bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of Hydroxy Aluminum Ions on pH Titration Curves of Hydronium‐Aluminum Clays
Authors: Schwertmann U. , Jackson M. L.
Published: July 2010

Vermiculite (particles 2 to 0.2 microns in diameter), after being treated with H‐Amberlite IR‐120, aged for 97 days, and suspended in 1N KNO3, showed a third buffer range between pH 5.5 and 7.6 on continuous titration with dilute NaOH. This third buffer range is attributed to neutralization of excess protons of Al‐OH2 groups in positively charged hydroxy aluminum polymers formed on interlayer surfaces of vermiculite under the influence of their negative charge. This conclusion was reached on the basis of observance of the same additional buffer range in titration curves of partially neutralized and aged AlCl3‐solutions (OH/Al ratios ranging from 1 to 2.25) and of vermiculite treated with the aged hydroxy aluminum solutions. The hydroxy aluminum polymers are only partly exchangeable by 1N KCl, and also are fairly resistant to treatment of the clay with H‐resin. The X‐ray diffractogram of the vermiculite shows an enhanced 7.2Å. (002) peak after H‐resin treatment and aging, indicating more interlayer material. Hydroxy aluminum treated vermiculite and aged acid vermiculite showed reduced collapsibility on K saturation and heat treatment, pointing also to the occurrence of the hydroxy polymers in the interlayer position. Compared with similar reactions with montmorillonite from bentonite previously reported, these compounds form with greater avidity in vermiculite, have a greater stability to subsequent H‐resin treatment, and have a higher resistance to exchange in KCl. These differences presumably arise because of the higher net negative charge of the vermiculite layers. Soil clays which give X‐ray diffraction evidence of interlayer hydroxy aluminum show the third buffer range on treatment with H resin, without aging time or treatment with hydroxy aluminum solutions.
Lime Requirement Related to Physical and Chemical Properties of Nine Michigan Soils
Authors: Ross G. J. , Lawton K. , Ellis B. G.
Published: July 2010

Lime requirement of 9 Michigan soils was determined by incubating the soils for 13 weeks in the greenhouse after addition of varying rates of agricultural limestone. The initial pH of all soils was approximately 5.5. Lime requirement was correlated with cation‐exchange capacity, organic matter content, exchangeable hydrogen per 100 g. soil, clay content, and lime requirement measured by the Shoemaker, McLean, and Pratt buffer method. Increase in soil pH after liming was significantly correlated with increase in percent base saturation within each soil type, but not between soil types. Liming did not appreciably affect the amount of exchangeable Mg and K or extractable P in the soils. At pH 5.5, liming increased yield of alfalfa on 6 soils, but not on the remaining 3 soils. Low yields were correlated with low calcium content in the plants.
A Soil Test for Phosphorus Based Upon Fractionation of Soil Phosphorus: I. Correlation of Soil Phosphorus Fractions with Plant‐Available Phosphorus
Authors: Al‐Abbas A. H. , Barber S. A.
Published: July 2010

The forms of P in 24 soils were determined by chemical fractionation. The available P was determined by plant growth experiments. Regression analysis of the P fractions with available P showed that iron P explained most of the variation. Water‐soluble P was the only other fraction significantly contributing to the explained variation.
The Residual Effect of Zinc Applied to Soils
Authors: Brown A. L. , Krantz B. A. , Martin P. E.
Published: July 2010

Greenhouse tests with sweet corn were studied to measure the residual effect of soil applied Zn.

Of the six soils, four had been shown to be Zn deficient by previous tests. Ten successive crops were grown in these soils to which had been applied, 0, 4, and 20 mg. Zn per 1,600 g. of soil.

Dry weight yields showed that the 4‐mg. Zn rate was adequate for 6 or 7 successive crops; the pots to which 20 mg. was added were not in the deficient range even after 10 crops. The two soils that were not deficient produced 10 crops without any deficiency symptoms developing or any growth response to the Zn applications.

Dithizone‐extractable soil Zn decreased gradually with cropping. When the values dropped below 0.55 ppm, there was a plant growth response to Zn.

Alfalfa was found to obtain adequate Zn from soils which were inadequate for sweet corn.
Early Growth of Corn as Affected by Soil Temperature
Authors: Allmaras R. R. , Burrows W. C. , Larson W. E.
Published: July 2010

Corn growth was measured in 23 location‐years in the eastern United States, where an average soil temperature reduction of 2.2°F. at the 4‐inch depth was obtained by a straw‐mulch treatment as compared to unmulched treatments during the first 6 weeks following planting. For soil temperatures ranging from 60° to 83°F., the ratio of the dry matter produced on the mulched treatment to that produced on the unmulched treatment was linearly related to the 4‐inch soil temperature. The validity of this linear relation was supported by data from experiments in the greenhouse and laboratory where growth of corn was observed under carefully controlled temperatures. For field conditions, a corn growth vs. soil temperature relation was constructed from the above linear relation, and the estimated optimum soil temperature for corn growth (dry matter production) was 81.3°F.

