The properties, genesis and significance of a man-made iron pan podzol near Castletownbere, Ireland

Beneath a layer of artificially deposited peat debris, an eluvial E horizon and thin iron pan (Bsm) has developed in the upper part of the A_p horizon of a brown podzolic soil (Haplorthod) near Castletownbere, Ireland. The thickness of the E horizon and the depth of the pan are directly related to the thickness of the layer of peat debris. The original soil (Haplorthod) was strongly podzolized with a significant accumulation of organic carbon, iron and aluminium in the spodic Bs. The iron pan of the upper sequum, on the other hand, is rich in iron. This iron pan seems to have developed as a result of reduction of iron in the E horizon, transport of divalent Fe²⁺ cations and precipitation in the Bsm as Fe₂(OH)₃, after the peat layer was deposited. We conclude that podzolization and iron pan development were fundamentally different processes. The study suggests a fundamental change in the iron pan-blanket peat development sequence previously postulated by palaeoenvironmentalists in Ireland.     

Soil hydraulic and physico-chemical properties of Ultisols and Inceptisols in south-eastern Nigeria

Understanding soil water dynamics and storage is important to avoid crop failure on highly weathered, porous and leached soils. The aim of the study was to relate soil moisture characteristics to particle-size distributions and chemical properties. On average, Atterberg limits were below 25% in the A-horizon and not more than26.56% in the B-horizon, whereas soil bulk density was between 1.27 and 1.66Mgm^?3. The saturated hydraulic conductivity (K_sat) was generally between 0.20 and 5.43 cm h^?1 in the top soil and <1.31 cm h^?1 in the subsoil. The higher K_sat values for the A-horizons were attributed to the influence soil microorganisms operating more in that horizon. The amount of water retained at field capacity or at permanent wilting point was greater in the B-horizons than in the A-horizons, suggesting that clay accumulation in the B-horizon and evapotranspiration effects in the A-horizon may have influenced water retention in the soils. Soil moisture parameters were positively related to clay content, silt content, exchangeable Mg²⁺, Fe₂O₃ and Al₂O₃, and negatively related to sand content, SiO₂, sodium absorption ratio, exchangeable sodium percentage and bulk density. The low clay content may explain why drainage was so rapid in the soils.     

Change of dry bulk density and Ksat after incubation of a soil in the presence of organic amendments

Abstract

Kamouraska Ap horizon samples were incubated in the presence of organic amendments, peat moss, straw, compost and green manure, applied at a rate equivalent to 7.5 t of carbon/ha. Water was added to reach 80% of field capacity. The soil‐amendement mixtures were incubated at 37°C for periods of 4, 8, 16, 32 or 64 weeks. Settling tests were performed using a jolting volumeter. Minimum dry bulk density (mDBD), saturated hydraulic conductivity (K_sat) and water content at field capacity were determined. For the unamended soil, mDBD corresponded to 1.1 g.cm^‐3 and K_{sat max} to 265 cm/h. After incubation, mDBD varied from 1.02 to 1.12 g.cm^‐3 and K_{sat max} values were generally below 150 cm/h. The results were discussed in relation to the decomposition of the organic amendments and the formation of stable aggregates.     

Linking fragipans,perched water tables,and catchment-scale hydrological processes

