Orals: Thu, 1 May | Room 0.51
Boosting Soil Carbon: Management Practices for Climate Change Mitigation
Soil is the second-largest active carbon reservoir, storing an estimated 1,500–2,400 gigatons of carbon globally, making it crucial for climate change mitigation (e.g., Lal, 2004). Soil carbon stocks are influenced by physicochemical properties, climatic conditions, and land management practices. Effective soil management has been shown to be critical for maintaining or enhancing soil carbon sequestration (e.g., Paustian et al., 2016). This study evaluates the impact of various soil management practices on carbon stocks and soil health. Soils were characterized by their physicochemical and microbiological properties, including organic matter content and microbial biodiversity. Adjacent plots with different management practices (e.g., conventional tillage, no-tillage, or grazing livestock integration) were compared to assess their effects on soil carbon dynamics. Carbon content was measured using the loss-on-ignition method, while the carbon-to-nitrogen (C:N) ratio provided insights into organic matter decomposition potential and carbon stabilization. Greenhouse gas fluxes (CO₂ and CH₄) were measured to quantify emissions across management regimes. Microbial diversity and community structure, indicators of soil health and carbon cycling potential, were assessed through fungal-to-bacterial (F:B) ratios and biomass counts of fungi, bacteria, protozoa, and nematodes. Preliminary findings suggest that management practices significantly influence microbial composition and diversity, as well as carbon stocks and greenhouse gas fluxes. Practices like no-till farming and the integration of planned herbivore grazing result in more biodiverse soils with higher carbon retention and lower greenhouse gas emissions.
References
Lal, R. (2004). Soil carbon sequestration impacts on global climate change and food security. Science, 304(5677), 1623–1627.
Paustian et al., (2016). Climate-smart soils. Nature, 532(7597), 49–57.
Beillouin et al., (2022). A global overview of studies about land management, land‐use change, and climate change effects on soil organic carbon. Global change biology, 28(4), 1690-1702.
How to cite: Huguet, C., Jimenez Amat, P., and Silva Tamayo, J. C.: Boosting Soil Carbon: Management Practices for Climate Change Mitigation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1467, https://doi.org/10.5194/egusphere-egu25-1467, 2025.
Understanding the intricate connections between soil organic matter (SOM), microbial communities, and land-use practices is critical for safeguarding soil health and mitigating global climate change. SOM biogeography, which examines the distribution and characteristics of SOM across diverse landscapes, offers vital insights into the relationships between SOM fractions and the microbial and mesofauna communities that underpin soil functionality.
With the recognition that soil carbon storage can significantly influence global warming through positive feedback loops, enhancing our understanding of the regulatory mechanisms linking SOM pools to ecosystem biological functions is paramount. This knowledge is essential to preserving ecological goods and services, including soil productivity and carbon storage.
Microbial biodiversity lies at the heart of soil fertility and carbon sequestration, yet the factors shaping soil biodiversity over broad spatial scales remain inadequately explored. Simultaneously, land-use changes have increasingly compromised soil health and SOM levels, adversely affecting natural ecosystems and agroecosystems alike. Given the pivotal role of soil microorganisms in carbon cycle regulation, this study sought to unravel the complex interactions between land-use practices and pedo-climatic factors driving soil biodiversity.
Through an extensive survey, this research harmonized and integrated large datasets encompassing soil biodiversity, climate, and geomorphology. The resulting comprehensive analysis provides actionable insights into optimizing future land-use strategies.
The project revealed the spatial patterns of microbial richness and diversity in soils, identifying the primary drivers behind these patterns. Specifically, it examined the covariance between soil bacterial communities, fungal and mycorrhizal populations, soil functions (as reflected by enzyme activity), and the abundance of key functional genes involved in the soil carbon cycle. By linking these dynamics to SOM fractions, land-use practices, and pedo-climatic factors, the study offers a robust framework for advancing sustainable land management and soil conservation practices.
How to cite: Comeau, L.-P. and Heung, B.: Exploring the Dynamic Interplay Between Soil Carbon Stocks, Microbial Communities, and Land-Use Practices, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14464, https://doi.org/10.5194/egusphere-egu25-14464, 2025.
The EJP SOIL program lasted for five years and yielded significant contributions addressing the challenges of sustainable and climate-smart soil management in Europe. Through a combination of surveys, reviews, and experimental research, it provides critical insights into the six Expected Impacts (EIs) of the program, including fostering sustainable soil management, understanding carbon sequestration, and promoting stakeholder adoption of best practices. The findings highlight the importance of harmonized soil data systems, cooperative research, and region-specific approaches to address fertilization and soil health challenges effectively. These contributions align with European Union goals, such as the Green Deal and the Soil Monitoring Law, offering actionable pathways to enhance the resilience and sustainability of Europe’s agricultural soils.
A key resource with further material for driving these efforts is displayed in the EJP SOIL Knowledge Sharing Platform which serves as a hub for collaboration among scientists, policymakers, and practitioners. In this presentation we will highlight outcomes concerning (1) the impact of land management on soil structure, (2) the chemical and biological responses of SOM to above-ground practices, (3) changes in SOC content under different agricultural practices, (4) the effect of crop diversification on soil quality, and (5) studies analysing the response of soil microbial communities to agricultural management. As the synthesis and publication of EJP SOIL outputs continues, the lessons and innovations presented will provide a foundation for future research, policy-making, and practice. All together this will help ensure that Europe’s soils are managed sustainably to meet the challenges of a changing climate and growing food demands.
How to cite: Zechmeister-Boltenstern, S.: Synthesis of exemplary EJP SOIL results on climate-smart sustainable soil management, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17715, https://doi.org/10.5194/egusphere-egu25-17715, 2025.
