bluuebunny/crossref_metadata_2025_split huggingface dataset:
Lysimeter and Centrifuge Soil Solutions: Seasonal Differences between Methods
Authors: Zabowski D. , Ugolini F. C. 
Published: July 2010

AbstractLysimetry and centrifugation were compared as variable‐tension (centrifugation) and low‐tension (lysimetry) soil‐solution collection methods. Low‐tension lysimetry and low‐ and high‐speed centrifugation with double‐bottom cups were used to collect soil solutions from each major horizon of a subalpine Spodosol. Solution samples were collected monthly and compared throughout a 1‐yr period. Few seasonal changes were observed in the cation, anion, pH, or C concentrations of the lysimetry solutions. Both low‐ and high‐speed centrifuge solutions showed a strong seasonal cycle for major cations, anions, and C; peaks occurred in winter and summer and were especially evident in the upper horizons. Centrifuge solution concentrations were frequently greater than those of the lysimeter solutions. Aluminum and Si were exceptions, with lysimetry solution concentrations equal to or greater than those of the centrifuge solutions. Centrifuge solution concentrations of Al and Si also showed increases in concentration during summer months only. Seasonal variations may be due to differences in soil water residence time or biological processes. Results suggest that both the methodology used for obtaining soil solutions and the time of sampling can influence solution composition.
Diffusion, Adsorption, and Predicted Longevity of Banded Phosphorus Fertilizer in Three Soils
Authors: Eghball Bahman , Sander D. H. , Skopp J. 
Published: July 2010

AbstractDiffusion of banded P fertilizer influences the residual P effect, root/P‐fertilizer contact, fertilizer‐P longevity (the time after which the contribution of applied band to plant P uptake is insignificant) and the probability that the P‐affected soil will be collected during soil sampling. An experiment was conducted to determine the extent of P diffusion from banded P application, diffusion coefficients, and the longevity of banded P fertilizer. Six P rates of 15, 22.5, 30, 37.5, 45, and 60 kg P ha−1 tagged with 32P were applied in a band in three soils and allowed to diffuse under field conditions for 94 d. Phosphorus‐fertilizer movement from the injected band centers (30‐cm spacing) after 94 d ranged from 1.8‐cm radius at the 15 kg P ha−1 rate in the Sharpsburg (fine, montmorillonitic, mesic Typic Argiudoll) and Coly (fine‐silty, mixed [calcareous], mesic Typic Ustorthent) soils to 3.9 cm at the 60 kg P ha−1 rate in the Nora (fine‐silty, mixed, mesic Udic Haplustoll) soil. The diffusion distances and apparent diffusion coefficients increased in a linear manner as the P application rate increased. The calculated longevity of banded P fertilizer ranged from 2.6 yr at 15 kg P ha−1 in the Sharpsburg soil to 6.5 yr at 60 kg P ha−1 in the Coly soil. The longevity of banded P fertilizer was shortest for the Sharpsburg soil with the highest P‐adsorption capacity and was longest for the Coly soil with the lowest P‐adsorption capacity. The probability of P‐affected soil being collected during soil sampling ranged from 11.7% at 11.7% at 15 kg P ha−1 in the Sharpsburg soil to 25.9% at 60 kg P ha−1 in the Nora soil. Soil sampling and soil‐test P calibration should be altered to account for the residual nature of applied P bands.
Clay Minerals of Two Eutrandepts of Hawaii, Having Isohyperthermic Temperature and Ustic Moisture Regimes
Authors: Wada K. , Kakuto Y. , Ikawa H. 
Published: July 2010

AbstractClay minerals of two pedons of Naalehu soils from Hawaii were studied by a combination of methods. According to Soil Taxonomy, they are classified as medial, isohyperthermic Typic Eutrandept. In the Andisol proposal, Naalehu‐1 is not an Andisol because its P retention is <85%, but Naalehu‐2 is classified as an Andisol because it meets all of the definitions of andic materials. Their clay content was high (49–85%), with no significant difference between the two soils. The Naalehu‐2 soil clays, however, had higher contents of oxalate‐oxalic acid soluble aluminosilicates and Fe oxides than the Naalehu‐1 soil clays. These clays also showed halloysite (1.0 nm), concentric spherules and curled flakes, and possibly hollow spherical aluminosilicates having a close structural relation with allophane. The Naalehu‐1 soil clays, on the other hand, showed smectite, halloysite (1.0 nm), and their interstratified species. Both soils contained X‐ray‐detectable amorphous Fe oxides in the clay and poorly crystalline maghemite, olivine, and plagioclase in the silt and sand fractions. The importance of the soil‐forming factors of parent material, climate (soil moisture and soil temperature), and age was inferred from comparison of the smectite and/or halloysite mineralogy of the isohyperthermic Naalehu soils with the imogolite and/or allophane mineralogy of the isothermic and isomesic Maui soils studied earlier.
Diffusion of Soil Extracts for Nitrogen and Nitrogen‐15 Analyses by Automated Combustion/Mass Spectrometry
Authors: Burke Ingrid C. , O'Deen Louise A. , Mosier Arvin R. , Porter Lynn K. 
Published: July 2010

