bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Computer Simulation Model for Soil Genesis Applications
Authors: Levine Elissa R. , Ciolkosz Edward J. 
Published: July 2010

AbstractA two horizon computer model was developed to simulate leaching and acidification processes occurring in the solid phase of soils of humid, temperate climates. The model used linear equations to describe processes of sulfate adsorption, cation exchange, mineral weathering, and precipitation and dissolution of sesquioxides within the soil. Standard soil characterization and precipitation chemistry data were used as inputs to quantitatively predict changes in soil properties over time. T‐test analysis showed no significant difference at the 0.01 level between field values and those predicted by the model for base saturation, pH, and exchangeable cations. Two examples illustrated the application of the simulation model for soil genesis investigations. In the first example, acidic soils with low buffer capacities reached 60% base saturation (Ultic Hapludalfs) and 35% base saturation (Typic Hapludults) sooner than more basic soils. Using regression analysis (excluding soils with high amounts of exchangeable bases), base saturation decreased at a rate of 0.01%/yr under deciduous forest, and 0.02%/yr under coniferous forest at precipitation pH 4.1. At precipitation pH 5.5, the rate of change was much slower. In the second example, a change in soil pH over time was predicted at precipitation pH values of 4.1 and 5.5 under deciduous and coniferous forest vegetation. In all simulations, a “steady state” soil pH level was predicted, with soils under coniferous forest reaching this level sooner than those under deciduous forest. The steady state pH was lower under precipitation pH 4.1 than under pH 5.5.
Pedogenesis on the Edwards Plateau, Texas: I. Nature and Continuity of Parent Material
Authors: Rabenhorst M. C. , Wilding L. P. 
Published: July 2010

AbstractOf 15 pedons sampled on the Edwards Plateau of Texas, four were evaluated to determine the relative contribution of limestone weathering and airborne dust additions to soil formation. Although dusts were collected at measurable rates, silt grain morphology by scanning electron microscopy indicates that dusts are not accumulating on stable land surfaces. Euhedral, prismatic quartz grains were prominent components of residues from hard crystalline limestones. These grains were used as marker minerals in identifying parent material discontinuities. Quartz grain morphology, particle size distribution, elemental assay, and mineralogical data indicate lithologic discontinuities between the solum and subjacent limestone. Noncarbonate residues from petrocalcic horizons show varying degrees of similarity to the overlying sola and subjacent limestone. These soils appear to have formed from overlying limestone residuum, rather than from the underlying rock, which is different in character.
Soils of the Mall in Washington, DC: II. Genesis, Classification, and Mapping
Authors: Short J. R. , Fanning D. S. , Foss J. E. , Patterson J. C. 
Published: July 2010

AbstractThe soils on the Mall in Washington, DC have formed in about 6 m of miscellaneous fill deposited in repeated applications to the site during filling operations. Some limited pedogenesis has occurred; cambic, or cambic‐like B horizons were recognized in 26% of the profiles examined. Buried A horizons were found in 42% of the profiles. Classification of these soils using Soil Taxonomy alone was not satisfactory, as variations in organic matter with depth caused many of the soils to be placed in Fluv‐classes that connoted deposition of the parent material as alluvium and did not show unique accessory characteristics such as high bulk density. Proposed Urbic and Spolic subgroups of Udorthents and Ochrepts, with criteria to exclude them from Fluv‐classes, were utilized to classify these soils in a manner more consistent with their genesis and characteristics. A detailed soil map was prepared for the Mall using the proposed classification, and recommendations are made for mapping such highly manipulated areas.
Soil Nutrient Distribution Under and Adjacent to Singleleaf Pinyon Crowns
Authors: Everett Richard , Sharrow Steven , Thran Diana 
Published: July 2010

