This session focuses on the measurement and modeling of soil properties and processes across landscapes, from the pore scale to the field or watershed scale. Organized in collaboration with the International Soil Modeling Consortium (ISMC), the session invites contributions that:
• Measure soil physical and chemical properties in the lab, field, or watershed using tools such as micro-scale imaging, in-situ soil sensors, drones, geophysical methods, radars, and remote sensing platforms.
• Model soil processes using analytical, empirical, statistical, or numerical approaches that link processes across scales, including upscaling and downscaling strategies to address heterogeneity in infiltration, evaporation, salinity dynamics, gas transport, and subsurface mass and energy fluxes.
• Investigate spatiotemporal changes in vadose zone properties at different scales through measurement or modeling campaigns, focusing on natural variability or human-driven changes such as climate variability, sea level rise and salinity intrusion, droughts, freeze-thaw cycles, heavy agricultural machinery impacts, and land management practices in forests, agricultural fields, wetlands, coastal zones, grasslands, deserts, urban soils, and mountainous regions.
Numerous reviews and meta-analyses have examined the vast body of literature evaluating the impact of the different agricultural soil preparation or of the various steps of cultural itinerary on plant growth, water regulation, carbon storage, etc… in short, on soil functions and services, which inherently depends on the soil processes occurring at the pore scale.
For example, the largest pores in the soil (macropores) significantly contribute in regulating the soil water cycle, as they improve infiltration capacity and drainage rates. There is however limited knowledge about the interactions between initial and boundary conditions with the topology and geometry of macropore networks in natural soils, and their influence on water flow. More long-term monitoring data, and dynamic experimentations, are needed to evaluate and model the impact of agricultural management practices on the soil resilience to maintain its functions.
One method to quantify the arrangement and the size distribution of the soil macropore network is X-ray computed tomography (X-ray CT), which is now routinely used world-wide. Images acquisition, pre- and post-processing, and pore structure quantification protocols are increasingly refined and tending towards standardization, thereby contributing to shared and comparable knowledge.
We initiated a research project aiming at monitoring the soil macropore network in agricultural soil and evaluate its response to different management practices (tillage recovery and multispecies cover cropping) using X-ray CT. We are developing a sampling device to extract soil samples (100 cm³) for analysis with X-ray µCT at time zero, after which the samples will be reinserted and embedded into the field for a six-months period before being extracted again. This process will be repeated at least four times.
We hypothesize that tillage, occurring above the sample, where it creates a connected isotropic soil pore structure with a low spatial extent, will modify the living and biochemical equilibrium of the soil and therefore modify the macropore network inside the sampling cylinder, located below the plough pan. On the opposite, we estimate that resistant macropore would remain when no tillage is applied, with an increased resistance under a covered soil. We also hypothesize that persistent macropore network is preferentially used by the main plant roots, as the macropores network created by roots is also the primary contributors of the network connectivity.
The experimental set up will be installed in the field in February 2026 for a short-term trial involving monthly sample extractions in order to assess the feasibility and accuracy of the method. The study per se will be conducted afterwards. We will present the encountered challenges with this initial trial as well as the first quantifications of temporal changes of the soil macropore network with time.
Sarah Smet, as a post-doctoral research fellow, acknowledges the support of the National Fund for Scientific Research (Brussels, Belgium).
How to cite: Smet, S.: Challenges in monitoring the undisturbed top soil pore scale structure of an agricultural field, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17900, https://doi.org/10.5194/egusphere-egu26-17900, 2026.
Soil evaporation is an essential component of the hydrological cycle. Within soil science, the fundamental mechanisms involved in soil evaporation are well-documented. However, within the realm of land surface modelling, the coarse spatial and temporal scale, as well as the computational limitations result in a simplified representation of this highly non-linear process.
Here, we evaluated the current representation of soil evaporation within the RMI evapotranspiration (ET) and surface turbulent fluxes (STF) model applied in the frame of the EUMETSAT Satellite Applications Facility (LSA) on support to Land Surface Analysis (SAF) (http://lsa-saf.eumetsat.int/). This model is used to produce remote-sensing based estimates of the fluxes, using Meteosat Second Generation (MSG) observations. With 30 minutes interval, estimates of these fluxes are provided in near real time, resulting in a data record that spans over 20 years.
We highlighted the discrepancies between the simplified representation of soil evaporation and the soil physical solution. To achieve this, synthetic experiments were performed using Hydrus as a reference for comparison with the LSA SAF ET-STF model. Additionally, a comparison was made with formulations in other land surface models (Surfex, ECLand & GLEAM), the resulting texture-dependent bias was demonstrated and impact of sub-grid heterogeneity was shown. Finally, an updated formulation was tested in large-scale ET simulations and evaluated using in situ observations.
Though widely recognised as one of the fundamental processes in the hydrological cycle, the perspective on soil evaporation is very different in soil physics compared to land surface modelling. Here, we attempted to harmonize both approaches in a pragmatic manner.
