bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nutrient Uptake in Fertilized Plantations of American Sycamore
Authors: Wittwer R. F. , Immel M. J. , Ellingsworth F. R. 
Published: July 2010

AbstractAnnual applications of ammonium nitrate (169 kg/ha elemental N), alone and in combination with concentrated superphosphate (112 kg/ha elemental P), increased biomass of 4‐ and 5‐year‐old American sycamore (Platanus occidentalis L.) by approximately 45 and 205% on a bottomland and a terrace site, respectively, in the Ohio River Valley region of western Kentucky. Growth response and nutrient contents of trees fertilized with N and P were not significantly different from those receiving N only. After 5 years, N fertilization has increased elemental content of aboveground tree components by 189% for N, 48% for P, 90% for K, 93% for Ca, and 106% for Mg. Initial spacing of the seedlings in these closely‐spaced (0.3 by 0.9 m, 0.9 by 0.9 m, 1.8 by 0.9 m) trials did not have a significant effect on nutrient contents. Recovery of added N, as indicated by increased above ground tree contents after 5 years, represented 11 and 14% of the quantity added in fertilizer applications on the bottomland and terrace, respectively. After 5 years, levels of available P in soils receiving annual P fertilization had increased by 140 kg/ha, representing about 25% of the total P added. After 5 years exchangeable Ca had decreased in the bottomland soils and exchangeable K, Ca, and Mg had decreased in the less fertile terrace soil.
Iron Coatings on Rice Roots: Mineralogy and Quantity Influencing Factors
Authors: Chen C. C. , Dixon J. B. , Turner F. T. 
Published: July 2010

AbstractRice (Oryza sativa L.) root coatings were investigated to determine the amounts and mineralogical properties of the coatings during plant growth and in different soils under field conditions. X‐ray diffraction, electron microscopy, high gradient magnetic separation, and chemical methods were employed. Determinations of oxygen transport by different rice cultivars were made in vitro.Rice cultivars, growth stage, and soil type were significantly related to the amount of iron oxyhydroxide (FeOOH) on field‐grown rice roots. Accumulation of FeOOH was < 2% of dry root weight 7 days after flooding of the soil, increased to a maximum of about 10% at plant maturity and decreased slightly thereafter. Of the four soils studied, two Vertisols had less FeOOH accumulation on root surfaces than two Alfisols. Of the four cultivars characterized (‘Brazos’, ‘Labelle’, ‘Lebonnet’, and ‘Bluebelle’), Brazos had the largest amount of O2 released from the roots and precipitated the largest amount of FeOOH on the roots when field grown in three of four soils. Lake Charles clay was the only soil in which Brazos rice did not rank highest in percent FeOOH on roots and in grain yield.Goethite (α‐FeOOH) and lepidocrocite (τ‐FeOOH) were identified in rice root coatings that were ultrasonically dispersed and concentrated by high gradient magnetic separation.
Mineralogy of Saudi Arabian Soils: Southwestern Region
Authors: Aba‐Husayn M. M. , Dixon J. B. , Lee S. Y. 
Published: July 2010

AbstractMineralogical properties of soils along a 500‐km north‐south transect in the mountainous Asir region were investigated. The transect represented areas of wide variations in climate, parent material, and topography. Soils developed on stable landscapes at higher elevation (> 2,000 m) have well‐developed profiles and near neutral soil pH's. Soils developed on alluvial terraces near wadi banks at lower elevations (> 1,500 m) have deep but less developed profiles, and slightly greater than neutral pH's with carbonates present. Quartz, feldspars, and micaceous minerals are the major components of the silt and sand fractions of the soils. Clay fractions of the soils are composed mainly of kaolinite, smectite, vermiculite, mica and chlorite minerals. Kaolinite is the most abundant clay mineral of the soils developed on well‐drained highland areas. Smectite is the most abundant clay mineral in the alluvial soils developed on lower terrace areas.
Experimental and Mathematical Description of Nonadsorbed Solute Transfer by Diffusion in Spherical Aggregates
Authors: Rao P. S. C. , Jessup R. E. , Rolston D. E. , Davidson J. M. , Kilcrease D. P. 
Published: July 2010

