bluuebunny/crossref_metadata_2025_split huggingface dataset:
Particle Size of Interrill‐eroded Sediments from Highly Weathered Soils
Authors: Miller W. P. , Baharuddin M. K. 
Published: July 2010

AbstractFifteen highly weathered Alfisols and Ultisols from Georgia were used in runoff/erosion pan studies to delineate sediment character istics of interrill‐eroding soils and their relationship to soil particle size. Simulated rainfall was applied to the pans at 11.2 cm h−1, and runoff and sediment parameters were measured at 5‐min intervals for 25 min. Runoff rates and sediment concentrations varied consistently over time for the soils used, with concentrations increasing until peaking at 10 to 15 min, then decreasing as crust formation caused surface consolidation and decreased detachability, despite continued high runoff rates for most of the soils. Sediment particle size became finer after the initial sampling period, and was dominated by silt‐sized particles, with lesser amounts of primary clay and sand. Silt‐sized particles in the sediments were related statistically to a measure of water‐dispersible (0.5‐h shaking) soil silt, whereas primary sediment clay was related to both water‐dispersible (36‐h shaking) and total soil clay. Dispersible and total soil clay were also correlated with sediment concentration and soil loss rate, emphasizing the role of clay and its dispersibility in erosion and crust formation on these soils. A quadratic equation using soil clay described sediment clay content, showing greater relative enrichment of primary clay in sediments from sandy vs. clayey soils. The high proportion of easily transportable sediment generated by interrill erosion on these soils poses a serious environmental problem in areas of active soil erosion.
Mass Loss and Nutrient Changes in Decomposing Upland Oak and Mesic Mixed‐Hardwood Leaf Litter
Authors: Kelly J. M. , Beauchamp J. J. 
Published: July 2010

AbstractNylon net litterbags (30 by 30 cm) containing ∼10 g of upland oak leaf litter were collected at 30‐d intervals over a 1110‐d period from two upland oak (Quercus sp.)‐mixed hardwood stands on the Cumberland Plateau of Tennessee. Statistically significant differences (P ≤0.01) in losses of mass, N, K, Ca, and S were found between sites, whereas P and Mg losses did not differ. Litterbags containing mesic mixed‐hardwood leaf litter were collected at 30‐d intervals over a 810‐d period from mesic mixed‐hardwood stands located on the same watershed study sites as the upland oak stands. Statistical comparisons indicated significant differences in mass, N, P, K, Ca, Mg and S loss between sites. Constant rate projections of the time required for the upland oak litter weight to reach 10% of the original bag content based on 365, 730, and 1095 d of data were 960, 1530, and 1770 d, respectively, at the Camp Branch Watershed and 870, 1230, and 1410 d at the Cross Creek Watershed. Estimates of decomposition times derived from constant rate projections for both cover types were considerably less than observed values. In an attempt to obtain more realistic projections of weight and nutrient loss, several mathematical models commonly used to examine decomposition data were evaluated. A modified exponential model gave the best data fit and provided estimates of 3240 and 2370 d as the time required to reach the 10% mass‐remaining value for the upland oak litterbags at Camp Branch and Cross Creek, respectively. Estimates for the mesic mixed‐hardwoods were 1590 and 2490 d at Camp Branch and Cross Creek, respectively. The weight of most nutrients in the litterbags was modeled with limited success by the modified exponential model. However, N and particularly P weights could not be described by the model since they generally increased with time ove rthe study period. The results of this analysis, in addition to suggesting that a longer time is required for decomposition than is normally projected, also suggest that a single model may not be appropriate to describe all response variables. Data presented here along with the modeling work also reiterate the fact that a decay rate derived from a single species or group of species must be applied with caution over larger landscape units because of the potential differences both within and among sites.
A Critical Assessment of Surface Adsorption Models
Authors: Schulthess C. P. , Sparks D. L. 
Published: July 2010

