bluuebunny/crossref_metadata_2025_split huggingface dataset:
Zinc Absorption by Wheat Seedlings: II. Inhibition by Hydrogen Ions and by Micronutrient Cations
Authors: Chaudhry F. M. , Loneragan J. F. 
Published: July 2010

AbstractAt very low concentrations of Ca2+ in solution both H+ and Cu2+ retarded Zn2+ absorption through two distinct effects—toxicity and inhibition. Concentrations of 350µM Ca2+ overcame toxic effects of H+ at pH 3 but even 500µM Ca2+ did not prevent toxicity of Cu2+ at 10µM.At Ca2+ concentrations commonly encountered in soil solutions no toxicities appeared. Copper inhibited Zn2+ absorption strongly and competitively, Co2+ competitively but weakly, and Mn2+ and Fe2+ had no effect. Also, Ca2+ had no effect on Cu2+ inhibition.Increasing H+ concentration from pH 7 to 3 in the presence of 350µM, 10mM, or 50mM Ca2+ severely inhibited Zn2+ absorption. Hydrogen ions inhibited Zn2+ absorption by two mechanisms—one Ca2+‐sensitive, the other Ca2+‐insensitive. The Ca2+‐sensitive mechanism only operated at very low Ca2+ or under very acid conditions. At the usual H+ and Ca2+ concentrations of soil solutions, H+ inhibited Zn2+ absorption only by the Ca2+ insensitive mechanism; in this mechanism H+ was non‐competitive with Zn2+.In soils the effects of Ca2+, Cu2+, and of H+ would be additive. However the effects of Cu2+ and especially of H+ on soil chemical reactions may operate in the opposite direction to their effects on Zn2+ absorption. More information is needed on the behavior of chelating compounds before the effects of Cu2+ on Zn2+ absorption from soils can be assessed.
An Improved Variable‐Intensity Sprinkling Infiltrometer
Authors: Rawitz E. , Margolin M. , Hillel D. 
Published: July 2010

AbstractImprovements of the Purdue‐Wisconsin infiltrometer are described. A winch was added to the tower to facilitate assembly and the windshield was redesigned. Water distribution was improved by changes in the revolving shutter and the surplus water collection trough. The nozzle mounting was simplified, and water level in the vacuum runoff tank was transmitted to an external recorder. Good uniformity was obtained over a wide range of application rates.
Salt and Water Movement in Unsaturated Frozen Soil
Authors: Cary J. W. , Mayland H. F. 
Published: July 2010

AbstractSalt and water movement was measured in unsaturated frozen soil columns incubated under a thermal gradient for 3, 6, or 9 weeks. Both water and salt moved from the warmer to cooler areas in the soil, creating a twofold concentration difference over a 24‐cm distance. Movement of CaCl2, LiI, and K2SO4 was studied in detail. Cation exchange reactions and salt solubilities at high concentrations affected the movement. Although the results suggested that mass flow of dissolved salts in a liquid film of water was the principal transfer mechanism, both vapor and salt diffusion were sometimes significant. Thermal diffusion and salt sieving did not appear to be important.Since the vapor pressure of ice controls the water potential in frozen soil, the amount of unfrozen water and matric suction could be calculated from a water release curve and data from ice suspensions in salt solutions. These results led to the conclusion that mass flow in the liquid phase is described by Darcy's law. Thus, salt flow as well as net water transfer can probably be predicted in unsaturated frozen soil using information available from unfrozen systems.
Characterization of the Oxidized and Reduced Zones in Flooded Soil
Authors: Patrick W. H. , Delaune R. D. 
Published: July 2010

