bluuebunny/crossref_metadata_2025 huggingface dataset:
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

The 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

A 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

Silica 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

Yields 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

A 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

A 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

Extractability 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

A 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

A 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

The 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

The 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

The 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

A 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

A 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

Dilute 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.
Residual Fertilizer Nitrogen in a Flooded Rice Soil
Authors: Reddy K. R. , Patrick W. H.
Published: July 2010

Residual effects of 15N‐labelled fertilizer (ammonium sulfate) nitrogen were measured during the second cropping season of rice (Oryza sativa L.). During the first cropping season, labelled fertilizer N was applied at 100 kg N/ha using different methods of N application. At the end of harvest the rice straw obtained during the first cropping season was incorporated back into the respective plots. During the second season half the plots were treated with an additional 100 kg N/ha of nonlabelled fertilizer N as an early season top dressing. The uptake of residual labelled N (that present in the native soil organic matter and in the incorporated rice straw) was measured during the growing season and at harvest time under fertilized and nonfertilized conditions.

The recovery of residual labelled N in grain and straw was 2.7 to 3.1 kg N/ha, with a large fraction of N (34.3 to 40.1 kg N/ha) still remaining in the soil. Approximately 3 to 5 kg of the residual labelled N/ha present at the beginning of the season was not accounted for in any fraction and was assumed to be lost from the system. Over a 2‐year period, about 66 to 82% of the applied labelled fertilizer N could be accounted for by plant uptake or in the soil with the remainder lost from the plant‐soil system.
Sodium Bicarbonate Extraction to Estimate Nitrogen, Phosphorus, and Potassium Availability in Soils
Authors: Bar‐Yosef B. , Akiri B.
Published: July 2010

The extractability of NO3‐N, P, and K from five calcareous soils differing in physical and chemical characteristics by NaHCO3 (0.5M, pH 8.5) was studied under laboratory conditions. The extracted amounts of the three ions were related to time since their application to the soils, to the equilibration period of the soils with the extractants, to the concentration of the ions in the soils, and to the clay content of the soils. After about 70 days in the soil, the extractability of each ion at a given application level was independent of time. The recovery percentage of P and K as a function of the applied amounts of these elements depended mainly on the clay content of the soils, while NO3‐N recovery was independent of the factors studied. Linear relationships were obtained between NaHCO3‐and NH4OAc‐extracted K, and NaHCO3‐ and KCl‐extracted NO3‐N. The slopes for NO3‐N were 45° for all soils, but were specific for each soil in the case of K.
Erosion Processes on Steep Granitic Road Fills in Central Idaho
Authors: Megahan W. F.
Published: July 2010

A set of thirty 20.2‐m2 (1/200‐acre) erosion plots was used to study erosion occurring on steep road fills constructed with granitic soil materials in the Idaho Batholith. Erosion data were collected for a 3½‐year period from 1969 through 1972. Erosion on bare control plots averaged 3.4 metric tons/km2 per day for water years 1970 through 1972. Erosion was reduced an average of 44% and 95% by tree planting and straw mulching, respectively. Daily erosion rates were consistently higher during summer periods than during snowfree winter periods, presumably because of greater rainfall energy during the summer. Dry creep accounted for at least 15% of the total annual erosion for the years sampled and was as high as 40% in 1971. The erodibility index was a poor predictor of erosion for rain periods. Observations in the area suggest that wind was an important erosion factor on the steep slope studied. The median particle size of eroded materials (D50) tended to decrease throughout the summer and fall until mid‐October when it abruptly increased. Soil crusting during the summer and soil freezing and thawing in the fall may have caused these seasonal trends.
Weathering of Micas by Mycorrhizal Soybean Plants
Authors: Mojallali H. , Weed S. B.
Published: July 2010

Two biotites, a phlogopite, and a muscovite, ground to yield sandsize flakes, were used as sources of K for soybeans [Glycine max (L.) Merrill] grown in pot culture with and without vesicular‐arbuscular mycorrhizal association. On the low‐fertility soil used, effects of the mycorrhizae were most pronounced in terms of P uptake. Plants in noninoculated pots were stunted and P deficient; no K deficiency was observed in these plants. Plants grown in inoculated soil were larger and did not exhibit P deficiency symptoms; they were, however, K deficient. When P deficiency was corrected, there was no difference in plant growth attributable to K source, though the micas differed markedly in their abilities to supply soluble K. The mycorrhizae appeared to accelerate weathering of the biotites and the phologopite, but no effect was observed on the muscovite. Electron microprobe analysis showed extensive removal of K and some removal of Al from edges of the readily weathered biotite flakes subjected to biological weathering.
Effect of Fulvic Acid on Adsorption of Methyl Parathion and Parathion by Ca2+ − and Fe3+‐Montmorillonite Suspensions.
Authors: Bowman Bruce T.
Published: July 2010

