bluuebunny/crossref_metadata_2025 huggingface dataset:
Modeling Limestone Dissolution in Soils
Authors: Warfvinge Per , Sverdrup Harald
Published: July 2010

In order to obtain a tool for the planning and evaluation of soil liming operations, a mathematical model for dissolution of limestone in acid soils was developed. The model includes four coupled reactions; dissolution of calcite in a stagnant aqueous system, cation exchange, leaching and accumulation of dissolved components as well as the carbonate equilibrium system. Two different modeling approaches for the over‐all rate of the cation exchange were evaluated, one based on rate limitation by the intrinsic exchange rate, and the other on the transport of substances from the bulk of the soil solution to the exchanger surface. The model calculations were compared with published dissolution data and suggest a mass transfer limitation imposed on cation exchange in limed soils. The ability of the soil liming model to reproduce data indicates that the model is successful in describing the key chemical processes involved in soil liming, and demonstrates the enhancing effect by the exchanger reaction on the over‐all dissolution rate. These results stress the need to consider a dynamic approach in soil chemistry models designated to describe changes with a resolution in the order of days.
Selenate Adsorption on Alluvial Soils
Authors: Neal Rosemary H. , Sposito Garrison
Published: July 2010

The adsorption of selenate by four alluvial soils from the San Joaquin Valley, CA, was investigated under conditions of varying pH and equilibrating solution composition. Soil samples were prepared in the form of Na‐saturated pastes. Adsorption experiments were carried out in 50 mol m−3 NaCl or NaClO4 background solution at initial selenate concentrations comparable to those found in field soils (5 mmol kg−1). The pH value and electrode potential (Eh) were monitored while the reaction mixtures were equilibrated using CO2‐free air for stirring in a constant temperature apparatus. In contrast to the results obtained previously for selenite, positive selenate adsorption by the four soils was not detected over the pH range of 5.5 to 9 in either the NaCl or NaClO4 electrolyte background. Selenate was found to behave in a manner similar to sulfate in these soils, but was not negatively adsorbed to the extent exhibited by chloride.
New Calibrations for Determining Soil Electrical Conductivity—Depth Relations from Electromagnetic Measurements
Authors: Rhoades J. D. , Lesch S. M. , Shouse P. J. , Alves W. J.
Published: July 2010

Soil salinity can be determined in the field from measurements of soil electrical conductivity (ECa). Measurements of depth‐integrated ECa can be made remotely using electromagnetic induction (EM) techniques. A means of determining ECa for the soil depth intervals of 0 to 30, 30 to 60, 60 to 90 cm, etc., from the EM measurements is needed for salinity appraisal. The EM and ECa measurements were made at about 900 sites in the San Joaquin Valley of California. This large data set was used, along with rigorous statistical techniques, to obtain empirical coefficients used in equations to predict ECa by depth intervals within the soil profile from EM readings taken above ground. Predictions were found to be more accurate using these new coefficients rather than those previously available.
The Stable Isotope Chemistry of Pedogenic Carbonates at Kyle Canyon, Nevada
Authors: Amundson Ronald G. , Chadwick Oliver A. , Sowers Janet M. , Doner Harvey E.
Published: July 2010

The C and O isotopic composition and radiometric ages of laminar pedogenic CaCO3 coatings were examined in limestone‐derived alluvium along an elevational and climatic transect of the Mojave Desert of Nevada. The δ13C of the soil CO2 decreased with increasing elevation and was related to plant density and available soil moisture. Laminar pedogenic carbonate coats which formed on the bottoms of clasts were separated into inner and outer laminae. The δ13C of carbonates in the outer laminae decreased with increasing elevation as a result of a decrease in the percentage of detrital carbonate in the sample and a decrease in the δ13C of the soil CO2. The δ18O of the outer laminae also decreased with elevation and, after correcting for contamination by detrital carbonate, appeared to correspond to changes in the isotopic composition of the precipitation. The δ13C of the carbonate in the inner laminae also decreased with increasing elevation; however, carbonate in the inner laminae was much purer than the outer laminae and appeared to be predominantly pedogenic in origin. The δ13C of these layers reflects the δ13C of soil CO2 and, for most samples, corresponded to expected values for modern carbonate. Based on uncertainties in dating techniques and the estimated range in isotopic composition of pedogenic carbonate, however, it was not possible to determine if some of the inner laminae formed in the latest pluvial period and reflect past pedogenic conditions.
Clay, Calcium Carbonate, and Sodium Polymetaphosphate Interactions in Soil Seal Formation
Authors: Ben‐Hur M. , Shainberg I.
Published: July 2010

The objective of this study was to investigate the interactive effects of sodium polymetaphosphate (NaPMP), CaCO3, and clay contents on seal formation and runoff. The NaPMP was applied in concentrations ranging from 0 to 300 kg ha−1 on calcareous and noncalcareous soils with clay content from 4 to 60%. Infiltration rates (IR) of these soils were measured by a rainfall simulator. Seal formation and amount of runoff increased with increased dispersant to an optimal value, above which more dispersant was not effective. Interaction between clay content and NaPMP was found; however, none was found between CaCO3 and NaPMP. In soils with approximately 20% clay content the NaPMP had no effect on seal properties, but did have an effect on the rate of seal formation. In soils with < 20% but > 7% clay content, the effect of NaPMP on the seal properties and its rate of formation increased as the clay percentage decreased. The lower the clay content in the soil, the more dispersant was needed. Conversely, the amount of NaPMP needed to form a seal in soils with > 20% clay increased with the amount of clay. In these soils since aggregate stability increases with clay content, the amount of NaPMP needed for dispersal correspondingly increased. In sandy soils, the amount of clay was not sufficient for seal formation and high infiltration rate (IR) was maintained. The NaPMP application in these soils increased the clay dispersion, which allowed clay particle migration through the sandy soil (0.2‐m layer).
Rubber Latex Encasement of Undisturbed Cores for Water Flow and Potential Measurements
Authors: Tomer M. D. , Ferguson A. H.
Published: July 2010

