bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mineralogy and Micromorphology of Soils from Volcanic Tuffs in the Humid Tropics
Authors: Goenadi Didiek H. , Tan Kim H. 
Published: July 2010

AbstractAn investigation was conducted to study mineralogy, chemical characteristics, and micromorphology of three pedons from andesito‐dacitic volcanic tuffs in Banten, West Java, Indonesia. The soils were strongly acid, had clayey textures, argillic horizons, and base saturations <35% in the control sections. The clay distribution suggested two of the soils to be Hapludults whereas the third was a Paleudult. Kaolinite was the dominant clay mineral, though the clay fractions did not meet the definition for low activity clays because of their relatively high cation exchange capacity (CEC) values. The sand and silt fractions contained substantial amounts of weatherable minerals (>10%). Micromorphic characteristics supported pedological features in the field. The Ap horizons exhibited soil fabrics composed of skeletal grains and plasma, and granular to crumb micropedal structures. In contrast, the Bt horizons had soil fabrics showing large amounts of plasma, angular blocky microstructures, and the presence of argillans.
Carbonate Phases in Calcareous Soils of the Western United States
Authors: Bui E. N. , Loeppert R. H. , Wilding L. P. 
Published: July 2010

AbstractThe carbonate phases of 39 calcareous soil samples, representing 23 soil series from the western US, were studied by wet‐chemical techniques, x‐ray diffraction (XRD), and electron microscopy to determine the particle‐size distribution, chemical composition, mineralogy, particle morphology, and Mg‐substitution patterns of the carbonate phases. The multivariate relationship between carbonate mineralogy and saturated‐paste extract composition was also investigated. Soil samples were fractionated into sand, coarse‐silt (5–50 µm), fine‐silt (2–5 µm) and clay particle‐size fractions. The silt‐size fraction accounted for a median proportion of 57% of the total soil carbonate. The percentage of the total carbonate in the clay‐size fraction was variable among soils, ranging from <1 to 60%. Calcite, Mg‐substituted calcite, and dolomite were identified by XRD, and each of these phases was identified in the clay‐size fraction of selected soils. The occurrence of clay‐ and fine‐silt‐size carbonates is indicative of the presence of pedogenic secondary carbonates (including dolomite). For the clay‐size fractions, the Mg/(Ca + Mg) molar ratios of the dissolution extracts of several of the samples were considerably higher than the theoretical ratios calculated from the experimentally determined calcite and dolomite contents, indicating the possible occurrence of poorly crystalline Mg‐rich carbonate phases that were too disordered or too small in particle size to give distinct XRD reflections. Dolomite had a predominantly euhedral particle morphology, compared with calcite, which appeared as aggregates of smaller (<1 µm) particles. The mineralogy and morphology of the specific carbonate phases probably reflect the environment of precipitation and seasonal differences in soil‐solution composition.
Determining Soil Salinity from Soil Electrical Conductivity using Different Models and Estimates
Authors: Rhoades J. D. , Shouse P. J. , Alves W. J. , Manteghi Nahid A. , Lesch S. M. 
Published: July 2010

AbstractThe appropriateness of two versions of a model describing electrical current flow in undisturbed soil was evaluated for purposes of diagnosing and mapping soil salinity (ECe). Different methods of measuring bulk soil electrical conductivity (ECa) and different ways of obtaining the values of other parameters required by the model were also evaluated using three different sets of data. The reliability of the variously predicted salinities were evaluated by comparing them against conventionally measured salinities using linear regression analyses, ranking tests, and a procedure based on the weighted sums of squared differences. It was found that salinity‐prediction accuracy, though relatively good, was underestimated for the instrumental/model techniques because of sample‐size differences and spatial‐variability effects. Conclusions arrived at from earlier sensitivity analyses about the suitability of the parameter‐estimation procedures were borne out by these results, i.e., that soil salinity appraisal and mapping can be quite adequately made using field measurements of ECa (by any one of three methods) and estimates of soil water content, bulk density, and surface conductance determined by “feel” methods.
Measurement of Calcite Ion Activity Products in Soils
Authors: Reddy K. J. , Lindsay W. L. , Workman S. M. , Drever J. I. 
Published: July 2010

