Soil Water Repellency Research Articles

Effect of hydrocarbonic pollutants on the stability and soil water repellency intensity: A case study in Bandar Abbas Oil Refinery, Hormozgan province, Iran

Background: The contamination of soil and water with hydrocarbonic pollutants is a major environmental problem. Soil water repellency will interrupt water infiltration, and may decline plant growth and potentially trigger soil erosion. The aim of this study was to investigate the effect of soil and water contamination by oil on soil water repellency, where the soil has been oil-contaminated due to mismanagement of the lands surrounding the refineries, and many of the trees in the area have dried up. Methods: Water drop penetration time test (WDPT) was performed on contaminated soils. To investigate the effect of the surface water contamination on soil, handmade soil samples were collected and successive dry/wet cycles were applied to them by contaminated and non-contaminated waters. Subsequently, soil water repellency tests, including molarity of ethanol droplet (MED), water and ethanol sorptivity were performed on soil samples. The soils were passed through a 2 mm sieve after being air-dried and the soil texture was determined by pipette method. The SWR was measured by WDPT in the area contaminated with petroleum compounds and 7 to 10 replicates were assigned to each location. In order to determine the effect of water contamination on the area soil and to measure water repellency in the laboratory, disturbed soil samples (36 samples) with a bulk density equal to 80% of the reference bulk density were prepared. Results: The results showed that soil oil-contamination causes water repellency, increased WDPT, a significant increase in water repellency index, and a significant decrease in cosθ at the level of 0.001. The effect of water contamination on the indices and cosθ were statistically significant at the 0.001 and 1% levels, respectively. Therefore, contaminated water increased the water repellency of the soil after successive dry/wet cycles. Conclusion: Significant positive correlations between organic and water repellency indices and significant negative correlations between cosθ and organic indices indicate the effect of oil-contamination of water and soil on creating and increasing the intensity of soil water repellency.

Greywater adsorption into soil during irrigation

The reuse of greywater has significant potential to reduce the demand on potable water. The greywater produced from laundry is free from oil and grease and hence makes it attractive to reuse for irrigation. This study investigates the adsorption of surfactant-rich laundry greywater into the soil surfaces during irrigation. A series of miscible displacement column experiments was conducted under water-saturated condition using non-reactive (NaCl solution of concentration 0.650 g/L) and reactive tracers (greywater solution of concentration 0.26–0.442 g/L with same background electrolyte). Plasterer’s sand was used as the porous medium. Samples collected at the column outlet every two minutes were measured for pH, electrical conductivity and greywater concentrations. Hydraulic conductivity for each experiment was also determined using constant head method. Separate experiments were conducted to determine the surface tension of greywater solution (with same background electrolyte) and modelled using Gibbs adsorption isotherm. Surface tension of greywater reduces with increasing greywater concentration and becomes constant at greywater concentration of 0.440 g/L. The results revealed that pH is improved and electrical conductivity decreased indicating it may increase the soil salinity. The comparison of breakthrough curves of reactive and non-reactive tracers showed that the greywater adsorptions occur into the soil surfaces and it increased with greywater concentrations, which may make the soil water-repellent. This may be a concern if soil becomes water-repellent, increases hydraulic conductivity and enhances the risk of groundwater pollution. The concentration of greywater needs to be checked before irrigation and if needed, it should be diluted to avoid any risk of soil water-repellence.

Estimation of groundwater recharge rates using soil-water isotope profiles: a case study of two contrasting dune types on Langeoog Island, Germany

The creation of artificial dunes for coastal protection may have important consequences for freshwater lenses in coastal aquifers. The objective of this study was to compare the recharge processes below such a young dune with scant vegetation to an older dune covered by grass and herbaceous vegetation. To this aim, soil and water samples were collected from the unsaturated zone at two sites on Langeoog Island in northern Germany, and the soil water was analysed for stable water isotopes and chloride. Recharge rates were calculated by using a new version of HYDRUS-1D, which was modified to simulate isotope fractionation during evaporation. Both the model outcomes and the data highlight the importance of fractionation, which is slightly more pronounced at the older, more vegetated dune. At the newly constructed dune, vegetation dieback seemingly reduces the importance of transpiration during summer. Recharge occurs year-round, albeit predominantly during the winter months. Calculated recharge rates are consistent with lysimeter measurements, but are significantly higher than previously reported rates based on groundwater age data, which is primarily attributed to the absence of dune shrub at the sites investigated here. More data are needed to establish the importance of soil-water repellency and overland flow. Based on the results, it is proposed that repeated isotope sampling can yield important insights into the dynamics of recharge processes, including their response to climate change.

