bluuebunny/crossref_metadata_2025_split huggingface dataset:
Orientation of Planar Voids in Vertisols and Soils with Vertic Properties
Authors: Bui E. N. , Mermut A. R. 
Published: July 2010

AbstractThe length, orientation, and area percentage of planar voids >75 µm in soil thin sections of several Vertisols from India and Ghana, and clayey soils with vertic properties from Saskatchewan were measured using an image analyzer. Cumulative lengths of planar voids for 10° intervals were expressed as a percentage of total length and plotted in polar coordinates to show the orientation of these voids. The orientation of planar voids was anisotropic in all the soils studied. The percentage of vosepic plasmic fabric (porostriated birefringence fabric) was determined by averaging counts from 40 fields of view under a petrographic microscope. The clay soils from Saskatchewan showed a predominance of vertically oriented planar voids; these probably developed as shrinkage cracks during drying. In the Vertisols from India, in accord with parallelepiped natural structural aggregates described for this soil order, the dominant orientation of planar voids was at an angle of 15° to 60° oblique to the horizontal, in either direction of the first or second quadrant. In those from Ghana, planar voids were oriented at various oblique angles as well as vertically. Together with plasmic fabric analysis, planar void orientation patterns were useful in determining whether soils have been subjected to stress‐strain forces.
Morphology of Calcite Crystals in Clast Coatings From Four Soils in the Mojave Desert Region
Authors: Chadwick Oliver A. , Sowers Janet M. , Amundson Ronald G. 
Published: July 2010

AbstractPedogenic calcite‐crystal coatings on clasts were examined in four soils along an altitudinal gradient on Kyle Canyon alluvium in southern Nevada. Clast coatings were studied rather than matrix carbonate to avoid the effects of soil matrix on crystallization. Six crystal sizes and shapes were recognized and distinguished. Equant micrite was the dominant crystal form with similar abundance at all elevations. The distributions of five categories of spar and microspar appear to be influenced by altitudinally induced changes in effective moisture. In the drier, lower elevation soils, crystals were equant or parallel prismatic with irregular, interlocking boundaries while in the more moist, higher elevation soils they were randomly oriented, euhedral, prismatic and fibrous. There was little support for the supposition that Mg2+ substitution or increased (Mg + Ca)/HCO3 ratios in the precipitating solution produced crystal elongation.
Estimation of Unsaturated Hydraulic Conductivity from Field Sorptivity Measurements
Authors: White I. , Perroux K. M. 
Published: July 2010

AbstractMeasurement or estimation of the unsaturated hydraulic conductivity of soils, K(Ψ), is of central importance to the understanding of soil‐water flows in many areas of hydrology and agriculture. Here we derive approximations that relate K(Ψ) to sorptivity, S0, measured over a range of negative supply pressures. We test the approximations against the Green‐Ampt, Knight, and Broadbridge‐White models of soil hydraulic properties. The last model covers the range from a Green‐Ampt like model to the weakly nonlinear Knight model. One of the derived approximations is found to give K(Ψ) accurate to within 5% over the entire range of soil‐water potential and the full range of the single Broadbridge‐White model parameter. Comparison of estimates of K(Ψ) using this approximation with conventionally determined K(Ψ) for repacked and intact soil samples shows good agreement. In an application of the technique we use measurements of S0 to identify the effect of rain, falling at the end of a severe drought, on K(Ψ) of the surface soil. We adapt these measurements to pinpoint the changes in characteristic pore size brought about by the rain. In addition, we show how the macroscopic capillary length of a soil may be estimated from sorptivity measurements at any supply pressure. One of the principal advantages of the technique is that measurements of sorptivity sample shallow soil depths. The technique therefore is suited to layered soils, shallow surface soils and soil tillage studies.
Potassium in Atlantic Coastal Plain Soils: I. Soil Characterization and Distribution of Potassium
Authors: Parker D. R. , Sparks D. L. , Hendricks G. J. , Sadusky M. C. 
Published: July 2010

