bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermodynamic Evaluation of Amorphous Aluminosilicate Binding Agents in Fragipans of Western Kentucky
Authors: Karathanasis A. D. 
Published: July 2010

AbstractComposition of soil solutions in contact with fragipan and nonfragipan horizons of Fragiudalfs in western Kentucky were related to the composition of soil amorphous constituents removed by various extractants. Increased amorphous Si/Al ratios in fragipan horizons were correlated well with reduced pH4SiO4 solute functions. A Si‐rich amorphous aluminosilicate precipitate of the general formula [Al(OH)3](1 − x) [SiO2]x and with a molar fraction ranging from 0.55 to 1.00 is proposed to account for the rigidity of the fragipan horizons. Similar free Al‐rich amorphous aluminosilicate precipitates are suggested to control Al and Si activities in solutions of nonfragipan horizons with pH >4.5. Silica and Al activities of soil solutions with pH <4.5 are consistent with the solubility of crystalline soil minerals. The amorphous aluminosilicate precipitates are considered to be weathering products of feldspar dissolution reactions. The composition, solubility, and rigidity of the amorphous aluminosilicate precipitates are believed to be controlled by conditions of loess deposition and drainage. Iron, Mg, and Na appear to make only minor contributions to the binding amorphous aluminosilicate agent, with Na having the most active involvement in the cementation process.
A Solenoid‐Operated, Variable Intensity Rainfall Simulator
Authors: Miller W. P. 
Published: July 2010

AbstractA portable, variable‐intensity, low‐cost rainfall simulator is described for use in small pan runoff‐erosion studies, and which can be adapted to larger plot studies for field use. Intensity is controlled by electrically operated solenoid valves into which wide square spray nozzles are fitted. The opening and closing of the solenoid valves, controlled via switches operated by a rotating cam or microcomputer, varies the intensity of rainfall from 0.0004 mm s−1 to approximately 0.024 mm s−1, at 29 kPa water pressure. Coefficients of uniformity for 1 m2 plots under a single nozzle are 90 to 95%, and 85 to 90% for 1‐ by 3‐m field plots using a three nozzle system. Kinetic energy of the rainfall, determined from drop size distributions, is about 23 J m−2 mm−1, which is within the range for natural rainfall.
Soil Surface Roughness Effects on Radiation Reflectance and Soil Heat Flux
Authors: Potter K. N. , Horton R. , Cruse R. M. 
Published: July 2010

AbstractSoil surface roughness provides a mechanism to alter soil reflectance and the surface energy balance. A field study was conducted to determine the effect of surface roughness on energy absorption and energy partitioning at the soil surface. A range of surface roughness conditions was created by varying the intensity of secondary tillage after moldboard plowing. Parameters measured included spectral reflectance, net radiation, soil temperature, and soil heat flux. Reflectance of solar radiation decreased with increasing surface roughness, with the greatest differences occurring among radiation wavelengths of 850 and 1350 nm. Reflectance was similar between 400 and 850 nm. Reflectance from a visibly dry surface was increased up to 25% in some wavelengths 5 d after a 47‐mm rainfall event, possibly because of decreased surface roughness. Although net radiation increased with increased surface roughness, soil heat flux at 0.01‐m was similar for all roughness conditions. This indicates that the latent and/or sensible heat flux was increased by increasing surface roughness. Theoretical considerations indicate that increasing surface roughness results in greater transport of energy from the soil surface to the atmosphere. Relationships between the change in net radiation due to surface roughness and the partitioning of net radiation among the surface energy balance components are developed and presented graphically.
Cohesion Development in Disrupted Soils as Affected by Clay and Organic Matter Content and Temperature
Authors: Kemper W. D. , Rosenau R. C. , Dexter A. R. 
Published: July 2010