AbstractThe theory on variable ionization energy of surface sites is criticized based on inconsistencies of traditional potentiometric titration data (singular reference curve methods) with electrophoretic mobility (EM) data, and on the nature of dissolution of the solid phase. The mathematical consequences of including the Boltzmann distribution term in models using intrinsic equilibrium constants are most probably merely to track the solubility behavior of the solid phase. The EM of an Al oxide was studied with respect to pH. The isotherm showed clear maximum mobility at low and high pH values with the zero point of charge (ZPC) ranging from pH 9.5 to 9.8. The ZPC lowers with increasing electrolyte concentration due to the increased competitive behavior of the cations in solution for the surface sites. Assuming a constant ionization energy of the surface sites, a mass balanced model that predicted both anion‐cation adsorption data and potentiometric titration data (backtitration technique) also correlated well with the EM data. The EM behavior was modeled based on the varying mobility of each type of surface species present on the oxide at various pH values. Whereas traditional models treat the oxide as being capable of forming a surface charge that induces ion adsorption, this model treats the oxide as being capable of undergoing ion exchange or substitution reactions resulting in surfaces that exhibit mobility in an applied electric field. The proposed model assumes that anion adsorption results in positive mobility, and cation adsorption results in negative mobility.
Sorption Characteristics of Organic Compounds on hexadecyltrimethylammonium‐Smectite
Authors: Boyd Stephen A. , Mortland Max M. , Chiou Cary T. 
Published: July 2010

AbstractWhen hexadedyltrimethylammonium (HDTMA) ion is exchanged for metal cations like calcium in smectite, the sorptive properties of the clay are greatly modified. The resultant HDTMA‐smectite complex behaves as a dual sorbent, in the sorption of organic compounds, in which the mineral fraction functions as a solid adsorbent and the organic (HDTMA) phase as a partition medium. Capacities of mineral adsorption and partition uptake by HDTMA in the HDTMA‐smectites are illustrated by sorption of benzene, trichloroethene (TCE), and water as vapors on the dry sample and by sorption of benzene and TCE from water. The exchanged HDTMA in clay is found to be a much more powerful partition medium than ordinary soil organic matter in the uptake of benzene and TCE. Based on this finding, HDTMA‐smectite appears to be an effective sorbent for removing organic contaminants from water. It is suggested that such sorptive organo‐clay complexes could be used to enhance the containment capabilities of clay landfill liners and bentonite slurry walls.
Relationship Between Microbial Biomass and Elemental Sulfur Oxidation in Agricultural Soils
Authors: Lawrence J. R. , Germida J. J. 
Published: July 2010

AbstractElemental sulfur oxidation in 28 agricultural soils was correlated with the size and activity of the microbial biomass. Sulfur oxidation increased linearly with microbial biomass C (r = 0.68, P < 0.01) and soil respiration rate (r = 0.88, P < 0.01). Canonical analyses of the same data set further emphasized the strong interrelationship of sulfur oxidation, microbial biomass C, and respiration. These results indicated that the size and activity of the microbial biomass determined the rate of elemental S oxidation in agricultural soils. Increasing the heterotrophic biomass by glucose additions caused an increase in sulfur oxidation that was proportional to the increase in biomass C. Application of cycloheximide or chloramphenicol to a Weyburn soil decreased S oxidation by 57%. When the two inhibitors were added together an 84% decrease was observed. These results and the absence of detectable populations of elemental S oxidizing autotrophs indicated that S oxidation in these soils was primarily a heterotrophic process.
Determination of Gaseous Selenium‐75 Evolved from Soil
Authors: Karlson U. , Frankenberger W. T. 
Published: July 2010

AbstractA rapid, cost‐effective and inexpensive method was developed to determine volatile microbial metabolites of Se. Labeled inorganic Se was applied to soil, and the gaseous products were captured in a specially designed activated C trap. After removal for sampling, the C trap was counted directly for 75Se, without further sample preparation. Maximum sampling intervals were 101 to 263 h, depending on Se emission rates. The limit of quantification was 8.2 ng Se using a specific activity of 5 Ci kg−1 Se. The relative standard deviation ranged from 1.3 to 4.1%. Recovery for the added label was 97.5%. The technique is well suited for large‐scale environmental kinetic investigations.
Dry Matter Yield and Nitrogen‐15 Uptake by Tomatoes Under Sodium Chloride Stress
Authors: Pessarakli M. , Tucker T. C. 
Published: July 2010

