bluuebunny/crossref_metadata_2025 huggingface dataset:
Soil‐Water Hysteresis: the Domain Theory Extended to Pore Interaction Conditions
Authors: Topp G. C.
Published: July 2010

Some inadequacies of the independent domain theory of hysteresis were overcome by modifying an extension to the theory to include two types of pore interactions. In the independent domain theory only the shapes of the pores determined the draining and filling characteristics of each pore. In this extension to the theory the draining and filling of each pore was assumed to depend on the state of neighboring pores as well as the pore geometry. The ratios of changes in water content of the soil during drying and rewetting over a given pressure head range were used to determine the importance of pore interactions and to separate the two types of pore blockage. Primary scanning curve data for porous materials ranging from glass beads to clay loam soil showed that pore blockage against air‐entry during drying of a soil near saturation and pore blockage against water‐entry during rewetting of a relatively dry soil were the two major types of pore interactions. The curves showing the degree of pore blockage appeared to be dependent only on the water content of the soil. This information in conjunction with a set of scanning curves was used to make satisfactory predictions of the other set of scanning curves.
Nutrient Uptake of Alfalfa as Influenced by Soil Processing and Greenhouse Potting Methods
Authors: Peterson G. A.
Published: July 2010

Uptake of P, K, Ca, Mg, Zn, Cu, Fe, and Mn by alfalfa (Medicago sativa L.) was studied as affected by soil processing and potting methods. Aggregate destruction resulted in increased uptake of all nutrients except K and Cu. Air‐drying of soils prior to potting decreased the uptake of P. There was no significant interaction or processing and potting methods with soil horizon being studied.
Contemporary Soil Wedge Formation in Western South Dakota
Authors: White E. M.
Published: July 2010

Subsoil wedges, ranging from narrow, dark‐colored infusions of surface soil between prisms to V‐shaped clay or light‐colored sandy wedges more than 1 meter across, occur in some semiarid soils of western South Dakota. Light‐colored wedges usually form in gravelly subsoils. A proposed explanation of how the wedges form is: (i) surface material falls downward into narrow subsoil desiccation cracks, (ii) in subsequent cycles of rewetting the dry soil, water drains more rapidly into the wedge than into the enclosing soils so the wedge swells first and closes the desiccation cracks in the adjacent dry soil, (iii) the wedge widens more at the top to form a V‐shape because the moisture content changes frequently near the soil surface, and (iv) growth ceases when individual sand grains in the wedge are bridged by clay to form stable peds or the V‐shape becomes sufficiently wide so water flows down along the inclined wedge boundary and wets and swells the enclosing soil as rapidly as the center of the wedge.
Soil Structure and Hydraulic Conductivity of Adjacent Virgin and Cultivated Pedons at two Sites: A Typic Argiudoll (silt loam) and a Typic Eutrochrept (clay)
Authors: Bouma J. , Hole F. D.
Published: July 2010

Soil morphology and hydraulic conductivity (K) of principal soil horizons of paired virgin and cultivated soil pedons were studied at two sites: a Tama silt loam (Typic Argiudoll) and an Oshkosh clay (Typic Eutrochrept). About a century of cultivation had led to reduction of K (measured by the Bouwer double‐tube method) in the upper part of the solum below the Ap. Corresponding changes in soil morphology are noted. The reductions in K are paralleled by increases in bulk density and decreases in porosity and organic matter content in the soil horizons. At a depth of 80 to 90 cm in the clay soil, K increased apparently as a result of formation of interpedal voids as the alfalfa crop (Medicago sativa L.) extracted moisture.
Rainfall Use Efficiency for Dryland Barley with Three Crop and Water Management Systems
Authors: Luebs R. E. , Laag A. E.
Published: July 2010

Three crop and water management systems for barley (Hordeum vulgare L.) were compared in a winter rainfall climate on Hanford sandy loam. These systems were (i) annual corpping with runoff retention, (ii) a fallow‐crop sequence with runoff retention, and (iii) induced runoff on one‐half the area for concentration and annual cropping on the remaining half. Land slope was 2–3% and runoff was retained with dikes at 7.6‐m intervals in the first two systems. Over a 3‐year period average grain yields were 1.58, 2.04, and 2.29 ton/ha with rainfall use efficiencies of 41, 29, and 31 kg/ha‐cm for annual cropping, fallow‐crop, and induced runoff concentration systems, respectively. The additional soil water in downslope areas of the annual and fallow‐crop systems and in areas receiving induced runoff was reflected in increased barley kernels per head and greater kernel weight. Holding runoff on the land and cropping annually increased rainfall use efficiency 42% over both that obtained where runoff occurred in the annual cropping system and that obtained for the entire plot area in the fallow‐crop system. The efficiency of fallow for storing water in the soil was 16.7%.
Soil Wettability in Utah Juniper Stands
Authors: Scholl David G.
Published: July 2010

Wettability varied widely between three ground‐cover zones and three soil horizons in a Utah juniper stand [Juniperus osteosperma (Torr.) Little]. Resistance to wetting in the surface soil increased from completely wettable in open areas to highly nonwettable in the litter under the juniper canopy. Resistance to wetting decreased with depth in the soil profile below the litter zone and increased with increasing organic matter. Changes in the soil moisture level also influenced the wettability of the various zones and horizons. Wettability was determined at ⅓ and 15 bars moisture tension and air‐dry, with the 15‐bar level showing the greatest resistance to wetting.
Charge Location as a Factor in the Dehydration of 2:1 Clay Minerals
Authors: Doner H. E. , Mortland M. M.
Published: July 2010