AbstractSoils were dispersed and separated into sand, silt, and clay fractions that were reconstituted to give mixtures of each soil with 5 to 40% clay. In the range from 0 to 35% clay, higher clay contents resulted in greater stability. Rate of cohesion recovery was over 10 times as fast at 90°C as it was at 23°C, showing that the processes involved are physical‐chemical rather than biological. Maximum rates of cohesion recovery occurred at moderate soil water tensions, probably because some tension is needed to pull the particles into direct contact, but a continuous water phase is also essential to allow diffusion of bonding agents to the contact points. Since diffusion rates in water increase 300%, while rate of cohesion recovery increased 1000% when temperature was raised from 23 to 90°C, other factors, such as higher solubilities at higher temperatures of compounds contributing bonding ions to the solution, probably play a role in the rate of cohesion recovery. Recovery of cohesion was more rapid in the soil with organic C contents of 0.004 kg/kg than in the soil with 0.012 kg/kg. When the organic matter was removed with H2O2 from the soil with 0.012 kg C/kg, its rate of cohesion recovery increased. Rate of cohesion recovery of this high organic matter soil was also increased by aging it at 0.1 kg H2O/kg soil compared to 0.2 kg/kg. A possible explanation is that organic coatings, tending to prevent direct contact and bonding of adjacent projections of mineral surfaces, are forced away from contact points by extremely strong forces that pull the adjacent minerals together when soil water tensions are high. When the higher organic matter soil had been consolidated by air‐drying and rehydrated, its rate of cohesion recovery was just as rapid as that of the soil with low organic matter.
Estimating Transport Parameters in Soils by a Maximum Likelihood Approach
Authors: Bresler Eshel , Naor Amos 
Published: July 2010

AbstractA maximum likelihood procedure that provides a powerful, convenient, and asymptotically unbiased means of estimating various salt transport parameters is briefly described. Details of estimating the dispersion coefficient or dispersivity and the volume of exclusion (per unit volume of soil) are specifically discussed. Data from laboratory column experiments are employed to illustrate the practical application of the estimation method and to compare with the least squares method. The uncertainty of estimating the parameters is incorporated in a systematic manner in the process of inference. The procedure can be expanded to implement additional solute transport parameters.
Transport and Ion Exchange of Calcium and Magnesium in an Aggregated Soil
Authors: Selim H. M. , Schulin R. , Flühler H. 
Published: July 2010

AbstractThe objective of this study was to describe the retention of Ca and Mg in an aggregated soil. Batch and transport experiments were carried out on two aggregate sizes (1–2 and 4–5 mm). These aggregates were separated by sieving an air‐dried Abist loam soil which was previously saturated with Ca ions. In the batch experiments, 0.005 M solutions containing various proportions of MgCl2 and CaCl2 were mixed with the soil for several time intervals up to 66 h. The dependence of ion retention on the time of reaction was not significant. For the transport experiments, a pulse of MgCl2 was introduced to soil columns which were saturated with a 0.005 M CaCl2 solution at a constant flux. The concentration of the pulse was either constant (0.005 M) or variable (from 0.005–0.05 M). Using independently measured parameters, we obtained good model descriptions of the transport of Ca and Mg in the soil. The model is based on ion‐exchange as the governing retention process with a measured cation exchange capacity (CEC) and selectivity coefficients using our batch data. Improvements in our predictions were achieved when the model was extended to the two‐region (mobile‐immobile) concept.
Influence of Organic Anions on the Speciation of Mononuclear and Polynuclear Aluminum by Ferron
Authors: Jardine P. M. , Zelazny L. W. 
Published: July 2010

AbstractThe kinetic reactions of ferron (8‐hydroxy‐7‐iodo‐5‐quinoline‐sulfonic acid) with unneutralized and partially neutralized Al solutions in the presence of various organic anions were investigated with the intent of distinguishing mononuclear and polynuclear Al. Mononuclear Al solutions containing malate, glutarate, succinate, salicylate, formate, malonate, and fulvate with ligand/Al molar ratios ranging from 0.4 to 7.5, reacted rapidly with ferron and were modeled using a single second‐order equation. Similarily, mononuclear Al solutions containing citrate, tartarate, and oxalate with ligand/Al molar ratios ⩽ 0.13, 0.08, and 0.38, respectively, also reacted rapidly with ferron and were modeled using a single second‐order expression. Model fitted ka values (rate of Al‐monomer reactions with ferron) for these organic‐Al solutions were similar to ka values determined for uncomplexed mononuclear Al solutions without added organic ligands. Increasing concentrations of citrate, tartarate, and oxalate that cause the ligand/Al molar ratios to exceed the critical values of 0.13, 0.08, and 0.38, respectively, form complexes with Al that are not easily degraded by ferron, thus limiting the credibility of accurate distinction between monomeric and polymeric Al. The interaction of ferron with Al‐polymers was not significantly affected by concentrations of organic anions whose ligand/Al molar ratio did not exceed these critical values. These conditions allowed the accurate distinction of mononuclear and polynuclear Al.
Chemical Modeling of Anion Competition on Oxides Using the Constant Capacitance Model‐Mixed‐ligand Approach
Authors: Goldberg Sabine , Traina Samuel J. 
Published: July 2010

