bluuebunny/crossref_metadata_2025 huggingface dataset:
Magnesium and Silicon Activities in Matrix Solutions of Montmorillonite‐Containing Soils in Relation to Clay Mineral Stability
Authors: Weaver R. M. , Jackson M. L. , Syers J. K.
Published: July 2010

Soils of varying geomorphological site characteristics were sampled in the southern Wisconsin catena for the preparation of soil matrix solutions used for solute activity determinations. The catena clays contained from 27 to 45% of montmorillonite and from 11 to 3% of kaolinite in the < 0.2µm fraction. The SiO2/Al2O3 molar ratios of the reactive fraction of these < 0.2µm clay fractions ranged from 2.1 to 2.4 for the more acid horizons, indicating kaolinite or aluminous chlorite weathering products. Those of the reactive fraction from the calcareous and poorly‐drained horizons ranged from 3.1 to 3.9, indicating montmorillonite or beidellite (dioctahedral smectite) stability. The solute activity functions, pH ‐½pMg2+ and pSi(OH)4, for the field‐fresh soil matrix solutions fell distinctly into areas indicative of either montmorillonite stability (poorly drained or calcareous horizons) or of kaolinite stability (moderately well‐ to well‐drained, acid horizons) in a phase stability diagram developed to include a Mg‐saturated montmorillonite phase. The solute activity functions of the matrix solutions from Mg‐saturated soils or clays approached the montmorillonite‐kaolinite phase join more closely, with less impress from the geomorphic and weathering environments of the sites.

The solute activity functions for montmorillonite‐free soils from northern Indiana, for montmorillonites of bentonites, and for kaolinites and chlorite (controls) fell in the appropriate areas of the diagram. The pH ‐½pMg2+ solute values of the kaolinite‐forming soils ranged from 2.3 to 4.6; the pSi(OH)4 values, from 3.2 to 3.9. The montmorillonite‐forming soils had pH ‐½pMg2+ solute values ranging from 4.7 to 6.2 and pSi(OH)4 from 3.0 to 4.0. Montmorillonite stability was indicated by higher values of the pH ‐½pMg2+ function and/or Si(OH)4 activities.
Calcium Complexing and the Enhanced Solubility of Gypsum in Concentrated Sodium‐Salt Solutions
Authors: Nakayama F. S.
Published: July 2010

Solubility of Gypsum in NaClO4, NaCl, NaNO3, and NaOAc solutions and their mixtures was determined experimentally and theoretically. The dissociation constants of CaCl+, CaNO3+, CaOAc+, NaOAc0, and NaNO30 were computed from the solubility behavior of the solid. The predicted solubility values corresponded closely to the measured values in mixed Na‐salt solutions when allowances were made for Ca‐complexing.
Retention of Three Insecticides on Different Size Soil Particles Suspended in Water
Authors: Richardson E. M. , Epstein E.
Published: July 2010

Studies were made to determine the retention of DDT, endosulfan and methoxychlor on different sized soil particles. The two soils used were Marshall silt loam from Iowa and Caribou silt loam from Maine. A portion of each soil was treated with H2O2 to study the effect of organic matter on pesticide retention.

Retention of DDT and methoxychlor was highest in the clay fraction of both treated and untreated soils. In the untreated soils the greatest retention of the three insecticides was on the colloidal (<0.08 µ) and 0.08–0.5 µ fraction. Removing the organic matter from both soils reduced the retention on the <0.08 µ and 0.08–0.5 µ clay fractions.

The two soils reacted differently to the H2O2 treatment, although the three insecticides followed very similar trends within a soil. It appears that although organic matter contributes to the retention of the insecticides studied, other soil properties also are responsible for adsorption.
An Application of Autoradiography to Study the Spacial Distribution of 33P‐Labelled Orthophosphate Added to Soil Crumbs
Authors: Evans T. D. , Syers J. K.
Published: July 2010

The penetration of orthophosphate (P) into soil crumbs was studied semiquantitatively using 31P, the low energy isotope 33P, autoradiography on a medium grained film, and solution analysis. Sorption of added P by the soil crumbs was rapid and was followed by penetration. Phosphate was not concentrated in discrete areas, suggesting that it was retained by a sorption rather than a precipitation mechanism. Native and added P, isotopically exchangeable in 1 hour, were confined to the crumb surface. Desorption for 7 days in Cl‐ or SO42‐ had little or no effect on the spacial distribution of sorbed added P; 0 and 2.4% of the sorbed added 31P was desorbed by Cl‐ and SO42‐, respectively. Desorption in HCO3‐ or citrate increased the mobility of sorbed added P resulting in a complete redistribution within the crumbs and release into solution of 14 to 18% or 10 to 61% of sorbed added 31P, respectively. Anomalous estimates of the amount of P sorbed or desorbed, obtained by 31P and 33P analyses, could not always be explained by isotopic exchange.
Response of Phaseolus Vulgaris to Zine as Influenced by Phosphorus Level and Source
Authors: Lessman Gary M. , Ellis Boyd G.
Published: July 2010

