bluuebunny/crossref_metadata_2025_split huggingface dataset:
Estimation of the Standard Free Energy of Formation of Metal Arsenates, Selenates, and Selenites
Authors: Essington M. E. 
Published: July 2010

AbstractAn empirical method developed for estimating the standard free energy of formation (ΔG°f) of solid phases is evaluated for metal arsenates, selenates, and selenites. A free energy function of a solid phase is found to be linearly correlated to a function of the metal oxide ΔG°f and the aqueous metal ion ΔG°f for the compound groups examined. The values estimated by this method are, on average, within ± 10.9, 10.4, and 12.0 kJ mol−1 of the experimental arsenate, selenate, and selenite values, respectively. A method for estimating the ΔG°f of hydrated metal arsenates and selenites is also evaluated. The estimated standard free energy of formation values of hydrated arsenates and selenites, on average, are within ± 23.7 and 10.0 kJ mol−1, respectively, of the observed values. The error involved in estimating metal arsenate, selenate, and selenite ΔG°f values are comparable to those obtained when the estimation technique was applied to other compound types.
Phosphorus Adsorption by Kaolinite and Montmorillonite: II. Organic Anion Competition
Authors: Kafkafi U. , Bar‐Yosef B. , Rosenberg Rivka , Sposito G. 
Published: July 2010

AbstractThe mechanisms by which roots affect the release of phosphate from soil surfaces into the solution is not clear. This study was undertaken to investigate the competition of several agents, reported as root exudates, with P on adsorption sites on kaolinite and montmorillonite. The agents studied were acetate, bicarbonate, citrate and oxalate, and the amino acids phenylalanine and alpha‐amino isobutyric acid. The adsorption or desorption of P on the clays in the presence of the noted agents at various fixed pHs and known ionic strength, and the effect of slurry density on P adsorption, were determined. Citrate, bicarbonate and oxalate decreased, and acetate and the amino acids increased P adsorption to the clays. A decrease in the solution‐to‐clay ratio from 100 to 10 L/kg resulted in enhanced P adsorption. The unifying principle that explains these findings is that P adsorption on a clay depends on the extent of the depression of the negative potential of the clay platelets. Bicarbonate and citrate anions at pH > 8 compete with P for active Al sites on the clay. The increased P adsorption in the presence of amino acids is suggested to stem from the fact that H‐bonding of the amino groups causes a decrease in interlamellar spacing, and produces quasicrystals. The quasicrystals reduce the spillover of negative charge from the surface to the edges and allow closer approach of the phosphate ion to the Al site.
Rapid Introduction of Acetylene into Large Assay Chambers for Acetylene Reduction Experiments
Authors: Peck R. L. , Hern J. L. 
Published: July 2010

AbstractA rapid and facile procedure has been developed for preparing the desired acetylene concentration in large sealed chambers for acetylene reduction assays. The gas dilution system incorporated an inexpensive manometer to monitor evacuation of a known amount of air from the chamber. A simple valving system then allowed for easy injection of acetylene to produce the desired assay conditions. Although 34‐L chambers were used, the procedure is amenable to sealed chambers of any size. The entire procedure takes <1 min and exhibits excellent precision. This technique facilitates the use of very large assay chambers, and resolves the cumbersome problems and time involved in handling large volumes of gas.
Effects of Carbon and Trace Element Addition on Alkylselenide Production by Soil
Authors: Karlson U. , Frankenberger W. T. 
Published: July 2010

AbstractMicrobial volatilization of selenium (Se) may be applicable for detoxifying Se‐contaminated soils, if high rates of volatilization can be maintained. This study was conducted to evaluate some of the factors affecting the rates of microbial production of alkylselenides. Field‐moist Los Baños clay loam, representing soils from Se‐affected areas, was treated with 100 mg kg−1 Se(IV), labeled with 75Se(IV). Gaseous Se was determined by direct gamma counting of activated charcoal traps. Without C amendments, the volatilization potential was 2.9% in 13 d; amendments with 2 g C(pectin) kg−1 soil increased that potential to 8.8%. With other C sources volatilization in 13 d was 6.6% [corn (Zea mays L.) leaves], 5.2% (starch), 3.7% (dairy manure), 3.3% (cellulose), and 2.7% (sewage sludge). Volatilization rates decreased as C was depleted, but increased again upon C reload. The addition of molybdenum (Mo), mercury (Hg), chromium (Cr), and lead (Pb) greatly inhibited Se volatilization, while arsenic (As), boron (B), and manganese (Mn) had little effect. The presence of cobalt (Co), zinc (Zn), and nickel (Ni) at relatively high levels (25 mmol kg−1) increased Se volatilization rates up to 2.5‐fold. After 37 d of incubation, recovery of added Se(IV) as alkylselenides was as high as 34, 30, and 23% with Co, Zn and Ni, respectively, applied along with C amendments. Zinc, Co, and Ni most likely serve as cofactors in the methylation reaction. Low levels of N in the presence of added C slightly enhanced alkylselenide production, while without C amendments, N had a slightly inhibitory effect.
Long‐term Annual Manure Applications Increase Soil Organic Matter and Nitrogen, and Decrease Carbon to Nitrogen Ratio
Authors: Sommerfeldt T. G. , Chang C. , Entz T. 
Published: July 2010