AbstractThe constant capacitance model was used to describe selenite‐o‐phosphate and silicate‐o‐phosphate competition on synthetic goethite (α‐FeOOH) and synthetic gibbsite (Al(OH)3) by direct optimization of mixed‐ligand adsorption data. The model assumes ligand exchange mechanisms for selenite, o‐phosphate, and silicate adsorption on oxide surfaces. The computer program, FITEQL, was used to fit intrinsic surface complexation constants to the competitive adsorption data. Values for the intrinsic protonation‐dissociation constants, surface capacitance density, surface site density, and specific surface area had been determined previously. The constant capacitance model was able to represent competitive anion adsorption for selenite‐o‐phosphate over the pH range of 4 to 10 and for silicate‐o‐phosphate from pH 5.5 to 9.5. The fit to the experimental data using the mixed‐ligand approach was much better than that obtained by prediction from single anion systems. The intrinsic surface complexation constants for o‐phosphate adsorption were found to be dependent upon the surface composition of the adsorbent oxide. We suggest that this composition dependence is due to heterogeneity of surface adsorption sites. Our findings suggest the utility of mixed‐ligand modeling for describing anion competition reactions using direct optimization of competitive adsorption data.
The Solodic Subgroup: A Proposed Amendment to Soil Taxonomy
Authors: McQuaid B. F. , Schumacher B. A. , Miller B. J. 
Published: July 2010

AbstractResults of characterization and field studies in Louisiana have shown that some soils have ≧ 15% exchangeable Na (ESP) at depths greater than those defined for the natric horizons in Soil Taxonomy (Soil Survey Staff, 1975). In these soils, horizons meet all criteria for the natric horizon with the exception of depth which ranges from 40 to more than 125 cm below the top of the argillic horizon. In many areas, reduction in crop yields of deep rooting annual or perennial plants growing in these soils is attributed to large quantities of exchangeable Na. It is proposed that a Solodic subgroup be included as an amendment to Soil Taxonomy to accommodate soils having an ESP of ≧15 (SAR ≧ 13) in some subhorizon within 1.25 m of the surface or an ESP ≧ 6 (SAR ≧ 5) and <15 (SAR < 13) within the upper 40 cm of the argillic horizon. The proposed subgroup does not affect the classification of soils with natric horizons.
Soil Temperature Profiles of Two Alaskan Soils
Authors: Ping C. L. 
Published: July 2010

AbstractSoil temperatures of a thawed phase of a Pergelic Cryaquept were measured with copper‐constantin thermocouples at 20, 50, 100, 150, 210, 240, and 300 cm under a fallow plot for 5 yr in Fairbanks, AK. Soil temperatures of a Typic Cryorthent were measured the same way at 5, 10, 20, 50, 100, 150, and 300 cm under both grass and fallow plots for 22 yr in Palmer, AK. Fairbanks has a wider amplitude in annual air temperature variation and colder mean annual air temperature than Palmer. The mean annual soil temperature at 50 cm in Fairbanks is slightly lower (2.1°C) than in Palmer (3.0°C) under fallow plots. The difference between mean annual air temperature (MAAT) and mean annual soil temperature (MAST) is greater in Fairbanks (4.7°C) than in Palmer (1.7°C). The mean summer soil temperature is 9.5°C in Fairbanks and 13.1°C in Palmer, and the mean winter soil temperatures are −3.1 and −3.2°C, respectively. These data suggest that soil temperatures in both locations generally reflect the fluctuations in air temperature during summer and autumn. In winter, Fairbanks experiences colder air temperature than Palmer, yet mean winter soil temperatures are nearly the same. Evidently soils in Fairbanks are protected by snow cover against further cooling throughout the winter while soils in Palmer lack such protection due to the “glacier” wind and the freezethaw cycles that reduce the snow cover. The records showed that snow on the ground rather than total snowfall is accountable for the difference in temperature profiles between the soils. Both soils have forest as native vegetation. The removal of forest cover caused warming up of the soils based on elevated MAST on fallow plots. The classification of a Typic Cryorthent is not affected by such an increase in MAST. The MAST of a Pergelic Cryaquept rose above O°C, and thus changed from the pergelic to cryic temperature regime. The drainage of the Pergelic Cryaquept has also been improved, from poorly to moderately well‐drained. Perennial grass cover resulted in higher mean annual soil temperatures. The data suggest that the pergelic soil temperature regime needs to be redefined and also a new pergelic great group be established to facilitate soil surveys and interpretations in permafrost areas.
Comparison of Soil Tests for Assessing Boron Toxicity to Alfalfa
Authors: Gestring W. D. , Soltanpour P.N. 
Published: July 2010

