bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dissolution of Biogenic Opal as a Function of its Physical and Chemical Properties
Authors: Bartoli F. , Wilding L. P. 
Published: July 2010

AbstractSeveral factors examined herein which control opal dissolution are: specific surface area, Al content, hydration state, age, and rate of organic matter biodegradation of the encasing vegetative tissues. These factors are covariable with opal of different origin. Recent (6 months old) opal phytoliths of deciduous origin are most hydrated (11%), have lower A1 content (2%) and highest dissolution (9 mg Si/liter, cold water; 50 mg Si/liter, hot water; and 3 mg Si/liter under natural environments). In contrast, opal of coniferous origin is older (30 months), more rigid, has higher Al content (3 to 4%), is encased within litter that is more slowly biodegradable and yields lower dissolution (2 to 3 mg Si/liter, cold water; 20 mg Si/liter, hot water; and 0.5 mg Si/liter under natural environments). Gramineous phytoliths associated with understory forest vegetation generally are intermediate in the above properties and dissolution. Biogenic opal has solubilities that approximate geologic opal‐A. It is relatively stable and not sufficiently labile under most soil environments to support observed soluble Si levels.
Comparison of One‐step Outflow Laboratory Method to an in situ Method for Measuring Hydraulic Conductivity
Authors: Jaynes D. B. , Tyler E. J. 
Published: July 2010

AbstractThe unsaturated hydraulic conductivity, K, of three soil horizons; the C horizon of a Plainfield sand (Typic Udipsamment), the C horizon of a Ringwood silt loam (Typic Argiudoll), and the B2t horizon of a Plano silt loam (Typic Argiudoll) was measured using a variation of the one‐step porous membrane outflow method. The method was adapted for measuring K using small (7.65 cm high by 7.65 cm in diam) undisturbed soil cores at soil water pressure potentials > −100 mbars. Comparison of these K values with values previously measured in situ for the same horizons with the crust test agreed within an order of magnitude or less. The discrepancy was probably due to hysteresis in the θ‐ψ relation.The one‐step outflow method yields satisfactory results near saturation but cannot be used to measure saturated K values. Compared to other methods, the one‐step outflow procedure requires less time to measure K for many types of soils and facilititates the running of many samples simultaneously.
Linearized Moisture Flow with Root Extraction for Three Dimensional, Steady Conditions
Authors: Warrick A. W. , Lomen D. O. , Amoozegar‐Fard A. 
Published: July 2010

AbstractA mathematical model is presented to simulate plant water uptake assuming steady‐state conditions and an unsaturated hydraulic conductivity as an exponential function of pressure head. By choosing the conductivity to be of this form, the moisture flow equation is linear, allowing analytical solutions to be developed in a closed form. Geometries considered possess radial symmetry and are appropriate to describe trickle irrigation. These include matrix potentials for points, discs, and cylinders which can be taken either as sources or sinks. These provide the basic building blocks to simulate varied steady‐state withdrawal patterns. The solution for the cylinder is newly derived; the other solutions were already available. Nonsymmetric cases can result from superpositions. Examples include pressure head distributions for four sink‐source combinations.
Irrigation Water Requirement for Dissolution of Gypsum in Sodic Soil
Authors: Hira G. S. , Singh N. T. 
Published: July 2010

AbstractLaboratory studies were conducted to determine the effect of exchangeable sodium content of the soil and the particle size of gypsum on the irrigation water needs for dissolving gypsum mixed in sodic soils. Gypsum dissolution increased with an increase in the exchangeable Na content of the soil. About 4 cm of water was sufficient to dissolve all the agricultural grade gypsum of <0.26‐mm size. The amount of water required to dissolve the added gypsum and to reclaim a sodic soil did not increase with the amount of gypsum added, provided it equalled the gypsum requirement.The effect of particle size of gypsum on its dissolution and the applicability of the equal‐reduction hypothesis were examined. The dissolution of gypsum was approximately predicted by a dissolution equation based on particle surface area if the initial particle sizes were neither very coarse (<0.5 mm) nor very fine (>0.1 mm). The water required for complete dissolution of gypsum computed from a dissolution equation, increased from 2.8 cm to 15.9 cm as gypsum particle size increased from < 0.1 mm to 0.5–2.0 mm.
Flocculation Value and Gel Structure of Sodium/Calcium Montmorillonite and Illite Suspensions
Authors: Oster J. D. , Shainberg I. , Wood J. D. 
Published: July 2010