The effect of soil temperature on four different growth measurements (height, dry matter production, yield of N, and yield of K) of corn was different for each growth measurement in both the field and the greenhouse.
Water Adsorption by Dry Soil and Its Thermodynamic Functions
Authors: Cary J. W. , Kohl R. A. , Taylor S. A.
Published: July 2010

The adsorption of increments of water vapor on Millville loam soil was studied in an air‐free system. The resulting data included the amount of water that would condense on the soil at different relative humidities up to 90% at 14.8°, 24.8°, and 34.8°C. The temperature rise of the samples during adsorption was also recorded and the heat liberated during the reaction was calculated. Both integral and differential thermodynamic values were computed. A critical evaluation of the entropy function showed the integral values to be more useful than the differential values so far as describing the physical state of the system was concerned. In general, calculations of thermodynamic quantities based on the temperature dependence of the systems proved to be unreliable at low relative humidities due to changes in the available surface.

Specific conclusions drawn from the data suggest that when equilibrium relative humidity is < 80% in an air‐free Millville loam system, the average entropy of the adsorbed film is a little greater than that of corresponding liquid water, but the average internal energy of the film is always less than that of liquid water, even though the heat content may become slightly greater as the relative humidity rises above 70%.
Viscoelastic Functions for Soil
Authors: Waldron Lawrence J.
Published: July 2010

Briquets of Yolo silt loam have previously been shown to be viscoelastic. Three viscoelastic functions which describe the stress, strain, and time relations for two types of loading were obtained when the soil was in equilibrium with humidities ranging from 15 to 90% at 70°F. These functions were the shear creep compliance, the distribution of retardation times, and the complex shear compliance. The functions were very sensitive to small changes in water content. Equal‐time shear creep compliances were exponential functions of water content. Increasing temperature from 40° to 100°F apparently did not change the rates of the deformation process uniformly since temperature coefficients of equal‐time compliances reversed sign as the stress duration passed from 1 to 7,200 seconds. The functions are discussed in terms of a two‐phase concept.
Reactions of Phosphate with Soluble and Exchangeable Nickel
Authors: Pratt P. F. , Bair F. L. , McLean G. W.
Published: July 2010

When solutions of NiCl2 and KH2PO4 were titrated with NaOH, the immediate reaction product was an amorphous precipitate having a composition corresponding to 6NiHPO4 · Ni(OH)2 · 7H2O or 4NiHPO4 · Ni3(PO4)2 · 9H2O. At all pH values < 7, the precipitate was free of Ni(OH)2 or had a constant Ni(OH)2 content, but at pH values > 7, the Ni(OH)2 increased with increase in pH. When the amorphous precipitate was incubated at 25°C., crystalline products began to appear at 4 weeks and at 12 weeks the crystallization appeared to be complete. The main crystalline product was Ni3(PO4)2 · 8H2O. Crystallization was accompanied by acidification and also by a large reduction in the solubility of Ni. In the pH range of 6.5 to 7 the solubility of Ni was reduced to about 2 ppm.

Nickel‐saturated clays treated with phosphate showed the same reactions as found in solution. The exchangeable Ni was reduced to about 3% saturation.
Penetration of Wax Layers by Cotton Roots as Affected by Some Soil Physical Conditions
Authors: Gardner H. R. , Danielson R. E.
Published: July 2010

The use of a wax layer for root penetration tests under controlled soil conditions has made it possible to separate from other factors in the soil the effect of mechanical impedance on the growth of plant roots. The penetration percentage of cotton roots increased as soil moisture tension was increased from 0.05 bar to 0.52 bar then decreased as tension was further increased to 10.8 bars. The penetration also decreased with increasing salt content in the soil solution. Decreased aeration as measured by CO2 content also lowered the penetrating ability of cotton roots. An increase in bulk density of the soil from 1.0 g. per cc. to 1.4 g. per cc. did not affect the penetrating ability of cotton roots into the wax layer.
Investigations Concerning Nitrogen Loss Through Chemical Reactions Involving Urea and Nitrite
Authors: Sabbe Wayne E. , Reed Lester W.
Published: July 2010

The urea‐nitrite Van Slyke reaction was studied to determine the conditions necessary for this reaction to contribute to evolution of nitrogen gas (N2) by chemical denitrification in soils. The reaction was carried out in buffer solutions and the evolution of gases was analyzed quantitatively. The variables studied were pH, acidity, time, and reactant concentrations. Two conditions necessary for N2 evolution under an anaerobic atmosphere from an urea‐nitrite solution are (1) pH 6.0 or lower, and (2) a concentration of each reactant of 0.05 mg. N per ml, or greater. Evolution of N2 increased with decreasing pH and increasing reactant concentration. Nitric oxide (NO) formation was increased by increasing acidity, increasing nitrite concentration, and decreasing urea concentration. Nitrite accumulation in soils following urea fertilization requires an alkaline media. Therefore, the possibility that this pathway (urea‐nitrite reactions) of nitrogen loss occurs in soils is doubtful.
Ammonia Sorption and Retention by Plant Residue Materials
Authors: Coffee R. Clifford , Bartholomew W. V.
Published: July 2010

Investigations were conducted to measure the quantities of NH3 physically sorbed and the quantities of sorbed NH3 retained against evacuation by some common plant residues when exposed to NH3 in a dry condition and with different amounts of moisture. With increases in NH3 pressure both moist and dry samples of each plant residue physically sorbed increasing quantities of NH3. When saturated with NH3, evacuated, and then saturated a second time each dry plant material sorbed less NH3 during the second than during the first saturation. Increases in moisture content resulted in increases in physical sorption of NH3 across the entire range of partial pressures of NH3 employed. Saturation of the moist plant residue samples with NH3 resulted in some measurable increases in NH3 content after evacuation.
A Study of Isotopic Dilution as a Method for Relating Phosphorus Retention to Availability of Phosphorus in Widely Different Soils
Authors: Baker Dale E.
Published: July 2010

