bluuebunny/crossref_metadata_2025_split huggingface dataset:
Post‐Mazama Natrargids in Dixie Valley, Nevada
Authors: Alexander E. B. , Nettleton W. D. 
Published: July 2010

AbstractSome of the youngest Natrargids in central Nevada are in basin‐fill containing volcanic ash. South of the salt flat in Dixie Valley they are associated with Torrifluvents and Torriorthents in a continental climate with mean temperatures about 12 to 14°C and mean annual precipitation between 10 and 15 cm. Since there are lenses of Mazama ash below the natric horizons in some of these Natrargids, they are know to be < 6,600 radiocarbon years old.A representative Typic Natargid in silty post‐Mazama basin‐fill sediments is described. Illuviation is confirmed by clay skins in the natric horizon. The present precipitation is adequate to account for its development.
Linear and Nonlinear Models of Infiltration From a Point Source
Authors: Ben‐Asher J. , Lomen D. O. , Warrick A. W. 
Published: July 2010

AbstractNumerical and analytical solutions for water flow from a point source are compared. The numerical solution was for the nonlinear moisture flow equation and the analytical solution for the corresponding linearized form. For cyclic conditions, results were approximately the same with regard to range in values between the wettest and driest values. However, the numerical results show a faster response both for wetting and drying. Computational times required of the analytical solution were of the order of 1/20 to 1/200th of that required for the finite difference solutions.
Effects of Soil Moisture on the Diffusion Coefficients and Activation Energies of Tritiated Water, Chloride, and Metribuzin
Authors: Scott H. D. , Paetzold R. F. 
Published: July 2010

AbstractDiffusion coefficients of tritiated water, chloride, and metribuzin were determined in Captina silt loam as functions of soil water content and soil temperature. Tritiated water and metribuzin were found to diffuse in both liquid and vapor phases, whereas chloride diffusion was restricted to the solution phase. For a given soil water content, values of the diffusion coefficients were larger in soil samples from the Ap horizon than in those from the B2t horizon for tritiated water and chloride. This was attributed to the greater tortuosity in the B2t horizon. Metribuzin had similar diffusion coefficients in both horizons, apparently reflecting offsetting effects due to the greater adsorption by the Ap and greater tortuosity in the B2t.Thermodynamic studies indicated that the energy requirement for diffusion of these solutes was inversely related to soil moisture content for tritiated water and metribuzin. Activation energies for chloride diffusion were lower than for other solutes at equal soil water contents.
Effects of Clay Type and Content, Exchangeable Sodium Percentage, and Electrolyte Concentration on Clay Dispersion and Soil Hydraulic Conductivity
Authors: Frenkel H. , Goertzen J. O. , Rhoades J. D. 
Published: July 2010

AbstractThe hydraulic conductivities and gradients along soil columns packed with montmorillonitic, vermiculitic, and kaolinitic soils adjusted to different levels of exchangeable sodium were determined at different salt concentrations. The data show that plugging of pores by dispersed clay particles is a major cause of reduced soil hydraulic conductivity for surface soils irrigated with sodic waters.
Sulfate Adsorbed on Hydrous Alumina, Ligands Displaced, and Changes in Surface Charge
Authors: Rajan S. S. S. 
Published: July 2010

AbstractTo obtain a better understanding of the short term reactions between sulfate and hydrous alumina the relationships between the amount of sulfate retained by the alumina and reaction time, concentration, ligands displaced by sulfate, and changes in surface charge were studied. Experimental conditions were 3 hours reaction time, 0.01M NaCl medium, pH 5.0, 30°C, and nitrogen atmosphere.Sulfate adsorption was very rapid and about 90% of the reaction was over in 10 min. There was little change in adsorption after 3 hours. The adsorption increased with increasing final solution concentration up to about 6 µeq/ml after which it decreased.Sulfate adsorption resulted in the release of OH‐ from, and the neutralization of positive charge on the surface. From the quantitative relationships between sulfate adsorbed, the ligands displaced, and the changes in surface charge it is proposed that sulfate is adsorbed on hydrous alumina as SO42‐ bridging across two aluminum atoms, forming a six‐membered ring. At low concentrations sulfate preferentially displaces aquo groups (Al‐OH2) from the positive sites. With increasing concentration, increasing proportions of hydroxo groups (Al‐OH) from the neutral sites are displaced. The decrease in adsorption above 6 µeq/ml of sulfate concentration is inexplicable at this stage.
Adsorption of Mercury(II) by Iron Hydrous Oxide Gel
Authors: Kinniburgh D. G. , Jackson M. L. 
Published: July 2010

