Pub Date : 2025-07-14DOI: 10.5194/soil-11-523-2025
Samuel Franco-Luesma, María Alonso-Ayuso, Benjamin Wolf, Borja Latorre, Jorge Álvaro-Fuentes
Abstract. Over the last decades and due to the current climate change situation, the study of the impacts of human activities on climate has reached great importance, with agriculture being one of the main sources of soil greenhouse gas. There are different techniques to quantify the soil gas fluxes, such as micrometeorological techniques or chamber techniques, with the last one being capable of assessing different treatments at the same site. Manual chambers are the most common technique. However, manual chambers are characterized by low sampling frequency; typically, one sample per day is considered to be a high sampling frequency. Therefore, a great deal of effort is required to monitor short-term emission events such as fertilization or rewetting. For this reason, automated chamber systems present an opportunity to improve soil gas flux determination, but their distribution is still scarce due to the cost and challenging technical implementation. The objective of this study was to develop an automated chamber system for agricultural systems and to compare it with a manual chamber system. Moreover, over a period of 1 month, the soil gas fluxes were determined by both systems to compare their capabilities in capturing the temporal variability of soil gas emissions. The automated system reported soil greenhouse gas (GHG) fluxes that were up to 58 % and 40 % greater for CO2 and N2O fluxes compared to the manual chamber system. Additionally, the higher sampling frequency of the automated chamber system allowed us to capture the daily flux variations, resulting in a more accurate estimation of cumulative soil gas emissions. Furthermore, the assessment of various sampling intervals for single-day measurements indicated that between 10:00 and 12:00 LT was the optimal time interval for soil gas sampling in order to obtain representative daily emissions. This study emphasizes the importance of chamber dimension and shape in the development of chamber systems, as well as the sampling frequency and sampling hour for manual chamber systems.
{"title":"Measurement of greenhouse gas fluxes in agricultural soils with a flexible, open-design automated system","authors":"Samuel Franco-Luesma, María Alonso-Ayuso, Benjamin Wolf, Borja Latorre, Jorge Álvaro-Fuentes","doi":"10.5194/soil-11-523-2025","DOIUrl":"https://doi.org/10.5194/soil-11-523-2025","url":null,"abstract":"Abstract. Over the last decades and due to the current climate change situation, the study of the impacts of human activities on climate has reached great importance, with agriculture being one of the main sources of soil greenhouse gas. There are different techniques to quantify the soil gas fluxes, such as micrometeorological techniques or chamber techniques, with the last one being capable of assessing different treatments at the same site. Manual chambers are the most common technique. However, manual chambers are characterized by low sampling frequency; typically, one sample per day is considered to be a high sampling frequency. Therefore, a great deal of effort is required to monitor short-term emission events such as fertilization or rewetting. For this reason, automated chamber systems present an opportunity to improve soil gas flux determination, but their distribution is still scarce due to the cost and challenging technical implementation. The objective of this study was to develop an automated chamber system for agricultural systems and to compare it with a manual chamber system. Moreover, over a period of 1 month, the soil gas fluxes were determined by both systems to compare their capabilities in capturing the temporal variability of soil gas emissions. The automated system reported soil greenhouse gas (GHG) fluxes that were up to 58 % and 40 % greater for CO2 and N2O fluxes compared to the manual chamber system. Additionally, the higher sampling frequency of the automated chamber system allowed us to capture the daily flux variations, resulting in a more accurate estimation of cumulative soil gas emissions. Furthermore, the assessment of various sampling intervals for single-day measurements indicated that between 10:00 and 12:00 LT was the optimal time interval for soil gas sampling in order to obtain representative daily emissions. This study emphasizes the importance of chamber dimension and shape in the development of chamber systems, as well as the sampling frequency and sampling hour for manual chamber systems.","PeriodicalId":48610,"journal":{"name":"Soil","volume":"7 1","pages":""},"PeriodicalIF":6.8,"publicationDate":"2025-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144622232","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-07-11DOI: 10.5194/soil-11-507-2025
Waqar Ali, Amani Milinga, Tao Luo, Mohammad Nauman Khan, Asad Shah, Khurram Shehzad, Qiu Yang, Huai Yang, Wenxing Long, Wenjie Liu
Abstract. In southern China, the island of Hainan faces land degradation risks due to a combination of soil physical, chemical, and climatic factors: soil physical properties like a high proportion of microaggregates (<0.25 mm), chemical properties such as low soil organic matter (SOM) content, and a climatic factor of frequent uneven rainfall. The cohesive force between soil particles, which is influenced by plant root properties and root-derived SOM, is essential for improving soil aggregate stability and mitigating land degradation. However, the mechanisms by which rubber plant root properties and root-derived SOM affect soil aggregate stability through cohesive forces in tropical regions remain unclear. This study evaluated rubber plants of different ages to assess the effects of root properties and root-derived SOM on soil aggregate stability and cohesive forces. Older rubber plants (>11 years old) showed greater root diameters (RDs) (0.81–0.91 mm), higher root length (RL) densities (1.83–2.70 cm cm−3), and increased proportions of fine (0.2–0.5 mm) and medium (0.5–1 mm) roots, leading to higher SOM due to lower lignin and higher cellulose contents. Older plants exhibited higher soil cohesion, with significant correlations among root characteristics, SOM, and cohesive force, whereas the random forest (RF) model identified aggregates (>0.25 mm), root properties, SOM, and cohesive force as the key factors influencing mean weight diameter (MWD) and geometric mean diameter (GMD). Furthermore, partial least squares path models (PLS-PM) showed that the RL density (RLD) directly influenced SOM (path coefficient 0.70) and root-free cohesive force (RFCF) (path coefficient 0.30), which subsequently affected the MWD, with additional direct RLD effects on the SOM (path coefficient 0.45) and MWD (path coefficient 0.64) in the surface soil. Cohesive force in rubber plants of different ages increased macroaggregates (>0.25 mm) and decreased microaggregates (<0.25 mm), with topsoil average MWD following the order control (CK) (0.98 mm) < 5Y_RF (1.26 mm) < mixed forest (MF; 1.31 mm) < 11Y_RF (1.36 mm) < 27Y_RF (1.48 mm) < 20Y_RF (1.51 mm). Rubber plant root traits enhance soil aggregate stability and mitigate land degradation risk in tropical regions, offering practical soil restoration strategies through targeted root trait selection to strengthen soil cohesion, ensure long-term agricultural productivity, and preserve environmental quality, highlighting the need for further research across diverse ecological zones and forest types.
