bluuebunny/crossref_metadata_2025 huggingface dataset:
Surface Textures of Quartz in Tropical Soils
Authors: Eswaran H. , Stoops G.
Published: July 2010

Studies of the surface textures of quartz grains from a range of tropical soils show the appearance of striations, etch features and dissolution pits, increasing in size and/or quantity in the more weathered soil materials. These features show a crystallographic symmetry, most probably related to the crystallographic orientation of the grain.

Monitoring the changes in a 19‐m deep weathering profile on granite showed that physical disintegration begins a few centimeters from the fresh rock. Chemical weathernig, which intensifies towards the soil surface, produces etching and dissolution pits. An additional phenomenon observed is the infusion of clayey materials and/or sesquioxides into the void system of the grains.
Incremental Soil Sampler for Use in Summer‐Fallowed Soils
Authors: Pikul J. L. , Allmaras R. R. , Fischbacher G. E.
Published: July 2010

An inexpensive, manually operated soil sampler has been developed for determining profiles of bulk density and water content in the top 10 cm of rod‐weeded summer‐fallowed soil. This sampler is especially suitable for sampling 1‐cm increments of loose dry soil overlying a firm soil at a 10‐ to 20‐cm depth. Field data obtained with this sampler showed true variations in soil moisture and bulk density with respect to depth and time even at depths of < 2 cm. Thus it is possible to estimate soil heat capacity over the whole 0‐ to 40‐cm profile.
The Swelling of Clay: I. Basic Concepts and Empirical Equations
Authors: Low Philip F. , Margheim James F.
Published: July 2010

The primary objective of the present study was to elucidate the relative contributions of exchangeable cations and surface forces to the swelling pressure, Π, of montmorillonite. To achieve this objective, measurements were made of the amount of water imbibed by Na‐saturated montmorillonites having different cation exchange capacities, b dimensions, and specific surface areas under applied pressures of 0, 1, 3, and 5 atm. The resulting data were used to develop the empirical equation (Π + 1) = exp [α/(mw/mm)] in which mw/mm is the mass ratio of water to montmorillonite and α is a linear function of the specific surface area and cation exchange capacity. Analysis of double‐layer theory in the light of this equation led to the conclusion that Π is affected less by exchangeable cations than by surface forces. It was suggested that exchangeable cations have a secondary effect because few of them dissociate from the layer surfaces.
Physical, Chemical, and Mineralogical Characteristics of Soils from Volcanic Ash in Northern Idaho: II. Phosphorus Sorption
Authors: Jones J. P. , Singh B. B. , Fosberg M. A. , Falen A. L.
Published: July 2010

Volcanic ash soils from northern Idaho sorbed considerable amounts of P depending upon the parent material, physical, chemical, and mineralogical characteristics of the soils. Upper horizons of the soil derived from volcanic ash sorbed more P than did lower horizons which were derived from glacial sediment. The magnitude of P sorption was related to the extractable allophane content and quantity of concretions. The clay fraction adsorbed more P than the silt fraction. Sorption of P was due mainly to the presence of Al in concretions and the presence of higher amounts of amorphous materials. Iron, Al, Mn and other clay minerals contributed to the sorption capacity of the soils. Detailed roles of these factors in sorption of P by soils, clays, and concentrations are discussed.
Response of Three Irrigated Crops to Deep Tillage of a Semiarid Silt Loam
Authors: Cary J. W. , Rasmussen W. W.
Published: July 2010

The growth and water relations of winter wheat (Triticum aestivum L.), sugarbeets (Beta vulgaris L.) and corn (Zea mays L.) were studied after deepening the root zone in the Portneuf silt loam soil (Durixerollic calciorthid). Roots of annual plants are largely restricted by a hard layer that lies between the 0.4‐ and 1‐m depths. This layer was disrupted to a depth of 1.2 m by complete mixing, by chiseling, or by trenching on 0.6‐ and 1.2‐m centers. The treatments included two irrigation levels to show any advantage in crop water relations due to deeper rooting after deep tillage.

Deeper rooting did develop on the deep‐tilled treatments, but the water supplied through net soil moisture depletion below 0.6 m was increased by < 4 cm, even when the crop was stressed for water late in the season. Deep soil water extraction was not always proportional to rooting density. Trenching on 0.6‐m centers was the most favorable treatment. Completely mixing the soil decreased yields, due in part to a lighter surface color and lower soil temperatures. Deep tillage seldom had a measurable effect on stomatal resistance or plant water potential. Management of this soil should be concentrated on providing the best possible root environment in the top 0.5 m of soil as this is the basis for maximum production in irrigated agriculture.
Managing Irrigated Winter Wheat Residues for Water Storage and Subsequent Dryland Grain Sorghum Production
Authors: Unger Paul W. , Wiese Allen F.
Published: July 2010

Better cropping and residue management systems are needed to improve precipitation‐use efficiency, minimize ground water depletion by irrigation, reduce pumping costs, and conserve energy. An irrigated winter wheat (Triticum aestivum L.)‐dryland grain sorghum [Sorghum bicolor L. (Moench)] cropping system was evaluated from 1972 to 1978 for water storage between wheat harvest and sorghum planting time and for subsequent grain sorghum growth and yields. No‐tillage, sweep, and disk methods were used during the 11‐month period between crops for wheat residue management and weed control. Precipitation stored as soil water during the 11 months of fallow averaged 35, 23, and 15%; available soil water contents to the 1.8‐m depth at sorghum planting averaged 21.7, 17.0, and 15.2 cm; sorghum grain yields averaged 3,140, 2,500, and 1,930 kg/ha; and water‐use efficiencies (WUE) for sorghum grain averaged 89, 77, and 66 kg/ha‐cm for the respective treatments. Sorghum forage yields were slightly higher than grain yields and, therefore, WUE for forage production were higher than for grain. The WUE for forage, however, decreased in the same order as for grain. Based on March 1978 production costs and grain prices, net returns (excluding land, taxes, and interest costs) for sorghum production were four and two times greater with no‐tillage and sweep tillage, respectively, than with disk tillage, the most widely used tillage method after irrigated wheat in the Southern Great Plains.
Relations Between Geometrical Properties of Glass Beads Media and Their Main ψ(θ) Hysteresis Loops
Authors: Laroussi Ch. , De Backer L. W.
Published: July 2010

