bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of Inorganic 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 inorganic anions were investigated for the purpose of differentiating mononuclear and polynuclear Al. Development of a general order reaction function indicated that ferron interactions with Al were modeled best by second‐order rate expressions. Mononuclear Al solutions containing ClO‐4, Cl‐, NO‐3, SO2‐4, H2PO‐4, and F‐ with anion to Al molar ratios of 13, 21, 15, 5, 0.75, and 0.08, respectively, expressed similar reactions with ferron that conformed to a single second‐order reaction. Ferron interactions with partially neutralized Al‐anion solutions were described by two simultaneous second‐order reactions that provided the rate of Al‐polymer interactions with ferron, kb, and the mole fraction of mononuclear Al species present, fa. Distinction of mononuclear and polynuclear Al in partially neutralized solutions with various anions is possible using ferron if the H2PO‐4/Al and F‐/Al molar ratios do not exceed ≈ 0.75 and 0.08, respectively. Phosphate and F‐ concentrations that reduce these ratios and SO2‐4/Al ratios of ≈ 5 still form complexes with Al, but are easily degraded by ferron and react identically to uncomplexed mononuclear Al solutions. Such complexes must be accounted for if an estimate of toxic mononuclear Al [Al(H2O)3+6, AlOH(H2O)2+5, Al(OH)2(H2O)+4] is desired.
The Kinetics of Soil Potassium Desorption
Authors: Sharpley A. N. 
Published: July 2010

AbstractThe kinetics of soil K desorption from five soils was investigated at different water/soil ratios (10:1–400:1), over a short period of time (30 min), so that the results could be related to K desorption from agricultural soils to rainfall and drainage water. Potassium desorption (Kd) was logarithmically related to contact time (t) at any given water/soil ratio (W) and K addition and to W at any given contact time and K addition. Potassium desorption was also directly related to the initial exchangeable K content of soil. The following kinetic equation previously developed for soil P desorption, described soil K desorption, Kd = k K0 tα WB where k, α, and β are constants. The kinetic constants, k (r2 = 0.91), α (r2 = 0.91), and β (r2 = 0.92) were related to cation exchange capacity (CEC). Unlike previous K desorption equations—(i) the uniformity of k, α, and β for a given soil, in accounting for the effects of reaction time, water/soil ratio, and soil K status on K desorption, and (ii) the fact that the constants can be estimated from CEC—may allow application of the equation to the prediction of soil K desorption in surface and groundwater quality and plant nutrient uptake modeling.
Dispersion of Clay From Some Salt‐Affected, Arid Land Soil Aggregates
Authors: Yousaf M. , Ali O. M. , Rhoades J. D. 
Published: July 2010

AbstractThe dispersion characteristics of five arid land soils were determined upon reaction with solutions having various levels of electrolyte concentration, C (C = 0, 1, 4, 10, 30, 50, and 100 mmolcL−1), and sodium adsorption ratios, SAR (0, 5, 10, 20, and 40) with either Ca or Mg as the divalent counter‐ion. With either divalent cation, clay dispersion increased as SAR increased and C decreased. Greater dispersion was observed with Mg as the divalent counter‐ion due to the higher SAR and lower C levels, which resulted in the Mg systems compared to the Ca systems when the soils were reacted with comparable SAR and C treatment solutions. Dispersion threshold relations are concluded to be a useful criterion for screening soils for their sodicity hazard potentials.
Utilization of Anhydrous Ammonia Fixed by Clay Minerals and Soil Organic Matter
Authors: Norman R. J. , Gilmour J. T. 
Published: July 2010

