Greenhouse Gas Fluxes from Selected Soil Fertility Management Practices in Humic Nitisols of Upper Eastern Kenya

Round 1

Reviewer 1 Report

The manuscript entitled “Greenhouse gas fluxes from selected soil fertility management practices in humic Nitisols of Upper Eastern Kenya” aims to assess GHGs fluxes and GWP for various soil treatments using field measurement. The experimental design is logically done for one year, reasonably for monitoring the dynamics of organic degradation into the soil. Unfortunately, the work is repeating the work done by the same scientists’ group for the same ecosystems with different sampling periods (see Musafiri et al., 2020).

Since the authors experiment for more than 1 year, the analysis should take advantage of the long-term measurement. Nonetheless, the authors did the analysis using only a 1-year dataset and there is no new conclusion obtained from this repeated work. To provide more useful information, I suggest the authors reanalyze using long-term dataset and criticize the comparisons between this work (2^nd cropping year) and those from Musafiri et al. (2020) (1^st cropping year). A discussion on sustainable applications of different soil treatments on soil fertility, productivity, and GHG emissions should be provided.

Reference

Musafiri, C. M., Macharia, J. M., Kiboi, M. N., Ng'etich, O. K., Shisanya, C. A., Okeyo, J. M., ... & Ngetich, F. K. (2020). Soil greenhouse gas fluxes from maize cropping system under different soil fertility management technologies in Kenya. Agriculture, Ecosystems & Environment, 301, 107064.

There are additional concerns as below:

1. From the title, this work emphasizes the humic Nitisols. The authors should provide the key characteristics of this soil and relate the characteristics to the concern of soil fertility and GHG gas emissions.
2. Since there are several data involved in the estimations and the experimental design is the key to this work. I suggest the author provides a clear illustration in the methodological part. Graphics of sampling location and experimental setup and a Table showing details on the measuring parameters are highly recommended.
3. The manuscript is difficult to read mainly due to many abbreviations which are not directly connected to the original meanings, such as LR, SR, Mf, RMf, ----. The author should avoid using abbreviations or make them easily understandable.
4. Add SOC measurement details in the methodology.
5. In section 3.1 Soil and site meteorological measurement. The authors, however, did not provide the details on meteorological measurement in the manuscript.
6. In Table 1 to 4, the authors show descriptive statistics of means for each treatment, which can be done. The ANOVA test for different means, however, is questionable since there are only 3 samples for each treatment. The authors did time-series measurements. I suggest the authors consider 1. T-test paired two samples (each treatment - control) for means (n = time-series measurements and 1 mean) and 2. 1-Way ANOVA for the paired two samples for all treatments (n = time-series measurements and 4 means).
7. Explain how to estimate GHGs fluxes and how come the negative measurement can be obtained from the measurement.

Author Response

Thank you for the comprehensive review, we appreciate the critical suggestions and input into our work It goes a long way in enhancing the quality of the manuscript.

We have addressed the comments and captured the details in the attached document for your review and further action

Thank you once more.

Author Response File: Author Response.docx

Reviewer 2 Report

Line 232: Normally, we dry the plant by oven at 60 t0 70 ^°C.

Line 291: It is better to use Tuky test instead of Duncan.

Author Response

Thank you for the comprehensive reviews and the critical input you have made into our manuscript. We appreciate. 

We have addressed all the raised concerns and captured the details on how we have one in the attached document.

Thank you once more, we appreciate it.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The authors did a good job on the revision. There are, however, some issues that the authors have not pinned to the point of concern.

1. The authors explained the difference with the Musafiti et al. 2020, but they did not explain the text. Key results obtained from Musafiti et al. 2020 should be mentioned in the introduction and then link to this research development. The readers then can understand the reason behind this experimental design.
2. The concerns on a small number of observations for ANOVA test for different means in Table 1 to 4 have not yet responded.
3. The authors added a new explanation on “Calculation of GHGs concentration in this study used linear and nonlinear models. The linear model was the default; when a greater correlation (R2 >=0.95) for the nonlinear model was observed, the second-degree quadratic was used [12].” This sentence is confusing. Do the authors mean estimating b (slope of concentration)? How come the nonlinear models can estimate slope? If not, what the concentration means? Same with flux? Please clarify.
4. The response to the negative measurement is reasonable. Please avoid using negative concentration since it is not practical. Negative flux is recommended. I think the author means to the negative flux, not concentration. Nonetheless, the explanation of the negative measurement in the manuscript is totally different. The lower than the minimum detection limit should not be the case for negative measurement. In such case, “ND = not detectable” should be reported.

 

Author Response

We have addressed all the raised concerns, amending where possible and giving rebuttals to those comments we thought otherwise. We have attached the details on how we have addressed them. Thank

Author Response File: Author Response.docx