AbstractSoil nutrient concentrations were examined by horizon and distance from the tree stem of singleleaf pinyon (Pinus monophylla Torr. & Frem.). Documenting tree impact on the soil system provided insights into observed understory distribution patterns and variations in understory yield among soil microsites reported previously. Nutrient concentrations were greater under the crowns of trees than in soils between trees. Cluster analysis showed a maximum of 80% similarity in the distribution among exchangeable K+, Na+, Ca2+, Mg2+; extractable Zn2+, Cu2+, Mn2+, Fe3+, SO2‐4, PO3‐4; water soluble C, mineralizable‐N, pH, total soluble salts, and HCO‐3 in relation to soil depth and distance from the tree. Soil nutrients and other measured parameters segregated into two main clusters based on distribution patterns. Extractable PO3‐4, Fe3+, Mn2+, Cu2+, Zn2+, mineralizable‐N, water soluble C, and HCO‐3 were found in highest concentrations at the soil surface. Exchangeable Ca2+, Mg2+, Na+, K+, total soluble salts, and pH had highest values in subsurface horizons. Phosphate, K+, pH, total soluble salts, and Na+ significantly increased from the interspace soils to soils under the tree canopy. Phosphate, mineralizable‐N, Zn2+, Fe3+, and HCO‐3 declined rapidly in concentration from surface to subsurface horizons under the tree crown. Small root density was directly correlated to concentrations of mineralizable‐N, Zn2+, Mn2+, Cu2+, and Fe3+. Nutrient accumulation in conjunction with soil moisture, light, and allelopathic effects is speculated to confer a competitive advantage to the tree species at the expense of the associated understory.
Microwave Drying of Clays for X‐ray Diffraction Analysis
Authors: McCallister D. L. 
Published: July 2010

AbstractClay specimens were dried in a microwave oven on glass slides for x‐ray diffraction analysis and their patterns compared with those produced by the standard air‐drying method. Drying a smectite clay at 50 or 100% power, while rapid, produced an irregular clay surface and thus a poor quality diffraction pattern. Drying at 10% power, on the other hand, gave results equivalent to air drying for hydrous mica, smectite, and kaolinite clays. Even fully expanded, glycerol treated smectite was unaffected. Equally acceptable results were found for clays fractionated from an Upshur Bt2 horizon (fine, mixed, mesic Typic Hapludalfs); a Dandridge Bw1 horizon (clayey‐skeletal, mixed, mesic Lithic Ruptic Alfic Eutrochrepts); and a Westmoreland Bt2 horizon (fine‐loamy, mixed, mesic Ultic Hapludalfs). Rapid microwave drying of highly expansible clays from a Sharpsburg A horizon (fine, montmorillonitic, mesic Typic Hapludalfs) produced severe cracking, and a poor diffraction pattern, however. Microwave drying is a rapid method of producing specimens for x‐ray diffraction that does not affect any mineralogical properties visible in the diffractogram.
Percolation of Water Below an Irrigated Field
Authors: Rice Robert C. , Bowman Robert S. , Jaynes Dan B. 
Published: July 2010

AbstractDeep percolation of excess irrigation water was measured on a 0.62‐ha bare soil field. Deep percolation rates were determined from bromide added to the soil as a tracer. Core samples were taken at a depth to 2.7 m within 14 subplots after each irrigation. The depth of the maximum bromide concentration was uniformly distributed over the field. The average deep percolation rate was determined from the arithmetic mean of the tracer velocities and water content. The deep percolation rate calculated from the tracer velocities was about five times greater than determined from a water balance. The discrepancy between the tracer and water balance rates indicates that much of the water is moving in preferential paths. The water balance may overestimate the travel times of solutes and pollutants to the groundwater.
Soil‐water Determination Using Fiber Optics
Authors: Alessi R. S. , Prunty Lyle 
Published: July 2010

AbstractLight transmission through a 1.0‐mm diam quartz rod was found to be consistently related to the water status of the surrounding soil. Increased soil water resulted in decreased light transmission. The measurements were made using a modified Tempe cell containing glass beads and a very fine sandy loam soil material. The major components of the measurement system were a quartz rod, a lightemitting diode, a phototransistor, fiber optic cable, and connectors. The rod was in the shape of a loop centered in the cell and separated from direct contact with the surrounding soil by a small pocket of glass beads. Increasing levels of air pressure were applied at the Tempe cell inlet; drainage volume and instrument voltage were recorded at equilibrium. These data were analyzed separately with pressure and volumetric water content as independent variables. The voltage had a highly significant response to either independent variable and there was no significant difference between slopes or intercepts of regression lines across repeated desorption cycles. The range of volumetric water content measured in the experiment was 0.10 to 0.40. It was concluded that this technique of soil water measurement is feasible and deserves further research.
Effects of Phenolic Compounds on Nitrification in Soil
Authors: McCarty G. W. , Bremner J. M. 
Published: July 2010

