field or catchment scale?
Response: Your consideration are very reasonable. However, our research is only a theoretical research in the laboratory, due to the limitations of conditions, it can not be fully transferred to filed. In the future, we will consider more comprehensive factors to fill gap in this top, so as to transfer to field as much as possible.
Author Response File: 
Author Response.docx
Reviewer 2 Report
Comments and Suggestions for AuthorsThe article deals with the influence of bedrock fragments on the hydrodynamic parameters, runoff and sediment yield, of slope surfaces under different rainfall patterns. The rationale was well exposed with the “Introduction” section, so the problem could be fully understood. In this way, the “introduction” section is very informative.
I got surprised by number of outlined objectives (lines 91-102) and, after this, it can be said that the Abstract section fulfill its role. The authors focused to show at this section, a high quantity of results but failed to present what was really done and its context. As most of the readers had their attention caught by the article’s Abstract, it is important to rewrite it, showing only the most important findings and a concise, overall conclusion. As example, none was said about the use of the WEPP model at the Abstract. Information on lines 35 – 37 can be fully suppressed.
For the keywords, none of them should be in the title. About the latter, it looks like “Bedrock fragment induced by Intensive tillage effect on soil hydrological properties and erosion processes under different rainfall patterns” would be a better title, using the word “soil” and regarding its general construction.
The sections 2.1 and 2.2 are confusing within their contexts, because there is repeated information on both, and information regarding the soil sampling process are in the “experimental design section” what does not make sense. Also, it is not clear if the experimental essays were conducted at the cited farmland located in Qianjin Township, or only the soil was collected and brought to a laboratory. So, all these preliminary information should be restructured. A 2.1 section must be “Bedrock fragments and soil sources, sampling and preparation”, with 2.2 being “Experimental design” with information starting at “A movable hydraulic lift test trough (…)”. It is important to make clear where the experimental procedures took place. A schematic of the experimental apparatus needs to be presented. Also, there is no citation in the text about the number of experimental replications of each treatment. Because of the great experimental imprecision within this type of study, replications are just essential. How authors could guarantee the representativeness of the soil placed into the trough, comparing it to the natural soil?
For 2.3: Shouldn't hydraulic parameters be hydraulic variables? In addition, this is the most problematic section of the Material and Methods. There is no detailing in how some of the variables were experimentally obtained or observed so, the procedures cannot be repeated by any other research team. There is a need for detail at the level that there can be no doubt as how everything was accomplished and/or obtained. The measure instruments must also be cited and adopted values, as the presented “n” exponent, as example, should be presented and referenced. The presentation of the water kinematic viscosity model is very poor. Briefly, 2.3 needs to be greatly improved. As suggestion, a schematic of the trough can be presented, showing where measures were obtained.
To make it very clear:
a) How was flow velocity measured or calculated?
b) How was the hydraulic radius measured?
c) How was the hydraulic gradient determined? What was measured to determine it?
d) What was the source of the Kr value? Linked to what? The same for critical shear stress and n exponent. Regarding the effective shear stress, how was it measured or calculated?
e) How was water temperature measured?
Moreover, NONE was presented about the Water Erosion Prediction Project, cited in the objectives, what is very, very strange. The authors must justify this, or present the needed information.
For the results section, there is no experimental statistical analysis. Why? How authors can state differences comparing the experimental treatments, without a formal statistical analysis?
Comparing the amount of results data and the presented discussion, the discussion can be considered very shallow and did not cover all the presented results. The conclusion section is overall poor, only repeating the results presented.
Comments on the Quality of English LanguageThe English language is good, in general.
Author Response
Response to Reviewer 2 Comments
The article deals with the influence of bedrock fragments on the hydrodynamic parameters, runoff and sediment yield, of slope surfaces under different rainfall patterns. The rationale was well exposed with the “Introduction” section, so the problem could be fully understood. In this way, the “introduction” section is very informative.
I got surprised by number of outlined objectives (lines 91-102) and, after this, it can be said that the Abstract section fulfill its role. The authors focused to show at this section, a high quantity of results but failed to present what was really done and its context. As most of the readers had their attention caught by the article’s Abstract, it is important to rewrite it, showing only the most important findings and a concise, overall conclusion. As example, none was said about the use of the WEPP model at the Abstract. Information on lines 35 – 37 can be fully suppressed.
Response: Your suggestion are very reasonable. We have revised the manuscript according to your suggestion. We have deleted the WEPP model in the manuscript. In addition, we have delete the original sentences for lines 35-37 according your suggestion.
For the keywords, none of them should be in the title. About the latter, it looks like “Bedrock fragment induced by Intensive tillage effect on soil hydrological properties and erosion processes under different rainfall patterns” would be a better title, using the word “soil” and regarding its general construction.
Response: Thank you very much for your careful reading and constructive comments. We have changed the title according your suggestion.
