bluuebunny/crossref_metadata_2025 huggingface dataset:
Lycopodium Fairy Rings: Effect on Soil Respiration and Enzymatic Activities
Authors: Spalding Brian , Duxbury J. M. , Stone E. L.
Published: July 2010

Lycopodium species (L. tristachyum, L. clavatum, and L. complanatum) sometimes occur as fairy rings—dense annuli of plants, 1 to 1.5 m wide, that grow radially outward at a rate of 20 to 50 cm/year and die within. The impact of these fairy rings on soil organic matter was investigated through studies of soil respiration and selected enzymatic activities. Respiration was enhanced in the soil under lycopodium rings compared with soil either outside or inside the rings. The activities of phosphatase, protease, dehydrogenase, catalase, polyphenol oxidase, amylase, and dextrinase were found to be independent of soil location. However, significant increases in cellulase, invertase, polygalacturonase, and peroxidase activities were observed in the soil under lycopodium rings. A model based on the infection of the lycopodium plant by its endophytic fungus and subsequent peroxidative degradation of soil organic matter is presented to explain both the increases in enzymatic activities and nutrient availability under lycopodium fairy rings.
Landform‐Soil‐Vegetation‐Water Chemistry Relationships, Wrigley Area, N.W.T.: I. Morphology, Classification, and Site Description
Authors: Walmsley M. E. , Lavkulich L. M.
Published: July 2010

Five landforms occurring in the intermittent permafrost region of the Mackenzie Valley are described. The five landforms, consisting of distinct soil and vegetative characteristics occur on a transect from the 1170 m ASL (above sea level) position at the summit of Cap Mountain, Wrigley area, N.W.T., to approximately 500 m ASL at the base of the slope. Two soils meet the requirement of a histic epipedon. An area of stone stripe and stone ring formation was encountered at approximately 1000 m ASL and an extensive area of lichen‐covered polygonal bogs occurred at approximately 500 m ASL. The soils are described in relation to environmental factors and the processes of cryoturbation causing intermittent horizons are discussed.
Yields and Water‐Use Efficiencies of Dryland Winter Wheat and Grain Sorghum Production Systems in the Southern High Plains
Authors: Jones Ordie R.
Published: July 2010

Grain yields and water‐use efficiencies were compared for conservation bench terraces, bench terraces, and common systems of dryland production of winter wheat (Triticum aestivum L.) and grain sorghum (Sorghum bicolor [L.] Moench). Grain production and water‐use efficiency were highest on a bench terrace cropped in continuous grain sorghum. Conservation bench terraces and continuous grain sorghum grown on sloping land also had higher water‐use efficiences and grain production than the common dryland systems of wheat‐sorghum‐fallow on graded terraces and continuous wheat or wheat‐fallow on sloping land. The management factors greatly influencing water‐use efficiencies were crop selection and land leveling to conserve potential runoff.
The Distribution of Creosotebush in West Texas and Eastern New Mexico as Affected by Selected Soil Properties
Authors: Hallmark C. T. , Allen B. L.
Published: July 2010

Morphological, physical, chemical, and mineralogical studies were made on 32 pedons from west Texas and southeastern New Mexico to evaluate edaphic factors related to creosotebush [Larrea tridentata (D.C.)] distribution.

Creosotebush grows on soils with a wide range of properties. The soils studied were well drained and generally moderately developed, as indicated by horizonation and carbonate redistribution. The data indicate that gravel content and depth to free CaCO3 are the most important soil factors affecting distribution of the shrub in the study area. Soils low in gravel and noncalcareous at the surface tend to be devoid of the shrub. Soils that support creosotebush are generally calcareous throughout the profile and many have significant amounts of gravel. The complex interactions among other edaphic factors such as texture, available water, salinity in deeper horizons, and gypsum content greatly complicate the resolution of properties influencing distribution.
Nitrate Measurements Using a Specific Ion Electrode in Presence of Nitrite
Authors: Francis C. W. , Malone C. D.
Published: July 2010

The presence of the nitrite anion (NO2‐) may lead to a significant error in measuring NO3‐N concentrations with a specific ion electrode. Interference by nitrite was found to be eliminated by complexing the nitrite with sulfanilamide in 0.01 N H2SO4. In this manner, nitrate levels can be read directly in concentrations ranging from 10 to 5000 ppm NO3‐N. The method is particularly useful in denitrification studies where HCO3‐ and CO3‐ anions as well as NO2‐ preclude direct NO3‐N measurements.
A Hydraulically Driven Soil Auger for Sampling Fine‐Textured and Wet Soils
Authors: Byrnes Bernard H.
Published: July 2010

A core‐type bucket auger was modified to fit the drive bar of a hydraulic soil probe with a rotor head. This auger satisfactorily samples claypan, fine‐textured and moderately fine‐textured soils in a wet condition. The auger system can readily be used alternately with tube core samplers.
A Laboratory Rainfall Simulator for Infiltration and Soil Detachment Studies
Authors: Römkens M. J. M. , Glenn L. F. , Nelson D. W. , Roth C. B.
Published: July 2010