A method of collection of minimally disturbed soil cores for use in laboratory studies is described. Cores were obtained with a standard soil sampling tube. The cores were then centered in a larger diameter PVC tube and covered with a liquid rubber latex molding compound that dries to a form fitting layer around the sample. The latex was covered with a thin layer of wax to prevent evaporation and the space between the covered core and the PVC was filled with a light weight concrete made of vermiculite and cement. These cores can be easily handled and cut to desired length with a table saw. Water flow and desorption data from cores are presented. Saturated conductivities of core samples (Ks) are compared to estimates of maximum field conductivity (Km) based on unit gradient approaches to flood plot drainage data. The geometric mean of Ks values gave a conservative estimate as compared to most Km values.
Soil Disturbance by the Emergence of Periodical Cicadas
Authors: Luken J. O. , Kalisz P. J.
Published: July 2010

Soil disturbance by animals is an important feature of soil genesis. This study evaluated the impact of cicada (Magicicada spp.) nymph emergence on soil redistribution in northern Kentucky forests. The excavation of burrows and the construction of turrets at burrow openings were the primary activities causing soil movement. The number of turrets ranged from 40 to 170 m−2, and quantity of soil deposited on the ground surface ranged from 626 to 2330 g m−2. Turret soil material came primarily from the A horizon. Nutrient concentrations in turret soil were significantly less than concentrations in the upper 5 cm of soil, except for P. Most cicada feeding cells were located in the AB horizon at depths of 7 to 36 cm.
Chromate Adsorption on Goethite: Effects of Aluminum Substitution
Authors: Ainsworth C. C. , Girvin D. C. , Zachara J. M. , Smith S. C.
Published: July 2010

The adsorption of CrO2‐4 to goethites varying in specific surface area and Al substitution was measured over a range in pH, sorbate and sorbent concentrations and ionic strength. The α‐(Fe, Al)OOH exhibited a lower pH50 (the pH at which 50% adsorption occurs) for the CrO2‐4 at all adsorbate concentrations (6 × 10−6 to 5 × 10−4 M CrO2‐4) than did the two α‐FeOOH samples; this difference could not be attributed to either variations in CrO2‐4 adsorption density or sorbent PZC. The overall proton coefficient (n), calculated from adsorption data for 5 × 10−7 M CrO2‐4, was identical for the two α‐FeOOH samples despite differences in the physical nature and sorbate‐to‐surface site ratio of the two samples. The observed n for the α‐ (Fe, Al)OOH system was larger than the n for the pure goethite systems. These data suggest that differences in the acid‐base properties and interaction with the background electrolyte for the Fe and Al sites affect the overall proton coefficient and CrO2‐4 adsorption on the substituted surface when compared to the pure surface. The surface coordination constants for the Triple Layer Model (TLM) were derived for CrO2‐4 adsorption on the α‐FeOOH solids using the FITEQL computer code. Using these and other TLM constants from the literature, adsorption on all three goethite samples was quantitatively simulated over a range in solute and sorbent concentrations, pH and ionic strength. The successful simulation of CrO2‐4 sorption onto α‐(Fe, Al)OOH required the use of a two‐site model which included the ionization and electrolyte complexation reactions of both Fe and Al sites. Site densities of Fe and Al were taken to be proportional to the mole fraction of each in the α‐(Fe, Al)OOH solid. However, the interaction of the CrO2‐4 species with the Al sites was not required to quantitatively describe the adsorption edge since the log K for the dominant FeOH+2‐HCrO‐4 species is three orders of magnitude greater than the ‐CrO2‐4 or ‐HCrO‐4 on Al sites.
A Method To Secure, Leach, and Incubate Undisturbed Soil Cores
Authors: Myers R. G. , Swallow C. W. , Kissel D. E.
Published: July 2010

Accurate N fertilizer recommendations depend upon knowing the amount of soil organic N that is mineralized. A promising method developed by Stanford and Smith (1972) to predict N mineralized with disturbed soil samples allows for adjustment in the mineralization rate due to field variations in soil temperature and water. Recent work has indicated that undisturbed soil cores could more closely represent the field soil and its mineralization characteristics. Therefore, a method was needed to secure undisturbed soil cores in a container that would maintain their field integrity and allow them to be incubated and leached periodically as per Stanford and Smith's technique. The method utilizes a 6.3‐cm i.d. polyvinyl chloride (PVC) compression coupler to hold an undistrubed soil core. The undisturbed soil sampling device consists of a lever and anchor system, which can put pressure on a soil cutter and adjustment bar to force soil into the coupler. After a soil core is obtained from the field, the coupler is adapted so that the soil within can be leached, equilibrated to a constant water potential, and incubated. In extensive sampling of 19 soils that varied widely in clay and organic C contents, samples could be obtained rapidly if soil was near field capacity. This method of sampling and incubation was relatively inexpensive and simple, and produced data of cumulative N mineralized with time that could be fit with a first‐order kinetic model.
Mineralogical and Chemical Characteristics of Adirondack Spodosols: Evidence for Para‐ and Noncrystalline Aluminosilicate Minerals
Authors: Johnson M. G. , McBride M. B.
Published: July 2010