Understanding soil organic carbon (SOC) stability is crucial given its influence on nutrient cycling and C storage. The biological and chemical properties of SOC offer valuable insights into its persistence and C retention capacity, and understanding these properties can help evaluate sustainable land management practices. In this study, we link thermal stability and chemical properties of SOC to its biodegradability using 108 soil samples collected from diverse ecological zones in Canada, New Zealand, and Scotland. We used Rock-Eval (RE) pyrolysis for thermal analysis to assess thermal stability (T50), conducted a 98-day incubation study to evaluate the biological stability of SOC, and utilized X-ray absorption near-edge structure (XANES) spectroscopy to determine the chemical characteristics of SOM. Our findings show a strong negative linear correlation between thermal stability, T50, and mineralized C in topsoil, which can be explained from an energetic perspective. The SOC characterized by stronger bonds, including organo-mineral associations or organic-organic bonds, requires more energy for breakdown. Higher thermal energy requirements reflect stronger soil organic matter (SOM) bonds, consequently leading to lower mineralization rates. Moreover, we observed a strong correlation between the Hydrogen Index (HI) derived from RE pyrolysis and mineralized C, affirming the validity of HI as a promising metric for assessing the labile pool of SOC.
Chemical functional groups identified using XANES spectroscopy, particularly alkyl-C and the alkyl/O-alkyl-C ratio, which signify the degree of decomposition, exhibited strong positive correlations with T50, highlighting their role in enhancing SOM thermal stability. In contrast, ketones and aromatic groups showed a strong negative correlation with T50. This inverse relationship could be attributed to ketones representing labile byproducts of microbial decomposition, which are less thermally stable. Similarly, the aromatic groups in this study, likely derived from lignin and tannins, may indicate early-stage decomposition products rather than highly condensed, recalcitrant aromatic compounds typically associated with stable SOM. This suggests that these functional groups are more indicative of labile SOM fractions in the studied soils. This research established a strong connection between thermal stability and the chemical and biological stability of surface SOM. It demonstrates the efficacy of RE thermal analysis as a potent tool across various landscape and ecological zones.
How to cite: Mesgar, M., Gillespie, A., Gregorich, E., Beare, M., Diochon, A., Drury, C., Haeriardakani, O., Ellert, B., and Janzen, H.: Linking thermal stability and organic chemistry with surface soil organic matter stability-A study across ecozones, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20728, https://doi.org/10.5194/egusphere-egu25-20728, 2025.
Increasing soil organic carbon (SOC) stocks in agricultural systems is vital for mitigating climate change, improving soil quality, and enhancing grain production. However, the mechanisms by which fertilization practices influence SOC, particularly at the microscopic level, remain poorly understood. This study investigated the impacts of inorganic fertilizers in terms of nitrogen (N), phosphorus (P), and potassium (K), along with shallow (0–20 cm) straw incorporation (S), on soil properties, C acquisition (C-acq) enzyme activity, active SOC fractions, soil aggregates, and microbial carbon cycle functional traits, based on a 34-year field experiment conducted in the North China Plain. Six treatments of CK (control, without any fertilizer), NP (nitrogen + phosphorus fertilizers), NK (nitrogen + potassium fertilizers), PK (phosphorus + potassium fertilizers), NPK (nitrogen + phosphorus fertilizers + potassium), and NPKS (NPK + straw) were examined. Results indicated that NPK and NPKS treatments created favorable soil nutrient conditions, characterized by elevated levels of N, P, and K, along with reduced bulk density. Compared with NPK treatment, NPKS treatment led to significant increases in SOC (+38%) and active SOC fractions, including microbial biomass carbon (MBC, +17%), easily oxidizable carbon (EOC, +105%), and light fraction organic carbon (LFOC, +103%). Under NPK treatment, MBC and EOC increased by 43% and 40%, respectively, compared with CK. Both NPK and NPKS treatments enhanced macroaggregate formation, contributing to improved soil structure stability. Straw incorporation significantly boosted C-acq enzyme activity, whereas inorganic fertilizers had minimal impact. The abundance of functional genes involved in C-degradation were correlated significantly with soil C and N contents, C-acq enzyme activity, active SOC fractions, and macroaggregates, with higher levels observed under NP, NPK, and NPKS treatments than CK. Different C-fixation pathways responded variably to the measured soil traits, revealing no consistent trends across treatments. Structural equation modeling indicated that C-acq enzymes exerted a greater total effect on SOC than soil properties, active SOC fractions, and soil aggregates. Additionally, the abundance of functional genes related to C-degradation and methane metabolism played a more important role in SOC dynamic than those associated with C-fixation. In conclusion, NPK and NPKS treatments significantly enhanced SOC accumulation mainly by improving soil nutrient conditions, C-acq enzyme activity (notably for NPKS), active SOC fractions, macroaggregate formation, and the abundance of C-degradation genes. This study highlights the critical role of balanced inorganic fertilizers and straw incorporation in SOC accumulation, further elucidating the mechanisms influencing SOC dynamics.
How to cite: Wang, N. and Li, F.: Influence of long-term inorganic fertilization and straw incorporation influence on soil organic carbon (SOC) by altering C acquisition enzyme activity, active SOC fraction, soil aggregates, and microbial compositional and functional traits, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5411, https://doi.org/10.5194/egusphere-egu25-5411, 2025.