Does biochar affect soil wettability and flow pattern?

Despite the known benefits of biochar application to soils, little is known about its effect on soil wettability and the consequences on soil water movement across the soil profile. Focusing on the latter, three types of commercial biochar derived from wheat, corn, and rice straw produced under low temperature (350–450 ℃) were mixed with a wettable sandy soil at rates of 0%, 2%, 5%, and 10% w/w. Soil water repellency (SWR) of the biochars and biochar–soil mixtures was determined by water drop penetration time (WDPT) test and sessile-drop contact angle (CA) measurement. The WDPT results (< 5 s) showed complete wettability for the biochar–soil mixtures, whereas CA results indicated some water repellency. The mean initial CA of the three biochars varied between 105.3° and 113.9°, with ∼ 30° for the pure sand, and between 56.8° and 75.7° for the biochar–soil mixtures. SWR increased with biochar-application rate, whereas biochar particle size (< 1 mm and > 1 mm) had no significant effects on SWR. A 2-D flow chamber experiment with point source water application at the surface was used to continuously monitor the flow pattern and soil water content (SWC) distribution across the soil profile during infiltration and redistribution periods. Biochar–soil mixtures (2% and 5% w/w) with the three biochar types were studied. Flow chamber results showed substantial differences in plumes shape and internal SWC distribution in the biochar–soil mixtures compared to the untreated sand during the wetting and drainage. The plumes' shape and nonmonotonic spatial SWC distribution suggested unstable flow in the biochar–soil mixtures. The internal fingers developed in the biochar treated sand indicate that SWR induced by biochar addition seemed to be physically induced via the blending of the biochar and soil particles, rather than chemically induced, via coating of the soil particles with amphiphilic molecules. Under field conditions, the primary and inner finger-like plumes may eventually form preferential flow paths that will affect the spatial distribution of water and fertilizer in soil profiles and their availability to plant roots.

Post-fire temporal trends in soil properties and revegetation: Insights from different wildfire severities in the Hengduan Mountains, Southwestern China

The Hengduan Mountains are frequently disturbed by high-risk wildfires. However, insufficient information is available on post-fire temporal trends in soil properties and revegetation of areas with various fire severities. To address this gap, two adjacent wildfires that occurred in 2010 and 2018 were selected. The study areas were divided into low (LS), moderate (MS), high (HS) severity fire burned areas and unburned (as control, UB) areas. Temporal trends in soil properties (0–5 cm): soil water repellency, saturated hydraulic conductivity, bulk density, soil moisture content (SMC), and soil organic matter content (SOM) were measured by in-situ and laboratory tests at 1, 7, 19 months (1MAF, 7MAF, 19MAF), and 10 years after the fires (10YAF), respectively. Temporal trends in post-fire revegetation were evaluated via on-ground surveys and remote sensing images. The statistical analysis results showed that the HS and MS fires significantly altered the soil properties and resulted in a remarkable decrease in vegetation coverage, leading to substantial bare soil 1MAF. The soil properties of the HS and MS fire burned areas had not recovered to normal due to the significantly decreased SOM and SMC 7MAF and 19MAF, and they had recovered to the pre-fire level 10YAF. The first three years following the fires were a crucial period for revegetation, during which the shrubs and bryophytes rapidly recovered, causing a rapid increase in vegetation coverage, and a corresponding sharp decrease in the coverage of bare soil. The incompletely recovered pines of the HS and MS areas provisionally resulted in a degeneration of the forest stand within a decade after the fire. We conclude that the fire-affected soil properties can return to normal within 10 years, and complete recovery of the vegetation requires a longer period than a decade. These results may provide scientific guidance for post-fire management of the burned area.

