SSS9.4 | Soil organic and inorganic carbon dynamics in agro-ecosystems: mechanisms, measurements and modelling strategies
EDI
Soil organic and inorganic carbon dynamics in agro-ecosystems: mechanisms, measurements and modelling strategies
Co-organized by BG3
Convener: Sergio Saia | Co-conveners: Viktoriia Hetmanenko, Laura Quijano, Alina Premrov, Jorge Alvaro-Fuentes
Orals
| Mon, 24 Apr, 14:00–15:45 (CEST)
 
Room -2.20
Posters on site
| Attendance Mon, 24 Apr, 16:15–18:00 (CEST)
 
Hall X3
Posters virtual
| Attendance Mon, 24 Apr, 16:15–18:00 (CEST)
 
vHall SSS
Orals |
Mon, 14:00
Mon, 16:15
Mon, 16:15
Soil is the largest carbon (C) reservoir in terrestrial ecosystems and soil organic carbon (SOC) is the basis for soil’s biodiversity, health and fertility. Furthermore, enhancing SOC storage in agricultural soils is key for food security, provision of the soil-related ecosystem services, and climate change mitigation.

Investing in productive, highly resilient agriculture, based on appropriate land and soil management requires the knowledge base on drivers and processes controlling soil C storage and its dynamics in agroecosystems. Thus, this session will provide a forum to exchange knowledge about the key mechanisms and proxies controlling dynamics of soil C (both organic and inorganic) in cropping systems and natural/semi-natural areas.
Studies, opinions and other contributions in this session will aim to a wide range of topics related to SOC and soil organic carbon (SIC) and soil traits depending on SOC and SIC. These topics may also include soil fertility, provision of ecosystem services, and their changes.

Types of contribution appreciated include, but are not limited to, definitive and intermediate results; project outcomes; proposal of methods or sampling and modelling strategies, and the assessment of their effectiveness; projection of previous results at the light of climate change and climatic extremes; literature surveys, reviews, meta-analysis; and opinions. These works will be evaluated at the light of the organization of a special issue in an impacted journal

Orals: Mon, 24 Apr | Room -2.20

Chairpersons: Sergio Saia, Laura Quijano, Alina Premrov
14:00–14:05
Inorganic Carbon and emissions (Oral)
14:05–14:15
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EGU23-4885
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ECS
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solicited
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On-site presentation
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Kazem Zamanian and Yakov Kuzyakov

Carbonate-containing minerals comprise an additional form of soil carbon known as soil inorganic carbon (SIC). Though SIC stocks are large, they have been disregarded in most studies to carbon sequestration. After reviewing the main forms of SIC (geogenic, biogenic and pedogenic carbonates) and the chemical processes leading to formation of pedogenic carbonates, we review the importance of SIC in the global C cycle and ecosystem functions. Besides pH regulation, SIC and dissolved Ca2+ from carbonates dissolution: i) increase plant growth due to better root growth, nutrient availability and acquisition, as well as provide protection against pathogens; ii) increase activities of soil microorganisms mineralizing nutrients; and iii) bind organic compounds which, consequently, stabilize organic matter, produce larger and stable aggregates, and control water permeability and balance. Consequently, the SIC is crucial not only for pH regulation, but also strongly contributes to many other soil functions and health. Finally, we assess future SIC losses under anticipated global change processes such as increased N deposition and fertilization, elevated CO2, invasive plant distribution and climate change. These SIC losses damage soil functionality and make it more vulnerable to a broad range of degradation factors, including erosion, topsoil and subsoil compaction, acidification and nutrient depletion. Crucial is that in contrast to organic carbon, the SIC losses are irrecoverable. We conclude that SIC is an important soil constituent responsible for a broad range of physical, chemical and biological soil properties and processes as well as ecosystem services such as cycles of C, N and other elements.

How to cite: Zamanian, K. and Kuzyakov, Y.: Soil inorganic carbon: stocks, functions, losses and their consequences, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4885, https://doi.org/10.5194/egusphere-egu23-4885, 2023.

14:15–14:25
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EGU23-7304
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ECS
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solicited
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On-site presentation
Yélognissè Agbohessou, Claire Delon, Manuela Grippa, Eric Mougin, Seydina Ba, Daouda Ngom, and Olivier Roupsard

Silvopastoral systems (SPS) are one of the most common livestock production systems in the Sahel. They are composed of a mix of trees, pastures, and livestock in the same area. Known for providing several beneficial services compared to traditional pastures, SPS can release or absorb greenhouse gases. So far, our understanding of the magnitude and spatial distribution of greenhouse gas emissions in Sahelian SPS is subject to many uncertainties. This is mainly due to a lack of experimental and modelling studies focused on the region.

We use a process-based model, STEP-GENDEC-N2O, that couples vegetation growth, biogeochemistry, and gas emissions to investigate the spatial and temporal pattern of carbon dioxide (CO2) and nitrous oxide (N2O) emissions from soil and estimate their annual budget in the Sahelian SPS. After model validation using in-situ data collected at the Dahra site (north-western Senegal), simulations were performed on the entire Sahelian area (latitude: 13°N to 18°N; longitude: 18°W to 20°E) divided into 18271 grid cells of 0.1° x 0.1°, from 2010 to 2021. Input variables were extracted from different datasets available at global or regional scales.

We found that the spatial pattern of CO2 and N2O emissions from soils in Sahelian SPS can be mainly explained by the spatial distribution of soil properties (soil temperature, soil sand, and clay content), climate, and animal load. The overall estimated CO2 and N2O emissions from Sahelian SPS during the 2010-2021 period were 0.054 ± 0.005 Tg C yr-1 (1 Tg = 1012 g) and 0.046 ± 0.008 Tg N yr-1, respectively. These values are relatively low compared to other estimates for grazing and cropping systems in other regions. Mapping CO2 and N2O emissions from soils in SPS at the Sahel-wide scale helps identify emission hotspots in order to establish more effective mitigation strategies and management policies for Sahelian SPS.

