bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparison of Sampling Methods for Estimating Pit and Mound Microtopography
Authors: Kabrick J. M. , Meyers N. L. , McSweeney K. 
Published: July 2010

AbstractWe developed a method for making rapid estimates of pit and mound microtopography for characterizing research sites, soil map units, and ecological land types. We conducted this study in the drumlinized uplands of northeastern Wisconsin, where pit and mound microtopography is extensive. We established one 10 by 30 m grid and one 300‐m transect on each of four drumlins and identified a pit, a mound, or neither at nodes 1 m apart (300 observations per grid or transect). Pit and mound microtopography was estimated by calculating the proportion of pits, mounds, and points lacking evidence of pit and mound microtopography at nodes within each grid or transect. The optimal node spacing for grid and transect sampling methods was determined by repeatedly subsampling data derived from each method and identifying the lowest mean square error. The precision of grid sampling vs. transect sampling was determined by comparing the standard errors estimated with each method. Transects were more precise and time‐efficient than grids for estimating pit and mound microtopography percentages. Satisfactory results were obtained with 300‐m‐long transects with 3‐m node spacing. Transect methods appear applicable to the quantification of other types of microtopography.
Quantitative Aspects of Weathering and Neoformation in Selected Costa Rican Volcanic Soils
Authors: Nieuwenhuyse A. , van Breemen N. 
Published: July 2010

AbstractGains and losses of major elements in eight soil profiles developed on volcanic parent material in the perhumid tropical Atlantic lowland of Costa Rica were calculated from total element contents, assuming Ti to be immobile. Initially soil formation (0–500 yr) in Tropopsamments involves dilation of the sandy deposits by incorporation of organic matter and formation of structure and biopores, without detectable gains or losses of elements. In 2000‐ to 5000‐yr‐old sandy Hapludands, primary minerals are still abundant, but up to 20% of the mineral soil consists of x‐ray amorphous materials. Dilation continues and losses of Mg, Ca, Na, and K, and to a lesser degree Si, become measurable. Within 18 000 yr, a Melanudand develops, which is depleted of primary minerals and especially volcanic glass in the fine‐earth fraction. A mixture of short‐range order material, metal‐humus complexes, and gibbsite and kaolin minerals dominate its upper horizon, while gibbsite, halloysite, and short‐range order material are the most important secondary minerals at greater depths. Dilation of the soil mass prevails in the A horizon, while collapse has occurred in the B horizon. The Melanudand has lost considerable amounts of mobile elements: 50 to 85% of Si, Mg, Ca, Na, and K have been leached from the fine‐earth fraction. Within 125 000 yr, a Haploperox has formed (thought to have formed from Andisols); it is strongly collapsed and is dominated by gibbsite, kaolin minerals, and Fe (hydr) oxides. The upper meters are devoid of primary minerals except for small opaques. Under the prevailing environmental conditions, weathering and neoformation of primary volcanic minerals lead to almost complete dissolution and leaching of basic cations, probably within 20 000 to 50 000 yr. The Si and P mineral reserves are depleted considerably, but part is still present after such long time periods.
A Source of Systematic Error in Transient‐Flow Air Permeameter Measurements
Authors: Smith James E. , Robin Michel J. L. , Elrick David E. 
Published: July 2010

AbstractThe data from transient‐flow air permeameters often exhibit curvature in the theoretically linear plots of the natual log of pressure vs. time. This was originally attributed to errors in water manometer data caused by the inertia of the water in the manometer. The resulting recommendation was to ignore the early time data when calculating the air permeability of a soil by these methods. We have demonstrated and quantified that the exhibited curvature is a direct consequence of small changes in temperature in the source air tank as a result of the cooling of the expanding air during the permeability determination. This was accomplished by interfacing the air permeameter with a computer to collect pressure and temperature data at a relatively high frequency. The data acquisition procedure facilitated the calculation of the change in pressure and temperature with respect to time, which allowed the direct solution of the differential form of the equations describing the mass flux of air from the tank through the core. The data is compared with the theoretical relationship expected for the core based on air permeability determined using a steady‐state method.
Mechanisms of Acifluorfen Interaction with Humic Acid
Authors: Celi Luisella , Gennari Mara , Khan Shahamat U. , Schnitzer Morris 
Published: July 2010

