bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of Pine Plantations and Adjacent Deciduous Forests on Soil Calcium
Authors: Wilson David M. , Grigal D. F. 
Published: July 2010

AbstractPotential depletion of soil Ca and forest sustainability continue to be concerns. Previous studies from the north‐central USA have reported depletion of Ca in soil but increased amounts in the overstory of deciduous compared with coniferous forests, with total system Ca remaining constant. To determine if those reports were generalizable, we sampled 38 pairs of red pine (Pinus resinosa Ait.) plantations and adjacent deciduous stands across the area. Records indicated site similarity before plantation establishment. Neither the texture of the rooting zone (0–32 cm), nor the texture, pH, or Ca content of the 32‐to 100‐cm soil layer differed between forest types, further supporting site similarity. Stands were similar in biomass, but because of lags in plantation establishment, the deciduous stands were older (60 vs. 45 yr). The deciduous stands had greater mass of Ca in the overstory and higher Ca concentration in the 0‐ to 4‐cm mineral soil layer. Both Ca concentration and mass were greater in lower layers of the rooting zone (to 32 cm) under pine. Neither mass of Ca in the forest floor nor in mineral soil to 100 cm differed between types. Contrary to earlier reports, total system Ca was greater in deciduous stands. Our results and others from glaciated areas suggest that deeper soil layers provide minimal Ca to forest stands during a normal rotation. The initial quantity of Ca in the near‐surface soil and the input‐output balance determine Ca status of a site, but the role of deciduous forests in conserving the inputs deserves further scrutiny.
Soil Sampling Technique for Band‐Fertilized, No‐Till Fields with Monte Carlo Simulations
Authors: James D. W. , Hurst R. L. 
Published: July 2010

AbstractBand application of P fertilizer in no‐till fields results in extremely variable soil test P (STP) along lines perpendicular to the bands. This variation may be represented by two interlaced populations, each with a unique STP mean and standard deviation. The objectives of this research were to: (i) characterize STP populations in a band‐fertilized field; (ii) use these population characteristics to calibrate a Monte Carlo based model to simulate STP populations; and (iii) use simulated STP populations to evaluate different soil sampling procedures. A corn (Zea mays L.) field was band fertilized with P, and 1 yr later STP (mg P kg−1) was measured on individual soil cores with the bicarbonate extraction procedure. Out‐band STP mean and standard deviation (SD) were 13.9 ± 4.75, in‐band STP mean and SD were 127.4 ± 29.7, and composite STP mean and SD were 23.3 ± 28.69. A computer simulation model based on the Monte Carlo technique reproduced the observed populations very closely. The results show that the number of completely random soil cores needed to represent a band‐fertilized field is prohibitive. Rapid collection of a single representative composite sample with equipment capable of taking a slice of soil across the fertilizer band and accurately weight in‐band and out‐band STP by volume is recommended.
Phosphorus Sorption Characteristics of Everglades Soils along a Eutrophication Gradient
Authors: Richardson C. J. , Vaithiyanathan P. 
Published: July 2010

AbstractWe examined the P sorption characteristics of northern Everglades peat soils along a eutrophication gradient to understand the P retention efficiency of the soils. The amount of phosphate adsorbed on the soils (Q) and the zero equilibrium phosphate concentration supported by the soils (EPCo) exhibited a linear decrease with distance from the inflow structures supplying agricultural drainage (r2 = 0.74 and 0.71, respectively; P < 0.05; n = 18). Values of Q and EPCo for the enriched soils are an order of magnitude higher than for unenriched soils. Estimated Q values of the soils compare well with the exchangeable P fraction determined by KCl and HCO3 extraction. Comparison of soil EPCo and pore water PO4‐P values with the surface water PO4‐P concentrations suggests that soils may serve as an additional internal source of P to the overlying water column in nutrient‐enriched areas. Linear phosphate adsorption coefficient (K) of the alkaline Everglades soils is higher than that of acidic pocosin bog peat soils of North Carolina but lower than wetland soils and sediments with a high mineral content. Phosphorus sorption characteristics of the Everglade soils are most likely regulated by CaCO3.
Properties and Variability of Soil and Trench Fill at an Arid Waste‐Burial Site
Authors: Andraski B. J. 
Published: July 2010