Olive is one of the most relevant crop in Mediterranean regions, in which regenerative agriculture (RA) might have a widespread potential impact providing environmental and economic benefits. However, research on its viability and actual impacts under specific local conditions remains limited. To address the effect of RA on soils and crops, an olive-farm in Southern Spain where regenerative practices have been implemented since 2019 was studied. These practices include no-till farming, the use of spontaneous cover crops, application of manure, biochar, and olive leaves to the soil, as well as directed grazing to manage the cover vegetation. Our study included two areas within the farm. In one area, the spontaneous cover crops were well-developed (RegG), while in the other, the soils were less favorable, and the cover crop had a poorer establishment (RegB). A forest area close-by the olive grove (Forest) served as a benchmark, alongside a neighboring farm with the same soil type, tree age, and planting framework but managed using conventional methods (Conv). Conventional management involved no spontaneous cover crops and the use of synthetic fertilizers and pesticides. Physical, chemical, and biological soil properties, along with the nutritional status of the trees were measured to compare the effect of RA on soil quality. The Forest soil had the highest organic matter content (13.5 %), followed by the regenerative olive groves, RegG and RegB (5.9 %), and finally, the conventional olive grove; Conv (4.7 %). RegB showed a need for further improvements in management practices to achieve the benefits seen in RegG. Regenerative practices also enhanced microbial activity and diversity (5.83 and 3.33, respectively), reaching levels comparable to the reference Forest soil (5.7 and 3.36, respectively), highlighting their effect in improving soil health. Globally, the regenerative practices contributed to improve soil quality, as determined by an increase in carbon and water storage, and biological activity, reaching values similar to those obtained in the natural ecosystems. Despite these promising results, long-term research is necessary to fully understand the effectiveness of RA across various soil types and planting frameworks, as well as its socioeconomic feasibility.
Acknowledgement: This work has been supported by the Projects “Monitoring, reporting and verification of soil carbon and greenhouse gases balance” (https://www.project-marvic.eu/) from HORIZON-MISS-2022-SOIL-01-05 (GA 101112942) and PID2020-114917RB-100 from Ministerio de Ciencia e Innovación, Spain.
How to cite: Torrús Castillo, M., Prado Fortuna Macan, G., Landa, B. B., and Gómez Calero, J. A.: Assessing the Impact of Six Years of Regenerative Agriculture on a Commercial Olive Orchard in Southern Spain, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-422, https://doi.org/10.5194/egusphere-egu25-422, 2025.
Large extensions of grasslands in Europe are managed with ungulate presence for food production, rural livelihoods, and (more recently) soil carbon sequestration goals. Grazing regimes hold grasslands in ecological balance, and it is not clear how ungulate management and succession dynamics impact SOC stabilization. While there is increasing recognition that integration of large herbivores into productive systems can be key for restoring soil carbon and soil quality, research is ongoing on under what conditions this may occur, and why.
Over three years, our research team has been monitoring changes in critical soil parameters in pasture and forest ecosystems with a wide gradient of domesticated and wild ungulate grazing pressure, in order to understand the ecological and practical repercussions of human management of the landscape. Through this monitoring, we have firstly identified that SOC accumulation diverges significantly depending on the ecological context. The mechanisms by which SOC stabilization occurs is understood to follow different paths, modulated by grazers in contrasting ways depending on this context. Secondly, our establishment of a grazing gradient by using GPS tracking collars has allowed the quantification of relationships between grazing pressure and soil processes. Most notably for SOC accumulation, we have seen that the grazing pressure of domesticated transhumant ungulates (sheep) is linearly and positively associated with both soil microbial processes and SOC accumulation. Importantly, contributions to the SOC pool are seen to depend on vegetation structure and plant composition (Figure).
Overall, the studies have elucidated relationships between vegetational characteristics and litter quality, herbivore action, and soil microbiology, aiding to unravel the main mechanisms driving SOC accumulation in ecosystems with large mammal ungulate grazers.
How to cite: Marks, E. A. N., Sánchez-Zapata, J. A., Mataix-Solera, J., García-Orenes, F., Rincon-Madroñero, M., Contreras, A., Arcenegui Baldo, V., Velamazán, M., and Magalhaes Barbosa, J.: What can the interaction between grazing regime and environment tell us about SOM stabilization mechanisms? Results from an ecological field laboratory in Spain, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3267, https://doi.org/10.5194/egusphere-egu25-3267, 2025.
Soil carbon is critical for feeding the global population and for mitigating climate change, yet agricultural intensification is leading to significant losses. Despite the need to stop agricultural soil carbon depletion and promote its restoration, uncertainties persist regarding agricultural practices that can enhance carbon accumulation across different pedological conditions.
Although soil carbon encompasses both inorganic and organic components, most research has focused on the effect of agricultural management on organic carbon due to its sensitivity to soil disturbances and role in soil functioning. However, there is growing evidence showing that agricultural activities can cause irrevocable losses of inorganic carbon, which may be detrimental for soil health and contribute to climate change. It is therefore crucial to study the response of both inorganic and organic carbon to agricultural management.
However, agricultural management includes a variety of practices that can be combined in different ways. This constitutes an obstacle in understanding how agricultural intensity impact soil organic carbon and in defining practices that promote its retention. This project investigates how soil agricultural management influences soil carbon storage across diverse pedological conditions.
Briefly, a total of 956 grasslands and arable soil samples from a wide range of agricultural management and pedological conditions were collected in the Netherlands. Detailed information on agricultural management was gathered using questionnaires to define management intensity and organic and inorganic carbon content were determined. In addition, explanatory variables such as aluminum and iron oxides content, pH, nutrient availability, soil texture, microbial biomass and environmental parameters such as air temperature, soil temperature and soil moisture were measured.
Here, we will show how agricultural management intensity affects soil organic and inorganic carbon content in grassland and arable fields in the Netherlands. Moreover, we will identify agricultural practices which can help promote soil carbon storage and how this varies with pedological conditions. These findings will improve our understanding of how agricultural management and soil proprieties interact to determine soil carbon storage, thus helping to develop targeted management practices to stop soil carbon depletion and promote restoration.
How to cite: vultaggio, G., Hogeveen, E., van Lent, T., Schram, M., Zagatto, F., Lejoly, J., Veen, C., and van der Putten, W.: Organic and inorganic carbon storage in Dutch agricultural systems, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10542, https://doi.org/10.5194/egusphere-egu25-10542, 2025.