A study was conducted to examine the effect of fulvic acid (FA) on the adsorption of methyl parathion and parathion by Ca2+ − and Fe3+‐montmorillonite suspensions, and to determine whether FA in solution could alter the water solubility of these insecticides. FA, in the 10‐ to 100‐mg/liter range, did not affect the water solubility of the two insecticides. In Ca2+‐montmorillonite suspensions, increasing FA concentrations first enhanced methyl parathion adsorption, followed by adsorption decrease at higher FA levels. Methyl parathion adsorption in Fe3+‐montmorillonite suspensions decreased, with increasing FA levels. Parathion adsorption was not significantly altered in either clay suspension. The order in which the FA, clay, and insecticide were mixed affected methyl parathion adsorption. The greatest effects were observed where FA was adsorbed by the clay before the insecticide solutions were added. FA adsorption by Ca2+‐montmorillonite fitted the Freundlich isotherm, whereas the much greater adsorption by Fe3+‐montmorillonite fitted the Langmuir isotherm. Although both CaCl2 and FeCl3 solutions greatly enhanced FA removal by their respective clay suspensions (even at low concentrations), parathion adsorption was not affected. The presence of FA in the FeCl3‐Fe3+‐montmorillonite suspensions appeared to prevent parathion degradation.
Organic Phosphorus Changes Over a Growing Season in Some Borolls and Associated Aquoll of South Dakota
Authors: Westin Frederick C.
Published: July 2010

The objective of this research was to study changes in soil organic phosphorus for five members of a soil catena over a growing season. Three horizons of each of five pedons were sampled on the South Dakota University Research Farm at 2‐week intervals 10 April–23 October. Samples were taken at noon each sampling date when temperatures were recorded using a dial thermometer. Precipitation was that recorded by the Research Farm gauge between sampling periods. Soil samples were analyzed for total and organic‐P, available‐P and pH. The pedons also were analyzed for CEC, exchangeable cations, total nitrogen and organic carbon. Catena members appeared to have seasonal changes in organic phosphorus but the change was significant only for the north‐facing member. When examined for each sampling date the organic phosphorus changes were significantly related to precipitation for the sloping Borolls but not in the Borolls occupying level positions nor the associated Aquoll.
Cesium Sorption and Desorption Behavior of Kaolinites
Authors: Komarneni Sridhar
Published: July 2010

Data for three kaolinites show that Cs was preferentially sorbed by kaolinites in NaCl and CaCl2 solutions. Cesium desorption behavior of kaolinites revealed that a variable proportion, 0–3.5% was strongly held. The Cs desorption behavior as well as the amounts of Cs fixed by kaolinites correlated well with the nature of impurities in them.
Determining Soil Gypsum Content and Expressing Properties of Gypsiferous Soils
Authors: Nelson R. E. , Klameth L. C. , Nettleton W. D.
Published: July 2010

The standard method for measuring the gypsum content of soils is a lengthy one, partly because of the presence of Na and Mg sulfates in most gypsic horizons, and partly because of the difficulty in dissolving all the gypsum in the sample. A more rapid method, sufficiently accurate for taxonomic uses, has been developed and is based on loss of crystal water of gypsum upon heating to 105° C. Percent gypsum, calculated on an oven‐dry weight basis from loss of crystal water, equals 1.038 × percent gypsum by the standard chemical method + 0.17. The standard error of estimate for the new method is ± 1.8% gypsum. Equations are given for expressing properties of gypsiferous soils on an oven‐dry + crystal water of gypsum weight basis.
Electron Probe Microanalytical Studies of Phosphorus Distribution within Soil Fabric
Authors: Qureshi R. H. , Jenkins D. A. , Davies R. I.
Published: July 2010

