bluuebunny/crossref_metadata_2025_split huggingface dataset:
Observed and Predicted Two‐Dimensional Soil Temperature Distributions Under a Row Crop
Authors: Horton R. , Aguirre‐Luna O. , Wierenga P. J. 
Published: July 2010

AbstractA two‐dimensional soil heat transfer model was developed to compute the soil temperature distribution between rows of crops which partially shaded the soil surface. The model is based on an explicit solution, using CSMP, of the heat conduction equation and allows for time and space dependence of soil thermal properties. Measured soil temperatures were taken as input for the upper boundary. Computed temperature distributions were compared with temperatures measured below a trickle irrigated row crop, which only partially shaded the soil. There was a large variation in the surface and near surface soil temperatures with distance from the row. Ranges of the daily surface soil temperature waves were about 5°C directly below the crop and about 40°C between two crop rows. Around noon the horizontal soil heat flux in the upper soil profile was much greater than the soil heat flux in the vertical direction. Better agreement was obtained between measured soil temperatures and predicted soil temperatures when horizontal heat flux was taken into account.
Transformations of Fall‐Applied Nitrogen‐15‐Labelled Fertilizers
Authors: Aulakh M. S. , Rennie D. A. 
Published: July 2010

AbstractIn conjunction with field studies on gaseous losses of nitrogen, the transformations of fall‐applied 15N‐labelled KNO3 and urea (with and without nitropyrin) were studied in black and dark brown Chernozemic (Typic Udics and Typic Haploborolls) soils during 1980–81 and 1981–82. The amount of fall‐applied N which could not be accounted for in the following spring ranged from 25 to 33% (2 sites) for KNO3 and only 10 and 5% from urea without and with nitropyrin, respectively. These losses occurred during the fall (before the soil was frozen) and in the following spring (after soil thaw) and were primarily due to denitrification. Nitrification of NH+4‐N from applied urea occurred at a slow rate during the cool late fall until freeze‐up and commenced again in early spring when the soil warmed up. Application of nitrapyrin in conjunction with urea delayed nitrification as well as downward movement of fertilizer N in the soil profile and was effective in decreasing the denitrification losses. Immobilization of fertilizer N was minimum under fallow conditions (7%) but ranged from 15 to 21% and 24 to 26% of the applied N as KNO3 and urea, respectively, in wheat stubble fields. Nitrapyrin did not affect the immobilization of fertilizer N or the amount of fertilizer N found in the microbial‐biomass.
Nature and Properties of Pseudoboehmites Formed in the Presence of Organic and Inorganic Ligands
Authors: Violante A. , Huang P. M. 
Published: July 2010

AbstractPoorly crystalline aluminum oxyhydroxides (pseudoboehmites), with similar x‐ray diffractograms, were synthesized at room temperature at the initial Al concentration of 2 × 10−3 mol L−1 and pH 8.2 in the presence of selected inorganic or organic ligands (1.4 mol L−1 chloride; 0.14 mol L−1 sulfate; 2 × 10−5 mol L−1 citric, tartaric, or tannic acid; 4 × 10−5 mol L−1 tannic acid). Electron micrographs show that these poorly crystalline materials range from fibrous shape to shapeless fine colloids (< 10 nm) or their aggregates before air drying. However, after air drying, the pseudoboehmites consist of fibrillar particles as well as many large aggregates (> 5 µm) even after ultrasonification. The amount of ligands in the precipitates varies from 0.1% for chloride (28 mmol kg−1) to 29.8% for tannate (175 mmol kg−1). The specific surface of the pseudoboehmites ranges from 30.0 hm2 kg−1 to 58.0 hm2 kg−1 due to the presence of foreign ligands which promote structural distortion in the precipitation products and/or aggregation of the particles. The PZC values of the pseudoboehmites formed in the presence of inorganic and organic ligands vary from 8.0 to 9.3. The net positive charge of the poorly crystalline aluminum oxyhydroxides varies with the kinds of ligands present during their precipitation. The data obtained in this study show that pseudoboehmite samples formed under the varying ionic environments differ significantly in their chemical composition and surface properties.
Simultaneous Determination of Calcite Surface Area and Content in Soils
Authors: Suarez D. L. , Wood J. D. 
Published: July 2010

