bluuebunny/crossref_metadata_2025_split huggingface dataset:
Iron Oxide Mineralogy of Well‐drained Ultisols and Oxisols: I. Characterization of Iron Oxides in Soil Clays by Mössbauer Spectroscopy, X‐ray Diffractometry, and Selected Chemical Techniques
Authors: Bigham J. M. , Golden D. C. , Bowen L. H. , Buol S. W. , Weed S. B. 
Published: July 2010

AbstractThe iron oxides in subsoil clays (<0.2 µm) from five North Carolina Ultisols and two Brazilian Oxisols were analyzed by Mössbauer spectroscopy, X‐ray diffractometry, and selected chemical techniques. Goethite and hematite were identified as the dominant crystalline iron oxides in these clays. Partial substitution of Al(III) or other nonmagnetic ions for Fe(III) in the oxide structures caused reduced unit cell dimensions and subnormal effective internal magnetic fields. All samples exhibited strong superparamagnetic relaxation, a collapse of the Mössbauer magnetic splitting at ambient temperatures due to the ultrafine size of the oxide particles. Negligible amounts of iron were solubilized with acid ammonium oxalate; however, the Ultisol clays did contain significant amounts of silicate and/or interlayer iron that was not extractable with dithionite‐citrate‐bicarbonate.
Ammonia Exchange Over a Corn Crop
Authors: Denmead O. T. , Nulsen R. , Thurtell G. W. 
Published: July 2010

AbstractA micrometeorological technique was used to calculate the net transfer of NH3 between a corn crop and the atmosphere. On the 10 days of measurement, there was continual interchange of NH3 between crop and atmosphere with a strong indication of a diurnal cycle. Ammonia absorption by the plant‐soil system (downward transfer of NH3) predominated when the soil surface was dry, but sustained losses of NH3 (upward transfer) occurred when it was moist. Net absorption rates of 6.6 g N ha−1 hour−1 were calculated in the former period, and net losses of as much as 27.6 g N ha−1 hour−1 in the latter.
Chloride as a Factor in Mobilities of Ni(II), Cu(II), and Cd(II) in Soil
Authors: Doner H. E. 
Published: July 2010

AbstractAn investigation was undertaken to study the mobility of chlorocomplexes of Ni(II), Cu(II), and Cd(II) through soil. Soil columns were leached with 0.1, 0.2, 0.3, or 0.5M NaCl or NaClO4 solutions, each containing 10 µg/ml Ni(II), Cu(II), or Cd(II). Sodium perchlorate solutions were used as a comparison with NaCl at the same ionic strength since perchlorate is not considered to form complexes with the metals. Leachates from columns and soils were collected and analyzed. Mobility of all metals tested in chloride solutions was from 1.1 to 4 times greater than that in ClO4‐ solution. Chloride increased the mobility of Cd(II) the most which corresponds to its having the largest stability constants. Cooper (II) was slowest to appear in the leachate and was strongest adsorbed as evidenced by analysis of soil by digestion with either 4N HNO3 or acidified NH2OH‐HCl. These results showed that Cl‐ has a marked effect on the mobility of Cd(II) and, to a lesser extent, Ni(II) and Cu(II).
Structural Study of Humic Acids by X‐ray, Electron Spin Resonance, and Infrared Spectroscopy
Authors: Eltantawy I. M. , Baverez M. 
Published: July 2010

AbstractComposts and soil humic acid structures were examined by X‐ray, ESR, and IR methods. X‐ray diffraction showed three bands at 3.6, 2.1, and 1.2Å for the studied humic acids. These bands occured on the same position as the (002), (10), and (11) of carbon black and were ascribed to aromatic structure or graphite‐like layers. The presence of a 7.5Å band in the X‐ray diffraction of the examined humic acids indicate to nonaromatic fraction too. IR spectra confirm the presence of aromatic and aliphatic fractions associated with various types of functional groups including quinone groups. The nature of these groups are discussed. ESR signal G ∼ 2 indicates the presence of free radicals within the humic substances, whereas very little is known about the ESR signal at G ∼ 4.125 observed in the studied humic acids. This signal was attributed to Fe3+ chelated to humic substances. Compost and soil humic acids showed some structural differences.
Soil Temperatures in Adjacent High Elevation Forests and Meadows of Montana
Authors: Munn L. C. , Buchanan B. A. , Nielsen G. A. 
Published: July 2010