AbstractA portion of anhydrous NH3 fertilizer applied to soil can be rendered nonexchangeable through fixation by clay minerals and soil organic matter. The plant availability of anhydrous NH3 fixed by these two soil fractions can be important agronomically if such fixation limits plant uptake of the fertilizer N. In this study, three soils (Drummer, Typic Haplaquoll; Blount, Aeric Ochraqualf; Cisne, Mollic Albaqualf) with clay and organic C contents ranging from 120 to 310 and 7.8 to 30.1 g kg−1, respectively, were injected with 15N‐labeled (2 atom % 15N) liquid anhydrous NH3 at a rate equivalent to 245 kg N ha−1. Soluble and exchangeable N were removed by leaching and the soil was cropped to ryegrass (Lolium multiflorum Lam.) in pots. Soils were analyzed before and after cropping for clay fixed N and organic matter fixed N. Four cuttings (harvests) were made at 3‐ to 4‐week intervals and roots were collected at the termination of the experiment. Aboveground dry matter, total N uptake, and fertilizer‐derived fixed N uptake (mg N pot−1) increased from the first to the second harvest and declined thereafter. Nitrogen recovered in the roots accounted for <11% of the total N and <7% of the fixed N utilized, and root dry matter accounted for 13 to 14% of the total dry matter produced. The ratio of fertilizer‐derived fixed N uptake to total N uptake declined with harvest suggesting that the fixed N became less available to the ryegrass with time. Fertilizer‐derived fixed N recovered in the ryegrass ranged from 19 to 26% of that originally fixed by the soil. The percentages of fertilizer‐derived clay fixed N removed from the soils during cropping (35–72%) were much larger than those of the fertilizer‐derived organic matter fixed N (<12%) suggesting that a majority of the plant uptake of fixed N originated in the clay fraction. Overall, fertilizer‐derived fixed N removal from the soils (21–30%) agreed well with plant uptake data.
Silica in Duric Soils: I. A Depositional Model
Authors: Chadwick O. A. , Hendricks D. M. , Nettleton W. D. 
Published: July 2010

AbstractMany alluvial Argids in central Nevada are cemented by illuvial silica and CaCO3. In loamy soils, microsite deposition of these authigenic components tends to be mutually exclusive, with silica being finely distributed throughout the plasma phase and calcite plugging packing voids formed by skeleton grains and root channels. The following model is proposed to explain the differences in depositional locations of silica and CaCO3. As soils dry, calcite precipitates rapidly in an ionic, diffusion‐controlled reaction while monosolicic acid, which requires greater activation energy for Si‐O bond breakage prior to precipitation, is concentrated in the solution phase. Monosilicic acid [Si(OH)4] can diffuse away from the evaporation front into smaller pores where, in contact with higher surface areas, it is absorbed onto clay, sesquioxide, and weathered primary mineral surfaces. Adsorbed silica is a template for further adsorption, and on drying, the precipitation of opaline silica (SiO2). The resulting SiO2 polymers form bonds between adjacent Si(OH)4 absorbing soil particles without necessarily plugging the voids between them. In contrast, CaCO3 plugs large voids by preferentially precipitating on previously deposited calcite crystals. Calcite is more easily redissolved than opaline silica and tends to move lower in the soil profile during wet years. Differences in precipitation processes result in silica‐rich, calcite‐poor argillic and upper duric horizons that grade to more strongly cemented duric/calcic horizons. The latter are characterized by horizontally distributed low calcite durinodes interspersed by more calcareous internodal areas.
Effect of Phenylphosphorodiamidate on Ammonia Volatilization as Affected by Soil Temperature and Rates and Distribution of Urea
Authors: O'Connor M‐J. , Hendrickson L. L. 
Published: July 2010

AbstractLaboratory incubation studies were conducted to evaluate the ability of phenylphosphorodiamidate (PPD) to inhibit urea hydrolysis and control NH3 volatilization losses. Complete hydrolysis of the uninhibited urea occurred within 8 d at all temperatures studied, and resulted in volatilization of more than 25% of the applied N within 10 d. Application of 20 mg PPD kg−1 of soil essentially prevented urea hydrolysis and resultant NH3 losses for 1, 2, 4, 8, and 17 d at 35, 25, 15, 10, and 5°C, respectively. This delay in the onset of NH3 losses due to PPD application kept NH3 losses during the first 10 d to <7% of the applied N at the three lower temperatures, but had little effect upon NH3 losses at 25 and 35°C. Such limited effectiveness of PPD at higher temperatures will no doubt reduce its utility for application to soils with surface temperatures above 25°C. Application of lower concentrations of urea gave reduced NH3 losses, both with and without PPD, likely due to a greater ability of other N transformations to compete for the reduced ammonium pools. Ammonia losses were also reduced, with and without PPD, when the urea was distributed throughout a larger soil volume, presumably due to a greater proportion of the urea being hydrolyzed below the immediate soil surface.
Low Temperature Dehydration Kinetics of Aluminum‐ and Calcium‐saturated Soil Clays
Authors: Karathanasis A. D. , Evangelou V. P. 
Published: July 2010

