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The aims of this study were to (1) examine the extent of bacterial contamination of soils subjected to exposure to dairy sewage sludge applied to soils as measured by determination of number of bacteria from the Escherichia coli family and (2) determine the effects of dairy sewage sludge and straw on populations of other microbial species present in gray-brown podzolic soil. The gray-brown podzolic soil was formed from heavy loamy sand, which is characterized by the following granulometric composition: a sand fraction, 65%; a silt fraction, 19%; and a silt and clay fraction; 16%. The brown soil was formed from silt-loam and characterized by the following granulometric composition of silty-clay deposit: sand fraction, 8%; silt fraction, 48%; and clay and silt fraction, 46%. In dairy sewage sludge the total bacteria number as defined by Alef and Nannipieri (1995) was 51 × 104 colony-forming units (cfu)/ kg dry matter (dm), fungi total number 10 × 103 cfu/ kg dm, and E. coli bacteria 9.5 × 103 most probable number (MPN)/kg dm. In dairy sewage sludge mixed with straw, total number of bacteria and total number of fungi decreased to 103 and 102, respectively. Competition for nitrogen, glucose, and lactose and organic acids such as acetic and succinic with soil microorganisms, as well as soil conditions such as lack of oxygen, lower soil pH, and temperature, may account for the reduction in the number of E. coli bacteria in soils to which dairy sewage sludge was applied. Dairy sewage sludge may provide a beneficial impact on soil environment and adversely affect microorganisms such that dairy sewage sludge may be used as a safe organic fertilizer. [ABSTRACT FROM AUTHOR]

Abstract: Effects of leachate addition on ammonia volatilization and N2O and CO2 emissions from two different soils were investigated using the 10-day laboratory incubation method at two levels of moisture content. Ammonia volatilization was dominated by soil pH and only occurred in alkaline clay soil, where 0.26–0.32% of soil ammonia could be lost. The N2O emission from the alkaline clay soil was one order of magnitude greater than that from the acidic sandy soil, when either water or leachate was irrigated. Increasing the moisture content from 46% water-filled pore space (WFPS) to 70% WFPS in the alkaline clay soil or the acidic sandy soil by either water or leachate irrigation increased the N2O emission by over twofold. The CO2 emission from each soil sample at the two WFPSs was almost the same. The CO2 emission from the alkaline clay soil with leachate addition was 72% lower than that from the acidic sandy soil with leachate addition, and 6.7 times higher than that from the alkaline clay soil with distilled water addition. Ammonia volatilization and N2O emission under leachate irrigation could be minimized by avoiding the excessively wet condition and by selecting the acidic sandy soil with low organic carbon and total nitrogen content. [Copyright &y& Elsevier]

Hydraulic lift can be a desirable characteristic for cotton growing in areas that experience frequent drying of the topsoil. This study employed specialized soil columns to test if cotton can hydraulically lift water and whether this hydraulically lifted water can facilitate P acquisition from the dry topsoil of a clay and a sandy soil. The role of subsoil P placement on cotton growth was also tested. By using a Theta probe, hydraulic lift was detected in the clay soil for 7 days after water was withheld from the topsoil. However, in the sandy soil, a significant overnight increase in soil water was only detected for one day for the treatment with subsoil P application. Where P was applied to the topsoil, and water was withheld, cotton roots showed significant root P uptake from the sandy soil, but negligible P uptake from the clay soil. Irrespective of topsoil watering, the higher root length density in the subsoil of the clay soil accounted for the pronounced response to deep P placement. This study demonstrated that soil texture affects the amount and longevity of hydraulic lift from cotton roots. Hydraulic lift detected in the clay soil did not aid P acquisition from dry surface soil by cotton plants. [ABSTRACT FROM AUTHOR]

Some peculiarities of water retention in a tropical lateritic soil of clayey nature are presented and discussed. The typical soil microstructure is shown through thin-layer plates emphasizing soil microaggregation and pore distribution and their repercussion on the soil-water retention curve and on hysteresis. It is shown that the clayey soil has a behavior that to a large extent resembles sandy soil, which is characterized by the relatively high saturated hydraulic conductivity, low air-entry value, and small suction range at which water drainage takes place. The severe weathering processes that originated this soil have produced an altered soil that seems to be homogeneous in terms of physical indices, hydraulic conductivity, and soil-water retention characteristics, up to 4.5 m in depth. [ABSTRACT FROM AUTHOR]

Abstract: The study investigated the performance of three model tillage tools (tines). The experimental tillages were made from flat 8mm plain carbon steel. They were designated T1, T5, and T20, corresponding to tine widths of 1, 5, and 20cm respectively. Experiments were carried out in a soil bin filled with sandy clay loam soil at average moisture content 11.5% (dry basis) and 600kPa average cone index. The plastic limit and liquid limit and plasticity index of the soil are 20%, 31% and 11% respectively. Tests were conducted at forward speeds of 0.28, 1.0, and 2.5m/s. Depths of operation considered were 35, 70, 150, 200 and 250mm. Draught measurements were made for the different tines and were also calculated using soil mechanics equation. There was reasonable agreement between measured and predicted draught forces. The effects of depth of operation on draught force of the tines were studied and evaluated. It was observed that draught increased at an increasing rate with depth; the relationship was a curvilinear one best fitted by exponential function. The soil disturbance created as a result was also evaluated and reported in this paper. The parameters used to define soil disturbance of a single tine were: ridge-to-ridge distance (RRD), maximum width of soil cut (WFS), maximum width of soil throw (TDW), after furrow depth (df), height of ridge (hr) and rupture distance (f). They all increased as the depth of operation of the tool increased but less proportionately. The critical depth of the tines was also estimated. The results of analysis of variance showed that tool type and operating depth significantly affected draught at 5% level of significance (p <0.05) and that, there was interaction between the two factors. [Copyright &y& Elsevier]

Abstract: Soils often exhibit a variety of small-scale heterogeneities such as inter-aggregate pores and voids which partition flow into separate regions. In this paper a methodological approach is discussed for characterizing the hydrological behaviour of a heterogeneous clayey–sandy soil in the presence of structural inter-aggregate pores. For the clay soil examined, it was demonstrated that, coupling the transfer function approach for analyzing BTCs and water retention data obtained with different methods from laboratory studies captures the bimodal geometry of the porous system along with the related existence of fast and slow flow paths. To be effectively and reliably applied this approach requires that the predominant effects of the soil hydrological behaviour near saturation be supported by accurate experimental data of both breakthrough curves (BTCs) and hydraulic functions for high water content values. This would allow the separation of flow phases and hence accurate identification of the processes and related parameters. [Copyright &y& Elsevier]

A new method of estimating the permeability of soils using an acoustic technique is proposed in this technical note. Biot’s coupled theory of mixtures from the mid-1950s, which addresses the relationship between the permeability of saturated soils and the characteristic frequency of elastic waves, is used. The characteristic frequency is determined from the attenuation versus frequency curves obtained by acoustic sweep tests. This study presents the experimental technique for measuring the characteristic frequency of soils and calculation procedure for estimating the permeability of sandy soils. This technical note holds discussion for silty or clayey soils. [ABSTRACT FROM AUTHOR]

The article focuses on solving problems on oblique penetration of axisymmetric impactors in soft soils because of the plane section hypothesis. It studies the problems on the effect and penetration of solids in porous soil media with penetration depth and resistance force developed when a hard impactor dawns into sandy and clay soils were experimentally determined. Thus, it shows that the suggested method of solving oblique penetration problem because of the plane section hypothesis.

