bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analytical Solution for Punctual Kriging in one Dimension
Authors: Hemyari Parichehr , Nofziger D. L. 
Published: July 2010

AbstractThe solution to the system of equations required for punctual kriging in one dimension was determined analytically for a linear semivariogram. The solution indicates that kriging in this situation is identical to linear interpolation between the two closest neighbors. The kriged values are independent of the coefficients in the linear semivariogram model. The estimation variance is linearly dependent upon the coefficients in the model. Although no analytical solution was obtained for the spherical and exponential semivariance models, kriged values for these models were found to be essentially the linearly interpolated values. These results provide insight into the behavior of the kriging estimator. They can be used to save substantial numerical computation and to guide the user in selecting the neighborhood of points used in one‐dimensional kriging.
Thermodynamics of Fluridone Adsorption and Desorption on Three California Soils
Authors: McCloskey William B. , Bayer David E. 
Published: July 2010

AbstractThe thermodynamic parameters associated with fluridone {1‐methyl‐3‐phenyl‐5‐[3‐(trifluoromethyl)phenyl]‐4(1H)‐pyridinone} adsorption and desorption on three California soils were calculated from the temperature dependence of the adsorption reaction. The standard free energy change for the adsorption reaction on all three soils was negative, signifying a spontaneous reaction. The isosteric heat of adsorption and the partial molar enthalpy change indicated that van der Waals or physical forces were involved in fluridone adsorption. The enthalpy changes also showed that fluridone adsorption became weaker as the amount adsorbed increased on Yolo sandy clay loam (Typic Xerorthents) and Hesperia fine sandy loam (Typic Xerorthents) while the reverse was true on Stockton clay (not classified). Fluridone adsorption was correlated with clay content and increased as the time of exposure to the soils increased (i.e., the desorption isotherms exhibited hysteresis). The isosteric heats of adsorption calculated from the desorption isotherms were similar to those calculated from the adsorption isotherms indicating that there was no change in adsorption mechanisms between adsorption and desorption equilibrations. Thus, the thermodynamic parameters provided evidence that fluridone adsorption on the three soils was reversible and that the hysteresis between adsorption and desorption isotherms was not due to an irreversible adsorption reaction (chemical or coulombic adsorption). The increased retention of fluridone with time was attributed to the diffusion of fluridone molecules to relatively less accessible binding sites on clay particles as the time of fluridone exposure to the soils increased.
Quantification and Compositional Characterization of Pedogenic Calcite and Dolomite in Calcic Horizons of Selected Aquolls
Authors: Sobecki T. M. , Karathanasis A. D. 
Published: July 2010

AbstractA combination of thermogravimetric analysis (TGA), x‐ray diffraction (XRD), and selective dissolution analysis (SD) was used to quantify and calculate structural formulae of carbonate mineral phases in silt fractions of calcic horizons in selected Texas Coastal Prairie Aquolls. The Algoa pedon (Aeric Calciaquolls) had about 11% poorly crystalline high‐Mg calcite [(Ca.87Mg.13)CO3], 12 to 20% dolomite, and approximately 25% low‐Mg calcite [(Ca0.95Mg0.05)CO3]. The dolomite was a Ca‐rich variety that was previously interpreted to be pedogenic. The Addicks pedon (Aquic Haplustolls) lacked dolomite. The upper calcic horizon was dominated by low‐Mg calcite [(Ca0.99Mg0.01)CO3] with about 7% poorly crystalline high‐Mg calcite [(Ca0.90Mg0.10)CO3]. The presence of dolomite and high‐Mg calcite in the Algoa pedon are related to elevated soluble Mg/Ca ratios. Thermodynamic relationships based on soil solution Mg/Ca activity ratios support these findings. It is suggested that poorly crystalline Ca‐Mg carbonates, including high‐Mg calcites, may be more abundant in calcic horizons than commonly believed. Their poor crystallinity makes them difficult to detect by standard XRD methods. However, TGA coupled with quantitative XRD and SD can be useful in detecting their presence and estimating their chemical composition.
A Pedogenic Chronology for Kilbourne Hole, Southern New Mexico: I. Soils in the Tuff
Authors: Gile Leland H. 
Published: July 2010

