bluuebunny/crossref_metadata_2025_split huggingface dataset:
Water Relations of Saturated Bentonite: Some Effects of Temperature and Solution Salt Concentration
Authors: Smiles D. E. , Barnes C. J. , Gardner W. R. 
Published: July 2010

AbstractTransient flow (constant pressure desorption) and equilibrium pressure membrane experiments were used to determine some water relations of bentonite pastes in the range of water content (volume of water per unit volume of solid) from 6 to 33. The pastes were prepared in equilibrium with three different sodium chloride concentrations (3.25 m mol L−1, 16.8 and 119 m mol L−1), and the experiments were performed at temperatures of 277, 293, and 306 K. It was found that for each solution salt concentration, the moisture characteristic was effectively temperature independent, and the effect of solution concentration was qualitatively, but not quantitatively, in agreement with electrical double layer theory. In the transient flow experiments, both the cumulative outflow (expressed as a function of the square root of time) and the water content profiles (determined by destructive sampling and expressed as a function of material distance divided by square root of time) revealed clear temperature dependence. This effect is wholly accounted for by the temperature dependence of the kinematic viscosity of water. The observations lead us to infer that temperature dependence, over and above effects on viscosity, in the moisture characteristic and flow properties in unsaturated soils arises not in double‐layer effects, but in effects on the air water interfaces in these systems.
Significance of Iron Oxides and Calcium Carbonate Particle Size in Phosphate Sorption by Calcareous Soils
Authors: Ryan J. , Curtin D. , Cheema M.A. 
Published: July 2010

AbstractThough many soil components are involved in reactions whereby soluble fertilizer P is converted to less soluble and therefore less available forms, the relative influence of each phase in this process is not clearly defined. While both crystalline and amorphous Fe oxides readily react with P in noncalcareous soils, the contribution of these forms to P sorption in calcareous soils has received little attention. Thus, in this study, samples of 20 mainly calcareous Lebanese soils, ranging widely in relevant properties, were equilibrated for 6 d with 25 mL P solutions ranging from 12.5 to 62.5 mg kg−1. The data did not conform to the conventional Langmuir isotherm. Correlations and regression coefficients with actual P rentention from solution indicated an involvement of oxalate Fe, but there was no effect of CaCO3 particle size. Removal of Fe prior to equilibration had an inconsistent effect on P retention. The P behavior of calcareous soils may be modified by Fe oxides in such soils.
Determination of Exchangeable Bases in Soils by Ion Chromatography
Authors: Basta N. T. , Tabatabai M. A. 
Published: July 2010

AbstractA simple, accurate, and precise ion chromatographic (IC) method for determination of exchangeable bases in soils was developed. It involves extraction of the bases with neutral 1M ammonium acetate (NH4 OAc), followed by ignition of the soil extract at 400°C for 30 min, dissolution of the residue in 5 mM HCl, and determination of exchangeable bases by using a Dionex Model 10 IC. The IC method is based on separation of the cations by a separator column containing a low‐capacity, cation‐exchange resin in the H+ form and converting the various cations to their corresponding hyroxide forms by a suppressor column in the OH‐ form. Solutions of 5mM HCl and 2.5 mM HCl + 2.5 mM m‐phenylenediamine dihydrochloride are used as the eluents for determination of monovalent and divalent exchangeable bases, respectively. Electrical conductivity is used as the mode of detection. Results showed that the average exchangeable K in 10 soils by IC, atomic absorption spectrophotometry (AA), and flame photometry (FP) were 0.49, 0.47, and 0.47 cmol(i)/kg soil, respectively. The corresponding average exchangeable Na values were 0.09, 0.09, and 0.08 cmol(i)/kg soil. The average exchangeable Ca values of the same soils by IC and AA methods were 13.5 and 13.5 cmol(i)/kg soil. The corresponding exchangeable Mg values were 3.50 and 3.54. The IC method has excellent sensitivity, with detection limits of 0.1, 0.05, 0.1 and 0.03 mg L−1 of K, Na, Ca and Mg. respectively. With the IC method, K and Na can be determined simultaneously in 6 min, or Ca and Mg can be determined in 7 min. A single operator can perform about 40 analyses of monovalent or divalent bases in a normal working day.
Acetylene Decomposition in Soils
Authors: Terry Richard E. , Duxbury John M. 
Published: July 2010

