bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pedoturbation by Artesian Action
Authors: Johnsgard G. A. 
Published: July 2010

AbstractMechanical mixing (pedoturbation) in soils can be caused by a variety of agencies and conditions. This paper proposes that water under artesian pressure below a frozen soil zone may be a cause of soil mixing as the frozen layer thaws in the spring. Thawing occurs at both the top and the bottom of the frozen soil zone. Points or areas of weakness in the frozen soil zone develop and become sites at which subsurface water breaks through the frozen zone. Artesian pressure, below the frozen zone, causes water and soil materials to move upward. It is proposed that among the consequences is the mixing of the soil in and above the frozen zone.
Bentonite Instability and Its Influence on Activation Energy Measurements
Authors: Brown D. S. , Miller R. J. 
Published: July 2010

AbstractA time‐dependent temperature hysteresis in a‐c conductance activation energy plots for dilute, neutral, and salt‐free Na+‐bentonite suspensions is reported. Fresh suspensions prepared by washing with NaOAc or NaCl had activation energies of 9,398 and 5,789 cal/mole initially which gradually decreased to 3,651 and 3,422 cal/mole, respectively, after several days.A‐c conductances, concentrations of free Na+ in solution, pH, and dissolved silica were monitored in suspensions aged at 30C. Conductance increases of 2–3 fold were observed, with the concentration of free Na+ released from the exchange sites increasing to 5.4 and 34 ppm, respectively, for the NaCl and NaOAc preparations. Dissolved silica in solution increased to 3–4 ppm over the same period indicating that degradation of the lattice had occurred. Results are interpreted in terms of the hydrolysis of the exchangeable Na+ ions as predicted by Donnan and diffuse double layer theory followed by an acid attack of the lattice. Free salts added to the suspensions were effective in suppressing the hydrolysis and stabilizing the activation energies.
Buffer Curves and Acid Strength of Humic Acid and Two Resins
Authors: Gilmour J. T. , Coleman N. T. 
Published: July 2010

AbstractTwo humic acids, Cellex‐CM, and IRC‐50 were placed in 10‐1, 10‐2, and 10‐3M NaCl or CaCl2 and titrated potentiometrically with NaOH or Ca(OH)2, respectively. Titration curves of Cellex‐CM and IRC‐50 in the NaOH‐NaCl system showed parallel 1 pH unit displacements for a 10‐fold change in NaCl concentration, while humic acid showed a 0.5 pH unit displacement. Buffer curves of humic acid, Cellex‐CM, and IRC‐50 in the Ca(OH)2‐CaCl2 system showed a 0.4 pH unit displacement for a 10‐fold change in CaCl2 concentration. The regular displacement of buffer curves led to development of a theory using ion exchange and surface ionization of H that described the buffer curves and assigned a salt independent pKa to the weak acid adsorbents.
Copper Accumulation in Citrus Roots and Desorption with Acid
Authors: Brams E. A. , Fiskell J. G. A. 
Published: July 2010

AbstractRoot accumulation of 04Cu from labelled Cu(NO3)2 in intact ‘Mandarin Orange’ (Citrus reticulata) seedlings had a constant rate for the first 15 min and then became curvilinear for periods from 15 to 180 min, when the ambient solution contained 0.6 ppm Cu. Over a 60‐min contact time uptake of Cu was linear for ambient Cu concentration range from 0.3 to 1.2 ppm. Extraction of 64Cu in roots by 0.1N HCl was linearly proportional to total root Cu and was 95% complete after 28 min. Colloidal phosphate reduced 64Cu accumulation in the roots by 12%. In roots of ‘Sour Orange’ (C. aurantium) seedlings grown in solution culture and in groves Cu was located in thin sections by ferrocyanide staining. Concentration of Cu occurred in the exodermis, endodermis, and pericycle cells. Electromicrographs of citrus roots suffering from Cu toxicity showed irregular deformation of cell walls in xylem vessels. In such cases roots became club shaped as root elongation ceased. Reactions of Cu with protein are suggested as mechanisms for Cu accumulation in roots.
Effect of Available Soil Calcium on Taproot Elongation of Loblolly Pine (Pinus taeda L.) Seedlings
Authors: Lyle E. S. , Adams Fred 
Published: July 2010

