bluuebunny/crossref_metadata_2025_split huggingface dataset:
Estimating Water Salinity with Geophysical Earth Resistivity Equipment
Authors: Halvorson A. D. , Reule C. A. 
Published: July 2010

AbstractA procedure is described for estimating salinity of water samples in the field using a geophysical earth resistivity meter and four‐electrode conductivity cell. Using field collected water samples, a linear relationship of Y = 1.02(X) + 0.12, r = 0.996, was obtained between EC25 values determined using a commercial laboratory bridge and cell (Y), and those determined using an earth resistivity meter and an easily fabricated, four‐electrode conductivity cell (X).
Hydraulic Properties of a Porous Medium: Measurement and Empirical Representation
Authors: Gillham R. W. , Klute A. , Heermann D. F. 
Published: July 2010

AbstractThe hysteretic water content‐pressure head relationship and the hydraulic conductivity‐water content relationship for a porous material are needed in the solution of the water flow equation to predict behavior of a given flow system. These hydraulic properties were measured in an unsteady‐state manner using gamma ray attenuation for the water content and strain gauge pressure transducer tensiometery for the pressure head. Envelope curves and four to six primary wetting and drying scanning curves of the water content‐pressure relationship were determined. A convenient method of representation of the scanning curves by an empirical function was developed for use in computer solutions of the water flow equation.
Determining the Hydraulic Conductivity of Soil Cores by Centrifugation
Authors: Alemi M. H. , Nielsen D. R. , Biggar J. W. 
Published: July 2010

AbstractTwo centrifugal techniques are proposed for determining the hydraulic conductivity of cores of natural soil. Experimental results are presented for one technique in which the change in weight of one end of the sample, previously centrifuged, is measured with a balance. The mathematical equations describing this redistribution process were developed and fitted to the data to ascertain the soil water diffusivity D. The value of the hydraulic conductivity K was obtained from K = bD, where b is also calculated. Calculated values of K agreed with previously published values. The second technique for which a theory is presented but no experimental values are provided depends upon the measurement of the volumetric outflow of water from a soil core when the speed of centrifugation is suddenly increased.
Free Energy of Formation of Carbonate Apatites in Some Phosphate Rocks
Authors: Chien S. H. , Black C. A. 
Published: July 2010

AbstractA constant ion‐activity product or solubility‐product constant for carbonate apatite (KCA) was found within a certain pH range in dilute HCl solutions equilibrated with each of a group of phosphate rocks that had been treated with an alkaline ammonium citrate solution to remove alkaline‐earth carbonates. The KCA values generally increased with an increase in the number of moles of carbonate/mole of apatite. As predicted theoretically, the free energies of formation calculated for the carbonate apatites (ΔG°f,CA) in various phosphate rocks increased linearly with an increase in the number of moles of carbonate/mole of apatite. The apatites in phosphate rocks extensively pre‐extracted with HCl had lower KCA values and lower ΔG°f,CA values than the apatites in phosphate rocks pre‐extracted with alkaline ammonium citrate solution. Empirical equations developed to relate the ΔG°f,CA values to the number of moles of carbonate/mole of apatite make possible the estimation of KCA for other phosphate rocks for which the empirical molecular formula of the apatite is known.
Denitrification Kinetics in Soil Systems: The Significance of Good Fits of Data to Mathematical Forms
Authors: Kohl D. H. , Vithayathil Francis , Whitlow Peggy , Shearer Georgia , Chien S. H. 
Published: July 2010

AbstractThe loss of NO3‐ added to two central Illinois soils was determined in experiments in which the soils were incubated under waterlogged conditions. The loss was measured as a function of substrate concentration in one experiment in which samples were incubated for a single time (24 hours) and as a function of time in a second experiment in which the concentration of the added NO3‐ was held constant (200 ppm NO3‐‐N). The rate of loss of NO3‐ was about 5.5 times higher in one of the soils than in the other. This difference was largely overcome by the addition of glucose (1% with respect to the soil) which also greatly enhanced the rate of denitrification in both soils.The experimental points representing the rate of NO3‐ loss plotted as a function of the concentration of added NO3‐, were equally well fit by Michaelis‐Menten and exponential equations as well as by the solution to a pair of nonlinear differential equations representing a system in which the product of one reaction (e.g., the reductant generated by the oxidation of carbon compounds) is a substrate in a second sequence (e.g., the denitrification of NO3‐). The significance of such fits is discussed. The authors point out that while such fits have certain uses, it is not possible to infer from them the mechanism of the reaction.
Denitrification Measured Directly from Nitrogen and Nitrous Oxide Gas Fluxes
Authors: Rolston D. E. , Fried M. , Goldhamer D. A. 
Published: July 2010