A laboratory rainfall simulator with high intensity precision and nearly uniform rain distribution was developed for studying rain infiltration into soils and soil detachability by rainfall. The rainfall simulator consists of an assembly of closely packed hypodermic syringes with plungers driven by a common plate. Rainfall intensity is determined by controlling the plunger speed at variable motor speeds. Rain is distributed uniformly by superpositioning three independent motions—rotation, and perpendicular and linear motions in the horizontal plane. Rainfall intensities were generally within 2.5% of predicted values. The average coefficient of variation of rain distribution for various rainfall intensities over a 100‐cm2 area was reduced from 31.9% with no motion to 8.5% with rotation and linear motions.
Origin of the Term Latosol
Authors: Cline Marlin G.
Published: July 2010

The term Latosol was coined in 1947. The general concept resembles that of Oxisol in current taxonomy, but the two terms are far from equivalents.
Precipitation of Calcium and Strontium Sulfates around Plant Roots and its Evaluation
Authors: Malzer G. L. , Barber S. A.
Published: July 2010

The flux of Ca2+, Sr2+, and SO42‐ to corn (Zea mays L.) roots was investigated to determine if accumulation at the root caused precipitates to form and if so to determine the influence of precipitate formation on Ca and Sr uptake. Autoradiographic techniques using 45Ca and 35S showed both Ca2+ and SO42‐ accumulated at root surfaces when supply by mass‐flow exceeded uptake. Petrographic studies of the roots confirmed the formation of CaSO4 precipitates.

The influence of the root precipitate on the relative Ca and Sr uptake was studied by comparing uptake by plants grown where precipitates occurred with those grown without precipitate formation. The corn plants were grown in solution culture. In order to have CaSO4 precipitation without SrSO4 precipitation a Ca/Sr molar ratio of 3670 was used. When SrSO4 precipitation without CaSO4 precipitation was desired the molar ratio was 0.45. The Ca and Sr in solution were labeled with 45Ca and 85Sr either from 9 days to harvest or for only 7 hours before harvest. Harvests were made after 13, 17, and 24 days.

Plant age at sampling did not affect the 45Ca/85Sr ratio absorbed, however the length of the labeling period did. When labeled for 7‐hours, and CaSO4 precipitate was present 45Ca uptake was reduced 16 to 20% relative to 85Sr uptake as compared to uptake where no precipitate was present. When labeled from day 9, no differences occurred. When SrSO4 precipitated, 85Sr translocation was reduced 10 to 20% compared to 45Ca with the long labeling treatment.

With a Ca/Sr ratio of 3670, the roots selectively accumulated Sr, however with a Ca/Sr ratio of 0.45, the roots selectively accumulated Ca. The Ca/Sr ratio present in the root was not correlated with the Ca/Sr ratio translocated to the shoot.
Frequency Distribution of Tract Productivity Indexes and Examples of Their Utilization in Rural Land Assessment
Authors: Mausel P. W. , Runge E. C. A. , Carmer S. G.
Published: July 2010

The soil conservation needs inventory 2% sample of soil data for Illinois was combined with productivity indexes to obtain state, county, and subcounty soil productivity characteristics that were used to evaluate variations in rural land quality. State soil productivity distributions were developed to provide a general framework of soil quality. Frequency diagrams (histograms) of county soil productivity indexes were constructed. Ratios comparing soil productivity histograms for the state and each county were developed and analyzed. Productivity characteristics of soil associations were provided for each county by a table that gives the percentage of the county in each soil association, the percentage of each soil association in each of seven productivity index categories used in the histogram format, and compares ratios between state and county soil association productivity indexes within the seven productivity index categories. The productivity index data using formats developed can be applied to evaluate the relative quality of soil for agricultural use between counties and between soil associations within counties. These data should aid county and state officials in evaluating rural land assessments.
Response of Three Semidwarf Mexican Wheats to Different Aeration Conditions in the Rooting Medium at a Constant Salinity Level
Authors: Aceves‐N. Everardo , Stolzy L. H. , Mehuys G. R.
Published: July 2010

The response of three newly developed Mexican wheat (Triticum aestivum L.) varieties, Nuri 70, Inia 66, and Siete Cerros 66, to low oxygen at constant salinity of −4 bars in the rooting medium was tested in a water culture experiment under growth chamber conditions. Oxygen concentrations in solution were maintained at 1.5, 5.2, and 7.6 ppm by bubbling gas mixtures containing 0, 12, and 21% oxygen, respectively.

All varieties were affected by low oxygen at high salinity, but Inia 66 had the greatest adaptability to low oxygen concentrations in the root zone. Oxygen concentrations of 0% in the aerating gas decreased plant dry‐matter production by 50%. Plant length was not affected, but the ability to produce tillers was inhibited. This same oxygen concentration reduced transpiration by 54, 66, and 65% for Inia 66, Siete Cerros 66, and Nuri 70. Root porosities increased with each decrease in oxygen content, with Inia 66 showing the largest increase. In general, for other measured plant characteristics, no significant differences were noted between plants grown at 12% oxygen and those at 21%.
Irrigation Method as a Determinant of Large Pore Persistence and Crust Strength of Cultivated Soils
Authors: Kemper W. D. , Olsen John S. , Hodgdon Alan
Published: July 2010

Air‐dried soils were wetted by flooding, immersion, slow immersion and capillary action; these actions resulted in successively slower rates of wetting. In general, slower rates of wetting left larger portions of the soil volume in large size pores. Slow capillary wetting of a weakly structured soil allowed retention of more large size pore space than was observed in a well structured soil that was wet rapidly.

