bluuebunny/crossref_metadata_2025 huggingface dataset:
The Morphology and Genesis of Some Alpine Soils in British Columbia, Canada: II. Physical, Chemical, and Mineralogical Determinations and Genesis
Authors: Sneddon J. I. , Lavkulich L. M. , Farstad L.
Published: July 2010

The results of selected physical, chemical, and mineralogical analyses, carried out on five soils occurring in three alpine regions in British Columbia, Canada, are presented and discussed. An evaluation of the genesis of these soils is made in relation to the analytical results and to the literature.

The soils have developed on relatively young post‐Pleistocene parent materials and are gravelly and have loamy sand to silt loam textures, in the fine earth fractions, the slight accumulations of silt and clay at the surface, are due primarily to more intense physical weathering and partly to surface additions of eolian material. Volcanic ash was found in the surface horizons at three of the sites.

Physical weathering is significant in these soils and chemical weathering is taking place as evidenced by the presence of spodic horizons, abundant amorphous iron and aluminum in all horizons, and the content of secondary minerals.

Several properties of these soils were correlated with total carbon contents and hence organic matter contents. Volcanic ash was believed to have had an influence, to a minor degree, on the soil properties where it occurred.

With sufficient leaching, soils with spodic characteristics develop. Under a coniferous or ericaceous vegetative cover Spodosols occur; however, under a cover of grasses, sedges, and forbs the spodic characteristics may be masked by organic matter accumulations in the surface mineral horizons.
Nitrogen and Phosphorous Content of Water from Tile Drains at Two Levels of Management and Fertilization
Authors: Zwerman P. J. , Greweling Thomas , Klausner S. D. , Lathwell D. J.
Published: July 2010

Average annual rates of 243.2 kg/ha N and 31.5 kg/ha P were applied as high rates of fertilization. Eighty‐six kg/ha of N and 12.2 kg/ha of P were applied as moderate rates of fertilization. Ammonium nitrate was used as the N source while 46% superphosphate was the P source. The soil was an association of Lima and Kendaia silt loam. (Glossoboric Hapludolf and Aeric Haplaquent fine loamy, mixed, mesic.) Effluent from drains was measured and analyzed for inorganic N and orthophosphate. Concentrations of NO3 calculated as N in drainage water ranged from 51.1 ppm to 3.0 ppm. The higher concentrations were associated with high fertilization. During two, 3‐week test periods, NO3 calculated as N delivered from the tile drains in kilos per hectare per week ranged from .225 to 2.75. Ammonium concentrations seemed to be only slightly related to fertilization, ranging consistently between .02 to .03 ppm. Weekly outputs of NH4 nitrogen calculated as N were less than .00258 kilos/ha. Orthophosphate concentrations calculated as P ranged from .004 to .01 ppm with a weekly output range of .00016 to .00088 kilos/ha. Nitrogen was applied as ammonium nitrate. Phosphorus was applied as 46% superphosphate.
Effects of Snow Removal, Litter Removal and Soil Compaction on Soil Freezing and Thawing in a Minnesota Oak Stand
Authors: Thorud David B. , Duncan Donald P.
Published: July 2010

The depths of soil freezing and thawing were measured periodically with a Veihmeyer tube in snow removed, litter removed, compacted, compacted‐snow removed, and undisturbed plots during the 1962–63 season near St. Paul, Minn. The soil was a sandy loam to a loamy sand with a high water content when the study began. Cold conditions and minimal snowfall resulted in deeply frozen soil throughout Minnesota this season. At a station near the study site, the mean monthly snowfall and mean daily air temperature were, respectively, 4 to 6 cm and 2 to 5C below normal during January and February.

The removal of a snow layer 13 cm or less in depth caused deeper and more persistent soil freezing than did either litter removal or soil compaction. For several weeks, frozen soil averaged 38 cm deeper in snowless plots than in snow‐covered control plots. For about the same period, frozen soil averaged 20 cm deeper in plots without litter than in litter‐covered control plots, and 13 cm deeper in snowless compacted plots than in snowless control plots. The presence of even a shallow snowpack (13 cm) seemed to reduce the individual effects of litter removal and soil compaction on the depth of soil freezing. “Concrete” and “porous concrete” were the types of frozen soil observed in all treatments. The most significant hydrologic effect of deep freezing in snowless plots may have been the 10 additional days required for complete thawing in comparison to snow‐covered plots. However, late in the thawing period, the top of the frozen layer was 60‐cm beneath the soil surface, and it was discontinuous as indicated by complete thawing at some sample points. A discontinuous frozen layer was observed in all treatments 1 to 2 weeks before the complete disappearance of frozen soil. Thawing began earliest in plots without litter.
Ion Selectivity in Three Soil Profiles as Influenced by Mineralogical Characteristics
Authors: Murdock L. W. , Rich C. I.
Published: July 2010

