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Soil organic and inorganic carbon stocks and dynamics in agro-ecosystems: mechanisms, measurements and modelling strategies

Soil is the largest carbon (C) reservoir in terrestrial ecosystems with twice the amount of atmospheric C and three times the amount in terrestrial vegetation. Carbon related ecosystem services include retention of water and nutrients, promoting soil fertility and productivity and soil resistance to erosion. In addition, changes in the soil C can have strong implications for greenhouse gas emissions from soil with implications in environmental health.

Drivers controlling C pools and its dynamics are multiple (e.g. land use/vegetation cover, climate, texture and bedrock, topography, soil microbial community, soil erosion rates, soil and other environment management practices, etc. ) and mutually interacting at various time and spatial scales. At the one time, rate of soil C loss can be high due to both climatic constrains or unsuitable management. Thus, investigating C dynamics include the adaptation of the management factors to the actual climate, the climate change and climatic extreme events to provide a better understanding of carbon stabilization processes and thus support decision making in soil management and climate adaptation strategies.

The present session highlights the importance of soil C changes, and the interaction among the mechanisms affecting C concentration and stocks in soil, including soil management. Discussion about proxies of measurement and modelling organic and inorganic C flows, concentration and stocks, with special emphasis to cropping systems and natural/semi-natural areas, is encouraged. These proxies should be approached at varying the availability of soil and environment information, including, e.g., soil texture, rainfall, temperature, bulk density, land use and land management, or proximal and remote sensing properties. Studies presented in this session can aim to a wealth of aims, including soil fertility, provision of ecosystem services, and their changes, and the implication for economy, policy, and decision making.

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, and meta-analysis. These works will be evaluated at the light of the organisation of a special issue in an impacted journal

Co-organized by BG3/GM3
Convener: Sergio Saia | Co-conveners: Viktoriia Hetmanenko, Calogero SchillaciECSECS, Laura QuijanoECSECS, Alina Premrov
| Tue, 24 May, 15:10–16:40 (CEST)
Room 0.49/50

Tue, 24 May, 15:10–16:40

Chairpersons: Calogero Schillaci, Marco Acutis, Elena Valkama

Julia Fohrafellner et al.

The number of meta-analyses published in the field of agriculture is continuously rising. As a consequence of this rising popularity, more and more publications refer to their synthesis work as a meta-analysis, despite applying less than rigorous methodologies. All this gives reason to assume that core criteria, necessary in producing meta-analyses, are not clear to many researchers. As a result, poor quality meta-analyses are published, which might report questionable conclusions and recommendations to policymakers and farmers. This study is therefore aiming to provide fellow soil and agricultural researchers with an easy-to-use set of criteria on how to produce high quality meta-analyses. Alongside, the incorporated scoring scheme supports researchers and policy makers in evaluating the quality of existing agricultural meta-analyses.

We analyzed 31 meta-analyses studying the effects of different management practices on SOC between the years 2005-2020. Moreover, the retrieved meta-analyses were structured according to eleven management categories which allowed us to analyze and assess the quality of the state-of-knowledge on these categories. We found that, although overall quality was rising, meta-analyses on SOC still do not reach sufficient quality and a maximum score may be reached only by the year 2032.

Especially for the reporting of literature search, application of standard metrics for effect size calculation, correct weighting, extraction of independent effect sizes and database presentation, major deficiencies were found. In some cases, the term “meta-analysis” is still falsely used to describe quantitative syntheses of any style. Only one out of 31 meta-analyses in the category “tillage” applied a rigorous meta-analytical methodology and received a high overall quality score.

We conclude that, in order for the scientific community to provide high quality synthesis work and to push forward the sustainable management of agricultural soils, we need to adapt rigorous methodologies of meta-analysis as quickly as possible.

How to cite: Fohrafellner, J., Zechmeister-Boltenstern, S., Murugan, R., and Valkama, E.: Quality assessment of meta-analyses on soil organic carbon research  , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-15, https://doi.org/10.5194/egusphere-egu22-15, 2022.

Josip Šušnjar et al.

Pedogenic carbonates are secondary carbonate deposits that are often found in soils developed over carbonate rocks in Mediterranean region. Their formation is a result of dissolution and reprecipitation of existing geogenic, biogenic and/or pedogenic carbonates. Intensity of the dissolution processes affecting carbonates depends on multitude of factors but is mostly controlled by soil water drainage and concentration of soil air CO2.

