bluuebunny/crossref_metadata_2025_split huggingface dataset:
Retention of Soil Water Following Forest Cutting
Authors: McColl J. G. 
Published: July 2010

AbstractEucalyptus globulus (Labill.) forests in the Oakland‐Berkeley hills, California, were clearcut in 1973–74 following severe damage from freezing in December 1972. The soil water regimes in clearcut and adjoining uncut areas, were compared during the two years following cutting.During the wet winter season (Dec.–May), surface drying and evapotranspiration by annual grasses were the only losses in the clearcut; more soil water was retained in the clearcut due to lack of evapotranspiration by the forest trees.Soil water rapidly decreased in both the clearcut and forest during the long, dry summer periods, and differences between the two areas widened. By midsummer soil matric suctions in the clearcut dropped below 15 bars (22.4% Pv, volumetric water content), and in the forest to below 70 bars (8.5% Pv). During the summer, Pv increased with profile depth in the clearcut, but in the forest, soil water was depleted uniformly with depth in the profile.Although volumetric water contents of soil (Pv) were significantly different between clearcut and forest areas, rates of water loss (k) during summer were not clearly related to forest cover. In the clay‐loam soil, k was dependent on the soil water storage at the beginning of the dry summer period, on the ability of trees in the uncut forest to withdraw water from parent material and from fractured bedrock in excess of that available in the soil profile, and on Pv which decreased during summer.
Occurrence Of Lepidocrocite And its Association With Goethite in Natal Soils
Authors: Schwertmann U. , Fitzpatrick R. W. 
Published: July 2010

AbstractHydromorphic soils (pseudogleys) in a highland‐montane climate of Natal (South Africa) contain appreciable amounts of lepidocrocite. Its occurrence appears to be restricted to imperfectly drained lower positions on southern (cooler) slopes at an altitude between 1,300–1,900 m. In these positions, Fe is reduced under anaerobic Conditions leading to lepidocrocite formation on reoxidation. Goethite is closely associated with lepidocrocite and increases on approaching better aerated microzones such as root channels and textural boundaries where it usually forms crusts. Both FeOOH forms were determined quantitatively by XRD. Simultaneous formation of the two Fe‐oxides is inferred from synthesis experiments in which an increasing partial pressure of CO2 in an O2‐CO2 gas mixture to oxidize a FeCl2 solution favored goethite at the expense of lepidocrocite. The crystallinity of lepidocrocite (as measured by XRD line broadening) decreased when approaching root channels. This is attributed to a decreased in pH and agrees again with synthesis experiments where the same effect was observed. Goethite is generally less crystalline than lepidocrocite.
Phosphate Adsorption on an Oxisol
Authors: Parfitt R. L. 
Published: July 2010

AbstractAdsorption isotherms for phosphate on the A and B horizon of an oxisol from Papua New Guinea showed high affinity adsorption at low solution concentrations and a linear increase in adsorption at higher solution concentrations. Adsorption increased with decrease in pH in the range 3 to 8. Comparison with data obtained under similar conditions with synthetic goethite (α‐FeOOH) and gibbsite [Al(OH)3] suggested that phosphate reacted with FeOH and FeOH2+ groups on soil iron oxide surfaces to form a binuclear bridging FeOP(O2)OFe complex and with exposed Al(OH)H2O on kaolinite edges and on hydroxy‐aluminum species to form a binuclear or bidentate phosphate complex. At higher phosphate concentrations isotherms showed continued adsorption which may be due to a further reaction involving hydroxy‐aluminum groups.
Adsorption of Aluminum by a Smectite: I. Surface Hydrolysis During Ca2+‐Al3+ Exchange
Authors: Bloom P. R. , McBride M. B. , Chadbourne B. 
Published: July 2010

AbstractThe exchange of Ca by Al in montmorillonite suspensions adjusted to low pH (∼4) was investigated by measurement of Ca, Al, and pH in the solution phase before and after the addition of clay. Adsorption of Al was accompanied by a release of protons to solution, indicating that the clay surfaces promoted hydrolysis of Al3+ when only partial coverage of exchange sites by Al had occurred. Calculations showed a two‐ to nine fold increase in the degree of hydrolysis at the surface relative to the value for solution. In suspensions with pKsp values near 33.3, Al(OH)3 was precipitated on interlamellar surfaces. However, at lower pH, the predominant form of adsorbed Al was Al3+, with hydroxy ‐Al monomers and/or polymers also present. The preference of the ions for the clay surface followed the order: hydroxy‐Al>Al3+>Ca2+>H3O+. The exchange systems were complicated by proton uptake by the montmorillonite, resulting from H3O+‐Ca2+ exchange as well as proton adsorption by edges concurrent with slow mineral dissolution reactions.
Design and Test of a Field Sampler for Ammonia Volatilization
Authors: Kissel D. E. , Brewer H. L. , Arkin G. F. 
Published: July 2010

