bluuebunny/crossref_metadata_2025_split huggingface dataset:
Spatial Distribution of Soil Heat Flux Under a Sour Cherry Tree
Authors: Fritton D. D. , Martsolf J. D. , Busscher W. J. 
Published: July 2010

AbstractThis paper presents data on the spatial variability of surface soil heat flux in an orchard (Prunus cerasus L.), evaluates the error involved in estimating the surface soil heat flux, and develops a method by which a spatial average may be taken. Surface soil heat flux was calculated from measurements of the heat flux at the approximately 5‐cm depth and of the heat stored above the heat flux plate. The heat flux plate calibrations were corrected for the thermal conductivity of the soil as measured in situ. Measurements were made at six sites both under an orchard tree and in the open between trees. Results showed that the nighttime flux under the tree was occasionally < 50% of the values measured in the open. In contrast, the daytime spatial and temporal variability was very high and occasionally a small upward flux was recorded under the trees while a near maximum downward flux was being recorded in the open or under the tree a short time earlier or later. A spatial average was calculated by weighting the soil heat flux values by the area of the orchard they represented using an integration procedure. The spatial averages showed that 50–80% of the nighttime net radiation loss from the orchard was derived from the soil.
Stability Constants of Cu2+, Pb2+, and Cd2+ Complexes with Humic Acids
Authors: Stevenson F. J. 
Published: July 2010

AbstractApplication was made of the potentiometric titration method for determining apparent stability constants for the complexes between Cu2+, Pb2+, and Cd2+ and three humic acids from diverse sources. Complexes of Cu2+ and Pb2+ were considerably more stable than those for Cd2+. Log K2 values, obtained from the relationship kj = bj/Ki (Ki = ionization constant) increased rather dramatically with decreasing salt concentration and were of the order of those reported in the literature for metal complexes with known biochemical compounds. Average log K2 values for the three humic acids (absence of neutral salts) were 8.9 for Cu2+, 8.7 for Pb2+, and 6.9 for Cd2+. Differences between humic acids in their ability to bind metal ions were slight. At least two major sites were involved in the binding of metal ions.
Phosphorus‐zinc Interaction in Relation to Absorption Rates of Phosphorus, Zinc, Copper, Manganese, and Iron in Corn
Authors: Safaya N. M. 
Published: July 2010

AbstractThe effects of P and Zn on growth, nutrient content in tops and roots, and the rates of absorption of P, Zn, Cu, Mn, and Fe per unit fresh weight of roots for two growth periods of corn (Zea mays L.) were studied in soil culture under greenhouse conditions. Visual symptoms of Zn deficiency appeared in plants when the level of applied P was raised to 75 µg P/g soil. Phosphate decreased tissue‐Zn concentration and Zn flux through roots. Zinc deficient plants had higher concentration of P in their tissues. Phosphate flux was mostly reduced with Zn, but during 27–48 days growth, Zn‐supplied plants retained near identical rates of P absorption (approximately 14 µg/g fresh root/day) irrespective of the level of P supplied. The rate of Cu absorption was reduced with both P and Zn as the plants aged. Manganese flux was initially stimulated by P but later on drastically reduced by Zn. Iron concentration in plants decreased with Zn application but significant reduction in Fe flux with Zn occurred during early growth of 25 ppm P‐supplied plants only. In general, nutrient fluxes diminished with plant age.
A New Method of Measuring Shrink‐Swell Potential Using Soil Pastes
Authors: Schafer William M. , Singer Michael J. 
Published: July 2010

AbstractA new method of measuring shrink‐swell potential of soil was developed using < 2‐mm sieved soil. Results obtained by this method were significantly correlated with COLE determined on natural soil clods (p < 0.001, r2 = 0.83). The new method is fast, requires little equipment, and should be a valuable test of shrink‐swell potential when clods cannot be obtained or when equipment for measuring COLE by the standard method is not available.
Evaluation of a Capillary Bundle Model for Describing Solute Dispersion in Aggregated Soils
Authors: Rao P. S. C. , Green R. E. , Ahuja L. R. , Davidson J. M. 
Published: July 2010