Adsorption and release of Rb and Sr by the 2–0.2µ fraction from the horizons of three vermiculitic soils was influenced by mineralogical properties of the 2:1 layer clays present. The lowest Rb/Sr ratio for absorption of these two ions occurred in a clay containing montmorillonite. The Rb/Sr ratio tended to increase as the degree of mica to vermiculite alteration increased. The presence of hydroxy‐Al interlayers had little effect on initial selectivity, but these interlayers markedly influenced release of Rb ions. Ammonium acetate released more Rb than did Mg(OAc)2 from all clay samples from the three soils. Generally, Mg(OAc)2 released more Sr than did NH4OAc. The differential exchange of Rb was most pronounced in the clay containing well‐developed interlayers. It is proposed that NH4 ions (and other ions of similar size) have two effects on exchange in vermiculite. NH4 tends to collapse the interlayer space and thus reduce exchange, but this slightly hydrated ion can also diffuse to wedge zones and exchange Rb, and other cations of similar size, that may be present. The presence of interlayers inhibits the first effect and thus reduces fixation to exchange by NH4 of ions in wedge zones.
The Use of Anion Exchange Resin for Determining Available Soil Molybdenum
Authors: Bhella H. S. , Dawson M. D.
Published: July 2010

An anion exchange resin (Dowex I‐X4) was used to extract soil Mo from 30 western Oregon hill soils of varying development and derived from different parent materials. The values of Mo extracted by the anion resin increased with soil pH and were reproducible using the thiocyanate colorimetric procedure. Soil Mo so obtained was found to be correlated with plant Mo, plant N, and soil pH.
Impregnating Soil Concretions for Electron Microprobe Analysis
Authors: Gallaher R. N. , Perkins H. F. , Radcliffe D.
Published: July 2010

Soil concretions were impregnated with two types of plastic resins to compare the quality of polish and surface relief, after mounting and polishing, for electron microprobe analysis. Soft or hard porous concretions impregnated with “Castaglas,” a cold‐setting epoxy resin, resulted in loss of surface material due to plucking during polishing. Impregnating the same type concretions, under vacuum, with a temperature‐dependent methacrolate resin, resulted in little or no loss by plucking, and good to excellent polished surfaces.
Swelling Pressures, Electric Potentials, and Ion Concentrations: Their Role in Hydraulic and Osmotic Flow Through Clays
Authors: Kemper W. D. , Shainberg I. , Quirk J. P.
Published: July 2010

Using mass balance and force balance equations, the mechanisms of convective transport through porous media are outlined.

Pressure differences across compressible porous media cause clay to concentrate at the outflow side until the resulting osmotic pressure gradient balances the hydraulic pressure gradient. The resulting gradient in mobile adsorbed cations causes a diffusion potential which moves solution by electro‐osmosis to the outflow side.

When midplane potentials in the pores are appreciable, solution concentration differences across incompressible media are translated into a hydraulic pressure gradient along the midplane of the pores which moves the solution to the high concentration side. Similar concentration differences across compressible porous media result in nonuniform clay distribution, and diffusion potential gradients, which cause electro‐osmotic movement of solution to the high concentration side of the media.

These mechanisms provide an explanation for the rapid rates of “osmotic” solution flow observed in response to solute concentration gradients across membranes and other porous media.
Solubility and Solubility Product of Gypsum in Soil Solutions and Other Aqueous Solutions
Authors: Bennett A. C. , Adams Fred
Published: July 2010

The solubility of CaSO4·2H2O in several soils and dilute aqueous electrolytic media was measured. The ionic strength of electrolytic media ranged from 0.059 to 0.314; the solubility product of gypsum in these solutions ranged from 2.13 × 10‐5 to 2.79 × .10‐5 with an average value of 2.51 × 10‐5. In displaced soil solutions, the solubility product of gypsum ranged from 2.41 × 10‐5 to 2.92 × 10‐5; the average was 2.73 × 10‐5. The solubility product of gypsum in water was 2.58 × 10‐5.

