bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Comparison of Batch‐ and Flow‐Generated Anion Adsorption Isotherms
Authors: Miller D. M. , Sumner M. E. , Miller W. P. 
Published: July 2010

AbstractSolute transport models often use batch‐generated adsorption isotherms to partition solute between the aqueous and adsorbed phases, but the relationship at equilibrium between aqueous and adsorbed solute concentrations may be different in closed (batch) and open (flow) systems. Adsorption isotherms were generated for orthophosphate/goethite, silicate/goethite, orthophosphate/soil clay and orthophosphate/arsenated‐goethite systems using batch and flow (miscible displacement) techniques. The contact times were 168 and 96 h in the batch and flow experiments, respectively. The shapes of the isotherms generated by the two methods were very similar in all cases, although the flow‐generated isotherms were displaced slightly upward relative to the batch isotherms. Simple Langmuir plots of both batch and flow data were nonlinear for all systems, while in all systems containing phosphate, flow‐generated distribution coefficients were greater than the corresponding batch‐generated values, particularly at low surface coverage. In addition, adsorption maxima and values of the two‐surface Langmuir parameter b1 were consistently greater in the flow systems. The results indicate that provided transport processes do not keep the flow system far from chemical equilibrium, batch‐generated anion adsorption isotherms are likely to underestimate the extent of adsorption in the corresponding flow system, particularly at relatively low aqueous phase sorbate concentrations. This appears to be due, in part, to the removal of competitive antecedent species in the flow system effluent. It is suggested that flow systems are thermodynamically equivalent to batch systems having very wide solid/solution ratios.
Molybdate Adsorption on Kaolinite, Montmorillonite, and Illite: Constant Capacitance Modeling
Authors: Motta M. Manuela , Miranda C. F. 
Published: July 2010

AbstractThe adsorption of molybdate by kaolinite, montmorillonite, and illite was investigated at 25 and 40 °C, in a 0.01 M NaCl background medium, for equilibrium Mo concentrations ranging from 0.1 to 100 mg L−1. The constant capacitance model was shown to be able to describe molybdate adsorption on the three minerals and for the two temperatures used. The model comprises five adjustable parameters for each mineral: two surface protonation‐deprotonation constants, two molybdate surface complexation constants, and a capacitance density parameter. However, for montmorillonite and illite the number of adjustable parameters was reduced to four since adsorption data could be fitted using only one molybdate complexation constant. The protonation‐deprotonation constants were obtained from potentiometric titration data and the molybdate complexation constants from adsorption data. The capacitance density was chosen on the basis of a literature compilation of values used in previous applications of the constant capacitance model to the adsorption of several ions on oxide minerals. Tentative estimations of thermodynamic functions of molybdate adsorption are presented.
Adsorption of Chromate by Subsurface Soil Horizons
Authors: Zachara J. M. , Ainsworth C. C. , Cowan C. E. , Resch C. T. 
Published: July 2010

AbstractChromate adsorption was measured with and without reactive cosolutes on four subsurface soil horizons differing in pH and mineralogy, and on clay fractions from two of the oxide‐containing subsoils. Chromate adsorption was greatest in lower pH materials enriched in kaolinite and crystalline iron oxides. Over a range in pH, chromate adsorption to subsoil was similar to that observed for pure‐phase oxides. Chromate binding was reversible to pH and was depressed in the presence of SO2‐4 and dissolved inorganic C, which compete for adsorption sites. A surface site density for crystalline Al‐substituted iron oxides in the subsoils was estimated from chromate adsorption on the clay fractions using the model FITEQL and outer sphere surface coordination constants from Al‐goethite. The estimated site density for soil crystalline iron oxides was well below that of clean oxides, suggesting surface saturation by indigenous soil ions. The calculated site density and surface binding constants for Al‐goethite were used in the Triple Layer Model to calculate the effect of ionic strength, cosolutes, solids concentration, and sorbate concentration on CrO2‐4 adsorption. Model calculations were in good qualitative agreement with experimental results.
Simulation by NCSOIL of Net Mineralization in Soils from the Deherain and 36 Parcelles Fields at Grignon
Authors: Houot Sabine , Molina J.A.E. , Chaussod R. , Clapp C.E. 
Published: July 2010