Recycling phosphorus (P) is crucial to meet future P demand for crop production. We investigated the possibility to use calcium phosphite (Ca-Phi) waste, an industrial by-product, as P fertilizer following the oxidation of phosphite (Phi) to phosphate (Pi) during green manure (GM) cropping in order to target P nutrition of subsequent maize crop. In a greenhouse experiment, four GM crops were fertilized (38 kg P ha−1) with Ca-Phi , triple super phosphate (TSP) or without P (Control) in sandy and clay soils. The harvested GM biomass (containing Phi after Ca-Phi fertilization) was incorporated into the soil before maize sowing. Incorporation of GM residues containing Phi slowed down organic carbon mineralization in clay soil and mass loss of GM residues in sandy soil. Microbial enzymatic activities were affected by Ca-Phi and TSP fertilization at the end of maize crop whereas microbial biomass was similarly influenced by TSP and Ca-Phi in both soils. Compared to Control , Ca-Phi and TSP increased similarly the available P (up to 5 mg P kg−1) in sandy soil, whereas in clay soil available P increased only with Ca-Phi (up to 6 mg P kg−1), indicating that Phi oxidation occurred during GM crops. Accordingly, no Phi was found in maize biomass. However, P fertilization did not enhance aboveground maize productivity and P export, likely because soil available P was not limiting. Overall, our results indicate that Ca-Phi might be used as P source for a subsequent crop since Phi undergoes oxidation during the preliminary GM growth. • Plant residues containing phosphite affected microbial properties in clay soil. • Decomposing rate of plant residues containing phosphite decreased in sandy soil. • Green manure oxidized phosphite to provided phosphate for a following maize crop. • Maize did not contain phosphite after green manure fertilized with calcium phosphite. • Calcium phosphite increased available P similarly as triple super phosphate. [ABSTRACT FROM AUTHOR]

Multivariate analysis of data from approximately 700 arable fields from France was carried out to partition the respective importance of environmental factors versus management practices on weed species richness and composition. Overall, canonical correspondence analysis indicated that the major variations in species composition between fields were associated with human management factors; (1) the current crop type and (2) the preceding crop type. Three main weed communities were identified according to sowing season: winter, spring and summer-sown crops. The third most important gradient was associated with soil pH and soil texture to a lesser degree, resulting in highly contrasting weed communities on basic clay soils against those on acidic sandy soils. The influence of climate and geographical region was less pronounced and identified mainly through relationships with precipitation and longitude. Within individual crop types, the effect of other management practices became more prominent. Species richness is dependant on factors other than, or in addition to those influencing species composition, like those describing landscape organisation and/or tillage depth. Species richness (α-diversity) and community composition (β-diversity) had, for example, contrasting relationship to altitude: 300–450m altitude giving high species richness but low species turnover. The variations observed in this large scale data set help to identify the agricultural practices which have had the most significant impact on the loss of species diversity in arable fields in recent decades. [Copyright &y& Elsevier]

Synchronous effects of biochar on heavy metals stress, microbial activity and nodulation process in the soil are rarely addressed. This work studied the effects, under greenhouse conditions, of selected heavy metals Cd2+, Pb2+ and Ni2+ on soybean plants grown in two different soils amended with biochar, and studied their effect on the microbial and enzymatic activity. As a result of the interference between heavy metals and biochar, biochar overcame heavy metal problems and maintained a microbial population of major groups (bacteria–fungi). There was an increase in the degree of resistance (RS) of the major microbial groups to heavy metals when biochar was added to the soil under study. Numbers of bacterial nodules significantly increased, particularly by using the higher rate of biochar compared to the control, either by adding biochar alone or by mixing it with the selected heavy metals. The arginase activity was increased by 25.5% and 37.1% in clay and sandy soil, respectively, compared to the control. For urease (UR), the activity was increased by 105% and 83.8% in clay and sandy soil, respectively, compared to the control. As a result, considerations of using biochar as a soil amendment should be first priority. [ABSTRACT FROM AUTHOR]

[Display omitted] • This is the first rigorous assessment of hydrologic soil group (HSG) classification. • The assumption used since 1955 for classification does not hold true. • HSG is governed by sealing and controlled by silt and organic matter. • The CN model works almost perfectly under a wide range conditions. • Spatial variability is pronounced and should not be ignored. The hydrologic soil group (HSG) is required for the determination of curve numbers (CN), which are used in a large number of hydrological models to calculate surface runoff during rain events of ungauged catchments. Despite the paramount importance of HSG, it is still based on an assumption made in 1955. We assessed HSG using 249 rainfall simulation experiments carried out in two sets of experiments examining seedbed conditions. One set analyzed the variation within a small (60 ha) catchment while the other examined 32 benchmark soils selected to cover the full range of arable soils on sloping land in temperate humid areas. The assumption made in 1955 that sandy and stony soils have a low HSG (A), while clayey soils of low permeability have a high HSG (D), cannot be supported. Instead, HSG appeared to be governed by surface sealing because CN increased with increasing silt content in the bulk soil and decreasing soil organic matter content in the fine earth fraction. An equation for calculating CN and, in turn, a HSG from these two parameters is provided. This equation also avoids classification-induced errors. The relation holds true for a wide range of rain properties (e.g., rain amount between 0.2 mm and 103 mm; event intensities between 2 mm h−1 and 80 mm h−1), slope gradients (2 %–24 %) and various soil properties (e. g., stone contents up to 40 %, clay contents up to 61 %, sand contents up to 87 %). The CN and, in turn, HSG remained constant throughout the events from the start of runoff until the end of the event, which was up to 49 h later in 32 cases. Autocorrelation within the catchment was strong and the full variation was found within 600 m. Even small catchments are, hence, heterogeneous and their runoff cannot be assigned to a single HSG or a single CN. Rejecting the assumption developed in 1955, which had not been verified since then, has important implications for hydrological modelling but also for the development, implementation and assessment of water conserving land use. [ABSTRACT FROM AUTHOR]