{"title":"Rubber plant root properties induce contrasting soil aggregate stability through cohesive force and reduced land degradation risk in southern China","authors":"Waqar Ali, Amani Milinga, Tao Luo, Mohammad Nauman Khan, Asad Shah, Khurram Shehzad, Qiu Yang, Huai Yang, Wenxing Long, Wenjie Liu","doi":"10.5194/soil-11-507-2025","DOIUrl":"https://doi.org/10.5194/soil-11-507-2025","url":null,"abstract":"Abstract. In southern China, the island of Hainan faces land degradation risks due to a combination of soil physical, chemical, and climatic factors: soil physical properties like a high proportion of microaggregates (<0.25 mm), chemical properties such as low soil organic matter (SOM) content, and a climatic factor of frequent uneven rainfall. The cohesive force between soil particles, which is influenced by plant root properties and root-derived SOM, is essential for improving soil aggregate stability and mitigating land degradation. However, the mechanisms by which rubber plant root properties and root-derived SOM affect soil aggregate stability through cohesive forces in tropical regions remain unclear. This study evaluated rubber plants of different ages to assess the effects of root properties and root-derived SOM on soil aggregate stability and cohesive forces. Older rubber plants (>11 years old) showed greater root diameters (RDs) (0.81–0.91 mm), higher root length (RL) densities (1.83–2.70 cm cm−3), and increased proportions of fine (0.2–0.5 mm) and medium (0.5–1 mm) roots, leading to higher SOM due to lower lignin and higher cellulose contents. Older plants exhibited higher soil cohesion, with significant correlations among root characteristics, SOM, and cohesive force, whereas the random forest (RF) model identified aggregates (>0.25 mm), root properties, SOM, and cohesive force as the key factors influencing mean weight diameter (MWD) and geometric mean diameter (GMD). Furthermore, partial least squares path models (PLS-PM) showed that the RL density (RLD) directly influenced SOM (path coefficient 0.70) and root-free cohesive force (RFCF) (path coefficient 0.30), which subsequently affected the MWD, with additional direct RLD effects on the SOM (path coefficient 0.45) and MWD (path coefficient 0.64) in the surface soil. Cohesive force in rubber plants of different ages increased macroaggregates (>0.25 mm) and decreased microaggregates (<0.25 mm), with topsoil average MWD following the order control (CK) (0.98 mm) < 5Y_RF (1.26 mm) < mixed forest (MF; 1.31 mm) < 11Y_RF (1.36 mm) < 27Y_RF (1.48 mm) < 20Y_RF (1.51 mm). Rubber plant root traits enhance soil aggregate stability and mitigate land degradation risk in tropical regions, offering practical soil restoration strategies through targeted root trait selection to strengthen soil cohesion, ensure long-term agricultural productivity, and preserve environmental quality, highlighting the need for further research across diverse ecological zones and forest types.","PeriodicalId":48610,"journal":{"name":"Soil","volume":"35 1","pages":""},"PeriodicalIF":6.8,"publicationDate":"2025-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144603107","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. Mineral-associated organic matter (MAOM), representing the dominant form of relatively stable C in soil, contains high physicochemical heterogeneity. The co-localization of organic matter (OM) with reactive aluminum (Al) and iron (Fe) phases in various MAOM fractions—across a range of natural and cultivated soils from five soil orders—has led to the “organo-metallic glue” hypothesis. The hypothesis proposes that coprecipitates formed between mineral-derived metals and microbially processed OM act as a binding agent, promoting the formation of stable microaggregates and thereby enhancing soil OM persistence. However, the formation mechanism remains unclear as the observed associations reflect multiple soil processes. We thus designed a simple laboratory experiment to test if the supply of metals and metalloids through rock weathering controls MAOM formation and if the OM-to-metal ratio of the material formed is consistent with complexation, sorptive association, or their mixture (i.e., coprecipitates). Two end-member igneous rocks (granite and basalt) crushed to have 38–75 µm size and, additionally, 20–38 µm size for basalt, as well as river sand (100–300 µm) as control were mixed with leaf compost (powdered to 100–250 µm) as single OM source. The mineral-OM mixtures were incubated aerobically at 30 oC with the natural soil microbial community and subjected to 8 wet-and-dry cycles using artificial rainwater (pH 4.73) over a 55-day experiment. The mixtures were then fractionated by density to examine the formation of meso-density, organo-mineral aggregates (1.8–2.4 g cm–3: MF) by distinguishing it from the compost-dominant low-density fraction (< 1.8 g cm–3: LF) and high-density fraction (>2.4 g cm–3: HF) consisting of the crushed rock. The MF formation assessed as C content was 1.49 ± 0.06 mg C g–1 rock (fine basalt), 1.04 ± 0.08 (coarse basalt), and 0.62 ± 0.06 (granite) over the 55 days, while the net MF mass increase was detected only in fine basalt due to the presence of meso-density materials in the crushed rock (< 7 % by mass). Faster chemical weathering of the fine basalt was indicated by a significant increase in extractable Fe and Al phases, largely in MF, and the highest leaching of Fe and base cations (esp. Na and Ca). The organo-mineral aggregates formed in the fine basalt treatment had the C-to-metal (Fe+Al) ratio of 0.36 ± 0.01 (molar basis), consistent with organo-metal coprecipitation. Further analysis focusing on the two basalt treatments revealed a significant decline in C:N ratios by 23–25 units and enrichment of δ13C and δ15N by 0.9–1.2 ‰ and 0.6 ‰, respectively, in MFs compared to LFs, indicating a strong contribution of microbial N-containing compounds to the MAOM formation. While microbial community composition differed among the treatments, no significant difference was found in q
