the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Biochar promotes soil aggregate stability and associated organic carbon sequestration, and regulates microbial community structures in Mollisols from Northeast China
Jing Sun
Xinrui Lu
Guoshuang Chen
Nana Luo
Qilin Zhang
Xiujun Li
Abstract. Since the 1950s, heavy plowing of Mollisols, combined with a lack of organic matter intake, has resulted in severe soil degradation in Northeast China. The use of biochar in combination with fertilizer is a sustainable method of improving soil quality. In this paper, we conducted field experiments to explore the response of the stability mechanism of the soil aggregates, the dynamic properties of organic carbon, and changes in the microbial community structure to biochar. The biochar input levels were C1, C2, and C3 (9.8, 19.6, and 29.4 Mg·ha-1, respectively), while the nitrogen (N) fertilizer rates were N1/2 (300 kg·ha-1) and N (600 kg·ha-1). The field test showed that the C2N treatment increased the aggregate contents of the > 2 mm and 0.25–2 mm fractions by 56.59 and 23.41 %, respectively. The mean weight diameter increased by 41.53 %, while the geometric mean diameter increased by 21.62 %. The organic carbon content of large aggregates shows a greater increase, with an average of 28.14 %. The phospholipid fatty acids analysis revealed that bacteria (B) were the most prevalent organisms in the soil, followed by fungi (F). The C3N treatment increased the F / B ratio by 36.46 %, whereas the C3 treatment increased the gram-positive (Gm+)/gram-negative (Gm−) ratio by 19.67 %. We concluded that the response of Mollisols to biochar is primarily determined by the interplay of aggregates, organic carbon, and microorganisms. Based on the sequestration of SOC and the sustainability and stability of the ecosystem, we selected the optimal ratio for biochar and N fertilizer application and provide a scientific basis for the sustainable utilization of Mollisols resources.
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Jing Sun et al.
Status: open (until 05 Apr 2023)
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CC1: 'Comment on egusphere-2022-1084', Liang Jin, 09 Dec 2022
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The authors evaluated the effects of different biochar gradients combined with nitrogen fertilizer on the size, proportion, stability, and carbon content of Mollisols soil aggregates. In addition, they also examine how biochar affects the structure of microbial populations and identify the main factors influencing changes in microbial composition and recommend an optimal biochar application ratio to improve soil quality by modifying aggregates and the soil microbial community structure of Chinese black soils. They concluded that microbial abundance increased significantly when biochar and fertilizer were combined, and soil aggregation and SOC of black soil were significantly improved. The graphic description in the paper is relatively clear and intuitive, which well summarizes the conclusions expressed by the author.
Field experiments are a more objective reflection of actual production issues, and it is a pity that we did not see the author's research on crop yields, but it is still an impressive work, and the findings are essential if we want to improve our understanding of the improvement of soil quality through biochar. However, in my opinion, it is very necessary to make proper revisions before acceptance.
Comments
Line 16-23, The summary of the Abstract section, the conclusions seem ambiguous. I suggest that the author provide a clear and reliable conclusion in concise language.
Line 44-47, There is large room for improvement in description and expression. Some sentences are long and contain a lot of repetitive information.
Line 60-61, awkward sentence with controversial expression. Try to explain the limited time for straw decomposition.
Line 87, "Principal ecological activities including…", double check the term or phrase.
Line 215, Please explain original profiled soil?
Line 227, please define "bottom soil".
Line 230, "combined application"? unclear expression.
Line 288-290, Not necessary to simply repeat the numbers or values in the figures.
Line 342, macroaggregates, small macroaggregates? Please be uniform in the text.
Line 410, Among the effects of biochar combined with N fertilizer on microbial communities, the authors suggest the effectiveness of reduced N fertilizer application to improve microbial richness, and the potential negative environmental effects after high doses of N fertilizer application should be further briefly discussed.
Line 418, Please explain the difference between toc and SOC. Both parameters are used.
Line 426-428, Repeated statement.
Line 430-432, the meaning of this sentence is unclear, rephrase the sentences to make the logic smooth and the meaning clear.
Line 454, delete "The PCA showed that".
Citation: https://doi.org/10.5194/egusphere-2022-1084-CC1 -
AC1: 'Reply on CC1', jing Sun, 20 Dec 2022
reply
We appreciate the reviewer very much for the positive and constructive comments and suggestions concerning our manuscript. The comments are very helpful for revising and improving our paper. The main corrections in the paper and the response to the comments are as following.