Soils with very slowly permeable fragipans and fragipan-like argillic horizons are extensive throughout the Palouse Region of northern Idaho and eastern Washington, USA. These soils develop seasonal perched water tables (PWTs) under the xeric moisture regime of the region. The objective of this study was to utilize a hydropedology approach to examine the linkages between fragipans, PWTs, and catchment-scale hydrological processes such as soil water storage, runoff, and lateral throughflow. A 1.7-ha catchment dominated by Fragixeralfs (Fragic Luvisols) was instrumented with 135 automated shallow wells to monitor PWTs. Soil water content was measured with water content reflectometry probes, and catchment outflow was measured with a flume. A 35 m × 18 m plot was isolated hydrologically from the surrounding hillslope using tile drains and plastic sheeting to measure perched water outflow. Results show that during the wet winter and spring months, the transition from unsaturated to saturated conditions is accompanied by changes in volumetric water storage of only 4–5%. PWT levels are at the surface of ∼ 26–45% of the catchment soils during periods of high rainfall and snowmelt, thereby generating saturation-excess surface runoff from hillslopes. Observed solute movement via subsurface flow is very rapid and ranges between 2.9 and 18.7 m d^− 1 when PWTs are maintained in more-permeable Ap and Bw horizons. Subsurface lateral flow accounts for as much as 90% of the incident precipitation and snowmelt during early spring. Data indicate that the relatively shallow depth to the fragipans and high K_sat in surface soil layers combine to create a very flashy hydrological system characterized by considerable temporal and spatial variation in patterns of saturation-excess runoff.     

Saturated hydraulic conductivity of soils in the Southern Piedmont of Georgia,USA: Field evaluation and relation to horizon and landscape properties

Saturated hydraulic conductivity (K_s) is one of the soil properties used most often to predict soil behavior and suitability for a variety of uses. Because of the difficulty in K_s measurement and its variability with depth and across the landscape, K_s is commonly predicted from other more easily evaluated properties including texture, clay mineralogy, bulk density, pedogenic structure and cementation. Of these, texture and pedogenic structure are most commonly used to estimate K_s, but the reliability of these estimates has not been evaluated for common soils in the Southern Piedmont of Georgia. Thus, the objectives of this study were to evaluate K_s for major horizons in soils and landscapes in the Georgia Piedmont and to relate K_s to morphological properties of these horizons. Ten sites across the region were selected, and 21 pedons arranged in three transects were described from auger holes and pits. For each pedon, K_s was measured in upper Bt horizons, at 140 cm below the surface (Bt, BC, or C horizon), and at a depth intermediate between the shallow and deep measurements (Bt, BC, or C horizon) with a constant head permeameter. The K_s of individual horizons ranged from 1 × 10^− 8 to 2 × 10^− 5 m s^− 1. At six of 10 sites evaluated, clayey upper Bt horizons had higher K_s than deeper horizons with less clay. This difference was attributed to weaker structure in the deeper BC horizons. Structural differences did not explain all variation in K_s with depth, however. Other soil and landscape properties including parent material composition, colluvium on lower slope positions, C horizon cementation, and depth of soil development also affected K_s of horizons in these soils and should be used to better estimate K_s.     

Calculation of hydraulic conductivities of horizons in some major soils in Wisconsin

Hydraulic conductivity between saturation and a tension of 100 cm water was calculated with moisture-retention data for nine soil horizons and compared with results from in situ measurements with the crust test. Agreement was good for sandy, apedal soil horizons with simple packing voids but only if matching factors were used. Results were unreliable in clayey, pedal soil horizons in which a few relatively large planar and tubular pores determine K in the measured tension range, whereas the greatest fraction of total porosity is composed of fine pores inside peds that hardly contribute to flow. Varying the number of pore classes (n) and the water-filled porosity at saturation made no significant difference in the calculations for the apedal soils, but drastically changed the shape of the calculated curves for the pedal soils. Matching factors based on K_sat measurement had to be used for all studied soil horizons, indicating that Marshall's pore-interaction model never predicted K_sat accurately.     