Water was removed from Cu(II)‐saturated smectites by methanol when the isomorphic substitution was in the octahedral layer. However, Cu(II)‐saturated tetrahedrally charged smectites and vermiculites were not completely dehydrated by this treatment. Similarly, when (CH3)4N+‐smectites and vermiculites were degassed, only those clays octahedrally charged were dehydrated. Deuteration of (CH3)4N‐montmorillonite and saponite showed the OD stretching frequency for D2O bonded to the silica surface was at a higher frequency for montmorillonite than saponite, indicating a stronger deuterium bond to the surface oxygen for the latter clay. These results showed water was bonded with greater energy to tetrahedrally charged clays, possibly resulting from their more localized charge on the silicate surface.
Isotopically Exchangeable Cobalt: The Effect of Soil pH and Ionic Saturation of the Soil
Authors: Gille G. L. , Graham E. R.
Published: July 2010

Large increases in the uptake of Co, Zn, and Mn by sudangrass (Sorghum vulgare sudanense) were observed when FeCl2, AlCl3, and CaCl2 were added to the soil in which the plants were grown. The isotopically exchangeable cobalt in the soil remained unchanged regardless of soil pH or the addition of Fe, Al, or Ca to the soil. Increases in the cobalt content of sudangrass result from changes in the soil solution concentration of cobalt in the soil rather than quantity of cobalt. The effect of Fe, Al, and Ca additions and soil pH in producing the changes in cobalt content of sudangrass was caused by soil factors rather than changes in plant response. One hundredth normal HCl was found to be a useful extracting agent for determining the quantity of cobalt in the soil and 0.1M CaCl2 would give the best indication of the potential soil solution concentration (I) of cobalt in the soil.
Computation of Soil Solution Composition Variation with Water Content for Desaturated Soils
Authors: Oster J. D. , McNeal B. L.
Published: July 2010

Mathematical models were evaluated which calculate the change in soil solution composition and electrical conductivity as water content is changed by evaporation or extraction by plants. Two models included consideration of precipitation of salts, cation exchange, soil pH buffer capacity, ionic activities, sulfate, bicarbonate and carbonate ion pairs of calcium, sodium, and magnesium, and partial pressure of carbon dioxide. These models differed in the form of the Debye‐Huckel equations used to calculate ionic activity coefficients. A third model included only the ion pair calcium sulfate. The reliability of the models was evaluated by comparing electrical conductivities measured by in situ salinity sensors with calculated conductivities. The calculated values were based on chemical data obtained from saturation extracts of soil samples taken from locations at which the sensors were installed. The best model considered the maximum number of ion pairs and used a form of the Debye‐Huckel equation with individual ion parameters. This model resulted in an average difference between calculated and measured values of 1.1 mmho/cm, which represented an error of 6% when compared to the average measured value of 17.1 mmho/cm.
Demixing of Exchangeable Cations in Free‐Swelling Bentonite Clay
Authors: Fink D. H. , Nakayama F. S. , McNeal B. L.
Published: July 2010

Hypothetical models for the crystalline, interlayer swelling of mixed‐ion (Na+ and Ca2+) saturated montmorillonites in water were developed for two types of cationic distributions on the clay minerals; namely, for complete demixing and for complete random mixing of cations. In addition, the model for demixing was expanded to include both the alternate layering of Ca‐ and Na‐saturated platelets and the complete demixing of cations into separate Na‐ and Ca‐domains. The theoretical development is based on the accepted principles of limited interlayer swelling (10Å maximum) for Ca‐montmorillonite, and free‐swelling for Na‐montmorillonite as the water content of the system is increased beyond approximately 120%. Experimental measurements of interlayer swelling using a low‐angle X‐ray diffraction technique showed that the relative distribution of Na+ and Ca2+ ions on the clay exchange complex was a function of the exchangeable sodium percentage (ESP): (i) the two cations were randomly mixed for ESP values greater than approximately 50%; (ii) they were partially demixed for ESP values between approximately 50 and 15%; and (iii) for ESP values less than approximately 10 to 15% no cation demixing in interlayer regions was evident, but the results did suggest that the interlayer exchange complex was predominantly Ca‐saturated and the exchange complex on external surfaces was predominantly Na‐saturated. Although the experimental techniques could establish that demixing occurred within certain ranges of ESP values, it was not sensitive enough to differentiate between demixing by domains and demixing by alternate layers.
Changes in Bray P‐1 Soil Phosphorus Test Values Resulting from Applications of Phosphorus Fertilizer
Authors: Peck T. R. , Kurtz L. T. , Tandon H. L. S.
Published: July 2010

Increases in soil test values (Bray P‐1) resulting from annual applications of P fertilizer were approximately 1 pp2m for each 4 pp2m of P added in fertilizer during a 3‐year period on six field experiments. In another field experiment, soil tests were made over a 5‐year period following a single fertilizer application, and again the addition of approximately 4 pp2m of fertilizer P was required to increase the P‐1 soil test by 1 pp2m. These results also indicated that the soil test values, though still changing, were sufficiently stable to be reliable 1 year after the application. When a more variable group of soils were incubated in the laboratory for 49 weeks, additions ranging from 2 to 10 pp2m of P were required to increase the soil test value by 1 pp2m.
Pedoturbation by Artesian Action
Authors: Johnsgard G. A.
Published: July 2010

