bluuebunny/crossref_metadata_2025_split huggingface dataset:
Geographic Patterns of Soil Water‐Holding Capacity in the Contiguous United States
Authors: Kern Jeffrey S. 
Published: July 2010

AbstractThe geographic patterns of soil water‐holding capacity are important for studying the response of vegetation and water supply to climate change. This study was conducted to evaluate which dataset to use for national‐scale water balance modeling. Spatial databases of soil properties for the contiguous USA were derived from the USDA national soil database (NATSGO) and the United Nations soil map of the world. The NATSGO data generally resulted in finer textures, greater rock fragment content, and more shallow soils. The organic matter content in the surface was similar, but the NATSGO database did not contain sufficient information to estimate organic matter content of the lower soil. The Rawls model was used to estimate soil water‐holding capacity of the 0‐ to 50‐cm depth from particle‐size distribution, organic matter content, rock fragment content, and soil depth data. The Saxton model was used to estimate the water‐holding capacity of the 50‐ to 150‐cm depth interval, because it didn't require organic matter data. The water‐holding capacity in the surface layer based on the NATSGO data was larger than that based on the soil map of the world despite greater rock fragment contents and shallower soil depths. There were few similarities in the water‐holding capacities of the 50‐ to 150‐cm depth layer because of large differences in rock fragment content and soil depth. The NATSGO dataset is recommended because the map unit composition was based on a statistical framework with a large sample size and it better characterizes rock fragment content and soil depth.
Evaluation of Soil Water Retention Models Based on Basic Soil Physical Properties
Authors: Kern Jeffrey S. 
Published: July 2010

AbstractAlgorithms to model soil water retention are needed to study the response of vegetation and hydrologic systems to climate change. The objective of this study was to evaluate some soil water retention models to identify minimum input data requirements. Six models that function with various combinations of particle‐size distribution, bulk density (ρb), and soil organic matter data were tested using data for nearly 6000 pedons. The Rawls model, which requires particle‐size distribution and organic matter data, had the lowest overall absolute value of the mean error (ME) with 0.020, 0.001, and 0.007 m3 H2O m−3 soil for matric soil water pressures of −10, −33, and −1500 kPa, respectively. The Saxton model, which requires particle‐size distribution data, had small MEs (0.018 and 0.007 m3 H2O m−3 soil) for −10 and −1500 kPa matric soil water pressures, and a moderately small ME (0.017 m3 H2O m−3 soil) at −33 kPa. The Vereecken model, which requires ρb, particle‐size distribution, and organic matter data, had small MEs (0.016 and 0.009 m3 H2O m−3 soil) at matric soil water pressures of −10 and −33 kPa, with a larger ME (0.020 m3 H2O m−3 soil) at −1500 kPa. The remaining three models had relatively large MEs for at least two of the three matric soil water pressures. For estimating water‐holding capacity only, the Saxton model is adequate. The Rawls model is recommended for characterizing the relationship of water content to matric soil water pressure.
Water Content Effect on Soil Salinity Prediction: A Geostatistical Study Using Cokriging
Authors: Vaughan Peter J. , Lesch Scott M. , Corwin Dennis L. , Cone David G. 
Published: July 2010

AbstractA geostatistical analysis of soil salinity in an agricultural area in the San Joaquin Valley included measurements of electrical conductivity of soil paste extract (ECe) and water content of soil samples supplemented by surface measurements of apparent electrical conductivity (EMH). Prediction of soil salinity at unsampled points by cokriging loge(ECe) and EMH is worthwhile because EMH measurements are quicker than soil sampling. This work studies how patterns of loge(ECe) predicted by cokriging with EMH are influenced by variation in gravimetric water content (W). The data are mean EMH = 1.00 ± 0.13 dS m−1 for 2378 locations, mean loge(ECe) = 1.40 ± 0.29 dS m−1, and mean gravimetric W = 0.260 ± 0.003, both averaged for four samples from 0.3‐m intervals to 1.2‐m depth for 315 locations. The coefficient of determination (R2) for EMH vs. loge(ECe) increased with depth from 0.05 to 0.54 whereas the R2 for EMH vs. W decreased from 0.48 to 0.28. A gray‐scale EMH map contained nine out of 56 quarter‐section boundaries coinciding with step variations in EMH. The t‐statistics for differences in mean W were six of nine significant at 0.001 and nine of nine at 0.05, but mean loge(ECe) had only two of nine at 0.05, implying that W caused EMH steps. Water‐affected EMH impaired prediction of ECe at depth by cokriging, because near‐surface variations in W masked ECe. Two subareas were defined, one where management factors, such as irrigation, controlled EMH, causing steps, and one where near‐surface W varied less, making cokriging predictions more reliable.
Phyllosilicate Distribution and Origin in Aridisols on a Granitic Pediment, Western Mojave Desert
Authors: Boettinger J. L. , Southard R. J. 
Published: July 2010

