bluuebunny/crossref_metadata_2025 huggingface dataset:
Derivation of Land Qualities to Assess Environmental Problems from Soil Surveys
Authors: Breeuwsma A. , Wösten J. H. M. , Vleeshouwer J. J. , van Slobbe A. M. , Bouma J.
Published: July 2010

A digitized soil map with scale 1:50 000 of a sandy area of 2000 ha in the Netherlands was used to derive interpretive maps showing gradations of three land qualities of importance in assessing environmental problems. An interactive graphics computer system (IGS) was used. The land qualities calculated from soil properties of the unsaturated zone were: (i) travel times of water, (ii) cation exchange capacity (CEC), and (iii) phosphate sorption capacity (PSC). Transfer functions were defined, relating soil characteristics (texture, organic matter content, and oxalate‐extractable Al and Fe, integrated across horizons designation) to the land qualities. Water‐table levels were defined in terms of the mean highest (MHW) and the mean lowest (MLW) levels. Land qualities were expressed in terms of classes that spanned the range of observed spatial variability. The IGS system can produce interpretive maps from the soil map almost instantly, given selected inputs such as specified water‐table levels.
Factors Affecting the Stability of Soil Crusts in Subsequent Storms
Authors: Levy G. , Shainberg I. , Morin J.
Published: July 2010

Conflicting results exist concerning the effect of drying on the properties of soil crusts. In this study the hypothesis that the stability of crust to drying depends on the processes that predominate during its formation was tested by studying the effect of application of distilled (DW) and saline water (SW) (EC = 5 dS m−1) on the infiltration rates (IR) of a crusted soil surface. A Typic Rhodoxeralf and a Calcic Haploxeralf saturated with low (< 3.5) and high (17 < ESP < 20) exchangeable sodium percentages (ESP) were exposed to simulated rain of low and high energy levels. The soils were oven‐dried at 35°C for 24 and 72 h between consecutive storms. The stability of the crust was found to depend on the mechanisms of its formation. The crusts of soils with low ESP exposed to DW and SW rain and the crust of a soil with high ESP exposed to SW rain were found to be unstable and to be affected strongly by (i) the salinity of the rain water in subsequent storms, (ii) the impact energy of the raindrops, and (iii) the length of the drying period between consecutive storms. Conversely, a crust in which chemical dispersion supplemented physical dispersion (a soil with high ESP exposed to DW rain) was found to be stable and to be less affected by the water salinity of the subsequent storm, by its impact energy, or by the extent of drying between storms.
Evaluating Mineral Dissolution in Laboratory Weathering Experiments Using Leachate Equilibria
Authors: Sullivan Patrick J. , Sobek Andrew A. , Rybarczyk James P.
Published: July 2010

A laboratory mineral weathering study was completed using pyrite and soxhlet leaching apparatus to demonstrate the application of the GEOCHEM computer model for identifying mineral weathering reactions from nonequilibrium leachates. Crushed crystals of pyrite were continuously leached at approximately 27°C for 144 h. Every 24 h, leachate was removed from the soxhlet and analyzed for pH, ferric Fe, ferrous Fe, SO2‐4, Ca, Mg, and silica. Based on the stoichiometry of pyrite oxidation, the GEOCHEM computer model was utilized to calculate leachate pH. By comparing the GEOCHEM calculated pH to the observed leachate pH, it was determined that pyrite oxidation in the soxhlet occurs through a reaction with atmospheric O2 and not with ferric Fe. The results of this study exemplifies the use of geochemical models to help identify and characterize weathering reactions under conditions of nonequilibrium.
Determination of Saturated Hydraulic Conductivity from Soil Percolation Test Results
Authors: Fritton D. D. , Ratvasky T. T. , Petersen G. W.
Published: July 2010