Six soils which were considered different with respect to release and retention of P were limed and allowed to equilibrate with a constant amount of P32 and 25, 100, and 400 ppm. of P31 by alternate wetting and drying 4 times prior to seeding Turghi millet and Tokyo buckwheat. The objective was to relate P retention characteristics to “availability of P” in different soils. “Active solid phase P” as determined by isotopic dilution was found to be an index of the amount of “available P” contained in a soil. A constant proportion of the active solid phase P was not in solution or removed from all soils by any of the extracting reagents. The percent active solid phase P removed by all extractants was affected by the rates of added P. From the results it was concluded that the percent active solid phase P removed by Bray's No. 1 extractant from each soil type was an index of its retention characteristics, if the native active solid phase P was in equilibrium with the added P32.
The Effect of Discrete Ped Density on Corn Root Penetration in a Planosol
Authors: Edwards W. M. , Fehrenbacher J. B. , Vavra J. P.
Published: July 2010

Corn root penetration studies in an Illinois Planosol, Weir silt loam, indicate that large corn roots are confined to the larger spaces between peds but that many medium and small roots penetrate about one‐half of the total discrete peds in the claypan B horizon directly under a corn hill. It appears that a discrete ped bulk density of about 1.80 g. per cc. is the threshold density above which peds are not penetrated by roots in this soil. The minimum intraped (within ped) porosity of peds penetrated by roots was about 33%. Mixing of the A and B horizons reduced the root restrictive effect of the A2 horizon.
Approximating Soil‐Moisture Storage in Experimental Watersheds by Means of Precipitation and Streamflow Records
Authors: Reinhart K. G.
Published: July 2010

An estimate of total soil‐moisture storage capacity of an experimental watershed is needed to understand its hydrology. A reliable estimate may be very difficult to obtain, particularly in a forested watershed, because of variations in and difficulties of measuring soil depth, root depth, texture, bulk density, stone content, and moisture content. A method is suggested for approximating storage from precipitation and streamflow records. Precipitation minus runoff—in selected periods when ample precipitation follows a dry spell—provides the estimate of soil‐moisture storage capacity. The method is illustrated with data from the Fernow Experimental Forest in West Virginia and is applied to two other watersheds in the Northeast. Limitations of the method are also discussed.
Relation Between Soil Aeration and Ethyl Alcohol Accumulation in Xylem Exudate of Tomatoes
Authors: Fulton J. M. , Erickson A. E.
Published: July 2010

Experiments were designed to measure the influence of soil oxygen stress and other environmental variables on the accumulation of ethanol in tomato plants. Oxygen stress was imposed by varying the soil moisture tension over a narrow range of low values. Ethanol was observed in the exudate samples when the rate of oxygen diffusion through the soil solution fell below 38 × 10‐8 g.cm.‐2min.‐1. A small reduction in oxygen supply below this value was associated with a large increase in ethanol. In cases of severe oxygen stress the physiological concentration of ethanol was sufficient to be toxic. Plants bearing flowers accumulated more ethanol than younger ones and those subjected to oxygen stress in bright light accumulated more ethanol than those in the dark.
Ion Diffusion: I. A Quick‐Freeze Method for the Measurement of Ion Diffusion in Soil and Clay Systems
Authors: Brown D. A. , Fulton B. E. , Phillips R. E.
Published: July 2010

The method combines a radioisotope‐tracer technique for measuring ion distribution by quick‐freezing the exchange medium and sectioning it into 50µ segments with a refrigerated microtome. Ten‐50µ sections were placed in separate counting pans for a quantitative radiation assay. From these data the distribution resulting from ion diffusion in montmorillonite and kaolinite clays and Sharkey and Dundee soils was obtained.

The accuracy of the freezing and sectioning method was determined by using replicate‐radioactive cores in which ion diffusion had not occurred. These cores were sectioned, counted for radiation, and then weighed. The coefficient of variation for the weight of clay or soil sections was 1.89, 2.14, 2.27, and 3.70% for kaolinite, montmorillonite, Dundee silt loam, and Sharkey clay, respectively. Coefficients of variation in the activity of the sections of exchange media were 2.39, 2.80, 3.18, and 1.29%, respectively. The coefficient of variation in the apparent diffusion coefficient for Rb86 in replicated cores of kaolinite clay was 6%.
Fragipan Soils: Morphological Relationships
Authors: Bailey H. H.
Published: July 2010

Field descriptions and certain laboratory data for 17 soil profiles representing Bedford, Calloway, Dickson, Grenada, Henry, Mercer, and Tilsit series in Kentucky were obtained. All of the soils contain fragipan horizons. Each genetic horizon of each profile was characterized by morphological description, including pH. Greatest thickness of pan development occurred in the poorly and somewhat poorly drained loessial soils; moderately welldrained soils developed in limestone residum with loess additions was second in thickness of pan development; well‐to‐moderately well‐drained sites from loess‐free limestone residium was third; moderately well drained mixed sandstone, shale, and siltstone residuum fourth; and moderately well‐drained deep loess least. The poorer the drainage the greater the pan development in deep loess. Colors in the pan horizons tended to differ from those above by having more yellowish hues and depressed chroma. Pan horizons generally contained more clay and correspondingly less silt than the horizon above the pan. Pans were generally more acid, ranging around pH 5, than horizons above or below. Pans tend to reversibly lose their characteristic consistency under wet conditions.
Fragipan Soils: Certain Genetic Implications
Authors: Hutcheson T. B. , Bailey H. H.
Published: July 2010