The percentage of fertilizer Zn which remained water soluble increased with increasing Zn additions until a Zn/P ratio of 1:29 was reached and then decreased with increasing quantities of ZnO incorporated in ammonium polyphosphate (APP). ZnO incorporated with ammonium orthophosphate (AOP) was less water soluble, in all cases, than the same quantity of ZnO incorporated into APP. Zn content of 3‐week‐old Phaseolus vulgaris L. (pea beans) was positively related to the water‐soluble Zn present in the fertilizer. Yield and Zn uptake from field experiments with pea beans grown on calcareous soils indicated that APP is a more effective carrier than AOP in supplying Zn to the plant. With APP, a Zn/P ratio of 1:15 was inferior to ratios of 1:21 or 1:3 as measured by water‐soluble Zn present, yield, and Zn uptake by pea beans.
Water Infiltration Control: a Channel System Concept
Authors: Dixon R. M. , Peterson A. E.
Published: July 2010

A channel system concept of infiltration was developed to describe the profound influence of large soil pores on the movement of soil water and air. This concept hypothesizes that soil surface conditions or channel system states control the flow of water and air in subsurface networks of large pores. Six channel system states (A through F), representing common soil surface conditions, form the basis for controlling infiltration within a range often exceeding one order of magnitude. Channel system states A, B and C represent rough surfaces with open, constricted and closed channel ports, respectively; whereas states D, E and F represent smooth surfaces with open, constricted and closed channel ports. Infiltration rates usually vary in the order A>B≃D>C≃E>F. Under state A the soil surface and subsurface channels are hydraulically and pneumatically connected, and under state F they are disconnected. Under state A water penetration rates are rapid and flow routes are relatively direct, whereas under state F rates are slow and routes are extremely tortuous. Soil surface management can be directed to achieving the desired channel system state and hence the design level of infiltration. The channel system concept appears applicable to a wide range of infiltration‐related problems.
Biogenic Opal in Ohio Soils
Authors: Wilding L. P. , Drees L. R.
Published: July 2010

Soils in the eastern extremity of the Prairie Peninsula have developed during most of their history under forested conditions. Biogenic opal isolated from the 50‐20µ fraction of 55 profiles representing different topo‐ and biosequences in western Ohio indicates that most Mollisols (Brunizems) of this area have similar total opal accumulations and depth‐distributions as their Alfisol (Gray‐Brown Podzolic) analogues. The prairie influence on both groups of soils has been calculated to be about 150 to 500 yars. Opal depth distributions decrease from 0.1 to 0.3% in surficial horizons to <0.03% below 50 cm. No evident differences in opal concentration occur among toposequence members. Opal isolated from leaves of deciduous trees common to Ohio is optically isotropic, has a specific gravity <2.3, and a refractive index between 1.44 and 1.48. With few exceptions, <2% of the forest opal occurs in the 50‐20µ size range with >75% in finer fractions. Scanning electron microscopy, reveals that opal in >20µ sizes isolated from tree leaves is sufficiently distinct morphologically that it would not normally be confused with that of grass origin. Opaline constituents of forest origin are generally 1 to 2µ fragile incrustations of the cell walls and seldom form solid rectangular or polyhedral structures characteristic of opalized cells of grass origin.
An Improved Form of Soil‐Water Diffusivity Function
Authors: Ahuja L. R. , Swartzendruber D.
Published: July 2010

The soil‐water diffusivity D(θ) is expressed by a functional form which becomes infinite as the soil‐water content approaches a constant value, such as the saturated or near‐saturated value. The function begins at the origin, and shows an approximately exponential rise in the intermediate soil‐water content range. When combined with a previously suggested form of unsaturated hydraulic conductivity function K(θ), qualitatively reasonable forms for the relationship between water content and suction head can be inferred. A computer program was developed to determine the characterizing parameters in the function by a least‐squares fit to experimental data for horizontal water absorption. The program used an optimum seeking technique with numerical solutions of the flow equations as obtained by Philip's method. For different types of soils and several bulk densities, the new functional form was compared with the commonly used exponential expression for D(θ), and was found to be more representative, particularly for soils which show a very rapid increase in D(θ) as saturation is approached.
Calcium Fluoride Formation During Extraction of Calcareous Soils With Fluoride: II. Implications to the Bray P‐1 Test
Authors: Smillie G. W. , Syers J. K.
Published: July 2010

Calcium fluoride formed during a 1‐min extraction of calcite (50‐2 µm) with the Bray P‐1 reagent (0.03M NH4F/0.025N HCl) sorbed added P. Because of the problem in identifying minor components of a whole soil matrix by X‐ray diffraction analysis, it was frequently difficult to positively identify CaF2 in residues following a 1‐min Bray P‐1 extraction of calcareous soils; CaF2 was, however, identified in a highly calcareous soil (59% CaCO3) following a 1‐min Bray P‐1 extraction. Added P sorbed by calcite and several calcareous soil horizons (containing more than 10% CaCO3) during 1‐min and 24‐hour extractions with the Bray P‐1 reagent was not recovered in a subsequent 1M NaCl or 0.1N NaOH extraction. By comparison with the data obtained for calcite and noncalcareous soils, the P sorbed during the Bray P‐1 extraction of calcareous soils was shown to be associated with CaF2 and not with CaCO3 or Al and Fe components. Formation of CaF2 and immobilization of P during a 1‐min Bray P‐1 extraction was demonstrated for a wide range of calcareous soils by comparing the amounts of added P recovered in subsequent NaCl and NaOH extractions with the amounts of added P recovered in NaCl and NaOH extractions subsequent to extraction with 0.03M NH4Cl/0.025N HCl. The low Bray P‐1 estimates of “available” P, frequently reported for calcareous soils, may be attributed to the formation of CaF2 when the dilute HCl is neutralized by CaCO3.
The Effect of Temperature on the Ion Activity Product (Al) (OH)3 and its Relation to Lime Potential and Degree of Base Saturation
Authors: Shah Singh S.
Published: July 2010