AbstractThree soils from Colorado that varied in texture and organic matter (OM) content were treated with sodium borate (Na2B4O7·10H2O) at rates of 0, 10, 20, and 40 mg B kg−1 soil. Alfalfa (Medicago sativa, ‘Ladak’, ‘Rambler’, ‘Riley’, and ‘Agate’) was planted in the soils in the greenhouse and cut twice at the 30% bloom stage. Plant tissue digests and soil extracts (ammonium bicarbonate‐diethylenetriaminepentaacetic acid [AB‐DTPA], saturation, hot water, and mannitol‐CaCl2) were analyzed for B using inductively coupled plasma atomic emission spectroscopy (ICP‐AES). Alfalfa yield was significantly (α = 0.01) reduced with increased B application rate in the Ascalon sandy loam and Ulysses loam soils, whereas no yield reduction was observed in the Keith silt loam soil (Aridic Argiustoll, Haplustoll, and Argiustoll, respectively). Yield response for the pooled soils were poorly correlated (r2 from 0.23–0.58) to the four soil extractants; however, yield reduction due to B toxicity corresponded to critical plant B levels of 850 mg B kg−1 and 975 mg B kg−1 for the first and second harvests, respectively. The inclusion of NH4OAc‐extractable Ca into the regression equation of soil B vs. yield significantly increased the correlation (r2 = 0.77). Multiple linear regression analysis utilizing Mallow's Cp statistic increased the adjusted coefficient of determination (R2) to 0.87 for all of the soil B extractants upon inclusion of soil variables (pH, % clay, OM content) into the equation. Although NH4OAc‐extractable Ca did not appear in any of the best subsets, this was probably the result of it's high correlation with percent clay (r2 = 0.98) and OM content (r2 = 0.98).
Soil Genesis in a Developmental Sequence of Soils Formed in Sillimanite Mica Schist Residuum
Authors: Schumacher Brian A. , Perkins H. F. 
Published: July 2010

AbstractDystochrepts formed in mica schist residuum occur on steeply sloping sideslopes, whereas associated Hapludults are found on gently sloping ridgetops in the Piedmont province of Georgia. In this study, morphological, physical, chemical, and mineralogical properties of Dystrochrepts and associated Hapludults were examined to determine the influence of weathering intensity differences within the pedon and across the Dystrochrept → Hapludult developmental sequence. More intense weathering at the soil surface has resulted in higher exchangeable Al contents, lower pH values, and a relative accumulation of total Si, quartz, sillimanite, opaque minerals, and clay‐sized mica and vermiculite. In contrast, biotite was more abundant at depth. Total Al was closely related to clay distribution within the pedon. Less intense weathering in the Dystrochrepts, apparently related to shorter development time, has led to coarser textured sola with higher base saturations, higher total Mg, K, and Na contents, and a greater abundance of fine sand‐sized biotite and K‐feldspar. Quartz in the fine sand fraction was concentrated in the Hapludult. Kaolinite was the dominant clay mineral in the Hapludult. Regularly interstratified mica‐vermiculite was identified in subsurface horizons of the Dystrochrept and is believed to be a transitory intermediate in the transformation of mica to vermiculite.
Soil Properties Influencing Corrosion of Steel in Texas Soils
Authors: Moore T. J. , Hallmark C. T. 
Published: July 2010