Modulus of rupture was determined on dried soils which had previously been wet by rapid immersion, capillary action, and capillary action followed by immersion. Breaking strength was much greater when those soils had been wet by rapid immersion than when wet slowly by capillary action. Immersion following capillary wetting resulted in soils with intermediate breaking strengths. A preliminary study on corn (Zea mays L.) seedling emergence showed that the range of soil strengths resulting from these irrigation methods on a weakly structured soil was sufficient to give < 50% emergence (flooding) up to essentially 100% (capillary wetting).
Utilization of Soil and Fertilizer Phosphorus Compounds by Slash Pine Seedlings in Relation to Their Solubility in Soil Test Extractants
Authors: Ballard R. , Pritchett W. L.
Published: July 2010

Eight P compounds, monocalcium and dicalcium phosphates, fluorapatite, colloidal aluminum and ferric phosphates, potassium taranakite, wavellite, and strengite were evaluated as sources of P for slash pine (Pinus elliottii var. elliottii Engelm.) seedlings grown on two acids soils in the greenhouse.

Potassium taranakite and both colloidal phosphates were as effective P sources as monocalcium and dicalcium phosphate in stimulating tree growth. Fluorapatite was an effective source on a soil of pH 4.3 but was ineffective on a soil of pH 5.3. Wavellite and strengite were ineffective P sources on both soils. The uptake of P by seedlings corresponded closely to the amount of H2O‐extractable P present following 2 months of incubation of the P compounds in the soils.
Percolation Losses of Phosphorus, Calcium, and Potassium from Some Minnesota Forest Soils
Authors: Severson R. C. , Grigal D. F. , Arneman H. F.
Published: July 2010

Studies were conducted on two soil types (Omega loamy sand and Cloquet sandy loam) representative of a large area of forested soils in the northcentral region of the United States. Three undisturbed soil columns were extracted from each soil under two vegetation types, hardwoods and conifers. The columns were leached both before and after laboratory‐simulated litterfall and following burning of the litter. Additional columns were extracted from an Omega‐conifer site which had undergone a prescribed burn in fall, and were used as a comparison with those burned in the laboratory. There were virtually no differences between ion concentrations in solution at the base of the columns following either laboratory burning or prescribed burning in the field. Severe leaching of freshly fallen litter or of burned litter resulted in similar losses of materials in solution. In general, all laboratory treatments had similar effects on ionic losses and in no case were losses large. The estimated annual losses from the soil were of the same magnitude as the annual inputs of ions to the soil system via precipitation. The small losses from the soil found in this study lead to the implication that major losses of materials following severe environmental disturbance are associated with surface runoff. If water percolates through soil material before entering streams, even after severe disturbance, small losses generally will occur.
Versatile Multirange Analytical Manifold for Automated Analysis of Nitrate‐Nitrogen
Authors: Jackson W. A. , Frost C. E. , Hildreth D. M.
Published: July 2010

This note describes a technique for extending up to 100 ppm the limits of determining nitrate‐nitrogen in solution using a Technicon Autoanalyzer system.3 The same modified analytical manifold can be used to determine three concentration ranges of nitrate nitrogen 0–1, 0–10, and 0–100 ppm. To change concentration range, change the sample entry point in the manifold and standardize the instrument within the proper range.
Two‐dimensional Transport of Solutes During Nonsteady Infiltration from a Trickle Source
Authors: Bresler Eshel
Published: July 2010

A simulation model for analyzing multidimensional simultaneous transfer of a noninteracting solute and water, applicable to infiltration from a trickle source, is developed. The equations describing transient two‐dimensional transport of a solute by diffusion and convection in unsaturated porous media are solved numerically by an approach that eliminates the effect of numerical dispersion. The noniterative alternating‐direction‐implicit finite difference procedure is used. Two mathematical models are considered: (i) a plane flow model involving the Cartesian coordinates x and z, and (ii) an axisymmetric flow model described by the cylindrical coordinates r and z. An example of transport in a homogeneous, isotropic and stable sand and loam soil systems is given. Results are shown for typical cases of trickle infiltration to demonstrate the effects of trickle discharge and soil‐hydraulic properties on the pattern of salt distribution in the wetted soil zone. The numerical results show that the approach presented may be useful in analyzing two‐dimensional solute transport processes in soils.
Interactions Between Organic Compounds, Minerals, and Ions in Volcanic‐ash‐derived Soils: II. Effects of Organic Compounds on the Adsorption of Phosphate
Authors: Appelt H. , Coleman N. T. , Pratt P. F.
Published: July 2010

The effects of organic compounds on phosphate adsorption by volcanic‐ash‐derived soils were studied using benzoate, p‐OH benzoate, salicylate, and phthalate, and by humic and fulvic acids extracted from a surface soil sample of a Typic Dystrandept. The adsorption of simple organic anions that are specifically adsorbed block to some extent the adsorption sites for nonspecifically adsorbed anions such as chloride and/or nitrate. But, organic anions did not compete for or block adsorption sites for phosphate anions, because of the much higher affinity of phosphates for the adsorption sites in these volcanic‐ash‐derived soils.