AbstractAcetyIene (C2H2) is useful in studies of nitrogen fixation and denitrification in soils. The objective of this study was to determine the soil environmental conditions under which microbial decomposition of acetylene occurs. Samples of Collamer sicl, Timpanogos cl, and Pahokee muck were exposed to carbon‐14 labeled acetylene in the laboratory. Less than 2.5% of the added gas was metabolized during the first 7 d of incubation, whether the soils were incubated aerobically or anaerobically. Adaptation to acetylene metabolism was observed in the two mineral soils during the second 7‐d period of aerobic incubation but adaptation did not occur during 42 d of anaerobic incubation or during a 21 d aerobic incubation of the Pahokee muck. Acetylene metabolism in soil samples adapted to acetylene utilization was stimulated by the addition of 10 mg N kg−1 soil of ammonium, nitrite, or nitrate. Addition of ≥ 100 mg N kg−1 soil of nitrate or nitrite or 1,000 mg N kg−1 soil of ammonium had a substantial inhibitory effect on acetylene utilization. The order of inhibition was ammonium < nitrate < nitrite. The addition of alfalfa, a source of readily available carbon, slowed microbial adaptation to acetylene decomposition and resulted in lower rates of transformation in the Collamer soil.Adaptation of soil microorganisms to acetylene utilization in the Collamer soil occurred in situ at a rate similar to laboratory incubation experiments. The ability of microorganisms in the soil to metabolize acetylene was maintained for at least 42 d after exposure of field plots to the gas was discontinued.
Factors Related to Urea Hydrolysis in Soils
Authors: Reynolds C. M. , Wolf D. C. , Armbruster J. A. 
Published: July 2010

AbstractThe use of urea as a nitrogen source for crop production has increased in recent years. Because the hydrolysis of urea to ammonia and carbon dioxide is mediated by the enzyme urease, efficient use of urea requires an understanding of factors that influence urea hydrolysis in soil. The purpose of this research was to relate the rate of urea hydrolysis to chemical, physical, and biological properties for soils in pasture and in cultivation. For each of 22 soils in Kansas, Missouri, and Oklahoma, samples were collected from paired fields, one in pasture and one in cultivation. The samples were taken from both 0 to 2.5 cm and 0 to 15 cm, and urea hydrolysis rates were measured in field‐moist and air‐dried samples. Urea hydrolysis rates in air‐dried soils ranged from 1 to 149 µg urea g soil−1 h−1 and from 1 to 117 µg urea g soil−1 h−1 in field moist soils. For each soil, the greatest urea hydrolysis rate was in the 0 to 2.5‐cm depth of pasture samples. The urea hydrolysis rate for each soil was greater in pasture samples than in samples from cultivated fields. For samples from cultivated fields, urea hydrolysis rates in both field‐moist and air‐dry samples were positively correlated with total nitrogen (TN) and organic carbon (OC). Only in the field moist soils were urea hydrolysis rates correlated with TN and OC in the soils from pastures. Urea hydrolysis rates in the 0 to 2.5‐cm depth of pastures exhibited the greatest change from field‐moist to air‐dry conditions. Rates generally decreased with drying, but did remain constant or increased with drying in some cases. Both the greatest rates and the greatest variation in urea hydrolysis rates between field‐moist and air‐dry soils were observed in the surface 0 to 2.5 cm samples from pastures.
Fractionation of Inorganic and Organic Phosphorus in Virgin and Cultivated Soils
Authors: Sharpley A. N. , Smith S. J. 
Published: July 2010