AbstractThree vertical split‐root experiments were performed to discover a method of describing Ca availability in soils that could be correlated with taproot elongation of loblolly pine seedlings and could be used to determine critical values at which elongation rate became inhibited.The first experiment, utilizing a vertical split‐root technique with a fertile topsoil overlying nutrient solutions, proved that loblolly pine roots will elongate in an ambient solution of CaCl2 and deionized water. However, elongation was much greater when other ions were also present in the ambient solution. The second and third experiments also utilized a vertical split‐root technique but the subsurface medium was an infertile loamy sand with varying amounts of Ca, Mg, K and NH4 salts added. It was found that aCa/aMg, MCa/MMg, and aCa/Σacation i ratios of soil solutions showed a close relationship with tap‐root elongation, and the relationship was continuous from extreme Ca deficiency to Ca sufficiency. The data show that tap‐root elongation was inhibited when MCa/MMg, aCa/aMg, and aCa/Σacation i ratios fell below 0.75, 0.75 and 0.10, respectively.
The Nature of K‐feldspars of a Chernozemic Soil in the Canadian Prairies
Authors: Somasiri S. , Huang P. M. 
Published: July 2010

AbstractThe nature of the K‐feldspars of an Orthic Brown Chernozemic (Aridic Haploboroll) soil profile developed from glacial till deposits in Saskatchewan, Canada, was studied. The K‐feldspars from selected size fractions between 20 and 2,000µ were concentrated by heavy liquid separation at a specific gravity of 2.59. X‐ray powder diffraction analysis was used to identify orthoclase and microcline, to estimate their relative proportion, and to determine the obliquity, which is the degree of departure from the monoclinic symmetry of K‐feldspars.The concentration of K‐feldspars by heavy liquid separation greatly facilitated the subsequent X‐ray diffraction analysis. All the samples studied contained both orthoclase and microcline, and at least some of the K‐feldspar crystals appear to be perthitic in nature and have a high degree of exsolution. The diffractograms of the comparable size fractions from the major genetic horizons were similar and the proportions of orthoclase to microcline were comparable in the same size fractions. The proportions of orthoclase to microcline usually increased as the particle size decreased in all of the horizons, indicating that this differentiation occurred at the time of deposition of the soil parent material. The obliquity values of microcline of the various size fractions, ranging from 0.82 to 0.87, appeared to be uniform throughout the profile.The obliquity of K‐feldspars and proportions of orthoclase to microcline may have a potential use as a guide in establishing the geological origin of soil parent material and in confirming its uniformity.
Iron Hydroxy Interlayers in Soil Clay
Authors: Singleton P. C. , Harward M. E. 
Published: July 2010

AbstractThe less than 2µ fraction of the A horizon of two western Oregon soils, a Typic Haplumbrept and a Xeric Haplohumult, were found to contain an intergrade mineral with properties intermediate to chlorite and montmorillonite. The mineral was subjected to a series of treatments designed to effect a progressive dissolution of associated Fe, Al, Si, and Mg compounds. Analysis of treatment extracts and measurements made of d‐spacings and cation exchange capacity before and after treatments indicated that the hydroxy material occupying the interlayer spaces of the 2:1 layers of the mineral may consist of Fe as well as Al and Mg.
Boundary Conditions and Conductivities used in the Isothermal Model of Evaporation from Soil
Authors: Staple W. J. 
Published: July 2010

AbstractThe surface boundary conditions in the isothermal model for computing evaporation from soil were expressed in terms of the wind speed, temperature, and humidity of the ambient air. Use of these parameters along with reduced nodal spacings near the surface produced evaporative fluxes that closely followed the differences in vapor pressure between soil and atmosphere. A simple evaporation experiment was used to show that evaporation rates and soil moisture distributions obtained with these revised boundary conditions were closer to experimental values than were those obtained with the usual conditions defined in terms of potential evaporation and moisture content.
The Influence of Soil‐Fertilizer Geometry on Nitrification and Nitrite Accumulation
Authors: Bezdicek D. F. , MacGregor J. M. , Martin W. P. 
Published: July 2010

AbstractNine granules (330 ppm N) of either urea, (NH4)2SO4, or diammonium phosphate (DAP) were spaced in a square pattern at distances of 0, 0.5, 1.0, or 1.5 cm on 30 g of soil. Samples were watered, incubated, and extracted with I N KCl. The extracts were analyzed for NH4+, NO2‐, and NO3‐. Generally NO2‐ accumulation for the three N carriers increased with granule spacing; the geometric effect was DAP > (NH4)2SO4 > urea. Nitrite varied from 140 to 265 ppm N. Increased NO2‐ accumulation with increased granule spacing was accompanied by a corresponding increase in NH4+ oxidation rate with little change in NO3‐. Geometric effect with four granules (55 ppm N) spaced up to 2.5‐cm apart showed that both NO2‐ and NH4+ decreased with increased granule spacing accompanied by increased NO3‐. Single‐granule studies suggested that the greater geometric effects of DAP resulted from the lower solubility and relatively low mobility of phosphate ions. The subsequent periphery pH decrease minimized outward movement of NH4+. These effects were less for (NH4)2SO4 and for urea.
Tensile Strength of Montmorillonite as a Function of Saturating Cation and Water Content
Authors: Dowdy R. H. , Larson W. E. 
Published: July 2010

