bluuebunny/crossref_metadata_2025_split huggingface dataset:
Diffusional Constraints on Denitrification in Soil
Authors: Myrold David D. , Tiedje James M. 
Published: July 2010

AbstractA model for NO−3 reduction and diffusion in aggregated soils is presented and used in conjunction with a derived constant, the Thiele modulus, to examine the conditions which could contribute to a NO−3 diffusion limitation of denitrification. The Thiele modulus is a function of the anaerobic radius of an aggregate, the maximum rate of NO−3 reduction for a given soil, the Km value for NO−3 reduction, and the intra‐aggregate NO−3 diffusion coefficient. Results from this theoretical exercise suggested that the anaerobic radius is the most important factor in determining whether denitrification is limited by NO−3 diffusion. The model predicts that under anaerobic conditions, only soils with a mean aggregate radius greater than 2 mm will experience a NO−3 diffusion limitation. This limitation may not be effective in practice if the bulk NO−3 concentration is much greater (100 times) than the Km for NO−3 reduction; this appears to often be the case in fertilized soils but may not be the case in soils of natural ecosystems. Under aerobic conditions, a diffusion limitation will exist in most aggregated soils, since only large aggregates have anaerobic microsites (i.e., large anaerobic radii) where denitrification can occur. A carbon limitation, through its lowering of the maximum denitrification rate, lessens the magnitude of any existing NO−3 diffusion limitation. Diffusive limitations were experimentally examined in two ways. First, the ratio of denitrification rates of anaerobic cores relative to anaerobic slurries were used to indicate the degree of any substrate supply limitation; the slurry rates were always greater suggesting either NO−3 or carbon was limiting. Second, soil cores were preincubated with either NO−3 or a diffusible carbon source (succinate) at 4°C to allow diffusion but to suppress biological responses. These results revealed that carbon, rather than NO−3, was limiting denitrification rates in this clay loam soil. These experimental results were in agreement with model predictions.
Predictability of Recreational Impact on Soils
Authors: Marion Jeff L. , Merriam L. C. 
Published: July 2010

AbstractBiophysical measurements were taken on 96 paired campsites and controls in the Boundary Waters Canoe Area Wilderness of north‐eastern Minnesota. Multiple regression analysis was used to identify and evaluate factors affecting changes in bulk density, organic horizon thickness, and exposed soil associated with campsite use. The best predictors of change in bulk density were campsite age, mineral soil organic content, organic horizon thickness, and offsite bulk density. Offsite organic horizon thickness and level of use were the best predictors of change in campsite organic horizon thickness. Level of use and campsite age were the best predictors of amount of exposed soil. Bulk density and exposed soil continued to increase with campsite age, even though all sites included in the study were > 5 yr in age. Other studies have not found this relationship. This information can be used to assist managers in selecting recreation site locations and appropriate site management techniques.
Hydroxylamine and Ammonium Oxalate Solutions as Extractants for Iron and Aluminum from Soils
Authors: Ross G. J. , Wang C. , Schuppli P. A. 
Published: July 2010

AbstractA comparison was made of acid hydroxylamine and acid ammonium oxalate methods for extracting Fe and Al from three clay mineral (chlorite) samples and 27 soil samples. Although the hydroxylamine solution was more acid than the oxalate solution, the hydroxylamine extraction did not increase dissolution of the chlorites markedly. It was concluded that overnight hydroxylamine extraction at room temperature using a 1:250 soil‐to‐solution ratio can be used as an alternative method to the 4‐h oxalate extraction method with the 1:40 soil‐to‐solution ratio commonly used in soil studies. This conclusion was based on the following reasons: (i) the results from both methods were comparable for nearly all samples; (ii) hydroxylamine solutions were more easily analyzed than oxalate solutions by atomic absorption analysis; (iii) overnight hydroxylamine extraction at room temperature required no specialized heating baths with compatible shaking equipment and is therefore suitable for most laboratories.
Inspectional Analysis in the Theory of Water Flow through Unsaturated Soil
Authors: Sposito Garrison , Jury William A. 
Published: July 2010