Climate change-induced extreme weather poses significant challenges. Enhancing soil organic matter (SOM) can help mitigate its effects by sequestering carbon and increasing soil resilience. Large carbon losses from land-use changes highlight the potential for carbon replenishment through restoration practices. Despite its lower concentration, subsoil carbon is more stable and has a larger pool than that in the topsoil, offering untapped opportunities against climate change. However, the dynamics of subsoil SOM after reducing or stopping cultivation are not yet well understood. This research aims to fill this gap. Three land-use types are studied on steppe soil: ancient grassland (AG), arable land abandoned 12 years ago (AAL), and arable land (AL). The changes in SOM are investigated across three soil horizons: A (0–30 cm), AC (30–60 cm), and C (> 60 cm). Two organic carbon (OC) pools are examined: i.) carbon bound to the fine fraction (stable pool) < 63 μm; ii.) carbon stored within aggregates (labile pool) > 63 μm. OC content is determined by the difference between total carbon (TC) and inorganic carbon (IC). TC and IC were measured by Dumas principle-based Vario Macrocube CHNS elemental analyzer and a TOC-L analyzer equipped with an SSM-5000A, respectively. The SOM composition was estimated by Fourier transform infrared (FTIR) spectroscopy (Vertex 70) in DRIFT mode with an RT-DLaTGS detector (Bruker, USA). Overall, due to tillage intensity reduction, SOM increases in the topsoil and decreases in the subsoil, and its composition varies significantly among horizons and pools. The OC content under AAL increased 12 years after abandonment in the A horizon, mainly via the labile pool. In the AC and C horizons, the higher OC content under AL indicates SOM transport to the subsoil, a phenomenon . Cultivation has caused OC increase in both pools of the AC horizon, with a greater degree for the stable pool. Following abandonment, the OC stored in the labile pool of the AC horizon decreased to levels comparable to AG, whereas the decline in OC stored in the stable pool has not yet reached AG levels. In the C horizon, the reverse is true. Cultivation reduced the variance of most investigated properties in all horizons. The highest C/N and variance were observed under AAL, suggesting spatially uneven decomposition due to fresh OM inputs and that a new equilibrium has not been established yet. The lowest C/N was under AL, indicating a higher role of necromass in SOM there. Aromaticity was the highest in the AC horizon across all land uses compared to the A and C horizons. In terms of land use, aromaticity was greatest under AAL.
The authors are grateful to the SediLab staff. The study was supported by the eköp-kdp-24 university excellence scholarship program cooperative doctoral program of the Ministry for Culture and Innovation from the source of the National Research, Development and Innovation Fund via ELTE/15573/1(2024).
How to cite: Dévény, Z., Szalai, Z., Karlik, M., and Jakab, G.: Land use change affects on subsoil organic matter in a steppe soil, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17610, https://doi.org/10.5194/egusphere-egu25-17610, 2025.
Posters on site: Fri, 2 May, 08:30–10:15 | Hall X3
C storage in grasslands has been estimated to comprise between 10-30% of global soil C. More than half of the world's land surface is grazed, accounting for approximately one fourth of potential C sequestration in world soils. Due to this large potential, significant research efforts have been oriented toward characterizing this potential for C sequestration in grazed lands. Many scientific studies concur that grazing may have a positive effect on soil C concentrations at low and moderate grazing levels, and negative at high grazing levels. However, this has not been characterized fully for extensive Mediterranean high mountain pastures. A study of extensive grazing effects on soil C stocks was carried out in the Parque Natural Sierras de Cazorla, Segura, y Las Villas, specifically within an area of the park (Campos Hernán Perea) where grazing has persisted for centuries. In this area, the majority of sheep herds are transhumant, with grazing over the extensive area from May-November each year. Digital maps of grazing intensity based on GPS tracking collar data from both day and night movements were elaborated for the whole region, allowing a fine-scale estimation of grazing intensity. Paired samples were taken un non-encroached (grassland) and encroached (shrub-covered) soils in this landscape. Soil sampling was to 5 cm depth with metallic cylinders (Ekjelkamp) of 5 cm height and with a volume of 100 cm3, and soils were analyzed for organic C with elemental analysis following decarbonatization. SOC stock was found to be positively associated with both grazing and encroachment in a non-antagonistic manner. SOC stocks to 5 cm were estimated to be a minimum of 13.8 Mg ha-1 with no grazing and encroachment, and 25.5 Mg ha-1 with high grazing intensity and encroachment. The results highlight the very crucial influence of grazing and landscape vegetation dynamics for SOC stock estimates in grazed lands.
How to cite: Mataix-Solera, J., García-Orenes, F., Barbosa, J. M., Sánchez-Zapata, J. A., Arcenegui, V., and Marks, E. A. N.: Soil organic carbon stock changes in a Mediterranean mountain pasture characterized by transhumant sheep grazing , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3458, https://doi.org/10.5194/egusphere-egu25-3458, 2025.
The warming climate and the decline in alpine pasture management are paving the way for the afforestation of currently unforested high-altitude areas. This shift holds significant potential for CO2 sequestration in tree biomass, yet the implications for existing soil carbon stocks remain uncertain. The BERGAUF project ("Biodiversity Conservation and Carbon Storage in Forested Highlands") aims to shed light on this issue by investigating five model reforestation areas at the treeline in the Austrian Alps, established in the 1960s and 1970s.
Our primary objective is to investigate how afforestation at high-altitude areas affects vegetation and soil carbon and nitrogen stocks, plant and microbial biomass, as well vascular plant diversity, certain insect groups, and the soil microbial community structure (including bacterial and fungal biodiversity).
Here we share our initial findings on soil-related parameters, including soil carbon and nitrogen contents and stocks in the organic layer, bulk soil, and soil extracts. We also examine the quality of soil organic carbon (estimated by FTIR), soil microbial biomass and community composition, and fine root biomass, from soil samples taken at four different depths (0-10 cm, 10-20 cm, 20-40 cm, 40-60 cm). To assess the effects of afforestation, we used directly adjacent alpine meadows as control sites, which were sampled and analysed in the same manner.