AbstractThe coupling of automated combustion instruments with mass spectrometry has streamlined total N and 15N analyses of soil and plant materials. New methods are needed for analysis of soil NH4 and NO3 15N to take advantage of the efficiency in automated combustion analysis. We have developed a method to quantitatively determine NO3, NH4, and 15N content of soil extracts by automated combustion/mass spectrometry. Soil extracts are made basic, and diffused into acid‐washed zeolite in tin combustion cups. Zeolite samples are then analyzed on the automated combustion/mass spectrometry system for N and 15N. Ammonium‐ and NO3‐N and 15N can be quantitatively recovered and analyzed during this procedure, reliably collecting 97% of the N and 15N in the extract, with a repeatability of ±2%.
Modeling Reactive Gas Uptake, Transport, and Transformation in Aggregated Soils
Authors: Rasmuson Anders , Gimmi Thomas , Flühler Hannes 
Published: July 2010

AbstractGas diffusion research in soils covers, to a large extent, the transport behavior of practically insoluble gases. We extend the mathematical description of gas transport to include reactive gaseous components that hydrolyze in water such as SO2 and CO2. The path between the free atmosphere and the microporous niches is modeled by assuming penetration through gas‐filled macropores, air‐water phase transfer, and diffusion and speciation in the liquid phase. For hydrolyzable gases, the rate of mass transfer into and the total absorption capacity of the soil solution may be high. Both the capacity and the transfer rate are influenced by the soil‐solution pH; for high pH, they become extremely high for SO2. The soil absorption of such gases is also influenced by soil structure. Well‐aerated, near‐neutral soils are a potentially important sink for SO2.
Kinetics and Mechanisms of Sulfate Adsorption/Desorption on Goethite Using Pressure‐Jump Relaxation
Authors: Zhang Peng Chu , Sparks Donald L. 
Published: July 2010

AbstractSulfate adsorption/desorption on goethite (FeOOH) in aqueous suspension was investigated thermodynamically and kinetically. The SO4‐adsorption isotherm indicated that adsorption decreased with increased pH of the goethite suspension. The triple‐layer model fit the experimental data well when adsorbed SO4 was assumed to be located at the β plane and held via outer‐sphere complexation. Pressure‐jump relaxation was used to determine the kinetics of SO4 adsorption/desorption on goethite. A single relaxation was observed due to adsorption/desorption processes. Based on the equilibrium and kinetic studies, we hypothesized and tested two reaction mechanisms for SO4 retention. The first postulated mechanism (Reaction 1) assumed that SO4 was adsorbed on a positively charged surface site through electrostatic attraction. This mechanism was rejected because of the poor conformity between the intrinsic equilibrium constant (Kinteq) determined from the static studies and that found from the ratio of forward (kint1) and backward (kint‐1) rate constants, i.e., Kint1 = kint1/kint‐1. It was found that the adsorption of SO4 on goethite occurred simultaneously with the protonation of a neutral surface site, as assumed in the second hypothesized mechanism (Reaction 2). Based on this mechanism, a linear relationship between the reciprocal relaxation time (τ−1) and various concentration terms was observed. From this relationship, kint2 and kint‐2 were calculated and were 2.02 × 108 mol−2 L2s−1 and 0.144 s−1, respectively. The intrinsic equilibrium constant from kinetic measurements (Kint2) was 109.14 mol−2L2, which was similar to the intrinsic equilibrium constant from the equilibrium studies, 109.60.
Analyses of Adsorption Kinetics Using a Stirred‐Flow Chamber: II. Potassium‐Calcium Exchange on Clay Minerals
Authors: Eick Matthew J. , Sparks Donald L. , Bar‐Tal Asher , Feigenbaum Sala 
Published: July 2010