AbstractThe amount of denitrification is generally the unknown in attempts to evaluate the fate of N fertilizers applied to soils. Substantial error can result when denitrification is determined from the difference between measurements of plant uptake, residual soil N, leaching, and the amount of N applied. An independent, direct measure of denitrification potentially has merit by containing only the error from direct measurement and not a cumulative error from several measurements. Nitrate at a rate of 300 kg of N/ha and enriched with 20 and 10 atom percent excess 15N was applied to laboratory columns and a field plot, respectively. The columns were maintained at soil‐water pressure heads of −22 and −70 cm. The field plot was maintained at a soil‐water pressure head of approximately −10 cm in the upper 10 cm of soil. The field plot was cropped with perennial ryegrass (Lolium perenne). The columns and field plot were instrumented with tensiometers, soil solution samplers, and gas samplers. The concentration and isotopic ratio of NO3, N2, and N2O were measured as a function of soil depth and time. The gaseous concentration gradients and measured apparent diffusion coefficients were used to calculate the fluxes of 15N2 and 15N2O gas from the soil. Residual soil N, plant uptake, and leaching were measured in order to calculate denitrification by difference. For the laboratory columns, the amount of denitrification determined directly compared favorably with that determined by difference. For the field plot, the disparity between denitrification calculated directly and by difference was attributable to the uncertainty in the gaseous concentration gradient near the soil surface and the spatial variability of the apparent diffusion coefficient near water saturation.
An Evaluation of Job's Method of Continuous Variations as Applied to Soil Organic Matter‐Metal Ion Interactions
Authors: MacCarthy Patrick , Mark Harry B. 
Published: July 2010

AbstractThe literature dealing with the application of Job's method of continuous variations to the study of soil organic matter‐metal ion interactions has been reviewed, and an introduction to the fundamental chemistry necessary for an understanding of these interactions is presented. The method of continuous variations was applied to simple systems consisting of metal ions and mixtures of discrete ligands. The behavior of these “model” systems was compared to that of the more complicated soil organic matter systems. Following a consideration of the fundamental principles of Job's method and of its boundary conditions and limitations, it was concluded that this method is not directly applicable to the study of soil organic matter‐metal ion interactions. This conclusion was substantiated by experiments carried out on the simple “model” systems as well as those on fulvic acid itself. Explanations are proposed to account for the deceptive results which were obtained when this method was erroneously applied by other workers to the investigation of soil organic matter‐metal ion interactions in the past. Possible interferences, due to scattering of light, during the study of soil organic matter‐metal ion reactions by UV‐visible absorption spectroscopy are considered.
Water Content and Bulk Density During Wetting of a Bentonite‐Silt Column
Authors: Nofziger D. L. , Swartzendruber D. 
Published: July 2010

AbstractAn improved method of dual‐energy gamma‐ray attenuation was used to measure water content and bulk density rapidly and accurately, during one‐dimensional, unsaturated water movement into a column of an equal‐part mixture of initially air‐dry, highly swelling bentonite and silt. The bulk density near the inlet end of the column decreased rapidly as water entered. Since the ends of the column were confined, the expansion of the wetted bentonite‐silt produced a compensating compression in the remaining air‐dry portion of the column. Several water‐content variables were plotted against the so‐called reduced material coordinate m/t1/2 (Boltzmann variable expressed in terms of the material coordinate m and time t). Neither the volumetric water content nor the volumetric water ratio would coalesce the data when plotted against m/t1/2. In contrast, a plot of water saturation vs. m/t1/2 did coalesce the data into a single curve, except for very early times at positions nearer than 1 cm to the water inlet.
Zinc Adsorption Isotherms for Soil Clays with and Without Iron Oxides Removed
Authors: Shuman L. M. 
Published: July 2010

