In managed agricultural and forestry systems, anthropogenic soil compaction remains one of the major soil degradation processes, with long-lasting impacts on soil structure - particularly in deeper horizons where damage is difficult to detect and slow to recover. Increasing machinery size, traffic intensity, and operation under unfavourable moisture conditions further elevate compaction risks. A particular emphasis is placed on characterizing the mechanical properties of the soil and the processes underlying soil structure formation, stabilization, and degradation. This includes interparticle and organic–mineral interactions, pore-water pressure, and matric potential effects on soil deformation, and biological or mechanical drivers of structural change such as root growth, rhizosphere reinforcement, and bioturbation. Integrative studies that combine hydraulic, biological, and mechanical viewpoints are particularly encouraged.
Understanding the processes and feedback that control soil structure and its functional implications is essential for designing climate smart and resilient management strategies. In this session, we invite contributions on the formation and alteration of soil structure and associated soil functions at all spatial and temporal scales. We encourage contributions that integrate complementary measurement techniques (e.g., geophysics, digital image correlation, rheometry, CT/µCT), bridge different spatial scales, propose solutions to mitigate compaction and enhance soil structural resilience. Special focus lies on:
• feedbacks between soil structure dynamics and soil biology,
• impacts of mechanical stress exerted by heavy machinery under land management operations
• mechanical processes shaping pore architecture.
Orals: Tue, 5 May, 08:30–10:15 | Room 0.16
Agricultural tillage and compaction create abrupt hydraulic interfaces in the vadose zone by forming contrasting tilled (loose) and untilled (compacted) soil layers with differing bulk densities. These interfaces influence pore connectivity, hydraulic conductivity, and water redistribution, thereby controlling infiltration and deep percolation in agricultural fields. This study used HYDRUS-2D to evaluate the performance of the single-porosity van Genuchten–Mualem model (VGM) against the dual-porosity Durner model (DM) for simulating water flow across a compacted interface in a two-layer silty loam profile representative of field conditions. Hydraulic parameters were obtained by inverse modeling of laboratory hood–tension disc infiltrometer experiments conducted under varying suction heads with and without intermittent stop-flow periods. Model performance was evaluated for both continuous and intermittent infiltration scenarios. A global Sobol sensitivity analysis was performed to identify the most influential hydraulic parameters across suction regimes. The dual-porosity Durner model markedly outperformed the single-porosity VGM, especially in capturing sharp wetting front advancement, preferential flow cessation during redistribution, and water partitioning between macropore and matrix domains during stop-flow periods. The VGM tended to overly smooth the hydraulic contrast at the interface, resulting in unrealistic infiltration behavior. Sobol analysis revealed that compaction shifts parameter sensitivity: at lower suction, macropore parameters (α, n) dominate due to reduced macroporosity, whereas at higher suctions, matrix-region parameters (α₁, n₁, w₂) in the DM become more influential as flow transitions to matrix-dominated conditions. These results emphasize the critical role of density-driven hydraulic interfaces in controlling infiltration and redistribution and strongly support the use of dual-porosity models such as the Durner for predicting water flow prediction in heterogeneous, compaction-affected agricultural soils. The results have direct implications for improved modeling of water dynamics and agrochemical movement under realistic field management practices.
How to cite: Yadav, S. and Swami, D.: Hydraulic Interfaces from Soil Compaction: Evidence from Experiments and Numerical Simulation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1179, https://doi.org/10.5194/egusphere-egu26-1179, 2026.
The adoption of conservation agriculture practices, such as zero-tillage (ZT), is increasingly being promoted to improve soil health and sustainability. However, the impacts of ZT on soil physical properties, root development, and crop productivity remain context-dependent and require further investigation. This study evaluated the effects of conventional tillage (CT) and ZT on soil macroporosity, penetration resistance, root density, and grain yield at two sites: Rothamsted (4 years of ZT, four wheat genotypes) and Sutton Bonington (10 years of ZT, one genotype). Soil cores were analysed using X-ray Computed Tomography (XRCT), revealing reduced macroporosity under ZT compared to CT at 0–10 cm depth, with particularly pronounced decreases from 11% to 3% at Rothamsted and from 19% to 2% at Sutton Bonington in the 0–5 cm layer. ZT also enhanced connected porosity at both sites with prominently more under long-term ZT (10-yr). Additionally, penetration resistance at 0-20 cm depth was 26% greater under ZT at Rothamsted and 109% greater at Sutton Bonington, with significant differences extending down to 20 cm and 45 cm depths at Rothamsted and Sutton Bonington, respectively. Despite these considerable differences in soil physical properties, root density remained largely consistent across both tillage treatments, except for increases in C_egt2_B20 and Rht-B1C genotypes at 40-50 cm depth under ZT, which could be due to an enhanced biopore network observed at this depth. No significant variation in grain yield was observed between CT and ZT treatments for most genotypes, except C_egt2_B20 where ZT decreased yield by 18%. These findings show that under ZT clear differences in soil structure develop, without compromising crop productivity or root development in most genotypes. This study highlights the trade-offs in tillage systems and shows ZT is a sustainable soil management practice that preserves yield potential while enhancing soil structure.
How to cite: Raza, S., Atkinson, B. S., Hossain, I., Shin, H.-C., Cooper, H. V., Sturrock, C. J., Riche, A. B., Hawkesford, M. J., and Mooney, S. J.: Zero tillage impacts on soil physical properties but not on crop yield, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2591, https://doi.org/10.5194/egusphere-egu26-2591, 2026.
Timber harvesting operations significantly impact soil hydrological parameters, particularly when heavy machinery is involved.
We quantified the recovery of skid trails by measuring soil physical properties and surface runoff one (H01) and three (H03) years after trafficking, and on a trail trafficked ca. 21 years prior (H21). Adjacent untrafficked plots served as controls to establish a baseline. The study site is a moderately sloped (18–26%) Stagnic Cambisol in the Flysch zone of the Vienna Woods. Soil properties were measured using undisturbed cores (250 cm³, n=3 per treatment and depth) at 5 and 15 cm depths. Surface runoff was assessed with high-intensity rainfall simulation experiments (100 mm h-1, 50 m² plots).
Bulk density in control plots was low at both depths (5 cm: 0.96±0.07 g cm-3; 15 cm: 1.00±0.12 g cm-3). Trafficking increased bulk density at 15 cm by approximately 25%, with only partial recovery after 20 years, whereas at 5 cm it recovered to control levels (H21: 1.00±0.03 g cm-3). Saturated hydraulic conductivity showed a similar trend, albeit with high variability. Water retention curves indicated a marked loss of macroporosity one and three years after trafficking at both depths. After 20 years, recovery was evident mostly in the topsoil. This produced a porous, recovered surface layer sitting on top a compacted hardpan at 15 cm depth.
Runoff dynamics reflected this stratification: H01 and H03 exhibited infiltration-excess overland flow with final surface runoff coefficients (Ψf) of 0.66 and 0.60 respectively, whereas H21 shifted to saturation-excess overland flow once the top layer was saturated (Ψf = 0.23).
These results demonstrate the long-term effect of subsurface compaction on clayey forest soils, underscoring the need to minimize trafficked area and to confine operations to permanently marked skid trails to safeguard soil functions and associated ecosystem services.