How to cite: De Pue, J., Barrios, J. M., Moutier, W., and Gellens-Meulenberghs, F.: Contrasting perspectives on soil evaporation in soil science and land surface modelling, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19707, https://doi.org/10.5194/egusphere-egu26-19707, 2026.
Evaporation of soil water is often characterised by water losses over time for a defined soil volume where soils are assumed to be homogeneous in texture and structure. In this study, we hypothesised that evaporation depends not only on climatic conditions, soil texture, and soil hydraulic properties but also on the soils’ macro-structure. Specifically, that the different distribution of air-filled macropores, stones, and the connectivity of soil matrix will affect bare soil evaporation and herewith the transition from stage 1 to stage 2 evaporation. In a climate constant room, we measured evaporation characteristics of undisturbed soil cores taken under various land uses and soil textures (clay and sandy loam) and compared the evaporation rates to columns with sieved soil repacked to the same bulk density. Tensiometers installed in two different depth provided information about the hydraulic gradient along the columns, while weight measurements continuously recorded the mass loss. Soil structure of undisturbed columns was determined by X-ray computed tomography (X-ray µCT) at a voxel size of 50 µm. In addition, we evaluated the effect of macro-structure on bare soil evaporation for unsaturated condition, i.e. visible porosity was air-filled, by 3D image-based simulations using HYDRUS 3D. The lab study showed that the well-sorted repacked samples lost significantly more water as the undisturbed samples. The differences cannot be explained by the total porosity and thus the total water reservoir. When using the time, the hydraulic gradient along the undisturbed columns was exponentially increasing, it was shown that the well-connected macropore volume could explain most of the evaporation characteristics. In addition, the presence of denser soil clods significantly shortened the time to build up the gradient. Neither stone nor particulate organic matter content had a significant effect on evaporation characteristics. The 3D image-based simulation indicated that air-filled macropores act as barriers for upward water flow and that the loss of water was limited by the connectivity of the soil matrix. It can be concluded that not only soil texture effects bare soil evaporation but also the soil macro-structure.
How to cite: Leuther, F., Nielsen, M., and Diamantopoulos, E.: The effect of soil macro-structure on bare soil evaporation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7438, https://doi.org/10.5194/egusphere-egu26-7438, 2026.
Desiccation cracking significantly impacts the engineering properties of soils, influencing fluid infiltration and structural stability. A key phenomenon in desiccation cracking is the size effect, where soil dimensions, including thickness and radius, alter cracking behavior. However, the size effect remains poorly understood, particularly in linking laboratory-scale findings to field conditions. Existing studies are often limited to small laboratory samples, leading to discrepancies in crack behavior across scales and a lack of standardized guidelines for determining suitable sample sizes in laboratory tests. This study investigates the size effect on desiccation cracking in clayey soils and identifies suitable laboratory sample sizes to represent field-scale cracking patterns. Desiccation tests were performed on soil samples with varying radii (25-100 mm) and thicknesses (5-18 mm). Cracking behavior during drying and equilibrium-state crack patterns were analyzed. A size parameter (λ), defined as the ratio of sample radius to thickness, was introduced to characterize the soil's volumetric size. Results reveal three distinct stages of the size effect: (i) the crack-free stage (λ <λc), with no visible cracks; (ii) the size-dependent stage (λc <λ <λt), where cracking behavior changes significantly; and (iii) the size-insensitive stage (λ >λt), where crack parameters stabilize. Two critical size parameters, the critical cracking size (λc ≈4.0) and the transition size (λt ≈9.0), were identified. The proposed size thresholds (λc and λt) were found to be applicable across different clayey soils, suggesting the general relevance of the framework for scaling desiccation cracking behavior in diverse geotechnical contexts. These findings enhance the understanding of size effects and provide a framework for optimizing laboratory tests to better reflect field conditions.
How to cite: Cai, Z., Cheng, Q., Tang, C.-S., Ji, X.-L., Xu, J.-J., Gu, Y.-D., and Shi, B.: Size effects of desiccation cracking behavior in clayey soil, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2306, https://doi.org/10.5194/egusphere-egu26-2306, 2026.
Soil moisture is a key variable impacting land–atmosphere interactions, hydrological extremes, ecosystem processes, and agricultural productivity among others. Reliable in situ observations are essential for understanding soil moisture dynamics and for evaluating satellite-based products and land surface models. However, ground-based soil moisture measurements are often scattered across independent networks and remain difficult to access in a harmonized form. The International Soil Moisture Network (ISMN) was established to overcome these limitations by providing a global, freely-accessible repository of quality-controlled in situ soil moisture observations. Its mission is to support Earth system science, remote sensing validation, and model development through standardized and traceable soil moisture data.
The ISMN collects soil moisture time series from a wide range of regional, national, and international monitoring networks. Contributing datasets are harmonized in terms of format, metadata, and temporal resolution and undergo a consistent quality control procedure. The database includes multi-depth measurements across diverse climates, land cover types, and soil conditions, complemented by ancillary site information. Data are distributed through a dedicated web interface (https://ismn.earth), enabling efficient data discovery and use for large-scale and local studies.
