Soil compaction caused by machinery traffic or livestock grazing typically reduces crop and pasture yields, lowering farmer incomes while increasing input costs for tillage, irrigation, and nutrients. However, few studies have quantified how yield responses to compaction vary across soil textures and climates. Here we synthesise published data to quantify the relationships between yield and soil physical indicators, and to evaluate the moderating roles of soil texture and climate. We extracted yield responses to bulk density (BD) and degree of compaction (DoC) from the literature and conducted a global synthesis using main-effect regression models. Across studies, yield responses followed two dominant patterns: a negative linear decline with increasing BD or DoC, or a quadratic response with yields increasing to an optimum and then declining. For quadratic relationships, coarse-textured soils tended to show a higher optimum BD but a lower optimum DoC than fine-textured soils. Dry climates tended to show a higher optimum BD and a lower optimum DoC than wet climates. Beyond the optimum, whether inferred from linear or quadratic relationships, wet conditions had a less negative yield–DoC slope than in dry conditions, suggesting greater vulnerability to compaction in drier climates once critical thresholds are exceeded. Knowledge gaps include the lack of studies relating pastoral and many crop responses specifically to dynamic structural values (e.g., air capacity, available water capacity, penetration resistance, and aggregate stability) across textures and climates.

Specific ion effects have important impacts on the interaction forces between soil particles, which could strongly affect soil structure, water infiltration and soil erosion. Nevertheless, little is known about how specific ion effects affect soil rheological properties. In this study, the specific ion effects (Na+, K+, and Cs+) on soil rheological properties were systematically investigated using rheometer and quantitatively interpreted through theoretical analysis of soil internal forces. The results showed that specific ion effects pose important effects on soil rheological properties. Specifically, soil rheological parameters such as stress (tau(LVR)) and strain (gamma(LVR)) at the end of the linear viscoelastic region (LVR), as well as shear stress (tau(YP)), strain (gamma(YP)), and storage modulus (G '(YP)) corresponding to the yield point (YP) initially remained relatively constant (10(-5)-10(-2) mol L-1), and then increased rapidly (10(-2)-1 mol L-1) for each cation system, indicating the enhanced soil shear resistance and viscoelasticity. At the same electrolyte concentration, the soil rheological parameters followed the order: Cs+ > K+ > Na+ across all cation systems. The soil rheological parameters for all three cation systems displayed a clear negative exponential relationship with the net force considering cationic non-classical polarization. Strong electric fields surrounding soil particles caused cationic non-classical polarization which significantly reduced electrostatic repulsion between soil particles and finally led to the increase of soil rheological parameters. Additionally, the differences in the ion dispersion forces increased as electrolyte concentration increase at high concentrations (> 10(-1) mol L-1), leading to greater discrepancies in the soil rheological parameters among different cation system. This study offers critical insights into the underlying mechanisms governing soil flow and deformation behavior and opens the possibility of improving soil structure by adjusting the soil internal forces.

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.

Peatland drainage disrupts hydrological functioning, degrades peat soils, and accelerates carbon loss. Although rewetting is increasingly promoted to reverse these impacts, the extent to which it can restore peat structure and hydro-physical properties remains unclear. Here, we examined peat structure and hydro-physical properties along a sequence of fen peatland states-near-natural, drained, and rewetted since 1997. The hydro-physical properties including bulk density (rho(b)), soil organic matter content (SOM), saturated hydraulic conductivity (K-s), soil water retention curves (SWRCs), and drainable porosity (phi(d)) were measured using peat cores of 250 cm(3). In parallel, undisturbed peat soil cores (10 cm in height) collected from the upper peat layer (0-15 cm depth) were analyzed using X-ray computed tomography (CT) to characterize CT-resolvable pore size and geometry. K-s was additionally measured on the same CT-imaged cores, enabling direct linkage between pore-network architecture and K-s. The results indicated that, relative to near-natural peat, rewetting only partially recovered rho(b) and SOM, whereas macroporosity, K-s, and SWRCs were fully recovered. A strong correlation was observed between phi(d) and log(10)K(s) (R-2 >= 0.73, p < 0.001), indicating that this easily measurable property may serve as a practical predictor of K-s in peat soils. CT-based analyses further showed that natural and rewetted peat soils had a greater mean macropore diameter of the limiting slice (MDLS; i.e., the CT slice with the lowest CT-resolvable air-filled porosity) and longer maximum macropore vertical extent (MVE) than drained peat. In contrast, the largest pore networks in drained peat lacked continuous pathways for water transmission at the CT-resolvable scale. In the 10-cm-high CT-imaged peat cores, three-dimensional pore-network metrics-particularly CT-resolvable air-filled porosity and MVE-explained more than 87% of the variability in K-s. Overall, our findings demonstrate that long-term rewetting, with the water table maintained near the ground surface, can substantially restore functional soil structure and water transmission capacity in the topsoil of previously degraded fens, with re-established pore connectivity emerging as a key mechanism driving near-surface hydrological recovery.