The sections 2.1 and 2.2 are confusing within their contexts, because there is repeated information on both, and information regarding the soil sampling process are in the “experimental design section” what does not make sense. Also, it is not clear if the experimental essays were conducted at the cited farmland located in Qianjin Township, or only the soil was collected and brought to a laboratory. So, all these preliminary information should be restructured. A 2.1 section must be “Bedrock fragments and soil sources, sampling and preparation”, with 2.2 being “Experimental design” with information starting at “A movable hydraulic lift test trough (…)”. It is important to make clear where the experimental procedures took place. A schematic of the experimental apparatus needs to be presented. Also, there is no citation in the text about the number of experimental replications of each treatment. Because of the great experimental imprecision within this type of study, replications are just essential. How authors could guarantee the representativeness of the soil placed into the trough, comparing it to the natural soil?
Response: Your suggestion are very reasonable. Indeed, it is important to make clear where the experimental procedures took place. We have restructured the preliminary information according your suggestion. We have rewritten the sections 2.1 and 2.2 to be more stated clearly. We have presented a schematic of the experimental apparatus in the manuscript. Please see the new Figure 1.
Each treatment was conducted two times.
During the compacting process, the gravel and soil layer were packed in 5-cm increments, and each packed soil layer was raked lightly before the next layer was packed to ensure uniformity and continuity in the soil structure. The soil amount of each layer was kept as constant as possible to sustain similar bulk density and uniform spatial distribution of natural soil particles.
For 2.3: Shouldn't hydraulic parameters be hydraulic variables? In addition, this is the most problematic section of the Material and Methods. There is no detailing in how some of the variables were experimentally obtained or observed so, the procedures cannot be repeated by any other research team. There is a need for detail at the level that there can be no doubt as how everything was accomplished and/or obtained. The measure instruments must also be cited and adopted values, as the presented “n” exponent, as example, should be presented and referenced. The presentation of the water kinematic viscosity model is very poor. Briefly, 2.3 needs to be greatly improved. As suggestion, a schematic of the trough can be presented, showing where measures were obtained.
Response: Yes, hydraulic parameters are hydraulic variables. We have carefully revised the section 2.3 to be stated more clearly.
We have added a picture of an experimental setup according to your suggestion (please see new Figure 1). In addition, we have also added some references in the manuscript.
To make it very clear:
- a) How was flow velocity measured or calculated?
Response: Surface flow velocity was determined at the upper, middle, and lower slope positions using means of KMnO4 solution during the simulated rainfall event, after the flow discharge stabilized. The upper, middle, and lower slope positions were marked from 0 m to 3 m, from 3 m to 6 m, and from 6 m to 8 m within the runoff plots, respectively.
- b) How was the hydraulic radius measured?
Response: We have explained the calculation of hydraulic radius in manuscapre. Please see Lines 179-180.
- c) How was the hydraulic gradient determined? What was measured to determine it?
Response: The hydraulic gradient is approximately substituted by the sine of slope gradient.
- d) What was the source of the Kr value? Linked to what? The same for critical shear stress and n exponent. Regarding the effective shear stress, how was it measured or calculated?
Response: Kr,τc and n can be obtained through regression analysis between Dr andτ(i.e., Kr becomes equal to the slope of the line, and the x-intercept isτ).
- e) How was water temperature measured?
Response: A centigrade thermometer was used to measure the flow temperature.
Moreover, NONE was presented about the Water Erosion Prediction Project, cited in the objectives, what is very, very strange. The authors must justify this, or present the needed information.
Response: Your suggestion are very reasonable. We have deleted the Water Erosion Prediction Project in the objectives.
For the results section, there is no experimental statistical analysis. Why? How authors can state differences comparing the experimental treatments, without a formal statistical analysis?
Response: Your suggestion are very reasonable. We have added the experimental statistical analysis. Paired-sample t-tests were used to analysis the significance of differences in Darcy–Weisbach friction factor between WB and CK under different rainfall patterns. The differences were assumed to reach statistically significant level at p < 0.05.
Comparing the amount of results data and the presented discussion, the discussion can be considered very shallow and did not cover all the presented results. The conclusion section is overall poor, only repeating the results presented.
Response: Your suggestion are very reasonable. We have carefully revised the manuscript. E.g., we have added some sentences in Discussion. “Rock fractures with multiscale behavior and high anisotropy nature have been regarded as preferential channels for runoff during rain event, making a great difference in the hydraulic conductivity of bedrock fragment”, “he high rainfall intensity creates the immediate ponding, and this prevents the soil air from escaping and thus retards water infiltration”.
Author Response File: Author Response.docx
Round 2
Reviewer 2 Report
Comments and Suggestions for AuthorsThe authors presented a revised version of the manuscript, with all requested amendments.
Comments on the Quality of English LanguageMinor English language corrections must be done.
