bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dispersive Erosion and Entisol‐Panspot Genesis in Sodium‐Affected Landscapes
Authors: Hopkins D. G. , Sweeney M. D. , Richardson J. L. 
Published: July 2010

AbstractIn Natriboroll complexes, commonly barren, eroded Entisol or remnant Natriboroll areas occur that are devoid of vegetation. This study investigates the genesis, stratigraphy, and characteristics of panspots. The study consists of a detailed grid sampling of 121 pedons in a 20 by 20 m area of panspots (Entisol), revegetated panspots (Entisol), and Glossic and Leptic Natriborolls. Topographic and soil morphological parameters were compared with electrical conductivity, soluble Ca, Mg, HCO3, Cl, SO4, exchangable H, sodium adsorption ratio (SAR), particle size, and water‐dispersible clay. Field evidence clearly showed dispersion‐induced erosion resulting from a documented rainstorm. Water‐dispersible clay supported these observations. Morphologic indicators of leaching intensity and results from a salinity survey showed soil properties consistently related to surface vegetation density. In barren panspots, no development was evident but, in revegetated panspots, a leaching regime was evident and modest structural development could be seen. Chemical and morphological data suggested two water‐movement regimes in panspot development. A diagrammatic model illustrates the role of throughflow and discharge of saline‐sodic water and mechanical/dispersive erosion in panspot genesis. Revegetated panspot zones result from a renewal of soil development that slowly reverses the effects of dispersive erosion. Lateral water flow in anisotropic, sodic parent materials is a major factor in the development of panspots.
Determination of Hydraulic Conductivity Using a Tension Infiltrometer
Authors: Reynolds W. D. , Elrick D. E. 
Published: July 2010

AbstractA new procedure is presented for in situ determination of saturated and near‐saturated hydraulic conductivity [Kfs and K(ψ), respectively] from a sequence of steady infiltration measurements made at several tensions on a single infiltration surface. The method applies to tension infiltration from either a surface disk or from within a ring inserted a small distance into the soil. The analysis employs a modification of Wooding's solution for infiltration from a shallow pond, combined with numerically determined shape factors that account for the interaction effects between flow geometry and soil properties. The method is found, via numerical simulations, to have an overall accuracy within about ± 7%, regardless of whether the predicted K(ψ) function is flat with an indistinct air‐entry value, steep with a distinct air‐entry value, or very steep with no air‐entry value. Some important practical features of the method are that it does not require measurement of the often‐difficult square‐root‐of‐time infiltration behavior, no special considerations are required regarding the thickness of the contact layer, it minimizes the effect of local spatial heterogeneity by using only one infiltration surface per set of K(ψ) measurements, it avoids the use of potentially unstable simultaneous‐equations solution procedures, and it can be applied to tension infiltration from both disk and ring infiltrometers.
Evaluation of Procedures for Aggregating Nonlinear Sulfate Adsorption Isotherm Data
Authors: Shaffer Paul W. , Stevens Donald L. 
Published: July 2010

AbstractAs part of a study to assess potential regional surface‐water acidification in the southern Blue Ridge region of the USA, more than 700 individual soils were sampled from 35 watersheds and analyzed. Sulfate adsorption isotherms were generated for all mineral soil horizons. Subsequent use of these data in dynamic watershed chemistry models required aggregation of adsorption data to two or three isotherms (one per soil mineral horizon) per watershed. This study evaluated several techniques for aggregation of the nonlinear adsorption‐isotherm data. The objective of the analysis was to identify a procedure for aggregation that would generate a function providing a representative weighted average of the SO2‐4 adsorption partitioning coefficients (isotherm slopes) of several individual isotherms, and would do so over a range of dissolved SO2‐4 concentrations. The most effective procedure involved a sequence of: (i) fitting isotherms for individual soils, (ii) computing values of adsorbed SO2‐4 corresponding to several reference concentrations of dissolved SO2‐4, (iii) computing weighted averages of adsorbed SO2‐4 at each of the reference concentrations, and (iv) fitting a new isotherm to the set of weighted points. Two alternate procedures for aggregation, computation of weighted averages of the coefficients of isotherms fitted to data for individual soils, or fitting a single isotherm to the raw data points for several soils, gave highly variable results that were usually skewed to low estimates of slope. Although specific results of this analysis relate to aggregation of SO2‐4‐adsorption isotherms, the strengths and weaknesses of the various aggregations have significant implications for aggregation of data sets for other nonlinear functions and for subsequent use of data. Use of an inappropriate aggregation procedure can lead to erroneous estimates of the capacity, efficiency, or response time of the system being described or modeled, and is likely to result in ineffective or inefficient treatment to supply putative adsorbates to the solid phase or to remove pollutants from solution.
Lignosulfonate Effects on Phosphate Reactions in a Clay Soil: Causal Modeling
Authors: Xie R. J. , MacKenzie A. F. , O'Halloran I. P. 
Published: July 2010