AbstractThe interaction of the herbicide acifluorfen (AC; 5‐[2‐chloro‐4‐(trifluoromethyl)phenoxy]2‐nitrobenzoic acid) with a humic acid (HA) extracted from an undisturbed Ah horizon of a Haploboroll, was studied at different pHs. Both the HA and AC were methylated to determine the possible role of O‐containing functional groups in the adsorption process. Fourier‐transform infrared spectroscopy (FT‐IR) was employed to establish the mechanism of interaction. The interaction was affected by the pH of the system and by the methylation treatment, as they changed the polarity of both the HA and AC. A nonpolar environment at low pH or HA after methylation increased retention of AC by the humic materials. Carboxyl and phenolic groups of the HA negatively affect the interaction by repulsing the herbicide, as indicated by the increased adsorption by the methylated HA over the unmethylated HA. The herbicide appeared to interact with the HA by physical adsorption or weak chemical bonding that could readily be broken by extraction with water. The FT‐IR spectra suggested limited involvement of H bonding in the interaction processes.
Silica‐Cemented Terrace Edges, Central California Coast
Authors: Moody L. E. , Graham R. C. 
Published: July 2010

AbstractThe morphologic development of soils on marine terraces is a function of terrace age and geomorphic evolution. In this study, interrelationships between terrace landscape evolution and pedogenic silica cementation were investigated. Soil morphology, micromorphology, selective dissolution, penetration resistance, and hydraulic conductivity were used to determine the nature and extent of the cementation and evaluate the effect of cementation on soil properties. Soils on the interior part of the terrace (coarse‐loamy, mixed, thermic Typic Epiaquolls) contain plinthite, continuous throughout the entire terrace, cemented to the extent that it is only slowly permeable. A seasonally perched water table develops above the plinthite, and water seeps out of soils at the terrace edges. Some of these soils are cemented by opaline silica, in both channels and interstitial voids. The silica cementation extends inward into the terrace soils only 4 m, but at the terrace edge is strong enough to result in block fall as the predominant mechanism of scarp retreat. Redoximorphic Fe depletions are prominent in deeper horizons at the edge, but are absent from the interior. These depletions are formed through seasonal saturation and Fe reduction, by water seeping laterally through preferential flow paths in and adjacent to shrinkage cracks above the regolith‐bedrock contact. Contrasting morphology and chemistry between terrace interior and edge both result from, and cause, the interaction of pedogenic processes and landscape evolution. Contrasts between interior and edge soils suggest that caution is essential in using edge exposures as representative of soils under a geomorphic surface.
Tillage and Cover Crop Effects on Saturated and Unsaturated Transport of Fluometuron
Authors: Wilson G. V. , Yunsheng L. , Essington M. E. , Tyler D. D. , Selim H. M. 
Published: July 2010

AbstractThis study compared flow parameters for no‐till (NT) and tilled (T) soils from Louisiana and Tennessee, with hairy vetch (Vicia villosa Roth ssp. villosa) or no winter cover crop, under saturated and unsaturated conditions and the multireaction characteristics of fluometuron [N,N‐dimethyl‐N′‐[3‐(trifluoromethyl) phenyl] under unsaturated conditions. Miscible displacement experiments were conducted under saturated flow at a rate of 2.13 cm h−1, and under unsaturated conditions with a matric head of −50 cm at a flow rate of 0.21 cm h−1. Preferential flow through these loessial soils was evident by asymmetric breakthrough curves (BTC) under saturated conditions for both NT and T systems. The dispersion coefficients describing the nonreactive BTC under saturated conditions for the NT columns were generally lower than for the T columns. Dispersion was substantially higher for saturated flow, with Peclet numbers nearly an order of magnitude lower than for unsaturated flow. The dispersion coefficients under unsaturated conditions were generally two times larger for NT than T systems. Nonreactive solute transport characteristics for the T‐vetch cover systems were similar to NT systems with no cover crop under both saturated and unsaturated conditions. Adsorption was enhanced by NT in Louisiana, whereas adsorption was enhanced by vetch cover in Tennessee columns. Tillage and cover crops did not affect the instantaneous reactivity (Kd), whereas the irreversible rate coefficient (Kirr) was four times higher under the vetch system than the no‐cover system. The forward and backward kinetic adsorption coefficients were two times higher under NT than T systems.
Analytical Solution for One‐Dimensional Heat Conduction‐Convection Equation
Authors: Shao Mingan , Horton Robert , Jaynes D. B. 
Published: July 2010

