Spatial and Temporal Variability of Soil Redox Potential, pH and Electrical Conductivity across a Toposequence in the Savanna of West Africa
Round 1
Reviewer 1 Report
The work is devoted to the study of oxidation-reduction processes in soils, which are important for understanding both the processes of soil formation and the bioproduction process.
The research methodology is carefully prescribed.
Interesting materials have been obtained on the dynamics of the oxidation potential, pH value, electrical conductivity, as well as soil temperature and moisture at different depths during two growing seasons. The interrelationships of the studied parameters with each other in the conditions of a particular region of study are traced.
However, the results of the work would be much more interesting if one more component of the ecosystem was taken into account - vegetation. The vegetation cycle significantly affects the course of physicochemical processes in the soil; it is one of the most important factors in soil formation.
Unfortunately, the authors do not report anything about the vegetation of the study site. It is not very clear whether we are talking about a natural or agro-ecosystem. To what extent has the soil been disturbed by humans? There is no information on the dynamics of plant matter during the observation period.
All this reduces the value of the work. It is highly desirable for the authors to supplement the article with information about the vegetation of the study site and its changes during the measurement period.
Two technical notes:
1 - in the reference [21], please write the names of the authors of the article correctly: Szafranek-Nakonieczna A., Stępniewska Z.
2 - in fig. 1 (right) does not indicate the place of sampling, but there is a lot of unnecessary information.
In further studies, it would be good to study the relationship between the production process and the values of Eh and soil pH that are important for its flow.
Author Response
Response to Agronomy review
Reviewer 1
Comments:
The work is devoted to the study of oxidation-reduction processes in soils, which are important for understanding both the processes of soil formation and the bioproduction process.
The research methodology is carefully prescribed.
Interesting materials have been obtained on the dynamics of the oxidation potential, pH value, electrical conductivity, as well as soil temperature and moisture at different depths during two growing seasons. The interrelationships of the studied parameters with each other in the conditions of a particular region of study are traced.
However, the results of the work would be much more interesting if one more component of the ecosystem was taken into account - vegetation. The vegetation cycle significantly affects the course of physicochemical processes in the soil; it is one of the most important factors in soil formation.
Unfortunately, the authors do not report anything about the vegetation of the study site. It is not very clear whether we are talking about a natural or agro-ecosystem. To what extent has the soil been disturbed by humans? There is no information on the dynamics of plant matter during the observation period.
All this reduces the value of the work. It is highly desirable for the authors to supplement the article with information about the vegetation of the study site and its changes during the measurement period.
Two technical notes:
1 - in the reference [21], please write the names of the authors of the article correctly: Szafranek-Nakonieczna A., Stępniewska Z.
2 - in fig. 1 (right) does not indicate the place of sampling, but there is a lot of unnecessary information.
In further studies, it would be good to study the relationship between the production process and the values of Eh and soil pH that are important for its flow.
Response:
Thanks for your comments.
Regarding technical notes, we corrected as requested:
We changed the figure 1, removing unnecessary information, and better locating the two study sites and the soil types at these locations.
We corrected the name of the author for reference 21.
We also corrected several English and subscript/superscript errors all over the text
Regarding the main comments, we totally agree that vegetation is a key factor affecting the course of the physico-chemical processes in the soil and we improved the introduction by mentioning this important aspect.
We also have added a paragraph describing the natural vegetation before land reclamation (which occurred in 2015, after more than 12 years of fallow) and we made it clearer that our study was conducted on recently reclaimed upland rice fields. Because of this strong perturbation in this agro-ecosystem by soil tillage and cultivation, and as it was not design to assess the relationships between vegetation and soil Eh-pH-EC conditions, there was no further monitoring of the natural vegetation. As a consequence, this study can’t present such results. However, in the discussion, we raise the hypothesis that the differences in natural vegetation between sites could reflect differences in soil EH-pH-EC conditions
Finally, we improved the conclusion and added the need and the conditions required for further studies on the relationships between the production process and the Eh-pH value of the soil.
We hope we have satisfactorily answered all your comments
Once again, thanks for doing this reviewing work.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The authors have chosen to analyze a very crucial parameter (soil redox potential) that provides significant information about soil conditions. In my opinion, the overall study is hardly satisfactory and the quality of presentation is very low and improvements are required.
- The legend and elements of map in fig.1 are not readable.
- fix resolutions in fig.3
- fix english, for example lines 23, 43-45, 97-98, put subscripts in chemical forms everywhere, etc.
I believe that the authors should stress the limitations of the study and the general limitations in the measurement of redox potential which is very sensitive. Do you believe that cation axchange capacity affects redox potential? and if yes could have any meaning in your study?
Author Response
Response to Agronomy review
Reviewer 2
Comments:
The authors have chosen to analyze a very crucial parameter (soil redox potential) that provides significant information about soil conditions. In my opinion, the overall study is hardly satisfactory and the quality of presentation is very low and improvements are required.
- The legend and elements of map in fig.1 are not readable.
- fix resolutions in fig.3
- fix english, for example lines 23, 43-45, 97-98, put subscripts in chemical forms everywhere, etc.
I believe that the authors should stress the limitations of the study and the general limitations in the measurement of redox potential which is very sensitive. Do you believe that cation axchange capacity affects redox potential? and if yes could have any meaning in your study?
Response:
Thanks for your comments.
Following these comments, we have made the following changes:
- We have changed figure 1 (also accordingly to reviewer 1 who recommended to have less information on this figure but better mention the site of the study). Thus, we removed the (hardly readable) legend of soil types and simply indicated the soil type on the two study sites, which are now clearly indicated.
- We fixed the problem of resolution in figure 3 (redrawing it better)
- We put subscripts on chemical forms everywhere (sorry for this problem which occurred during the transfer of the file to the required format)
Furthermore, we reviewed the English and made several corrections (in revision mode)
Regarding the possible relationship between CEC and Eh, we did not mention it in this study. The only interaction we’ve found in the literature mentions that iron reduction at very low Eh in waterlogged soils leads to iron solubilization and as a consequence, increase in CEC (Favre et al. European Journal of Soil Science. 2002.53:175-183). However, this is not relevant to our study as most of the time soils were in (strongly) aerobic conditions.
Finally, we ‘ve added a concluding paragraph on the limitations of the study.
We hope we have satisfactorily answered your comments and would like to thank you again for this reviewing work.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
No further comments.
Author Response
Dear Editor,
The authors would like to thank the scientific reviewers whose constructive comments allowed us to improve this manuscript.
Best regards,
Firmin Tano on behalf of all authors.