How to cite: Behringer, M., Froemel, M., Katzensteiner, K., Kitzler, B., Kohl, B., Lechner, V., Malli, A., Markart, G., Meißl, G., and Scheidl, C.: Timber harvesting shows persistent effects on soil hydrology and surface runoff 20 years past trafficking, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3722, https://doi.org/10.5194/egusphere-egu26-3722, 2026.
Trends in mechanised agriculture and drought events are leading to soil compaction, a form of degradation that increases soil’s mechanical strength, resulting in deleterious effects on a soil’s ability to provide critical ecosystem services. Despite this, plant roots have been shown to grow in mediums with high mechanical constraints. Hence, understanding roots’ underpinning biomechanical growth processes and limitations could inform on how best to harness roots for regenerating degraded soils and restoring desirable soil structure. We initially assessed this with two modelling frameworks and use limited X-Ray CT data to infer root pressures via Digital Volume Correlation. Our first model simulated direct root tip penetration into surrogate (solid gypsum) and natural soils, modelled as elastoplastic von Mises materials. We included geometric non-linearity through finite strain theory. Simulations used hydromechanical properties of unsaturated soils from literature to better estimate field conditions and compare these trends with surrogate soil material properties. We quantified ease of penetration via average pressure on the root tip face, thus estimating the soil moisture content that acts as a limit for root penetration. Subsequently, we explored the utility of roots using crack propagation to overcome pressure limits under dry and brittle conditions. We varied exerted root pressure and by altering boundary conditions, we modelled root growth in both experimental and field scales. Results showed that roots can overcome their direct penetration limits via crack propagation. However, coupling experimental and model results suggest roots invoke a combination of local softening through exudation and successive crack propagation to extend in mechanically harsh mediums.
How to cite: Wright, C., Ramsdale, E., McKay Fletcher, D., Williams, K., Le Houx, J., and Ruiz, S.: Understanding root biomechanics in high-strength environments- assessing the feasibility of penetration and fracture FE models with SRXCT., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7232, https://doi.org/10.5194/egusphere-egu26-7232, 2026.
Coastal saline agriculture in the Yellow River Delta (YRD, China) is constrained by salt accumulation driven by shallow groundwater–evaporation coupling and by mechanical limitations imposed by soil compaction. Because soil strength and pore connectivity control root penetration, aeration and preferential flow, root–soil–water interactions in the YRD are inherently hydro-mechanical. We ask how depth-dependent compaction reorganizes water–salt dynamics and root system architecture.
We integrate multi-season field experiments, controlled “transparent-soil” microcosms, and coupled modelling. In the field, three compaction levels (non-, light- and heavy-compacted) are crossed with contrasting tillage (mouldboard ploughing, rotary tillage and no-till) and crop types (soybean/maize rotation and winter wheat). Soil water content, electrical conductivity, temperature and matric potential are monitored at multiple depths. Soil mechanical state (penetration resistance and bulk density) and key hydraulic functions (water retention) are measured on undisturbed samples, while root traits are quantified by excavation and image analysis. Microcosms tune substrate stiffness via hydrogel crosslink density to isolate mechanical impedance effects; the datasets are interpreted using flow–transport simulations linking root uptake, water flow and salt movement.
Preliminary results show that heavy compaction can increase short-term near-surface water storage after rainfall but restricts rooting to the upper 0–10 cm, decreases aeration and intensifies salinity stress, causing marked biomass and yield losses. In contrast, moderate compaction combined with conservation practices reshapes preferential flow and capillary return, moderating salt accumulation while maintaining root penetration. Microcosms reveal a mechanical “optimal window” where roots maximize elongation and branching; both insufficient strength (unstable pore network, hypoxia) and excessive strength (high impedance) suppress root exploration.
Overall, we identify a feedback loop in which soil strength controls rooting depth and biopore formation, which in turn reorganizes pore connectivity and preferential flow, ultimately governing salt leaching and capillary re-salinization. The framework supports targeted mechanical management (hardpan alleviation, controlled traffic and structured surface–subsurface layering) for resilient saline agriculture in the YRD.
How to cite: Zhao, Y.: Root-soil-water interaction process and its mechanism in saline agriculture in the Yellow River Delta, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15059, https://doi.org/10.5194/egusphere-egu26-15059, 2026.
Effective stress in partly saturated porous media is a crucial question to understand the mechanical stability and the erodability of soils. In general, two-phase flow in unconsolidated granular media is a common process. It takes place during rain infiltration in soils, in sandcastles, and numerous situations in the critical zone.
The mechanical stability of slopes and materials is expressed by considering stability envelope of the stress tensor supported by the solid material. In one phase flow, this leads to criterias on Terzaghi stress, or effective stress when the contacts between solid elements are not reduced to points.
In two-phase flow, the stress carried by solids is usually expressed using an effective average fluid pressure in the effective stress formulation, following Bishop. We show that this approach does not take the explicit stress carried by the two-dimensional interface between the two fluids into account: the explicit effect of surface tension is missing. This term is called Bachelor stress in the framework of foam mechanics, but is usually not incorporated in two-phase flow in porous media formulation
We evaluate the importance of this effect from a micromechanical perspective, and show how to incorporate it in a generalized large scale effective stress formulation. We show how this formulation can take into account an anisotropic tensor reflecting the stress carried by the fluids and the fluid/fluid interfaces, depending on the anisotropy of the fabrics of these interfaces.
We bridge the gap between microscopic interactions and macroscopic behavior, offering a robust model for evaluating and predicting forces in multi-phase systems. Numerical simulations comparing the standard model with the new framework demonstrate that incorporating surface tension significantly refines slope stability predictions, especially during intense rainfall events.
How to cite: Toussaint, R., Abbasov, R., Fahs, M., Flekkøy, E. G., and Måløy, K. J.: How surface tension in two-phase flow leads to anisotropic effective stress, and affects soil erodability and slope stability , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18263, https://doi.org/10.5194/egusphere-egu26-18263, 2026.
Vegetation restoration can improve soil structural stability and erosion resistance, However, the effects of forest composition on the rheology-based stability of soil microstructure and its relationship with erosion are still unclear. Therefore, this study investigated typical plantation soils on the Loess Plateau to explore differences in soil rheological properties and their stratification under different afforestation models. Our results show that: (1) Afforestation significantly altered soil physicochemical properties. Mixed forests of Robinia pseudoacacia (RP) and Platycladus orientalis (PO) (1:1) notably enhanced the accumulation of organic carbon in the surface layer (0–20 cm). (2) PO plantations promoted the retention of water-stable macro-aggregates (> 0.25 mm). Despite mechanical and water-induced disruption, these soils maintained a higher proportion of macro-aggregates, with significantly greater mean weight diameter and lower aggregate disruption rates (p < 0.05). (3) With increasing strain, soil structure progressively approached its shear strength limit until failure occurred. Mixed forest soils exhibited both a wider linear viscoelastic region (γLVR) and higher integral Z (Iz), suggesting an elastic and tough structure. In contrast, PO soils showed the highest γLVR but the lowest Iz, indicating structural rigidity with weak internal cohesion. (4) Modeled soil erodibility (K) was lowest in mixed forests and highest in PO soils. In fine-textured, low-organic-matter soils, high mean weight diameter may accompany high rigidity and brittleness, resulting in poor erosion resistance. Overall, high aggregate stability does not invariably indicate strong erosion resistance. Through rheological analysis can identify healthy soil structures that combine strength and resilience. This study elucidates the intrinsic relationships among soil rheological properties, aggregate stability, and soil erodibility, providing new insights into the soil conservation functions of forests from a mechanical perspective.
