the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 06 May 2024
Biochar reduces early-stage mineralization rates of plant residues more in coarse than fine-texture soils – an artificial soil approach
Abstract. Quantifying the impact of biochar on carbon persistence across soil textures is complex, owing to the variability in soil conditions. Using artificial soils with precise textural and mineral composition, we could disentangle the effects of biochar from the effects of soil particle size. We can show that biochar application significantly reduces early-stage carbon mineralization rates of plant residues in various soil textures (from 5 to 41 % clay) but more significantly in sandy soils. This finding suggests that biochar can compensate for the lack of clay in promoting C persistence in soil systems. This short report significantly contributes to understanding soil texture and biochar application interactions.
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RC1: 'Comment on egusphere-2024-1143', Marie-Liesse Aubertin, 11 Jun 2024
General comments (specific comments and technical corrections are in the pdf file):
Soil texture is believed to have a strong impact on the response of biochar amendment on C sequestration, although little is known about the mechanisms involved. This short communication sheds light on potential mechanisms involved in the role of particle size and mineral composition on the early-stage decomposition of soil organic matter. The use of an artificial soil where particle size and mineral composition is fully controlled is, to my point of view, a relevant approach to focus on these specific mechanisms. Comparing the effect of biochar with soils from different textures is very interesting.
However, all parts could be improved since there are still some missing points and lack of precisions. In the results, it is not clear if the effect of biochar addition on the plant mineralization is due to the composition of biochar or to its particle size. Therefore, I think necessary to precise the size of biochar particles added and maybe to discuss this point.
To me, this study doesn’t evidence a clear effect of the texture on plant respiration in the control soil (without biochar). It is written that there is a statistic effect, but (1) results from statistics made on very small samples (n=3) should be treated with caution, (2) I am not convinced by the choice of the statistic test and (3) the curve does not show a clear trend. Hence, the results and discussion should not emphasize too much on this small tendency and not consider it as a clear result.
In the discussion, only physical explanations are presented to explain the effect of pH on plant mineralization. Additional explanations should be proposed regarding the effect of pH changes on the microbial communities and on the nutrient availabilities from the plant for the microorganisms.
The discussion should include more comparison with other studies using artificial soils. Indeed, the results from studies using artificial soils can be very different from studies using field soils (e.g. Gross et al. 2021). Although the approach of using artificial soil is relevant, the study should more emphasize on its limits to extend these results to real field soils.
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RC2: 'Comment on egusphere-2024-1143', Anonymous Referee #2, 26 Jun 2024
The authors present a study investigating the effect of biochar on carbon mineralization in soils of different texture. Although technically sound and well presented, in my opinion, the study as written is insufficient to conclusively corroborate the assertions and conclusions made by the authors. I strongly feel the authors could rewrite and present a stronger case for their study with more experimentation (e.g. utilizing more biochars from different feedstocks and comparing or using the same feedstock but varying temperature of pyrolysis or investigating effect of pH change alone without biochar. Increased pH or liming alone has been well documented to impact C mineralization with increased pH encouraging aggregation of clays and thus increased protection of carbon within the aggregates and binding to Ca2+ and clay surfaces.
Citation: https://doi.org/10.5194/egusphere-2024-1143-RC2
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