While percolating through soils and carbonate rocks, water dissolves carbonate minerals until reaching saturation state. Change in environmental conditions impacting concentration of soil air CO2 (e.g., increase of temperature, decrease of soil water content), change of the soil water chemistry and evapotranspiration can lead to supersaturation of water in regard to Calcite and formation of pedogenic carbonates. In case of physicochemical precipitation, pedogenic carbonates precipitate in form of diffuse, small crystals and nodules. On the other hand, biologically influenced precipitation commonly results in different morphologies such as rhizolits, bacterial/fungal mats, etc. Pedogenic carbonates can occur in wide range of climates, thus their morphology and accumulation depth depend on mean annual precipitation. If sufficient time has passed, translocation of carbonates in the soil profile results in formation of calcic horizon.

We studied a 0.6 m deep Red Mediterranean Soil profile in Dalmatia (Croatia) having a calcic horizon at the bottom. Diffuse calcite particles and small nodules forming this horizon record different events of dissolution and precipitation. Based on data on soil temperature, soil water content, soil bulk electrical conductivity and soil air CO2 collected during a 3-month monitoring period we developed a thermodynamic model for dissolution and precipitation of calcite in the soil. Results show that soil air CO2 (affected by soil water content and temperature) is the main control of the calcite reactions. Furthermore, during the monitoring period 83% of the calcite dissolved was reprecipitated as pedogenic carbonate. Therefore, although dissolution is the main process governing denudation rate of karst areas (i.e., lowering of the surface), formation of pedogenic carbonates in soils could impact denudation rate of carbonate terrains.


This work is part of the research project “Inter-comparison of karst denudation measurement methods” (KADEME, IP-2018-01-7080) and “Young Researchers’ Career Development Project – Training New Doctoral Students” (DOK-2021-02) financed by Croatian Science Foundation.

How to cite: Šušnjar, J., Domínguez-Villar, D., Bensa, A., Švob, M., and Krklec, K.: Modelling of pedogenic carbonates formation in karst soils – a case from Dalmatia (Croatia), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-175, https://doi.org/10.5194/egusphere-egu22-175, 2022.

Mauro De Feudis et al.

The role of soil organic carbon (SOC) in avoidance, mitigation and control land degradation in forest ecosystems is largely recognized. For these reasons, a satisfactory SOC monitoring aimed to drive sustainable SOC management is necessary to avoid soil forest degradation. In this work we thus aimed to a) compare the soil organic carbon stock (OC stock) obtained by pedogentic horizons (PED) and fixed depth layer (FIX) in different forest ecosystems; b) discuss the differences in SOC data provided by the two soil sampling approaches, clarifying their major advantages and drawbacks; and c) to assess the ability of PED and FIX sampling approaches to keep information about horizontal and vertical SOC distribution. On the Apennine chain (North Italy), uneven–aged sweet chestnut, European beech and Norway spruce forests were selected. In each site, a representative area (18 m × 18 m) has been selected and, in the centre of the area, a soil profile has been investigated. Further, within the representative areas 8 additional sampling points were identified. Both for soil profiles and the additional sampling points, soil collection was performed both by PED and FIX (0–15 and 15–30 cm). For each forest stand, no difference of OC stock in 0–30 cm soil depth was found between PED and FIX sampling approaches, however SOC distribution along 0-30 cm provided by PED sampling was more informative on SOC dynamics. The findings obtained through the sampling by FIX would indicate a positive effect of conifers on SOC storage, the PED sampling allowed to assess that SOC under spruce forest was greatly stored in the organic horizons (Oe and Oa) because of the recalcitrant nature of the spruce litter, that does not allow the organic carbon stabilization through the association with mineral particles. Therefore, the spruce forest soil would not lead structural stability and resilience to soil degradation. Sampling by PED also preserved the information about the spatial variability within each study site. In fact, we noted higher coefficient of variation when soil horizons were considered compared to FIX (from 19.2 to 72.8% and from 16.5 to 25.7%, respectively). Overall, in a view of SOC monitoring, our findings demonstrated that the sampling by PED draws a better picture of SOC distribution along depth and its potential susceptibility to external factors leading to degradation. Further, the loss of information about SOC stabilization process and spatial variability would indicate the inability of FIX sampling to support decision–making plans addressed for sustainable use of soil resource.

How to cite: De Feudis, M., Falsone, G., Vianello, G., Agnelli, A., and Vittori Antisari, L.: Efficacy of pedogenetic horizons sampling for site-specific assessment of soil organic matter, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1216, https://doi.org/10.5194/egusphere-egu22-1216, 2022.

Orracha Sae-Tun et al.

Conservation tillage has been widely applied to improve soil health, sustain crop production, and promote carbon (C) sequestration in soil. Positive effects often depend on the degree of tillage intensity and time of adoption. This study was thus aimed to determine temporal changes of selected soil health indicators under different tillage intensities in a long-term tillage trial.