AbstractRecent literature reflects considerable interest in the hypothesis that climax vegetation inhibits nitrification in soil and that this is due to the production in such vegetation of phenolic compounds that inhibit oxidation of NH+4 by nitrifying microorganisms. This hypothesis is based largely on the detection of tannins and phenolic acids in climax vegetation and in soil under such vegetation and on a report that very small amounts of these phenolic compounds completely inhibited NO‐2 production in an aqueous suspension of soil treated with (NH4)2SO4 and a nutrient solution suitable for growth of Nitrosomonas. To test the validity of this hypothesis, we studied the effects of different amounts of eight phenolic acids (p‐hydroxy‐benzoic acid, p‐coumaric acid, vanillic acid, ferulic acid, caffeic acid, ellagic acid, gallic acid, and chlorogenic acid) and five tannins [mangrove (Rhizophora mangle), quebracho (Quebrachia lorentzii), mimosa (Albizia julibrissin), chestnut (Castanea dentata), and sumac (Rhus coriaria)] on nitrification in soils incubated at 30°C after treatment with (NH4)2SO4. These studies provided no support for the hypothesis that climax vegetation inhibits nitrification in soil by producing phenolic compounds because they showed that phenolic acids and tannins did not significantly affect nitrification in soil even when the amounts applied greatly exceeded the amounts that have been reported to inhibit nitrification or to occur in soil.
Morphology and Mineralogy of a Pre‐Wisconsinan Paleosol in Iowa
Authors: Thompson Michael L. 
Published: July 2010

AbstractA paleosol covered by Wisconsinan till was studied to investigate pedological development before burial and to explore the effects of glacial overriding on certain morphological features. Samples of the paleosol were collected from an exposure in a limestone quarry. Particle size distribution, pH, total K2O content of the clay fraction, and clay mineralogical analyses were conducted on disturbed samples. Undisturbed samples were impregnated with a polyester resin and examined in thin section. The paleosol was divided into three zones that appeared to correlate with lithologic and/or pedologic discontinuities. The upper zone consisted of fine‐textured accretionary material that perhaps was deposited ahead of the advancing Wisconsinan ice. A lack of clay films in the field and pore argillans in thin section coupled with evidence of minimal smectite alteration suggested that this segment of the paleosolum was weakly developed. On the other hand, plasma separations, papules, and slickensides indicated that some physical reorganization of the soil had probably occurred. The middle zone, characterized by Al‐interlayered smectite in the clay fraction, illuviation argillans, and a sand content higher than the zone above, was interpreted to be an older segment of the paleosol developed in fine‐textured erosional debris of Pre‐Illinoian age under poorly drained conditions. The lower zone was heterogeneous with respect to both macromorphological and micromorphological features. It was interpreted to be a weakly weathered, Pre‐Illinoian till.
Variability of Nitrogen and Carbon in Surface Soils of Six Forest Types in the Oregon Cascades
Authors: McNabb D. H. , Cromack K. , Fredriksen R. L. 
Published: July 2010

AbstractSoil samples were collected from sites typical of six forest habitat types in the western Oregon Cascades to determine the variability in total N, C, and mineralizable N. Within each type, 20 samples of surface soil (0‐15 cm deep) were removed from around the outside perimeter of a 0.25‐ha plot. Averages of 23, 28, and 70 samples were needed to estimate the population mean of total N, C, and mineralizable N, respectively, with an accuracy of ±10% at a 95% probability. Variability was not reduced by reporting data on the basis of mass per area rather than concentration, but the method of reporting data affected the relative ranking of sites. Within‐site variability was not generally related to microsite differences in slope or coarse fragment content.
Quantitative Evaluation of Feldspar Weathering in Two Boralfs (Gray Luvisols) from Saskatchewan
Authors: Mermut A. R. , Ghebre‐Egziabhier K. , St. Arnaud R. J. 
Published: July 2010