AbstractThere is considerable uncertainty about the extent of mineral weathering and neosynthesis in arid soils. Although researchers have speculated that smectite neosynthesis can occur in soils containing opaline silica cement, no evidence has been presented to support this hypothesis. We investigated the mineralogy of two Aridisols in the western Mojave Desert, California, to study phyllosilicate distribution and origin in soils with opaline silica. The clay fraction of both soils is dominated by Al‐rich, dioctahedral smectite, characterized by a Mg‐saturated d(001) spacing of 1.52 nm and a d(060) spacing of 0.149 to 0.150 nm. This smectite is also present in silt and sand fractions of deeper horizons, where it exists mainly as microagglomerates of clay‐sized crystals. Biotite is most abundant in silt and sand fractions of near‐surface horizons of both pedons, where physical weathering is greatest. Deep, alkaline, silica‐rich horizons of both pedons contain more silt‐ and sand‐sized vermiculite than biotite, probably due to rapid chemical weathering of biotite to trioctahedral vermiculite. Clay‐ and silt‐sized hydroxy‐interlayered 2:1 minerals are present in the upper horizons of these soils. Given the lack of gibbsite and substantial amounts of kaolinite and Al hydroxy‐interlayered 2:1 phyllosilicates, we propose that neosynthetic dioctahedral smectite was the dominant sink for Al released by feldspar weathering in these Aridisols. Silica not consumed in smectite neosynthesis can cement microagglomerates. We further speculate that minimal physical weathering in the alkaline, high‐silica environment of deep horizons favors aggregation of smectites to silt‐ and sand‐sized microagglomerates.
Measurement of Divalent Lead Activity in Lead Arsenate Contaminated Soils
Authors: Kalbasi M. , Peryea F. J. , Lindsay W. L. , Drake S. R. 
Published: July 2010

AbstractMany soils used for tree fruit production before 1968 contain elevated Pb concentrations resulting from use of lead arsenate pesticides. The chemical form of Pb in these soils may influence its bioavailability and the need for and type of remediation actions. The competitive chelation method was used to determine the single‐ion activity of Pb2+ in aqueous suspensions of 11 lead arsenate contaminated soils and, for comparison, three Pb‐enriched roadside soils. The activity of Pb2+ ranged from 10−9.37 to 10−7.21, consistent with values published elsewhere, and was inversely related to pH. The soils appeared to fall into two solubility groups, one where Pb2+ activity was consistent with control by a Pb‐phosphate mineral, possibly Pb5(PO4)3OH or Pb3(PO4)2, and a second group where Pb2+ activity was consistent with control by Pb(OH)2. Both groups contained calcareous soils. Adding monocalcium phosphate to two of the soils from the higher Pb solubility groups shifted one soil to the lower solubility group but had no effect on the second soil. The experimental results suggest that Pb solubility in lead arsenate contaminated soils is not appreciably higher than in soils contaminated by Pb from gasoline and that phosphate amendment may not always reduce soil Pb solubility.
Effect of Adsorbed Phosphate on Transport of Arsenate through an Oxisol
Authors: Melamed R. , Jurinak J. J. , Dudley L. M. 
Published: July 2010

AbstractCompetitive oxyanion adsorption can increase the mobility of toxic trace elements in soils leading to groundwater contamination and a potential threat to the environment. We conducted a study to determine how phosphate fertilization might affect arsenate mobility in soil. The competitive nature of sorbed phosphate on arsenate mobility was investigated using laboratory soil columns constructed from an aggregated Oxisol. The soil was incubated with four levels of phosphate (0–48.6 mmol P kg−1) before being leached with 0.66 mmol KH2AsO4 L−1 in 0.05 M KCl. Arsenate mobility was greatly enhanced by treatment with increasing amounts of phosphate. The As breakthrough curves (BTCs) were divided into two phases. The initial phases of arsenate interaction was consistent with ligand exchange of Me‐OH+2 groups, where Me is the coordinating metal atom at the oxide surface. This phase was characterized by the constant pH of the effluent. The second phase was consistent with ligand exchange of As with Me‐OH groups and surface‐completed P. The asymmetry of the As BTCs suggested that the physical structure of the matrix influenced the convective flow path of the As and subsequently its reaction and movement through the soil.
Chamber Measurement of Soil‐Atmosphere Gas Exchange: Linear vs. Diffusion‐Based Flux Models
Authors: Anthony W. H. , Hutchinson G. L. , Livingston G. P. 
Published: July 2010