AbstractCorrosion of steel specimens was monitored in 15 Texas soils in order to test the current system for assessing soil corrosivity. Corrosion, measured in situ at two depths using electrical resistance probes, was a function of many soil properties and could not be adequately described using any single property. The current system, developed by the USDA‐SCS, which places soils into corrosion potential classes based on soil characterization data and descriptions, was found to overestimate corrosivity of many soils. A revised system was developed that more accurately predicted corrosion rates of buried steel under field conditions. Soil properties used in the revised system include electrical conductivity, texture, exchangeable acidity, and wetness class. When the two systems were tested using an independent set of data collected by the National Bureau of Standards, soil corrosion potential classes of the revised system correlated with actual corrosion better than the current SCS system.
Effects of Furrow Dikes on Water Conservation and Dryland Crop Yields
Authors: Jones Ordie R. , Clark R. Nolan 
Published: July 2010

AbstractEliminating or reducing storm runoff in the Southern Great Plains can increase soil‐water storage, decrease erosion, and increase crop yields. The primary objectives of this study were (i) to examine the potential of furrow dikes as a conservation practice to retain runoff and increase crop yields, and (ii) to examine the effects of furrow diking on sorghum [Sorghum bicolor (L.) Moench] and sunflower (Helianthus annuus L.) production. Analyses of 28 yr of runoff records show furrow diking has the potential to retain 25 to 30 mm of runoff annually. The maximum annual runoff retention by diking observed during the 14 crop years of research (three separate experiments conducted between 1980 and 1985) was 111 mm. The maximum increase in sorghum yield measured as a result of diking was 2.46 Mg/ha. Conditions responsible for maximum yield responses of sorghum to diking were: (i) annual cropping, (ii) large rainfall/runoff events occurring prior to or early in the growing season, and (iii) limited growing season precipitation. Diking increased annual cropped sorghum yields on graded and contour furrow treatments by 49 and 14%, respectively, whereas water use efficiencies were increased by 25 and 16%. Yields and water use efficiencies from diked treatments on graded and contour furrows were as great as yields and water use efficiencies from a leveled minibench treatment, indicating that from a crop production standpoint, furrow diking was as effective as land leveling in retaining runoff and increasing crop yields. Sunflower yields were increased significantly by diking during 1 yr out of 3 when sunflower was grown after 76 weeks of fallow, whereas sorghum yields were not affected by diking after fallow. Decreasing row spacing from 1.0 to 0.75 m resulted in a significant increase in the 3‐yr avg yield of sorghum and sunflower of 1.0 and 0.14 Mg/ha, respectively, when grown after fallow, indicating that considerable opportunity for improving summer crop production may exist simply by changing to a narrow row spacing. A regression equation relating runoff from graded furrows to runoff from contour flat‐tilled graded terraces showed increased runoff from graded furrows, particularly from small storms.
Infiltration and Soil Loss of Three Gypsum‐Amended Ultisols under Simulated Rainfall
Authors: Miller W. P. 
Published: July 2010

AbstractBy‐product phosphogypsum (PG) was applied to the surface of topsoil samples from three sandy Georgia Ultisols at a rate of 5 Mg ha−1 in 0.3‐m2 runoff trays to test the efficacy of this amendment in enhancing infiltration of these soils. Simulated rainfall was applied at 50 mm h−1 for 2.5 h in an initial 1‐h (dry) event and three subsequent 0.5‐h (wet) events applied 24 h later. In the absence of gypsum, infiltration rate stabilized at 10 mm h−1 for the Cecil soil (Typic Hapludults), 5 mm h−1 for the Wedowee (Typic Hapludults), and 1 mm h−1 for the Worsham (Typic Ochraquults), with surface crusting and sand sorting apparent on all the soils. Surface‐applied PG roughly doubled the final infiltration rate of the Cecil and Wedowee soils, and increased infiltration of the Worsham to a lesser degree. Cumulative and average infiltration was significantly higher on all of the PG‐amended soils. Soil loss on the Worsham and Wedowee soils was decreased by 50% with the use of PG, and was reduced by 30% on the Cecil. Sediment concentrations were somewhat lower during the wet events with PG treatment for the Worsham and Wedowee soils, showing that less detached soil was available for transport. Although sediment particle sizes for control soils were 15 to 30% clay and 60 to 75% silt, PG‐amended soils showed no clay‐sized sediment in the runoff, but higher silt contents. Electrical conductivity measurements of the runoff suggest the very low electrolyte concentrations in the untreated soils promote dispersion, resulting in pore blockage and high sediment transportability, whereas PG maintained a high enough electrolyte level (0.5–1.3 dS m−1) to keep soil clays flocculated, thereby reducing crusting and sediment availability.