AbstractThe kinetic parameters of the isothermal dehydration of standard bentonitic and soil clays with montmorillonitic, mixed, illitic, and kaolinitic mineralogy were studied under Al and Ca saturation. The isothermal temperatures employed under a constant water vapor pressure of P/Po = 0.995 were 32, 38, 46, and 54°C. Dehydration rates under Al saturation were lower than those observed under Ca saturation in all clays. The differences were greater in clays with abundant interlayer space. The reaction mechanisms best describing the dehydration process were either a first‐order, random nucleation (F1) or a phase‐boundary controlled mechanism with spherical (R3) or cylindrical (R2) symmetry. The cylindrical symmetry, phase boundary was only applicable to the kaolinitic clays. The mechanisms were mostly independent of the type of the saturation (Al or Ca). Dehydration rate constants (k) were consistently lower and activation energies (Ea) of dehydration were generally higher in Al‐saturated clays. These kinetic relationships indicate that increased Al saturation of the exchange phase may slow down considerably the dehydration process by reducing dehydration rate constants and by requiring greater energy for the initiation of the desorption reaction.
Direct Measurement of Dinitrogen Evolution from Soil Using Nitrogen‐15 Emission Spectrometry
Authors: Kjeldby M. , Eriksen A. B. , Holtan‐Hartwig L. 
Published: July 2010

AbstractWhen a 15N‐enriched N source is added to the soil, denitrification results in a nonrandom distribution of N2 isotopes. As a result, it has been necessary to apply highly enriched 15N‐fertilizers to allow mass spectrometry (MS) determinations of 28N2, 29N2, and 30N2 to quantify the N2 evolution. An alternative method, based on the determination of N2 evolution by measurement of the 28N2/29N2 ratio with emission spectrometry (ES), is proposed. An apparatus consisting of a cuvette and a sampling system was developed. The sampling system was evacuated to <10−1 Pa before gas from the cuvette system was fed into a reservoir (10 mL), through a liquid N2 trap and into five discharge tubes for ES. The final pressure in the tubes was 4 to 5 × 102 Pa before they were sealed off, and the 28N2/29N2 ratios in the gases were determined with ES. It was verified that random distribution of 28N2, 29N2, and 30N2 was obtained in different N2‐gas mixtures made from natural atmosphere and 98 atom % 15N‐N2 by the high frequency discharge of the ES. The system was used to measure fertilizer N2 loss when 15N‐enriched KNO3 was applied at a depth of 2.5 cm in flooded soil. After 60 d, 18% of the applied KNO3 was lost as N2.
Evaporite Mineralogy and Groundwater Chemistry Associated with Saline Soils in Eastern North Dakota
Authors: Skarie R. L. , Richardson J. L. , McCarthy G. J. , Maianu A. 
Published: July 2010

AbstractSoil salinization has resulted from seepage of water from drainage ditches in eastern North Dakota. The present study was undertaken to determine the effect of these processes on the geochemistry of shallow groundwater and on the evaporite mineralogy of the affected soils. In the chloridic system studied, SO2‐4 concentrations of groundwater and saturation extracts were controlled by the solubility of gypsum. Calcium concentrations were controlled by gypsum solubility in the sulfatic system. Shallow groundwater samples collected near the recharge sources were undersaturated with respect to gypsum and oversaturated with respect to calcite. Considerable redistribution of gypsum was observed in soil profiles of strongly salinized transects of the chloridic system. Sulfate enrichment relative to Ca2+ was observed in groundwater and soil extracts collected near drainage ditches of chloridic sites. Mineralogy of efflorescent crusts included gypsum, epsomite, hexahydrite, thenardite, and konyaite in the sulfatic system, and halite, eugsterite, thenardite, konyaite, bloedite, and gypsum in the chloridic system.
Soil Science in the Next Twenty‐Five Years: Does Biotechnology Play a Role?
Authors: Läuchli A. 
Published: July 2010