AbstractCoupled conduction and convection heat transfer occurs in soil when a significant amount of water is moving continuously through soil. Prime examples are rainfall and irrigation. We developed an analytical solution for the heat conduction‐convection equation. The solution for the upper boundary of the first type is obtained by Fourier transformation. Results from the analytical solution are compared with data from a field infiltration experiment with natural temperature variations. The predicted temperature values are very similar to the observed values. Temperature changes with time for different soil depths are predicted from conduction‐convection theory and from conduction theory alone. During infiltration, convective heat transfer contributed significantly to the temperature changes at all soil depths monitored. The theory also quite accurately predicts temperature effects on surface infiltration.
Proton Adsorption on an Aluminum Oxide in the Presence of Bicarbonate
Authors: Schulthess C. P. , Wijnja H. , Swanson K. 
Published: July 2010

AbstractThe aqueous species of CO2 [CO2(aq), H2CO3, HCO−3 and CO2−3] are often ignored in adsorption studies despite the fact that CO2 in soil air can be hundreds of times greater than in the atmosphere. Adsorption studies that do not account for CO2 species may be under‐estimating proton adsorption in natural environments. The objective of this study was to discern the effect CO2 species have on proton adsorption to an Al oxide. The backtitration method was used to produce proton adsorption curves as a function of pH for samples of Al oxide with and without aqueous bicarbonate. Sodium chloride was used to vary the ionic strength. Proton adsorption increased in the presence of the bicarbonate below pH 9.7. The greater the concentration of bicarbonate, the greater the proton adsorption. The point of zero salt effect (PZSE = 8.30) was unaffected by the bicarbonate. The data presented show an approximate 1:1 stoichiometry for proton removal with inorganic‐C (HCO3 plus all other species) adsorption data. That is, this research directly quantified that every inorganic C adsorbed (expressed as HCO3 adsorbed) is accompanied by the removal of one proton (more precisely, 1.10 ± 0.28) from the aqueous phase by the Al oxide. Thus, the net removed from the liquid phase is equivalent to one H2CO3 in mass‐balanced terms. The use of traditional titration methods, rather than the backtitration method, resulted in a questionable pH‐dependent pattern that reflects the impact of Al dissolution on these measurements.
Interaction of Mugineic Acid with Iron (Hydr)oxides: Sulfate and Phosphate Influences
Authors: Hiradate S. , Inoue K. 
Published: July 2010

AbstractInteractions of 100 µmol L−1 mugineic acid (MA) with synthetically produced Fe (hydr)oxides (goethite, hematite, lepidocrocite, and ferrihydrite) as influenced by 100 mmol L−1 SO2−4 and phosphate were studied at equilibrium in the pH range from 3 to 11. In the presence of SO2−4, the concentrations of total MA [i.e., free MA + Fe(III)‐MA complexes] and Fe(III) dissolved by MA in the filtrates were higher than those in the presence of 100 mmol L−1 Cl− at pH < 7. Sulfate increased the formation of Fe(III)‐MA complexes indirectly by reducing the adsorption of MA and Fe(III)‐MA by the Fe (hydr)oxides. The adsorption of MA by the Fe (hydr)oxides and consequently the MA‐promoted dissolution of Fe(III) from ferrihydrite and lepidocrocite were greatly inhibited by the adsorption of phosphate. The slight dissolution of Fe(III) between pH 5 and 9 is partly attributed to the formation of soluble Fe(III)‐phosphate complexes. Although MA does not react directly with Fe (hydr)oxides in the presence of excess phosphate, MA would promote the dissolution reaction of Fe(III) by phosphate. The sequence of adsorption affinity for the Fe (hydr)oxides was found to be: phosphate >> MA > Fe(III)‐MA, SO2−4 > Cl−. Our results suggest that SO2−4 and especially phosphate applied as fertilizers may inhibit the MA‐promoted dissolution of Fe(III) from Fe (hydr)oxides in soils mainly by displacement of MA from the surface of Fe (hydr)oxides.
Spectroscopic Characterization of Pyrophosphate Incorporation during Extraction of Peat Humic Acids
Authors: Francioso O. , Ciavatta C. , Gessa C. , Tugnoli V. , Sanchez‐Cortes S. 
Published: July 2010