AbstractDiffusion of nonadsorbed solutes (3H2O and 36Cl‐) out of two sizes of porous ceramic spheres (0.55‐ and 0.75‐cm radius) was measured. These data were analyzed to provide independent estimates of the input parameters required in two simulation models for describing solute transport in aggregated porous media with distinct mobile and stagnant pore‐water regions. Tracer‐saturated porous spheres were placed in tracer‐free 0.01N CaCl2 solution and the rate of tracer diffusion out of the porous spheres was measured by monitoring the increase in tracer concentration with time in the external electrolyte solution. Experimental results were analyzed using two mathematical models. Fick's second law, written in spherical coordinates, formed the basis for Model I. In Model II, the time‐rate of solute transfer into or out of the porous spheres was assumed to be proportional to the difference in tracer concentration inside and outside the porous spheres. The analytical solution to Model I for given initial and boundary conditions was substituted into Model II, to derive an explicit expression relating the empirical mass transfer rate coefficient (α) in Model II and known physical constants of the system. This theoretical analysis indicated that the α value is dependent upon the sphere radius, time of diffusion, volumetric water contents inside and outside the sphere, and the molecular diffusion coefficient. Over a range of experimental conditions, excellent agreement was found between measured α values and those calculated using the analytic expression developed here.
Effect of Particle Surface Roughness on Densification of Coarse‐Textured Soil
Authors: Cruse R. M. , Cassel D. K. , Averette F. G. 
Published: July 2010

AbstractIt has been observed that soils on the Atlantic Coastal Plain compact to different bulk densities under the same compactive effort. It is hypothesized that densification differences observed among Ap horizon materials of these soils are partially due to variations in soil particle surface roughness. Surface roughness of Coastal Plain soil materials and sand size fractions derived from these materials were photographed and/or characterized by measuring the dense soil angle of response (DSAR) over a range of bulk densities. Altering the particle size distribution of a given material did not significantly influence the DSAR vs. Db (soil bulk density) relationship; the slopes and intercepts of these linear plots were not statistically different. However, plots of DSAR vs. Db for materials with different particle surface roughness had similar slopes, but different intercepts. It is proposed that the intercept of the DSAR vs. Db curve, or the value of DSAR at a given Db, be used to characterize soil particle roughness for coarse‐textured materials.It was further hypothesized that the DSAR at a given Db was directly related to particle packing arrangement stability, or resistance to further densification, of the soil material. To test this hypothesis, different levels of vibrational energy were applied to materials with different particle roughness but similar particle size distributions. Soil materials with the smoothest particles, i.e., those with the lowest DSAR at each Db, consistently produced the highest Db at each vibrational energy level.
Studying Dried, Stored Soil Samples — Some Pitfalls
Authors: Bartlett Richmond , James Bruce 
Published: July 2010

AbstractDried, pulverized, and sieved soil samples are prepared and stored for laboratory research convenience. Drying and increasing time of storage both tend to push soil, which is metastable, toward increased surface acidity, reduced Mn, and increased solubility and oxidizability of soil organic matter. Reformation of metastable moist soil is a slow process mediated by environmental conditions interacting with life in the soil. Similar effects undoubtedly occur in the field as soils are dried.Two sets of problems confront the researcher using dried soil samples: those associated with drying itself and those associated with remoistening. The behavior of a dried sample immediately after adding water to it is different from that of the continuously moist soil. Remoistening for a longer period is followed by a microbiological explosion. The behavior of the soil for an extended period, perhaps more than a month after rewetting, may be anomalous, or at least unpredictable. Keeping a soil moist and aerobic, though certainly inconvenient, is the most satisfactory method of storage for many research uses.
Nitrogen Mineralization in Florida Histosols
Authors: Terry Richard E. 
Published: July 2010