How to cite: Zhou, L., Hu, F., and Peth, S.: The influence of tree species composition on soil microstructure stability and its relation with erosion resistance, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18663, https://doi.org/10.5194/egusphere-egu26-18663, 2026.
Skid trails in forests experience repeated traffic by heavy machinery, leading to pronounced soil compaction. Wheeling is often visible at the soil surface in the form of deep ruts and lateral soil displacement. These structural changes are not restricted to the topsoil but also affect soil water dynamics down to the subsoil. This study aimed to quantify the effects of skid trails on soil physical properties and water dynamics compared to adjacent areas (within the lane and 50 cm outside the wheel track) and unwheeled forest soil.
Three sites in Lower Saxony, Germany, were investigated: two sites in the Solling region (beech and spruce) and one site near Braunschweig (oak). Soil samples were collected at 15, 30, 45, and 60 cm depth in each plot to determine bulk density and soil water retention characteristics using the simplified evaporation method. Simultaneously, soil moisture was monitored at the same depths, and soil water tension was measured at 30 and 60 cm depth from July 2024 to February 2026.
At the Solling sites, skid trails exhibited the highest compaction, with bulk densities reaching up to 1.62 g cm⁻³ in the topsoil and 1.75 g cm⁻³ in the subsoil. Adjacent areas showed moderate compaction (up to 1.46 g cm⁻³), whereas unwheeled soils remained comparatively loose, ranging from 1.17 g cm⁻³ at 15 cm depth to 1.62 g cm⁻³ at 60 cm depth. Macroporosity in wheeled soils was significantly reduced by up to more than one order of magnitude down to the subsoil, while mesopores were only slightly affected. This effect was less pronounced in adjacent areas.
Soil moisture monitoring at the Solling sites showed that skid trails were consistently wetter throughout the year. During winter months, waterlogging occurred, while in summer skid trails remained moist, whereas unwheeled soils experienced pronounced drying. At the Braunschweig site, differences in soil moisture were less pronounced, with only slightly higher water contents in wheeled soils.
The study highlights the strong local effects of skid trails on soil structure and water balance. Soil compaction leads to significant alterations of the pore size distribution, resulting in reduced hydraulic conductivity and increased soil moisture. These changes limit the potential for soil-friendly machine traffic, emphasizing the need for adapted forest management strategies to mitigate soil compaction in skid trails.
How to cite: Rolfes, L. and Kuhwald, M.: Soil compaction and water balance in skid trails: a three-year analysis of German forest sites , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20868, https://doi.org/10.5194/egusphere-egu26-20868, 2026.
The seemingly never-ending increase in the size and hence weight of agricultural machinery induces an urgent need for tools to evaluate the risk of subsoil compaction. The scientific community is fully aware of this as witnessed by a large number of papers addressing soil strength across soil textures, drainage conditions and other drivers of the carrying capacity of soils. The concept of soil precompression is appealing as it implies a threshold level of stress that soils may experience without plastic / permanent deformation. Much effort has been devoted to the quantification of soil precompression stress and to the potential of predicting it from soil properties. The classical procedure in determining the precompression stress from compression tests include a log-transformation of the stress imposed to the soil sample. Mathematically, the log transformation in itself introduces a bend in the strain-stress relation that does not relate to the material properties. For all procedures applied in estimating this bend for soil compression data, the estimated ‘threshold’ in the strain-log(stress) relation is an artefact or at least affected by the mathematical transformation of stress data. Despite this, efforts are still undertaken to analyze how the ‘precompression’ stress deriving from the classical procedure relates to soil properties. In the present study, we analyze data from confined, uniaxial compression tests applied to undisturbed soil cores. Our results show that it was possible to detect a local minimum of compressibility reflecting a true precompression stress. In addition, our study investigated the potential of estimating a local minimum in soil compressibility observed in studies that have measured strain at a limited number of stresses.
How to cite: Lamandé, M., Schjønning, P., Koppelgaard, M., and Arthur, E.: Soil precompression stress assessed from linear scale stress and strain, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21956, https://doi.org/10.5194/egusphere-egu26-21956, 2026.
Rainfall-induced landslides cause millions of pounds in damage to infrastructure in Great Britain (GB) annually and occasionally result in human fatalities. Despite the risks, Great Britain has few policies or guidelines to mitigate landslides, and limited research has characterised their regional incidence. Peat landslides, found mainly in the British Isles and a handful sub-Antarctic islands, have recently gained attention for their destructive impacts and the loss of valuable terrestrial carbon. Given the environmental significance of peat, we examine the current knowledge gaps regarding the mechanical conditions that trigger peat failures and compare these with those governing failures in mineral soils. We start by empirically characterizing landslide incidence in GB considering landslide events recorded in the British Geological Survey (BGS) database. Soil texture, topographic, and antecedent rainfall data were acquired for the considered landslides. Organic landslides had significantly steeper slopes and higher antecedent rainfall sums than mineral landslides and occurred most frequently in late summer and early autumn months. Landslides in loam-textured soils were an order of magnitude more frequent than in other textures, and remained the most frequent after normalisation by soil-texture area, although other groups exhibited comparable area-normalised failure rates. Using a K-means clustering analysis, landslide groups exhibiting similar slope, soil, and rainfall characteristics were identified revealing unique inter-cluster spatial and temporal patterns. Organic landslides in the database could be roughly segregated as those that failed on shallow slopes with low antecedent rainfall in summer months ‘bog flows') and those that failed on steep slopes with varying antecedent rainfall which were interpreted to largely be mineral failures with a peat veneer (‘peaty-debris flows'). The failure mechanism of the former was likely seasonal drops in peat moisture content, which facilitated rainwater infiltration through desiccation cracks raising pore pressures within the peat mass, increasing peat landslide susceptibility in late summer months. These results can be used to guide more accurate landslide risk management considering region and preconditioning factors which is pertinent for recent peatland restoration activities in GB.
How to cite: McKay Fletcher, D., Elliot, J., and Ruiz, S.: An analysis of landslides in Great Britain using soil texture, rainfall, and topography reveals contrasting failure conditions between organic and mineral soils, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22771, https://doi.org/10.5194/egusphere-egu26-22771, 2026.
Posters on site: Tue, 5 May, 14:00–15:45 | Hall X3
Soil compaction commonly occurs as compacted layers with reduced permeability, which can significantly affect water flow and retention throughout the soil profile, shortening drainage time and altering soil penetration resistance. The objective of this study was to investigate the impact of a compacted layer on soil water flow and penetration resistance using numerical modeling based on Richards’ equation implemented in COMSOL Multiphysics. A two-dimensional problem representing a soil profile was constructed with and without the presence of a compacted layer. The effect of compaction was examined by systematically increasing both the thickness of the compacted layer and the degree of compaction. Model parameterization was based on literature data for a clayey soil, including soil water retention curves, saturated hydraulic conductivity, and parameters describing soil penetration resistance. These parameters were used to numerically solve Richards’ equation for drainage from saturated conditions and to assess the influence of compacted layers on the temporal evolution of penetration resistance as a function of drainage time up to 10 days free drainage. The results showed that the presence of a compacted layer caused only minor changes in matric potential along the soil profile over time. The dominant factor controlling changes in penetration resistance in the simulations was the degree of compaction itself, as the lower permeability of more compacted layers promoted greater water retention in their vicinity, thereby alleviating soil penetration resistance. In conclusion, numerical simulations showed that compacted layers induced only minor changes in soil matric potential during drainage for actual compaction degree conditions. The degree of compaction was the primary factor controlling the temporal evolution of soil penetration resistance, outweighing the effect of layer thickness. Lower permeability in highly compacted layers promoted greater local water retention, which mitigated increases in penetration resistance over time. The scenario examined in this study should be extended to soils with varying textures and permeability in order to assess the broader applicability of these conclusions.