AbstractLittle published data exist reporting growing season soil temperatures under native vegetation in the Northern Rocky Mountains. In this study soil and air temperatures were measured in meadow, ecotone, and forest vegetation at 2,300 m elevation on the Bangtail Ridge near Bozeman, Montana. Mean annual soil temperature measured at 50 cm was 3.0°C for meadow sites, 2.6°C for ecotone, and 1.8°C for forest sites. Winter soil temperatures for the three types were similar but summer soil temperatures were nearly 5° C warmer in meadows than in forests and intermediate in the ecotone. Temperature variation was greatest in the meadow, intermediate in the ecotone, and least in the forest.
Flow Patterns During Extended Saturated Flow in Two, Undisturbed Swelling Clay Soils with Different Macrostructures
Authors: Bouma J. , Wösten J. H. M. 
Published: July 2010

AbstractLarge, undisturbed soil columns with an average height of 30 cm, a diameter of 25 cm, and with two different types of macrostructure were sampled in moist clay soil. Type 1 had vertical wormchannels and “rough” peds; type 2 had no worm channels and “smooth” peds. Flow patterns were characterized by repeatedly measuring Ksat and chloride breakthrough curves. Effective pore size distributions were calculated from the latter with the Klinkenberg procedure.Initial chloride breakthrough was most rapid in soil columns of type 1 after displacement of < 1 vol. % of the initial water, whereas 3 vol. % was displaced in type 2. Rapid chloride breakthrough was associated with a high volume of immobile water (60 vol. % and 2 vol. % for types 1 and 2 respectively). These phenomena can be explained by the presence of relatively large, continuous pores (particularly in type 1), that occupy only a small volume, as was confirmed by micromorphometric analysis and calculations of effective pore diameters. Application of a gypsum crust on soil columns of type 1 erased the differences with type 2. Crusts induced pressure potentials of __5 mbar, thus excluding the largest pores only. Extended ponding and associated continued swelling of peds did not change flow phenomena in type 1; in type 2, Ksat, the volume of immobile water and the effective pore diameters gradually decreased. Equivalent pore diameters, calculated from the soil moisture characteristic, were quite different from the effective diameters and could not be used to independently predict the breakthrough curves. Direct measurement of the latter and empirical extrapolation to soils with identical texture, mineralogy, and macrostructure is recommended for field work because replicate columns, sampled in a large geographical area and with the two types of macrostructure, showed significantly different flow phenomena.
Decomposition of Microbial Cells and Components in Soil and Their Stabilization Through Complexing with Model Humic Acid‐Type Phenolic Polymers
Authors: Nelson D. W. , Martin J. P. , Ervin J. O. 
Published: July 2010

AbstractAxenic cultures of bacteria, yeasts, and filamentous fungi were cultured on 14C‐glucose‐peptone medium. Cells were fractionated into cell wall and cytoplasm components and the components were complexed into model phenolic polymers or intimately mixed with preformed polymers prior to incubation in soil. Whole cells, cell walls, and cytoplasm fractions readily decomposed in soil; by 12 weeks of incubation from 50 to 79% of added 14C had evolved as 14CO2. Complexing of cell walls with polymers prepared from hydroxybenzoic acids and from hydroxytoluenes plus phenols reduced decomposition an average of 31 to 56%, respectively. Incorporating cytoplasm components into phenolic polymers reduced decomposition by an average of 49%. Intimately mixing cell walls with preformed polymers prepared from hydroxybenzoic acids and from hydroxytoluenes reduced decomposition an average of 14 and 28%, respectively. Mixing cytoplasm components with preformed polymers reduced decomposition by an average of 11%. Addition of whole cells or cellular components did not increase the decomposition of native soil organic matter. A higher proportion of residual 14C after incubation was recovered in the humic acid fraction in samples treated with cell walls complexed into phenolic polymers as compared to samples receiving uncomplexed cell walls. The implications of the study with regard to humus formation in soils are discussed.
Studies in Soil Manganese: II.: Extractable Manganese and Plant Uptake
Authors: Salcedo I. H. , Ellis B. G. , Lucas R. E. 
Published: July 2010