This study of a number of fragipan soils derived from a wide range of parent materials was undertaken to test an hypothesis concerning fragipan formation which had as its foundation data obtained from loessial soils. Particle size distributions and selected chemical properties were determined and comparisons of the data for the Bx and adjacent horizons were made. The portion of the original hypothesis suggesting that fragipan soils were severely leached prior to pan formation and that pan formation resulted from tight packing of dispersed clay particles is acceptable with certain limitations. On the other hand, it cannot be accepted that Ca:Mg or Ca:Mg + Na ratios are factors of general importance in fragipan formation.
Grass Opal in Some Chestnut and Forested Soils in North Central Oregon
Authors: Witty John E. , Knox Ellis G.
Published: July 2010

The practicability of using grass opal as an indicator of the vegetative history of soils was investigated in a forest‐grassland transition. Opal phytoliths isolated from grass and other plants were used as standards in the identification of grass opal from soils. Soil horizon samples were selected from 12 locations. Grass opal content was calculated from grain counts of the 15 to 100µ fraction.

The content was about 10 times greater in grassland soils than in forest soils. This indicates that the vegetative boundary has been generally stable throughout the time period required for accumulation of the grass opal, estimated to be about 4,000 to 7,000 years. Some change of vegetation was indicated at only two sites. Study of grass opal may be expected to yield much information about the vegetative history of soils.
A Steady‐State Method for Laboratory Measurement of the Oxygen Diffusivity of Porous Materials
Authors: Willey C. R. , Tanner C. B.
Published: July 2010

A steady‐state system using a large membrane‐covered electrode as a quantitative oxygen reducing sink and small membrane‐covered electrodes to measure oxygen concentrations was devised for measuring the oxygen diffusion coefficient D of soil or other porous material artificially packed in a sample‐holding tube. With this system, D was measured both with a zero net nitrogen flux through the sample in a close‐end system and with the counter‐current molar fluxes of oxygen and nitrogen made equal by injecting nitrogen into the system. For 100µ and 300µ diameter glass beads these methods gave values of D that agreed within 3% and were within 8% of values of D measured with a transient method for the same samples. Diffusion coefficients determined for air were in the range of those reported in literature.
Strength and Bulk Density of Compacted Mixtures of Kaolinite and Glass Beads
Authors: Lotspeich Frederick B.
Published: July 2010

Compacted mixtures of kaolinite and glass beads were used to test a hypothesis that the number of contact points of a matrix influences its strength. Four glass bead mixtures were used: (1) a single‐sized bead, (2) 2 sizes of beads designed to permit cubic, but not tetrahedral, packing of the largest size beads, (3) 2 sizes of beads designed to permit tetrahedral packing of the largest sized beads, and (4) 4 sizes of beads designed to permit tetrahedral packing. From 2 to 40% clay was added to each glass bead mixture; moisture tension at time of compaction ranged from 1/3 to 15 bars.

The 4‐component mixture with clay contents above 25% gave the highest dry strength. Maximum bulk densities in all glass bead mixtures were attained at clay contents of 20 to 30%. Maximum strength and bulk density for each mixture was attained at a moisture content between 1 and 5 bars tension regardless of clay content.
Effect of Carbon Dioxide on Cotton Seedling Root Penetration of Compacted Soil Cores
Authors: Tackett J. L. , Pearson R. W.
Published: July 2010

The level of CO2 and of subsoil density were varied in a growth chamber study of the interaction of these two factors on root growth of cotton seedlings at constant O2 concentration. At very low density root elongation rate decreased progressively with increasing CO2, although moderate to good growth occurred even at 24% CO2, the highest concentration used. At higher subsoil level densities, CO2 had little effect on root penetration. Retardation by CO2 was somewhat more severe for roots growing into solution culture than for those growing into loose subsoil, indicating that application of results of aeration experiments in nutrient solution to soils should be made with caution. Results suggest that in well‐drained, medium‐to‐coarse‐textured soils such as the Norfolk, CO2 will seldom be a limiting factor for root growth even in compacted zones near the surface. The mechanical impedance of such zones, will definitely restrict root penetration and proliferation in subsoils.
The Relationship between pH and Ammonia Equilibria in Soil
Authors: du Plessis M. C. F. , Kroontje Wybe
Published: July 2010

Investigation of the relationship between pH and NH3 equilibria in soils revealed that an increase in the concentration of NH4+, applied as (NH4)2 SO4, stimulated NH3 losses from fine‐textured soils at pH's ranging from 4.5 to 7.1. Ammonia volatilization was directly related to the initial pH of the soil and increased with an increase in pH. It was postulated that NH3 may be volatilized, even from acid soils, due to the equilibrium NH4+ + OH‐ ⇄ NH3 + H2O. By using initial concentrations of NH4+ from (NH4)2 SO4 applied, initial pH of an aqueous suspension of the soil and a value Kb = 1.80 × 10‐5, values of NH3 losses were predicted. The linear relationship found between predicted and measured amounts of NH3 losses from acid as well as neutral soils, was interpreted as evidence of the existence of the proposed volatilization mechanism in soils.
Changes in Exchangeable Potassium Observed on Drying Soils after Treatment with Organic Compounds: I. Release
Authors: Bates T. E. , Scott A. D.
Published: July 2010

When Marshall subsoil samples were dried in an oven at 110°C. for 48 hours, the NH4OAc extractable K increased from 27 to 210 ppm. This release of K was reduced to varying degrees by adding a wide variety of organic compounds to the soil samples before they were dried. The effect of these additives was not related to their solubility in water, dielectric constant or dipole moment. On the other hand, compounds with a high molecular weight and high boiling point were particularly effective in preventing K release.