AbstractAmounts of phosphorus (P) in inorganic and organic pools were determined for three noncalcareous and five calcareous surface soils (0–150 mm) which had been cultivated for at least 15 yr, and their virgin analogues, to ascertain if relative pool sizes or soil P fertility are being changed by cultivation and associated fertilizer application. The soils were representative of major agricultural areas of the USA, with total P concentrations ranging from 200 to 1920 mg kg−1 (approximately 50% inorganic P) and P applications from 0 to 90 kg ha−1 yr−1. P forms in the pools and extractants used were as follows: inorganic P; loosely‐bound (1.0M NH4Cl), nonoccluded (0.5M NH4F + 0.1M NaOH), occluded (citrate‐dithionite‐bicarbonate + 0.5M NH4F + 0.1M NaOH), and Ca bound (1.0M HCl) (calcareous soils only): organic P; labile (0.5M Na HCO3), moderately labile (1.0M H2SO4 + 0.5M NaOH), moderately resistant (0.5M NaOH/HCl soluble), and resistant (0.5M NaOH/HCl insoluble). Distribution of inorganic P in virgin noncalcareous soils was, on average, 2% loosely‐bound, 52% nonoccluded, and 46% occluded. Cultivation resulted in an increase in nonoccluded and decrease in occluded P. Average distribution in the virgin calcareous soils was 2% loosely‐bound, 11% nonoccluded, 9% occluded, and 78% Ca‐bound, with no significant change in pool size with cultivation observed. On average, organic P in the virgin soils was 7% labile, 48% moderately labile, 33% moderately resistant, and 12% resistant, with no significant change in relative amounts due to cultivation. A mounts of fertilizer P applied and organic P mineralized and immobilized in stable inorganic P pools during cultivation, were related to P sorption index of the soils. The conversion of organic to inorganic P may be reversed by management practices allowing a build up of soil organic matter. Since little change in amounts of loosely‐bound inorganic and labile organic P was observed during cultivation, the more stable pools may represent a better estimate of long‐term soil fertility.
Soil pH Buffering Revisited
Authors: Magdoff F. R. , Bartlett R. J. 
Published: July 2010

AbstractThe buffering relationships of a wide variety of Vermont soils were investigated by adding either acid (H2SO4) or base (CaCO3). Soils were found to be very well buffered above pH 7 and below pH 4. When amendment added is expressed on an organic matter (OM) basis [mmol (H+ or 1/2 CaCO3) g−1 OM] and the check treatment is transposed to a common curve, all soils appear to follow a similar relationship (a unified buffer curve). Thus, OM appears to strongly influence the degree of pH buffering of Vermont soils. For practical purposes, pH buffering of soils in the pH 4.5 to 6.5 range is linear with added amendment. However, the change in slope of the unified buffer curve indicates that of the entire pH range soils may be least well buffered between pH 5 and 5.6. The low degree of pH buffering in this range may be due to a high degree of cation exchange capacity (CEC) buffering. The pH vs. percent base saturation (%BS) relationship has been misinterpreted as being the same as a pH vs. lime addition titration curve. In a soil without appreciable exchangeable Al, the %BS is essentially the soil's CEC at its current pH expressed as a percent of the CEC at pH 8.2. Ranges in pH where the %BS increases only slightly may be zones of low pH buffering.
Soybean Shoot and Root Growth and Phosphorus Concentration as Affected by Phosphorus Placement
Authors: Borkert C. M. , Barber S. A. 
Published: July 2010

AbstractEffect of P placement on shoot and root growth and their relation to recovery of applied P is important for economic crop production. Few studies have investigated the effect of varying the P‐fertilized soil volume on soybean (Glycine max L. Merr.) root growth, P uptake and soybean yield. The objective of this research was to investigate the effect of localizing P in decreasing volumes of soil on soybean seedling root morphology and distribution, and P uptake in order to determine the placement giving maximum plant growth. An experiment with soybeans grown in Raub silt loam (Aquic Argiudoll) was conducted in 3‐L pots in a controlled climate chamber. Adding the same amount of P per pot (60 mg/kg soil) in decreasing volumes of soil stimulated root length in the fertilized portion while the root radius became smaller in this zone. The relation between soil volume fraction fertilized with P and fraction of total root length in the fertilized soil could be described by y = x0.70 (r2 = 0.96), where x is the proportion of the soil volume treated with P and y is the predicted proportion of the total root length in the P‐treated soil. Shoot P concentration increased as the volume of fertilized soil was reduced to 0.125 but did not increase further as fertilized soil volume was reduced to 0.0625. Also, maximum shoot dry weight was obtained when 0.125 of the soil was P fertilized and did not increase further as P‐treated soil volume was reduced to 0.0625.
Genesis of Cambic and Argillic Horizons in Two Northern Utah Aridisols
Authors: Southard R. J. , Southard A. R. 
Published: July 2010

