bluuebunny/crossref_metadata_2025_split huggingface dataset:
Zinc and Cadmium Effects on Rhizobia and White Clover using Chelator‐Buffered Nutrient Solution
Authors: Ibekwe A. M. , Angle J. S. , Chaney R. L. , van Berkum P. 
Published: July 2010

AbstractToxicity of metals to plants and microbes depends on the chemical activities of metals in the soil solution. To examine the effects of Zn2+ and Cd2+ activities on white clover (Trifolim repens L.), Rhizobium leguminosarum bv. trifolii, the infection process, and nodulation, a growth chamber study was conducted. The chelator EGTA [ethylenebis(oxyethylenetrinitrilo) tetraacetate] was used to buffer Zn2+ and Cd2+ activities in nutrient solution from pZn2+ = 8.0 to 5.0 and pCd2+ = 10.5 to 8.0 mol L−1. Plants grown in pZn2+ = 5.0 and pCd2+ = 8.75 and 8.65 were stunted and chlorotic with interveinal necrosis. Shoot concentrations of Zn and Cd averaged >200 and 40 mg kg−1, respectively, in these treatments. This resulted in a 60% yield reduction for plants grown in pZn2+ = 5.0. In pCd2+ = 8.75 and 8.65, 40 and 60% yield reductions, respectively, were observed. In treatments where mineral N was supplied to plants, 20 to 35% greater shoot yield was recorded compared with plants inoculated with rhizobia, presumably due to a period of starvation for N due to the delay in the onset of fixation. Nodulation was observed at all Zn2+ and Cd2+ activities. At pCd2+ = 8.75 and 8.65, however, there was a delay in nodulation. Most nodules were effective in N2 fixation irrespective of Zn2+ and Cd2+ activity. Enumeration of viable cells showed a significant decline of total cell counts from 105.5 cells mL−1 in the control to 105.0 and 104.5 cells mL−1 at the highest Zn2+ and Cd2+ activities, respectively. At the activities studied, Cd was more toxic to rhizobia and nodulation than Zn. At the highest Cd2+ activity, however, plants were killed within 48 h due to metal toxicity. This technique showed for the first time that toxicity of Zn and Cd was greater to plants than to rhizobia.
Two Indices of Soil Structure Based on Prediction of Soil Water Processes
Authors: Geeves G. W. , Murphy B. W. , Cresswell H. P. 
Published: July 2010

AbstractEvaluation of soil structure should reflect the nature and degree of soil physical limitations to land use for local climatic conditions. This can be achieved through mechanistic simulation of soil‐plant‐atmosphere processes. We propose two alternative indices of soil structure, based on predicted infiltration. The potential runoff index (PRI) is the runoff predicted from a 1‐in‐20‐yr average recurrence interval storm event of 30‐min duration using an event‐based soil water infiltration model that utilizes Richards' equation. The runoff recurrence index (RRI) is the average recurrence interval of a 30‐min duration storm of intensity just sufficient to result in runoff. These indices were applied to data from 37 sites (mainly Palexeralfs, but including Natrixeralfs, Rhodoxeralfs, and Haploxeralfs) in southeastern Australia, where rainfall partitioning between infiltration and runoff can significantly affect agricultural production. Sites with different land use histories were ranked on the basis of the RRI. Woodland sites have a significantly greater mean ranking (mean ranking [RRI] = 33.5), indicating more favorable soil structure, compared with less conservative agricultural land uses such as heavily grazed pasture (mean ranking = 11.7) or intensively cultivated cropping where stubble was not retained (mean ranking = 12.4). Both indices integrate the effects of soil structure, as represented through soil hydraulic properties, with local rainfall characteristics. They also account for soil horizon interactions influencing infiltration. The saturation‐excess runoff generation predicted for 12 of the 37 sites indicates that structural amelioration of B horizon soil should be a high priority at these sites.
Forest Soil Sulfur in the Adirondack Mountains: Response to Chemical Manipulations
Authors: Mitchell Myron J. , Santore Robert C. , Driscoll Charles T. , Dhamala Bhesh R. 
Published: July 2010

