bluuebunny/crossref_metadata_2025_split huggingface dataset:
Competitive Adsorption of Aqueous Carbonic and Acetic Acids by an Aluminum Oxide
Authors: Schulthess C. P. , McCarthy J. F. 
Published: July 2010

AbstractThe prominence of carbonates in nature and their potential competitiveness with organic acids for sorption sites in soils may be underestimated by researchers who study the mobility of natural organic matter. The pH‐dependent adsorption envelopes of Na salts of acetic acid (AcOH) and carbonates (H2CO3, HCO−3, CO2−3) on an Al oxide were studied to elucidate the effect of carbonates on the adsorption behavior of organic acids. Using 10−3.48 and 10−3 M concentrations of the carbonate salt reduced the amount of acetate adsorbed by 29 and 48%, respectively. Using 10−3.48 M concentrations of acetate, however, did not affect the carbonate adsorption at equimolar concentrations. The relative affinity of the aqueous compounds for adsorption by the Al oxide was determined based on the pH value of their adsorption edges (i.e., based on their adsorption competitiveness relative to the aqueous OH anions). The relative affinity for adsorption by the Al oxide was OH > carbonate > acetate > Cl. The amount of both the acetate and carbonate adsorbed by Al oxide are reduced in the presence of competitive OH anions at high pH and high concentrations of Cl anions at low pH. The adsorption mechanisms of the carbonate and acetate compounds are suspected to be similar based on the chemical structure of these compounds. Batch adsorption studies, however, cannot unequivocally identify a bonding mechanism, which may include ligand exchange or H bonding. We additionally stress that both the affinities and concentrations of the aqueous compounds play an important role in competitive adsorption behavior.
Exchange Capacity and Adsorbed‐Cation Charge as Affected by Chloride and Perchlorate
Authors: Rhue R. Dean , Reve W. H. 
Published: July 2010

AbstractPrevious reports in the literature have indicated that apparent differences in adsorbed‐cation charge can be obtained with Cl and ClO4 media as a result of the adsorption of the bivalent cation complex CaCl. Since the original studies dealt only with smectite clay, it was of interest to determine whether these differences could be observed for other soil and clay materials. Both cation‐exchange capacity (CEC) and adsorbed‐cation charge were measured in Cl and ClO4 media using Na or Ca as the exchangeable cations. In no case was there an effect of the anion on either CEC or adsorbed‐cation charge when Ca was the predominant exchangeable cation. Furthermore, CEC and adsorbed‐cation charge were not significantly different. Studies with SAz‐1 clay showed that, when Na was the only exchangeable cation in the system, the adsorbed‐cation charge was significantly less than the CEC. This difference was attributed to negative adsorption of the anion and its contribution to the total adsorbed charge. Greater adsorbed‐cation charge in Ca‐saturated systems, compared with Na‐saturated systems, was observed for SAz‐1 clay in both Cl and ClO4 systems.
Sorbed Ortho‐ and Pyrophosphate Effects on Zinc Reactions Compared in Three Autoclaved Soils
Authors: Xie R. J. , MacKenzie A. F. 
Published: July 2010

AbstractInformation on interactions between ortho‐ (OP) or pyrophosphate (PP) and Zn in soils are fragmentary. Evaluating the relative effects of the two phosphates on Zn reaction in the soil requires autoclaving the soil in order to minimize biological hydrolysis of PP to OP. Sequential reactions between OP or PP and Zn in three autoclaved soil samples were compared using Zn sorption, desorption and fractionation at an initial pH 6.0 and ionic strength 0.03 M as KClO4. Soil materials were surface samples of a Typic Haplorthod, Typic Eutrochrept, and Typic Humaquept. One mmol sorbed P as OP resulted in greater increases in cation‐exchange capacity (CEC) than 1 mmol sorbed P as PP. At the same rate of P addition, the absolute increase in CEC was greater with PP than OP, because of greater P sorption as PP than as OP. Both sorbed OP and PP increased Zn sorption and decreased Zn desorption. The sorption of Zn was described best by Freundlich sorption isotherms, rather than Gunary, Langmuir, or Temkin isotherms. Results suggested that complexes of OP‐ or PP‐Zn‐soil materials have formed, particularly in the coarser textured materials, with PP being more effective in complexing Zn than OP.
Particle Density of Volcanic Soils as Measured with a Gas Pycnometer
Authors: Bielders C. L. , De Backer L. W. , Delvaux B. 
Published: July 2010