AbstractPhosphate adsorption reduces the effectiveness of P fertilizers. Lignosulfonate (LS) is expected to compete with P for adsorption sites on soil particle surfaces and reduce P retention. A Dalhousie clay soil (a fine, mixed, nonacid, frigid Typic Humaquept) was incubated with various amounts of CaLS (0–150 g kg−1 soil) and phosphate (0–792 mg P kg−1 soil) for 240 h under moist conditions. A subsample was extracted with deionized water and the supernatant analyzed for P, Ca, pH, and organic C. Additions of CaLS increased P retention, compared with zero addition, with maximum increase occurring with LS at 50 g kg−1 soil. Adsorption of organic C was greater with nondesugared (BD) than with desugared CaLS (SF), but P retention was greater with SF than with BD. Recursive causal modeling indicated that, with LS additions, P retention was mainly related to concentrations of P (path coefficient β = 0.79), Ca (β = 0.30), and organic C (β = −0.39), and retained LS‐C (β = 0.32). Supernatant pH was mainly a function of retained LS‐C (β = −1.22), and concentrations of Ca (β = 0.49) and P (β = −0.27). The data suggested that Ca added with CaLS precipitated P, probably forming hydroxapatite [Ca5(PO4)3OH]. Further studies with NH4LS showed low P retention with high NH4LS additions after soluble native Ca had been removed. The results confirmed that P retention was decreased by LS under the conditions that soil Ca was below the level required to form Ca‐P precipitates and that organic C had been adsorbed on the soil surface.
Separating Ion‐Exchange Resin From Soil
Authors: Thien Steve J. , Myers R. 
Published: July 2010

AbstractUse of ion‐exchange resins in soil science lacks a suitable technique for separating loose resin from soil. Implanting porous, resinfilled bags has been used, but limits soil‐resin contact. Grinding soil fine enough to sieve the resin may not be appropriate for some applications. We have developed a technique for separating loose resin from soil. A 1.31 M sucrose solution was added to a soil‐resin mixture and centrifuged 3 min at 1900 × g. Density differences caused the soil (2.65 kg m−3), sucrose solution (1.17 kg m−3), and exchange resin (1.12 kg m−3) to separate. The resin accumulated on top where it could easily be recovered by decanting for further analysis. Average recovery of resin was 99.0% from eight different soils. Resin added and resin recovered were highly correlated (r = 0.99) and were independent of soil/resin ratio. The use of sucrose, a nonionic solution, had no effect on resin composition in this procedure.
Collimated Neutron Probe for Soil Water Content Measurements
Authors: Klenke John M. , Flint Alan L. 
Published: July 2010

AbstractThe use of uncollimated (undirected) neutron moisture meters is common in the biological and geophysical sciences. A collimated neutron probe was designed to enable measurements in specific directions from the access tube. To determine the size and shape of soil volume affecting the neutron counts, experiments were conducted to evaluate: (i) the vertical distance of soil above and below the probe that influences neutron counts, (ii) the horizontal distance away from the probe into the soil that influences neutron counts, (iii) the angle of soil viewed by the probe from the collimator, and (iv) the three‐dimensional thermal‐neutron density field. The distance and the angular dimensions of the volume of influence were defined as the horizontal distance of neutron penetration from the edge of the probe, the vertical distance above and below the center of the effective measurement point of the probe, and the angle from the center of the probe, which would allow the determination of relative water content to within 95%. The vertical distance was ≈0.5 m, the horizontal distance was ≈0.2 m, and the angle of soil viewed by the probe from the collimator was ≈120°. Thermal neutrons detected from distances or angles larger than these values influence the determination of relative water content by 5% or less.
Air‐Drying and Pretreatment Effects on Soil Sulfate Sorption
Authors: Comfort S. D. , Dick R. P. , Baham J. 
Published: July 2010