Electron probe microanalysis has been used to follow the distribution of phosphorus and associated elements within soil features to establish the composition of the immediate root environment. Various qualitative analytical modes of using the instrument are described involving either specimen traverse or spectrometer scanning with a static beam, line scanning, one‐dimensional scanning, area scanning, or successive rast counting. By these means phosphorus has been found to occur variously as discrete grains of rare‐earth phosphates, in preferential association with iron in iron/manganese concretions, as concentrations within undifferentiated soil matrix and ferrans at void surfaces, and to be associated with calcium in a fresh root and possibly with iron rather than calcium, aluminium, or potassium in an old root.
Cation Exchange Equilibria in a Mixed Soil System Containing Three Heterovalent Cations
Authors: Wiedenfeld R. P. , Hossner L. R.
Published: July 2010

Cation exchange equations used with soils have been suitable only for systems containing two cations. Theoretical exchange equilibria relationships for a mixed soil system containing three heterovalent cations; Ca2+, Mg2+, and Na+; are presented. Predictive equations for this tertiary system are derived using solid phase activity coefficients and thermodynamic equilibrium constants for the three binary systems obtained from experimental data. Theoretical cation exchange equilibria described for this tertiary system are in agreement with recognized exchange properties for these three cations. Interactions between two cations as they affect the exchange behavior of a third cation are also predicted. The methods presented are applicable to systems containing any number of heterovalent cations.
Decomposition in Soil of the Humic Acid‐type Polymers (Melanins) of Eurotium echinulatum, Aspergillus glaucus Sp. and Other Fungi
Authors: Linhares L. F. , Martin J. P.
Published: July 2010

Studies were conducted to compare the decomposition rates in soil of 14C‐labeled humic acid‐type polymers (melanins) of Eurotium echinulatum and Aspergillus glaucus sp. with those of other fungal melanins, soil and peat humic acids, fungal cells, nondialysable culture medium polymers not precipitated by acid, and other organic residues. Carbon and N contents, COOH groups, and total acidity were also determined for the fungal products. After 12 weeks incubation at 22°C the percentages of the added 14C activity evolved as 14CO2 from the acid‐precipitable fungal melanins ranged from 4–6% for E. echinulatum, 4–13% for A. glaucus, 6–8% for Hendersonula toruloidea and 6 to 50% for Stachybotrys atra. The fungal polymers were almost as resistant to biodegradation as soil or peat humic acids. The fungal cells and culture medium polymers not precipitated by acid lost from 26–58% of the applied C, which compared with losses of 50–75% for hyaline fungal cells, corn stalks, and wheat straw. The N source and growth conditions did not influence biodegradability. The C contents of the melanins ranged from 51–60%, the N from 1.4–6.8%, COOH groups from 81–385 meq/100g, and total acidity from 375–876 meq/100 g.
Field Testing of Several Nitrogen Availability Indexes
Authors: Fox R. H. , Piekielek W. P.
Published: July 2010

With no quick, reliable soil N availability test for humid region soils, N fertilizer recommendations in these areas are being made on the basis of crop N requirements. When the variability in N‐supplying capability of soils is not taken into account, most N fertilizer recommendations will be inaccurate, leading to inefficient use of N, less economical crop production, and the potential for N pollution of the nation's air and water. Although several N availability indexes have proved to be well correlated with the N‐supplying capability of a soil in greenhouse or laboratory experiments, very little testing of these indexes has been done with field experiments. Eight N availability indexes were correlated with the capability of eight Pennsylvania soils to supply N to field‐grown corn (Zea mays L.) in 1976 and 1977. Boiling 0.01M CaCl2 and 0.01M NaHCO3‐extractable N were both significantly correlated at the 1% level (r = 0.86 and 0.77, respectively) with the N‐supplying capability of the soils from the combined 1976 and 1977 experiments. Autoclave‐extractable NH4‐N and total soil N were significantly correlated with the soil supplying capability at the 5% confidence level (r = 0.70 and 0.68, respectively). Walkley‐Black soil organic matter, soil NO3‐, and H2SO4‐extractable and KCl‐extractable N were not significantly correlated with N availability in the field. Though four of the indexes were well correlated with the N availability in the soil, time and expense necessary for these analyses may preclude their being used routinely by soil testing laboratories.
Mottling in Soil Profiles Containing a Coarse‐textured Horizon
Authors: Clothier B. E. , Pollok J. A. , Scotter D. R.
Published: July 2010