AbstractArid sites commonly are assumed to be ideal for long‐term isolation of wastes. Information on properties and variability of desert soils is limited, however, and little is known about how the natural site environment is altered by installation of a waste facility. During fall construction of two test trenches next to the waste facility on the Amargosa Desert near Beatty, NV, samples were collected to: (i) characterize physical and hydraulic properties of native soil (upper 5 m) and trench fill, (ii) determine effects of trench construction on selected properties and vertical variability of these properties, and (iii) develop conceptual models of vertical variation within the soil profile and trench fill. Water retention was measured to air dryness (ψ = 2 × 106 cm water suction). The 15 300‐cm pressure‐plate data were omitted from the analysis because water‐activity measurements showed the actual suction values were significantly less than the expected 15 300‐cm value (avg. difference = 8550 ± 2460 cm water). Trench construction significantly altered properties and variability of the natural site environment. For example, water content ranged from 0.029 to 0.041 m3 m‐3 for fill vs. 0.030 to 0.095 m3 m‐3 for soil; saturated hydraulic conductivity was ≈ 10‐4 cm s‐1 for fill vs. 10‐2 to ≈ 10‐4 cm s‐1 for soil. Statistical analyses showed that the native soil may be represented by three major horizontal components and the fill by a single component. Under initial conditions, calculated liquid conductivity (Kl) plus isothermal vapor conductivity (Kv) for the upper two soil layers and the trench fill was ≈ 10‐13 cm s‐1, and Kl was ≤ Kv. For the deeper (2–5 m) soil, total conductivity was ≈ 10‐10 cm s‐1, and Kl was >Kv. This study quantitatively describes hydraulic characteristics of a site using data measured across a water‐content range that is representative of arid conditions, but is seldom studied.
Characterizing the Dependence of Gas Diffusion Coefficient on Soil Properties
Authors: Jin Yan , Jury William A. 
Published: July 2010

AbstractKnowledge of the gaseous diffusion coefficient is necessary to properly model gas movement in porous media. In this study, a nonreactive tracer (freon‐12) and a reactive tracer (hexafluorobenzene) were used to evaluate the relationship between the ratio of the gas diffusion coefficient in soil (Dsg) to that in free air (Dag) and the volumetric air content (a) with a two‐chamber diffusion system. The measured Dsg/Dag values in our experiments (i.e., the relative gas diffusion coefficients) showed a similar relationship to air content as data obtained from various studies reported in the literature. Our data and values taken from other studies were used to test the validity of various models. When compared with data obtained from experiments with disturbed soils, the Penman model Dsg/Dag = 0.66 a was found to overestimate the measured relative diffusion coefficient, whereas the Millington‐Quirk model Dsg/Dag = a10/3/ϕ2, where ϕ is the soil porosity, underestimated it. Another Millington‐Quirk relationship Dsg/Dag = a2/ϕ2/3, which has been largely overlooked in the literature, was found to provide significantly better agreement with measured relative diffusion coefficients in various disturbed soils of different texture. On the contrary, no universal relationship was found when data from both disturbed and undisturbed soil experiments were evaluated. The Troeh model Dsg/Dag = [(a − u)/(1 − u)]v had the flexibility to fit all of the experimental data when both of the model parameters were varied simultaneously; however, no obvious correlation was found between soil properties and the parameters. The limitations of any universal form for gas tortuosity model in natural soils were analyzed with percolation theory.
Adsorption Isotherms of Poly(vinyl alcohol) on Silicon Oxide
Authors: Schulthess C. P. , Tokunaga S. 
Published: July 2010

AbstractPoly(vinyl alcohol), PVA, is a water‐soluble polymer that is made up of repeating alcoholic and acetate units. Because this polymer is sometimes applied to soils, it is advantageous to fully understand the relative impact on the adsorption behavior of this polymer by each of the functional groups on the polymer. Using adsorption isotherm data, our objective was to elucidate the effect of the alcoholic and acetate groups on the macromolecule's affinity for a Si oxide surface. Seven PVA polymers were chosen for this study to cover a range of polymer sizes (10 000–128 000 g mol‐1) and degree of hydrolysis (78–99%). As the percentage of hydrolysis of the polymer increases (increase in the alcoholic groups, decrease in the acetate groups), the adsorption of the polymer decreases on a mass basis. We propose that the acetate functional groups on the PVA chains encourage the formation of loops by the polymer on the Si surface, which also increases the amount adsorbed on a mass basis. The larger polymers also adsorbed more than the smaller ones. Conformity of the polymer to the Langmuir isotherm indicates that the adsorption is site‐specific. The Langmuir equilibrium constant (K) was determined for the polymer above low surface coverage conditions because the energy of adsorption was stronger at low surface coverage. As the hydrolysis percentage of the polymer was lowered, K increased; this was semi‐independent of the polymer size. Consequently, the acetate functional groups on the PVA chains also enhance the affinity of the polymer toward the surface.
Micromorphologies and Stabilities of Chromium (III) Surface Precipitates Elucidated by Scanning Force Microscopy
Authors: Fendorf Scott E. , Li Guangchao , Gunter Mickey E. 
Published: July 2010

