bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stability of Montmorillonites: II. Aberdeen Montmorillonite
Authors: Kittrick J. A. 
Published: July 2010

AbstractSix montmorillonite samples from Aberdeen, Mississippi were equilibrated with various solutions for 3–4 years. Under the conditions of these experiments, Aberdeen montmorillonite was found to be less stable than Belle Fourche montmorillonite and kaolinite. Locating the Aberdeen solubility line under conditions where it is metastable was difficult because of the tendency of the samples to approach the nearest stable solubility line. It was possible to locate the position of the metastable montmorillonite solubility line only because two of the six samples resided there briefly before approaching the more stable kaolinite solubility line. The resulting three points were in close agreement with the calculated slope and intercept of the montmorillonite solubility line on pH‐⅓pAI3+ vs. pH4SiO4 axes, as derived from the unit cell formula of Aberdeen montmorillonite. A ΔG of −2450.3±0.1 kcal per mole was obtained for Aberdeen montmorillonite, based upon the assumption that Fe3+ in solution was controlled by hematite.
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

AbstractSoils 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

AbstractSolubility 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

AbstractStudies 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

AbstractThe 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

AbstractThe 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

AbstractA 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

AbstractSoils 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

AbstractThe 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

AbstractCalcium 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

AbstractEquations 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

AbstractSeveral 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

AbstractOrganic 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

AbstractThe 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

AbstractThis 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

AbstractA 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

AbstractThe 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

AbstractA 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

AbstractSoluble 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

AbstractUrease 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.