AbstractIn the absence of actual data, the particle density of soil is often assumed to be 2.65 Mg/m3. In this study, we will discuss whether this hypothesis applies with reasonable accuracy to various types of soils from Martinique. Thirty‐nine samples taken from seven different subgroups of soils derived from volcanic materials were considered: Andeptic Troporthent, Typic Hydrandept, Typic Dystrandept, Andic Humitropept, Typic and Oxic Dystropept, and Entic Pellustert. Particle density was measured in triplicate on undisturbed, oven‐dried samples by means of a gas pycnometer. The measurements were performed using air and He. Values found in He pycnometry ranged from 2.38 to 2.72 Mg/m3. The organic‐matter content was a major factor in explaining low particle densities, but other soil constituents may be significantly involved also. Reproductibility of He pycnometry was found to be good. Air‐pycnometry measurements revealed strongly distorted values for many soil materials when compared with He‐pycnometry results. This was assigned to a gas adsorption phenomenon and found to be linearly related to the surface area of the soil samples as measured by ethylene glycol monoethyl ether.
Functional Sensitivity Analysis of Four Methods to Generate Soil Hydraulic Functions
Authors: Wösten J. H. M. , Schuren C. H. J. E. , Bouma J. , Stein A. 
Published: July 2010

AbstractRapid advances in model building have led to the understanding that applicability of future simulations depends, to a great extent, on the availability of accurate soil hydraulic functions obtained with efficient methods rather than on new models. In this study, four different methods were used to generate hydraulic functions: Method A, direct on‐site measurement; Method B, use of measured hydraulic functions averaged on a regional scale; Method C, use of measured hydraulic functions averaged on a national scale; and Method D, use of van Genuchten parameters correlated with soil texture and organic‐matter content. Accuracy of these methods was tested by comparing the simulated water storage with the measured water storage of the upper 0.5 m of three soil profiles over a period of 7 yr. Differences in performance of the four methods were not significant. Agreement between measured and simulated water storage was best, however, when directly measured hydraulic functions (Method A) were used. Next best agreement was obtained when continuous (Method D) and two types of class pedotransfer functions (Methods B and C) were used, which relate textures and soil horizons to physical characteristics. Costs involved in obtaining directly measured soil hydraulic functions are prohibitively high, compared with costs for the other methods. With regard to both accuracy and costs, the development of a data base of measured soil hydraulic functions and use of this information to derive continuous and class pedotransfer functions assures, in many cases, optimal spending of limited available resources.
Fly Ash Use as a Time Marker in Sedimentation Studies
Authors: Jones Robert L. , Olson Kenneth R. 
Published: July 2010

AbstractFly ash from coal burning often takes the form of magnetic spherules, making it easy to separate and identify. Illinois soils near to and remote from known sources of fly ash were studied to evaluate ash incidence and accumulation of ash‐bearing sediments in the profile. Soils from both types of areas contained magnetic fly‐ash spherules. Concentrations >75% occurred in the magnetic fraction of the surface horizon (mostly in the top 12.5 cm) of a soil on an uncultivated, stable ridgetop near Springfield, IL. On the nearby Sangamon River floodplain, fly ash occurred in large numbers to the 25‐cm depth, and in lesser numbers to 45 cm, the top of a buried, organic‐C‐rich layer. This buried layer may represent the surface in the 1850s, when railroads and perhaps also industrial boilers were introduced. In depositional horizons of soils from remote sites, fly ash occurred at levels of <1%; it probably came from steam locomotives and, perhaps, steam‐powered farm machinery. From the 1850s to the late 1920s, railroads in Illinois increased to about 16 000 km of track; consequently, fly ash is ubiquitous in surface soils and is easily assayed. Steam‐powered farm machinery (although not always fueled by coal) was common from 1880 until about 1920. At depositional sites, the buried A horizon contained fly ash, but subjacent horizons did not. This pattern indicates that fly ash occurrence is useful in distinguishing the presettlement surface, thereby making possible the determination of rates of sedimentation at a particular site.
Crop Yield Variation Associated with Coastal Plain Soil Map Units
Authors: Karlen D. L. , Sadler E. J. , Busscher W. J. 
Published: July 2010