We will discuss the potential of afforestation in high-altitude areas for carbon sequestration and its effects on carbon allocation and microbial biodiversity within the soil profile.
How to cite: Inselsbacher, E., Sbabo, R., König, A., Heinze, B., Reich, J., Zheng, X., Keiblinger, K., and Schindlbacher, A.: High-Altitude Afforestation in the Austrian Alps: Effects on Soil Organic Carbon and Microbial Communities, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7866, https://doi.org/10.5194/egusphere-egu25-7866, 2025.
Land-use type has a strong impact on soil organic matter (SOM) content which shows higher level in permanent grasslands than in arable lands. The inclusion of temporary grasslands in crop rotation is an efficient practice to limit SOM loss in arable lands. Nonetheless, temporary grasslands can be seen in competition with food-production for human consumption as they produce forage to feed livestock.
In a context of agricultural specialization and reduction of animal-based protein consumption, it is imperative to evaluate the impact of a decrease of temporary grasslands and their frequency in crop rotation on SOM content. Moreover, it is crucial to assess if the decrease of temporary grasslands frequency, SOM content and soil quality is a linear process or if an optimum exists that maximize soil quality while minimizing temporary grasslands in the rotation.
Here, we used a 40-year-old soil monitoring network in South-West Switzerland (FRIBO Network) to assess the relationship between temporary grasslands frequency, SOM loss and soil quality. Soil organic carbon (SOC) dynamics was estimated by sampling the monitoring sites every 5 years. SOC stocks were measured down to 50 cm depth. Permanent grasslands were used as reference for estimating SOM loss, controlling for variations in soil characteristics (e.g., clay, pH) and site characteristics (e.g., altitude, precipitation, crops type) among sites. The SOC-to-clay ratio was used as indicator of soil quality.
Our results showed that SOM loss is proportional to the decrease of temporary grasslands frequency so that any change of frequency has the same consequence on SOM loss independently from the absolute frequency of the temporary grasslands. This suggests that there is not an optimal frequency of temporary grasslands in a soil C sequestration perspective. This contribution, however, will also show that soil quality indictors related to SOM such as the SOC-to-clay ratio exhibits thresholds that enable to define an optimal frequency of temporary grasslands in order to maintain a level of soil quality that minimizes the negative impacts on soil functioning. Hence, providing a decision framework to target agricultural fields where temporary grasslands should be promoted or could be reduced with less impact.
How to cite: Guillaume, T., Sinaj, S., Bragazza, L., and Carlen, C.: Is there an optimal frequency of temporary grasslands in crop rotation to maintain SOM at a level sustaining agricultural soil quality?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10560, https://doi.org/10.5194/egusphere-egu25-10560, 2025.
Recent studies observed that long-term no-tillage (NT) management enhanced soil carbon stock in Japanese Andosols. However, limited quantitative data about residue decomposition characteristics under NT hinder a full understanding of its mechanisms. To address this, we conducted a field incubation study to examine how different residue application methods, related to tillage management, affect residue decomposition and priming effect in Japanese Andosol. Using PVC cylinders (0-15 cm), we collected undisturbed soils from NT plots, while we also collected disturbed soils from conventional tillage (CT) plots at a long-term experiment site (Ibaraki, Japan). We applied 13C-labelled residue (Ryegrass, C:N=25.8, 13C=7 atm%) at a rate of 2 kg C m-2 under three treatments: (1) surface application on NT soil (NTSA), (2) mixing residue with CT soil (CTMIX), and (3) surface application on disturbed CT soil (CTSA), with two controls (NTCK and CTCK) (n=4). We monitored the flux of soil- and residue-derived CO2 for three month incubation period, including the priming effect, and measured the microbial biomass carbon (MBC). The total C content at the 0–5 cm depth was significantly higher in NT soil (64 g kg-1) compared to CT soil (45 g kg-1), while the bulk density was slightly greater in CT soil (0.78 g cm-³) than in NT soil (0.72 g cm-³) at the same depth. Cumulative residue C mineralization in surface residue treatments, such as NTSA (92 g C m-²) and CTSA (88 g C m-²), were clearly larger than in CTMIX (44 g C m-²) after three months. This suggests different physical protection and accessibility of surface residue particles under NT or CT, as mixing residues into the soil enhances adsorption to mineral surfaces under CT, reducing microbial decomposition, and probably promoting aggregation, which decreases the residue decomposition physically. Cumulative soil C mineralization was also enhanced in soils treated with labelled residue compared to control soils, reflecting positive priming effect. The priming effect was greatest in CTSA (120 g C m-²), followed by NTSA (83 g C m-²), with the lowest priming effect observed in CTMIX (32 g C m-²) after three month. The results of one month of incubation showed that relative changes in MBC with respect to each control soil was negative in NTSA (-13%), while it was positive in CTSA (33%) at 0–2.5 cm depth. This implies that MBC in NTSA was more stable to residue application compared with CTSA contributing to its lower priming effect. Less changes in MBC observed in CTMIX (9%) than CTSA may be due to dilution of carbon inputs by the mixing effect, which also contributed to lower priming effects. In summary, surface residue application enhanced the residue mineralisation with larger priming effect, compared to mixing residue application, for three month in Japanese Andosols.
How to cite: Asiamah Aboagye, D., Lyu, H., Yasuno, H., Komatsuzaki, M., Tanaka, H., and Sugihara, S.: Effect of Residue Application Methods and Long-Term No-Tillage Management on Residue Decomposition and Priming Effect in Japanese Andosol: Evidence from a Field Incubation Experiment, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17221, https://doi.org/10.5194/egusphere-egu25-17221, 2025.