AbstractPotassium‐calcium adsorption kinetics on a Llano vermiculite and an Arizona montmorillonite were studied using a stirred‐flow technique. Various experiments were conducted to distinguish between (i) instantaneous equilibrium and time‐dependent reactions, and (ii) solution‐concentration‐dependent kinetic models vs. those that are independent of solution concentration. These experiments included varying the flow rate and influent concentration and stopping the flow for a period of time. It was found that K‐Ca exchange on montmorillonite was too rapid to be measured with the stirred‐flow technique, while exchange rates on vermiculite could be ascertained. Adsorption kinetic parameters should be included in transport models to more accurately predict the fate of ions in soils dominated by vermiculitic and micaceous clay minerals.
Potassium Supply Characteristics of Thirty‐three Soils as Influenced by Seven Rates of Potassium
Authors: Kovar J. L. , Barber S. A. 
Published: July 2010

AbstractLimited information is available on the effect of applications of multielement fertilizer materials on the concurrent changes in Kl (soil‐solution K) and Ks (exchangeable K). The objectives of this research were to: (i) investigate the relative increases in both Kl and Ks after addition of graded amounts of a 3‐4‐7.5 solution fertilizer; and (ii) determine if the changes in Kl and Ks with fertilizer additions were related to some measurable physical or chemical property of the soil. Thirty‐three surface soils were equilibrated moist for 3 wk after addition of 0, 21, 42, 104, 208, 415, and 1245 mg K per kg of soil. High rates of application were used because they occur when the same total amount of K is placed in a small fraction of soil, e.g., band application. Values of Kl were determined from water‐displaced soil solution. Values of Ks were obtained from K extracted with 1.0 M NH4OAc at pH 7.0 minus θKl, where θ is the volumetric water content g−1 of sample. The increase in Kl with K addition was described by Kl = axc + d, where x is the amount of added K and a and d are regression constants. Values of c, the curvilinearity coefficient, varied from 1.00 (linear) to 1.59. The increase in Ks with K addition was described by Ks = g + hx. The value g represents the amount of exchangeable K in the untreated soil. Values of h, the slope, varied from 0.42 to 1.13. The coefficients describing the relation of both Kl and Ks to added K were not correlated with any of the measured soil properties. There was no significant correlation between c and h. Characterization of the changes in Kl and Ks after addition of K gives information useful for determining the effectiveness of K placement.
Antecedent Water Content and Rainfall Energy Influence on Soil Aggregate Breakdown
Authors: Truman C. C. , Bradford J. M. , Ferris J. E. 
Published: July 2010

AbstractStability of soil aggregates under rainfall plays an important role in determining the magnitude of soil loss from cultivated fields. Soil and environmental factors controlling aggregate breakdown have yet to be fully defined. The objective of this study was to determine the influence of soil water condition, aggregate size, and rainfall intensity and duration on aggregate breakdown. Five soils ranging in texture from sandy loam to clay were studied. Using the wet‐sieving method, median aggregate diameter values (D50) were determined on both whole‐soil samples (0–19 mm) and aggregate samples (2–4, 4–8, and 8–19 mm in diam.) at three water conditions (−0.5 kPa, −1.0 kPa, and air dried). A companion set of whole‐soil samples was subjected to 64 and 127 mm h−1 simulated rainfall for 5, 15, and 30 min, and a set of aggregate samples was exposed to 64 mm h−1 simulated rainfall for 15 min; all samples were then wet sieved. Prewetting from air dry to −1.0‐kPa matric potential provided the greatest increase in D′50 values (D50 corrected for primary particle size) for the wet‐sieved Broughton clay (0.49–1.91 mm). Prewetting the Broughton clay also decreased the difference (ΔD50) between Broughton D50 values obtained from whole‐soil samples receiving rain plus wet sieving and D50 values of only wet‐sieved samples by 1.4 mm for all rainfall energies. Changes in D′50 and ΔD50 values due to rainfall energy were greatest for the air‐dried Heiden clay. Rainfall energy (0.26 J cm−2) decreased D′50 values from 0.87 to 0.33 mm and increased ΔD50 values from 0.32 to 0.54 mm. Results of this study indicate that an increase in initial water condition increases the resistance of an aggregate to the forces of raindrops and flowing water, thereby lessening particle detachment (if other hydraulic variables are held constant).
Factors Determining Differences in Soil pH in Adjacent Conifer and Alder‐Conifer Stands
Authors: Binkley Dan , Sollins Phillip 
Published: July 2010