AbstractA simple capillary bundle model was evaluated for describing solute dispersion in two well‐aggregated soils of Hawaii. The model enables the use of pore‐water velocity distribution rather than an average pore‐water velocity. The pore‐size distribution was calculated from the soil water characteristic data. The position and relative shape of the break‐through curves calculated by the capillary bundle model was dependent more on the pore‐water velocity distribution than on dispersion owing to mixing within a pore. The predicted breakthrough curves were extremely skewed and did not describe the measured curves. The mixing of solute between adjacent flow paths, a process not accounted for in the model, apparently resulted in failure of the model. A measure of pore accessibility and interconnectedness of pore sequences is essential for quantitative description of the influence of soil pore geometry on solute dispersion.
Coupling Phenomena in Saturated Homo‐ionic Montmorillonite: II. Theoretical
Authors: Groenevelt P. H. , Elrick D. E. 
Published: July 2010

AbstractA theory is presented for the formulation of flux equations which describe the transport of water, salt, and electric charge through clays. This theory is based on thermodynamic principles. Model considerations lead to analytical expressions for the transport coefficients. These model calculations are based on electric double layer theory and produce a symmetric matrix of coefficients.The difference with former theories and model calculations is that the analysis is for electrodes which are reversible to the anions instead of the cations. The impact of this difference on the magnitude of some of the coefficients and on some of the physico‐chemical responses of the system is formidable.
Potassium Status of Some Alluvial Soils in Kentucky
Authors: Rasnake Monroe , Thomas Grant W. 
Published: July 2010

AbstractSix alluvial soils from Kentucky were intensively cropped to ‘Midland’ bermudagrass (Cynodon dactylon L. Pers.) to determine K availability in each soil. Potassium removal by the bermudagrass was compared to exchangeable K, to labile K estimated from Beckett quantity/intensity plots and to Gapon coefficients before and after cropping. Exchangeable K was not a good measure of uptake (r = 0.61 not significant), but labile K determined on soils before cropping and the Gapon coefficient after cropping gave highly significant linear correlations with K removed by bermudagrass. Exchangeable K after cropping changed an average of only 23 ppm K in the soils, but availability of K to plants was lowered drastically in all soils. This study shows that exchangeable K is an insensitive measurement of K availability to plants. Exchangeable K is a useable measurement only because wide ranges are used in determining classes of availability in soil testing.
Weathering of Serpentinite in Matanzas Province, Cuba: Mass Transfer Calculations and Irreversible Reaction Pathways
Authors: Dirven J. M. C. , van Schuylenborgh J. , van Breemen N. 
Published: July 2010

AbstractWeathering processes of serpentinite rock in the Province of Matanzas, Cuba, were studied by means of detailed mineralogical and chemical analyses of three pedons in a toposequence. The observed mineralogical composition was compared with that predicted theoretically by mass transfer calculations.All soils are extremely rich in ferric oxides. The lowest, poorly drained soil, a Gleysol, is smectitic and contains carbonates (magnesite and siderite). Its subsoil appears to meet the requirements for application of the model most closely. Here weathering proceeds at high CO2 concentrations leading to the formation of siderite, magnesite, smectite, and amorphous silica. Reduction of colluvial goethite to siderite may be involved also. Carbonates are lacking in the two well‐drained soils (Chromic Cambisols) which contain appreciable kaolinite in addition to smectite. This agrees with the stronger leaching at the well‐drained sites. Yet, the presence of amorphous silica implies that the rate of leaching only slightly exceeds the rate of weathering.Published water analyses from serpentinite areas are in good agreement with the water composition predicted by the model.
Geomorphic Surfaces and Soil Development in the Upper Rogue River Valley, Oregon
Authors: Parsons R. B. , Herriman R. C. 
Published: July 2010

AbstractSoil‐geomorphology studies in the upper Rogue River Valley in Jackson County, Oregon have related soil distribution to a step sequence of six geomorphic surfaces ranging in age from late Holocene to middle Pleistocene. Haploxerolls of the two flood plains have only A horizons. The soils of the low Holocene terrace have developed an argillic horizon within 2,350 years and are classified as Argixerolls. Durochrepts and Argixerolls of the two late Pleistocene surfaces have two kinds of periglacial patterned ground and one soil has a duripan that greatly affects land use. The middle Pleistocene surface has Haploxeralfs and Chromoxererts. The surfaces and soils are compared to those previously studied in the Willamette Valley.
Transport of Reactive Solutes through Multilayered Soils
Authors: Selim H. M. , Davidson J. M. , Rao P. S. C. 
Published: July 2010