How to cite: Agbohessou, Y., Delon, C., Grippa, M., Mougin, E., Ba, S., Ngom, D., and Roupsard, O.: Soil CO2 and N2O emissions in Sahelian Silvopastoral systems: spatial distribution and annual budget estimation, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7304, https://doi.org/10.5194/egusphere-egu23-7304, 2023.

14:25–14:35
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EGU23-10777
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ECS
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Virtual presentation
Santos Martinez-Santiago, Gerardo Sergio Benedicto-Valdés, Armando López-Santos, Hilda Victoria Silva-Rojas, Enrique Ojeda-Trejo, Elsa Marcela Ramírez-López, and Julian Delgadillo-Martínez

Calcareous soils are characterized by containing a greater amount inorganic carbon (SIC) than organic carbon (SOC), and both contribute to CO2 emissions to the atmosphere. SOC mineralization and SIC dissolution are related to soil moisture content, but their effect on CO2 emissions from calcareous soils is unclear. This investigation aimed to evaluate the effect of moisture content on CO2 emission of a calcareous soil in the Comarca Lagunera, Mexico.

Calcareous soil samples were taken from a cropland and shrubland of Comarca Lagunera, Mexico and their physical and chemical properties were determined. For a 30-day period, 100g of soil were incubated in closed-jars and two moisture treatments, related to field capacity (FC) and permanent wilting point (PWP) values were applied. The CO2 emission assessment was performed every two days using an infrared gas analyzer (IRGA, PP Systems, UK).

For cropland, the FC, PWP, SIC and SOC values were 27.2 %, 14.6 %, 7.3 % (140.4 Mg ha-1) and 0.23 % (4.4 Mg ha-1), while for shrubland, the values were 27 %, 11 %, 7.6 % (152.8 Mg ha-1) and 0.08 % (1.6 Mg ha-1), respectively. Average emission of CO2, every two days, from cropland soil was 2.1 g CO2 m-2 h-1 for moisture at FC, while to PWP was 1.7 g CO2 m-2 h-1, and for shrubland soil was 1.8 g CO2 m-2 h-1 for moisture at FC, while to PWP was 1.6 g CO2 m-2 h-1.

In both cases, cumulative CO2 emissions were significantly higher in FC compared to PWP. For cropland, cumulative CO2 emissions were 23.4 g CO2 m-2 h-1 and 29.4 g CO2 m-2 h-1, but for shrubland were 21.7 g CO2 m-2 h-1 and 25.3 g CO2 m-2 h-1. Cumulative CO2 emissions for moisture content at FC were equivalent to a soil carbon (C) loss of 1.9 Mg ha-1 and 1.7 Mg ha-1 for cropland and shrubland, respectively. This result implies the loss of 43.2% (1.9 Mg C ha-1 / 4.4 Mg SOC ha-1) of the SOC content in the cropland, but for the shrubland it suggests the total loss of the SOC (1.6 Mg C ha-1 / 1.6 Mg SOC ha-1) and a part of the SIC content (0.1 Mg C ha-1 / 152.8 Mg SIC ha-1).

Our study shows that soil moisture content has a significant effect on CO2 emissions from calcareous soils, such as Comarca Lagunera, where an increase in soil moisture corresponds to increases in CO2 emissions into the atmosphere, where SIC and SOC reserves are involved.

How to cite: Martinez-Santiago, S., Benedicto-Valdés, G. S., López-Santos, A., Silva-Rojas, H. V., Ojeda-Trejo, E., Ramírez-López, E. M., and Delgadillo-Martínez, J.: Effect of moisture content on carbon dioxide emissions in calcareous soils of the Comarca Lagunera, Mexico, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10777, https://doi.org/10.5194/egusphere-egu23-10777, 2023.

14:35–14:45
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EGU23-1998
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On-site presentation
Leidivan Almeida Frazão, Evander Alves Ferreira, Warley Rodrigues de Oliveira, Igor Costa de Freitas, Carlos Eduardo Cerri, João Marcos Vilela, Mauricio Cherubin, Dener Oliveira, and André Franco

The use of agroforestry systems and integrated production models have been considered as viable options for tropical regions. Several studies have reported that these sustainable production systems have decreased the GHG emissions into the atmosphere and increased soil carbon stocks. If successful, the integration of crops, forests, and livestock will account for around 23% of Brazil’s 112 million ha of pasture. Every ha of integrated agriculture and livestock farming (IALF) pasture has the potential to remove an average of 3.79 tCO2e from the atmosphere per year. However, given the dynamics and complexity of soil management required when integrating different production components, it is necessary to perform regionalized research about soil carbon storage capacity. According to the Fourth National Communication of Brazil to the United Nations Framework Convention on Climate Change (UNFCCC), greenhouse gas (GHG) emissions in Brazil totaled 1,467 teragrams (Tg) of CO2e in 2016. In the search for more sustainable agricultural systems that increase the productivity of cultivated areas and at the same time can mitigate GHG emissions, the National Plan for Low Carbon Emission in Agriculture (ABC Plan), now renamed ABC+, was created aiming to incorporate new practices to mitigate GHG emissions for the 2020–2030 period. The objective of ABC Plan is to expand the agricultural land using the technologies outlined in the plan by 72 million ha - the area is currently close to 50 million ha - and achieve an estimated mitigation capacity of 1.1 billion tCO2e by 2030. Areas that integrate agriculture, livestock and forests, known as agrosilvopastoral systems are projected to expand by over 10 million ha in the period, according to ABC+ Plan.  In order to make recommendations about the adoption of agrosilvopastoral systems, the objective of this study was to summarize the data from literature using the meta-analysis to evaluate the effect of integrated production systems introduction on soil carbon stocks, considering the different biomes in Brazil. When we compared the land use with low-productivity pastures and integrated production systems, we found an increase in soil C stocks under agropastoral, silvopastoral and agrosilvopastoral systems. Considering all the evaluated Brazilian biomes, higher soil C stocks were found for the integrated production systems when compared to low-productivity pastures. The Cerrado and Atlantic Forest biomes showed a higher sampling value, and this is due to the fact that  integrated production systems are more adopted in these two Brazilian biomes. Additionally, the agrosilvopastoral systems in the Cerrado biome showed the highest soil C stocks, but did not differ in relation to the Atlantic Forest and Pampa biomes. The agrosilvopastoral and silvopastoral systems were efficient on soil C inputs, and the values were 65.58 and 57.14%, respectively, higher than in low productivity pasture at 0-30 cm depth. These findings indicate that the land use with pastures and the introduction of trees in productive systems can reverse soil carbon losses. Additionaly, the introduction of trees can increase soil carbon stocks, supporting the potential of agroforestry systems to recover low-productivity areas in Brazil.