Mechanical mixing (pedoturbation) in soils can be caused by a variety of agencies and conditions. This paper proposes that water under artesian pressure below a frozen soil zone may be a cause of soil mixing as the frozen layer thaws in the spring. Thawing occurs at both the top and the bottom of the frozen soil zone. Points or areas of weakness in the frozen soil zone develop and become sites at which subsurface water breaks through the frozen zone. Artesian pressure, below the frozen zone, causes water and soil materials to move upward. It is proposed that among the consequences is the mixing of the soil in and above the frozen zone.
Bentonite Instability and Its Influence on Activation Energy Measurements
Authors: Brown D. S. , Miller R. J.
Published: July 2010

A time‐dependent temperature hysteresis in a‐c conductance activation energy plots for dilute, neutral, and salt‐free Na+‐bentonite suspensions is reported. Fresh suspensions prepared by washing with NaOAc or NaCl had activation energies of 9,398 and 5,789 cal/mole initially which gradually decreased to 3,651 and 3,422 cal/mole, respectively, after several days.

A‐c conductances, concentrations of free Na+ in solution, pH, and dissolved silica were monitored in suspensions aged at 30C. Conductance increases of 2–3 fold were observed, with the concentration of free Na+ released from the exchange sites increasing to 5.4 and 34 ppm, respectively, for the NaCl and NaOAc preparations. Dissolved silica in solution increased to 3–4 ppm over the same period indicating that degradation of the lattice had occurred. Results are interpreted in terms of the hydrolysis of the exchangeable Na+ ions as predicted by Donnan and diffuse double layer theory followed by an acid attack of the lattice. Free salts added to the suspensions were effective in suppressing the hydrolysis and stabilizing the activation energies.
Buffer Curves and Acid Strength of Humic Acid and Two Resins
Authors: Gilmour J. T. , Coleman N. T.
Published: July 2010

Two humic acids, Cellex‐CM, and IRC‐50 were placed in 10‐1, 10‐2, and 10‐3M NaCl or CaCl2 and titrated potentiometrically with NaOH or Ca(OH)2, respectively. Titration curves of Cellex‐CM and IRC‐50 in the NaOH‐NaCl system showed parallel 1 pH unit displacements for a 10‐fold change in NaCl concentration, while humic acid showed a 0.5 pH unit displacement. Buffer curves of humic acid, Cellex‐CM, and IRC‐50 in the Ca(OH)2‐CaCl2 system showed a 0.4 pH unit displacement for a 10‐fold change in CaCl2 concentration. The regular displacement of buffer curves led to development of a theory using ion exchange and surface ionization of H that described the buffer curves and assigned a salt independent pKa to the weak acid adsorbents.
Copper Accumulation in Citrus Roots and Desorption with Acid
Authors: Brams E. A. , Fiskell J. G. A.
Published: July 2010

Root accumulation of 04Cu from labelled Cu(NO3)2 in intact ‘Mandarin Orange’ (Citrus reticulata) seedlings had a constant rate for the first 15 min and then became curvilinear for periods from 15 to 180 min, when the ambient solution contained 0.6 ppm Cu. Over a 60‐min contact time uptake of Cu was linear for ambient Cu concentration range from 0.3 to 1.2 ppm. Extraction of 64Cu in roots by 0.1N HCl was linearly proportional to total root Cu and was 95% complete after 28 min. Colloidal phosphate reduced 64Cu accumulation in the roots by 12%. In roots of ‘Sour Orange’ (C. aurantium) seedlings grown in solution culture and in groves Cu was located in thin sections by ferrocyanide staining. Concentration of Cu occurred in the exodermis, endodermis, and pericycle cells. Electromicrographs of citrus roots suffering from Cu toxicity showed irregular deformation of cell walls in xylem vessels. In such cases roots became club shaped as root elongation ceased. Reactions of Cu with protein are suggested as mechanisms for Cu accumulation in roots.
Effect of Available Soil Calcium on Taproot Elongation of Loblolly Pine (Pinus taeda L.) Seedlings
Authors: Lyle E. S. , Adams Fred
Published: July 2010

Three vertical split‐root experiments were performed to discover a method of describing Ca availability in soils that could be correlated with taproot elongation of loblolly pine seedlings and could be used to determine critical values at which elongation rate became inhibited.

The first experiment, utilizing a vertical split‐root technique with a fertile topsoil overlying nutrient solutions, proved that loblolly pine roots will elongate in an ambient solution of CaCl2 and deionized water. However, elongation was much greater when other ions were also present in the ambient solution. The second and third experiments also utilized a vertical split‐root technique but the subsurface medium was an infertile loamy sand with varying amounts of Ca, Mg, K and NH4 salts added. It was found that aCa/aMg, MCa/MMg, and aCa/Σacation i ratios of soil solutions showed a close relationship with tap‐root elongation, and the relationship was continuous from extreme Ca deficiency to Ca sufficiency. The data show that tap‐root elongation was inhibited when MCa/MMg, aCa/aMg, and aCa/Σacation i ratios fell below 0.75, 0.75 and 0.10, respectively.
The Nature of K‐feldspars of a Chernozemic Soil in the Canadian Prairies
Authors: Somasiri S. , Huang P. M.
Published: July 2010

The nature of the K‐feldspars of an Orthic Brown Chernozemic (Aridic Haploboroll) soil profile developed from glacial till deposits in Saskatchewan, Canada, was studied. The K‐feldspars from selected size fractions between 20 and 2,000µ were concentrated by heavy liquid separation at a specific gravity of 2.59. X‐ray powder diffraction analysis was used to identify orthoclase and microcline, to estimate their relative proportion, and to determine the obliquity, which is the degree of departure from the monoclinic symmetry of K‐feldspars.