AbstractSoils often show supersaturation with respect to calcite. This study was undertaken to test alternative methods of measuring Ca2+ and CO2‐3 activities to assess their effects on measured ion‐activity products (IAP) of calcite in soils. Soils were reacted with atmospheric CO2(g) and distilled H2O for 1, 3, and 7 d. The soil extracts were analyzed for pH, electrical conductivity (EC), cations, anions, and dissolved organic carbon (DOC). Carbonate activities in soil extracts were obtained by two methods. The first consisted of titrating the soil extracts with standard HCl to pH 4.0 (direct‐titration method). The second method consisted of acidifying soil extracts to pH 4.0 and trapping the evolved CO2 gas in a NaOH + BaCl2 solution (CO2 gas release method). The IAP values for calcite were calculated in two ways. First, Ca2+ activity was obtained by speciating total soluble Ca while CO2‐3 activity was obtained from the direct titration of soil extracts. This method gave mean log IAP values of calcite ranging from −7.90 to −7.78 compared with a log Ko (Ca2+)(CO2‐3) (equilibrium constant) of −8.48 for calcite. These results suggest supersaturation with respect to calcite. Secondly, when Ca2+ activity was measured with a Ca2+‐specific ion electrode and CO2‐3 activity was estimated by the CO2 gas release method, the mean log IAP values of calcite ranged from −8.45 to −8.35, which is very near equilibrium with calcite. The apparent supersaturation in the first case was probably caused by DOC, which both complexed Ca2+ and contributed to titratably alkalinity over that of carbonate and bicarbonate alone.
Aliphatics in Soil Organic Matter in Fine‐Clay Fractions
Authors: Schulten H. ‐R. , Schnitzer M. 
Published: July 2010

AbstractFine‐clay fractions were separated from three agricultural soils and extracted sequentially with n‐hexane, chloroform and supercritical n‐pentane. The resulting extracts were analyzed by field ionization (FI) and field desorption (FD) mass spectrometry (MS). The major components indentified included C11 to C94 n‐alkanes, C13 to C34 n‐fatty acids, n‐C16 and n‐C24 diols, and C38 to C67 n‐alkyl monoesters. Minor components were C22, C32, and C34 n‐alcohols, C27 and C29 sterols, C56 to C91 n‐alkyl diesters, C83 to C99 n‐alkyl triesters, and C17 to C21 unsaturated monocarboxylic acids in extracts of one clay only. The highest molecular weight compound identified was the C99 n‐alkyl triester (m/z 1478). Especially noteworthy was that: (i) similar aliphatics were extracted from the three clays, (ii) the compounds identified were typical of components of natural waxes, which appear to be present in the organic matter in fine‐clay fractions, and (iii) the soft ionization mass spectrometric methods employed were found to be eminently suitable for the identification of medium to high molecular weight aliphatics in the organic matter in fine‐clay fractions.
Long‐Term Conventional and No‐Tillage Effects on Selected Soil Physical Properties
Authors: Hill R. L. 
Published: July 2010

AbstractSoil management systems can affect soil physical properties and, thus, have a direct bearing on crop performance. This study determined the effects of continuous long‐term conventional and no‐tillage management on selected soil physical properties and compared observed yield differences between these tillage systems with soil physical properties. Three Maryland locations, each having randomized complete‐block designs with three replications of continuous corn (Zea mays L.) under conventional and no‐tillage management, were used. Sites 1 and 2 were in their 12th yr of tillage and Site 3 was in its 11th yr. Soils at all three sites were silt loams (fine‐loamy, mixed, Aquic Hapludults). Tillage affected bulk density at the 0.05 level at Site 1 and the 0.10 level at Site 2. No‐tilled soils generally had higher bulk density at all soil depths for Sites 1 and 2. Tillage affected soil strength at Sites 1 and 2, but not at Site 3. Soil strength for no‐tilled soils was consistently greater than for conventionally tilled soils. Conventionally tilled soils had greater pore volume in pores with radii >15 µm at Sites 1 and 2, and, therefore, should drain more readily than no‐tilled soils. More importantly, the amount of pore space available for the storage of plant‐available water was greater for conventionally‐tilled soils at Sites 1 and 2. Although soil physical properties within the Ap horizon are not adequate to account for differences in corn yield response, tillage differences in soil physical properties were found for the soils at Sites 1 and 2, which had previously shown tillage yield differences.
Dry Aggregate Size Distribution of Sandy Soils as Influenced by Tillage and Precipitation
Authors: Zobeck T. M. , Popham T. W. 
Published: July 2010