AbstractTree species may differ in their influence on biogeochemical cycles, leading to differing rates of soil acidification. Over time, quantitative and qualitative changes develop in the characteristics of the soil exchange complex. Three such characteristics regulate soil pH: (i) the quantity of acids present, which can be represented as the total cation‐exchange capacity (CEC); (ii) the degree of dissociation of the acids, commonly called base saturation; and (iii) the affinity of the acids for H+, or acid strength, which represents the composite pKa (negative log of the acid ionization constant) of the exchange complex. We examined the importance of these three factors in explaining the differences in soil pH between adjacent stands of conifers [primarily Douglas fir, Pseudotsuga menziesii (Mirbel) Franco] and conifers mixed with N‐fixing red alder (Alnus rubra Bong.). At a low‐productivity site (Wind River, WA), the pH of 0 to 0.15 m of soil from both alder‐conifer and conifer stands averaged 4.3 in 0.01 M CaCl2. The pH values were the same, however, only because higher base saturation in the alder‐conifer stand was offset by greater acid strength. At a more productive site (Cascade Head, OR), soil pH (in 0.01 M CaCl2) averaged 3.7 in the alder‐conifer stand but 4.4 in the conifer stand. The difference in pH resulted primarily from greater acid strength of soil organic matter under alder, and secondarily from lower base saturation of the exchange complex. These results underscore the importance of considering qualitative changes in soil organic matter as factors driving changes in soil pH and other parameters.
Predicting Cation Mobility in Montmorillonitic Media Based on Exchange Selectivities of Montmorillonite
Authors: Gaston L A. , Selim H. M. 
Published: July 2010

AbstractCation‐exchange reactions influence the distribution of species between soil solution and sorbed phases and, in turn, the rate of movement of species through the soil. This study was undertaken to determine whether cation‐exchange selectivity coefficients of montmorillonite could be used to adequately describe cation movement in a montmorillonitic soil. Literature data for Ca‐Mg, Ca‐Na, and Mg‐Na exchange on pure montmorillonite in ClO4 and Cl anionic backgrounds were used to calculate average values for binary exchange selectivity coefficients. These selectivity coefficients were subsequently used in transport models in attempts to describe experimental binary (Ca‐Mg or Ca‐Na) and ternary (Ca‐Mg‐Na) miscible displacement in columns of bulk montmorillonite (admixed with sand) and Sharkey clay soil (a very‐fine montmorillonitic, non‐acid, thermic Vertic Haplaquept) from Louisiana. In general, use of Ca‐Mg exchange selectivity coefficients produced transport simulations in good agreement with experimental results. Use of heterovalent exchange coefficients tended to predict somewhat later breakthroughs of Na than were observed. Although cation‐exchange selectivities of montmorillonite could be used to adequately describe Ca, Mg, and Na transport in Sharkey soil, generalization of these results requires additional confirmation using other montmorillonitic soils.
Kinetics of Sulfate Desorption from Soil
Authors: Sharpley Andrew N. 
Published: July 2010

AbstractSulfate desorption and mobility in soil can be of both environmental and agronomic importance. This study was conducted to describe the desorption of SO4 from agricultural soils under experimental conditions applicable to the movement of SO4 in overland flow and runoff waters. The kinetics of SO4 desorption from soil were investigated at five different water/soil ratios (10:1–400:1), five time periods (5–180 min), and four SO4 additions (0–200 mg kg−1). Sulfate desorption (Sd) was logarithmically related to contact time (t) and water/soil ratio (W) and was a linear function of the initial extractable SO4 content of soil (Se). The kinetics of SO4 desorption was described by the equation Sd = K Se tα Wβ, where K, α, and β are constants for a given soil. This equation has previously been shown to describe desorption of soil P and K. The kinetic constants, K (r2 = 0.88), α (r2 = 0.83), and β (r2 = 0.88), were related to extractable soil Al content for 107 U.S. soils. The uniformity of equation constants for a given soil and the ease with which they can be estimated from extractable soil Al indicate the potential use of the equation in modeling SO4 desorption from soil and subsequent movement in surface runoff water.
Phosphorus Chemistry and Mineralogy in Excessively Fertilized Soils: Quantitative Analysis of Phosphorus‐rich Particles
Authors: Pierzynski G. M. , Logan T. J. , Traina S. J. , Bigham J. M. 
Published: July 2010