AbstractResults from a greenhouse pot experiment with 12 Michigan and Indiana soils of different characteristics were used to evaluate effectiveness of six extractants in predicting Mn uptake by soybean (Glycine max., cv. Hark) plants. Three levels of Mn as MnSO4 were added to each soil. Correlation between extractable Mn and uptake of Mn by plants decreased in the following order: 0.1N H3PO4 > steam/1N NH4OAc > 1.5M NH4H2PO4 > 0.1N HCl > 1N NH4OAc > 0.005M DTPA. Inclusion of pH and (Ca+Mg)/K ratio in prediction equations for each soil test increased percentages of variation in uptake data explained by the tests. Of the soil characteristics, Mn oxide fractions explained 66% of the variation in Mn uptake; inclusion of pH, bases ratio and total Mn in the equation accounted for 82% of this variation. Critical levels of extractable Mn in these soils were 12 ppm for 0.1N H3PO4 and 14 ppm for steam/1N NH4OAc or 1.5M NH4H2PO4.
Determination of Map Unit Composition by a Random Selection of Transects
Authors: Steers C. A. , Hajek B. F. 
Published: July 2010

AbstractA procedure for random sampling of mapping units and a statistical method for analyzing field data have been evaluated in five Alabama soil surveys. Taxonomic composition, consistency of delineations, and minimum number of transects needed for mapping unit characterization were determined by routine field examination, investigation of randomly selected transects, and statistical analysis of field data. The method requires that soil delineations be identified by landscape features with minimum traversing and observations and that potential transects (transects that may be selected for study) be located while mapping. Each delineation is represented by at least one potential transect; potential transects should traverse areas that represent the concept of a mapping unit. These transects make up the total available population of a mapping unit. From this population, randomly selected transects are sampled for detailed study. A minimum of 10 point observations is made on each. This procedure has shown that many mapping units in a survey area can be characterized at 80% confidence level by determining soil occurrence along less than 10 transects. In some cases it may be necessary to group soil series into similar interpretive units to reduce transect numbers and to present data that can be used.
Derivation of the Langmuir Equation for Ion Exchange Reactions in Soils
Authors: Sposito Garrison 
Published: July 2010

AbstractThe form of the Langmuir adsorption isotherm equation that is appropriate for ion exchange reactions is derived rigorously using statistical mechanics. It is shown that, in addition to the usual assumptions of localized, monolayer adsorption and no interactions between adsorbed ions, the restriction that the exchange process be one‐to‐one must be imposed. However, there is no inequality condition on the equilibrium solution concentrations and affinity parameters for the exchanging ions as has been suggested previously by several investigators. The Langmuir equation is valid for all nonzero values of the ion activities and affinity parameters.
Analytical Properties of the Soluble, Metal‐Complexing Fractions in Sludge‐Soil Mixtures: IV. Determination of Carboxyl Groups in Fulvic Acid
Authors: Holtzclaw Kenneth M. , Sposito Garrison 
Published: July 2010

AbstractA detailed experimental examination of the titration behavior and reaction with calcium acetate of a series of model organic acids led to the conclusion that the standard Ca(OAc)2 method for the determination of COOH groups in organic matter would be ineffective for sludge‐derived fulvic acid. In particular, it was shown that positive interferences from SO3H groups and acidic OH groups could be expected. A modified Ca(OAc)2 method was developed, consisting of: (i) conversion of fulvic acid to K/H fulvate, (ii) reaction with 1N calcium acetate, (iii) distillation of the acetic acid product, and (iv) titration of the acetic acid with 0.1N NaOH, in which these positive interferences do not occur. The modified method was applied successfully to two representative sludge‐derived fulvic acids, a soil‐derived fulvic acid, and two model humic polymers, all of which exhibited positive interferences with the standard Ca(OAc)2 method.
Bacterial Effects on Hydraulic Conductivity of Soils
Authors: Frankenberger W. T. , Troeh F. R. , Dumenil L. C. 
Published: July 2010

AbstractLaboratory experiments were performed to determine the relationship between bacterial pore clogging and soil hydraulic conductivity. When soils were submerged and hydraulic conductivity was plotted against time, the conductivity decreased and eventually stabilized at a constant value. The time required, the stable value, and the coefficient of variability were all influenced by the treatment applied to the soil. Sterile soils had the highest hydraulic conductivity and lowest C. V. of all treatments. The lowest hydraulic conductivity resulted from the addition of both a C and a N source. Continuous submergence and wetting and drying cycles were compared in their effects on hydraulic conductivity. A specific portion of the total biological activity (as determined by the acid phosphatase assay) and a selective bacterial population (accounted for by the medium used) were significantly and negatively correlated with hydraulic conductivity. As the bacterial population and phosphatase activity increased, the hydraulic conductivity decreased. The decrease in hydraulic conductivity under prolonged periods was primarily due to the excretion of metabolic products produced by bacteria within the soil pores.
Sand Content of Sand‐Soil‐Peat Mixtures for Turfgrass
Authors: Taylor D. H. , Blake G. R. 
Published: July 2010