AbstractCorn (Zea mays L.) grown on sandy Atlantic Coastal Plain soils is often unresponsive to applications of K fertilizer. As part of a field study on the response of irrigated, intensively managed corn to K applications, we characterized four representative Hapludults from the Delaware Coastal Plain and evaluated their K status. The soils were generally quite sandy with maximum clay contents of 11.4 to 26.5%, had low (≤2.0%) organic matter contents, and had correspondingly low cation exchange capacities (1 to 4 cmolc kg−1 by summation). The clay fractions were dominated by kaolinite and hydroxy‐interlayered 2:1 expansible minerals; the latter may play a crucial role in the overall chemistry of K in these soils. The soils were quite high in total K, with means for the four soils (across horizons) ranging from 23.6 to 43.9 cmolc kg−1, and this was ascribed to the K‐rich parent material and relatively young age of these soils. Most (97–98%) of the total K was in mineral forms, and the majority (65–87%) was in the sand fractions, virtually all as K‐feldspars. Exchangeable and nonexchangeable (fixed) K levels were relatively low and were of comparable magnitude. Consideration of particle size distribution, K distributions, and published studies of weathering rates suggested that the sand fractions of these soils represent significant sources of plant‐available K.
Estimating Soil Salinity from Saturated Soil‐Paste Electrical Conductivity
Authors: Rhoades J. D. , Manteghi Nahid A. , Shouse P. J. , Alves W. J. 
Published: July 2010

AbstractA method is presented for estimating the electrical conductivity of the saturated soil‐paste extract (ECe) from measurement of the electrical conductivity of the saturated soil‐paste (ECp) and estimated saturated soil‐paste water content (SP), for purposes of soil salinity appraisal. The method is suitable for both field and laboratory applications. Empirical relations are provided to estimate values of several parameters required for the method. The appropriateness of the method was tested using two groups of soil samples, one of which varied widely in geographical sources and parent materials, in addition to texture and salinity. The method estimated the soil salinities very accurately (r2 > 0.9; slope ≈ 1.0; intercept ≈ 0.0).
Soil Electrical Conductivity and Soil Salinity: New Formulations and Calibrations
Authors: Rhoades J. D. , Manteghi N. A. , Shouse P. J. , Alves W. J. 
Published: July 2010

AbstractA new model describing the relation between bulk soil electrical conductivity (ECa), volumetric content (θw) and electrical conductivity of soil water (ECw) is given along with supporting evidence for its validity. The new model distinguishes between the water and salt present in the soil in the “immobile” (fine pores) and “mobile” (large pores) phases. It provides a possible physical meaning to the transmission coefficient (T) previously used in an earlier model and eliminates a limitation of that model which existed under conditions of low salinity. New empirical relations are provided to estimate the parameters needed in the new and old models in order to utilize them for diagnosing soil salinity, in terms of the electrical conductivity of the extract of saturated soil pastes (ECe).
Hydrogen Sulfide Production from Cysteine (Cystine) in Soil
Authors: Morra M. J. , Dick W. A. 
Published: July 2010

AbstractHydrogen sulfide (H2S) production in aerobic soils amended with cysteine (cystine) is thought to result from cystathionase γ‐lyase (EC 4.4.1.1) activity. This enzyme yields thiocysteine (2‐amino‐2‐carboxylethyl hydrodisulfide), which reacts spontaneously with free sulfhydryl groups to produce H2S. Hydrogen sulfide, however, may also be produced in soil as a result of sulfate reduction. This work was conducted to evaluate the physical and chemical parameters that affect H2S production in cystine‐amended soil and to test the hypothesis that sulfate reduction is involved. Hydrogen sulfide, evolved from 4 g of soil placed in a 25‐mL Erlenmeyer flask, was trapped in a center well containing pleated filter paper and 0.5 mL of 1 M zinc acetate. Three soils brought to a water potential of −0.033 MPa and incubated at 37 °C with 50 µmol L‐cystine evolved 2.08 to 3.62 mg H2S‐S kg−1 soil 24 h−1. Maximum rate of H2S evolution occurred at 57°C. Propargylglycine (12.5 mmol kg−1 soil), a specific inhibitor of cystathionine γ‐lyase, reduced H2S evolution by 90 to 98%. Incubating the soils under waterlogged conditions also reduced H2S evolution in two of the three soils studied, with no change observed in the third soil. Hydrogen sulfide evolution was not affected by the addition of 12.5 mmol kg−1 soil of sulfate or nitrate, thus providing additional evidence that sulfate reduction was not involved. The apparent Michaelis constant (Km) value for H2S production from cystine in soil was 2.3 mmol kg−1 soil. It is concluded that production of H2S in soil, which is a significant reaction of the S cycle, can occur as a result of the mineralization of cysteine (cystine) via participation of the enzyme cystathionine γ‐lyase.
Pedogenic Carbonates in a Calciaquoll Associated with a Recharge Wetland
Authors: Knuteson J. A. , Richardson J. L. , Patterson D. D. , Prunty Lyle 
Published: July 2010

