Biochar Stability in a Highly Weathered Sandy Soil under Four Years of Continuous Corn Production

Round 1

Reviewer 1 Report

energies-1359576-Novak-BC-peer-review-v1

Novak and colleagues investigated the stability effects of two contrasting biochars (BC); one used pine residues and the other poultry litter as feedstock. The difference in ash% and C% between those two BC is remarkable. Less than 20% of the applied BC is lost through a period of 4 y of continues corn cultivation under conservation tillage and residues return practices. It appears that disk ploughing stabilizes BC on the upper soil layer, directly increasing SOC%. The study is well balanced among technical, practical and theoretical aspects and could definitely inspire further investigation on the field of agronomic BC application. The study is written in an approachable format considering wider audiences (researchers, field agronomists, policy makers etc)

I have noted some suggestions and questions in the PDF that could further improve the significance of this work. One would appreciate the importance of BC in the long term effects in soil fertility, water retention, priming etc if the authors wish to elaborate a bit more in their discussion. Some indication of the beneficial effects of BC amendment could be presented in terms of seed-yield and biomass production if available.

The statistical tests are appropriate for the experimental design that consists of two factors and their interaction; depth and year. However it is not clear if the authors tested their datasets for homogeneity and normality, a required assumption for ANOVA. Also, were the datasets transformed in any way? Alternatively, datasets could be statistically tests using all three factors and their interactions; depth, year and BC type. Additionally, a PCoA or another appropriate test could be used, to illustrate the drivers of SOC% variability.

I haven’t looked for spelling/typing mistakes, this could be done to a latter stage of proof corrections.

My recommendation is to accept the article with minor revisions and I am happy to receive the improved version of this very interesting work.

Comments for author File: Comments.pdf

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

The manuscript of Noval et al 2021, presents interesting findings on the stability of biochar under particular soil type with continuous corn production for 4 years. I recommend this for publication once key suggestions/comments are addressed. 

Title: Relevant and appropriate

Abstract:

Line 18: Please indicate the absolute value or percentage of increase.

Introduction:

Lines 59-76

The author discussed the chemical and microbial shifts in soils due to addition of biochar with emphasis on the negative and positive priming effects. This is good but it would be interesting to improve this paragraph by presenting specific mechanism involved in this shifts. What about the role of soil pH? Are key nutrients play role in this chemical and microbial shifts?

Overall for introduction section, it would be interesting if the author would pay attention to presenting the potential mechanisms involve in the chemical and microbial dynamics in soils after addition of biochar.

Materials and methods

Section 2.3.2 Biochar application

Does both biochar (PL and Pc) have the same texture?  It would be better to present the textural differences (if there are any) of both biochar treatments. How did you ensure evenness of the treatment application in the field? This needs to be addressed clearly here.

Results:

Table 1, please add pH data of both biochar treatments and textural analysis if these are available.

Table 2. Table 2 may be better to present also the corn cropping seasons from 2015 to 2020 to give the reader a spot on idea on total corn cropping seasons against the sampling events.

Discussion

Lines 416 to 420.

Please indicate the potential factors affecting the differences in SOC mineralization of both PC and PL. Is it chemically or physically driven? If you have data on pH and texture of these biochar treatments, please present them and these may help improve the narratives of your findings and conclusion.

Conclusion

This can be improved when additional data will be presented.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 3 Report

The study addresses the temporal dynamics of SOC after the application of two types of biochar. The study is well conducted and the results and conclusions are well aligned. It has been a pleasant read. Much emphasis is placed on the type of soil which, being a relevant factor, detracts from the gerenalization of the results and may narrows the scope to reach a larger readership. I add further comments in the file attached

Comments for author File: Comments.pdf

Author Response

Please see the attachments.

Author Response File: Author Response.docx