AbstractFreshly prepared iron hydrous oxide gel suspensions, 0.093M and 0.001M with respect to Fe, strongly adsorb Hg(II) from solutions containing 2.5 × 10−5M Hg(II) and 1.0 × 10−6M Hg(II), respectively. The pH at which 50% of the total adsorption occurred in the latter system is 4.3. In the presence of chloride (Cl/Hg(II) mole ratio of 4/1), the adsorption of Hg(II) is considerably reduced, with no significant coadsorption of 36Cl, indicating that Hg(II)‐Cl complexes are not adsorbed by Fe gel.
In Situ Study of Podzolization on Tephra and Bedrock
Authors: Singer Michael , Ugolini F. C. , Zachara J. 
Published: July 2010

AbstractA study was initiated in the Washington Cascades to examine processes of soil genesis in situ through the analysis of soil solution chemistry. Suction plate lysimeters were used to continuously extract soil solution held below 0.1 atm from the O2, A2, IIB2hir, and IVB32 horizons of a forest soil. Movement of elements was in the order Si > Al > Fe > Mn. The O2 and A2 were the source of the Fe, Al, and Si which entered the IIB2hir. Most of the Mn originated in the A2. Virtually all of the Fe, 48.5% of the Al, 50% of the Mn, and 15% of the Si which left the A2 remained in the IIB2hir. According to the soil's morphology, it appears to be a Spodosol, and the lysimeter data indicates that podzolization is the major process of soil formation. The soil does not meet the criteria of a Spodosol in Soil Taxonomy. Two explanations for this are: (i) the soil has not become a Spodosol yet because the intensity of weathering is low or (ii) soil taxonomy criteria for the Spodosol order are not broad enough and need to be broadened to include soils of this type.
Sulfur Status of Some Central Oregon Pumice Soils
Authors: Will G. M. , Youngberg C. T. 
Published: July 2010

AbstractIn a fertilizer experiment established in a 45‐year‐old stand of ponderosa pine (Pinus ponderosa Laws) on a pumice soil, 112 kg S/ha added as gypsum resulted in a small increase in tree growth in the first 5‐year period. The combination of S with 224 kg N/ha gave a greater response. Over a 10‐year period, basal area growth was 50% greater than in untreated plots. The soil layers in the tree rooting zone at this and four other sites were collected for a pot trial bioassay of their S status. In all cases the growth of Monterey pine (Pinus radiata D. Don) seedlings was improved by the addition of S. At all sites the soil layer least deficient in S was the A1 horizon which varied from 5 to 15 cm in thickness. Although the results indicated that the field trial site is more S deficient than the others, they also show that many of the pumice soils in central Oregon are marginally deficient in S. Forest management operations, such as site preparation, which remove the surface soil, will seriously lower the S as well as the N and P levels of the soil and if productivity is to be maintained, the use of fertilizers will be essential.
Relationships of Soils to Mountain and Foothill Range Habitat Types and Production in Western Montana
Authors: Munn L. C. , Nielsen G. A. , Mueggler W. F. 
Published: July 2010

AbstractSoils at 23 sites representing eight western Montana mountain and foothill range habitat types were characterized and classified in accordance with Soil Taxonomy. The soils ranged from Borollic Calciorthids at the dry end of a moisture and soil development gradient to Pachic Cryoborolls on the moist end. Corresponding vegetation was a Stipa comata‐Bouteloua gracilis community on the dry end and a Festuca idahoensis‐Agropyron caninum community on the moist end. Soil taxonomic units and vegetation habitat types were ordered along the moisture gradient. Multiple linear regression analysis was used to model above‐ground dry‐matter productivity of the sampled sites. Eighteen significant variables were identified including thickness of the mollic epipedon, total soil organic matter, total N content, elevation, depth to free carbonates, estimated annual precipitation, aspect, solum thickness, summer soil temperature at 50 cm, percent coarse fragments in the A horizon, and extractable K. The thickness of the mollic epipedon was the variable most highly correlated with productivity (r=0.89**) and the best regression model accounted for 90% of the variability in total productivity between sites (based on 2 years' productivity data). Soil morphological characteristics proved more useful in models of site productivity than estimated climatic data or site nutrient data.
A Study of a Deep Weathering Profile on Granite in Peninsular Malaysia: I. Physico‐Chemical and Micromorphological Properties
Authors: Eswaran H. , Bin Wong Chaw 
Published: July 2010