All alcohols tested reduced K release. Their effect increased with the amount added and their boiling point. Thus, the effect of normal primary alcohols increased with chain length and the effect of butyl alcohols decreased with chain branching. K release was eliminated by adding normal alcohol with a molecular weight equal to or greater than butanol.

Glycerol, dextrose, sucrose, and n‐octanol additions were particularly effective in preventing K release. The relative effect of these additives was related to the volume of each added, not the number of moles or hydroxyl groups involved. The addition of less than 2 ml. of these compounds per 10 g. soil eliminated K release entirely.
Chemical and Mineralogical Studies on Slick Spot Soils in Idaho
Authors: Lewis G. C. , White J. L.
Published: July 2010

A study of a slick spot and associated soils showed the slick spot soil to be characterized by high salts and exchangeable Na throughout the profile whereas the high concentration of salts and exchangeable Na occurred at progressively greater depths in the profile in proceeding from the slick spot into the adjacent associated soils.

They clay‐size minerals found in both the slick spot soils and the associated soils were illite, montmorillonite, kaolinite, quartz and feldspars. Montmorillonite maxima occurred at progressively lower depths in the profile in proceeding from the slick spot into the associated soils.

Partial dissolution studies on the clay‐size fraction of the soils showed large amounts of amorphous material with the greatest amount being present in the slick spot soil. It was postulated that this amorphous material together with the high Na content contributed to the impermeability of these soils.
Significance of Biological Sulfate Reduction in Soil Salinity
Authors: Ogata G. , Bower C. A.
Published: July 2010

The effect of native and applied organic matter (straw) on sulfate reduction under anaerobic conditions in arid‐zone soils was studied in the laboratory. Changes in the composition of dissolved and adsorbed ions as a consequence of SO4 reduction was also studied. The results indicate that SO4‐reducing microorganisms are generally present in arid‐zone soils. Appreciable reduction of any SO4 present does not occur when arid‐zone soils become anaerobic by waterlogging, however, unless undecomposed organic matter (plant residue) is present or the soil organic matter content is high (e.g., > 5%). Sulfate reduction results in the formation of equivalent amounts of carbonates which, upon reaction with soluble or exchangeable Ca and precipitation as CaCO3, cause decreases in soil salinity and increases in the exchangeable sodium percentage.
Mica Surface Morphology Changes During Weathering
Authors: Raman K. V. , Jackson M. L.
Published: July 2010

Electron microscopic observations of mica surfaces by the carbon replica technique indicate that weathering, a major process of K release in soils, proceeds at the (hkO) fracture edges and at the crystallographic dislocations distributed on the (001) cleavage faces of mica crystals. Fresh cleavage surfaces of a paragonite with muscovite inclusions show discontinuity of the layers and marginal rolling at edges of K mica cores 3 to 5µ in diameter. A closely intergrown mosaic of the two micas is indicated rather than a true solid solution of the K,Na. Much of the interlayer Na in paragonite readily exchanges for K on treatment with 1N KCl solution and the surface assumes the smoother morphological features of K mica. Fresh cleavages of muscovite and margarite show some folding and scrolling of layers at dislocation edges. Artificial laboratory weathering of biotite to vermiculite by treatment with MgCl2 produces surface morphology similar to that of natural vermiculites. Removal of K from biotite with tetraphenylboron causes the surfaces to crack open, yielding fresh (hkO) fracture edges. Weathering with NaOH or HCl produces characteristic surface changes. Treatment of biotite with HF for one minute produces humps scattered at 0.1 to 1µ intervals over the (001) cleavage surfaces. Desilication for a longer period produces characteristic etch pits and corroded surfaces with serrated edges.

These surface studies provide a new model of mica weathering at (hkO) edges formed on the (001) cleavages, and shows layer flexibility on cation exchange which greatly aids in explanation of K release and fixation in soils.
Differential Aluminum Tolerance of Two Wheat Varieties Associated with Plant‐Induced pH Changes Around Their Roots
Authors: Foy C. D. , Burns G. R. , Brown J. C. , Fleming A. L.
Published: July 2010

Differential Al tolerance of Atlas 66 and Monon wheat varieties in nutrient solutions and in acid Bladen soil was attributed, at least in part, to plant‐induced differential pH changes around their roots.