AbstractThe flocculation value, the minimum salt concentration which causes flocculation within 24 hours, was determined for mixtures of Na‐ and Ca‐montmorillonite (API‐25) and Fithian illite (API‐35). The equivalent fraction of exchangeable Na+, ENa, varied from 0 to 1. We prepared Na/Ca clay suspensions by adding the appropriate amounts of homoionic dry clays to a series of Na/Ca chloride solutions (0.2 to 80 molc m−8; 0.2 to 80 meq liter−1) with appropriate sodium adsorption ratio and shaking the mixture for 1 hour. The flocculation value of Ca‐montmorillonite (0.25 molo m−3) increased rapidly with small amounts of exchangeable Na+: the flocculation value for an ENa of 0, 0.2, 0.4, and 1 was 0.25, 6, 9, and 12 molc m−3, respectively. The flocculation values for Ca‐ and Na‐illite were 0.25 and 55 molo m−3, respectively, and increased linearly with ENa. Van der Waals attraction forces are mainly responsible for flocculation of Ca‐montmorillonite and illite systems. Edge‐to‐face attraction is dominant in flocculating Na‐montmorillonite. The large effect of small amounts of exchangeable Na+ in montmorillonite suspensions results from demixing of exchangeable ions whereby Na+ is the predominant cation on the external surfaces when ENa < 0.20.
Heterovalent, Ternary Cation Exchange Equilibria: NH4+‐Ba2+‐La3+ Exchange on Montmorillonite
Authors: Elprince A. M. , Vanselow A. P. , Sposito Garrison 
Published: July 2010

AbstractData were obtained at 25°C on the composition of the aqueous solution and exchanger phases in NH4‐Ba‐La, La‐Ba, La‐NH4, and Ba‐NH4 aqueous systems comprising the chloride salts of the three cations and a montmorillonite clay from Nevada. The data for the three binary cation exchange systems were incorporated into a thermodynamic model which was used to predict the composition of the aqueous solution phase of the ternary NH4‐Ba‐La system as a function of exchanger phase composition. The model employed, known as the subregular model, involved a MacLaurin expansion of the exchanger phase rational activity coefficients to third order in the mole fractions of the exchanger components. The constant coefficients in the MacLaurin expansion could be determined solely with experimental data on the infinite‐dilution, rational activity coefficients of exchanger components in binary exchange systems. Thus no data on ternary exchange systems were required to apply the model. The model calculations were in reasonably good agreement with experiment, suggesting that further efforts to predict ternary exchange behavior from binary exchange data are warranted.
Potential Errors in the First‐order Model for Estimating Soil Nitrogen Mineralization Potentials
Authors: Smith J. L. , Schnabel R. R. , McNeal B. L. , Campbell G. S. 
Published: July 2010

AbstractNitrogen mineralization incubations were conducted using an aerobic leaching procedure. Two agricultural soils and one forest soil were incubated under aerobic conditions, including periodic leaching of mineral N using either 100 ml of 0.01M CaCl2, 30 ml of 0.01M CaCl2, or 30 ml of 0.05M CaCl2. Mineral and organic N were determined for each leachate. Significant amounts of organic N were leached with the mineral N. Leaching with 30 ml of 0.05M CaCl2 removed significantly less mineral N, but the 100 ml 0.01M of CaCl2 and 30 ml of 0.01M CaCl2 treatments were not significantly different. Although not statistically significant, 30 ml of 0.01M CaCl2 consistently leached less organic N than did the other two treatments. Amounts of organic N leached ranged from 13 to 163% of total mineralized N.The mineralization reactions were assumed to follow first‐order kinetics. A comparison was made between root mean square (RMS) deviations of experimental data from a nonlinear least squares (NLLS) equation and the more traditional least squares fit of a straight line to log‐transformed data. The NLLS equation gave a more precise fit to the data and hence more accurate estimates of both the N mineralization potential (N0) and the mineralization rate constant (k) for each soil.
Critical Soil Manganese Deficiency Levels for Four Extractants for Soybeans Grown in Sandy Soil
Authors: Shuman L. M. , Boswell F. C. , Ohki K. , Parker M. B. , Wilson D. O. 
Published: July 2010