Little is known about the para‐ and noncrystalline inorganic mineral phases in the soils of the northeastern USA. This research was conducted to obtain information on the chemistry, mineralogy, and reactivity of these materials in representative soils from this region. Using a combination of classical and nonclassical chemical and mineralogical methods, four Spodosols from Adirondack State Park, New York, were characterized. The principal clay‐sized layer silicates identified included: kaolinite, hydroxy‐interlayered vermiculite, and hydroxy‐interlayered smectite. These tended to be concentrated in E horizons. Minor amounts of clay‐sized feldspar and mica were also identified. Para‐ and noncrystalline materials were the most abundant constituents of the <2‐µm clay from B and C horizons. Up to 720 g/kg of the <2‐µm B horizon clay was para‐ or noncrystalline materials. In contrast, these materials, on average, accounted for only 65 g/kg in the E horizon <2‐µm clays. Reaction with NaF indicated that these materials have very high surface reactivities. Infrared spectrophotometry, Mössbauer, electron microscopy, and selective dissolution studies were used to characterize the <2‐ and <0.5‐µm clay fractions. Imogolite‐like materials, so called because of the lack of a characteristic imogolite doublet near 1000 cm−1 in the infrared, indicating poor development in the imogolite c‐axis direction, were identified in the <0.5‐µm clays from B and C horizons. Characteristic imogolite tubular morphology was not observed by electron microscopy. Mössbauer experiments indicated the presence of microcrystalline goethite and ferrihydrite; electron microscopy confirmed their presence. Para‐ and noncrystalline aluminosilicates appear to be a significant component of these soils; their high surface reactivities may have large influence on the chemical reactivity and physical characteristics of these soils.
Vegetation Indicators of Organic Soil Properties in Minnesota
Authors: Swanson David K. , Grigal David F.
Published: July 2010

Vegetation is the main surface indicator for properties of organic soils. The presence of certain taxa of common vascular plants can be used to classify sites as oligotrophic (surface soil water pH < 4.4), mesotrophic (pH 4.4–5.6), or eutrophic (pH > 5.6) with about 90% accuracy. The significance of trophic status to plants and the ease with which it can be mapped from native vegetation suggest that trophic phases of certain organic soil mapping units should be recognized in soil survey. Vegetation structure (the basal area of coniferous and hardwood trees, and the percent cover of shrubs, herbaceous plants, and mosses) and pH are weakly related to the degree of peat decomposition, the basis for suborders of organic soils in Soil Taxonomy. Extensive field sampling is therefore necessary to map taxonomically based units of Histosols.
Arthropic Epipedons in the Tombigbee Valley of Mississippi
Authors: Pettry D. E. , Bense J. A.
Published: July 2010

Anthropic epipedons resulting from prolonged habitation were characterized in midden mounds of natural fluvial origin in the Tombigbee River Floodplain of Mississippi. Radiocarbon ages ranged from 300 yr before present (YBP) in surface layers to 7000 (YBP) in deeper zones of the dark‐colored epipedons. The loamy epipedons ranged from 1‐ to 1.5‐m thick and contained 0.6 to 3% organic C and 1 to 5% charcoal fragments. Munsell hues were 5YR and 7.5YR with values and chromas of 3 or less due to particle coatings of humic materials that promoted granular structure and H2O repellency. Base saturation ranged from 24 to 73% with pH levels one unit higher than adjacent off‐site soils. Calcium/Mg values exceeded 10:1 due to Ca enrichment. Total N decreased with depth and C/N ratios exceeded 30:1 due to C accumulation and N depletion. Phosphorus extracted with 1% citric acid exceeded 250 mg kg−1 in the anthropic epipedons and readily distinguished the habitation sites from adjacent soils. Nonoccluded‐P and occluded‐P were dominant P forms with lesser organic‐P and Ca‐P.
Ferro‐Humic Podzols of Coastal British Columbia: I. Morphology, Selected Properties, and Classification
Authors: Sanborn P. , Lavkulich L. M.
Published: July 2010

Ferro‐Humic Podzols (Cryorthods and Cryochrepts) of loamy texture on western Vancouver Island, British Columbia, have distinctively high organic matter and sesquioxide concentrations and limited albic horizon development. Their properties and taxonomic status were evaluated in relation to Spodosols of other maritime regions. Oxalate‐extractable Al concentrations (10–70 g kg−1) are comparable to those in podzolized soils containing tephra. Free Fe concentrations exceed 35 g kg−1 in most Bhs horizons, with approximately half in crystalline forms. Oxalate‐extractable Si concentrations suggest a substantial allophane content in some Bhs horizons. Maximum C concentrations (110–180 g kg−1) occur at 0.5‐ to 2.0‐m depth above root restricting layers or in channel‐like features initiated by tree roots. The maximum organic C content (170 g kg−1) allowed by the Canadian classification for mineral soil horizons may be too restrictive. Clay concentrations are high enough to exclude some pedons of podzolic morphology from the Spodosols of the U.S. system of soil taxonomy. Adoption of a required (Alp + Fep)/clay ratio lower than the current minimum of 0.2 for spodic horizons in the U.S. system would provide a more realistic classification of these soils.
Aluminum Release from Solid‐Phase Components of Forest Soil Leached with Citric Acid
Authors: Jersak Joseph M. , McColl John G.
Published: July 2010