AbstractThere is ample opportunity for biotechnology applications in future soil science research. In principle, all organisms are amenable to genetic engineering, including soil organisms and plants. Obviously, the researcher needs to have molecular biology and genetics skills to tackle genetic improvement of organisms. But for the geneticist to succeed in this endeavor, the input by soil and plant scientists is crucial, because geneticists usually do not have the basic understanding of the issues in soil science that are involved, nor do they know how to assess the relative merits of the genetically engineered organism in its specific environment. Notwithstanding the complex legal aspects of releasing genetically engineered organisms, biotechnology opens exciting new possibilities in soil science. Close cooperation between geneticists on the one side and soil scientists and plant scientists on the other must be fostered if biotechnology is to be utilized for the benefit of maintaining the quality of our natural, agricultural, and urban environments.
Mechanical Equilibrium in Externally Loaded Unsaturated Granular Similar Media
Authors: Snyder V. A. 
Published: July 2010

AbstractThe physics of soil deformation under applied external loads is still very poorly understood. This is especially true in the case of unsaturated soils, where very complex internal force systems arise as a result of applied loads, stresses in the pore fluid phases, and surface tension forces in the air‐water interface. The present paper attempts a theoretical description of these forces, for the relatively simple case of nonswelling cohesionless granular soils in static equilibrium. The analysis concentrates on systems which are similar according to the rules defined by Miller and Miller (1956) in their theory of capillary flow phenomena in granular media. Applied loads, gravity, and stresses in the pore fluid phases are analyzed in terms of their effects on the interparticle contact forces which determine soil behavior. For isotropic similar media under similar applied loads, interparticle contact forces can be approximated as linear combinations of the scalar groups (σ̄‐µa) λ21, ρgλ31 and γλ1, where σ̄ is the mean applied stress, µa is the pore‐air pressure, ρ is particle density, g is the gravitational constant, γ is the surface tension of the air‐water interface, and λ1 is the microscopic characteristic length. The coefficients of these groups are dimensionless vector arrays (each vector corresponding to a particular interparticle contact point) which depend on the geometry of the soil‐air‐water system, but are independent of its characteristic length when gravitational effects on pore‐water pressure can be neglected relative to surface tension effects. The relationship of the theory to continuum mechanics and probabilistic approaches to force transmission in soils is briefly discussed.
Solutions for Transport of Two Sorbed Solutes with Differing Dispersion Coefficients in Soil
Authors: Angelakis A. N. , Kadir T. N. , Rolston D. E. 
Published: July 2010

AbstractSimultaneous transformation and transport in the soil of two solutes with different dispersion coefficients were described by two, one‐dimensional linear partial differential equations. Linear, equilibrium adsorption‐desorption relationships for both solutes and irrerversible microbial first‐order kinetics as an overall transformational mechanism were assumed. Consecutive analytical solutions were developed using Laplace transforms for zero initial concentrations, pulse input conditions and semi‐infinite media. Special cases in which the first solute moved only by mass flow and both solutes described by the same dispersion coefficient were considered. Sample problems to demonstrate the applicability of the solutions and their sensitivity to dispersion coefficients of both solutes are presented. Computed concentration profiles of the first or second solute are sensitive to their respective dispersion coefficient, especially under low degree of adsorption of both species. The sensitivity of the concentration profiles of the second solute to the dispersion coefficient of the first species occurs, however, only under a low degree of adsorption and low decay rates of that species.
Models to Predict Water Retention in Semiarid Sandy Soils
Authors: Meng Tan Piow , Taylor H. M. , Fryrear D. W. , Gomez J. F. 
Published: July 2010

AbstractObjectives of this research were to (i) develop statistical models for predicting water content at three matric potentials, using three levels of input data; (ii) compare predictive capability of the locally calibrated models with those of three published models; and (iii) illustrate the changes that occur in water retention when texture of sandy soils is altered by deep plowing or wind erosion. At −10 kPa, accuracy of predicting gravimetric water contents increased with increased number of inputs. The R2s and the slopes between predicted and measured water contents for 50 samples increased, and the intercepts came closer to zero as the inputs progress from clay only to soil texture plus organic matter and CaCO3 and on to sand separates plus texture, organic matter, and CaCO3. At the −33‐ and −1500‐kPa matric potentials, the clay‐only model predicted soil‐water content equally as well as the two local models with more inputs. A previously published clay‐only model that had been calibrated using semiarid soils performed almost as well as the locally calibrated models. Two other published models performed unsatis‐factorily in predicting water retention at any of the matric potentials. Deep plowing increased clay content of one specific soil from 4 to 14%. Wind erosion subsequently reduced clay to 6% after 5 yr. Predicted water contents were 0.281, 0.341, and 0.293 kg kg−1, respectively, at −10 kPa, and 0.012, 0.050, and 0.020 kg kg−1, respectively, at −1500 kPa.
Shrinkage Curve Indices to Quantify Cultivation Effects on Soil Structure of a Vertisol
Authors: McGarry D. , Daniells I. G. 
Published: July 2010