In nutrient solutions the Al‐sensitive Monon variety lowered the pH and the Al‐tolerant Atlas variety raised the pH, resulting in differences as large as 0.7 pH unit in the nutrient media. In acid Bladen soil this difference was much smaller, and a high root‐to‐soil ratio was necessary to produce observed pH differences that were significant. The factor responsible for higher Al‐tolerance of Atlas was not transferred to Monon in mixed cultures in Bladen soil. The evidence indicates that the layer of plant‐altered soil surrounding the roots was extremely thin.
Clay Mineralogy of a Sassafras Soil in New Jersey
Authors: Douglas Lowell A.
Published: July 2010

The clay mineralogy of a Sassafras soil was studied. Illite was found to be the dominant clay mineral in the C horizon, and aluminum‐interlayered vermiculite was the dominant clay mineral in the A1 horizon. The weathering series: Illite → expanding‐vermiculite → vermiculite → aluminum‐interlayered vermiculite accounted for the major clay mineral alterations in this soil. The distribution of kaolinite suggested that kaolinite is being formed in the soil. Lepidocrocite was found in horizons containing large amounts of easily reducible iron.
Interpretation of Chloride and Nitrate Ion Distribution Patterns in Adjacent Irrigated and Nonirrigated Panoche Soils
Authors: Dyer Kenneth L.
Published: July 2010

Salt profiles of sprinkler‐irrigated soils, with known crop histories, were compared with those of adjacent soils which had not been irrigated. The methods described offer, for some areas, new techniques for estimating salt movements toward the water table and for evaluating past performance of irrigation projects.

Theoretical concentration curves obtained using van der Molen's application of the Glueckauf theory of chromatography were successfully fitted to CI‐ and NO3‐ concentration curves found in soils being leached under field conditions.

The accumulation of Cl‐ in the soil profile was used in conjunction with Cl‐ concentration in the soil solution to obtain an independent estimate of moisture dissipated by evapotranspiration. Evapotranspiration losses of sprinkler applied irrigation water were estimated by this method to range from 78 to 85% in the soils under investigation. Estimates of total applied irrigation water calculated from the accumulation of Cl‐ in the soil profile were in general agreement with estimates made from crop history.
Soil Anisotropy and Its Relation to Aggregate Stability
Authors: Cagauan B. , Uehara G.
Published: July 2010

For kaolinitic soils containing more than 5% free iron oxide, variations in percentage aggregate stability can be related to soil anisotropy. Soil anisotropy, as used in this paper, refers to the degree of particle orientation. In thin sections, increasing parallel orientation of clay particles within soil aggregates allows increasing reaction of the soil material to polarized light. For soils having essentially identical mineralogies, the amount of light transmitted through crossed polarizers can be related to particle orientation or soil anisotropy. The amount of transmitted light, which is used to measure soil anisotropy, can be measured with a photometer. When percentage aggregate stability was plotted as a function of photometer readings, a significant curvilinear relation was found to exist between these two variables.
Depth to Fragipan in Cabot Silt Loam—Variability in a Characteristic Area
Authors: Bornstein Joseph , Bartlett Richmond J. , Howard Montague
Published: July 2010

A drainage research projec thas been established at East Franklin, Vermont on a Cabot silt loam to study and improve interception drainage methods. To be able to interpret the resulting data with greater meaning it was necessary to determine the variability of depth to fragipan and the relations between this variability, the slope of the surface, and the thickness of the Ap horizon. Two methods of determining depth to the fragipan surface were used. The more feasible one, auger borings taken on a 100‐foot grid was evaluated for precision in relation to the method of examining drain trench walls. Thickness of Ap horizon and the depth to the fragipan surface were measured at 161 locations 2 feet apart along tile drain trenches. Fragipan surface at 143 points over the research area was located by the auger grid system.

The mean depth of the Ap horizon was 7.4 inches and 83% of the measurements fell in the 6‐ to 9‐inch range. Of all fragipan depths, 74% were in the 11‐ to 17‐inch range. Mean depth by augering was 13.9 inches; along the trench profile it was 14.4 inches. In this area of Cabot silt loam, the lower boundary of the Ap and the fragipan surfaces generally follow surface slopes. The auger method data follow the trend of the measurements derived from the trench profile.
Effect of Gypsum and Starch on Water Movement and Sodium Removal from Solonetzic Soils in Illinois
Authors: Padhi U. C. , Odell R. T. , Fehrenbacher J. B. , Seif R. D.
Published: July 2010

The improvement of solonetzic soils depends upon the replacement of excess exchangeable sodium and its removal by drainage. Gypsum and starch, both singly and in various combinations, were tested to determine their effect on water movement through and sodium removal from a solonetzic soil in Illinois. Significant amounts of leachate were collected and sodium was removed from columns of disturbed B2 horizon from a solonetzic soil treated with 8 tons/acre of gypsum and a combination of 8 tons of gypsum and 5 tons of starch/acre. There was less leachate and sodium removed by other treatments. Leaching and sodium removal were considerably reduced when the application rate of starch was raised to 10 tons/acre in combination with gypsum. This may be due to the low solubility of gypsum and the linkage between calcium and starch. Leachate and sodium removed were less from undisturbed cores 24 inches and 6 inches long than from columns of disturbed soil equivalent to the 6‐inch cores. Results were more variable from undisturbed soil cores than from disturbed soil columns. Results indicate that soil disturbance plus appropriate treatment, especially with gypsum, increase water percolation and sodium removal from these solonetzic soils. Starch was not effective.
Root Growth Through Porous Media Under Controlled Conditions II. Effect of Aeration Levels and Rigidity
Authors: Aubertin G. M. , Kardos L. T.
Published: July 2010