Equations are derived for the relation between corrected lime potential (CLP) and degree of base saturation for temperatures 15, 25, and 35C. The effect of temperature on the activity of Al(OH)3 in solution and on the exchange constant is discussed. It is shown that there is a significant effect of temperature on the relation between CLP and percent base saturation. The CLP values decreased 0.15 units on the average for an increase of 10C in clay and soil systems. It is also shown that experiments should be done at a constant temperature for calculating the degree of base saturation from the corrected lime potential.
Effects of Vesicular‐Arbuscular Mycorrhizae on Growth and Phosphorous Content of Three Agronomic Crops
Authors: Jackson Nelroy E. , Franklin R. E. , Miller R. H.
Published: July 2010

Several placements of vesicular‐arbuscular (VA) mycorrhizal inoculum in soil were compared in a greenhouse study of the potential use of VA fungi for increasing yields of agronomic crops on low P‐status soils. Placement of VA mycorrhizal inoculum and rock phosphate was considered an integral treatment. Inoculation with VA fungi increased corn yields about 50% over the increases due to indigenous mycorrhizal fungi. Placements of inoculum in a layer 5 cm below the seeds or mixed with a 5‐cm layer of soil below the seeds were effective; while two other placements, with the seeds or in a band with rock phosphate, were ineffective in increasing yields. None of the treatments that used rock phosphate were as effective as concentrated superphosphate in increasing yields, which indicated that lack of P was still limiting plant growth in the rock phosphate treatments. There were no effects of VA mycorrhizal inoculation of soil on growth of soybeans (Glycine max L. Merrill ‘Harosoy 63’) and only a minor effect on sudangrass (Sorghum bicolor var. sudanense) for the placements that were tested.
High Molecular Weight Organic Phosphorus Complexes in Soil Organic Matter: Inositol and Metal Content of Various Fractions
Authors: Veinot R. L. , Thomas R. L.
Published: July 2010

Organic P compounds extracted from soil and fractionated on Sephadex G‐75 yielded an excluded fraction containing 39% of the organic P. Further fractionations yielded a fraction excluded from Sephadex G‐200 containing 32% of the organic P of the original extract and a fraction partially excluded from G‐150 containing 7%. The fraction excluded from G‐200 was higher in Fe and Al but lower in Na, K, and inositol than the fraction obtained from G‐150. The presence of inositol in these high molecular weight fractions suggests that inositol phosphates may be present even though they could not be identified. Stability studies indicated that changes in molecular weight distribution could occur even with mild extraction techniques.
Temperature Influence on Ammonium and Nitrate Absorption by Lettuce
Authors: Frota J. N. E. , Tucker T. C.
Published: July 2010

The uptake patterns of NH4+ and NO3‐ in lettuce plants (Lactuca sativa L., cultivar ‘Climax’) were determined using inverse 15N isotope dilution techniques under air and root temperatures of 8, 13, 18, and 23C and the same air temperatures with an initial root environmental temperature of 2C. The absorption patterns for both NH4+ and NO3‐ at each nutrient solution and air temperature were linear functions of time. The absorption rates for NH4+ and NO3‐ were increased by increasing the air, root, or both air and root environmental temperatures. Nitrate uptake was influenced more by temperature than the absorption of NH4+. The NH4+ to NO3‐ absorption ratio increased when the temperature decreased. A higher temperature coefficient for NO3‐ was obtained. The translocation rates to tops for NH4+ increased as temperature increased from 8 to 23C, but reached a maximum at 18C for NO3‐.
Estimating Deep Drainage Between Irrigations
Authors: Miller D. E. , Aarstad J. S.
Published: July 2010

This paper treats the situation, common in irrigation, in which the water table is deep enough to be ignored and applied water moves downward by drainage and is taken up by plants. When plants are transpiring, soil water content is reduced by both deep drainage and plant extraction. Drainage rates from a wetted depth of soil are related to the total water contained in that depth when there is no plant use. This same relation can be used to estimate drainage following an irrigation when the soil is cropped. However, in a series of irrigations, there is a delay between the end of irrigation and the beginning of drainage, and drainage is overestimated. If reduced irrigation efficiencies can be tolerated, overirrigation can lengthen time between irrigations, especially if evapotranspiration rates are low.
Computer Simulation Analysis on Reclamation of Salt‐Affected Soils in San Joaquin Valley, California
Authors: Tanji K. K. , Doneen L. D. , Ferry G. V. , Ayers R. S.
Published: July 2010

A computer land reclamation model was developed and applied to a field leaching study of moderately salt‐affected profiles. Leaching was accomplished by ponding 15 cm of water intermittently in 3 m by 3 m basins every 1 to 2 weeks. Computer predictions on the degree of reclamation were compared with measured changes in soluble salts, soluble boron, and SAR to soil depths of 274 cm. The differences between computed and measured field data were no more than the horizontal variations found in salt‐affected lands in this area and elsewhere. Also reported are predicted drainage water quality and a method for computing gypsum requirements of sodium‐affected profiles.
Nutrient Accumulation and Cycling in Loblolly Pine (Pinus taeda L.) Plantation Ecosystems: The First Twenty Years
Authors: Switzer G. L. , Nelson L. E.
Published: July 2010

The mass of the system increased by 10‐fold during this period; and in terms of the system's initial nutrient fund, the quantities of N, P, K, Ca, Mg, and S increased approximately 4, 4, 11, 7, 5, and 3 times, respectively. The quantity of nutrients present in the above ground portion of the system at 20 years ranges from 298 for N to 24 kg/ha for S, about a 12‐fold difference.

