bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nitrosation of Soil Organic Matter: III. Nature of Gases Produced by Reaction of Nitrite with Lignins, Humic Substances, and Phenolic Constituents Under Neutral and Slightly Acidic Conditions
Authors: Stevenson F. J. , Harrison R. M. , Wetselaar R. , Leeper R. A. 
Published: July 2010

AbstractMolecular nitrogen, nitrous oxide (N2O), nitric oxide (NO), and CO2 were identified in the gases formed by reacting NO2‐ with soils, humic and fulvic acids, lignins, lignin‐building units, and polyphenols in aqueous buffer solutions of pH 6 and 7 in the absence of oxygen. The composition of the mixture of gases was dependent upon the nature of the material examined, with relatively larger amounts of N2 being produced from the humic and fulvic acids. Compounds containing methoxyl groups failed to yield detectable amounts of methyl nitrite (CH3ONO) at the pH levels found in most soils. The reaction of NO with humic substances in the absence of oxygen led to the production of N2O and CO2.
Volatilization of Lindane and DDT from Soils
Authors: Guenzi W. D. , Beard W. E. 
Published: July 2010

AbstractFour soils ranging in texture from a loamy sand to a clay were amended separately with 14C‐labeled lindane and DDT to give a concentration of 10 ppm. Pesticide volatilization was determined each day for three consecutive drying cycles at 30C and 55C by liquid scintillation counting of trapped pesticide vapors. Soils were initially wetted to ⅓ bar suction and dried by passing dry air over the soil surface.Neither pesticide was volatilized at either temperature after the soils contained less than a monolayer of water. Since these soils became dry at different times during the 14‐day drying cycle, two factors were important in describing pesticide volatilization. First, the rate of pesticide loss was constant for each soil in the moisture range from ⅓ bar to 15 bars. Second, since essentially the same amount of water was lost from each soil per day until dryness, the pesticides were volatilized over a longer period of time from the finer textured soil than from the coarser textured soils. A mechanism is proposed.Volatilization rates for DDT and lindane from soil containing moisture greater than 15 bars tension were dependent on temperature, adsorptive characteristics of the soil, and concentraction of the pesticide (lindane). For lindane and DDT at 30C, the rate of volatilization from soil was in the order Valentine loamy sand > Hand loam > Raber silty clay loam > Promise clay.Degradation of lindane to PCCH occurred at 30C and 55C. After three wetting and drying cycles at 55C, the amount of DDT converted to DDE ranged from 6.7% for Valentine loamy sand to 21.2% for the Raber silty clay loam.
Micromorphology of Soil Fabric at Tree Root‐Soil Interface
Authors: Blevins R. L. , Holowaychuk N. , Wilding L. P. 
Published: July 2010

AbstractThe influence of tree roots on physical properties and spatial arrangement of adjacent soil materials were studied. Soil fabric in the vicinity of tree root‐soil interface was observed microscopically using specially prepared soil thin sections from samples obtained from forest soils by a freezing in situ technique. Micromorphological observations showed that within the 0‐ to 0.4‐mm radial interval from the root‐soil interface there was a relative decrease in grains and pores > 20µ. An increase in oriented clay, and percentage elongate grains oriented within 30° tangent to the root surface was observed. These features imply that the matrix adjacent to tree roots (within 1 to 2 mm) contain more fine‐grained materials, with a consequent pore‐size distribution shift toward smaller pore diameters (20–50µ or less). Microscopic measurement of pore size distribution compared closely to aeration porosity values calculated from bulk density, particle density, and moisture content at 60‐cm tension data. Percent pores determined microscopically on soil thin sections without reference to distances from soil‐root interfaces agreed closely with values measured at a distance interval of 2.0 to 4.0 mm from root‐soil interface. Aeration porosity, measured microscopically in the area of close proximity to actively growing roots at time of sampling, was very low.These data and inferences suggest that physical properties of the soil contiguous to a tree root may differ appreciably from such factors farther away from the root.
Gaseous Diffusion Evaluation in Forest Humus
Authors: Ballard T. M. 
Published: July 2010

AbstractPenman's ratio of direct length to effective diffusion path length, L/Le, is not directly predictable from the air content of forest humus, probably because of anisotropic pore orientation. The diffusion coefficient of a gas in the unsaturated porous medium can be estimated from temperature, air pressure, porosity, water content, and an empirically determined value of L/Le. A steady state CO2 diffusion method is proposed for measuring L/Le and gaseous diffusion coefficient in either loose or structurally intact forest humus samples.
Freezing and Thawing Effects on Drainage
Authors: Benoit G. R. , Bornstein J. 
Published: July 2010

AbstractLaboratory studies were conducted on insulated models containing coarse sand (1–2 mm), fine sand (0.5–1 mm) and soil (0–2 mm and 2–4.8 mm) to determine the effects of freezing and thawing on sloping land drainage. Interrelations between structure and texture, rates and extent of ice formation, and rates and magnitudes of drainage were determined. Decreasing temperatures and subsequent ice formation decreased the relative mobility of water, thereby increasing water retention and decreasing rates of water transmission. The magnitude of the short‐term, freeze‐thaw effects on soil water retention and transmission was influenced by soil aggregate size, aggregate stability, and soil water content during freezing. On a long‐term basis, drainage that results in a consistently lower water content during freeze‐thaw cycles may lead to a changed soil structure and thus a changed drainage requirement.
A Gamma‐photoneutron Method for Laboratory Studies of Soil Water
Authors: Corey J. C. , Hawkins R. H. , Overman R. F. 
Published: July 2010