The effect of four different compositions of aeration gases on the root growth of maize seedlings (Zea mays) grown in rigid and nonrigid systems of a given pore diameter was evaluated. Best root growth of maize seedlings occurred where the aerating gas contained 10% oxygen rather than 21%. Root growth at 5% oxygen and 21% oxygen were similar but at 2.5% oxygen root growth was markedly decreased. Adverse effects of the lowest oxygen concentration were magnified when the pore system was rigid. A comparison of various root parameters indicated that root volume, root length, and root weight were all significant indexes of root response to oxygen levels and rigidity. Differences in root weight appeared to reside in differences in weight per unit length rather than in weight per unit volume.
Aluminum in Soils: VI. Changes in pH‐Dependent Acidity, Cation‐Exchange Capacity, and Extractable Aluminum with Additions of Lime to Acid Surface Soils
Authors: Bhumbla D. R. , McLean E. O.
Published: July 2010

Surface soils differing in extractable aluminum and organic matter were limed at various rates, moist incubated, and analyzed for pH‐dependent acidity by extracting KCl‐leached soils with triethanolamine (TEA) buffered BaCl2 solution‐pH 8.2. The pH‐dependent acidity decreased markedly with rate of liming. Aluminum was extracted with 1n KCl and with 1n NH4OAc‐pH 4.8 using varying amounts of solution and extraction times. Increased amounts of KCl solution removed more Al from unlimed soils, and the pH‐dependent acidity decreased correspondingly. More Al was extracted with NH4OAc‐pH 4.8 than with KCl, and differences in pH‐dependent acidity of limed and unlimed soils were relatively less pronounced, especially in soils high in soluble Al. Prolonged leaching with NH4OAc‐pH 4.8 reduced these differences more. Cation‐exchange capacities (CEC) measured with NH4OAc‐pH 7 or with TEA buffered BaCl2‐pH 8.2 did not vary appreciably with rate of liming. In soils high in soluble Al, CEC measured by leaching with unbuffered salt solutions were much lower than those obtained with NH4OAc, but increased markedly with liming. The data suggest that acidity measured in KCl‐leached soils includes not only the weak acid H+ ions which become reactive or displaceable at higher pH, but also acidity related to organic‐complexed Al or hydroxy‐Al polymer.
Naturally Occurring Fixation of Cesium‐137 on Sediments of Lacustrine Origin
Authors: Lomenick T. F. , Tamura T.
Published: July 2010

White Oak Lake formerly served as a final settling basin for contaminated waste water discharged from the Oak Ridge National Laboratory. The site, which now serves as an ecological study preserve, covers an area of 44 acres and contains approximately 1,000,000 ft3 of contaminated sediment. The most abundant radionuclide present in the sediment of lacustrine origin is Cs137, 704 ± 35 curies. Concentrations of Cs137 on the sediment were observed to be as high as 77 × 10‐3 µc/g. More than 80% of the Cs137 is associated with the clay fraction of the material, which was found to be predominantly illite. Significant quantities of Cs137 were removed from the material only by treatment with strong acids. Studies of several selected clays showed illite to have a high affinity for Cs137 at levels of the same order of magnitude as those observed in lake bed sediment and that desorption is only accomplished after disruption of the lattice structure.
The Dickson and Zanesville Soils of Washington County, Arkansas: II. Micromorphology of Their Fragipans
Authors: Horn M. E. , Rutledge E. M.
Published: July 2010

The micromorphological features of fragipan horizons of a Dickson silt loam and a Zanesville silt loam were studied by means of thin sections of known orientation with respect to the soil surface. The features observed were classified according to the system developed by Brewer and co‐workers in Australia. Their abundance, particularly those classified as plasmic separations and concentrations, was found to be much greater in fragipan horizons than in overlying B subhorizons. Plasma aggregates are larger, more easily recognized, and separations more common (sepic fabric) in fragipans than in overlying horizons. In the latter, plasma aggregates are recognizable although small, and randomly distributed. The resultant fabric is basically asepic but an incipient sepic fabric exists in the subhorizon immediately overlying the fragipan where plasmic separations become more noticeable.

The salient micromorphological feature of both soils is the striking increase in number and degree of development of illuviation cutans within their fragipan horizons. These cutans are associated with the void system and increase in thickness with depth. Corresponding increases in per cent clay content in the fragipans, however, are not of the magnitude expected from the observed increase in cutan development. This suggests that an important difference between fragipan and nonfragipan horizons is in the nature of clay arrangement (i.e., its plasmic structure) within the soil matrix rather than amount of clay.

Conclusions are: (i) Brewer's classification provides a useful tool in this kind of study; (ii) micromorphology of the Dickson and Zanesville profiles are very similar except that the Dickson contains lithorelicts of chert whereas in the Zanesville they are siltstone or sandstone; and (iii) much of the silt in these soils can be accounted for through weathering of chert or siltstone. Further tentative conclusions are that fragipan brittleness and polygonal color pattern apparently result from the precipitation of iron oxides and clays through diffusion processes within the soil matrix associated with movements of water suspensions and solutions in the void system of the soil, and that fragipans in the soils studied have formed coincidentally with the rest of the solum and can be explained by processes of soil genesis in operation today.
Cryorthods of the Cook Inlet‐Susitna Lowland, Alaska
Authors: Rieger Samuel , DeMent James A.
Published: July 2010