AbstractKilbourne Hole, in southern New Mexico, was formed by steam explosions and is a maar volcano surrounded by tuff, most of which is prominently stratified. Although a few carbonate nodules are in unstratified materials of soils at stablest sites, a banded carbonate horizon is the most prominent and extensive pedogenic feature and has formed in stratified tuff. The carbonate bands are commonly about 1 to 2 mm thick, have formed along some of the primary strata of the tuff, and are separated from each other by tuff with little or no macroscopic carbonate. Development of the carbonate bands is attributed to the character of the parent materials, which are stratified, cohesive sands deposited by base surge and differing considerably in size and consistence. These factors have caused pedogenic carbonate to accumulate in banded form instead of the nodules and cylindroids that are more common in other materials which have little or no gravel. The bands consist of both laminar and nonlaminar types. The stratified tuff constitutes a special case in which the laminar horizon would form much faster than in the conventional sediments of basin floors, alluvial fans, and fan piedmonts that dominate many arid regions. Most of the studied soils are sandy Entisols that have been classified as Typic Torriorthents, sandy, mixed, thermic. They have been classified as Orthents instead of Psamments because hazards are minimal for blowing and for the support of wheeled vehicles. An exclusion for soils of stratified, cohesive sands of base surge origin is needed in the definition of Psamments. Minor areas of Typic Haplargids, coarse‐loamy, mixed, thermic, are also present.
Extraction Time Requirements for Determination of Exchangeable Bases with a Mechanical Vacuum Extractor
Authors: Hammer R. David , Lewis Russell J. 
Published: July 2010

AbstractDetermination of extractable bases with neutral 1 M NH4OAc is a commonly performed soil analysis. Introduction of a mechanically controlled vacuum extractor permits control of extraction time across the range of soil textures. Comparisons of organic soil materials, montmorillonitic and low cation exchange capacity (CEC) soils revealed that complete base extraction is possible with reduced extraction times. Fourteen‐hour extraction is required for base removal from organic soils, but 8‐ and 4‐h extractions removed bases from montmorillonitic and low CEC soils, respectively. Decreased extraction times permit increased capacity for laboratory soil analyses, increase the effective life of the vacuum extractor, and decrease analysis time.
Experimental and Numerical Analyses of Perched Groundwater Mounds Below Septic Systems
Authors: Wilson G. V. , Scott H. D. , Wills L. D. 
Published: July 2010

AbstractFor purification, effluent must move through unsaturated soil for an adequate time and distance before contacting the saturated zone. Formation of perched groundwater mounds may limit the purification processes. The dynamics of groundwater mounds associated with septic systems must be understood in order to reduce the potential for contamination from septic systems. Previous models for perched mounds have not been verified with in situ measurements. A septic tank filter field system consisting of a triple line source was installed in a Captina silt loam (Typic Fragiudult). The soil has a fragipan at the −0.7 m depth with a wavy, irregular boundary. Tensiometers were used to monitor the temporal and spatial distributions of soilwater potential. The results revealed that steady‐state soil water conditions existed during spring and fall. Soil water pressure potentials at unmeasured locations were kriged from in situ data with quadratic drift removed using universal kriging. The kriged pressure potentials were contoured resulting in equipotential lines, with the zero equipotential line representing the water table. The Laplace equation in two dimensions, including a source term, appropriate for these flow conditions, was solved using a Galerkin finite element technique. Contours of equal pressure potential predicted by the model for various flow conditions were obtained. The two‐dimensional simulation model was verified with the in situ data by overlaying the contour graphs of the kriged values with the model's predicted values. The effect of highly variable saturated hydraulic conductivity on the model's prediction was also investigated. The finite element model adequately predicted the depth of the water table as well as the range in equipotential lines and their locations when based on the mean saturated hydraulic conductivity. Therefore, the finite element model can be considered acceptable for modeling a perched water table below septic systems under steady‐state conditions.
Determination of FeEDDHA in Soils and Fertilizers by Anion Exchange Chromatography
Authors: Barak Phillip , Chen Yona 
Published: July 2010