Ongoing efforts are focusing on expanding the database by incorporating additional stations and data providers from institutional or governmental sources, as well as enhancing data quality and consistency to support more robust long-term analyses. Further resources are directed towards fortifying the operational system and improve usability to better serve our users. Beyond research applications, the ISMN increasingly contributes to the data-to-value chain of international initiatives that are led by the World Meteorological Organization (WMO), the Food and Agriculture Organization (FAO), and the Global Climate Observing System (GCOS). One example is the contribution of ISMN data to WMO’s annual State of the Global Water Resources report, supporting global assessments of hydrological conditions.
How to cite: Zink, M., Olarinoye, T., Böhmer, F., Kramer, K., and Korres, W.: The International Soil Moisture Network (ISMN): A data service providing free access to in situ observations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16443, https://doi.org/10.5194/egusphere-egu26-16443, 2026.
Soil is a complex medium that supports numerous biological and chemical processes across multiple phases. The transformation of inorganic and organic compounds can lead to the accumulation of harmful substances in soil and the emission of reactive gases that affect air quality and climate. However, quantitative measurements remain limited by the lack of methods for in situ monitoring of multiphase processes and by approaches restricted to one or a few compounds at a time, measured either in the liquid or the gas phase. Thus, gaps persist in quantifying and monitoring transformation processes occurring at the gas-liquid interface.
Here, we describe a newly developed method to continuously measure gas fluxes and solute concentrations in soil by coupling a dynamic gas flux chamber (DC) with an open-flow microperfusion (OFM) technique, hereafter termed OFM-DC. The latter OFM method had previously been applied in medicinal research for drug development, and we have optimized it for the utilization in soil. OFM enables the continuous sampling and concentration measurement of soil solutes (e.g., microbial metabolites) in both laboratory and field settings, whereas DC quantifies soil trace-gas emissions (e.g., CO2, NOx, and HONO) over time.
We will present first experiments using the novel setup with synthetic soil systems that have characterized microbial activity and chemical properties. Our case studies on in situ measurements of microbial nitrogen (N) processes and reactive N gas (NO, HONO) emissions reveal the effectiveness of our methods for investigating multiphase soil transformation mechanisms under dynamic soil water conditions.
The OFM–DC measurement setup demonstrates its potential for long-term field monitoring of soil–air quality and the related impacts on planetary health. The obtained data can support improved soil management, which in turn can minimize soil degradation and trace-gas emissions.
How to cite: Melo Silva, L., Schwingenschuh, S., Kim, M., Weber, J., Holeček, C., Birngruber, T., Weber, B., and Maier, S.: Development of an in situ monitoring system for tracking solutes and gas emissions in soil, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14368, https://doi.org/10.5194/egusphere-egu26-14368, 2026.
Mediterranean grasslands operate near the edge of water limitation and are strongly driven by short, discrete rainfall events. Yet, we still know little about how the event-scale dynamics of soil moisture (SWC), soil temperature (ST) and soil respiration (reorganize between wet and dry years. Here we use multifractal detrended fluctuation analysis (MFDFA) on time series in El Escorial (central Spain) to characterise post-rain dynamics in two contrasting years: a relatively wet year (2022) and a dry year (2024). We focus on April (spring) and September (), and six series and interactions of the soil–plant–atmosphere system: SWC, ST, CO₂ and the pairs SWC–ST, SWC–CO₂, ST–CO₂. For each post-rain window (several days after individual events) we quantify for these six series, and compare their behaviour across seasons and years.
In April 2022, Δα is moderate and H2 shows a stable, moisture-dominated backbone: SWC–SWC and SWC–ST are highly persistent, while CO₂–CO₂ and ST–CO₂ are often antipersistent while still moderately multifractal, indicating that CO₂ acts mainly as a reactive signal to water and temperature. In April 2024, Δα increases markedly for CO₂–CO₂ and SWC–CO₂, and their H2 shifts towards stronger persistence, while ST–CO₂ becomes more antipersistent. This points to a reorganisation whereby, under early-season water stress, carbon–moisture couplings become the main carriers of complexity and memory, and ST becomes a more reactive pathway. In September 2022, multifractality remains moderate but a strongly negative asymmetry in SWC–SWC and SWC–CO₂ reveals sharp rewetting and respiration pulses driven by soil moisture. In September 2024, Δα becomes very high for SWC–SWC, SWC–ST and CO₂–CO₂, with H2 ≈ 0.9–1.0 for SWC–SWC, SWC–ST and CO₂–CO₂, while asymmetry shifts: extremes move from moisture-dominated (negative in SWC–CO₂) to carbon-dominated (positive in CO₂–CO₂) and ST–CO₂ becomes strongly antipersistent.