The solubility of solid‐phase Al pools within size fractions of a forest soil A horizon was evaluated using aqueous citric acid to determine the rates and cumulative amounts of Al released over time. Particle‐size fractions were also characterized by the nature and sizes of various solid‐phase Al pools present. The magnitude of particular Al pools explained the rate of Al release over time. Sizes of organically bound Al pools (quantified by Na pyrophosphate extraction) were similar to those amounts of Al rapidly released in the early stages of citric acid leaching, indicating that organically bound Al was the most soluble of the solid‐phase Al pools. The steady, but slower, subsequent release of soil Al is attributed to solubilization from primary and secondary crystalline lattice minerals. Results reaffirm the use of Na pyrophosphate extraction as a method for quantifying reactive solid‐phase soil Al pools because of its ability to extract a unique and reactive Al pool from a range of soil particle sizes.
Nitrogen Transformations in Soils Previously Amended with Sewage Sludge
Authors: Boyle Michael , Paul E. A.
Published: July 2010

This short‐term (10‐d) incubation experiment established the rates of nitrogen (N) transformations occurring in sludge‐amended and nonamended soil. Utilizing a nitrification block (C2H2) with (15NH4)2SO4, first‐order rate constants were calculated for N immobilization, ammonification, nitrification, and denitrification. These rate constants were compared to values obtained after a long‐term (87‐wk) incubation performed on soils sampled from the same field plots. The short‐term rates of ammonification were still higher than the controls 4 yr after the last sludge addition. Sludge applications over an 8‐yr period (180 Mg ha−1 yr−1) reduced soil nitrification potential compared to the controls when spiked with 15N. Denitrification did not cause a significant loss of N during either a short‐ or long‐term incubation period. The microbial biomass in the sludge‐amended soil contained more N, which resulted in a microbial C/N ratio of approximately 4:1 vs. 5:1 for the controls. Initial (short‐term) N immobilization rate constants were 0.43 for the sludge‐amended and 0.35 for the nonamended soil.
Characterization of Humic Acid from No‐Tilled and Tilled Soils Using Carbon‐13 Nuclear Magnetic Resonance
Authors: Stearman G. K. , Lewis R. J. , Tortorelli L. J. , Tyler D. D.
Published: July 2010

Chemical composition of humic acids is important due to their reactivity with soil‐applied pesticides and fertilizer amendments. Humic acids from continuously (7 yr) no‐tilled and tilled cotton, corn, and soybean plots in West Tennessee were characterized by 13C‐NMR from soils sampled at various depths. Humic acids were extracted with dilute NaOH solution and purified with KOH‐KCL and HCL‐HF solution, respectively. NMR solution spectra generated on a Jeol FX 90Q spectrometer (Jeol Co., Tokyo, Japan) were divided into six regions (0–40, 40–62, 62–105, 105–150, 150–170, and 170–190 ppm) and peak areas compared. Humic acid composition differed by soil depth and crop. Small differences were observed between tillage systems. Aliphatic and aromatic carbons ranged from 48 to 65% and 25 to 40% of total peak area, respectively. Carboxyl groups of humic acids as determined by 13C‐NMR ranged from 9 to 13%. Humic acids extracted from those soils containing larger amounts of C (surface no‐tilled treatments) had greater aliphatic to aromatic ratios, perhaps due to earlier stages of decomposition.
Strength Analysis of Fragipans in Some Loess‐derived Soils in Louisiana
Authors: Inman B. L. , Bryant R. B. , Hudnall W. H.
Published: July 2010

The objective of this study was to quantify the strength characteristics of fragipans found in selected loess‐derived soils in northeastern Louisiana. Three study sites were selected on the Macon Ridge, which is blanketed by a Peoria loess. Two sites were selected on the Bastrop Ridge, which is covered by a pre‐Peoria loess. The unconfined compression (UC) test was used to quantify the strength characteristics of (i) undisturbed fragipan material taken at field moisture, (ii) remolded fragipan material equilibrated to the same moisture content and packed to the same density as the undisturbed samples, and (iii) oven‐dried undisturbed fragipan samples. A range of strength occurred among the undisturbed samples due to natural fabric differences. Remolded samples had lower strengths compared to the undisturbed samples. In general, higher sensitivity values for fragipan horizons from the Macon Ridge sites indicated that rigidity in these fragipan horizons is derived in part from binding agents. Low sensitivity values measured on fragipans from the Bastrop Ridge sites indicated that cohesive binding agents have little effect in providing rigidity for these fragipan horizons. Dried undisturbed fragipan material exhibited strength values a full order of magnitude greater than those measured on samples tested at field moisture contents. Results indicate that the fragipans in soils developed in older loess deposits on the Bastrop Ridge have a lower component of strength derived from interparticulate binding agents than those fragipans in soils developed in the younger loess deposits on the Macon Ridge.
A Differential Scanning Calorimetry Evaluation of Quartz Status in Geogenic and Pedogenic Environments
Authors: Bartenfelder D. C. , Karathanasis A. D.
Published: July 2010