AbstractVariation among soil map units needs to be quantified so farmers can implement more economically and environmentally acceptable production practices. We conducted a 4‐yr field study at an 8‐ha research site near Florence, SC, to quantify yield variation for a southeastern Coastal Plain field. Nineteen soil map units, classified as Ultisols and representing seven soil series were identified by Soil Conservation Service cooperators. Corn (Zea mays L.) was grown in 1985, 1986, and 1988, while in 1987 wheat (Triticum aestivum L.) and grain sorghum [Sorghum bicolor (L.) Moench] were double‐cropped. All soils received conventional disk tillage, fertilization based on soil‐test recommendations, and uniform planting rates. Crop yield was measured by harvesting transects throughout the field and subsequently identifying soil map units for each plot. Average corn yield among soil map units ranged from 3.7 to 8.0 Mg ha−1 in 1985, 0.1 to 2.8 Mg ha−1 in 1986, and 1.1 to 5.0 Mg ha−1 in 1988. Yields were lower in 1986 because of severe drought. Wheat yield ranged from 3.5 to 6.2 Mg ha−1, while sorghum yield ranged from 1.7 to 5.2 Mg ha−1 in 1987. Extractable P, K, Ca, Mg, Mn, and Zn; soil organic matter and pH; and depth to an argillic horizon (Bt) were measured to identify causes for yield variation among soil map units. Depth to Bt had the best statistical relationship between crop yield and soil map unit, but yield variation within an individual map unit was almost as large as variation between map units. Our results demonstrate how measurements of crop yield by soil map unit can be determined and used to study soil variation. They also provide a data base that can be used to evaluate plant growth and soil management models for individual soil map units.
Relationship between Diagnosis and Recommendation Integrated System (DRIS) Optima and Foliar Nutrient Critical Levels
Authors: Needham Ted D. , Burger James A. , Oderwald Richard G. 
Published: July 2010

AbstractOptimum nutrient levels for loblolly pine (Pinus taeda L.) were estimated by applying DRIS techniques to 504 randomly selected trees from loblolly pine plantations in Georgia and South Carolina. Levels of 12.0 g/kg N, 1.1 g/kg P, and 0.8 g/kg Mg were determined through this method. These values were slightly higher than the generally accepted critical levels of 11.0, 1.0, and 0.7 g/kg for these nutrients, which illustrates the theoretical relationship between critical levels and DRIS optima. This study shows that DRIS methods applied to field survey data can be used to estimate optimum foliar nutrient levels while circumventing many problems associated with traditional critical‐level derivations.
Simulation Model of Banded Ammonia in Soils
Authors: Izaurralde R. C. , Kissel D. E. , Cabrera M. L. 
Published: July 2010

AbstractThe efficient use of anhydrous NH3 as a fertilizer depends on factors such as N rate, knife spacing, depth of application, and soil properties like NH3‐retention capacity. We developed a computer model that predicts some characteristics of an NH3‐retention zone in soil. Soil titratable acidity to pH 9 using NH4OH as the base was an input to the model used to estimate the NH4‐N (NH3 and NH4) concentration at the line of injection 24 h after NH3 application. Data for the model were collected using a laboratory apparatus that applies anhydrous NH3 in a band. Ammoniacal‐N concentration with distance away and normal to the line of injection was predicted using a nonlinear equation and values of N rate, band spacing, and soil bulk density. Soil pH was calculated as a linear function of the ammoniacal‐N concentration in soil with ammoniacal N at pH 9 equal to titratable acidity. Direct losses of NH3 by volatilization were assumed to occur because of insufficient depth of application or rates of N application that were too high. Concentrations of NH4 and NH3 in solution were calculated using the Gapon cation‐exchange and Henderson‐Hasselbach equations, respectively. Observed vs. predicted ammoniacal N and pH at different distances from the injection line for seven soils and 13 rates (1.6–8.4 g N m−1) correlated at P < 0.01 (r2 = 0.85 and 0.84, respectively). The model provided reasonable estimates of direct NH3 loss and concentration of ammoniacal species in solution. This tool could help to better understand the behavior of NH3 in soil and, therefore, to manage its application to reduce N losses. Information on ammoniacal‐N distribution and on soil pH in an NH3 band could also be used for simulating transformations of banded N.
Soil pH and Phosphorus and Potassium Uptake by Maize Evaluated with an Uptake Model
Authors: Chen Jen‐Hshuan , Barber S. A. 
Published: July 2010