Expansion by native shrub Euryops floribundus affects soil and vegetation in Machubeni communal land, South Africa

The socio-economic and environmental effects of invasive alien plants have been well documented; however, little is known about expansion by expansive native species. In this study, the effects of expansion by the expansive native shrub species Euryops floribundus on soil and vegetation were examined in Machubeni communal land in the Eastern Cape Province of South Africa. Using a comparative approach, topsoil samples were collected in a 1 m2 quadrat from expanded and non-expanded sites and were quantified for concentrations of soil macronutrients (total N, C, and P), pH, exchangeable cations (K, Ca, Mg, and Na), soil moisture, penetration, and soil water repellency. Detailed vegetation surveys were conducted on similar quadrats. Expansion by the expansive native shrub E. floribundus resulted in increased soil pH, total C, K, Ca, and soil moisture, but did not affect other soil properties such as soil water repellency. Euryops floribundus expansion had no effect on species diversity, although it reduced abundance and cover of graminoids. Principal component analysis showed that E. floribundus co-occurs with some species such as Centella asiatica, Cynadon dactylon, and Brachiaria serrata. Litter cover was significantly higher in the expanded than the non-expanded sites. The study suggests that expansion by E. floribundus might alter some soil properties and displace some plant species. The study recommends that the expansive shrub E. floribundus be removed to reduce its expansion and subsequent impact on soil and vegetation.

Unveiling soil temperature reached during a wildfire event using ex-post chemical and hydraulic soil analysis

Wildfires affect different physical, chemical, and hydraulic soil properties, and the magnitude of their effects varies depending on intrinsic soil properties and wildfire characteristics. As a result of climate change, the frequency and intensity of wildfires have increased, and understanding their impact and predicting the temperature to which soils were exposed in previous events is becoming increasingly critical. Hence, the objectives of this study were to develop a soil-heating laboratory procedure to (a) identify changes in soil properties at different temperatures and (b) to infer the temperature ranges to which heated soils have been exposed. Saturated (Ks) and unsaturated (Ku) hydraulic conductivity, pH, electrical conductivity (EC), wet aggregate stability (WAS), soil water repellency index (RIm), and soil organic matter content (SOM) were measured in six laboratory heated (LH) soils at 300, 500, 700, and 900 °C for 2 h. Bulk density (BD) and soil texture were measured in unheated (UH) and wildfire-unheated (WH) samples. UH samples were used as baselines to quantify changes in soil properties, and WH and LH samples were compared to determine the temperatures to which WH soils were exposed. The results show that in the studied temperature range, WAS exhibited a U-shaped trend, opposite to that of pH and EC. Ks and Ku (negative tension of −3 cm) tend to increase with temperature, reaching a maximum of 1.27·10–4 and 5.62·10–5 (m/s) at 900 °C, respectively. RIm was highly dependent on texture; loam soils had an average minimum and maximum of 1.84 and 2.73, at 900 and 300 °C, respectively, while sandy loam soils had an average minimum and maximum of 1.29 and 2.08 at 300 and 900 °C, respectively. Finally, the parameters that provided laboratory variation and a temperature range consistent with the results observed in naturally heated soils were WAS, RIm, pH, and EC.

Impact of Duration of Land Abandonment on Infiltration and Surface Runoff in Acidic Sandy Soil

Sandy soils are less fertile and, therefore, often abandoned in the Central European region. Land abandonment can cause the recovery of ecosystems by the replacement of crop species by vegetation that disperses from surrounding habitats and will be subsequently established (secondary succession). The objective of this study was to find the impact of secondary succession during more than 30 years of lasting abandonment of agricultural fields with acidic sandy soil on infiltration and surface runoff. The method of space-for-time substitution was used so that the fields abandoned at different times were treated as a homogeneous chronosequence. The impact of abandonment on infiltration and surface runoff was characterized by the changes in soil organic carbon content, pH, water and ethanol sorptivity, hydraulic conductivity, water drop penetration time, repellency index, time to runoff, and surface runoff coefficient. It was found that the abandoned soils previously subjected to agriculture showed a decrease in pH, a significant increase in soil water repellency, and a decrease in infiltration, which can lead to serious problems in terms of surface runoff and soil erosion. The pH(H2O) and pH(KCl) decreased monotonously and ethanol sorptivity did not change significantly during abandonment. The time to runoff did not change significantly between 10 and 30 years of abandonment, and it was not measured after 1 year of abandonment because no runoff occurred. The dependence of the other characteristics on the duration of field abandonment was not unambiguous. Water sorptivity and hydraulic conductivity showed a decrease between 1 and 10 years followed by a slight increase between 10 and 30 years of abandonment. On the other hand, soil organic carbon content, water drop penetration time, repellency index, and surface runoff coefficient showed an increase between 1 and 10 years followed by a slight decrease between 10 and 30 years of abandonment. To prevent soil water repellency and its consequences in sandy soils, an adequately high soil water content should be maintained, and mixed forest afforestation should be preferred to pine afforestation. This is extremely important in the context of climate change and the increasing frequency of prolonged dry periods.