AbstractA study of the mineralogy and morphology of two northern Utah Aridisols (Camborthid and Haplargid) formed from ancient Lake Bonneville sediments revealed small but important differences between the two soils in the degree of weathering and soil development. The B horizons of both pedons meet the argillic horizon textural requirement. An incipient argillic horizon was identified in the Haplargid on the basis of thin, discontinuous pore argillans observed with a scanning electron microscope. The Camborthid Bw horizon is a cambic horizon, as indicated by partial removal of carbonates, development of structure, and lack of illuviation argillans. The Camborthid is calcareous throughout, and interlayering of mica‐smectite in the clay fractions is extensive. Stronger weathering in the Haplargid is inferred from the nearly complete removal of carbonates from surface horizons and more complete alteration of mica to smectite (i.e., less interlayering). The argillic horizon has formed in about 9000 yr under the influence of at least two pluvial periods. The cambic horizon formed in an environment at least as dry as at present, and it is still calcareous after about 6000 yr. The scanning electron microscope is a valuable tool for inferring soil‐forming processes from soil fabric morphology, especially in weakly‐developed horizons.
Effect of Disturbed Soil Thickness on Soil Water Use and Movement under Perennial Grass
Authors: Merrill S. D. , Smith S. J. , Power J. F. 
Published: July 2010

AbstractPrevious research has shown that plant growth on minespoil of lower plant productivity is dependent upon thickness of soil replaced. Sodium‐affected strip‐mine spoils are a significant reclamation problem in the northern Great Plains. The purpose of this work was to develop understanding of plant growth response to soil thickness over sodic minespoils by measurement of water movement, water use, and root growth. Soil water storage and use were measured in each of three growing seasons under crested wheatgrass (Agropyron desertorum) grown on 0.25‐, 0.5‐, 0.75‐, and 1.0‐m thicknesses of disturbed soil. Soil profiles were constructed from Haploboroll topsoil (0.2 m for all treatments), placed over varying thicknesses of subsoil (B and C horizon materials), which in turn was placed over sodic (Sodium adsorption ratio = 30) drag‐line spoil at a semiarid, steppe‐land site in western North Dakota. Forage yield was 2‐ to 3.5‐fold greater on 1.0 m soil thickness than on 0.25 m. Both total soil water potentials and root weight densities were similar in minespoil and in subsoil at the same profile depths. Root water uptake was much less from the minespoil (mean saturated hydraulic conductivity (HC) = 1 × 10−3 cm/d) than from subsoil (mean HC = 0.2 cm/d). Low HC per se appeared to be the dominant factor limiting sodic minespoil as a plant growth medium because low HC resulted in less use of stored soil water from minespoil compared to subsoil. Depletion from a 120‐cm profile was 0.2, 3.3, 7.9 and 9.8 cm for 0.25‐, 0.50‐, 0.75‐ and 1.0‐m soil thickness, respectively. Relative differences in evapotranspiration (ET) between the 0.25‐m and 1.0‐m soil thickness treatments were much less than yield differences, reflecting progressively reduced water use efficiency with less soil thickness.
Effect of Slope and Rainfall Intensity on Erosion from Sodium Dispersed, Compacted Earth Microcatchments
Authors: Evett Steven R. , Dutt Gordon R. 
Published: July 2010

AbstractKnowledge of erosion in microcatchment systems is needed for the design of water harvesting systems. This study was therefore conducted on the effects of microcatchment slope and length on runoff and erosion rates under natural rainfall. Two replicates of a two factor experimental plot design, including 1, 5, 10 and 15% slopes and 3 and 6 m lengths, were built on a gravelly sandy clay loam using 11.2 Mg/ha of NaCl mixed into the surface 2 to 5 cm of soil followed by compaction with a 6‐Mg roller after a heavy rain. Most of the erosion was from interrill erosion. Length (m) and storm energy, E, (MJ/ha) had no significant effects on erosion. The effects of slope, s, (m/m) and maximum 30 min rainfall intensity, I30, (mm/h) were significant at the 0.1% level for the 11 storms studied. These effects were significantly different from those in the USLE (Universal Soil Loss Equation), which underpredicted erosion at low slopes. The best fit equation was A = (0.0595s0.998 + 0.0068)I301.86 where A is the estimate of erosion (Mg/ha). The sodium treated surface layer is estimated to last up to 20 yr under our conditions if slopes are kept to 5% or lower on these microcatchments of less than 6m length.
Changes In Solum Chemistry Following Clearcutting of Northern Hardwood Stands
Authors: Snyder K. E. , Harter R. D. 
Published: July 2010