Abstract Numerous methods are available for sampling, extracting, and detecting microplastics (MP; 0.001–5 mm) in soil. However, previous studies mostly focused on pristine MP and changing surface properties due to ageing (e.g. surface photooxidation) that will impact transport in soils are not considered. This study primarily aimed at MP recovery from soil by density separation, focusing on the impact of UV-aging on recovery rates while monitoring MP surface properties to avoid analytical artifacts. Thus, we mixed sandy loam and silt loam topsoil with both, pristine and UV-aged polyethylene terephthalate (PET) and polystyrene (PS) MP, produced from PET bottles and PS plates in three size classes. MP particles were recovered by density separation, using oversaturated NaCl and NaI, solutions, followed by H2O2-treatment to oxidise soil organic matter. Recovery rates were determined gravimetrically after filtration of the supernatant. MP surface properties were characterised by FTIR, Nile red staining, contact angle (CA), and XPS analysis before and after recovery. Recovery rates averaged 81.0%, ranging from 56.5% to 89.7%, with no defined differences between MP type, size, and variant (pristine, UV-aged). Before recovery, FTIR analysis revealed an increase in carbonyl groups, Nile red staining showed a darker colour, CA was significantly decreased, and XPS indicated an increase in surface O/C ratio for UV-aged MP. After recovery, FTIR and Nile red analysis showed no changes, CA of UV-aged MP, however, was found to be increased, probably due to H2O2-treatment that may have removed the oxidised surface layer. In summary, the separation procedure applied was found to successfully recover pristine and UV-aged MP from both, sand and silt soil, regardless of MP type tested (PET, PS).

Land-use changes in Patagonian wetlands, locally known as Vegas and Turbales, remains insufficiently studied particularly regarding its effects on soil-structure-dependent. This study assessed wetland under similar pedoclimatic conditions but contrasting management in southern Chile: three sedge-dominated Vegas under low grazing intensity (LGI) and high grazing intensity (HGI), and a Sphagnum peatland exploitation area. Samples from surface horizon (0–5 cm) and deep horizon (~70 cm), nearly above the glacial parent material or water table, were taken and analyzed for bulk density (BD), water loss behavior during soil shrinkage, air permeability, and organic matter quality. Linear mixed- models showed a significant overall effect of grazing intensity on BD at both surface and deep horizon (p < 0.05). However, pairwise comparisons revealed heterogeneous responses among Vega pairs at surface horizon, with lower BD under HGI (0.17 Mg m-3), while high BD 0.28 Mg m-3) were observe undel LGI. Soil shrinkage, measured as COLE, was not affected by grazing in the surface horizon (p = 0.576). However, at the deepest horizon, soils under high grazing intensity (HGI) showed significantly greater shrinkage (COLE = 0.492; p < 0.001). Air permeability (Ka) did not differ between grazing intensities at either horizon (p > 0.289). Shrinkage curve analysis showed predominantly class A behavior, indicating that soils experienced the full sequence of shrinkage stages during drying, including a structural phase associated with macroporosity. In contrast, SJ and some managed Vegas lacked residual and zero-shrinkage phases, suggesting reduced stability of meso- and micropores. Higher TOC contents were generally associated with higher transmittance in FTIR spectra and lower BD, highlighting a strong coupling between OM quality and soil structural functioning. Overall, grazing intensity produced contrasting responses among Vegas, whereas peat extraction represented a clearer degradation pathway, underscoring the need for site-specific indicators and thresholds to protect wetland soil functions.