AbstractTo facilitate description and study, the deep profile is divided into several morphological zones, via., α, γm, γp and δ zones. Clay content progressively increases from the rock zone δ to the soil zone α. The silt/clay ratio increases from the δ to the upper part of the γp zone and then decreases again. These changes are explained in terms of the fragmentation or aggregation of various minerals during the clay separation procedure. Estimates of the mineralogical composition in the fine earth shows differences in the zones, and the charge characteristics are related to these.Changes in the microfabric are monitored with thin‐sections. Micrographs are presented showing fabric characteristics and some examples of pseudomorphic alteration. A brief discussion on the genesis of the profile is given.
Rapid Estimate of Unsaturated Hydraulic Conductivity Function
Authors: Bresler E. , Russo D. , Miller R. D. 
Published: July 2010

AbstractFrom results of Reichardt, Nielsen, and Biggar and of Russo and Bresler, it is inferred that a laboratory horizontal infiltration experiment with air‐dry soil yields an estimate of the saturated‐unsaturated hydraulic conductivity function given by K(h) = 0.27 m4 (he/h)2.6 or K(θ) = 0.27 m4 [(θ − θd)/(θw − θd)]7.2. Here m = dx/d (t1/2); x is distance to the wetting front and t is infiltration time; θd and θw are water contents of air‐dry and “saturated” soil; h is pore water pressure head, and he is the air entry value of h. These relationships can serve as a general approximation of K(θ) and K(h) in nonsodic stable soils. Field measurements of he and saturated K can also be used to derive K(θ) and K(h).
Hydrodynamic Dispersion During Absorption of Water by Soil
Authors: Smiles D. E. , Philip J. R. , Knight J. H. , Elrick D. E. 
Published: July 2010

AbstractThe paper reports an experimental study of hydrodynamic dispersion of low concentration solutions during absorption into horizontal columns of soil with initially uniform moisture and solute contents. The initial soil solutions were of relatively high salt concentration. It was found that both the water and salt concentration profiles preserved similarity in terms of distance divided by the square root of time. This observation implies that the longitudinal dispersion coefficient is insensitive to pore water velocity and may be taken as a function of the volumetric water content only, at least for a given initial (low) moisture content.The formulation which follows is frankly phenomenological. It provides a simple means of predicting dispersion during flow in unsaturated soils which promises to be sufficiently accurate for most purposes.
The Distribution of Micronutrient Cations in Soil Under Conditions of Varying Redox Potential and pH
Authors: Sims J. L. , Patrick W. H. 
Published: July 2010

AbstractA laboratory study was conducted to determine the influence of redox potential and soil pH on the distribution of Fe, Mn, Zn, and Cu in Mhoon silty clay loam soil (Typic Fluvaquents) and to provide insight into factors affecting micronutrient dissolution and mobility in soil. Generally, greater amounts of Fe, Mn, Zn, and Cu were found in the Na acetate (exchangeable) and pyrophosphate (organic) extractions at low pH and Eh than at high pH or Eh. In contrast, the amounts (except Mn) in the water‐soluble, NH2OH·HCl, and oxalate fractions were greater at high pH or Eh. Although the micronutrients were brought into solution at low pH and Eh, much of the soluble cations soon associated with the exchangeable and organic fractions. After reduction, mobilized Fe associated about equally with the exchangeable, organic, and NH2OH·HCl fractions; mobilized Mn with the exchangeable and water‐soluble fractions; mobilized Zn with the organic fraction; and the mobilized Cu with the organic and water‐soluble fractions. Separation of the water‐soluble fraction into free ions and those complexed by soluble organic matter indicated that micronutrient cations were complexed by organic matter to a greater extent in reduced soil.
Measurement of Exchangeable NH4+ in Tropical Rice Soils
Authors: Sahrawat K. L. , Ponnamperuma F. N. 
Published: July 2010

AbstractMeasurement of exchangeable NH4+ by two methods—steam distillation of the filtrates of KCl extracts and of soil‐KCl suspensions with MgO—was compared for 17 tropical soils covering a wide range in texture, pH, and organic matter. Distillation of soil suspensions gave significantly higher values for NH4+ both for aerobic and anaerobic soils, but the differences were much greater in the anaerobic soils. The higher values obtained by direct distillation of KCl‐soil suspensions were probably due to hydrolysis of soil organic matter at the high pH values (9.9 to 10.7) brought about by the boiling MgO suspensions. We recommend the use of a filtered KCl extract instead of a soil suspension to measure exchangeable NH4+ in tropical rice soils.
Phosphodiesterase Activity of Soils
Authors: Browman M. G. , Tabatabai M. A. 
Published: July 2010