Mottling often characteristically occurs in fine‐textured soil just above an underlying coarse‐textured layer. Interpretation of such mottling as representing a normal drainage impedance is misleading as a perched or ground water table may never occur in the profile. In this paper a simple soil water drainage model is discussed that aids interpretation of the pattern of mottling in a soil horizon above a coarse‐textured layer. Also the influence of various soil physical parameters on mottling phenomena is analyzed, suggesting that the more coarse‐textured the underlay the greater the propensity to mottle. The tendency to mottle is shown to be greatest in the soil immediately above the coarse‐textured layer. The model is applied to the naturally‐layered Manawatu fine sandy loam, a Dystric Fluventic Eutrochrept.
Determination of the Apparent Dispersion Coefficient of Solutes in Unsaturated Soil
Authors: Paetzold R. F. , Scott H. D.
Published: July 2010

A method for determining the apparent dispersion coefficient of a solute in unsaturated soils at relatively low soil water flow rates is presented. Two soil cores with different initial water contents were joined and water allowed to flow between the soil cores for a specified time interval. The distribution of a radioactively tagged solute, initially present in one of the soil cores, was subsequently determined by freezing the cores in liquid air, sectioning the soil with a refrigerated microtome, and analyzing the soil sections for solute content using liquid scintillation techniques. Apparent dispersion coefficients could be determined either with or against the water flow. The solutes used in this study were tritiated water, chloride, and metribuzin (a herbicide).
Surface Charge Manipulation in Constant Surface Potential Soil Colloids: II. Effect on Solute Transport
Authors: Wann S. S. , Uehara G.
Published: July 2010

Potassium breakthrough curves from soil columns containing samples collected from an oxic horizon of a Typic Torrox shifted to the right as the sample was treated with increasing levels of P. The shift in the breakthrough curve was significantly related to a lowering of the zero point of charge. The lowering of the zero point of charge was in turn related to levels of applied P. The anion accompanying K also had a marked effect on the position of the breakthrough curve. When the accompanying anion was Cl, S, and P respectively, the K concentration in the effluent attained one‐half of influent concentration at 4.25, 5.30, and 8.20 pore volumes.
Long‐Term Denitrification Studies in Soils Fertilized With (15NH4)2SO4
Authors: Focht D. D. , Stolzy L. H.
Published: July 2010

A 2‐year study was conducted in lysimeters containing four different soils with successive summer and winter crops of corn and barley, respectively. The crops were fertilized with (15NH4)2SO4 at application rates equivalent to 134, 108, 415, and 440 Kg N/ha for the respective summer 1973, winter 1974, summer 1974, and winter 1975 crops. The frequency of 15N dinitrogen samples was higher in the summer and higher at the lower fertilizer rates, while the reverse was true for NO3‐ concentrations in leach water and N2O concentrations in the soil profile. Emissions of N2O from soil, even where the higher concentrations were observed, were low in terms of N losses with the greatest mass emission at any time amounting to 6.5 g/ha over a 1‐day period. Nitrogen gas emissions over a 1‐week period in one instance were estimated at 5.2 kg N/ha: it was observed that this amount could be generated from low (1 ppm or less) concentrations of N2O.
Residual Nitrate‐N in Fine Sand as Influenced By N Fertilizer and Water Management Practices
Authors: Smika D. E. , Watts D. G.
Published: July 2010

A better understanding of the severity of NO3‐N movement out of the crop root zone in irrigated sandy soils is needed. The objective of this study was to determine residual NO3‐N after the corn (Zea mays L.) growing season from N applied at rates of (i) 112, (ii) 224, and (iii) 336 kg/ha in 1974 and (iv) 168, (v) 250, and (vi) 324 kg/ha in 1975. Nitrogen was applied as a single broadcast (B) application at the beginning of the corn growing season or injected (S) through the irrigation system at five equal increments before tasseling. Water application for both N application methods was attempted to be 0.8 W2 water application treatment, residual NO3‐N averaged 0.22 kg/during all but the first 6 weeks of corn growth.

When N was broadcast‐applied at seeding very little residual NO3‐N remained in the 150‐cm sampling depth after the crop growing season, regardless of N application rate or water application amount. When the N was applied through the irrigation system (injected N), only the W3 water application treatment resulted in leaching all NO3‐N below the crop root zone. With injected N and W2 water application treatment, residual NO3‐N averaged 0.22 kg/ha for each kg/ha of N applied. With injected N and W1 application treatment NO3‐N increased linearly at 0.43 kg/ha for each kg/ha of applied N above the B4 rate. At lower N application rates, residual NO3‐N was very low because this amount of N nearly equalled plant uptake. No overwinter NO3‐N was lost with the injected N treatments. These results showed that the injected N application method with proper water application management can greatly reduce the potential for NO3‐N movement below the corn crop rooting zone on fine sand soils.
Copper Chloride as an Extractant for Estimating the Potentially Reactive Aluminum Pool in Acid Soils
Authors: Juo A. S. R. , Kamprath E. J.
Published: July 2010

The reactive Al pool in selected Ultisols, Oxisols, and Histosols from Africa, South America, and North Carolina was estimated by extraction with 1N CuCl2. The Al‐saturated clay minerals with and without interlayered hydroxy‐Al were used to compare the extractability of Al by 1N CuCl2 and 1N KCl.