AbstractThe effects of long‐term annual applications of cattle (Bos taurus) feedlot manure on the accumulation, decomposition (amounts and rates), and movement of organic matter (OM) and Kjeldahl‐determined N (total N) in soil were determined. Manure was applied annually since 1973 at three different levels to nonirrigated and irrigated Dark Brown Chernozemic (Typic Haploborolls) clay loam soil. Significant increases in soil OM and total N content in the first 8 and 6 yr, respectively, as affected by the level of manure application, were limited to the surface 30 cm of soil of the nonirrigated and irrigated land. Tillage did not affect the amount of OM and total N accumulated in the soil, but it did affect their distribution within the 0 to 30‐cm depth, which is attributed to placement during incorporation. The accumulation of OM and total N were similar under nonirrigated and irrigated conditions. Manure (C/N ratio of ca. 10.2) lowered the C/N ratio of the soil (ca. 8.2) by small amounts. The accumulation of OM and total N was described by a Michaelis‐Menten type of function. A response surface was generated for the accumulation of OM and total N with increasing levels and years of manure application, from which the rates of accumulation and decomposition were derived. The rates of accumulation decrease with years of application such that after two or three decades increases will be small. The model can be used to develop general guidelines for use and disposal of feedlot manure under similar conditions.
Effect of Soil pH and Clay Content on the Zinc Soil Test Interpretation for Corn
Authors: Lins I. D. G. , Cox F. R. 
Published: July 2010

AbstractSoil test interpretations are usually improved by considering at least one soil property in addition to the extractable nutrient concentrations. Greenhouse and field experiments were carried out to evaluate the effects of soil pH and clay content on the Zn soil test interpretation for corn (Zea mays L.). In a greenhouse experiment, four Oxisols with 68, 63, 57 and 21% clay were adjusted to pH 5.2, 5.7 and 6.2. Five Zn levels within each soil pH were created by applying Zn at 0, 0.8, 1.6, 3.2 and 6.4 mg L−1. Three crops of Cargill 111‐S corn were grown, each for about 4 weeks. Soil Zn extracted with Mehlich‐1 was not affected by changes in pH, but plant Zn decreased as soil pH was increased. Plant growth was depressed at the highest soil pH and lowest soil Zn concentration, and the prediction of dry matter as a function of soil Zn was markedly improved by including soil pH for three of the four soils. The soil‐Zn critical level was calculated and was not affected by clay content, but did increase with an increase in pH. The critical levels in the greenhouse were 1.0, 1.4, and 2.0 mg L−1 for soils of pH 5.2, 5.7, and 6.2, respectively. In the field, the same variety of corn was grown one season in a residual experiment on a Typic Haplustox. Lime and zinc levels had been established by treatments imposed 13‐yr prior. Current pH ranged from 6.0 to 6.7, and the soil Zn from 0.6 to 1.6 mg L−1. The results were similar to those obtained in the greenhouse. The effect of pH on the soil Zn critical level, however, was not as striking, perhaps because of the high average and more narrow range in soil pH.
Vertical Distribution in Soil of Unincorporated Surface‐applied Phosphorus Under Sprinkler Irrigation
Authors: Lauer D. A. 
Published: July 2010

AbstractDetermining vertical distribution of P is important in irrigated conservation cropping systems for evaluation of P fertilization because soil‐immobile phosphorus accumulates near the soil surface where limited tillage reduces soil mixing. The objective was to determine in field and laboratory experiments the vertical distribution of P from surface‐applied monoammonium phosphate (MAP; 227 g P kg−1), triple superphosphate (TSP; 197 g P kg−1), and ammonium polyphosphate (APP; 149 g P kg−1). Following P application, vertical distribution was determined from 2‐cm depth increment samples in a Quincy sand (mixed, mesic, Xeric Torripsamments), a Warden silt loam (coarse‐silty, mixed, mesic, Xerollic Camborthids), and a calcareous subsoil of the Warden. There was little effect on P distribution from antecedent moisture; fertilizer rates at 30, 60, 120, or 240 kg P ha−1; or from preirrigation reaction times of 1, 4, or 16 d. Continuous postapplication irrigation totals of 40 or 160 mm at 10 mm d−1 moved P somewhat deeper into the soil, principally at 160 mm on the Quincy sand. Overall mean penetration depths of P were as follows: (i) APP moved the farthest in the Quincy sand (mean = 6.1; SD = 1.05 cm); (ii) penetrations were practically the same for MAP or TSP on the Quincy sand (mean = 5.4; SD = 1.32 cm) and on the noncalcareous Warden silt loam (mean = 5.5; SD = 1.25 cm); (iii) depth of penetration was intermediate for APP on the noncalcareous Warden (mean = 4.0; SD = 0.98 cm); and (iv) downward movement in the calcareous Warden of P from all fertilizer P materials was much more restricted (MAP/TSP: mean = 3.1; SD = 0.10 cm and APP: mean = 3.3; SD = 0.52) than on the two noncalcareous soils. Overall, the most apparent conclusion from this study is that the reactivity of P fertilizer material with the soil is the dominant and overriding determinate of the vertical distribution of surface‐applied P.
X‐ray Technique to Evaluate Pedon and Erosion Variability of an Ava Map Unit
Authors: Olson K. R. , Darmody R. G. , Steiner J. S. , Beavers A. H. 
Published: July 2010