AbstractThe specific conditions for the quantitative analysis of FeEDDHA (ethylenedimine di‐o‐hydroxyphenylacetic acid) by high pressure liquid chromatography (HPLC) were studied and defined. Using a 3‐cm anion exchange column and 5 mM H2SO4 + 0.01 mM Fe2(SO4)3 as an eluent, FeEDDHA was separated into the dl‐racemic and meso isomers. With the same column and 3 mM H2SO4 + 50 mM Na2SO4 + 0.01 mM Fe2(SO4)3, FeEDDHA eluted as a single peak. Standard calibration curves for FeEDDHA were obtained with regression coefficients of 0.9999 at concentrations up to 0.25 mM. The coefficient of variation is 1.5%, or 1.8 µmol L−1 using a 50‐µL sample; the detection limit was 1.2 µmol L−1. FeEDDHA was separated easily on anion exchange HPLC columns from other chelates such as CDTA, EDTA, and DTPA. The proposed method was used to determine FeEDDHA concentrations in water extracts of soils that were incubated with the compound. With variation of the eluent, separation of ferrated and unferrated EDDHA is possible.
Calcite Supersaturation in Soils as a Result of Organic Matter Mineralization
Authors: Amrhein C. , Suarez D. L. 
Published: July 2010

AbstractSolutions equilibrated with soils under laboratory conditions often exhibit Ca2+ and CO2‐3 activities that exceed calcite saturation. This supersaturation has been attributed to various possibilities, none of which have been fully able to explain the phenomenon. In this study we report on the attainment of calcite supersaturation in calcite + water + organic matter systems under controlled CO2 conditions. The decomposition of alfalfa shoots (Medicago sativa L.) and soybean roots (Glycine max L. merr.) in batch reactors under CO2 pressures of 1.0, 10.0, and 99.5 kPa was found to result in HCO3 as an end product of aerobic decomposition. The rate of HCO3 production from mineralizing organic matter exceeded calcite precipitation rates and, thus, calcite supersaturation resulted. The decomposition of pure organic compounds (dextrose, inositol, glucosamine, glucuronic acid, citric acid, and sodium citrate) was studied to elucidate the mechanism of HCO3 production. It was determined that the decomposition of organic anions associated with inorganic cations always results in HCO3 as an end product. The rates of calcite dissolution and precipitation were greatly inhibited in the presence of decomposing organic matter.
Diversity within Iowa Bradyrhizobium japonicum Serogroup 123
Authors: Hickey W. J. , Loynachan T. E. , Ayanaba A. , Zablotowicz R. M. 
Published: July 2010

AbstractBradyrhizobium japonicum serogroup 123 dominate soybean [Glycine max (L.) Merr.] nodules in the midwestern USA, but the diversity within this group has been little characterized. This study examined three collections of serogroup 123: nine USDA serogroup 123 strains (representing organisms from several states), 98 isolates collected from several counties and soils across Iowa, and 78 isolates from an intensively sampled 22.8‐m2 area in central Iowa. The organisms were characterized by sodium dodecyl sulfate‐polyacrylamide gel electrophoresis of proteins (SDS‐PAGE) and growth response to antibiotics, arginine, and succinate. Of the two methods, SDS‐PAGE was more useful for differentiating organisms. By using SDS‐PAGE, 74 strains were identified from 176 Iowa serogroup 123 isolates. No relation was evident between strain distribution and soil characteristics or geography. Strain USDA 123 was found not to be representative of the Iowa isolates.
New and Conventional Evaporative Systems in Concentrating Nitrogen Samples Prior to Isotope‐ratio Analysis
Authors: Lober R. W. , Reeder J. D. , Porter L. K. 
Published: July 2010