AbstractConventional inspectional analysis is applied to the one‐dimensional Richards equation to provide a unified classification scheme for three macroscopic scaling approaches which have been used to describe soil water flow phenomena under laboratory or field conditions. It is shown that the scaling parameters and similarity groups developed in an inspectional analysis of the Richards equation depend on the boundary and initial conditions imposed as well as on the special physical hypotheses invoked. Nielsen similarity analysis is based on a zero‐flux boundary condition and the assumption that the hydraulic conductivity, soil water diffusivity, and matric potential are exponentional functions of water content. Warrick similarity analysis, on the other hand, is formulated independently of the boundary and initial conditions while adopting three scaling parameters to define reduced forms of the water content, hydraulic conductivity, and matric potential. Field experiments have shown that two of these parameters often are correlated. Macroscopic Miller similarity analysis is based on the physical postulate that water transport through unsaturated soil is governed by viscous flow and capillary forces. It differs from the classical Miller similar media concept in that it requires a scaling parameter for the volumetric water content and makes no direct reference to the geometric structure of a soil at the pore scale.
Analysis of Soil Water Content and Temperature Using State‐space Approach
Authors: Morkoc F. , Biggar J. W. , Nielsen D. R. , Rolston D. E. 
Published: July 2010

AbstractSeveral statistical methods have been developed to smooth or interpolate observations taken spatially and temporally. Most of these methods require that the observations manifest stationarity, meaning that the expected value of the observations is constant over the domain considered. The authoregressive moving average method requires the above condition but can also be used to estimate missing observations. The exponential smoothing method is available for nonstationary time or space series but generally requires evenly spaced observations. The state‐space model can be used for smoothing or estimating and forecasting a relatively short, nonstationary series of observations. A first order state‐space model was used here to estimate the missing observations of 0‐ to 5‐cm gravimetric soil water content. This was accomplished using joint analysis of observed water content and soil surface temperatures from a sorghum field irrigated by two line source irrigation system. The parameters of the model indicated the degree of spatial correlation between the two measured parameters. The expectation maximization algorithm and Kalman smoothed estimators were used to estimate the first order state‐space model parameters by maximum likelihood.
Kinetics of Post‐reclamation Boron Dissolution
Authors: Peryea F. J. , Bingham F. T. , Rhoades J. D. 
Published: July 2010

AbstractThe <0.25‐mm particle size fractions of four natively high boron (B) soils were reacted in suspension with a B‐specific exchange resin. By separating the resin from the suspension after selected times of reaction, four subsamples of each soil were obtained, representing increasing degrees of reclamation. The subsamples were reacted with deionized water and release of residual B to the supernatant was measured as a function of time. The data for each soil subsample were plotted according to an integrated form of the Elovich reaction rate equation. The release of B from the soils closely conformed to a linear function of the natural logarithm of time. Linear regression analysis was used to calculate the reaction rate constants for each treatment. The rate of post‐reclamation B dissolution and the equilibrium concentrations of regenerated B were inversely related to the amount of B removed from each soil during reclamation.
Mechanisms for Boron Regeneration
Authors: Peryea F. J. , Bingham F. T. , Rhoades J. D. 
Published: July 2010

AbstractThe ability of reclaimed natively high B soils to re‐establish elevated soluble B concentrations has been termed “boron regeneration”. Potential mechanisms for this phenomenon were qualitatively examined. Soil samples reclaimed in columns contained appreciable concentrations of residual, potentially reactive B and Cl−. Reclamation by multiple batch extraction removed 100 percent of the Cl−; however, the soils could not be completely reclaimed of B. Boron regeneration was observed in both column and batch reclamation systems, while Cl− regeneration occurred only in the column systems. The data suggest that two mechanisms may account for B regeneration. Post‐reclamation release of B from residual sparingly soluble or desorbable B‐containing sources is confirmed by the batch and column experimental results. The column data suggest that portions of the soil were bypassed by the leaching solution during reclamation. By analogy with Cl− behavior, post‐reclamation diffusion of B from bypassed to leachable pores also contributes to the B regeneration phenomena.
Predicting the Most Efficient Phosphorus Placement for Soybeans
Authors: Borkert C. M. , Barber S. A. 
Published: July 2010