AbstractAn improved method to assay phosphodiesterase activity in soils is described. It involves extraction and colorimetric determination of the p‐nitrophenol released when 1 g of soil is incubated with 5 ml of 1mM buffered [0.05M tris (hydroxymethyl) aminomethane (THAM), pH 8.0] bis‐p‐nitrophenyl phosphate solution at 37°C for 1 hour. The reagents (0.5M CaCl2 and 0.1M THAM pH 12) used for extraction of the p‐nitrophenol released give quantitative recovery of p‐nitrophenol added to soils and do not cause chemical hydrolysis of the substrate, bis‐p‐nitrophenyl phosphate. Results showed that this soil enzyme has its optimum activity at buffer pH 8.0. The initial rates of p‐nitrophenol release obeyed zero‐order kinetics. The phosphodiesterase activity of six surface soils studied ranged from 16 to 147 µg p‐nitrophenol released · g−1 soil · hour−1. Steam sterilization and formaldehyde destroyed and toluene increased the activity of this enzyme. At 5mM, PO43‐, EDTA, and citrate inhibited phosphodiesterase activity. The inhibition by orthophosphate showed competitive kinetics. The temperature dependence of the rate constant conformed to the Arrhenius equation up to the point of enzyme inactivation (70°C). The activation energy of phosphodiesterase of the six surface soils studied ranged from 7,860 to 10,390 (avg. = 8,720) calories · mole−1. By using the Lineweaver‐Burk plot, the Km values ranged from 1.26 to 2.02 (avg. = 1.69)mM and the Vmax ranged from 52 to 530 (avg. = 303) µg p‐nitrophenol released · g−1 soil · hour−1. Phosphodiesterase activity was significantly correlated with organic C in each soil profile and in the surface soils studied.
Nutrient Effectiveness in Relation to Rates Applied for Pot Experiments: II. Phosphorus Sources
Authors: Mortvedt J. J. , Terman G. L. 
Published: July 2010

AbstractThree greenhouse pot experiments were conducted with corn (Zea mays L.) grown on infertile soils to evaluate four fertilizers as sources of P. The granular sources were concentrated superphosphate (CSP, 90% of P water‐soluble), monoammonium phosphate (MAP, 100% of P water‐soluble), a mixture of 30% of the P as CSP and 70% as dicalcium phosphate (DCP, water‐insoluble), and a 10‐90% mixture of CSP and DCP. Rates of 0, 50, 200, 400, and 800 mg of P/pot from each source were compared in Exp. 1; and 0, 60, 120, and 480 mg rates of P in Exp. 2 and 3. These P sources and rates were compared at various levels of N and K. The order of effectiveness was the same at all levels of applied N and K: MAP ≥ CSP > 30% CSP + 70% DCP > 10% CSP + 90% DCP. This indicates that on these soils, P was the chief limiting nutrient at all levels of N and K. However, yield levels and the precision of determining differences in effectiveness among sources relative to experimental error increased greatly at higher rates of applied N and K.These results show that effectiveness of P sources and also source differences relative to experimental error are greater at adequate than at deficient levels of nontest nutrients or other growth‐limiting factors. Adequate levels of nutrients for greenhouse pot experiments are much higher per pot equivalent than the normal recommended application rates for crops grown under field conditions.
Loess Deposits of the Eastern Shore of Maryland
Authors: Foss J. E. , Fanning D. S. , Miller F. P. , Wagner D. P. 
Published: July 2010

AbstractA silty mantle on the upper Eastern Shore of Maryland was studied to determine its origin and characteristics. Thickness of the silts was studied by selecting traverses in an east‐west direction from the Chesapeake Bay and also scattered borings between traverses. These deposits are believed to be loess; they are characterized by 50 to 75% silt‐sized particles. The material is also carbonatefree, nonstratified, and yellowish brown in color. In addition, the silty mantle shows a reduction in thickness and particle size with increasing distance from the Chesapeake Bay, which was the probable source area. In areas of thin loess (< 90 cm), increasing amounts of sand were apparently incorporated into the loess at the time of deposition. Based on 14C date of a 11A1b horizon of a buried paleosol below the loess, deposition of the silts took place after 10,520 ± 240 years B.P. Profile characteristics of soils developed in the loess show moderately well expressed argillic horizons with the soil in this study having an increase of 9% clay from the A to the B2t horizon or a B2t/A clay ratio of 1.65.
Soils of a Grassland‐Forest Ecotone in Eastern Nebraska
Authors: Al‐Barrak Saad , Lewis David T. 
Published: July 2010