In conclusion, these results show that using SWC, ST and and their interactions it is possible to identify distinct post-rain “modes” of ecosystem functioning: (1) a wet-year regime with a persistent SWC–ST backbone and moisture-driven pulses, and (2) a dry-year regime where long-range memory strengthens in SWC–ST–CO₂ but extremes and intermittency shift into the carbon subsystem, indicating loss of hydrological buffering and increased carbon–thermal stress after rainfall events. Such event-scale indicators could be used to inform adaptive grassland and land management strategies in Mediterranean regions, by identifying when ecosystems are approaching critical thresholds of water and carbon stress.
Acknowledgement: This paper is part of the project Clasificación de Pastizales Mediante Métodos Supervisados—SANTO, from Universidad Politécnica de Madrid (project number: RP220220C024). And funded by the European Union. Views and opinions expressed are however those of the author(s) and do not necesarily reflect those of the European Union or European Research Executive Agency (REA). Neither the European Union nor the granting authority can be held responsible for them.
How to cite: Sanz, E., Cicuendez, V., Inclán, R. M., Yagüe, C., and Tarquis, A. M.: Multifractal fingerprints of rain events on soil moisture and respiration in a Mediterranean grassland, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14166, https://doi.org/10.5194/egusphere-egu26-14166, 2026.
Soil greenhouse gas (GHG) emissions in agricultural, forestry, and other land uses are driven by coupled biological and physical processes. To monitor these fluxes, automatic chamber systems are now widely used as point-scale measurement techniques. Their high-frequency records provide richer observational coverage across meteorological and hydrogeological conditions, thereby improving the accuracy of annual soil carbon budgets.
Despite advances in monitoring, long-term soil carbon models usually focus solely on simulating soil carbon turnover and decomposition, omitting mechanisms of soil gas transport. Although this simplification may be reasonable in the topsoil, sharp changes in soil saturation or other meteorological factors are not necessarily captured, which can lead to underestimating short-term emissions and biasing annual GHG budgets.
We investigated this issue in a pilot site in the agricultural region (Seeland region, Switzerland) where the water table depth was controlled. We simulated a short flooding event and continuously monitored soil gas flux at high frequency. And our results showed a dampening in CO2 soil gas flux for the flooded plot compared to our control plot, which persisted after it was drained. While this decrease in CO2 flux can be partly attributed to a reduction in aerobic microbial activity, the timescale to recovery to background CO2 fluxes can be attributed to other mechanisms, including advection-diffusion gas transport in the unsaturated zone.
To interpret these dynamics, we employed a 1-D model to assess the role of advection-diffusion, including pressure-driven gas transport, during short-term events. Our model couples water, heat, and gas transport with microbially driven CO2 production. We conducted a sensitivity analysis evaluating different soil conditions and event intensities.
Finally, the integration between high-frequency soil gas flux monitoring systems and gas transport in the unsaturated zone helps deconvolute the soil gas flux signal, while improving the accuracy of the soil GHG budget. This will enhance the process understanding, which can support agricultural management strategies to minimize GHG emissions.
How to cite: Asato Kobayashi, A. N., Widmer, N., Roques, C., Hunkeler, D., ThomasArrigo, L., and Brunner, P.: Resolving Event-Driven Soil Gas Fluxes by Coupling High-Frequency Chamber Measurements with Advection–Diffusion Modeling, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19852, https://doi.org/10.5194/egusphere-egu26-19852, 2026.
The accelerated urbanization of the Chinese Loess Plateau has promoted the wide application of engineering explosion on the rapid excavation in loess regions. However, blasting in loess typically causes the various degrees of damage and failure to the remaining soil mass, compromising the bearing capacity and stability of the surrounding loess. Therefore, understanding the damage characteristics and microstructure changes of loess under explosion loading is essential for the construction of explosion projects in loess regions. In this study, the in-situ explosion experiment, dynamic triaxial tests, and micro-computed tomography (μ-CT) technology were employed to reveal the development characteristics of the blasting cavity, explore the dynamic properties of loess following the explosion, and visualize and quantitatively analyze the variation regulations of the loess microstructure. The results indicated that the shape of the blasting cavity was approximated as an ellipsoid. Explosion caused the breakage and rearrangement of particles and aggregates, significantly increasing the compaction of the loess mass, which promoted the evolution of loess dynamics properties towards high dynamic shear modulus and low dynamic damping ratio. In addition, the explosion loading significantly changed the size, number, morphology, and orientation of the loess pores, thereby causing a degradation in the pore network structure, and reducing its connectivity. Based on the spatial differentiation characteristics of the loess microstructure, the explosion zone outside the blasting chamber was divided into broken, plastic, and elastic zone. These findings provide valuable insights into the damage mechanism of loess under blasting loading.
How to cite: Tang, D., Deng, L., Wang, T., and Zhang, W.: Damage mechanism and spatial heterogeneity of loess subjected to explosion loading, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20805, https://doi.org/10.5194/egusphere-egu26-20805, 2026.