AbstractPlant growth and nutrient uptake by plants have been shown to be affected by soil pH. However, the effects have not been evaluated with a mechanistic uptake model that can evaluate the relative influence of soil pH changes on changes in soil supply parameters that influence predicted P uptake. The objectives of this research were to verify the Barber‐Cushman nutrient‐uptake model under a range of soil pH conditions and to use the model to evaluate the influence of soil pH on the model parameters supplying P and K to maize (Zea mays L.) roots. A pot experiment was conducted to evaluate the accuracy of the model for predicting P and K uptake at soil pH levels of 3.8, 4.7, 5.7, 6.5, 7.6, and 8.3 in Chalmers silt loam (fine‐silty, mixed, mesic Typic Haplaquoll). This study showed that the nutrient‐uptake model accurately predicted the effect of the soil pH on P uptake (Y = 0.44 + 0.93X, r2 = 0.99) when the change of P from H2PO4 to HPO4 at the higher pH values was accounted for, and predicted K uptake (Y = 67 + 0.94X, r2 = 0.99) without modification for pH.
Soil Nitrogen Mineralization in a Clearcutting Chronosequence in a Northern California Conifer Forest
Authors: Frazer D. W. , McColl J. G. , Powers R. F. 
Published: July 2010

AbstractSoil ammonification, nitrification, and N mobility were studied for 1 yr in three Sierra Nevada (USA) mixed‐conifer stands to examine the long‐term influence of timber harvesting on soil N dynamics. Clearcutting had a persistent effect on soil N mineralization, detectable by in situ incubation but not by conventional low‐tension lysimetry. Mineralization rates were greater in 5‐ and 17‐yr‐old regenerated clearcuts than in an adjacent 100‐yr‐old uncut forest. Annual rates of N mineralization averaged 12 kg ha−1 for the uncut forest, and 49 and 31 kg ha−1 for the 5‐ and 17‐yr‐old clearcuts, respectively. Mineralization continued throughout the summer, even when soil matric potentials were <‐1500 kPa. Soil solution NO3 concentrations were much higher in the younger clearcut than in either the older clearcut or the uncut forest. Sustained effects of clearcutting seem due largely to higher substrate availability and to moisture and temperature conditions favoring microbial activity. Chemical inhibition of nitrification may become important as the forest floor develops.
Adsorption of Humic Substances by Hydroxyaluminum‐ and Hydroxyaluminosilicate‐Montmorillonite Complexes
Authors: Inoue K. , Zhao L. P. , Huang P. M. 
Published: July 2010

AbstractThe interaction between humic substances purified from an Andisol and montmorillonite (Mt) complexed with hydroxyaluminosilicate (HAS) or hydroxyaluminum (HyA) ions was studied. The HAS ions were formed from solutions containing HyA ions and orthosilicic acid at an Al concentration of 4 mM; Si/Al atomic ratios of 0, 0.25, 0.5, 0.75, and 1.0; and a NaOH/Al molar ratio of 2.0. The adsorption of humic substances by HAS‐Mt and HyA‐Mt complexes increased as pH decreased in the adsorption systems. At concentrations of 10 to 1000 mg humic substance L−1 and pH 5.5, the adsorption of humic acid by these complexes decreased with an increase in the Si/Al atomic ratio of hydroxy materials fixed in interlamellar spaces of Mt, whereas the adsorption of fulvic acid followed almost the opposite trend. When the adsorption data of humic substances by these complexes were evaluated using the Eadie‐Hofstee plot of the Langmuir adsorption equation, multiple linear relationships were obtained, indicating the presence of multiple populations of sites that have a differing affinity for humic substances. A ligand exchange reaction, in which humic substances displaced OH or OH2 groups from the coordination shells of structural Al on the edges and HAS or HyA polymers fixed on the edges, external planar surfaces, and/or the interlamellar spaces of Mt, may be involved in the adsorption processes. The results indicate that besides HyA ions, the reactivity of HAS ions in humus accumulation and the pedogenic implication in soil environments merit attention.
Critical Evaluation of Methods for Determining Total Organic Phosphorus in Tropical Soils
Authors: Condron L. M. , Moir J. O. , Tiessen H. , Stewart J. W. B. 
Published: July 2010

AbstractThe determination of total organic phosphorus (TOP) in soils presents several methodological problems, particularly on strongly weathered and tropical soils. We reviewed the application of several methods for TOP determination to soils from different zones of the globe and evaluated the applicability of one ignition and two extraction methods to tropical soils from Brazil and Ghana. Reproducibility (coefficients of variation) was within 6% for the ignition method, and 13% for the extraction methods, due to the simplicity of the former. The two extraction methods produced results similar to each other, while the ignition method generally gave higher TOP contents. Unusually low C to organic P ratios indicate that the ignition method overestimated TOP in several soils. The Bowman extraction method, developed on weakly weathered soils, appeared also suitable for a variety of tropical soils.
Phosphate Sorption‐Desorption Characteristics by Magnetically Separated Soil Fractions
Authors: Saying M. , Mermut A. R. , Tiessen H. 
Published: July 2010