Evaluating the Impact of Combined Application of Biochar and Compost on Hydro-physical Properties of Loamy Sand Soil

ABSTRACT

Biochar, compost and their combination are important organic amendment materials for improving the hydro-physical properties of sandy soils. Series of soil columns experiments were conducted for investigating the application effects of date palm biochar and compost on evaporation, moisture distribution, infiltration, sorptivity (Sp), saturated hydraulic conductivity (K_sat) and water holding capacity (WHC) at application rates of 1%, 2%, 3% and 4% (10, 20, 30 and 40 g kg^?1). The columns were filled manually with air-dried soil with 35 cm depth and the thickness of surface amended layer was 10 cm (T10) and 20 cm (T20) from soil surface at bulk density of 1400 kg m^?3. The results showed that the behavior of soil moisture distribution was influenced by application of biochar, compost and biochar-compost mixture. Moreover, in the amended layer T10, applying biochar at rate of 1%, 2%, 3% and 4% reduced significantly cumulative evaporation by 5.8%, 10.8%, 12.8% and 16.1%, respectively. Meanwhile, the reduction for the biochar-compost mixture at application rates of 1%, 2%, 3% and 4% was 10%, 12.2%, 14.5% and 20%, respectively. In layer T20, applying biochar at rate of 1%, 2%, 3% and 4% reduced cumulative evaporation by 10.24%, 13.0%, 18.3% and 21.5% but this reduction amounted to 18.2%, 21%, 23% and 24% for the biochar-compost mixture, respectively. It was generally observed that the highest application rate (4%) for applied amendments was the most effective impact on Sp, K_sat and WHC compared with other rates.     

A reassessment of podzol formation processes

Translocated (oxalate-soluble) Al and Fe are present predominantly in inorganic forms in the B₂ horizons of the five pcdzol profiles examined: A1 as imogolite and proto-imogolite allophanes, and Fe as a separate oxide phase. Below the top few cm of the B₂ horizon, over 75 per cent of the extractable (acid-plus alkali-soluble) organic matter is present as Al-fulvates, largely sorbed on allophanic material. The Bh horizons of the Iron Humus Podzol and Iron Podzol intergrades are distinguished by very high levels of organically bound Fe (soluble in EDTA solution), five to ten times more than in immediately adjacent A₂ or B₂ horizons, and also by larger humic acid contents than in comparable B₂, levels in typical Iron Podzols. Inorganic forms of translocated Al and Fe are probably absent from two of the three Bh horizons examined, and also from the Bhg horizon overlying the thin iron pan in the Peaty Podzol. The organic matter in this Bhg horizon is saturated with Al rather than Fe. Chemical and physical processes which could lead to evolution of a profile along the genetic sequence, Iron Podzol, Iron Humus Podzol, Peaty Podzol, are postulated. During the formation of an Iron Podzol, positively charged inorganic sols carry aluminium, silicon and iron from the A₂ and deposit them in the B₂ horizon; subsequently, with the development of an H layer, colloidal humus migrates through the A₂ and precipitates on the positive colloids at the top of the B₂ horizon to form a Bh horizon, in which remobilized ferric species are trapped by the organic matter. In higher rainfall areas, occasional waterlogging above the oxide-impregnated B₂ leads to a thin iron pan, separating permanently oxidizing conditions below from seasonally waterlogged and reducing conditions above.     

Effects of Cow Dung Biochar Amendment on Adsorption and Leaching of Nutrient from an Acid Yellow Soil Irrigated with Biogas Slurry

Knowledge of the saturated hydraulic conductivity (K _sat) of porous filters used in water treatment technologies is important for optimizing the retention of nutrients and pollutants. This parameter determines the hydraulic capacity, which together with the chemical properties of the filter media, affects the treatment performance of the filter system. However, measuring K _sat is time consuming and expensive. This study developed a novel transfer function to predict K _sat of coarse porous media from easily measured parameters. The hydro-physical parameters determined were K _sat, grain size distribution, bulk density, uniformity coefficient, particle density, and porosity of 46 porous media fractions. The fractions ranged in grain size from 0.5 to 20 mm and were obtained from seven commercial available coarse filter materials. A backward stepwise regression analysis was performed between K _sat and 10 variables obtained from the grain size distribution and bulk density. The optimal model for predicting K _sat contained two parameters, D₂₀ and D₅₀, which describe respectively the particle diameters, where 20 and 50 % of all particles are finer by weight. The predicted K _sat values were in good agreement with the measured values (R ²?=?0.91). The transfer function can find potential usage in relation to dimensioning of permeable agricultural drainage filters or subsurface-flow constructed wetlands. The predicted values of K _sat can also be used as input to numerical models that simulate filter treatment performance.     