AbstractSoil N and C mineralization was measured from the Deherain and 36 Parcelles fields at the experimental station of Grignon, France. In the Deherain plots, manure and inorganic N effects have been compared on a wheat‐sugarbeet rotation since 1875. In the 36 Parcelles field, the effect of composted straw and inorganic N on the soil organic matter have been studied since 1959 on bare plots. Control plots without any organic or inorganic additions were maintained in both fields. In cultivated and bare plots, rates of C mineralization were similar when soils had been organically amended (farm manure or composted straw). The addition of inorganic N increased the soil total organic N and C content in comparison to the respective control plots, but it did not change the rates of N and C mineralization. Net N mineralization was linear and the determination of potentially net mineralizable N (No) as the asymptotic value of an exponential kinetic gave aberrant values. A new approach to measure No was proposed using the model NCSOIL which simultaneously simulates N and C dynamics in soil. The No was quantified as the initial N content of the model's pool I plus pool II which represent the soil active organic matter involved in N and C turnover.
Evaluation of Factors Affecting Emergence of Winter Wheat Planted with Seed‐Banded Nitrogen Fertilizers
Authors: Mahler R. L. , Lutcher L. K. , Everson D. O. 
Published: July 2010

AbstractNitrogen use efficiency by cereal crops may be increased by the placement of fertilizer with the seed; however, high N concentrations often cause injury and reduce both germination and emergence. Two studies were conducted under controlled greenhouse conditions to evaluate factors affecting emergence of winter wheat (Triticum aestivum L.) planted with seed‐banded N fertilizers. Soil from the Ap horizon of a Palouse silt loam (fine‐silty, mixed, mesic Pachic Ultic Haploxeroll) was used in both studies. Two N materials (ammonium nitrate and urea) were banded with the winter wheat seed (‘Stephens’) at N rates of 0, 11, 22, 33, 44, 55, and 66 kg ha−1, and placed in soils at soil matric potentials of −0.15, −0.25, and −0.35 MPa. The tolerance of five winter wheat cultivars ‘Daws’, ‘Hill 81’, ‘Nugaines’, ‘Peck’, and Stephens to sulfur‐coated urea (SCU) materials SCU‐10, SCU‐20, and SCU‐30 was evaluated in a separate study. Nitrogen rates of 0, 50, 100, and 150 kg ha−1 were used at a soil matric potential of −0.20 MPa. In the first study significant N source × water potential (P < 0.0003) and water potential × N rate (P < 0.0001) interactions were observed. In the second study, significant N source × N rate × cultivar (P < 0.0001), N source × N rate (P < 0.0001), and N source × cultivar (P < 0.0001) interactions were found. The N source, N application rate, soil‐water potential, and winter wheat cultivar main effects were all significant for winter wheat emergence. Ammonium nitrate reduced winter wheat emergence 5 to 26% less than urea when comparable quantities of N were placed with the seed. Winter wheat emergence decreased as soil‐water potential decreased (became more negative). These studies demonstrated how the evaluated factors are interrelated with regard to winter wheat emergence. Consequently, guidelines routinely used for seed‐banded N fertilization that only consider N application rate should be modified to also consider N source and soil moisture.
Mechanism of Native Manganese Release in Salt‐Treated Soils
Authors: Khattak Riaz A. , Page A. L. , Jarrell Wesley M. 
Published: July 2010

AbstractThe release of native soil Mn was evaluated under laboratory conditions in Aiken (fine, kaolinitic, thermic Abruptic Durixeralfs) and Redding (fine, kaolinitic, thermic Abruptic Durixeralfs) clay loam soils saturated with either deionized water, or 75 and 150 mmol L−1 NaCl‐CaCl2 solution. As the NaCl‐CaCl2 concentrations increased, soil solution Mn increased and exchangeable Mn decreased proportionately. The regression of the net increases (Δ) in soluble Mn vs. the corresponding decreases (Δ) in exchangeable Mn produced the relationship, Δ exchangeable Mn (mg kg−1) = 0.788 + 0.868 Δ soluble Mn (mg kg−1), R2 = 0.63** (P < 0.01). This suggested that in these salt‐treated soils Mn was released into solution by a cation exchange reaction involving Ca and Na. The increases (122 to 252%) in exchangeable Mn after 5 d incubation, as compared to untreated air‐dried soils, and the favorable pH (4.44 to 6.01) and Eh (redox potential) values (+202 to 254 mV) suggested that Mn(III,IV) was reduced to Mn(II). The Mn(II) primarily accumulated on the exchange phase and was subsequently displaced from the exchange sites by added Na+ and Ca2+. At equal equivalent concentrations, almost twice as much Mn entered the soil solution with Ca2+‐salts (Cl, ClO4, and NO‐3) as with Na+‐salts. The sum of soluble + exchangeable Mn did not increase (rather decreased significantly at the highest salt treatments). It was concluded that salinity had no effect on the extent to which Mn(III,IV) were reduced to Mn(II). These results indicated that management practices that increase soil solution salinity on soils high in native Mn could elevate soil solution Mn to concentrations potentially toxic to Mn‐sensitive crops.
Organic Matter and Natural Carbon‐13 Distribution in Forested and Cultivated Oxisols
Authors: Vitorello V. A. , Cerri C. C. , Andreux F. , Feller C. , Victória R. L. 
Published: July 2010