The balance between soil organic carbon (SOC) input and mineralization is fundamental to understanding the potential of agricultural soils as carbon sinks. Isotopic signatures (δ13C, δ15N) are effective tools for investigating carbon turnover, particularly when distinct differences exist between SOC fractions or inputs and outputs, such as those between C3 and C4 plant-derived carbon. This study utilizes long-term data from a large field lysimeter system to explore SOC dynamics in loess and sandy soils. Established in 1980, the lysimeter station includes large lysimeters (3 m in diameter) with loess and sandy soils. For the four loess lysimeters, SOC-free, CaCO3-containing loess sediments were used. In the three sandy lysimeters, the top 30 cm of soil was mixed with peat, incorporating 3.5% organic material by volume. Maize, a C4 plant, was cultivated in all lysimeters until 2024, with complete removal of above-ground biomass after harvest. Soil samples from 1980, 1995, and 1998 provide a timeline to track SOC changes. In 2024, soil sampling was conducted at three depths (0–30 cm, 30–60 cm, and 60–90 cm) using Göttinger Bohrstock probes, with five subsamples per depth composited into a mixed sample. Samples were dried, sieved, and analyzed for C and N content, as well as δ13C and δ15N, following carbonate removal. The lysimeters also recorded water leachate volumes, revealing significant differences in groundwater seepage rates between loess and sandy soils. Preliminary results indicate that loess lysimeters show SOC accumulation, while sandy lysimeters exhibit a net loss of SOC, likely due to peat mineralization. Leachate from loess lysimeters was free of dissolved organic carbon (DOC), whereas leachate from sandy lysimeters consistently showed a brownish color and substantial DOC content. Isotopic analysis enables the partitioning of SOC sources and provides estimates of peat loss.In 2024, Silphium perfoliatum was planted in half of the lysimeters to assess its influence on SOC accrual and isotopic dynamics.
How to cite: Lahi, A. and Maier, M.: Investigating Soil Organic Carbon Dynamics in Long-Term Lysimeter Systems, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17812, https://doi.org/10.5194/egusphere-egu25-17812, 2025.
As a result of the impacts of global warming and anthropogenic activities, agroecosystems are currently experiencing an unprecedented crisis of soil degradation, characterized by nutrient depletion, biodiversity loss, and decline of their services. Intercropping, practiced for thousands of years in agriculture, has recently emerged as a promising strategy to traditional farming methods to enhance soil health and productivity. However, the effects of intercropping on soil microbial ecology remain underexplored. This study assessed soil enzymatic activities, microbial biomass C and N, and microbial community’s composition (determined by PLFAs analyses) in bulk soil and rhizosphere from a randomized field experiment in semiarid central Spain established in 2022. The treatments included monocropping of alfalfa, monocropping of barley, and alfalfa-barley intercropping. Soil samples were collected in May 2023, one month before harvest, at the peak of microbial activity.
The results revealed distinct patterns in soil microbial dynamics depending on the cropping system. Enzyme activities in the rhizosphere were significantly higher under alfalfa monocropping, likely due to enhanced microbial diversity and availability of root-derived exudates metabolites, while they were lower under barley monocropping, reflecting a higher nutrient demand or a lower substrate availability that stimulate the synthesis of those enzymes. In intercropping, C-cycling enzymes (β-glucosidase and cellulose) were mainly influenced by barley while N-cycling enzyme (leucine aminopeptidase) was by alfalfa, and P-cycling enzyme (acid phosphatase) showed intermediate activity, indicating balanced contributions from both crops. In bulk soil, enzymatic activities exhibited minimal differences across treatments. For all treatments, microbial biomass C and N were consistently higher in the rhizosphere compared to bulk soil, emphasizing the influence of root exudates in stimulating microbial growth and activity. The intercropping system showed the highest microbial biomass values within each soil compartment, suggesting an enhanced biological activity and nutrient cycling efficiency. Regarding microbial composition, mycorrhizal abundance peaked under intercropping in both the bulk soil and rhizosphere, highlighting the synergistic effect of the crop mixture on mycorrhizal communities. Fungal abundance also increased under intercropping but only in the rhizosphere. Gram-positive and gram-negative bacteria were most abundant in the rhizosphere under alfalfa monocropping, while in bulk soil, their levels showed no significant differences across treatments.
The alfalfa-barley intercropping system demonstrated strong potential to enhance soil microbial communities’ composition, particularly mycorrhizal associations, which are essential for nutrient cycling and soil functionality. Intercropping fosters beneficial plant-microbe interactions, especially in the rhizosphere, where microbial activity is most dynamic. These findings highlight intercropping as a sustainable agricultural practice that optimizes soil microbial processes and supports soil ecosystem services. Future studies should investigate the mechanisms driving these responses and the long-term sustainability of intercropping in diverse agroecological contexts.
Acknowledgments: This research was supported by the LEGUMINOSE project (grant ref. 101082289). M.J.C thanks to MINECO for her “Juan de la Cierva-Formación” postdoctoral contract.
How to cite: Carpio Espinosa, M. J., Poll, C., Kandeler, E., Benavente-Ferraces, I., García-Gil, J. C., and Plaza, C.: Impact of Intercropping on Microbial Dynamics and Functionality in Bulk Soil and Rhizosphere, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17969, https://doi.org/10.5194/egusphere-egu25-17969, 2025.