Soil water repellence increased early wheat growth and nutrient uptake

PurposeSoil water repellence causes uneven soil wetting which can constrain dryland crop and pasture establishment and yield. The same processes are likely to affect nutrient availability from soil and fertiliser, but the effects of repellence on crop growth and nutrition per se have seldom been reported. Here, we investigated early wheat (Triticum aestivum cv. Mace) growth and nutrient uptake responses to repellence.MethodsWheat was furrow-sown in severely repellent sandy loam soil (with a wettable furrow base to allow for germination) or completely wettable soil, under uniform plant density and variable topsoil thickness (20 or 100 mm) and fertiliser band placement (below or away from the seed). Tiller number, shoot dry matter, shoot N concentration, total nutrient uptake, and root length density (RLD) were determined.ResultsContrary to expectations, repellence significantly increased tiller number (by up to 2 tillers per plant), shoot dry matter (by 82%), shoot N concentration (by 0.3% N), and total nutrient uptake (by 87%) at 51 days after sowing, regardless of topsoil thickness and fertiliser placement. In the furrow, RLD of repellent treatments was also nearly double that in wettable treatments when fertiliser was banded below the seed. Results suggest that preferential soil wetting of the furrow in repellent treatments favoured plant nutrient uptake under regular but low water supply.ConclusionWe conclude that for water-repellent soils with limited water supply, water harvesting techniques such as furrow sowing and banding wetting agents could boost water and nutrient uptake and early crop growth.

Hydrophobicity of soils affected by fires: An assessment using molecular markers from ultra-high resolution mass spectrometry

Soil water repellency (SWR) is a physical property due to a complex interaction of factors (e.g., fire, soil organic matter, soil texture) that reduces the soil water infiltration capacity. Traditionally, SWR is attributed to the accumulation and redistribution of hydrophobic compounds within soil profile. To obtain further insight into chemical compounds, which could be associated with SWR, a study was done on coarse (1–2 mm) and fine (< 0.05 mm) granulometric fractions of burned and unburned sandy soils under two Mediterranean vegetation biomes from Doñana National Park (Spain). The water drop penetration time (WDPT) test was used to assess the SWR. The molecular composition of extracted humic substances from the soil organic matter (SOM) was determined by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR/MS). Partial least squares (PLS) regressions showed that the SWR can be predicted (P = 0.006) solely based on the abundances of approximately 1200 common compounds determined by FT-ICR/MS. This model confirmed the significant correlation between a specific SOM molecular composition and the SWR. The comparative analysis revealed that the SWR in the burned samples was significantly (P < 0.05) related to the abundance of aromatic and condensed compounds, while in the unburned samples there was a significant influence of aromatic hydrocarbons and lignin compounds. In the fine fraction, lipid compounds were significantly associated with the SWR. Contrastingly, the coarse fraction did not show any correlation. Alternatively, soils with a high SWR were significantly related to the presence of lipids and lignin. This analysis showed that combining FT-ICR/MS molecular characterizations with statistical treatments is a powerful approach for exploratory analysis suggesting that the structural features associated with SWR in the studied soils are different depending on the types of vegetation or the soil physical fractions with different particle size.

Effect of long-term cropping systems on soil hydrophobicity of a clay loam soil under dryland conditions in southern Alberta

The objective was to quantify the effect of crop rotations, crop type, life cycle, nitrogen fertilizer, manure application, and fallow on soil hydrophobicity (SH). The SH was measured for a long-term (16 yr) dryland field experiment on a Dark Brown clay loam soil in southern Alberta, Canada. Mean SH was significantly (P ≤ 0.05) greater in rotations with grass, perennial crops, manure application, and continuous cropping; whereas cereal–legume rotations and N fertilizer effects were undetectable. A strong, positive correlation occurred between SH and soil organic carbon concentration (r = 0.73). Soil water repellency should be measured on these plots using water-based methods.