The concentration of K‐feldspars by heavy liquid separation greatly facilitated the subsequent X‐ray diffraction analysis. All the samples studied contained both orthoclase and microcline, and at least some of the K‐feldspar crystals appear to be perthitic in nature and have a high degree of exsolution. The diffractograms of the comparable size fractions from the major genetic horizons were similar and the proportions of orthoclase to microcline were comparable in the same size fractions. The proportions of orthoclase to microcline usually increased as the particle size decreased in all of the horizons, indicating that this differentiation occurred at the time of deposition of the soil parent material. The obliquity values of microcline of the various size fractions, ranging from 0.82 to 0.87, appeared to be uniform throughout the profile.

The obliquity of K‐feldspars and proportions of orthoclase to microcline may have a potential use as a guide in establishing the geological origin of soil parent material and in confirming its uniformity.
Iron Hydroxy Interlayers in Soil Clay
Authors: Singleton P. C. , Harward M. E.
Published: July 2010

The less than 2µ fraction of the A horizon of two western Oregon soils, a Typic Haplumbrept and a Xeric Haplohumult, were found to contain an intergrade mineral with properties intermediate to chlorite and montmorillonite. The mineral was subjected to a series of treatments designed to effect a progressive dissolution of associated Fe, Al, Si, and Mg compounds. Analysis of treatment extracts and measurements made of d‐spacings and cation exchange capacity before and after treatments indicated that the hydroxy material occupying the interlayer spaces of the 2:1 layers of the mineral may consist of Fe as well as Al and Mg.
Boundary Conditions and Conductivities used in the Isothermal Model of Evaporation from Soil
Authors: Staple W. J.
Published: July 2010

The surface boundary conditions in the isothermal model for computing evaporation from soil were expressed in terms of the wind speed, temperature, and humidity of the ambient air. Use of these parameters along with reduced nodal spacings near the surface produced evaporative fluxes that closely followed the differences in vapor pressure between soil and atmosphere. A simple evaporation experiment was used to show that evaporation rates and soil moisture distributions obtained with these revised boundary conditions were closer to experimental values than were those obtained with the usual conditions defined in terms of potential evaporation and moisture content.
The Influence of Soil‐Fertilizer Geometry on Nitrification and Nitrite Accumulation
Authors: Bezdicek D. F. , MacGregor J. M. , Martin W. P.
Published: July 2010

Nine granules (330 ppm N) of either urea, (NH4)2SO4, or diammonium phosphate (DAP) were spaced in a square pattern at distances of 0, 0.5, 1.0, or 1.5 cm on 30 g of soil. Samples were watered, incubated, and extracted with I N KCl. The extracts were analyzed for NH4+, NO2‐, and NO3‐. Generally NO2‐ accumulation for the three N carriers increased with granule spacing; the geometric effect was DAP > (NH4)2SO4 > urea. Nitrite varied from 140 to 265 ppm N. Increased NO2‐ accumulation with increased granule spacing was accompanied by a corresponding increase in NH4+ oxidation rate with little change in NO3‐. Geometric effect with four granules (55 ppm N) spaced up to 2.5‐cm apart showed that both NO2‐ and NH4+ decreased with increased granule spacing accompanied by increased NO3‐. Single‐granule studies suggested that the greater geometric effects of DAP resulted from the lower solubility and relatively low mobility of phosphate ions. The subsequent periphery pH decrease minimized outward movement of NH4+. These effects were less for (NH4)2SO4 and for urea.
Tensile Strength of Montmorillonite as a Function of Saturating Cation and Water Content
Authors: Dowdy R. H. , Larson W. E.
Published: July 2010

The tensile strength, tensile axial strain, and tensile strain energy were determined for Na‐, K‐, Ca‐, Al‐, and Fe‐saturated montmorillonite over the water vapor pressure range (P/Po) from 0.02 to 0.92. The procedure used was direct tensile stressing of oriented clay films. Measured tensile strengths ranged from 366 kg cm‐2 for Fe montmorillonite at 0.02 P/Po to 19 kg cm‐2 for Ca montmorillonite at 0.92 P/Po. Strength decreased rapidly with added increments of water during initial interlamellar expansion and continued to decrease at a slower rate with further additions of water. In general, strength decreased in the following order: Fe > K ≥ Na > Al > Ca. The tensile strength of Na montmorillonite was of the same order of magnitude as the force required to separate two Na clay platelets as determined from adsorption/desorption water isotherms.

Axial strain was independent of P/Po above 0.4 for all systems except the Na‐saturated clay. For Fe montmorillonite, strain was insensitive to water content above 0.15 P/Po. Monovalent clay specimens required the most energy to rupture and divalent samples required the least energy. Aluminum and Fe clays required an intermediate rupture energy.