Accordingly, bulk and rhizosphere soil samples were taken after 8 and 13 years of adoption from topsoil under four different tillage systems ranging from conventional (high intensity), reduced, minimum, to no-tillage (low intensity).  Aggregate stability and soil fungal indicators (ergosterol and glomalin-related soil protein) were analysed. Soil organic carbon stocks were assessed at 10 and 13 years of adoption. To determine long-term effect of tillage on soil microbial necromass accumulation, amino sugars were measured after 13 years of adoption.

Aggregate stability and soil fungal indicators increased with lower tillage intensity for both sampling time points. Conservation tillage practices promoted the accumulation of soil organic carbon and microbial necromass. Interestingly, among conservation tillage practices, the soil fungal indicators showed highest values for reduced and minimum tillage compared to no-tillage at 13 years of adoption. This suggests that fungal growth could potentially benefit from slight soil disturbance in the long-term. Therefore, reduction of tillage intensity evidently improved soil health by promoting soil carbon sequestration and aggregate stability via fungal growth as well as soil microbial necromass accumulation.

Conventional tillage is most detrimental to soil health indicators, while reduced tillage seem to promote soil biological processes via gentle mixing of soil substrate. Instead, no-tillage is most beneficial to aggregate stability but not for fungal indicators.  

How to cite: Sae-Tun, O., Bodner, G., Rosinger, C., Weninger, T., Zechmeister-Boltenstern, S., Mentler, A., and Keiblinger, K.: Conservation tillage practices facilitate soil organic carbon sequestration and aggregate stability via fungal abundance and necromass, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2206, https://doi.org/10.5194/egusphere-egu22-2206, 2022.

Alina Premrov et al.

In this study we used the biogeochemical model ECOSSE-6.2b [1] in site-specific mode to evaluate/test model accuracy to estimate soil organic carbon (SOC) in Irish grassland systems under mineral soils. The selection of sites and management practices, as well as model inputs and model initialization followed procedures explained in Premrov et al. (2021) and (2020) [2],[3]. Results indicated a possible overestimation of modelled SOC for some grassland management categories, highlighted the sensitivity of the model to the initial SOC inputs and demonstrated the need for replicated measurements of SOC over time [4]. One of the challenges faced in this study was the lack of availability of site-specific data for the selected Irish sites, such as data on livestock stocking rates (SR) for grazed grasslands, which can differ greatly from year to year. SR could be only estimated as a single numeric value for each site, which demonstrated the need for greater availability and more detailed site-specific data for Irish grasslands. The availability of repeated measurements of SOC over time for the whole country represented another major challenge in modelling SOC for Irish grassland systems [4]. It is thought that the modelling undertaken here could be further enhanced using additional time-dependent SOC soil-point data, such as LUCAS data [5], as this would provide datasets that have repeated measurements of SOC needed for further model evaluation and parameterization. This work also showed a significant potential for further model improvement; grazing-induced vegetation changes, and associated impacts on SOC, could be accounted by introducing new types of grazed grassland vegetation parameters into the ECOSSE model [4]. These modelling opportunities could also have significant potential for further assessment of SOC dynamics and for spatial and temporal upscaling.



SOLUM project is funded under the Irish EPA Research programme 2014-2020.



[1] Smith, J., et al. (2010). ECOSSE. User Manual.

[2] Premrov, A., et al. (2021). Insights into ECOSSE modelling of soil organic carbon at site scale

from Irish grassland sites and a French grazed experimental plot. EGU21-1879. https://doi.org/10.5194/egusphere-egu21-1879; (CC BY 4).

[3] Premrov, A., et al. (2020). Insights into modelling of soil organic carbon from Irish grassland sites using ECOSSE model. EGU2020-8090. doi.org/10.5194/egusphere-egu2020-18940; (CC BY 4).

[4] Saunders, M. et al. (2021) Soil Organic Carbon and Land Use Mapping (SOLUM) (2016-CCRP-MS.40). EPA Research Report.

[5] JRC (2020). LUCAS 2015, ESDAC. JRC. EC.

How to cite: Premrov, A., Zimmermann, J., Dondini, M., Green, S., Fealy, R., Fealy, R., Decau, M.-L., Klumpp, K., Afrasinei, G. M., and Saunders, M.: ECOSSE biogeochemical modelling of soil organic carbon from Irish grassland systems - challenges and opportunities, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2944, https://doi.org/10.5194/egusphere-egu22-2944, 2022.

Lena Katharina Öttl et al.

