bluuebunny/crossref_metadata_2025_split huggingface dataset:
Wind‐erosion Direction Factors as Influenced by Field Shape and Wind Preponderance
Authors: Skidmore E. L. 
Published: July 2010

AbstractThis investigation expands and improves the procedure for determining median travel distance of wind in traversing a field, information used in solving the wind‐erosion equation. Wind‐erosion roses were simulated by the equation of an ellipse in polar coordinates. The ratio of semimajor axis to semiminor axis was varied to give preponderance values from 1.0 to 4.0. The axis was rotated to simulate field orientation from 0 to 90° relative to prevailing winderosion direction. Length/width ratio for rectangular fields was varied from 1 to 10. The wind‐erosion direction factor, a number that when multiplied by field width gives median travel distance, was calculated for many combinations of variables. When preponderance was 1.0, the wind‐erosion direction factor was 1.03, 1.42, 1.48, and 1.48 for rectangular fields with length/width ratios of 1, 2, 4, and 10, respectively; the factor was not influenced by field orientation. As preponderance increased, the wind‐erosion direction factor approached unity for small angles of deviation and approached the length/width ratio for large angles of deviation. For circular fields surrounded by a nonerodible surface, the wind‐erosion direction factor was 0.91, regardless of wind direction and preponderance.
Storage Effects on Identification of Rhizobia in Soybean Nodules by Elisa
Authors: Matheny T. A. , Kasperbauer M. J. , Hunt P. G. 
Published: July 2010

AbstractSerological analyses of rhizobia in soybean [Glycine max (L.) Merr.] nodules are time‐consuming and often must be delayed for extended periods. The objective of this study was to assess the impact of drying and long‐term storage on identification of rhizobia in soybean nodules by indirect enzyme‐linked immunosorbent assay (ELISA). Nodules formed on ‘Coker 338’ by Bradyrhizobium japonicum strains USDA 3I1b110, NC1004, and B587 were either air‐dried at 40°C or freeze‐dried, and then stored for 1 month at either ambient temperature, 5, −5 or −60°C. Rhizobia within nodules from all drying and storage combinations were suitable for identification by ELISA. Results of this study indicate that large numbers of nodules can be collected and analyzed for serological identification of rhizobia at a later date, without loss of accuracy.
Water Movement in a Finite Layer: Absorption for Constant Water Content at the Surfaces
Authors: Hornung U. , Parlange J.‐Y. , Hogarth W.L. , Connell L.D. , Peters R. 
Published: July 2010

AbstractAn accurate, analytical formulation describes very simply the outflow of water from a soil layer when the potentials (water contents) are maintained constant at both surfaces. The analytical formulation is adapted from a previously developed approach to the present problem. The accuracy of the results is checked by comparison with a precise numerical simulation which is greatly simplified for a Brooks and Corey type diffusivity. It is suggested that a laboratory experiment using this configuration would yield the soil properties relevant for adsorption.
Ionic Diffusion Coefficients as Predicted by Conductometric Techniques
Authors: Jurinak J. J. , Sandhu S. S. , Dudley L. M. 
Published: July 2010

AbstractIon diffusion coefficients were determined for Na, Ca, and Cl in three soils under various moisture regimes. The Nernst‐Einstein equation was used in conjunction with bulk soil specific electrical conductivity data to obtain the diffusion coefficient values. The conductivity data were measured in special cells designed to control both solution composition and moisture content. The contribution of both the solution and the surface phases to the total diffusivity of each ion was estimated. The ion diffusion coefficient values were corrected for the nonideality of system. Anion repulsion corrections were also made to account for the surface contribution to Cl diffusion.
Sulfate and Gypsum Determination in Saline Soils
Authors: Skarie R. L. , Arndt J. L. , Richardson J. L. 
Published: July 2010

AbstractDespite advances in instrumentation for direct determination of SO2‐4, many investigators analyzing saline soils continue to estimate SO2‐4 by difference between the sums of major cations and anions and to measure gypsum by methods that avoid direct SO2‐4 determination. The present study compares SO2‐4 in saturation extracts as estimated by difference with SO2‐4 measured by single‐column ion chromatography for saline Aeric Calciaquolls and Typic Haplaquolls in eastern North Dakota. Results should be applicable throughout the Northern Great Plains. For extracts of sulfatic, saline soils, estimation of SO2‐4 by difference compared favorably with SO2‐4 determined directly. Results were more variable for highly chloridic soil extracts because errors from other methods were large relative to the amount of SO2‐4 present. Gypsum was determined by using a sufficiently dilute extract to completely dissolve the gypsum present in the soil sample. Gypsum content was calculated in two ways, based either on Ca2+ or SO2‐4 measured in the dilute extract. For highly chloridic soils, gypsum contents based on Ca2+ determination were essentially equal to the results based on SO2‐4 data. For sulfatic soils, gypsum contents were lower when Ca2+ values were used due to loss of Ca2+ to the exchange complex during the extraction process.
Soil pH and Extractable Sulfate‐Sulfur Distribution as Influenced by Tree Species and Distance from the Stem
Authors: Wolfe M. H. , Kelly J. M. , Wolt J. D. 
Published: July 2010