Abstract Increasing soil organic carbon (SOC) aims to increase and maintain soil quality for sustainable crop production and to achieve carbon removal targets. Agronomic practices are therefore needed to reduce carbon losses and increase SOC stocks, especially in deep soil layers, which promote long-term storage. Regenerative agriculture is an approach aimed at increasing soil quality for sustainable production and therefore should be suitable for achieving the required goals under organic farming conditions. We analysed SOC content down to a depth of 1 m and calculated the SOC stock based on bulk density after ten years of regenerative farming practices, i.e., reduced tillage, dead organic mulch, and high-quality yard waste compost application, in two organic field trials set up one year apart in Central Germany and we calculated the carbon (C) and nitrogen (N) input to the soil from organic amendments and from main crops and cover crops by applying C allocation factors for crop residues, roots, and rhizodeposition. C derived from crops was the main carbon input source over ten years. Increasing C input promoted an increase in the cumulative SOC stock down to 1 m. We observed greater SOC stocks dominated by topsoil changes with reduced tillage and compost application and with the combination of all practices (+ 16%) than in the control with conventional ploughing and no external carbon input while none of the farming practices affected the subsoil SOC stock. Mulch application had no effect at all on SOC stocks. Crop biomass contributed most C input. Farming practices, especially the combination of reduced tillage and compost application, enhanced topsoil SOC stocks and N but not subsoil C storage. Other farming practices and crop rotation adjustments must be identified to increase crop production as well as subsoil SOC stocks and promoting long-term C storage, e.g., by fostering deep-rooting crops and cover crops.

Agricultural soil arsenic (As) pollution threatens food security, with its transport governed by soil redox conditions. Soil compaction limits gas/water exchange, promoting reducing conditions under waterlogging. However, mechanisms of As dynamics in compacted soil–plant systems remain unclear. This study investigated As transformation and plant uptake under varying compaction levels. A 60-day column experiment was conducted on a clay loam Alfisol during the wheat seedling stage. Four compaction treatments including no compaction (CK), low compaction (LC), moderate compaction (MC), and heavy compaction (HC) treatments were established within 0–25 cm profile, using bulk densities of 1.30 and 1.65 g cm⁻3 and compacted layer thicknesses of 0, 10, 15, and 20 cm within a 0–25 cm soil profile, respectively. Soil redox potential (Eh), As speciation, fractionation, and As concentrations in roots and shoots were monitored under waterlogging. Compaction reduced soil air and hydraulic conductivity, creating prolonged anaerobic conditions in compacted layers and enhancing As mobility. Compaction substantially increased root As uptake but restricted translocation to shoots. The root bioaccumulation factor (BAF) rose from 1.16 (CK) to 5.41 (HC), while the translocation factor (TF) decreased from 0.19 to 0.07. Under HC, a “root entrapment” effect initially limited As translocation, but enhanced mobility, prolonged exposure, and increased root-soil contact ultimately raised shoot As concentrations to 5 mg kg⁻1. Soil physical degradation alters contaminant behavior through redox driven speciation changes and modified plant uptake, highlighting the need to incorporate compaction effects in contamination risk assessments and soil management.

Vegetation restoration is an effective measure to improve soil structure stability and thus decrease soil erosion. However, fewer studies have examined the effect of vegetation restoration on the mechanical stability of soil structure at the micro-scale level. In this study, we collected soil samples across a restoration chrono sequence spanning 160 years (from unrestored farmland to mature arbor forests). The soil microstructure stability derived from rheological parameters (shear strength and viscoelasticity) were investigated using a compact modular rheometer. Our results showed that restoration time had a positive effect on shear strength and then increased soil microstructure stability. With increasing restoration time, soil shear strength and elasticity generally improved across vegetation types. Forests exhibited a non-linear trend, with strength peaking at 110 years before declining in older stands (130–160 years). Correspondingly, the viscoelastic parameters (e.g., γYP, Iz) also peaked at 110 years, indicating that soil structure is most stable and deformation resistance is greatest during this phase. The partial least squares path modeling revealed that increases of organic carbon and divalent cation contents were the main reason contributing to the enhancement of soil microstructural stability. In summary, the vegetation restoration process increased organic carbon and divalent cation content, thereby enhancing soil shear strength and elasticity, which subsequently stabilized the soil microstructure. This work provides important indicators for understanding the evolution of soil microstructure during vegetation restoration and supports a theoretical basis for the development of soil structure improvement and ecological restoration techniques suitable for loess derived soils.