AbstractDrying, freezing, and refrigeration are commonly employed to facilitate the handling and storage of soil samples on which chemical, biological, and physical analyses are to be performed. These laboratory protocol have the potential to alter soil chemical characteristics and may result in unrealistic estimates of in situ chemical processes. We determined the effect of air drying, storage temperature, and time on SO4‐sorption characteristics. Sulfate‐sorption experiments were conducted in the field on moist samples and compared with laboratory results for the same soils that had been kept frozen (−5 °C), refrigerated (4 °C) for 14 or 60 d, or air dried. Only air drying significantly altered SO4‐sorption characteristics. The impact of air drying on SO4‐sorption capacities was then determined on 29 pedons (84 horizons) from four northeastern USA (NE) and three southern Blue Ridge province states. A suite of physico‐chemical properties of soils whose sorption capacities were affected by drying were also measured. The SO4‐sorption capacity increased as much as 320% when dried soils were compared with field‐moist samples. Soils whose sorption capacities were most affected by air drying included the NE soils group, which had a higher percentage of the clay fraction in the form of amorphous minerals and were high in exchangeable acidity and total organic C. Air drying caused significant decreases in ethylenediaminetetraacetic acid (EDTA) extractable Fe and Al, oxalate‐extractable Al, and KCl‐extractable Al. This suggests the formation of new solids on drying, which increase SO4 sorption. Development of a multivariate model, however, indicated that total organic C, change in Fe extracted by pyrophosphate, dry minus moist; change in Fe extracted by oxalate, dry minus moist; and H+ solution concentration in 0.01 M CaCl2, dry minus moist were the best predictors of the change in SO4 sorption capacity with drying.
Potassium Quantity‐Intensity Relationships in Calcareous Vertisols and Inceptisols of Southwestern Spain
Authors: Jimenez C. , Parra M. A. 
Published: July 2010

AbstractQuantity‐intensity (Q/I) curves and derived parameters provide general information about soil K availability. This investigation was conducted to study the relationship between the K Q/I parameters and the properties of 24 calcareous Inceptisols and Vertisols of southwestern Spain. Three Q/I parameters were considered: activity ratio at equilibrium (ARo), buffer power at equilibrium (BPo), and buffer power in the 20 × 10−3 to 30 × 10−3 activity‐ratio range (BP20‐30). Close linear correlations were found between buffer powers (BP20‐30 and BPo) and cation‐exchange capacity (CEC) (r2 = 0.949 and 0.888, respectively), and between ARo) and initial exchangeable K percentage (EPPo) (r2 = 0.762). A good correlation (r2 = 0.873) was also found between EPP and AR for all the soils within the range of K saturation studied. Twelve of the 24 soil samples were intensively cropped (nine wheat [Triticum aestivum L.] croppings); the K balance showed that 80% of the K extracted by the crops came from the nonexchangeable K pool. The Q/I curves of the soil samples after cropping were displaced upward with respect to the original ones, and the ARo values were, consequently, lower; the displacement of the Q/I curves was similar to the decrease in exchangeable K. Following cropping, the BP20‐30 values increased slightly. In spite of these changes, the shape of the Q/I curves remained nearly unchanged; therefore, this can be considered a characteristic of the soils studied. The good correlations between ARo and EPPo and between buffer powers and CEC allow prediction of the Q/I parameters of these soils.
Silica and Carbonate Sources for Aridisols on a Granitic Pediment, Western Mojave Desert
Authors: Boettinger J. L. , Southard R. J. 
Published: July 2010

