bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nitrogen Use Efficiency and Nitrogen Budget for Conservation Tilled Wheat
Authors: Sharpe R. R. , Harper L. A. , Giddens J. E. , Langdale G. W. 
Published: July 2010

AbstractThe understanding of nitrogen (N) cycling in the soil‐plant‐atmosphere is necessary to maximize N use efficiency and to develop N budgets for wheat (Triticum aestivum L.) production. The objectives of this study were to determine the relative uptake rates of residual soil N and fertilizer N in conservation tilled winter wheat. These data were combined with soil mineralization and aerial NH3 flux data to present a N budget for the soil‐plant‐atmosphere system. Fertilizer N uptake was determined using ammonium nitrate (15NH415NO3) tagged with 3.78 atomic % 15N. The buried polyethylene bag technique was used to determine N mineralization. Fertilizer N uptake and N mineralization rates were determined four times during the spring growing season. Amounts of NH4 and NO3 in the top 0‐ to 300‐mm soil layers were determined biweekly. Fertilizer N levels in the surface to 75‐mm soil layers decreased rapidly due to plant uptake and immobilization. Of the N fertilizer utilized by the plants, 61% was absorbed in the first 28 d after application. During early vegetative growth stages (Feekes stages 3–5), fertilizer N uptake was 1.33 kg ha−1 d−1. During the elongation stage (Feekes stages 5–8), however, fertilizer N was immobilized and uptake of fertilizer N ceased. This resulted in a period of soil N insufficiency which was associated with atmospheric NH3 influx to the plants. After 4 to 5 wk, mineralization of fertilizer N became apparent and fertilizer N uptake rates increased until harvest. Influx of atmospheric N was small but total NH3 efflux from the soil‐plant system was 15.5 kg N ha−1. About 21% of the spring applied fertilizer N was lost through NH3 volatilization and losses of this magnitude need to be considered in N balance studies. Placement of fertilizer N below the surface soil layer may decrease immobilization and increase plant uptake of N.
Nature of Cementing Materials in Ortstein Horizons of Selected Florida Spodosols: I. Constituents of Cementing Materials
Authors: Lee F. Y. , Yuan T. L. , Carlisle V. W. 
Published: July 2010

AbstractFive pairs of ortstein and nonortstein spodic horizons of Haplaquods were studied in an attempt to identify the nature of cementing materials. The ortstein horizons had significantly larger amounts of dithionite‐citrate‐extractable Al, significantly higher silt plus clay contents, and significantly higher bulk density values than did nonortstein spodic horizons. Moist and air‐dried ortstein samples had similar shear strengths, but the strength significantly decreased by 14 to 82% for oven‐dried samples. The strength had a significant correlation with the dithionite‐citrate‐extractable Al. Energy‐dispersive spectra showed that Si and Al were major constituents of both ortstein and nonortstein samples. Ortstein samples had stronger Al peaks, however. More cementing materials were observed in the ortstein than nonortstein samples in scanning electron micrographs. These cementing materials consisted of gel‐like substances and fine particles. Cracks in dry gel‐like substances between coarse particles were also observed. Electron‐dot pictures revealed that the gel‐like substances were Al‐dominated.
Effects of Fallow Length on Organic Carbon and Soil Fabric of Some Tropical Udults
Authors: Wadsworth G. , Southard R. J. , Singer M. J. 
Published: July 2010

AbstractSoil samples representing eight different ages of forest regrowth (0–50 yr following clearing) from fields in a pineapple slash and burn agricultural system were collected for organic carbon (OC) analysis and study of soil physical properties. The OC content of the surface soils decreased for 10 yr following clearing, then gradually increased close to the original level after 50 yr. Major micromorphological differences were apparent in surface horizons as a function of OC content. Soils with higher OC contents were more strongly aggregated and have more visible porosity than those with less OC. Bulk density and OC are statistically, significantly, negatively correlated (r2 = 0.64, p < 0.05), for combined data from all four representative pedons. Particle size distribution had a large effect on subsoil micromorphology. Argillic horizon fabric within the finest grained pedon was mostly mosepic with few discrete cutans suggesting that in situ weathering is a dominant clay forming process. Coarser textured pedons had well‐oriented argillans in the skelvosepic to vo‐masepic fabric of the argillic horizons. The short‐cycle slash and burn methods studied here have no observable effects on the micromorphology of the argillic horizons.
Polymer and Water Quality Effects on Flocculation of Montmorillonite
Authors: Aly Saleh M. , Letey J. 
Published: July 2010