The greater tensile strength and low axial strain of the Fe montmorillonite suggested that a different mechanism controlled the failure characteristics of this clay. Hydroxy iron material may be the major cementing agent in the Fe system. The data show that saturating cation played a dominant role in the strength‐energy properties of the other homoionic clays.
Hydration of Cations Adsorbed on a Clay Surface from the Effect of Water Activity on Ion Exchange Selectivity
Authors: Laudelout H. , Van Bladel R. , Robeyns J.
Published: July 2010

Ion exchange equilibria for four pairs of singly charged ions in a montmorillonite clay were carried out at different total normalities of the equilibrium solution at 25C. Only the trace region for the preferred ion was investigated. The effect of solvent activity aw on the selectivity coefficient Kc was established. In each case the expected linear relationship between ln Kc and ln aw was observed. The values for the differences of the ion hydration numbers, nwA ‐ nwB, calculated from this purely thermodynamic relationship, were consistent and were comparable with values that could be deduced from basal spacings or anion exclusion volume data.
Percent of Copper Diffusing in the Adsorbed and Electrolyte‐Solution Phases in Kaolinite and Montmorillonite
Authors: Phillips R. E. , Barnhisel R. I. , Ellis J. H.
Published: July 2010

The apparent diffusion coefficient, De, of a cation diffusing in soil was proposed to be Dem = [Dsm(dCs/dCsa} + 1Dam (dCa/dCsa)] / [1 + dCp/dCsa] where Dsm and 1Dam are the diffusion coefficients of the cation in the electrolyte‐solution phase and in the adsorbed phase (exchangeable cations), respectively, and where the frame of reference in each case is with respect to the entire soil mass. The symbols Cs, Ca and Cp are concentrations of electrolyte‐solution cations, adsorbed cations, and precipitated or immobilized cations, respectively; Csa is defined to be the sum of Cs and Ca. The concentrations are expressed with respect to the total volumetric water content of the system. The quantities, dCs/dCsa, dCa/dCsa, and dCp/dCsa were evaluated in experiments independent of the measurement of Dem. The relative contributions of Dsm and 1Dam to Dem were evaluated over a large range of Csa values for Cu2+ diffusing in water‐saturated kaolinite and montmorillonite. In kaolinite clay with a cation exchange capacity (CEC) of 0.065 meq g‐1, the percent of total diffusion due to diffusion in the adsorbed phase was 100, 52, 34, 22, 18, 9, and 7 at Csa concentrations of 0.015, 0.02, 0.03, 0.04, 0.05, 0.06, and 0.08 meq g‐1, respectively. In montmorillonite clay with a CEC of 0.70 meq g‐1, the percent of total diffusion due to diffusion in an adsorbed phase was 100, 57, 42, 34, 28, 20, and 13 at Csa concentrations of 0.03, 0.05, 0.10, 0.15, 0.20, 0.40, and 0.70 meq g‐1, respectively.
Fractionation of Organic Phosphorus in Lake Sediments
Authors: Sommers L. E. , Harris R. F. , Williams J. D. H. , Armstrong D. E. , Syers J. K.
Published: July 2010

The organic phosphorus of 10 Wisconsin lake sediments of diverse properties was fractionated on the basis of extractability and anion exchange properties. The fractionation procedure involved sequential extraction of the sediments with 1N HCl for 1 hour (HCl‐Po), cold 0.3N NaOH for 16 hours (Cold NaOH‐Po), and hot 0.3N NaOH for 8 hours (hot NaOH‐Po) followed by anion exchange chromatography of the NaOH extracts into three fractions: fraction I, the 0.3N NaOH eluate, contained organic P that was not retained by the resin; fraction II, the 0.5M LiCl eluate, contained organic P with exchange properties similar to inorganic orthophosphate and monophosphate esters; fraction III, the 1M LiCl + 0.2N HCl eluate, contained organic P comparable to polyphosphate esters in exchange properties.

Total organic P extracted by the fractionation method was comparable to that removed by the standard Mehta et al. extractants indicating that the fractionation method provided valid total organic P data as well as information on the forms of organic P present in sediments.

HCl‐Po constituted 6 to 17%, cold NaOH‐Po 60 to 80%, and hot NaOH‐Po 10 to 30% of the total organic P of the sediments. Anion exchange chromatography of the NaOH extracts showed that most of the organic P (48 to 80%) was present in fraction I, the fraction likely composed of high molecular weight humic‐fulvic complexes. Fraction II contained 14 to 36% and fraction III less than 10% of the organic P in the NaOH extracts. Total inositol penta‐ and hexa‐phosphates comprised less than 10% of the total organic P of the sediments. The total and major fractions of sediment organic P were related to organic C, total N and oxalate‐extractable Al, but were not related consistently to any other sediment property or to the trophic level of the lake.
Growth of Two Root‐Rot Fungi as Affected by Osmotic and Matric Water Potentials
Authors: Cook R. J. , Papendick R. I. , Griffin D. M.
Published: July 2010

Growth of Ophiobolus graminis in response to a range of water potentials was maximal with the wettest treatments (‐1.2 to ‐1.5 bars), reduced by half at about ‐20 bars, and prevented at ‐45 to ‐50 bars. This pattern held for growth measured as colony diameters on agar media with osmotically‐controlled water potentials, or as linear hyphal growth along the surface of straws in soil with matrically‐controlled water potentials.

In contrast, growth of Fusarium roseum f. sp. cerealis ‘Culmorum’ was progressively stimulated as the osmotic potential was lowered over the range, ‐1.5 to ‐8.2 bars, then declined with further decrease in potential. The effect was independent of the solute type, either salts or sucrose in agar media, or with salts in soil. Stimulation did not occur when the fungus was subjected to a range of matric potentials in soil; rather the response was similar to O. graminis with maximal growth in the wettest soil. However, unlike O. graminis, growth of Culmorum was reduced by half at about ‐40 bars matric potential, or ‐45 to ‐50 bars osmotic potential, and was prevented at ‐70 to ‐75 bars matric potential, or about ‐80 bars osmotic potential. The differential effects of osmotic and matric potentials on Culmorum growth in autoclaved soil, and similarly the absence of an osmotic stimulatory effect on O. graminis probably relate to physiological factors inherent with the individual fungus.