Twelve quartz samples of geologic and soil materials were investigated by differential scanning calorimetry (DSC) to evaluate the effects of origin, crystal deformation, depositional environments, and weathering conditions on the α‐β inversion temperature, enthalpy of inversion (ΔH), and activation energy (Ea) characteristics of quartz. The 50‐ to 20‐µm particle size fraction was found to be the most suitable for thermal and x‐ray analyses. There was little variation (<2 °C) in the inversion temperature of quartz in the studied samples, which appeared to depend on apparatus and conditions. The ΔH of inversion demonstrated more sensitivity than inversion temperature, to structural substitutions or deformations, with values ranging from 1.70 to 5.86 J/g. The igneous and metamorphic samples had the highest, whereas the soil samples had the lowest ΔH. The use of apparent activation energies (Ea) showed the most promise in distinguishing the materials with respect to quartz origin, environment of deposition and extent of weathering. Activation energies were higher in igneous than metamorphic materials, decreased with age of deposit in the sedimentary materials, and generally decreased with extensive weathering of soil materials with some dependence on material type. The data suggest that Ea values may represent the integrated effect of geothermal, geogenic and pedogenic environments on the quartz structure.
Micromorphology and Mineralogy of Illuviated Clay in a Davidson Soil
Authors: Goenadi Didiek H. , Tan Kim H.
Published: July 2010

Clay illuviation was studied in a highly weathered soil of the Southern Piedmont by macro‐ and micromorphological techniques. Five pedons of a Davidson soil (Rhodic Paleudult) were sampled from four counties for preparation of thin sections and analysis of soil matrix, illuviated clay and argillans. The related distribution pattern of the soil fabric in the epipedon was different than that in the argillic horizon or saprolite. A single‐spaced porphyric fabric was found in the A horizon, which had no illuvial clays. The argillic horizon exhibited an open‐spaced porphyric fabric with illuvial clay ranging in concentrations from 2.4 to 5.6%. A double‐spaced porphyric fabric was noticed in the saprolite, which contained 1.4% illuvial clay. X‐ray diffraction analysis of clays in the soil matrix vs. argillans showed strong evidence for kaolinite as the major mineral eluviated from the upper horizon. The data also suggested that, in the argillic horizon, kaolinite was formed in situ through alteration of K‐feldspar minerals. The relatively high contents of kaolinite and iron‐oxide minerals, together with the presence of prominent argillans in the argillic horizons, indicated that the soil has undergone an intensive weathering and leaching process.
Influence of Copper or Cadmium on Soil Potassium Availability Properties
Authors: Yang Jae E. , Skogley Earl O.
Published: July 2010

The objective of this research was to determine the nature and extent of increased soil levels of Cu or Cd on K availability properties. Bozeman silty clay (Typic Argiborolls) samples were equilibrated at soil water potentials of −33 or −100 KPa, at temperatures of 5 or 20 °C for 3 or 14 d after additions of three levels of K and three levels of Cu or Cd. Soil solution was extracted by an immiscible liquid displacement technique. The activity of Ca, Mg, and K in soil solutions were increased by Cu or Cd additions (aCa > aMg > aK). The ratio of K to Ca + Mg (K intensity) was decreased by Cu or Cd additions when no K was applied, but increased at high levels of K addition. Soil temperature and water potential interacted with Cu or Cd additions to alter cation activities. Soil K buffer capacity was decreased by Cu or Cd additions. Increasing addition of K increased the proportion of K in both exchange and solution phases, at the expense of both Ca and Mg. Increasing additions of Cu or Cd decreased the fractional saturation of K and Mg, but increased that of Ca in the solution phase, with the reverse influence being exhibited on the exchange phase. Results indicate that Cu had a stronger influence than Cd (at equal rates of addition) on soil properties which regulate K availability.
Anion Exchange Chemistry of Middle Atlantic Soils: Charge Properties and Nitrate Retention Kinetics
Authors: Toner C. V. , Sparks D. L. , Carski T. H.
Published: July 2010

The negative impact of nitrate (NO3) on groundwater supplies has sparked a great deal of interest and concern in recent years, particularly in areas where coarse‐textured soils abound. In light of this concern, the anion exchange chemistry of eight soils from the Middle Atlantic region was studied with particular emphasis on NO3 retention and kinetics. The soils were chosen to encompass a range of physicochemical and mineralogical properties and were extensively characterized. Anion exchange capacity (AEC) was determined on Cl‐saturated samples by desorption of Cl with SO4. Anion exchange capacity ranged from 0 to 1.35 cmolc kg−1 for the eight soils and was found to parallel increases in clay and Fe oxide contents in the soil profiles. Point of zero salt effect (PZSE) values were determined by potentiometric titration with 0.001, 0.01, and 0.1 M NaCl as the indifferent electrolyte. These were of little value in predicting the development of AEC for the soils. The kinetics of NO3 adsorption and desorption were studied using a stirred‐flow reaction chamber and a first‐order reaction best described the data. Nitrate adsorption was found to be completely reversible, indicating a simple electrostatic retention mechanism. The effect of pH and NO3 concentration on cumulative NO3 adsorbed (CNA) and on NO3 adsorption kinetics was also studied. The CNA was found to increase with a decrease in pH below 5.5 and to increase with increasing NO3 concentration. The latter indicated an increase in competitiveness by NO3 for positively charged sites.
Temporal Relations of Phosphorus Fractions in an Oxisol Amended with Rock Phosphate and Thiobacillus thiooxidans
Authors: Muchovej Rosa M. C. , Muchovej J. J. , Alvarez V. V. H.
Published: July 2010