Because of the characteristics of humic acid and noncrystalline alumino‐silicates (“allophane”) colloidal particles, humic acid‐allophane interactions are probably mainly between external surfaces because of steric hindrance. Hence, if there are blocking effects of humic acid on phosphate adsorption, they would affect only part (⅓) of the reactive surfaces of the “allophane.” The complexes formed between humic acid and soluble Al ions extracted from “allophane” are active in phosphate adsorption, and this reactivity depends on the OH/Al ratio of the complexed Alx(OH)y(3x‐y) species.
Interactions of Micronutrients in Barley Grown on Zinc‐polluted Soils
Authors: Singh B. R. , Steenberg K.
Published: July 2010

Barley (Hordeum vulgare var. Varde) grown in zinc‐polluted soils with variable levels of Zn, Mn, and Fe showed no marked differences in the yield attributable to these variables in both soils investigated. However, in direct contrast to results reported by other investigators, concentrations of 65Zn and total zinc were found to increase with increased levels of added Mn and/or Fe with few exceptions. Similarly, concentrations of 54Mn and total Mn also increased with increased levels of Zn and/or Fe. The effects of Zn and Mn on the concentrations of 59Fe and total Fe were inconsistent. The concentration of Mo was found to decrease with increased levels of Zn, Mn, and Fe and the decrease was more pronounced in one soil than in the other. Although concentration of Cu also showed a slight tendency to decrease with Zn, Mn, and Fe application, the results were inconsistent in both the soils. In general, labelled nutrient elements were more mobile in barley plants than corresponding soil‐derived nutrients as evident in the relative percentage distributions between roots and tops.

The percentage distribution of Zn, Mn, Fe, Mo, and Cu between roots and tops was apparently not affected by the presence of their interacting ions. The effects of Zn on Mn distribution and that of Mn on Mo distribution, were, however, noticeable.

It is concluded that though Zn, Fe, and Mn ions in barley appear to have limited influence on translocation within the plant, these ions exert strong synergistic effects at the site of transport. There appeared to be pronounced antagonism between Mo‐Zn, Mo‐Fe, and Mo‐Mn in the metabolism of barley.
Soil‐Geomorphic Relationships in a First‐Order Valley in Central New York
Authors: Hanna W. E. , Daugherty L. A. , Arnold R. W.
Published: July 2010

Morphologically the soils in Hemlock Creek watershed are related to geomorphic development since glaciation. Initial drift deposits covering the 75‐ha area in south‐central New York were modified by mass movement (solifluction) and then altered by fluvial aggradation‐degradation under a periglacial environment, and by erosion in more recent times. Eight soil profiles representative of the geomorphic components forming the watershed were evaluated.

Fragiochrepts dominate the shoulder, backslope, and upper footslope components. They are also the major soils on congeliturbate terraces and on step‐treads of the upper basin. Fragiaquepts are common on the lower footslope and toeslope components and also occur on portions of the step‐treads of the cirque‐like basin. Fragipans have formed in both glacial till and congeliturbate deposits indicating a pedologic origin. Structural expression and density of the pans increase with a decrease in natural drainage in both deposits. Dystrochrepts are dominant soils on the summit and on the intermediate level fluvial terraces; Entisols occur on the low level alluvial terraces. Pan formation is thought to be precluded by nearness of bedrock (< 1 m) to the surface in the summit area and by matrix textures in the fluvial terraces. Stratigraphic changes that produce distinct discontinuities in fluvial terrace profiles are readily evident. Incipient stratification in congeliturbate deposits appears to affect soil morphology, especially horizon thickness, in these relatively young soils.
Design and Use of Closed‐top Infiltrometers
Authors: Dixon R. M.
Published: July 2010

Several similar closed‐top infiltrometers were designed and used to simulate effective surface heads ranging from −3 to +1 cm of water. Design was based on the principle that natural positive soil air pressure may be simulated by creating an equivalent negative air pressure above ponded surface water. Effective surface head hs, defined as the difference between the ponded water depth hw and either the actual or simulated soil air pressure head ha, is negative when ha is greater than hw. Under natural field conditions, negative hs often causes counterflow of soil air during water infiltration. Narrow ranges in hs surrounding zero greatly affect infiltration by controlling air and water flow in soil macropores and weakly hydrophilic micropores. Thirty‐minute cumulative infiltration increased 19% per centimeter increase in hs for one soil and 33% per centimeter for another soil.

Closed‐top infiltrometers make possible realistic infiltration measurements under the negative hs commonly produced by rain and irrigation waters as they infiltrate natural soils. These devices may also be useful in studying the infiltration effects of several interacting parameters that are related to hs including soil surface macroporosity and roughness, macropore space extent and continuity, antecedent soil air and water, surface wettability and water repellency, wetted surface area and shape, and surface crust and slope.

The infiltration response to hs in the range −3 to +1 cm is of practical significance since such a range results from common soil and water management practices.
Soybean and Corn Rooting in Southwestern Minnesota: II. Root Distributions and Related Water Inflow
Authors: Allmaras R. R. , Nelson W. W. , Voorhees W. B.
Published: July 2010

Root length density (RLD) of corn (Zea mays L.) and two isolines (determinate and indeterminate) of Harosoy soybean (Glycine max. L. Merr.) in a Nicollet soil were measured from 1 July to 15 Aug. 1971. These measurements, along with water uptake sinks in these vertically developing root systems, were used to evaluate water relations of these three crops.