AbstractAscertaining the stability of immobilized contaminants in soils is necessary to assess their potential risk in the environment. The composition, structure, and surface morphology are the principal determinants of a sorbate's reactivity. We investigated Cr(III) precipitates on goethite (α‐FeOOH) and silica (amorphous SiO2) using scanning force microscopy to ascertain the morphology of the surface precipitates. Imaging was performed on both colloidal and single‐particle solids. The colloidal materials were used to simulate solids found within soils, while the single particles provide in situ investigations. Scanning force micrographs reveal that Cr(III) forms a precipitate on α‐FeOOH that distributes over the surface, while on SiO2(amorphous) discrete surface clusters are observed. Based on these results, one would predict that at coverages exceeding monolayer capacity, Cr(III) precipitates on silica would be more reactive and thus have a greater potential for remobilization in the environment than Cr(III) precipitates on goethite. To test this hypothesis we reacted the surface precipitates with oxalate, a common root exudate, and measured the rate and extent of Cr(III) dissolution. The expected greater reactivity of Cr(III) on silica relative to Cr(III) on goethite was supported by the more rapid and extensive oxalate‐induced dissolution of Cr(III); initial dissolution rates were 0.166 mol L‐1 h‐1 for Cr(III)‐silica while only 0.0420 mol L‐1 h‐1 for Cr(III)‐goethite.
Rapid Estimation of Cation‐Exchange Capacities of Soils and Clays with Methylene Blue Exchange
Authors: Wang M. K. , Wang S. L. , Wang W. M. 
Published: July 2010

AbstractFour methods to determine the cation‐exchange capacities (CEC) of soils and clays were evaluated: (i) conventional NH4‐Na exchange, (ii) methylene blue (MB) capacity with MB acid, (iii) CEC of tetrasodium pyrophosphate (TSPP), and (iv) MB‐water filter paper spot test titration methods. Eighteen surface soils (0–15 cm) from farm fields in Taiwan and four reference clays obtained from the Source Clay Repository (Clay Minerals Society, Columbia, MO) were used in this work. Under appropriate conditions of concentration, equilibration period, and flocculation of MB solutions, MB absorption can be used to determine the CEC of soils and clays. Regression analyses gave R2 values 0.91, 0.99, and 0.74 for MB‐acid, MB‐TSPP, and MB‐water titration methods, respectively, vs. NH4‐Na exchange. The CEC values of MB‐TSPP titration showed a good linear correlation with values from the NH4‐Na exchange method. Thus, the method of MB‐TSPP filer paper spot‐test titration is recommended for rapid CEC determination in field test of soils.
Legume Productivity and Soil Nitrogen Dynamics in Lowland Rice‐Based Cropping Systems
Authors: Ladha J. K. , Kundu D. K. , Angelo‐Van Coppenolle M. G. , Carangal V. R. , Peoples M. B. , Dart P. J. 
Published: July 2010

AbstractRice (Oryza sativa L.) in wet season (WS) preceded by a dry season (DS) fallow, commonly practiced in rainfed lowlands, causes large losses of N through NO3 leaching and denitrification. The green‐manure legumes as NO3 catch crops is economically unattractive to farmers. In a 2‐yr study, we (i) assessed productivity of one grain and four forage legumes (pigeonpea [Cajanus cajan (L.) Millsp.], crotalaria (Crotalaria juncea L.), clitoria (Clitoria ternatea L.), desmanthus [Desmanthus virgatus (L.) Willd.], and siratro [Macroptilium atropurpureum (Mocino & Sessé ex DC.) Urban]) grown in the DS, (ii) examined NO3‐N and NH4‐N dynamics in soil (a Typic Tropaquept), and (iii) evaluated legume residues as a N source for succeeding rice. Nitrate‐N was dominant in the 30‐cm topsoil and was higher under legumes compared with weedy fallow. The legumes produced 4.9 to 9.1 t aboveground biomass ha‐1, accumulated 132 to 306 kg N ha‐1 of which 67 to 81% was derived from N2 fixation. After harvests, 2.9 to 5.2 t ha‐1 of residues containing 81 to 162 kg N ha‐1 were returned to soil. By 3 to 4 wk after flooding, legume‐treated plots had as much as 33 to 40 kg mineral N ha‐1 in topsoil compared with 10 to 13 kg N ha‐1 in weedy fallowed plots. Residues significantly increased rice yield and N uptake. Rice recovered 15 to 31% of the residue N. Failow plots required 25 to 50 kg fertilizer N ha‐1 to produce comparable plant growth responses to that obtained after the legumes. Belowground residues of the legumes apparently contributed 13 to 37 kg N ha‐1 to rice. Such DS legumes that improve farm productivity as well as increase soil fertility might ensure sustainability of production in rainfed lowlands.
Chemical Conditions Conducive to the Release of Mobile Colloids from Ultisol Profiles
Authors: Kaplan Daniel I. , Sumner Malcolm E. , Bertsch Paul M. , Adriano Domy C. 
Published: July 2010