AbstractWyoming Na‐montmorillonite (SWy‐1) was equilibrated with two synthesized waters, representing Friant‐Kern Canal or a typical well water of San Joaquin Valley (EC 0.05 and 0.7 dS m−1, respectively). Adsorption isotherms and flocculation patterns of the clay with three anionic and one nonionic polyacrylamide polymers and cationic, nonionic and anionic derivatized guar polymers, were observed. Polymer solutions of concentrations 0, 5, 10, 20, 50, and 100 mg L−1 were prepared and clay was added at a concentration of 1 g L−1. The test tubes were shaken and then periodically photographed to record floc formation and settling. Adsorption was in the general order: cationic > nonionic > anionic with the exception of the nonionic guar which was adsorbed about equally as the cationic guar. Adsorption of anionic polymers was greater from well water than canal water, whereas the opposite was true for the cationic polymer. Significant polymer water quality interactions on flocculation were observed. Anionic polymers promoted flocculation in the well water for polymer concentrations ≥ 5 mg L−1, but enhanced clay suspension stability in canal water. Floc volume increased with increasing cationic and nonionic polymer adsorption, whereas changes in floc volume were insignificant with anionic polymers. An optimal polymer concentration was found with well water. Flocculation with cationic polymer was attributed to charge neutralization, whereas flocculation with anionic polymers was explained by bridging and osmotic attraction.
Nonexchangeable Potassium Associated with Hydroxy‐Interlayered Vermiculite from Coastal Plain Soils
Authors: Harris W. G. , Hollien K. A. , Yuan T. L. , Bates S. R. , Acree W. A. 
Published: July 2010

AbstractHydroxy‐interlayered vermiculite (HIV) from a Quartzipsamment, a Haplaquod, and a Paleudult from Florida was studied to determine levels of nonexchangeable K associated with this mineral. Mineralogy was characterized by x‐ray diffractometry (XRD) and thermal analysis. A scanning electron microscope equipped with an energy‐dispersive x‐ray system was used to examine morphology of silt‐sized phyllosilicate grains and to qualitatively determine elements present. An electron microprobe equipped with a wavelength‐dispersive x‐ray system was used to obtain K x‐ray images and determine elemental oxide compositions of 82 randomly selected grains. Total K was determined for bulk samples using Na2CO3 fusion. Extractable K by double acid, HNO3, and H2SO4 was determined for clay fractions. Results confirmed that most phyllosilicate grains from quartz‐ and HIV‐dominated silt fractions of all samples contained sufficient K to be detected in K x‐ray dot images, though little or no mica was detectable by XRD. Mean K2O contents for mediumsilt grains from the Quartzipsamment, Haplaquod, and Paleudult were 2.3, 4.1, and 5.6%, respectively. Fine‐silt grains averaged 1.3, 1.3, and 2.3%, respectively, despite lack of infinite thickness. High K2O values, mica‐like grain morphology, and relatively large size of these grains suggest that they are transformation products of mica. Acid extracts from the clay also contained detectable levels of K. Nonexchangeable K may reside within grains as small occluded mica zones with insufficient periodicity for XRD detection, or could be retained in the 1.4‐nm structure. Results suggest a more direct transformation of mica to HIV rather than one involving a significant vermiculite intermediate.
Estimating Spatial Patterns in Water Content, Matric Suction, and Hydraulic Conductivity
Authors: Mulla D. J. 
Published: July 2010