AbstractThree pedons on a granitic pediment in the western Mojave Desert, a Typic Durorthid, a noncalcareous Typic Haplargid, and a Typic Haplargid with carbonates below 80 cm, were studied to evaluate the potential of mineral weathering as a source of Si and Ca for the duripan and Bk horizons. Calcareous and noncalcareous soils occur as contiguous polypedons on the pediment surface, with calcareous soils overlying calcareous saprolite, and noncalcareous soils overlying noncalcareous saprolite. The irregular distribution of opaline silica and CaCO3 in these pedons cannot be attributed to a uniform input of eolian deposits across the pediment. Micromorphological and chemical evidence indicates that primary crystalline silicates in the calcareous horizons of these Aridisols have been weathered and replaced by opaline silica and calcite. Dissolution of plagioclase is a probable source of Ca in soil and saprolite carbonates. The lack of silt‐ and volcanic‐glass‐enriched vesicular A horizons suggests that eolian deposits of carbonates and volcanic ash are less significant in the formation of these soils than the contributions of weathering primary crystalline silicates in the granitic saprolite. The contribution of the weathering of crystalline silicates to soil formation in arid regions should not be overlooked.
Mechanical Strength of Clay Minerals as Influenced by an Adsorbed Polysaccharide
Authors: Chenu C. , Guérif J. 
Published: July 2010

AbstractThe water‐stabilizing action of polysaccharides on soil aggregates has been ascribed to the binding together of soil particles by polymer bridges. This study was conducted to investigate the ability of polysaccharides to increase the strength of interparticle bonds by measuring the mechanical strength of clay‐polysaccharide complexes. Kaolinite, montmorillonite, and the polysaccharide scleroglucan were used. Cores were prepared from dilute suspensions of the complexes, air dried, and manufactured either into small briquets or into spherical aggregates to measure respectively the modulus of rupture and the tensile strength. The polysaccharide increased the mechanical strength of both clay minerals. The modulus of rupture of montmorillonite increased from 265 to 580 × 105 Pa at the maximum adsorption of scleroglucan, which was 140 g kg−1 clay. In the case of kaolinite, modulus of rupture measurements indicated that particle‐orientation effects were small and could be neglected. The tensile strength of kaolinite increased from 1 to 20.6 × 105 Pa at the maximum adsorption of scleroglucan (29.9 g kg−1 clay). In this case, the mechanical properties were not due to changes in the clay microorganization, since scleroglucan affected neither the fabric nor the porosity of the kaolinite. Increases in strength were thus intercepted as the formation of polymer bridges between the clay particles and were related to the progressive coverage of the surface area of the clay by the polysaccharide. We concluded that the aggregating action of polysaccharides is predominantly due to an increased strength of interparticle bonds.
Chloride and Perchlorate Influence on Calcium‐Potassium and Magnesium‐Potassium Exchange
Authors: Karmarkar S. V. , Dudley L. M. , Jurinak J. J. , James D. W. 
Published: July 2010

AbstractThere is some uncertainty regarding the effect of the background electrolyte on Ca‐Na and Mg‐Na exchange. We conducted a study to see if any of the effects attributed to the background electrolyte in heterovalent exchange with Na could be observed when K was the monovalent cation. The influence of the competing cations Ca2+ and Mg2+ on K+ exchange was evaluated by examining quantity/intensity parameters (Q/I), Gapon‐convention selectivity coefficients, and adsorbed metal charge with Cl and ClO4 as the background electrolyte. Exchange reactions were unaffected by the background electrolyte for four of the five soils studied. In those soils where exchange was unaffected by the background electrolyte, there was a significant difference between Ca‐K and Mg‐K Q/I curves and Gapon selectivity coefficients; Ca was preferred over Mg relative to K. The Q/I curves from Ca‐K and Mg‐K systems differed in the Cl media, but not in the ClO4 media. Further, the Ca‐K curve was affected by the media. Calcium‐K and Mg‐K selectivity coefficients differed in both Cl and ClO4 media. The Ca‐K selectivity coefficients determined in ClO4 media were closer to Mg‐K selectivity coefficients than those determined in Cl media. The adsorbed metal charge did not increase when the exchanger composition was changed from Mg‐K to Ca‐K in Cl media. The effect of the background electrolyte on Ca‐K exchange was attributed to competition between K+ and CaCl+ for external exchange sites.
Evaluation of an In Situ Method for Measurement of Gas Diffusivity in Surface Soils
Authors: Rolston D. E. , Glauz R. D. , Grundmann G. L. , Louie D. T. 
Published: July 2010