Regenerative agriculture has been associated with improved soil structure and soil fertility. However, conclusive evidence of its efficacy has remained elusive owing to a lack of long-term experimental studies. In this study, we assessed the impact of diverse regenerative agricultural measures on soil mechanical and hydraulic properties and indicators. Tested treatment factors included reduced tillage versus plowing, along with different levels of compost, mulch, and the application of ferments and compost tea. We measured in situ soil strength via soil penetration (from 0 to 0.8 m depth) and shear resistance (at 0.08 and 0.23 m depth) and assessed field-saturated hydraulic conductivity and ex situ soil aggregate stability (at 0.07 and 0.23 m depth). The experiments were conducted at five sites in Hesse, Germany, including one organic long-term experiment (LTE, since 2010) in NeuEichenberg and three organic and one conventional on-farm experiments to cover different soil types, weather conditions, and field practices. The soil types are classified as Luvisol and Vertic Cambisols, and the soil texture ranges from silt loam to silty clay loam. In the LTE, significant differences in aggregate stability and shear resistance were noted between treatments, with a higher geometric mean aggregate diameter at 0.07 m depth in 2021 and 2022 and a higher shear resistance at 0.19 m and 0.23 m in 2020 and in 2021, respectively, in the reduced tillage systems. However, no significant differences were observed among treatments for field-saturated hydraulic conductivity, which was overall very high, showing that reduced tillage did not negatively influence saturated infiltration, albeit bulk density is higher than in the conventionally plowed system. The soil penetration resistance was generally higher for the reduced tillage treatments across depths of 0.0-0.30 m, albeit not statistically significant (p > 0.05). Significantly higher water-stable aggregates and geometric mean diameters were observed for regenerative agricultural treatments in three of the on-farm experiments at a depth of 0.07 m. The shear resistance was significantly higher in regenerative agriculture units in specific years and depths. Although the outcomes are encouraging, the variability of the effects of reduced tillage and organic amendments in affecting soil properties highlights the need for further long-term research including farm trials. This is essential to fully understand the effects of regenerative practices on soil physical quality.

The heavily strained water resources in Bengaluru, India, as a result of rapid urban expansion are increasingly at risk of overexploitation and pollution due to intensified agriculture practices, such as increased nitrogen (N) use and irrigation. In recent years, thermal cameras mounted on Unmanned Aerial Vehicles (UAVs) have proven useful in detecting crop water stress and managing irrigation. However, the use of these cameras in managing N fertilization in the subtropics has been understudied. We employed this technology in two agricultural field experiments in Bengaluru to study the effects of N fertilization on canopy temperatures of maize, finger millet, and lablab, and their correlations with Leaf Chlorophyll Content (LCC), and soil temperature. The results showed that the effect of N was more pronounced at the rainfed experimental site, where the soil is highly acidic and porosity is low. At this site, N significantly affected the canopy temperature of maize and finger millet, particularly under sunny conditions (p = 0.000245), resulting in plots receiving higher nitrogen dosages showing canopies with 2.1 degrees C and 1.3 degrees C cooler temperatures, respectively. Lower temperatures with higher N application were also observed in the irrigated experiment (p value = 0.118), albeit only under sunny conditions. Additionally, canopy temperatures and LCC significantly correlated for maize (R = -0.68, p = 0.015) in the rainfed experiment and millet (R = -0.7, p = 0.011) in the irrigated experiment. However, the correlation of LCC with NDVI was stronger on both sites. Canopy and soil temperatures correlated significantly only when analysed without considering crop species. The use of thermal cameras, equipped with uncooled microbolometers, is accompanied by the dilemma of temperature drift, which affect measurement accuracy. We introduced a drift correction process, which effectively reduced drift by up to 45%, and decreased the drift standard deviation to less than 1 degrees C, that resulted in homogeneous thermal maps suitable for robust statistical analysis. In my submission i added keywords, are they going to be included in the publication ??