The mean ionic activity coefficient of gypsum in solutions of different ionic strengths was computed using analytical data from aqueous electrolytic media and the known solubility product, i.e., 2.58 × 10‐5. The plot of this mean ionic activity coefficient versus the square root of gross solution ionic strength, i.e., no correction for ion pairing, for mixed‐SO42‐ systems allowed accurate determination of the solubility product of gypsum in the soil solutions using only analytical data.
Electron Spin Resonance Spectrometry of Humic Substances
Authors: Riffaldi R. , Schnitzer M.
Published: July 2010

Concentrations of free radicals, g‐values, and line widths were determined for humic acids, fulvic acids, and humins originating from soils of widely differing geographical origins and pedological histories and for humic acids synthesized by fungi in the laboratory. Free radical content decreased in the following order: humins > humic acids > fulvic acids. Line widths decreased in the order: fulvic acids > humins > humic acids, while the g‐values were more or less constant at 2.0030 ± 0.0003. Methylation of humic and fulvic acids greatly increased the free radical content, but decreased g‐values and line widths. The spectrometric characteristics of the fungal humic acids were of the same order as those of fulvic acids. Plots of spin concentration vs. % H and of spin concentration vs. % O showed inverse and direct statistically significant correlation between the parameters, respectively. This is interpreted as an indication that the free radicals were formed via oxidative removal of H from ‐OH groups. Statistically significant correlations between spin concentration and absorbance at 465 mµ and between spin concentration and atomic C/H ratios were taken as evidence that the free radical content of humic substances is related to their dark color and increases as the molecular complexity increases.
Iron Fertilization of Calcareous Soils in the Greenhouse and Laboratory
Authors: Hodgson J. F. , Neeley K. L. , Pushee J. C.
Published: July 2010

Four crops of corn (Zea mays L.) were grown over a period of 2 years on a calcareous soil supplied with 56‐2,200 kg/ha Fe as Fe2(SO4)3. The iron was mixed with the soil and the plants grown for about 6 weeks. The pots remained barren in the greenhouse during periods between crops. All levels of Fe additions improved crop growth with optimum response coming at 186 µg/g and above. There was no appreciable decrease in relative response to the Fe additions with successive cropping. Iron content of the corn plants and the readily extractable phase of iron in the soil both increased following iron supplementation. Iron additions to other calcareous soils, followed by successive wetting and drying in the laboratory, increased the readily extractable Fe in every case, but considerable variation was observed among soils.
Zinc Absorption by Wheat Seedlings: I. Inhibition by Macronutrient Ions in Short‐Term Experiments and its Relevance to Long‐Term Zinc Nutrition
Authors: Chaudhry F. M. , Loneragan J. F.
Published: July 2010

Short‐term Zn2+ absorption by intact wheat seedlings (Triticum aestivum L.) was studied to resolve large discrepancies between Zn2+ absorption in short‐term experiments with excised roots and in long‐term experiments with whole plants.

Excision, pretreatment, and age of seedlings had no effect on short‐term Zn2+ absorption.

Zn2+ absorption responded to changes in temperatures with Q10 values of 6.1, 1.8, and 1.9 for the temperature ranges 2 to 10, 10 to 20, and 20 to 29C, respectively. Addition of macronutrient salts to 250µM Ca(NO3)2 in the absorbing solution decreased Zn2+ absorption by about 80%. Micronutrient salts had a small additional effect on Zn2+ absorption.

Cations rather than anions inhibited Zn2+ absorption. Nitrate salts of alkali and alkaline earth cations strongly depressed Zn2+ absorption. In the presence of 250µM Ca(NO3)2, nitrates of alkali cations at 750µM and of additional Ca2+ at 250 and 375µM depressed Zn2+ absorption from 1µM ZnCl2 in the order NH4+ > Rb+ > K+ > Cs+ > Ca2+ > Na+ > Li+. Nitrates of alkaline earth cations at concentrations of 250µM depressed Zn2+ absorption in the order Mg2+ > Ba2+ ≥ Sr2+ = Ca2+. Replacing NO3‐ with Cl‐, SO42‐, or H2PO4‐, had no effect on Zn2+ absorption.

The inhibitory effects of alkali and alkaline earth cations appeared to be mutually competitive. Large effects of K+ at low concentrations of Ca2+ decreased and finally disappeared with increasing concentrations of Ca2+.