CH4 emissions and leachate disposal are recognized as the two major concerns in municipal solid waste (MSW) landfills. Recently, leachate recirculation was attempted to accelerate land-filled waste biodegradation and thus enhanced landfill gas generation. Leachate irrigation was also conducted for volume reduction effectively. Nevertheless, the impacts of leachate recirculation and irrigation on landfill CH4 emissions have not been previously reported. A field investigation of landfill CH4 emissions was conducted on selected sandy soil cover with leachate recirculation and subsurface irrigation based on whole year around measurement. The average CH4 fluxes were 311±903, 207±516, and 565±1460 CH4 m−2 h−1 from site A without leachate recirculation and subsurface irrigation, lift B2 with leachate subsurface irrigation, and lift B1 with both leachate recirculation and subsurface irrigation, respectively. Both gas recovery and cover soil oxidation minimized CH4 emissions efficiently, while the later might be more pronounced when the location was more than 5m away from gas recovery well. After covered by additional clay soil layer, CH4 fluxes dropped by approximately 35 times in the following three seasons compared to the previous three seasons in lift B2. The diurnal peaks of CH4 fluxes occurred mostly followed with air or soil temperature in the daytimes. The measured CH4 fluxes were much lower than those of documented data from the landfills, indicating that the influences of leachate recirculation and subsurface irrigation on landfill CH4 emissions might be minimized with the help of a well-designed sandy soil cover. Landfill cover composed of two soil layers (clay soil underneath and sandy soil above) is suggested as a low-cost and effective alternative to minimize CH4 emissions. [Copyright &y& Elsevier]

A field study was conducted to determine nitrogen (N) mineralization from broiler litter (BL) in two Coastal Plain soils of differing texture, sandy (Tifton loamy sand) or clayey (Greenville sandy clay loam). These soils represented the broad range in surface textures commonly found in soils used for agricultural production in the southeastern Coastal Plain. Published protocols used for the study were designed by the ARS mineralization team. In addition to measuring ammonium (NH4-N) and nitrate (NO3-N) in the soil as a measure of N mineralization, both total C and total N were measured to determine the impact of a single BL amendment on C sequestration and N accumulation. Amounts of N in the soil from BL mineralization over 70 days were identical for both soils, 46.4 mg N kg-1 soil (0.046%), but differences occurred in timing of the mineralization processes. In the sandy Tifton soil, depletion of NH4-N and nitrification of the NH4-N to NO3-N occurred simultaneously. The NH4-N from the BL was depleted in 21 days while peak NO3-N concentrations in the soil were found at 28 days. In the clayey Greenville soil, NH4-N concentrations from BL mineralization increased for 21 days and then decreased until reaching background levels by 70 days. Nitrate concentrations never did increase in the BL amended Greenville soil, indicating both that the nitrification rate was much slower than the ammonification rate, and most likely, that what NO3-N was produced was lost from the soil by denitrification under wet conditions. The combination of soil textural and microclimate differences along with greater protection of the BL residues in the clayey soil than in the sandy soil are believed responsible for the observed N mineralization differences between the two soils. Previous research has shown that N mineralization rate is positively correlated with sand content and negatively correlated with clay content of soils, and the results of this study concurred with those findings. Measurements of total C and total N in both Coastal Plain soils showed that overall increases were small with a single BL amendment, and it was concluded that long- term studies are needed to investigate C sequestration and N accumulation. It was concluded from the study that there is a high probability that BL mineralization rates will be significantly slower on the more clayey Coastal Plain soils than on very sandy ones, and that farm managers should take these rates into consideration when planning timing and amounts of BL applications. [ABSTRACT FROM AUTHOR]

The paper examines the influence of soil strength and stiffness on the end resistance mobilised by a cone or displacement pile in a two-layered soil profile (i.e. strong soil overlying or underlying weak soil). The investigation involved a series of numerical analyses that idealise pile/ cone penetration assuming the spherical cavity expansion analogue. It is shown how the end resistance mobilised by a penetrometer in a dense sand (i.e. strong soil) varies with the number of penetrometer diameters (D) from a weak soil (assumed here to be either a loose sand or soft clay), and depends on the ratio of the steady-state penetration resistances of the strong and weak layers. The penetrometer resistance in the weak soil is not affected by an adjacent strong layer at penetrations greater than 2D. A design procedure based on a numerical parametric study is proposed, and this is subsequently shown to compare well with centrifuge test data and with previous numerical research. [ABSTRACT FROM AUTHOR]

Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) reflectance and emissivity data were used to discriminate nonphotosynthetic vegetation (NPV) from exposed soils, to produce a topsoil texture image, and to relate sand fraction estimates with elevation data in an agricultural area of central Brazil. The results show that the combination of the shortwave infrared (SWIR) bands 5 and 6 (hydroxyl absorption band) and thermal infrared (TIR) bands 10 and 14 (quartz reststrahlen feature) discriminated dark red clayey soils and bright sandy soils from NPV (crop litter), respectively. The ratio of the bands 10 and 14 was correlated with laboratory measured total sand fraction. When applied to the image and associated with topography, a predominance of sandy soil surfaces at lower elevations and clayey soil surfaces at higher elevations was observed. Areas presenting the largest sand fraction values, identified from ASTER band 10/14 emissivity ratio, were coincident with land degradation processes. [ABSTRACT FROM AUTHOR]

A resonant method for determination of the absorption coefficient, which characterizes the damping properties of soils, is developed for implementation of computer programs for analysis of dynamic interaction between structures and their beds. A series of experiments with sandy and clayey soils of various moisture content, density, and depth of embedment, which are based on investigation of the forced oscillations of these specimens and continued processing of resonance curves within the framework of notions of the linear theory of viscoelasticity of soils, are conducted. [ABSTRACT FROM AUTHOR]

A method of analyzing the strengthening of foundation beds with crushed-stone piles is discussed. [ABSTRACT FROM AUTHOR]

Removal of pyrene, a representative PAH, was studied using laboratory tests in two different types of solid media: an organic matter collected on the surface of a vertical flow constructed wetland (VFCW) and a formulated clay silicate sand (inorganic matter). The aim of this study was to evaluate the capacity of pyrene biodegradation in these media in order to use them for treating run-off water. The sorption process, the kinetics of pyrene biodegradation and the influence of selected bacteria were also investigated. The sorption process was evaluated by adsorption isotherms and desorption kinetics using a batch equilibration method. The adsorption coefficient values of 28.8 and 2.1 for the organic and the inorganic matter respectively, confirmed the relationship of adsorption with organic carbon content. A small proportion of the sorbed pyrene was available for desorption (8% and 15% for the organic and the inorganic matter, respectively), indicating that sorption was partially irreversible, with the presence of hysteresis. For the formulated clay silicate sand inoculated with a specific bacteria (Mycobacterium sp.6PY1), selected for its ability to degrade PAHs, pyrene removal was complete in 32 days. With the organic matter, these values ranged from 40% to 95% for the different experiments, following a lag time of 3 weeks before observation of a significant degradation. Indigenous bacterial species in the organic medium had the metabolic capacity to degrade pyrene, and microbial populations pre-exposed to the PAH degraded pyrene faster than similar unexposed populations. Three metabolites of pyrene degradation by Mycobacterium were found. They accumulated in both organic and inorganic matter, indicating that the enzymes catalyzing them have slow kinetics. [Copyright &y& Elsevier]