AbstractSurface soil dry aggregate size distribution (ASD) has a significant effect on the amount and intensity of wind‐induced soil erosion. The ASD of cropland varies through time primarily due to the effects of management and climatic factors. A method of predicting ASD is needed to make accurate estimates of wind erosion. The effects of tillage on ASD are described and models proposed to estimate changes in ASD after precipitation has further modified a sandy soil surface. The ASD and bulk density of the near‐surface soil were measured on four west Texas sandy soils immediately after tillage and after up to 130 mm subsequent rainfall. Tillage methods included moldboard plow, lister, chisel, and tandem disk. Results indicated that the four tillage methods tested could be separated into two groups to produce reliable estimates of ASD. Moldboard plowing produced significantly larger aggregates than a tillage‐tool group comprised of lister, chisel, and tandem disk. The combined effects of tillage and precipitation after tillage produced significant differences (P < 0.002) in ASD for each soil tested. Regression models to estimate ASD using bulk density in the near‐surface soil and cumulative precipitation as independent variables accounted for up to 80% of the variation.
Tensiometer Data Acquisition System for Hydrologic Studies Requiring High Temporal Resolution
Authors: Nyhan John W. , Drennon Barry J. 
Published: July 2010

AbstractCommercially available differential pressure transducers, tensiometers, and a data acquisition system were combined to evaluate soil water tension changes with time within two landfill cover designs used for the shallow land burial of waste materials. A typical error for the differential pressure transducers in the voltage‐pressure calibration curve was estimated to be 0.14 V at a transducer output of 4 V. Tensiometer data collected simultaneously using the data‐acquisition system and a hand‐held manual pressure‐transducer system agreed well (r2 = 0.994). The utility of the tensiometer data acquisition system to collect field data was demonstrated successfully using reference tensiometers with known hydraulic heads. Diurnal fluctuations in tensiometer data collected in the field are discussed relative to future experiments to be performed with the system. In addition, tensiometers with unknown and variable hydraulic heads were used to determine tensiometer response times of approximately 50 min.
Ion Transport during Unsteady Water Flow in an Unsaturated Clay Soil
Authors: Bond W. J. , Phillips I. R. 
Published: July 2010

AbstractThe transport of many solutes through soils is strongly affected by their reaction with the solid constituents. One of the most common of such reactions is cation exchange. It is, therefore, important to be able to predict the effects of cation‐exchange reactions on cation transport. The purpose of this study was to examine experimentally the effects of two different types of cation exchange on the transport of cations through soil, and to compare the results with simple mathematical predictions. The experiments also permitted an examination of the effect of cation exchange on anion transport via its effect on anion exclusion. The effects of both K‐Ca and Na‐Ca exchange were studied because these have quite different isotherm shapes, Na‐Ca exchange being much less favorable than K‐Ca exchange. The spatial distributions of water, tritium, Cl, Na, K, and Ca were measured following constant‐flux horizontal infiltration of tritiated NaCl or KCl solutions into a Ca‐saturated clay soil. The concentrations of cations both in solution and in the sorbed phase were measured independently. Soil water fluxes throughout the experiments were small enough to ensure that physical and chemical equilibrium was attained. Anion exclusion caused the Cl front to move faster than the tritium front (which moved with the average pore‐water velocity), while exchange resulted in the monovalent cations moving more slowly than tritium. The position of the Cl front was independent of the cation in the invading solution, being determined by the anion‐exclusion properties of the soil in equilibrium with the cation in the initial solution. The shape of the cation profiles, the relationship between the position of the cation fronts in the solution and sorbed phases, and the average position of the cation fronts depended on the shape of the exchange isotherm and the inflowing solution concentration. The penetration of the center of mass of the combined cation fronts (total cation mass per unit soil volume) was successfully predicted using the effective distribution coefficient and a moving coordinate based on the water.
Divalent Zinc Activity in Arid‐Zone Soils Obtained by Chelation
Authors: Ma Qiying , Lindsay W. L. 
Published: July 2010