AbstractThe effect of placement of P fertilizer on P uptake and plant growth has been predicted for corn (Zea mays L.) but not soybeans [Glycine max (L.) Merr.]. The objective of this paper is to predict the effect of P placement on soybeans and compare it with predictions made earlier for corn. Data for operation of the model were obtained from a pot experiment reported in an earlier paper. Calculations were for soybeans, cv. Century, growing on Raub soil (fine silty, mixed, mesic, Aquic Argiudolls). Calculations were made for P rates of 30, 60, 120, 240, and 480 mg kg−1 each with fractional volumes of soil fertilized ranging from 1.0 to 0.01. Predicted P uptake was converted to predicted plant weight using an experimental relation between P uptake and plant weight. The placement giving the greatest predicted P uptake interacted with P rate. At each P rate as P was mixed with an increasing volume of soil, predicted P uptake reached a maximum and decreased. The greatest predicted P uptake occurred when P was placed in 0.04 of the soil volume when the P rate was 30 mg kg−1, 0.10 when the rate was 60 mg kg−1, 0.20 when the rate was 120 mg kg−1, and 1.0 when the rate was 240 mg kg−1. The results were comparable to those obtained with corn.
Use of By‐product Gypsum to Alleviate Soil Acidity
Authors: Oates Kenneth M. , Caldwell A. G. 
Published: July 2010

AbstractBy‐product gypsum has been accumulating in large mounds in southern Louisiana for over 25 yr and little has been utilized. The objective of this study was to determine if large applications of byproduct gypsum could be used to alleviate soil acidity. A column leaching experiment was conducted using an acid subsoil amended with 5.0 gypsum equivalents of phosphogypsum, hydrofluorogypsum, or pure gypsum. In addition, several rates < 5.0 were used for the pure gypsum. Soybeans (Glycine max L.) var. ransom were then grown in a greenhouse experiment on an acid subsoil amended with 5.0 gypsum equivalents of phosphogypsum, hydrofluorogypsum, or pure gypsum. (One gypsom equivalent is defined as 4.2 cmol (+) kg−1.) Results of the column leaching experiment showed that both by‐ product gypsums removed more Al from the soil than did pure gypsum. They also removed Al at a faster rate than pure gypsum. Hydrofluorogypsum was the most effective. It removed 81% of the KC1‐extractable Al and increased the soil pH from pH 4.9 to pH 5.3. The increased effectiveness of the by‐product gypsums was shown to be due to the fluoride impurity. The Al removed by pure gypsum increased linearly as described by the regression equation of Al leached = −0.0137 + 0.276 (gypsum equivalent) [R2 = 0.99] Soybeans grown on soil amended with by‐product gypsum and leached had significantly higher plant weights than soybeans grown on nonleached amended soil.
Morphology of Late Holocene Soils at the Lubbock Lake Archeological Site, Texas
Authors: Holliday Vance T. 
Published: July 2010

AbstractThree soils have been identified in late Holocene deposits at the Lubbock Lake site, a well‐ stratified archaeological locality on the Southern High Plains. The soils have been informally named and their ages firmly established by radiocarbon dating. The soils formed in quartzose, sandy loam to sandy clay loam, dominantly eolian sediments with illite and mixed‐layer illite‐smectite clay mineralogy and lesser amounts of smectite and kaolinite. The Lubbock Lake Soil formed in material deposited between 5000 and 4500 yr BP and has had 4500 yr to form or, where buried, 3500 yr. The soils exhibits mollic and ochric (buried) epipedons, cambic and argillic and, in some positions, a partically gleyed B horizon, and Stage I or II, often multiple, calcic horizons. It is classified as either a Calciustoll, Haplustoll, Haplustalf, or Ustochrept. The Apache Soil formed in sediments deposited from 800 to 450 yr BP and is 450 yr old where not buried and 200 yr old where buried. The soil usually has a mollic epipedon but in some buried situations it is ochric. The B horizon is normally cambic but sometimes qualifies as argillic. Secondary carbonate accumulation, sometimes qualifying as calcic, commonly attains a Stage I morphology. The Apache Soil is classified as either an Ustochrept, Haplustoll, Calciustoll or possibly minimally developed Haplustalfs. The Singer Soil formed in sediments deposited from 250 and 100 yr. BP, allowing 100 yr for soil formation. The soil has an ochric epipedon and either a C, Bw, or a cambic horizon. Weak Stage I carbonate horizons are common but never qualify as calcic. The Singer Soil is classified as an Ustorthent. These three soils define a chronosequence that will allow a study of pedogenesis in Holocene sediments in a semiarid environment. The discovery of soils elsewhere on the southern High Plains of similar age, parent material, and landscape setting to the Lubbock Lake Soil and possibly the two younger soils, indicate that these late Holocene soils will be useful stratigraphic markers and dating tools.
Sulfate Adsorption Relationships in Forested Spodosols of the Northeastern USA
Authors: Fuller R. D. , David M. B. , Driscoll C. T. 
Published: July 2010