Biochar amendment is widely promoted as a means to sequester carbon while improving soil physical properties. Its hydraulic effects depend strongly on particle size and application rate. Available studies mainly focus on enhanced water retention in sandy soils. Studies that include fine-textured soils and quantify effects on unsaturated hydraulic conductivity remain limited, hampering the development of reliable management strategies. Here, we present the effects of biochar addition on the soil hydraulic properties (SHP) of two agricultural topsoils with contrasting textures. Water retention and hydraulic conductivity of a loam and a loamy sand were measured after amendment with wood-derived biochar of three particle sizes (<0.5, <2, and <10 mm) applied at three dosages (1, 2 and 4 wt.%). All samples were packed under identical force and characterized over the full moisture range using the simplified evaporation method, complemented by saturated conductivity measurements and dew-point measurements of dry-range water retention. A comprehensive soil hydraulic model incorporating adsorption and film flow was fitted to all data, enabling systematic analysis of how biochar size and amount affect hydraulic behavior. Relative to the controls, all biochar treatments increased porosity and saturated water content. Saturated hydraulic conductivity increased by up to 200% for the loam but decreased for the sand. In the loam, biochar application improved air capacity by up to 6 vol.% but had no effect on plant-available water. In contrast, biochar quantity and particle size had no effect on the air capacity of the sand, but increased its available water content by up to 3 vol.%. Higher biochar application rates were strongly associated with lower air-entry values, reduced bulk density, and a broader pore-size distribution. This indicates a shift toward smaller pores in the loamy sand and larger pores in the loam. Smaller biochar particles slightly increased unsaturated hydraulic conductivity between 100 and 300 cm suction for both soils, but reduced water retention in the sand at suctions greater than 100 cm compared to coarser biochar. Overall, our findings demonstrate a substantial influence of biochar on soil hydraulic conductivity and water retention, with effects being stronger in coarse-textured soils and more sensitive to application rate than to particle size.
How to cite: Bosse, J., Sut-Lohmann, M., Durner, W., and Iden, S. C.: Biochar effects on soil hydraulic properties: high-resolution analysis for contrasting soil textures, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21721, https://doi.org/10.5194/egusphere-egu26-21721, 2026.
Simulation of unsaturated water movement in porous media has conventionally been based on the Richards equation (RE), coupled with hydraulic conductivity functions that account solely for capillary-driven liquid flow. This approach, however, overlooks the presence of thin water films adsorbed on solid surfaces, which may contribute appreciably to transport processes under moderately dry to dry conditions. Recent advances, particularly the Peters–Durner–Iden (PDI) framework, enable a physically consistent representation of film flow and isothermal vapor diffusion within formulations of unsaturated hydraulic conductivity.
In this work, we introduce the Virtual Soil Simulator, a finite-volume, OpenFOAM-based implementation of the RE augmented with the PDI model to explicitly represent capillary, film, and vapor transport processes. Model performance was assessed using a suite of benchmark tests with analytical or well-established numerical reference solutions, including one-dimensional infiltration, infiltration under steep hydraulic gradients, and two-dimensional nonlinear infiltration scenarios. The results demonstrate high numerical accuracy and robust mass conservation.
The applicability of the model is further demonstrated through two case studies. In the first, inverse simulation of a 12-day soil core drying experiment showed that the classical RE formulation reproduced measurements only during the early, wet stage, whereas the PDI-enhanced model remained consistent with observations over the entire drying period and accurately represented regimes dominated by film and vapor flow. In the second case, a synthetic desaturation analysis conducted across 467 soil types indicated that film flow markedly accelerates drainage, with significant effects persisting even at comparatively high pressure heads (−10 m). These findings indicate that neglecting film flow leads to systematic underestimation of unsaturated hydraulic conductivity and distorted predictions of drying and drainage behavior. Moreover, simulations at very low pressure heads emphasize that reliable representation of transport processes requires the combined consideration of both film and vapor fluxes.
Acknowledgments
This research was founded by the National Science Centre within contract 2021/43/B/ST10/03143.
How to cite: Lamorski, K., Kozyra, M., and Sławiński, C.: Virtual Soil Simulator - unsaturated pore media water transport model including film flow and isothermal vapor transport phenomena, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18983, https://doi.org/10.5194/egusphere-egu26-18983, 2026.
Climate-induced droughts and increasingly erratic precipitation patterns are stressing water resources and underscore the need for a better understanding of soil water flow and storage. Soil hydraulic properties, in particular the water retention curve and the hydraulic conductivity curve, are fundamental inputs for predicting soil water dynamics and for simulating variably-saturated flow with the Richards equation. The simplified evaporation method is a common laboratory technique for estimating SHP. It relies on linearization assumptions that introduce only negligible errors when sample heights are small. While a handful of theoretical studies have addressed how sample height affects SHP estimates, a systematic experimental assessment of this scale-dependence is still lacking.