How to cite: Frazão, L. A., Ferreira, E. A., de Oliveira, W. R., de Freitas, I. C., Cerri, C. E., Vilela, J. M., Cherubin, M., Oliveira, D., and Franco, A.: Sustainable intensification of agriculture andlivestock production in Brazil: a meta-analysis of soil C changes in integrated systems, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1998, https://doi.org/10.5194/egusphere-egu23-1998, 2023.

14:45–14:55
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EGU23-1749
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ECS
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On-site presentation
Shuai Wang, Qianlai Zhuang, Mingyi Zhou, Xinxin Jin, Na Yu, and Ting Yuan
Soil organic carbon (SOC) and soil inorganic carbon (SIC) has important effects on soil physical, chemical and biological properties. They play an important role in coordinating the relationship between soil water and air, increasing soil water holding capacity and improving plant productivity. In this study, a boosted regression trees (BRT) model was developed to map the spatial distribution carbon stocks in the semi-arid region of Northeast China in 1990 and 2015. During the two periods, 10-fold cross-validation technology was used to test the performance and uncertainty of BRT model. In order to construct the model, 9 environmental variables (derived from climate, topography and biology) and 173 (1990) and 223 (2015) topsoil (0–30 cm) samples were used. The comparison between estimated and observed data shows that the RMSE of SOC and SIC stocks were 0.53 kgm− 2 and 0.19 kgm− 2 in 1990, and 0.65 kgm− 2 and 0.20 kgm− 2 in 2015, respectively. Elevation, normalized difference vegetation index, mean annual precipitation and Landsat band 3 were identifies as critical environmental factors for simulating the spatial distribution of SOC, accounting for 76.6 % and 70.3 % of the total relative importance in 1990 and 2015, respectively. Mean annual precipitation, mean annual temperature and topographic wetness index were the critical environmental factors for simulating the spatial variation of SIC during the two periods. Land use change also played an important role in the spatial variability of SOC and SIC stocks. In the past 25 years, soil carbon stocks decreased from 6.2 kg m− 2 in 1990 to 5.9 kg m− 2 in 2015. The spatial distribution pattern of SOC was high in northeastern area and low in southwestern area during the two periods, while the spatial distribution pattern of SIC was opposite to that of SOC stocks. The mapped soil carbon stock distribution is fundamental to future study of soil carbon cycle and regional carbon balance in semi-arid regions.

How to cite: Wang, S., Zhuang, Q., Zhou, M., Jin, X., Yu, N., and Yuan, T.: Temporal and spatial changes in soil organic carbon and soil inorganic carbon stocks in the semi-arid area of northeast China, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1749, https://doi.org/10.5194/egusphere-egu23-1749, 2023.

Organic carbon modelling and management (Oral)
14:55–15:05
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EGU23-1489
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On-site presentation
Moritz Laub, Magdalena Necpalova, Marijn Van de Broek, Marc Corbeels, Samuel Mathu Ndungu, Monicah Wanjiku Mucheru-Muna, Daniel Mugendi, Wycliffe Waswa, Bernard Vanlauwe, and Johan Six

Sustainable intensification practices, such as integrated soil fertility management (ISFM), form a strategy to close yield gaps while maintaining soil fertility and, typically, are locally tested in field trials. However, to estimate the potential impact of ISFM on a regional scale, field trials are insufficient and biogeochemical models are required. These models need to be calibrated and evaluated when applied to new environments. Here, we present a robust calibration of the DayCent agroecosystem model to simulate the impact of ISFM practices on maize productivity in Kenya, using a probabilistic Bayesian calibration technique with data from long-term field trials at four sites in central and western Kenya. We assessed the efficiency of DayCent in simulating: 1) maize grain yield, 2) changes in soil organic carbon (SOC), and 3) nutrient use efficiency of applied nitrogen (N) fertilizer under different ISFM treatments, which consisted of different organic resources combined with the addition or absence of mineral N fertilizer. After model calibration, both the simulations of maize yield (Nash Sutcliffe Efficiency, NSE 0.51) and change in SOC (NSE 0.54) improved significantly compared to runs using the standard DayCent parameters (NSE of 0.33 and -1.3 for yield and SOC change, respectively). A leave-one-site-out cross evaluation indicated the robustness of the approach for spatial extrapolation, i.e., the significant improvement of model simulations was achieved by calibrating the model with data from three sites and then evaluating it with data from the remaining site. The values of model parameters related to SOC decomposition were most altered  by the calibration, i.e., they were an order of magnitude higher compared to the default parameter values (derived for temperate climates). This suggests that the DayCent temperature function is not suitable to capture SOC decomposition across climates with a single set of parameter values. Further, similar maize yields were simulated for all treatments that received mineral N fertilizer and DayCent underestimated the yield increase observed in the field trials of the combined application of organic resources and mineral N compared sole mineral N application. In contrast, at low levels of nutrient inputs DayCent proved sufficiently sensitive to capture differences in maize yield levels. Finally, while mean yields by treatment were simulated well, year-to-year yield variation was not captured well by DayCent. In summary, our results indicate that DayCent is capable to estimate the mean impact that ISFM practices at typical rates of mineral fertilizer and organic resource applications have on yield and SOC, but may not be capable to estimate the differences in yield potential at very high inputs. While the cross evaluation indicated a robustness for upscaling, the suboptimal representation of year-to-year yield variabilities shows that future projections under a changing climate may be biased by the DayCent model. Consequently, improved model structures, such as improved soil moisture representation, are needed to reduce uncertainty.