摘要。矿物伴生有机质（MAOM）是土壤中相对稳定的碳的主要形式，具有较高的物理化学异质性。有机物质（OM）与活性铝（Al）和铁（Fe）相在各种MAOM组分中的共定位-跨越了五个土壤目的自然和栽培土壤-导致了“有机-金属胶”假说。该假设认为，矿物来源的金属与微生物处理的OM之间形成的共沉淀作为一种结合剂，促进稳定微团聚体的形成，从而增强土壤OM的持久性。然而，由于观察到的关联反映了多种土壤过程，形成机制尚不清楚。因此，我们设计了一个简单的实验室实验，以测试通过岩石风化作用的金属和类金属的供应是否控制了MAOM的形成，以及形成的材料的om -metal比例是否与络合作用、吸附结合或它们的混合物（即共沉淀）相一致。两个端元火成岩（花岗岩和玄武岩）被粉碎成38-75微米的尺寸，另外，玄武岩的尺寸为20-38微米，以及河砂（100-300微米）作为对照，与树叶堆肥（粉末至100-250微米）混合作为单一OM源。在30℃的条件下，与天然土壤微生物群落一起培养矿物质- om混合物，并在55天的实验中使用人工雨水（pH为4.73）进行8次干湿循环。然后根据密度对混合物进行分馏，通过将其与堆肥占主导地位的低密度组分(<；1.8 g cm-3: LF)和由碎石组成的高密度组分（>2.4 g cm-3: HF）。在55天内，MF地层的C含量分别为1.49±0.06 mg（细玄武岩）、1.04±0.08 mg（粗玄武岩）和0.62±0.06 mg（花岗岩），而净MF质量仅在细玄武岩中检测到增加，这是由于岩石破碎中存在中密度物质(<；7%（质量）。细粒玄武岩的化学风化速度加快，主要表现在可提取的Fe和Al相显著增加，且铁和碱阳离子（尤其是Na和Ca）的浸出量最高。细粒玄武岩处理形成的有机矿物团聚体的c -金属（Fe+Al）比为0.36±0.01（摩尔基），符合有机-金属共沉淀。对两种玄武岩处理的进一步分析表明，与低碳层相比，中碳层的C:N比值显著下降了23-25个单位，δ13C和δ15N分别富集了0.9-1.2‰和0.6‰，表明微生物含氮化合物对MAOM的形成有重要贡献。微生物群落组成在不同处理间存在差异，但基于qpcr的细菌数量和物种丰富度无显著差异。使用SEM和STXM进行的显微分析证实，从选定的MF样品中，MF中存在抗振动微聚集体和C、Fe和Al的共定位。总之，我们的研究结果有力地支持了有机金属胶假说，并提供了玄武岩诱导MAOM形成的实验室证据，以及在将碎岩应用于土壤时对早期成土作用和有机矿物相互作用的一些见解。
{"title":"Formation of mineral-associated organic matter via rock weathering: an experimental test for the organo-metallic glue hypothesis","authors":"Kaori Matsuoka, Jo Jinno, Hiroaki Shimada, Emi Matsumura, Ryo Shingubara, Rota Wagai","doi":"10.5194/egusphere-2025-2840","DOIUrl":"https://doi.org/10.5194/egusphere-2025-2840","url":null,"abstract":"<strong>Abstract.</strong> Mineral-associated organic matter (MAOM), representing the dominant form of relatively stable C in soil, contains high physicochemical heterogeneity. The co-localization of organic matter (OM) with reactive aluminum (Al) and iron (Fe) phases in various MAOM fractions—across a range of natural and cultivated soils from five soil orders—has led to the “organo-metallic glue” hypothesis. The hypothesis proposes that coprecipitates formed between mineral-derived metals and microbially processed OM act as a binding agent, promoting the formation of stable microaggregates and thereby enhancing soil OM persistence. However, the formation mechanism remains unclear as the observed associations reflect multiple soil processes. We thus designed a simple laboratory experiment to test if the supply of metals and metalloids through rock weathering controls MAOM formation and if the OM-to-metal ratio of the material formed is consistent with complexation, sorptive association, or their mixture (i.e., coprecipitates). Two end-member igneous rocks (granite and basalt) crushed to have 38–75 µm size and, additionally, 20–38 µm size for basalt, as well as river sand (100–300 µm) as control were mixed with leaf compost (powdered to 100–250 µm) as single OM source. The mineral-OM mixtures were incubated aerobically at 30 <sup>o</sup>C with the natural soil microbial community and subjected to 8 wet-and-dry cycles using artificial rainwater (pH 4.73) over a 55-day experiment. The mixtures were then fractionated by density to examine the formation of meso-density, organo-mineral aggregates (1.8–2.4 g cm<sup>–</sup><sup>3</sup>: MF) by distinguishing it from the compost-dominant low-density fraction (< 1.8 g cm<sup>–</sup><sup>3</sup>: LF) and high-density fraction (>2.4 g cm<sup>–</sup><sup>3</sup>: HF) consisting of the crushed rock. The MF formation assessed as C content was 1.49 ± 0.06 mg C g<sup>–1</sup> rock (fine basalt), 1.04 ± 0.08 (coarse basalt), and 0.62 ± 0.06 (granite) over the 55 days, while the net MF mass increase was detected only in fine basalt due to the presence of meso-density materials in the crushed rock (< 7 % by mass). Faster chemical weathering of the fine basalt was indicated by a significant increase in extractable Fe and Al phases, largely in MF, and the highest leaching of Fe and base cations (esp. Na and Ca). The organo-mineral aggregates formed in the fine basalt treatment had the C-to-metal (Fe+Al) ratio of 0.36 ± 0.01 (molar basis), consistent with organo-metal coprecipitation. Further analysis focusing on the two basalt treatments revealed a significant decline in C:N ratios by 23–25 units and enrichment of δ<sup>13</sup>C and δ<sup>15</sup>N by 0.9–1.2 ‰ and 0.6 ‰, respectively, in MFs compared to LFs, indicating a strong contribution of microbial N-containing compounds to the MAOM formation. While microbial community composition differed among the treatments, no significant difference was found in q","PeriodicalId":48610,"journal":{"name":"Soil","volume":"697 1","pages":""},"PeriodicalIF":6.8,"publicationDate":"2025-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144594127","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-07-08DOI: 10.5194/soil-11-489-2025
Victoria Nasser, René Dechow, Mirjam Helfrich, Ana Meijide, Pauline Sophie Rummel, Heinz-Josef Koch, Reiner Ruser, Lisa Essich, Klaus Dittert
Abstract. Cover crops (CCs) are acclaimed for enhancing the environmental sustainability of agricultural practices by aiding in carbon (C) sequestration and reducing losses of soil mineral nitrogen (SMN) after harvest. Yet, their influence on nitrous oxide (N2O) emissions – a potent greenhouse gas – presents a complex challenge, with findings varying across different studies. This research aimed to elucidate the effects of various winter CCs – winter rye (frost-tolerant grass), saia oat (frost-sensitive grass), and spring vetch (frost-sensitive legume) – compared to a bare fallow control on SMN dynamics, N2O emissions, and C sequestration. These effects were determined by measuring SMN dynamics and N2O emissions in field experiments. The effects of CCs on soil C sequestration over a 50-year period were predicted by soil organic C (SOC) models using measured aboveground and belowground CC biomass. While CCs efficiently lowered SMN levels during their growth, they slightly increased N2O emissions compared to bare fallow. In particular, winter frost events triggered significant emissions from the frost-sensitive varieties. Moreover, residue incorporation and tillage practices were associated with increased N2O emissions in all CC treatments. Winter rye, characterized by its high biomass production and nitrogen (N) uptake, was