AbstractSolute transport through saturated and unsaturated multilayed soils was studied using laboratory experiments and finite difference approximations of the solute transport equation. Soil‐water and physical characteristics as well as solute sorption properties were measured and/or calculated for each soil layer. Linear and nonlinear equilibrium and kinetic adsorption processes were used to predict adsorption in each layer. Water flux was assumed constant for water‐saturated and unsaturated layered soil profiles. For all adsorption processes considered, the calculated results showed that the order in which the soil layers were stratified in a water‐saturated profile did not influence the effluent solute concentration distribution. For unsaturated layered soil profiles, the results showed that effluent solute distributions can be predicted with an average water content within individual soil layers. Experimental results from the miscible displacement of 36Cl and 14C‐labeled 2,4‐D [(2,4‐dichlorophenoxy) acetic acid], through a two‐layered soil column (Norge loam and Eustis sand) supported the calculated results.
Predictions of the Soil Water Flux Based upon Field‐measured Soil‐water Properties
Authors: Warrick A. W. , Mullen G. J. , Nielsen D. R. 
Published: July 2010

AbstractPredictions of soil water flux are made taking into account spatial variability of the soil water parameters. A conductivity of the form K = Ko exp [α(θ − θo)] is utilized where θ is the volumetric water content with Ko and θg the values of hydraulic conductivity and water content for steady‐state intake from water ponded on the soil surface. The value of α is an empirical constant for each site and for each depth. Monte Carlo simulations are used to simulate the flux distribution from the simplified drainage equation JL = Ko (1 + α Ko t/L)‐1. The flux of JL is a random output dependent upon the stochastic nature of Ko and α. Long‐normal distributions of Ko and α are chosen from field data published for Panoche soil. Output of JL is approximately lognormal for all times studied. The mean value of JL is larger than the flux calculated using the average Ko and α values in the above equation. Sample numbers necessary to estimate the means of the flux at t = 0, 1, and 10 days are plotted. For t = 0, samples of 1,000, 100, and 50 result in estimates of JL within 16, 50, and 60% of the true mean 95% of the time. For t = 1 and 10 days similar figures for samples of 1,000, 100, and 50 are 4, 14, and 20%. Values of water content stored in the profile using the above equations are also examined as a random function. Unlike the flux values the range in values stays about the same for at least 20 days. The research points out a need for meaningful methods for sample stratification in order to reduce variances.
Fritted Glass Bead Materials as Tensiometers and Tension Plates
Authors: Chow T.L. 
Published: July 2010

AbstractA maximum temperature of 655°C which was reached in six steps with approximately 100°C/step/hour for 90 min was used to frit glass beads. Tensiometer or tension plate with desired dimension and operational characteristics can be constructed from the product. Uniformity tests on the product indicate negligible horizontal temperature variations during the fritting process and slow heat dissipation during the cooling phase tends to limit its thickness. Tests on the particle size distributions suggest that glass beads graded to very narrow distribution are required to produce fritted material with both the maximum saturated hydraulic conductivity and maximum air‐entry value.
Ion Exchange Reactions in Nondried Chambers Montmorillonite Hydroxy‐Aluminum Complexes
Authors: Keren Rami , Gast R. G. , Barnhisel Richard I. 
Published: July 2010

AbstractThe extent and mechanisms by which hydroxy‐Al interlayers may reduce the CEC of Chambers montmorillonite were studied using 22‐Na labeled clay. Clay‐hydroxy‐Al complexes were formed by added AlCl3 and NaOH at pH 7.5–9.5 (OH/Al ratio of about 2.80). AlCl3 was added at 4, 8, or 16 meq/g clay and either before, after, or simultaneously with NaOH. Addition of 16 meq AlCl3/g clay followed by NaOH resulted in CEC reductions of 60, 40, and 10% at pH 7.5, 8.5, and 9.5 as measured by Na adsorption. However, there was no trapped or nonexchangeable 22‐Na observed in any of the systems. Since the charge on the hydroxy‐Al is negligible at these pH's, the CEC reduction is apparently due to trapped Al. CEC reduction was much less when NaOH was added prior to rather than after AlCl3 even though X‐ray results indicated the presence of Al‐interlayers after drying in all except physical mixtures of hydroxy‐Al and clay. Since CEC reduction is apparently due to formation of hydroxy‐A1 interlayers and entrapment of A1 on the surface of the clay, it will vary with the amount and sequence in which AlCl3 and NaOH are added and the pH of the system due to varying solubility of the hydroxy‐Al and charge on the precipitate. As a result, studies where AlCl3 and NaOH are added simultaneously may give varying results depending on which is leading during the titration. Studies using 137‐Cs and 85‐Sr labeled Cs‐and Sr‐clay were conducted to further confirm the mechanism of hydroxy‐Al interlayer formation and subsequent CEC reduction.
Chemical Reduction of Nitrite and Nitrous Oxide by Ferrous Iron
Authors: Moraghan J. T. , Buresh R. J. 
Published: July 2010