Environmental Behaviour of Metolachlor and Diuron in a Tropical Soil in the Central Region of Brazil

The environmental behaviour of metolachlor and diuron was studied in the Central-western region of Brazil, by means of a field study where six experimental plots were installed. The soil was classified as a Latosol, and the soil horizons were characterized. Sorption of metolachlor and diuron was evaluated in laboratory batch experiments. Metolachlor and diuron were applied to the experimental plots on uncultivated soil in October 2003. From this date to March 2004, the following processes were studied: leaching, runoff and dissipation in top soil. K _oc of metolachlor varied from 179 to 264 mL g^?1 in the soil horizons. K _oc of diuron in the Ap horizon was 917 mL g^?1, decreasing significantly in the deeper horizons. Field dissipation half-lives of metolachlor and diuron were 18 and 15 days, respectively. In percolated water, metolachlor was detected in concentrations ranging from 0.02 to 2.84 μg L^?1. In runoff water and sediment, metolachlor was detected in decreasing concentrations throughout the period of study. Losses of 0.02% and 0.54% of the applied amount by leaching and runoff, respectively, were observed confirming the high mobility of this herbicide in the environment. In percolated water, diuron was detected with low frequency but in relatively high concentrations (up to 6.29 μg L^?1). In runoff water and soil, diuron was detected in decreasing concentrations until 70 days after application, totalizing 13.9% during the whole sampling period. These results show the importance of practices to reduce runoff avoiding surface water contamination by these pesticides, particularly diuron.     

Soil formation as affected by pit and mound microrelief in Massachusetts,USA

The influence of pit and mound microrelief on soil formation was investigated by detailed observations of a cross-section through a pit and mound in a hemlock (Tsuga canadensis) forest in western Massachusetts, in the northeastern United States.Soil forming processes during the last 140 years have led to taxonomically different soils due to this microrelief. Part of the annual precipitation apparently does not infiltrate into the mound but moves laterally through organic surface layers into the pits. This resulted in more intensified translocation of Fe, Al and organic matter in the pit profile. The ensuing soil met the spodic horizon criteria as defined in Soil Taxonomy and was classified as a Lithic Haplorthod. Neighboring, undisturbed soils had pronounced E, Bhs, and Bs horizons, the latter qualifying as spodic horizons on the basis of chemical criteria. These soils, however, did not meet the minimum depth requirement of 12.5 cm for spodic horizons and therefore, were classified as Typic Dystrochrepts. The soil developed in the mound showed less horizon development and was classified as a Typic Dystrochrept.Taxonomic changes resulting from the pit and mound microrelief affected less than 6% of the area and appeared not to have a significant impact on the purity of map delineations.     

Strengths of a densipan,humus-pan and clay-pan in a Spodosol developed under kauri (Agathis australis) and the implications for soil classification

Three hard layers have formed in a Spodosol developed on aeolian coastal sands under the influence of litter from kauri (Agathis australis). A densipan in the albic horizon and a humus-pan in the spodic horizon slaked in water whereas a clay-pan in a buried soil only softened in 1 M HCl. Blocks sawn from these three pans showed a maximum of unconfined compressive strength in the humus-pan.Specimens made from remoulded pan materials with minimum compaction developed only a proportion of the original strength. Greater compaction enhanced the strength of all three materials. Raising the pH during remoulding caused a marked increase in strength, but above pH 10.5 all the pan materials lost strength when silicate was solubilised from surfaces of clay and quartz particles.Scanning electron micrographs showed that the densipan was a close-fit configuration of sand- and silt-sized quartz particles that attained a high density without cementation of particles. In the humus-pan organic matter bridged across a third of the surfaces of the quartz particles and prevented a close-fit configuration. The clay-pan below the spodic horizon had all its particles thickly coated with clay and humus and these were aggregated into an open-fit arrangement of lower density.According to Soil Taxonomy procedures, the Te Kopuru sand lies within the Aquod sub-group of Spodosols. In the absence of a non-slaking duripan it was the presence of a fragipan below the spodic horizon that directed the soil into being a Fragiaquod. It is the densipan in the albic horizon above the spodic horizon, however, that controls plant roots and cannot be ignored in soil classification. We suggest that a new great group, Densiaquod, be recognized for these soils.     