Physical and chemical properties of four Cryorthods (Podzols) developed in silty materials in the Cook Inlet‐Susitna Lowland of south central Alaska were studied. Intensity of development of the soils was directly related to precipitation rates. Cryorthods in the southern part of the Lowland appear to have developed from previously existing Cryandepts (Andos) following replacement of grasslands by forest. In the northern part, the loess was probably subject to podzolization immediately after its deposition.
Effects of Plastic Mulch on the Growth, Maturity, and Yields of Corn
Authors: Free G. R. , Bay Clyde
Published: July 2010

Slit translucent plastic covers on field plots of two corn hybrids (Zea mays L.) on Honeoye silt loam in New York increased soil temperatures, rate of early growth, final grain yields, and percentage of dry matter in ears at harvest. The mean yields of shelled corn over a 3‐year period for corn hybrids, Cornell M‐10 and Robson 350, were increased by 1,456 and 896 lb/acre (26 and 16 bu/acre), respectively.

When the plastic cover was not slit, but was sealed to the stalks to suppress evaporation and to prevent the entrance of rain, yields were at or above the 5,600‐lb/acre level (100‐bu/acre), and were consistently higher than yields for unmulched plots. Apparent use of soil moisture for crop production under the sealed treatment was about one–third of the total evapotranspiration from crop and soil under the bare or slit treatments.
Effect of Tree Spacing and Understory Vegetation on Water Use in a Pumice Soil
Authors: Barrett James W. , Youngberg C. T.
Published: July 2010

Water use in a pumice soil in central Oregon increased significantly with increased density of a sapling ponderosa pine (Pinus ponderosa Laws.) stand.

Study plots were thinned to 62, 125, 250, 500, and 1,000 trees/acre and replicated six times. Soil moisture measurements were begun 2 years after thinning and continued for three successive growing seasons. Soil moisture was measured with a neutron probe at three permanent stations on each plot at 3‐week intervals during the summer.

Total amount of water use was 1.6 times greater on plots containing 1,000 trees/acre than on plots containing 62 trees/acre. Moisture use on plots where understory vegetation was allowed to develop normally was 45% greater than on plots where vegetation was removed. Soil in the area is a Regosol developed in dacite pumice, approximately 7,300 years old, from the eruption of Mount Mazama (Crater Lake).
Effect of Drying on Volcanic Ash Soils in Chile
Authors: Schalscha E. B. , Gonzalez C. , Vergara I. , Galindo G. , Schatz A.
Published: July 2010

Air drying produces significant irreversible changes in volcanic ash soils. Air‐dried samples with clay texture in the field appear to have sandy texture according to laboratory analyses. Air‐drying also markedly affects cation‐exchange capacity, soluble P, and soluble Fe. The nature and extent of changes in the latter two properties vary with different methods of analysis. Air‐drying decreases the pH slightly. These results show that mechanical and chemical analyses of volcanic ash soils more accurately indicate field conditions when samples contain moisture at field capacity.
The Effect of Lime on the Phosphate Potential and Resin‐Extractable Phosphate in Five Acid Soils
Authors: Taylor A. W. , Gurney E. L.
Published: July 2010

The equilibrium phosphate concentrates in five acid soils showed little change on the addition of excess calcium carbonate, but the amounts of phosphate extracted on shaking with anion exchange resin increased significantly with rising pH. Liming apparently effects some alteration in the soil phosphates, perhaps by causing more phosphate to be adsorbed in a readily removable form.
The Movement of Sulfate Salts in Soils
Authors: Swoboda A. R. , Thomas G. W.
Published: July 2010

The movement of potassium sulfate in columns of calcium‐saturated Cecil soil was studied. The desorption by hydrolysis of adsorbed SO42‐ ions was found to influence the distribution of other ions in the columns. Leaching with 10.4 inches of water caused only slight hydrolysis of adsorbed SO42‐ and adsorbed cations. Excessive leaching with 104 and 207 inches of distilled water caused considerable hydrolysis and displacement of adsorbed SO42‐ as well as K+ and Ca2+.

The amount of hydrolysis in columns of calcium‐saturated Yolo soil which does not adborb SO42‐ was found to be much lower than in the Cecil soil columns.

Soil profiles taken from central Piedmont of Virginia showed substantially the same distribution of SO42‐ as found in laboratory columns. The highest concentration of Mg2+ always was found to occur at the same depth as a maximum concentration of SO42‐.
Calcium Requirement for Penetration of Subsoils by Primary Cotton Roots
Authors: Howard D. D. , Adams Fred
Published: July 2010

Short‐term, split‐root experiments were conducted with cotton seedlings (Gossypium hirsutum) in which the upper portion of the root medium was a sandy loam surface soil and the lower portion was either a nutrient solution or a subsoil material at various Ca levels. The Ca required in subsurface media for penetration was dependent upon the Ca/total‐cation ratio rather than the Ca concentration per se. The Ca requirement was apparently the same in soil solutions in situ as in nutrient solutions, namely, between Ca/total‐cation ratios of 0.10 and 0.15 in all cases. Critical levels of exchangeable Ca were equal in Norfolk and Dickson subsoils when Ca was expressed as a ratio of Ca to total exchangeable cations even though the clay fraction of Norfolk is kaolinite while the clay fraction of Dickson is vermiculite with some montmorillonite. Norfolk subsoil at pH 5.0 and Dickson subsoil at pH 4.6, as obtained from the field, contained adequate Ca for normal growth of primary cotton roots.