AbstractA system is needed to measure ammonia volatilization from N fertilizer applied under field conditions. This study was undertaken to develop a device for making these measurements and still maintain a field environment. The basic system developed consists of a vacuum pump, a chemical trap to capture ammonia, and the volatilization chamber.The volatilization chamber consists of a steel cylinder 21.8‐cm I.D. by 15‐cm long that is forced into the soil with its top flush with the soil surface to provide a microplot. The lid assembly attached to the cylinder includes a hinge and reversible electric motor that allows the lid to be automatically rotated from the microplot. The volatilization chamber was designed with the removable lid so that the lid is closed only for short intervals during the day while ammonia loss is measured. The total ammonia loss is calculated by integrating the rates of loss over time. Between measurements, the lid is open to allow normal environmental conditions of temperature, wind movement, etc., on the micro‐plot. The volatilization chamber has five air intake ports and one exhaust port. Ammonia loss was unaffected by air flow rate if air movement through the chamber exceeded 15 exchange volumes/min.Our complete system consisted of eight volatilization chambers with a system of multiple chemical traps that can operate automatically without attention for 24 hours. When tested in the field, duplicate measurements of ammonia loss from ammonium sulfate agreed quite closely, both in the rates of loss and the total ammonia loss. In another test, ammonia loss from ammonium chloride agreed reasonably well with other laboratory results.
Characteristics of Silica Sorption and Solubility as Parameters to Evaluate the Surface Properties of Tropical Soils: I. The Index of Silica Reactivity
Authors: Gallez A. , Herbillon A. J. , Juo A. S. R. 
Published: July 2010

AbstractSilica sorption by some Alfisols and Ultisols from southern Nigeria was studied. The percentage of silica lost from a solution brought into contact with a soil is called the index of silica reactivity (ISR).For reference samples, the scale of ISR follows the order kaolinite < < goethite < gibbsite. For soils where Iron oxides are the only sorbing phases, ISR is ruled by the part of the total specific surface area due to these oxides. More generally, however, ISR is sensitive to both the nature and the magnitude of the surface area so that soils rich in gibbsite exhibit higher ISR than the soils devoid of this mineral. To become useful as a comparative index, ISR should be amended so as to also take into account the specific reactivity of the different minerals with respect to soluble silica.
Alfalfa Production on a Profile‐Modified Slowly Permeable Soil
Authors: Eck Harold V. , Martinez Tito , Wilson G. C. 
Published: July 2010

AbstractYields of irrigated alfalfa (Medicago sativa L.) are lower on Pullman clay loam than on more permeable soils in the same climatic area. The objectives of this study were to determine (i) the residual effect of thoroughly mixing the soil profile on alfalfa growth and production, and (ii) the amounts and timing of irrigations required for maximum alfalfa production on modified and unmodified soil profiles.Alfalfa was grown under three profile modification treatments (thoroughly mixing the soil profile to 0‐, 90‐, or 150‐cm depth) on Pullman clay loam. For the first 3 years, all plots were either irrigated similarly (1970 and 1972) or unmodified plots were irrigated twice between harvests when necessary (1971). During the next 3 years, we expanded the study to include three irrigation treatments (two 10.2‐cm, one 17.8‐cm, or two 15.2‐cm irrigations between harvests). During the first 3 years, when single irrigations were applied between harvests, profile modification increased dry‐matter yields 40% (90‐cm modified) to 60% (150‐cm modified) over those for the unmodified check. However, with two irrigations between harvests, effects of modification were less marked.In the second phase of the study, with two 10.2‐cm irrigations between harvests, profile modification increased yields 30% (14.1 to 18.4 metric tons/ha). On 90‐cm modified soil, 3‐year average yields were 16.6, 18.3, and 20.1 metric tons/ha with one 17.8‐, two 10.2‐, or two 15.2‐cm irrigations between harvests, respectively. Respective yields on 150‐cm modified soil were 17.4, 18.5, and 18.6 metric tons/ha.Yields, water intake rates, bulk densities, and surface elevations showed that profile modification treatments made in 1964 were still effective 12 years later.
The Gapon and the Vanselow Selectivity Coefficients
Authors: Sposito Garrison 
Published: July 2010