AbstractA relatively rapid method for surveying and estimating field‐scale variability of water content, hydraulic conductivity, and matric suction using geostatistics is described. Two 660‐m long transects located 8 km west of Steptoe, WA were intensively sampled at 5‐m spacings for surface temperature. Soil samples were also collected to a depth of 12 cm at spacings of 20 m, and these were analyzed for sand, clay, and soil water content. The spatial variability in each property was described using spherical semivariograms. Kriging was used to estimate spatial patterns in clay and sand content along each transect at 5‐m spacings. Spherical cross‐semivariograms of surface temperature and water content were used along with cokriging techniques to estimate water content at 5‐m spacings. The geostatistical estimates of spatial patterns in water content, clay content, and sand content were used for texture‐based estimates of matric suction and hydraulic conductivity at 5‐m spacings along both transects. A comparison of texture‐based and laboratory‐based estimates of matric suction showed that although the two estimators gave similar spatial patterns and means, they had significantly different standard deviations. If it is important for a researcher to make quantitative predictions of matric suction, laboratory‐based estimates would be better than the texture‐based estimates. On the other hand, if what is important is estimating spatial patterns in matric suction, the texture‐based estimator would be acceptable.
A Comparison of Gas Diffusivity Models for Unsaturated Porous Media
Authors: Collin Marie , Rasmuson Anders 
Published: July 2010

AbstractThe effective gas diffusivity in a porous medium decreases rapidly with increasing water content. Comparisons are made between experimental diffusivity data for different materials at various moisture contents, and estimation methods from the literature. The estimation methods proposed by R.J. Millington and R.C. Shearer in 1971 give the best predictions of the effective diffusivity. The methods are extended here to account for the contribution of diffusion in the water‐filled pores. The method for aggregated media should be used for undisturbed clayey soils, and the method for nonaggregated media may be used for sandy soils and for other materials that are not aggregated, e.g., laboratory packed clayey soils. The experimental data show that very low effective diffusivities may be obtained in practice in soils with high moisture content.
Solubility of Barium Arsenate
Authors: Essington M. E. 
Published: July 2010

AbstractCurrent thermodynamic data suggest barium arsenate [Ba3(AsO4)2(c)] to be a highly stable phase. However, sufficient evidence is available to question the validity of the current data. In order to determine the solubility (pKsp) and calculate the standard free energy of formation (ΔG°f) of Ba3(AsO4)2(c), an equilbrium solubility study was conducted. The equilibrium experiments were carried out under three different ionic strength conditions for reaction times up to 45 d. Equilibrium was approached from both undersaturated and supersaturated initial conditions. The pKsp for the dissolution of Ba3(AsO4)2(c) was calculated to be 21.62. Correspondingly, a ΔG°f of − 3101.2 ± 2.0 kJ mol−1 was calculated. This value is 166.9 kJ mol−1 more positive than the current literature value. Reevaluation of the solubility data from a previous work suggests that the pKsp for the dissolution of BaHAsO4 · H2O(c) is 24.64 and the corresponding ΔG°f is − 1587.0 ± 2.5 kJ mol−1.
Adsorption of Thiram and Dimethoate on Almeria Soils
Authors: Valverde‐García A. , González‐Pradas E. , Villafranca‐Sánchez M. , del Rey‐Bueno F. , García‐Rodriguez A. 
Published: July 2010

AbstractThe adsorption process of thiram and dimethoate on Almería (East‐Andalucía, Spain) soils from aqueous solution at 30 °C has been studied. The adsorption isotherms may be classified as L type of the Giles classification. The Kf values (Freundlich equation) vary between 4.81 to 13.73 for fungicide thiram (tetramethylthiuram disulfide) and between 1.06 to 8.95 for insecticide dimethoate [O,O dimethyl S‐(N methylcarbamoylmethyl) phosphorodithioate] depending on the soil type. In relation to the correlations between adsorption parameters and soil properties, the adsorption process of thiram seems be conditioned by the soil organic matter content whereas the adsorption of dimethoate is fundamentally conditioned by specific surface area and by cation exchange capacity.
Sulfur Supplying Capacity of Some Missouri Soils
Authors: Hanson R. G. , Haron K. B. 
Published: July 2010