AbstractThe oxidized and reduced layers in flooded soil were characterized by vertical distribution of the oxidation‐reduction (redox) potential and concentrations of manganous manganese, ferrous iron, sulfide, nitrate, and ammonium. Redox potential was measured with a special motor‐driven assembly which advanced a platinum electrode at a rate of 2 mm/hour through the flooded soil profile. Vertical distribution of reduced forms of manganese, iron, and sulfur and of nitrate and ammonium was determined by freezing and slicing the flooded soil into segments 1 or 2 mm thick. The apparent thickness of the oxidized layer was different when evaluated by the distribution of the various components in the profile, with the sulfide profile indicating the thickest oxidized zone, the manganese profile indicating the thinnest oxidized zone, and the iron profile showing an intermediate thickness. The thickness of the oxidized layer increased with duration of flooding.
Influence of Water and Temperature on Adsorption of Parathion by Soils
Authors: Yaron Bruno , Saltzman Sarina 
Published: July 2010

AbstractTemperature and water effect on the adsorption of parathion (O, O‐diethyl O‐p‐nitrophenyl phosphorothioate) by soils was studied using 14C‐tagged parathion. The parathion was applied in aqueous solutions and in hexane over a concentration range of 1–10µg/ml. It was found that the parathion is adsorbed by soils from aqueous solution without any appreciable thermic effect. In a dry soil‐hexane‐parathion system the slightly polar parathion molecules efficiently compete with the apolar hexane molecules for adsorption sites. In hydrated soil‐hexane‐parathion systems there was no parathion adsorption. Generally as the soil water content increases, parathion adsorption decreases. The water‐temperature composite effect in a soil‐hexane‐parathion system was also studied. The rise of temperature in the soilhydrated parathion‐hexane system favors the endothermic process of water desorption, resulting in greater free adsorption sites, and consequently, in increasing parathion adsorption.
Electrochemical Properties of Some Oxisols and Alfisols of the Tropics
Authors: Van Raij Bernardo , Peech Michael 
Published: July 2010

AbstractA study of the distribution of the electric charges in the Ap and B2 horizons of two highly weathered Oxisols and one Alfisol from Brazil was made by means of potentiometric titration and by direct measurement of adsorption of ions in the presence of varying concentration of electrolyte. The titration curves at different ionic strengths crossed at the common point of intersection, the zero point of charge (ZPC), or the pH at which the net electric charge is zero. Thus, the electrochemical behavior of these soils was found to be similar to that exhibited by many metallic oxides in which the surface potential of a reversible double layer is determined solely by the activity of potential determining H+ and OH‐ ions in the bulk solution. Direct determination of the adsorption of ions from NaCl, CaCl2, and MgSO4 solutions showed that pH, electrolyte concentration, and valence of the counter ion influence the magnitude of the electric charges on the soil particles. From known surface areas and ZPC of these soils, the values for the net electric charge calculated by the application of the Stern model of the double layer theory were found to be in good agreement with the experimental results.
Effect of Nitrogen on Phosphorus Transport Systems in Zea Mays L.
Authors: Thien S. J. , McFee W. W. 
Published: July 2010

AbstractThe effect of N preconditioning on P uptake and translocation was studied using 10‐day‐old corn (Zea mays L.) in solution culture. Nitrogen preconditioned plants had significantly higher P uptake rates and translocation. Plants remained capable of stimulated P absorption and translocation for periods dependent upon the time interval between N pretreatment and P uptake. The degree to which P uptake was stimulated was dependent upon the N level used for preconditioning. A rather low level, 4mM, resulted in maximum increase in P uptake over control plants. Phosphorus transport to the upper part of the plant increased as N levels in the pretreatment increased. Nitrogen preconditioning stimulated P uptake and translocation maximally when P was supplied at 0.1mM. At lower concentrations only uptake was stimulated while at higher levels, only translocation was stimulated.Observations suggest involvement of more than one P uptake mechanism and separate physiological influence of N on uptake and translocation.
Climate, Time, and Organisms in Relation to Podzol Development in Michigan Sands: I. Site Descriptions and Microbiological Observations
Authors: Messenger A. S. , Whiteside E. P. , Wolcott A. R. 
Published: July 2010

