bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evaluation of Methods for Determining the Apparent Thermal Diffusivity of Soil Near the Surface
Authors: Horton R. , Wierenga P. J. , Nielsen D. R. 
Published: July 2010

AbstractField‐measured values of soil temperature were used to calculate the apparent thermal diffusivity of the upper 10 cm of soil with six different methods. The limitations of the six methods were analyzed both in terms of the calculated results, and for the quantity and quality of data required to make the calculations. Four of the six methods, Amplitude, Phase, Arctangent, and Logarithm, provided explicit equations for the thermal diffusivity. These explicit methods required only a few measurements of temperature, and calculations were simple to perform; however, the results were found to be erratic and in general inconsistent with known or more reliable estimates of the apparent thermal diffusivity. Two methods, Numerical and Harmonic, which made use of larger numbers of temperature measurements to implicitly solve for the apparent thermal diffusivity, generally provided more reliable estimates. Calculated values of the apparent thermal diffusivity by both methods were used in predicting soil temperature for comparison with measured temperature. Even under partly cloudy conditions both methods predicted temperatures very well. In general the data requirement of the Numerical method was 12 to 24 measures of temperature per day at three depths, while the Harmonic method only required 8 to 12 measures of temperature per day at two depths.
Copper(II) Binding by Humic Acid Extracted from Sewage Sludge: An Electron Spin Resonance Study
Authors: Boyd Stephen A. , Sommers Lee E. , Nelson Darrell W. , West Douglas X. 
Published: July 2010

AbstractElectron spin resonance (ESR) spectroscopy was used to study the binding of Cu2+ by humic acid (HA) extracted from sewage sludge. Electron spin resonance spectral data of the Cu‐HA complex and some adducts with nitrogen donors (pyridine, 1,10‐phenanthroline, ethylenediamine) showed that Cu2+ formed two equatorial bonds with HA oxygen donor ligands. The ESR data presented were consistent with the formation of a Cu‐chelate in the original Cu‐HA complex. The ligand field strength of the HA oxygen donor ligands coordinated to Cu2+ was stronger than that of H2O. The above results were consistent with an earlier ESR characterization of a soil Cu‐HA complex. The Cu2+ ion also appeared to form axial bonds with HA donor ligands originating from proteinaceous materials associated with the sludge HA fraction. Characterization of an adduct with glycylglycine showed that the dipeptide formed coordinate honds with Cu2+ bound to HA.
Sodium‐Calcium and Sodium‐Magnesium Exchange on Wyoming Bentonite in Perchlorate and Chloride Background Ionic Media
Authors: Sposito Garrison , Holtzclaw Kenneth M. , Charlet Laurent , Jouany Claire , Page A. L. 
Published: July 2010

AbstractThe exchange of calcium and magnesium for sodium at 298 K on Wyoming bentonite was investigated in perchlorate and chloride background media maintained at pH 7.0 and at a total cation normality of 0.05N. In the perchlorate medium, the apparent total adsorbed metal charge was independent of the exchanger composition and equal to 0.97 ± 0.06 molc kg−1 (average for Na‐Ca and Na‐Mg exchanges). In the chloride medium, the apparent total adsorbed metal charge increased with the amount of calcium or magnesium adsorbed, tending to a value near 1.3 molc kg−1 as the clay became saturated with the bivalent metal cation. These results were interpreted as evidence for the adsorption of CaCl+ or MgCl+ complexes in the exchange experiments conducted in the chloride medium. A detailed analysis of the exchange data led to the conclusion that a Ca‐montmorillonite or Mg‐montmorillonite suspension in a chloride background consists of quasicrystals with bivalent cations adsorbed on the internal surfaces and monovalent metal‐chloride complexes adsorbed on the external surfaces.
Melanoidins and Soil Organic Matter: Evidence of Strong Similarities Revealed by 13C CP‐MAS NMR
Authors: Benzing‐Purdie Laure , Ripmeester John A. 
Published: July 2010