associated with the highest cumulative N2O emissions, highlighting the influence of biomass management and tillage practices on N cycling and N2O emissions. The CC treatment resulted in a slight increase in direct N2O emissions (4.5±3.0, 2.7±1.4, and 3.1±3.8kgN2O-Nha-1 for rye, oat, and vetch, respectively) compared to the fallow (2.6±1.7kgN2O-Nha-1) over the entire trial period (18 months). However, the potential of non-legume CCs to reduce indirect N2O emissions compared to fallow (0.3±0.4 and 0.2±0.1kgN2O-Nha-1a-1 for rye and oat, respectively) and their contribution to C sequestration (120–150 kgCha-1a-1 over a period of 50 years when CCs were grown every fourth year) might partially counterbalance these emissions. Thus, while CCs provide environmental benefits, their net impact on N2O emissions requires further research into optimized CC selection and management strategies tailored to specific site conditions to fully exploit their environmental advantages.
{"title":"Evaluating N2O emissions and carbon sequestration in temperate croplands with cover crops: insights from field trials","authors":"Victoria Nasser, René Dechow, Mirjam Helfrich, Ana Meijide, Pauline Sophie Rummel, Heinz-Josef Koch, Reiner Ruser, Lisa Essich, Klaus Dittert","doi":"10.5194/soil-11-489-2025","DOIUrl":"https://doi.org/10.5194/soil-11-489-2025","url":null,"abstract":"Abstract. Cover crops (CCs) are acclaimed for enhancing the environmental sustainability of agricultural practices by aiding in carbon (C) sequestration and reducing losses of soil mineral nitrogen (SMN) after harvest. Yet, their influence on nitrous oxide (N2O) emissions – a potent greenhouse gas – presents a complex challenge, with findings varying across different studies. This research aimed to elucidate the effects of various winter CCs – winter rye (frost-tolerant grass), saia oat (frost-sensitive grass), and spring vetch (frost-sensitive legume) – compared to a bare fallow control on SMN dynamics, N2O emissions, and C sequestration. These effects were determined by measuring SMN dynamics and N2O emissions in field experiments. The effects of CCs on soil C sequestration over a 50-year period were predicted by soil organic C (SOC) models using measured aboveground and belowground CC biomass. While CCs efficiently lowered SMN levels during their growth, they slightly increased N2O emissions compared to bare fallow. In particular, winter frost events triggered significant emissions from the frost-sensitive varieties. Moreover, residue incorporation and tillage practices were associated with increased N2O emissions in all CC treatments. Winter rye, characterized by its high biomass production and nitrogen (N) uptake, was associated with the highest cumulative N2O emissions, highlighting the influence of biomass management and tillage practices on N cycling and N2O emissions. The CC treatment resulted in a slight increase in direct N2O emissions (4.5±3.0, 2.7±1.4, and 3.1±3.8kgN2O-Nha-1 for rye, oat, and vetch, respectively) compared to the fallow (2.6±1.7kgN2O-Nha-1) over the entire trial period (18 months). However, the potential of non-legume CCs to reduce indirect N2O emissions compared to fallow (0.3±0.4 and 0.2±0.1kgN2O-Nha-1a-1 for rye and oat, respectively) and their contribution to C sequestration (120–150 kgCha-1a-1 over a period of 50 years when CCs were grown every fourth year) might partially counterbalance these emissions. Thus, while CCs provide environmental benefits, their net impact on N2O emissions requires further research into optimized CC selection and management strategies tailored to specific site conditions to fully exploit their environmental advantages.","PeriodicalId":48610,"journal":{"name":"Soil","volume":"2 1","pages":""},"PeriodicalIF":6.8,"publicationDate":"2025-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144577912","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. In Iran, a considerable proportion of agricultural soils are contaminated with various heavy metals (HMs), including nickel (Ni), necessitating remediation to mitigate their transfer into the food chain. However, there remains a scarcity of research on the effectiveness of applying organic and inorganic materials, either individually or in combination, for Ni immobilization in contaminated calcareous soils. To address this gap, an incubation experiment as completely randomized design with three replications was conducted to compare the effect of different soil amendments, either individually or combined (municipal solid waste compost (M), bentonite (B), municipal solid waste compost biochar (MB), M+B, MB+B, MB+M each applied at 2 % wt.) on Ni immobilization in a calcareous soil with three Ni contamination levels (0 (Ni0), 150 mg kg-1 (Ni1) and 300 mg kg-1 (Ni2). The study employed analytical techniques such as SEM-EDX, XRD, FTIR, sequential extraction, and DTPA-release kinetics to assess the efficiency of these amendments on stabilizing Ni in the soil. Elevating Ni levels from Ni0 to Ni2 increased Ni concentrations across all soil fractions, especially in Fe/Mn oxides (FeMnOx) and organic matter (OM). All amendments except M enhanced Ni immobilization by converting more labile fractions (WsEx, Car, FeMnOx) into residual (Res) form. While combined amendments were not more effective than single treatments, MB was the most efficient in stabilizing Ni. MB also exhibited the lowest 'a' and highest 'b' values attributed to the power function kinetics model, indicating superior Ni desorption reduction. These finding are likely due to its alkaline pH, ash content, and phosphorus content, which facilitate Ni precipitation. In contrast, M increased Ni desorption by raising its bioavailability (WsEx and Car fractions). The combined application of biochar (MB) with either bentonite (B) or compost (M) did not exhibit synergistic effects on the immobilization of Ni in the soil. In conclusion, the independent application of municipal solid waste-derived biochar appears to be a potentially effective amendment for enhancing Ni immobilization in contaminated calcareous soils.