AbstractStemflow influence on the distribution of soil (NaH2PO4 extractable) SO4‐S and pH was evaluated as a function of tree size class and distance from the stem for red maple (Acer rubrum L.) and scarlet oak (Quercus coccinea Muenchh.) at two locations in Tennessee which have received different historical inputs of S from atmospheric sources. Soil profiles around the base of each study tree were sampled by horizon at 25, 50, 100, and 200 cm from the stem along four transects radiating from the stem at 90° angles. Distance from the stem influenced soil pH of A horizons at 25 cm from the stem of red maple and scarlet oak at both sites. Species had an effect on Bt2 and Bt3 soil SO4‐S concentrations. The Bt2 (0.49 cmol kg−1) and Bt3 (0.67 cmol kg−1) horizons beneath scarlet oaks had greater SO4‐S concentrations than corresponding horizons beneath red maple (0.29 and 0.43 cmol kg−1, respectively). The results of this study indicate that increased sampling intensity combined with tracer studies will be need to clearly determine the effect of stemflow, tree species, and tree size on subtlety‐manifested soil properties such as pH and SO4‐S as well as other elements of interest.
Effect of Phenylphosphorodiamidate on Immobilization and Ammonia Volatilization
Authors: Hendrickson L. L. , Omholt T. E. , O'Connor M‐J. 
Published: July 2010

AbstractLaboratory incubation experiments were conducted to evaluate the ability of the urease inhibitor phenylphosphorodiamidate (PPD) to reduce NH3 volatilization and immobilization of urea (100 mg N kg−1 of soil). Application of 20 mg PPD kg−1 of soil effectively inhibited urea hydrolysis for approximately 4 d in both soil and oat straw‐amended soil systems. This delayed urea hydrolysis reduced NH3 losses after 7 d from 82 to 19% in the straw‐amended soil, and from 26 to 14% in the soil system. When urea was applied to soil incubated in closed vessels, only 80% of the applied urea could be recovered as inorganic N after 3 d of incubation. This apparent immobilization of N was prevented for 7 d by application of PPD. Immobilization of N in the straw‐amended soil exceeded 40% within 7 d, but the onset of these losses was delayed for at least 3 d by PPD. These results demonstrate that losses of surface‐applied urea via both NH3 volatilization and immobilization can be prevented by application of an effective urease inhibitor.
Diagnosing Nutritional Status of Containerized Tree Seedlings: Comparative Plant Analyses
Authors: Timmer V. R. , Armstrong G. 
Published: July 2010

AbstractContainerized red pine (Pinus resinosa Ait.) seedlings were fertilized to test the effectiveness of three approaches (critical levels, optimal ratios, and vector analysis) to diagnose seedling nutrient status. Treatments involved a balanced nutrient solution and six imbalanced solutions lacking (−) or enriched (+) with N, P, or K applied to seedlings raised in peat‐filled paperpots. Growth was significantly reduced by ‐N, ‐P, and +N treatments indicating N and P deficiencies and N toxicity, respectively, and probable sufficiency or luxury consumption of P or K for the other treatments. Diagnosis by vector analysis agreed closely with actual growth and nutritional responses to treatments, and was more precise than the other approaches. Vector analysis was independent of predetermined standards or critical values, and improved identification of dilution effects and nutrient interactions which tend to complicate conventional diagnostic techniques.
Two‐site Model for Aluminum Oxide with Mass Balanced Competitive pH + Salt/Salt Dependent Reactions
Authors: Schulthess C. P. , Sparks D. L. 
Published: July 2010