The portion of the system's total nutrient fund that is cycling to meet the annual requirement during the 20th year is small, ranging from a minimum of 7% for Ca to a maximum of 28% for K. This range is principally a reflection of the disposition and mobility of the nutrients. A technique of accounting for the system's nutrient budget is developed and an example presented. This technique indicates that, with some nutrients in these perennial systems, a sizable portion of the annual requirements is met by transfer within the living fraction of the system. Thus, in addition to the geochemical and biogeochemical cycles, a biochemical cycle is proposed which encompasses the internal transfer relationships or translocations of nutrients within the trees. Consideration of this phenomena leads to a more realistic concept of nutrient cycling within these and similar systems.
Source‐Detector Geometry Effect on Neutron Probe Calibration
Authors: McCauley G. N. , Stone J. F.
Published: July 2010

A laboratory experiment was conducted to develop a method for the nondestructive determination of the midpoint of the anode wire and the center of the sensitive volume of a boron trifluoride neutron detector tube. These points were found to coincide and would be expected to do so for all such detector tubes of symmetrical construction. The measurements on the detector tube were determined from X‐ray radiographs by triangulation. This center point coincides with the midpoint of the portion of the detector between the bottom and seam near the top.

Using the center of the sensitive volume as a reference point, the effect of position of the neutron source on the count rate in hydrogenous media was studied. Four hydrogenous media were used: urea, aluminum sulphate, water, and the paraffin shield for the probe (Nuclear‐Chicago, model P‐19). Materials were contained in 210‐liter drums. Second degree curves fit the data of count rate vs. distance between source and reference point. The center of the sensitive volume coincided with the point of greatest count rate. The center was also the position for greatest sensitivity to water content. Results indicate that changes of source position as small as 0.5 cm from the position at original calibration will significantly change the calibration curve. Users can detect such changes by monitoring ratios of readings in two different hydrogenous media in the laboratory. Any such change in source‐detector geometry will produce a change in ratio. Positional changes may be the result of either a source movement or replacement of detector tube with one of different dimensions.
Arsenic Solubility in a Reduced Environment
Authors: Deuel Lloyd E. , Swoboda Allen R.
Published: July 2010

Soluble As levels were determined in flooded soils and found to be related to the total As content and the reduced environment obtained. The flooded soils equilibrated at 25C contained a soluble As concentration which ranged from 0.06 to 0.18 ppm when treated with 0.568 mg of As/100 g soil, applied to the soil as NaAsO2. No appreciable As was found in the samples equilibrated at 25C which had not been treated with As. The equilibration of samples at 38C resulted in much higher concentrations of soluble As. The concentration of soluble As ranged from 0.15 ppm for a sample with no added As to 0.79 ppm for a sample which received 1.135 mg of As/100 g of soil. A reduced environment resulted in a greater soluble As concentration. Samples equilibrated at 38C were more reduced than those equilibrated at 25C. The increase in soluble As at lower reduction potentials was attributed to the reduction of Fe and not the reduction of As itself. Arsine was not detected in any of the soil samples.
Concerning the Location and Persistence of Soil Urease
Authors: Burns R. G. , Pukite A. H. , McLaren A. D.
Published: July 2010

Urease activity in soil is persistent for long periods under low water, low temperature, and sterile regimes, and it has been suggested that some form of enzyme‐protective mechanism exists in soil.

Dublin soil was sonicated in water and extracted by adding a mixture of salts. Urease activity is associated with the organomineral complex thus obtained and is resistant to the activities of proteolytic enzymes. Clay‐free soil organic matter prepared subsequently by filtration also exhibits urease activity which is resistant to proteolysis. Models consisting of enzymes with bentonite and lignin were found to mimic this resistance to proteolysis. Models consisting of enzymes with bentonite and lignin were found to mimic this resistance to proteolysis.

A model system is presented which suggests both the origin and location of soil ureases and a reason for their persistence in nature.
Argixerolls on Late Pleistocene Surfaces in Northwestern Oregon
Authors: Gelderman F. W. , Parsons R. B.
Published: July 2010

Argixerolls in the Yamhill Valley in Polk County, Oregon, have characteristics that are determined by the age, topography, and parent materials of three late Pleistocene geomorphic surfaces. The newly defined Bethel surface is in the highest topographic position. Four Willamette‐like pedons were sampled as representative of three topographic positions on the Senecal and Bethel surfaces. The Senecal surface is characterized by level and nearly level valley terraces and the Bethel surface by low, rounded hills that are graded to the level, intermediate Calapooyia surface. The soils of the upper slopes of the Bethel surface have characteristics of Ultic Argixerolls. Those on the nearly level Senecal and Calapooyia surfaces and the lower slopes of the Bethel surface have characteristics of Pachic Ultic Argixerolls. The soils on the level to depressional hill crests of the Bethel surface and level valley terraces of the Senecal surface have characteristics of Aquultic Argixerolls. Characterization of the soils emphasized similarities among them. Subgroup differences are due primarily to topographic position and are related to the stratigraphy of the region.
An Evaluation of Zonal Centrifugation as a Research Tool in Soil Science: II. Characterization of Soil Clays
Authors: Francis C. W. , Tamura Tsuneo
Published: July 2010