Tillage erosion is known to be a major soil degradation process that is mainly associated with increasingly mechanised agriculture since the early 1950s. However, especially soil truncation on convex hilltops and slope shoulders can be already identified on historical aerial photos of our study region in Northeast Germany from the 1950s.

The aim of the study is to better understand the effect of mechanised and especially long-term non-mechanised soil redistribution processes on soil organic carbon (SOC) dynamics over the past 1000 years since the beginning of widespread soil cultivation in our study region and their contribution to the question of soil being a carbon (C) sink or source.

Therefore, a modified version of the spatially explicit soil redistribution and C turnover model SPEROS-C was applied on a large-scale catchment (approx. 200 km²) to simulate lateral soil and SOC redistribution, SOC turnover and erosion-induced vertical mixing within the profile (spatial and vertical resolution 5 m x 5 m and 0.1 m soil depth increments, respectively). The uncertainty of the modelling approach was estimated by varying the input variables according to different realisations of the development of agricultural management over the past 1000 years. The results were validated with an erosion classification derived from Sentinel-2 data and UAV based estimation of topsoil SOC. The lowest SOC stocks were found on hilltops, which points at tillage erosion as the major driver of soil degradation.

Our results show that the beginning influence of tillage erosion on catchment wide vertical SOC fluxes can be traced back to around 500 years ago. This clearly indicates that non-mechanised tillage erosion from the early stage of cultivation affected the SOC patterns in the study area and hence impacts todays C cycling.

How to cite: Öttl, L. K., Wilken, F., Degg, M.-R., Wehrhan, M., Juřicová, A., Sommer, M., and Fiener, P.: Tillage erosion as an important driver of soil organic carbon (SOC) dynamics long before agricultural mechanisation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3501, https://doi.org/10.5194/egusphere-egu22-3501, 2022.

Valentina Brombin et al.

Forest soils contain a large amount of carbon and play an important role in its global cycle. As forest soil organic carbon (SOC) mineralization is one of the major sources of atmospheric carbon, small changes of SOC can have effects on climate. Therefore, the Rural Development Programme (RDP) of Emilia-Romagna Region (Northeastern Italy) financed our SuoBo project, which aims to assess and preserve the quantity and quality of soil organic matter (SOM) in mountainous forest ecosystems located on the Apennine chain of the Emilia-Romagna Region. Our specific goal was to explore the response of SOC pools to forest thinning under two vegetation types. For this purpose, a chestnut forest of Beghelli farm (BEG), located at about 550 m a.s.l., and a mixed forest of Branchicciolo farm (BRA), located at about 225 m a.s.l, were selected. Soil samples were collected from each forest stand at 0-15 cm and 15-30 cm depths, in October 2020 in both farms and then in July 2021 in BRA farm and September 2021 in BEG farm. The soil samples were analyzed for the elemental contents and isotopic ratios (δ13C) of the soil total (TC), organic (SOC) and inorganic (SIC) carbon using an elemental analyzer coupled with an isotope ratio mass spectrometer. In October 2020, forest soil in BRA had higher TC, SOC, and SIC content in 0-30 cm (average: 7.1, 4.8 and 2.3 wt%, respectively) than in BEG (3.0, 2.8 and 0.1 wt%, respectively). The δ13CTC of the BRA soil is less negative than that of the BEG farm (–17.3‰ and –25.9‰, respectively) due to the higher SIC content, inherited by the parent rock mainly composed by limestones. In 2021, after one year since the thinning intervention, the TC and SOC contents in BEG soil were like those recorded in 2020, whereas those in BRA soils showed lower values. In particular in the superficial layer of BRA soils (0-15 cm), the SOC decreased from 6.9% to 4.1% in 2020 and 2021, respectively, while SIC content was unchanged (2.0 vs 2.1 wt%). Even in the deepest layer (15-30 cm) SIC remained the same over time (2.5 vs 2.4 wt%), while SOC decreased (2.5 vs 1.2 wt%). Also, the changes of δ13CSOC underlined a loss of organic matter from 2020 to 2021 (0-15 cm: –27.0 vs –26.2‰; 15-30 cm: –26.2 vs –25.9‰). Different concomitants may be contributing to this significant decrease in SOC: a) the different period of soil sampling (autumn vs summer), considering that the year 2021 is one of the seven warmest years on record globally and BRA has a lower altitude than BEG; b) the high slope (>45°) and the triggering of erosion process after the thinning intervention, which took away the surface soil, mainly characterized by organic hemitransformed horizons (e.g., Oe horizons). The future planned analyses of the quality of the SOM through i) chemical extraction and separation of the different humic fractions and ii) stability of the C fractions at different temperatures with a SoliTOC analyzer will shed a light on the prevailing phenomenon.