The authors evaluated the effects of different biochar gradients combined with nitrogen fertilizer on the size, proportion, stability, and carbon content of Mollisols soil aggregates. In addition, they also examine how biochar affects the structure of microbial populations and identify the main factors influencing changes in microbial composition and recommend an optimal biochar application ratio to improve soil quality by modifying aggregates and the soil microbial community structure of Chinese black soils. They concluded that microbial abundance increased significantly when biochar and fertilizer were combined, and soil aggregation and SOC of black soil were significantly improved. The graphic description in the paper is relatively clear and intuitive, which well summarizes the conclusions expressed by the author.
- Field experiments are a more objective reflection of actual production issues, and it is a pity that we did not see the author's research on crop yields, but it is still an impressive work, and the findings are essential if we want to improve our understanding of the improvement of soil quality through biochar. However, in my opinion, it is very necessary to make proper revisions before acceptance.
Response: Thank you very much for your careful review and constructive suggestions regarding our manuscript. The improvement of soil structure and quality is an important prerequisite for improving crop yield and quality. Therefore, this paper focuses on the analysis of the effect of biochar on soil improvement. However, we have not ignored the trends in crop yield and quality in the improved soils, which have been analysed in detail in subsequent manuscript.
- Line 16-23, The summary of the Abstract section, the conclusions seem ambiguous. I suggest that the author provide a clear and reliable conclusion in concise language.
Response: Thanks for the advice. We have revised the “Abstract” part as you suggested. We combed through sentences that were relatively vague in meaning to make them clearer and more logical:" Field trials showed that organic carbon accumulation in large aggregates was higher, averaging 28.14%. Biochar application with N fertilizer significantly increased the proportion of aggregates (> 0.25mm), effectively increasing soil carbon storage and agglomerate stability. The phospholipid fatty acids analysis revealed that the accumulation of exogenous carbon and nitrogen effectively improved the microbial community structure (P < 0.05). The C3N treatment increased the F/B ratio by 36.46%, whereas the C3 treatment increased the gram-positive (Gm)/gram-negative (Gm+−) ratio by 19.67%."
- Line 44-47, There is large room for improvement in description and expression. Some sentences are long and contain a lot of repetitive information.
Response: Thanks for the advice. The sentence has been amended to: "The principal manifestations of the soil degradation were a significant loss of soil organic carbon (SOC), a decrease in soil aggregation (Zhang et al. 2018), and degradation of soil structure (Luo et al. 2020; Zhang et al. 2019). "
- Line 60-61, awkward sentence with controversial expression. Try to explain the limited time for straw decomposition.
Response: Thank you for the valuable suggestion. We further explain the constraints of straw decomposition and add references to the literature. The sentence has been amended to: "This is especially likely in high-latitude Chinese Mollisols, where decomposition rate of returning straw is very limited due to long cold time and low temperature. The decomposition time of straw is from 3 months to one year, and the effect is poor. (Wang et al. 2011)."
- Line 87, "Principal ecological activities including…", double check the term or phrase.
Response: Thanks for catching this. The phrase was modified as: "Principal ecological activities in soil".
- Line 215, Please explain original profiled soil?
Response: The "original profiled soil" means "the soil without adding any foreign substances". The phrase was modified as: "The surface soil (0–10 cm) had the highest moisture content in the CK treatment".
- Line 227, please define "bottom soil".
Response: The "bottom soil" means "the 0-40cm soil layer". To make the sentence clear and understandable. The phrase was modified as: "First, the number of macroaggregate components was lower in the 10–40 cm soil layer than in the surface soil".
- Line 230, "combined application"? unclear expression.
Response: "combined application" means "Biochar combined with nitrogen fertilizer"
- Line 288-290, Not necessary to simply repeat the numbers or values in the figures.
Response: The interpretation of the diagram has been simplified as requested.
- Line 342, macroaggregates, small macroaggregates? Please be uniform in the text.
Response: Made the change as suggested.
- Line 410, Among the effects of biochar combined with N fertilizer on microbial communities, the authors suggest the effectiveness of reduced N fertilizer application to improve microbial richness, and the potential negative environmental effects after high doses of N fertilizer application should be further briefly discussed.
Response: Thank you for the valuable suggestion. Based on your suggestions, the potential negative environmental effects have been supplemented:" In this study, C2N1/2 treatment had the best improvement effect on microbial community structure. Nitrogen source always an important source of microbial nutrients. However, when nitrogen fertilizer application exceeds crop absorption capacity and soil retention capacity, the excess nitrogen may be leachated to deep soil and pollute groundwater. Meanwhile, the unbalanced C/N ratio also became the main factor for the significant decline of soil biodiversity (Yuan et al. 2017)."