AbstractThe clay fraction from four predominant Georgia soils sampled at two depths was separated and the iron oxides removed from a portion of each clay sample. These clays were equilibrated with five Zn solutions to measure Zn adsorption. The data conformed to the Langmuir adsorption isotherm. Langmuir coefficients were used to evaluate the Zn adsorptive capacities of the clays and the bonding energies for Zn. Adsorptive capacities and CEC values for the clays from Decatur cl and Leefield ls soils were higher than those for clays from the Cecil sl and Norfolk ls soils. Differences in adsorptive capacities were not consistent between depths nor between samples with or without Fe oxides. However, removal of the Fe oxides increased the capacity to adsorb Zn in more instances than it decreased this capacity. Zinc adsorptive capacities were directly related to the CEC values for the clays. When comparing those samples with and without Fe oxides removed, bonding energies were inversely related to adsorptive capacities.
Decomposition of Specifically Carbon‐14‐labeled Ferulic Acid: Free and Linked into Model Humic Acid‐type Polymers
Authors: Martin J. P. , Haider K. 
Published: July 2010

AbstractSide chain 1‐14C, 2‐14C, and 3‐14C, O14CH3 and ring 14C‐labeled ferulic acids were synthesized and incubated with Greenfield sandy loam top soil at rates of 100 and 1,000 ppm. The loss of the specifically labeled carbons as 14CO2 over a 12‐week period ranged from 44 to 78% and averaged 64 and 68% for the 100 and 1,000 ppm additions, respectively. The smallest loss occurred from the 2‐14C (side chain) and the greatest from the 3‐14C (side chain) and the O14CH3 carbons. Losses of 14CO2 from specifically 1 and 2‐14C‐labeled acetic, and 1‐, 2‐, and 3‐14C pyruvic acids and from 14COOH‐labeled vanillic and protocatechuic acids, all of which are common metabolic products noted during the microbial decomposition of ferulic acid, averaged about 84%. After linkage into model humic acid type polymers from hydroxyphenols and toluenes by phenolase oxidative polymerization, losses of 14C ranged from 7 to 25%. Greatest losses were from the 3‐carbon of the side chain and least from the ring carbons. Losses for ring and side chain carbons after linkage into polymers from hydroxybenzoic acids varied from 3 to 7%. Losses of about 21% occurred from the O14CH3 groups. When labeled ferulic or vanillic acids were added to cultures of Stachybotrys chartarum or Hendersonula toruloidea, from 11 to 52% of the ring 14C was incorporated into the humic acid‐type phenolic polymers formed in the nutrient solutions. Only 3 to 4% of the ring carbons of veratric acid were incorporated into the “humic acid” fraction of these fungi.
Soil Shear Strength Variation in Soils of a Batavia Silt Loam Mapping Unit
Authors: Veneman P. L. M. , Bouma J. , Edil T. B. 
Published: July 2010

AbstractSoil shear strength values obtained in situ in soils in a mapping unit of the Batavia silt loam (Mollic Hapludalf, fine silty, mixed, mesic) with the vane shear test for a wide range of natural moisture contents were compared with values obtained with the widely used unconfined compression test in the laboratory. The comparison was made to evaluate the tests for soil survey characterization, to express soil variability within an important mapping unit and to define functional relationships between shear strength and different soil properties.The vane shear test was preferred because: (i) tests required less time and involved less cost, (ii) tests could be made in relatively dry, pedal soil where the laboratory method did not work, and (iii) test results of both methods were not significantly different. Graphical representation of shear strength (X) as a function of the moisture content (θw = percent by weight) allowed an estimate of the minimum shear strength of the studied soils at any natural moisture content. A more accurate estimate of shear strength could be made by considering also the liquid limit (LL) and plasticity index (PI) of the soil material in a multiple regression equation as follows: X = −3.84 −0.18θw + 0.47LL −0.4PI. Clay content and bulk density were insignificantly correlated. This type of analysis may provide quantitative data for soil survey interpretations.
Measuring Hydrologic Properties of Soil with a Double‐ring Infiltrometer and Multiple‐depth Tensiometers
Authors: Ahuja L. R. , El‐Swaify S. A. , Rahman A. 
Published: July 2010