EXTRACTABLE SESQUIOXIDES IN SIX MEDITERRANEAN SOILS DEVELOPED ON BASALT AND SCORIA

Iron, Al, and Mn were extracted by oxalate and dithionite from two Brown Mediterranean Soils, two Red Mediterranean Soils, one Vertisol and one Gley soil, all derived from basalt or scoria in the sub-humid and humid Mediterranean regions of the Golan Heights. Ratios of oxalate: dithionite extracted iron (Fe_o:Fe_d) were low in all soils, indicating that the predominant form of free iron is crystalline. Fe_o accumulates in the argillic B horizons of the Mediterranean soils, while Fe_d accumulates in the surface horizons. A large part of the free iron oxide in the surface horizons of Mediterranean soils is associated with non-clay fractions. While manganese behaves in a manner somewhat similar to that of iron, no definite trends could be discerned in the vertical distribution of free aluminium. In the Vertisol, Fe_o and Mn_o accumulate in the subsoil. Fe_d and Mn_d increase slightly with soil depth. In the Gley soil, amorphous iron accumulates in the surface horizon, total free iron in the bottom horizon. Both amorphous and total free Mn had been depleted from the upper horizons of the Gley soil.     

Assessment of Eco-Physiological Performance of Quercus ilex L. Leaves in Urban Area by an Integrated Approach

Bioretention cells, also known as raingardens, are increasingly being constructed as a means to collect, infiltrate, and treat stormwater runoff. There are concerns, however, about how stormwater management practices might function in terms of infiltration and pollutant removal as they age. Saturated hydraulic conductivity (K _sat) values were obtained for eight cells in 2006 and again for three of those cells in 2010 using an infiltrometer. A strong positive correlation of mean K _sat with service time was observed (slope = 10.2?±?2.4 cm/h per year, R ² = 0.67). Results from metals analyses of bioretention media cores collected from six bioretention cells showed the expected trend of Cu and Zn enrichment at the surface while Cd was detected only in one out of 72 media samples analyzed. Sorption isotherms from batch testing of field media samples (T = 22.5 °C, pH = 7.2) were used to estimate metal sorption capacities based on representative stormwater Cd and Zn concentrations. Cu was not considered, as very little of the metal is dissolved under these conditions (22.8?±?7.1 %). The mean equilibrium sorption capacities for Cd (10.2?±?3.1 mg/kg) and Zn (294.9?±?14.9 mg/kg) far exceeded observed levels in the bioretention media such that the remaining sorption capacity was ≥83 % for Zn and ≥90 % for Cd for the cells. Overall, the results of this investigation suggest that bioretention cells can provide many years of effective infiltration (>6 years) and metals removal performance (>25 years).     

Aluminium chemistry of the soil solution in an acid forest soil as influenced by percolation rate and soil structure