Andosols have the potential to store more organic carbon than any other mineral soil group. In Iceland, agricultural land commonly resides on drained peatlands which comprise of Histosols, Histic Andosols and Gleyic Andosols. The physical properties of these soils depend heavily on land-use regimes which in turn can affect the microbial life within. Bacteria and fungi are primarily responsible for processing deposited organic material into a more stable form and are also important for many other soil processes such as aggregate formation. Stressful environments can select for a more resilient microbial community at the cost of the carbon sequestration potential. For example, responses to stressful events such as droughts may select for organisms which excel in tolerance to desiccation by increasing osmolyte production at the cost of biomass production. Recalcitrant biomass may be more favourable for carbon sequestration than the maintenance-focused resource allocation. The functional traits of microbial communities can have significant impact on the carbon sequestration potential in soils. This may be of significance for agricultural land in Iceland as it often is located on drained peatlands, has rich carbon stocks, and is heavily influenced by anthropogenic activities. In this study, first of its kind for Icelandic agricultural land, we investigate the possible effects of the soil microbiome on soil carbon dynamics, and we ask what the patterns of functional diversity are at varying soil conditions. To evaluate the interplay between functional groups, land-use regimes and environmental conditions, we determine physicochemical properties of agricultural soils in Iceland, such as C and N content, C/N ratios, pH and dry bulk density. Furthermore, we determine the functional grouping of each microbial community through metagenomic analysis.
How to cite: Arnarsson, R. Í., Möckel, S. C., Björnsdóttir, S. H., and Erlendsson, E.: The functional diversity of microbial communities in Icelandic organic soils and its impact on carbon dynamics, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18039, https://doi.org/10.5194/egusphere-egu25-18039, 2025.
Grasslands and forests play an important role in the global carbon cycle and management intensity in grassland and forests influences the uptake and storage of carbon. Organic carbon stock changes in grasslands and forests depend not only on the management intensity but also on the site on which they grow. However, long term studies in real world ecosystems and along land use gradients in forests and grasslands are rare. Therefore, it is unclear how management intensity and site conditions and the interaction between the two influence soil organic carbon stock changes on the long term. Since 2011, we have been studying the mineral soil organic carbon stocks in topsoils of 150 forests and 150 grasslands in 3 German regions (Schorfheide-Chorin, Hainich-Dün and Swabian Alb). In 2011, 2014, 2017, 2021 and 2023, the organic layer (only forests) and the topsoil (0-10 cm) were sampled at 14 sampling points per plot with a split tube corer (diameter 5 cm) and a representative composite soil sample was prepared for each the 300 plots. The silvicultural management intensity index (SMI) introduced by Schall and Ammer (2013) and the land use intensity index (LUI) introduced by Blüthgen et al. (2012) are used to quantify forest and grassland management intensity, respectively, at all plots. Linear mixed effects models showed that organic carbon stock change after 12 years in 0-10 cm varied between ‑18 g C m-2 and 61 g C m-2 year-1 in grasslands and ‑20 g C m-2 and 50 g C m-2 year-1in forests. First results indicate that the magnitude of organic carbon stock change is related to management intensity and soil properties. Further statistical analyses will be carried out using the respective management indices for grassland and forest to study this. On average, we find a significant increase of organic carbon stocks (+23 g C m-2) at our experimental sites. This suggests that global change might offset some of the management and site effects in forests and grasslands with CO2 fertilization being one potential driver.
How to cite: Schöning, I. and Schrumpf, M.: Twelve years of soil monitoring in forests and grasslands to study changes in organic carbon stocks in topsoils under control of management intensity, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19973, https://doi.org/10.5194/egusphere-egu25-19973, 2025.
Urban waste management remains a global challenge, with a significant portion landfilled or dumped, exacerbating environmental issues. Converting organic waste into biochar offers a sustainable solution, particularly in regions with limited waste infrastructure. Biochar application can improve composition, enhance carbon retention, and influence microbial activity, especially in degraded soils. This study evaluates the effects of biochar derived from urban waste under varying pyrolysis conditions (temperature and residence time) on the biochemical properties of a semiarid soil. Soils amended with biochar and control soils were incubated for 8 months, with periodic measurements of CO₂ emissions. After incubation, total organic C and microbial biomass C were analyzed. Results revealed that pyrolysis temperature is the primary factor influencing the role of biochar in microbial activity, while residence time plays a significant role only at lower temperatures. These findings underscore the importance of optimizing biochar production to improve soil quality through C sequestration and mitigate environmental challenges linked to urban waste management.
How to cite: Benavente-Ferraces, I., Méndez, A. M., Carpio Espinosa, M. J., Plaza, C., and Gascó, G.: Harnessing pyrolysis conditions as a tool to enhance urban waste biochar on soil microbial dynamics, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20255, https://doi.org/10.5194/egusphere-egu25-20255, 2025.
Coastal marshes play a crucial role in global carbon (C) cycles as net C sinks, making them valuable for offsetting anthropogenic greenhouse gas emissions through C stock preservation or wetland restoration. However, the capacity of restored marshes to sequester organic C often falls below expectations, even decades post-restoration. This discrepancy highlights gaps in our understanding of biogeochemical processes that influence soil organic matter (SOM) dynamics and C sequestration potential. Specifically, the quality and molecular composition of SOM and its interaction with microbial communities remain underexplored. This study investigates the chemical composition of SOM and its relationship with biogeochemical processes and biome composition in marshes within the Doñana National Park, a globally significant biodiversity hotspot in Andalusia, Spain. The park has historically undergone significant human-driven transformations, necessitating large-scale restoration efforts.
Our research focuses on three representative sites within the Doñana. The first site, “Marisma Gallega” (MG), is a high marsh that remains in its natural state, having never been cultivated. The second site, the “Finca de Caracoles” (FC), is undergoing active restoration and includes two distinct zones: a northern zone (FCN) with a lower degree of restoration due to a shorter time since cultivation ceased, and a southern zone (FCS) that has been uncultivated for a longer period. The third site is a fully transformed paddy soil (PS) currently used for rice cultivation. Soil samples were collected from each site at three depths (0–10; 10–20; and 20–30 cm) to analyze soil organic carbon (SOC), soil organic matter (SOM), total nitrogen (TN), total phosphorus (TP), and other key nutrients. Microbial activity was assessed through soil respiration (MicroResp technique), whereas microbial diversity and abundance were evaluated using phospholipid fatty acid (PLFA) analysis and metagenomic shotgun sequencing of 16S rRNA genes. Bioinformatic analyses provided insights into microbial richness, alpha diversity indices, and the relative abundance of different microbial communities.