We performed evaporation experiments on packed soil columns (5, 10 and 15 cm high) using both a sandy and a silty soil. Throughout each run, we recorded column mass to track water content and evaporation rate, and we measured matric potential with mini-tensiometers. Applying the simplified evaporation method, we derived point data for the water retention curve and hydraulic conductivity curve. A flexible model which accounts for capillary and non-capillary storage and flow was fitted to the data using the program SHYPFIT. Inverse simulations with Hydrus-1D were then applied to assess the influence of sample height without relying on the assumptions of the simplified evaporation method. This allowed to discriminate between an actual scale-dependence of soil hydraulic properties and differences which are caused by the assumptions of the simplified evaporation method.
Our findings reveal that column height has a minimal impact on the water retention curve, with a tendency of a slight broadening of the pore size distribution and a modest increase in residual water content. The effect on hydraulic conductivity was even less pronounced. The results of inverse simulations substantially attenuate these height-related discrepancies in soil hydraulic properties, leaving only marginal differences.
How to cite: Khatua, P., Bosse, J., Das, B. S., Durner, W., and Iden, S. C.: Scale Dependence of Soil Hydraulic Properties Obtained from Evaporation Experiments: Effect of Sample Height, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13322, https://doi.org/10.5194/egusphere-egu26-13322, 2026.
Non-rainfall water inputs (NWRIs; i.e., dew, fog, and water vapor adsorption (WVA)) are significant sources of water in arid environments. Amongst all NRWIs, WVA is likely the most common, yet it is the least studied. There is increasing evidence that water vapor adsorption occurs in many arid and hyper-arid regions, that together occupy 26% of the earth’s terrestrial surface. Quantifying WVA is therefore essential to fully understand the water cycle in these regions. While some studies quantified WVA as a function of the surface properties, they were either laboratory trials or limited to a specific location. No studies, to date, have presented a general model to quantify WVA. Given the complexity of the process, we propose an initial step towards bridging this knowledge gap, with the introduction of a new “reference water vapor adsorption” (Ao). Ao is the adsorption of water vapor from the atmosphere to a reference surface, conceptually similar to the “reference evapotranspiration” (ETo) that quantifies the evapotranspiration rate from a reference surface. We propose to calculate Ao as Ao = raCp(ea-es)/lgra where ρa is the density of air, Cp is the specific heat capacity of air, ea and es are the water vapor pressure in the air and in the air-filled pores, respectively, γ is the psychrometric constant, and ra is the aero dynamic resistance. Assuming a completely dry surface (similarly to assuming well-watered crop to calculate ETo), es is set to zero. To test this new concept, we conducted measurements in the Negev desert, Israel, from July to October 2025. Ao was calculated from continuous measurements of temperature and relative humidity at 2m height, and wind speed at two heights (3 and 0.8 m). In parallel, Ao was directly measured every two hours during multiple 24-h campaigns by exposing dry silica gel to the atmosphere. The calculated Ao followed closely the trend of measured Ao, encouraging further development of this index, and potentially allowing mapping of reference adsorption based on simple meteorological measurements.
How to cite: Hagos, M. W., kool (RIP), D., and Agam, N.: Modeling reference water vapor adsorption in desert soils, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2422, https://doi.org/10.5194/egusphere-egu26-2422, 2026.
Soil salinization dynamics are driven by complex interactions among climatic conditions, hydrological processes, and anthropogenic activities. Due to this complexity, traditional single global models often struggle to capture spatial heterogeneity, leading to high prediction uncertainty and limited robustness at the pixel scale.
To address these challenges, this study proposes a multi-source data-driven framework based on environmental similarity matching to enhance prediction adaptability in heterogeneous environments. We compiled a dataset of approximately 35,000 topsoil samples from arid and semi-arid regions and constructed a multidimensional covariate system grounded in soil-forming factor theory. The framework comprises three components: (1) heterogeneity-based stratification, partitioning samples by climate and land use; (2) model library construction, developing candidate machine learning ensembles within each stratum via repeated cross-validation; and (3) similarity-based prediction, which employs Gower distance to quantify environmental similarity between target locations and training samples to select the optimal model.
Evaluations indicate that the Random Forest algorithm exhibits robust stability across stratified regions. Compared to single models, the environment similarity–constrained selection strategy significantly improved performance in heterogeneous regions; notably, the coefficient of determination (R2) in arid cropland areas increased from 0.748 to 0.807. Feature contribution analysis supports the necessity of stratified modeling, revealing that soil salinity in arid regions is primarily driven by vegetation variables and geographic, whereas remote sensing indices and soil pH dominate in semi-humid regions. The methodological framework developed in this study provides a new approach for high-precision soil salinity mapping.
KEYWORDS: Soil salinization; Environmental similarity; Heterogeneous environments; Machine learning.
How to cite: She, X., Frankl, A., and Luo, G.: Soil salinization prediction for heterogeneous environments: an environmental similarity–based modeling framework, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16578, https://doi.org/10.5194/egusphere-egu26-16578, 2026.