The rates of Zn2+ absorption by 6‐day‐old, intact wheat seedlings closely approximated those reported for long‐term experiments over a wide range of solution Zn2+ concentrations from 0.05 to 5.0µM when the temperature and the composition of the absorbing solutions were identical. These results suggest that it may be possible to relate short‐term studies of Zn2+ absorption to long‐term studies of Zn nutrition.
Zinc Absorption by Wheat Seedlings: II. Inhibition by Hydrogen Ions and by Micronutrient Cations
Authors: Chaudhry F. M. , Loneragan J. F.
Published: July 2010

At 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

Improvements 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

Salt 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

The 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

Temperature 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

A 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

The 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

Direct 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

The 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

Bulk 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

A 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

Percolation 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

The 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

Hydrous 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

A 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

A 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

Chemical, 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

Calculation 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.
Soil Air Pressure and Water Infiltration Under Border Irrigation
Authors: Dixon R. M. , Linden D. R.
Published: July 2010

Soil air pressure and water infiltration were measured during actual and simulated border irrigation of a uniform loam soil having a water table about 2 m beneath the surface. These measurements were made with instrumentation specifically designed to distinguish between displaced and entrapped air; to separate hydraulic and pneumatic pressure sources; and to isolate infiltration effects of displaced air pressure. Displaced air pressure decreased downslope and across slope from center to edge of the border strips. A maximum displaced air pressure of 21 cm of water was observed in the upslope central part of the border strip. Air entrapment commonly occurred at a 50‐cm depth next to border dikes but rarely occurred midway between dikes, which implies that water penetration was greatest in the region of lowest displaced air pressure. Infiltration measurements, made under actual and simulated border irrigation, indicated that displaced air pressure, building to a maximum of about 19 cm, reduced total infiltration by about ⅓. Such pressure appears to impede infiltration mainly by preventing or retarding direct flow of surface water into and within open macropores. In the central region of the border strip where displaced air pressure exceeds the surface water head, macropores vent displaced soil air upward; whereas along the border dikes where surface head exceeds air pressure, macropores conduct free surface water downward. A leaking‐system form of Boyle's Law is used to interpret typical displaced air pressure‐time curves and to suggest possible ways of controlling displaced air pressure. This research implies that soil air pressure and its infiltration effects are not negligible as is commonly assumed by Darcy‐based flow theory and that soil air can be a useful tool for controlling infiltration in some important situations.
A Flow Path Ground Water Sampler
Authors: Willardson L. S. , Meek B. D. , Huber M. J.
Published: July 2010

A sampling system is described that enables collection of water samples from different flow paths in the ground‐water system around a tile drain. The sampler can be installed as a regular part of a tile drainage system.
A Conveniently Constructed Divisor for Splitting Low Water Flows
Authors: Coote D. R. , Zwerman P. J.
Published: July 2010

For monitoring the quality of water running off agricultural land it is necessary to obtain representative and conveniently small samples of water. A divisor has been designed for attachment to a Coshocton wheel to enable small samples to be collected. The materials cost for the divisor described in this note is $2. A skilled technician, equipped with adequate tools, can construct and install the divisor in 4 hours.
Artificial Weathering of Oxidized Biotite: II. Rates of Dissolution in 0.1, 0.01, 0.001M HCl
Authors: Gilkes R. J. , Young R. C. , Quirk J. P.
Published: July 2010

Rates of dissolution of biotite in 0.1, 0.01, 0.001M HCl decrease as the proportion of ferric iron in octahedrally coordinated sites increases. This is interpreted as being partly due to a decrease in the rate of K exchange from oxidized biotite so that a smaller surface area is exposed to acid attack. The availability of structural cations (Mg, Mn, Zn, K, etc.) to plants growing on biotite rich soils will be a function of the oxidation state of structural iron in the biotite.
Infiltration and Water Table Effects of Soil Air Pressure Under Border Irrigation
Authors: Linden D. R. , Dixon R. M.
Published: July 2010

Field studies investigated infiltration and water table responses to soil air pressure under border irrigation. The water table was depressed in the center and elevated near the edge of a border strip in response to differences in soil air pressure during an irrigation. Also, water table elevations indicated that infiltration and subsequent groundwater recharge rates were greater in the vicinity of a border dike than at the center of the border. An infiltration response was measured by: (i) venting soil air during an actual irrigation and (ii) pumping air into the soil during simulated irrigations. An actual border irrigation experiment indicated that displaced soil air pressure ha (expressed as equivalent heads of water) rising to values of 13 to 24 cm of H2O reduced infiltration over a 70‐min period from 14.3 to 10.3 cm. Simulated border irrigation experiments indicated that displaced soil air pressure ha must exceed surface head hs to have significant influence on infiltration and that the first few minutes of infiltration may determine the ha‐to‐hs relationship and subsequent infiltration effects. In the simulated irrigations with hs = 6.3 cm, total infiltration in 1 hour was 6.0 and 1.5 cm when ha was 0 and 10 cm of H2O, respectively. Infiltration was only slightly reduced during the first 5 min when ha was 5 cm of H2O.
Mathematical Evaluation of Factors Affecting Gully Stability
Authors: Bradford J. M. , Farrell D. A. , Larson W. E.
Published: July 2010

Because large amounts of sediment come from gully banks in the coarse loess soils of the Lower Missouri River Basin, a study was made of the factors influencing the stability of gully banks. The approach was to consider the action of forces within the soil mass forming the wall of the gully. A two‐dimensional stability analysis was made using the Simplified Bishop Method of Slices.