The root and foot rot of wheat caused by Culmorum is generally most severe in the low rainfall (30 cm or less annual precipitation), non‐irrigated areas of the Northwest USA whereas O. graminis is most destructive in areas of higher rainfall or on irrigated wheat or barley. The natural association of these two pathogens with dry or wet field conditions may relate to their respective responses to the soil‐ and plant‐water potentials associated with the different environments.
Variations with Distance in Selected Fertility Measurements of Pedons of Western Kansas Ustoll
Authors: Cipra Jan E. , Bidwell Orville W. , Whitney David A. , Feyerherm A. M.
Published: July 2010

This investigation of the fertility status of Richfield silt loam, 0 to 1% slope, indicates that adequate fertility characterization of a soil series requires many more samples than are commonly taken. Sixteen sampling sites were used in each of seven 2.4‐ha (6‐acre) fields 8 to 145 km (5 to 90 miles) apart. We located four plots 90 m (300 feet) apart in each field and four sampling sites 3 m (10 feet) apart in each plot. Samples of Ap, B2t, and C horizons were collected from each site. Organic matter, P, K, Zn, and pH were determined in duplicate using procedures of the Kansas State Soil Testing Laboratory. Within‐plot variance component estimates were small for most horizon and fertility‐test combinations. Variance among plots was greater than within plots for 11 of the 15 combinations. Variance among fields was predominant in 8 of the 15 combinations, and accounted for more than 50% of the total variance in 5 of the 15 combinations. Results indicate that estimating the series means within ± 10% would require the most samples for P and the least for pH.
The Prediction of Soil Occurrence in Certain Desert Regions of the Southwestern United States
Authors: Gile L. H. , Hawley J. W.
Published: July 2010

Extensive areas of desert soils in the southwestern United States have not been mapped. Conclusions concerning soil genesis and soil distribution have been reached in a study of desert soils in a study area typical of large parts of the Southwest. Observations in other desert regions indicate that results of the study should be useful in the prediction of soil occurrence in places similar to the study area. Important factors considered in making the predictions are topography, soil parent materials, soil age, climate, and soil biota. Airphotos and geologic, topographic, and hydrologic maps are useful in predicting soil occurrence. Soils for which occurrence may be predicted include Torripsamments, Torrifluvents, Torriorthents, Camborthids, Haplargids, Paleargids, Calciorthids, and Paleorthids. Boundaries to adjacent Mollisols are also discussed.
Numerical Analysis of Drainage of a Heterogeneous Porous Medium
Authors: Watson K. K. , Whisler F. D.
Published: July 2010

The gravity drainage of a heterogeneous porous medium was studied using a numerical solution of the flow equation. The medium was assumed to exhibit scale heterogeneity, the heterogeneity being specifically defined in terms of a linear variation of the saturated hydraulic conductivity with depth. Within the restrictions imposed by scale heterogeneity, the hydrologic characteristics were chosen so that their form validly represented real data. The spatial variation of the hydrologic characteristics was initially defined in terms of the air entry value of the medium at the point in question and an empirical relationship between the air entry value and the saturated hydraulic conductivity. Pressure head and water content profiles were obtained for three hydraulic conductivity distributions in which the conductivity decreased with depth. The pressure head profiles for these distributions revealed clearly the zones of positive pressures in the profiles and the slow decay of these pressures during drainage.
Instrumentation Effects on Errors in Nuclear Methods for Soil Water and Density Determination
Authors: Stone J. F.
Published: July 2010

The commonly used ratio calibration of neutron scattering soil moisture meters tends to obscure errors due to random event counting, dead time, and drift phenomena not fully compensated for by the ratio. These effects are analyzed in the light of the demands of the very high count rates in many scintillation systems being currently reported. Dead time is always reduced by using high pulse‐rate resolution equipment. Such is not always available for experimental work and the errors entailed are discussed. Equations describing the errors in ratio counting are discussed. The size of the standard material is a factor in some of the error terms. Some of the errors reduce to zero at the point where the count obtained in the soil is equal to the reading in the standard. Thus, it is desirable to construct the standard such that the ratio = 1 appears on the calibration curve (preferably above the center).
A Simple Titrimetric Method for Determination of Inorganic Carbon in Soils
Authors: Bundy L. G. , Bremner J. M.
Published: July 2010

A simple method of determining inorganic carbon in soils is described. The soil sample is treated with 2M HCl at room temperature for 16–24 hours in a stoppered bottle containing 2M KOH in a small beaker, and the CO2 released from carbonates by this treatment is determined by titration of the KOH solution with standard HCl. The method is accurate and precise, and tests reported indicate that it is not subject to interference by organic soil consituents. It gives quantitative results with carbonate standards, and its results with soils agree closely with those obtained by the methods proposed by Allison and by Anderson and Harris.
Effect of Soil Factors on the Distribution of Rhizobium japonicum Serogroups
Authors: Bezdicek D. F.
Published: July 2010

The soybean variety ‘Kent’ was planted at 19 sites representing two soil types located on Maryland's Eastern Peninsula. Routine soil tests including soil organic N were performed and correlated with serological distribution of R. japonicum. Nodule samples reacted with 16 Beltsville antisera with no serogroup occupying more than 20% of the total. Beltsville serogroup 110 was positively correlated with several organic N fractions, soil NH4+, and soil NO3‐ for the Sassafras soil. Serogroup 123 showed a positive correlation with soil pH and exchangeable Mg. When the Matapeake soil was considered, serogroup 94 was positively correlated with soil N status much like 110 was for the Sassafras soil.
Clay Mineral Genesis of Some New York Spodosols
Authors: Coen Gerald M. , Arnold Richard W.
Published: July 2010