AbstractExtraction procedures represent a crucial point in the study of the molecular structure of humic substances (HS). Although alkaline extractants such as NaOH plus Na4P2O7 are usually employed for the extraction of the HS from soil and peat, little information concerning the interaction between extractants and humic acids is available. In this study, the results on the molecular structure of humic acids (HA) extracted and separated from a Sphagnum Irish peat sample with an alkaline pyrophosphate solution (0.1 M NaOH + 0.1 M Na4P2O7) are reported. The HA were redissolved in 5 mM NaCl, fractionated in six cut‐off fractions (nominal molecular weight: HA >300, 100–300, 50–100, 20–50, 10–20, and 5–10 kDa) using a tangential ultrafiltration system. All samples were dialyzed against distilled water and then freeze‐dried. Fourier‐transform infrared (FT‐IR) and 31P nuclear magnetic resonance (NMR) spectroscopies were applied to characterize the incorporation of pyrophosphate (PP) in both the unfractionated HA and in the six HA fractions. Spectroscopic analyses showed that it was possible to assign a given pattern of bands to define the structure of phosphate: PP was present only in the unfractionated HA, whereas orthophosphate was present in both the high molecular weight and lower molecular weight fractions. The high concentration of phosphate found in the lower molecular weight HA fractions has been attributed to the presence of metals and the oxygenated groups of HA. The changes in the relative intensity of the bands attributed to oxygenated functional groups observed in the FT‐IR spectra could be assigned to the interaction of phosphate groups with metal cations, which are involved in a coordination complex with the oxygenated groups.
Isotropic Smectite Coatings and Spheroids in Holocene Volcanic Deposits under Temperate Climate, France
Authors: Jongmans A. G. , Denaix L. , van Oort F. 
Published: July 2010

AbstractIsotropic clay coatings and spheroids were observed in Holocene, excessively drained, basaltic scoria deposits underlying a Hapludand at the Puy de la Vache volcano in the Massif Central in France. The morphology, chemistry, and mineralogy of these neoformed clay fabrics were studied by optical microscopy and analytical scanning and transmission electron microscopy. Optical microscopy of samples taken at 1‐ to 3‐m depth in the deposit showed thin, isotropic coatings and spheroids inside vesicles of the scoria fragments. In addition, isotropic coatings, occasionally up to 200 µm thick, covered scoria fragments, forming bridges between them. The isotropic coatings indicated a post‐depositional, pedogenic origin. The internal fabric of coatings and spheroids were similar, suggesting a common genetic relationship. Although isotropic behavior of coatings generally points to an amorphous mineralogical composition, analytical electron microscopy showed the presence of small (<1 µm) crinkly dioctahedral phyllosilicate particles, forming a honeycomb pattern. Periodically restricted drainage conditions in the numerous meso‐ and microvesicular pores of the scoriae were assumed to cause local and temporary stagnation of Si‐rich soil solutions and, consequently, to favor smectite formation despite the overall high permeability. Since scoria fragments at 3‐m depth were unaltered, formation of the secondary clay coatings was ascribed to co‐precipitation of leached elements liberated by weathering in the overlying Hapludand. The small size and random orientation patterns of the smectite clay particles and their occasional association with amorphous compounds explained the isotropic properties of the clay coatings when observed under the polarizing microscope.
Simple Method for Determining Cable Length Resistance in Time Domain Reflectometry Systems
Authors: Reece C. F. 
Published: July 2010

AbstractTime domain reflectometry (TDR) based electrical conductivity (EC) measurements underestimate solution conductivity (σ) as salinity increases unless a correction parameter, Rcable, is incorporated into the EC calculation. The parameter Rcable accounts for series resistance of cable, connectors, and cable tester. The main objective of this study was to propose and verify a simple method of directly measuring Rcable from the load resistance on waveguides that are shorted together. Also, the dependence of Rcable on cable length vs. other resistances was investigated. The parameter Rcable was found to be a function of cable length and a constant probe resistance. Errors caused by ignoring Rcable in EC determinations increased with both salinity and series resistance. Although there may be cases where Rcable has a negligible effect on EC determinations, there are also situations where it is important. This study shows that the measurement of Rcable is so simple that there is little reason not to routinely incorporate it in all TDR‐based EC determinations.
Complex Formation of Soil Minerals with Nitroaromatic Explosives and other π‐Acceptors
Authors: Weissmahr Kenneth W. , Haderlein Stefan B. , Schwarzenbach René P. 
Published: July 2010