{"title":"Comparative efficacy of individually and combined application of compost, biochar, and bentonite on Ni dynamics in a calcareous soil","authors":"Hamid Reza Boostani, Zahra Jalalpour, Ali Behpouri, Ehsan Bijanzadeh, Mahdi Najafi-Ghiri","doi":"10.5194/egusphere-2025-2147","DOIUrl":"https://doi.org/10.5194/egusphere-2025-2147","url":null,"abstract":"<strong>Abstract.</strong> In Iran, a considerable proportion of agricultural soils are contaminated with various heavy metals (HMs), including nickel (Ni), necessitating remediation to mitigate their transfer into the food chain. However, there remains a scarcity of research on the effectiveness of applying organic and inorganic materials, either individually or in combination, for Ni immobilization in contaminated calcareous soils. To address this gap, an incubation experiment as completely randomized design with three replications was conducted to compare the effect of different soil amendments, either individually or combined (municipal solid waste compost (M), bentonite (B), municipal solid waste compost biochar (MB), M+B, MB+B, MB+M each applied at 2 % wt.) on Ni immobilization in a calcareous soil with three Ni contamination levels (0 (Ni<sub>0</sub>), 150 mg kg<sup>-1 </sup>(Ni<sub>1</sub>) and 300 mg kg<sup>-1</sup> (Ni<sub>2</sub>). The study employed analytical techniques such as SEM-EDX, XRD, FTIR, sequential extraction, and DTPA-release kinetics to assess the efficiency of these amendments on stabilizing Ni in the soil. Elevating Ni levels from Ni<sub>0</sub> to Ni<sub>2</sub> increased Ni concentrations across all soil fractions, especially in Fe/Mn oxides (FeMnOx) and organic matter (OM). All amendments except M enhanced Ni immobilization by converting more labile fractions (WsEx, Car, FeMnOx) into residual (Res) form. While combined amendments were not more effective than single treatments, MB was the most efficient in stabilizing Ni. MB also exhibited the lowest 'a' and highest 'b' values attributed to the power function kinetics model, indicating superior Ni desorption reduction. These finding are likely due to its alkaline pH, ash content, and phosphorus content, which facilitate Ni precipitation. In contrast, M increased Ni desorption by raising its bioavailability (WsEx and Car fractions). The combined application of biochar (MB) with either bentonite (B) or compost (M) did not exhibit synergistic effects on the immobilization of Ni in the soil. In conclusion, the independent application of municipal solid waste-derived biochar appears to be a potentially effective amendment for enhancing Ni immobilization in contaminated calcareous soils.","PeriodicalId":48610,"journal":{"name":"Soil","volume":"18 1","pages":""},"PeriodicalIF":6.8,"publicationDate":"2025-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144577913","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-07-04DOI: 10.5194/soil-11-467-2025
Marine Casetta, Sylvie Philippe, Lucie Courcot, David Dumoulin, Gabriel Billon, François Baudin, Françoise Henry, Michaël Hermoso, Jacinthe Caillaud
Abstract. In urban and industrialized areas, soil contamination and degradation caused by industrial dust deposition may pose significant health and environmental risks. Generally, the mobility and thus bioavailability of potentially toxic elements (PTEs) are key factors in these issues. In the Dunkerque agglomeration, one of the most industrialized regions in France, the soils are periodically exposed to metallurgical dust fallout, rich in PTEs. However, no study has reported on the behavior of these PTEs once integrated into the soils. The aim of this study is therefore to assess the fate of PTEs in the urban soils of Dunkerque in terms of vertical migration and potential bioavailability. Four soil short cores were collected in the city of Gravelines (Dunkerque agglomeration) along a gradient from industrial emitters to deposition sites. Each soil core was cut into discrete 1 cm sections for PTE concentration analyses (ICP-AES/MS). Single HCl extractions were performed to evaluate PTE mobility in soils and their behavior according to the current soil parameters. For this purpose, key soil properties were identified, including grain-size distribution, mineralogy, pH, cation exchange capacity (CEC), TOC (total organic carbon), calcium carbonates and water contents in addition to the soil chemical composition (XRF, ICP-AES/MS). The studied soils revealed globally low absorbent capacities for pollutants (CEC averaging 5.3meq/100g), partially counterbalanced by the buffering effect of calcium carbonates (contents ranging from 8 %–30 %). Near the industrial emitters, minor (160 % for Mn and Cd and about 44 % for Zn). Our study points out the stability of industrial PTEs in soils under the current physicochemical conditions (calcareous soils with a slightly basic pH of 7.8). In this context, the monitoring of industrial PTEs in these urban soils is highly recommended, considering (1) the presence of allotment gardens in the vicinity of emitters and (2) the potential evolution of soil conditions due to increasing flood events.