Diuron ( N′-[3,4-dichlorophenyl]- N,N-dimethylurea) is one of the most frequently used herbicides in olive groves in Spain and other Mediterranean countries. The main objective of this work was to investigate the effect of the dissolved organic carbon (DOC) from a commercial humic amendment, derived by composting the liquid waste of the olive-mill process (LF), and a solid residue from the olive oil production industry (AL) on the sorption and leaching behaviour of diuron in soil. For this purpose, a clay and a sandy soil were selected. Soil sorption coefficients of diuron increased with LF (32%) and AL (76%) amendment in the sandy soil, whereas sorption decreased in the clay soil upon amendment, especially in the case of the liquid LF (52%). The DOC from LF and AL is composed of very poorly humified molecules, which are strongly sorbed onto the clay soil and thus compete with diuron for the same sorption sites. Dialysis experiments revealed that diuron forms stable complexes with DOC from LF and AL. Leaching of diuron in columns of the sandy soil treated with the organic amendments caused earlier breakthrough and maximum concentration peaks at fewer pore volumes when compared with leaching with 0.01m CaCl2. Competition between diuron and DOC molecules for sorption sites and diuron–DOC interactions can both account for the enhanced leaching of diuron. [ABSTRACT FROM AUTHOR]

In order to process large soil samples containing potato cyst nematodes, the Seinhorst (1964) cyst elutriator was scaled up to process both sandy and marine-clay soils in batches of up to 2.5 kg. Several modifications were implemented. To maintain the required upward current of 3.01 min-1, an inflow of 8.01 min-1 was necessary in the enlarged, 7.5 cm diam. sedimentation tube. Also water inflow is now regulated using a flow meter with pressuriser. Several experiments were undertaken, using artificial sandy soil and marine-clay soil, both naturally infested with potato cyst nematodes. In the final experiment, using the 8.01 min-1 inflow for 4 min, there was a loss of 0.65% and 0.74% of cysts, and eggs and juveniles, respectively. This indicates that the yield (99%) of the scaled-up elutriator matches that of the original Seinhorst elutriator and, therefore, is suitable for statutory and scientific research. [ABSTRACT FROM AUTHOR]

A study of the effect of a clayey soil modified in situ and ex situ with the cationic surfactant octadecyltrimethylammonium bromide (ODTMA), on the retention of linuron, atrazine and metalaxyl was carried out. Leaching of these compounds was studied in columns of a natural clayey soil and the same clayey soil modified by direct injection of the surfactant in situ, and in columns of a natural sandy soil and the same sandy soil modified by intercalation of a barrier of the clayey soil saturated ex situ with the surfactant. Breakthrough curves indicated the total immobilization of linuron in modified soils and a decrease in the leaching kinetics of atrazine and metalaxyl compared to what was obtained in the natural soil. The results indicate the use of the clayey soil modified in situ or ex situ with the surfactant ODTMA could be of interest in the immobilization of pesticides of different hydrophobicities. [Copyright &y& Elsevier]

The laboratory and field test data on the response of piles under the combined action of vertical and lateral loads is rather limited. The current practice for design of piles is to consider the vertical and lateral loads independent of each other. This paper presents some results from three-dimensional finite-element analyses that show the significant influence of vertical loads on a pile’s lateral response. The analyses were performed in both homogeneous clayey soils and homogeneous sandy soils. The results have shown that the influence of vertical loads on the lateral response of piles is to significantly increase the capacity in sandy soils and marginally decrease the capacity in clayey soils. In general, it was found that the effect of vertical loads in sandy soils is significant even for long piles, which are as long as 30 times the pile width, while in the case of clayey soils, the effect is not significant for piles beyond a length of 15 times the width of the pile. The design bending moments in the laterally loaded piles were also found to be dependent on the level of vertical load on the piles. [ABSTRACT FROM AUTHOR]

A viscoplastic cap model of the Perzyna type was developed for simulating high strain rate behaviors of soils. An associative viscous flow rule was used to represent time-dependent soil behaviors. The viscoplastic cap model was validated against experimental data from static and dynamic soil tests. The model was also compared with soil behaviors under creep and stress relaxation with good agreement. However, the model was unable to represent tertiary creep where strain softening became significant. The model was subsequently integrated into LS-DYNA for finite-element simulations of high strain rate behaviors of sandy and clayey soils in explosive tests. The significance of strain rate effect on the soil responses is presented herein. It is concluded that the viscoplastic cap model is adequate for simulations of soil behaviors under high strain rate loading, creep, and stress relaxation, covering a wide range of time-dependent problems. [ABSTRACT FROM AUTHOR]

This study examined the effect of soil type on burrowing behaviour and cocoon formation during aestivation in the green-striped burrowing frog, Cyclorana alboguttata (Günther, 1867). Given a choice, frogs always chose to burrow in wet sand in preference to wet clay. Frogs buried themselves faster and dug deeper burrows in sandy soil. However, under my laboratory conditions, there was little difference in the pattern of soil drying between the two soil types. Frogs in both sand and clay soil experienced hydrating conditions for the first 3 months and dehydrating conditions for the last 3 months of the 6-month aestivation period, and cocoons were not formed until after 3 months of aestivation. After 6 months, there were more layers in the cocoons of frogs aestivating in sand than those aestivating in clay. Frogs were able to absorb water from sandy soil with water potentials greater than –400 kPa, but lost water when placed on sand with a water potential of –1000 kPa. [ABSTRACT FROM AUTHOR]

Abstract: Adsorption and desorption characteristics of endosulfan in four Indian soils were studied extensively. The soils used were clayey soil (CL—lean clay with sand), red soil (GM—silty gravel with sand), sandy soil (SM—silty sand with gravel) and composted soil (PT—peat) as per ASTM (American Society for Testing and Materials) standards. Adsorption and desorption rates were calculated from kinetic studies. These values varied for alpha and beta endosulfan depending on the soil type. Maximum specific adsorption capacities (q max) for different soils were calculated by Langmuir model. The values varied from 0.1 to 0.45mgg−1 for alpha endosulfan and 0.0942–0.2722mgg−1 for beta endosulfan. Maximum adsorption took place in clay soil followed by composted soil and red soil. Adsorptions of alpha and beta endosulfan were negligible in sand. The binding characteristics of various functional groups were calculated using Scatchard plot. Effect of functional groups was more predominant in clayey soil. Organic matter also played a significant role in adsorption and desorption of endosulfan. Endosulfan adsorption decreased drastically in clay soil when the pH was reduced. Desorption was higher at both acidic and alkaline pH ranges compared to neutral pH. Results indicated that alpha endosulfan is more mobile compared to beta endosulfan and mobility of endosulfan is maximum in sandy soil followed by red soil. It can be inferred that crystal lattice of the clay soil plays a significant role in endosulfan adsorption and desorption. Immobilization of endosulfan is more advisable in clay soil whereas biological and or chemical process can be applied effectively for the remediation of other soil types. [Copyright &y& Elsevier]

