bluuebunny/crossref_metadata_2025_split huggingface dataset:
Long‐Term No‐tillage Effects on Soil Properties and Continuous Corn Yields
Authors: Ismail Isro , Blevins R. L. , Frye W. W. 
Published: July 2010

AbstractLack of soil disturbance in no‐tillage changes some of the most important basic soil properties. Short‐term changes have been well documented by previous research, but little is known about long‐term changes. This study was to determine the effects of 20 yr of continuous corn (Zea mays L.) under no‐tillage (NT) and conventional moldboard plow tillage (CT) with 0, 84, 168, and 336 kg N ha−1 on soil properties and grain yields and, to the extent possible, compare 20‐yr results with previously published 5‐ and 10‐yr results. Soil organic C and N; extractable P; exchangeable Ca, Mg, and K; and pH were significantly higher with NT than CT in the 0‐ to 5‐cm depth. Below the 5‐cm depth, Mehlich III P; pH; and exchangeable Ca, Mg, and K were higher with CT than NT. Organic C and N increased with increasing N rates. Conversely, pH and exchangeable Ca and Mg declined with high N rates. Bulk density was not significantly different among NT, CT, and bluegrass sod (Poa pratensis L.), but increased with depth. Comparisons of 1989 results with those obtained in 1975 and 1980 revealed that the soil's organic C was restored to the level of the bluegrass sod following a decline of 19% with CT and 9% with NT between 1970 and 1975. Grain yields, which declined along with organic C, have not recovered. Changes in organic matter content, with their many ramifications, are probably the most important long‐term effects of tillage differences on basic soil properties.
Eliminating Nitrate Interference During Kjeldahl Digestion of Soil Extracts for Microbial Biomass Determination
Authors: Wyland L. J. , Jackson L. E. , Brooks P. D. 
Published: July 2010

AbstractNitrate interference in Kjeldahl digestion of soil and plant samples presents a significant problem in establishing N budgets in agricultural systems, where NO−3 is frequently abundant. During digestion, NO−3 can be reduced or it can cause volatilization of reduced N, resulting in either over‐ or under‐estimation of Kjeldahl N. A method has been developed to volatilize NO−3 from K2SO4 extracts of soil prior to Kjeldahl digestion for determination of microbial biomass N. Extracts were pretreated with H2O2 and H2SO4 at 97 °C for 48 h, and then were Kjeldahl digested using a procedure modified for microbial biomass extracts. This method volatilizes >99% of NO−3 in K2SO4 extracts, as determined by 15N recovery from spiked samples.
Synthesizing Bulk Density for Soils with Abundant Rock Fragments
Authors: Vincent Kirk R. , Chadwick Oliver A. 
Published: July 2010

AbstractBulk density is a fundamental soil property that is difficult to determine for gravelly to extremely gravelly soils because results vary significantly with sample volume. For such coarse soils, the representative volume (for whole‐soil bulk density) should be large, but guidelines for selecting an appropriate sample volume do not exist. We evaluated the representative volume for a soil with abundant rock fragments, by comparing measured properties of samples ranging in volume from 0.03 to 410 L. For whole‐soil bulk density determination, the representative volume is 4 L or larger for a soil horizon containing 34% (v/v) gravel and is between 5 and 50 L for a soil horizon containing 54% gravel. Intact samples of that size are prohibitively large, so we developed an alternative approach that starts with measurement of fine‐earth bulk density. For fine‐earth bulk density, the sample volume needed for representative results is between 0.2 and 1 L for gravelly to extremely gravelly soils. The alternative approach reliably synthesizes whole‐soil bulk density using (i) fine‐earth bulk density from modest‐sized samples, (ii) mass‐size distribution from large (>40 kg) representative disturbed samples, and (iii) rock fragment bulk densities. The mass and volume of rock fragments that should be in a sample are added to the mass and volume used to calculate fine‐earth bulk density. This method allows integration of lateral variability in the soil without the consequence of averaging properties across a large depth range.
Formation of a Transient Magnesium‐Aluminum Double Hydroxide in Soils of Southeastern Ohio
Authors: Smeck N. E. , Saif H. T. , Bigham J. M. 
Published: July 2010