AbstractSoil extractants for Mn are often assigned critical deficiency levels based on indirect experimental evidence. This research was undertaken to calibrate four soil Mn extractants for critical deficiency levels using soybeans [Glycine max (L.) Merr. cv. ‘Ransom’]. Two adjacent field experiments were conducted on Olustee‐Leefield sand (Ultic Haplaquod‐Arenic Plinthaquic Paleudult) with soil pH, microelement, and Mn rate variables. Leaf samples taken at the R‐2 growth stage were analyzed for Mn and soil samples were analyzed for pH and extractable Mn by four separate procedures. Critical deficiency levels were determined using the Cate‐Nelson procedure as well as by comparing tissue Mn critical levels with soil Mn levels using a regression method. The latter method was unsatisfactory for determining critical levels except for two extractants for 1 year. Critical deficiency levels based on the Cate‐Nelson method averaged over the 3‐year experiment period were Double Acid—2.6 ppm, DTPA — 0.22 ppm, Mehlich (NH4Cl‐NH4F) — 1.8 ppm, and AB‐DTPA (NH4HCO3‐DTPA) — 0.4 ppm. Leaf Mn vs. extractable soil Mn correlation coefficients were best for the two DTPA‐based extractants, but all four coefficients were similar when soil pH was included in multiple regression equations.
Calcium Carbonate in a Calcareous Soil from the Jordan Valley, Israel: Its Origin as Revealed by the Stable Carbon Isotope Method
Authors: Magaritz Mordeckai , Amiel Abraham J. 
Published: July 2010

AbstractThe development of calcareous soil in semiarid zones is accomplished by dissolution and reprecipitation of calcium carbonate (CaCO3) minerals. The proportion of carbonate in the soil of the Jordan Valley that is pedogenic in origin was determined using the stable C isotope method. Forty to sixty percent of the carbonate remaining in soil horizons A and B undergo dissolution and reprecipitation processes. These changes were detected by the decrease in the 13C/12C ratio from the parent material average (−2.5‰) to the B horizon value (−7.4‰). A scale is proposed to determine the percentages of pedogenic carbonate in soil.
Iron Coatings on Rice Roots: Morphology and Models of Development
Authors: Chen C. C. , Dixon J. B. , Turner F. T. 
Published: July 2010

AbstractScanning electron microscopy and X‐ray microanalysis were employed to characterize the morphological properties of iron coatings on rice roots at different growth stages. This information is needed for further understanding of the influence of Fe coatings on rice plant development. Rice root coatings are visible about 1 week after flooding as a brownish discoloration which thickens with age of the root. No coating was found on younger parts of major roots near their tips or on young secondary roots which are critical regions of nutrient uptake. Roots of ‘Brazos’ cultivar rice (Oryza sativa L.) plants grown in Beaumont clay soil had a relatively thin coating of FeOOH mixed with soil particles before panicle differentiation. As a rice plant approached maturity and the outermost cell wall of the root decomposed, a mixture of FeOOH and soil particles began to fill the rectangular spaces that had once been occupied by epidermal cells. Casts in open cell cavities are porous and rough on the exterior side of the root. There were many shapes of casts and they generally matched the varied shapes of the outer layer of epidermal cells of rice roots. Roots of Brazos cultivar rice grown to maturity in Katy fine sandy loam soil have completely developed polyhedral casts. Precipitation of relatively pure FeOOH on cell walls formed hollow casts with the shapes of the original cells. The models presented describe hypothetical steps in the formation of the two types of casts observed by the oxidation of Fe2+ by O2 and precipitating of iron on the walls of closed and open cell cavities.
Gas Chromatographic System for Precise, Rapid Analysis of Nitrous Oxide
Authors: Mosier A. R. , Mack L. 
Published: July 2010

AbstractA gas chromatographic (GC) system for the sensitive, rapid, and precise analysis of nitrous oxide (N2O) was developed. The system employs a two‐part GC column that can be separated and the first section back‐flushed to remove contaminants while sample analysis continues. Nitrous oxide was detected by an electron capture detector. The GC system was suitable for analyzing small volumes of gas samples for ambient levels of N2O at the rate of 10 samples per hour with a precision of about 1 ppb.
Soil Consistence: Effect of Particle Size
Authors: Ibanga Iniobong J. , Bidwell Orville W. , Powers William L. , Feyerherm Arlin M. , Williams Wayne W. 
Published: July 2010