How to cite: Brombin, V., Salani, G. M., Mistri, E., De Feudis, M., Falsone, G., Vittori Antisari, L., and Bianchini, G.: Organic and inorganic carbon in managed forest soils of the Emilia-Romagna Region (Northeastern Italy), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3667, https://doi.org/10.5194/egusphere-egu22-3667, 2022.

Sastrika Anindita et al.

 Land use through its control on vegetation and fertilization can impact on soil geochemistry which in turn also
influences the stabilization of soil organic carbon (SOC). Here, we assess soil organic carbon pools following a
fractionation method by Zimmermann et al. (2007), and analyse the fate of SOC with a process-based soil genesis
model, SoilGen2. We hypothesized that geochemical properties influenced the distribution of SOC and these
properties can be applied in a model context to modify the decay rate of soil carbon pool. A set of volcanic soils
data from Mt.Tangkuban Perahu and Mt. Burangrang in Indonesia covering different land uses (primary forest,
pine forest, and agriculture) from Holocene age was used in this study. In the model, calibration was done
sequentially including (i) weathering of amorphous and primary minerals, and (ii) decay of soil organic carbon.
These processes are represented by various process parameters, and each simulation was run on a 8-10k year
time scale. Our SOC fractionation study showed that the dominant SOC pool was located in sand-aggregate
fractions and was higher with agricultural land use. This pool was positively correlated to pH, exchangeable Ca,
aluminum-oxalate extraction (Al
o), and amorphous materials. This result is also in line with a better performance
in the SOC model by applying geochemically-modified rates. Our calibrated model shows the advantage of
including geochemical rate modifier in the volcanic soils. Further, the SOC levels will also be investigated under
different climate projection using SoilGen model.

How to cite: Anindita, S., Sleutel, S., and Finke, P.: Evaluating the distribution and mineralization of soil organic carbon pool in relation to soil geochemistry under different land use in volcanic soil, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4661, https://doi.org/10.5194/egusphere-egu22-4661, 2022.

Lichao Fan et al.

Terrestrial ecosystems play a significant role in global warming by regulating CO2 concentration in the atmosphere. A comprehensive understanding of carbon (C) sources and stocks in soils, as well as the driving mechanisms, are critical to reducing CO2 emission from soil and thus mitigating climate change. To date, most studies have solely focused on processes involving soil organic C (SOC), but few studies have addressed the potential contribution of soil inorganic C (SIC) mostly CaCO3 pool to ecosystem C fluxes. SIC can potentially be a regulator of atmospheric CO2. However, so far the effects of plant species (i.e. variations in nitrogen (N) demand and N use efficiency (NUE)) as well as soil temperature on SIC-derived CO2 are unclear. We hypothesized that 1) relatively less SIC-derived CO2 is expected from soils covered under plant species with lower N demand and higher NUE. We conducted a 4-month field experiment from June to October 2021 at the research station of the University of Göttingen in Deppoldshausen (51.58oN, 9.97oE) with ca. 6% CaCO3 equivalent in the topsoil. We analyzed the effects of two plant species 1) wheat (high N demand and low NUE), 2) legume (low N demand and high NUE) and two N fertilization (urea) levels, 1) low (50 kg N ha-1), 2) high (200 kg N ha-1) on CO2 emission out of SIC. Each treatment had four replicate plots (1×1 m2), and at least a 0.5 m gap was established between plots. We measured CO2 fluxes weekly by using the static chamber method. The δ13C natural abundance was used to determine the contribution of SIC and SOC in the emitted CO2. The total CO2 emission and its δ13C signature increased with soil temperature, indicating that the portion (%) of SIC-derived CO2 was stimulated by temperature (oC) (slope = 0.33). The portion of SIC-derived CO2 stimulated by temperature increased faster under wheat than under legume (slope = 0.36 vs. 0.26), especially under high N treatment (slope = 0.65 vs. 0.54). The portion of SIC-derived CO2 under wheat (13.0%) was higher than that under legume (11.3%). Moreover, the portion of SIC-derived CO2 was 1.2% higher under wheat than under legume at high N fertilization level, whereas it was increased to 2.2% under low N fertilization. This indicates a significant role of plant species with different N demand and NUE on dynamics of SIC pool and its contribution in CO2 emission from soil. The rate of SIC-derived CO2 was comparable between wheat and legume under high N fertilization, but it was 1.6 times higher under wheat than that under legume at low N fertilization. The contribution of SIC-derived C to the atmosphere was ~63.7 g C m-2 yr-1 under legume with low N demand vs. ~82.1 g C m-2 yr-1 under wheat with high N demand. In this regard, the impacts of plant species and their N demand and NUE are important controlling factors determining the dynamics of the SIC pool in agroecosystems.

