Determination of Soil Erodibility by Different Methodologies in the Renato and Caiabi River Sub-Basins in Brazil

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This paper attempts to distinguish differences in soil characteristics and to (2) determine the soil erodibility or K Factor part of the USLE equation in both cultivated farmland and pasture in two sub-basins located in the Middle and Upper Teles Pires River region, in the northern part of Mato Grosso state, Brazil. However, I think this   manuscript is not ready for published, because there are so many contents are not clearly explained, which made me very confused.

1.    What is the Rainfall Simulation? rainfall simulator?

2.    Which scale did the author conduct the experiment, in the sub-basin or the plot? And how did the rainfall simulator apply in the sub-basin? if it used in the plot, there is no detail information about the plots

3.    Line133-135, simulated rainfall controls whether the rainfall intensity is 75mm / h? How many times was the rainfall simulated, and how much was the simulation period? I think the author needs an introduction.

4. according to the author, one sub-basin is Cultivated and the other is Pasture, are all the landuse in the sub-basin is uniform with single vegetation?

5. How did the author calculate the K value of rainfall simulation

6 What the temporal scale of the data such as the soil loss for each sub-basin? Each rainfall events or yearly?

7. What is the Eq.2 mean? I think is not an equation?

8. In line 169, the author said the C and P were 1, but in the two sub-basins, the landuse was not baresoil, so the C value could not be 1. are the P factor and C factor of cultivated land and pasture in the two sub-basins (Renato and Caiabi) both 1? Does the cultivated land have any vegetation cover during the experiment? I think the author needs a brief introduction

9.Is the Length and Slope in Table 6 the product of the L factor and the S factor of the standard runoff plot? Are the three sub-basin region (Source, Middle and Mouth) of the two sub-basic (Renato and Caiabi) all standard runoff plots?

10. The author list and compared with so many method of K value calculation? Why there is not the most common used method which is used in MUSLE or SWAT? Please see the reference below.

https://doi.org/10.1016/j.jhydrol.2022.128598; https://doi.org/10.1016/j.iswcr.2019.05.004.

11. which method could be the best model with better performance, the author didn’t tell us.

12. Table 9 The Correlation Coefficients units (%) in the problem head should be removed.

 

Comments on the Quality of English Language

Minor editing of English language required

Author Response

1. What is the Rainfall Simulation? rainfall simulator?

Rain simulation is a technique used in various fields of study, such as agriculture, environmental science, and water resource management, to replicate natural rainfall conditions in a controlled environment. This allows for experiments and data collection under specific conditions without relying on actual weather events. Portable rain simulators: Equipment that can be easily transported and used directly in the field. Parameters that can be controlled include rainfall intensity and duration.

2. Which scale did the author conduct the experiment, in the sub-basin or the plot? And how did the rainfall simulator apply in the sub-basin? if it used in the plot, there is no detail information about the plots

The experiment plots were conducted on a larger scale for the sub-basins. The InfiAsper device was used for simulated rainfall events on plots within the larger scale of the study's sub-basins, considering the complexity and size of the area.

3. Line133-135, simulated rainfall controls whether the rainfall intensity is 75mm / h? How many times was the rainfall simulated, and how much was the simulation period? I think the author needs an introduction.

The intensity of the simulated rainfall was adjusted to 75 mm/h throughout the process. The reference value is based on previous studies that measured rainfall intensity for the region. The device was calibrated before the simulated rainfall according to the methodology of Sobrinho et al. (2003). During the tests, and based on the study by Sabino et al. (2021), rainfall with maximum precipitation intensities was determined.

4. according to the author, one sub-basin is Cultivated and the other is Pasture, are all the landuse in the sub-basin is uniform with single vegetation?

No, there are variations within the sub-basins. For example, the cultivated sub-basin may have different types of crops in various areas, such as corn, soybeans, and cotton.

5. How did the author calculate the K value of rainfall simulation

Soil erodibility can be estimated using Equation 3, which involves the soil loss (A) and the soil erosivity index (EI30).

6 What the temporal scale of the data such as the soil loss for each sub-basin? Each rainfall events or yearly?

Soil loss was assessed in terms of individual rainfall events. Each rainfall event was conducted to understand the immediate soil erosion response to different intensities and durations of rainfall. Soil loss was measured after each significant precipitation event.

7. What is the Eq.2 mean? I think is not an equation?

Formula/equation, but it was better described in the text.

8. In line 169, the author said the C and P were 1, but in the two sub-basins, the landuse was not baresoil, so the C value could not be 1. are the P factor and C factor of cultivated land and pasture in the two sub-basins (Renato and Caiabi) both 1? Does the cultivated land have any vegetation cover during the experiment? I think the author needs a brief introduction

The C factor is equal to 1 because, under the standard conditions established by Wischmeier and Smith (1978), it is assumed that there is no cover or special management practice to reduce erosion, meaning the soil is completely exposed (bare soil). Under these conditions, the C value is set at 1, reflecting the maximum susceptibility to erosion. The same applies to the P factor, which is also 1. Again, according to Wischmeier and Smith's (1978) standard conditions, it is assumed that no conservation practices are being applied. Therefore, the P value is 1, indicating the absence of measures that could reduce erosion.