AbstractCalcic horizon formation was studied in an Aeric Calciaquoll (Bearden series) adjacent to an occasionally ponded Typic Argiaquoll (Lindaas series) on the Lake Agassiz Plain of eastern North Dakota. Carbonates in the Calciaquoll accumulated from groundwater additions. Soil water monitoring during a year with near‐normal rainfall and temperatures showed that an upward soil water flux existed during a 13‐wk period from late spring through midsummer. Unsaturated hydraulic conductivity (UHC) values indicated that the 2BC horizon controlled upward water flux in this soil. Upward water movement through this horizon during the 14‐wk period was estimated to be 36 mm. In late summer, evapotranspirative demand far exceeded the UHC of the horizon. As the soil dried, UHC values were further reduced. Assuming time of soil formation of 4000 to 9000 yr and detrital carbonate mineral levels of 10 to 15% by weight, annual additions of calcium carbonate equivalent (CCE) to the calcic horizon range from 0.1 to 0.2 mol m−2 yr−1 in this soil based on the amount of carbonate in the calcic horizon. Annual average levels of CCE in rising groundwater must be between 2.6 and 8.2 mmol kg−1 for the observed amount of carbonate to accumulate. The current amount of CCE in calcic horizon soil solution, as estimated by mathematically concentrating saturation past soluble ions to the observed constant water content, was 3.5 mmol kg−1, a value within the range estimated.
Landscape and Soil Property Effects on Corn Grain Yield Response to Tillage
Authors: Simmons F. W. , Cassel D. K. , Daniels R. B. 
Published: July 2010

AbstractDeep tillage practices such as chiseling and in‐row subsoiling generally increase crop yields on well‐drained sandy soils of the Atlantic Coastal Plain. Although attempts have been made to relate deep tillage response to measurable soil physical and chemical properties, little information is available relating within field corn (Zea mays L.) yield responses to topographic factors. This study was initiated to analyze the interactive effects of landscape and soil properties with tillage treatment on corn yields. Disking (D), chiseling (C), and in‐row subsoiling/bedding (SB) tillage treatments were applied across a Norfolk‐Wagram (Typic and Arenic Paleudults) complex. Grain and stover yields and grain weights, were measured in 1984 and 1985. Deep tillage provided a 25% yield increase compared to disking both years. Of all soil‐related variables examined, in‐row curvature explained the most yield variability. Grain yields in concave plots were more sensitive to changes in curvature than those in convex plots. Landscape influence on yields was greatest in 1985, a year with severe early season drought. Yield components at footslope and deep linear slope positions were greater than those of the interfluve and shallow linear slope positions. At the footslope position in 1984, SB increased yields more than C, suggesting that SB promotes higher yields than C when soil moisture conditions are favorable. Shallow tillage (treatment D) was the most susceptible of the three tillage treatments to yield reductions at drought‐prone landscape positions.
Oxygen Flux, Air‐filled Porosity, and Bulk Density as Indices of Vertisol Structure
Authors: Hodgson A. S. , MacLeod D. A. 
Published: July 2010

AbstractThe structure of irrigated Vertisols in Australia is frequently damaged by cultivating wet soil. This may reduce crop growth and yield, but there is a lack of suitable indices that characterize the physical damage to the soil. Oxygen flux density (F), air‐filled porosity (ε), and bulk density (ρb) were compared as indices of soil structure in undisturbed soil cores of a cracking gray clay (Vertisol, Typic Pellustert) at Narrabri, New South Wales, Australia. All three parameters were measured on the same cores. The soil had received two cultivation treatments: cultivating when wet and cultivating when dry. Samples were taken from each treatment on six occasions over a range of soil‐water content at five depth increments from 0 to 0.075 m to 0.4 to 0.475 m. Wet cultivation decreased F and ε relative to dry cultivation at most sampling times, but effects on ρb were smaller and inconsistent. All three parameters increased as gravimetric water content (θg) decreased. The variation of each parameter with respect to θg was obtained by linear regression, and the ratio of the slopes of these regressions between the two cultivation treatments was called the sensitivity ratio. Sensitivity ratios for F, ε, and ρb were 22.7, 6.9, and 1.2, respectively, for the 0.2‐ to 0.275‐m depth, which was most affected by cultivation treatments. Low sensitivity of ρb was related to low ε of the wet soil, which precluded compaction during wet cultivation. The sensitivity of ε was attributed to the greater structural shrinkage (conservation of pore volume on drying) observed in soil cultivated when dry compared to soil cultivated when wet. The high sensitivity of F is related to the dependence of F on ε and on the tortuosity and continuity of air‐filled pores, all of which appeared to be adversely affected by wet cultivation. Oxygen flux density is therefore recommended as the most sensitive of the three indices for detecting structural changes.
Soil Macropore Size Distribution from Water Breakthrough Curves
Authors: Radulovich R. , Solorzano E. , Sollins P. 
Published: July 2010