- Line 418, Please explain the difference between TOC and SOC. Both parameters are used.
Response: For TOC in soil (measured in the experiment), it consists of soil organic carbon (SOC) and soil inorganic carbon (SIC). SIC is generally present in the form of carbonate, which was negligible in the soil samples in this experiment, so TOC was used in this paper to represent the amount of organic matter in the samples. However, since microorganisms are unable to use SIC and mainly use SOC as carbon source. It is therefore generally more accurate to use the term SOC for the interpretation and justification of conclusions.
- Line 426-428, Repeated statement.
Response: Thanks for your careful checks, we are very sorry for our carelessness. It has been corrected
- Line 430-432, the meaning of this sentence is unclear, rephrase the sentences to make the logic smooth and the meaning clear.
Response: Thank you for the valuable suggestion. The phrase was modified as: " The increased fungal abundance has been proposed as an important biological factor in soil aggregate formation (Yuan et al. 2015; Zheng et al. 2020). Previous research has shown that the improvement of aggregate stability and carbon storage is an important condition to improve the microbial communities (Zhang et al. 2021)."
- Line 454, delete "The PCA showed that".
Response: Made the change as suggested.
Citation: https://doi.org/10.5194/egusphere-2022-1084-AC1
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AC1: 'Reply on CC1', jing Sun, 20 Dec 2022
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RC1: 'Comment on egusphere-2022-1084', Anonymous Referee #1, 02 Mar 2023
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Sun et al. conducted field experiments to explore the response of the stability mechanism of the soil aggregates, the dynamic properties of organic carbon, and changes in the microbial community structure to biochar. The results help to the sustainable utilization of Mollisols resources. I have several suggestions that may improve the manuscript.
- Line 37, (Zhang et al. 2018; Eswaran et al., 2011).
- Line 39, increased poor?
- Line 94, E.-L. et al. 2014?
- Line 166, 𝑊t = 𝑀i/𝑀t × 100%?
- Lines 186-188, remove these sentences as they are not methods.
- Line 222, in figure 1, the X axis represents different treatments, how to fit the data with the Y axis? So please remove the fit line in the figure. It is more suitable to use a box plot to show the results. Similar mistakes also occurred in figure 4 and figure 7, please revise carefully.
- Line 266, change C3+N1/2 to C3N1/2, please keep consistency in the MS
- Line 272, in figure 5, please remove the correlation coefficient with 1, no need to show.
- Lines 305-306, the results showed that the first 3 principal components (F1-F3) explained 90.13% of the total variance.
- Line 376, where is Table 2?
- Lines 445-446, the authors conclude that “Based on the sequestration of SOC and the sustainability and stability of the ecosystem, we selected C3N1/2 as the most reasonable biochar ratio.”, however, according to table 1, C2N1/2 is the best.
- More discussion is needed to explain why N addition affects soil aggregate stability.
- In short, I think this study is interesting, however, more revisions are needed, as I listed above. Please also check English carefully and make the MS more concise, logical, and readable.
Citation: https://doi.org/10.5194/egusphere-2022-1084-RC1 -
AC2: 'Reply on RC1', jing Sun, 17 Mar 2023
reply
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2022/egusphere-2022-1084/egusphere-2022-1084-AC2-supplement.pdf
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RC2: 'Comment on egusphere-2022-1084', Anonymous Referee #2, 22 Mar 2023
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This paper describes the effects of biochar and mineral fertilizer applications on soil aggregation, aggregates associated C, and microbial community structure. Few studies have examined the limpact of biochar on soil aggregation and microbial community structure that related to soil C and N cycles under field conditions. Furthermore, the study considers the interactions between biochar and mineral fertilizer on these processes linking to SOC sequestration. This paper provides important new information that will be of value to many researchers and students and the data are worthy of publication.
However, some issues should be revised before further consideration.For the introduction section, some statements should be cited the references (E.g., L49-50, L65-66;)
For L86, A summary is needed to grasp the research gaps here and other palaces in the introduction.
For 322 to 328, these discussion should be mixed with your own data.
L334-345, this statement should be supported by citation.
L338, In the end of subsection, a summary is heavily needed to conclude what they get from the complete discussion.
L447, The novelty and significance of these findings should be mentioned.
For the detailed comments and suggestion, please see the attached file.
Jing Sun et al.
Jing Sun et al.
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