Data revealed little resolution in banding is gained in centrifuging for 40 compared to 17 hours in a conventional centrifuge (force field less than 623 × g). On the other hand, the resolution obtained by centrifuging in an ultracentrifuge is considerably better than that obtained in a conventional refrigerated centrifuge. The clay fraction from a Dodge silt loam banded into nine fractions after centrifuging at 15,000 rpm (38,500 × g) for 17 hours. Characterization of each band allowed a much more extensive evaluation as to the quantities of each specific clay mineral present than the conventional estimates presently being made by examining X‐ray diffractograms of the total clay fractions.
Measuring Chloride in Effluent Flowing from a Soil Column
Authors: Mansell R. S. , Elzeftawy Atef
Published: July 2010

An inexpensive flow cell and combination chloride electrode system is described for continuously recording the chloride concentration in effluent flowing from a soil column. The response was observed to be sufficiently fast for monitoring effluent at flow rates normally encountered in column studies of soils. Break‐through curves for three different volume “slugs” of chloride solution displaced through a column of glass beads were in close agreement with corresponding breakthrough curves obtained by argeniometric titration of aliquots collected from the same effluent.
Systematic and Random Errors in Dual Gamma Energy Soil Bulk Density and Water Content Measurements
Authors: Gardner Walter H. , Campbell Gaylon S. , Calissendorff C.
Published: July 2010

Soil bulk density and water content may be obtained concurrently through measurement of the attenuation of gamma photons from two different gamma ray sources and simultaneous solution of the resulting attenuation equations. Errors in the soil bulk density and water content measurements result from random emission from the sources, random errors in attenuation coefficients and soil column thickness measurements, presence of a small, higher energy peak in the 241Am spectrum, and counting equipment dead time. Using gamma photons from 241Am at 0.060 Mev and from 137Cs at 0.662 Mev, attenuated in 10‐cm soil columns, the standard deviation in both water content and bulk density measurements is primarily due to random emission and is about 0.007 g/cm3 for 106 counts measured in air and about 0.005 g/cm3 for 2.5 × 106 counts. However, as larger counts are used the precision of measurement of column thickness and soil and water attenuation coefficients becomes limiting. If, by obtaining large counts, the variance due to random emission is reduced to the same magnitude as that associated with measurement of column thickness or attenuation coefficients, precision limit would be about 0.0035 g/cm3 at midrange values of water content and bulk density. At high count rates instrument dead time corrections are made to get accurate counts. Gamma rays scattered down from the small 0.103 Mev peak in the 241Am spectrum result in attenuation dependent attenuation coefficients for which appropriate corrections must be made. For narrow collimating slits the spatial resolution is only a little greater than slit thickness. Collimater and shielding requirements are shown.
Seepage Through Soil Bedding or a Hillside Due to a Steady Rainfall: II. Soil Surface of Arbitrary Shape
Authors: Selim M. Sami , Kirkham Don
Published: July 2010

In a companion paper (I), the authors presented a theoretical solution for the seepage of steady rainfall through soil bedding or a hillside, with constant slope soil surface. In the present work, the case of an arbitrarily shaped soil surface is investigated. Two different shapes for the soil surface are considered in detail. The first shape is taken as part of the boundary of an ellipse, and the second is an arbitrary shape that includes ponded water‐depressions. The depth of water standing in the ponded depressions and drainage furrows is taken into account. Flow nets, seepage velocities, and infiltration rates are determined. As in paper I, but now for the new conditions, the seepage patterns show that some of the rainwater seeps into the soil on the uphill part of the slope and then flows through the soil more or less parallel to the soil surface. The water then seeps upward out of the soil on the downhill part of the slope. In one example, the inward and then outward flow occurs three times. With an elliptical shaped water table, the upward seepage occurs over a smaller portion of the bedding than for rectilinear (constant slope) bedding. The in and out seepage of water may cause leaching of nutrients and other chemicals from the soil.
Solubility of Silica in Soils
Authors: Elgawhary S. M. , Lindsay W. L.
Published: July 2010

A solubility diagram was developed that shows the activity of various ionic and molecular species of Si in equilibrium with amorphous silica as a function of pH. Below pH 8.0 only uncharged Si(OH)4 contributes significantly to total soluble Si.

The solubility of Si was measured on two soils in which equilibrium was approached from both undersaturation and supersaturation over a 50‐day period. In this study, 0.02M CaCl2 was included in all suspensions during their equilibration to flocculate colloidal Si and preclude its inclusion as soluble Si. The acid Paxton soil supported approximately 19 ppm of Si in solution while the calcareous Ulysses soil supported 25 ppm. These levels are intermediate between the solubility of quartz (2.8 ppm Si) and amorphous silica (51 ppm Si) and lie very near the level predicted for equilibrium between kaolinite and montmorillonite based on Kittrick's thermodynamic calculations.
Volatility of Organochlorine Insecticides from Soil: I. Effect of Concentration, Temperature, Air Flow Rate, and Vapor Pressure
Authors: Farmer W. J. , Igue K. , Spencer W. F. , Martin J. P.
Published: July 2010

The volatilization of dieldrin from Gila silt loam as influenced by soil pesticide concentration was determined in the laboratory at two air flow rates at 20 and 30C. The influence of pesticide vapor pressure on volatilization was measured by comparing the volatilization from Gila silt loam of dieldrin with that of lindane and DDT. No net water movement to or from the soil occurred during any of the volatilization processes.