The predicted activity of Al in the soil solutions of acid forest soils often differs from that observed in the field. We have investigated the influence of soil structure and flow rate of the soil solution on the aluminum release to explain this divergence. Disturbed and undisturbed samples of soil were collected from the A and B horizons of a dystric cambisol at Waldstein (Fichtelgebirge, Germany). The samples were irrigated with solutions mixed according to field data on throughfall or soil solution composition with pH 3.5 with flow rates of 4 mm d^?1, 12 mm d^?1 and 36 mm d^?1. The percolates were analysed for major ions. Resulting relations between pH and pAl were compared with batch experiments. In neither the A horizon nor in the B horizon did soil structure influence the relation between pH and pAl. The apparent equilibrium between pH and pAl was described as the pK_app value with pK_app= pAl—a pH (where a is an empirical constant). It was found that the pK_app values for the column percolates were in the range of variation of those found in batch experiments. Flow rate had no influence on pK_app at 4 and 12 mm d^?1. At 36 mm d^?1 a significant increase of pK_app was observed. This relative undersaturation of Al was more pronounced in the A horizon than in the B horizon. When flow is fast Al release into the percolating soil solution might be limited by diffusion.     

Microbially available carbon in buried riparian soils in a glaciated landscape

Buried horizons and lenses in riparian soil profiles harbor large amounts of carbon relative to the surrounding soil horizons. Because these buried soil horizons, as well as deep surface horizons, frequently lie beneath the water table, their impact on nitrogen transport across the terrestrial–aquatic interface depends upon their frequency and spatial distribution, and upon the lability of associated organic matter. We collected samples of 51 soil horizons from 14 riparian zones Rhode Island, USA, where soil profiles are characterized by glacial outwash and alluvial deposits. These soil samples came from as deep as 2 m and ranged in carbon content from <1% to 44% in a buried O horizon 54–74 cm deep. We used these samples to: (1) determine the extent to which carbon in buried horizons, and deep surface horizons, is potentially microbially available; (2) identify spatial patterns of carbon mineralization associated with surface and buried horizons; and (3) evaluate likely relationships between soil horizon types, chemical characteristics and carbon mineralization. Carbon mineralization rates associated with buried horizons during anaerobic incubations ranged from 0.0001 to 0.0175 μmol C kg soil^?1 s^?1 and correlated positively with microbial biomass (R=0.89, P<0.0001, n=21). Excluding surface O horizons from the analysis, carbon mineralization varied systematically with horizon type (surface A, buried A, buried O, lenses, A/C, B, C) (P<0.05) but not with depth or depth x horizon interaction (overall R²=0.59, P<0.0005, n=47). In contrast to this result and to most published data sets, ¹³C-to-¹²C and ¹⁵N-to-¹⁴N ratios of organic matter declined with depth (¹³C?26.9 to ?29.3 per mil, ¹⁵N+5.6 to ?0.8 per mil). The absence of a relationship between horizon depth and C availability suggests that carbon availability in these buried horizons may be determined by the abundance and quality of organic matter at the time of horizon formation or burial, rather than by duration since burial, and implies that subsurface microbial activity is largely disconnected from surface ecosystems. Our results contribute to the emerging view that buried horizons harbor microbially available C in quantities relevant to ecosystem processes, and suggest that buried C-rich soil horizons need to be incorporated into assessments of the depth of the biologically active zone in near-stream subsurface soils.     

Accumulation of free oxyhydroxides in termite (Macrotermes bellicosus (Smeathman)) mounds and the implications for their dynamics in an African savannah Ultisol

The present study aimed to assess the dynamics of oxyhydroxides via termite mounds in a tropical savannah of Central Nigeria, where the soils often contain oxyhydroxides as a major component of soil minerals. To this end, the quantities of oxyhydroxides stored in mounds built by Macrotermes bellicosus (Smeathman) were compared to those stored in surface (Ap1) soils, and their turnover rates were estimated. Both the mound wall and nest of M. bellicosus were enriched two- to 10-fold with acidified ammonium oxalate soluble iron (Fe_o) and aluminum (Al_o) and dithionite-citrate-bicarbonate (DCB) soluble iron (Fe_d) and aluminum (Al_d) relative to the adjacent surface soil horizon. These oxyhydroxide contents were positively correlated with the clay content (P < 0.05), suggesting that M. bellicosus preferentially used silicate clay-associated oxyhydroxides for mound construction. The Fe_d, Al_d and DCB-soluble manganese (Mn_d) preserved in the M. bellicosus mounds ran up to 112 ± 25.6, 5.72 ± 1.41 and 2.17 ± 0.68 kg ha^?1, accounting for 1.91 ± 0.23%, 1.00 ± 0.60% and 0.35 ± 0.09% of the total amount stored in the surface soil horizon, respectively. Furthermore, the estimated turnover rates of Fe_d, Al_d and Mn_d were 6.6, 0.33 and 0.14 kg ha^?1 year^?1, respectively. These findings suggest that the mound-building termites significantly impacted the dynamics of free oxyhydroxides in an African savannah soil.     