A main hysteresis loop in the volumetric water content (θ)‐suction (ψ) relation was determined experimentally for each of seven narrow size fractions of glass beads.

Geometrical properties of these media were separately obtained with a Purcell apparatus based on mercury intrusion. A linear relation between the mean radius of beads and the mean radius of pores was established. A computational model was established to relate the main hysteresis loops of porous media to their geometrical properties. As a consequence a diagram expressed in nondimensional variables ψ* and θ* is proposed to predict the main hysteresis loop of a similar porous medium whose geometrical properties are deduced by similitude from one of the explored fractions.
Adsorption of Copper and Lead by Ap and B2 Horizons of Several Northeastern United States Soils
Authors: Harter Robert D.
Published: July 2010

Adsorption of Cu and Pb by surface and subsurface samples of fifteen soils was ascertained. Soil adsorption maxima were derived from the reciprocal of the slope obtained by a least squares fit of “Langmuir” plots for each soil. The adsorption maxima were then regressed against various chemical and mineralogical properties of the soils in an attempt to deduce mechanisms of adsorption as well as to determine whether any commonly measured soil quantity could serve as a predictor of adsorption. The best predictor of adsorption by all samples was sum of bases, which explained 84 and 76% of the variation in Cu and Pb adsorption, respectively. In the subsurface horizons, the adsorption of both Cu and Pb was significantly related to vermiculite content (r2 = 0.78 and 0.85, respectively), but sum of bases was still a better prediction for these horizons alone (r2 = 0.83 and 0.92, respectively). Organic matter content had no significant relationship to adsorption by surface horizons.
Influence of Phosphate Fertilization on Zinc Adsorption by Tropical Soils
Authors: Saeed M. , Fox R. L.
Published: July 2010

Zinc adsorption isotherms were constructed for five soils from Hawaii which varied in mineralogy and history of phosphate fertilization. Equilibrating conditions were: 25°C, 0.01M CaCl2, soil solution ratio of 1:10, and 6 days. The amount of Zn added ranged from 0 to 600 µg/ml as ZnSO4 · 7H2O. Equilibrium was reached by 72 hours.

Unfertilized soils which contained predominantly constant charge colloids absorbed more Zn than soils with variable charge colloids. Phosphorus fertilization increased Zn adsorption by soils that contained colloids predominantly of the variable charge type. The results support the hypothesis that phosphate additions to soils increase Zinc adsorption by increasing the negative charge on iron and aluminum oxide systems. For soils containing constant charge colloids, prior P applications decreased Zn sorption because the fertilizer contained Zn as an accessory element. Zinc sorption conformed to the Freundlich model at concentrations greater than 0.1 ppm Zn in solution.
Phosphorus Availability in a Calcareous Soil After High Loading Rates of Animal Manure
Authors: Meek B. D. , Graham L. E. , Donovan T. J. , Mayberry K. S.
Published: July 2010

The fixing of phosphorus (P) added to calcareous soils is rapid but can be reduced by applying organic sources. The objectives of this study were to measure in the field the residual NaHCO3‐extractable P resulting from manure applications at high rates and to contrast the NaHCO3‐extractable P levels for manure vs. inorganic P fertilizers.

When inorganic P was applied at 490 kg/ha for each of 2 years the NaHCO3‐extractable P was increased from 16 to 31 ppm at the 0‐ to 30‐cm depth. The application of 98 kg/ha of P as triple superphosphate each of 2 years applied just before planting lettuce (September‐October) was as effective for increasing NaHCO3‐extractable P during the lettuce‐growing season (November 1976) as applying 490 kg/ha of P in May or June each of 2 years.

High rates of P (5,344 kg/ha) applied from manure sources (treatment 720E) resulted in high levels of NaHCO3‐extractable P up to 377 ppm. Total application of more than 360 metric tons/ha of manure (2,672 kg P/ha) resulted in movement of P to the 30‐ to 60‐cm depth. The increased level of NaHCO3‐extractable P from a manure application (treatment 360B) was still evident in the 0‐ to 30‐cm depth 6 years after manure application had ceased.