AbstractSoil carbon (C) distribution, natural 13C abundances and their changes as a consequence of cropping were studied in three neighboring areas on an Oxisol from Brazil. One site (T0) was under forest, while the two other sites (T12 and T50) had been deforested, then cultivated with sugar cane for 12 and 50 yr, respectively. Soil morphological, chemical and mineralogical characteristics in all three sites were very similar. Total C content of the 0.06‐m layer of T0 was twice that of T12 and T50, then decreased sharply with depth, to values similar to the other profiles. Delta 13C had practically constant values of −25.1, −22.8, and −20.4‰, throughout the 0 to 0.30‐m layer of T0, T12, and T50 respectively. These values increased in deeper layers, to about −17‰, due to increased humification and possibly to deposition of organic matter from a former 13C‐rich vegetation. The 0.10‐ to 0.20‐m layer was separated into particle‐size fractions and alkaline extract. Carbon contents decreased from T0 to T50 in the sand‐size fractions and alkaline extracts, but did not change in the clay‐size fractions. Delta 13C values were used to estimate the proportions of C derived from forest (Cdff) and from sugar cane (Cdfc). Carbon derived from sugar cane represented 17.3 ± 3.2% and 40.5 ± 2.2% of total C in T12 and T50, respectively. It reached its maximum value (67 ± 3.7%) in the coarse sand fraction of T12 and T50 and decreased with decreasing fraction size, to 13.8 ± 9.4% and 30.5 ± 6.5% in the fine clay fractions of T12 and T50, respectively. Thus, Cdff persisted mainly in the clay‐size fraction.
Dynamics of Evaporite Distribution in Soils on a Fan‐Playa Transect in the Carrizo Plain, California
Authors: Eghbal M. K. , Southard R. J. , Whittig L. D. 
Published: July 2010

AbstractInvestigation of the distribution and dynamics of evaporites along an alluvial fan‐playa transect in the Carrizo Plain, CA, shows that the overall salt concentration increases toward the center of the playa. Within profiles along the transect, the highest salt concentrations are found in the lower part of profiles. Sodium, K, Mg, Cl, and SO4 concentrations increase along the transect toward Soda Lake. Calcium concentration, in the form of gypsum, is generally higher in profiles in the middle of the transect. Concentrations of Na, Ca, Mg, Cl, and SO4 increase with depth in profiles away from Soda Lake as a function of a greater degree of leaching; higher concentrations of these ions are found toward the surface in profiles closer to Soda Lake due to capillary movement from the groundwater. Halite is the only mineral in the surface horizons. Gypsum is more common in lower horizons, closer to ground water, and is the common salt in soils farther away from Soda Lake. Other soluble evaporites, including halite, loeweite [Na12Mg7(SO4)13 · 15H2O], and bloedite [Na2Mg(SO4)2 · 4H2O], together with gypsum, are found in extracts of soils near Soda Lake. A seasonal influence on the anion and cation distribution generally is noticeable only in soils with intermediate salt concentrations. Higher concentrations of anions and cations are found following the dry season. The orderly differences in anion and cation concentrations within most of the profiles and along the transect reflect the well established differences in solubility of the different salts.
Soil Erosion Has Limited Effect on Field Scale Crop Productivity in the Southern Piedmont
Authors: Daniels R. B. , Gilliam J. W. , Cassel D. K. , Nelson L. A. 
Published: July 2010

