Cover Crops Affect Soil Mineral Nitrogen and N Fertilizer Use Efficiency of Maize No-Tillage System in the Brazilian Cerrado

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The scientific manuscript shows quality and scientific merit to be published in Land.

 

Some corrections and comments are in the attached file.

 

Best Regards,

Comments for author File: Comments.pdf

Author Response

"Please see the attachment." 

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript presents an interesting study on the effects of different cover crops on soil mineral nitrogen (N) dynamics and nitrogen fertilizer use efficiency (NFUE) of subsequent maize crop in a long-term no-tillage system in the Brazilian Cerrado region. The authors have conducted a comprehensive study and provided valuable insights into the role of cover crop residue quality in regulating soil N availability and NFUE. The study has important implications for sustainable N management in maize-based cropping systems.

 

Specific Comments:

1. Abstract:

   - The abstract provides a good overview of the study and its key findings. However, it could be strengthened by including a clear statement of the research hypothesis and objectives.

   - The concluding statement in the abstract could be more concise and focused on the main takeaways.

- Line 13-15: The statement "This study evaluated the mineral nitrogen concentration of soil under cover crops grown after maize topdressed or not with nitrogen (N)" could be more concise and specific, e.g., "This study evaluated the effects of different cover crops on soil ammonium (NH4+) and nitrate (NO3-) concentrations in a long-term no-tillage system, with and without N topdressing on the preceding maize crop."

- Line 23-26: The statement about Mucuna aterrima having the highest mineral N concentrations and lowest NFUE of the subsequent maize could be expanded to explain the underlying mechanisms (e.g., the higher lignin concentration and lignin:N ratio of this cover crop).

 

2. Introduction:

   - The introduction could be further strengthened by including a clearer statement of the research gap and how the current study aims to address it.

- Line 29-30: The statement "Nitrogen (N) is a key element to ensure maximum crop yields and food security" could be strengthened by citing relevant references to support this claim.

- Line 39-41: The statement "An inadequate N management can be a limiting factor for maize yield and cause unnecessarily high production costs" could be made more specific by quantifying the potential yield and cost impacts of poor N management.

- Line 53-57: This paragraph could be reorganized to better flow and connect the points about the importance of understanding N dynamics in cover crop-based systems and how this can inform more efficient fertilizer use.

- Line 70-76: This paragraph provides good background on the importance of N and its environmental impacts, but it could be more concisely written to improve the flow of the introduction.

 

3. Materials and Methods:

   - The authors could consider providing more details on the climatic conditions during the experimental period, as this is an important factor in N dynamics.

- Line 93-96: Consider providing more details on the climatic conditions (e.g., average monthly temperatures, rainfall patterns) during the experimental period, as this information is crucial for understanding the N dynamics.

- Line 119-130: The details provided on the cover crop management and fertilization of the preceding maize crop are thorough and well-described.

- Line 139-151: The soil sampling and analysis methods are clearly explained, which is important for the reproducibility of the study.

 

4. Results:

   - The inclusion of the PCA analysis helps to visualize the relationships between the studied variables, which is a useful addition.

- Tables 1-5: These tables effectively present the soil mineral N data and the statistical differences among the treatments. Consider adding letters to indicate significant differences within each column, as this would improve the readability of the tables.

- Table 7: This table provides valuable information on the cover crop biomass characteristics. Consider adding standard error or standard deviation values to the means, to give a sense of the variability in the data.

- Figure 2: The PCA analysis is a useful tool to visualize the relationships among the studied variables. Consider adding labels to the axes to clarify the meaning of PC1 and PC2.

 

5. Discussion:

   - The authors could consider strengthening the discussion by highlighting the potential mechanisms underlying the observed differences in N dynamics among the cover crop treatments.

- Line 363-364: The explanation for the increase in mineral N from the end to the beginning of the rainy season due to the "Birch effect" and low microbial activity during the dry season could be further elaborated, as this is an important aspect of the N dynamics in the system.

- Line 375-380: The discussion on how the structural components of the cover crops (lignin, hemicellulose, etc.) influenced N mineralization and availability is well-done. Consider adding references to support the specific mechanisms described.

- Line 387-396: The discussion on the cover crop effects on maize yield and NFUE is thorough and effectively connects the results to the existing literature. However, it could be further strengthened by discussing the potential practical implications of these findings for N management in maize-based systems.

- Addition of organic matter due to cover crop, may induce soil priming effect, and thus effect soil carbon and nitrogen turnover, particularly for nitrous oxide emission, please consider cite this paper to the relevant discussion, Organic matter contributions to nitrous oxide emissions following nitrate addition are not proportional to substrate-induced soil carbon priming.

 

6. Conclusions:

The authors could consider adding a sentence or two on the potential practical applications of the study and future research directions.

Author Response

"Please see the attachment." 

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

Thanks for addressing my comments.