AbstractDispersed colloidal clay particles may enhance the transport of environmental contaminants adsorbed to the colloid surfaces. The objective of this study was to determine how soil pH (4.3–6.9), low total electrolyte concentration (TEC, 0.4–2.8 molc m‐3), and low Na adsorption ratios (SAR, 0.3–1.8 [molc m‐3]0.5) affected the concentration of mobile colloids released from 13.5‐m3 reconstructed Ultisol profiles. Critical flocculation concentration (CFC, the minimum TEC to induce flocculation of a clay suspension) tests were conducted using the water‐dispersible clay fraction of the Ap horizon of these profiles, which is the primary source for the mobile colloids. Surface soil pH, TEC, and SAR levels of the profiles that released high concentrations of colloids fell within the dispersion domain identified by the laboratory CFC tests. The effect of SAR on dispersion appears to be a continuum that approaches zero, and this effect is significantly (P ≤ 0.01) dependent on TEC. The dispersible nature of these soils is in part attributed to their very low TEC, generally <2 molc m‐3, which results from low concentrations of weatherable minerals. The TEC of 10 of the 13 profiles were <2 molc m‐3, the CFC for SAR = 1 (molc m‐3)0.5, indicating that if the pH is not limiting (pH greater than ≈6.0), colloidal dispersion will occur. Thus, these weathered soils can be highly dispersive within limited chemical conditions, and only small increases in SAR or pH may induce dispersion. By identifying these limits, the risk of enhancing subsurface contaminant transport by soil‐derived mobile colloids can be reduced.
Assessing Forest Soil Disturbance through Biogenic Gas Fluxes
Authors: Dulohery C. J. , Morris Lawrence A. , Lowrance Richard 
Published: July 2010

AbstractSoil damage from wet‐weather timber harvests may persist after some physical and chemical properties have been restored through tillage and fertilization. This study's objective was to determine if the gaseous products of aerobic and anaerobic soil biological activity could reveal harvest‐damage effects, even after applying costly mitigation treatments. Fluxes of CO2, CH4, and N2O across the soil surface were measured in Ultisols of a Coastal Plain pine flat damaged during timber harvest, then mitigated by bedding and fertilization (100 kg ha‐1 N, P, and K). Gas fluxes were measured with large static chambers (0.5 by 1.0 m sampling area) to compensate for high microsite variability and the presence of coarse debris on the forest floor. Carbon dioxide evolution was a robust and consistent indicator of residual damage, declining an average of 34% in planting beds on damaged vs. undamaged soils. For example, in a late summer reading, efflux of CO2‐C from beds installed over former skid trails was 143 mg m‐2 h‐1 vs. 258 mg m‐2 h‐1 from undamaged beds and 231 mg m‐2 h‐1 from undisturbed forest floor. Methane and N2O fluxes were ephemeral and, thus, generally unreliable as indicators of harvest damage — though bedding produced scattered high peaks in both. Carbon dioxide was also the only gas flux that responded significantly to fertilization, with an average 26% increase up to 4 mo after fertilization. These results suggest that suppression of gross soil biological activity by harvest damage was not restored by intensive mitigation in the next rotation's establishment phase.
Forest Fire Effects on Soil Phyllosilicates in California
Authors: Ulery A. L. , Graham R. C. , Bowen L. H. 
Published: July 2010