AbstractMany studies show that slightly eroded soils outyield severely eroded soils. We believe the yield differences between slightly and severely eroded soils is in part a misinterpretation of the data based on the assumption that all parts of a field were equally productive before man‐induced erosion began. The purpose of this study was to quantify the effects of surface horizon variability on the productivity of a soil map unit. Yield data from farmer‐managed Piedmont fields show that all parts of a field or soil map unit are not equally productive, regardless of erosion class. When yields are compared across erosion classes by landscape position, slightly eroded soils usually outyield severely eroded soils, but the differences are small. Because the area of severely eroded soils in most fields is small, their impact on field production is slight. Our analysis shows that when landscape position and erosion class variables are combined with the area of each, the average economic loss resulting from lower crop yields of eroded Piedmont soils is only $4.44 ha−1 yr−1 at 1987 prices.
Effects of Different Urea Fertilizers on Soil and Trees in a Young Thinned Stand of Western Hemlock
Authors: Radwan M. A. , DeBell D. S. 
Published: July 2010

AbstractEffects of three different urea fertilizers on selected chemical characteristics of soils and foliage, and on growth per tree of a 24‐yr‐old thinned stand of western hemlock [Tsuga heterophylla (Raf.) Sarg.] were compared at a site in coastal Oregon. Treatments were the following: untreated control (C), urea (U), urea treated with N‐Serve®1 [nitrapyrin, 2‐chloro‐6‐(trichloromethyl) pyridine] (U + NS), and sulfur‐coated urea (SCU). Fertilizers were uniformly applied by hand to 0.03‐ha plots in March at 224 kg N ha−1. Soil, to a depth of 20 cm, and current‐year foliage were sampled periodically for 2 yr. Height and diameter of 10 dominant or codominant trees per plot were measured annually for 6 yr. Treatment effects on soil pH varied by fertilizer and sampling date; throughout, pH was lower with U + NS than with U, and the smallest change in pH was associated with SCU. Effects of fertilizer on inorganic N in the soil and on foliar nutrients varied by fertilizer and sampling date. Initially, N‐Serve inhibited nitrification and produced the highest NH4‐N concentrations. In general, all fertilizers increased inorganic N in the soil and total N in the foliage. Fertilizers significantly reduced foliar concentrations of some other macronutrients, especially in the first year after fertilization; some depressions were significantly less with SCU than with the other two fertilizers. Height growth per tree was not significantly affected by any of the fertilizers. Basal‐area and volume growth per tree were significantly greater with the SCU treatment than with the control, U, or U + NS treatments. Beneficial effects of SCU seemed to be mostly due to the slow release of N from the fertilizer, although some positive effect of S cannot be ruled out.
Conditions for Formation of Allophane in Soils
Authors: Parfitt R. L. , Kimble J. M. 
Published: July 2010

AbstractThe Al/Si atomic ratio of allophane was obtained from analyses of soil horizons for a range of New Zealand soils and for a wide range of volcanic soils from around the world. Imogolite‐like allophane (Al/Si = 2) occurs very frequently in soil horizons with >1 or 2% allophane, suggesting that it is more stable, or is more readily formed, in soils than other allophanes. Generally, allophane forms from glass (at pH(H2O) 5 to 7), and feldspar and/or biotite (at pH about 5) in soils with udic moisture regimes and with good drainage. Under these conditions silicic acid and hydroxy‐aluminum cations react to give allophane. A pH >4.7 is required for allophane to precipitate. The Si‐rich allophanes are present in environments where Si in soil solution is likely to be high, and Al‐rich allophanes are present in acid soils where the Si in soil solution is likely to be low. Examples are given of some different types of soils that contain allophane.
Solubility and Phosphorus‐31 Magic Angle Spinning Nuclear Magnetic Resonance of Phosphorus in Sludge‐Amended Soils
Authors: Hinedi Zeina R. , Chang Andrew C. 
Published: July 2010

AbstractThe solubility of P in two sludge‐amended soils was studied. Solubility and activity ratio diagrams for P in sludge‐amended soils were constructed and were compared with those of selected Ca‐P, Fe‐P, and Al‐P minerals. The solid phase controlling P solubility in the sludge‐amended soils appeared to be a carbonated apatite formed through coprecipitation. The 31P magic angle spinning nuclear magnetic resonance (31P MAS NMR) examinations confirmed that P in the sludge‐amended soils was in form of calcium phosphate. The resonant peak [at isotropic chemical shift (δlso) = 3.1 ppm] is indicative of an apatitic calcium phosphate environment characterized by carbonate substitution. Additionally, pyrophosphate was detected by the presence of a peak at δlso = −9 ppm.
Flow‐Through Incubation System for Monitoring Aerobic Soil Nitric and Nitrous Oxide Emissions
Authors: Hutchinson G. L. , Andre C. E. 
Published: July 2010