AbstractDirect microscopic counts of microflora, nitrification patterns, and water‐soluble organic matter production in upper humic horizons of seven soils were studied in an attempt to determine the processes responsible for correlations between forest types and Podzol development in Michigan.The volume and surface area of fungal mycelia, the number of bacterial cells, and the length of actinomycete filaments per gram of organic matter were substantially greater in a mull humus horizon under 100% northern hardwoods than in a mor humus horizon under a forest stand dominated by hemlock.Maximum crenic acid production occurred in the mor humus horizons, these being associated with forest stands dominated either by hemlock or white pine. Leachates from these horizons contained no nitrate until incubated with periodic leaching for over 5 months. In a mull and a duff mull horizon, nitrification was nil during the period of maximum crenic acid production and the initial appearance of nitrate was closely accompanied by sharp decreases in pH of the leachates and sharply reduced production of crenic acid.Data obtained in these studies point to mor humus layers (Oh or O2 horizons) as a major site of production of water‐soluble organic materials having properties which suggest that they may be active agents in podzolization and contribute to the composition of Podzol illuvial horizons. Production of these materials is intimately linked with patterns of nitrogen transformation peculiar to forest soils, notably under conifers.
Soil Morphology and Water Table Relations: II. Correlation Between Annual Water Table Fluctuations and Profile Features
Authors: Simonson G. H. , Boersma L. 
Published: July 2010

AbstractThe frequency of occurrence of water tables at certain depths below the soil surface and the length of time water tables remained at or above these depths were calculated on the basis of rainfall records from a 29‐year period. Results were correlated with soil morphological features.Faint and distinct mottling correlated with water table behavior. The average depth below the surface to the midpoint of the uppermost mottled horizon increased as the drainage condition of the series improved. At the depth of a given degree of mottling, the percentage of time a soil was submerged was essentially the same in a given month for all series. Color designations of Munsell value and chroma for dry crushed material were also correlated with the percentage of time a soil was submerged during the first 6 months of the year. The relations were not consistent for all soils within the drainage sequence, but the poorly‐drained Dayton and Concord soils had the highest values and lowest chromas.Munsell hues of 10YR occurred in horizons of well‐drained soils, whereas Munsell hues of 2.5Y and 5Y occurred in horizons of poorly‐drained soils. The size and abundance of iron and manganese concretions increased in a consistent manner in the sequence from well‐drained to poorly‐drained soils. The sequence of bleached A2 horizons over “clay pan” IIB2t horizons was specifically related to the perched water tables of the Dayton and Concord series.Attempts to isolate relationships between water table regimes and a single color feature of the soil which might be useful as a tool for quantitatively appraising water table regimes were not successful. However, when color features were considered jointly, the morphological assessment of natural drainage class was found consistent with the water table regimes of the soils. The results illustrate the relationship between morphological indicators of soil drainage and water table regimes under climatic conditions peculiar to the Pacific Northwest.
Bulk Density of a Fragipan Soil in Natural and Disturbed Profiles
Authors: Fritton D. D. , Olson G. W. 
Published: July 2010

AbstractBulk density of horizons and layers in soil profiles at two locations (for natural soil and soil above pipelines and a tileline) showed that modification of the Erie channery silt loam fragipan by mechanical disturbance alone results in re‐establishing dense soil layers in less than 11 years. Buried topsoil, however, was much less dense after 12 years.
Density Slicing Techniques for Soil Survey
Authors: Frazee C. J. , Myers V. I. , Westin F. C. 
Published: July 2010

AbstractA density slicing system is used by experienced soil surveyors to interpret photographic tone patterns associated with soils of the Lake Dakota Plain area of north‐central South Dakota. The density slicing system color encodes the variation in optical density of film transparencies and measures the percent area of each color encoded density level. Field checking verified that the soil boundaries were more accurately located on the color encoded density maps than on the existing soil maps of the area.
Wetting Front Instability in Layered Soils
Authors: Hill D. E. , Parlange J.‐Y. 
Published: July 2010