How to cite: Fan, L., Tao, J., Shao, G., Ai, J., and Zamanian, K.: Nitrogen use efficiency of plant species matters: CO2 emission from soil inorganic carbon and its temperature dependence in a calcareous soil, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5018, https://doi.org/10.5194/egusphere-egu22-5018, 2022.

Thomas Guillaume et al.

Soil organic carbon (SOC) accumulation in agroecosystems is a promising solution to simultaneously improve food security and mitigate climate change. Indeed, because of their large carbon deficit, cropland soils can potentially sequester a substantial amount of atmospheric carbon (C). To estimate the soil C-sequestration potential, it is critical to derive reliable estimations of the current soil C-saturation level. This step is essential to obtain an accurate quantification of C-deficits in cultivated soils. In addition, it is important to identify agricultural practices that favor SOC accumulation in order to reduce the soil C-deficit. Based on a 30-year old soil monitoring network of multiple cropland (CR) and permanent grassland (PG) sites established in western Switzerland, we (i) quantified the C-deficit in croplands, (ii) identified the factors driving the C-deficit and (iii) evaluated the assumption that grasslands can be used as C-saturated reference sites. We demonstrated that SOC in CR were depleted by a third compared to PG. The main factor affecting C-deficit in CR was the proportion of temporary grasslands (TG) within the crop rotation. We also showed that PG have not reached their C-saturation level in the study area and that additional C could be stored in PG soil under optimal management. When accounting for pedo-climatic differences, the C-deficit of CR that do not include TG in the rotation was equivalent to 3 kg C m-2 down to 50 cm depth. The relationship between the proportion of TG in the rotation and SOC stocks in the topsoil (0-20 cm) and subsoil (20-50 cm) was linear and similar at both depths, revealing the strong potential of the subsoil to sequester C.

How to cite: Guillaume, T., Makowski, D., Elfouki, S., Bragazza, L., Libohova, Z., and Sinaj, S.: Increasing topsoil and subsoil organic carbon storage with improved rotation in cropland-grassland agroecosystems, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5184, https://doi.org/10.5194/egusphere-egu22-5184, 2022.

Jingjing Tao et al.

Soil acidification has increasingly become a critical issue for sustainable production due to the excessive nitrogen (N) fertilization in agricultural systems. Application of N fertilizers and the consequent nitrification yield protons (H+), which strongly and irreversibly accelerate dissolution of soil inorganic carbon (SIC) e.g., CaCO3, leading to CO2 release in the atmosphere. Here, 14C-labeled CaCO3 was added to calcareous soil (0.75% CaCO3) to investigate the effects of chicken manure, urea, NH4NO3, KNO3 and (NH4)2SO4 on soil acidification and to estimate the SIC contribution to CO2 emission. 250 mL gas-tight jars were filled with a cropland soil (pH = 7.2), homogenously mixed with 1.3% Ca14CO3 powder (14C activity = 11.3 kBq pot-1). Following fertilization in rates of 0.1, 0.15, 0.25 g N kg-1 soil, NaOH was applied to trap the emitted CO2 and to determine 14C activity. CaCO3 addition increased soil pH values by 0.17-0.43 units. Addition of ammonium-based fertilizers ((NH4)2SO4, NH4NO3) strongly decreased pH up to 0.3 units. All fertilizers increased CO2 emission (5.1%-180%) compared to the unfertilized soil after 44 days of incubation except KNO3. SIC-originated CO2 due to fertilization was ranged from 2.9 to 160 mg C kg-1 (1.1% to 48% of total emitted CO2). Manure and urea had lowest impacts on SIC-driven CO2 during the first 5 days (2.9-34 mg C kg-1) irrespective of the application rate. Thereafter, the effects of fertilizers on SIC-originated CO2 increased in the order: urea < manure < KNO3 < NH4NO3 < (NH4)2SO4. As nitrification of (NH4)2SO4 yields in 4 mol H+, which neutralizes 2 mol carbonates, it initially caused the highest SIC-originated CO2 until 9 days. Urea and NH4NO3 release by nitrification 2 mol H+ per mole of fertilizer, but urea initially hydrolyses to NH4OH, which increases soil pH. So, urea addition had the minimum SIC loss as CO2 in the first 5 days, but starting from 16th day, CO2 emission sharply increased and reached to highest values among the fertilizers. Manure increased SIC-originated CO2 emission from 23rd day of incubation. Gradual and incomplete mineralization of organic N of chicken manure duration 44 days explains the smallest released CO2 from CaCO3 and slowest acidification in the first 16 days. Furthermore, Ca2+ and Mg2+ in manure may be precipitated as carbonates, which decrease the SIC share in the emitted CO2. Generally, the higher the applied fertilizer amounts, the larger was the proportion of CO2 released from SIC. Both the fertilizer chemistry and the application rate played significant roles in dissolution of carbonates. Summarizing, the correct selection of the type and amount of fertilizers based on soil properties and plant demand is necessary to decrease SIC-originated CO2 emission to mitigate global warming, and also save various ecosystem services such as organic matter stability and increase C sequestration.