AbstractIn Otoe County, in eastern Nebraska, loessal soils on very steep slopes along the bluffs of the valley of the Missouri River exhibit weakly developed characteristics that are often associated with soils formed under deciduous forests. While these soils are Mollisols and show the dominant effects of the prairie, they have superimposed on the Mollisol characteristics what appear to be effects of having existed under forests for some time. In spite of the fact that these soils are on very steep slopes, they appear to be more highly weathered than adjacent soils on the divides. Evidence of this weathering includes a weakly developed A2 horizon and an argillic horizon, discontinuous cutans in the argillic horizon, gray coatings on ped surfaces to a depth of over 120 cm, and a much deeper solum than nearby soils within the Marshall and Monona Soil Series that show none of the above characteristics. Data suggest that the soils on the bluffs accumulate more moisture than those on the divides. The additional moisture, plus the effects of the forest may be the factors that are related to the differences in morphology.
A Technique for Studying the Kinetics of Adsorption in Suspensions
Authors: Zasoski R. J. , Burau R. G. 
Published: July 2010

AbstractExperimental techniques are described for study of both the kinetics and equilibria of metal sorption in colloidal managanese dioxide suspensions. The techniques and apparatus appear not to contaminate the reactants or to sorb metal ions onto the reaction vessel walls, even at pH's as high as 8 and metal concentrations in parts per billion. Products and reactants can be monitored simultaneously, and a complete accounting made of the ions thought to participate in the reaction. This system allows description of the sorption process from mixing to equilibrium. Repeated sequential sampling does not alter the ratio of solution to suspension, and accurate equilibrium data can be obtained from kinetic experiments over extended periods.
An Analysis of Sensible and Latent Heat Flow in a Partially Frozen Unsaturated Soil
Authors: Fuchs M. , Campbell G. S. , Papendick R. I. 
Published: July 2010

AbstractA heat flow theory has been developed which can be used to predict freezing and thawing cycles of a temperate soil. The latent heat of fusion is incorporated into the classical heat flow equation with the heat capacity and the thermal conductivity of the soil modified to include terms which account for the phase transformation. Computations for a Palouse silt loam soil show that the ice‐liquid phase transformation occurs over a defined temperature range where the apparent heat capacity and the apparent thermal conductivity may take on values which are several orders of magnitude larger than those either in the unfrozen or in the near completely frozen soil. The computations also indicate that the presence of solutes in the soil water significantly lowers the temperature range over which the freeze‐thaw zone develops and may allow considerable transport of water and heat at lower temperature than in the absence of solutes.
Development of a DTPA Soil Test for Zinc, Iron, Manganese, and Copper
Authors: Lindsay W. L. , Norvell W. A. 
Published: July 2010

AbstractA DTPA soil test was developed to identify near‐neutral and calcareous soils with insufficient available Zn, Fe, Mn, or Cu for maximum yields of crops. The extractant consists of 0.005M DTPA (diethylenetriaminepentaacetic acid), 0.1M triethanolamine, and 0.01M CaCl2, with a pH of 7.3. The soil test consists of shaking 10 g of air‐dry soil with 20 ml of extractant for 2 hours. The leachate is filtered, and Zn, Fe, Mn, and Cu are measured in the filtrate by atomic absorption spectrophotometry.The soil test successfully separated 77 Colorado soils on the basis of crop response to Zn, Fe, and Mn fertilizers. Critical nutrient levels must be determined separately for each crop using standardized procedures for soil preparation, grinding, and extraction. The critical levels for corn using the procedures reported herein were: 0.8 ppm for Zn, 4.5 ppm for Fe, and tentatively 1.0 ppm for Mn, and 0.2 ppm for Cu.Development of the soil test was based, in part, on theoretical considerations. The extractant is buffered at pH 7.30 and contains CaCl2 so that equilibrium with CaCO3 is established at a CO2 level about 10 times that of the atmosphere. Thus, the extractant precludes dissolution of CaCO3 and the release of occluded nutrients which are normally not available to plants. DTPA was selected as the chelating agent because it can effectively extract all four micronutrient metals. Factors such as pH, concentration of chelating agent, time of shaking, and temperature of extraction affect the amount of micronutrients extracted and were adjusted for maximum overall effectiveness.