How to cite: P. de Lima, R., Nadalete, G., Pinheiro, E., Moraes, M., Tormena, C., and Souza, Z.: Numerical assessment of soil water dynamics and penetration resistance in the presence of compacted layers, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21202, https://doi.org/10.5194/egusphere-egu26-21202, 2026.
Soil structure can recover after compaction through the combined action of roots, soil fauna, microbial activity, and physical wetting-drying and freeze-thaw processes. We investigated the extent to which such natural processes restore pore architecture in compacted sandy loam soil cores buried for approximately 30 months under contrasting vegetation types. Intact sandy loam cores (20 cm height × 20 cm diameter) with an initial bulk density of 1.7 g cm-3 were extracted from compacted headlands of an agricultural field near Copenhagen, Denmark, using perforated cores that allowed root and faunal entry. The pore network was characterised at field-moist conditions prior to burial using X-ray computed tomography (CT), quantifying tortuosity, macroporosity, macropore density, and pore network skeleton and branching properties. Four replicate cores each were buried at 30 cm depth in a forest and a grassland site, both located in the same region and characterised by sandy loam soils. After 30 months, the cores were retrieved and rescanned using the same CT protocol. Changes in pore metrics were assessed relative to initial conditions to evaluate structural recovery. In parallel, microbial biomass, enzyme activity, organic matter content, pH, and other soil properties were measured at all sites to support interpretation of biological and biogeochemical drivers. The results are used to assess the capacity of natural processes to restore pore structure in compacted soils and to identify key mechanisms controlling recovery under different land use.
How to cite: Arthur, E., Fouladidorhani, M., Nawaz, M. M., Devkota, L., and Lamandé, M.: Natural drivers of soil pore-structure recovery in compacted intact cores: a 30-month burial experiment in forest and grassland, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22003, https://doi.org/10.5194/egusphere-egu26-22003, 2026.
Agriculturally induced subsoil compaction degrades soil structure, negatively affecting spatiotemporal soil moisture dynamics and root growth. Natural and mechanical recovery of the soil structure in sandy soils is limited, making the degraded layers very persistent and hard to alleviate. Subsoil compaction compresses the soil resulting in a decrease in pore sizes and pore connectivity while increasing the penetration resistance. In the compacted layer and the soil layer above, subsoil compaction intertwines the effects on important soil physical and biological processes related to the water retention, water and air transport, and soil strength. These processes influence root development and thereby reduce crop yields by increased aeration-, drought-, and mechanical stresses exerted on roots. This complexity makes it urgent to further understand fundamental processes regarding subsoil compaction in order to accurately simulate both soil moisture dynamics and root growth. Earlier research showed that root growth is affected by subsurface compaction but this effect is often missing in agro-hydrological models.
This study aims to bridge this gap by implementing the effect of soil strength and soil moisture regime on root penetration in the SWAP (Soil Water Atmosphere Plant) model to simulate the influence of soil compaction on the root growth. Therefore, the existing SWAP concept of soil moisture dependent root growth will be extended with a module for mechanical strength dependent root growth based on a theoretical equation of the influence of bulk density, soil moisture and soil texture on root growth (Jones et al., 1991). In a first step the influence of the extended module on soil moisture regime and root growth will be validated against root development data from greenhouse soil column experiments where silage maize was grown under different subsoil compaction scenarios. For the soil physical parameterization of SWAP, the soil physical characteristics were measured for these specific soil columns.
After validation, the new module will be used to simulate the effect of subsoil compaction in an agricultural field. Field samples from a Dutch sandy soil are collected and artificially compacted with a load of 300 kPa in the laboratory, representing loadings exerted on the subsoil because of agricultural machinery. For these samples the water retention and hydraulic conductivity curve, and the bulk density will be determined. These results are used to parameterise a soil profile with and without compaction, in order to simulate the influence of compaction on soil moisture dynamics and root growth for silage maize under natural hydrological conditions in the field.
This study aims to improve the overall understanding and simulation of changes in soil moisture dynamics and root penetration due to compacted sublayers. The addition of a soil strength module in SWAP-WOFOST will enable soil hydrological- and agronomical simulations, potentially improving assessment of agricultural practices and their resilience to different hydrological scenarios.
References
Allan Jones, C., Bland, W. L., Ritchie, J. T., & Williams, J. R. (1991). Simulation of Root Growth. Modelling Plant and Soil Systems, 31, 91-123.
How to cite: Flier, B., van Schaik, L., and Mulder, M.: Explicit simulation of the impact of subsoil compaction on root growth dynamics, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-453, https://doi.org/10.5194/egusphere-egu26-453, 2026.
In agroecosystems, various factors, from soil management to bioturbation, affect the structure of soils throughout the season. It has been hypothesised that soil structure mainly affects the water retention curve (WRC) and the hydraulic conductivity curve (HCC) close to saturation. Still, the existing experimental data on the magnitude of changes, the potential range affected by soil structures, and their seasonal dynamics are limited.
In this study, we collected undisturbed soil cores at six different times over two growth seasons (mid-season, post-harvest, and after seedbed preparation) from the topsoil (5–10 cm depth) and the subsoil (35-40 cm depth) in a 30-year-long-term field trial run by the Bayerische Landesanstalt für Landwirtschaft. The field trial aims to study the long-term effects of various tillage systems on yield and soil properties. We sampled plots managed with conventional ploughing and direct seeding, all of which had the same loamy soil texture and crop rotation. To quantify the soil hydraulic properties from saturation to oven dryness, four laboratory methods were employed for the same soil core: the Falling Head method, the Multistep Flux method, the evaporation method and the dewpoint method.
Under conventional ploughing, we found a decrease in total porosity of 5 vol.-% after harvest, which was recovered after seedbed preparation and did not change throughout the growing season. In addition, the WRC changed the shape of the curves after tillage, indicating soil settlement and significant changes in the soils pore size distribution. In contrast, we found that the WRC of the direct seeding maintain the shape but were scaled with seasonal changes in total porosity. For both treatments, seasonal changes in WRC were observed from saturation up to pF 3, and greatest changes were observed after harvest and after tillage/seedbed preparation. For the HCC, we observed a highly bimodal behaviour and seasonal dynamics near-saturation (0-1.5 pF) indicating the effect of tillage voids and biopores on near-saturation conductivity.
We conclude that agricultural management operations and seasonal dynamics in soil structure controls the wet range of HCC and the WRC from saturation up to pF3. Overall, this study presents experimental evidence on the effect of soil structure on SHP and its potential effect on soil water dynamics.
How to cite: Nielsen, M., Leuther, F., Ebertseder, F., and Diamantopoulos, E.: Do agricultural management operations and seasonal dynamics in soil structure affect soil hydraulic properties?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9751, https://doi.org/10.5194/egusphere-egu26-9751, 2026.
Soil compaction is a severe soil degradation process that affects important soil functions. Understanding how much area is already compacted is important for grasping the scale of this issue.