The time-dependent behavior of soils has been investigated extensively through one-dimensional and triaxial test conditions. Most of the observations in literature have focused on the determination of the time-dependent behavior of clayey soils, whereas the reported experimental studies of granular materials are few. This paper presents an up-to-date review of the various observed time- and rate-dependent phenomena that are known to exist for both clay and sand. The description is carried out separately for creep, stress relaxation, rate dependency, and structuration in laboratory experiments. All of the above-mentioned phenomena are present in both sand and clay. The time-dependent phenomena are more pronounced in clay than sand. However, sand exhibits relatively large deformations at high confining pressures because of grain crushing. Furthermore, the review revealed an essential characteristic situation for soils. That is whether the time-dependent behavior can be characterized as isotach or nonisotach. It seems that the isotach behavior is adequate for describing the time effects in clays in most situations. But for sand, the isotach description is inadequate. Further, the phenomenon of structuration plays a role in both clay and sand. [ABSTRACT FROM AUTHOR]

Different classes of constitutive models have been developed to capture the time-dependent viscous phenomena (creep, stress relaxation, and rate effects) observed in soils. Models based on empirical, rheological, and general stress-strain-time concepts have been studied. The first part is a review of the empirical relations, which apply only to problems of specific boundary conditions and frequently involve natural time alone. The second part deals with different rheological models used for describing the viscous effects in the field of solid mechanics. The rheological models are typically developed for metals and steel but are, to some extent, used to characterize time effects in geomaterials. The third part is a review of constitutive laws that describe not only viscous effects but also the inviscid (rate-independent) behavior of soils, in principle, under any possible loading condition. Special attention is paid to elastoviscoplastic models that combine inviscid elastic and time-dependent plastic behavior. Various general elastoviscoplastic models can roughly be divided into two categories: Models based on the concept of overstress and models based on nonstationary flow surface theory. Although general in structure, both have shortcomings when used for modeling of soils. [ABSTRACT FROM AUTHOR]

This study extended the association between hookworm transmission in KwaZulu-Natal and the sandy coastal plain by investigating the parasite's occurrence in isolated areas of sandy soils further inland. A school-based prevalence survey was carried out in selected inland sandy areas and in surrounding areas dominated by clay soils within a narrow altitudinal range of between 500 and 700 m to reduce the effect of altitude on climate-related factors (rainfall and temperature). Sandy areas situated on the coastal plain were included in the analysis for comparative purposes. Soil samples (0–50 mm depth) were collected from each locality to assess their nematode loadings and to analyse selected physical and chemical properties. Significant differences were found between the moderate prevalence of hookworm infection among children living in inland areas with sandy soils (17.3%) and the low prevalence in surrounding non-sandy areas (5.3%, P < 0.001), and between infection among children living in all inland areas (9.3%) and the high prevalence on the coastal plain (62.5%, P < 0.001). Amounts of fine and medium sand were highest in both the coastal plain soils and in inland sandy areas and these fractions showed a significant positive correlation with hookworm prevalence and nematode loadings. Clay, coarse sand and organic matter contents were highest in surrounding non-sandy soils and showed a significant negative correlation with the nematode variables. No statistically significant correlations were found with soil pH at study localities. We conclude that properties of inland sandy soils, particularly particle size distribution, correlate well with hookworm prevalence and nematode loadings and therefore provide a more suitable habitat for nematodes than surrounding non-sandy areas. These results suggest that particle size distribution of sand fractions, organic matter and clay content in the soil influence the survival of hookworm larvae and hence the parasite's transmission. [ABSTRACT FROM AUTHOR]

This paper concerns a study of the influence of fines on the resistance to liquefaction of a clayey sand. The study is carried out using a triaxial apparatus on a reconstituted sand-clay mixture containing a low fraction of clay. After a description of the soil used in this study, the paper presents results of undrained compression tests together with cyclic liquefaction tests performed on soil samples containing different fractions of clay. Experimental results show that the increase in the fines content up to 15% reduces the resistance to liquefaction of the sand-clay mixture. This result is due to the role of fines in reducing the dilatant tendency of the clayey sand used in this study. [ABSTRACT FROM AUTHOR]

Aims: To compare a range of enrichment broths and enrichment temperatures for the isolation of Escherichia coli O157 by immunomagnetic separation (IMS) from sandy, loam and clay soils. Methods and Results: Soils were spiked with cocktails of four atoxigenic strains of E. coli O157 and four strains of commensal E. coli . The organisms were stressed by subjecting soils to cycles of freeze/thawing, followed by drying at 20°C for up to 4 days. Nine enrichment broths were trialled based on buffered peptone water, tryptone soya broths and EC broths supplemented with a range of selective additions. Enrichments were incubated for 6 h and assessed by target recovery after IMS on cefixime tellurite sorbitol MacConkey agar (CTSMAC) incubated at 37°C for 24 h. A comparison of enrichment temperatures (37 and 42°C) was also performed. Buffered peptone water (with or without vancomycin) and tryptone soya broth (with or without novobiocin) gave significant increases in recovery of E. coli O157 compared to others tested. In addition, broths incubated at 42°C were superior to those at 37°C for the recovery of E. coli O157. Significance and Impact of the Study: This study showed that sub-lethally damaged E. coli O157 surviving in soil can be sensitive to antimicrobial additions. The choice and concentration of these additions is vitally important to optimize target recovery. Some IMS protocols, established for the isolation of E. coli O157, may be unsuitable for the examination of soil samples. [ABSTRACT FROM AUTHOR]

Focuses on a study that discussed a four-parameter model that can represent the shear modulus factors and damping coefficients for granular soils. Information on nonlinear soil behavior; Effect of confining pressure on modulus and damping; Experimental data on cohesionless soils; Details on the MIT-S1 stress soil model for clays and sands.