{"title":"A quantitative assessment of the behavior of metallic elements in urban soils exposed to industrial dusts near Dunkerque (northern France)","authors":"Marine Casetta, Sylvie Philippe, Lucie Courcot, David Dumoulin, Gabriel Billon, François Baudin, Françoise Henry, Michaël Hermoso, Jacinthe Caillaud","doi":"10.5194/soil-11-467-2025","DOIUrl":"https://doi.org/10.5194/soil-11-467-2025","url":null,"abstract":"Abstract. In urban and industrialized areas, soil contamination and degradation caused by industrial dust deposition may pose significant health and environmental risks. Generally, the mobility and thus bioavailability of potentially toxic elements (PTEs) are key factors in these issues. In the Dunkerque agglomeration, one of the most industrialized regions in France, the soils are periodically exposed to metallurgical dust fallout, rich in PTEs. However, no study has reported on the behavior of these PTEs once integrated into the soils. The aim of this study is therefore to assess the fate of PTEs in the urban soils of Dunkerque in terms of vertical migration and potential bioavailability. Four soil short cores were collected in the city of Gravelines (Dunkerque agglomeration) along a gradient from industrial emitters to deposition sites. Each soil core was cut into discrete 1 cm sections for PTE concentration analyses (ICP-AES/MS). Single HCl extractions were performed to evaluate PTE mobility in soils and their behavior according to the current soil parameters. For this purpose, key soil properties were identified, including grain-size distribution, mineralogy, pH, cation exchange capacity (CEC), TOC (total organic carbon), calcium carbonates and water contents in addition to the soil chemical composition (XRF, ICP-AES/MS). The studied soils revealed globally low absorbent capacities for pollutants (CEC averaging 5.3meq/100g), partially counterbalanced by the buffering effect of calcium carbonates (contents ranging from 8 %–30 %). Near the industrial emitters, minor (1<EF<3) to moderately severe (5<EF<10) enrichment factors (EFs) were highlighted for industrial PTE (Cr, Ni, Mo, Mn, Cd and Zn) in the top 3 cm of soils near the industrial emitters. The contamination profiles of these soils are assigned to atmospheric inputs of metallurgical dust. Using a relatively strong leaching reagent (1 M HCl), we estimated a low vertical mobility for Cr, Ni and Mo (average leached ratios<25 %) in soils, suggesting their association with refractory phases (natural or anthropogenic). In contrast, Mn, Cd and Zn, which are related to industrial and/or urban sources, present a higher mobility (average leached ratios>60 % for Mn and Cd and about 44 % for Zn). Our study points out the stability of industrial PTEs in soils under the current physicochemical conditions (calcareous soils with a slightly basic pH of 7.8). In this context, the monitoring of industrial PTEs in these urban soils is highly recommended, considering (1) the presence of allotment gardens in the vicinity of emitters and (2) the potential evolution of soil conditions due to increasing flood events.","PeriodicalId":48610,"journal":{"name":"Soil","volume":"4 1","pages":"467-488"},"PeriodicalIF":6.8,"publicationDate":"2025-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144565904","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-07-01DOI: 10.5194/egusphere-2025-2583
Ariane Lentice de Paula, Luis Miguel Schiebelbein, Regiane Kazmierczak Becker, Eduardo Augusto Agnellos Barbosa, Fabrício Tondello Barbosa, Carolina Weigert Galvão, Rafael Mazer Etto, Heverton Fernando Melo, Adriel Ferreira da Fonseca, Neyde Fabiola Balarezo Giarola
Abstract. Soil health assessment depends on the appropriate selection of indicators and robust, sensitive methods for its determination. In this study, four integrative approaches were evaluated to assess the impacts of no-till with and without agricultural terraces on soil health in Southern Brazil. The different methods used were: (1) Principal Component Analysis (PCA); (2) expert opinion (EO); (2) FERTBIO; and (4) Soil Management Assessment Framework (SMAF). All approaches followed four steps: (i) selection of indicators; (ii) interpretation of indicators; (iii) integration of indicators; and (iv) calculation of soil health indices. The methods varied in the steps of indicator selection, interpretation, and the method of indicator integration. The indicators used included physical (bulk density, total porosity, soil penetration resistance, and water retention capacity), chemical (pH, calcium, phosphorus, potassium, organic matter, CEC, and base saturation), and biological indicators (microbial biomass carbon, β-glucosidase, and arylsulfatase). Crop yield was evaluated for maize (2019/20 and 2021/22 harvests), wheat (2021 harvest), and soybean (2020/21 harvest). Descriptive statistics, median comparisons, principal component analysis and spearman correlation analysis were applied for the analysis of results. The results showed that only the EO and FERTBIO approaches were sensitive enough to detect differences in soil health between management systems, indicating that no-till with terraces had better soil health. Biological indicators were more sensitive in differentiating treatments, showing a rapid response in the short term. Maize (2019/20 harvest) and wheat (2021 harvest) yields were higher under the no-till with terraces treatment. Over time, yield showed a stronger relationship with soil health. The results highlight the importance of selecting appropriate indicators for soil health assessment and reinforce the benefits of agricultural terracing for the sustainability of production systems.