Some Spodosols in northern New York previously shown to have well crystallized montmorillonite in the albic horizon but only amorphous clay sized material in the spodic horizon were studied to determine the source or genesis of the montmorillonite. The soils used to test several hypotheses of the clay mineral genesis represented Orthods, Humods, and Aquods. These soils were also shown to be deficient in mica and chlorite in the sand, silt, and clay fractions. This allowed a test of the hypothesis that montmorillonite in albic horizons weathers from mica, a process which previously has been reported to be active. The presence of only traces of mica and chlorite in the sand and silt fractions would indicate that weathering of sand and silt sized minerals directly to clay sized minerals should not be important. However, the small amount (generally less than 3%) of clay sized materials in the pedons makes this assumption inconclusive.

Soil solution studies, coupled with equilibrium diagrams, provide evidence that clay mineral synthesis from ions does not occur in these soils.

The well crystallized clay sized minerals detected in the upper solum of the pedons studied may have (i) weathered directly from sand and silt sized minerals, (ii) been added as dust, or (iii) weathered from minerals added as dust. There is recent evidence that appreciable amounts of montmorillonite, illite, vermiculite, and kaolinite are deposited as dust throughout the northern United States. If projected figures are valid, dust could account for most of the montmorillonite in the albic horizons studied. Concomitant additions of chlorite and mica are not detected. Chlorite and mica added as dust, as well as any traces of these minerals present as sand or silt, must be weathered to some other species in the clay fraction, because they are not detected in the clays.

It is proposed that in the Spodosols studied (i) any chlorite in the albic horizon is weathered to amorphous aluminosilicates and translocated to the spodic horizon, and (ii) mica is weathered to montmorillonite in the albic horizon, to vermiculite in the Bh horizon, and to “chloritized” vermiculite in the Bir horizon.
Forest Site Productivity Among Soil Taxonomic Units in Northern Lower Michigan
Authors: Shetron Stephen G.
Published: July 2010

Growth measurements (site index and cubic meter volume) and soil descriptions for 195 field plots on 12 soil taxa were obtained to evaluate the variation in tree growth of jack pine (Pinus banksiana L.), northern red oak (Quercus rubra L.), sugar maple (Acer saccharum Marsh.), and bigtooth aspen (Populas grandidentata Michx.) in northern lower Michigan.

Jack pine had significant differences in growth among five of eight soil taxa. Red oak showed significant differences among four soil taxa. Sugar maple showed no significant differences in growth among five soil taxa. Bigtooth aspen exhibited significant differences in growth among four of eight soil taxa.

Soil properties recorded for soil profile descriptions were related to the range in site index of each study species. Regression equations were developed for depth to mottling, depth to loamy sand lenses in sandy soils, and thickness of A and B horizons. The significance of the effect of the soil property on tree growth differed between species.

Soil‐tree growth ratings are possible, but the precision is affected by the lack of significant site differences among soil taxa. Within soil taxa, variation should be recognized for some soil series.
Ion Mobilities and Electric Charge of External Clay Surfaces Inferred from Potential Differences and Osmotic Flow
Authors: Kemper W. D. , Quirk J. P.
Published: July 2010

Bentonite, illite, and kaolinite clays were compacted, made homoionic with various cations, and placed between chloride solutions of the respective cations of different concentrations. Rates of osmotic flow, electric potentials in the solutions and streaming potentials were measured across these compacted clay membranes. The osmotic flow was often from the high salt to low salt concentration side and was generally in the direction of more negative potential, indicating electroosmosis as the mechanism involved in osmotic flow. Diffuse layer theory was used to estimate the concentration ranges in which the measured external potential differences were not appreciably different from the respective potentials in solution inside the clay. Assuming the osmotic movement to be electroosmosis, the ζ potentials were calculated from the observed potential gradients and the osmotic flux. The portion of adsorbed cations participating in the diffuse portion of the double layer was then calculated from ζ. This “mobile” fraction of the adsorbed cations appears to decrease for multivalent cations as the equilibrium solution concentration decreased. La3+ kaolinite and Willalooka illites were positively charged and adsorbed Cl‐ as diffuse layers. The mobile fractions estimated by this method for bentonite are in reasonably good agreement with mobile fractions estimated from diffusion and conductance measurements.
Volatility of Organochlorine Insecticides from Soil: II. Effect of Relative Humidity and Soil Water Content on Dieldrin Volatility
Authors: Igue K. , Farmer W. J. , Spencer W. F. , Martin J. P.
Published: July 2010

The influence of soil water content and soil water loss on the volatilization of dieldrin, a representative weakly polar insecticide, was investigated to test the “codistillation” theory of pesticide volatility. Dieldrin volatilization from Gila silt loam was dependent on soil water content, but was not dependent on rate of water loss from the soil. Air relative humidity indirectly influences dieldrin volatilization by influencing soil water content. Dieldrin volatilization from moist soil was always at a maximum when soil water loss was zero. With air at 100% relative humidity, volatilization remained high, and only decreased gradually as the dieldrin concentration at the soil surface decreased. When air was at less than 100% relative humidity, volatilization decreased rapidly as the soil water content decreased and was essentially zero below a soil water content of 2.8%. The influence of soil water content and soil water loss on dieldrin volatility was similar at 20 and 30C, at 2 and 8 ml/sec flow rate and at 5 and 10 µg/g dieldrin concentration. The results show that soil water content influences pesticide volatilization by competing for soil adsorption sites and thereby controlling the vapor density of the pesticide. These experimental results offer conclusive evidence that for dieldrin and probably for all pesticides, the term “codistillation” does not apply to volatilization from soils.
Calcite Contributions by Earthworms to Forest Soils in Northern Illinois
Authors: Wiecek C. S. , Messenger A. S.
Published: July 2010