AbstractThere has been little success with direct methodologies in isolating or characterizing phosphate minerals or P‐bearing solids in soils, due primarily to the fact that P solids represent a relatively minor component of the soil matrix. This study was conducted to evaluate a method for concentrating P in soils and to characterize P‐solids phases by a variety of direct mineralogical methods. Eleven soil samples representing six soil series from Illinois, Michigan, Wisconsin, and New York were fractionated according to particle size, with the clay‐sized fractions being further separated into the density ranges of <2.2, 2.2 to 2.5, and >2.5 Mg/m3. The density separates were examined by scanning transmission electron microscopy in conjunction with energy dispersive x‐ray analysis, x‐ray diffraction (XRD), and Fourier‐transformed infrared (FTIR) spectroscopy. Total P concentrations were generally highest in the clay‐sized fractions, compared with the sand‐ and silt‐sized fractions, and always highest in the lowest‐density separates, compared with the remaining two density fractions. Discrete P‐rich particles were found in most density separates, with the highest abundances occurring in the < 2.2 and 2.2 to 2.5 Mg/m3 fractions. Particles generally contained detectable quantities of Al and Si and various combinations of K, Ca, and Fe. Phosphorus concentrations within individual P‐rich particles were highly variable. Analysis of the density separates with XRD and FTIR spectroscopy was not successful in identifying discrete P minerals.
Hard and Soft Acid‐Base Model Verified for Monovalent Cation Selectivity
Authors: Xu Shihe , Harsh James B. 
Published: July 2010

AbstractExperimental support was obtained for a quantitative ion‐exchange model based on the principle of hard and soft acids and bases (HSAB) applied to monovalent cation exchange on clay minerals, oxides, and exchange resins. According to the model, the thermodynamic exchange constant (Kex) can be obtained from the differences in absolute electronegativity (ϰ) and absolute softness (S) between the exchanging cations in binary exchange as follows:
urn:x-wiley:03615995:saj2sssaj198503615995004900030046x:equation:saj2sssaj199003615995005400060014x-math-0001 where the subscripts M and R denote exchange and reference cations, respectively, and α and β are coefficients dependent only on the exchanger surface properties, temperature, pressure, and ionic strength. This study was conducted to test the applicability of this model to monovalent cation exchange on clay minerals and ionic‐exchange resins. Exchange isotherms for Li, K, Rb, Cs, Ag, and Tl+ vs. Na on vermiculite, smectites, hydrous Zr oxides, silica gel, and ion‐exchange resins were obtained experimentally or from the literature and α and β were obtained by fitting the data to the above equation. An excellent fit (R2 ≥ 0.954, n = 5) of the alkali metal cation‐exchange data to the model resulted on all of the tested exchangers, whereas Ag and Tl+ exchange was successfully fit only on hard surfaces such as a vermiculite and on highly hydrated surfaces such as certain ion exchange resins. According to the HSAB model, coefficients α and β determine the relative contribution to Kex from ionic or covalent bonding in surface complexation. The |α/β| ratio depended on the layer charge of clay minerals and on the acid strength of the exchange resins and hydrous oxides.
Temporal Patterns of Soil Denitrification: Their Stability and Causes
Authors: Christensen Søren , Simkins Stephen , Tiedje James M. 
Published: July 2010

AbstractThe temporal stability of denitrification activity was assessed by monitoring N2O production in 30 rings installed in an acid sandy loam soil in which N2O was the only gaseous product of denitrification. When soil water was kept at field capacity or above, in the absence of NO3 limitation, some locations showed high denitrification compared with the average activity. These high‐activity locations persisted for up to several weeks. The ranking of locations with respect to denitrification rates was more stable over time than would have been expected due to chance alone. Additions of particulate organic matter (POM) that stimulated denitrification within 2 h in anaerobic soil slurries did not increase denitrification until 5 d after addition to soil cores. The increase in denitrification was preceded by an increase in respiration. The denitrification activity within the “hot spots” created by addition of POM was not limited by diffusion of NO3 in the soil. The addition of glucose 9 d before the injection of POM into field rings reduced the lag time preceding increased denitrification. Therefore, the delayed response of denitrification following POM addition in aerobic soil probably reflects the time required to establish an anaerobic soil volume.