AbstractThe N‐mineralization rates of several Florida Histosols and the effects of soil moisture tension and organic C amendments on these rates were measured in the laboratory with an 15N‐tracer technique. An enhancement of microbial activity by crop residues was exhibited by greater N mineralization in cropped vs. uncropped soils. Nitrogen mineralization was not affected by soil moisture tension over the range of 0.1 to 3.0 bar. Exogenous C supplies such as glucose or St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntz] stimulated mineralization of native soil organic matter. Mineralization of soil organic N was increased by 91% in glucose amended soil samples. The N‐mineralization rate for a 75‐cm profile of Pahokee muck was estimated to be 686 kg N/ha for each centimeter of soil lost to microbial oxidation.
The Partial Inactivation of Degradative Soil Enzymes by Residual Fertilizer Copper in Histosols
Authors: Mathur S. P. , Sanderson R. B. 
Published: July 2010

AbstractSamples of 14 neighboring fields of Histosols (organic soils) were similar in all but one of their 24 physical and chemical properties examined. The Cu content of these soils varied from 18 to 275 µg/g. Activities of C1‐cellulase, Cx‐cellulase, cellobiase, xylanase, amylase, inulase, lichenase, and lipase enzymes in the air‐dried and stored soil samples were found to correlate posiitvely with soil respiration and negatively with soil Cu content. Similarly, when samples from many border strips kept free of plants by cultivation in the same 14 fields were collected, air‐dried at about 23°C, and assayed within 1 week in summer, soluble Cu content of the soils was found to be negatively correlated with the cellobiase and invertase activities, and the enzyme activity levels similar to those of the air‐dried samples in storage for 2 years. Evidence presented therefore supports earlier suggestions that Cu may restrain the mineralization and subsidence of some organic soils through inactivation by the Cu of certain extracellular soil enzymes which normally facilitate biochemical oxidation of nonhumic soil organic matter.
Nitrate Movement Under Corn and Fallow Conditions
Authors: Long F. Leslie , Huck Morris G. 
Published: July 2010

AbstractNitrate movement under corn (Zea mays L.) and fallow conditions was studied in a simulated field soil profile of Dothan loamy sand (Plinthic Paleudults) in the Auburn rhizotron. The rates of N applied were 250 and 500 kg N/ha. The nitrate movement was monitored by analysis of soil solution samples taken at 48‐ to 72‐hour intervals over a 120‐day period from the 20‐, 40‐, 60‐, 80‐, 100‐, and 140‐cm depths. Nearly all the nitrate applied to the surface of fallow plots moved with percolating water and was leached below the 100‐cm depth within 65 days; this was true for both N rates. Actively‐growing corn roots intercepted nitrate from the 250 kg N/ha treatment before it reached the 80‐cm depth and from the 500 kg N/ha treatment before it reached the 100‐cm depth. At maturity the above‐ground portion of the corn contained 20% more N than was applied at the 250 kg N/ha rate and 75% of that applied at 500 kg N/ha. Corn roots effectively prevented leaching of nitrate.
Predicting the Effects of Changing Water‐Table Levels and Associated Soil Moisture Regimes for Soil Survey Interpretations
Authors: Bouma J. , de Laat P. J. M. , van Holst A. F. , van de Nes Th.J. 
Published: July 2010

AbstractA one‐dimensional computer model for simulating the soil moisture regime was used to calculate evapotranspiration and equivalent productions of grass for six different soils. Input data consisted of rooting depths, moisture retention curves and hydraulic conductivity curves. Physical boundary conditions were derived from climatic data and depths to water table. Average relative production was calculated for actual water table fluctuations and for lowered levels, thus simulating the effects of ground water extraction. Productions for the six soils reacted quite differently to lowering of the water table. A classification was developed to characterize the different reactions. A SYMAP computer program was used to produce maps (which were based on soil maps) showing the effects in different soils to lowering of the water table. Storage of basic data on tape allows the production of many maps on demand for natural conditions and for conditions changed by man. Soil survey interpretation thus becomes a matter of offering many choices rather than a qualitative judgement based on actual conditions. The model can be used to express variability of mapping units on a soil map by simulating moisture regimes for the range of soil properties observed within the mapping unit.
Rebound of Five One‐Dimensionally Compressed Unsaturated Granular Soils
Authors: Stone J. A. , Larson W. E. 
Published: July 2010