How to cite: Tao, J., Fan, L., Zhou, J., Kuzyakov, Y., and Zamanian, K.: Nitrogen fertilizers control CO2 emission from calcareous soils: implications for land management and global warming, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5503, https://doi.org/10.5194/egusphere-egu22-5503, 2022.

Carmela Marangi et al.

The effects of environmental change on ecosystem dynamics is nowadays a major research question. Soil organic carbon (SOC) models are integrated into many ecosystem models for projecting the effects of these changes in the achievement of land degradation neutrality. The  Rothamsted Carbon (RothC) model, initially developed to simulate the effects of different practices for long-term agricultural experimental sites, can be successfully used to monitor and project the SOC indicator of land degradation. Here, continuous and discrete versions of the RothC model are firstly compared on classical long-term experiments carried out at the Rothamsted Experimental Station; then a non-standard monthly time stepping procedure is used to evaluate the response of the model to changes of temperature, Net Primary Production (NPP), and land use soil class (forest, grassland, arable)  in the protected areas of Alta Murgia National Park in the Italian Apulia region and Magura National Park in Polish Subcarpathian Voivodeship.  

How to cite: Marangi, C., Diele, F., Luiso, I., Martiradonna, A., and Wozniak, E.: SOC indicator of land-degradation: responses of continuous and non-standard discrete RothC  models to environmental changes  , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5894, https://doi.org/10.5194/egusphere-egu22-5894, 2022.

Alessia Perego et al.

In the LANDSUPPORT project (H2020-RUR-2017-2/No. 774234), we have developed a web-based “Best Practices tool” that runs on the fly (https://dev.landsupport.eu/template.html) to identify optimized solutions for enhancing soil fertility and reducing nitrate leaching. The tool works at a regional scale (average area of approximately 2500 km2) in three case studies (Marchfeld – Austria, Campania Region – Italy, Zala County – Hungary) with a what-if scenario approach. The tool is dynamically linked to the ARMOSA process-based model, which simulates at a daily time step many combinations of farming systems (conservation, organic, conventional), crops, nitrogen fertilization rates, tillage solutions, crop residues management (up to 2520 combinations). ARMOSA simulates crop growth, soil water dynamics, nitrogen and carbon cycling.

The tool is meant to be applied by public authorities, such as regional environmental agencies, to find the best solutions out of feasible management practices according to the overall goal (e.g., increase in soil organic carbon stock, reduction of nitrate leaching) or by farmers who want to evaluate the crop production under current and optimized management.

The user defines the region of interest (ROI). To this ROI the tool automatically associates the soil profiles, having properties (texture, initial soil organic carbon, bulk density) described for each horizontal layer.

For a given region of interest within the case study being characterized by specific soil properties, the user sets the combination of agronomic practices with the interface: climate scenario (20 years), crops, system, fertilization rates, residues management, tillage, and the use of cover crops. The user-friendly interface hides the high complexity of the soil and crop processes which are simulated by ARMOSA, which has many crop and soil parameters. Parameters have been calibrated using the dataset available in the project and in previous studies.

For each of the simulated soils and scenarios, the tool returns the mean annual value of (1) the crop yield, (2) the nitrate leaching at the bottom of the soil profile, and (3) the change of the soil organic carbon stock in the upper soil layer (0-0.4 m). The tool also provides the value of the synthetic “best practices index” (IBP) that is computed as a linear combination of the three variables and the weights that the user dynamically assigns to each of the variables according to the specific goal (e.g., increase in soil organic carbon). The user can then sort by descending order the IBP values to identify the most suitable solutions (i.e., combinations of practices). The mean value of IBP is plotted in charts for each of the simulated combinations.

Due to the link to the ARMOSA process-based model, the tool offers the great opportunity of a close representation of actual and optimized cropping systems with the possibility of further applications at a larger scale (e.g., European scale), in other regional case studies, and in tailored scenarios in which the user enters her/his own data of soil properties and climate. 