AbstractBriquets composed of sand (0.05–2.00 mm) silt (0.002–0.05 mm), and clay (<0.002 mm) mixtures were hardest when dominantly clay and/or sand and softest or least hard when dominantly silt. Where soils had equal amounts of clay, those with highest amounts of sand, with one exception, were the hardest. Low surface area of sand requires much less clay “mortar” to cement the fewer sand grains per given volume than do the more numerous, smaller silt particles.
Absorption of Water by Soil: Some Effects of a Saturated Zone
Authors: Smiles D. E. , Perroux K. M. , Zegelin S. J. 
Published: July 2010

AbstractAbsorption by soil of water supplied at constant pressure and at constant rate is described. Particular attention is paid to the process when the surface water potential is greater than that at which the soil saturates.Analyses, which directly integrate Darcy's law for both saturated and unsaturated regions using the flux‐potential relation (related to the flux‐concentration relation of Philip through the appropriate moisture characteristic), predict behavior in accord with experimental data. Analyses which treat the unsaturated region as a problem of diffusion‐of‐θ are “correct” only if the soil water diffusivity, measured using the method of R. Bruce and A. Klute, is interpreted with care.To avoid erroneous prediction it is imperative that the measurement of diffusivity be preceded by an independent measurement of the moisture characteristic. This latter relation is a necessary specification of the soil water system. It should always be presented in a test of flow theory, and it identifies the suction at which the soil saturates and hence the suction at which Bruce and Klute type experiments should be performed.
Changes in the Humic Acid Fraction of Soil Resulting from Sludge Application
Authors: Boyd Stephen A. , Sommers Lee E. , Nelson Darrell W. 
Published: July 2010

AbstractHumic acids (HA) extracted from sludge, soil, and sludge‐amended soil were characterized by elemental and functional group analyses and visible and infrared spectroscopy. Humic acid extracted from a Chalmers soil appeared to be similar to an average HA (Schnitzer, 1978). Humic acid extracted from Chicago sludge, as compared to the average HA and Chalmers HA, had a lower C/H ratio, increased N content, decreased total acidity and carboxyl content, and a lower absorptivity. With respect to the average HA and Chalmers HA, the sludge HA appeared to be a more aliphatic, N‐enriched polymer with decreased amounts of carboxyls and phenolic hydroxyls. Proteinaceous materials associated with the sludge HA appeared to be the major source of N enrichment. In general, HA's extracted from the sludge‐amended soil had increased N contents, lower C/H ratios, lower values of total acidity and phenolic hydroxyl, somewhat lower values of CO2H groups, and lower absorptivities as compared to HA from soil not receiving sludge amendment. Sludge organic matter was apparently recovered in HA extracted from soil 2 and 14 months after sludge application. The association of sludge‐borne proteinaceous and aliphatic materials with the sludge and sludge‐amended soil HA fractions was indicated by increased amide and C‐H stretch infrared absorptions as well as by the increased N contents and decreased C/H ratios. The observation of proteinaceous materials associated with HA extracted from sludge‐amended soil as long as 14 months after application suggested these proteinaceous materials were resistant to decomposition, possibly as a result of their incorporation into the HA structure. Fatty acids may be associated with HA's extracted from sludge and sludge‐amended soil through esterification to phenolic hydroxyls.
Effects of Titration Rate, pH, and Drying Process on Cation Exchange Capacity Reduction and Aggregate Size Distribution of Montmorillonite Hydroxy‐Aluminum Complexes
Authors: Keren R. 
Published: July 2010

AbstractThe effects of rate of titration of montmorillonite + AICI3 with NaOH, and of drying on CEC reduction, C‐axis spacing, and aggregate size distribution of montmorillonite hydroxy‐Al complexes at the pH range of 5–10, were studied. The CEC reduction was found to be influenced by the titration rate. While the CEC of the montmorillonite was 0.92 meq/g, the CEC of the clay hydroxy‐Al complexes was 0.27, 0.31, 0.39, and 0.45 at titration rates of 0.025, 0.1, 0.4, and 0.8 meq NaOH/min, respectively. The mean aggregate size and the C‐axis spacing of the clay hydroxy‐Al complexes decreased as the pH of the suspensions increased. The CEC of the montmorillonite hydroxy‐Al complexes after drying was higher than the nondried systems at a pH above 7.5, whereas no difference was observed at the lower pH range (pH 5–6). The CEC and the C‐axis spacing for both the dried and nondried systems were highly correlated.
Determination of Soil Solution Electrical Conductivity from Bulk Soil Electrical Conductivity Measurements by the Four‐Electrode Method
Authors: Nadler A. , Frenkel H. 
Published: July 2010