Event-based quickflow simulation with OpenLISEM in a burned Mediterranean forest catchment

Recently burnt areas typically reveal strong to extreme hydrological responses, as a consequence of loss of protective soil cover and heating-induced changes in topsoil properties. Soil water repellency (SWR) has frequently been referred to as one of the explanatory variables for fire-enhanced surface runoff generation but this has been poorly demonstrated, especially at the catchment scale. This study employs a process-based modelling approach to better understand the relevance of SWR in the hydrological response of a small, entirely burnt catchment in central Portugal, in particular by comparing hydrological events under contrasting initial conditions of dry vs wet soils. The OpenLISEM model was applied to a selection of 16 major rainfall runoff events that occurred during the first 2 post-fire years. The automatic calibration procedure resulted in good model performance, but it worsened for validation events. Furthermore, uncertainty analysis revealed an elevated sensitivity of OpenLISEM to event-specific conditions, especially for predicting the events’ total and peak flows. Also, predicted spatial patterns in runoff poorly agreed with the runoff observed in microplots. Model performance improved when events were separated by dry and wet initial moisture conditions, particularly for wet conditions, suggesting the role of variables other than initial soil moisture.

Soil Water Repellency and Micro-Aggregate Fractions in Response to Crop Growth Periods in a Purple Soil Sloping Cropland Subjecting to Long-Term Fertilization Management

Soil Water Repellency and Micro-Aggregate Fractions in Response to Crop Growth Periods in a Purple Soil Sloping Cropland Subjecting to Long-Term Fertilization Management

Effect of the Litter Layer on in Situ Water Repellency and Moisture Conditions of Surface Mineral Soil Under a Humid-Temperate Forest

Effect of the Litter Layer on in Situ Water Repellency and Moisture Conditions of Surface Mineral Soil Under a Humid-Temperate Forest

Soil Water Repellency Increases with Land-Use Changes from Native Pastures to Forest Plantations

Soil Water Repellency Increases with Land-Use Changes from Native Pastures to Forest Plantations

Alterations in Aggregate Characteristics of Thermally Heated Water-Repellent Soil Aggregates Under Laboratory Conditions

Alterations in Aggregate Characteristics of Thermally Heated Water-Repellent Soil Aggregates Under Laboratory Conditions

Molecular Characterization of Burned Organic Matter at Different Soil Depths and Its Relationship with Soil Water Repellency: A Preliminary Result

Soil water repellency (hydrophobicity) prevents water from wetting or infiltrating soils, triggering changes in the ecosystems. This physical property is directly correlated to the erodibility grade of a soil. Wildfire events may develop, enhance, or destroy soil hydrophobicity, modifying the erodibility grade of a soil and increasing the loss of its most reactive layer (organic matter). To assess the main organic family of compounds (biomarkers) surrogates to fire-induced water repellency, a study was carried out on a fire-affected soil under eucalyptus canopy at two depths (0–2 and 2–5 cm) from Portugal. The potential soil water repellency was measured using the water drop penetration time (WDPT) test. The molecular characterization of hydrophobic biomarkers was carried out using analytical pyrolysis (Py-GC/MS) in combination with multivariate statistical analysis (PCA, MLR). The upper burned soil layer (0–2 cm) displayed a significant contribution of fresh biomass (lignin and polysaccharides), while the deepest (2–5 cm) one showed more humified organic matter (lipids). The soil hydrophobicity was directly correlated to non-polar organic compounds, such as lipids and polycyclic aromatic hydrocarbons (PAHs), and inversely to unspecific aromatic compounds. The combination of mass spectrometry techniques and chemometric analysis allowed obtaining a preliminary forecast model of hydrophobicity degree in fire-affected soil samples under eucalyptus canopy. This analytical approach opens the door to developing more sensitive mathematical models using molecular organic compounds to predict the alteration of hydrophobicity and other soil physical properties induced by fires.