AbstractA general thermodynamic relation between the Gapon and the Vanselow cation exchange equilibrium constants is derived and is shown to be violated by the expressions given traditionally in the soil chemistry literature for the Gapon and the Vanselow selectivity coefficients. This result suggests that the selectivity coefficient expressions are mutually in conflict. The traditional expression for the Gapon selectivity coefficient is shown to be in error, fundamentally because the Gapon convention—according to which cations react with an exchanger in equivalents—has no direct molecular interpretation. Therefore, the thermodynamic activity of an exchanger phase cannot be equated numerically with an equivalent fraction, even in some limiting case. The correct expression for the Gapon selectivity coefficient is derived and is discussed briefly for the case of Na‐Ca exchange. It is shown that the traditional expression and the correct one will not be very different numerically if the exchangeable sodium percentage is < 20.
Dispersion in Soil Columns: Effect of Boundary Conditions and Irreversible Reactions
Authors: Parlange J.‐Y. , Starr J. L. 
Published: July 2010

AbstractA closed form approximate analytical solution is provided which describes the transport of a solute in a soil column. The effects of convection, dispersion, and adsorption are included. The latter can include both linear adsorption and first‐ or zero‐order reactions. The effect of the finite length of a soil column on the miscible displacement of the solute is discussed in detail. It is shown in particular that the standard solution used in the past is accurate to describe the breakthrough curve but not the profile within the column.
Extractability of 238Pu and 242Cm From a Contaminated Soil as a Function of pH and Certain Soil Components: HNO3‐NaOH System
Authors: Nishita H. , Hamilton M. , Steen A. J. 
Published: July 2010

AbstractExtractability of 238Pu and 242Cm from a contaminated soil as a function of pH and certain soil components has been examined. This was done with an equilibrium batch technique using HNO3‐NaOH extracting system. The influence of various soil components on 238Pu and 242Cm extractability was determined indirectly by selectively removing them from the soil. Soil organic matter, free iron oxides, and free silica, alumina, and amorphous alumino‐silicates influenced the chemical extractability of 238Pu and 242Cm. The influence of these soil components depended on the pH of the soil suspension. Below pH ∼4.5, 238Pu appeared to be more strongly sorbed on the mineral fraction of the soil than 242Cm, but above pH ∼4.5, both were strongly sorbed on the mineral fraction. With the contaminated virgin soil, the 238Pu and 242Cm extractability ranged from 4.82 to 53.05% and 0.15 to 64.58% of dose, respectively, depending on the pH of the extracting solution. The liquid to solid K′d values ranged from 4.1 × 10−3 to 9.1 × 10−2 and 1.2 × 10−4 to 1.5 × 10 for 238Pu and 242Cm, respectively. The lowest extractability occurred around pH 7.1 for 238Pu and in the range of pH 4.7 to 5.6 for 242Cm.
Residual Effects of Calcium Silicate in Tropical Soils: II. Biological Extraction of Residual Soil Silicon
Authors: Khalid R. A. , Silva J. A. 
Published: July 2010

AbstractA modified Neubauer seedling method utilizing rice (Oryza sativa, L.) as a test plant, was employed to study the bioavailability of residual Si in a Hawaiian Gibbsihumox soil. Adsorbed soil Si was also removed with 0.1N acetic acid adjusted to pH 3.5 and containing 50 ppm P (phosphate solution). The results show that more Si was extracted by plant and ratoon crops of rice combined than by phosphate solution because of longer extraction time during plant growth and also because of possibly greater efficiency of Si removal by rice roots. Rice seedlings extracted proportionately more native Si than did phosphate solution, which resulted in comparable amounts of applied Si being recovered by the two methods, i.e., 8 to 30% for rice and 13 to 23% for phosphate extraction. The results of this study show that 55 to 72% Si applied 5 years ago was still adsorbed by or precipitated in the soil in a form that these techniques could not measure. However, the findings of this study strongly indicate that the modified Neubauer technique can be efficiently employed to estimate the pool of potentially available soil Si in the highly weathered soils of the tropics.
Age of Soil Landscapes in the Coastal Plain of North Carolina
Authors: Daniels R. B. , Gamble E. E. , Wheeler W. H. 
Published: July 2010