AbstractSoils subjected to intensive foot‐traffic in areas used for sports usually require modification in order to maintain physical properties conducive to turfgrass growth. Commonly this is achieved by mixing soil with large quantities of sand and often some peat. Though present recommendations for quantity of sand are made using a great deal of experience, published supporting information is limited. The purpose of this research was to provide additional data.Seven sand‐soil‐peat mixtures were prepared giving a series that varied in sand contents from 75 to 97% by weight and in which organic matter remained essentially constant. A 35‐cm layer of sand‐soil‐peat mixture underlain by a gravel layer was placed in large pots and bentgrass (Agrostis palustris, Huds.) was established. Mixtures were watered as needed and were compacted daily for 53 days to simulate foot‐traffic, following which degree of compaction and infiltration rate were measured. Saturated hydraulic conductivities, variation in air‐filled pore volumes with water potential, and bulk densities of extracted core samples were also measured. Turfgrass yield and quality as well as root growth were evaluated.The data show that under the experimental conditions, sand‐soil‐peat mixtures having 87% or more sand by weight provided infiltration rates of 2.3 cm/hour or greater, and air‐filled porosities of 10% or greater at a soil water potential of −30 mbars. Sand‐soil‐peat mixtures with 87% sand gave as good turfgrass growth as those with greater amounts although the mixtures with > 90% sand supplied a greater safety margin for infiltration rate. Lower sand contents resulted in poorer grass yields, low infiltration rates and low drainable porosities.This minimum acceptable value of 87% sand by weight in a sand‐soil‐peat mixture was found using a predominantly medium sand, Nicollet loam soil and reed‐sedge peat. This value could vary with different sands and soils due to differing compaction characteristics and clay types.
Surface Textures of Quartz in Tropical Soils
Authors: Eswaran H. , Stoops G. 
Published: July 2010

AbstractStudies of the surface textures of quartz grains from a range of tropical soils show the appearance of striations, etch features and dissolution pits, increasing in size and/or quantity in the more weathered soil materials. These features show a crystallographic symmetry, most probably related to the crystallographic orientation of the grain.Monitoring the changes in a 19‐m deep weathering profile on granite showed that physical disintegration begins a few centimeters from the fresh rock. Chemical weathernig, which intensifies towards the soil surface, produces etching and dissolution pits. An additional phenomenon observed is the infusion of clayey materials and/or sesquioxides into the void system of the grains.
Incremental Soil Sampler for Use in Summer‐Fallowed Soils
Authors: Pikul J. L. , Allmaras R. R. , Fischbacher G. E. 
Published: July 2010

AbstractAn inexpensive, manually operated soil sampler has been developed for determining profiles of bulk density and water content in the top 10 cm of rod‐weeded summer‐fallowed soil. This sampler is especially suitable for sampling 1‐cm increments of loose dry soil overlying a firm soil at a 10‐ to 20‐cm depth. Field data obtained with this sampler showed true variations in soil moisture and bulk density with respect to depth and time even at depths of < 2 cm. Thus it is possible to estimate soil heat capacity over the whole 0‐ to 40‐cm profile.
The Swelling of Clay: I. Basic Concepts and Empirical Equations
Authors: Low Philip F. , Margheim James F. 
Published: July 2010

AbstractThe primary objective of the present study was to elucidate the relative contributions of exchangeable cations and surface forces to the swelling pressure, Π, of montmorillonite. To achieve this objective, measurements were made of the amount of water imbibed by Na‐saturated montmorillonites having different cation exchange capacities, b dimensions, and specific surface areas under applied pressures of 0, 1, 3, and 5 atm. The resulting data were used to develop the empirical equation (Π + 1) = exp [α/(mw/mm)] in which mw/mm is the mass ratio of water to montmorillonite and α is a linear function of the specific surface area and cation exchange capacity. Analysis of double‐layer theory in the light of this equation led to the conclusion that Π is affected less by exchangeable cations than by surface forces. It was suggested that exchangeable cations have a secondary effect because few of them dissociate from the layer surfaces.
Physical, Chemical, and Mineralogical Characteristics of Soils from Volcanic Ash in Northern Idaho: II. Phosphorus Sorption
Authors: Jones J. P. , Singh B. B. , Fosberg M. A. , Falen A. L. 
Published: July 2010