Low‐grade phosphate rock plus elemental S were added to an oxisol in combination with organic matter (OM) and/or Thiobacillus thiooxidans to study the change in P fractions with time and then study availability of P solubilized. The addition of any amendment caused a significant increase in Al‐bound P. These values remained stable during the 7‐wk incubation period. Soluble P and OM‐bound P peaked within 3 wk and then decreased during the remaining period. The addition of T. thiooxidans plus S caused a rapid drop in soil pH to levels below 4.0 and a concurrent increase in P levels in the soil. After incubation, lime was added to the soils and sorghum grown for 30 d; even though, no additional P was incorporated. Solubilized P was sufficient for plant growth and dry matter produced by plants in soil amended with T. thiooxidans plus OM was similar to that of plants grown in soil amended with superphosphate.
Response of Irrigated Corn to Sulfur Fertilization in the Atlantic Coastal Plain
Authors: Kline J. S. , Sims J. T. , Schilke‐Gartley K. L.
Published: July 2010

Accurate prediction of yield response by corn (Zea Mays L.) to S fertilization on the coarse‐textured soils of the Atlantic Coastal Plain requires information on availability and persistence of subsoil SO4‐S, potentially mineralizable soil S, and S added in irrigation and precipitation. A 3‐yr study was conducted with irrigated corn on four soils possessing characteristics commonly associated with S deficiency. A factorial combination of S application rate (0, 33, 67, 101 kg ha−1) and method (single broadcast at planting, split) was used. Grain yield, and S concentrations and N/S ratios of early whole plants (EWP) and ear leaves (EL) were determined. Extractable SO4‐S (0–100 cm) levels and inputs of S from irrigation and precipitation were measured in each year; mineralizable S in Ap horizons of all soils was determined by two incubation methods (leached and nonleached). Although application of S generally increased plant S concentrations, significant yield increases occurred in only three of the 12 site‐year combinations. Critical values for S and N/S, based on combined data from responsive sites, were 2.1 and 1.6 g S kg−1 and 18.7 and 20.3, for EWP and EL, respectively. Lack of yield response was attributed to subsoil SO4‐S, (average, 0–100 cm = 170 kg S ha−1, mineralizable S (average = 80 kg ha−1, leached method) and S contained in irrigation or precipitation (annual average = 7.5 kg ha−1). Yield increases obtained at the most responsive site may have been caused by increased immobilization of S, due to no‐tillage management, the presence of a physical barrier to root penetration at 40 to 60 cm, or subsoil Al. Successful prediction of corn response to S fertilization in Coastal Plain soils will require a comprehensive program that combines subsoil sampling and selective plant analysis, concentrated on sites identified as potentially responsive based on soil properties.
Polymers as Soil Conditioners Under Consecutive Irrigations and Rainfall
Authors: Ben‐Hur M. , Faris J. , Malik M. , Letey J.
Published: July 2010

Low water infiltration caused by crust formation during rain or sprinkler irrigation is a significant problem in some arid and semiarid regions. Polymers may be applied in irrigation water through a sprinkler system, but must be applied directly to the soil under rainfall conditions. The objectives of this rainfall simulator study were to: (i) determine the effect of drying of crusted vermiculitic soil on the subsequent crust properties and infiltration rate (IR) values, (ii) determine the effect of polymers applied at low concentration in irrigation water of two qualities on the IR under consecutive water applications, and (iii) determine the effectiveness of polymer application to the soil as would be required under rainfall conditions. Two cationic polysaccharide guar derivatives having a higher (HCCP) and a lower (LCCP) charge density and a polyacrylamide (PAM) with a low negative charge density were used in the study. Applications of polymers with the sprinkler water maintain IR in the order HCCP > LCCP > PAM > untreated. Except for PAM, the polymer applications were relatively ineffective in subsequent sprinkler applications with plain water applied with impact energy. The beneficial effects were preserved under water application without impact energy. Spraying concentrated polymer solutions on the soil surface was not effective in preventing crust formation by following rain events except for the case when LCCP was sprayed on in a CaCl2 solution. The results are explained on the basis of polymer adsorption and penetration into the soil surface layer and aggregates.
Modeling Potassium‐Calcium Exchange Isotherms in Soils
Authors: Dufey Joseph E. , Delvaux Bruno
Published: July 2010

Ion exchange equilibria involving K cannot be described by a constant selectivity coefficient for all surface compositions. The main reason is that the soil exchanger contains various types of sites with different affinities for K ions. This paper makes use of a multi‐site model, the main assumption of which is that the exchange reaction is governed by single values of the Vanselow selectivity coefficient, Kv, for each type of site. The simplest model—i.e., the two‐site model—is tested. Three parameters must be adjusted: the proportion of high and low selective sites, and the Kv's for these two classes of sites. Simulated K‐Ca exchange isotherms are shown, with various combinations of the parameters. The model has been adjusted to experimental K‐Ca exchange data, using a non‐linear regression procedure. A fair agreement between the experimental and calculated curves is obtained. As a consequence, this simple model proves to be a powerful tool for a quantitative description of exchange data involving K ions.
Use of Referential Coordinates in Deforming Soils
Authors: Baveye Philippe , Boast Charles W. , Giráldez Juan V.
Published: July 2010