AbstractA new method for characterizing macropore size distribution is presented for a well‐aggregated Oxic Dystropept at La Selva, Costa Rica, known to exhibit macropore flow. Samples were taken as undisturbed cores from a secondary forest and an abandoned pasture. The method is based on hydraulic principles including the Poiseulle equation, and on water breakthrough curves obtained by timing and measuring water flow through the cores from a drained state (simulating field capacity) to a saturated steady‐state flow condition. Application of the method to the La Selva soil (0‐ to 20‐cm depth) yielded macropore radii between 50 and 200 µm, with a peak between 80 and 140 µm. The macropore size distributions thus obtained were coupled to micropore size distributions calculated from moisture release curves to yield a set of complete pore size distributions. The method is simple, and the results are based on dynamic measurements, making them more applicable to flow models.
Aluminum Fractionation of Soil Solutions from Unperturbed and Tephra‐Treated Spodosols, Cascade Range, Washington, USA
Authors: Dahlgren R. A. , Ugolini F. C. 
Published: July 2010

AbstractFractionation of aqueous Al was investigated in leachates from a subalpine Spodosol (Typic Cryohumod) located in the Cascade Range of Washington state. Leachates were collected from major genetic horizons with tension lysimeters during the fall, winter, and spring seasons. Solutions were collected from unperturbed profiles and from profiles that had received artificial additions of Mt. St. Helens tephra 4 yr prior to this study. Fractionation of Al was performed by a column cation exchange technique that minimized alterations in pH and ionic strength during the fractionation procedure. Organically complexed Al was the dominant form of soluble Al in the Oa, E, and Bhs horizons, while organically complexed and inorganic forms were nearly equal in the Bs horizon. These results are consistent with the metal‐fulvate theory of podzolization. The effects of tephra deposition were only apparent in the Bs horizon, where inorganic Al concentrations were twice the concentrations measured in nondisturbed profiles. Laboratory experiments showed that the ability of natural organic acids in soil solutions to complex Al increased as the pH was increased from 3.8 to 5.0. Aqueous Al3+, added as AlCl3 to solutions at pH = 4.5, was found primarily as organic complexes when organic C/metal atomic ratios were >50. At organic C/metal ratios <50, the additional Al was found primarily in inorganic forms.
A Comparison of Mineral Weathering Trends Between Two Management Systems on a Catena of Loess‐Derived Soils
Authors: Karathanasis A. D. , Wells K. L. 
Published: July 2010

AbstractThis study was an attempt to predict potential long‐term mineralogical transformation trends in soils under continuous no‐tillage management using the in situ soil solution composition as a sensitive index of changes occurring in the soil system. Mineralogical and soil solution compositions of surface and subsurface horizons of a catena of loess‐derived soils (Memphis, Grenada, Calloway) under continuous (16 yr) no‐till (NT) and conventional‐till (CT) management suggested a shift in weathering patterns as a result of the differential tillage management. This shift was evident primarily as a buffer effect of the NT management on drainage characteristics. Interstitial soil solutions of surface NT horizons were generally two to three times higher in Si and K than respective surface CT horizons. The elevated soluble Si and K concentrations maintained in the NT horizons correlated well with increases in organic matter content. The Si‐enrichment of the NT‐solutions combined with the reduced Al3+ activities, due to increased complexation, appeared to favor a hydroxyinterlayered vermiculite/vermiculite metastable state over the hydroxyinterlayered vermiculite/kaolinite of the CT system. This slowdown of the weathering process under continuous NT management should have important implications on K equilibria of these soils.
Microscopic and Ultramicroscopic Porosity of an Oxisol as Determined by Image Analysis and Water Retention
Authors: Bui E. N. , Mermut A. R. , Santos M. C. D. 
Published: July 2010