The vapor density of the soil‐applied pesticide was the main factor controlling volatilization. The rate of volatilization of dieldrin from Gila silt loam increased with increasing soil pesticide concentration until the soil dieldrin concentration reached approximately 25 µg/g. This is the soil dieldrin concentration required to give a maximum saturation vapor density equivalent to that of the pure compound. An increase in temperature of 10C increased the rate of volatilization approximately fourfold. Increasing the rate of air movement over the soil surface from 0.005 to 0.018 mile/hour increased the rate of volatilization twofold. The order of rate of volatilization of three insecticides was: lindane > dieldrin > DDT. This is the same order for increasing vapor pressures of the three insecticides. The increase in rate of volatilization of the three insecticides was less than the increase in saturation vapor density of the pure compounds. This resulted because the concentrations of lindane and dieldrin in the soil rapidly decreased below that required to give a maximum vapor density of the pesticides. The maximum volatilization rates obtained represent potential losses of lindane, dieldrin, and DDT from soils of 202, 22, and 5 kg/ha/year, respectively. The volatilization rates decreased rapidly as soil pesticide concentration decreased. Extrapolation of the laboratory data to field situations suggests that the rate of volatilization could account for a significant proportion of these applied pesticides lost under normal field conditions.
Nitrogen Mineralization Potentials of Soils
Authors: Stanford George , Smith S. J.
Published: July 2010

Net mineralization of N in 39 widely differing soils was determined over a 30‐week period at 35C, using incubation intervals of 2, 2, 4, 4, 4, 6, and 8 weeks. Mineral N was leached from the soils before the first incubation and following each of seven incubations by means of 0.01M CaCl2 and a minus‐N nutrient solution. Soil water contents were adjusted by applying suction (60 cm Hg), and losses of water during incubation under aerobic conditions were negligible. With most soils, cumulative net N mineralized was linearly related to the square root of time, t½. The pH of soils changed very little in the course of 30 weeks' incubation. Because of the generally consistent results, the data were employed in calculating the N mineralization potential, No, of each soil, based on the hypothesis that rate of N mineralization was proportional to the quantity of N comprising the mineralizable substrate. Values of No ranged from about 20 to over 300 ppm of air‐dry soil. The fraction of total N comprising No varied widely (5 to 40%) among soils. Mineralization rate constants did not differ significantly among most of the soils. The most reliable estimate of the rate constant, k was .054 ± .009 week‐1. The time required to mineralize one‐half of No, t½, was estimated to be 12.8 ± 2.2 weeks. Results suggest that the forms of organic N contributing to No were similar for most of the soils.
Wheat Response to Different Soil Water‐Aeration Conditions
Authors: Anaya M. G. , Stolzy L. H.
Published: July 2010

A graphical yield surface was constructed for wheat (Triticum aestivum L.) grown on Yolo silt loam with 13 different soil water‐aeration combinations. The experiment was conducted in a growth chamber under controlled environmental conditions. Oxygen over the soil surface was maintained at different percent O2 concentrations from 0.9 to 21%. Various soil water regimes were obtained by irrigation at different soil suctions from 8 to 99 centibars (cbars). The highest grain yields were obtained in two treatments, one of 9.6% O2 watered at a soil suction of 15 cbars, and another treatment of 4.3% watered at 8 cbars. The lowest production was in the treatment of 0.9% O2 weatered at 99 cbars, and the difference between the highest and lowest yields was 347%. From the data, the regression equation for grain yield was: Y = 15.94 − 0.1324 X1 + 3.1813 X2 − 0.1297 X22, where Y = grain yield in g/pot, X1 = soil suction in cbars, and X2 = percent O2. The maximum predicted yield calculated from the equation is at a level of 12.0% of O2 irrigated at a soil suction of 8 cbars. However, the maximum production recorded was obtained at 9.6% O2.

There was a high correlation coefficient (0.94) between water consumption and grain production. An inverse relationship existed between grain yield and protein content. The highest level of grain protein content (22.6%) was obtained in the lowest producing treatment, while the lowest level of grain protein content (16.5%) occurred in the highest producing treatment. The difference in grain protein content between treatments was 37%.
Adsorption Interactions of Monosilicic and Boric Acid on Hydrous Oxides of Iron and Aluminum
Authors: McPhail Malcolm , Page A. L. , Bingham F. T.
Published: July 2010

Reactions of monosilicic acid and boric acid with hydrous oxides of aluminum and iron were studied. Adsorption of B by hydrous iron oxides was satisfactorily described by the Langmuir equation over the range of equilibrium solution concentrations investigated (0–14mM). Adsorption by hydrous aluminum oxides conformed to the Langmuir equation at equilibrium solution concentrations less than 6mM B. Maximum adsorption of boric acid by aluminum hydrous oxides was found to occur at approximately pH 7.5. Aging freshly precipitated hydrous aluminum and iron oxides up to 12 hours markedly reduced B adsorption; beyond 12 hours the effects of aging diminished.