AbstractA ring infiltrometer with varying width of buffer zone in combination with multiple‐depth tensiometers was tested for determining the hydrologic properties of a Typic Dystrandept (Tantalus silty clay loam) soil profile on a Hawaii forested watershed. With location of one multiple‐depth tensiometer at the vertical axis of the axi‐symmetric flow system and one or more at a given radius outside the inner ring, both vertical and radial hydraulic gradients could be simultaneously measured. It was thus possible to estimate the lateral flow components and determine vertical infiltration rates and hydraulic conductivities (at field saturation) of the different soil horizons. Lateral flow decreased with time during infiltration. Under the moist to wet conditions of the soil under study, lateral flow was not appreciable. From an inner ring of 30‐cm diameter, the latter was practically eliminated when a buffer ring of 90‐cm diameter was employed. Its effect on the final infiltration rate was negligible even when a buffer ring of 60‐cm diameter was used.
Viscosity of Interlayer Water in Montmorillonite
Authors: Low Philip F. 
Published: July 2010

AbstractThe viscosities of water in Na‐montmorillonite systems at various water contents were calculated by different equations using data from experiments conducted by different investigators on: (i) viscous flow of water at different temperatures, (ii) self‐diffusion of water, and (iii) neutron scattering by water. The results were remarkably consistent and showed that the viscosity of the interlayer water is greater than that of bulk water and increases exponentially with decreasing water content. Evidence was also presented to show that the viscosity of this water depends on the b‐dimension of the associated montmorillonite. By combining the data on viscosity with data on hydraulic conductivity, it was possible to determine the permeability of the montmorillonite at different water contents.
Ammonium Diffusion as a Factor in Nitrogen Loss from Flooded Soils
Authors: Reddy K. R. , Patrick W. H. , Phillips R. E. 
Published: July 2010

AbstractThe role of NH4+‐N diffusion in a flooded soil on nitrogen (N) loss through the nitrification‐denitrification process was investigated under laboratory conditions. The distribution of applied NH4+‐N in both the aerobic and anaerobic soil layers of a flooded soil was experimentally determined and compared with the values obtained from theoretical equations. The total loss of NH4+‐N from the flooded soil system (15‐cm depth) by nitrification‐denitrification was equivalent to 12.43 g N/m2 for a 120‐day incubation period when the initial concentration of NH4+‐N was 44.84 g N/m2. Diffusion of NH4+‐N from the anaerobic soil layer to the aerobic soil layer accounted for more than 50% (7.16 g N/m2) of the total NH4+‐N loss with the remainder being lost from NH4+‐N originally present in the aerobic layer. The NH4+‐N that diffused upward into the aerobic soil layer was nitrified to NO3‐‐N, which readily diffused back down into the anaerobic soil layer and was subsequently denitrified. The experimental distributions of NH4+‐N were not in close agreement with calculated distributions in the surface aerobic soil layer, but were in close agreement in the anaerobic soil layer. It is possible that the rate constant (k) for NH4+‐N oxidation varied considerably with depth in the aerobic soil layer and thus resulted in the disagreement. The total NH4+‐N loss calculated from the experimental distributions tended to agree with the values obtained theoretically from rate constant (k) values of 3.18, 5.00, and 6.67 µg cm‐3 day‐1. The first rate constant value was obtained from an independent experiment (for same soil), the second from matching the concentration of NH4+‐N at the aerobic‐anaerobic layer interface of the theoretical and experimental distribution at 90 days after flooding, and the third from the NH4+‐N disappearance in the aerobic soil layer of the soil columns described in this study. These rate constants indicate that the rate of nitrification is one of the factors controlling N loss from flooded soil.
Effect of Pretreatment on Loss of Nitrogen‐15‐labelled Fertilizer Nitrogen from Waterlogged Soil During Incubation
Authors: McKenzie E. , Kurtz L. T. 
Published: July 2010