AbstractDetailed analysis of soil porosity in an Oxisol from Brazil was performed by image analysis in order to understand the unique water retention behavior of Oxisols. In addition to pores, the quantification of skeleton grains and plasma was made by image analysis of thin section micrographs. Due to the high quantity of skeleton grains and micro‐aggregates, interaggregate pores formed a network of interconnected simple and compound packing voids. Interaggregate porosity was an average of 39% for the profile. Micro‐aggregates of about 50‐ to 100‐µm in size were impregnated with Spurr's resin and ultrathin sections were made to measure ultramicroscopic pores. Image analysis of the transmission electron microscope (TEM) micrographs indicated approximately 9% intra‐aggregate pores. Ultramicroscopic pores were formed by the arrangement of kaolinite, halloysite and Fe‐ and Ti‐bearing minerals, with an average area of 1250 nm2. Their circularity was low, reflecting their irregular outline and high number of protrusions. The combined use of petrographic, TEM and image analysis techniques can complement other methods used to determine soil porosity and can provide a better understanding of the nature of the porosity of soils because it allows for quantification of size and shape of microscopic and ultramicroscopic pores as well as visual appreciation of their spatial arrangement.
Spatial Variability of Saturated Hydraulic Conductivity of the Subsoil of Two Forested Watersheds
Authors: Wilson G. V. , Alfonsi James M. , Jardine P. M. 
Published: July 2010

AbstractSubsurface flow has been shown to be greater in soils with spatially dependent hydraulic properties. The objective of this study was to quantify the spatial dependency in saturated hydraulic conductivity, Ksat, of two potential shallow waste disposal sites in eastern Tennessee. The Guelph Permeameter was used to determine Ksat of the subsoil of two forested watersheds, Walker Branch and Melton Branch. The simultaneous equations approach resulted in more than 50% negative Ksat values and was concluded to be invalid for these forested subsoils. As an alternative, flux density was used as an index of the saturated hydraulic conductivity for spatial correlation analysis and for determination of scaling factors. the spatial realizations of hydraulic conductivity for both watersheds were found to be intrinsic random functions of order zero, i.e., stationary, with a generalized covariance function for Walker Branch consisting of a pure nugget and for Melton Branch a nugget with a linear term. Semivariograms revealed no spatial dependency for separation distances >4.2 m at Walker Branch. Spatial dependency at Melton Branch for separation distances <30 m was described by an exponential model. The hydraulic conductivity of Walker Branch subsoils had a greater arithmetic mean (1.50 vs. 0.76 × 10−5 m s−1) and greater random variability than Melton Branch subsoils. These findings suggest that soils common to Walker Branch Watershed are hydrologically preferable for shallow waste disposal.
Diffuse Reflectance and Transmission Fourier Transform Infrared (DRIFT) Spectroscopy of Humic and Fulvic Acids
Authors: Baes A. U. , Bloom P. R. 
Published: July 2010

AbstractThe infrared spectra of a humic and a fulvic acid from a peat were obtained using diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy and were compared with transmission Fourier transform infrared (FTIR) spectra using KBr pellets. The DRIFT spectra showed similar resolution to KBr pellet transmission spectra. Elimination of interference due to water bands is easy with DRIFT and possible changes in the spectra due to modification of H bonding and ionization of carboxylate groups in the KBr pellet is avoided. Comparison of the DRIFT spectra of humic substances with the DRIFT spectra of some reference compounds suggests that phenolic OH groups in fulvic acids are more H‐bonded than those in humic acids, but the COOH groups are similarly H‐bonded. Comparison of the C=O stretching band with those of the reference compounds suggests that either intramolecular H‐bonding between COOH and phenolic OH is not significant in humic substances or alkyl COOH groups contribute considerably in the 1720 cm−1 band. The DRIFT spectra of Na and Cu(II) forms of humic acid powders show the capability of the method for metal‐ion binding studies. The possibility of using DRIFT spectroscopy for quantitative and semiquantitative evaluation is suggested by the similarity in the Kubelka‐Munk transformed DRIFT spectra and absorbance spectra using KBr pellets.