• There was no great variation in wavelength sizes between sandy and clayey soil. • For the frequency of 45 kHz, specimens of at least 200 mm are required. • Between 5 and 7 waves are required to have flat waves. • The smallest discontinuity detected by the ultrasound was between 8 and 19 mm. Considering this parameter, the minimum length of a soil test specimen to be compacted, to enable its characterization, was determined using ultrasonic testing. The experimental stage involved the production of specimens in different lengths for two types of soils (clayey and sandy) and three compaction energies (normal, intermediate, and modified). Ultrasound tests were performed after molding (0 days) and 28 days of compaction, using 45 kHz frequency longitudinal transducers and compression wave. The results indicated that the minimum length of the specimen should be 200 mm when the velocity stabilization occurred for the Clayey and Sandy soils. However, the factors considered (transducer frequency, compaction energy and apparent specific mass) may infer significant changes in wavelength. [ABSTRACT FROM AUTHOR]

The major objective of this study is to correlate rocking foundation performance parameters with their capacity parameters and earthquake demand parameters using results obtained from 142 centrifuge and shaking table experiments, which include a variety of soil conditions, foundation geometries, structural models, and types of ground motions. The analysis presented in this paper considers all experimental results together, collectively as big data, through nondimensional parameters to identify hidden relationships among different parameters in a capacity-demand-performance framework. Rocking system performance parameters such as seismic energy dissipation in soil, permanent settlement, peak and permanent rotation, tipping-over stability ratio, self-centering ratio, rocking moment capacity, and acceleration amplification ratio are correlated with rocking system capacity parameters such as critical contact area ratio, rocking coefficient, and slenderness ratio of rocking systems and the earthquake demand parameters such as Arias intensity and peak ground acceleration of earthquake. It is found that energy dissipation and settlement correlate reasonably well with rocking coefficient and Arias intensity of earthquake, while peak rotation and acceleration amplification ratio correlate reasonably well with slenderness ratio, rocking coefficient, and peak ground acceleration of earthquake. Rocking foundations in clayey soils show superior performance in terms of seismic energy dissipation and permanent settlement compared to those in sandy soils, especially for relatively small to medium intensity shakings, and the ability of rocking foundations to de-amplify the earthquake motion increases as the magnitude of shaking increases. • The research presented in this paper analyzes the results obtained from 142 dynamic base shaking experiments on rocking foundations conducted in centrifuges and shake tables. • The analysis presented in this paper considers all experimental results together, collectively as big data, through nondimensional parameters to identify hidden relationships among rocking foundation parameters. • Rocking foundation performance parameters are correlated with rocking system capacity parameters and earthquake demand parameters using experimental results. [ABSTRACT FROM AUTHOR]

Eight-year-old Loblolly pine (Pinus taeda) plots located in South Carolina were evaluated using high resolution aircraft multispectral scanner data to determine if biomass could be accurately measured. Sixteen pine plots located on both sandy and clay soils were treated with 0, 180, or 360 kg. (approximately 0, 400, or 800 lb.) of nitrogen per plot. Indices of biomass from remote sensing data were significantly correlated with in situ biomass measurements made in each plot. A ratio of infrared (9 - 1.1 μm) and red ( 65-70 μm) channels yielded the best correlation. The indices were not sensitive to differences in soil type (sandy or clay). [ABSTRACT FROM AUTHOR]

• Biochar aging increased microbial carbon use efficiency (CUE) due to increase in pH. • Biochar aging decreased soil microbial biomass turnover time (BTT). • CUE was soil specific with higher CUE in sandy-textured soil than clay rich soil. • BTT was longer in a clay rich soil than in a sandy soil. Biochar amendment causes immediate increases in soil organic carbon (SOC), but long-term effects are unclear. Biochar properties change with time (biochar aging) potentially affecting how efficiently SOC remains in soil after decomposition, indicated by microbial carbon use efficiency (CUE, the ratio of microbial growth over carbon uptake). Effects of fresh and aged biochar amendments on microbial CUE and biomass turnover time (BTT) were determined using the H 2 18O-DNA incorporation method. Biochar aging increased CUE (control vs. fresh vs. aged of 0.6 vs. 0.6 vs. 0.7) but decreased BTT (51 vs. 37 vs. 27 days) due to changes in soil pH. Moreover, a greater CUE but shorter BTT was found in the sandy-textured Tenosol compared to the clayey Dermosol, possibly due to protection by clay minerals. Biochar aging and associated increase in soil pH may promote soil biogenic carbon sequestration through increasing microbial CUE or decreasing BTT. [ABSTRACT FROM AUTHOR]

• Sandy soils reach moderate penetration resistance at field capacity. • In semi-arid climates and sandy soils, low penetration resistance occurs infrequently. • Penetration resistance in clay soils is below 10 MPa even during the dry season. • In seasonally dry climates, penetration resistance follows a beta distribution. • Wet season rainfall affects year-round penetration resistance distribution. In water-controlled environments, because rainfall is one of the primary hydroclimatic forcings, its variability can affect the dynamics of soil water content and other related processes such as soil penetration resistance (PR), plant growth, and food production. The objective of this study was to simulate the relative soil water content (s) and PR year-round considering semi-arid rainfall conditions for different soil classes. An experiment was conducted to obtain relative soil water content (s) and PR data in sandy soil and this information was combined with a data set of four soils from a similar experiment conducted on different soil texture classes. The relative soil water content and PR were simulated at a daily timescale using a stochastic soil water balance model for the five soils. The parameters of the PR - s model can be estimated from the soil texture and bulk density. Under rainfed conditions, there is a short window for tillage (plowing and cultivation) of sandy soils compared with clay soils. During the majority of a typical hydrological year, the PR reaches high values (greater than 5.0 MPa) imposing a moderate to high physical limitation for root growth in sandy soils. In the same soils, limiting PR is reached at s levels very close to the field capacity during the drying process. This indicates that an extra input of water through irrigation may be required during the establishment of crops with a well-developed root system in order to prevent impairments to root growth. The daily PR values modeled over the course of a hydrological year followed a beta distribution with shape parameters (α and β) which were strongly correlated with the frequency of rainfall events during the wet season (λ wet). The modeling framework presented here for simulating relative soil water content and soil penetration resistance can be applied to agricultural systems in order to prevent physical limitations on crop growth and to plan tillage management schedules. [ABSTRACT FROM AUTHOR]

The rate-dependent uniaxial compressive behavior of frozen clay soil is strongly affected by its minerals, void ratio, stress history, and pore fluid salinity. Previous studies show that an extremely low deformation rate applied on a clay soil tends to result in a lower bound compressive strength. However, the lower bound stress-strain behavior of frozen clay soil under the uniaxial compressive condition was not studied. A thorough understanding of the rate-dependent behavior of frozen clay and its relationship with temperature requires a large number of specimens with similar compositions and micro-structures. In this study, a series of laboratory tests were carried out on artificial frozen sandy clay soils to measure the rate-dependent uniaxial compressive behavior at temperatures ranging from −15 °C to 0 °C. We used two types of artificial frozen clay soils with pre-determined clay fraction, clay mineralogy, stress history, and moisture content. Our results conclude that a low temperature and a high deformation rate tend to generate brittle failure with post-peak softening behavior. A temperature close to the freezing temperature and a low deformation rate result in a diffuse failure associated with strain hardening. Temperature-dependent uniaxial compressive mechanical properties were measured and modeled using empirical relations, which are highly dependent on the applied deformation rate. A series of step-loaded relaxation tests were carried out on those artificial clay soils and creep parameters were estimated using relaxation test results and a power law creep model. A new approach of deriving the lower bound of stress-strain curve of frozen soil is proposed accordingly. The idea of determining the lower bound of stress-strain curve is based on the isotache concept, which was previously used in the soil consolidation theory. • Temperature-dependent uniaxial compressive and relaxation behaviors of artificial frozen sandy clay soils are measured. • Relations between creep parameters and temperatures of frozen clay soils are displayed. • A new approach of deriving the lower bound of stress strain curve of frozen soil is proposed. [ABSTRACT FROM AUTHOR]