AbstractFine (0.10‐0.25 mm) and medium (0.25‐0.50 mm) sand size fractions of two Boralfs (Gray Luvisols) under Boreal forest were used in this study to characterize the nature of feldspars and the extent of their weathering in glacial till soils in northern Saskatchewan. Feldspars were separated into four different specific gravity fractions by heavy liquids. This facilitated subsequent x‐ray diffraction (XRD) and chemical analyses used for more accurate quantitative determination of feldspars. Distinctive etch pits were observed by scanning electron microscopy. Infilling of voids in the grains by mostly Fe oxides and some clay minerals was observed under the petrographic microscope. While there is evident recent weathering of feldspars within the solum horizons, there is also evidence of ancient weathering as observed in minerals within the parent materials. The studies verified the presence of microcline, orthoclase, and several solid solution series of plagioclase (mostly oligoclase with inclusions of labradorite‐anorthite series). Sodic plagioclases (An 10‐30) were dominant in both profiles, followed by K‐feldspars in Profile 1 and calcic plagioclases (An50‐100) in Profile 3; this confirmed some differences in mineral composition of the two soil parent materials. Stability of feldspars was calculated using a newly developed pedogenic index. As compared to the E horizons, the lower weathering rates in the Bt horizons were attributed to the illuvial clay, which may have played the role of a protective barrier around the feldspar.
Kinetics of Ion Exchange on Clay Minerals and Soil: I. Evaluation of Methods
Authors: Ogwada R. A. , Sparks D. L. 
Published: July 2010

AbstractThe effect of kinetic methodology on adsorption rate coefficients (ka) and energies of activation for adsorption (Eaa) were investigated using five different techniques. These techniques were: miscible displacement, batch, static, stirred, and vortex batch. Kinetics of K adsorption were studied on Ca‐saturated kaolinite, a Chester soil (fine‐loamy, mixed mesic Typic Hapludults) and vermiculite. The ka values were highest for kaolinite and lowest for vermiculite. The higher ka values observed for kaolinite would be expected since a relatively pure kaolin would exhibit only easily accessible planar surface sites for K exchange. The ka values for the Chester soil were a reflection of the intermediate properties of this soil between kaolinite and vermiculite. The type of kinetic technique greatly affected the time required for equilibrium to be attained in K adsorption. From greatest to least time, the order was: static > miscible displacement > batch > stirred > vortex batch. Both static and miscible displacement techniques yielded the lowest ka and Eaa values for all three colloids. This is primarily because these methods represent systems where the influence of diffusion on the rate of K adsorption is at its maximum. Only for kaolinite did the ka and Eaa values of both the stirred and batch techniques approximate, in magnitude, those of the vortex method. With the Chester soil and vermiculite, which contain appreciable interlayer sites, the stirred and batch techniques yielded ka and Eaa values much lower than those for the vortex batch method. These results indicate that in colloids where more significant intraparticle diffusion occurs, the batch or stirring technique as used in this study is not effective in eliminating the influence of diffusion.
Role of Extracellular Polysaccharide Production and Clays in the Desiccation Tolerance of Cowpea Bradyrhizobia
Authors: Hartel Peter G. , Alexander Martin 
Published: July 2010

AbstractA study was conducted to determine the roles of extracellular poly‐saccharide and clays in the desiccation tolerance of cowpea bradyrhizobia. Seven nonmucoid strains of cowpea Bradyrhizobium were more resistant to drying in a sandy soil than five mucoid strains. A significant correlation was not observed (r = 0.26) between the amount of extracellular polysaccharide produced by these strains and their desiccation tolerance in a sandy soil. Investigation of two strains showed that they survived better in two sandy soils subjected to slow than to rapid drying, but the rate of drying had little effect in quartz sand. The percentage survival of the two strains in both soils was less at an inoculum density of 109 than at 106 cells/g of soil, but the reverse was true in quartz sand. The effect of desiccation on the number of survivors was similar if the drying was carried out with sterile or nonsterile soil. At the lower inoculation density, survival of the two strains in quartz sand increased if the clay fractions from the soils were added. The clay fractions consisted primarily of kaolinite. When the clay percentage of Ibadan soil was reduced by adding sand, the survival of the two strains was similar to that of Maradi sand. Thus, survival was affected by the amount but not the type of clay. The data suggest that inoculation density and the length of drying are important in the survival of cowpea bradyrhizobia undergoing desiccation in soil, and biotic factors and extracellular polysaccharide production are unimportant. Clay is important because it affects drying time.
Inhibition of Nitrification in Soil by Acetylenic Compounds
Authors: McCarty G. W. , Bremner J. M. 
Published: July 2010