Both soybean isolines had about 0.2 cm/cm3 RLD in the Ap layer with values < 0.1 below the Ap layer. This RLD distribution persisted with depth as the root system expanded vertically. Corn RLD were about 0.3 initially in the Ap layer, and as the root system expanded vertically, maximum RLD of about 0.3 was produced even to the 100‐cm depth on 9 Aug. Vertical extension rates of corn after 1 July were 1.3 cm/day as compared with 1.7 for soybeans, but maximum rooting depths on 9 Aug. were 145 and 120 cm, respectively.

Modal specific water inflows were 0.03 cm3/cm root per day—maximal values for soybeans were 0.2; maximal values for corn were about 0.05. Maximum soybean rooting depths coincided with maximum depth of water uptake sink, but corn rooting depths ranged 15 to 30 cm deeper than the water uptake sink.

Specific water inflow generally increased as soil hydraulic conductivity increased and RLD decreased, which agrees with models for steady‐state water flow into single roots. At low RLD, specific water inflows were either constant or increased as hydraulic conductivity decreased. This increased root resistance to water flow at the lower fringes of rooting may have resulted from low soil temperatures. Soybean root conductivities decreased with decreasing soil water potential. Corn root conductivities were largest at about −700 mbars and decreased as soil water potential decreased. Decreases of corn root conductivity resulted from potentials > −700 mbars when soil temperatures were low.
Linear Dispersion in Finite Columns
Authors: Parlange J.‐Y. , Starr J. L.
Published: July 2010

The effect of the finite length of a soil column on the miscible displacement of a solute is analyzed. The boundary conditions at both ends of the column affect the breakthrough curve, while only the boundary condition at the entrance of the column affects the profile within the column to any extent. The interaction between boundary conditions and column length is such that while the breakthrough curve is essentially that given by the standard solution for a semi‐infinite column, even for relatively short columns, the concentration profile is greatly affected by the finite length of the soil column.
Redox Potential in Irrigated Desert Soils as an Indicator of Aeration Status
Authors: Meek B. D. , Grass L. B.
Published: July 2010

The redox potential (Eh) of irrigated desert soils was evaluated under a wide range of conditions. Factors important in controlling Eh were temperature, flooding time, soil water content, and energy source. Field heterogeneity necessitated using 10 to 20 electrodes (placed in a 30‐cm square) to characterize a treatment. The Eh varied over a short distance with variations not due to poisoning or erratic electrode readings.

A 5C increase in temperature at the 15‐cm depth resulted in a 50‐mV decrease in redox potential. The length of soil saturation time correlated directly with the decrease in Eh. When the soil was not saturated during irrigation (sprinkler or drip), Eh decreased less than when the soil was flooded. The amount of energy available to microorganisms has a major effect on how low the Eh decreased in a flooded soil.
Boron Toxicity in Red Pine Following Municipal Waste Water Irrigation
Authors: Neary Daniel G. , Schneider G. , White D. P.
Published: July 2010

Foliar boron toxicity symptoms, a needle tip necrosis and discoloration, appeared in a 20‐year‐old red pine plantation (Pinus resinosa Ait) after two growing seasons (a total of 34 weeks) of spray irrigation with municipal waste water. Irrigation rates of 25, 50, and 88 mm/week produced significant increases in the boron contents of current foliage, forest humus, and mineral soil. Foliage, humus and upper 15 cm of mineral soil of the unirrigated plots contained 22 ppm, 16 ppm, and 1 kg/ha of boron, respectively. The high irrigation rate increased boron levels to 75 ppm, 90 ppm, and 4 kg/ha, respectively. Despite low boron concentrations (1 ppm) in the waste water, total boron loadings were equivalent to applications of 67.3, 135.7, and 230.1 kg/ha of borax fertilizer (11.3% B).
A Compaction Apparatus for the Preparation of Soil Cores of Different Bulk Densities and Thicknesses
Authors: Baligar V. C. , Nash V. E. , Shuman F. L.
Published: July 2010

The apparatus reported herein enables one to prepare soil cores with a desirable bulk density and having different thicknesses for use in soil compaction and plant growth studies.
Tests of the Concept of Secondary Frost Heaving
Authors: Loch J. P. G. , Miller R. D.
Published: July 2010

Heaving tests were conducted with 2–4, 4–8, and 8–16 µm soil fractions in special apparatus in which sliding friction (during heaving) was eliminated by confining the specimen as in standard triaxial test apparatus. Maximum pressures developed by heaving exceeded those computed by a primary heaving model (using air intrusion data) by factors as large as 3 to 6. Maximum pressures and rates of heave at constant pressures depended on temperature gradient and were maximal at gradients between 1 and 3C cm‐1.

Comparisons with simplified transport equations for a frozen fringe adjacent to a growing ice lens (the characteristic feature of secondary heaving) indicate that pore ice in the frozen fringe contributes to water transport for lens growth but this may be offset by plastic counter‐flow of ice at large temperature gradients, accounting for the gradient‐dependent maxima.