Our results indicate that MG and both FC zones exhibited higher SOC, SOM, TN, and TP contents compared to PS, suggesting higher C accumulation and improved SOM quality in the restoration sites, with values not significantly differing from MG. However, MG and both FC zones displayed lower concentrations of available P and NO₃⁻ relative to PS. These findings can be attributed to the conditions in degraded wetlands like PS, which disrupt N and P storage and cycling, promoting the mineralization of organic nutrients, such as organic N, and its transformation to NO₃⁻. Microbiological analyses revealed higher microbial respiration rates and greater fungal and bacterial biomass in MG and FC compared to PS, along with shifts in microbial community composition. These variations were influenced by the degree of naturalization and restoration. Accumulated organic C, combined with aerobic conditions, likely supports microbial growth, thereby accelerating microbial respiration.
By characterizing SOM properties and linking them to microbial and biogeochemical processes, this study provides insights into how restoration and land-use change impact C storage and ecosystem services in marshes. The findings will inform future restoration strategies and improve the monitoring of these ecosystems’ health and functionality.
How to cite: Knicker, H., Aguilar-Romero, I., Borja Barrera, C., Díaz del Olmo, F., and Moreno Racero, F. J.: Linking Biogeochemical Processes and Ecosystem Health in Restored Marshes of the Doñana National Park, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18965, https://doi.org/10.5194/egusphere-egu25-18965, 2025.
Decomposition and stabilization of organic C in soils of different cultivation systems
Soil organic carbon (SOC) is an important component of the global carbon stock, and supports functions related to soil health. It is therefore of great importance that we invest in new methodologies and research on increasing SOC stocks globally. On a farm-level, conservation agriculture aims to manage SOC content by, for example, using cover crops, crop rotations or minimal tillage.
The aim of our study is to investigate the C sequestration potential of different farming systems as well as their efficiency at stabilizing C from plant residue inputs. To do so, we incubated using 13C labeled plant material in field plots under contrasting long-term management histories. The incorporation of 13C into mineral associated organic matter (MAOM) and particulate organic matter (POM) was determined by physical size fractionation followed by isotope ratio mass spectrometry. Furthermore, the microbial carbon use efficiency was investigated with stable isotope probing using 18O-H2O.
The 13C labeled plant material was incubated in situ with soil using litter bags for one growing season, at the long-term experiment (LTE) of NIBIO Apelsvoll. The LTE was established in 1989, with four treatments included in this study. These treatments are a long-term and a short-term conservation agriculture system, as well as conventional crop production and a forage production system. The treatments are replicated “mini-farms”, with 4-year crop rotations and different management strategies.
Preliminary results show that the forage production system has the highest soil C content at 3%, which is significantly higher than in the other systems. Additionally, there are significant differences in the weight fractions of MAOM and POM between systems. Carbon and isotopic analyses of these fractions will be presented and discussed.
How to cite: Storholt, T. A., Dörsch, P., Eischeid, I., Budai, A., and Rasse, D.: Decomposition and stabilization of organic C in soils of different cultivation systems , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18800, https://doi.org/10.5194/egusphere-egu25-18800, 2025.
Posters virtual: Fri, 2 May, 14:00–15:45 | vPoster spot 3
EGU25-13615 | ECS | Posters virtual | VPS15
Soil organic matter and carbon fractions within aggregates and in soil profile in double- and cover cropping systemsFri, 02 May, 14:00–15:45 (CEST) | vP3.6
Understanding the distribution of soil organic matter, carbon (C) and nitrogen (N) within aggregates and across soil profiles is critical for improving soil fertility, nutrient cycling, and long-term sustainability in agricultural systems. This study evaluates the short-term effects of various crop rotations and cover cropping systems on soil organic matter (SOM), aggregate-associated C and N fractions, and their vertical distribution in the soil profile. A three-year field experiment was conducted at the Agronomy Research Farm, Southern Illinois University Carbondale, with treatments including: (1) corn (Zea mays L.)-soybean (Glycine max L.) rotation without cover crop (CNSN), (2) corn-soybean rotation with rye cover crop (CRSR), (3) corn-wheat (Triticum aestivum L.)-soybean rotation without cover crop, and (4) corn-wheat-soybean rotation with a cereal rye (Secale cereale L.) cover crop (CWSR). Soil aggregates were collected from 0-5 and 5-15 cm depth and used for assessing aggregate size distribution, aggregate stability, SOM, soil C and N. Bulk density and soil C and N along with soil organic matter was measured from samples collected from 0-90 cm depth. CRSR and CWSN, significantly increased medium-sized aggregates (1-2 mm and 0.5-1 mm) as compared to the CNSN treatment. Including cereal rye into double cropping systems (CWSR) improved soil’s aggregate stability. Cropping systems, particularly those with winter wheat and cereal rye, increased soil organic matter in 2-4.75 mm aggregate fraction as compared the CNSN control. Soil organic matter concentration decreased with depth, with the highest values at 0-5 cm across all cropping systems. Soil bulk density by depths, soil C and N within aggregate and by depth will also be presented at the meeting. Our current findings indicate that utilizing CWSR could provide economic and soil benefits to growers in Illinois.
How to cite: Sheikhi Shahrivar, F., Ola, O., Javid, M., Brevik, E., Williard, K., Schoonover, J., Gage, K., and Sadeghpour, A.: Soil organic matter and carbon fractions within aggregates and in soil profile in double- and cover cropping systems, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13615, https://doi.org/10.5194/egusphere-egu25-13615, 2025.