How to cite: Laub, M., Necpalova, M., Van de Broek, M., Corbeels, M., Mathu Ndungu, S., Mucheru-Muna, M. W., Mugendi, D., Waswa, W., Vanlauwe, B., and Six, J.: A robust DayCent model calibration to represent the impact of integrated soil fertility management on maize yields and soil carbon stocks in Kenya, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1489, https://doi.org/10.5194/egusphere-egu23-1489, 2023.

15:05–15:15
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EGU23-2269
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ECS
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On-site presentation
Julia Fohrafellner, Sophie Zechmeister-Boltenstern, Rajasekaran Murugan, Katharina Keiblinger, Heide Spiegel, and Elena Valkama

Greenhouse gas emission can be partly compensated by enhancing soil organic carbon (SOC) levels in soils, e.g. in croplands, which have the highest potential due to their losses in SOC by intensive management. This can be achieved by adopting SOC enhancing soil management practices, such as the cultivation of cover crops (CC). So far, only few long-term experimental studies have investigated the effects of CC on a SOC pool level. There are still uncertainties how CC affect SOC fractions and the stability of the sequestered carbon.

By conducting a meta-analysis, we aim to quantitatively summarize studies related to CC effects on SOC pools throughout soil depths (up to 100 cm) in cropland soils relevant for Europe, as such an analysis is not available so far. We included global studies located in the dry, temperate, and boreal climatic zones, as these are present Europe. The pools chosen for this analysis are the microbial biomass carbon (MBC), the particulate organic matter (POM) and the mineral associated organic matter (MAOM) pool, as well as total SOC. Alongside, we study the effects of a broad range of moderators, such as pedo-climatic factors (e.g., climatic zones, soil texture), other agricultural management practices (e.g., effects of tillage, irrigation, liming, fertilization) and CC characteristics and their management (e.g., CC types, species number, frost resistance, residue management).

By searching several scientific and grey literature databases, we identified 64 studies, of which the majority was conducted in North and South America, whereas only five are available for Europe. The MBC, POM and MAOM pool are studied in 24, 44 and 19 of these studies, respectively. The mean experimental duration is eight years, with a maximum of 39 years. 54% of studies were conducted in a warm temperate climatic zone, 32% in a boreal and 14% in an arid zone. Means values for SOC pools, standard deviations and sample sizes for treatments with CC and controls without CC will be extracted from tables and figures. In order to perform a meta-analysis, logarithm response ratio as an index of effect size will be calculated for each study, which will then be summarized across studies by using weighing procedure. This meta-analysis will provide valuable information on the state of knowledge on SOC pool specific sequestration rates influenced by CC, corresponding quantitative summary results and the source of heterogeneity across studies. These results will offer guidance for future research and assist decision-making processes regarding climate friendly management of agricultural soils.

How to cite: Fohrafellner, J., Zechmeister-Boltenstern, S., Murugan, R., Keiblinger, K., Spiegel, H., and Valkama, E.: Cover Crops Affecting Pool Specific Soil Organic Carbon Sequestration in Cropland – A Meta-Analysis, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2269, https://doi.org/10.5194/egusphere-egu23-2269, 2023.

15:15–15:25
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EGU23-8716
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ECS
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On-site presentation
Sabine Huber, Christoph Rosinger, Orracha Sae-Tun, Gernot Bodner, and Katharina Keiblinger

Increasing pressures on agriculture related to climate change, as well as recent policy frameworks, have generated widespread attention towards research on soil organic carbon (SOC) sequestration. Promoting SOC accrual is of immediate interest for maintaining and restoring soil health in order to ensure continuous soil fertility and functioning. However, despite extensive research regarding soil health promoting farming practices, studies reflecting realistic management outcomes from farms are still scarce. We therefore conducted an on-farm study comprising 21 sites in North-Eastern Austria to compare two farming systems (an innovative ‘pioneer’ and a standard system) and undisturbed field margins as a reference. Pioneer soils have been managed according to soil health-oriented principles with e.g., minimal tillage, high-diversity cover crops and organic amendments to improve soil biology for many years, whereas neighbouring fields under ‘standard’ cultivation represent the current state-of-the-art conventional practices. Based on recent findings suggesting a predominant role of microbial-derived compounds in the long-term accumulation of organic C, the study focused on available nutrients, microbial biomass C, nitrogen (N) and phosphorus (P), ergosterol, potential activities of C-, N- and P-liberating enzymes as proxies for microbial functioning, and amino sugar contents as proxies for microbial necromass. In addition to management effects, we also investigated whether differences in texture composition across the study sites and soil depth (0-5, 5-20, 20-35 cm) affect microbial biomarkers. Our results indicate that microbial parameters, especially microbial biomass and necromass C, are significantly enhanced in soils of pioneer farming systems. Yet, pioneer cultivation did not reach the levels prevailing in the undisturbed reference system. Moreover, differences between systems were strongly pronounced in the topsoil and declined in deeper soil layers. Soil texture had a profound leverage on management effects. In addition, we could identify significant management predictors for dissolved C contents, which is an important pathway for microbial-mediated SOC sequestration. Our on-farm approach provides meaningful information on how farming systems can be changed towards more sustainability and higher C sequestration.

How to cite: Huber, S., Rosinger, C., Sae-Tun, O., Bodner, G., and Keiblinger, K.: On-farm research on innovative pioneer farms in North-Eastern Austria: microbial indicators affecting soil organic carbon (SOC) sequestration, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8716, https://doi.org/10.5194/egusphere-egu23-8716, 2023.

15:25–15:35
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EGU23-13128
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On-site presentation
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Stephan Haefele, Jonah Prout, Steve McGrath, and Guy Kirk

Realistic targets for soil organic carbon (SOC) concentrations are needed, accounting for differences between soils and land uses, to help farmers manage the SOC across their farms. We assess the use of SOC/clay ratio for this purpose using data from the the National Soil Inventory of England and Wales and (b) two long-term experiments under ley-arable rotations on contrasting soils in the East of England. The results showed that normalising for clay concentration provides a more meaningful separation between land uses than changes in SOC alone. The results suggest realistic long-term targets for SOC/clay in arable, ley grass, permanent grass and woodland soils. Given the wide range of soils and land uses across England and Wales in the datasets used to test these targets, they should apply across similar temperate regions globally, and at national to sub-regional scales. We use these results to outline a strategy for organic amendment management at the farm level, enabling optimal use of this scarce resource.