AbstractWe compared linear regression with a diffusion‐based model for N2O flux estimation using non‐steady‐state chamber gas concentrations from a long‐term study of N cycling in a managed grass pasture on sandy soil in southern Texas. Of 2224 chamber deployments, 449 met criteria established for using the diffusion‐based model, which yielded flux estimates that averaged 54% larger than linear regression (n = 3). Although they represented only about 20% of all chamber deployments, this group included most of the data with greatest influence on the magnitude and dynamics of total N2O exchange at our site; e.g., of the 263 fluxes >10 g N ha−1 d−1, 192 (or 73%) were included. Apparently, application of a linear model to nonlinear chamber concentration data represents a potentially serious source of measurement bias that may influence not only summary statistics for the experiment, but also larger scale budgets based partially or wholly on those data.
Semicontinuous Measurement of Soil Atmosphere Gases with Gas‐Flow Soil Core Method
Authors: Swerts M. , Uytterhoeven G. , Merckx R. , Vlassak K. 
Published: July 2010

AbstractTo study denitrification, a method was developed for simultaneous measurement of CO2, N2, N2O, and NO production in soil cores. The technique does not interfere with biochemical processes in the soil and is fully automated to enable highly time‐resolved measurements for prolonged periods. Soil cores (intact or repacked) are connected to individual gas‐tight circuits (up to nine). Gas is continuously circulated through the soil cores to avoid diffusional problems. Each individual circuit can be automatically sampled for chromatographic gas analysis. The N2O production rates can be measured accurately down to 0.04 µg N kg−1 measuring interval−1 (MI). Determination of N2, CO2, and O2 production rates is less sensitive: 0.09 mg N kg−1 MI−1, 0.04 mg C kg−1 MI−1, and 0.02 mg O kg−1 MI−1, respectively. Dynamically changing gas production rates are monitored accurately, and total N gas production under anaerobiosis is balanced by NO3− disappearance.
Differential Effects of Soil Water Content and Temperature on Nitrification and Aeration
Authors: Grundmann G. L. , Renault P. , Rosso L. , Bardin R. 
Published: July 2010

AbstractEnvironmental concerns have stimulated increased interest in NO−3 accumulation in soils. The aeration status of the soil, which is mainly governed by the water content and temperature, is a central factor. The biological process responsible for NO−3 accumulation, nitrification, was measured to estimate the combined effects of water content and temperature and determine their joint effect on soil aeration. The effects of temperatures of 15, 20, 25, 30, and 35°C and water contents equivalent to 0.35, 0.42, 0.50, 0.52, 0.57, and 0.60 relative water content (volumetric water content/total porosity) on the nitrification activity of soil samples containing 2‐mm sieved soils taken at 0 to 20 or 20 to 40‐cm depth were determined by measuring NO−3 accumulation for 17 h. A descriptive model including three biological parameters, maximum nitrification rate (Nrmax), optimal relative water content (Θopt), and temperature, was developed. Maximum Nrmax occurred at 25.5°C in 0‐ to 20‐cm soil and at 20°C in 20‐ to 40‐cm soil, suggesting an adaptation of soil nitrifying populations to the temperature regime of the soil. The Nrmax value was negatively related to Θopt, and Θopt was dependent on temperature (T). This Θopt (T) relationship was parabolic in nature, with Θopt being at a minimum between 20 and 25°C. It could be simulated using O2 diffusion and respiration rates, inferring that these processes influenced Θopt and T correlation. The ranges of O2 concentrations favorable to maximum nitrification within an aggregate volume fraction were estimated for different temperatures. Nitrification was generally maximum when the intraaggregate pore spaces were saturated with water, with no water in the interaggregate pore space (i.e., 0.44 relative water content at 25°C and 0.36 at 20°C at 0‐ to 20‐ and 20‐ to 40‐cm depths).
Physical Property Variation of a Soil and Saprolite Continuum at Three Geomorphic Positions
Authors: Schoeneberger P. J. , Amoozegar A. , Buol S. W. 
Published: July 2010