In intensive, highly mechanised agriculture, a field is typically divided into a core field and a headland according to traffic intensity. However, studies that provide data on the area affected by compaction often only analyse the core field, ignoring the headlands. However, the headlands exhibit the highest intensity of field traffic (wheel load and wheel pass frequency), which is associated with a high risk of soil compaction.
This study focuses on deriving compacted headlands area using field geometry and working width at regional scale. Germany, a nation of modern agriculture, served as the study area. Firstly, field boundaries and working widths (tramlines) were digitised across Germany in QGIS. To take regional variations into account, 11 soil regions were selected, with two 3x3 km squares in each region serving as the digitisation boundary. In a second step, Python scripts were coded to calculate the position and size of the headlands as well as the different traffic intensity zones within the headland. According to Ward et al. 2020, headlands can be differentiated into three zones: (i) the turning zone, (ii) the transition zone, and (iii) the field edge. The turning zone exhibits the highest compaction risk.
The results show that, on average, 19.9% of a field is occupied by the headland. Depending on the size and geometry of the field, this area share can vary significantly, ranging from 3.5% to 100%. On average, the turning zone accounts for 9.8% of the total field area. The transition zone and the field edge account for 4.7% and 5.5%, respectively.
This study reveals that headlands occupy a significant proportion of agricultural land in Germany. Due to high traffic intensity, headlands are prone to soil compaction. Therefore, the headland area should be considered in the spatial assessment of soil compaction. As traffic intensity varies within the headland, the 'turning zone' is a realistic area in which severe soil compaction can be assumed. This part of the field should therefore be included in the spatial estimation of areas already affected by compaction, thereby increasing the percentage of compacted soils assumed in previous studies that excluded headlands.
How to cite: Kuhwald, M. and Augustin, K.: How much area of a field is compacted? An approach for estimate the headland zones at regional scale, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10860, https://doi.org/10.5194/egusphere-egu26-10860, 2026.
The market for autonomous agricultural robots is rapidly developing, with models differing in size, weight, and field applications. Operations range from tilling and seeding to pest and weed control and harvesting. In the transition from simplified to more diversified cropping systems, agricultural robots could support the implementation of labour-intensive, spatially diversified cropping systems by operating autonomously in the field. They may also enhance soil health by replacing herbicide applications with mechanical weed control. However, there are very few studies that quantify the effects of (lightweight) agricultural robots performing mechanical weed control on soil physical properties and overall soil health.
In this study, we aim to assess the impact of mechanical weed control conducted by the autonomous field robot FarmDroid FD20 (FARMDROID APS, Denmark), a solar-powered robot with a working width of 3.5 m and a weight of approximately 1250 kg, on soil physical parameters. It can conduct seeding and subsequently, inter- as well as intra-row harrowing and hoeing with different tools, like blades, cutting knives, disks and wires, equipped to the robot. The weeding depth is approximately 4 cm.
The assessed parameters include bulk density and penetration resistance across three contrasting sites in Germany, sampled at two time points in 2025: before tillage in spring and after several weeding interventions in summer.
The sites span approximately 545 – 830 mm of annual precipitation and differ strongly in soil texture, ranging from sand in eastern Germany to loess-derived silt in central Germany to clay-rich soils in southeast Germany. In block designs with three to four replications, either cultivated with maize (Zea mays) or sugar beet (Beta vulgaris), we assessed the absence of mechanical weed control (herbicide application) compared to mechanical weeding with the FD20. In one of the experiments, two intensity levels of mechanical weeding were also included.
We determined bulk density in trafficked and non-trafficked areas by collecting a total of 570 soil cores (100 cm³) at three depth intervals: 2 – 7, 11 – 16, and 20 – 25 cm. Dried bulk density samples were sieved and corrected for stone content. Moreover, penetration resistance was measured in a transect in the topsoil using a penetrometer (Penetrologger, Royal Eijkelkamp, The Netherlands).
Preliminary bulk density results indicate that robotic weed control and its traffic mainly affected the upper 0 – 7 cm, while effects diminish at greater depths. The analysis of penetration resistance data is still ongoing and will complement the assessment of soil physical responses to robotic weed control.
How to cite: Rohlmann, L., Peth, S., and Grahmann, K.: Impact of autonomous robotic weeding on soil physical properties across a soil texture gradient, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10929, https://doi.org/10.5194/egusphere-egu26-10929, 2026.
The activity of macro- and mesofauna is a key driver for soil structure turnover, thus affecting various soil functions such as soil carbon storage and nutrient cycling. However, there are still few quantitative studies on the rates and efficiency of soil structure turnover induced by different soil fauna groups. In mesocosm experiments, we examined how earthworms (Eisenia fetida, Lumbricus terrestris, Aporrectodea caliginosa), enchytraeids (Enchytraeus albidus), and ants (Lasius niger) alter the spatial arrangement of minerals, particulate organic matter (POM), and pores by using X-ray μCT imaging. Soil structure turnover was quantified by structure labelling and tracking the randomisation of garnet particles. The ratio between particle-pore distance and soil matrix-pore distance was used as an indicator for soil structure turnover¹, and the POM-pore distance as an indicator for organic matter incorporation. Faunal species were placed in cylindrical mesocosms and incubated for 22-24 days. Subsamples were then analysed to quantify the spatial relationships among POM, garnet particles, pore space, and the soil matrix. The predominantly anecic species Lumbricus terrestris mainly elevated POM incorporation into the soil matrix but contributed less to soil structure turnover because of limited burrowing activity. In contrast, the endogeic species Aporrectodea caliginosa promoted structure turnover but with limited POM incorporation because of greater, but predominantly horizontal burrowing activity. Structural impacts of the epigeic species Eisenia fetida were insignificant and largely restricted to surface cast formation. The much smaller enchytraeid worm, Enchytraeus albidus, caused only minor changes in particle-pore relationships, with no new pore formation, and its activity was mainly limited to the soil surface. Preliminary results from experiments with Lasius niger suggest that nest and burrow formation occurred, but there was limited particle transport and no evidence of cast formation. We found that soil structure turnover at the pore scale followed species-specific patterns: Earthworms re-shaped the soil structure, and thus, the particle-pore relationships, ants mainly modified the existing pore architecture, while enchytraeids had only minor effects as they mainly inhabited the existing pore space and soil surface. Overall, our study demonstrated that particle-pore relationships provide a robust way to assess how groups of soil fauna drive soil structure turnover and influence carbon availability.
1 Schlüter, Steffen; Vogel, Hans-Jörg (2016): Analysis of Soil Structure Turnover with Garnet Particles and X-Ray Microtomography. PLoS One 11 (7), e0159948. DOI: 10.1371/journal.pone.0159948.
How to cite: Khosravi, M., Haworth, J., Adami, M., Kaiser, K., Mikutta, R., Schlüter, S., and Leuther, F.: Soil structure turnover driven by soil fauna revealed by particle-pore relationships, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11228, https://doi.org/10.5194/egusphere-egu26-11228, 2026.