AbstractThe gamma‐photoneutron method is unique among nuclear methods used to study water movement in soil because the heavy water (2H2O) content of laboratory soil columns can be measured independently of bulk density of soil, soil texture, light water (1H2O) content, and type of clay mineral. The method requires a radioactive source that emits gamma photons in excess of 2.23 Mev and a neutron detector. The neutron detector measures photoneutrons produced when the deuterium nuclei in the gamma radiation field split into a photoneutron and a proton. The number of photoneutrons detected is linearly related to the heavy water content of the soil column.
Comparison of Inorganic Nitrogen Contents of Undisturbed, Cultivated, and Barnyard Soil Profiles in Wisconsin
Authors: Olsen R. J. , Hensler R. F. , Attoe O. J. , Witzel S. A. 
Published: July 2010

AbstractIn a group of 25 soil profiles, the total content of NO3‐N to a depth of 240 cm was about 55, 230, 165, and 135 kg/ha for the undisturbed, cultivated, poorly‐drained, and well‐drained barnyard profiles, respectively, and 35, 30, 995, and 240 kg/ha for exchangeable NH4‐N. Similarly, the average concentration of NO3‐N in the soil solution at the 180–240 cm depth was 8, 11, 9, and 11 ppm. The concentration tended to decrease with soil depth, apparently due to plant uptake, denitrification, and microbial immobilization processes. The total content of NO2‐N to the 240‐cm depth ranged from 6 to 25 kg/ha.
Conditions Affecting Cesium Fixation and Sodium Entrapment in Hydrobiotite and Vermiculite
Authors: Klobe W. D. , Gast R. G. 
Published: July 2010

AbstractThe effect of residual and added K on Cs fixation was studied, using samples of K‐extracted Transvaal, South African hydrobiotite with 66, 60, 23, and < 1% K saturations. Fixation was measured by the availability of the cations for rapid isotopic exchange in a well‐stirred system.Over 95% of the sorbed Cs was fixed above 1% Cs saturation of the exchange capacity regardless of K levels or whether the K was in the form of residual K in hydrobiotite or K added to the vermiculite prior to addition of the Cs. In contrast, trace levels of Cs (i.e., carrier‐free 137Cs) were fixed to a much lesser extent, indicating that it may be more available for plant uptake.X‐ray and Na entrapment results indicate that Cs saturations below 40% of the exchange capacity result largely in interstratified Na‐ and Cs‐rich layers with little edge collapse. Higher Cs saturations resulted in increased edge collapse and Na entrapment. Formation of interstratified layers vs. edge collapse of the particles tends to be associated with smaller and larger particles, respectively.
Comparison of Organic Matter Destruction by Hydrogen Peroxide and Sodium Hypochlorite and Its Effects on Selected Mineral Constituents
Authors: Lavkulich L. M. , Wiens J. H. 
Published: July 2010

AbstractThe destruction of organic matter from widely different soils was evaluated by using hydrogen peroxide and sodium hypochlorite oxidation procedures. The amounts of extractable Si, Mn, Al, and Fe were determined on the residues following treatment with the oxidizing agents by using acid ammonium oxalate and 0.5N NaOH extraction procedures. In addition, the amount of Si, Mn, Fe, and Al in the extracting solutions was determined. It was found that NaOCl extracted more organic matter with less destruction of the oxides than procedures employing H2O2. This was substantiated statistically using the t‐test as applied to paired values. Three treatments with NaOCl were concluded to be satisfactory for destruction of organic matter with minimum removal of Si, Mn, Fe, and Al.
The Characteristics, Classification and Genesis of Some Tropical Spodosols
Authors: Tan K. H. , Perkins H. F. , McCreery R. A. 
Published: July 2010

AbstractMorphological, chemical, and mineralogical properties are presented for three tropical spodosols. Based on the occurrence in different climatic zones, the soils were distinguished as lowland podzols and mountain or highland podzols.The lowland podzol had a low organic matter content, a weakly developed Bh and a well developed argillic horizon below the spodic horizon. The name Humic Alfic Tropoferrod is proposed for this type of podzol. The A horizon contained predominantly amorphous clay, but the B horizon had appreciable amounts of kaolinite.Highland podzol I was high in organic matter, had a well developed Bh, but lacked an argillic horizon, and was classified as a Typic Tropohumod. Highland podzol II had similar properties, but was relatively young in degree of development and was classified as an Entic Tropohumod. The clay fraction of the humods was characterized by high amounts of amorphous clay, probably allophane. Kaolinite was not detected.
Tensile Strength of Clay Films: A Measuring Technique
Authors: Dowdy R. H. , Larson W. E. 
Published: July 2010

AbstractA technique is presented for quantitatively measuring tensile strength and axial tensile strain of clay films over a relative water vapor pressure range (P/P0) from 0.02 to 0.92. The tensile strain energy is calculated from these data. With this technique, relative electrostatic and chemical interactions of different clay systems can be assessed with a minimum interference from frictional force components. Data for Mg‐mont‐morillonite showed a maximum tensile strength of 210 kg cm‐2 at P/P0 = 0.02, exhibited an axial strain of 173µ cm‐1 and required 0.22 joules cm‐3 of tensile strain energy to rupture.
Soil‐Water Hysteresis: the Domain Theory Extended to Pore Interaction Conditions
Authors: Topp G. C. 
Published: July 2010

AbstractSome 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

AbstractUptake 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

AbstractSubsoil 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

AbstractSoil 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

AbstractThree 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

AbstractWettability 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

AbstractWater 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

AbstractLarge 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

AbstractMathematical 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

AbstractHypothetical 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

AbstractIncreases 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.