AbstractRecent work has shown that acetylene (ethyne) is a potent inhibitor of nitrification in soil. To discover if substituted acetylenes inhibit nitrification in soil, we determined the effects of seventeen monosubstituted (HC ≡ CR) acetylenes (propyne, 1‐butyne, 2‐ethynylpyridine, phenylacetylene, 3‐butyn‐2‐one, 1‐phenyl‐2‐propyn‐1‐ol, 1‐pentyne, 4‐phenyl‐1‐butyne, 5‐phenyl‐1‐pentyne, 1‐ethynylcycloh‐examine, 2‐propyn‐1‐ol, 2‐propyn‐1‐amine, 1‐hexyne, 3‐butyn‐1‐ol, 1‐heptyne, 1‐octyne, acetylene monocarboxylic acid) and of seven disubstituted (RC ≡ CR′) acetylenes (2‐butyne, 3‐phenyl‐2‐propyn‐1‐ol, diphenylacetylene, 2‐butyn‐1‐ol, 2‐butyn‐1,4‐diol, acetylene dicarboxylic acid, 2‐butynoic acid) on production of (NO‐3 + NO‐2)‐N in soils treated with (NH4)2SO4. The data obtained showed that most of the substituted acetylenes tested inhibited nitrification in soil and that some were potent inhibitors of nitrification. The results with the four gaseous compounds tested showed that acetylene, propyne, and 1‐butyne inhibited nitrification in soils at partial pressures as low as 0.1 or 1.0 Pa, whereas 2‐butyne had little or no effect on nitrification at partial pressures as high as 10 Pa. The data obtained with the 21 nongaseous compounds tested showed that 2‐ethynylpyridine, phenylacetylene, and 3‐butyn‐2‐one had the greatest inhibitory effect on nitrification and that acetylene monocarboxylic acid, acetylene dicarboxylic acid, and 2‐butynoic acid had the least effect. Studies to measure production of C2H2 in soils treated with the nongaseous compounds showed that the inhibition of nitrification observed with these compounds was not due to C2H2 formed by their decomposition in soil. Experiments reported indicate that 2‐ethynylpyridine and phenylacetylene compare favorably with nitrapyrin (N‐Serve) and etridiazole (Dwell) as soil nitrification inhibitors and have potential practical value for retarding nitrification of fertilizer N in soil.
Release of Nitrogen from Crimson Clover Residue under Two Tillage Systems
Authors: Wilson D. O. , Hargrove W. L. 
Published: July 2010

AbstractThe N contained in winter cover crops (particularly legumes) is a potentially important source of N for succeeding crops. The purpose of this study was to determine N release from crimson clover (Trifolium incarnatum L.) residue under no‐tillage and conventional tillage conditions. Residues contained in nylon mesh (53 µm) bags placed either on the surface of no‐tillage plots or buried at plowlayer depth in conventional tillage plots were removed for dry matter, C, and N determinations at 1, 2, 4, 8, and 16 weeks after placement in mid‐May. The rate of N disappearance was more rapid under conventional than no‐tillage conditions. The percentage of initial residue N remaining at 4 and 16 weeks under conventional tillage conditions was 40 and 31, respectively. The corresponding values for no‐tillage were 63 and 36% at 4 and 16 weeks. The C/N ratio of the residue remained relatively unchanged over the 16‐week period under no‐tillage conditions. However, under conventional tillage conditions, the C/N ratio declined from 15.9 to 12.7. Under humid, subtropical conditions, release of N from both surface and buried residue from winter legumes, is sufficiently rapid to be of significant benefit to the summer crop.
Physical Basis of the Length‐slope Factor in the Universal Soil Loss Equation
Authors: Moore Ian D. , Burch Gordon J. 
Published: July 2010

AbstractThe length‐slope factor in the universal soil loss equation (USLE) is a purely empirical relationship that was derived from an extensive data base. A physically based length‐slope factor was independently derived in this paper by using unit stream power theory to describe the erosion processes associated with sheet and rill flow on hill‐slopes. It was shown that the two length‐slope factors are equivalent. Therefore, the USLE length‐slope factor is a measure of the sediment transport capacity of runoff from the landscape, but fails to fully account for the hydrological processes that affect runoff and erosion. The strength of the theoretically derived length‐slope factor is that it explicitly accounts for the dual phenomena of catchment convergence and rilling. The empirically derived factor can not account for changes in either surface flow or erosion processes, nor slope geometry, and this may explain why the values derived for other factors in the USLE, especially soil erodibilities, have been found to be inconsistent.