The application of 392 kg P/ha as triple superphosphate for each of 2 years increased the NaHCO3‐extractable P over the check by 11 ppm (November 1976). In contrast, the application of 334 kg P/ha from applied manure (treatment 180B) each of 2 years increased the NaHCO3‐extractable P over the check (after harvest in 1972) by 100 ppm.
Relationship of Ammonium Nitrogen Distribution to Mineralogy in a Hapludalf Soil
Authors: Sparks D. L. , Blevins R. L. , Bailey H. H. , Barnhisel R. I.
Published: July 2010

Distribution of fixed and exchangeable ammonium were examined in three soil profiles of the Shrouts series from the Knobs region of eastern Kentucky. Shrouts soils (fine, mixed, mesic, Typic Hapludalfs) have high base status; exhibit strong, prismatic structure; and are derived from calcareous, high magnesium, soft (weakly cemented) clay shale. Soil pH ranges from 6.3 in the Ap horizon to 7.9 in the C. Analyses, using the Silva and Bremner procedure, showed considerable fixed NH4+‐N in all horizons of each profile. Mean fixed NH4+‐N in the profiles was 365 ppm for the Ap, 463 ppm for the B21t, 433 ppm for the B22t, 469 ppm for the C, and 543 ppm for the Cr horizons. Exchangeable NH4+‐N also increased with depth, with values being about 1.2 to 1.5% of the fixed NH4+‐N values. X‐ray diffraction analyses of the clays and silts revealed predominantly mica in the 2–0.2 and <0.2 µm fractions, with some vermiculite present, and large quantities of mica in the silt fractions. High correlation (r = 0.92) was found between fixed NH4+‐N and exchangeable NH4+‐N. A correlation exists between fixed NH4+‐N and mica + vermiculite content with an r value of 0.68. The fixed NH4+‐N in the lower horizons is presumed to be indigeous, since no NH4+‐N has been added recently to the soil.
A Compact, Low‐Cost Circuit for Reading Four‐Electrode Salinity Sensors
Authors: Austin R. S. , Rhoades J. D.
Published: July 2010

An electrical circuit is described that uses a minimal number of components to measure soil electrical conductivity using the four‐electrode salinity sensor. The portable circuit is compact, inexpensive, reliable, and easy to construct.
Titration Behavior of Aluminum Organic Matter
Authors: Bloom P. R.
Published: July 2010

An Aluminum (Al)‐substituted peat containing one equivalent of Al3+ per equivalent of carboxyl groups was titrated potentiometrically in a range of NaCl concentrations. The family of titration curves generated was similar to that obtained with many acid soils. Comparison of the data from the Al‐peat with soils having a similar pH (3.9) at the apparent zero point of charge showed that the contribution of Al organic matter to H+ and OH‐ adsorption during potentiometric titrations is likely very significant and that Al on organic matter likely influences the displacement of the apparent zero point of charge from the zero point of titration.
Soil Heat Transducers and Water Vapor Flow
Authors: Cary J. W.
Published: July 2010

The heat flow through a silt loam, silty clay, and loamy sand were measured in a calorimeter at 7 and 36°C under matrix potentials near −0.3 bars. The transient thermal conductivity probe, the heat flux transducer, and deVries's theoretical method all gave low values of the apparent thermal conductivity at 36°C. An empirical correction was proposed for deVries's method that improved its agreement with the observed conductivities. The thermal vapor diffusion coefficients for the three soils were then calculated from his equation and compared with experimental values from the calorimeter. It was also shown that the thermal water vapor flow can be estimated if one knows the soil's saturated thermal conductivity, quartz content, water content, bulk density and temperature distribution.
Zinc and Copper Solubility as a Function of pH in an Acid Soil
Authors: McBride M. B. , Blasiak J. J.
Published: July 2010

Studies of the effect of pH and competing cations on Zn2+ and Cu2+ solubility in an acid mineral soil indicate the probable involvement of hydrous oxides of iron, aluminum, or manganese in the adsorption process. Adsorption on permanent charge sites of clays, or complexation with organic matter could not account for the apparent fixation of Zn2+ in a nonexchangeable form in the pH range of 5 to 7. Nucleation of Zn hydroxide on clay mineral surfaces may have produced the strongly pH‐dependent retention in the soil; however, Cu2+ showed more evidence of being controlled by organic complexation mechanisms. All soil solutions were undersaturated with respect to the least soluble hydroxides and carbonates of Cu2+ and Zn2+, at least at pH values below 7, indicating that simple precipitation was not involved in metal retention in the soil.
Purines and Pyrimidines in Soils and Humic Substances
Authors: Cortez J. , Schnitzer M.
Published: July 2010

Purines and pyrimidines were determined by ion‐exclusion chromatography in soils and humic substances of widely differing origins. Concentrations of purines + pyrimidines ranged from 20.9 to 137.7 µg per g of dry soils, from 210.8 to 810.0 µg per g of dry, ash‐free humic acids, and from 294.3 to 1086.6 µg per g of dry, ash‐free fulvic acids. Quantitatively the distribution in soils was as follows: guanine > cytosine > adenine > thymine > uracil. Humic acids were richer in guanine and adenine but poorer in cytosine, thymine and uracil than were fulvic acids. Guanine + cytosine over adenine + thymine ratios for soils and humic substances averaged > 2 and methyl cytosine was not detected, suggesting a microbial DNA origin for the nucleic acid bases extracted. The proportion of total N in purines + pyrimidines was inversely proportional to the total N content. An average 3.3% of the total N in the inorganic soils but only 0.3% of the total N in the organic soils analyzed were found to occur in nucleic acid bases.
Phosphorus Toxicity as a Factor in Zinc‐Phosphorus Interactions in Plants
Authors: Loneragan J. F. , Grove T. S. , Robson A. D. , Snowball K.
Published: July 2010

This study examined the hypothesis that accumulation of P to toxic levels in plant tissues may explain reported effects of high P in increasing the Zn requirement of plant tissues. It also examined the contribution of other mechanisms to the complex interaction of Zn and P fertilizers on plant growth.

Three levels of Zn and P fertilizers were applied to a siliceous and a ferruginous sand with low and high capacities to react with P, respectively. Application of P fertilizer induced or enhanced symptoms resembling Zn deficiency in subterranean clover (Trifolium subterraneum L.) in three distinct ways:

1) On the ferruginous sand but not on the siliceous sand, it induced Zn‐deficiency by depressing Zn absorption.