AbstractTo assess the role of the soil in retaining nutrients after clearcutting, the sola beneath three even‐aged pin cherry (Prunus pensylvanica L.)‐birch (Betula alleghaniensis Britton and B. papyrifera Marsh.) stands were analyzed for post harvest changes in Ca, Mg, K, pH, organic carbon, titratable acidity, and loss‐on‐ignition. A 93‐year‐old second‐growth northern hardwood stand served as the preharvest comparison. The stands were located in central New Hampshire. The sites were selected to reduce influences from such external parameters as elevation, aspect, physiographic position, and parent material. Within each site, morphologically matched pedons of a single soil series were sampled. Mineral soil analysis indicated that organic matter may be translocated into the upper mineral horizon following the post‐harvest initiation of surface decomposition. A large influx of Ca, Mg, and K into the mineral soil was associated with this decomposition. Potassium concentrations showed a rapid increase throughout the solum soon after harvesting. Following an assumed reduction in counter ion leaching, Ca and Mg accumulation was apparent, particularly in spodic horizons high in soil organic matter. Exchangeable nutrient levels remained two to three times higher at the 30 yr post‐harvest relative to the preharvest site.
Micromorphological and Submicroscopical Features Related to Pyrite Oxidation in an Inland Marine Shale from East Central Saskatchewan
Authors: Mermut A. R. , Curtin D. , Rostad H. P. W. 
Published: July 2010

AbstractThe micromorphology and submicroscopy of a soil mapped within the Arborfield Association in east central Saskatchewan, which is derived from Cretaceous marine shale, were investigated. Qualitative analysis of well‐formed monomineralic crystals in the oxidation zone by energy dispersive analysis of x‐ray (EDAX) system attached to transmission electron microscope (TEM) confirmed them to be jarosite in which most of the monovalent cation positions were occupied by sodium with minor quantities of Potassium (natrojarosite, Na(K)Fe3(SO4)2(OH)6). They occur as void natrojarositans, neonatrojarositans, and quasinatrojarositans. Persistence of natrojarosite in some aggregates within the upper Cgk and Cg horizons with high pH is attributed to the low solubility of this mineral. A comparison of the size, shape and distribution of pyrite and natrojarosite suggest that natrojarosite is essentially formed by crystallization from solution rather than in situ replacement of pyrite. Ferric glaebules in the form of nodules and concretions, found only in the upper part of the profile, were characterized as the ultimate development phase of pyrite oxidation. Stabilization of iron as glaebules leaves the sodium and sulphate in the soil solution. These are generally the major soluble ion species in saline soils in Saskatchewan. Presence of planar voids (craze and skew planes) and their orientation pattern, especially in the lower part of the profile, were ascribed to the poor drainage conditions, which is an important factor affecting the persistence of pyrite and natrojarosite in the profile studied.
A Spot Test with Toluidine Blue for Allophane and Imogolite
Authors: Wada Koji , Kakuto Yasuko 
Published: July 2010

AbstractToluidine blue is adsorbed on negatively charged colloids and exhibits a characteristic color change from blue to purplish red (metachromasis). A procedure to test the metachromasis for the soil was developed and tested for Chile and Ecuador soil samples containing and not containing allophane and imogolite. The results show that the absence of the metachromasis can be used for the test of allophane and imogolite.
A New Equilibration Method for Cation‐Exchange Capacity Measurement
Authors: Matsue Naoto , Wada Koji 
Published: July 2010

AbstractA method is proposed for the measurement of cation‐exchange capacity (CEC) of leached soils carrying both variable and constant negative charges at conditions pertinent to the field. The method consists of equilibrating a soil with 0.01 M SrCl2 (five centrifuge washings), replacing the retained Sr with 0.5 M HCl (one centrifuge washing) and determining the replaced Sr by atomic absorption spectrophotometry. The equilibrium pH is measured with the final 0.01 M SrCl2 washing. If desired, exchangeable bases and Al can be determined by collecting the 0.01 M SrCl2 washings. This method was developed because we found that the Gillman's BaCl2‐MgSO4 CEC method has problems due to specific adsorption of SO2−4. For evaluation, the CEC obtained by the proposed method was compared with the sum of exchangeable bases and Al and with the CEC obtained by other methods including saturation‐equilibration with 1 M SrCl2‐0.01 M SrCl2 and 1 M NH4OAc‐0.05 M NH4OAc (pH 7.0), respectively.