{"title":"Soil health approaches to assess the impacts of no-tillage with agricultural terraces in southern Brazil","authors":"Ariane Lentice de Paula, Luis Miguel Schiebelbein, Regiane Kazmierczak Becker, Eduardo Augusto Agnellos Barbosa, Fabrício Tondello Barbosa, Carolina Weigert Galvão, Rafael Mazer Etto, Heverton Fernando Melo, Adriel Ferreira da Fonseca, Neyde Fabiola Balarezo Giarola","doi":"10.5194/egusphere-2025-2583","DOIUrl":"https://doi.org/10.5194/egusphere-2025-2583","url":null,"abstract":"<strong>Abstract.</strong> Soil health assessment depends on the appropriate selection of indicators and robust, sensitive methods for its determination. In this study, four integrative approaches were evaluated to assess the impacts of no-till with and without agricultural terraces on soil health in Southern Brazil. The different methods used were: (1) Principal Component Analysis (PCA); (2) expert opinion (EO); (2) FERTBIO; and (4) Soil Management Assessment Framework (SMAF). All approaches followed four steps: (i) selection of indicators; (ii) interpretation of indicators; (iii) integration of indicators; and (iv) calculation of soil health indices. The methods varied in the steps of indicator selection, interpretation, and the method of indicator integration. The indicators used included physical (bulk density, total porosity, soil penetration resistance, and water retention capacity), chemical (pH, calcium, phosphorus, potassium, organic matter, CEC, and base saturation), and biological indicators (microbial biomass carbon, β-glucosidase, and arylsulfatase). Crop yield was evaluated for maize (2019/20 and 2021/22 harvests), wheat (2021 harvest), and soybean (2020/21 harvest). Descriptive statistics, median comparisons, principal component analysis and spearman correlation analysis were applied for the analysis of results. The results showed that only the EO and FERTBIO approaches were sensitive enough to detect differences in soil health between management systems, indicating that no-till with terraces had better soil health. Biological indicators were more sensitive in differentiating treatments, showing a rapid response in the short term. Maize (2019/20 harvest) and wheat (2021 harvest) yields were higher under the no-till with terraces treatment. Over time, yield showed a stronger relationship with soil health. The results highlight the importance of selecting appropriate indicators for soil health assessment and reinforce the benefits of agricultural terracing for the sustainability of production systems.","PeriodicalId":48610,"journal":{"name":"Soil","volume":"16 1","pages":""},"PeriodicalIF":6.8,"publicationDate":"2025-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144533251","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-07-01DOI: 10.5194/egusphere-2025-2700
Manon S. Ferdinand, Brieuc F. Hardy, Philippe V. Baret
Abstract. Conservation Agriculture (CA) aims to enhance soil quality through three main principles: minimizing mechanical soil disturbance, maximizing soil organic cover, and diversifying crop species. However, the diversity of practices within CA makes the effect on soil quality hardly predictable. In this study, an evaluation of soil quality in CA fields across Wallonia (Belgium) was conducted for four distinct CA-types. Three soil quality indicators were examined: the soil structural stability, the soil organic carbon:clay ratio (SOC:Clay), and the labile carbon fraction (POXC). Results revealed significant variations among CA-types. The CA-type characterized by substantial temporary grassland and tillage-extensive crops (e.g., cereals, meslin, rape, flax) in the crop sequence had the highest soil structural stability and SOC:Clay ratio. In contrast, the CA-type characterized by strict non-inversion tillage practices and frequent tillage-intensive crops (e.g., sugar beet, chicory, potatoes, carrots) had the lowest scores for the three indicators. Temporary grassland in the crop sequence appeared as the most influential factor improving soil quality. These findings highlight the need to consider the diversity of CA-type when evaluating the agronomic and environmental performance of CA systems, whose response depends on local soil and climatic conditions, the crops cultivated, and the specific combination of practices implemented.
{"title":"Digging Deeper: Assessing Soil Quality in a Diversity of Conservation Agriculture Practices","authors":"Manon S. Ferdinand, Brieuc F. Hardy, Philippe V. Baret","doi":"10.5194/egusphere-2025-2700","DOIUrl":"https://doi.org/10.5194/egusphere-2025-2700","url":null,"abstract":"<strong>Abstract.</strong> Conservation Agriculture (CA) aims to enhance soil quality through three main principles: minimizing mechanical soil disturbance, maximizing soil organic cover, and diversifying crop species. However, the diversity of practices within CA makes the effect on soil quality hardly predictable. In this study, an evaluation of soil quality in CA fields across Wallonia (Belgium) was conducted for four distinct CA-types. Three soil quality indicators were examined: the soil structural stability, the soil organic carbon:clay ratio (SOC:Clay), and the labile carbon fraction (POXC). Results revealed significant variations among CA-types. The CA-type characterized by substantial temporary grassland and tillage-extensive crops (e.g., cereals, meslin, rape, flax) in the crop sequence had the highest soil structural stability and SOC:Clay ratio. In contrast, the CA-type characterized by strict non-inversion tillage practices and frequent tillage-intensive crops (e.g., sugar beet, chicory, potatoes, carrots) had the lowest scores for the three indicators. Temporary grassland in the crop sequence appeared as the most influential factor improving soil quality. These findings highlight the need to consider the diversity of CA-type when evaluating the agronomic and environmental performance of CA systems, whose response depends on local soil and climatic conditions, the crops cultivated, and the specific combination of practices implemented.","PeriodicalId":48610,"journal":{"name":"Soil","volume":"19 1","pages":""},"PeriodicalIF":6.8,"publicationDate":"2025-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144533252","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-06-25DOI: 10.5194/egusphere-2025-2696
Dario Autovino, Antonio Coppola, Roberto De Mascellis, Mohammad Farzamian, Angelo Basile
Abstract. Salt accumulation in the root zone limits agricultural productivity and can eventually lead to land abandonment. Therefore, monitoring the spatial distribution of soil water content and solution salinity is crucial for effective land and irrigation management. However, assessing soil water content and salinity at the field scale is often challenging due to the heterogeneity of soil properties. Electromagnetic induction (EMI) offers a fast, non-invasive, in situ geophysical method to map spatial variability in soil. EMI instruments measure the apparent soil electrical conductivity (ECa), which reflects the integrated contribution of the bulk electrical conductivity (σb) of different soil layers. By inverting the measured ECa, it is possible to obtain the distribution of the σb along the soil profile, which provides indirect information on soil salinity. However, in saline soils, σb is influenced by both water content (θ) and soil solution electrical conductivity (σw) (the salinity), making it difficult to independently quantify these two variables through a single, straightforward procedure. The objective of this study is to separate the respective contributions of θ and σw to σb, as obtained from the EMI inversion. To achieve this, ECa was measured using a CMD-MiniExplorer instrument in two maize plots irrigated with saline and non-saline water, respectively, in an agricultural field in southern Italy. The dataset was then inverted in order to obtain the σb distribution. By employing a site-specific calibrated Rhoades linear model and assuming homogeneity between the two plots, the spatial distribution of θ and σw in the saline plot was successfully estimated. To validate the results, independent measurements of soil water content by Time Domain Reflectometry (TDR) and direct measurement of soil solution electrical conductivity, σw, were performed. The proposed procedure enables the estimation of θ and σw with high accuracy along the soil profile, except in the soil surface, where EMI reliability is limited. These findings demonstrate that the integration of EMI with a site-specific θ - σb - σw model is a reliable and efficient in-situ approach for mapping soil salinity and water content at field scale, offering valuable insights for optimizing agricultural irrigation management in systems using saline water.