AbstractBecause of the low solubility of Zn in alkaline soils, it is virtually impossible to measure Zn activity directly. In the present study Zn activities in 10 arid‐zone soils were obtained by chelation. The Zn activities were extremely low, ranging from 10−7.9 to 10−10.9 M and were inversely related to pH, with a correlation coefficient of 0.94. Direct identification of solid phases controlling Zn solubility in these soils has not been achieved. The Zn activities measured in these soils can be expressed by the relationship soil Zn + 2H+ ⇌ Zn2+ with log Ko = 5.7 ± 0.38, where Ko is the equilibrium constant expressed in terms of activities. This is nearly identical to that reported earlier from this laboratory. This observed solubility relationship could be explained by the formation of ZnFe2O4 (franklinite), but that possibility awaits further study.
Modeling Magnesium Uptake from an Acid Soil: I. Nutrient Relationships at the Soil‐Root Interface
Authors: Rengel Z. , Robinson D. L. 
Published: July 2010

AbstractAnnual ryegrass (Lolium multiflorum Lam.), an important forage crop in the southeastern USA, is often grown on soils with potentially toxic levels of soluble Al. Effects of Al on nutrient uptake are poorly understood. Two ryegrass cultivars were grown on an acid Stough soil (a coarse‐loamy, siliceous, thermic Fragiaquic Paleudult) in a greenhouse. Lime (CaO) at three rates to give soil pH values of 3.8, 4.4, and 5.6, and Mg (as MgCl2) at rates of 0, 12, and 36 mg kg−1 were applied in factorial combination. Magnesium application increased shoot Mg concentration, especially in plants grown on unlimed soil. Net Mg influx increased with increased Mg and lime application but decreased with plant age. Liming and plant uptake each caused significant decreases in soil‐solution Mg concentrations. Calculated concentrations of Mg and Ca were higher and K concentrations lower at the root surface than were corresponding concentrations in the bulk soil solution. Concentrations of monomeric hydroxy‐Al species (Almon) at the root surface varied widely. Concentrations of Mg at the root surface were significantly related to net Mg influx only for plants grown in unlimed soil (r2 = 0.89, P < 0.005, and r2 = 0.81, P < 0.014, for 23‐ and 35‐d‐old plants, respectively). For plants grown on limed soil, the ratios of concentrations at the root surface (Mg/Ca, Mg/K, and Mg/Almon), rather than Mg concentration alone, were significantly related to net Mg influx, substantiating existence of the complementary‐ion effect.
Conservation Tillage Effects on the Potassium Status of Some Kentucky Soils
Authors: Karathanasis A. D. , Wells K. L. 
Published: July 2010

AbstractChanges in the soil K status occurring as a result of shifting from conventional to no‐tillage management in selected fields were evaluated in this study. The fields were on loess‐ and limestone‐derived soils in western and central Kentucky and have been under no‐tillage management for the last 6 to 16 yr. Two‐ to three‐fold increases in exchangeable and soluble K were evident in most upper surface horizons (Ap1) of soils receiving no‐tillage management, and these increases correlated well with organic matter (OM) accumulations. Adsorption of exchangeable K appeared to be favored over that of Ca and Mg with increases in OM up to a maximum value, beyond which additional OM accumulations had a negative or no effect. Notillage management resulted in a lower overall affinity for K of the exchange sites in all soils (especially the Memphis soil) apparently due to OM accumulations. Quantity/intensity plots reflecting the tillage‐shift effect on K relationships suggested that the loessial soils could reach K‐availability equilibria sooner than the limestone soils due to mineralogical and textural differences. This could mean less fertilizer‐K use on loess‐ than on limestone‐derived soils to attain maximum crop yields under no‐till management.
Differential Chemoreductive Dissolution of Iron Oxides in a Brazilian Oxisol
Authors: Bryant R. B. , Macedo J. 
Published: July 2010