New technologies have been developed to slow down the phosphorus release in the soil and prevent the loss to the environment by using layered double hydroxides (LDH). However, slow-releasing mechanisms in inorganic matrices are not often discussed in the literature, and post-release sorption-desorption processes have also not been taken into account. Thus, kinetic and sorption processes of P in soils were herein investigated employing a modified LDH. The modification was carried out by the reconstruction method in the P solution. The material (HTCP) was characterized by FT-IR and XRD. The release of P to the soil solution was slow. Around 11% of the P introduced in the LDH was released to the clayey soil solution, and 5.5% to the sandy soil solution over 45 days (1080 h). Kinetic models of first-order and second-order, Elovich, intraparticle diffusion, and power function were applied. The intraparticle diffusion model best described the P release in clayey soil, characterizing ion exchange, while the second-order model better adjusted the release in sandy soil. The dual-mode Langmuir-Freundlich model appropriately described the sorption of P in the soil samples, being the desorption almost null. Although some of the P was sorbed, the post-sorption pH remained in a viable range for making P available to the plants, revealing the benefits of using HTCP for slow-release fertilizers. Unlabelled Image • Mimicking soil solution for phosphorus release. • Rigorous statistic methods for interpretation of release results. • Kinetic models described in detail for support the release hypothesis. • Sorption-desorption studies of phosphorus after slow-release. • Availability of phosphorus species after slow-release. [ABSTRACT FROM AUTHOR]

Management of the soil microbial community to increase crop productivity is one of the main challenges of modern agriculture, and bacterial inoculants can help to overcome this challenge. In this work, two plant growth-promoting (PGP) bacteria were evaluated under contrasting soil conditions, in order to test a rhizosphere ecology model. This model states that plants select for phosphate (P) solubilizers in poor nutrient soils and Indolic Compounds (ICs) producers in rich nutrient soils. Rice plants were single- or co-inoculated with strains of Burkholderia and Enterobacter genera in clayey and sandy soils. Diversity gradients were generated in each soil type using the dilution-to-extinction approach. Inoculant survival, colonization, and effect on plant biomass were evaluated, besides P solubilization and ICs production from both rhizospheric and endophytic bacterial communities. The PGP efficiency of the Burkholderia strain was highest in the sandy soil, which had the highest bacterial P solubilization potential, whereas the PGP efficiency of the Enterobacter strain was highest in the clayey soil, which had the highest bacterial ICs production potential. These behaviors occurred as hypothesized by the model, which can be useful for PGPB testing and bioprospection. We highlight a strong dependency of the Enterobacter strain on the diversity level as the most critical factor affecting PGP efficiency, possibly related to the increased influence of keystone taxa in lower diversity as indicated by network analysis. • Bacterial plant growth promotion effect was successfully predicted by functional traits. • Microbial inoculation efficiency was diversity-dependent, with greater effects in low diversity. • Microbial production of plant hormones was negatively correlated to nutrient solubilization. • Number of keystone taxa decreased with diversity, but their network influence increased. [ABSTRACT FROM AUTHOR]

The damping-off incidence caused by Pythium aphanidermatum in chilli was 20.0 and 58.0% post-emergence at 7 and 20 days after sowing, respectively in clay soil. Among 4 different soils, clay soil favoured the disease most and recorded the maximum fungal population of 12.46×103 cfu/g of soil at 20 days after sowing. The incidence of disease was comparatively low in sandy soil. [ABSTRACT FROM AUTHOR]

Wireless Underground Sensor Networks (WUSNs), an important part of Internet of things (IoT), have many promising applications in various scenarios. Signal transmission in natural soil undergoes path loss due to absorption, radiation, reflection and scattering. The variability and dynamic of soil conditions and complexity of signal attenuation behavior make the accurate estimation of signal path loss challenging. Two existing propagation models for predicting path loss are reviewed and compared. Friis model does not consider the reflection loss and is only applicable in the far field region. The Fresnel model, only applicable in the near field region, has not considered the radiating loss and wavelength change loss. A new two stage model is proposed based on the field characteristics of antenna and considers four sources of path loss. The two stage model has a different coefficient m in the near field and far field regions. The far field distance of small size antenna is determined by three criteria: 2 D2/λ, 5 D, 1.6 λ in the proposed model. The proposed two stage model has a better agreement with the field experiment data compared to Friis and Fresnel models. The coefficient m is dependent on the soil types for the proposed model in near field region. It is observed from experiment data that the m value is in the range of 0~0.20 for sandy soils and 0.433~0.837 for clayey silt. [ABSTRACT FROM AUTHOR]

• The mechanism in the interaction of the low water clays and jet grout is a combination of erosion and cutting. • Clays at low water content interact with jet pressure similar to silt and sandy soil. • An equation was proposed to estimate the diameter of the soilcrete column in low water content clays. • Optimum injection pressure for single-fluid jet grouting in clayey soil at low water content is 45 MJ/m. One drawback to the application of jet grouting for soil improvement is quality control, especially the determination of the diameter and strength of the column, which depends on the technical specifications of the injection and soil type. It has been reported that the initial water content of the clay effects the erosion of cohesive particles. The compressive strength and diameter of a soilcrete column in clay/sand at different jet grouting specifications have been well documented. However, the effect of the initial water content of clay on the performance of the jet grouting method has not been reported. Researchers have not proposed technical specifications for single-fluid jet grouting in remoulded clay with a low water content. The present study carried out 10 full-scale tests to analyse the effect of single-jet grouting specifications on the diameter and uniaxial compressive strength of soil-cement columns in a reclaimed area with low water content clay. The clay-jet grout interaction was evaluated using a microstructural approach and revealed that there is insufficient cohesion between the particles of remoulded clay. The mechanisms of interaction between the particles and the jet grouting is a combination of erosion and penetration of the grout into the soil and into air-filled cracks. In this case, it caused the particles to behave in a manner that is similar to that of silt and sandy soil. The efficiency of jet grouting in this type of soil was better than in clayey soil with a high water content. Thus, the equation previously used to estimate the diameter of the column has been modified by increasing the reference diameter from 50 to 60 cm for clayey soil with a low water content. The results show that an increase in the time interval and decrease in lifting step reduced the number of clayey clods in the core and increased the strength of the soil-cement. The maximum strength and diameter were achieved at an energy of 25 MJ/m with an optimum injection pressure of 45 MPa for single-fluid. [ABSTRACT FROM AUTHOR]