AbstractThe ability of soil minerals to interact with organic solutes exhibiting π‐acceptor properties was studied using batch adsorption experiments. Among the major groups of naturally occurring minerals, only phyllosilicates were capable of forming strong electron donor‐acceptor (EDA) complexes with such solutes, including nitroaromatic explosives (e.g., trinitrotoluene [TNT]) and other priority pollutants. Depending on the minerals and the solutes involved, adsorption constants due to such EDA interactions may exceed those caused by nonspecific interactions by several orders of magnitude. Two major factors controlled the ability of phyllosilicates to form EDA complexes: the n‐donor properties of their siloxane oxygens and the accessibility of such sites for π‐acceptors. The donor properties of siloxane oxygens are enhanced by isomorphic substitution, but their accessibility for π‐acceptors is restricted by the steric effects of hydrated exchangeable cations. Relative adsorption constants (Kad values) for a given set of π‐acceptors were independent of the mineral structure, indicating that similar sites are involved in EDA complex formation on phyllosilicates. Thus, Kad values measured on any type of model phyllosilicate may be used to estimate the relative extent of adsorption of π‐acceptors to natural subsurface matrices, irrespective of the types and abundance of phyllosilicates present. Cation exchange on phyllosilicates is a crucial geochemical process that controls the accessibility of their siloxane sites to π‐acceptors due to the different sizes of the hydrated cations. Injection of electrolytes may be a promising but so far unexplored way to control the adsorption and thus the bioavailability and transport of TNT and other contaminants with significant π‐acceptor properties in the subsurface.
Critical Tissue Concentration and Chloride Requirements for Wheat
Authors: Engel R. E. , Bruckner P. L. , Eckhoff J. 
Published: July 2010

AbstractPrevious research in the Pacific Northwest and Great Plains has provided evidence that wheat (Triticum aestivum L.) yields are often improved by Cl− fertilization. Published reports on critical tissue concentrations and Cl− requirements for wheat are few in number. Our objectives were to define a critical plant Cl− concentration (head emergence) for maximum yield, develop a Cl− fertilizer recommendation, and determine the effect of Cl− fertilizer on grain protein. Thirty‐two field experiments (18 winter and 14 spring wheat) were conducted in Montana between 1988 and 1995. Experiments included comparisons with multiple cultivars and Cl− rates (0–90 kg ha−). Relative yield vs. plant Cl− concentration relationships were assessed from 219 cultivar × experiment episodes. Three zones of Cl− status were identified: (i) a deficiency zone, plant Cl− <1.0 g kg−1, where significant (P < 0.10) yield responses to applied Cl− occurred in 59 of 86 episodes (69%); (ii) an adequate Cl− status zone, plant Cl− ≥4.0 g kg−1, where yield responses occurred in only 2 of 44 episodes (<5%); and (iii) a critical range between these two zones, where responses were observed in 25 of 89 episodes (28%). Regression of plant Cl− concentration on soil (0–60 cm) plus fertilizer Cl− revealed that deficient, critical range, and adequate Cl− zones were associated with <7.5, 7.5 to 32, and ≥33 kg Cl− ha−1, respectively. The proposed guideline for wheat is to add sufficient Cl− to reach the upper end of the critical range (4.0 g kg−1 plant Cl−). This recommendation ensures adequate Cl− nutrition for maximum yield and kernel weight, although at some sites a slight reduction in grain protein (0.5%) may result.
Hydraulic Device for Transect Sampling Soil
Authors: Janssen K. A. , Havlin J. L. , Horstick E. H. 
Published: July 2010

AbstractA soil sampler capable of hydraulically coring, extracting, and sectioning rectangular columns of soil was constructed. The purpose was to facilitate our transect sampling of P in banded P and other nonuniform P‐fertilized soils. The soil sampler was constructed to attach to a tractor's three‐point hitch and to operate using the tractor's hydraulic system. The sampler consisted of a primary and secondary frame, two hydraulic cylinders, a rectangular‐shaped box corer, and a grid divider with press plate. The soil sampler performed well with our silt loam, claypan soil. Computer isoline maps of the concentrations of P in the soil cores we collected showed a wide diversity of distributions of P. Knowing the patterns of P and other nutrient distributions that result from different tillage and fertilization practices will be helpful for studying fertilizer‐placement effects on crops, and for formulating producer soil‐sampling strategies.