Calcite spheroids and recognizable spheroid fragments originating in earthworm calciferous glands, contribute up to 56 kg/ha CaCO3 to the upper portions of the Al horizons of some forested, deeply‐leached soils. Horizons with a fresh pH from 6.3 to 7.5 may contain calcite spheroids; soil pastes of these horizons reach a pH between 7.2 and 8.0 upon incubation.

The data are consistent with the hypothesis that the weathering of calcite spheroids is partly responsible for pH values in excess of 7.0 in the undried Al horizons of otherwise acid soils under forest cover.
Temperature Effects on Interlayer Potassium Exchange in Micaceous Minerals
Authors: Ismail F. T. , Scott A. D.
Published: July 2010

The potential range of temperatures that can be used with NaCl‐NaTPB solutions for the extraction of interlayer K in micaceous minerals has been established. Temperatures up to 45C proved suitable for all minerals and prolonged extraction periods. Higher temperatures have limited use, particularly with dioctahedral micas, because changes in TPB stability and KTPB solubility occur. For short contact periods, however, temperatures up to 105C may be used with trioctahedral micas.

The release of K by dioctahedral and trioctahedral mica samples and by illite and soil fractions was determined with solutions that contained NaTPB to minimize K blocking and were maintained at 5, 25, or 45C. In coarsely‐ground samples of mica, where edge weathering was the dominant mechanism of K release, the rate of interlayer K exchange increased with the temperature. With finely‐ground mica samples there was no temperature effect on the initial release of K by layer weathering, but once K release by layer weathering was completed, temperature affected the rate of K release from small particles as well. Such differences in the effect of temperature on K release by edge and layer weathering provide a means of identifying the release mechanism involved in a particular mineral sample. Accordingly, it was found that fractions of Grundite, illite, and Marshall soil are unlike finely‐ground micas in that they do not release a major portion of their K by layer weathering. Changes in reaction temperature do not alter the limited degree of K exchange encountered with small mica particles.
Influence of Added Ca(OH)2 on Acidity in Submerged and Subsequently Dried Lateritic Rice Soils
Authors: Savant N. K. , Kibe M. M.
Published: July 2010

Two acid lateritic soils of the Maharashtra State (India), treated with increasing amounts of Ca(OH)2 equivalent up to about 92% total acidity (exchange acidity + pH‐dependent acidity) were submerged under water at room temperature (27 ± IC). Changes in soil pH were determined periodically during submergence. The soils were then air‐dried or oven‐dried and analysed for pH, exchange acidity, and pH‐dependent acidity. On 0‐day submergence, the addition of increasing amounts of Ca(OH)2 increased soil pH, but with time, the pH values of submerged soils converged in the neutral range of pH. The buffer curves of pH values of 30‐day submerged and subsequently dried soils against amounts of Ca(OH)2 added, indicated resemblance to that of weak acid titrated with weak base. The progressive neutralization curves of 30‐day submerged soils treated with Ca(OH)2 and then dried, showed that pH‐dependent acidity was neutralized concurrently with the neutralization of the major portion of exchange acidity. On addition of Ca (OH)2 equivalent to 92% of total acidity, exchange acidity was completely neutralized, whereas pH‐dependent acidity was not proportionately neutralized.
Salt Dispersion Coefficients Near an Evaporating Surface
Authors: Todd R. M. , Kemper W. D.
Published: July 2010

A series of laboratory experiments was conducted to gain detailed information on water and salt movements near an evaporating surface.

Columns instrumented with tensiometers and Richards' salinity sensors were used with coarse‐ and fine‐textured soils. Water was supplied to a water table at the base of the columns and approximately steady state evaporation from the soil surface was established. Dispersion coefficients were calculated from salt gradients and evaporation rates in regions of the soil where suctions ranged from 0.1 to several bars. Dispersion increased with increased solution flux and average solution velocity. Values obtained for dispersion coefficients corresponded closely with those obtained by other workers under more nearly saturated conditions at similar rates of solution flux.
Water Transmission Properties of an Asphalt Barrier
Authors: Palta J. P. , Blake G. R. , Farrell D. A.
Published: July 2010

The water transmission properties of an asphalt barrier were studied using samples taken from a barrier formed in Zimmerman fine sand. Steady flow experiments using a 9.0‐cm diameter soil column showed that water movement through the barrier was affected by the capillary potentials on both sides of the barrier if these potentials exceeded a critical value or ‘break point’ which ranged from −32 to −20 cm depending on the flow rate. When the potential below the barrier dropped below the critical value, the potential above the barrier remained relatively unchanged. This steady value increased from −4.3 to −1.5 cm when the flow rate was increased from 0.009 to 0.058 cm/hour. The hysteretic flow properties of the barrier are explained using a model based on the following assumptions: (i) flow occurs mainly through cracks of varying width, and (ii) the ratio of the draining to wetting potentials of the cracks exceeds unity and is independent of crack size.