AbstractA stratigraphic and geomorphic study of surficial sediments in the Neuse drainage was completed as part of a general study of the relations between geomorphology and soils in the Coastal Plain of North Carolina. The depositional‐erosional surfaces on the interstream divides have been stable since they were formed, or there have been no recognizable additions or removals on these surfaces except for minor amounts of aerosols. The oldest geomorphic surfaces in the Neuse drainage are in the upper Coastal Plain and are (?) Miocene‐Pliocene, i.e., they may range from >5 to >3.3 million years. The surfaces in the middle Coastal Plain are Pliocene to early Pleistocene, i.e., they range from >5 to 0.5 million years. Surfaces in the lower Coastal Plain are all Pleistocene and are from about 400 to 115, possibly as young as 50 to 35 thousand years. Holocene surfaces, <10 thousand years, are the organic areas of pocosins and most of the valley slopes throughout the Coastal Plain. The Holocene valley slope surfaces are extensive in the middle and upper Coastal Plain, but occupy minor areas of the lower Coastal Plain.The (?) Miocene‐Pliocene‐Pleistocene ages of the Coastal Plain surfaces are estimates of when subaerial weathering of the sediments and soil formation started. These are the time frames against which all changes produced by soil formation must be measured.
Effect of Plant Ash on Nitrogen Fertilizer Transformations and Ammonia Volatilization
Authors: Raison R. J. , McGarity J. W. 
Published: July 2010

AbstractThe influence of plant ash on the transformation of N‐containing fertilizers and the volatilization of NH3 was studied in the presence and absence of soil. In moist ash alone, urea and KNO3 were unaffected, but 63 and 70% of N applied as (NH4)2SO4 was volatilized from autoclaved and nonautoclaved ashes, respectively, over a 4‐day period.Volatilization of NH3 was greater when urea or (NH4)2SO4 was topdressed to soil treated with a surface layer of ash than when they were added to bare soil. The effect of ash resulted from its ability to increase surface soil pH, saturate surface soil exchange sites with basic cations, and increase soil urease activities.These findings suggest that volatile loss of N can be expected when NH4‐N yielding compounds (e.g., fertilizers, urea excreted by wildlife) are added to surface accretions of plant ash. This factor should be considered in the timing of surface applications of N fertilizer to forests.
Soil Kaolinite, Vermiculite, and Chlorite Identification by an Improved Lithium DMSO X‐ray Diffraction Test
Authors: Abdel‐Kader F. H. , Jackson M. L. , Lee G. B. 
Published: July 2010

AbstractThe thermal treatment of K‐saturated soil clays does not reliably differentiate between kaolinite and chlorite by the 7Å XRD peak loss. Dimethylsulfoxide (DMSO) treatment for expansion of soil kaolinites to 11.2Å is effective in expanding the vermiculite 14Å peak from that of chlorite by Li, H2O, time, and temperature control in a group of kaolinite‐rich soils (Eau Pleine, Marathon, Rietbrock, Dolph, and Kert series, all from Marathon and Wood Counties) from central Wisconsin. Only partial expansion of soil vermiculite to 18.8Å occurs when the sample is Na+‐saturated, but expansion is complete with Li+ saturation after the sample has been allowed to stand in a dilute (<0.01N) LiCl solution. The intercalation of expansible clays by DMSO is optimum only when the liquid contains H2O, but <10% H2O, and the clay is allowed to stand in the DMSO‐H2O‐LiCl at 90°C overnight. A 50‐mg sample of clay in a 15‐ml plastic centrifuge tube is washed twice with 5 ml 1N LiCl and once with 4 ml 0.1N LiCl ml−1 cake (paste) volume, the suspension in this third washing being allowed to stand for 2 hours at 50°C to promote flocculation before centrifugation. The sample is washed twice with 9 ml of DMSO ml−1 of cake volume, the suspension in the second washing (>90% DMSO, <10% H2O solution of <0.01N LiCl) being allowed to stand overnight at 90°C. The tube is centrifuged and 70° of the supernatant is discarded. The remaining sample is stirred, spread on a porous, dry ceramic tile to dry partially by imbibition, and X‐rayed while still moist to prevent the collapse of the vermiculite‐ and montmorillonite‐DMSO 18.8Å complexes. The diagnostic X‐ray diffractogram peaks are: kaolinite, 11.2Å; vermiculite and montmorillonite, 18.8Å; chlorite, 7.2 and 14.4Å; mica, 10Å. Intergrade chlorite‐vermiculite mainly remains at 14.4Å; mixed‐layer systems remain mixed‐layered, according to the component minerals present.
The Role of Nitrate Diffusion in Determining the Order and Rate of Denitrification in Flooded Soil: I. Experimental Results
Authors: Reddy K. R. , Patrick W. H. , Phillips R. E. 
Published: July 2010