AbstractA method to simultaneously determine calcite surface area and content in soils has been developed. The proposed procedure is based on rates of CO2 production upon reaction of soil with buffered acid solutions under controlled conditions. A pressure transducer connected to a chart recorder allows determination of soil calcite dissolution rate, which is directly proportional to calcite surface area. Sample size typically ranges from 0.3 to 10.0 g. The coefficient of variation for surface area was 0.05, based on nine replicated analyses of the same soil.
Soil Properties in Creosotebush Communities and their Relative Effects on the Growth of Seeded Range Grasses
Authors: Cox Jerry R. , Parker James M. , Stroehlein Jack L. 
Published: July 2010

AbstractSoils were collected to 15 cm along the four cardinal directions at three locations around 10 creosotebush [Larrea tridentata (DC.) Cov.] plants at five sites in the southwestern United States. The sampling locations were: (i) at the canopy center, (ii) along the outer canopy edge, and (iii) in open areas between plant canopies. A portion of the soil from each sampling location was analyzed for particle size distribution, pH, EC, CaCO3, Ca, K, Na, Mg, NO‐3‐N, organic C, available P, and Mn. The remaining soil from each sampling location was seeded with either Lehmann lovegrass (Eragrostis lehmanniana Nees) or blue panicgrass (Panicum antidotale Retz.). Grass seeds were germinated and grown for 42 d in a greenhouse. Nitrate was significantly (∝ = 0.05) lower in open areas between creosotebush canopies than near the shrub canopy center at all sites. Grass seedling growth decreased as the distance from the canopy center increased and seedling growth was highly correlated with nitrate concentrations. Spatial distribution patterns for the other measured soil properties did not occur in a consistent fashion across all sampled sites. The action of mechanical tillage to limit creosotebush competition, and corresponding dilution of NO‐3‐N in the soil volume, may reduce the probability of establishing perennial grasses.
Preparation of Large Core Samples from Stony Soils
Authors: Buchter B. , Leuenberger J. , Wierenga P. J. , Richard F. 
Published: July 2010

AbstractA method was developed to take large, undisturbed soil cores in stony soils. An undisturbed soil core was surrounded with concrete, frozen to −22°C and cut to shape with a diamond circular saw, leaving only core sample. The core sample was surrounded with paraffin to maintain its shape.
Comparison of Field Denitrification Rates Determined by Acetylene‐Based Soil Core and Nitrogen‐15 Methods
Authors: Parkin Timothy B. , Sexstone Alan J. , Tiedje James M. 
Published: July 2010

AbstractA soil core method to measure field denitrification rates was evaluated by comparing the results with denitrification rates measured by the 15N difference method. In the core method, acetylene amended air was recirculated through an undisturbed soil core and short‐term (ca. 1 h) nitrous oxide production monitored. Denitrification rates were obtained on soil cores from two field sites and a set of sieved, repacked soil cores in a laboratory incubation. Cumulative N‐losses were estimated by interpolating between sample dates. Denitrification rates obtained by the core method were found to approximate a log normal distribution at both sites studied and at all sampling times. Statistical calculations appropriate for this distribution resulted in improved estimates of the mean rates and confidence intervals. For the 15N difference method, 15N enriched nitrate was added to microplots of 30 cm diameter and the total gaseous losses were estimated by considering the change in the total nitrate pool, the isotope ratio of that pool and the 15N not recovered from the microplots. Experiments were conducted over periods of 32 to 45 d on sandy loam and clay loam soils, respectively. Denitrification rates from the acetylene‐core method were not significantly different than the estimates by the 15N method. Denitrification rates as measured by both methods were highly variable.
Shrink‐Swell Potential of Montmorillonitic Soils in Udic Moisture Regimes
Authors: Karathanasis A. D. , Hajek B. F. 
Published: July 2010