AbstractTo assess the potential for Mg‐Al double hydroxide formation in acid, Al‐rich soils of southeastern Ohio under native conditions, laboratory studies were conducted to determine if Mg‐Al double hydroxide could be produced with Al‐saturated clays and soils of mixed mineralogy common to the region. Aluminum‐saturated clays suspended in dilute Mg solutions and titrated with NaOH to pH 9.5 yielded pronounced buffer regions between pH 8.3 and 8.5 attributable to the formation of Mg‐Al double hydroxide. Equilibration of the clays titrated to pH 9.5 for 55 d showed a gradual decline to pH 8.0 to 8.4. The decline was attributed to the precipitation of additional Mg‐Al double hydroxide caused by the slow release of interlayer hydroxy Al, which showed a correlation with the rate of pH decline. X‐ray diffractograms of the equilibrated clays yielded peaks at 0.78 and 0.39 nm that were indicative of Mg‐Al double hydroxide. Aluminum‐saturated soils equilibrated with Ca solutions at pH 8.4 retained only 50 to 70% as much added cation as soils equilibrated with solutions of combined but equal total quantities of Ca and Mg. Furthermore, the soils equilibrated with Ca and Mg retained 2.4 to 4 times more Mg than Ca. The enhanced retention of Mg was attributed to Mg‐Al double hydroxide formation. Sequential leaching of the equilibrated soils with NaOAc at pH 8.2, 7.0, and 5.0 and 0.05 M HCl indicated that Mg‐Al double hydroxide was not readily solubilized until the pH dropped below neutral. It was concluded that the pedogenic formation of an ephemeral Mg‐Al double hydroxide was a probable consequence of calcareous loess deposition on acid, residual soils during the Wisconsinan glaciation.
Emissions of Non‐Methane Organic Compounds and Carbon Dioxide from Forest Floor Cores
Authors: Hanson P. J. , Hoffman W. A. 
Published: July 2010

AbstractForest floor emissions of CO2 and non‐methane volatile organic compounds (NMOCs) were measured to determine their contribution to C losses from forests. Forest floor cores 19 cm in diameter and approximately 10 cm deep were obtained from beneath loblolly pine (Pinus taeda L.), oak‐maple (Quercus‐Acer), and yellow‐poplar (Liriodendron tulipifera L.) trees on the Walker Branch Watershed, Oak Ridge, TN. The cores were enclosed in an open system gas exchange instrument from which inlet and outlet concentrations of NMOC emissions were sampled. The NMOCs were quantified with a C trap/cryofocus/gas chromatography approach. Total NMOC emissions from the forest floor cores ranged from 15 to 90 nmol C m−2 s−1, and differed beneath each tree species. Cores from beneath yellow‐poplar trees had nearly an order of magnitude greater C equivalent efflux than cores from beneath either the pine or oak‐maple trees. Monoterpenes comprised virtually all of the NMOC emissions from the cores. The C equivalent efflux of NMOCs from the forest floor cores was one to two orders of magnitude less than rates of CO2 efflux (4–8 µmol m−2 s−1), indicating a very minor role for litter and soil NMOC emissions in stand C cycling.
Extractable Anions in Soils following Wildfire in a Sagebrush‐Grass Community
Authors: Blank Robert R. , Allen Fay , Young James A. 
Published: July 2010

AbstractField and laboratory research was conducted to measure changes in extractable anions following wildfire in sagebrush (Artemisia tridentata Nutt.)‐grass communities. Two sites were studied along the eastern Sierra Nevada front in northeastern California on coarse‐textured Haploxerolls and Haplargids formed from granitic parent materials. Soils were extracted with 0.15% KCl and analyzed with high‐performance anion exchange chromatography. Compared with unburned soils, significant (P ≤ 0.05) decreases in NO−3 and orthophosphate, and significant increases in SO2−4, acetate, formate, oxalate, and glycolate occurred immediately after wildfire in the surface 5 cm of under‐shrub soil. Concentrations of organic acids in burned under‐shrub soils increased significantly (P ≤ 0.05) in the weeks following a wildfire. In shrub interspaces, largely occupied by cheatgrass (Bromus tectorum L.), concentrations of anions were similar in unburned and post‐wildfire soils. Laboratory heating of under‐shrub soil indicated that maximum amounts of KCl‐extractable organic anions are produced at temperatures between 150 and 350°C, and that the length of time (up to 30 min) the soil was exposed to a given temperature considerably affected these amounts. Elevated concentrations of organic acids may influence seed germination, plant establishment, and mineral nutrition.
A Solute Transport Model for the Acid Leaching of Copper in Soil Columns
Authors: Montero Juan Pablo , Muñoz José Francisco , Abeliuk Roberto , Vauclin Michel 
Published: July 2010