AbstractAn absorption study was conducted in nutrient solution with seedlings of tomato (Lycopersicon esculentum Mill.; cv. Columbia) to observe the effects of NaCl on (15N) uptake and distribution in plant roots and shoots. The 14‐d‐old seedlings were grown for 16 d (14 d as group of 6 plants per container and 2 d after the final transfer of 2 plants per container) in complete Hoagland solution no. 1, then salinized (except the controls, −0.03 MPa) to −0.3, −0.6, and −0.9 MPa osmotic potentials with NaCl. Nutrient solutions were sampled daily for N loss after addition of 15NH415NO3 to the pots. The cumulative 15N loss was considered to be absorbed by plants. Lowering the osmotic potential of the culture solution decreased total N uptake at all salinity levels, and 15N uptake of the plants at medium (−0.6) and high (−0.9 MPa) salinity levels. A low level of salinity (−0.3 MPa) did not affect 15N uptake compared with the control (−0.03 MPa). Water uptake and dry matter yield were affected to a greater extent than 15N absorption. Nitrogen‐15 concentration was slightly higher in roots than in shoots.
Rheology of Aqueous Suspension of Sodium/Calcium Montmorillonite
Authors: Keren R. 
Published: July 2010

AbstractThe rheological characteristics of montmorillonite suspension as a function of exchangeable sodium percentage (ESP), (when the complementary cation is Ca2+), Na‐polymetaphosphate adsorption by clay, and suspension pH were studied in aqueous media at a clay concentration of 25 g kg−1 and temperature of 25 °C. The differential viscosity (the derivative of shear stress with respect to the shear rate at a given shear rate), the extent of deviation from Newtonian flow, and the extrapolated shear stress values all increased with ESP at the range between 20 and 60%, but the values remained constant at 60 < ESP < 100. The rheology of Na‐montmorillonite suspension changed from non‐Newtonian to Newtonian as the Na‐polymetaphosphate (NaPO3)13 concentration in suspension increased. The rheology of montmorillonite suspension was pH‐independent when the clay was saturated with Ca ions, but pH‐dependent when the clay was saturated with Na ions. The differential viscosity increased as the pH decreased. At pH 10.0, Na‐montmorillonite suspension showed a Newtonian behavior, whereas at pH 7.0 non‐Newtonian behavior was observed. The power law coefficients and the extrapolated shear stress values indicate that the particle‐particle linkages increase by introducing Na ions to the exchangeable complex in the range 10 < ESP < 60. The edge surfaces were associated with the formation of linkage between clay platelets and were responsible for the pseudoplastic characteristics of the suspension.
Stability of Soil Aggregates as Inferred from Optical Transmission of Soil Suspensions
Authors: Abu‐Sharar T. M. 
Published: July 2010

AbstractStability of the semiarid Zezia soil aggregates was evaluated by measuring the optical transmission (%T) of suspensions of two size fractions (<2 and <5 µm) dispersed at decreasing electrolyte concentration of constant sodium adsorption ratio (SAR). At a given SAR, the %T decreased linearly with decreasing electrolyte concentration. Slopes of the equations decreased with increasing SAR; indicating a decreasing dependence of %T on electrolyte concentration as SAR increased. Such slopes were called stability indices (SIs). The clay‐SI was on the average 5.6 times greater than that of the <5‐µm fraction. At a given SAR, electrolyte concentrations corresponding to maximum clay dispersion (minimum %T values of 10) or very little clay dispersion (%T values of 20) were called critical concentrations (CCs) and threshold concentrations (TCs), respectively. At SAR values of 0, 5, 10, 25, and ∞, the CCs were 1.0, 3.7, 5.4, 10.3, 10.0, and 13.0 mol m−3, respectively, and the TCs were 2.2, 5.5, 9.2, 16.7, 17.8, and 32.6 mol m−3, respectively. Both CCs and TCs increased linearly with increasing SAR to a limiting value of 20. The TC for the <5 µm dispersed size fraction also increased linearly with increasing SAR. The TCs were 11.8, 40.4, 49.0, and 61.7 mol m−3 at SAR 0, 10, 15, and 20, respectively. These relatively high values imply that slaking of soil aggregates into sizes >2 µm can take place without a significant clay dispersion.
Simultaneous Determination of Urea and Ammonia Nitrogen in Soil Extracts and Water by High Performance Liquid Chromatography
Authors: Abshahi A. , Goyal S. S. , Mikkelsen D. S. 
Published: July 2010