Pre-consolidation stress is a measure of mechanical stability on the bulk soil scale while aggregate stability and penetration resistance measurements can be used to assess soil strength at the micro/root scale. Starting from initial soil deposition soil stability is expected to develop over time by processes like consolidation, shrinking-swelling, root reinforcement or exudation of mucilage by roots. We studied the development of soil stability over a cropping period from 2019-2024 in Bad Lauchstädt (Germany) where excavated plots were refilled with homogenized loam and sand and planted with two contrasting maize (Zea mays, L.) genotypes. On the field scale loam plots showed a distinct increase of pre-consolidation stress for the first three years while sand plots did not display any temporal pattern (Rosskopf et al. 2022a). In a second laboratory study employing the same homogenised substrates we investigated the combined effect of mucilage concentration and soil water content on penetration resistance PR (Rosskopf et al. 2022b). A stainless-steel cone resembling the maize root geometry was mounted on a high-precision material testing device and pushed through the remoulded soil samples to simulate root growth. Loam and sand were mixed with chia (Salvia hispanica, L.) seed mucilage at various concentrations and samples were adjusted to a range of water contents. Higher mucilage concentrations significantly lowered PR in the driest loam, thus reducing the energy cost of plant root growth whereas in moister conditions it had the opposite effect. In a third study we investigated the direct effect of root growth on local soil deformation in the rhizosphere using X-ray mCT measurements and digital image correlation (Rosskopf et al. 2025). We could show that the extent of the deformation zone depended on soil texture and genotype. Our results provide valuable information on soil stabilisation processes during initial soil formation and highlight the complex interaction of physical and biological stabilisation mechanisms on various scales.
Acknowledgments
This work was conducted within the framework of the Priority Program 2089, funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – 403627636.
References
Rosskopf, U., Uteau, D. & Peth, S. 2022a. Development of mechanical soil stability in an initial homogeneous loam and sand planted with two maize (Zea mays L.) genotypes with contrasting root hair attributes under in-situ field conditions. Plant and Soil, 478, 143–162.
Rosskopf, U., Uteau, D. & Peth, S. 2022b. Effects of mucilage concentration at different water contents on mechanical stability and elasticity in a loamy and a sandy soil. European Journal of Soil Science, 73, e13189.
Rosskopf, U., Uteau, D. & Peth, S. 2025. Deformation patterns around growing roots using X-ray CT and digital volume correlation. Geoderma, 464, 117613.
How to cite: Peth, S., Rosskopf, U., and Uteau, D.: Development of soil mechanical stability during initial soil formation – from field to rhizosphere scale, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12942, https://doi.org/10.5194/egusphere-egu26-12942, 2026.
Global climate change, driven by rising atmospheric CO2 concentrations, is increasing the frequency and duration of extreme weather events, such as droughts and heavy rainfalls. The implications of these changes for soil-plant interactions in managed grasslands remain poorly understood. To investigate the combined effects of increased CO2 (+300 ppm) and elevated temperature (+3 °C), along with a 2-month summer drought, we conducted a study using undisturbed topsoil and subsoil samples from a 10-year climate change experiment (ClimGrass) in a submontane grassland in Gumpenstein, Austria. We hypothesize that elevated CO2 and temperature will enhance above- and below-ground biomass, leading to increased root growth and a corresponding rise in soil porosity, particularly of the proportion of biogenic macropores, which is expected improve aeration and boost gas diffusion rates.
We analyzed potential changes in soil structure by scanning 66 undisturbed samples with a high-resolution x-ray computed tomography system (only topsoil). Additionally, we measured water retention curves and oxygen diffusion rates (single chamber method) at different matric potentials (-60, -150, -300 hPa) for the topsoil and subsoil, to examine how potential changes in total porosity, pore size distribution and pore connectivity affect gas exchange from the soil to the atmosphere at different moisture levels. As was expected, first results indicate that elevated CO2 led to a lower bulk density and a higher amount of macropores, which also caused gas diffusion rates to increase. The moderating effects of elevated temperatures and droughts will also be discussed.
How to cite: Osiander, S., Felde, V., Schmidt, H., Herndl, M., Schaumberger, A., Zacher, G., Richter, A., and Peth, S.: Effects of Increased Temperature, Elevated CO2 Concentrations and Drought on Soil Structure and Gas Diffusion in a Submontane Grassland Soil, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21327, https://doi.org/10.5194/egusphere-egu26-21327, 2026.
Subsoil compaction a one of the major threats for crop production and soil ecological functioning in Europe. To quantify its field-scale extent, field investigations were conducted on 26 agricultural fields across Lower Saxony state in northern Germany, covering four dominant soil textures (clay loam, sandy loam, silt, and silty loam) and two field management zones (machinery turning area and main field area). In-situ measurements of penetration resistance and shear strength were conducted on field at 10 cm (topsoil) and 40 cm (subsoil), and bulk density (ρb), saturated hydraulic conductivity (Ks), air permeability (Ka) were measured on undisturbed soil samples at the same depth. The results showed that most machinery turning zones showed clear signs of subsoil compaction. About 80% fields showed 5~60% higher penetration resistance and shear resistance in machinery turning area. For sandy loam soil in the east and north part of Lower Saxony, penetration resistance frequently exceeded 3 MPa, reaching >5 MPa at 40 cm, which is above root limiting thresholds. Compared to main field zone, bulk density in machinery turning area increased by 2-5%, with silty loam field exhibiting the largest increase of bulk density. Additionally, soil pore functions of Ka and Ks in machinery turning area exhibited obvious decline compared to field area especially in the subsoil of silty loam and sandy loam fields. For both machinery turning area and field area, a significant correlation was found between hydraulic conductivity and soil bulk density (R2=0.21, p=0.023) in topsoil with ρb from 1.25~1.60 g cm-3, while in subsoil with ρb from 1.45~1.65 g cm-3 no such correlation was found, indicating the pore functions in subsoil mainly depends on connective pores during the structure formation process. These results demonstrate that traffic-induced subsoil compaction is widely altering soil physical structure and pore functions in Lower Saxony, and the texture-dependent responses highlight the need for specific compaction mitigation strategies during the future field managements.
How to cite: Huang, X., Don, A., Poeplau, C., Horn, R., and Peth, S.: Field-scale Assessments of Subsoil Compaction and Soil Structural Functions in Lower Saxony, Germany, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19675, https://doi.org/10.5194/egusphere-egu26-19675, 2026.
Soil structure plays a crucial role in mediating several soil physical and biological processes that underpin important ecosystem services. Soil structure metrics are typically inferred either empirically and/or based on bulk scale soil hydraulic or mechanical properties. Such large-scale measurements obscure fundamental pore-scale processes that govern soil aggregation and the evolution of soil structure based on hydrodynamic cycles. This study develops a mathematical model that describes the evolution of a liquid meniscus between two solid soil particles and the resulting forces that cause the particles to displace. The liquid meniscus was simulated using a multiphase two fluid model considering gas (air and water vapor) and liquid (water), evolving under a series of variably imposed wetting and drying cycles. The meniscus curvature was then used to estimate the tensile and expansive forces driving particle movement, as well as an effective soil elastic modulus. We consider both block and spherical-shaped solid soil particles, identifying differences resulting from their geometry. Our results identify the magnitude of forces associated with shrink-swell processes that influence soil structure over several drying and wetting cycles. Importantly, shrinking and swelling only occurred for the block shaped particles, while changes in effective soil elastic modulus for varying moisture conditions was only present between spherical particles. Effective soil elastic modulus provides information associated with aggregate stability, and thus these results may point to moisture conditions that can enhance soil carbon sequestration and generally lead to healthier soil.