AbstractSoil SO2−4 adsorption has important implications in the study of acidic deposition effects on terrestrial and aquatic systems, because this process results in the release of alkalinity or prevents leaching of H+ and cations. Forested Spodosols of the northeastern USA have generally been considered poor adsorbers of SO2−4, in part due to the interfering effects of soil organic matter. Soils from both the Adirondack Mountains, NY and the Hubbard Brook Experimental Forest, NH (Typic and Lithic Haplorthods and Aquic Fragiorthods, respectively), however, contained SO2−4 in Bs horizons predominately in an insoluble (nonwater‐extractable) form and were capable of adsorbing additional SO2−4 given higher SO2−4 concentrations than currently found in situ. Concentrations of insoluble SO2−4 in Bs horizons ranged from 0.3 to 2.1 × 10−3 mol SO2−4 Kg−1 by H2PO−4 extraction. Fractionation of free Fe and Al suggest that both elements were present largely in organically complexed forms. Insoluble SO2−4 was highly correlated with several forms of free Fe and Al, but crystalline Fe and organic Al content appeared to explain most of the variability in SO2−4 adsorption capability. These soils may not presently be accumulating SO2−4 through the adsorption process on an annual basis. Their SO2−4 adsorption capability, however, indicates that the adsorption process may well buffer seasonal variations in SO2−4 concentration or serve as a net source or sink of SO2−4 subsequent to conditions which either influence concentrations of SO2−4 in the soil solution (eg. atmospheric inputs) or affect the adsorbent phase.
Layer Charge Evaluation of Expandable Soil Clays by an Alkylammonium Method
Authors: Senkayi A. L. , Dixon J. B. , Hossner L. R. , Kippenberger L. A. 
Published: July 2010

AbstractThe interlayer charge of five reference smectites (hectorite, saponite, two montmorillonites, and a nontronite) and clay samples from strongly acidic smectitic soils of Alabama, Mississippi (Ultisols), and Texas (Alfisol) were investigated by an alkylammonium method (AAM). The total layer charge of the reference smectites based on the chemical formula ranged from 0.31 to 0.50 mol(−) per O10(OH)2. The interlayer charge density by AAM linearly increased with increasing total charge. Nontronite had the highest tetrahedral charge and exhibited the highest interlayer charge density. A qualitative distinction of soil clay samples containing low charge and high charge smectite or vermiculite was based on the d‐spacings of the complexes formed by a single alkylammonium compound. Changes in relative peak intensities indicated that the low charge smectite increases whereas the high charge smectite decreases with profile depth. The low charge smectite in these soils appears to have been mostly inherited from the underlying Tertiary and Cretaceous sediments whereas the high charge smectite appears to be a weathering product of the mica present in these sediments.
Use of Peltier Coolers as Soil Heat Flux Transducers
Authors: Weaver H. L. , Campbell G. S. 
Published: July 2010

AbstractPeltier coolers were modified and calibrated to serve as soil heat flux transducers. The modification was to fill their interiors with epoxy. The average calibration constant on 21 units was 13.6 ± 0.8 kW m−2 V−1 at 20°C. This sensitivity is about eight times that of the two thermopile transducers with which comparisons were made. The temperature coefficients of the Peltier cooler transducers avg −0.034 kW m−2 V−1 °C−1, whereas those of the two thermopile transducers were only 25% as large, relative to their calibration constants. The thermal conductivity of the Peltier cooler transducers was 0.4 W m−1 °C−1, which is comparable to that of dry soil. The cost of an unmodified Peltier cooler is around $20.
Zeta Potential and Surface Area of Calcium Carbonate as Related to Phosphate Sorption
Authors: Amer Fathi , Mahmoud A. A. , Sabet Violette 
Published: July 2010