AbstractA soil sample from the surface horizon of a Paleustollic Torrert from southeastern Turkey was size fractionated, then subfractionated further by magnetic separation to study P sorption and desorption behavior of these separates. Citrate‐dithionite (CD) extractable Fe constituents (Fed) were found effective P sorbers in silt‐size particles, especially in the coarse‐silt fraction (50–20 µm). A five‐fold increase in P sorption was noted with an 8.5‐times increase in Fed content, suggesting that, in this fraction, P sorption is largely controlled by Fe oxyhydroxides. Carbonates in sand and coarse‐silt fractions as well as CD‐extractable Al and Si, and oxalate‐soluble Al and Si in all fractions had no significant effect on P sorption. In the coarse‐clay fraction, besides the Fed content, clay minerals also affected P sorption. Desorption of P was, in general, lower in the highly magnetic fractions, and decreased with decreasing particle size. Fluctuations in P desorption among different concentrations of added P in each particular fraction cannot be explained clearly. This may suggest the possibility of P precipitation in a 24‐hr experimental time period. Removal of about 2.9% Fed from the fine clay (<0.2 µm) resulted in a 22% decrease in sorption, and an increase in desorption, from 32 to 44% to 62 to 80%. The results suggest that Fe oxyhydroxides and other Fe‐bearing constituents are important P sorbents not only in tropical soils, but also in soils of the temperate semiarid regions.
Effect of pH on Permeability of Clay‐Sand Mixture Containing Hydroxy Polymers
Authors: Keren R. , Singer M. J. 
Published: July 2010

AbstractThis study was conducted to determine if the effectiveness of hydroxy‐Al and ‐Fe polymers in stabilizing the hydraulic conductivity of smectite‐sand mixture increases with their charge density. The effect of pH 5.5 and 7.5 on the saturated hydraulic conductivity (HC) of Na/Ca‐smectite‐sand mixtures (5% clay and 95% sand) and in the presence of hydroxy‐Al and ‐Fe polymers was studied by leaching with NaCl‐CaCl2 solutions at sodium adsorption ratios (SAR) of 10 and 20 of electrolyte concentrations of 500, 100, 50, 10, 5, 3, 2, and 1 molc m−3 and deionized water. The HC of the mixtures essentially remained unchanged as long as the electrolyte concentration of the leachate was ≥50 molc m−3. A further decrease of the solution concentration produced a drop in HC for both the untreated and treated systems at pH 7.5. No HC reduction occurred at pH 5.5 when hydroxy‐Al polymers were present. The HC of both treated and untreated systems at pH 5.5 was higher than that at pH 7.5. The HC reduction was two and three orders of magnitude smaller for the treated systems than for the systems without hydroxy polymers. Hydroxy‐Fe polymers also reduced the effect of electrolyte concentration in the leaching solution on the HC of the clay‐sand mixture, but to a lesser extent. The effect of pH on the charge density of the hydroxy polymers explained their effectiveness in stabilizing the system at the lower pH. The lower HC of the clay‐sand mixture in the presence of hydroxy‐Fe polymers suggests that the aggregates with this polymer are weaker than those with hydroxy‐Al polymers. This difference in stability is due to the higher point of zero charge (PZC) for the hydroxy‐Al polymers.
Characterization of Phosphorus Efficiencies of Two Winter Wheat Cultivars
Authors: Gardiner D. T. , Christensen N. W. 
Published: July 2010

Abstract‘Stephens’ and ‘Yamhill’ winter wheat (Triticum aestivum L.) cultivars respond differently to P fertilization on low‐P soils. The objective of this study was to determine the reason for greater P efficiency in Yamhill. The cultivars were grown in three growth‐chamber experiments to describe response to a factorial combination of P levels and soil fumigation, and to compare root growth rates, root hair formation, and tissue P concentrations. Cultivars did not differ in root growth rate, total P uptake, or response to fumigation. Root hair length was affected by an interaction between cultivars and P concentrations in the growth medium. At the 2 µM P level, Yamhill had significantly (P = 0.05) longer root hairs than Stephens. Yamhill produced significantly greater shoot dry weight per unit of P taken up (0.20 g mg−1) than Stephens (0.17 g mg−1). The greater P efficiency of Yamhill was attributed to greater P‐use efficiency rather than to differences in P uptake.