How to cite: Ruiz, S., McKay Fletcher, D., Walkder, N., and Roose, T.: Shape Matters - Comparison of Block- and Spherical-Shaped Soil Particle-Meniscus Dynamics Under Wetting and Drying Conditions and their Effect on Soil Mechanical Properties, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10173, https://doi.org/10.5194/egusphere-egu26-10173, 2026.
Background: Forest soils in Austria's Flysch zone are highly productive but susceptible to compaction from mechanized timber harvesting. Soil compaction alters soil structure, porosity, aeration, and greenhouse gas (GHG) dynamics.
Objectives: This study compared the effects of different timber harvesting systems on soil GHG fluxes of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) and quantified recovery following soil disturbance.
Methods: At the Steinplattl experimental site (Klausen-Leopoldsdorf, Austria), we performed a controlled before-after study in a thinned beech stand using three harvesting systems: tracked harvester and forwarder (H+), non-tracked harvester and forwarder with tracks on uphill axles only (H-), and manual felling with cable yarding (MC). From 2022-2024, we measured soil GHG fluxes tri-weekly in treatment plots (H+, H-, MC) and uncompacted control plots (C) using closed-chamber technique. Random forest models trained on environmental predictors (soil temperature, moisture, precipitation) were used to generate daily soil GHG flux predictions for calculating GHG budgets per hectare for each treatment over 435 days post-harvest (March 10, 2023 to June 17, 2024). Additionally, we assessed long-term recovery using 24-hour soil GHG monitoring (six chambers per treatment, 5-minute measurement cycles) at skid trails from non-tracked operations (H16) in a 2016 thinning and adjacent uncompacted forest soil (C16).
Results: Ground-based harvesting substantially altered all three soil GHG fluxes, while cable yarding effects varied by GHG. Cumulative N2O budgets in ground-based systems (H+ and H-) were more than 3-fold higher than controls, with peak emissions comparable to fertilized cropland. MC showed intermediate N2O fluxes with emission peaks occurring primarily after rainfall events. Soil CH4 uptake was severely reduced in all treatments, with H+, H-, and MC showing 94%, 89%, and 51% reductions compared to C, respectively. CO2-equivalent budgets revealed that H+ generated the highest climate impact (~77 t CO2-eq ha-1), 32% above controls, though high spatial variability precluded statistical significance. Long-term monitoring revealed that 9 years after trafficking, H16 skid trails showed persistent GHG alterations compared to C16. N2O emissions remained elevated with episodic hot moments after rainfall, CH4 uptake remained reduced under dry conditions but approached zero during wet periods, and CO2 emissions remained elevated.
Conclusions: Compared to H-, H+ systems mitigate soil physical impacts but generate elevated GHG emissions. MC minimizes disturbance but exhibits high N2O emission potential after rainfall. Effects on soil GHG dynamics were most pronounced for H+ and H- during the first post-harvest year. However, even after 9 years, skid trails did not recover to pre-disturbance conditions but rather stabilized in an altered state, characterized by a persistent vegetation shift from beech understory to graminoid-dominated communities and thicker litter layers accumulating in wheel track ruts. These changes resulted in elevated CO2 emissions in H16, while CH4 uptake rates remained reduced and episodic N2O hot moments continued during periods of high soil moisture and temperature. Our results emphasize the importance of permanent skid trail networks and site-adapted technology selection for sustainable forest management on compaction-susceptible soils.
How to cite: Malli, A., Behringer, M., Gartner, K., Katzensteiner, K., Schlögl, M., and Kitzer, B.: Quantifying Invisible Losses: Greenhouse Gas Budgets from Three Timber Harvesting Systems and Nine-Year Recovery of Compacted Skid Trails, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5533, https://doi.org/10.5194/egusphere-egu26-5533, 2026.
The monitoring and understanding of the movement of water through soil has broad applications not limited to irrigation and food security, flood risk, landslide rick assessment and wildfire risk management and many other applications relating to water resources.
The Richards Equation has become one of the most common ways to describe and quantify the transient movement of water in unsaturated porous media. The unsaturated hydraulic conductivity is important for both physical based models such as HYDRUS and for machine learning statistical based models to predicting soil moisture. Hydraulic conductivity is determined from a water retention curve which is a plot of soil moisture verses unsaturated hydraulic head. The numerical solution for the unsaturated hydraulic conductivity from the water retention curve is the van Genuchten equation. The water retention curve, however, is often difficult to obtain in the laboratory and difficult to apply to soil moisture data in the field. Development of the soil water retention curve while continuous logging soil moisture on the individual soil samples could reduce error, speed up the analyses time, and can be applied directly to soil moisture data collected with permanently installed soil sensors in the field
A fixture has been developed to hold a soil sensor in a soil sample during the laboratory development of a soil water retention curve. This fixture consists of a soil core sample in a metal ring with a volume of 400 cc, an SDI-12 HydraProbe soil sensor, and a mesh on the bottom holding the soil sample in place while allowing the exchange of water in and out of the sample. The fixture was placed on ceramic plates and equilibrated to pressures from 0 to 1500 kPa while collecting data every minute. A special bulkhead was developed to get sensor communication out of the pressures plate extractor. Data on a smaller soil sample 21 cc in volume were collected alongside the lager soil sample for comparison. Gravimetric data was collected on all samples at the end of each cycle. Because it takes longer for a larger 400 cc soil sample to de-water, equilibrium was approximated using an exponent regression.
Six soil samples 400 cc and twelve 21 cc soil sample were analyzed. The soil was an alpine soil from the Siera Nevada Mountain range in Southern California representing three depths of 10, 50 and 100 cm. The 10 cm depth was highly organic while the 50 and 100 cm depths were mostly sand.
The van Genuchten parameters, alpha, n, saturation and water residual were determined and comparisons were made between the larger 400 cc samples with the soil sensors and the smaller 21 cc soil samples. The site-specific soil moisture calibrations for the HydraProbe soil sensor had R2 values from 0.98 to 0.9985 with RMSE values from 0.002 to 0.015 wfv.
How to cite: Bellingham, K.: Soil Water Retention Curve Development with Continues Time Series Soil Moisture Data , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5875, https://doi.org/10.5194/egusphere-egu26-5875, 2026.
The Yellow River Delta region suffers from pronounced soil salinization, attributed to its shallow groundwater depth and an evaporation rate that exceeds precipitation. Flood irrigation, widely adopted locally as the primary means of salt leaching, further aggravates pressure on the already limited freshwater resources. This study investigates the effects of combined drip irrigation and soil compaction on soil water and salt movement in saline-alkali farmland of the region, aiming to propose a new approach for regional water conservation and salt control. Field experiments and model simulations were integrated in this research. Based on experimental data collected from cotton fields over two consecutive years, the Hydrus-2D model parameters were calibrated and validated. Several scenarios were then simulated, including conventional irrigation, conventional irrigation with soil compaction, and drip irrigation with soil compaction, to analyze soil water and salt dynamics under different conditions. The results show that drip irrigation delivers water precisely to the plant root zone through small, frequent applications, reducing evaporation and deep percolation losses. Soil compaction effectively increases post-irrigation soil volumetric water content and, within a reasonable “compaction threshold,” significantly inhibits upward salt movement. The combined use of drip irrigation and soil compaction reduces both the water required for pre-sowing salt leaching in the root zone and the irrigation demand during the crop growth period, thereby markedly improving water use efficiency. This study provides a novel strategy for regulating soil water and salt in saline-alkali farmland, which can help alleviate agricultural water scarcity in the Yellow River Delta region.