{"title":"An in-situ methodology to separate the contribution of soil water content and salinity to EMI-based soil electrical conductivity","authors":"Dario Autovino, Antonio Coppola, Roberto De Mascellis, Mohammad Farzamian, Angelo Basile","doi":"10.5194/egusphere-2025-2696","DOIUrl":"https://doi.org/10.5194/egusphere-2025-2696","url":null,"abstract":"<strong>Abstract.</strong> Salt accumulation in the root zone limits agricultural productivity and can eventually lead to land abandonment. Therefore, monitoring the spatial distribution of soil water content and solution salinity is crucial for effective land and irrigation management. However, assessing soil water content and salinity at the field scale is often challenging due to the heterogeneity of soil properties. Electromagnetic induction (EMI) offers a fast, non-invasive, in situ geophysical method to map spatial variability in soil. EMI instruments measure the apparent soil electrical conductivity (EC<sub>a</sub>), which reflects the integrated contribution of the bulk electrical conductivity (σ<sub>b</sub>) of different soil layers. By inverting the measured EC<sub>a</sub>, it is possible to obtain the distribution of the σ<sub>b</sub> along the soil profile, which provides indirect information on soil salinity. However, in saline soils, σ<sub>b</sub> is influenced by both water content (θ) and soil solution electrical conductivity (σ<sub>w</sub>) (the salinity), making it difficult to independently quantify these two variables through a single, straightforward procedure. The objective of this study is to separate the respective contributions of θ and σ<sub>w</sub> to σ<sub>b</sub>, as obtained from the EMI inversion. To achieve this, EC<sub>a</sub> was measured using a CMD-MiniExplorer instrument in two maize plots irrigated with saline and non-saline water, respectively, in an agricultural field in southern Italy. The dataset was then inverted in order to obtain the σ<sub>b</sub> distribution. By employing a site-specific calibrated Rhoades linear model and assuming homogeneity between the two plots, the spatial distribution of θ and σ<sub>w</sub> in the saline plot was successfully estimated. To validate the results, independent measurements of soil water content by Time Domain Reflectometry (TDR) and direct measurement of soil solution electrical conductivity, σ<sub>w</sub>, were performed. The proposed procedure enables the estimation of θ and σ<sub>w</sub> with high accuracy along the soil profile, except in the soil surface, where EMI reliability is limited. These findings demonstrate that the integration of EMI with a site-specific θ - σ<sub>b</sub> - σ<sub>w</sub> model is a reliable and efficient in-situ approach for mapping soil salinity and water content at field scale, offering valuable insights for optimizing agricultural irrigation management in systems using saline water.","PeriodicalId":48610,"journal":{"name":"Soil","volume":"21 1","pages":""},"PeriodicalIF":6.8,"publicationDate":"2025-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144478950","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-06-25DOI: 10.5194/egusphere-2025-2405
Hui Rong, Zhangliu Du, Weida Gao, Lixiao Ma, Xinhua Peng, Yuji Jiang, Demin Yan, Hu Zhou
Abstract. Manure is known to improve soil organic carbon (SOC) in Fe-rich red soils, while the underlying stabilization mechanisms remain poorly understood. In this study, four treatments were selected: (1) no amendment (Control), (2) low manure (LM, 150 kg N ha-1 yr-1), (3) high manure (HM, 600 kg N ha-1 yr-1), (4) high manure with lime (HML, 600 kg N ha-1 yr-1 plus 3000 kg Ca (OH)2 ha-1 3yr-1). The quantity and quality of topsoil (0–20 cm) organic carbon were investigated by physical fractionation, 13C-nuclear magnetic resonance (NMR) spectroscopy and thermogravimetry (TG) analysis. Manure application increased total SOC by 65.1 %–126.7 % (primarily in the particulate organic matter (POM) fraction), while the mineral-associated organic matter fraction (MAOM), despite its higher C content (4.18–7.09 g C kg⁻¹), contributed less (65.4 %–71.0 %) compared to the control (82.4 %). POM C was stabilized via hierarchical aggregation: fresh manure inputs acted as binding nuclei, increasing macroaggregates (>0.25 mm) while reducing microaggregates (0.05–0.25 mm), physically isolating labile C from microbial decomposition. Concurrently, manure amendments triggered Fe-mediated chemical stabilization. Elevated pH (4.8 to 5.4–7.1) enhanced non-crystalline Fe oxide (Feo) content (+25.4 %), which positively correlated with MAOM C (R² = 0.56, P < 0.05). Despite a chemical composition shift toward aliphaticity and reduced aromaticity, thermally stable organic matters increased by 8 %–12 %, revealing critical role of Feo (aggregates were destroyed before TG analysis) in offsetting inherent molecular lability. Overall, this study establishes a dual SOC stabilization framework for subtropical red soils, highlighting physical protection through aggregation processes and chemical protection via Fe-carbon associations.
摘要。众所周知，肥料可以改善富铁红壤的土壤有机碳（SOC），但其潜在的稳定机制尚不清楚。本研究选择4个处理：(1)不加氮肥（对照），(2)低肥（LM， 150 kg N ha-1年-1），(3)高肥（HM， 600 kg N ha-1年-1），(4)高肥加石灰（HML， 600 kg N ha-1年-1 + 3000 kg Ca (OH)2 ha-1 3年-1）。采用物理分馏、13c -核磁共振（NMR）谱和热重（TG）分析研究了表层土壤（0 ~ 20 cm）有机碳的数量和质量。施用有机肥增加了总有机碳65.1% - 126.7%（主要是颗粒有机质（POM）部分），而矿物相关有机质（MAOM）尽管其碳含量较高（4.18-7.09 g C kg⁻¹），但与对照（82.4%）相比，贡献较少（65.4% - 71.0%）。POM C通过分层聚集得到稳定：新鲜肥料的投入作为结合核，增加了大团聚体（>0.25 mm），减少了微团聚体（0.05-0.25 mm），从微生物分解中物理隔离了不稳定的C。同时，肥料修正触发了铁介导的化学稳定。pH升高（4.8 ~ 5.4 ~ 7.1），非晶氧化铁（Feo）含量升高（+ 25.4%），与MAOM C呈正相关(R²= 0.56,P <；0.05)。尽管化学成分向脂肪性和芳香性转变，但热稳定有机质增加了8% - 12%，揭示了Feo（在TG分析之前聚集物被破坏）在抵消固有分子不稳定性方面的关键作用。总体而言，本研究建立了亚热带红壤有机碳的双重稳定框架，强调了通过聚集过程的物理保护和通过铁碳结合的化学保护。
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