AbstractRebound (decrease in bulk density after removal of mechanical stress) of five agricultural soils from four soil orders was measured at stresses of 1,000, 5,000 and 10,000 g cm−2 and pore water pressures from 0 to −1 bar.Rebound was usually < 0.05 g cm−3. It was larger in soils containing expanding clays than in soils containing nonexpanding clays. It increased with stress in soils containing expanding clays but not in soils containing nonexpanding clays. Rebound decreased with repeated loading. It could not be delineated in terms of soil type, pore water pressure, or water content. In the prediction of bulk density of unsaturated agricultural soils based on their compression characteristics, rebound is usually small enough that it can be neglected.
Estimating Water Used by Irrigated Corn in West Central Minnesota
Authors: Dylla A. S. , Timmons D. R. , Shull H. 
Published: July 2010

AbstractIrrigation development in Minnesota is expanding rapidly on the sandy and droughty soils of which there is considerable area. Construction of suitable wells into underlying gravel aquifers has facilitated the rapid growth. The objective of this study was to measure water use by irrigated corn in west central Minnesota for comparing with current estimating methods for irrigation scheduling. Lysimeters, 1.75 m diam by 1.22 m deep, located in irrigated corn (Zea mays L.) plots were used to measure water use or evapotranspiration (ET) amounts. Four years of comparisons were made of measured ET to amounts calculated with the standard and refined Jensen‐Haise potential ET equations and corn crop coefficients from southeastern North Dakota data. Measured ET was also compared with ET estimates determined by the Lundstrom‐Stegman “checkbook method,” and by crop coefficients with pan evaporation. Crop coefficients with pan evaporation provided the better ET estimates, however, the “checkbook method” was the simplest and was about as accurate for estimating ET as the Jensen‐Haise potential ET equation with southeastern North Dakota crop coefficients.
A Closed‐form Equation for Predicting the Hydraulic Conductivity of Unsaturated Soils
Authors: van Genuchten M. Th. 
Published: July 2010

AbstractA new and relatively simple equation for the soil‐water content‐pressure head curve, θ(h), is described in this paper. The particular form of the equation enables one to derive closed‐form analytical expressions for the relative hydraulic conductivity, Kr, when substituted in the predictive conductivity models of N.T. Burdine or Y. Mualem. The resulting expressions for Kr(h) contain three independent parameters which may be obtained by fitting the proposed soil‐water retention model to experimental data. Results obtained with the closed‐form analytical expressions based on the Mualem theory are compared with observed hydraulic conductivity data for five soils with a wide range of hydraulic properties. The unsaturated hydraulic conductivity is predicted well in four out of five cases. It is found that a reasonable description of the soil‐water retention curve at low water contents is important for an accurated prediction of the unsaturated hydraulic conductivity.
First Integrals of the Diffusion Equation; An Extension of the Fujita Solutions
Authors: Parlange J.‐Y. , Braddock R. D. , Chu B. T. 
Published: July 2010

AbstractIn general, solutions of the nonlinear diffusion equation have to be obtained by numerical or analytical iterative integration. It is shown here that if the diffusivity has a dependence on the water content which obeys a power law, then iterations can be avoided, and the solution obtained at once. This unique case results from the existence of a first integral of the diffusion equation. Previously known analytical results, i.e., the constant diffusivity solution, the delta‐function solution, and the Fujita solutions belong to that general class.For this general class of solutions it is also possible to show that the sorptivity has a dependence on the surface water content which obeys a power law. This represents the only known case when such an analytical relationship exists. This relationship is used to discuss the representation of the square of the sorptivity as an integral of the diffusivity, when the latter has an arbitrary dependence on the water content.
Prediction of Diffusion Coefficients from the Electrical Conductance of Soil
Authors: Palmer C. J. , Blanchar R. W. 
Published: July 2010