How to cite: Haefele, S., Prout, J., McGrath, S., and Kirk, G.: Organic carbon to clay ratios can help to optimize organic amendment use at the farm level, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13128, https://doi.org/10.5194/egusphere-egu23-13128, 2023.

15:35–15:45
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EGU23-8046
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On-site presentation
Mojtaba Houballah, Julia Le Noé, Fabien Ferchaud, Hugues Clivot, Pierre Barré, Bertrand Guenet, and Nicolas Delpierre

To partially compensate for CO2 emissions, the 4 per 1000 initiative proposed an annual 4‰ soil organic carbon (SOC) stock increase. Yet, the feasibility of such an ambitious target is still under debate. The most efficient way to increase the SOC stocks is to increase the C input to the soil. Yet, knowing how much of an increase of SOC should be an objective is subjected to how much carbon is already stored within soils, and the prediction of the change of carbon pool with time. The objective of this work is to predict the carbon trends in forest soils to be able to better assess the target carbon sequestration. To this end, we use the AMG SOC model to simulate the carbon increase in French forests. AMG is a simple, two-pools model that consider the influence of environmental conditions and litter inputs to simulate the dynamics of SOC. AMG has been designed for agricultural soils, and has proved able to simulate SOC dynamics in croplands but has never been tested on forest soils. The model was run over the French RENECOFOR sites network where SOC measurements have been realized 17 years apart (1994-1996 and 2008-2012) on 95 sites and over which an average increase of +0.35 tC ha-1 yr-1 has been evidenced. We have applied the RockEval method, which mixes machine learning with thermal analysis techniques, in order to initialize AMG, separating the passive from the active carbon pool. We calibrated the model with the aim of simulating the SOC dynamics observed in the RENECOFOR. The results show that even if the model can be successful in predicting the carbon trends locally, there is no general parameterization allowing to reproduce SOC stock evolution trends at the scale of the 95 sites. Our findings suggests that even with a good performance in the case of agricultural soils, there is a need to better represent the litter inputting within the AMG model in the case of forests.

How to cite: Houballah, M., Le Noé, J., Ferchaud, F., Clivot, H., Barré, P., Guenet, B., and Delpierre, N.: Applying the AMG Soil Organic Carbon model to assess the carbon trends within French forests, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8046, https://doi.org/10.5194/egusphere-egu23-8046, 2023.

Posters on site: Mon, 24 Apr, 16:15–18:00 | Hall X3

Chairpersons: Viktoriia Hetmanenko, Sergio Saia, Jorge Alvaro-Fuentes
On-site poster session
X3.111
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EGU23-17591
Temporary grassland is not a miracle solution for soil quality of arable land: beyond the keywords, the agronomic factors must be considered
(withdrawn)
Xavier Dupla, Téo Lemaître, Ophélie Sauzet, and Pascal Boivin
X3.112
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EGU23-17575
System Dynamic model of Mangrove Restoration Projectin Klawalu Mangrove Park of Sorong West Papua
(withdrawn)
Aplena Elen Bless, Syafrudin Raharjo, Thomas Pattiasina, Ihwan Tjolli, Krisma Lekito, and Meky Sagrim
X3.113
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EGU23-2799
Reconciling farmers’ expectations with the demands of the emerging UK agricultural soil carbon market
(withdrawn)
Guy Ziv, Lisette Phelan, and Pippa Chapman
X3.114
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EGU23-13354
Kirstine Skov, Tzara Bierowiec, Ifeoma Edeh, Mike Kelland, Amy Lewis, Melissa Murphy, Ryan Pape, Will Turner, Peter Wade, Jez Wardman, and Xinran Liu

Enhanced weathering of silicate rock is a promising natural carbon dioxide removal technology, both due to its scalability and associated agronomical benefits. During silicate rock weathering, dissolved carbon dioxide in the form of carbonic acid, reacts with rock minerals to form stable soil pore water bicarbonate or soil calcium carbonate. The carbon dioxide removal potential of enhanced weathering has been successfully demonstrated in short-term lab and mesocosm studies. Due to the transient nature of bicarbonate in the aqueous soil solution, in-field quantification of the carbon dioxide sequestered is tedious, labour-intense and poorly scalable for the verification of carbon credits. Various methods have been suggested in order to quantify the amount of carbon dioxide sequestered through rock weathering. This quantification is essential for verification bodies to award carbon credits. Although various methods have been proposed to demonstrate that in-field weathering is occurring, there is still no consensus for a scalable, profitable solution. In recent years, an increasing number of field trials have seen the light of day. However, large uncertainties about in-field weathering rates and the influence of natural environmental variability, such as drought and vaying temperatures, still exist. 

In this study we focus on two proxies affected by the weathering process, namely pH and EC. We compare field measurements of pH and EC from both in-situ sensors and extracted soil pore water with model predictions from a 1D-reactive transport model. The data originates from an ongoing field trial on an acidic, clay rich soil used for grassland pasture in central Scotland. Such in-field proxy measurements may provide information to help boost confidence in model predictions.

How to cite: Skov, K., Bierowiec, T., Edeh, I., Kelland, M., Lewis, A., Murphy, M., Pape, R., Turner, W., Wade, P., Wardman, J., and Liu, X.: Preliminary findings from comparison of in-situ measurements of enhanced weathering proxies with model predictions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13354, https://doi.org/10.5194/egusphere-egu23-13354, 2023.

X3.115
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EGU23-13503
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ECS
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Helen Hughes and Jonathan Hillier

Managing soil carbon (C) is an important part of agriculture’s role in both mitigating and adapting to climate change, whilst feeding a growing global population. Adding organic materials to the soil surface can be a valuable practice for C storage. However, regular on-farm measurement to monitor soil C is often impractical due to costs and spatial heterogeneity of soil C stocks. Soil C models can be utilised instead, but their data requirements must be reasonable to provide a useful alternative to farmers.

Ideally, decision support tools should provide the most information from the fewest data points. Sub-field scale equilibrium and saturation dynamics of the soil C pool introduce complexity. The result is that environmental, management and time factors must be represented within modelling approaches.