How to cite: Wang, H., Zhao, Y., Zhan, X., and Fu, W.: Influence of Drip Irrigation and Soil Compaction on Soil Water and Salt Transport in Saline-Alkali Farmland of the Yellow River Delta, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11508, https://doi.org/10.5194/egusphere-egu26-11508, 2026.
Visual evaluation of soil samples is a powerful and efficient method to assess quality and stability of soil aggregation. For cropland and pasture (open land), it was shown that a good score assigned to the visual evaluation is correlated to low bulk density (no compaction) and high ratio of soil organic carbon (SOC) to clay content (a measure for the stabilization of organic carbon. However, in forest soils, aggregate formation conditions are different due to lower mechanical disturbance, higher biological activity, higher organic input of different quality, enhanced weathering, and the absence of liming. Under these conditions, we expect the link between visual score, bulk density, and SOC-clay ratio to be less consistent, which challenges the applicability of the visual evaluation method for forest soils.
To quantify and interpret the visual evaluation method for forest soils, 27 forest sites in Switzerland were sampled across a wide range of texture, organic carbon, and acidity levels. Various soil structure-related properties were measured directly in the field (score of visual evaluation) and in the lab (macropore geometry and soil hydraulic properties). No general relationship between visual scores and basic soil health parameters (porosity, SOC-clay ratio, saturated hydraulic conductivity) was found, which illustrates the fundamental difference between forest and open land soils. In a next step, the parameter space defined by basic soil properties (texture, SOC, and pH) was subdivided into subregions using cluster analysis. Initial results indicate that VESS and basic soil health parameters correlated but varied across pH- and clay-defined subregions. Interpretation of VESS therefore requires consideration of basic soil properties, yet in combination the method provides a promising field-based assessment of soil structural health.
How to cite: Schmücker, N., Nussbaum, M., Johannes, A., Guidi, C., and Lehmann, P.: A Novel Multi-Factor Interpretation of Visual Evaluation of Soil Structure in Forest Soils, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11550, https://doi.org/10.5194/egusphere-egu26-11550, 2026.
Conservation agriculture is a farming system based on three main principles: reduced soil disturbance, permanent organic cover, and crop rotation. It is widely promoted as a sustainable solution to reduce soil degradation, restore and maintain soil health, enhance climate resilience in crop production, and mitigate greenhouse gas emissions. However, its universal applicability across diverse biophysical and socioeconomic contexts remains highly debated due to inconsistent agronomic performance. Using a global meta-analysis, we evaluated the effect of conservation practices under different climate and soil conditions on soil properties that regulate soil-water movement, storage, accessibility to crops, soil aeration, and crop yield. Performances of five conservation agricultural practices, namely no-till without residue (NT), reduced tillage without residue (RT), no-till with residue (NT+RR), reduced tillage with residue (RT+RR), and conventional tillage with residue retention (CT+RR), were compared with conventional tillage without residue (CT) based on observations from 328 studies across 361 experimental sites.
Mean yield responses to conservation practices ranged from a reduction of 6.3% (p=0.02) for NT to no significant yield effects (+3.4%; p=0.29) under CT+RR as compared to CT. Increasing tillage intensity (from NT to CT) and residue retention were associated with higher crop yields (p=0.046). Yield outcomes varied with climatic and soil conditions. In semi-dry climates (aridity index: 0.3-0.65) NT increased yields by 16.3% (p=0.004), likely related to changes in infiltration (+24%, p=0.12), although the mean change was not significant for the latter. In contrast, NT reduced yields in humid climates (-7.2%, p<0.001) and in dry regions, where irrigated agriculture was expected to dominate (8.9%, p=0.031). The largest yield reductions occurred in clayey soils (NT -22.2%, p=0.07 and RT -25.8%, p = 0.004), whereas the smallest reductions and occasional gains were observed in sandy soils, which also aligns with a significant trend in infiltration responses (p=0.007), ranging from a mean reduction of 26% (p=0.15) in clayey to a mean increase of 21% (p=0.16) in sandy soils.
Sensitivity analysis revealed that crop yield under NT is strongly influenced by bulk density, possibly due to its cascading effects on soil hydraulic and mechanical properties that regulate water availability, air circulation, root growth, and thus crop-water and nutrient uptake. Although bulk density increased only non-significantly by 5.4% under NT, this was accompanied by 40% (p<0.001) increase in penetration resistance, 18.6% (p<0.001) reduction in air-filled porosity, and overall increase in plant-unavailable water capacity (wilting point). We conclude that while NT and RT can enhance infiltration and soil moisture, crops benefit minimally from these improvements due to a simultaneous soil compaction that 1) hinders root penetration, 2) decreases available water, and 3) limits soil aeration.
How to cite: Wakjira, M. T., Hijbeek, R., van Heerwaarden, J., Six, J., and Descheemaeker, K.: Changes in soil-plant-water relationships and crop yield under conservation agricultural practices, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14163, https://doi.org/10.5194/egusphere-egu26-14163, 2026.
Posters virtual: Wed, 6 May, 14:00–18:00 | vPoster spot 2
EGU26-276 | ECS | Posters virtual | VPS17
Evaluating the Effect of Compaction on Soil Hydraulic PropertiesWed, 06 May, 14:15–14:18 (CEST) vPoster spot 2
Soil compaction is commonly viewed by agronomists as an undesirable consequence of intensive agricultural activities arising from heavy machinery or livestock trampling. However, when induced at the bottom of furrows, it might help reduce the water loss during furrow irrigation. As such, understanding of how compaction alters soil hydraulic properties is essential for developing sustainable soil and water management practices. This study aimed to investigate the impact of compaction on soil hydraulic properties of a clay-textured Nitisol. Thirty undisturbed soil samples were collected from a depth of 15 cm in Koga irrigation scheme, Ethiopia, and subjected to five compaction levels: control (0%), 5%, 10%, 15%, and 20% volume reduction, each with six replicates. Saturated hydraulic conductivity was measured using the KSAT® apparatus with the falling head technique, while water retention and unsaturated hydraulic conductivity were measured using the HYPROP® system based on the modified evaporation method. Compaction reduced water retention and hydraulic conductivity, particularly in the wet range up to pF 3. Saturated hydraulic conductivity decreased by 9% to 78% from the lowest to highest compaction level tested. Compaction also increased bulk density (8% – 40%) and relative field capacity (4% – 10%) and decreased total porosity (6% – 33%), macroporosity (28% – 82%), air capacity (25% – 61%), and plant-available water content (8% – 17%). When compared with soil quality thresholds, compaction of 15% or more reduced plant-available water below optimal range (< 0.2 m3 m-3) and lowered saturated hydraulic conductivity below the threshold (8.64 cm day-1). While this study was designed to evaluate the efficiency of furrow irrigation subjected to compaction, the findings also emphasize the need for sustainable soil management to improve crop yield and soil resilience.
Keywords: Hydraulic properties, HYPROP2®, KSAT®, Soil compaction, Soil physical quality
How to cite: Yimam, A. Y., Asmamaw, D. K., Chen, M., Tilahun, S. A., Beyene, A. A., Dessie, M., Walraevens, K., Tsegaye, E. A., Frankl, A., and Cornelis, W.: Evaluating the Effect of Compaction on Soil Hydraulic Properties, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-276, https://doi.org/10.5194/egusphere-egu26-276, 2026.