Percolation times and saturated hydraulic conductivity rates from 28 test holes were used with data from the literature to relate saturated hydraulic conductivity, K, to percolation time, P. Sites were chosen to represent seven central and western Pennsylvania soils developed in shale and sandstone colluvium, alluvium, glacial outwash, or residual limestone parent materials. Saturated hydraulic conductivity was determined by the shallow well pump‐in method, an in‐situ test that measures three‐dimensional water flow into the soil. Percolation time was determined using a modification of approved procedures of the Environmental Protection Agency and the Pennsylvania Dep. of Environmental Resources. Linear regression analysis performed on the base 10 logarithm of the 28 pairs of data from this study resulted in the equation: log K = −0.309 log P −4.296 (with P in units of s/m and K in units of m/s). This equation was compared to an equation derived from literature data and to a steady‐state three‐dimensional infiltration equation derived from soil‐water flow theory. It was concluded that the literature data and the theoretical equation were different from that generated in this study due to the use of a saturated hydraulic conductivity technique that was sensitive to the layered nature of the soils used. It was further concluded that an equation derived from theory, log K = ‐log (P) − log (1 + 4/παro), could be used to convert percolation times, P, to saturated hydraulic conductivity values, K.
Symbiotic and Free‐living Denitrification by Bradyrhizobium japonicum
Authors: Smith Geoffrey B. , Smith M. Scott
Published: July 2010

Denitrification by Bradyrhizobium japonicum (formerly Rhizobium japonicum) was characterized in two strains, USDA‐110 and USDA‐23, to determine the extent of denitrifying enzyme expression during symbiotic growth with soybean [Glycine max (L.) Merr.]. The rhizobia grew in anaerobic batch cultures, depleting NO3‐ and producing N2O in the presence of C2H2. Specific denitrifying activities of resting cells of rhizobia were compared with those of the common soil denitrifier Pseudomonas fluorescens, and were found to range from 14 to 18% of the P. fluorescens activity. Bacteroid specific activities were less than activities of free‐living rhizobial cells, though the ratio depended on the growth stage of the cells. Denitrification was observed in detached whole nodules containing either of the strains, but not in nodules formed by a NO3‐ reductase mutant of B. japonicum 110. Denitrification rates of nodules were unaffected by the presence of external O2, though the rates were limited by the external NO3‐ concentration. Denitrification by intact, nodulated soybean plants under aerobic conditions was observed. In the presence of NO3‐ denitrification and N2 fixation (C2H2 reduction) occurred simultaneously. The estimated ratio of N denitrified to N fixed ranged from 0 to 0.3, depending on assay conditions. The observations suggest that denitrification in soybean nodules in the field can be a continuous process, independent of soil aeration. However, it is likely to be slow relative to N2 fixation under most conditions.
Soil and Slash Pine Response to Sludge Applications in Florida
Authors: Lutrick M. C. , Riekerk H. , Cornell J. A.
Published: July 2010

A study was made of the mineral uptake by slash pine (Pinus elliottii Engelm.), and of the movement of nutrients through the profile of an extremely sandy soil to which liquid digested sewage sludge containing 26 g kg−1 (2.6%) solids had been applied as a source of plant nutrients. The sludge was applied only once to an area planted to pine seedlings, at rates of 0, 20, 40, 60, 80, and 100 Mg ha−1 dry matter. The large amount of N (730‐3650 kg ha−1) in the sludge treatments would limit the amount of sludge that would be applied to slash pine grown on a Troup fine sandy loam (Grossarenic Paleudults), since NO3‐ could leach into the ground water if sludge were applied in excessive amounts. Large amounts of P and Zn also were added to the soil from the sludge, but neither moved down the soil profile beyond the 90‐cm sampling depth. After 4 yr of growth, the N and P concentration in pine needles had increased significantly from the sludge treatments, but after 8 yr, the N and P concentration in needles was not significantly different among treatments. However, the Ca concentration in the pine needles increased due to treatment after 8 yr but was not different after 4 yr. Addition of sludge increased individual tree growth by 0.8 dm3 yr−1 and increased annual yield by 1.0 m3 ha−1 per 10 Mg ha−1 sludge. Annual yields were probably diminished because the addition of sludge to the planted pines caused some damage and mortality. A deep sand of low fertility, such as this Troup fine sandy loam, would respond better to an application of −10 to 20 Mg ha−1 yr−1 of sludge over a 2‐ to 3‐yr period.
Incorporation of 35S‐sulfate Into Inorganic and Organic Constituents of Two Forest Soils
Authors: Schindler S. C. , Mitchell M. J. , Scott T. J. , Fuller R. D. , Driscoll C. T.
Published: July 2010