AbstractCombining the separation efficiency of high performance liquid chromatography (HPLC) and the catalytic solid phase urease reactor, a simple, sensitive, and highly specific method for simultaneous determination of urea and ammonia nitrogen is possible. In this system the immobilized urease catalyzes the hydrolysis of urea to ammonium ions, which is then measured fluorometrically after postcolumn derivatization with o‐phthalaldehyde (OPA). The fluororphore is detected on‐line with a fluorometric detector, 344(ex) and 455(em) nm. The method is rapid and can be used to accurately monitor the urea and ammonia‐N content of soil, water, and fertilizer materials.
Quaternary Cation Exchange on Silver Hill Illite
Authors: Thellier Catherine , Sposito Garrison 
Published: July 2010

AbstractThe simultaneous exchange of Na, K, Ca, and Mg on Silver Hill illite suspended in 5 mol m−3 perchlorate background at pH 7 was investigated systematically. Composition data for both the exchanger and the equilibrium aqueous solution phase were obtained directly. The data showed that the total adsorbed metal charge was independent of exchanger composition provided that all four cations were considered. Analysis of the composition data with exchange isotherms and calculated Vanselow selectivity coefficients showed that: (i) K+ was preferred over Na+, Ca2+, and Mg2+, and the preference decreased as EK decreased (E = charge fraction on the clay mineral); (ii) bivalent cations were preferred only slightly over Na+ for ENa > 0.01, whereas for ENa ≤ 0.01, the reverse was true; (iii) no preference was shown in Ca‐Mg exchange at ENa values between 0 and 0.13.
Determination of Soil Characteristics from Thematic Mapper Data of a Cropped Organic‐Inorganic Soil Landscape
Authors: Lee Kyoo‐seock , Lee G. B. , Tyler E. J. 
Published: July 2010

AbstractMethods of determining soil characteristics from thematic mapper (TM) data were investigated at a site in southern Wisconsin. These methods utilized the soil‐sensitive spectral region of TM. Because there was little correlation between soil mapping units (soil phases) and the TM soil spectral classes, the former were grouped by wetness class, as determined from natural soil drainage classes, and by organic matter content. Agreement between wetness class and the April and September classifications, with absolute radiance and raw ratio transformation was 65.1, 61.3, 64.0, and 64.7%. When organic matter content was used instead of wetness class, the agreement ratio with TM was 74.0, 73.9, 68.4, and 66.0%. The April image correlated better with the soil map than the September image. Vegetative cover was a primary reason for difficulty in interpretation. The soil brightness image contributed most to classification accuracy, and can be used for manual soil interpretation. The stretched thermal IR image was also effective in discriminating between mineral soils and Histosols.
A New Technique for Evaluating the Presence of Preferential Flow Paths in Nonstructured Soils
Authors: van Ommen H. C. , Dekker L. W. , Dijksma R. , Hulshof J. , van der Molen W. H. 
Published: July 2010

AbstractA new technique for determining the presence of preferential flow paths in a nonstructured soil profile is described. The presented method is easily applicable in the field, and is based on the formation of an intensely colored complex of I2 with starch. Moreover, the method can be applied to all kinds of nonstructured soils, irrespective of their color. An illustration of the technique is given in case of water and solute movement in a water‐repellent soil, where formation of preferential flow paths was known to occur.
Comparison of a Laboratory Procedure and a Textural Model for Predicting In Situ Soil Water Retention
Authors: Schuh W. M. , Cline R. L. , Sweeney M. D. 
Published: July 2010

AbstractA physico‐empirical model proposed by L.M. Arya and J.F. Paris in 1981 for predicting the soil moisture characteristic curve using particle size and bulk density data was compared with a commonly used laboratory method using undisturbed core samples and a pressure plate extractor, for precision in estimating in situ water retention measured with paired neutron probe and tensiometer installations. An empirical factor for the Arya and Paris (A&P) model was found to average close to the value (α = 1.38) proposed by its authors. Values for this experiment were different between texture classes. Loam and silt loam values were constant, while values for soils of sand, loamy sand, and sandy loam texture were nonconstant. The empirical factor was calibrated for (i) loam and coarse loam; (ii) silt loam; and (iii) sand, loamy sand, and sandy loam texture groups. The sandy soil values required linear calibration as a function of soil water potential. Results for the calibrated A&P model compared well, overall, with laboratory determinations on soils ranging in texture from sand to loam and silt loam. Laboratory estimates were slightly better for A and B horizon materials, while A&P estimates were better for C horizons. Error for estimation of field volumetric water content using A&P and lab methods was approximately twice the error for estimation of θ using a second field neutron‐tensiometer installation within one meter of the first field apparatus.
Potassium‐Calcium and Sodium‐Calcium Exchange on Kaolinite and Kaolinitic Soils
Authors: Levy G. J. , van der Watt H. v. H. , Shainberg I. , du Plessis H. M. 
Published: July 2010