Results were interpreted as supporting the concept of secondary heaving.
Infrared Study of Exchangeable Cation Hydration in Montmorillonite
Authors: Sposito Garrison , Anderson Duwayne M.
Published: July 2010

Infrared absorption spectra in the 3000 cm‐1 and 1600 cm‐1 regions are reported for thin films of Na‐, K‐, Li‐, and Ca‐Wyoming bentonite previously dehydrated over P2O5 and over LiCl · H2O at room temperature. The spectra of Na‐ and K‐clay exhibited very similar features in the 3000–3500 cm‐1 region, which, together with other data, lead to the proposal that the exchangeable cations on these montmorillonites are dehydrated at relative humidities less than about 11%. The spectra of Li‐ and Ca‐clay are very different from those of Na‐ and K‐clay. A sharp doublet structure appears to be centered near 3650 cm‐1 and the absorption in the 3000–3500cm‐1 region generally is much deeper and broader. These differences are interpreted as evidence of the hydration of the exchangeable cations Li+ and Ca2+ at relative humidities less than about 11%. The conclusions drawn here are in agreement with previous findings based on infrared, differential thermal analysis, and desorption isotherm studies.
Effect of Lime on Boron Transport to and Uptake by Cotton
Authors: Scott H. D. , Beasley S. D. , Thompson L. F.
Published: July 2010

Deficiencies of Boron have occurred in cotton (Gossypium hirsutum L.) grown in coarse textured soils during periods of moisture stress and in those soils which have been recently limed. These B deficiencies have generally been attributed to a decrease in soil B availability to cotton. As a result a greenhouse experiment was conducted to study (i) the amounts of adsorption and diffusivity rates of B in two silt loams and (ii) B absorption by cotton grown in pots.

Addition of lime increased B adsorption by both a Taloka silt loam and a Calloway silt loam. Maximum B adsorption occurred on the seventh day after its addition but did not differ appreciably from the one day equilibration time. The adsorption data could not be accurately described by the Langmuir adsorption equation.

Increasing amounts of lime and decreasing soil water content caused a decrease in B diffusivity in the two soils. Diffusivity values when averaged over all treatments were 4.6 × 10‐6 and 2.7 × 10‐6 cm2/sec for the Calloway and Taloka soils, respectively.

The addition of lime to the Taloka soil reduced the growth and rate of development of cotton grown in greenhouse pots. Plant parameters such as date of emergence, plant height, dry weight accumulation, total B content, root length and root surface were reduced by the lime addition. The rate of B absorption by cotton decreased until square initiation then increased. This result suggests that cotton has differing B requirements during the growing season and that these requirements are highest during the early growth stages and fruit formation. Even though the total amount was lower, the rate of absorption of B by those plants growing in the limed soil was greater than those growing in the soil which received no addition of lime. This was attributed to the lime having a greater effect in reducing the magnitude of root surface area as compared to its effect in reducing the rate of B transport within the soil.
Effect of Surface Applied Sulfuric Acid on Water Penetration into Dry Calcareous and Sodic Soils
Authors: Yahia T. A. , Miyamoto S. , Stroehlein J. L.
Published: July 2010

Sulfuric acid, a surplus by‐product of copper smelters in the Southwest, was studied to determine a possible role in reclamation and revegetation of calcareous and sodic range soils. The rate of water penetration into dry calcareous soils was measured in columns as well as boxes after concentrated (93%) sulfuric acid was applied to the soil surfaces. The rate of penetration increased with increasing acid application rates, but then decreased, with optimum application rates ranging from 5 to 15 metric tons/ha. Acid was especially effective in increasing the rate of penetration into sodium‐affected calcareous soils. When acid was applied as a band on the soil surface, the wetting front advanced in an elongated semicircular form with depth. Surface applied acid was more effective than surface applied gypsum in increasing water penetration into sodiumsaturated soils. Sulfuric acid may be useful for increasing water penetration into and subsequently aiding in revegetation of sodium‐affected soils of semi‐arid regions.
Quartz Oxygen Isotopic Stability in Relation to Isolation from Sediments and Diversity of Source
Authors: Sridhar K. , Jackson M. L. , Clayton R. N.
Published: July 2010

The NaOH boiling treatment to remove amorphous silica relics in the quartz isolation procedure is unnecessary because the subsequent H2SiF6 treatment dissolves both the amorphous silica relics and feldspars. Washing with 0.1N HF, water, and saturated boric acid in the new procedure removed fluorates that precipitate during the H2SiF6 treatment. Failure to remove the fluorates depressed the oxygen yield (to as much as 85%) of theoretical SiO2 and slightly raised the quartz weight percent, but the oxygen isotopic ratio of quartz derived from various sources was not affected by these washings, by Na2S2O7 fusion, or by H2SiF6 treatment.

When 35 to 45% of the outer shells of the 1–3.5, 3.5–7, and 7–10 µm quartz size fractions from Cretaceous (Pierre) marine shales was dissolved with 3N HF, the quartz δ18O decreased by 0.8, 2.1, and 2.6 o/oo for a central‐basin shale and 0.7, 1.2, and 0.8 o/oo for a near‐shore shale, respectively. The trend, the greater the particle size the greater the δ18O decrease, is the opposite of that expected (finer particles, higher specific surface) if the δ18O decrease by HF treatment is a result of dissolving an isotopically exchanged portion and/or overgrowths in outer shells. The decrease appeared by scanning electron microscopy (SEM) to result from preferential dissolution of the cements holding fine quartz crystals (formed at low temperature) together as silt‐size clusters. A systematic increase in δ18O with decreasing grain size occurred in the quartz from the near‐shore shale (> 10 µm quartz, 16.1 o/oo; < 1 µm quartz, 21.8 o/oo). The increase was 6.7 o/oo from the central‐basin shale (> 10 µm quartz, 18.8 o/oo; < 1 µm quartz, 25.5 o/oo). The wide variation appears, from quartz particle morphology (SEM) and the response to partial dissolution, to result mainly from a mixing within each size fraction of different proportions of individually homogeneous quartz grains formed at various temperatures. Because of quartz oxygen isotopic stability, the isotopic ratio can be reliably used to trace source or provenance of fluvial and eolian sediments and soil parent materials.
The Slow Reaction which Continues After Phosphate Adsorption: Kinetics and Equilibrium in Some Tropical Soils
Authors: Munns D. N. , Fox R. L.
Published: July 2010