AbstractVolcanic ash soils from northern Idaho sorbed considerable amounts of P depending upon the parent material, physical, chemical, and mineralogical characteristics of the soils. Upper horizons of the soil derived from volcanic ash sorbed more P than did lower horizons which were derived from glacial sediment. The magnitude of P sorption was related to the extractable allophane content and quantity of concretions. The clay fraction adsorbed more P than the silt fraction. Sorption of P was due mainly to the presence of Al in concretions and the presence of higher amounts of amorphous materials. Iron, Al, Mn and other clay minerals contributed to the sorption capacity of the soils. Detailed roles of these factors in sorption of P by soils, clays, and concentrations are discussed.
Response of Three Irrigated Crops to Deep Tillage of a Semiarid Silt Loam
Authors: Cary J. W. , Rasmussen W. W. 
Published: July 2010

AbstractThe growth and water relations of winter wheat (Triticum aestivum L.), sugarbeets (Beta vulgaris L.) and corn (Zea mays L.) were studied after deepening the root zone in the Portneuf silt loam soil (Durixerollic calciorthid). Roots of annual plants are largely restricted by a hard layer that lies between the 0.4‐ and 1‐m depths. This layer was disrupted to a depth of 1.2 m by complete mixing, by chiseling, or by trenching on 0.6‐ and 1.2‐m centers. The treatments included two irrigation levels to show any advantage in crop water relations due to deeper rooting after deep tillage.Deeper rooting did develop on the deep‐tilled treatments, but the water supplied through net soil moisture depletion below 0.6 m was increased by < 4 cm, even when the crop was stressed for water late in the season. Deep soil water extraction was not always proportional to rooting density. Trenching on 0.6‐m centers was the most favorable treatment. Completely mixing the soil decreased yields, due in part to a lighter surface color and lower soil temperatures. Deep tillage seldom had a measurable effect on stomatal resistance or plant water potential. Management of this soil should be concentrated on providing the best possible root environment in the top 0.5 m of soil as this is the basis for maximum production in irrigated agriculture.
Managing Irrigated Winter Wheat Residues for Water Storage and Subsequent Dryland Grain Sorghum Production
Authors: Unger Paul W. , Wiese Allen F. 
Published: July 2010

AbstractBetter cropping and residue management systems are needed to improve precipitation‐use efficiency, minimize ground water depletion by irrigation, reduce pumping costs, and conserve energy. An irrigated winter wheat (Triticum aestivum L.)‐dryland grain sorghum [Sorghum bicolor L. (Moench)] cropping system was evaluated from 1972 to 1978 for water storage between wheat harvest and sorghum planting time and for subsequent grain sorghum growth and yields. No‐tillage, sweep, and disk methods were used during the 11‐month period between crops for wheat residue management and weed control. Precipitation stored as soil water during the 11 months of fallow averaged 35, 23, and 15%; available soil water contents to the 1.8‐m depth at sorghum planting averaged 21.7, 17.0, and 15.2 cm; sorghum grain yields averaged 3,140, 2,500, and 1,930 kg/ha; and water‐use efficiencies (WUE) for sorghum grain averaged 89, 77, and 66 kg/ha‐cm for the respective treatments. Sorghum forage yields were slightly higher than grain yields and, therefore, WUE for forage production were higher than for grain. The WUE for forage, however, decreased in the same order as for grain. Based on March 1978 production costs and grain prices, net returns (excluding land, taxes, and interest costs) for sorghum production were four and two times greater with no‐tillage and sweep tillage, respectively, than with disk tillage, the most widely used tillage method after irrigated wheat in the Southern Great Plains.
Relations Between Geometrical Properties of Glass Beads Media and Their Main ψ(θ) Hysteresis Loops
Authors: Laroussi Ch. , De Backer L. W. 
Published: July 2010

AbstractA main hysteresis loop in the volumetric water content (θ)‐suction (ψ) relation was determined experimentally for each of seven narrow size fractions of glass beads.Geometrical properties of these media were separately obtained with a Purcell apparatus based on mercury intrusion. A linear relation between the mean radius of beads and the mean radius of pores was established. A computational model was established to relate the main hysteresis loops of porous media to their geometrical properties. As a consequence a diagram expressed in nondimensional variables ψ* and θ* is proposed to predict the main hysteresis loop of a similar porous medium whose geometrical properties are deduced by similitude from one of the explored fractions.