AbstractFormation and escape of the gaseous products of aerobic soil N transformation processes such as nitrification are logically studied in the laboratory using an incubation system that neither interferes with the diffusive transport of gases within the soil nor allows accumulation and further reaction of gaseous intermediates after their escape through the soil surface. In addition to satisfying these criteria, our flow‐through incubation system provides for continuously monitoring soil emissions of nitric oxide, nitrous oxide, and carbon dioxide, while also permitting soil analysis as frequently as required to characterize changes in the pool sizes and transformation rates of precursors involved in the production of these gases. Treated soil is placed both in the bottom of each incubation jar and in the eight (maximum) sample vials contained therein. The former serves as a continuous, undisturbed source of the measured gases while the latter provides convenient, preweighed samples for periodic chemical or microbiological analysis. Other features of the incubation system include (i) provision for anaerobic and sterile treatments, and (ii) automated air analyses and data acquisition controlled by a programmable timer that provides the flexibility to quickly and easily tailor the system's sampling, analytical, and recording functions to meet the specific needs of each experiment. Because the yield and composition of gases produced during soil N transformation processes is sensitive to incubation conditions, we propose that important features of this system be adopted by other laboratories to facilitate the comparison of research results by eliminating differences due to methodology.
Elevated Carbon Dioxide and Solution Phosphorus in Soil with Vesicular‐Arbuscular Mycorrhizal Western Wheatgrass
Authors: Knight W. G. , Allen M. F. , Jurinak J. J. , Dudley L. M. 
Published: July 2010

AbstractPlants infected by mycorrhizae may exhibit increased root/fungal respiration and elevated concentrations of CO2 in the root zone. Carbon dioxide is a thermodynamically viable calcium phosphate weathering agent in calcareous soils. The weathering of phosphate minerals in soils releases P to the soil solution. This study was conducted to determine if differences in soil atmosphere CO2, of consequence to plant P availability, may exist between mycorrhizal and nonmycorrhizal plants. Western wheatgrass (Agropyron smithii Rydb.) was inoculated with raw soil that contained propagules of Glomus spp. and grown in prefumigated soil columns in the greenhouse. Soil atmosphere CO2 levels for inoculated plants averaged twice those of noninoculated plants in two separate experiments. The mean concentrations of CO2 in the soil atmosphere, measured at discrete weekly intervals, ranged between 0.13 and 2.63 kPa for inoculated systems and was significantly higher in 10 of 19 sampling events than for noninoculated systems (range of 0.05 to 1.02 kPa). Total plant P uptake was also significantly higher for inoculated compared with noninoculated plants. Total solution P, measured monthly in saturation throughput from experimental columns, was significantly higher in three of seven sampling events for inoculated compared with noninoculated plant systems. In treatments where noninoculated plants were grown under an imposed soil CO2 regime, total solution P was highly correlated with CO2. In soil systems where P availability is governed by the solubility of Ca‐phosphate minerals, mycorrhizae may contribute to the P nutrition of host plants via a CO2‐enhanced mineral weathering mechanism.
Effect of Tillage Practices on Microbial Biomass Dynamics
Authors: Follett R. F. , Schimel D. S. 
Published: July 2010

AbstractChanges in microbial biomass dynamics and N cycling were studied in soils from a site derived from native grassland in western Nebraska managed under three tillage systems: no‐till, stubble mulch, and moldboard plow (bare fallow). A treatment of native sod was maintained in each replication. The site was in native sod until 1970 when it was plowed and an alternate wheat (Triticum aestivum L.)‐fallow rotation established. After 16 yr of cultivation, total N concentration in the top 10 cm of soil had decreased to 73, 68, and 50% of native sod in the no‐till, stubble mulch, and plow treatments, respectively. Soil microbial biomass levels were decreased to 57, 52, and 36% for the corresponding tillage treatments as compared to the native sod. In laboratory incubation studies, CO2 respiration was proportional to microbial biomass. Nitrogen mineralization, however, was not proportional to microbial biomass. Immobilization of added 15N was highest for the native sod treatment and amounts of 15N extracted by KCl were inversely related to microbial biomass. Respiration rates per unit of mineralized N (r/Nmin ratio) increased in the order of plow, stubble mulch, no‐till, and sod treatments, suggesting that C availability for microbial growth declined with increased tillage intensity. In these tillage experiments, increased tillage intensity decreased the ability of soil to immobilize and conserve mineral N.