AbstractThe effect of NO3‐‐N diffusion on the order and rate of denitrification reaction was studied in 15 soils from various locations in the U.S. The soils were amended with 0.5% rice straw and incubated under saturated conditions without O2, either with no excess floodwater or with a 3‐cm overlying layer of floodwater. The disappearance of added and native NO3‐‐N and its conversion to N2 and N2O followed apparent zero‐order reaction kinetics when all the NO3‐‐N was present in the active soil layer (no excess floodwater). When added NO3‐‐N was present in both the floodwater and the soil layer, NO3‐‐N disappearance followed apparent first‐order reaction kinetics. A decrease in NO3‐‐N concentration in the soil layer caused NO3‐‐N in the floodwater to diffuse into the soil layer (a first‐order reaction with respect to NO3‐‐N concentration) where it was denitrified. Thus where NO3‐‐N loss involved both diffusion from the overlying floodwater and denitrification, NO3‐‐N disappearance appeared to be a first‐order rather than a zero‐order reaction.The rate of denitrification was faster in soils incubated with no excess floodwater compared to soils incubated under 3 cm of floodwater. One soil (Crowley silt loam), when incubated with no added carbon source and no excess floodwater, showed NO3‐‐N disappearance to follow first‐order kinetics. When this soil was incubated with an additional carbon source, NO3‐‐N disappearance was zero order.
The Role of Nitrate Diffusion in Determining the Order and Rate of Denitrification in Flooded Soil: II. Theoretical Analysis and Interpretation
Authors: Phillips Ronald E. , Reddy K. R. , Patrick W. H. 
Published: July 2010

AbstractA theoretical analysis of denitrification occurring in submerged soil in a test tube, when assumed to be a zero‐order reaction with available organic carbon nonlimiting, appears to be a first‐order reaction if the effects of diffusion are neglected. In this case, denitrification appears to be a first‐order reaction because denitrification occurs at a faster rate than the diffusive flux can supply NO3‐‐N to the soil. After some length of time, the concentration of NO3‐‐N in the lower portion of the flood‐water‐soil interface will be equal to the concentration in the flood‐water. After which time, denitrification occurs only in the upper portion of the soil sample. When the role of diffusion is neglected, it is generally assumed that denitrification occurs uniformly throughout the soil sample. It is for this reason that denitrification can appear to be a first‐order reaction when it may actually be a zero‐order reaction. The true order of reaction and rate constant of denitrification in a test tube can be evaluated experimentally by eliminating the floodwater above the soil sample; with this experimental geometry some of the confounding effects of diffusion of NO3‐‐N can be minimized. If diffusion is neglected, not only is the order of reaction misjudged but the depth of floodwater above the soil has a significant effect on the magnitude of the calculated rate constant of the apparent first‐order reaction also.
Colorimetric Determination of Urea in Soil Extracts Using an Automated System
Authors: Douglas L. A. , Sochtig H. , Flaig W. 
Published: July 2010

AbstractA method is described for using an automated system to determine urea in 2M KCl soil extracts that contain a urease inhibitor (phenylmercuric acetate). The method is sensitive and precise and allows 90–120 extracts to be analysed per day.
Ultraviolet Irradiation of Dilute Fulvic Acid Solutions
Authors: Chen Y. , Khan S. U. , Schnitzer M. 
Published: July 2010

AbstractDilute aqueous fulvic acid (FA) solutions were exposed to UV irradiation for various lengths of time at pH 3.5, 7.0, and 11.0. The rate of photo‐oxidation of FA was pH dependent, increasing with increase in pH.In acid solution most of the FA appeared to be oxidized to CO2 + H2O. Organic S was converted to inorganic sulfate. Under neutral and alkaline conditions, organic C was oxidized to inorganic carbonate. About 90% of the initial FA was decomposed by UV irradiation. Only the most stable components, which were benzenecarboxylic and allphatic n‐fatty acids, resisted decomposition. Phenolic acids, the chromophores responsible for the color of FA, were destroyed.Ultraviolet irradiation could be used as a degradative method if one is interested in isolating and identifying the most stable FA components only.