AbstractConfirmed S deficiencies on some Missouri soils necessitated a study to determine their capacities to supply S to plants. Surface (0–30 cm) and subsurface (30–60 cm) depths of two Alfisols (Bosket loamy fine sand, Dubbs fine loamy sand) and one Entisol (Malden fine sand) from southeastern Missouri, and surface depths (0–30 cm) of an Alfisol (Kennebec silty clay loam) and Mollisol (Mexico silt loam) from northern Missouri were used. The soil properties measured included pH, organic matter, cation exchange capacity (CEC), Bray & Kurtz P1 (BK1) and P2 (BK2), labile SO4 (LAS), SO4 buffer index (SBI), extractable SO4 (500 mg P L−1 in 2 M HOAc), and soil texture (sand, silt, and clay). Soils were amended with 0 and 22 mg S kg−1, and corn (Zea mays L., hybrid DeKalb 1189TX) dry matter yield and S uptake were measured through five 35‐d intensive cropping cycles. There was little S uptake from unamended Bosket (0–30 and 30–60 cm), Dubbs (0–30 and 30–60 cm), and Malden (0–30 and 30–60 cm) zero‐S soils after the second cropping cycle. The Kennebec and Mexico soils exhibited a plant growth response during the second and fifth cropping cycles, respectively. The significant increase in yield response to S fertilization suggests the Dubbs (0–30 and 30–60 cm), Malden (0–30 and 30–60 cm), and Bosket (30–60 cm) to have inadequate capacities to supply S to plants. Of these three southeastern Missouri soils, the Bosket 30‐ to 60‐cm depths yielded the highest plant S uptake. This suggests that soils of this region with similar surface textures may possess differences in total plant available S when subsoil available S is included in this total. The SO4 buffering index (SBI) correlated negatively with BK1 and BK2 available P suggesting that high or excess P fertilization would decrease the capacity of these soils to adsorb SO4. With the 22 mg S kg−1 treatment, using total SO4 (TSO4 = extractable SO4 + added SO4) as the independent variable, S uptake was not dependent on this TSO4 quantity during the first 35‐d cropping period. For the 0‐ to 70‐d cropping, S uptake was significantly dependent on the TSO4. The relationship (r = 0.99) between the extractable SO4 and SO4 labile pool (LAS), and their relationships to plant S uptake during the 0 to 35 d (r = 0.98, r = 0.97) and cumulative 0 to 70 d (r = 0.95, r = 0.95) cropping periods indicates that SO4 extracted with 500 mg P L−1 in 2 M HOAc to be a good estimate of plant available SO4‐S. The relationships (r = 0.84 for 0–35 d and r = 0.90 for 0–70 d) between CEC and plants S uptake suggests the need to investigate the potential mechanism of CEC to SO4 availability and other soil properties that may be correlated to CEC.
Comparison of Kinetic Models for Describing Net Sulfur and Nitrogen Mineralization
Authors: Ellert B. H. , Bettany J. R. 
Published: July 2010

AbstractNet S and N mineralization in forested and cultivated Typic Cryoboralfic soils was monitored over 37 wk in a laboratory incubation experiment with intermittent leaching. Patterns of net S and N release depended on the management histories of the soils. Several kinetic models were evaluated for the ability to accommodate continuously decreasing rates, a large initial flush of mineralization, a mineralization lag within the first 13 wk of incubation, or a constant rate of release near the end of incubation. Mineralization in the forest E horizon was best described by a modified first‐order model with contributions from an easily mineralizable pool to account for an initial flush of S mineralization. Initial flushes of mineralization could be described by two simultaneous first‐order reactions, but the additional complexity of the model was unjustified, because contributions from the rapidly mineralizing pool did not extend beyond the first incubation interval. Soils from a field cultivated since 1905, a recently cleared field and, the organic layer from a native forest had fluctuating mineralization rates which appeared as lags in the cumulative amounts of inorganic element released over time. The lagged mineralization patterns were best described by consecutive reaction or Gompertz models. The Guggenheim method of fitting the first‐order model was demonstrated as an alternative to nonlinear regression. Fitting nonlinear kinetic models to incremental data from each incubation interval was superior to conventional approaches which use cumulative data obtained by summing the incremental observations. Information from net mineralization patterns was maximized by improving the methods of data analysis.
Characterization of a Pimple Mound‐Intermound Soil Complex in the Gulf Coast Prairie Region of Texas
Authors: Carty D. J. , Dixon J. B. , Wilding L.P. , Turner F.T. 
Published: July 2010