Peatlands acquire only 3% of the terrestrial earth's surface; however, they store up to 30% of the global soil carbon. These peatlands also dominate the northern Hemisphere, which is covered by more than 25% of permafrost. An accelerating trend in the rate of permafrost degradation due to climate warming has been observed in most regions of the Northern Hemisphere. An indicator of permafrost degradation is the active layer depth, which is situated in the variably saturated zone. The hydraulic properties of the peatland top soil layer are influenced by its unstructured porous media, high organic matter, and high porosity. The water content in the variably saturated zone in cold regions is influenced by both drying-wetting and freezing-thawing cycles. The soil water characteristic curves (SWCC) define the relationship between unfrozen water content and matric potential. The soil freezing characteristic curves (SFCC) define the relationship between unfrozen water content and temperature around 0°C. The SWCC, SFCC, and the similarities between them have been intensively investigated for mineral soils in comparison to organic soils. The three main goals of the study for peatland permafrost mires are as follows: (i) Determine the SWCC using inverse modeling of transient evaporation experiments. (ii) Estimate the SFCC using field-based volumetric water content measurements using a simple empirical function. (iii) Compare and develop a relationship between the SWCC and SFCC. The lowland permafrost mires in the Abisko region, located in the northern part of Sweden, were investigated. For the SWCC evaporation experiments, 12 soil samples at six locations and two depths (10 and 25 cm) were taken. Inverse numerical modeling was used to fit and compare the three pressure-saturation functions: (i) Van Genuchten model. (ii) Peter Durner Iden (PDI)-variant of the Van Genuchten model (iii) PDI-variant of the bimodal van Genuchten model. The goodness of fit was checked by Root Mean Square Error and Akaike Information Criterion. It was observed that the PDI-variant of the bimodal van Genuchten model was most suitable for all the soil samples. 12 soil moisture sensors were also installed at the six locations and five depths (10 to 50 cm). An exponential logarithmic function with two parameters (transition temperature and temperature dispersion) was fitted to individual freezing and thawing curves from the soil moisture sensor data. The function showed a very good fit, and it was observed that the two fitting parameters were higher for thawing curves compared to freezing curves. A new SFCC function was developed based on the PDI variant of the bimodal van Genuchten model. This function was compared with the fitted SFCC logarithmic function. Reasonable differences were identified, which could be attributed to the field-installed soil moisture sensors and laboratory-conducted evaporation experiments. It is one of the few hydrological studies that has investigated the effects of bimodal behavior in organic soils on soil freezing and thawing. The measured parameters and datasets provide the necessary functions for developing cryohydrogeological models. The cryohydrogeological models can be used to assess the impacts of climate change on permafrost.

Microplastics (MP) in soils are considered an emerging environmental pollutant of global concern. The transport processes of MP in soils are poorly understood, which indicates a major knowledge gap regarding the environmental impact and behaviour of MP. Mobility and surface charge can be affected by ageing, mainly via UV irradiation. In the present study, 1 µm polystyrene microspheres (PS-MP) were aged with UV irradiation using an irradiance of 2.05 W m−2 (ultraviolet A, UVA; 365 nm) and 5.58 W m−2 (ultraviolet C, UVC; 254 nm) and different exposure times between 24 und 1176 hours to generate a gradient in MP ageing. The UV-ageing effects on PS-MP were characterised in terms of changes in particle size, zeta potential, and surface functional groups as determined by attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR). Non-irradiated PS-MP microspheres were used as a control. Column tests were performed by percolating PS-MP microspheres suspended in CaCl2 solution (ionic strength 7.5 mM) through a quartz sand matrix (0.3 mm particle diameter). PS-MP sizes steadily decreased with increasing ageing time from 24 h to 1176 h for both UVA and UVC treatment. ATR-FTIR results revealed that UV irradiation induced a transformation of PS-MP surfaces with especially the appearance of a carbonyl (C=O) peak due to C-H bond breaking during the oxidation process. The increasing presence of oxygen-containing functional groups in UV-treated PS-MP led to an increasing negative surface charge and zeta potential and enhanced PS-MP transport through the quartz sand column. With increasing irradiation time, the aged PS-MP showed continuously increasing transport rates compared to the transport rates of non-aged PS-MP, ranging from 46 to 85% and 48 to 91% for UVA- and UVC-treated samples, respectively. The fastest breakthrough was observed for highest negative zeta potential and amount of O-containing functional groups as compared to control PS-MP, which enhanced electrostatic repulsion between aged PS-MP and quartz sand particles as was demonstrated from calculation of the interaction free energy. Our findings imply that UV irradiation changes the PS-MP surface physicochemical characteristics and transport potential by increasing the mobility of PS-MP and hence the risk for contamination of deeper soil layers and water bodies.