AbstractPercolation of a one‐dimensional wetting front in homogeneous soil is known to be stable. On the other hand, in a layered soil whose upper layer is finer and less conductive than the coarser layer beneath, the wetting front becomes unstable and breaks into narrow wetting columns, or “fingers,” in which flow is three‐dimensional. The instability originates at the interface but takes some time to develop, hence the wetting fingers appear some distance below the interface. The fingers move downward at a velocity equal to the saturated conductivity divided by the saturated volumetric water content of the bottom layer. The fingers consist of a saturated inner core percolating downward surrounded by an unsaturated outer layer. Experimental results indicate that the width of the fingers is independent of the flow rate and of irregularities at the interface. The number of fingers per unit area of interface is directly proportional to the flow rate. Instability of the wetting front in layered soil following rain or irrigation makes it possible for smaller volumes of water to penetrate deeper than would have been possible had the wetting front remained stable.
Transformation of Manganese in a Waterlogged Soil as Affected by Redox Potential and pH
Authors: Gotoh S. , Patrick W. H. 
Published: July 2010

AbstractThe distribution of different forms of manganese in waterlogged soil was studied over a wide range of closely controlled Eh‐pH conditions. At pH 5 almost all of soil manganese was converted from the reducible to the water soluble plus exchangeable fraction even at a redox potential as high as +500 mV. In sharp contrast, at pH levels between 6 and 8 most of the conversion took place at relatively lower redox potentials of +200 to +300 mV. When the water soluble plus exchangeable fraction was further divided into its two components, low pH, and low Eh were found to increase water soluble manganese at the expense of the exchangeable form. Cation exchange reactions were apparently important in regulating the equilibria between water soluble and exchangeable manganese. Labelled manganese added to the soil showed an almost identical distribution among the various manganese fractions to that of native soil manganese. The observed pMn/pH slope and Eo were much lower at pH 6 to 8 than those calculated for pure equilibrium systems. It may be concluded from this study that the Eh and pH of flooded soils provide general control of manganese transformation which probably include both chemical and biological processes, the complexity of which make it difficult to explain the reactions in terms of simple chemical systems.
Selective Dissolution of Manganese Oxides from Soils and Sediments with Acidified Hydroxylamine Hydrochloride
Authors: Chao T. T. 
Published: July 2010

AbstractHydrous manganese and iron oxides of soils and sediments are strong scavenging agents for heavy metal ions. Information on heavy metals extracted along with manganese and iron oxides has been used in mineral exploration. But currently used methods do not differentiate metal ions associated with manganese oxides and those associated with iron oxides. Manganese oxides differ from iron oxides in solubility in response to oxidation‐reduction conditions, charge characteristics, and the quantity and kind of metal ions scavenged. This paper reports the development of an extraction method for the selective dissolution of manganese oxides from soils and sediments with minimal attack on the coexisting iron oxides, based on the difference in behavior of manganese oxides and iron oxides toward reduction under various conditions. By dissolving manganese oxides and iron oxides separately and determining respective metal ions which are released in the process, the geochemical significance of interelement relationships may be established.Manganese oxides in soils and sediments are found to be readily dissolved by a hydroxylamine hydrochloride (NH2OH · HCl) solution, leaving the major part of iron oxides in the residue. Although dissolution of manganese oxides is relatively independent of pH (pH 1, 2, and 3) and concentration of the NH2OH · HCl solution (0.025 to 0.25M), and time of equilibration (15 to 60 min), progressively greater amounts of iron oxides are released with lower pH and higher concentration of NH2OH · HCl solution, and with longer time of equilibration. A 0.1M NH2OH · HCl solution prepared in 0.01M HNO3 (pH 2) dissolves, on the average, 85% of manganese oxides and about 5% of iron oxides from various sediments after equilibrating for 30 min. Dissolution of manganese oxides and of iron oxides from four highly weathered soils by this solution amounts, respectively, to 50% and less than 1%. At pH 2, most heavy metal ions released during the dissolution of manganese oxides will be prevented from forming insoluble hydroxides or basic salts through hydrolysis, and then they can be determined in solution by appropriate analytical methods.
Uptake of Phosphorus by Plants Growing Under Field Conditions: I. Theoretical Model and Experimental Determination of its Parameters
Authors: Bar‐Yosef B. , Kafkafi U. , Bresler E. 
Published: July 2010