The 1N solutions of KCl and CuCl2 were equally effective in extracting exchangeable Al from an Al saturated montmorillonite. The 1N CuCl2 solution, however, extracted almost twice as much Al from an Al saturated vermiculite containing a hydroxy Al interlayer as compared with 1N KCl. Generally, more than twice as much Al was extracted from acid surface soils (< pH 5) by 1N CuCl2 than by 1N KCl suggesting that Al bound by organic matter was being extracted by the CuCl2.
Direct Measurement of Denitrification Loss from Soils: I. Laboratory Evaluation of Acetylene Inhibition of Nitrous Oxide Reduction
Authors: Ryden J. C. , Lund L. J. , Focht D. D.
Published: July 2010

The rate and extent of denitrification in soils incubated under helium atmospheres in the presence of acetylene (C2H2) concentrations ranging from 0.1 to 5.0% (vol/vol) was equivalent to that measured in the absence of C2H2. In the absence of C2H2, gaseous nitrogen (N) appeared as a mixture of nitrous oxide (N2O) and dinitrogen (N2), usually dominated by N2, whereas in the presence of C2H2 gaseous N appeared exclusively as N2O. An C2H2 concentration of 1.0% was also sufficient to maintain inhibition of N2O reduction even when the soil nitrate supply had been exhausted. Overall respiration of incubation systems, measured as carbon dioxide evolution, was also unaffected by the presence of C2H2. Similar findings were obtained when soils were incubated under argon‐oxygen (4:1) atmospheres containing 1.0% C2H2. The inhibitory effect of C2H2 was virtually instantaneous when a 1.0% C2H2 concentration was established in an actively denitrifying soil. Diffusion of C2H2 into soils packed to their maximum bulk density and held at 5% air‐filled porosity was also sufficiently rapid to induce essentially complete inhibition of N2O reduction during incubation in air using a 15N‐labeled nitrate addition to the soil. The extent of denitrification varied among soils and ranged from 54 to 154 µg N/g under helium atmospheres, and from 15 to 106 µg N/g under argon‐oxygen atmospheres, after 200 hours incubation. Ratios of N2/N2O were essentially the same whether measured directly or calculated from the difference in N2O production in the presence and absence of C2H2. The findings are discussed with respect to the use of the C2H2 inhibition technique for direct infield measurement of denitrification.
A Reevaluation of Phosphorus‐32 and Resin Methods in a Calcareous Soil
Authors: Bowman R. A. , Olsen S. R.
Published: July 2010

Four experiments were run to evaluate the resin and 32P methods as valid laboratory methods in a calcareous soil. Recovery of four levels of added KH2PO4, after several cycles of wetting, drying, and mixing was evaluated. Total‐exchangeable P (TEP24) was determined by the carrier‐free method, and resinextractable P by equilibrating 1 g soil sample with 2 g resin overnight. Equilibrium of 31P and 32P on the soil‐solid phase was evaluated by measuring specific activities with time. Different soil‐solution ratios, using water and 0.01M CaCl2 as extractants, were evaluated to determine their effects on the total exchangeable P. Water and four different salts at three different molarities were used as extractants with 1 and 2 g resin to determine total released P in solution and on the resin.