AbstractA backtitration technique was used to collect proton isotherm data for an Al oxide, and was found to be stoichiometrically related to the cation and anion isotherm behavior. The adsorption of various ions by the Al oxide surface was modeled based on: (i) two surface sites, (ii) pH + salt‐dependent reactions (H+ and Cl‐, 2OH‐, or Na+ and OH‐), (iii) competitive salt‐dependent reactions (Na+ or Cl‐), (iv) CO2(aq) pH‐dependent reactions with the surface‐OH groups, and (v) presence of an unknown M+Cl‐ salt (0.0005 M). The total number of Al sites was 1.7 µmol m−2 or 3.4 µmol m−2 of total available sites. The pH of point of zero salt effect (PZSE) represented the surface condition in which the negative charges (or cation surfaces) equaled the positive charges (or anion surfaces); the cation exchange capacity (CEC) equaled the anion exchange capacity (AEC) at this value. The CEC‐AEC data and proton isotherm data were stoichiometrically correlated. The pH of PZSE values ranged from 7.50 to 7.76 depending on the electrolyte concentration present, with lower values as the concentration increased. The negative shifts in the PZSE values are due to anion impurities initially present on the surface and positive shifts are due to cation impurities.
Selenium Adsorption by Goethite
Authors: Balistrieri Laurie S. , Chao T. T. 
Published: July 2010

AbstractThe adsorption of Se by goethite was studied as a function of time (10 min–24 h), temperature (295.5 and 303.5 K), pH (4–11), particle concentration (3–300 mg/L), total Se concentration (0.02–5 × 10−5 M), oxidation state [Se(IV) and Se(VI)], and competing anion concentration [(anion)/(Se(IV) = 0.25 to 50 000] in order to assess the influence of these factors on Se mobility. The data indicate that (i) the surface sites of goethite are heterogeneous, (ii) the adsorption of selenite [Se(IV)] reaches equilibrium in 2 h and is completely reversible with respect to pH, (iii) the removal of selenite from solution increases with decreasing pH and increasing particle concentration, (iv) the adsorption edge for selenite shifts to lower pH values with increasing total selenite concentrations, (v) selenite adsorbs much more strongly than selenate [Se(VI)], and (vi) the influence of additional anions on selenite adsorption depends on the relative affinity of the anions for the surface and the relative concentrations of the anions. For a given anion concentration ratio, the competition sequence with selenite is phosphate > silicate ≥ citrate > molybdate > bicarbonate/carbonate > oxalate > fluoride > sulfate. Therefore, the conditions that favor the mobility of Se in the environment with respect to adsorption are alkaline pH, high Se concentrations, oxidizing conditions, and high concentrations of additional anions that strongly adsorb.
Pedon Zonation of Hydroxy‐interlayered Minerals in Ultic Haplaquods
Authors: Harris W. G. , Carlisle V. W. , Van Rees K. C. J. 
Published: July 2010

AbstractThe distribution of hydroxy‐interlayered minerals (HIM) was studied in Ultic Haplaquods with respect to horizon and location within the soil matrix. Mineralogy of the clay fraction and of tenacious grain coatings was determined for selected horizons by means of x‐ray diffraction and differential scanning calorimetry. Smectite and kaolinite were the dominant layer silicates in A and E horizons, where sand grains were stripped of coatings and clay occurred as floccules. Hydroxy‐interlayered minerals were the dominant layer silicates in Bh and E′ horizons where grains were coated. Tenacious coatings removed by ultrasound from sands occurring in the Bh and E′ horizons contained more HIM and less quartz than any other portion of the soil matrix. Podzolic stripping of coatings in A and E horizons and transformation of HIM to smectite via interlayer depolymerization could explain the observed HIM depth distribution. Higher HIM concentrations in tenacious coatings in Bh and E′ horizons suggest that the coatings predated podzolization. Hydroxy‐interlayered minerals in Btg1 horizons dispersed in deionized water more readily than did kaolinite, suggesting that differential dispersion in conjunction with a fluctuating water table may be a factor in pedogenic redistribution of clay minerals.
Soil Core Sampling for Hydraulic Conductivity and Bulk Density
Authors: Rogers J. S. , Carter C. E. 
Published: July 2010

AbstractThe Uhland type soil core sampling equipment was used to obtain cores 74 mm in diameter and 76 mm high from the surface 0.25 m of an alluvial soil in Louisiana. Samples were taken in pairs; one sample was taken by hammering the cutting head into the soil, and the other sample was taken by pressing the cutting head into the soil using a hydraulic cylinder. Data for 26 pairs of samples showed that the saturated hydraulic conductivity for the hammered samples averaged 2.36 µm/s, and that for the pressed samples averaged 4.28 µm/s. The difference was statistically different at the 99.5% level. Average oven‐dry weight of soil in the cores was 6 g greater for the hammered than for the pressed cores.
Sensitivity Analysis on the Comparison between the Gapon and Vanselow Exchange Coefficients
Authors: Evangelou V. P. , Phillips R. E. 
Published: July 2010