AbstractLittle is known about the reduction of NO2‐ and N2O by Fe2+ in the pH range from 6 to 8, a range of importance in many natural environments. Reduction of 25 mg NO2‐‐N (approximate concentration=25 ppm) and 5 mg N2O‐N in a distilled‐water medium containing 800 mg Fe2+ with a helium atmosphere in the presence and absence of Cu2+ at pH 6 and 8 was studied at 26°C. Reduction of NO2‐ to N2O (the principal product), N2 and NH4+ was rapid and quantitive at pH 8 and not greatly affected by Cu2+. However, addition of Cu2+ decreased the mole ratio of N2O to N2 in the evolved gas mixture from 4.2 to 3.1. Reduction of NO2‐ at pH 6 was incomplete, but was favored by Cu2+ addition. Nitrous oxide was the dominant reduction product at this pH value. Small quantities of NO accumulated at pH 6.Irrespective of Cu2+ addition, N2O was stable in the Fe2+ medium at pH 6. In the pH 8‐system in the presence of Cu2+ 84% of the N2O was reduced to N2. Nitrous oxide was relatively stable at pH 8 in the absence of Cu2+. Small quantities of H2 accumulated in the atmospheres of vessels containing the pH 8, plus Cu2+ N2O − N treatment. No H2 accumulated in the NO2‐ series of treatments.
The Nitrogen Isotope Effect Associated with Nitrate and Nitrite Loss from Waterlogged Soils
Authors: Chien S. H. , Shearer Georgia , Kohl Daniel H. 
Published: July 2010

AbstractChanges in the isotopic composition of added NO3‐, during the course of its disappearance from two central Illinois soils are reported. The only known difference in the two soils is the cultural history of the fields from which they were taken. A large (approximately three‐fold) difference between the two soils was observed in the isotopic fractionation factor associated with NO3‐ loss. Large differences in the two soils with respect to both the rate of NO3‐ loss and the isotopic fractionation associated with it were apparently related to differences in the two fields rather than to temporal or spatial variation within the fields. Addition of glucose (1% with respect to dry soil weight) caused the difference between the two soils to disappear. It also appreciably reduced the apparent isotopic fraction factor in both soils.When NO2‐, rather than NO3‐, was added as substrate, the isotopic fractionation factor associated with its loss was the same in the two soils. The effect of glucose was similar whether NO3‐ or NO2‐ was the substrate; i.e., the isotopic fractionation factor was substantially reduced.Possible explanations for the observed variations in isotope effect associated with substrate loss are discussed. In addition, the implications of these variations for the study of denitrification in natural systems are discussed.
Evaluation of Soil Nitrogen Mineralization Potentials under Modified Field Conditions
Authors: Smith S. J. , Young L. B. , Miller G. E. 
Published: July 2010

AbstractAmounts of mineral N obtained by a calculation procedure and measurement in fallow plots were compared during two cropping seasons and annually with eight Oklahoma soils. The calculation procedure involved adjusting the N mineralization potentials for varying soil temperature and water content. The field N measurements involved the use of soil in plastic bags and glass filter tubes. Cropping season and annual field amounts for the eight soils, on the average, ranged from 54 to 78 ppm N. In general, the calculated amounts compared favorably to the field amounts, differences frequently being <10 ppm N. Calculated amounts correlated as well or better with the field amounts than a variety of other N availability indexes.
Soil Formation on Loess in Southwestern Indiana: II. Distribution of Clay and Free Oxides and Fragipan Formation
Authors: Harlan P. W. , Franzmeier D. P. , Roth C. B. 
Published: July 2010