9.Is the Length and Slope in Table 6 the product of the L factor and the S factor of the standard runoff plot? Are the three sub-basin region (Source, Middle and Mouth) of the two sub-basic (Renato and Caiabi) all standard runoff plots?

The experimental area was developed in a plot with a measured size of 0.70 m² (0.70 m wide and 1.0 m long), which remained fixed throughout the simulation event using a plot delimiter constructed from steel plate. The slope variation for the study areas ranged from 3 to 5 degrees, being corrected by the equation 4.

10. The author list and compared with so many method of K value calculation? Why there is not the most common used method which is used in MUSLE or SWAT? Please see the reference below.

https://doi.org/10.1016/j.jhydrol.2022.128598; https://doi.org/10.1016/j.iswcr.2019.05.004.

This is an excellent question.

It is very common for initial erosion research to praise the USLE method, given its ease of use and reasonable data collection, and often to focus only on modeling, without data verification.

Using other models, such as physical models, requires more and more detailed data, and does not always lead to better results.

This work aims to address one of the suggestions listed by the authors of the work cited by the reviewer, which is to estimate and measure erosion to improve the original USLE coefficients, and in this work we focus on the soil erodibility factor (K).

Obviously, these studies are processes, and starting erosion measurements is not always possible on a large scale, such as larger plots or sub-basins, but rather on small plots, as was our case.

11. which method could be the best model with better performance, the author didn’t tell us.

CORRECTED IN THE TEXT: The indirect methodologies that showed reasonable correlation and better performance were Equations 2 and 3 from Roloff and Denardin (1994), which use iron and aluminum as parameters.

12. Table 9 The Correlation Coefficients units (%) in the problem head should be removed.

The (%) were removed from the header of Table 9.

Reviewer 2 Report

Comments and Suggestions for Authors

Journal: Land (ISSN 2073-445X)

Review Manuscript ID: land-3107076

Title: Determination of Soil Erodibility by Different Methodologies in the Renato and Caiabi River Sub-Basins in Brazil

Hello, it's my honor to review your manuscript. First of all, I agree with your contribution in this research. This manuscript is very important for the field of soil erosion, as it enables the improvement of erosion models and the verification of results from practice. I found some problems in the process of trial. I hope you can further explain or improve them.

1.      At the end of the abstract and at the end of the introduction, it is necessary to emphasise the importance of the research, what distinguishes this research from others and what is new about the research.

2.      The beginning of the introduction should be improved to include more examples from the world of how land use affects changes in soil erosion. It is recommended to give examples for other countries, regions and continents as well as examples for other specific crops (36-47 lines).

3.      USLE is the most commonly used erosion model in the world. In this context, it is necessary to list several studies from different parts of the world in which this method has been used with special attention to the K-factor (see researchs by Panos Panagos and Pasquale Borrelli - doi: 10.1016/j.scitotenv.2021.146494).

4.      Materials and Methods is well explained, systematic.

5.      Discussion the discussion is well thought out, with particular reference to the importance of such research (Implications of Research).

 The manuscript “Determination of Soil Erodibility by Different Methodologies 2 in the Renato and Caiabi River Sub-Basins in Brazil” addresses an interesting topic, which adhere to Land journal policies

Author Response

1. At the end of the abstract and at the end of the introduction, it is necessary to emphasise the importance of the research, what distinguishes this research from others and what is new about the research.

The introduction has been revised to emphasize the importance of the experiment “The importance of this research is reflected in the determination of the K factor indirectly for soils in the region, which is crucial for understanding the erosion process and enabling the mitigation of erosive effects in different land uses. This will allow for more effective soil conservation. Additionally, this approach will stimulate reflection on the necessary care in soil management, especially in the context of agribusiness. It will also promote scientific debate and may encourage the development of new studies on other perspectives regarding soil erodibility”.

2. The beginning of the introduction should be improved to include more examples from the world of how land use affects changes in soil erosion. It is recommended to give examples for other countries, regions and continents as well as examples for other specific crops (36-47 lines).

The introduction has been revised to emphasize the importance of the experiment “In Latin America, deforestation for agriculture and livestock, such as in the Brazilian Amazon, results in high soil erosion due to direct exposure of the soil. In Sub-Saharan Africa, subsistence farming and expansion into pastures also cause severe soil degradation. In Europe, the outcomes vary with agricultural practices and soil conservation regulations.”

3. USLE is the most commonly used erosion model in the world. In this context, it is necessary to list several studies from different parts of the world in which this method has been used with special attention to the K-factor (see researchs by Panos Panagos and Pasquale Borrelli- doi: 10.1016/j.scitotenv.2021.146494).

The introduction has been improved with insights from these quotes.

4. Materials and Methods is well explained, systematic.

Ok. Thanks.

5. Discussion the discussion is well thought out, with particular reference to the importance of such research (Implications of Research).