• A two-year field experiment with rooting depth treatment was performed in clay and sandy soil. • Deep roots in maize contribute to increase N uptake and grain yield in sandy soil. • Increasing root length below 40 cm depth can reduce nitrate leaching in clay soil. Increasing rooting depth via subsoiling is suggested to increase nitrogen (N) uptake and reduce nitrate leaching in maize. In a two-year field experiment, this hypothesis was evaluated with two levels of N supply (120 and 240 kg N ha−1) in two soils with different leaching potential (infertile sandy soil and fertile clay soil). Maize rooting depth was limited to either the 0–20 cm (D20) or 20–40 cm (D40) soil layer using a nylon net (30 μm), or was not limited (control). There was no water stress during the growing seasons for both soils. Compared to the control, root length with the D20 and D40 treatments was longer in the 0–20 and 20–40 cm soil layers, respectively. However, total root length per plant differed less among the treatments. In clay soil, the D20 treatment did not affect N uptake, shoot biomass, or maize yield, but increased nitrate leaching. In sandy soil, the D20 treatment greatly reduced plant N accumulation, shoot biomass, and grain yield, while nitrate leaching was similar across the three treatments. It is concluded that deeper roots in maize contribute to increase N uptake and grain yield in sandy soil, but only help to reduce nitrate leaching in clay soil. [ABSTRACT FROM AUTHOR]

Statistical characterization of model uncertainty has been exclusively focused on reliability-based design of soil nail walls against ultimate limit states; little has been accomplished for predictions of horizontal and vertical displacements at the top of the wall for analysis of serviceability limit states. To fill the gap, this study first develops a database containing 461 measured wall horizontal and vertical displacements from 75 fully instrumented soil nail walls under working conditions reported in the literature. Then, the database is used to evaluate the accuracies of simplified wall displacement models currently adopted in four national soil nail wall design manuals. The results show that on average the current models tend to over-predict displacements for walls in sandy soils, but under-predict displacements for walls in clayey soils. Predictions using the current models are moderately to highly dispersive. Simple models are developed and calibrated for prediction of displacements based on the established database. Predictions using the developed models are demonstrated to be accurate on average and significantly less dispersive. In addition, a simple model for prediction of horizontal wall displacement along depth is developed and optimized. The present work is practically valuable for reliability-based design of soil nail walls against serviceability limit states. [ABSTRACT FROM AUTHOR]

Soils are among the most biodiverse and densely inhabited environments on our planet. However, there is little understanding of spatial distribution patterns of belowground biota, and this hampers progress in understanding species interactions in belowground communities. We investigated the spatial distribution of nematodes, which are highly abundant and diverse metazoans in most soil ecosystems. To gain insight into nematode patchiness, we mapped distribution patterns in twelve apparently homogeneous agricultural fields (100 m × 100 m each) with equal representation of three soil textures (marine clay, river clay and sandy soil). Quantitative PCRs were used to measure the abundances of 48 distinct nematode taxa in ≈1200 plots. Multivariate analysis showed that within this selection of sites, soil texture more strongly affected soil nematode communities than land management. Geostatistical analysis of nematode distributions revealed both taxon-specific and field-specific patchiness. The average geostatistical range (indicating patch diameter) of 48 nematode taxa in these fields was 36 m, and related to soil organic matter. Soil organic matter content affected the spatial variance (indicating within-field variation of densities) in a life-strategy dependent manner. The r-strategists (fast-growing bacterivores and fungivores) showed a positive correlation between organic matter content and spatial variance, whereas most K-strategists (slow-growing omnivores and carnivores) showed a negative correlation. Hence, the combination of two parameters, soil organic matter content and a general life-strategy characterisation, can be used to explain the spatial distribution of nematodes at field scale. • Nematode distribution maps show taxon- and field-specific levels of patchiness • Distributions of nematodes with similar food preferences show little or no overlap • Soil organic matter affects nematode patchiness in a life-strategy dependent manner • Stochasticity is a dominant driving factor for mesoscale distribution of nematodes • Distribution maps enable the design of soil sampling schemes with known accuracies [ABSTRACT FROM AUTHOR]

DNA-tagged particle tracers have been the subject of several researches as a new tracer for hydrological applications. This tracer potentially permits the production of a large number of identically transported but distinguishable tracers. Such technique facilitates multi-point and multi-time tracer experiments in a specific location without confounding the signal of the different tracers. All of those potential benefits of DNA-tagged particles can effectively improve our understanding on contamination flow origin and its pathways in the subsurface environment.In this study the effect of soil size on the transport of DNA-tagged silica particles is evaluated. We assumed that the presence of preferential flow pathways or dual porosity in a clayey soil can lead to negligible mass recovery rate of tracer in comparison to matrix flow in sandy soil. Thereto, a series of soil column laboratory tests under saturated conditions were conducted. The columns are custom-designed with a diameter of 25 cm and a height of 25 - 28 cm. The columns were in-situ excavated from a clayey Holocene soil from West of the Netherlands; and from a sandy Pleistocene soil from the East of the Netherlands. We not only determined mass recovery rates and advective-dispersive transport parameters of the colloidal DNA-tagged silica particle tracer, but also compared DNA tracer data with deuterium tracer data, applied to the same columns. Finally, we defined the role of preferential flow paths in the columns. [ABSTRACT FROM AUTHOR]

Soil microbiome play very important role in development of soil profile and implementation of soilbiochemical processes, especially for initial stages of soil regeneration after strong antropogenic impact. The developing soils of postmining landscape of Central Yamal (Russia, Yamal demi-island) and soil microbiome composition was investigated for the first time by use metagenomic approaches.The study includes sampling from heaps of abandoned mines of chromatic ore and sand quarries, reclaimed sand heap and mature larch forest as a reference. We analyzed several agrochemical parameters (pH, C- and N-content, basal respiration and other) and microbial community structure, measured quantitatively by RT-PCR and qualitatively by use high-throughput sequencing of 16s rRNA gene sequence libraries.Investigated soils showed low content of organic carbon and total nitrogen. Soil regeneration and soil basal respiration rate were considered as slow for tundra and forest tundra zones, which indicates the low level of soil microbiological activity. The highest total content of bacteria, acrchaea and fungi was revealed for soils of sandy and clay texture heaps and reclaimed soils. Reclamation practice result in sharp increasing of bacteria, archaea and fungi counts. At the same time, reclaimed soils showed the lower values diversity indexes in comparison with soils of abandoned mines.In taxonomic analysis composition of microbiomes that were revealed, many taxa was described previously as dominant groups in different cold environments, including alpine soils. Among them are Chthoniobacteraceae, bacteria from order Ellin 6513, Koribacteriaceae, Gaiellaceae and other.This work was supported by the Russian Scientific Foundation projects 17-16-01030, 'Soil biota dynamics in chronoseries of post-technogenic landscapes: analyses of soil ecological effectiveness of ecosystems restoration'. [ABSTRACT FROM AUTHOR]