AbstractModeling solution mining technique has recently received much attention in order to estimate metal recovery rates. We studied the acid leaching of Cu minerals found in mine tailings using a mathematical transport model and lab‐scale experiments on both batches and saturated soil columns. The model is a one‐dimensional macroscopic solute transport model that considers simultaneously (i) the convection, dispersion, and consumption of H2SO4, and (ii) the convection, dispersion, solubilization, and adsorption‐desorption of Cu. Time‐dependent batch experiments were carried out to understand the relationship between H2SO4 consumption and Cu extraction in tailing Cu materials under stagnant conditions. Additionally, miscible‐displacement experiments were conducted to obtain empirical data on Cu recovery in saturated soil columns that receive a constant pulse of H2SO4 and were designed to check the model's capability to simulate the transport phenomena. This was done by estimating the model parameters independently from the batch experiments. Since some findings from both experiments were consistent with each other, modeling assumptions, such as a second‐order kinetic relationship for Cu dissolution (by H2SO4) and a first‐order equilibrium isotherm for Cu, were appropriate in order to simulate the Cu recovery concentration at the outlet of each column. Finally, model equations were solved using finite differences and analytical solutions for Cu and H2SO4 transport equations, respectively, and model parameters were estimated using least squares techniques.
Oxide Surface‐Catalyzed Hydrolysis of Carboxylate Esters and Phosphorothioate Esters
Authors: Torrents Alba , Stone Alan T. 
Published: July 2010

AbstractPathways and rates of organic pollutant transformation may be altered through interaction with the surfaces of oxides and other soil minerals. We examined oxide surface‐catalyzed hydrolysis of representative carboxylate esters and phosphorothioate esters. Ester and hydrolysis product concentrations were monitored in acetate‐buffered suspensions containing 10 g L−1 oxide. Carboxylate esters found susceptible to catalysis in this work possess an auxiliary ligand donor group that, along with the carbonyl O group, form a chelate with surface‐bound metal atoms. Esters possessing an O‐donor auxiliary group (e.g., phenyl salicylate) are susceptible to catalysis by Al2O3, TiO2, and FeOOH surfaces. Esters possessing a N‐donor auxiliary group (e.g., phenyl picolinate) are no longer susceptible to catalysis by Al2O3, reflecting the poor affinity of N‐donor groups for Al complexation. Methyl chlorpyrifos is the most susceptible of the three phosphorothioate esters to oxide‐catalyzed hydrolysis; it possesses an auxiliary ligand donor group analogous to the carboxylate esters examined. Methyl parathion and ronnel, which do not possess a suitable auxiliary ligand donor group, are also susceptible to oxide‐catalyzed hydrolysis, indicating that chelate formation is not required in order for surface catalysis to occur. The presence of methanol and acetonitrile cosolvents diminishes the catalytic effect. The widespread use of these cosolvents in fate studies may have caused rates of oxide and mineral surface‐catalyzed hydrolysis reactions to be underestimated.
Organic Phosphorus Effects on Sink Characteristics of Iron‐Oxide‐Impregnated Filter Paper
Authors: Robinson J. Stephen , Sharpley Andrew N. 
Published: July 2010

AbstractThe effect of dissolved organic P (DOP) (p‐nitrophenyl phosphate, sodium myo‐inositol hexaphosphate, and β‐glycerophosphoric acid) on the ability of Fe‐oxide‐impregnated filter paper (Pi test) to act as a sink for dissolved inorganic P (DIP) was investigated. The efficiency of DIP recovery from strips equilibrated with DIP plus DOP was also studied. This information is needed to assess the accuracy of the Pi test to estimate bioavailable P (BAP) in soils and agricultural runoff containing high concentrations of DOP (up to 5 mg L−1). Iron‐oxide strips removed on average 100% DIP and 99% DOP during a 16‐h solution‐strip equilibration at 25°C. Thus, none of the DOP compounds affected the P‐sink characteristics of the Fe‐oxide strip. Recoveries of DIP by 0.1 M H2SO4 and 0.5 M NaOH, from strips equilibrated with DIP plus p‐nitrophenyl phosphate, averaged 95%; with DIP plus β‐glycerophosphoric acid, recoveries averaged 97%. However, amounts of DIP recovered by 0.1 M H2SO4 from strips equilibrated with DIP plus sodium inositol hexaphosphate were greater than those added. As 0.5 M NaOH did not hydrolyze sodium inositol hexaphosphate and DIP recovery averaged 95%, use of NaOH as strip extractant is recommended for soils and runoff samples containing high DOP concentrations.
Determining Root Activity Distribution by Measuring Surface Carbon Dioxide Fluxes
Authors: Ben‐Asher J. , Ephrath J. E. , Cardon G. E. , Phene C. J. , Peters D. , Rolston D. E. , Biggar J. W. 
Published: July 2010