AbstractThirty‐two montmorillonitic soil pedons representative of Vertisols, Inceptisols, and aquic, typic, or vertic subgroups of Alfisols and Ultisols in the udic moisture regime of Alabama were evaluated for their shrink‐swell properties. Soil shrink‐swell potential was evaluated on control section samples from coefficients of linear extensibility (COLE) measured by thermo‐mechanical analysis (TMA), percent volume change (PVC) of remolded samples measured by a micrometer, interlamellar shrinkage (IS) determined by x‐ray diffraction analysis, and from field expression of soil cracking. No significant differences in COLE, PVC, IS, smectite or clay content were encountered between soils with and without vertic characteristics. Discrepancies were found between laboratory measured and field observed shrinking potential of aquic/typic/vertic Ultisols primarily due to lack of wide cracks. The poor field expression of cracking in montmorillonitic Hapludults was better explained by a combination of physical and morphological characteristics such as texture and thickness of the surface layer, size and type of structural units, solum thickness and depth to Cr, soil moisture deficit, drainage and vegetation than by variation in physical, chemical, or mineralogical properties. At present, classification of montmorillonitic Hapludults in vertic subgroups is proscribed by lack of evidence of wide or deep cracking. Modifications in the current vertic subgroup definition are suggested to account for agronomic and/or engineering limitations of these soils.
Soil‐Saprolite Profiles Derived from Mafic Rocks in the North Carolina Piedmont: II. Association of Free Iron Oxides with Soils and Clays
Authors: Rice T. J. , Weed S. B. , Buol S. W. 
Published: July 2010

AbstractThe association of free Fe oxides with soils and clays from two Enon sandy loam (Ultic Hapludalfs, fine, mixed, thermic) soil‐saprolite profiles was studied. Goethite was the dominant Fe oxide identified. Lepidocrocite was detected in trace amounts in some samples. FeCBD/clay ratios were highest in the epipedons of these soils suggesting the concentrating of Fe oxides as a result of aluminosilicate mineral weathering. External (BET‐N2) surface area measurements of non‐deferrated and deferrated clays were analyzed in conjunction with electron micrographs of selected clay fractions to determine the association of free Fe oxides with aluminosilicate clays as a function of depth in the profile. Free Fe oxides were found to exist mainly as small, discrete clusters in the A and B horizons of both profiles and specific of the clay surface decreased as a result of treatment for Fe removal. However, external surface areas increased for the saprolite (Cr) horizon clays after deferration. One subfraction identified as having an increase in surface area after deferration was fine clay from the Cr2 horizon, Enon (metagabbro) profile. Chemical data and electron micrographs suggest that either partial dissolution of small, poorly crystalline aluminosilicate clays or removal of some Fe or non‐Fe oxide aggregating agent results in breakdown of the fine clays into smaller particles of higher net specific surface.
Automated Analysis of Nitrous Oxide
Authors: Parkin T.B. 
Published: July 2010

AbstractAn autosampler was developed to interface with a gas chromatograph for N2O analyses. The sampler was comprised of a modified fraction collector and pneumatic valves all controlled by a microprocessor unit. Cost of the autosampler system including the fraction collector was estimated to be less than $3500. The sampler was designed to analyze gas samples stored in rubber‐stoppered, glass vials. Use of vials resulted in a slight loss of sensitivity due to dilution and absorption of N2O; however, accuracy was the same as could be obtained by manual syringe injections.
Formation of Methyl Nitrite in Soil Treated with Nitrous Acid
Authors: Magãlhaes A. M. T. , Chalk P. M. , Rudra A. B. , Nelson D. W. 
Published: July 2010

AbstractThe formation of methyl nitrite was detected when two clay soils were treated with nitrous acid (260 ± 20 mg N kg−1 soil) in the dark in a closed chamber. The presence of the gas was positively identified by mass spectrometry. There was a consistent trend with time in the concentrations of methyl nitrite in the atmospheres above the soils. A rapid buildup occurred following addition of nitrous acid, but this was soon followed by a gradual decline in concentration. The peak concentrations occurred approximately 15 min or 30 min after nitrous acid addition, and 5‐h concentrations were < 50% of peak concentrations. Methyl nitrite was formed under mildly to moderately acid conditions (pH 6.3 and 4.8) at −33 kPa soil water potential. The results indicate that methyl nitrite may form under conditions encountered in the field, and that soil can be a sink as well as a source of methyl nitrite.
Hydrolysis of Trimetaphosphate in Soils
Authors: Busman L. M. , Tabatabai M. A. 
Published: July 2010