This analysis will compare the utility of several model approaches (including IPCC Tier 1) for predicting the impact of organic amendments in realistic farmer data scenarios. The impact of equilibrium concepts will be considered through factors such as time, baseline soil C values, as well as climate, environment and soil type. How should these factors be prioritised to focus farmer data requirements when providing decision support? What is the information cost of reducing the data burden?

How to cite: Hughes, H. and Hillier, J.: Soil C Impacts of Organic Amendments: Practical Models for Farmer Decision Support, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13503, https://doi.org/10.5194/egusphere-egu23-13503, 2023.

X3.116
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EGU23-13478
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ECS
Mara Bortolini, Federica C. Agnoletto, Elena Argiriadis, Cristiano Nicosia, David B. McWethy, Yannick Devos, Angela M. Stortini, Maela Baldan, Marco Roman, Tiziano Vendrame, Raffaella Scaggiante, Brunella Bruno, Giulio Pojana, and Dario Battistel

Cultural layers are deposits resulting from settlement and human activity on natural soil in the past. Materials from past domestic activities that become buried in the soil can be used to reconstruct human impact in a specific area in the past. The use of fire from early human societies since our times produced an enrichment of fire-related products such as charcoal. The presence and fluxes of charcoal particles in soils and sediments have been associated with the human occupation of a site in specific periods. But not only does the presence of charcoal permits us to infer the presence of human populations, but, in addition, assessing the abundance and degradation level of charcoal fragments can clarify anthropic activities in cultural deposits. In European towns, cultural layers with similar characteristics, have been defined as urban “Dark Earth” (DE) but their age, formation, and composition often differ significantly across sites. This study examined three archaeological sites in Verona, Italy, where DE layers with similar characteristics had been identified. The primary aim of this research was to understand the anthropogenic influence on the development of DE layers, by characterizing their geochemistry and the carbonaceous materials. To pursue this goal, we provided a micromorphological description of the soil and the abundance of charred material. The characterization of the amorphous/crystalline degree through µ-Raman spectroscopy was also investigated. Bulk material was described in terms of amounts of total organic carbon (TOC), recalcitrant organic carbon (ROC), total inorganic carbon (TIC), and trace element concentration. Radiocarbon dating of charred and humin fractions was performed to clarify the dynamics underlying DE origin. The different aspects studied were compared to outline the behavior and the development of the soil under the conditions of human exploitation, investigating the correlations and relationships of the variables. The results showed that a diverse pattern of human activities, including metal tools and/or ceramic manufacturing, was related to the formation of DE layers in urban contexts. Moreover, the investigation of carbonaceous fractions highlighted differences in soil organic carbon and charred material fraction, even if both of which were correlated with human influence.

How to cite: Bortolini, M., Agnoletto, F. C., Argiriadis, E., Nicosia, C., McWethy, D. B., Devos, Y., Stortini, A. M., Baldan, M., Roman, M., Vendrame, T., Scaggiante, R., Bruno, B., Pojana, G., and Battistel, D.: Carbonaceous fraction contents of soil cultural layers from different ages from the area of Verona (NE Italy), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13478, https://doi.org/10.5194/egusphere-egu23-13478, 2023.

X3.117
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EGU23-14174
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ECS
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Luca Giuliano Bernardini, Christoph Rosinger, Katharina Keiblinger, and Gernot Bodner

Soil organic carbon (SOC) constitutes the largest terrestrial biological carbon pool globally. SOC in croplands has declined by approximately 50% since the intensification of agriculture. In light of climate change due to rising greenhouse gas concentrations in the atmosphere, the 4p1000 initiative was launched, suggesting that anthropogenic CO2 emissions could be offset by increasing SOC stocks in arable land by 0.4% per year by implementing more sustainable agronomic measures. In order to estimate the potential effect of different measures on SOC at the national scale, modelling approaches are required. In the last decades, a wide array of SOC models have been developed and validated for different soils, climate conditions and land uses across the globe. These models all have their own advantages, disadvantages, and sources of uncertainty. Carbon inputs into soil, a major driver of SOC dynamics, are an estimated quantity in all modelling procedures and represent an additional, large source of uncertainty. To reduce uncertainties, multi-model ensembles are suggested to outperform single model runs. The objective of this study is to determine the optimal SOC model ensemble to reduce estimation errors in future studies.

Therefore, a combination of four carbon turnover models (RothC, Yasso07, ICBM, and C-TOOL) and five published carbon input estimation methods was evaluated by comparing simulations to experimental data from six long-term experiments with 56 treatments on arable land in Austria, with durations from 10 to 32 years to obtain a possible optimal combination for future SOC modelling studies in Austria. Evaluation of model prediction was performed by calculating the absolute mean error (AME), Root Square Mean Error (RMSE) and coefficient of determination on yearly SOC changes to eliminate the effect of different experimental durations on model evaluation.

We show that obtained models strongly differ in their stock estimates, and our selected ensemble strongly improved the estimations of SOC against single model runs with significantly lower absolute mean errors and root mean square error. This is in accordance with literature results and presents a way forward towards a more accurate modelling. We thus argue that multi-model ensembles to estimate SOC stocks in arable soils in Austria should be preferred over single-model approaches due to improved accuracy.

How to cite: Bernardini, L. G., Rosinger, C., Keiblinger, K., and Bodner, G.: Improved prediction of soil organic carbon sequestration potentials in Austrian arable soils as simulated by multi-model ensembles, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14174, https://doi.org/10.5194/egusphere-egu23-14174, 2023.