The active layer thickness (ALT) refers to the seasonal thaw depth of a permafrost body and in high alpine environments represents an essential parameter for natural hazard analysis. The aim of this study is to model ALT based on bedrock temperature data measured in four shallow boreholes (SBs, 0.1 m deep) in the summit region of the Kitzsteinhorn (Hohe Tauern Range, Austria, Europe). We set up our heat flow model with temperature data (2016-2021) from a 30 m deep borehole (DB) drilled into bedrock at the Kitzsteinhorn north face. For modeling purposes, we assume one-dimensional conductive heat flow and present an analytical solution of the heat transport equation through sinusoidal temperature waves resulting from seasonal temperature oscillations (damping depth method). The model approach is considered successful: in the validation period (2019-2021), modeled and measured ALT differed by only 0.1 +/- 0.1 m, with a root mean square error (RMSE) of 0.13 m. We then applied the DB-calibrated model to four SBs and found that the modeled seasonal ALT maximum ranged between 2.5 m (SB 2) and 10.6 m (SB 1) in the observation period (2013-2021). Due to small differences in altitude (similar to 200 m) within the study area, slope aspect had the strongest impact on ALT. To project future ALT deepening due to global warming, we integrated IPCC climate scenarios SSP1-2.6 and SSP5-8.5 into our model. By mid-century (similar to 2050), ALT is expected to increase by 48 % at SB 2 and by 62 % at DB under scenario SSP1-2.6 (56 % and 128 % under scenario SSP5-8.5), while permafrost will no longer be present at SB 1, SB 3, and SB 4. By the end of the century (similar to 2100), permafrost will only remain under scenario SSP1-2.6 with an ALT increase of 51 % at SB 2 and of 69 % at DB.

Soil structure influences important soil functions like hydraulic conductivity and air permeability, which in turn influence plant growth. The physical structure of soils is thus, besides chemical and biological parameters, one major component of soil fertility. Unfortunately, this physical fertility is often impaired by agricultural practices. To study the structural status and the relationships between structural and functional parameters, 45 representative arable sites in Schleswig-Holstein, Germany, were sampled at three depths in top- and subsoil. Soil structure was described quantitatively using X-ray computed tomography of soil cores (continuity and size distribution of macropores). Measured soil functions included saturated hydraulic conductivity, air permeability, air capacity, and pore size distribution (via water retention curves). The results not only help elucidate relations between structural and functional soil parameters. They also give a detailed and comprehensive insight into the structural state and their relation to soil physical functions of typical arable sites across Schleswig-Holstein that has not existed before.

Understanding soil organic carbon fractions in southern India is crucial for enhancing soil health, crop productivity, and sustainable land management. It is majorly affected by cropping systems, nitrogen levels, irrigation management, etc. Therefore, the present study aimed to investigate the effects of varying nitrogen doses [N1: No nitrogen, N2:100% of recommended dose of N (RDN), and N3: 200% RDN] and different cropping systems (fieldbean, finger millet, and maize) on aggregate-associated soil organic carbon and its fractions, as well as their impact on aggregate stability under rainfed and irrigated conditions. Aggregates were separated into different classes and analyzed for organic carbon and its fractions (dissolved organic carbon, microbial biomass carbon, potassium permanganate oxidizable carbon, and non-labile organic carbon). Applying 200% RDN enhanced total organic carbon (TOC) and its fractions. Conversely, aggregate stability was not influenced by N levels as determined by mean weight diameter and tensile strength. Macroaggregates (> 250 μm) had higher total organic carbon and their fractions than microaggregates (< 250 μm). The effect of the cropping systems was significant and the maize cropping system had the highest content of TOC and other fractions, followed by fieldbean and finger millet cropping systems. Mean weight diameter (MWD) was significantly higher in finger millet-grown soils. The impact of nitrogen fertilizer and cropping systems on aggregate-associated organic carbon was more pronounced in irrigated than rainfed conditions, indicating the potential for carbon sequestration under irrigated conditions. Thus, the optimum level of nitrogen and the type of cropping system adopted influence the distribution pattern of aggregate-associated organic carbon, along with its fractions that play a pivotal role in carbon accumulation and stabilization.