AbstractPotassium‐Ca and Na‐Ca exchange isotherms were obtained for two kaolinite samples and two kaolinitic soils (Hutton and Avalon forms). The Gapon, Vanselow, and Gaines‐Thomas corrected selectivity coefficients were usually greater for K‐Ca exchange than for Na‐Ca exchange, as was expected. The exchange isotherms and selectivity coefficients suggested a preference for K relative to Ca on all four exchangers. The contribution of micaceous impurities to the observed high affinity for K was taken into consideration, by reasoning that exchange sites with high affinity for K resulting from these impurities are first saturated with K [i.e., at low exchangeable potassium percentage (EPP) values]. It is suggested that the high charge density of kaolinite enhances K dehydration, resulting in a high affinity of kaolinite per se for K.
A Rapid Method to Determine Total Phosphorus in Soils
Authors: Bowman R. A. 
Published: July 2010

AbstractPresent methods for extracting total phosphorus (P) from soil samples are tedious and time consuming. A rapid and precise extraction procedure was developed in which sequential additions of concentrated H2SO3, H2O2, and HF were made to soil samples. This was followed by 10 min of heating (≃ 423 K) to eliminate excess peroxide. The entire procedure required about 30 min. The proposed method was compared to standard Na2CO3‐fusion and HClO4‐extraction methods. Almost equal amounts of P were extracted by the proposed and Na2CO3‐fusion methods. About 7% less P was found in HClO4 extracts. In the proposed method, treatment with H2O2 was used to oxidize P associated with the organic carbon. Treatment with HF was necessary to solubilize P associated with the aluminosilicate minerals found in sandy soils that are low in organic C. The proposed method is not only more rapid than those previously used, but is easily performed at minimal cost with simple laboratory equipment. It is especially useful for analyzing small numbers of soil samples, and should be useful to evaluate P dynamics in sediment transport (erosion) studies, and in soil formation and degradation studies.
Plant and Microbial Responses to Sorghum‐Soybean Cropping Systems and Fertility Management
Authors: Roder W. , Mason S. C. , Clegg M. D. , Kniep K. R. , Doran J. W. 
Published: July 2010

AbstractMonoculture production of soybeans (Glycine max (L.) Merr.) and grain sorghum (Sorghum bicolor (L.) Moench) generally results in declining grain yields. To better understand biological and chemical interactions causing yield declines with continuous cropping, microbial biomass, crop root dry weight, soil organic matter, and total N content were measured in a cropping system experiment on a Sharpsburg silty clay loam (Typic Argiudoll). The cropping treatments included continuous soybeans, continuous sorghum, and sorghum‐soybean or soybean‐sorghum rotations. These treatments were initiated 5 y prior to taking the reported measurements. Fertilizer treatments consisted of no amendment (control), N (45 kg ha−1 on soybean plots and 90 kg ha−1 on sorghum plots), and manure applied at 15.8 Mg dry matter ha−1 yr−1. In summer 1986, the microbial biomass C for the 0–30‐cm layer of soil averaged across fertility treatments was 1.37, 1.49, 1.43, and 1.58 Mg ha−1 for continuous soybeans, rotated soybeans, rotated sorghum and continuous sorghum, respectively. Soil microbial biomass C and soil organic matter contents for manured treatments were 11 to 14% and 6 to 16% greater, respectively than those of unfertilized controls. Root dry weights for the 0–30‐cm depth were 26 and 77% higher for soybeans and sorghum if the previous crop was sorghum instead of soybeans. In summer 1986, microbial biomass in the 0–15‐cm depth was correlated with root density and water‐filled pore space in sorghum plots and with bulk density in soybean plots. Previous crop, present crop, and fertilizer treatment affected dry matter partitioning between above‐ and below‐ground plant parts and microbial biomass. With sorghum as a previous crop, a higher proportion of the total production occurred below ground as roots and microbial biomass.