AbstractOrthophosphate (OP) sorption by eight reagent‐grade CaCO3 samples and a natural limestone, as influenced by the surface area and zeta potential (ZP), was investigated in the absence and presence of pyrophosphate (PP) as a crystal growth inhibitor. Reacting the nine CaCO3 samples for 24 h with 1 mmol OP L−1 indicated a rapid 0.08‐h adsorption reaction and a 2‐h induction period that preceded OP precipitation. The amount of adsorbed OP was proportional to the CaCO3 surface area which ranged from 250 to 12 780 m2 kg−1 and accounted for 92.8% of the variation in OP adsorption. The surface area was generally proportional to the ZP, as five CaCO3 samples were positively charged with ZP values ranging from 17.7 to 25.3 mV, three samples were noncharged, and only limestone was negatively charged with a ZP of −6 mV. The ZP decreased with OP adsorption and again increased after OP precipitation. Addition of PP did not interfere with OP adsorption, but inhibited OP precipitation during the 24‐h reaction period by extending the induction period, and markedly reduced the ZP. Negativity of the CaCO3 particles per se was not considered the main factor in retarding P precipitation, as polyacrylamide was very effective in lowering ZP but had no effect on OP sorption. The added PP was also subject to adsorption by the CaCO3 and, therefore, the amount of PP needed for inhibiting growth of the calcium phosphate crystals depended on CaCO3 reactivity as well as on OP concentration.
Sodium‐Calcium‐Magnesium Exchange on Silver Hill Illite
Authors: Sposito Garrison , LeVesque C. S. 
Published: July 2010

AbstractBinary and ternary cation exchange reactions involving sodium (Na+), calcium (Ca2+), and magnesium (Mg2+) on Silver Hill illite suspended at pH 7 in a 50 mol m−3 perchlorate background were investigated. The binary exchange experiments indicated a preference of the clay mineral for Ca and Mg over Na and for Ca over Mg. The principal ternary exchange data, on the other hand, indicated no selectivity difference between Ca and Mg in the presence of adsorbed Na at a nominal exchangeable sodium percentage (ESP) of 25. No differences among the values of the total adsorbed metal charge (Qo) were observed in a set of binary and ternary Na→M (M = Ca and/or Mg) exchange experiments carried out at the same time. There was, however, a systematic increase in the value of Qo on a time‐scale of months in Na‐illite suspended in NaClO4. The increase in Qo was produced by adsorbed Na+ that could be displaced by ammonium (NH+4) but not by Ca2+ or Mg2+ ions. The quantity of this “quasi‐exchangeable” Na present in the principal ternary exchange experiments was determined to be about 13% of the value of Qo, an amount concluded to be sufficient to cover the high‐energy exchange sites on the illite and thereby relegate Ca‐Mg exchange to sites having relatively low selectivity differences, as observed experimentally.
Determination of Nitrate in Soil Extracts by Dual‐wavelength Ultraviolet Spectrophotometry
Authors: Norman Richard J. , Edberg Jeffrey C. , Stucki Joseph W. 
Published: July 2010

AbstractA rapid method is described for determining nitrate concentration in a soil extract solution based on its UV absorbance at 210 nm. The interference of nonnitrate species is accounted for by subtracting an empirically‐determined multiple of the absorbance of the extract solution at 270 nm from its absorbance at 210 nm. The value of the multiplication factor, R, is calculated from the 210: 270 nm absorbance ratio of the extract solution after it has been treated with Raney‐Nickel catalyst to remove nitrate. The method was tested using 10 Illinois soils. The composite value of R for these soils was 3.05 ± 0.22. This value, as well as each individual value of R for the respective soils, was used to calculate the nitrate concentration. The results were then compared to one another and to results obtained by the steam distillation method. Correlation among these various methods was very high, giving values of r2 of 0.9987 and 0.999. Large errors occurred when no correction for nonnitrate species was made.