Analysis of hydrological processes in deforming soils generally involves use of some form of a referential, or material, coordinate transformation. In the most commonly used of these relationships, there appear two macroscopic soil mass density factors, that associated with the configuration of the soil at a reference time t = 0, and that associated with its configuration at a later (arbitrary) time. In some previous work, the assumption was made that these bulk densities could be evaluated at the same space‐fixed point. In an illustrative application to dual‐energy gamma‐ray data on the swelling of a clay loam during infiltration, this approximation is shown here to predict vertical displacement values that are as much as 7 mm in excess of values obtained without the approximation. Moreover, the approximation fails to satisfy macroscopic mass balance. It is also shown that the direction, downward or upward, of the vertical displacement of macroscopic body‐points depends on the boundary condition used in the integration of the referential coordinate transformation; i.e., depends on whether the integration begins at the soil surface or at a point below the wetting front. Since these two integration pathways are mathematically equivalent, it is argued that a systematic comparison between results obtained using them can serve a useful purpose in detecting occurrences of lateral expansion or systematic errors in the experimental data.
Use and Hydrological Robustness of Time‐to‐Incipient‐Ponding
Authors: White I. , Sully M. J. , Melville M. D.
Published: July 2010

Both the use and hydrological robustness of time‐to‐ponding, tp, have been questioned recently. We examine these questions here for variable rainfall rates. Using a nondimensional analytic form for tp, we show that for rainfall rates, R, greater than about 1.5 times the saturated hydraulic conductivity, Ks, tp is relatively robust. Only in the region Ks ≤ R ≤ 1.5 Ks is tp sensitive to small changes in R/Ks. We also show a comparison between field measurements of tp using a rainfall simulator on a structurally unstable, sodic and saline gravelly silty clay loam and those predicted using the analytic expression and measured values of Ks and sorptivity determined under ponded conditions with disc permeameters. The good agreement found, together with the ease and reproducibility of the field measurements, indicate that both the determination and prediction of tp are soundly based provided R > 1.5 Ks. Finally, we use the analytic expression for tp in the inverse sense to determine the soil's sorptivity, hydraulic conductivity and characteristic mean pore size, a measure of soil pore structure, from values of tp, R and the steady state runoff during rainfall. These hydraulic properties agree well with those measured under a constant head. We conclude that tp is a useful and hydrologically robust property provided R(tp) > 1.5 Ks.
Carbazole Sorption by Surface and Subsurface Materials: Influence of Sorbent and Solvent Properties
Authors: Ainsworth C. C. , Zachara J. M. , Smith S. C.
Published: July 2010

Sorption of 9H‐carbazole was investigated from aqueous and co‐solvent solutions on soils with different physical and chemical properties. Sorption was nonlinear, but well correlated to the organic carbon (OC) content of the soils. The variability of the Freundlich adsorption constant (Kt), normalized to OC (Kfoc) is small between A horizons of two Mollisols and two Ultisols but increases to about 0.8 log units between C horizons of the Mollisols and Ultisols. This variability combined with the absence of linear partitioning leads to poor predictability by C reference partitioning based on octanol/water or water solubility parameters in the highly weathered soils. Differences in structure and type of the associated OC may be a factor affecting predictability. The presence of methanol and acetone induces a log‐linear decrease in carbazole sorption with mole fraction cosolvent. For a given solvent (i.e., MeOH, acetone) the log‐linear behavior is independent of sorbent properties and exhibits a common slope, thus attesting to the importance of the solvent interaction. In contrast, pyridine as a cosolvent is actively sorbed by some soils creating a more oleophilic surface and a tendency to increase carbazole partitioning to the soil surface.
A Continuous‐Flow Stirred Reaction Cell For Studying Adsorption In Suspensions
Authors: Miller D. M. , Miller W. P. , Sumner M. E.
Published: July 2010

Solute sorption by inorganic colloids is currently studied using either batch or miscible displacement techniques, but continuous‐flow stirred reaction cells may represent a desirable alternative to these methods in certain situations. A practical limitation of current cell designs is the inadequate mixing effected by magnetic stirrers, which allows the sorbent to rapidly deposit onto the filter membrane. We have designed a continuous‐flow stirred reaction cell in which the suspension is efficiently and vigorously mixed by means of a two‐blade impeller powered by an electric motor. The impeller shaft is bearing‐mounted and sealed with a rubber O‐ring. The entire cell is water jacketed for temperature control. Joule heating appears to be insignificant at the impeller speeds required for mixing at flow rates of up to 60 mL h−1. Runs with orthophosphate solution and no adsorbent indicate that mixing is ideal. Data reduction is illustrated using a phosphate/goethite system.
Exchange Properties of an Argiustoll: Effects of Long‐Term Ammonium Nitrate Fertilization
Authors: Schwab A. P. , Ransom M. D. , Owensby C. E.
Published: July 2010

Soil acidification can result from the application of high rates of ammonia‐based fertilizers, but little information is available concerning the effects of long‐term, annual applications at moderate rates. In this study, plots that were mapped as Smolan silt loam (fine, montmorillonitic, mesic Pachic Argiustolls), 1 to 4% slopes, containing an established stand of smooth bromegrass (Bromus inermis Leyss.) were fertilized continuously with rates of 0, 22, 67, 112, 157, and 224 kg N/ha for 40 yr, or for 20 yr followed by 20 yr without N fertilizer. The objective of this research was to determine the effects of such long‐term applications of NH4NO3 on exchange properties. In the continuously fertilized plots, pH and exchangeable Ca2+, Mg2+, and K+ decreased in the upper 20 cm of the soil, and neutral‐salt cation exchange capacity decreased in the upper 10 cm, whereas exchangeable Al (1 M KCl) and BaCl2‐triethanolamine (BaCl2‐TEA) extractable acidity increased. In all cases, significant changes were observed only when N application exceeded plant demand. Discontinuation of fertilization for 20 yr resulted in a significant, but incomplete, trend of the exchange properties toward values of the unfertilized soils. Thus, the acidification resulting from NH4 application, which occurred at even low application rates, was reversed somewhat after fertilization ceased.
Selection of Reference Plants and Methods for Estimating N2 Fixation in Mycorrhizal Leguminous Plants
Authors: Schoeneberger M. M. , Volk R. J. , Davey C. B.
Published: July 2010