AbstractA model for P uptake by plants growing in the field or under controlled growth conditions was developed. The model makes allowance for the apparent diffusion coefficient of P in the soil (D), and the biologically determined parameter relating flux to concentration (α) to be concentration‐dependent. The values of D(C) and α(C) were determined directly by new laboratory techniques. The phosphate soil diffusion coefficient (Dp) was practically independent of concentration when the volumetric water contents (θ) of the soil was 0.40. When θ was 0.57, the dependence of Dp on concentration increased. The dependency of α(C) on the age of a unit root surface area of corn (Zea mays L.) was taken into consideration in the model.
Nitrogen, Salinity, and Acidity Distribution in an Irrigated Orchard Soil as Affected by Placement of Nitrogen Fertilizers
Authors: Felizardo B. C. , Benson N. R. , Cheng H. H. 
Published: July 2010

AbstractA field experiment was conducted to determine the vertical and lateral changes in the distribution of nitrogen, salinity, and acidity occurring in an irrigated orchard soil following addition of (NH4)2SO4, NH4NO3, or Ca(NO3)2 by broadcast, in broad band, or in narrow band. The NH4 and NO3 contents in soil decreased rapidly even under narrow band placements. Considerable nitrate movement was observed. After 1 year, neither the total nor the inorganic N level in the fertilized plots was significantly different from that of the control. High salinity was detected under the narrow band placements, but the level diminished rapidly with time. Little salinity was evident under the broad band or broadcast placements. However, the acidity produced by the ammonium fertilizers persisted after 1 year. Changes in soil properties under narrow bands were drastic, whereas changes under broad bands were insignificant.
Genesis of Argillic Horizons in Ochraqualfs Derived from Fine Textured Till Deposits of Northwestern Ohio and Southeastern Michigan
Authors: Smith Horace , Wilding L. P. 
Published: July 2010

AbstractChemical, physical, mineralogical, macro‐ and micro‐morphological data are presented for Bt and C horizons of Nappanee profiles (Aeric Ochraqualfs); three of which were sampled in the lake plain region of Ohio and the fourth on the Defiance Moraine in Michigan. Calcareous till deposits are similar across the study area: lake plain sites average 36% clay vs. 40% for the Michigan site; carbonate equivalents average 24%, with 20% of the total consisting of carbonate clays; and calcite/dolomite ratios average 2.5. Bt/C total clay and Bt fine/coarse clay ratios average 1.3 and 0.7, respectively, for these profiles. A lithological break was identified between the Ap and argillic horizon of all profiles which negates the use of A/B clay ratios in establishing argillic horizons in these soils. Under such conditions B/C total and/or fine clay ratios would be more appropriate as supporting criteria of an argillic horizon.Maximum fine clay gain usually occurs in upper Bt horizons. The Michigan profile has strong continuous illuviation argillans along conducting voids, but profiles of the lake plain exhibit only striated illuviation and stress cutans. More strongly expressed illuviation features of the former are attributed to the higher frequency of wetting‐drying cycles on the older, more strongly dissected Defiance Moraine. The Michigan Nappanee profile is similar to the Blount soils of Ohio in its argillic horizon expression but lacks the degradation in the upper Bt horizons characteristic of the Blount.
A Modified Ion‐Exchange Technique for the Determination of Stability Constants of Metal‐Soil Organic Matter Complexes
Authors: Ardakani M. S. , Stevenson F. J. 
Published: July 2010

AbstractCalculation methods based on Schubert's ion‐exchange equilibrium method were developed for determining stability constants of metal‐soil organic matter complexes. The methods, which were free of certain assumptions and errors inherent in the ion‐exchange technique as applied previously to soil organic matter, were verified using Mn(II)‐citrate and Mn(II)‐oxalate systems. Apparent stability constants (log K) of Zn (II)‐humic acid complexes ranged from 3.13 to 5.13 at pH 6.5.