AbstractSoil electrical conductivity (ECa) by the four electrode method was studied in the laboratory as a function of soil water electrical conductivity (ECw) and water content in six soil types. A linear relationship between ECa and ECw was valid only at salinities > 4 mmho/cm. At very low salinity levels the contribution of the surface conductance was not constant and had a higher contribution than ECw to measured ECa. A method for calculating the partial contribution of surface conductance to ECa as a function of ECw and clay content is applied including a correction for dependence on the soil water content.
A Comparison of Cross‐Contamination in Distillation Units Used in Total Nitrogen and Nitrogen‐15 Analyses
Authors: Reeder J. D. , O'Deen W. A. , Porter L. K. , Lober R. W. 
Published: July 2010

AbstractA laboratory study was conducted to investigate 15N cross‐contamination errors between distilled standards [1 mg N as (NH4)2SO4] with various 15N excess contents (0, 3, or 10% excess 15N). Several stills differing in rate of distillation and construction were tested. We also compared the effectiveness of the ethanol (ETOH) cleansing technique with the (NH4)2SO4 cleansing technique in reducing cross‐contamination errors. The ETOH wash was less effective than the (NH4)2SO4 wash in reducing cross‐contamination errors for samples with normal abundance 15N but was equally effective in reducing cross‐contamination errors for samples with high‐enrichment 15N. The (NH4)2SO4 wash sometimes significantly diluted high‐enrichment 15N samples.Ammonia seemed to be absorbed and sporadically released from the nonglass components of the partial‐glass still. Replacing the rubber and teflon components with glass and decreasing the glass surface area of the distillation unit decreased cross‐contamination errors and increased the percent recovery of atom % 15N from the distillation unit.
Predicting Slash Pine Response to Nitrogen and Phosphorus Fertilization
Authors: Kushla J. D. , Fisher R. F. 
Published: July 2010

AbstractThe Cooperative Research in Forest Fertilization (CRIFF) soil groups based on soil drainage class and depth to and nature of the B horizon, were as good as or better than Soil Conservation Service soil series or Coile soil units at predicting slash pine (Pinus elliottii var. elliottii Engelm.) response to N and P fertilization. Some CRIFF soil groups demonstrate much greater uniformity of response than others. Within these soil groups, soil properties and foliar analyses were used to better predict fertilizer response. The properties valuable for predicting response varied from soil group to soil group, but those most consistently valuable were measures of available soil water, extractable soil P, the amount of silt plus clay in the surface soil, and foliar N and P. A model with from two to four significant variables was developed for each CRIFF soil group. The coefficients of determination (R2) for these models ranged from 0.52 to 0.99.
Mineralizable Soil Nitrogen as an Index of Nitrogen Availability to Forest Trees
Authors: Powers Robert F. 
Published: July 2010

AbstractSoil N mineralized during 14‐day anaerobic incubation at 30°C is evaluated as an index of forest soil fertility and site productivity. Mineralizable soil N determined under standard conditions correlates significantly with N mineralized anaerobically for 6 months in the field, with site index and yield potential of Pinus ponderosa L. growing on volcanic, metavolcanic, and metasedimentary soils, and with foliar concentrations of N. Soils testing less than 12 ppm of mineralizable N are judged clearly deficient, but stands of pine and fir on soils testing as high as 16 ppm of N still may respond well to fertilization. Absolute variability in mineralizable soil N decreases with soil depth and increases with the magnitude of the soil test mean, but relative variability is constant. Comparing ammonium produced during laboratory incubation with that mineralized over 6 months in the field shows that field soil temperature has a strong bearing on the interpretation of the laboratory test.
A Method for Obtaining Soil‐Free, Soil‐Solution Grown Plant Root Systems
Authors: Cappy J. J. , Brown D. A. 
Published: July 2010

AbstractA method has been developed by which soybean plants are grown deriving all nutrients from the soil solution without direct root‐soil contact. This soil‐packet plant culturing system consists of approximately 125 soil packets arranged in a plexiglas growth box to provide maximum packet surface area for root proliferation. Each soil packet consists of 35 g of soil enclosed in an envelope constructed from semipermeable filtration membrane material. The membrane allows the passage of water and ions between the soil and root but does not allow direct root‐soil contact. Thus, an intact soil‐free root system develops. Soybean plants grown using the soil‐packet system were larger than those grown in an equivalent amount of soil in a pot. Root systems of packet‐grown plants required less time and effort for removal and suffered less damage than did root systems of pot‐grown soybeans.