How to cite: Perego, A., Acutis, M., Botta, M., Tadiello, T., Langella, G., Terribile, F., Bancheri, M., and Basile, A.: The LANDSUPPORT best practices tool identifies optimized solutions for the health of agricultural soils , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10997, https://doi.org/10.5194/egusphere-egu22-10997, 2022.

Kilian Walz et al.

Peatlands play a crucial role in the global carbon cycle and are a major ecosystem with potential to remove greenhouse gases from the atmosphere. Ombrotrophic peatlands constitute the largest soil organic carbon (SOC) stock in Republic of Ireland (ROI) and cover an estimated 20% of the land surface. Peatland nitrogen (N) stock remains unknown, despite its crucial role in peatland degradation with subsequent nitrous oxide (N2O) emissions and eutrophication of downstream ecosystems. Land use impacts are major drivers of both peatland carbon and N stock degradation and disturbance of the peatland carbon sink function. Hence, in the context of this research it is assumed that past and present land use activity, including afforestation, grazing, and domestic and industrial peat extraction for energy and horticultural use, are likely to affect peat SOC and N stocks.

To date, estimation of the peat SOC-stock in ROI was based on non-directly measured values of SOC-concentration, dry bulk density and peat depth. In this study, these properties were measured for the first time along the entire peat soil profile at national scale across the major ombrotrophic peatland types and land uses. A predictive modeling approach, which compared linear and additive mixed-effects models, formed the basis for quantifying SOC and N stocks. The approach encompassed a model evaluation that used an iterative data-splitting algorithm, combined with an assessment of the bias-variance trade-off.

Our results depict a similar pattern for both SOC and N stocks, with mean stock estimates (t ha-1) largest for near-natural bogs. The largest total amount (Mt) of SOC and N was stored in bogs (recently) used for domestic peat extraction. Stock calculations based on modelled SOC and N values resulted in initial estimates for the entire national peatland area and peatland type-land use strata of Irish peatlands. They revealed that national peatland SOC is nearly twice as large as previously calculated. Mixed-model analysis of main stock determinants revealed major influence of peat depth for quantification of stocks. It confirmed that land use exerts a strong influence on bulk density and SOC, whereas peat depth was found to be strongly associated with land use category.

The presented approach allowed quantification of SOC and N stocks for larger areas based on clustered soil data. It provided a methodology for identifying the best performing model to be implemented in stock assessments, thereby avoiding under- or over-parameterization. The study fills a gap in peat SOC quantification in ROI by updating existing uncertain estimates for peat SOC stock, and by providing the first estimates for national ombrotrophic peat N stock, based on measured covariates.

How to cite: Walz, K., Renou-Wilson, F., Wilson, D., and Byrne, K. A.: Estimation of soil organic carbon and nitrogen stocks in Irish peatlands using a predictive modeling approach, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12599, https://doi.org/10.5194/egusphere-egu22-12599, 2022.

Reza Khalidy et al.

Among the several methods that have been proposed for mitigating carbon concentration in the atmosphere, enhanced rock weathering is regarded as a low-cost, low-energy and readily scalable approach that can store atmospheric CO2 for up to thousands of years through converting alkaline earth metals into stable carbonates. Application of silicate-rich minerals (e.g., wollastonite, basalt and olivine) has been found effective for capturing atmospheric carbon in different terrestrial mediums, including agricultural and urban soils.

In Ontario, Canada, we have been performing long-term research on pedogenic carbonate formation in agricultural soils amended with crushed wollastonite/dolomite rock mined in Ontario. The mineral has been applied to the topsoil of a number of experimental and farming fields, and shallow soil samples are periodically collected at different depths (including 0-15 cm, 15-30 cm, 30-60 cm, and 60-100 cm profiles) from these plots in order to estimate the rate and amount sequestrated carbon, and its migration across soil/sub-soil horizons over several years.

These experiments are part of our effort to develop analytical and modeling toolboxes for verifying soil inorganic carbon sequestration, in view of qualifying this practice for carbon credits. Such toolboxes can become valuable for private and governmental entities in contributing to meet emissions reduction goals, and in encouraging the adoption of ERW as a reliable and verifiable negative emissions technology. This presentation will present the status of the field trials and toolbox development, and our latest findings and research directions.

How to cite: Khalidy, R., Chiang, Y. W., and Santos, R. M.: Long-term field studies in Canada on monitoring pedogenic carbonate formation in agricultural soils via enhanced weathering of wollastonite: status and latest findings, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13056, https://doi.org/10.5194/egusphere-egu22-13056, 2022.

Discussion: Q&A