2) Where P limited growth, additional P depressed Zn concentrations and induced Zn deficiency in plants by promoting growth thus diluting available Zn supplies.

3) Where P did not limit growth, additional P increased P concentrations to toxic levels producing necrotic symptoms in old leaves and depressing growth.

Where plant tops had high Zn concentrations (> 40µg/g), P toxicity produced nectrotic symptoms in the absence of any of the characteristic symptoms of Zn deficiency. Where plant tops had low Zn concentrations (< 16µg/g), the necrotic symptoms developed in addition to the characteristic Zn‐deficiency symptoms of bronzing and chlorosis of old leaves and “little leaf” of young leaves thus strongly enhancing the apparent severity of Zn deficiency. Zn deficiency strongly enhanced P toxicity at the middle and high levels of P application apparently by limiting plant growth and concentrating the available P in plant tissues.

The enhancement of P toxicity by Zn deficiency explains reports that high P increases Zn requirements of plant tissues. It will occur more easily in plants grown in sand and water culture than in plants grown on soils with some capacity to react with P.
Fate of Tagged Fertilizer Nitrogen Applied to Winter Wheat
Authors: Olson R. V. , Murphy L. S. , Moser H. C. , Swallow C. W.
Published: July 2010

A field experiment using ammonium sulfate tagged with 7.65 A% 15N was conducted to assess how rates and times fertilizer is applied influence the fate of N applied to winter wheat (Triticum aestivum L.). Bottomless metal boxes were pressed 142 cm into the soil to confine the tagged fertilizer. Treatments, replicated four times, consisted of two rates (50 and 100 kg N/ha) and two application times (fall and spring). Fertilizer N used by the crop and that remaining in the upper 180‐cm of the soil after harvest were measured. Amounts of ammonium‐N and nitrate‐N from the fertilizer in the 0 to 10‐cm layer also were determined.

The N balance indicated 9.7 – 10.3 kg N/ha were unaccounted for at the 50‐kg N rate and 19.7 · 23.4 kg, at the 100‐kg rate. Losses did not differ significantly between application times. With 100 kg/ha the crop removed significantly more fertilizer N, and significantly less remained in the soil with spring than with fall applications. The crop used similar amounts of total N in each case, but with the spring applications more fertilizer N but less soil N was taken up. Fertilizer applications caused no priming effect on mineralization of indigenous soil N. Most of the fertilizer remaining in the soil was in the 0 to 10‐cm layer, with no evidence of N moving deeper than 50 cm, so losses were from gaseous loss rather than leaching.

Most of the fertilizer N in the 0 to 10‐cm layer of soil after harvest was immobilized, with only 9.6 – 11.5% remaining in inorganic forms. Immobilization was the principal reason for differences in spring and fall applications and for limited leaching. The percentages of NH4+‐N and NO3‐‐N, which originated from the fertilizer were 4 – 8 times the percentages of total N from the fertilizer, so more fertilizer N was in inorganic forms than was the case with indigenous soil N. Since there was a direct relationship between amounts of NO3‐‐N in the surface soil from fertilizer and amounts of N unaccounted for, it was concluded that gaseous losses resulted from denitrification processes.
The Role of Mycorrhizae in the Interactions of Phosphorus with Zinc, Copper, and Other Elements
Authors: Lambert D. H. , Baker D. E. , Cole H.
Published: July 2010

Mycorrhizae increase the uptake of Zn and Cu by many plants, but mycorrhizal activity is suppressed by P fertilization. Soybean (Glycine max Mer.) and two lines of corn (Zea mays L.) were used to determine if this mechanism is a major cause of P‐induced Zn and Cu deficiencies. Shoot dry weights and concentrations or total uptake of P, Zn, Cu, Fe, Mn, K, Ca and Mg were determined for mycorrhizal and nonmycorrhizal plants given 0, 25, 75, or 200 ppm P. Phosphorus fertilization significantly reduced Zn and Cu concentrations in mycorrhizal soybeans, but concentrations in nonmycorrhizal treatments were not affected. Concentrations of Zn and Cu in mycorrhizal and nonmycorrhizal corn were reduced by P fertilization, but the reduction for mycorrhizal plants was significantly greater than the decrease for nonmycorrhizal plants. Reductions in Zn and Cu concentrations in nonmycorrhizal corn were the result of a dilution effect and could be attributed to increased plant size rather than increased P fertility per se. The concentrations of the other analyzed elements were all affected by P level and/or mycorrhizal condition. In general, mycorrhizal and non‐mycorrhizal dry weights and element concentrations converged as soil P was increased. Patterns of response to P and mycorrhizae differed slightly between corn lines, and such differences were marked for certain elements when corn was compared with soybean.
The Nature and Forms of Sulfur in Organic Matter Fractions of Soils Selected Along an Environmental Gradient
Authors: Bettany J. R. , Stewart J. W. B. , Saggar S.
Published: July 2010