AbstractDifferences in selected parameters and derived variables of models fitted to soil shrinkage curves were used to investigate soil structural degradation of an irrigated Pellustert in northern New South Wales, Australia. Significant differences between clods taken from the same depths in land prepared for cotton (Gossypium hirsutum L.) when “dry” and “wet” were found in specific clod volume at zero water content, the slope of the line in the normal shrinkage zone, the airfilled specific pore volume throughout normal shrinkage, and the range in water content in the structural shrinkage zone. These indicators showed that this soil prepared wet exhibited increased bulk density, decreased porosity, loss of structural pores, and tended to have weak structural development.
Influence of Oak in Pine Forests of Central Arizona on Selected Nutrients of Forest Floor and Soil
Authors: Klemmedson James. O. 
Published: July 2010

AbstractThis study focused on the effect of Gambel oak (Quercus gambelii Nutt.), a common subdominant and understory species in a ponderosa pine (Pinus ponderosa Laws.) forest in central Arizona, on selected nutrient properties of the forest floor and soil. Samples of the L, F, and H layers (Oi, Oe, and Oa horizons, respectively) of the forest floor and the 0‐ to 5‐ and 5‐ to 15‐ cm layers of mineral soil from 33 randomly selected stands of ponderosa pine with varying amounts of Gambel oak (from 0 to about 75% of total basal area) were collected and analyzed for total N, P, S, total and exchangeable Ca, Mg, and K, and organic C. Chemical properties of fresh litterfall suggested the potential for oak to strongly influence soil fertility of the pine forest. In the forest floor as a whole, only C and Mg concentrations were not positively correlated with oak basal area. In separate layers (L, F, and H) of the forest floor, the concentration of all measured nutrients increased with oak. Increases in nutrient concentration for these layers ranged up to 133% for K in the H layer at 70% oak basal area. Increased oak influenced C and N concentration more than other nutrients in the 0‐ to 5‐ and 5‐ to 15‐ cm soil layers. Increase in oak basal area to 70% resulted in a downward shift (i.e., redistribution) of C, N, P, and S within the forest floor. Hence, these nutrients were more heavily concentrated in the H than in the L and F layers with increases in oak from 0 to 70% of total basal area. Elemental ratios (C/N, C/P, C/S, C/Ca, C/Mg, and C/K) for all layers of the forest floor declined sharply as percentage oak basal area increased.
Impacts of Acid Atmospheric Deposition on Woodland Soils in the Netherlands: II. Nitrogen Transformations
Authors: van Breemen N. , Mulder J. , van Grinsven J. J. M. 
Published: July 2010

AbstractInorganic N budgets were estimated for four oak‐birch (Quercus robur L.‐Betula pendula L.) woodland soils in the Netherlands, that receive high inputs (40–60 kg ha−1 yr−1) of atmospheric N, mainly as (NH4)2SO4‐. Budgets were based on measured inputs in through‐fall water, measured soil solution concentrations, and simulated soil‐water fluxes. Substantial nitrification occurred in both highly acidic (pH 3–4) and calcareous (pH 6.5–7.5) soils. The acidity formed during N transformations (3–9 kmolc ha−1 yr−1) accounted for a major part of all soil acidification taking place. Extreme soil acidification due to nitrification (4–14 kmolc ha−1 yr−1) in the 10‐cm surface soil in three of the four plots was partly alleviated at greater depth by removal of NO‐3. Presumably, most of this NO‐3 was removed by plants and microorganisms and, perhaps, in part by denitrification. In two of the four soils, leaching of inorganic NO‐3 exceeded atmospheric throughfall input. This trend indicates that N inputs were still higher, e.g., due to direct assimilation of atmospheric NH3 by tree leaves, or that the pool of soil N decreased by mineralization in excess of uptake. In one of the four soils, most of the atmospheric N2 was assimilated and soil acidification due to N transformations was relatively small. The differences in N budgets and associated soil acidification may be related to (i) consistent differences in N input over many years, and (ii) differences in accumulation of N in biomass. Variation in these two factors may be responsible for differences in the degree to which the ecosystems are now “saturated” with N.