AbstractChemical manipulations were conducted on plots during the growing seasons from 1991 through 1993 in four forest ecosystems (Woods Lake [WL], Pancake‐Hall Creek [PHC], Huntington Forest [HF], and Pack Forest [PF]) in the Adirondack Mountains of New York. Sulfate was added as (NH4)2SO4 (all sites at 1000 and 2000 molc ha−1 yr−1), H2SO4 (WL and HF at 1000 molc ha−1 yr−1), or (Ca,Mg)SO4 (WL and HF at 1000 molc ha−1 yr−1). At WL and HF additional sets of plots were also treated with HNO3 (1000 molc ha−1 yr−1). Soil solutions were sampled at 15 and 50‐cm depths. Changes in the S constituents of the soil were evaluated by buried mineral soil bags installed below the forest floor. Additions of SO2−4 increased solution SO2−4 and total S and phosphate‐extractable SO2−4 in soil. Although organic S constituted >71% of the total soil S, no treatment effects on organic S were found. The response of SO2−4 was not influenced by the form of addition. Extractable sulfate and soil solution SO2−4 both increased with increases of (NH4)2SO4. For the three hardwood sites (WL, PHC, and HF), there was a positive relationship (P < 0.05) between soil solution SO2−4 concentration at 15 cm and extractable SO2−4 in soil bags, suggesting that these Haplorthod soils responded similarly to S inputs. For the Typic Udipsamment at PF, beneath red pine (Pinus resinosa Aiton), no such relationship was found. The similarity of response of Haplorthod soils suggests that similar soils across the Adirondack Mountains will show synchronous responses to S inputs.
Nonhydrolyzable Organic Nitrogen in Soil Size Separates from Long‐term Agricultural Experiments
Authors: Leinweber P. , Schulten H.‐R. 
Published: July 2010

AbstractTotal N (Nt), hydrolyzed N, NH3‐N, and nonhydrolyzed N were determined in soil particle‐size separates from unfertilized or manured treatments in five long‐term (15–108 yr) experiments in Germany. The concentrations of all N fractions (i) increased with decreases in particle size and (ii) were higher in samples from manured treatments. Irrespective of particle size and soil management, nonhydrolyzed N accounted for 7 to 31% of Ni (mean: 19%). On average, 53% of nonhydrolyzed N could be volatilized by pyrolysis. Field ionization mass spectra of the pyrolyzates of two hydrolysis residues showed that N heterocycles are major constituents of nonhydrolyzed N. In addition, 28 to 34% of total ion intensity was assigned to low‐mass N compounds and aliphatic nitriles and amides. Shifts to higher volatilization temperatures with maxima at 450 to 520°C in the thermograms of all N compounds indicated that chemical stability, or strong bonds to soil minerals, are main reasons for the resistance of these molecules to acid hydrolysis. Curie‐point pyrolysis‐gas chromatography/mass spectrometry using a N‐selective detector and library searches enabled the identification of aliphatic, carbocyclic, and aromatic amines and nitriles, benzothiazole, substituted imidazoles, substituted pyrroles and pyrrolidine, substituted pyrazoles, an isoquinoline derivative, substituted pyrazines and piperazine, pyridine, and methylpyridine. In addition, low‐mass N compounds such as hydrocyanic acid, N2, nitrogen monoxide, isocyanomethane, and hydrazoic acid were assigned so that, in total, 37 compounds were identified in the pyrolyzates of nonhydrolyzed N. Within this fraction, we distinguished (i) proteinaceous materials, nonhydrolyzable probably due to binding or occlusion by pedogenic oxides, and (ii) highly alkyl‐substituted N heterocycles, which are structural constituents of stable humic substances.
Soil Solution Speciation of Lead(II): Effects of Organic Matter and pH
Authors: Sauvé Sébastien , McBride Murray , Hendershot William 
Published: July 2010

AbstractThe effects of adjusting the levels of soil organic matter in a Pb‐contaminated soil on the solubility and free Pb2+ speciation were studied within the pH range 3 to 8. A contaminated orchard soil containing 284 mg Pb kg−1 was treated with leaf compost to increase soil organic matter and with H2O2 to decrease it, yielding six soil organic matter levels between 25.6 and 83.7 g C kg−1. The equilibrated solutions were then analyzed for total dissolved Pb by graphite furnace atomic absorption spectrometry and for labile Pb by differential pulse anodic stripping voltammetry (DPASV). The labile Pb values were used to calculate the free Pb2+ activity based on the assumption that organo‐Pb complexes are not DPASV‐labile. The data showed that 30 to 50% of dissolved Pb is present as soluble OM complexes at low pH and up to 80 to 99% at near‐neutral pH. The solubility of Pb shows a linear decrease from pH 3 to 6.5 and is independent of soil organic matter in that pH range. From pH 6.5 to 8, higher pH promotes the formation and dissolution of organo‐Pb complexes, which increase Pb solubility. In this pH range, higher organic matter content results in higher concentrations of dissolved and labile Pb.
Survival of Pseudomonas fluorescens 2‐79RN10 in Clay Powders Undergoing Drying
Authors: Morra Matthew J. , Chaverra Martha H. , Dandurand Louise‐Marie , Orser Cindy S. 
Published: July 2010