The role of S in humus formation and transformation was hypothesized on the basis of C/N/S ratio and percent HI‐reducible S determinations on organic fractions obtained from soil Ap horizons by a 0.1M NaOH − 0.1M Na4P2O7 (pH 13.0) extraction‐separation technique. Differences in C/N/S ratios of the conventional humic acid (HA‐A) fractions were greater (from 113:10.6:1 to 270:23.3:1) than those of the total soil organic matter (61:6.5:1 to 112:9.7:1) in soils along an environmental gradient delineated by semiarid Chernozemic Brown to sumhumid Luvisolic Gray soils. This fraction (HA‐A) is thought to represent the end product of the humification process. Differences in C/N/S ratios of conventional fulvic acid (FA‐A), clay associated humic acid (HA‐B) and <2 µm humin were smaller than for HA‐A along the gradient. On the basis of C/N/S ratios and the average percentage of HI‐reducible S in each fraction, e.g. HA‐A, 26%; HA‐B, 44%; FA‐A, 82%; and <2 µm humin, 52%; it was postulated that FA‐A, HA‐B, and <2 µm humin contained the majority of potentially labile S.
Nutrient Losses from a Forest Soil as Affected by Nitrapyrin Applied with Granular Urea
Authors: Bengtson George W.
Published: July 2010

Nitrapyrin (2‐Chloro‐6‐(trichloromethyl)pyridine) effects on nitrate production in a forest soil (Bladen fsl) of the Lower Coastal Plain of Florida were evaluated in a pot study. Nitrapyrin (as N‐Serve® 24) was applied to the soil with two rates (25 and 100 ppm) of N as granular urea; for each N rate a range of nitrapyrin concentrations (0, 0.5, 1.0, 2.0, and 4.0% of the urea‐N) was evaluated. Postfertilization leaching of N and of other nutrients and growth and nutrient uptake by seeded slash pine (Pinus elliottii var. elliottii Engelm.) were observed in unlimed (pH 5.2) and limed (pH 6.5) soil.

Nitrapyrin effects were most apparent in limed soil and at the higher N and nitrapyrin rates. In general nitrapyrin concentrations below 2.0% of the urea‐N and below approximately 4.0 kg of nitrapyrin/ha were ineffective. Effectiveness increased up to the highest concentration (4.0%) and the highest rate (8.0 kg/ha). Leaching data indicate that the duration of the nitrapyrin inhibition of nitrification was from 5 to more than 10 weeks. Nitrapyrin to 8.0 kg/ha did not affect germination of slash pine seed.

Seedling N uptake and growth were reduced in proportion to nitrate‐N leaching losses. Quantities of K, Ca, and Mg in leachates were also correlated with leached nitrate‐N, but tissue analyses indicated that growth deficits associated with leaching were due primarily to N deficiency. In limed soil heavily fertilized with urea‐N, results also suggest some benefits to pine seedling growth and N utilization associated with inhibition of nitrification apart from those attributable to reduced leaching losses of nitrate.
A Hysteresis Model Based on an Explicit Domain‐Dependence Function
Authors: Mualem Y. , Miller E. E.
Published: July 2010

A quantitative model of hysteresis is proposed, assuming the pore‐water blockage against air entry to be a direct function of the volume of pore domains located in the completely‐filled region of the state diagram. The relative volume of the porewater domains θo, evaluated from the history of the capillary head ψ assuming the domains are independent, is employed in a dependency correction function P*d(θo). For calibration, this model requires only the main loop of hysteresis and one drying scanning curve. The merit of this “Model IIIexpl” compared with Model III (Y. Mualem, 1974b, Y. Mualem and G. Dagan, 1975) is that any hysteretic process of wetting and drying is expressed analytically in explicit form. This property simplifies the computational procedure and saves computer time in practical application.

The overall agreement between predicted and measured hysteretic behavior is acceptable. However, the study reveals that in the range of the air entry value the model does not reproduce the main drying curve accurately if it diverges considerably from the drying scanning curve. This deficiency may reflect the less physical ground for Model IIIexpl compared to the implicit Model III.
Statistical Considerations for Evaluating Micronutrient Tests
Authors: Keisling T. C. , Mullinix Ben
Published: July 2010

For the purposes of making recommendations, micronutrient soil or tissue tests are basically classification procedures. The empirical test variable usually groups samples into three areas, i.e. a group containing mostly samples with no micronutrient problems, a second group containing mostly samples with the micronutrient problems, and a third group containing samples both with and without micronutrient problems. The third group described above can be thought of as occurring at a “transition zone” where the correct status of a sample is unidentifiable by the micronutrient test. Statistical methods using an interaction Chi‐Square are presented for identifying the boundaries of the “transition zone.”

It is proposed that a micronutrient test be evaluated in terms of the proportion of successful recommendations. A successful recommendation results when the proper status of a sample is identified by the test. Under the assumption of random sampling from a stable population, the above evaluation scheme follows a binomial distribution. The computation of variances and confidence intervals is shown and discussed for the proportion of successful recommendations. A statistically valid method for comparing different empirical tests, such as extracting solutions, is shown and contrasted to previously used methods.
Ferruginous Beidellites in Turkish Soils
Authors: Özkan A. I. , Ross G. J.
Published: July 2010

Smectites were found to be dominant in the clay fraction of five calcareous soils of different great soil groups from various areas of Turkey. Characterization by X‐ray, thermal, infrared, and chemical analyses of these smectites in a Terra Rossa, Vertisol, Rendzina, and Volcanic Ash profile showed that they resemble each other and are ferruginous beidellites having the average formula
urn:x-wiley:03615995:saj2sssaj197903615995004300060039x:equation:saj2sssaj197903615995004300060039x-math-0001

The smectites also have relatively high Mg content and are similar to the beidellites in some African and Indian soils formed under alkaline weathering conditions. Soil solution analysis indicates that the smectites in the Turkish soils are stable. The smectites in these soils appear to be mainly inherited since they already are the dominant layer silicate in the parent material. The results of this and other investigations show that ferruginous smectites are of widespread occurrence and may be found in alkaline soils formed not only on ironrich but also on iron‐poor material.
Comparison of Field and Laboratory Determined Hydraulic Conductivity Values
Authors: Dane J. H.
Published: July 2010