AbstractMethods for determining root characteristics and distributions are time consuming and tedious. Indirect approaches could decrease the effort required to obtain information on root distributions. The objectives of this study were to measure soil surface CO2 flux and to relate these measurements to root properties. Two chambers to measure CO2 fluxes at the soil surface were tested for use in root activity studies. One chamber was a 0.75‐L cylinder and the other was a 7.1‐L cubic chamber. The bottom edges of both chambers were inserted 1 to 2 cm into the surface soil. The increase in CO2 concentration in the chambers was measured with infrared gas analyzers. The following were used to evaluate the applicability of the approach for root studies: (i) test of the relationship between CO2 surface fluxes and root characteristics (length, area, mass, and number) in the root zone of a mature almond (Prunus amigdalus Batsch. cv. Butte) orchard and a corn (Zea mays L.) field, and (ii) evaluation of temperature and solar radiation effects on CO2 soil surface flux. The results showed that surface CO2 fluxes were proportional to the logarithm of root characteristics, i.e., large changes in root characteristics were associated with small changes in flux. Soil temperature had a distinct effect on measured CO2 surface flux. There was a clear diurnal cycle for soil surface CO2 flux, which peaked near solar noon and maximum solar radiation. Acceptable correlations between the major root characteristics and surface CO2 flux suggest that this approach can provide vital information on root activity.
Clay‐Fixed Labeled Ammonium as a Source of Available Nitrogen
Authors: Feigenbaum Sala , Hadas Aviva , Sofer M. , Molina J. A. E. 
Published: July 2010

AbstractIn soils low in organic matter but high in clay mineral content, the fixation and release of NH4 by soil clay may have a significant impact on available N, in addition to the organic N. The objective of this work was to evaluate the contribution that nonexchangeable NH4, newly fixed by clay minerals, may have in KCl‐extractable N in soil. The source of clay‐fixed NH4 was beidellite clay equilibrated with (15NH4)2SO4 and then washed with either KCl or CaCl2 solutions. Two calcareous soils were mixed with differently treated beidellite at a 2:1 ratio, mixed with sand, and incubated for 56 d at 30°C and 60% of water‐holding capacity. Periodically, NH+4 and NO−3 extractable in 1 M KCl and their 15N abundance were determined. Controls for each beidellite treatment were incubated without soil. Concentrations of KCl‐extractable N were considerably higher when beidellite was saturated with Ca than when it was saturated with K throughout the experiment. They increased with time in the presence of soil and remained unchanged in the controls. The recovery of beidellite‐15NH4 as KCl‐extractable N in soil showed a continuous release of clay‐fixed NH4 from K‐beidellite, from 4.8 and 6.5% of added NH4 at 1 d to 10.2 and 12.5% at 56 d in the two soils. The recovery of N from Ca‐beidellite was approximately 30% of added N already at 1 d, but the change with time was inconsistent in the two soils. The difference in the release of N from Ca‐saturated beidellite compared with that of K‐saturated beidellite was attributed to incomplete collapse of the mineral lattice in the Ca‐saturated clay, which enabled renewal of exchangeable NH4 and rendered the interlayer nonexchangeable NH4 more accessible to exchange with K or to biological activity. In K‐saturated clay, the interlayer nonexchangeable NH4 was trapped and, consequently, the release was slow.
Spatial Variability in Alluvium Properties at a Low‐Level Nuclear Waste Site
Authors: Istok J. D. , Blout D. O. , Barker L. , Johnejack K. R. , Hammermeister D. P. 
Published: July 2010