AbstractAlthough clay minerals differentially alter bacterial survival during desiccation, the mechanism responsible is speculative. Our objective was to determine how clay water content might control the enhanced survival of Pseudomonas fluorescens (Migula) 2‐79RN10 in the presence of various clays. Pseudomonas fluorescens 2‐79RN10 was suspended in phosphate buffer, mixed into Ca2+‐saturated pyrophyllite, kaolinite, clinoptilolite, and montmorillonite (0.5 mL of cell suspension g−1 clay), and air dried at 20°C. Bacterial colony‐forming units (CFU), gravimetric water, and water activity (aw) were determined when mixed and at 9, 14, 19, 28, and 48 h after mixing. Bacterial survival was greatest in air‐dried montmorillonite and lowest in kaolinite. The rate of change in aw, final aw values, and rate of gravimetric water loss were similar for all clays. However, aw values during the initial stage of drying varied because the same cell‐suspension volume was amended to equivalent weights of clays possessing different surface areas. The length of time prior to decreases in aw varied in the order: kaolinite > clinoptilolite > pyrophyllite > montmorillonite, a sequence inversely proportional to survival. Alteration of clay particle size and amendment with different cell‐suspension volumes showed that increased bacterial survival could be achieved by shortening the time aw remained elevated. Increased survival of 2‐79RN10 is thus promoted by cell‐clay interactions resulting from more rapid decreases in aw values during the initial stages of drying. Our results have relevance to bacterial survival in clay formulations and soil.
Human‐Influenced Soils from an Iron and Steel Works in Naples, Italy
Authors: Buondonno C. , Murolo M. , Pugliano M. L. , Ermice A. , Buondonno A. 
Published: July 2010

AbstractThe study of soils formed by human activities is one of the concerns of modern pedology. In Italy, data on highly human‐disturbed soils are not available. We investigated the soils from a recently dismantled iron and steel production plant, and compared them with natural soils in undisturbed adjacent areas. The industrial activity in question started 80 yr ago. The dominant morphology of the disturbed soils results from the stratification of materials used in and derived from the industrial process, which were variously mixed with earthy materials. Layers with variable thickness occur up to the 2‐m depth. The spoil layer sequence is rarely interrupted by an applied natural soil, or in situ formed horizons, indicating the continuity of material deposition. Natural subsurface primary horizons are either obliterated or highly disturbed. We also recognized highly disturbed soils without significant spoil materials. All soils show high variability in their characteristics. They also have morphological and chemical features, such as horizonation, pH, organic C and total N content, distinctly different from those of natural soils. Problems emerged in classifying the investigated soils consistently with the current requirements of the U.S. soil taxonomy. To overcome such difficulty, we propose the adoption of the foundric subgroup of the Xerorthents. Such soils may be of interest in the discussion of the International Committee on Anthropogenic Soils (ICOMANTH), which is charged with studying and defining criteria for an appropriate taxonomic classification of highly human‐influenced soils.
Duripans of Southwestern Idaho: Polygenesis during the Quaternary Deduced through Micromorphology
Authors: Blank R. R. , Cochran B. , Fosberg M. A. 
Published: July 2010