X3.118
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EGU23-14030
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ECS
Sofia Biffi, Pippa Chapman, and Guy Ziv

Recent policy initiatives have placed a strong focus on the use of agricultural soils for atmospheric CO2 removal by adopting practices for sequestering and storing SOC. In the UK, changes in agricultural land use, such as the integration of woody species in the form of hedgerows--lines of regularly trimmed shrubs commonly used to delimit agricultural fields--, have been recommended for climate change mitigation. The Climate Change Committee has proposed a 40% increase in hedgerow length across the country as a key contribution to net-zero targets. In England, this would equate to 193,000 km of newly planted hedgerows. However, the contribution of hedgerow planting to reaching net-zero goals remains unclear due to a lack of data on the rate at which CO2 is taken up and stored in the soil beneath them. In our study, seventy-eight hedgerows across six different pedo-climatic conditions in England were classified into four age categories. Soil organic carbon (SOC) stocks were quantified at 10 cm intervals for the top 50 cm of soil beneath hedgerows and in adjacent grassland fields. Moreover, we examined the distribution of SOC among particle-size fractions to investigate how hedgerow planting may influence SOC dynamics by affecting the quality and long-term stability of organic matter in soils, particularly to illustrate why hedgerow-associated SOC stocks are rapidly lost after hedgerow removal. SOC stocks beneath hedgerows were higher than adjacent fields for all age categories and hedgerows stored an average additional 40% SOC stock in the top 50 cm of soil compared to adjacent fields and 30% in the top 30 cm of soil. The additional SOC stock beneath hedgerows was 40.9 Mg C ha-1 at 0-50 cm depth, or 6.1 Mg C km-1. We used a 37-year-old SOC sequestration rate to show that if England were to reach its goal of 40% increase in hedgerow length, 6.3 Tg of CO2 will be sequestered and stored in the soil over 40 years (9.9 Tg with aboveground biomass). However, it will take ~200 years to reach this target with current rates of planting in national public agri-environment schemes. These results contribute measurable outcomes towards the estimate of targets for net-zero 2050 and the extent of ecosystem services provision by hedgerow planting in agricultural landscapes. 

How to cite: Biffi, S., Chapman, P., and Ziv, G.: Sequestering soil organic carbon by planting hedgerows in agricultural landscapes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14030, https://doi.org/10.5194/egusphere-egu23-14030, 2023.

X3.119
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EGU23-12398
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Mingming Zong, Diego Abalos, Ji Chen, Zhi Liang, Lars Elsgaard, and Uffe Jørgensen

Perennial crops can be as a sustainable alternative to annual crops owing to plant traits and management practices that improve productivity and may contribute to soil carbon (C) accumulation. However, our understanding of the mechanisms behind the potential differences in C stocks between perennials and annuals is incomplete, especially in terms of how the changers and drivers vary at different soil depths. Based on a 10-year cropping experiment in Denmark with perennials (tall fescue, grass-legume mixture) and annuals (triticale monoculture, triticale in a crop rotation), we investigated soil C stock changes and driving mechanisms at depths of 0-20 cm (topsoil) and 20-50 cm (subsoil). We observed that tall fescue and grass-legume mixture systems increased soil C stock by 6-20% in the topsoil as compared to annual crops. In the subsoil, the tall fescue system even enhanced soil C storage by up to 56%, but there was no difference in soil C stock between grass-legume mixture, triticale, and triticale in a rotation. Most importantly, we found that the major determinants of soil C stock depended on soil depth. In the topsoil, enzymes exerted a dominant effect on soil C stock. Perennials with low C/N for aboveground biomass and high root biomass seemed to depress oxidase (phenol oxidase and peroxidase) activities and stimulated the nutrient-acquiring enzymes (leucine amino peptidase, β-1,4-N-acetylglucosaminidase), thus depressing the decomposition of recalcitrant C and maintaining plant growth, which facilitated soil C storage. In the subsoil, microbial biomass, rather than the balance between functional enzymes, seemed to be controlling the soil C storage. In their entirety, our results highlight that it is feasible to enhance soil C storage in systems with perennials with higher aboveground biomass quality and root biomass. Furthermore, there is a link to biological drivers (i.e., extracellular enzyme activity and microbial biomass), which may play a differential role in topsoil and subsoil. With improved mechanistic understanding, such biological drivers of soil C stock for agricultural systems should be considered in Earth system models to improve the accuracy of predicting agricultural soil C dynamics.

How to cite: Zong, M., Abalos, D., Chen, J., Liang, Z., Elsgaard, L., and Jørgensen, U.: Perennial crops increase soil carbon stocks in the topsoil compared to annuals by modifying enzymatic activities, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12398, https://doi.org/10.5194/egusphere-egu23-12398, 2023.

X3.120
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EGU23-16372
Benjamin Loubet, Pauline Buysse, Nicolas Saby, Maryam Ghebleh, Jean-Philippe Chenu, Céline Ratie, Claudy Jolivet, Denis Loustau, and Dominique Arrouays

According to the latest estimates, soils globally store 1500 to 2400 Gt of carbon (C) at a depth of 1 m in the form of organic matter. Almost the same amount of inorganic C is estimated to be stored at a depth of 2 m. Soils contain about twice as much organic carbon as the atmosphere and three times as much as vegetation. Small changes in this large soil reservoir could therefore have major effects on atmospheric carbon dioxide (CO2) concentrations. Soil organic carbon (SOC) stocks are strongly influenced by land use, and soils have lost an estimated 140-150 Gt C globally due to disturbance and cultivation since agriculture began 8000 years ago. Global warming is disrupting the carbon cycle and could lead to a decrease in SOC worldwide. Increased nitrogen (N) deposition and intensification of N use in agriculture since the 20th century are also affecting soil inorganic carbon (SIC) stocks through carbonate weathering on agricultural sites, a process that could counteract efforts to increase SOC by changing land management.

Long-term carbon observation sites, such as ICOS ecosystem sites, are unique networks for assessing soil carbon stock evolution by comparing changes in SOC stock over time through soil sampling with the annual ecosystem carbon budget combining CO2 fluxes through eddy covariance, carbon imports and exports through organic fertilization and harvesting, and dissolved carbon leaching. In this study, we compared the evolution of the SOC stock over 14 years with the carbon balance over the same period on the French crop site ICOS FR-Gri near Paris. The site is a wheat-barley-maize rotation with occasional oilseed rape. We find that SOC decreased by 68 ± 18 g C m-2 y-1 over the 14-year period in the 0-60 cm layer, with 70% of the loss coming from the 0-30 cm layer. Integration of carbon fluxes at field boundaries over the period 2006-2011 led to an estimated total carbon loss of 130 ± 110 g C m-2 y-1 in this field, an estimate close to pan-European studies (138 ± 239 g C m-2 y-1). Carbon leaching was estimated over the same period at 28 g C m-2 y-1 of which 21 g C m-2 y-1 was inorganic. The difference between the carbon balance and the SOC stock change amounts more than 50 of g C m-2 y-1, suggesting an additional carbon loss that may partly be carbonate weathering at a site that contains carbonates in part of the field.