The effects of plant species and mycorrhizae on reference plant suitability were examined with regard to estimating N2 fixation in two leguminous plants via the 15N isotope dilution technique (ID). Atom percent excess (A % E) 15N values of ryegrass (Lolium perenne L. ‘PennSinn’), nonnodulated big trefoil (Lotus pedunculatus Cav. ‘Marshfield’), and nonnodulated subterranean clover (Trifolium subterraneum L. ‘Mt. Barker’), each with or without mycorrhizae, were compared at fertilizer N rates of 10 and 100 kg N ha−1. Precision of the ID method was compared to the total nitrogen difference (ND) method. Atom percent excess 15N values of the reference plants had lower coefficients of variation than total N yields (mg plant−1), and were unaffected by mycorrhizal treatment. Overall shoot values of A % E 15N were similar in trefoil and ryegrass, but were lower in clover in the 100 kg N ha−1 fertilizer treatment. In roots, the A % E 15N values for clover were significantly larger than those for ryegrass. There were no differences between the values of N derived from the atmosphere (Ndfa) (percent and amount for shoot, root, and total plant) in clover, as estimated by the ID method, using nonnodulated clover and ryegrass as reference plants. Values for Ndfa (percent and amount), as estimated by the ND method, differed significantly from the ID values. The ND values were either smaller or larger than ID values, depending on N rate and inoculation treatment. In the 100 kg N ha−1 rate, the ND method resulted in negative values for root Ndfa. Given the similarity of A % E 15N shoot values in all three reference plants, and the insensitivity of Ndfa to the reference plant used for its calculation, ryegrass was found to be an appropriate reference plant for determining N2 fixation via the ID method in both big trefoil and subterranean clover.
Cultivated and Adjacent Virgin Soils in Northcentral South Dakota: II. Mineralogical and Micromorphological Comparisons
Authors: Blank R. R. , Fosberg M. A.
Published: July 2010

Cultivated and adjacent virgin soils [Williams (fine‐loamy, mixed, Typic Argiboroll) and variants of Williams] from northcentral South Dakota were compared, by horizon, to examine the effects of cultivation on mineralogical and micromorphological properties of the soils. Two major mineralogical differences were noted. Silt‐sized material from the Btk, Bk, and C horizons of a cultivated pedon had smaller calcite‐to‐dolomite peak‐height ratios, as determined by x‐ray diffraction, than similar horizons from a virgin pedon. These findings, combined with the results of additional experimentation, suggest calcite is being leached from Btk horizons and is accumulating in Bk horizons of cultivated pedons. The A, Bt, and Btk horizons of a virgin pedon had more subdued x‐ray peak intensities for the 001 spacing of smectite than similar horizons from a cultivated pedon. When similar horizons of a cultivated and a virgin pedon were compared, micromorphological differences were as follows: (i) the Ap horizon displayed less macroporosity, more diffuse and lighter‐colored organic glaebules, fewer and less pronounced microaggregates, and fewer surface coatings on sand‐sized particles; (ii) the Bt horizon from the virgin pedon had greater macroporosity; (iii) the Btk and Bk horizons of the virgin pedon contained more particles coated with and more composite particles bound with organo‐mineral material; (iv) a far greater proportion of voids were filled with black, opaque cutans in the Btk horizons of the cultivated pedons that, by electron microprobe analysis, was dominantly Si.
Partitioning of Clay‐Sized Minerals in Coastal Plain Soils with Sandy/Loamy Boundaries
Authors: Cabrera‐Martinez F. , Harris W. G. , Carlisle V. W. , Collins M. E.
Published: July 2010

Four soils with sandy/loamy boundaries occurring at various depths were studied with respect to distribution of clay‐sized minerals within the soil matrix. Mineralogy of coarse and fine clay was determined by horizon using x‐ray diffraction. Also, mineralogy of clay from ped interiors vs. exteriors (coatings) was determined for the Bt horizon of one soil. Mineralogical differences in coarse‐clay distribution were observed with respect to location above or below the sandy/loamy boundary. Clay above the boundary was consistently high in hydroxy‐interlayered vermiculite (HIV) and quartz, regardless of depth to the boundary. One exception was the A horizon of a Spodosol, which consisted essentially of quartz; however, the Bh horizon of this soil (above the boundary) did contain appreciable HIV. Below the boundary, the upper Bt horizon exhibited an increase in kaolinite and a sharp decrease in quartz relative to overlying E or Bh horizons. A marked decrease in HIV below the upper Bt horizon was also evident. Fine clay contained more kaolinite and less HIV and quartz than did coarse clay, and exhibited less intra‐pedon variation. Possibly HIV comprises a greater proportion of the clay residue in eluvial horizons because of the greater size of its precursor, which could be mica, and subsequent resistance to translocation. The greater abundance of HIV in ped coatings relative to ped interiors suggests that some contemporary translocation of coarser clay from HIV‐dominated eluvial horizons has occurred along major voids between peds. The d001 peak shift with heat treatment for HIV was similar for all samples, suggesting that depth and landscape position have had little influence on degree of interlayer polymerization in these soils.