AbstractMelanoidins of molecular weight higher than 12000 were synthesized by reaction of xylose with glycine (I), xylose with ammonium sulfate (III), and glucose with glycine (II) and compared with a well‐humified fraction of an organic soil. Microanalytical data for all four substances were very similar. The CP‐MAS spectra of the three melanoidins strongly resemble that of the organic soil fraction. Melanoidins (I) and (II), like the organic soil fraction, are highly aliphatic and have the same distribution of carbon types: aliphatic, carbons bonded to the electronegative atoms O and N, aromatic, carboxyl, and carbonyl. Acid hydrolysis of melanoidin (I) yielded no xylose and < 1% glycine, indicating that these starting components are not main constituents of the polymer. These findings not only add weight to Maillard's hypothesis, that melanoidin formation “may be at the origin of humic substances in nature,” but allow us to suggest that some of the nitrogen in soil which is still unidentified may exist in melanoidin‐type polymers.
Growth of Rhizobium in Unamended Soil
Authors: Pena‐Cabriales J. J. , Alexander Martin 
Published: July 2010

AbstractA study was conducted to determine the conditions in unamended soil that favored growth of Rhizobium. Moistening a dry soil resulted in growth of R. japonicum and a strain of Rhizobium nodulating cowpeas but not of R. meliloti. The extent of decline resulting from desiccation was usually greater than the increase following wetting. The extent of growth varied among soils. A freezing‐thawing cycle did not promote growth of R. phaseoli and the cowpea Rhizobium. The latter bacterium was more tolerant to a freezing‐thawing cycle than the former. Rhizobium japonicum and R. phaseoli grew readily in the presence of germinating seeds and developing root systems of soybeans, kidney beans, red clover, cowpeas, oats, wheat, and corn; the population size varied among the plant species, and legumes were no more stimulatory than nonlegumes. The numbers of R. phaseoli in the rhizosphere of several plants declined in 1 week, the abundance of R. japonicum fell after 6 weeks in the soybean rhizosphere, but the population size of the cowpea Rhizobium was high for at least 20 weeks. Counts of R. japonicum in soil increased after the soil was amended with soybean nodules. It is suggested that appreciable rhizobium growth in unamended soil occurs only in the presence of germinating seeds, growing roots, and decomposing nodules.
Chemical Factors Affecting Root Growth in Subsoil Horizons of Coastal Plain Soils
Authors: Adams Fred , Moore B. L. 
Published: July 2010

AbstractLack of root growth into the acid subsoils of the Coastal Plain of the southeastern U.S. is a recognized yield‐limiting problem for many crops, but little has been done to identify root‐limiting factors by soil horizon. In an effort to delineate Al toxicity and Ca deficiency by horizon, representative profiles of six major soil series of Alabama's Coastal Plain were sampled by horizon to a depth of 1 m. Horizon samples were subdivided and treated with one of the following: (i) check, (ii) CaSO4, (iii) MgO, and (iv) Ca(OH)2. Growth rate of primary roots of cotton (Gossypium hirsutum L.) into each soil material was measured, and visual symptoms of Ca deficiency and Al toxicity on roots were noted. Five untreated soil horizons grew roots showing only symptoms of Al toxicity (all were Bt horizons, previously designated as B2t); five grew roots showing only Ca‐deficiency symptoms (all were E, EB, BE horizons, previously designated as A2, A3, and B1, respectively); three grew roots showing both Al toxicity and Ca deficiency (all were Bt horizons); five horizons grew normal‐appearing roots (E, BE, and Bt horizons). Calcium deficiency occurred when soil‐solution Ca activity was 0.27 mM or less and Ca saturation was 17% or less. Aluminum toxicity occurred in some Bt horizons with soil‐solution Al at <0.4 µM but not in E, EB, and BE horizons with Al ranging between 9 and 134 µM. This apparent contradiction in toxic levels of Al was probably the result of solution Al being chelated in eluviated horizons but not in illuviated horizons.
Organic Carbon, Nitrogen, and Phosphorus Concentrations and pH in Soil Profiles as Affected by Tillage Intensity
Authors: Dick W. A. 
Published: July 2010