AbstractGeological and statistical models for the spatial variability of soil properties are needed to predict field‐scale water flow and solute transport but only limited information is currently available on unsaturated soils below the root zone. Spatial variability of selected physical and hydrologic properties was quantified for fine‐ and coarse‐grained alluvial deposits at a low‐level nuclear waste disposal site on the Nevada Test Site. Gravimetric water content (w), bulk density (ρb), saturated hydraulic conductivity (Ks), and particle‐size distribution were determined for vertical and horizontal core specimens and bulk samples collected from 183‐m‐long horizontal transects in two existing waste disposal trenches located on a single alluvial fan. The transects were approximately aligned parallel and perpendicular to the principal direction of sediment transport. Properties were modeled as either normally or lognormally distributed random variables. Sample coefficients of variation were smallest for ρb and largest for log(Ks); a weak correlation was identified between log(Ks) and the grain‐size parameter d10. Particle‐size distributions for the fine‐ and coarse‐grained materials were different and significant differences in the natural logarithm of saturated hydraulic conductivity, log(Ks), existed between coarse and fine layers in an excavation aligned with the principal direction of alluvium deposition but not in a perpendicular direction. Differences in log(Ks) for vertical and horizontal cores were not significant. Sample variograms were described by combinations of pure nugget and spherical model structures with correlation lengths ranging from <2 to 61 m.
Converting Root Numbers Observed at Minirhizotrons to Equivalent Root Length Density
Authors: Merrill S. D. , Upchurch D. R. 
Published: July 2010

AbstractRoot length density (RLD) is the measure of plant root growth having greatest general utility. The use of clear material observation tubes, known as minirhizotrons (MR), in field soil has proved to be an effective method for measurement of root growth dynamics. To convert numbers of roots observed at MRs to equivalent bulk soil RLD, workers have used empirical and time‐costly calibrations with soil sample‐derived RLD. A modified version of an earlier theory for converting MR observations to soil RLD is presented. The theory is based on calculation of the mean root length that would occur inside a MR if it were not present and if all possible root growth orientations at a root interception by the MR are considered. The theory indicates that a dimensionless factor ranging in value from 3.0 to 3.8 will convert MR interceptions per incremental observation area to equivalent soil RLD for MR tubes ranging in diameter from 9.6 to 2.5 cm. An experimental test with cotton (Gossypium hirsutum L.), presented here, and one from the literature using wheat (Triticum aestivum L.), both give numerical support to the theory. Another test from the literature using cotton appeared to indicate that the theory numerically overpredicted RLD. In contrast, a test in corn (Zea mays L.) presented here showed the theory underpredicting RLD. Methodological factors appeared to weaken the significance of the latter test. Inaccuracies in RLD determination from soil sampling may affect the accuracy of empirical calibrations of MR tubes to an extent comparable to uncertainties about the predictive accuracy of the theory.
Effect of pH and Ionic Strength on Boron Adsorption by Pyrophyllite
Authors: Keren R. , Sparks D. L. 
Published: July 2010

AbstractThe negative electrical field around clay particles whose edge thickness is small relative to the Debye length of the diffuse double layer associated with the planar surfaces may spill over into the edge region. Such a spillover may affect B adsorption by the clay. This study was conducted to determine the effect of edge surface properties of 2:1 clay on B adsorption. Pyrophyllite, which shows little deviation from the ideal formula of dioctahedral structure of 2:1 clay type, was used for that purpose. Boron adsorption by pyrophyllite was studied at 25.0 ± 0.5°C at ionic strengths of 0.005, 0.01, and 0.1 mol L−1 for pH 7 and 9 and ionic strengths of 0.01 and 0.1 mol L−1 for pH 5. It was suggested that B is specifically adsorbed via ligand exchange to the structural Al located on the edge surfaces. Boron adsorption increased with increasing ionic strength. The effect of ionic strength on B adsorption was smaller at pH 7 than at pH 9, consistent with the decrease in B(OH)−4 activity fraction in equilibrium solution at pH 7 and the low affinity of the clay to B(OH)3. The effect of ionic strength on B adsorption was small at pH 5, attributable to the weak electrical field at this pH (electrical potential, ψo = −47 mV) together with the low B(OH)−4 concentration and the low affinity of the clay for B(OH)03. The higher capacity of pyrophyllite, in comparison to montmorillonite, to adsorb B at pH 9 where the ψo at the edge surfaces of the clay is ‐285 mV, supports the hypothesis that the negative electrical field associated with this planar surfaces affects B adsorption.