AbstractThe tensile strength, tensile axial strain, and tensile strain energy were determined for Na‐, K‐, Ca‐, Al‐, and Fe‐saturated montmorillonite over the water vapor pressure range (P/Po) from 0.02 to 0.92. The procedure used was direct tensile stressing of oriented clay films. Measured tensile strengths ranged from 366 kg cm‐2 for Fe montmorillonite at 0.02 P/Po to 19 kg cm‐2 for Ca montmorillonite at 0.92 P/Po. Strength decreased rapidly with added increments of water during initial interlamellar expansion and continued to decrease at a slower rate with further additions of water. In general, strength decreased in the following order: Fe > K ≥ Na > Al > Ca. The tensile strength of Na montmorillonite was of the same order of magnitude as the force required to separate two Na clay platelets as determined from adsorption/desorption water isotherms.Axial strain was independent of P/Po above 0.4 for all systems except the Na‐saturated clay. For Fe montmorillonite, strain was insensitive to water content above 0.15 P/Po. Monovalent clay specimens required the most energy to rupture and divalent samples required the least energy. Aluminum and Fe clays required an intermediate rupture energy.The greater tensile strength and low axial strain of the Fe montmorillonite suggested that a different mechanism controlled the failure characteristics of this clay. Hydroxy iron material may be the major cementing agent in the Fe system. The data show that saturating cation played a dominant role in the strength‐energy properties of the other homoionic clays.
Hydration of Cations Adsorbed on a Clay Surface from the Effect of Water Activity on Ion Exchange Selectivity
Authors: Laudelout H. , Van Bladel R. , Robeyns J. 
Published: July 2010

AbstractIon exchange equilibria for four pairs of singly charged ions in a montmorillonite clay were carried out at different total normalities of the equilibrium solution at 25C. Only the trace region for the preferred ion was investigated. The effect of solvent activity aw on the selectivity coefficient Kc was established. In each case the expected linear relationship between ln Kc and ln aw was observed. The values for the differences of the ion hydration numbers, nwA ‐ nwB, calculated from this purely thermodynamic relationship, were consistent and were comparable with values that could be deduced from basal spacings or anion exclusion volume data.
Percent of Copper Diffusing in the Adsorbed and Electrolyte‐Solution Phases in Kaolinite and Montmorillonite
Authors: Phillips R. E. , Barnhisel R. I. , Ellis J. H. 
Published: July 2010

AbstractThe apparent diffusion coefficient, De, of a cation diffusing in soil was proposed to be Dem = [Dsm(dCs/dCsa} + 1Dam (dCa/dCsa)] / [1 + dCp/dCsa] where Dsm and 1Dam are the diffusion coefficients of the cation in the electrolyte‐solution phase and in the adsorbed phase (exchangeable cations), respectively, and where the frame of reference in each case is with respect to the entire soil mass. The symbols Cs, Ca and Cp are concentrations of electrolyte‐solution cations, adsorbed cations, and precipitated or immobilized cations, respectively; Csa is defined to be the sum of Cs and Ca. The concentrations are expressed with respect to the total volumetric water content of the system. The quantities, dCs/dCsa, dCa/dCsa, and dCp/dCsa were evaluated in experiments independent of the measurement of Dem. The relative contributions of Dsm and 1Dam to Dem were evaluated over a large range of Csa values for Cu2+ diffusing in water‐saturated kaolinite and montmorillonite. In kaolinite clay with a cation exchange capacity (CEC) of 0.065 meq g‐1, the percent of total diffusion due to diffusion in the adsorbed phase was 100, 52, 34, 22, 18, 9, and 7 at Csa concentrations of 0.015, 0.02, 0.03, 0.04, 0.05, 0.06, and 0.08 meq g‐1, respectively. In montmorillonite clay with a CEC of 0.70 meq g‐1, the percent of total diffusion due to diffusion in an adsorbed phase was 100, 57, 42, 34, 28, 20, and 13 at Csa concentrations of 0.03, 0.05, 0.10, 0.15, 0.20, 0.40, and 0.70 meq g‐1, respectively.
Fractionation of Organic Phosphorus in Lake Sediments
Authors: Sommers L. E. , Harris R. F. , Williams J. D. H. , Armstrong D. E. , Syers J. K. 
Published: July 2010