Dissolved phosphate was mixed with topsoil samples, and the decline in solution phosphate concentration (P) was followed for 200–300 days by periodically shaking and extracting subsamples with 1 or 10 mM CaCl2 (1:10).

During the first 20–40 days, (P) declined faster in soil suspensions that were being shaken than it did in undisturbed soil at 0.1 bar moisture. After 40 days of reaction, shaking time had little effect.

The slow fixation had first‐order kinetics with respect to (P). The relative rate was faster in an Andept than in three Oxisols. It was unaffected by lime, though lime increased the strength of adsorption.

Equilibrium was achieved at 50 days in an Andept and 100–200 days in three Oxisols. At equilibrium, the amount of adsorbed phosphate remaining labile was estimated from values of (P), using 6‐day adsorption isotherms. Labile phosphate so estimated amounted to 30–50% of the added phosphate, implying that the residual value of phosphate added to these soils should be substantial and permanent except for removal by crops and erosion.

Desorption isotherms diverged from adsorption isotherms less markedly with increasing time after phosphate addition, as if the slow reaction caused much of the apparent hysteresis.
Adsorption of Selenite and Phosphate on an Allophane Clay
Authors: Rājan S. S. S. , Watkinson J. H.
Published: July 2010

Selenite was adsorbed on an allophane clay from solutions of different concentrations at pH 5.0, at 30C, and under a N2 atmosphere, and the amounts of sulfate, silicate and hydroxyl ions released were measured. The results were compared with those from a similar study with phosphate on the same clay.

The results indicate that at low concentrations both phosphate and selenite exchanged with adsorbed sulfate, adsorbed silicate, and aquo and hydroxo groups. About three times more phosphate than selenite was adsorbed, due mainly to phosphate displacing more aquo groups and thus making the surface less positive.

At high concentrations, whereas the selenite adsorption reached a maximum, phosphate continued to be adsorbed. The latter was due to phosphate displacing structural silicate and probably also to disruption of hydrous oxide polymers. A two‐term Langmuir equation distinguished adsorption by surface ligand exchange from these other reactions at high concentration.

A selenite desorption experiment showed that phosphate displaced all of the selenite adsorbed. Phosphate was adsorbed with greater strength, the selectivity coefficient, KSeP, being 2.2.
Defining Ranges of Soil Characteristics
Authors: Jansen I. J. , Arnold R. W.
Published: July 2010

A method is developed for using quantitative sample data to characterize mappable bodies of soil. Inclusions are separated into two kinds. The first consists of included bodies of soil that are recognized as separate entities, but not mappable because of scale limitations. The second consists of scattered areas having extreme expression of some significant property but not recognized as separate geographic entities.

Inclusions of the first kind are sampled separately and treated as separate entities. The location and setting of these inclusions can be described in relation to the dominant soil body. A range of expression for each measurable soil property of interest is determined separately for each soil entity. The ranges are derived from the sample data and are designed to include a fixed portion of the total population of values rather than to be all inclusive. Soil areas having extreme expression of some particular property (falling outside of the defined range) are inclusions of the second kind. The location and setting of those soil areas cannot be readily described but their extent is controlled.

The tolerance interval procedure is used to calculate range limits from sample data when a normal distribution can be assumed. The resulting range can be said to include a predetermined portion of the total population of values with a specified degree of confidence. When the distribution is believed to deviate markedly from normal, the range limits are set subjectively by observing a frequency distribution of the sample data. Ranges set by the tolerance interval procedure were generally somewhat wider than those set subjectively, because the tolerance interval procedure allows for the imperfect relationship between the sample and the population and enables one to make confidence statements about the ranges defined.
An Evaluation of Sulfur‐coated Urea as a Preplant Total Season Nitrogen Supply for Trellised Tomatoes
Authors: Shelton J. E.
Published: July 2010

The use of a controlled release N source for the production of trellised tomatoes (Lycopersicon esculentum) which require frequent topdressings would be desirable. Three sulfur‐coated urea (SCU) materials having release rates of 11.4, 21.5, and 29.3% over a 7‐day period were compared to NH4NO3 applied preplant or as multiple applications. Nitrogen rates were 392, 560, and 729 kg N/ha. Marketable yields from an application of SCU11.4 at 392 or 560 kg N/ha were greater than with the same rate of N as NH4NO3 either as preplant or split applications. When SCU21.5 or SCU29.3 was used, the yields were comparable to a single application of NH4NO3. Differences in fruit number per plot were not significantly related to treatments. However, there was a significant difference in average fruit weight which was correlated with total yield. Tissue N content was highest at the first sampling from a single application of NH4NO3 and lowest from SCU11.4. However, at later sampling periods the N content was maintained at a higher level with SCU11.4. Although 729 kg N/ha as a single application of NH4NO3 detrimentally affected plant growth and production, this effect was not noted with the sulfur‐coated urea materials.
The Release of Nitrogen from Sulfur‐coated Urea as Affected by Soil Moisture, Coating Weight, and Method of Placement
Authors: Prasad M.
Published: July 2010

Information on the release of N from sulfur‐coated urea (SCU) as affected by soil moisture in the aerated range is lacking. Laboratory incubation experiments were therefore conducted on two soils to study the release of N from SCU as affected by soil moisture in the aerated range, coating weight (SCU‐28 and SCU‐9), and method of placement (on one soil only).