How to cite: Loubet, B., Buysse, P., Saby, N., Ghebleh, M., Chenu, J.-P., Ratie, C., Jolivet, C., Loustau, D., and Arrouays, D.: Comparison of soil organic carbon stock change with eddy covariance carbon balance at an ICOS crop ecosystem site reveals unexplained carbon losses, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16372, https://doi.org/10.5194/egusphere-egu23-16372, 2023.

X3.121
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EGU23-12575
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ECS
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Johanne Lebrun Thauront, Christian Walter, Philippa Ascough, Pierre Barre, and Samuel Abiven

Naturally occuring pyrogenic carbon (PyC) is produced during wildfires under oxygen limiting conditions. After a fire event, PyC is fragmented, dissolved and transported at the soil surface1,2 and/or downward into the soil3,4. PyC represents on average 15 % of organic carbon in soils and sediments5.Its residence time in soil ranges from 50 to 1000 years6,which makes it the most persistent form of organic carbon in soils. However, at the mouth of the world’s largest rivers, PyC is on average 16,000 years old. This difference is probably due to isolated measurements of turnover time in surface soil horizons which does not take into consideration transport and accumulation processes happening at the landscape scale. We make the following hypothesis : (i) PyC accumulates at depth in soil and in lowland and hill-foot positions, and (ii) PyC in accumulation zones is significantly older than PyC from other sites/depths.

We studied the dynamics of PyC in a well characterized, 120 ha watershed in Brittany, France (ORE AgrHys). We collected soil cores at different topographic positions along three transects and quantified PyC using standard (chemo-thermal oxidation, hydrogen pyrolysis) and novel (Rock-Eval thermal analysis) analytical methods. We also measured the 14C ages of the PyC fraction. We show that relative to total SOC, PyC is preferentially redistributed to depth and that the subsoil (30 to 60 cm) represents about a third of the total soil PyC stock. We do not observe accumulation of PyC at the hill-foot except where superficial erosion products are retained before reaching the stream. We discuss the potential sources and redistribution mechanisms of PyC in the area over the last 10000 years.

1. Bellè, S.-L. et al. Biogeosciences Discuss. 1–35 (2021)

2. Rumpel, C., Ba, A., Darboux, F., Chaplot, V. & Planchon, O. Geoderma 154, 131–137 (2009).

3. Soucémarianadin, L. et al. Soil Biol. Biochem. 133, 12–15 (2019).

4. Schiedung, M., Bellè, S. L., Sigmund, G., Kalbitz, K. & Abiven, S. Biogeosciences 17, 6457–6474 (2020).

5. Reisser, M., Purves, R. S., Schmidt, M. W. I. & Abiven, S. Front. Earth Sci. 4, 1–14 (2016).

6. Singh, N., Abiven, S., Torn, M. S. & Schmidt, M. W. I. Biogeosciences 9, 2847–2857 (2012).

How to cite: Lebrun Thauront, J., Walter, C., Ascough, P., Barre, P., and Abiven, S.: Pyrogenic carbon redistribution in the landscape: example of a small, cultivated temperate watershed, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12575, https://doi.org/10.5194/egusphere-egu23-12575, 2023.

Posters virtual: Mon, 24 Apr, 16:15–18:00 | vHall SSS

Chairpersons: Alina Premrov, Sergio Saia, Laura Quijano
Pedogenic carbonate (Virtual presentation)
vSSS.12
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EGU23-17289
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ECS
Reza Khalidy, Yi Wai Chiang, and Rafael M. Santos

Deemed an inexpensive and low-energy method for mitigating atmospheric CO2 levels, enhanced rock weathering offers a long-term stable sink of soil carbon by converting alkaline earth metals into stable carbonates. Several silicate-rich minerals (e.g., basalt, olivine, and wollastonite) have been a matter of particular interest of researchers investigating the applicability of this approach for sequestrating atmospheric CO2 in agricultural and urban soils. Several field-scale and laboratory-scale experiments have been conducted in our research group investigating the impact of the wollastonite amendment on the agricultural soil of Ontario. This includes monitoring pedogenic carbonate formation and migration in soil and subsoil systems (through collecting shallow and deep samples down to 1-meter profiles) as well as the effect on various plant growths in soils amended with crushed wollastonite.

The water (e.g., rainfall or irrigation water) infiltrating the porous medium of soil could transport and relocate solid particles over the vertical profile of the soil. Accordingly, when crushed silicate minerals (e.g., wollastonite) is applied to topsoil, the recurring introduction of water leads to the dissolution of mineral as well as downward migration of weathering products which could be settled in subsoil layers. Furthermore, the dissolution of wollastonite alters the chemical properties (e.g., pH, EC, etc.) of migrating water, which finally find its way to the water table below the soil medium. In the present study, we have looked into evidence of the vertical distribution of weathering products in soils amended with crushed wollastonite, whose relatively rapid weathering rate helps in the shorter-term to inform what occurs in the longer-term with slower weathering minerals. The experimental setup includes soil columns with and without wollastonite enrichment, located under two situations of lab environment (with regular hand-operated irrigation) and outdoor (with natural rainfall-fed). We also investigated the leachate collected from the bottom of columns in term of physiochemical properties.

The current study is part of the analytical and modelling framework we are developing in order to account for newly formed pedogenic carbonate as a qualified implementation for carbon capture credits. Such verified methods would encourage private and governmental entities to contribute to meeting emissions reduction goals and encourage the adoption of enhanced rock weathering as a reliable negative emissions technology.

How to cite: Khalidy, R., Chiang, Y. W., and Santos, R. M.: Transport and fate of wollastonite weathering products through soil and subsoil under realistic irrigation/rainfall conditions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17289, https://doi.org/10.5194/egusphere-egu23-17289, 2023.