AbstractThe organic phosphorus of 10 Wisconsin lake sediments of diverse properties was fractionated on the basis of extractability and anion exchange properties. The fractionation procedure involved sequential extraction of the sediments with 1N HCl for 1 hour (HCl‐Po), cold 0.3N NaOH for 16 hours (Cold NaOH‐Po), and hot 0.3N NaOH for 8 hours (hot NaOH‐Po) followed by anion exchange chromatography of the NaOH extracts into three fractions: fraction I, the 0.3N NaOH eluate, contained organic P that was not retained by the resin; fraction II, the 0.5M LiCl eluate, contained organic P with exchange properties similar to inorganic orthophosphate and monophosphate esters; fraction III, the 1M LiCl + 0.2N HCl eluate, contained organic P comparable to polyphosphate esters in exchange properties.Total organic P extracted by the fractionation method was comparable to that removed by the standard Mehta et al. extractants indicating that the fractionation method provided valid total organic P data as well as information on the forms of organic P present in sediments.HCl‐Po constituted 6 to 17%, cold NaOH‐Po 60 to 80%, and hot NaOH‐Po 10 to 30% of the total organic P of the sediments. Anion exchange chromatography of the NaOH extracts showed that most of the organic P (48 to 80%) was present in fraction I, the fraction likely composed of high molecular weight humic‐fulvic complexes. Fraction II contained 14 to 36% and fraction III less than 10% of the organic P in the NaOH extracts. Total inositol penta‐ and hexa‐phosphates comprised less than 10% of the total organic P of the sediments. The total and major fractions of sediment organic P were related to organic C, total N and oxalate‐extractable Al, but were not related consistently to any other sediment property or to the trophic level of the lake.
Growth of Two Root‐Rot Fungi as Affected by Osmotic and Matric Water Potentials
Authors: Cook R. J. , Papendick R. I. , Griffin D. M. 
Published: July 2010

AbstractGrowth of Ophiobolus graminis in response to a range of water potentials was maximal with the wettest treatments (‐1.2 to ‐1.5 bars), reduced by half at about ‐20 bars, and prevented at ‐45 to ‐50 bars. This pattern held for growth measured as colony diameters on agar media with osmotically‐controlled water potentials, or as linear hyphal growth along the surface of straws in soil with matrically‐controlled water potentials.In contrast, growth of Fusarium roseum f. sp. cerealis ‘Culmorum’ was progressively stimulated as the osmotic potential was lowered over the range, ‐1.5 to ‐8.2 bars, then declined with further decrease in potential. The effect was independent of the solute type, either salts or sucrose in agar media, or with salts in soil. Stimulation did not occur when the fungus was subjected to a range of matric potentials in soil; rather the response was similar to O. graminis with maximal growth in the wettest soil. However, unlike O. graminis, growth of Culmorum was reduced by half at about ‐40 bars matric potential, or ‐45 to ‐50 bars osmotic potential, and was prevented at ‐70 to ‐75 bars matric potential, or about ‐80 bars osmotic potential. The differential effects of osmotic and matric potentials on Culmorum growth in autoclaved soil, and similarly the absence of an osmotic stimulatory effect on O. graminis probably relate to physiological factors inherent with the individual fungus.The root and foot rot of wheat caused by Culmorum is generally most severe in the low rainfall (30 cm or less annual precipitation), non‐irrigated areas of the Northwest USA whereas O. graminis is most destructive in areas of higher rainfall or on irrigated wheat or barley. The natural association of these two pathogens with dry or wet field conditions may relate to their respective responses to the soil‐ and plant‐water potentials associated with the different environments.
Variations with Distance in Selected Fertility Measurements of Pedons of Western Kansas Ustoll
Authors: Cipra Jan E. , Bidwell Orville W. , Whitney David A. , Feyerherm A. M. 
Published: July 2010