AbstractStabilities of naturally occurring hematite and goethite in the Bol horizon of a well‐drained Brazilian Oxisol, and their rate of reductive dissolution by sodium dithionite, were investigated. The soil has codominant hematitic and goethitic Fe oxide mineralogy and a reddish hue (2.5YR). There was no apparent foreign‐ion substitution in the hematite, but the goethite contained 34 mole percent of AlOOH substituting for FeOOH. Results of limited additions of sodium dithionite and measured redox‐potential (Eh) development during the reaction showed that hematite and Al goethite were metastable at Eh = 98 mV, pH = 7.3, and 25 °C. Aluminum goethite was metastable at Eh = −2 mV, pH = 7.3, and 25 °C. Hematite dissolution at low Eh occurred readily at 25 °C. Aluminum‐goethite dissolution at low Eh was imperceptible at 25 °C, but occurred readily at 75 °C.
Influence of Plant Uptake on the Performance of Bromide Tracer
Authors: Kung K.‐J. S. 
Published: July 2010

AbstractBromide has been used to study solute transport in unsaturated soils. However, no field studies have addressed the impact of plant uptake on the performance and reliability of Br as a tracer. Field experiments were conducted in a Russet Burbank potato (Solanum tuberosum L.) field on a Plainfield loamy sand soil (mixed, mesic Typic Upidsamment) at the Hancock Research Station in central Wisconsin. At emergence, a 6.8‐mm pulse of KBr solution with 15 kg m−3 concentration was banded at the center of each potato row. The application rate was equivalent to 111.2 kg ha−1 of Br. At 65 d after Br application, soil, potato canopies, tubers, and residues of dead potato leaves and vines from four vertical profiles were collected and the total mass of Br from each sample was measured. The results showed that at least 53% of applied Br mass was absorbed by potato plants. About 44% of the absorbed Br ions could be redistributed to the soil surface when the dead leaves and vines decayed. Leaching of some chemicals, which are metabolized or degraded after being taken up by the plant, can therefore be grossly overestimated by using Br breakthrough curves under certain conditions. Before using Br as a tracer in a field experiment, preliminary laboratory studies should be conducted to determine whether Br uptake and redistribution will be significant under a particular cultivar, Br‐application concentration and mode, and water‐application scheme.
Design of Soil Map Units on a Karst Area in West Central Florida
Authors: Puckett W. E. , Collins M. E. , Schellentrager G. W. 
Published: July 2010

AbstractThe objectives of this research were to identify soil taxa and to evaluate soil‐landscape relationships in order to design map units that accurately describe soil distribution on the Chiefland Limestone Plain (CLP) in west central Florida. A conceptual soil‐landscape model for mapping the CLP was derived based on information from similar karst areas in adjacent counties. Preliminary field observations using the model along with analysis of initial ground‐penetrating radar (GPR) data indicated intricate soil patterns and little relationship between soil occurrence and landscape position. Flexgrid surveys were conducted and 61 GPR transects were performed to design map units and to facilitate placement of map‐unit boundaries. Confidence levels of 95 and 80% were used to establish confidence intervals for named and similar soils in each map unit. A new kind of map unit termed “intriplex” was defined to bridge the gap between complexes and undifferentiated groups.
Surface Soil Acidification under Red Pine and Norway Spruce
Authors: Pallant Eric , Riha Susan J. 
Published: July 2010

AbstractNear‐tree patterns of forest‐soil pH under red pine (Pinus resinosa Ait.) and Norway spruce [Picea abies (L.) Karst.] were examined in order to evaluate the role of trees in acidification processes of surface soils. Variability in soil pH was analyzed by comparing samples obtained at different distances and directions from the base of a tree, at different times within a year, under live and dead trees, trees of different sizes, and trees of the same species growing on different soil types. Accumulation of soil organic matter, pH of freshly fallen litter, and the concentration of oxalate in water extracts of Oe horizons were measured as a function of distance from the base of selected trees. A significant decrease in soil pH from the edge of the canopy to the base of the tree was found in the upper mineral soil and organic horizons beneath live trees of both species. In general, the direction of sampling, the percent organic matter within a soil sample, and the time of year for sampling did not significantly affect soil pH. Mass of organic matter above the mineral soil did not exhibit a distinct pattern with distance from a tree. Twelve years after thinning red pine trees, a significant depression in pH existed in Oi and Oe horizons near the base of a dead tree or stump. Near‐tree depression in pH of the Oi horizon, where tree roots are not present, and of the Oi and Oe horizons around previously thinned trees where no stemflow occurs, suggests that soil fungi endemic or more active in the near‐tree environment of red pine and Norway spruce could make a significant contribution to acidification of soil surface horizons.