The recovery experiment showed a high correlation between added and recovered P, using both TEP24 and resin methods; the time‐equilibration study indicated a lack of complete equilibrium between 31P and 32P after 2 hours shaking, and a near complete or complete equilibrium at 24 hours; different soil‐solution ratios did not affect total exchangeable P, and water extracted the most resin‐P and 0.01M CaSO4 the least (roughly one‐half of pure water):
Morphology and Water Regime of a Dothan Soil
Authors: Guthrie R. L. , Hajek B. F.
Published: July 2010

The water regime in a Dothan soil was characterized by installing piezometers at 137‐, 183‐, and 285‐cm depths. Monthly water table measurements differed for each piezometer throughout a 4‐year study period, indicating a perched water table. There was a water table at the greatest depth on only five occasions during the study period. On all but a few occasions, a water table was encountered at the two shallower depths. Morphological properties and seasonal precipitation were related to the water regime. The perched water table fluctuated in a continuous zone of saturation in the B horizon above the horizons containing appreciable amounts of plinthite. A discontinuous zone of saturation is bounded on the bottom by the B3 horizon. The piezometer that had perforations in the C horizon showed no water table, which indicated that a “dry” zone exists between the perched and regional ground‐water tables. Fluctuations in the depth to perched water corresponded to seasonal precipitation patterns.
A Lithosequence in Coastal Plain Sediments in Alabama
Authors: Hoyum R. A. , Hajek B. F.
Published: July 2010

A lithosequence was used to explain the morphology and genesis of soils from the Tuscahoma Sand Formation in Crenshaw County, Alabama. Position‐slope‐geology computer displays were used for sampling and determining the distribution and extent of soils in the analysis area. The Tuscahoma Sand Formation has a locally distinctive topography and suite of soils that are closely related to the characteristics of three outcrop beds on 8–12% side‐slopes. The lower stratum, exposed farthest inland, is dominated by clayey soils. In argillic horizons the CEC ranges from 5.4 to 17.2 meq/100 g even though smectites dominate in one profile. Fine‐loamy soils with siliceous mineralogy dominate the middle stratum. The youngest sediments, superpositioned above the middle stratum, are clayey with mixed mineralogy. The pH of argillic horizons ranged from 4.9 to 5.2. All clayey soils were Hapludults while the fine‐loamy soils are now classified Paleudults; however, morphological properties suggest that all soils studied may be Hapludults. With all other soil‐forming factors relatively constant, the differences encountered in soils across the study area relate directly to parent material.
Rates of Weathering and Soil Formation on Granite in Rhodesia
Authors: Owens L. B. , Watson J. P.
Published: July 2010

Rates of weathering and soil formation on granite were studied in two areas of Rhodesia using small watersheds. The Juliasdale watershed of 0.91 km2 is hilly and has a mean annual rainfall of 1,220 mm. The Rusape watershed of 7.33 km2 is more nearly level and has a mean annual rainfall of 920 mm.

Streamflow was measured in the two catchments over a period of at least 7 years. Streamwater, rainwater, soil, and rock samples were analyzed for Ca, Mg. K, Na, Si, and Al.

The rate of granite weathering was calculated using Barth's equation which links the rate of weathering to the amount of an element removed in solution per unit time, its concentration in the rock and its concentration in the weathered product. Sodium and Ca were the elements used in the Barth equation. The weathering rates in the Juliasdale and Rusape watersheds were estimated at 400 and 150 kg/ha per year, respectively, or 15.4 and 5.8 mm/1000 years. The concepts of C. E. Marshall and J. F. Haseman as well as S. W. Buol include changes in bulk density during the weathering process and give soil formation rates more acceptable than those of Barth. Thus, the rate of soil formation was found to be 11.0 mm/1000 years in the Juliasdale watershed and 4.1 mm/1000 years in the Rusape watershed.
Aqueous Solubility Studies of Muscovite: Apparent Nonstoichiometric Solute Activities at Equilibrium
Authors: Mattigod S. V. , Kittrick J. A.
Published: July 2010

Solubility studies were conducted on three different muscovites. The experiments were designed to conform with a number of well‐established criteria for studying the equilibrium solubility of sparingly soluble compounds. The compositions of the aqueous phase in contact with mixtures of muscovite and a synthetic gibbsite of known solubility, were monitored for over a period of 2 years. At the start of the experiments, the solid phases were characterized by various techniques such as chemical analysis, optical microscopy, X‐ray diffraction, infrared spectroscopy, and electron microscopy. The solids present at the end of the experiments were also examined. Free ion activities and activity ratios were computed from the measured total concentrations of various solutes. The attainment of equilibrium between the solid phases and the solution phase were established by rigorous chemical criteria. Analysis of the equilibrium solubility data indicated that the observed solute activity ratios were incompatible with the dissolution reaction based on the original chemical composition of muscovite. The stoichiometry of the muscovite phase was derived from solution equilibria and the standard free energy of formation of this phase was calculated to be −5501.1 kJ/mol.