AbstractTrimetaphosphate (TMP), a cyclic polyphosphate that is not sorbed by soils, is hydrolyzed by a series of biochemical reactions to yield triphosphate, pyrophosphate, and orthophosphate; phosphates that are sorbed by soils. In addition to its hydrolysis to triphosphate in soils by the enzyme trimetaphosphatase (trimetaphosphate hydrolyase, EC 3.6.1.2), TMP is hydrolyzed chemically by metal ions such as Ca2+ and Mg2+. A method was developed for assaying the activity of trimetaphosphatase and for determining the rate of nonenzymic (chemical) hydrolysis of TMP in soils. The method involves incubating 1 g of soil with 3 mL buffered (100 mM Tris) 25 mM TMP at 37°C for 5 h followed by determination of the unaltered substrate. Steam‐sterilized soil is used as a control to account for the amount of TMP hydrolyzed nonenzymically. Trimetaphosphatase activity in soils was maximum at a buffer pH of 8 and a temperature of 40°C. Nonenzymic hydrolysis of TMP increased up to the highest incubation temperature (80°C) tested. Trimetaphosphatase in three Iowa surface soils showed apparent Km values ranging from 6.8 to 7.2 mM TMP, Vmax values from 590 to 1200 mg TMP‐P hydrolyzed kg−1 soil 5 h−1, and energy of activation values from 17 to 26 kJ mol−1. The activation energy values of the nonenzymic hydrolysis ranged from 29 to 39 kJ mol−1. Enzymic and nonenzymic hydrolysis rates in the six soils used ranged from 231 to 928 and from 101 to 888 mg TMP‐P kg−1 soil 5 h−1, respectively. Formaldehyde and EDTA inhibited, and toluene had no effect on, trimetaphosphatase activity in soils. The addition of Ca2+ and Mg2+ increased nonenzymic hydrolysis rates in two soils tested with Ca2+ being twice as effective as Mg2+.
Organic Carbon in Soils of North Central United States
Authors: Franzmeier D. P. , Lemme G. D. , Miles R. J. 
Published: July 2010

AbstractOrganic carbon contents in the upper 0.2 m and upper 1.0 m of soils in the 12‐state North Central Region are presented in this study with tables and maps. The information was summarized by pedologists in each state from laboratory analyses of pedons typical of a soil series and the areal composition of soil associations by soil series. Much of the data was gathered in connection with the cooperative soil survey. Associations of mineral soils range in carbon content to a depth of 1 m from about 2 kg m−2 in the Badlands of North Dakota to 21 kg m−2 in some poorly‐drained, fine‐textured soils of eastern North Dakota. Organic soils contain about 75 kg m−2. The average for all soils of the region is 11.7 kg m−2 carbon. Organic C levels are related largely to parent material, natural vegetation, and topography factors in this geographic region. The information contributes to our knowledge of the amount of carbon in soils, one of the important global carbon reservoirs, which is of interest to those who study atmospheric CO2 changes. It is also important relative to soil management operations such as herbicide application.
Iron Distribution in a Developmental Sequence of Soils from Mica Gneiss and Schist
Authors: Rebertus R. A. , Buol S. W. 
Published: July 2010

AbstractUpland residual soils formed from mica gneiss and schist in the Piedmont and Blue Ridge provinces of North Carolina represent developmental sequences where particle‐size class, profile development, and mineralogy are related to landscape position and slope. In this study the distribution of total and free iron in 10 Hapludult and Dystrochrept pedons is examined and interpreted with respect to degree of profile development. Primary mineral alteration and B horizon free iron/total iron ratios vary nearly systematically with particle‐size class and solum thickness. The latter two parameters were found to be good indicators of degree of profile development and hence of relative soil age. The free iron/total iron ratio was found to be a particularly sensitive indicator of relative soil development. The ratio reflects the degree of primary mineral alteration, the amount of clay formed, as well as the pedogenic process of illuviation. The B horizon ratios are much better indicators of relative soil development than those from either C or A horizons. Ratios of free iron/total iron in A horizons are influenced by downslope movement of surficial material, the low extractability of iron oxides of large particle size, and clay content differences. Free iron/total iron ratios of C horizons are dependent on sampling depth, the amount of clay formed, and the degree of illuviation that has occurred below the solum. All soils had oxidic ratios (%Fe2O3 + %gibbsite/%clay) > 0.2; however, all but one was excluded from the oxidic mineralogy class due to having >40% mica. A simple free iron/total iron ratio in B horizons, which is systematically related to the degree of weathering of primary minerals and the degree of morphological soil development, better serves as soil family criteria than the present % Fe2O3 + % gibbsite/% clay.
Mechanisms of Aluminum Adsorption on Clay Minerals and Peat
Authors: Jardine P. M. , Zelazny L. W. , Parker J. C. 
Published: July 2010