Lateral flow in loamy to sandy Kandiudults of the Upper Coastal Plain of Georgia (USA)

Interest in site-specific agronomic management in intensively cropped regions necessitates characterization of subsurface water movement for efficient water management (irrigation timing) and control of off-site agrichemical movement. Soils formed in fluvial sediments in portions of the Upper Coastal Plain of Georgia (USA) are extensively used for peanut, cotton, and corn production. Certain proximate soils in this region possess contrasting subsoil properties, and it was hypothesized that these differences would have major effects on water redistribution across the landscape. This could be important in irrigation management, where soils possessing increased impedance to vertical flow could require decreased irrigation as opposed to soils without vertical flow restrictions. At a site near Plains, GA. (USA), hydraulic properties of soils with differences in overlying sand thickness and contrasting argillic horizon textures (sandy vs. loamy) were evaluated. The soils were predominantly in loamy and sandy families of Typic, Arenic, and Grossarenic Kandiudults. Laboratory measurements, field monitoring of matric potentials under simulated and natural rainfall, and modeling (VS2DT) were utilized to evaluate soil hydraulic properties. Reduction in vertical K_s occurred in horizons containing higher clay (argillic horizon). Changes in tension and build ups in hydraulic gradients associated with infiltration and redistribution events existed above and within horizons with low K_s. Evidence suggested there was less groundwater recharge occurring in the loamy than in the sandy pedons, suggesting more pronounced lateral flow occurred in the loamier soils. Model simulations of water movement across a slightly sloping (1%) simulated landscape indicated lateral gradients of flow existed within the solum of these soils. Analyses of tracer (Br) movement suggested a very slight lateral redistribution occurred within a relatively short monitoring period within the sandy pedon's Bt1 horizon, and the Bt2 and Bt3 horizons of the loamy pedon. Evidence suggested both loamy and sandy argillic horizons slightly, but not overwhelmingly, induced lateral flow on these landscapes.     

Anisotrope Variation der gesättigten Wasserleitfähigkeit einer unterschiedlich beweideten Salzmarsch im Deichvorland

Anisotropic variation of saturated hydraulic conductivity of a variously grazed salt marsh soil Undisturbed core samples were taken in horizontal and vertical direction from a variously grazed salt marsh soil for investigation of the anisotropic variation of saturated hydraulic conductity K_sat, bulk density, and pore size distribution. The results show that saturated hydraulic conductivity varies significantly anisotropically. The average Kv/Kh ratio is 0.38 for the soil profile and 0.44 for the surface soil. This anisotropy of K_sat is mainly attributed to the stratified structure of soil due to the sedimentation conditions in the salt marsh environment and decreases if soil structure development through pedological processes progresses. Furthermore. K_sat decreases significantly if the stocking rate of grazing is larger than 1.0 sheep unit/ha and the effect is more pronounced near the dike. However, both the Kv and Kh are affected by grazing in the same manner, so that the anisotropy of K_sat is independent from grazing. Bulk densitiy and macroporosity are affected by grazing but not by the direction of sampling. There are significant correlations between K_sat and > 50 μm as well as > 10 μm pore volume. The correlation between K_sat and total porosity is however not significant. The anisotropy of K_sat implicates the favouring of the lateral water flux and in the hydrological research and modelling of the salt marsh ecosystem the anisotropy of K_sat should be taken into account.