AbstractStudies were conducted to quantify and compare the efficiencies of various evaporative systems used in evaporating 15N samples prior to mass spectrometric analysis. Two new forced‐air systems were designed and compared with a conventional forced‐air system and with an open‐air drybath technique for effectiveness in preventing atmospheric contamination of evaporating samples. One of the new system designs was compared with the conventional forced‐air evaporative system and with the open‐air drybath technique for levels of 15N cross‐contamination among evaporating samples. The forced‐air evaporative systems significantly reduced the time needed to evaporate samples as compared to the open‐air drybath technique; samples were evaporated to dryness in 2.5 h with the forced‐air systems as compared to 8 to 10 h on the open‐air drybath. The effectiveness of a given forced‐air system to prevent atmospheric contamination of evaporating samples was significantly affected by the flow rate of the airstream flowing over the samples; the optimum flow rate was different for each of three forced‐air systems tested. When operated at optimum air flow rate, the forced‐air evaporative systems reduced atmospheric contaminants to <0.2µg N per sample, even when a contaminant of ∼77 µg NH3‐N per sample vial was added upstream of the scrubbing systems. The average atmospheric contaminant N found in samples evaporated on the open‐air drybath was 0.3 µ N, indicating very low concentrations of atmospheric NH3 during this study. Both these contaminant levels are sufficiently low to be of little or no significance in most tracer N studies. However, in previous studies we have experienced significant contamination of 15N samples evaporated on an open‐air drybath because the level of contaminant N in the laboratory atmosphere varied and could not be adequately controlled, even when NH3‐containing chemicals, cleansers, and paints were not stored or used in or around the working area. Average cross‐contaminant levels of 0.28, 0.20, and 1.01 µ of N were measured between samples evaporated on the open‐air dry‐bath, the newly‐designed forced‐air system, and the conventional forced‐air system, respectively. The cross‐contamination level is significantly higher on the conventional forced‐air system than on the other two systems, and could significantly alter the atom % 15N of high‐enriched, low [N] evaporating samples. The data from this study demonstrate that effectiveness in preventing atmospheric contamination and potential for cross‐contamination vary from system to system; thus, a given evaporative system should be carefully tested before being used in routine 15N sample processing.
Titratable Acidity to Estimate Ammonia Retention
Authors: Izaurralde R. C. , Kissel D. E. , Cabrera M. L. 
Published: July 2010

AbstractSimulation models of fertilizer behavior in soils are potentially useful tools to improve fertilizer use efficiency. Presently, there are no satisfactory models that describe NH3 retention in soils. In order to develop such a model, a better understanding of how soils retain NH3 and a quantitative measure of soils' NH3 retention capacity are needed. We compared soil cation exchange capacity (CEC) and several measures of soil titratable acidity for predicting the amount of NH3 retained in the center of a band resulting from anhydrous NH3 application to soil. The titratable acidity to pH 9 estimated with NH4OH was a much better predictor than CEC of the NH3 retained. In some soils, the pH in the center of an NH3 retention zone differed slightly from pH 9, resulting in some error in estimating the NH3 retained. This error was greatest on a salty soil because of the small slope of the buffer curve near pH 9. We found soil titratable acidity to be stoichiometrically related on a 1:1 basis to the amount of NH3 retained. Apparently, CEC is a poor predictor of the amount of NH3 retained by soil because many of the cation exchange sites do not participate in a soil's capacity to adsorb NH3. Since a soil's titratable acidity to pH 9 is a stoichiometric predictor of NH3 retention capacity in soils, it may be used to more easily model the properties of an NH3 retention zone as affected by factors such as N fertilizer rate applied, spacing between application points, and soil bulk density.
Phosphorus Fertilizer Carriers and Their Placement for Minimum Till Corn Under Sprinkler Irrigation
Authors: Raun W. R. , Sander D. H. , Olson R. A. 
Published: July 2010

AbstractSeveral methods of placement and sources of P were evaluated for sprinkler irrigated corn (Zea mays L.) grown under minimum tillage on a Sharpsburg silty clay loam (Typic Argiudoll) and a Coly silt loam (Typic Ustorthent). Nitrogen and P, dual placed in a localized band (anhydrous ammonia applied with liquid P sources), accomplished greater P uptake and higher corn grain yields on a P deficient calcareous soil than P banded to the side of the seed or banded below the seed, although both methods increased early plant growth compared to either broadcast or P dual placed with NH3. Broadcast preplant applications of P were equally as effective as dual placed P in this study. Explanation of yield and P uptake enhancement by dual placement may lie in the synergistic effect of ammoniacal N and P placed together. The superior performance of the broadcast method of P application was apparently due to root activity near the surface of the soil or in the soil residue interface. In contrast, starter band applications gave higher yields than broadcast or dual placed methods of P application on a slightly acid medium P soil. While it is not known why differences were obtained between the performance of methods of P application on these two soils, low subsoil P levels in the calcareous soil compared to the acid soil was believed to be a contributive factor. Enhanced early P uptake with such row applications may increase yields where high subsurface P levels exist. Urea phosphate (UP) provided greater yields, grain P uptake, and total P uptake than ammonium polyphosphate (APP) and diammonium phosphate (DAP) at the calcareous site—especially when band (side), broadcast, and dual placement methods of P application were used. Total P concentration from plant tissue taken at the eight‐leaf stage was greater for UP than APP and DAP on the slightly acid soil, but no yield differences could be attributed to sources at this site.
Inexpensive Equipment for Evaluation of Tillage Power Requirements
Authors: Jones A. J. , Bruce S. , Krall J. L. , Ferguson A. H. 
Published: July 2010