AbstractNo‐tillage (NT), minimum tillage (MT), and conventional tillage (CT) practices were continuously applied to a Hoytville silty clay loam (Mollic Ochraqualf) soil (18 years) and a Wooster silt loam (Typic Fragiudalf) soil (19 years) in Ohio. The effect of the various tillage intensities on the profile (0–30 cm) distribution of organic C, N, and P concentrations and pH was investigated. Results showed that NT resulted in significantly (P < 0.05) higher organic C and N concentrations in the 0‐ to 15‐cm soil increment of the Hoytville soil but significantly lower concentrations in the 15‐ to 30‐cm soil increment. For the Wooster soil, NT resulted in higher concentrations in the 0‐ to 7.5‐cm soil increment. No significant differences were observed among tillage intensities in the 7.5‐ to 30‐cm soil increment. Comparison of organic C concentrations in the plow layer (0–22.5 cm) of the soils at the beginning of the long‐term tillage experiment and at present showed that concentrations remained constant or decreased 11% under NT in the Hoytville and Wooster soils, respectively. Present organic C concentrations in the Hoytville soil were decreased 12 to 14% by long term MT or CT while a 23 to 25% decrease was observed for the Wooster soil. Organic P concentrations under NT were significantly (P < 0.05) higher in the 0‐ to 7.5‐cm increment of the Wooster soil and significantly lower in the 22.5‐ to 30‐cm soil increment. Organic C/N, C/P, and N/P ratios were calculated and higher ratios were observed under NT than under MT or CT in the surface soil increments. Tillage intensity, however, had little effect on the ratios averaged over the entire profile (0–30 cm). Soil pH was 0.1 to 0.3 units lower (P < 0.05) under NT in all soil increments except in the 22.5‐ to 30‐cm increment of the Wooster soil where no significant differences in pH were observed among the tillage intensities.
Estimating Thermal Diffusivity Near the Soil Surface Using Laplace Transform: Uniform Initial Conditions
Authors: Asrar G. , Kanemasu E. T. 
Published: July 2010

AbstractA simplified method based on the numerical integration of the Laplace transform of the one dimensional heat conduction equation in porous media was used to estimate the thermal diffusivity near the surface. The method is based on the analytical solution of the equation of heat conduction and accepts any functional relationship that realistically describes the surface soil temperature as a boundary condition. An optimization scheme was suggested for selecting proper values of Laplace transform parameter s based on maximum duration of the experiment. The method was used to compute thermal diffusivities of two different soil types for a wide range of soil moisture and temperature conditions. Thermal conductivities for each soil were calculated using the computed diffusivities and heat capacities. A comparison of the conductivities estimated with the Laplace transform and the measured values by a transient method showed good agreements between the two methods. A similar comparison between the Laplace transform and the DeVries' model showed significant differences between the two methods.
A General Soil Volume Change Equation: I. The Two‐Parameter Model
Authors: Giráldez Juan V. , Sposito Garrison , Delgado Carlos 
Published: July 2010

AbstractA physically based equation containing two adjustable parameters (the slope of the load line and the air‐entry water content) is proposed to describe the volume of a swelling soil as a function of its water content. This equation was shown to give an excellent representation of 18 sets of soil volume change data for both laboratory and field measurements. In many cases, a satisfactory description of volume changes could be obtained by setting the slope of the load line equal to the specific volume of liquid water and adjusting only the value of the air‐entry water content. The proposed equation should be useful in computer models of water movement in swelling soils.
Applicability of Fick's Law to Gas Diffusion
Authors: Jaynes D. B. , Rogowski A. S. 
Published: July 2010

AbstractThe comparison of Fick's Law for the diffusion of gas i in a vapor to the equations based on the kinetic theory of gases shows that only for certain special conditions is the Fickian diffusion coefficient, DFi, independent of the mole fraction of i and the diffusional fluxes of the other gases. These conditions include the diffusion of a trace concentration of gas through a gas mixture of any composition, equimolar, counter‐current diffusion in a binary gas mixture, and diffusion in a ternary mixture where one gas is stagnant. In an O2, CO2, N2 atmosphere, variations in diffusion coefficient of at least 10% from the tracer values are possible with variations in the mole fractions of the gas or the relative magnitude of their fluxes. The temperature and pressure dependency of the diffusion coefficient must also be recognized.
A Chelating‐Resin Method for Characterizing Soluble Metal Complexes
Authors: Hendrickson L. L. , Corey R. B. 
Published: July 2010