Soil shrinkage significantly alters hydraulic and thermal properties in peatland-dominated permafrost regions. This study examines the impact of shrinkage on soil water characteristic curves and thermal conductivity drying curves in Storflaket Mire, Sweden. Seven peat samples were collected at three depths close to the surface. The HYPROP and WP4C devices determined the soil water characteristic curve parameters. The HYPROP device is a transient evaporation experiment that measures soil water potential heads and corresponding volumetric water content. The WP4C measures the dry-range soil water potential and the corresponding volumetric water content. The VARIOS device was used to determine the thermal conductivity drying curves of the peat samples. The shrinkage effects were accounted for by measurements taken with a vernier caliper, followed by validation using a three-dimensional structured light scanner under air-dried conditions. The results from the hydrological experiments showed that shrinkage effects were most pronounced in the deepest layers. Comparing cases with and without shrinkage revealed a 40% reduction in volume under air-dried conditions. The hydraulic conductivity curves showed minimal changes between the cases with and without shrinkage, assuming that tortuosity remains constant with shrinkage. Including dry-range measurements was essential for a more reliable soil water characteristic curve representation. Shrinkage alongside dry-range measurements showed that the pore size distribution shifts from macropores (300–3000 μm) to micropores (3–30 μm), indicating reduced bimodality with depth. This change likely explains the higher matric potential in the deepest layers. The results from the thermal experiments revealed near-linear thermal conductivity drying curves, with dry surface peat exhibiting lower conductivity than saturated deeper layers. Empirical models based solely on volumetric water content outperformed traditional parameter-based models in predicting thermal conductivity.

Soil organic carbon (SOC) depletion is often a result of human land use, which is intensified by climate change. As SOC is closely linked to the stabilization of soil structure, the loss of SOC in a soil may induce soil structure breakdown and turnover processes that are not yet well understood. In order to study soil structure turnover with respect to OC loss, we designed an incubation experiment with soil microcosms that allowed OC loss by leaching and microbial respiration, while avoiding any mechanical disturbance. We incubated intact soil cores of an arable Luvisol from Loess deposits in southeastern Germany for 300 days at constant water tension and 25 °C to promote microbial activity. During incubation, CO2 release from the microcosms was monitored. A subset of the microcosms was sampled monthly to assess the effect of progressive OC depletion on the stability and architectural features of the soil structure. The incubation resulted in a reduction of the initial OC (11.2 mg g-1) by approx. 20% and a narrower C:N ratio, corresponding to a reduced OC coverage of the mineral surfaces (1.7 m² g-1 to 0.9 m² g-1, as determined by N2-BET). Despite the OC reduction, the aggregate size distribution (as determined by both wet and dry sieving) did not change significantly, although there was a trend toward a reduction in the mean weight diameter of the aggregates. The mechanical stability of isolated soil aggregates (as determined by dry crushing) even increased slightly with lower OC content in the bulk soil. Microscopic analysis of resin-embedded soil aggregates revealed a lower bulk density in the center, suggesting a progressive carbon depletion from the outside to the inside of the soil aggregates. These observations highlight that early stage OC depletion along with reduction of OC-covered mineral surface area, without additional mechanical influence, does not immediately lead to the degradation of soil structure. This suggests the existence of OC storage sites that are not susceptible to OC loss by leaching or microbial degradation. In contrast, the sites of initial OC loss may not contribute to the structural stability of a soil.

As roots grow into soils, particles are displaced causing a process of soil restructuring in the vicinity of the roots. To date, a systematic approach to the investigation of factors influencing deformation patterns, including displacement and strain, has not been conducted. To achieve this objective, a soil column experiment was performed within a growth chamber, designed to compare the impact of two factors – substrate and maize (Zea mays L.) genotype – on the observed patterns. X-ray computer tomography (X-ray CT) scans obtained prior to the initiation of root growth provided a reference state, while the deformed state was examined after a period of six days. Digital volume correlation (DVC) was applied with DaVis (LaVision, Göttingen, Germany) and resulting values were localized in relation to the root. In sand, the ratio of root volume to soil volume was higher, and diameters of tap roots and seminal roots were larger than in loam. The extent and the magnitude of radial displacement (displacerad) around roots were more pronounced in the sand, and a wider strain zone was found around tap roots in this substrate. In loam, the roots with a larger diameter (>0.8 mm) cause more deformation, whereas in sand diameter class had less impact on the amount of deformation. The genotype with root hairs was associated with a larger extent of soil deformation around the root. As high displacement values throughout the samples overshadowed local particle movement, strain has been shown to be a more reliable measure for depicting deformation patterns around roots.