AbstractPortable inexpensive equipment is described for measurement of tillage power requirements. Equipment consisted of (i) a modified chisel plow; (ii) a four‐wheel drive pickup; (iii) a hydraulic system including pressure transducer; and (iv) a voltage integrator‐timing device. A calibration curve related the voltage output from the pressure transducer to force required to pull the chisel plow. Coefficients of variation among test fields ranged from 4.3 to 5.9% for voltage output, 3.7 to 5.0% for velocity, and 7.2 to 11.0% for calculated tillage power requirements. Construction cost was approximately $1000 plus labor. The chisel plow was transported in the pickup or on a small trailer.
Ammonia Volatilization from Liquid Digested Sewage Sludge as Affected by Placement in Soil
Authors: Adamsen F. J. , Sabey B. R. 
Published: July 2010

AbstractIn a laboratory study, liquid sewage sludge was added to an Olney sandy loam (fine‐loamy, mixed, mesic, Ustollic Haplargids) at a rate equivalent to 7.6 Mg ha−1 either on the surface or 25 mm below the surface. The sludge contained 11.2 g kg−1 NH4‐N and 21.6 g kg−1 organic‐N on a dry weight basis and 27 g L−1 solids. Surface applied sludge lost 40.3% of its NH4‐N as NH3 in the first 2 weeks (95% of the total loss) while subsurface applied sludge lost 0.35% of added NH4‐N as NH3 in the same period. Total NH3‐N loss from surface applied liquid sludge was 36.0 kg ha−1, which was 42.4% of added NH4‐N. Soil analyses at the end of the study showed that 96% of the inorganic‐N was in the form of NO3 in sludge amended treatments. Fertilizer value of liquid sludge will be greater with subsurface injection than surface application. Where available N limits sludge loading rates surface application would reduce land requirements.
Effect of Fertilizer Amendments, Bulk Density, and Moisture on Calcium and Magnesium Diffusion
Authors: Mullins G. L. , Edwards J. H. 
Published: July 2010

AbstractThe fertility of acid subsoils may be improved by the injection of fertilizer materials into narrow slits that can be cut in subsoils during tillage operations. Little information is available to describe the effects that soil properties and added fertilizers have on the diffusion of Ca2+ and Mg2+ in acid subsoils. Laboratory studies were conducted with an acid subsoil of a Marvyn sandy loam soil (fine loamy, siliceous, thermic, Typic Hapludult) to determine the effects of fertilizers, bulk density, and volumetric moisture (Θ) on the diffusion of Ca2+ and Mg2+. The soil was treated with either dolomitic limestone, NH4NO3, NH4H2PO4, Ca(H2PO4)2, or Ca(NO3)2. Limestone was applied at a ratio of 79 g kg−1, whereas the remaining treatments were applied to provide 2.64 g kg−1 of either NO‐3 or H2PO‐4. The rates were used to simulate the concentrations that would occur in the zone of injection if the amendments were injected into the subsoil under field conditions. Calcium diffusion coefficients (De) measured with a cation exchange resin paper method ranged from 2.4 × 10−9 cm2 s−1 in the check to 3.9 × 10−6 cm2 s−1 in the Ca(NO3)2 treatment, and counter De for Mg2+ ranged from 3.6 × 10−9 cm2 s−1 in the check to 5.1 × 10−6 cm2 s−1 in the Ca(NO3)2 treatment. All treatments increased De for Ca2+ and Mg2+ relative to the check. In general, De increased as the concentration of Ca2+ and Mg2+ in the soil solution increased, and as the proportion of the extractable cation associated with the solid phase decreased. Diffusion coefficients for Ca2+ and Mg2+ increased as Θ increased from 0.12 to 0.30. Calcium and Mg2+ De reached a maximum at a bulk density of 1.6 to 1.7 Mg m−3 and then decreased slightly as bulk density increased to 1.9 Mg m−3. Bulk density effects were more pronounced at soil‐water pressure head values <0.033 MPa.