AbstractA method is presented to differentiate between free and complexed trace metals in solution at concentrations at or below the sensitivity of flameless atomic absorption spectrophotometry using a pH and solution composition consistent with natural systems. The method utilizes a pH‐adjusted chelating resin saturated with Ca and selected trace metals that maintains pH and solution metal activities essentially constant when equilibrated with a Ca(NO3)2 solution. Equilibration of this solid‐phase buffer with a Ca(NO3)2 solution containing a soluble complexing agent results in a soluble metal concentration in excess of that obtained when equilibrated with Ca(NO3)2 alone. The increase in the soluble metal concentration is attributed to the formation of soluble metal complexes. The resin method was verified by evaluating Cd, Zn, and Ca complexation by EDTA (ethylenediaminetetraacetic acid). Relative selectivity coefficients were consistent with published values, and the concentration of EDTA added to the system was accurately determined. Solution Cd concentrations were also increased by Cl‐ addition to an extent consistent with published formation constants. The ability of the method to evaluate complexation of several metals simultaneously may make it more attractive than existing methods for characterizing simple monofunctional complexing agents. The method was also used to characterize soluble complexing agents extracted from a sludge‐amended soil. The results indicated that a portion of the ligands had approximately 105.5 times greater affinity for Cd and Zn than for Ca. This marked selectivity for Cd and Zn is much greater than existing selectivity data for similar systems obtained under conditions of low pH and/or unrealistically high metal levels and is likely attributable to the much greater Ca to metal ratios maintained by the resin system.
Behavior of Bromacil and Napropamide in Soils: II. Distribution After Application from a Point Source
Authors: Gerstl Z. , Yaron B. 
Published: July 2010

AbstractThe distribution of napropamide [2‐(α‐naphthoxy)‐N,N‐diethylpropionamide] and bromacil (5‐bromo‐3‐sec‐butyl‐6‐methyluracil) when applied from a point source was determined in several soils. The parameters studied were application rate (4 and 1.5 L/h) and the effect of wetting and drying cycles. In general, napropamide, which was moderately adsorbed by the soils, was concentrated around the emitter; at a high application rate the compound moved laterally more than vertically and at a lower application rate it penetrated to a greater depth. After several cycles of wetting and drying, napropamide was partially leached out of the emitter zone into the soil volume, the amount of leaching being related to the soil texture. Bromacil, which was weakly adsorbed by the soils, was more uniformly distributed in the soil but did exhibit slight retardation in the heavier soils. The effect of application rate was similar to that observed for napropamide; however, after several cycles of wetting and drying, bromacil was completely leached from around the emitter in all soils and was concentrated at the outer edges of the wetted zone.
Evaluation of an Automated Assay System to Measure Soil Radionuclides by L X‐Ray and Gamma‐Ray Spectrometry
Authors: Nyhan J. W. , Drennon B. J. , Crowell J. M. 
Published: July 2010

AbstractAn automated radionuclide assay system was evaluated for performing soil radioassays using L x‐ray and gamma‐ray spectrometry. Wet chemistry assay procedures were shown to be considerably more time consuming than similar analyses of soils on this radionuclide assay system. The detection limits of 241Am and Pu were determined, as well as the reproducibility of radionuclide assay results. The L x‐ray spectrometric measurements were compared with radiochemical analysis on several tuff samples. The assay system's intrinsic germanium detector was found to respond linearly to varying low concentrations of 241Am and Pu, both of which were easily detected in the presence of elevated concentrations of 137Cs.
Competitiveness and Symbiotic Effectiveness of Five Strains of Rhizobium Trifolii on Red Clover
Authors: Materon L. A. , Hagedorn C. 
Published: July 2010