Several new methods of determining hydraulic conductivity (K)‐volumetric water content (θ) relations have been developed recently. Emphasis is on simplification of procedures that determine K(θ) relations in the field. This paper compares four different procedures by which K(θ) relations were determined for several horizons of a Troup loamy sand (Grossarenic Paleudults). The first procedure consisted of in situ measurements of water content and pressure head profiles following irrigation. All measurements were obtained with the soil surface covered to prevent evaporation. The data were used to calculate K(θ) values. The second procedure consisted of a model that used water retention curves and saturated K values determined on undisturbed core samples. The third method was a variation of the second in that water retention data were used as measured in situ. The fourth method used in situ measured water content data only. For the coarse textured soil used in this investigation the latter method was modified in that two empirical equations were needed instead of one to represent one K(θ) relation. All four methods resulted in K(θ) relations that were in fairly good agreement.
Freeze‐Dried and Critical‐Point‐Dried Clay — A Comparison
Authors: Murray R. S. , Quirk J. P.
Published: July 2010

The results of experiments conducted with an illitic soil, which has been freeze‐dried and critical‐point‐dried, confirm that the freeze‐drying process fails to preserve the structure of the swollen material. The pore structures, associated with clay “domains” (<10 nm), in samples freeze‐dried from a wide range of soil‐moisture potential, are improbably similar to that of an air‐dried sample. In addition, the presence of large pores (about 1 µm), which should have drained at the equilibrium suctions, in the normal swelling range, which the samples experienced prior to freeze‐drying, is inconsistent with the capillary rise equation. Furthermore, soil which has been freeze‐dried from 10 kPa suction swells when placed at 5 MPa suction (p/p0 = 0.96). During mercury intrusion, freeze‐dried samples retain most of their total porosity while critical‐point‐dried samples collapse; this collapse is thought to be consistent with the metastable nature of a dry, but swollen, clay structure.
Extractable Chromium as Related to Soil pH and Applied Chromium
Authors: Grove J. H. , Ellis B. G.
Published: July 2010

The objective of this study was to evaluate the soil chemistry of added Cr(III), Cr(VI), and sludge Cr as affected by initial soil pH. Treatments of 0 and 500 ppm Cr as CrCl3 and CrO3, and sludge Cr at a rate of 1,400 ppm Cr were applied to Rubicon sand (Entic Haplorthod, pH 4.7), Morley clay loam (Typic Hapludalf, pH 6.0), and limed Morley clay loam (pH 7.5). Pots were sampled at 24 hours, 1, 2, 4, 8, and 16 weeks of incubation. Soil samples were extracted in succession with distilled water, 1M NH4Cl, 0.1M CuSO4, 0.3M (NH4)2C2O4, and citrate‐dithionite‐bicarbonate.

Chromium(III) addition reduced soil pH while sludge raised soil pH. Chromium(VI) treatment initially lowered soil pH but then raised it above the pH of control soils after a short time period. Water‐soluble Cr(III) decreased with time, though more rapidly as soil pH increased. When added as Cr(VI), water‐soluble Cr also decreased with time but less rapidly as soil pH increased. Exchangeable (1M NH4Cl extractable) and organic‐bound Cr (0.1M CuSO4 extractable) were negligible. Oxalate and dithionite extractions removed large quantities of Cr from all treatments. Water‐soluble Cr compounds appeared to convert to insoluble compounds of Cr(III) in soils. Sludge Cr is probably a colloidal precipitate prior to incorporation.
Serogroup Distribution of Rhizobium Leguminosarum in Peas in the Palouse of Eastern Washington
Authors: Mahler R. L. , Bezdicek D. F.
Published: July 2010

The serogroup distribution of Rhizobium leguminosarum in peas (Pisum sativum L. cv. ‘Alaska’) was determined for a Palouse catena in the summer of 1976. Three major serogroups were found, although the distribution was uneven across the catena. Thirty‐four and thirty‐eight percent of the nodules on the bottomland and north slope, respectively, were of serogroup WA‐01, whereas it comprised only 5 to 12% of the root nodule population on the south slope and ridgetop, respectively. Serogroup WA‐02 distribution of 81 to 89% was dominant for the ridgetop and south slopes. Only on the bottomland and soil did serogroup WA‐03 represent a sizeable portion (12%) of the root nodule population.

Nine Palouse catenas were selected as study sites in the summer of 1977 to determine the geographical distribution of the three serogroups of R. leguminosarum. The three serogroups represented > 94% of the root nodules sampled. Chisquare analysis suggested that serogroup distribution was related to temperature, moisture, and slope position on a catena. Microclimate as well as macroclimate were responsible for serogroup distribution in the Palouse. Cooler temperatures and higher soil moisture appeared to favor serogroup WA‐01, as its largest population existed in the northern part of the Palouse, and on north‐slope and bottomland soils. Population of serogroup WA‐02 was maximum under the warmer and drier conditions of the southern and western Palouse as well as on south slopes and ridgetops. No pattern was found for the distribution of serogroup WA‐03.
Soilscape Analysis in Terms of Pedogeomorphic Fabric: An Exploratory Study
Authors: Habermann Gail M. , Hole Francis D.
Published: July 2010

Ten representative published soil photo‐map sheets from Hawaii, Florida, Wisconsin, and selected intervening states were subjected to exploratory analysis for the characterization of soilscapes in terms of pedogeomorphic fabric. Data on size distribution of soil bodies were displayed on a soilscape “textural triangle” in a manner to indicate the degree to which a given soilscape was dominated by unusually large soil bodies. A relationship was indicated between natural drainage condition of soilscapes and number of soil series per km2.
Sources and Properties of Loess Deposits on Crowley's Ridge in Arkansas
Authors: West L. T. , Rutledge E. M. , Barber D. M.
Published: July 2010