Evolution of meniscus structures in hydrophobic granular systems

Hydrophobic soils, which form naturally in arid regions or after forest fires, can be problematic for land managers and engineers as they are often associated with impeded or preferential flow paths, increased surface runoff and soil erosion. However, the reduced rainwater infiltration capacity of water-repellent soils can also result in the improvement of the stability of slopes, landfills and capillary barrier cover systems, amongst others. Understanding the hydraulic conditions within these materials is critical if issues of stability and seepage are to become tractable.Traditional understanding of unsaturated hydrophobic soils suggests that convex water menisci, and so positive water pressures, should form between soil particles. However, the limited experimental results presented in the literature do not support this theory. In this work, the effect of particle shape on the formation and evolution of water meniscus structures is investigated at the macro (multiple particles) and particle scales, contrasting meniscus behaviours between spherical glass beads and angular sand grains. The spreading of a sessile drop in the macro-scale is examined and found that the angularity of the sand grains has a significant effect on the apparent contact angle of a sessile drop when deposited on a mono-layer of particles. At the particle scale, Environmental Scanning Electron Microscopy was used to investigate the formation and evolution of capillary bridges and the water retention hysteresis during two wetting and drying cycles. Again, it is shown that the shape and surface roughness of the particles are controlling factors in both the formation and evolution of liquid bridges and that stable convex and concave menisci can co-exist simultaneously between hydrophobic particle surfaces. Additionally, it was found that the hydrophobic nature of the particles allowed menisci to form across much larger separation distances than could be achieved through film coalescence between hydrophilic surfaces, with possible consequences for infiltration and imbibition modelling and, more broadly, manufacturing processes relying on hydrophobic substrates. Lastly, the hydrophobic soils qualitatively exhibited overall much less hysteresis of the water retention curve than their hydrophilic counterparts.

Surface runoff and losses of phosphorus from hydrophobic pastoral soils

The impact of soil water repellency (SWR) on soil phosphorus (P) mobility in surface water runoff remains contentious. Although SWR may cause a significant increase in surface runoff, especially in post-summer rainfall events, whether it contributes to background phosphorus losses remains unclear. Surface runoff and P concentrations in runoff were measured on hilly Allophanic pastoral soils with different water repellency levels using seven runoff collectors. Phosphorus fertilizer was broadcasted at 18 kg P ha−1 in the summer over dry soils. Runoff volumes and P concentrations were measured after each natural rain event prompting surface runoff. The highest runoff/rainfall ratios were observed at the early rainfall events following the dry summer and then decreased significantly by the end of autumn and winter. The post-summer surface runoff correlation with SWR had an R2 of 0.46, and hydrophobic soils had significantly higher runoff ratios than wettable soils. Measurements of the dissolved reactive phosphorus (DRP) and total phosphorus (TP) in the surface runoff showed decreasing exponential trends, with the highest values recorded in the first runoff event following P fertilizer application, where over 90% of losses occurred (incidental losses). After the incidental loss phase, DRP concentrations were related to surface runoff ratio, soil P extractability by water, and SWR. Our data point to non-incidental TP loads being related to SWR (R2 = 0.53). The present results will improve the understanding of the SWR effect on surface runoff and will reconcile the controversy regarding its contribution to non-incidental P losses.

Vertical distribution of soil water repellency in ortsteinic soils in relation to land use

Land use, soil organic carbon content and bulk density are important factors influencing the occurrence of soil water repellency (SWR) and water flow through the soil profile. This study elucidated the relations between the repellency index (RI) and contents of soil organic carbon (SOC), organic-complexed aluminium (Alp) and iron (Fep), pH, specific surface area (SSA) and bulk density in the ortstein horizon and the overlying and underlying horizons in two podzolic soils under grassland and forest. The soil under grassland was originally used as a cropland. The RI was quantified from the ethanol/water sorptivity ratio. The results showed that the RI in the ortstein horizon (20.6–27.3) in the air-dried state in both soils was many times greater than in the overlying (7.2–19.0) and underlying (6.1–11.5) horizons, whereas in moist conditions (from soil water content at sampling and air-dried state), all horizons were not repellent. The RI in the air-dried soil in the overlying horizon was higher under grassland than forest, whereas the inverse was true in both the ortstein and underlying horizons. SOC, organic-complexed Alp and Fep contents, and SSA were the highest in the ortstein horizons. The pH value increased from 5.3 in the overlying horizon to 6.0 in the underlying horizon in the grassland soil. The corresponding values in the forest soil were 4.2 and 5.0. The RI values in the dry condition were significantly correlated with Alp (R2 = 0.976), Fep (R2 = 0.798), SSA (R2 = 0.724), and SOC (R2 = 0.638). The study provides new information about the vertical distribution of soil water repellency in ortsteinic soils depending on the soil water status and the type of land use. The potential mechanisms of the distribution of SWR are discussed.