Efficient water management is a critical challenge in agriculture, particularly in regions such as Navarra, Spain, where irrigation accounts for up to 87% of total freshwater consumption. Capacitive soil moisture probes are widely adopted in precision agriculture; however, a notable inconsistency persists between the sensing ranges claimed by manufacturers (typically 5–15 cm) and those reported in the scientific literature (generally <6 cm). This discrepancy arises largely from the absence of standardized criteria to define the effective sensing volume of these sensors.
This study presents a replicable empirical methodology to characterize the volume of influence of four commercially available capacitive probes: AquaCheck, EnviroPro, Gerbil, and Sentek. Controlled laboratory experiments were conducted under air and water conditions, using 0.2 mm paper layers to incrementally simulate increasing distances from the moisture source. Sensor outputs were normalized to enable direct comparison across heterogeneous measurement units, including Volumetric Water Content (VWC%) and Scaled Frequency Units (SFU%).
All probes exhibited a logarithmic decrease in signal intensity with increasing distance from the water source. By modeling the sensing domain as a cylindrical volume with a 10 cm height and defining its effective extent at the 99.5th percentile of cumulative signal response, substantial differences among probes were observed. The estimated sensing volumes ranked as follows: Gerbil (710.59 cm³), EnviroPro, AquaCheck, and Sentek (236.71 cm³).
The results demonstrate that sensing volumes vary considerably among manufacturers and are strongly dependent on the percentile threshold used to define the effective volume of influence. These findings confirm the lack of uniformity in probe sensing behavior and underscore the need for technical standardization. Although derived from controlled laboratory conditions and therefore comparative in nature, the results provide critical insight for interpreting soil moisture measurements and offer a more reliable technical basis for informed decision-making in irrigation management.
How to cite: Bellosta-Diest, A., Echeverría, M., and Campo-Bescós, M. Á.: Evaluation of the volume of influence of four tubular capacitive probes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10739, https://doi.org/10.5194/egusphere-egu26-10739, 2026.
Feedback loops between plants and soil shape and stabilize plant communities. In savanna-like landscapes, which are common in arid and semi-arid regions, trees and grasses coexist at close spatial scales. These different growth forms can influence soil formation and properties within just a few meters of each other.
In this study, we investigate soil hydraulic properties in an extensively managed Holm oak savanna-like ecosystem (Dehesa) in central Spain by comparing soils beneath trees and in adjacent open grass areas. We analyze saturated hydraulic conductivity, soil water characteristic curves, derived parameters such as field capacity and permanent wilting point, and associated soil texture and organic carbon content. In addition, we analyze a 10-year time series of in situ soil water content and micrometeorological variables within microhabitats to determine whether differences in the static properties also translate into water availability differences within the ecosystem.
On average, the topsoil below trees contained 6.2% more pore space within the range of plant-available water than the topsoil below open grass areas. This was associated with, and likely driven by, higher levels of organic carbon beneath the trees. There was no significant difference in clay content between the two microhabitats.
However, field observations of soil moisture showed high heterogeneity, with the soil beneath the trees not remaining significantly wetter than in the open area despite the higher storage capacity and reduced radiative energy input due to shading. Data from two eddy covariance towers showed that, unlike grasses, trees sustain transpiration throughout the year, suggesting enhanced water uptake near the trunk.
Together, these results illustrate how different vegetation types affect the same soil just a few metres apart. They also show that, although trees increase soil water storage capacity, it remains unclear whether this positive effect is offset by the large amounts of water extracted by trees and higher interception losses, ultimately leading to the soil being similarly dry beneath trees as in the open area during the Mediterranean summer.
How to cite: Wittig, M., Paulus, S. J., Moreno, G., Carrara, A., Nadolski, L., Hildebrandt, A., and Lee, S.-C.: Differences in soil water retention properties and plant available water below trees and grasses in a Mediterranean savanna, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16325, https://doi.org/10.5194/egusphere-egu26-16325, 2026.
Soil salinization is a pervasive problem in arid environments, frequently exacerbated by anthropogenic activities. Remediation commonly involves soil leaching through natural precipitation or controlled, human-made flooding events. Accurate prediction of solute transport during these leaching processes is complex, as it is controlled by soil physical and hydraulic properties, climatic conditions, evaporation rates, and the volume and timing of infiltration. Precise physically-based numerical models are necessary for exact descriptions but demand detailed input regarding soil and environmental parameters.
This study examines a simplified, physically-based alternative: the Surface Evaporation Capacitor (SEC) concept proposed by Or and Lehmann in 2019. Originally developed to predict soil porewater evaporation, the SEC model posits that porewater shallower than the soil capillary length is consumed by surface evaporation, while deeper porewater remains protected from this process.
We adopt the SEC concept to estimate solute dynamics within the vadose zone and predict long-term salt accumulation profiles. By integrating soil capillary length, ambient evaporation, and the depth of natural or artificial wetting, the SEC allows for a simple determination of salt fate, specifically estimating the leaching depth required to prevent salinization in the root zone and near the surface.