AbstractThere is uncertainty regarding the pedogenesis of duripans on the Owyhee Plateau of southwestern Idaho. Micromorphology was used to deduce the role of polygenesis in their formation. Data suggest that during the Pleistocene, duripans were cyclically subaerially exposed, then recovered by eolian dust. Two lines of evidence indicate past duripan exposure. First, sinuous laminar fabrics with lenticular voids, which occur within most duripan plates, are similar to the fabrics produced in arid regions by the action of lichens and cyanobacteria at the soil surface. Second, a laterally extensive air‐fall tephra layer in the middle of a duripan plate was deposited at one sampling location, indicating the duripan or protoduripan was exposed at the ground surface. A suggested model to explain the data is as follows: (i) during cold stages of the Quaternary, periglacial processes, possibly assisted by eolian deflation, caused the truncation of loose soil material overlying the duripan; (ii) cryptogamic organisms then colonized the exposed duripan surface and produced distinctive fabrics; (iii) in response to the increased production and delivery of eolian dust during interglacials, the duripan was recovered. Pedogenesis during interglacial times resulted in precipitation of CaCO3, thereby thickening the upward‐developing duripan and preserving micromorphological signatures of subaerial exposure. At higher elevations in this region, large‐scale removal of unconsolidated soil may have occurred during full glacial stages of the middle and earlier Pleistocene. Maximal development of duripans may require polygenesis.
Kinetics of Crop Residue Decomposition: Variability among Crops and Years
Authors: Gilmour John T. , Norman Richard J. , Mauromoustakos Andy , Gale Paula M. 
Published: July 2010

AbstractA kinetic description of crop residue decomposition makes assessment of the global C cycle and nutrient cycling possible for a wide variety of crop production systems. It was the objective of this study to compare decomposition kinetics of soybean [Glycine max (L.) Merr.], rice (Oryza sativa L.) and grain sorghum [Sorghum bicolor (L.) Moench.] residues for 3 yr to determine if variability among years was similar to that among crops. Crop residues were incorporated into a Crowley silt loam (fine, montmorillonitic, thermic Typic Albaqualf) soil and incubated at 25°C under optimum soil moisture for 54 to 66 d. Initial (0–2‐wk) decomposition was related to crop residue organic N and C/N ratio, while subsequent decomposition was not related to these factors. Decomposition data were evaluated using first‐order kinetics and sequential and simultaneous decomposition models. As a result of the variability among crops and years, which was not related to residue characteristics (organic N or C/N ratio), it was concluded that mean estimates of rate constants and the rapid fraction would provide a reasonable estimate of crop residue decomposition for a variety of crops using either decomposition model. For the sequential model, mean rapid‐ and slow‐fraction rate constants were 0.025 and 0.0091 d−1, respectively, while the rapid fraction was 31%. Parallel values for the simultaneous model were 0.21 and 0.0080 d−1 and 20%.
Redox Status, Poultry Litter, and Phosphorus Solubility in Atlantic Coastal Plain Soils
Authors: Vadas P. A. , Sims J. Thomas 
Published: July 2010

AbstractArtificially drained, agricultural soils in Delaware's Inland Bays watershed are high in P from poultry litter and fertilizer applications. The potential loss of P from these soils to drainage waters during soil reduction and reoxidation was investigated. Soil from three artificially drained, cultivated fileds and two wooded areas was collected and characterized as Fallsington sandy loam (fine‐loamy, mixed, mesic Typic Ochraquult), Pocomoke loamy sand (coarse‐loamy, siliceous, thermic Typic Umbraquult), and Osier loamy sand (siliceous, thermic Typic Psammaquent). Topsoils, unamended and amended with poultry litter (PL), and subsoils were reduced for 28 d and reoxidized for 14 d at 25 and 35°C. The soils were analyzed for pH, redox potential (Eh), soluble P and Fe2+, and P fractions (unoccluded Fe‐P and Al‐P, occluded Fe‐P and Al‐P, and Ca‐P) under oxidized, reduced, and reoxidized conditions. Reduction decreased Eh to moderately reduced (200–350 mV) and reduced (−100 to 100 mV) values, and increased pH (0.8 ± 0.1) and soluble Fe2+ (44 ± 24 mg/kg). Reoxidation returned Eh, pH, and Fe2+ to near initial values. Reduction increased soluble P in unamended cultivated topsoils (0.69 ± 0.42 mg/kg), decreased soluble P in amended cultivated topsoils (1.42 ± 1.31 mg/kg), but had little effect in subsoils or wooded soils. Reoxidation decreased soluble P in cultivated topsoils, but increased soluble P in subsoils and wooded soils. Reduction increased the extractability of all P fractions in cultivated topsoils (20 ± 12 mg/kg), but increased only Ca‐P extractability in subsoils and wooded soils (9 ± 3 mg/kg). Reoxidation decreased the extractability of these fractions to near initial values.
In Situ Estimation of the Gaseous Nitrous Oxide Diffusion Coefficient in a Sandy Loam Soil
Authors: van Bochove Eric , Bertrand Normand , Caron Jean 
Published: July 2010