AbstractAn uneroded map unit of Ava soil was examined to determine the presence of and variability in depth to the upper and lower boundaries of the argillic horizon, the second parent material, the horizon of maximum x‐ray mass absorption coefficient, the fragipan, the A and E horizons, and the clay maximum prior to accelerated erosion. Twelve pedons from six pits were examined to address the depth variability of selected soil features. These features have often been used as reference markers to provide a basis from which to estimate the soil loss from erosion. Considering all sampled pedons in an Ava map unit on a ridgetop, all selected soil parameter boundaries but the depth to the upper boundary of the fragipan were found to be reliable reference markers. The mean depth to the lower boundary of the horizon with the maximum coefficient of x‐ray mass absorption coincided with the mean depths to the lower boundary of the clay maximum, Fe maximum, and top of the second parent material, but did not coincide with the mean depth to the lower boundary of the argillic horizon. Iron content and x‐ray mass absorption coefficient were highly correlated because elements with high mass, such as Fe, increase the x‐ray mass absorption coefficient in a horizon. Where accelerated erosion occurred on a landscape segment, the lower boundary of the horizon of maximum x‐ray mass absorption coefficient, as well as other lower boundaries of subsoil parameters, could be used as reference markers to provide a basis for estimating soil loss from erosion.
Characteristics of Histic Materials in Wisconsin as Arrayed in Four Classes
Authors: Lee G. B. , Bullington S. W. , Madison F. W. 
Published: July 2010

AbstractSamples of histic materials were collected throughout Wisconsin and analyzed for characteristics common to these materials. On the basis of resistant fiber content, they were ordered into four classes. Fibric and Hemic materials are similar to those in Fibrist and Hemist suborders. Sapric A materials are defined here as those containing from 8 to 20% fiber; sapric B materials contain 0 to 7%. Fiber, moisture, and organic C content decrease from fibric to sapric B material. Sodium pyrophosphate extract color (SPEC) values and C/N ratios follow the same trend. Percentage N and ash content increase in value, as does pH and bulk density. The low fiber content, which is indicated directly by volume and indirectly by SPEC values, low moisture content and C/N ratios, high N and bulk density values, and ash content, are characteristic of sapric B materials, and should be used in further definition of this class.
Time Series Analysis for Statistical Inferences in Tillage Experiments
Authors: Roseberg R. J. , McCoy E. L. 
Published: July 2010

AbstractSpatial dependence of soil physical properties often invalidates parametric inferencing of tillage treatment effects. Spectral analysis was examined as a possible means to generate inferences on tillage treatments from an observation set that is spatially dependent. The method was tested using surface elevation data from a long‐term tillage study. Three tillage treatments were imposed on a continuous corn cropping system in a randomized complete block design beginning in 1962. Surface elevations were measured in 1971, 1976, 1980, and 1987 along four transects oriented perpendicular to the imposed treatments with each transect running the length of the field. The power spectrum from the 1971 observations yielded a significant spectral peak at a wavelength equal to one‐plot width. The power spectra from the 1976, 1980, and 1987 observations yielded a significant spectral valley at a wavelength equal to one‐plot width. The significant spectral valleys in the 1976, 1980, and 1987 power spectra represent low variance within the plot spacing as compared to variance between plots. In a randomized complete block design, this significant spectral valley represents an inference on the effect of tillage on surface elevation using spectral analysis. Calculation of number of observations needed to show significant spectral differences at wavelength equal to one‐plot width compared to within and beyond plot wavelengths indicate that 75, 161, 223, and 149 observations were necessary for 1971, 1976, 1980, and 1987 sampling dates, respectively.
Modeling Limestone Dissolution in Soils
Authors: Warfvinge Per , Sverdrup Harald 
Published: July 2010

AbstractIn 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

AbstractThe 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

AbstractSoil 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

AbstractThe 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

AbstractThe 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

AbstractA 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

AbstractSoil 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.