AbstractElectrical conductance may be used to predict salt movement through soil by diffusion. A two‐component model was used which considers electrical conductance in soil to be a combination of a solution and a surface process. It has the form: ECa = ECwθT8 + EC8 where ECa is the specific conductance of the soil, ECw is the conductance of the solution, θ is the volumetric moisture content, ECr is the surface conductance, and T8 is the tortuosity. It was assumed that T8 and EC8 did not vary with changes in solution concentration, and these two parameters were calculated by measuring ECa and ECw on two soil samples which differed only in electrolyte concentrations. These values were used to calculate the equivalent conductance and the diffusion coefficients for Na+ and K+.The alternating current measurement of conductivity was frequency (f) dependent due to electrode‐electrolyte interactions known as the Warburg impedance. The specific conductance was found by plotting the measured conductance against f‐0.5 and extrapolating to zero. At low electrolyte concentrations, the conductivity of the soil varied as a linear function of the logarithm of frequency and this factor was evaluated before predicting diffusion coefficients from the conductance of the soil.The diffusion coefficient for K+ in four soils with 0.0133M KCl varied from 1.64 × 10−6 to 0.50 × 10−6 cm2/sec when computed from electrical conductivity but varied from 1.84 × 10−6 to 0.33 × 10−6 cm2/sec when computed from self‐diffusion. The fraction of the electrical current carried by the 0.0133M KCl in the soil solution varied from 0.85 to 0.13 and was inversely related to the cation exchange capacity. A comparison of diffusion coefficients estimated from the self‐diffusion of 42K and 24Na in concentrated and dilute systems indicates good agreement except for 0.0133M K+ in the Mexico Ap soil. The data suggest that diffusion measurements made by electrical conductance are more reproducible than those made by self‐diffusion, but give estimates of the diffusion coefficient that are of similar magnitude.
A Comparison of the Use of Phenolase and Peroxidase for the Synthesis of Model Humic Acid‐type Polymers
Authors: Martin J. P. , Haider K. 
Published: July 2010

AbstractYields of HA (humic acid) and FA (fulvic acid) fractions of mushroom phenolase‐catalyzed humic acid‐type polymers varied considerably. The higher yields from 4 g of phenol mixture alone or with 1 g of various amino acids, glucosamine, or protein; and with 150 to 300 mg of phenolase varied from 1.5 to 2.5 g with about equal amounts in both fractions. As determined by use of 14C‐labeled compounds, about 33% of the ferulic acid; 55% of catechol; 5 to 14% of glycine, lysine, and glucosamine; 50% of cysteine; and 100% of the protein present in the reaction mixtures were recovered in the ploymers. Using an adaptation of the peroxidase — H2O2 method for preparing model lignins the yields of humic polymers were more consistent, varied from 2.5 to 3.5 g, and about 80% of each polymer was recovered as HA. Also about 77% of the ferulic acid; 95% of catechol; 23 to 34% of glycine, lysine, and glucosamine; 63% of cysteine; and essentially all of the protein present in the reaction mixtures were recovered in the polymers. All model polymers were resistant to biodegradation in the soil. During 12 weeks 4 to 8% of benzene ring carbons and 8 to 25% of ferulic acid side group, amino acid, glucosamine, and protein carbons were evolved as CO2.
Plant Effects on Soil Manganese Availability
Authors: Godo Gnahoua H. , Reisenauer H. M. 
Published: July 2010

AbstractRelationships differ greatly between soil Mn solubility and pH, between plant uptake of Mn and soil pH, and between plant uptake of Mn and nutrient solution pH. The discrepancies suggest that soil Mn availability is controlled by neither soil nor plant characteristics per se but by the combined effects of soil properties, plant characteristics, and the interactions of plant roots and the surrounding soil.Experiments were done to evaluate the contributions of root/soil interactions, specifically those of root exudates, to Mn availability. The solubility of soil Mn and of MnO2 in root exudates and in rhizosphere and bulk soils was measured over the pH range of 4.5 to 6.5. The relationships between pH and MnO2 solubility in solutions of root exudates and selected root exudate components closely resembled those between plant uptake of Mn and soil pH. Similarly, the relationship between CaCl2‐soluble Mn in the rhizosphere soil and soil pH resembled that between plant uptake of Mn and soil pH. The pattern with pH of the CaCl2‐soluble Mn of the bulk soil was that of soil alone and fell below that of the rhizosphere soil. These relations establish that root exudates make an important contribution to plant uptake of soil Mn. Exudate compounds, such as hydroxy‐carboxylates, increase soil Mn solubility through reducing MnO2 and complexing the divalent Mn released. The effect is particularly marked in systems more acid than pH 5.5 and explains many of the apparent anomalies of soil Mn availability.