AbstractDiffusion of gases across the soil/atmosphere interface is a major mechanism in water evaporation, soil aeration, and volatilization of N species, pesticides, and volatile organic compounds. Rapid methods to directly measure the soil‐gas diffusivity of surface soils in the field are needed. An in situ method for measuring the soil‐gas diffusivity was evaluated both theoretically and experimentally in order to provide guidelines for using the method with minimal experimental error. The method involves insertion of a cylinder into the surface of field soil and supplying a tracer gas to the confined soil core from a well‐stirred reservoir of finite volume placed over the inserted cylinder. An analytic solution for unsteady diffusion of a gas in one dimension in semiinfinite porous media is used to determine the soil‐gas diffusivity. In order to establish an estimate of the amount of time for which a diffusion experiment may be conducted without resulting in error due to finite soil core length, calculations of gas reservoir concentration were made for two extreme cases of the lower soil boundary condition. These calculations indicate that tests using a 10‐cm soil cylinder can be conducted for >50 min for soils with soil‐air contents (ε) <0.3 cm3 cm−3. For dry soil (ε > 0.3), soil cylinder depths of 15 or 20 cm should be used to extend the sampling time. Diffusivities determined from the in situ method are in reasonable agreement with cores removed from the field and analyzed in the lab using an independent method. The method should be used for times greater than ≈15 min in order to minimize errors associated with experimental measurements and perturbations associated with initiating the initial gas reservoir concentrations. The method offers a relatively rapid approach for measuring the diffusivity of surface soils in situ as long as the initial concentration of the tracer gas is accurately estimated and the assumption of uniform soil‐air content within the soil depth of interest is not greatly violated.
Soil Organic Matter Influence on Adsorption and Desorption of Boron
Authors: Marzadori C. , Antisari L. Vittori , Ciavatta C. , Sequi P. 
Published: July 2010

AbstractThe role of soil organic matter in B adsorption and desorption processes in soil is not yet clearly understood. Adsorption/desorption isotherms of B were compared in three soils before and after organic‐matter removal by NaOCl. The amount of B adsorbed was considerably greater after the organic matter had been removed from the soil, and the release of B showed a hysteretic trend or, in any case, the hysteretic nature of the B release increased. An increase in oxalate‐extractable Fe and Al occurred after destruction of the organic matter. It is suggested that a portion of the Fe and Al oxides, as well as other possible adsorption sites, are generally coated or occluded by organic matter and become active only after removal of the organic matter.
Pressure Solution: Possible Mechanism for Silicate Grain Dissolution in a Petrocalcic Horizon
Authors: Monger H. Curtis , Daugherty LeRoy A. 
Published: July 2010

AbstractIn the petrocalcic horizon of a middle Pleistocene soil in southern New Mexico, up to 58% of the silicate grains have dissolution features, such as embayed and serrated edges. The purpose of this study was to determine if pressure solution produced the dissolution features. Samples were analyzed in thin section using light and electron microscopy, and by measuring pH and Si concentration of saturated paste extracts. Four lines of evidence support the pressure‐solution mechanism in the petrocalcic horizon: (i) silicate grains are smooth where they contact pores, but serrated where they contact calcite; (ii) dissolution pits on silicate grains generally match the shapes of impacted calcite crystals; (iii) silicate grains are concentrated into horizonal layers in the upper petrocalcic horizon, which testifies to the pressure generated by crystallizing calcite; and (iv) outside the petrocalcic horizon where crystallization pressure is less, silicate grains coated with calcite crystals have fewer dissolution features than grains in the petrocalcic horizon. No relationship was apparent between silicate‐grain dissolution and petrocalcic‐horizon pH or Si concentration. The pH (7.6) was below, and the Si concentration (8.6 mg L−1) was above the levels required for dissolution. Thus, pressure generated by crystallizing calcite appears to have caused dissolution features on the silicate grains in the petrocalcic horizon.