AbstractThis investigation of the fertility status of Richfield silt loam, 0 to 1% slope, indicates that adequate fertility characterization of a soil series requires many more samples than are commonly taken. Sixteen sampling sites were used in each of seven 2.4‐ha (6‐acre) fields 8 to 145 km (5 to 90 miles) apart. We located four plots 90 m (300 feet) apart in each field and four sampling sites 3 m (10 feet) apart in each plot. Samples of Ap, B2t, and C horizons were collected from each site. Organic matter, P, K, Zn, and pH were determined in duplicate using procedures of the Kansas State Soil Testing Laboratory. Within‐plot variance component estimates were small for most horizon and fertility‐test combinations. Variance among plots was greater than within plots for 11 of the 15 combinations. Variance among fields was predominant in 8 of the 15 combinations, and accounted for more than 50% of the total variance in 5 of the 15 combinations. Results indicate that estimating the series means within ± 10% would require the most samples for P and the least for pH.
The Prediction of Soil Occurrence in Certain Desert Regions of the Southwestern United States
Authors: Gile L. H. , Hawley J. W. 
Published: July 2010

AbstractExtensive areas of desert soils in the southwestern United States have not been mapped. Conclusions concerning soil genesis and soil distribution have been reached in a study of desert soils in a study area typical of large parts of the Southwest. Observations in other desert regions indicate that results of the study should be useful in the prediction of soil occurrence in places similar to the study area. Important factors considered in making the predictions are topography, soil parent materials, soil age, climate, and soil biota. Airphotos and geologic, topographic, and hydrologic maps are useful in predicting soil occurrence. Soils for which occurrence may be predicted include Torripsamments, Torrifluvents, Torriorthents, Camborthids, Haplargids, Paleargids, Calciorthids, and Paleorthids. Boundaries to adjacent Mollisols are also discussed.
Numerical Analysis of Drainage of a Heterogeneous Porous Medium
Authors: Watson K. K. , Whisler F. D. 
Published: July 2010

AbstractThe gravity drainage of a heterogeneous porous medium was studied using a numerical solution of the flow equation. The medium was assumed to exhibit scale heterogeneity, the heterogeneity being specifically defined in terms of a linear variation of the saturated hydraulic conductivity with depth. Within the restrictions imposed by scale heterogeneity, the hydrologic characteristics were chosen so that their form validly represented real data. The spatial variation of the hydrologic characteristics was initially defined in terms of the air entry value of the medium at the point in question and an empirical relationship between the air entry value and the saturated hydraulic conductivity. Pressure head and water content profiles were obtained for three hydraulic conductivity distributions in which the conductivity decreased with depth. The pressure head profiles for these distributions revealed clearly the zones of positive pressures in the profiles and the slow decay of these pressures during drainage.
Instrumentation Effects on Errors in Nuclear Methods for Soil Water and Density Determination
Authors: Stone J. F. 
Published: July 2010

AbstractThe commonly used ratio calibration of neutron scattering soil moisture meters tends to obscure errors due to random event counting, dead time, and drift phenomena not fully compensated for by the ratio. These effects are analyzed in the light of the demands of the very high count rates in many scintillation systems being currently reported. Dead time is always reduced by using high pulse‐rate resolution equipment. Such is not always available for experimental work and the errors entailed are discussed. Equations describing the errors in ratio counting are discussed. The size of the standard material is a factor in some of the error terms. Some of the errors reduce to zero at the point where the count obtained in the soil is equal to the reading in the standard. Thus, it is desirable to construct the standard such that the ratio = 1 appears on the calibration curve (preferably above the center).
A Simple Titrimetric Method for Determination of Inorganic Carbon in Soils
Authors: Bundy L. G. , Bremner J. M. 
Published: July 2010

AbstractA simple method of determining inorganic carbon in soils is described. The soil sample is treated with 2M HCl at room temperature for 16–24 hours in a stoppered bottle containing 2M KOH in a small beaker, and the CO2 released from carbonates by this treatment is determined by titration of the KOH solution with standard HCl. The method is accurate and precise, and tests reported indicate that it is not subject to interference by organic soil consituents. It gives quantitative results with carbonate standards, and its results with soils agree closely with those obtained by the methods proposed by Allison and by Anderson and Harris.
Effect of Soil Factors on the Distribution of Rhizobium japonicum Serogroups
Authors: Bezdicek D. F. 
Published: July 2010

AbstractThe soybean variety ‘Kent’ was planted at 19 sites representing two soil types located on Maryland's Eastern Peninsula. Routine soil tests including soil organic N were performed and correlated with serological distribution of R. japonicum. Nodule samples reacted with 16 Beltsville antisera with no serogroup occupying more than 20% of the total. Beltsville serogroup 110 was positively correlated with several organic N fractions, soil NH4+, and soil NO3‐ for the Sassafras soil. Serogroup 123 showed a positive correlation with soil pH and exchangeable Mg. When the Matapeake soil was considered, serogroup 94 was positively correlated with soil N status much like 110 was for the Sassafras soil.