If the angle of internal friction is ≤ 35°, calculated factors of safety indicate that vertical, saturated, or near‐saturated gully walls in loessial soils will fail if a ground water table exists at the base of the wall and if the cohesion for the saturated soil system is zero at a hydrostatic pressure of zero. Although gully bank stability is sensitive to the angle of internal friction, the calculated stability is relatively insensitive to slope height and soil bulk density. Tension cracks that frequently open at some distance back from the gully face do not materially influence stability. The effect of infiltration rate into the soil on the stability of the gully wall depends upon the rate of water conductivity through the soil and upon the cohesion of the soil or the level of the ground water table. Increasing the infiltration rate decreases the stability.
Analytical Solution of the Convective‐Dispersive Equation for Cation Adsorption in Soils
Authors: Cleary Robert W. , Adrian Donald Dean
Published: July 2010

The analytical solution of a cation adsorption soil problem is derived in detail by an integral transform method. The solution applies to the case of unsteady‐state, one‐dimensional flow through soils where a linear equilibrium exists between the cation in the flowing solution and the cation adsorbed on the exchanger phase. The effects of axial dispersion are also included in the solution.
Physiological Aspects of Iron‐Phosphorus Nutrition in Two Varieties of Maize: I. Uptake and Accumulation Characteristics Under Greenhouse and Field Conditions
Authors: Estes G. O. , Bruetsch T. F.
Published: July 2010

Two varieties of corn (Zea mays L.) showed differences in efficiency of Fe utilization when grown in hydroponic solutions and under field conditions. Under hydroponic conditions, ‘Seneca XX155’ showed greater susceptibility to P‐induced Fe stress than ‘Wisconsin 335A’, although its foliage contained more Fe. This susceptibility was related to reduced Fe translocation caused by relatively high P concentrations. Levels of P > 22 ppm in the nutrient solution produced significant reduction in foliage Fe of both varieties. Field studies showed significant reduction of tissue Fe at a fertilization level of 50 kg/ha compared to controls. Unlike results from hydroponic studies, no change in Fe status occurred at progressively higher rates of applied P (50–400 kg/ha) under field conditions. Levels of tissue Fe were never < 160 ppm following soil P applications.
Quantifying Pedogenesis for Soils with Discontinuities
Authors: Wang Chang , Arnold R. W.
Published: July 2010

Comparing calculated values of changes with observable features in relatively young soils is one way of testing genetic assumptions. If the agreement is acceptable, then the probability that the assumptions are correct increases. Two sites similar in most properties other than initial carbonate content of parent materials were examined and found to also have similar lithologic discontinuities. Soil development across parent material boundaries necessitates additional judgments about the initial state, consequently different trends of bulk density and selected mobile and immobile constitutents were estimated for each material in each profile and changes in the systems calculated. The reported values are not based on vertical homogeneity, and yet the changes seem to correspond to, and be supported by, morphological observations. It is concluded that this Hapludalf and this Fragiochrept developed under similar soil systems.
Collapsible Loess in Iowa
Authors: Handy Richard L.
Published: July 2010

The collapsibility, or tendency towards rapid consolidation or settlement upon saturation by water, of many C‐horizon loess soils constitutes and important physical property pertinent to soil genesis, erosion, and engineering. The potential of a loess soil to collapse upon saturation by water may be established from undisturbed samples saturated while under load in a consolidation testing machine. A more convenient criterion, that the saturation moisture cntent must not exceed the liquid limit, was regressed against 0.005 mm clay content determined by the hydrometer method, and indicated that C‐horizon loess containing less than 20% 0.005 mm clay is very likely to be collapsible; with 30% clay there is a 50% probability of collapse, and with over 40% clay there is only a small likelihood of collapse. These percentages were compared to published clay content contours to estimate the areal extent of collapsible loess in Iowa. To convert to 0.002 mm clay content, hydrometer test 0.005 mm clay contents were regressed against pipette test 0.002 mm clay contents to give X002 = 0.8X005; thus the 0.002 mm clay contents corresponding to high, medium, and low probabilities of collapse are < 16%, 24%, and > 36% caly, respectively.