AbstractLittle information is available on seasonal Rhizobium‐red clover (Trifolium pratense L.) interactions, competitiveness, and persistence, and dinitrogen fixation rates in livestock production areas of the southeastern United States. Five introduced strains of Rhizobium trifolii were examined on red clover at two locations (on a ultisol and a vertisol) over two consecutive growing seasons. Double antibiotic resistance acquisition and intrinsic antibiotic tolerance were used to measure the proportions of nodules produced by the inoculum strains. Strains 162BB1, RP113‐7, and LM1 were highly competitive and persistent, and accounted for > 94% of the assayed nodules at both soils over both seasons. Strain 162P17 occupied 90 to 93% of the nodules in the establishment year at both sites. However, in the following season nodule occupancy of 162P17 declined to 83 and 59% at the ultisol and vertisol sites, respectively. A major decline in nodule occupancy by strain TA1 was observed to the extent of its being virtually eliminated by the indigenous Rhizobium populations of both soils during the second season. Higher forage and crude protein production were associated with strains 162BB1, RP113‐7, and LM1 at both locations and seasons. Results showed that red clover, when effectively nodulated by competitive and persistent strains of R. trifolii, can become established and productive under conditions found in the Lower South.
Nodulation of Cowpeas and Survival of Cowpea Rhizobia in Acid, Aluminum‐Rich Soils
Authors: Hartel Peter G. , Whelan Anne Marie , Alexander Martin 
Published: July 2010

AbstractA study was undertaken to determine whether the reduced nodulation of cowpeas [Vigna unguiculata (L.) Walp.] grown in certain acid, Al‐rich soils resulted from the poor survival of the potentially infective rhizobia. Two strains of Rhizobium capable of nodulating cowpeas were used. The lowest pH for growth in defined liquid medium was 4.2 for one strain and 3.9 for the other. Only the latter was Al tolerant and could grow in a defined liquid medium containing 50 µM KAl(SO4)2. The survival of the bacteria and their ability to nodulate cowpeas in three soils were measured after the soils were amended with Ca or Al salts to give pH values ranging from 5.7 to 4.1 and extractable‐Al concentrations from <0.1 to 3.7 cmol(p+)/kg of soil. Only small differences in survival in 7 or 8 weeks were noted between the two strains. Plants inoculated with the Al‐sensitive strain bore significantly fewer nodules in the more acid, Al‐rich soils than in the same soils with higher pH values and less extractable Al. No significant reduction in nodule number was evident for plants inoculated with the Al‐tolerant strain and grown in the more acid, Al‐rich soils compared to cowpeas grown in the same soils with higher pH values and less extractable Al. It is suggested that the Al content of soil is not a major factor in the survival of cowpea rhizobia but that it does have a significant effect on nodulation.
Soil Water Matric Potential Effects on Aggregate Stability
Authors: Francis P. B. , Cruse R. M. 
Published: July 2010

AbstractThe effect of soil water matric potential (ψm) is not considered with most techniques utilized to evaluate aggregate stability. Rather, aggregate stability usually is measured at ψm of 0 Pa or at an unknown ψm. The objective of this study was to determine ψm effects, in the range of 0 to −3,000 Pa, on stability of natural soil aggregates obtained from a fencerow and from plots having a range of management histories. Aggregate stability, considered inversely related to the mass of soil detached by impact of falling water drops, increase markedly as ψm decreased from 0 to −500 Pa. Similar ψm changes at ψm < −500 Pa had smaller effects on aggregate stability. Significant differences in stability of aggregates obtained from plots with different cropping and/or manuring histories, were sometimes undetectable at ψm ≤ −500 Pa but were more consistently detected at ψm = 0 Pa. Data from this study indicate that aggregate stability is very sensitive to ψm, particularly at ψm near zero. Techniques for comparing aggregate stability between soils or soil treatments should ensure equal values of ψm exist for all aggregates. Measurements made over a range of ψm should yield better comparisons of aggregate stability between soils than measurements made at one ψm.
Replications and Subsamples Needed to Show Treatment Responses on Forest Soils of the Coastal Plain
Authors: Lloyd F. Thomas , McKee William H. 
Published: July 2010

AbstractThis research illustrates how randomized, complete‐block designed field studies can be insensitive to detecting treatment‐caused differences in the concentration of soil nutrients. An example shows that variation without compositing can be so large that 727 blocks are needed to be 90% confident of detecting a difference in total nitrogen of 100 µg g−1. Graphs are presented for determining the optimum numbers of blocks and chemical determinations per plot. The results show that compositing does not affect the number of chemical determinations per plot, but does reduce the number of blocks in direct proportion to the reduction in variance resulting from compositing. A hypothetical example shows that the number of blocks can be reduced from 727 to 15 by constructing blocks with less natural variation between treatment plots and by compositing 20 sample cores for each chemical determination.