Successive treatments with 1.4mM solutions of Si(OH)4 were applied to freshly precipitated aluminum‐ and ironhydrous oxides until an apparent saturation was attained. The adsorption of Si followed the Langmuir equation, with maximum adsorption of 2.96 and 2.67 millimoles of Si per gram of aluminum and iron hydrous oxide, respectively. Boric acid at concentrations of 1.85 and 18.5mM were applied to individual samples after each Si(OH)4 treatment. Aluminum‐ and iron‐Si complexes retained less B as the amount of adsorbed Si on these hydrous oxides increased.
Effect of Storage Conditions on Activities of Urease, Invertase, Amylase, and Dehydrogenase in Soil
Authors: Pancholy Sunil K. , Rice Elroy L.
Published: July 2010

There were no significant decreases in the activities of urease, invertase, and amylase after 30 days' storage of an Oklahoma mollisol at 4C. However, storage at room temperature (21C) was unsatisfactory. Significant loss in activity was noted in the case of dehydrogenase after 15 and 30 days of soil storage at both 4C and room temperature. Fresh soil was used for assay of dehydrogenase.
Dynamics of Ion Transport During Moisture Flow from a Douglas‐Fir Forest Floor
Authors: McColl J. G.
Published: July 2010

The dynamics of ion transport during periods of moisture flow from the forest floor was studied using automated equipment in a second‐growth Douglas‐fir (Pseudotsuga menziesii (Mirb.) Franco) forest in western Washington. This transport process was related to the environmental parameters of temperature in the forest floor, the duration of time before flow, and the amount of moisture flow. Seasonal climatic changes are related to the ion transport process, and changes in solution concentration during a few representative wetting cycles are also presented. The results provide a base for predicting possible effects of manipulating natural forest ecosystems. A warning is given of the possible effects of some common forest‐management practices.
Kinetics of Phosphate Adsorption by Calcium Carbonate and Ca‐Kaolinite
Authors: Kuo S. , Lotse E. G.
Published: July 2010

The objective of the present investigation was to elucidate the time‐dependence of phosphate adsorption by calcium carbonate and Ca‐kaolinite and to suggest a mechanism of adsorption. The phosphate adsorption by calcium carbonate and Ca‐kaolinite at low phosphate concentrations in solution could be described by Langmuir adsorption isotherms, indicating that a monolayer of phosphate is formed on the surface. The calculated maximum surface saturation was 25µg/g for calcium carbonate and 187µg/g for Ca‐kaolinite. A second‐order kinetic equation was developed which considers both the change in phosphate concentration in solution and the surface saturation of the adsorbent during the adsorption process. The rate constant of phosphate adsorption was about 30,000 times greater for calcium carbonate than for Ca‐kaolinite. About 80% of the phosphate adsorption by calcium carbonate was completed within 10 sec. The variation of the second‐order rate constant with phosphate concentration was different in the two systems. The rate constant decreased in the calcium carbonate‐phosphate system and increased in the Ca‐kaolinite‐phosphate system with increasing phosphate concentration. It was suggested that phosphate ions are adsorbed by displacing coordinated water molecules and/or coordinated anions.
Exchange Adsorption of Trace Quantities of Cadmium in Soils Treated with Chlorides of Aluminum, Calcium and Sodium
Authors: Lagerwerff J. V. , Brower D. L.
Published: July 2010

The exchange adsorption of Cd has been studied in Cecil sandy loam (clay fraction 45% kaolinite and 25% vermiculite), Winsum clay loam (clay fraction 80% illite), and Yolo silt loam (clay fraction 47% montmorillonite and 22% mica). Experimental variables were the major cations Al3+, Ca2+, and Na+, salt (chloride) levels (from 5 to 50 meq/liter), and the initial concentration of CdCl2 (from 22 to 170 µeq/liter). The exchange of Cd2+ in Al3+‐ and Ca2+‐treated soils was normal in that the adsorption was greater in the presence of Ca2+ than of Al3+, and decreased with increasing concentration of AlCl3 or CaCl2. In the Na+‐treated, alkalized soils, Cd2+ did not precipitate. The exchange was unusual because the adsorption of Cd2+ decreased as NaCl concentrations decreased. The same behavior was shown by 109Cd2+. At NaCl concentrations decreasing below 30 meq/liter, the adsorption of Ca2+ by Na+‐treated soils also decreased, as did the adsorption of Na+. The result was attributed to decreasing soil exchange capacity with decreasing NaCl concentration due to increased adsorption of products derived from alkaline corrosion of the soil matrix.
Measurement of the Diffusion Coefficient of Boron in Soil Using a Single Cell Technique
Authors: Sulaiman Wan , Kay B. D.
Published: July 2010

The porous system diffusion coefficient, Dp, of boron in a loam soil was measured by means of a single cell technique. Boron diffused from a semi‐infinite medium of uniform initial concentration to a sink of constant concentration which was separated from the soil by a dialysis membrane. A polyethylene glycol (PEG) 6,000 solution circulated through the sink and controlled the soil matric suction osmotically. The diffusive flux at the soil and membrane interface was treated as an evaporative process. The value of Dp was found to be 2.44 ± 0.17 × 10‐6 cm2/sec when the bulk density of the soil and the volumetric moisture content were 1.30 gm/cm3 and 0.31, respectively.