AbstractThousands of hectares of forests are burned annually in wildfires and prescribed burns nationwide. Our objective was to determine the effects of such fires on soil phyllosilicates. At five sites throughout California representing Inceptisols, Andisols, and Mollisols, surface soil samples from similar depths were collected in burned and nearby unburned areas. Fires produced no visible soil alterations except in 1 to 2% of the land area where concentrated fuel such as logs or stumps burned slowly and at higher temperatures, effectively baking the underlying soil. Within the upper 1 to 8 cm at these severely burned areas, kaolin was completely destroyed or substantially depleted and d001 spacings of clay‐sized vermiculite, chlorite, chlorite‐vermiculite, and hydroxy‐interlayered vermiculite collapsed toward 1.0 nm or were decomposed as shown by x‐ray diffraction. Dehydroxylation of severely burned Fe‐bearing phyllosilicates was indicated by Mössbauer spectroscopy. The decomposition of virtually all phyllosilicates in the upper 2 cm of the soil was observed at one site after burning. The effects of severe burning on the soil phyllosilicates remained clearly expressed at least 3 yr after a fire.
Evaluation of a Line Heat Dissipation Sensor for Measuring Soil Matric Potential
Authors: Reece Clive F. 
Published: July 2010

AbstractThe accuracy and operational limits of a new heat dissipation sensor for measuring soil matric potential are evaluated. The measurement is based on the rate of temperature rise from a line heat source embedded in a cylindrical porous ceramic that is in equilibrium with soil water. Different heating currents or times can be accounted for by basing calibration on sensor thermal conductivity rather than temperature rise. Six sensors were calibrated against pressure plate and psychrometer measurements of matric potential. Inverse of sensor thermal conductivity was linearly related to the logarithm of matric potential between −10 and −1200 J kg−1. This range of measurable matric potentials is much larger than previous heat dissipation sensor designs. The heat dissipation sensor was accurate to within 20% of the independently measured matric potential. Normalizing sensor readings by sensor thermal conductivity after oven drying results in a calibration that accounts for between‐sensor variability. In a growth chamber experiment with fluctuating soil temperatures, heat dissipation sensor estimates of soil matric potential compared favorably with tensiometer and psychrometer measurements. Heat dissipation sensors based on this design appear useful when a wide range of matric potentials needs to be studied.
A High‐Temperature Catalytic Oxidation Technique for Determining Total Dissolved Nitrogen
Authors: Merriam J. , McDowell W. H. , Currie W. S. 
Published: July 2010

AbstractA high‐temperature catalytic oxidation method for determination of total dissolved N has been developed and tested on soil solution and throughfall. Unlike methods generally used for total dissolved N, this method is rapid, quantitative, and does not require use of strong acids or bases. The technique couples a commercially available chemiluminescent N detector with the combustion furnace of a commercially available C analyzer. An aqueous sample is combusted in an ultra pure oxygen environment at 680°C, converting all forms of N to nitric oxide, which then reacts with ozone. The product, metastable NO2, is measured chemiluminescently by the N detector. The method is appropriate for samples collected in studies of forest soil solution and throughfall, having a method detection limit of 0.03 mg L−1 total N, and a range from 0.03 to 10.0 mg L−1. Tests of several organic and inorganic N‐containing compounds showed recoveries >90% for concentrations up to 5.0 mg N L−1. Urea was the only compound tested with recoveries <90%. Numerous field samples were analyzed and compared with results obtained using persulfate oxidation and high‐temperature oxidation (uncatalyzed oxidation at 1100°C). Results from this high‐temperature catalytic oxidation method compare well with persulfate oxidation and high‐temperature oxidation.
Proton Binding and Cadmium Complexation Constants for a Soil Humic Acid Using a Quasi‐particle Model
Authors: Bolton K. A. , Sjöberg S. , Evans L. J. 
Published: July 2010

AbstractIn order to better understand the fate of Cd in soils it is important to ascertain the influence of soil humic substances on the retention of Cd in soils. In this study the acid‐base and Cd complexation properties of a humic acid fraction extracted from a soil were investigated using potentiometric titrations. A number of electrostatic and nonelectrostatic equilibrium models were considered in order to obtain the simplest model that would best describe the titration data. All proton binding and Cd complexation constants were determined using the optimization procedure in the computer program FITEQL. The model that best fit the experimental data was a nonelectrostatic model, which included two diprotic acids, H2 A and H2B. The dissociation constants for H2A were calculated to be log β‐1,0,1,0 = −4.00 ± 0.02 and log β‐2,0,1,0 = −9.32 ± 0.03 and for H2B were calculated to be log β‐1,0,0,1 = −7.43 ± 0.24 and log β‐2,0,0,1 = −16.66 ± 0.31. The model indicated the presence of four Cd complexes, CdHA+, CdA0, CdH‐1A− and CdHB+, with complexation constants calculated to be log β‐1,1,1,0 = −1.29 ± 0.09, log β‐2,1,1,0 = −5.92 ± 0.07, log β‐3,1,1,0 = −14.39 ± 0.09, and log β‐1,1,0,1 = −3.72 ± 0.18.