AbstractEffective land use planning for waste disposal purposes requires knowledge of water movement in the vadose zone in and below the soil solum. This study was conducted to assess the changes in the saturated hydraulic conductivity (Ksat), water retention, particle‐size distribution, and bulk density of a Typic Kanhapludult soil and its underlying gneiss‐schist saprolite across a typical landscape in the Piedmont region of North Carolina. Intact cores (6.6‐cm diam., 8.0‐cm length) were collected from Bt, B/C, and C (saprolite) horizons at the center of 15 by 30 m areas located at three adjacent geomorphic positions (ridge top, shoulder, and ridge nose). Large L‐shaped observation pits were then excavated over the sample locations for profile description and other data collection. In situ Ksat of the three horizons was also determined by the constant‐head well permeameter technique around each of the observation pits. Regression analysis was employed to assess the relationship between Ksat and depth at each geomorphic position, and an analysis of variance was used to compare Ksat values between horizons and geomorphic positions. At all three geomorphic positions, the laboratory‐determined Ksat was consistently the highest in the clayey Bt horizon (arithmetic mean values 1.56 × 10−6 to 2.19 × 10−6 m s−1), diminished with depth until reaching a minimum value in the transitional, less clayey B/C horizon (arithmetic mean values 7 × 10−8 to 2.3 × 10−7 m s−1), and then increased with depth into the upper part of the massive, low clay content saprolite (arithmetic mean values 8.1 × 10−7 to 1.57 × 10−6 m s−1). The patterns of Ksat with depth were consistently associated with major horizons and not strongly influenced by texture or bulk density.
Analysis and Field Evaluation of the Ceres Models Water Balance Component
Authors: Gabrielle Benoît , Menasseri Safya , Houot Sabine 
Published: July 2010

AbstractThe soil water status partly determines the N losses from soilcrop systems. With the ultimate objective of estimating N losses, the capacity‐based water balance module of the Ceres models was tested against field data collected from various pedoclimatic regimes in France. A process‐oriented analysis of initial simulation results for a loamy soil prompted introduction of Darcy's law in the drainage and capillary rise parts of the model. As a result, a more accurate prediction of the soil water storage and surface water content was achieved. This was confirmed by comparing model output against independent data from bare or maize (Zea mays L.)‐cropped conditions and for silt loam or sandy loam soils. For a 1‐yr period, the mean square error between modeled and measured water storages was in the range 1.9 to 3 cm2 water for the modified model, in contrast with 4 to 12 cm2 using the original model (which performed best on well‐drained soils). A unidimensional sensitivity analysis was conducted with regard to the three new parameters introduced in the revised model: the saturated hydraulic conductivity and two texture‐dependent constants used in simple analytical representations of the moisture retention and hydraulic conductivity curves. The sensitivity analysis proved that this more physical approach in capacity‐based models required less rigorous parameterization than mechanistic models. Moreover, the accuracy of the simulations performed with the modified model fell within the experimental error in the measurements.
Soil Organic Carbon in a Mountainous, Forested Region: Relation to Site Characteristics
Authors: Homann P. S. , Sollins P. , Chappell H. N. , Stangenberger A. G. 
Published: July 2010

AbstractSoil organic C content (SOC, kilograms C per square meter) and its relation to site characteristics are important in evaluating current regional, continental, and global soil C stores and projecting future changes. Data were compiled for 499 pedons in the largely forested, mountainous western Oregon region. The SOC of mineral soil ranged from 0.9 to 24 kg C m−2 (mean = 6.5) for 0‐ to 20‐cm depth and 2.3 to 88 kg C m−2 (mean = 15.8) for 0‐ to 100‐cm depth. Variability in each of the three terms that determine SOC − C concentration, bulk density, and rock volume ‐ contributed substantially to SOC variation. Regression analysis of 134 forest pedons indicated that combinations of site characteristics explained up to 50% of the SOC variability. The SOC increased with annual temperature, annual precipitation, actual evapotranspiration, clay, and available water‐holding capacity and decreased with slope. Relations for western Oregon differed qualitatively and quantitatively from those for other regions and contrasted with the decrease in SOC associated with increased temperature in Great Plains grasslands. Of the variability not explained by regression analysis, one‐half may be due to the combined uncertainty associated with measurements of C concentrations, bulk density, and rock volume; natural within‐site variability; and site‐characteristic measurements. Other unexplained variability is probably due to potentially important but poorly documented site characteristics, such as recent vegetation composition, geomorphic disturbance regime, and fire history.
Colloid Chemistry of Kaolinitic Tropical Soils
Authors: Chorover Jon , Sposito Garrison 
Published: July 2010