Crowley's Ridge is a north‐south trending erosional remnant of Coastal Plains sediments capped by multiple loess deposits. Due to activities of ancestors of the Mississippi and Ohio rivers, the extensive flood plains, both immediately east and west of this ridge, were plausible loess source areas. This long, narrow ridge was transected normal to its long axis to separate and investigate the multiple loess deposits and to determine the source area of each loess. Morphology, total Ca and K distribution, and clay distribution were used to differentiate the loess deposits. Particle size, expressed on the clay‐free basis, was used to determine the source area of each loess.

Three loess deposits were identified on Crowley's Ridge. The surface loess is 2.8 to 7.4 m thick and contains the surface soil which has undergone sufficient development to form a fragipan. This loess was correlated as Peoria Loess and was deposited from the flood plain east of Crowley's Ridge. The middle loess shows evidence of weak soil development. This thinner, 1.3 to 1.8 m thick, loess was correlated as Roxana Silt and evidently also had its source in the flood plain east of Crowley's Ridge. The basal loess contains a strongly developed paleosol at its surface and ranges from 2.3 to 8.6 m thick. This deposit was correlated as Loveland Silt and apparently had been deposited from the flood plains on both the east and west sides of Crowley's Ridge.
Variability of Measured Properties in Morphologically Matched Pedons
Authors: Mausbach M. J. , Brasher B. R. , Yeck R. D. , Nettleton W. D.
Published: July 2010

Variability in data from morphologically matched pairs of pedons was assessed to establish operational norms in sampling and to consider alternative sampling procedures.

Coefficients of Variation (C.V.'s) were computed for the physical properties—percent sand, silt, clay, and 1,500 kPa moisture—and range from 9 to 40% for loess, 23 to 35% for glacial drift, 33 to 47% for alluvium and residuum, 18 to 32% for A and B horizons, and 33 to 51% for C horizons. C.V.'s were computed for the chemical properties—extractable acidity, sum of bases, cation exchange capacity (CEC), base saturation, pH, and organic carbon—and range from 12 to 50% for Alfisols, 4 to 71% for Aridisols, 6 to 61% for Entisols, 10 to 63% for Inceptisols, 9 to 46% for Mollisols, 16 to 132% for Spodosols, 10 to 100% for Ultisols, and 8 to 46% for Vertisols. Cation exchange C.V.'s are directly related to pH dependent charge.

On the average, clay content for central concepts of phases of series can be estimated within ± 5% clay (95% confidence level) by 1 to 4 samples in loess soils, 2 to 8 samples in glacial drift soils, and 4 to 24 samples in alluvial and residual soils.

Similar estimates of base saturation (sum of cations) within ± 10% (95% confidence level) require 2 samples for Aridisols and Vertisols; 5 for Mollisols; 10 for Alfisols, Ultisols, Entisols, and Inceptisols; and 16 for Spodosols.

Vertical distribution of properties and properties of important horizons are efficiently evaluated by sampling one complete pedon plus satellite samples of important horizons from other pedons. To assess a single horizons efficiently, sample only that horizon in several pedons. Sampling of paired pedons is a good first approach technique to study soils in an area.
Silicate and Phosphate Adsorption on Gibbsite Studied by X‐ray Photoelectron Spectroscopy Angular Distributions
Authors: Alvarez Robustiano , Fadley Charles S. , Silva James A.
Published: July 2010

A surface‐sensitive technique based on the angular distributions of X‐ray photoelectron intensities has been used to study the adsorption pattern of Ca, Si and P on gibbsite surfaces. The profile distributions of ions extending from the average Al(OH)3 surface plane appear to be in the order: Ca closer to the surface than Si for CaSiO3 as adsorbate and Ca at nearly the same plane and above Si for CaCl2 + Si(OH)4 as adsorbates irrespective of adsorbate pH. The average positions, relative to the Al(OH)3 atoms are: Si and P appear above the surface level when adsorbed from their respective acid forms, as is the case for more complex adsorbates like Si(OH)4 + H3PO4 + CaCl2, where Ca appears at the surface level. An atomic rearrangement on the gibbsite surface seems to occur in the latter case. These experiments have demonstrated that it is possible to apply the XPS (X‐ray photoelectron spectroscopy) angular distribution technique for adsorption studies on powdered soil materials, a subject of relevant interest in earth sciences.
Differential Bonding of Potassium and Rubidium‐86 in Soils of Differing Clay Type and Degree of Weathering
Authors: Eckert D. J. , McLean E. O.
Published: July 2010

A Clermont silt loam and Paulding silty clay were amended with three levels of K and one level of 86Rb. The soils were moist‐incubated and leached with NH4OAc, followed by hot HNO3 extraction to remove more strongly bound cations. Both soils fixed added K against NH4OAc extraction, some of which K was also not quantitatively extracted by HNO3. The added 86Rb was found in NH4OAc extracts, HNO3 extracts, and in the soil residum following extraction. Addition of K to the Clermont soil forced 80Rb from the NH4OAc‐extractable fraction to a “sink” in this soil not accessible to either extractant. Adding K to the Paulding soil had the opposite effect. Independent reactions of K and Rb and the influence of soil type on K‐Rb interactions cast doubt on the possibility of using 86Rb as a tracer for K in soil systems.
Modification of Tempe Pressure Cell for the Measurement of Saturated Hydraulic Conductivities
Authors: Palmer Craig J. , Blanchar Robert W.
Published: July 2010