AbstractFourteen soil profiles from southwestern Indiana were studied to determine the effects of loess thickness and natural soil drainage on the profile distribution of clay and free oxides (CBD‐extractable) of Fe, Al, Mn, and Si. In all soils, Fe and Al curves follow the clay curve, suggesting that the oxides are adsorbed on clays and move with them. Natural soil drainage had little effect on profile distribution of clay, Si or Fe. Free Al2O3 contents increase slightly with poorer drainage. With thinning loess, clay and free Fe2O3 distribution changes little, free Al2O3 contents increase slightly, free MnO2 curves have more pronounced minima and maxima, and free SiO2 increases significantly in fragipan horizons. We propose that free silica moves down the profile in solution and precipitates, possibly with aluminum hydrous oxides on clays. The resulting silica or alumino silicate binds particles together to form the hard, brittle soil material of fragipans.
Soil‐landscape Relationships in the Occidental Plateau of São Paulo State, Brazil: II. Soil Morphology, Genesis, and Classification
Authors: Lepsch I. F. , Buol S. W. , Daniels R. B. 
Published: July 2010

AbstractNine profiles representing the major soils in the Occidental Plateau of São Paulo State, Brazil, were characterized after detailed geomorphic and soil mapping were completed on a 70.8 km2 area. The stable upland geomorphic surface had Oxisols, surrounded by younger erosional surfaces with Ultisols, Alfisols, and Inceptisols. Mollisols formed where the erosional surfaces exposed calcareous sandstone. The argillic horizons of the Ultisols and Alfisols in these positions apparently have formed in material that would qualify as an oxic horizon before it was exposed. Laterally moving water at these sloping sites is believed to initiate free Fe removal and lessivage. Lateral water movement at the contact between the surficial deposits of oxic composition and the underlying calcareous sandstones appears to supply the bases for the Alfisols developed in the oxic material.Kaolinite dominates the clay mineralogy of the soils formed in unconsolidated deposits, but attapulgite and smectite are present in the calcareous sandstone. In the soils shallow to calcareous sandstone the attapulgite apparently has weathered to smectite within a few centimeters of the rock.
Gully Wall Stability in Loess‐derived Alluvium
Authors: Bradford J. M. , Piest R. F. 
Published: July 2010

AbstractA field study was made on an instrumented vertical slope to investigate the triggering mechanisms that initiate gully wall failure in loess‐derived alluvium. The relevance of hydrology, soil morphology, and soil mechanics to an understanding of gully slumping is examined. Conventional limit equilibrium slope stability methods were of little value in predicting failure volumes or in understanding the failure mechanics. The geometry and time of failure are greatly influenced by the structural features of loess‐derived alluvium and by the dependence of the shear strength on the pore water pressure within the soil.
On the Chemical Foundation of the Sodium Adsorption Ratio
Authors: Sposito Garrison , Mattigod Shas V. 
Published: July 2010

AbstractThe theoretical chemical basis of the sodium adsorption ratio (SAR) was examined in order to clarify two important issues that arise in connection with the problem of estimating potential sodium hazard: (i) the relation between SAR and the theory of cation exchange, and (ii) the implications of the universal practice of replacing SAR by what may be termed the practical SAR, which employs total concentrations of Na, Ca, and Mg instead of their free cationic concentrations. In regard to (i), it was confirmed that SAR can be given a chemical basis in terms of the Gapon cation exchange equilibrium constant which is provided in this paper with a rigorous derivation for the first time. The Gapon constant is shown to differ from the Vanselow exchange constant only because of the (arbitrary) convention adopted as to what entity is termed the ligand in the cation exchange reaction. In regard to (ii), it was shown through a direct calculation of SAR and the practical SAR for 161 different soil solutions or water extracts, utilizing a comprehensive chemical equilibrium computer program, that an exact functional relationship between the two parameters does not exist. Only a statistical correlation between SAR and practical SAR could be established because of the random variation in the composition of metal‐complexing anions in the soil solutions or water extracts. These anions reduce the free cationic concentrations of Na, Ca, and Mg, but their amounts are not chemically related to the presence of the metals and, therefore, to the value of the practical SAR. It follows that the practical SAR has no exact chemical relation to the theory of cation exchange, although its use in strictly empirical studies of Na hazard may be justified, in a statistical sense, by its acknowledged practical value.