AbstractMechanisms of Al adsorption on Ca‐saturated kaolinite, montmorillonite, and peat were studied by miscible displacement methods. Partially neutralized 1.0 × 10−4 M AlCl3 solutions with basicities of 1.0 were leached through monomineralic columns and effluent analyzed for monomeric and polymeric Al, titratable acidity, and desorbed Ca as functions of time. Polymeric Al was preferentially adsorbed by kaolinite throughout the displacement experiment whereas montmorillonite preferentially adsorbed monomers at short times and polymers at longer times. Selective adsorption of monomeric or polymeric Al on peat was not evident. Aluminum adsorption kinetics on kaolinite, montmorillonite, and peat was described by two simultaneous reactions—a relatively rapid reaction involving Al‐Ca exchange and a slower reaction involving Al polymerization on the adsorbents. This scenario is supported by potentiometric titrations of effluent Al and by analyses of effluent Ca, and adsorbed, exchangeable and nonexchangeable Al basicities. Negligible adsorption of Al on gibbsite and quartz indicated that surface bound Al on kaolinite and montmorillonite may serve as a template for adsorption of more Al.
Transient Microsite Models of Denitrification: III. Comparison of Experimental and Model Results
Authors: McConnaughey P. K. , Bouldin D. R. , Duxbury J. M. 
Published: July 2010

AbstractExperiments were designed to investigate the validity of proposed reaction‐diffusion models of denitrification. Brass respirometers were used to measure fluxes of oxygen (O2), carbon dioxide (CO2), and nitrous oxide (N2O) from a 5 × 10−3‐m layer of saturated soil incubated at 25°C. Gaseous fluxes were measured as a function of time after wetting, with and without 0.42 mol m−3 of acetylene (C2H2) present in the headspace. The presence of C2H2 in the headspace doubled O2 fluxes 35 to 60 h after incubations commenced. When C2H2 was not present, N2O evolution was negligible after 25 h of incubation. Nitrous oxide fluxes predicted by the models were compared to those observed experimentally. When C2H2 was present, the models predicted N2O fluxes reasonably well (r2 = 0.90 and 0.78) for initial nitrate (NO−3) N levels of 7.1 and 15.9 mg N kg−1 soil, respectively. When C2H2 was not present, the models predicted the experimentally observed initial flux of N2O if an 8 to 10 h lag in N2O reductase activity was included in the models. The best model for describing N2O fluxes in these experiments used differential rates of Michaelis‐Menten reduction without NO−3 and nitrite (NO−2) inhibition of N2O reduction. Experimental techniques and parameter characterization, however, need considerable refinement. Independent measurements are needed to quantify relationships between reaction order and kinetic parameters. Still, given the general agreement between observed and predicted fluxes, there can be little doubt that the reaction‐diffusion models are essential to a better understanding of denitrification.
Tillage Effects on Soil Thermal Properties
Authors: Potter K. N. , Cruse R. M. , Horton R. 
Published: July 2010

AbstractTheoretical considerations indicate soil thermal properties may be altered by tillage, but few field studies have been conducted to compare soil thermal properties as affected by conservation or notill management systems. Surface‐soil thermal properties were determined in the row zone for three soils in three tillage systems: conventional till, chisel plow, and no‐till. The apparent thermal diffusivity was determined by harmonic analysis of soil temperature data, volumetric heat capacity from the volume fraction of the soil components, and thermal conductivity by the line source heat‐probe method. Soil volumetric heat capacity was similar for all tillage treatments. Thermal diffusivity was significantly greater in the notill system than in conventional and chisel plow tillage systems, indicating that thermal conductivity also was greater in the no‐till system. Direct determination of thermal conductivity by the line source heat‐probe method at one site indicated that thermal conductivity was more than 20% greater in no‐till than in the conventional till system. Percentage surface residue cover had a greater influence on soil temperature and soil heat flux than soil thermal properties.