AbstractThe traditional nonthermodynamic Gapon exchange selectivity coefficient (KG) for Na‐Ca exchange has previously been shown in the literature to be in close agreement with the Vanselow coefficient (Kv) for Na equivalent fractions (NNa) in the exchange of <0.20. Furthermore, it has previously been shown for a heterogeneous group of soils that the traditional empirical ESP‐SAR relation (ESP = NNa × 100; ESP = exchangeable sodium percentage and SAR = sodium adsorption ratio) is indistinguishable from the ESP‐SAR relation predicted by the Vanselow equation for NNa <0.40. This study is a sensitivity analysis of the comparison between the Kv and KG for Na+ replacing Ca2+ in the exchange phase. It is carried out by mathematically deriving and graphically demonstrating the interrelationships between Kv and KG. These interrelationships are established on the basis that the Na‐Ca exchange system obeys ideal solid solution theory and thus Kv is reduced to a thermodynamic exchange constant. The results point out that generally, the greater the Kv, the greater the NNa range for which an apparent linear relationship between NNa and SAR is observed. This relationship, however, does not ensure that for the same NNa range the condition KG ≃ Kv is also met. The results show that as NNa approaches 0, KG = 0.50 Kv, and as NNa approaches 1, KG approaches infinity. The results also demonstrate that the condition KG ≃ Kv is dependent on the magnitude of Kv or KG for a limited NNa range, and it is independent of the magnitude of the cation exchange capacity (CEC). The condition KG ≃ Kv appears to have the potential to be met experimentally for Kv values in the range of <0.015 and up to a NNa value of approximately 0.60. At the larger Kv values (≫0.015), the condition KG ≃ Kv is less likely to be met because the absolute difference between Kv and KG is significant even at NNa values <0.20. The Kv, however, is always equal to the KG at NNa = 0.60. This cross‐over point is independent of the magnitude of Kv and CEC.
Crop‐water Production Functions for Sweet Corn and Cotton Irrigated with Saline Waters
Authors: Russo David , Bakker Derk 
Published: July 2010

AbstractThe effect of irrigation water quality (salinity) and quantity on the yields of sweet corn (Zea mays cv. Jubilee) and cotton Gossypium hirsutum L. cv. Acala SJ‐2) was studied in a sandy loam (Typic Torrifluvent) soil. For each of the irrigation water salinities of Co = 1.8, 3.6 and 6.7 dS/m (for corn) and Co = 3.6, 6.7, and 10.5 dS/m (for cotton), 10 amounts of irrigation water (Q) ranging from 0.15 to 2.7 times the class A pan evaporation (Eo) were applied via trickle irrigation. Root zone soil‐water matric potential, water content, and salinity were monitored, and corn and cotton yield components were measured. Time‐averaged root zone soil water content (θ) and soil salinity (EC), as well as crop yield components (Y) were affected by both Q and Co. Results of the analyses of the crop‐water production functions suggest that increasing the amount of irrigation water may compensate only in part for the adverse effects of the salinity of the irrigation water. For corn, using irrigation water of Co = 3.6 and 6.7 dS/m, maximum ear yields were reduced by 8 and 27%, respectively, relative to the maximum ear yield obtained using water of 1.8 dS/m. For cotton, using irrigation water of Co = 6.7 and 10.5 dS/m, maximum seed cotton yields were reduced by 6.5 and 30%, respectively, relative to the maximum seed cotton yield obtained using water of 3.6 dS/m. Analysis of the Y(θ, EC) relationship for each of the corn and the cotton yield components suggested that, due to the mutual effect of θ and EC on Y, the crop response to salinity curve is affected by θ and, in general, should be described by a nonlinear concave expression rather than by the piecewise linear expression of Maas and Hoffman (1977).
A Closed Tube Method for Measuring Gas Diffusion Coefficients
Authors: Tokunaga T. K. , Waldron L. J. , Nemson J. 
Published: July 2010

AbstractA transient, closed tube method for measuring both ordinary gas diffusivities and porous media effective diffusivities is presented. The current method is suitable for measuring gas diffusivities in air‐dry systems over a range of temperatures. Gas concentrations are continuously monitored in a well‐stirred volume of a single end chamber, which is connected to a closed sample chamber during experiments. An analytic solution for this diffusion process is available in which, after a sufficient time, the diffusivity of the sample is obtained from the slope of the logarithm of dimensionless concentration excess versus time. The method was checked by comparing measurements of N2‐O2 gas diffusivities at 0, 30, and 60 °C to various previously reported values in the literature. The measured diffusivities fall within the uncertainties of these earlier works.
Soil Properties Affecting the Availability of Potassium in Highly Weathered Soils
Authors: Uribe E. , Cox F. R. 
Published: July 2010