In the calcareous Princes Town soil the release of N from SCU increased with increasing moisture throughout the 9 weeks of study. In acid Talparo soil similar trends were present up to 3 weeks, but at 6 and 9 weeks maximum release of N occurred at medium moisture (soil moisture at pF 2.4) and minimum release at low moisture (soil moisture at pF 3.5).

In Princes Town soil the difference in release of N from SCU‐28 and SCU‐9 remained throughout the 9 weeks. By 9 weeks SCU‐9 (heavy coat) released more N at high moisture level (soil moisture at pF 1.0) than SCU‐28 (light coat) at low moisture. In Talparo soil the effect of coating weight on the release of N at three moisture levels was considerably reduced from 6 weeks onwards.

Ammonia volatilization losses were recorded only with Princes Town soil but they never exceeded 2.5% of the total N applied. The release of N from SCU was faster when the granules were mixed with the soil rather than surface applied. This difference between surface and mixed application was greater at high soil moisture levels.
Determination of 14C‐Labeled Pesticides in Soils by a Dry Combustion Technique
Authors: Cheng H. H. , Farrow F. O.
Published: July 2010

A dry combustion method for oxidation of 14C‐labeled pesticides in soils and determination of total 14C is described. The method is a modification of the procedure using a Leco high‐temperature induction furnace for oxidation and determination of total C in soils. In the modified system, the CO2 evolved from sample oxidation is trapped in a NaOH solution, which can be analyzed for total 14C radioassay and for total C by titrimetry.
Estimating Water Salinity with Geophysical Earth Resistivity Equipment
Authors: Halvorson A. D. , Reule C. A.
Published: July 2010

A procedure is described for estimating salinity of water samples in the field using a geophysical earth resistivity meter and four‐electrode conductivity cell. Using field collected water samples, a linear relationship of Y = 1.02(X) + 0.12, r = 0.996, was obtained between EC25 values determined using a commercial laboratory bridge and cell (Y), and those determined using an earth resistivity meter and an easily fabricated, four‐electrode conductivity cell (X).
Hydraulic Properties of a Porous Medium: Measurement and Empirical Representation
Authors: Gillham R. W. , Klute A. , Heermann D. F.
Published: July 2010

The hysteretic water content‐pressure head relationship and the hydraulic conductivity‐water content relationship for a porous material are needed in the solution of the water flow equation to predict behavior of a given flow system. These hydraulic properties were measured in an unsteady‐state manner using gamma ray attenuation for the water content and strain gauge pressure transducer tensiometery for the pressure head. Envelope curves and four to six primary wetting and drying scanning curves of the water content‐pressure relationship were determined. A convenient method of representation of the scanning curves by an empirical function was developed for use in computer solutions of the water flow equation.
Determining the Hydraulic Conductivity of Soil Cores by Centrifugation
Authors: Alemi M. H. , Nielsen D. R. , Biggar J. W.
Published: July 2010

Two centrifugal techniques are proposed for determining the hydraulic conductivity of cores of natural soil. Experimental results are presented for one technique in which the change in weight of one end of the sample, previously centrifuged, is measured with a balance. The mathematical equations describing this redistribution process were developed and fitted to the data to ascertain the soil water diffusivity D. The value of the hydraulic conductivity K was obtained from K = bD, where b is also calculated. Calculated values of K agreed with previously published values. The second technique for which a theory is presented but no experimental values are provided depends upon the measurement of the volumetric outflow of water from a soil core when the speed of centrifugation is suddenly increased.
Free Energy of Formation of Carbonate Apatites in Some Phosphate Rocks
Authors: Chien S. H. , Black C. A.
Published: July 2010

A constant ion‐activity product or solubility‐product constant for carbonate apatite (KCA) was found within a certain pH range in dilute HCl solutions equilibrated with each of a group of phosphate rocks that had been treated with an alkaline ammonium citrate solution to remove alkaline‐earth carbonates. The KCA values generally increased with an increase in the number of moles of carbonate/mole of apatite. As predicted theoretically, the free energies of formation calculated for the carbonate apatites (ΔG°f,CA) in various phosphate rocks increased linearly with an increase in the number of moles of carbonate/mole of apatite. The apatites in phosphate rocks extensively pre‐extracted with HCl had lower KCA values and lower ΔG°f,CA values than the apatites in phosphate rocks pre‐extracted with alkaline ammonium citrate solution. Empirical equations developed to relate the ΔG°f,CA values to the number of moles of carbonate/mole of apatite make possible the estimation of KCA for other phosphate rocks for which the empirical molecular formula of the apatite is known.