The significance of the equilibria between absorbed and solution B on the diffusion rate of B was also studied. Addition to the soil of boric acid solutions of concentrations lower than 1 ppm resulted in a capacity factor and solution B concentration which were lower than the corresponding values when water containing no B was added. As a consequence, the quantity of B diffusing into the sink from the boron‐treated soil was less than that from the untreated soil.
Resistance of Sawdusts, Peats, and Bark to Decomposition in the Presence of Soil and Nutrient Solution
Authors: Maas E. F. , Adamson R. M.
Published: July 2010

The ability of sawdusts, peats, and bark to withstand decomposition when used as soil substitutes in greenhouse culture was determined for differing particle sizes, nutrient additions, and admixtures with soil by means of incubation in the laboratory over a 36‐month period. Particle size was not an important factor but the presence of soil greatly increased the rate of decomposition of bark, sawdusts, and sphagnum peats, which shows the necessity of avoiding contamination of these media by soil. The additions of a nutrient solution containing fairly low levels of N, P, and K increased the rate of decomposition greatly in red alder (Alnus rubra Bong.) sawdust, moderately in Douglas‐fir (Pseudotsuga menziesii (Mirb.) Franco) sawdust, but by only a small amount in Douglas‐fir bark, and decreased the rate of decomposition in the peats. The combination of soil and nutrient solution was particularly detrimental to alder and Douglas‐fir sawdusts but had less effect on Douglasfir bark. The addition of sand to Douglas‐fir and alder sawdusts did not increase their decomposition rates either with or without nutrient solution and its inclusion in a growing medium may be useful in facilitating the establishment of new transplants.
Prediction of Runoff and Erosion from Natural Rainfall Using a Rainfall Simulator
Authors: Young R. A. , Burwell R. E.
Published: July 2010

Field rainfall simulators have been used extensively for runoff and erosion studies. To more accurately interpret and apply the results of studies using simulated rainfall, it is necessary to know the relative effects of natural vs. simulated rainfall.

A comparison was made of the soil and water losses from three natural storms and three simulated storms on cultivated fallow plots under similar rainfall and soil conditions. A rainulator was used to apply the simulated storms. Soil losses from the three simulated storms averaged 77% of those from the natural rainstorms. This compares closely, considering that the average EI value for the simulated storms was 78% of that for natural rainstorms. The runoff from the simulated storms compared quite closely to runoff from the natural storms.

The study showed that, in general, the rainulator can be used to simulate rainfall for runoff and erosion research with confidence that the results will reflect the runoff and soil loss that would occur under similar conditions of natural rainfall.
Impact of Wetting on Microbial Respiration in Desert Soil
Authors: Macgregor A. N.
Published: July 2010

When naturally air‐dried soil from the surface layer of the Sonoran Desert was brought into contact with water, there was an immediate release of gases. Carbon dioxide was identified as a major gas component and was released in amounts equivalent to 50µliter/g of dry soil. It was estimated that following rainfall the air‐layer above natural areas of desert may temporarily experience up to a ten‐fold increase in CO2‐concentration due solely to the above phenomenom.

Wetted soil immediately proceeded to take up O2 at a rate equivalent to approximately 2.5µliter/g soil/hour over a 5‐hour incubation period. Soil treated only with water had a respiratory quotient of 0.63 and soil treated with 1.0M KCN a respiratory quotient of 0.54.
Water Movement in Undisturbed Swelling Clay Soil
Authors: Ritchie J. T. , Kissel D. E. , Burnett Earl
Published: July 2010

Hydraulic conductivities of Houston Black clay were measured in two field basins, in 73‐cm and 21‐cm diameter undisturbed cores, and in small cores prepared from sieved soil. Conductivities averaged about 2.5 cm/day for the field basins, about 0.3 cm/day for the undisturbed cores, and 0.1 cm/day for the disturbed soil cores. After steady‐state flow through the larger, undisturbed cores was obtained, water tagged with fluorescein was used to displace water in the cores until tagged water first appeared in the effluent. Examination of cross sections of the cores at different depths showed distinctive isolated areas where tagged water was present in the soil pores. The results imply that most water contained within structural units was inactive in the flow process compared to water flow around the units. The core walls apparently cut off some large pores associated with the soil structure, causing the decreased conductivities. Therefore, only field‐determined hydraulic conductivities are appropriate for use when predicting water flow in natural profiles of a swelling clay soil.
Desorption of Ammonia from Soil During Displacement
Authors: Rolston D. E. , Nielsen D. R. , Biggar J. W.
Published: July 2010

The displacement and desorption of ammonia from ovendry and moist soil were evaluated using a miscible displacement technique. An ammonia saturated soil atmosphere was displaced from soil columns with nitrogen at flow velocities of approximately 2.5 cm min‐1. Samples of gas from within and at the end of soil columns, analyzed by titration methods, were used to obtain elution curves. Two different soils were studied at several water contents. Experimental, steady‐state sorption isotherms (sorption as a function of gaseous concentration) were determined for oven‐dry soil. An assumption that gas is perfectly mixed within the soil column during desorption was used to derive a model describing displacement with ammonia desorbing according to a nonlinear isotherm. This perfect mixing model in conjunction with calculated sorption isotherms adequately predicted the displacement of ammonia from oven‐dry and moist soils during desorption.
Reduction of Inorganic Compounds by Soil Microorganisms
Authors: Bautista Elena M. , Alexander M.
Published: July 2010

Isolates of Pichia guillermondii and Micrococcus sp. obtained from soil converted selenate, selenite, tellurate, and tellurite to the elemental forms, vanadate to a vanadyl compound, molybdate and molybdenum trioxide to a molybdenum blue compound, arsenate to arsenite, MnO2 to the manganous ion, nitrate to nitrite, and chlorate to a less oxidized form. Resting cell suspensions and cell‐free extracts of the two organisms also effected the reduction of most of the inorganic compounds and anions. The capacity to reduce selenate, selenite, tellurate, tellurite, vanadate, molybdate, molybdenum trioxide, arsenate, chlorate, and MnO2 was found to be common to soil microrganisms. It is suggested that these microbial reactions may be important in changing the solubility, availability, or toxicity of certain elements in soil.