The Tempe pressure cell, which is used in studies of moisture retention, was evaluated for the measurement of saturated hydraulic conductivities. By the simple addition of a groove and O‐ring, the pressure cell was altered so that it would hold a vacuum. This modification allowed for complete saturation of the soil cores and prevented the adverse effects of entrapped air on the saturated hydraulic conductivity measurement. The ability of the cell to function in its original purpose was not altered. The multiple use of this cell may allow for monetary savings in equipment purchases.
A Comparative Electron Spin Resonance Study of VO2+ Complexation in Synthetic Molecules and Soil Organics
Authors: McBride M. B.
Published: July 2010

The vanadyl ion, VO2+, has been used as an ESR (electron spin resonance) probe of adsorption sites in pure organic complexing agents and natural peat to obtain information on the nature of the metal‐organic bond in soils. Oxygen ligands of soil organics displace on the average about two ligand H2O molecules from VO(H2O)52+ in forming an inner‐sphere complex with the metal. The bonding mechanism of natural organics is very similar to that of polycarboxylic acids such as uronic acid. Unlike soluble low molecular weight carboxylic acids, the solid polycarboxylates are not able to bond to all four equatorial ligand positions of VO(H2O)52+. Evidence is presented that Fe and Al in the soil organics occupy complexation sites and partially block VO2+‐carboxylate bond formation. The heterogeneous nature of natural organic complexing sites is demonstrated by the broadened nature of VO2+ ESR spectra when the metal is adsorbed on soil organics in comparison with pure polycarboxylic acids.
Relative Effect of Vesicular‐Arbuscular Mycorrhizal Fungi on the Growth and Yield of Soybeans
Authors: Carling D. E. , Brown M. F.
Published: July 2010

The growth and yield response of greenhouse‐grown soybean plants to colonization by 19 isolates (including 6 Glomus and 3 Gigaspora species) of vesicular‐arbuscular mycorrhizal fungi is reported. Each isolate was evaluated in a high (169 kg/ha Bray‐I P2O5) and a low (50 kg/ha Bray‐I P2O5) fertility soil. Colonization by most Glomus isolates significantly increased plant top dry weight and seed yields, and of these isolates most produced larger increases in dry weight in the low fertility soil. Colonization by five of the Gigaspora isolates did not significantly affect top dry weight and seed yield in the high or Iow fertility soil. The value of comparative testing of species is discussed.
Relation of Parent Material Geology to Reaction Classes of Flood Plain Entisols in the Coastal Plains
Authors: Perkins H. F. , Hutchins Ann
Published: July 2010

Soil reaction class is a criterion used in classifying Entisols. A total of 122 pedons of alluvial Entisols were sampled in eight major geologic areas of the Atlantic and Gulf Coastal Plains. Soil reaction values were determined in water and 0.01M CaCl2. Geologic formation may be used to predict the soil reaction class at the family level when the formation is relatively uniform. Areas having highly dissected terrain are somewhat unpredictable.
Computerized Processing and Storing of Soil Descriptions and Characterization Data
Authors: Smeck Neil E. , Norton L. D. , Hall G. F. , Bigham J. M.
Published: July 2010

In Ohio, an interactive time‐sharing computer is utilized to process, store, and retrieve soil morphological, chemical, physical, and mineralogical data for pedons analyzed by the Ohio Soil Characterization Laboratory. Morphological information is coded into the computer using connotative abbreviations for soil parameters such as texture, structure, and color, while the computer is used to process this information into narrative‐like profile descriptions. Chemical, physical, and mineralogical data are stored either directly from calculations or entered from data sheets and printed out in a fixed format. The time involved preparing and editing morphological descriptions and soil data sheets has been reduced by as much as one half.
Field Determinations of Soil Hydraulic Properties for Statistical Analyses
Authors: Russo David , Bresler Eshel
Published: July 2010

A procedure for repetitive determinations of soil hydraulic properties is based on the assumption that the functional relationships between soil water content (θ) and soil water pressure head (h), and between the hydraulic conductivity (K) and h, can be expressed mathematically. The parameters in the mathematical expression are: saturated hydraulic conductivity (Ks) and water content (θs), residual (or irreducible) water content (θr), water entry value of h (hw), and the parameters η and β, characterizing the pore size distribution of the soil. Values of Ks and hw are measured by the air‐entry permeameter of H. Bouwer. The parameters η and β were calculated with measured values of Ks, hw, θs, θr, and the sorptivity, S, as measured by C. Dirksen's method. The variability in the determination of the K(θ) function is evaluated in the field, from 30 measurements of each of the six parameters made in a single 2 by 2 m site. This variability is smaller than the variability of K(θ) as calculated from a simulation of a transient drainage. The K(h) and θ(h) functions are rapidly obtained and thus suitable for performing large numbers of measurements for the determination of the probability density functions (and joint probability density functions) of the soil hydraulic conductivity, K(θ), and soil water retentivity, h(θ), functions.
A Comparison of Column‐Displacement and Centrifuge Methods for Obtaining Soil Solutions
Authors: Adams Fred , Burmester Charles , Hue N. V. , Long F. L.
Published: July 2010

Four soils, ranging in texture from loamy sand to clay, were fertilized differently and equilibrated moist for several days. Soil solutions were then separated by column‐displacement, by simple centrifugation, and by immiscible displacement with CCl4 via centrifugation. The ionic compositions of soil solutions were unaffected by the method used to obtain the solutions.