AbstractThe interpretation of soil tests for K in highly weathered soils may be improved if the K buffering power is considered in addition to extractable K. This study was conducted to determine if cation exchange capacity (CEC) and humic matter (HM) should be included in the development of more meaningful K availability indices. Seventeen soils from the Coastal Plain, Piedmont, and Mountain regions of North Carolina and two soils from the Amazon Basin of Peru were studied. The buffering power tended to correlate positively with CEC, but that of soils high in HM was lower and less affected by CEC than that of the low‐HM soils, indicating a lower capacity to replenish K removed from the soil solution upon depletion of K. The K concentration in the equilibrium solution increased linearly with percent K saturation of the CEC, and high HM soils had a higher concentration of K in the equilibrium solution at any given percent K saturation than low HM ones. A larger portion of extractable K was found in solution as HM increased and CEC decreased. It was noted that high HM soils were behaving similarly to low CEC and low HM ones so the soils were grouped into two categories: (i) soils of low K buffering power, which are those with HM ⩾ 1.9% and a CEC ⩽ 4.6, and (ii) soils of higher buffering power, which are those with HM < 1.9% and CEC ⩾ 4.6. The use of this grouping should improve K fertilizer recommendations in highly weathered soils.
Prediction of the Calcium to Calcium Plus Magnesium Ratio in Soil‐Grown Winter Wheat Forage
Authors: Rossi N. , Nye P. H. , Grunes D. L. , Sanchirico C. A. 
Published: July 2010

AbstractThe purpose of the research was to predict the Ca/(Ca + Mg) ratio in soil‐grown winter wheat forage from a knowledge of (i) Ca/(Ca + Mg) in the soil solution, or from Ca/(Ca + Mg) calculated from exchangeable plus soluble ions in the soil, and (ii) Ca/(Ca + Mg) in the tops of plants grown in nutrient solutions of regulated Ca/(Ca + Mg). Winter wheat (Triticum aestivum L. ‘Centurk’) was grown in a controlled light‐temperature chamber and harvested after 10, 20, and 30 d. The same Ca/(Ca + Mg) ratios were used in both nutrient solution and soil experiments. In the nutrient solution experiment, the Ca level varied from 5.90 to 0.78 mM, while the Ca + Mg equalled 6 mM. In the soil experiment, the amounts of liming materials for the different treatments (in mg kg−1 of soil‐sand mixture) varied from 2 400 (CaCO3) + 0 (MgCO3) to 0 (CaCO3) + 2020 (MgCO3). Growth was similar in nutrient solution and in soil, and was unaffected by Ca‐Mg treatment. Concentrations of Ca and Mg in tops and roots were higher in the plants grown in nutrient solutions than in the soil‐grown plants. The observed and predicted Ca/(Ca + Mg) ratios in the tops agreed excellently. The concentrations of Ca and Mg at the root surfaces of the soil‐grown plants were calculated using diffusion, mass flow, and root absorbing power. The calculated valuves differed little from those found in the bulk of the soil solutions. Implications for Ca and Mg deficiency of grazing ruminants are discussed.
Compositional Differences in Organic Matter among Cultivated and Uncultivated Argiudolls and Hapludalfs Derived from Loess
Authors: Zhang Hailin , Thompson Michael L. , Sandor Jonathan A. 
Published: July 2010

AbstractTwelve paired pedons were sampled to investigate the effects of vegetation and ∼120 yr of cultivation on Iowa soils. The study focused on organic matter in unfractionated and fractionated soil materials. Climate, parent material, time, and slope were held as constant as possible. Prairie‐derived mollic epipedons had higher organic C and total N contents than did forest‐derived ochric epipedons. Cultivated epipedons generally had lower organic C and total N contents than their uncultivated counterparts, but the C/N ratio was lowered markedly by cultivation only in the mollic epipedons. Although most of the organic C and total N was associated with the fine silt and coarse clay fractions of the uncultivated pedons, cultivation was associated with a relative shift of organic matter from the sand and silt fractions toward the fine clay fractions. Humic acid/fulvic acid ratios of organic matter in particle‐size fractions were always lower in the cultivated horizons than in the uncultivated horizons. The E4/E6 ratios of humic materials in the particle‐size fractions suggested that humic acids in mollic epipedons consisted of larger organic particles than those in ochric epipedons. Interpretations of the effects of cultivation on the soil organic matter must be made cautiously because of other agricultural influences on the uncultivated sites.