AbstractSoil preparation treatments (field‐moist, intact cores; oven‐dried, intact cores; and oven‐dried, crushed, screened soil) greatly influenced fertilizer nitrogen loss under waterlogged conditions in the laboratory. Nitrogen (300 pp2m) as 15N‐labelled calcium nitrate was added to samples from selected horizons of Drummer silty clay loam (Typic Haplaquol) and they were subsequently covered with water and incubated for 0, 4, 8, 16, and 32 days. Samples of upper (above 51 cm) soil horizons were incubated at 21°C while those from deeper horizons were incubated at 18°C.Oven‐drying and crushing of the soil during preparation increased fertilizer nitrogen loss. Only 34% of the fertilizer nitrogen disappeared from field‐moist, intact soil cores while approximately 90% disappeared from both oven‐dried, intact cores and crushed screened samples.Maximum rate of dentrification of fertilizer nitrogen in field‐moist, intact cores was 3.58% of the applied nitrogen per day. This rate was approximately one‐third of that in the oven‐dried, intact cores and one‐ninth of that in the oven‐dried, crushed samples.Apparently oven‐drying and crushing soil samples increased the accessibility of the energy source for the denitrification process. However, crushing apparently did not increased the quantity of energy since total nitrogen losses after 32 days were similar for both oven‐dried, intact‐ and oven‐dried, crushed samples.
Evaluation of the Parameters of Soil Phosphorus Availability Factors in Predicting Yield Response and Phosphorus Uptake
Authors: Dalal R. C. , Hallsworth E. G. 
Published: July 2010

AbstractThe importance of quantity, intensity, capacity, and rate factors of soil P availability to account quantitatively for the variation in P uptake and wheat grain yield in pot and field experiments was studied. Among the parameters of the quanitity factor (L, E, Ec, E1.0, Q0 value, NH4F‐P, NaOH‐P, H2SO4‐P, organic P, Olsen P, Colwell P, carbonate P, and anion‐exchange resin, AER‐P), L value was found to be highly correlated with P uptake at 35 and 150 days after planting (maturity) when all the soils were considered. However, the carbonate P (soil P extracted for 16 hours with 0.25M NaOH‐0.1M Na2CO3 at a soil/solution ratio of 1:100) was found to be the best parameter of the quantity factor when the soils containing high amounts of hematite/goethite (> 20%) were excluded. The parameters of the intensity factor (0.01M CaCl2 soluble P, aH2PO4i and phosphate potential) were significantly correlated with P uptake at early growth (35 days) whereas the parameter of the capacity factor (maximum buffering capacity, Mb) was bezter correlated with P uptake at the later stage (150 days). The rate factor, as measured by AER was better correlated with P uptake at 35 days than with P uptake at 150 days after planting. The quantity factor as measured by the carbonate P accounted for 75 and 93% of the variation in P uptake and grain yield, respectively. The capacity factor, Mb when combined with the quantity factor accounted for more of the variation in P uptake (150 days) from 75 to 86%. The intensity and the rate factors had a smaller effect.
Distribution of Water and Ions in Soils Irrigated and Fertilized from a Trickle Source
Authors: Bar‐Yosef B. , Sheikholslami M. R. 
Published: July 2010

AbstractSimultaneous distributions of water, NO3‐N and P in clay and sandy soils irrigated daily from a trickle source were studied in the laboratory. Hydraulic conductivity data, water retention curves and adsorption isotherms to the soils were determined to enable verification of mathematical models against the experimental results obtained under various conditions. It was found that when adding identical amounts of water, but increasing the trickle discharge rate in the sandy soil from 250 to 2,500 ml/hour, the vertical movement of the wetting front increased and the horizontal movement decreased. In a sequence of three cycles of irrigation with a nutrient solution, losses of nitrate were observed in the clay soil, probably due to denitrification processes. The restricted mobility of the phosphate ions, even in the sandy soil, implies that a preirrigation mixing of P in the soil, supplemented by its addition to the irrigation solution, is necessary to obtain a uniform P concentration in the soil volume.
Use of the Green‐Ampt Equation with Variable Conductivity
Authors: Ahuja L. R. , Tsuji G. Y. 
Published: July 2010

AbstractA comparison with Phillp's two‐term equation, derived from a series solution involving t1/2, indicates that the hydraulic conductivity in the Green‐Ampt equation of vertical infiltration varies with time when the soil water content of the transmission zone is assumed to be constant. Use of the Green‐Ampt equation with a continuously variable conductivity or a piecewise application of the equation as an extension of Philip's two‐term equation resulted in improved prediction of infiltration in two Hawaii soils. Both these forms of application require three parameters, hydraulic conductivity, sorptivity, and constant A, which have well‐established physical meaning.