AbstractThe estimation of gas exchanges with the soil is important when assessing gas emission to the atmospheric environment or gas consumption by the soil. This estimation often requires the measurement of the diffusion coefficient of the investigated gas. The aim of this study was to develop an experimental method creating limited soil disturbance and based on simple calculation procedures to determine the diffusion coefficient, Ds, for N2O in soils. This objective was achieved using a N2O mass flow meter that supplied a continuous and constant flow of gas from below the soil surface until a steady‐state N2O concentration gradient with depth was obtained. The coefficients of diffusion were calculated daily for 6 d, under steady‐state concentration gradient, using Fick's first law. The mean value of the diffusion coefficient for N2O was 1.26 × 10‐6 m2 s‐1 (CV = 25%) at 0.16 m3 m‐3 of air‐filled porosity. This value was validated by a transient‐state laboratory method using soil cores and compared with empirical estimations of Ds from air‐filled porosity determinations. The two experimental methods produced similar values for Ds and both provided more accurate estimates than the empirical models. The proposed method can be applied to other gases provided an empirical model relating Ds to Do (gas diffusivity in free air) is first established. A theoretical study identified the threshold air‐filled porosity values below which the flux density must be adjusted to maintain the validity of the Ds calculations.
Estimating Microscale Spatial Distribution of Conductivity and Pore Continuity using Computed Tomography
Authors: Rasiah V. , Aylmore L. A. G. 
Published: July 2010

AbstractDespite the importance of information on the spatial distribution of unsaturated hydraulic conductivity (Kus) at microscale in soil, experimental determination of this property is difficult. The objectives of this study were to: (i) seek a simple, but reliable, procedure for the estimation of Kus at microscale and (ii) determine the sensitivity of the estimates to wetting‐induced changes in selected structural parameters (porosity, ɛ, surface fractal dimension, D, and pore continuity, PC). Using computer‐assisted tomography (CAT), spatial distributions of soil water content (θ) and changes in ɛ that occurred during wetting were monitored at 2 by 2 mm resolution at 1‐cm depth increments in water‐stable (WSA) and unstable aggregate (USA) columns. The Fuentes theoretical equation, which requires data on saturated hydraulic conductivity (Kɛ), θ, ɛ, and D, was used for the estimation of the spatial distribution of Kus. The spatial distribution of θ in WSA columns ranged from 0.113 to 0.327 cm3 cm‐3 and from 0.175 to 0.567 cm3 cm‐3 in the USA columns. The spatial distribution of ɛus ranged from 0.46 to 0.74 and was used in the computation of D and PC. Values of Kɛ ranged from 0.006 to 0.745 cm h‐1. The spatial distribution of Kus ranged from 6.87 × 10‐4 to 1.49 × 10‐2 cm h‐1 in WSA compared with 7.3 × 10‐4 to 4.11 × 10‐2 cm h‐1 in USA. Pore continuity, θ, D, and initial aggregate diameter (x) accounted for 94 to 95% of the variability in Kus distributions. The results indicate that reliable estimates of Kus distributions at microscale can be computed from single‐source CAT‐derived data on θ and ɛ.
Use of Statistical Tests to Describe the Basic Distribution Pattern of Iron Oxide Nodules in Soil Thin Sections
Authors: Arocena J. M. , Ackerman J. D. 
Published: July 2010

AbstractSoil formation is often associated with the spatial reorganization of soil components, particularly Fe oxides. However, the methods available to describe the spatial distribution of Fe oxides generally lack measurable parameters that allow comparison between different types of soils. In this work, we demonstrate the use of statistical methods (e.g., χ2 goodness‐of‐fit test, mean, variance, and cluster coefficient) to describe the basic distribution pattern of Fe oxide nodules in soil thin sections. Using a computer, we mapped the spatial distribution (i.e., x and y coordinates) of Fe oxide nodules in six soil thin sections from the B horizons of three sandy soils from Alberta, Canada. We calculated the statistical tests at a range of grid sizes (2–10 mm) with a Fortran program to (i) examine the effect of grid size on the statistical description of the distribution and (ii) determine the “appropriate scale of observation” for each thin section. We defined this scale as the grid size at which the mean number of observation is at least five, which was found to vary in size from 5 to 9 mm in our samples. We recommend the determination of the appropriate scale of observation before any statistical description of the Fe nodule distribution. In all but one of our six samples, the statistical distribution of nodules was clustered; the remaining one was uniform in distribution. The methods described in this study provide statistical methods whereby results from different studies can be compared.