OK. Thanks.

 The manuscript “Determination of Soil Erodibility by Different Methodologies 2 in the Renato and Caiabi River Sub-Basins in Brazil” addresses an interesting topic, which adhere to Land journal policies

Thanks.

Reviewer 3 Report

Comments and Suggestions for Authors

Comment on Land 3107076

 

I recommend that this paper be rejected on scientific grounds

 

1.      USLE K values focus on the “unit” plot, an area 22 m long on a 9 % slope. No details are provided by the authors but references are given to previous papers which do so. Clearly the rainfall simulator cannot rain on an area of the size of the unit plot or the 11 m long plots that used rainfall simulation a long time ago to supplement the data collected on USLE plots in the USA.

2.      Eq.1 is not appropriate for determining kinetic energy for the rainfall simulator used. It was developed from rainfall data obtained at one specific location in the USA and then applied throughout the USA despite that.

3.      Eq. 4 cannot be used to extrapolate the data obtained by the authors on their microplot to the size of the unit plot because the flow depths and velocities between the two sizes are very different. Consequently, the detachment and transport systems that operate in the authors experiments differ considerable from those that operate of USLE plots. The authors need to familiarize the modern literature about soil erosion mechanisms

 

Comments on the Quality of English Language

no comment

Author Response

1. USLE K values focus on the “unit” plot, an area 22 m long on a 9 % slope. No details are provided by the authors but references are given to previous papers which do so. Clearly the rainfall simulator cannot rain on an area of the size of the unit plot or the 11 m long plots that used rainfall simulation a long time ago to supplement the data collected on USLE plots in the USA.

The information related to the plots studied has been completed, better characterizing the experimental area and the design.

In addition, it should be noted that erosion studies are very costly and laborious, and although we are not working with universal plots (Wischmeier and Smith, 1978) of 6 m x 22 m and 9% slope, the plots used in rainfall simulators allow for the beginning of larger erosion studies.

2. Eq.1 is not appropriate for determining kinetic energy for the rainfall simulator used. It was developed from rainfall data obtained at one specific location in the USA and then applied throughout the USA despite that.

We do not understand it that way. Let us defend what we did.

The studies by Wischmeier and Smith (1978) demonstrated the rules and calculations to be able to use the rainfall from the location of the erosion study.

Continuing the defense, the works by Sobrinho et al., 2003, 2008, demonstrate that, with the construction and study of rain simulators, the conceptualization of kinetic energy is made explicit, relative to the size of drops and fall height of the simulated precipitation, correlating the simulated values ​​to those of natural and/or projected rainfall, if the frequency of occurrence for the latter is considered.

Furthermore, in the work by Sabino et al. (2021), we can highlight studies by our research group that have studied rainfall intensities in different regions of the state of Mato Grosso, and for this reason we found a rainfall of 75 mm h-1 for a 10-year return period as the design rainfall adopted in this work.

We did not use formulas or data from the USA, but rather from Brazil and the state of Mato Grosso.

3. Eq. 4 cannot be used to extrapolate the data obtained by the authors on their microplot to the size of the unit plot because the flow depths and velocities between the two sizes are very different. Consequently, the detachment and transport systems that operate in the authors experiments differ considerable from those that operate of USLE plots. The authors need to familiarize the modern literature about soil erosion mechanisms

We understand and partly agree with the reviewer's statement.

Although the slope in the universal plot of Wischmeier and Smith (1978) is larger than the one we used in this work, there are correlations proposed in their own formula for the different slopes and different slopes (LS factor - eq. 4).

And yet, if we consider that extrapolations of microscale plots cannot be extrapolated to larger scales, what can we say about specific field measurements that are extrapolated to larger areas when we use simulation models with hydrological units of tens or hundreds of m2.

Finally, it is necessary to draw attention to the object and material of study, so that they can be compared across different types of scientific and research activities. However, we think we can take into account the differences obtained, since initial studies, in most cases, allow us to reach new heights with learning and, in particular, with the results obtained in small works.

Round 2

Reviewer 3 Report

Comments and Suggestions for Authors

This paper is not acceptable for publication in any self respecting scientific journal.

1) The authors do not have appropriate knowledge of the protocols that need to be adhered to to determine USLE K values from rainfall simulator experiments. 1 m long plots are not appropriate to determine USLE K values which focus on slopes that are 22 m long. Slope lengths of the order  of 1 m may be relevant to determining interrill soil erodibilities for models like WEPP. They are not appropriate for determining USLE Ks.  See https://doi.org/10.1016/j.catena.2021.105283 for a review of the use of rainfall simulators in erosion research.

2) The equation used to determine rainfall kinetic energy values for the rainfall simulator by the authors (Eq.1)  is not appropriate. That equation  is assumed to apply to natural rainfall in many parts of the world but does not apply to the type of rainfall simulator used by the authors.

Consequently, the results presented in Table 9 in the paper are not credible.

The paper is not acceptable for publication an any scientific journal  on scientific grounds.

The article has serious flaws, additional experiments needed, research not conducted correctly