AbstractNatural mound and intermound soil pedons were characterized to investigate native mound‐intermound formation and soil properties that may explain unfavorable plant growth that has been observed on sites of truncated mounds. Subrounded mounds average 26‐m apart, 15 m in diam., and 0.5 m in local relief. Mound soil has a thick silt loam A horizon, silt loam E, B/E, and BE horizons, and thick, weakly expressed Bt (argillic) horizons of silt loam to clay loam texture. Upper mound horizons are acid, and the lower Bt horizon is neutral to calcareous. Calcareous intermound soil, originally mapped as Morey (fine‐silty, mixed, thermic Typic Argiaquolls) silt loam, has a silt loam A horizon above clay loam cambic and calcic horizons. Better infiltration and drainage in the mound contrasts with very slow runoff and poor infiltration and drainage in the intermound. Mound and intermound mineralogy is similar, with mainly quartz in coarse silt and very fine sand separates, kaolinite and quartz in coarse clay, and smectite and kaolinite in the fine clay fractions. Carbonate, base saturation, pH, and illuviation argillan distributions suggest predominantly downward water flow with desiccation and rewetting cycles in the mound soil, contrasted with more prolonged periods of wetness in the intermound soil. Particle size and Ti and Zr distributions indicate a definite parent material break above the mound Bt horizon, but no clear break in the intermound. Properties of the loamy mound soil investigated are consistent with a mechanism of local wind or water deposition around clumps of vegetation. Soil surface exposed by mound truncation is a poor plant growth medium because it consists of acid, silty, slightly buffered material with low organic matter content and weak structure.
Exploitation of Soil Potassium in Layered Profiles by Root Systems of Cotton and Barley
Authors: Gulick S. H. , Cassman K. G. , Grattan S. R. 
Published: July 2010

AbstractOn vermiculitic soils of the San Joaquin Valley, cotton (Gossypium hirsutum L.) often responds to K fertilization where other annual crops do not. These soils have markedly higher available K in surface soil than in subsoil. A pot study was conducted to compare rooting patterns, K uptake, and dry matter production of cotton and barley (Hordeum vulgare L.) in soil profiles with layered K availability. Topsoil (0.15 cmolc K kg−1) was layered to each of six depths above subsoil (0.09 cmolc K kg−1) in 17‐L pots with a total soil depth of 45 cm in all treatments. Two irrigation regimes were imposed and nutrients other than K were adequately supplied. For both crops, plant dry matter and K uptake increased linearly with increased topsoil depth but K uptake per unit increase in topsoil depth was 6.5‐ and 3.6‐fold greater by barley than for cotton with frequent and infrequent irrigation, respectively. Increased K uptake per unit increase in topsoil depth reflected coincident root and K distribution: barley root length density (RLD) was 2.7 times greater than RLD of cotton in topsoil layers but little different in subsoil layers. Poor exploitation of topsoil layers by the cotton root system was attributed to greater sensitivity to low soil water potential. A root system with little compensatory root development in the surface soil when the subsoil is low in nutrients may limit K uptake and crop productivity on layered soils in the San Joaquin Valley and may require management systems designed to promote more congruent root and nutrient distribution.
Contribution of Ferrimagnetic Minerals to Oxalate‐ and Dithionite‐Extractable Iron
Authors: Fine P. , Singer M. J. 
Published: July 2010

AbstractMagnetic removal of magnetite particles to minimize Fe contribution from a well crystallized iron oxide to the acid ammonium oxalate (AAO) extractable iron (Feo) has been recommended as a pretreatment in chronosequence studies. Samples from two soil chronosequences in California were examined to determine the efficacy of using a hand magnet to remove magnetic particles from soils, and sediments. Magnetic susceptibility (χ) was used as a measure of treatment effect. Samples from 74 horizons retained 74 ± 20% of their original (χ) after treatment with a small hand‐held magnet. Clay and silt‐sized ferrimagnetic particles, which were responsible for 4 to 91% of the soils' χ, were not removed from the samples. Also sand‐sized ferrimagnetics could not be fully removed. Ferrimagnetics were more successfully removed from beach sand deposits. These retained only 14 ± 7% of their χ value. The AAO extraction of 31 magnetically depleted soil samples from typical soil horizons lost an additional 31 to 95% of their residual susceptibility, mostly as maghemite. The retention of a greater fraction of the ferrimagnetics within the soils, and their contribution to the Feo, proved the magnetic cleaning technique to be neither quantitative nor systematic. Magnetite was more resistant than maghemite to AAO. Magnetite was also fully resistant to the citrate‐bicarbonate‐dithionite (CBD) extractant whereas authigenic soil maghemite was completely dissolved in CBD. Magnetic monitoring of AAO‐ and CBD‐treated soils offers some insight into the nature and distribution of the ferrimagnetics in the soil profile.