We validated the SEC approach by comparing its predictions against detailed field measurements collected in a super-arid region of Israel, alongside results from a detailed physically-based numerical model. Results confirm the Evaporation Capacitor Model's validity as an accurate proxy for estimating annual solute dynamics and salt accumulation in saline soils. While the complex numerical model provides exact temporal descriptions, the simplified SEC model offers an accurate and easily implementable net estimation of salt transport, making it highly valuable for large-scale practical remediation assessment and management.
How to cite: Nachshon, U., Golan, R., and Katzir, R.: Modeling Saline Soil Remediation Using the Surface Evaporation Capacitor Approach., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1349, https://doi.org/10.5194/egusphere-egu26-1349, 2026.
Soil is a critical resource for global food security, yet conventional physical soil analyses, remote sensing and geophysical methods are often labour-intensive and time-consuming. This study explores the potential of ultra-high-frequency (>500 Hz) hammer-source seismology to characterise soil physical properties at the decimetre scale.
Field experiments were conducted within a long-term trial near Harper Adams University (UK) comparing Conservation and Conventional agricultural practices. Two 1.5 m transects were surveyed in each treatment using 16 geophones, with soil samples collected at matching horizontal resolution. P-wave velocity (vp) was estimated in the upper 40 cm of the soil profile and compared with bulk density derived from physical samples.
Results show a strong and statistically significant correlation between vp and bulk density. This relationship is consistent throughout the depth profile, with good agreement between seismic velocity images and interpolated bulk-density measurements from soil cores. The findings demonstrate that ultra-high-frequency seismic methods can reliably resolve small-scale soil structure relevant to agricultural management.
Our results indicate that ultra-high-frequency seismic analysis is a promising and cost-effective approach for estimating soil bulk density. This technique has clear potential to support agronomic and land-management decision making.
How to cite: Tsekhmistrenko, M., Collins, J., Ritsema, J., Jeffery, S., and Nissen-Meyer, T.: Between two Furrows: Soil bulk density from Non-Invasive Seismology, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18251, https://doi.org/10.5194/egusphere-egu26-18251, 2026.
Posters virtual: Thu, 7 May, 14:00–18:00 | vPoster spot 1a
EGU26-1128 | ECS | Posters virtual | VPS15
A Molecular Simulation Study on Sodium-Montmorillonite Clay Soil Stabilization through Calcium-Based StabilizersThu, 07 May, 14:27–14:30 (CEST) vPoster spot 1a
The most prevalent clay mineral found in soil is montmorillonite. Montmorillonite-rich soils also known as expansive soils can pose hazards that bring geotechnical challenges because their swelling or shrinking behaviour arises due to the large water retention capacity of montmorillonite-rich soils. This soil swelling reduces the shear strength of soil and results in differential settlement of foundation, which compromises the structural integrity of the infrastructure. Montmorillonite is made up of multiple-layer structures, and these interlayers contain free cations that enable attachment of water molecules, which cause volumetric expansion of the soil. To prevent swelling, calcium-based stabilizers are often utilized for sodium-montmorillonite (Na-MMT) clay stabilization. These calcium-based stabilizers replace sodium ions with calcium ions with creating a diffuse layer around clay particles that affects the water adsorption capacity of Na-MMT. Therefore, to ensure structural safety and soil stability, it is essential to predict accurate soil properties, which depend on soil-water interactions; a pore-scale study of soil stabilization provides an enhanced understanding of soil-water interactions and water adsorption in the clay, which is responsible for swelling in Na-MMT. This study examines water adsorption and soil-water interactions inside montmorillonite clay pores using the Monte Carlo molecular simulations to quantify the systematic exchange of sodium with calcium cations and their influence on swelling behaviour in montmorillonite. The pore width (multiple of d-spacing) ranges from 10 to 20 Å, and varied pH environment via change in Ca²⁺ cation exchange compositions upto 100% have been simulated under in-situ conditions of temperature range of 288 to 308 K and at a pressure of 1 atm. The ClayFF forcefield was used to modelled Na-MMT clay pore, and the SPCE forcefield was used to modelled the water molecules. The simulated bulk densities of water were validated with literature data at the considered thermodynamic conditions. The Ca²⁺ exchange indicated an influence on the hydration behaviour of Na-MMT and altered the molecular ordering of water inside the pore. The adsorption of water shows dependency on interactions between water and the pore surface, as well as the available pore volume. Furthermore, these simulations analysed the percentage change in cation composition on the surface using local density distribution profiles and pore pressure across the height of the pore. This study aims to provide molecular insights into the performance of calcium-based stabilisers on expansive soils and clay-water interactions, which will help to predict pore pressure, swelling and softening and improved stability of expansive soils.
How to cite: Singh, A., Sengupta, A., and Guha Roy, D.: A Molecular Simulation Study on Sodium-Montmorillonite Clay Soil Stabilization through Calcium-Based Stabilizers, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1128, https://doi.org/10.5194/egusphere-egu26-1128, 2026.