AbstractHighly weathered soils of the humid tropics may exhibit loss of aggregate stability and dispersion of hydroxyl‐bearing soil constituents as a result of management‐induced changes in soil solution chemistry. The effects of pH and 1:1 “indifferent” electrolyte concentration on the surface charge and flocculation of colloids extracted from four representative kaolinitic tropical soils were examined by microelectrophoresis and light scattering methods. Electrophoretic mobilities (u) of clay‐sized particles (0.1‐1.0‐µm diameter) were predominantly negative between pH 2 and 6 for all soils, but decreased in magnitude with increasing solution proton concentration. Measured u values were between −3.0 × 10−8 and +0.5 × 10−8 m2s−1V−1, with isoelectric points (i.e.p.) ≤ 2.5. Photon correlation spectroscopy revealed an abrupt change from small to large particle size with increasing proton concentration in the pH range 2.5 to 3.5. Light scattering by whole‐soil suspensions indicated a proton‐induced transition from kinetically stable to kinetically unstable suspensions in the same pH range. Rapid flocculation occurred in the electrophoretic mobility range −1.2 to −1.8 × 10−8 m2 s−1 V−1. The pH and ionic strength dependence of colloidal stability observed for the soils is consistent with an electrostatic stabilization mechanism among their clay‐sized particles.
Stability Constants of Metal‐Humate Complexes: Titration Data Analyzed by Bimodal Gaussian Distribution
Authors: Manunza Bruno , Deiana Salvatore , Maddau Vittoria , Gessa Carlo , Seeber Renato 
Published: July 2010

AbstractA continuous multiligand model was applied to the study of the systems Cu(II)‐, Pb(II)‐, Mn(II)‐, and Cd(II)‐humate. The model is essentially based on a bimodal Gaussian distribution of the binding sites. It allows the calculation of pH‐independent metal‐binding thermodynamic constants which are more representative than simple empirical curve‐fitting parameters. This model was applied to the study of the potentiometric titration data of an humic acid extracted from an Andosol of Macomer (Sardinia, Italy) in order to calculate the formation constants of the complexes of humic acids with four metal ions. Its application to the potentiometric titration experiments showed that different classes of sites are involved in the binding of the metal ions considered. The affinity to the humic matrix followed the order: Cu(II) > Pb(II) > Mn(II) >> Cd(II); phenolic groups play a relevant role in Cu binding while Cd appears to bind exclusively to carboxylic groups.
DNA Probe Analysis of Microbial Community Selected in Field by Long‐Term 2,4‐D Application
Authors: Ka J. O. , Burauel P. , Bronson J. A. , Holben W. E. , Tiedje J. M. 
Published: July 2010

AbstractThe 2,4‐D (2,4‐dichlorophenoxyacetic acid)‐degrading microbial populations selected by 2,4‐D amendments to soil were analyzed by DNA probes during a 4‐yr field study. Two were control subplots not treated with 2,4‐D, and the other six were treated with 2,4‐D in replicates at three different concentrations. Total soil bacterial DNA was regularly extracted from each subplot soil and analyzed on slot and Southern blots using the gene probes tfdA and Spa that detect two different 2,4‐D‐degrading populations. Slot blot analyses revealed that the hybridization signal of the probes to total soil bacterial DNA substantially increased with time and continued 2,4‐D application, indicating a shift from a more diverse 2,4‐D‐degrading microflora to populations that shared greater homology to the two probes. More hybridization signal was obtained with the Spa probe, suggesting that microorganisms with this gene sequence were more dominant than degraders with tfdA‐like genes. The Southern blot band patterns indicated that the dominant Spa‐hybridizing strain was Sphingomonas paucimobilis strain 1443 and the dominant tfdA hybridizing strain was Burkholderia (formerly Pseudomonas) pickettii strain 712, similar to the results of a previous laboratory microcosm study. At the highest 2,4‐D application rate (100 mg kg−1), Southern blots probed by 16S rRNA genes showed a limited number of bands, suggesting that the total soil microbial community had been shifted to one or two dominant strains, presumably 2,4‐D degraders.