Incorporation of 35S‐sulfate into phosphate‐extractable S, hydriodic acid‐reducible S (HI‐S), and total S was measured in three horizons of Spodosols from the Huntington Forest, New York and Hubbard Brook Experimental Forest, New Hampshire. After 56 d 35S incorporated into nonwater‐extractable S constituents was 92, 65, 92, 63, 72, and 91% of the total 35S‐activity for the Huntington Forest Oa, Bh, Bsl, and Hubbard Brook Oa, Bh, and Bsl horizons, respectively. Immobilization of 35S‐sulfate into carbon‐bonded S (total S — HI‐S) was the major incorporation pathway in the Oa horizons. Adsorption of 35S‐sulfate (phosphate‐extractable) was most evident in the Bh and Bsl horizons. Incorporation of 35S‐sulfate into ester sulfate (HI‐S — inorganic S) occurred in all horizons. The influence of immobilization‐mineralization and adsorption‐desorption on S dynamics of these forest soils was evaluated.
Neutron Moisture Meter Calibration for Minespoils Containing Coal
Authors: Halvorson Gary A.
Published: July 2010

Laboratory calibrations were used to determine the effect of coal in spoil on neutron moisture meter measurements. Calibrations were conducted on clay loam and loamy sand minespoils from western North Dakota, with and without coal added. Volumetric water contents were overestimated by 3.7% in clay loam containing 8% coal by weight, and 4.7% in loamy sand containing 9% coal by weight using a calibration curve based on similar material without coal. The equivalent water content of the coal (θc) was calculated from the H content of the coal. Correction of calibration curves containing coal by adding θc to volumetric water contents substantially accounted for differences between calibration curves with and without added coal. Due to the large variability in both concentration and size of coal fragments in minespoil, accurate calibration is difficult at best. Since the slope of the calibration curve is unaffected by the presence of coal, changes in soil‐water content over time can be accurately determined from one calibration curve. At sites containing coal fragments, absolute measurements of soil‐water content are difficult, and therefore, only relative differences in water content over time should be determined.
Effect of Fertilizer Source on Denitrification and Nitrous Oxide Emissions in a Maize‐field
Authors: Duxbury J. M. , McConnaughey P. K.
Published: July 2010

The C2H2‐block method was used to measure denitrification in a maize (Zea mays L.) field over the 85‐d period between sidedressing with N fertilizer and harvest. Measurement locations were changed weekly in order to avoid problems associated with microbial utilization of C2H2 and inhibition of nitrification. Nitrous oxide (N2O) fluxes were measured both with and without C2H2 addition to soil. Without C2H2 addition to soil, 0.3 kg N ha−1 was evolved from both unfertilized and Ca(NO3)2 treated soil, whereas 2.5 kg N ha−1 was evolved from urea treated soil. This difference was attributed to formation of N2O during nitrification of NH+4 liberated from urea. With C2H2 addition to soil, 1.6, 2.0, and 2.4 kg N ha−1 were evolved as the result of denitrification in the zero N, Ca(NO3)2, and urea treated sites, respectively. Total gaseous N loss from a particular N treatment was approximated by adding together the N2O‐N loss with and without C2H2 addition to soil. The gaseous N loss associated with fertilizer addition was <3% of that applied. The ratio of N2/N2O evolved without C2H2 addition to soil was estimated to be in the range of 4:1 to 7:1 for the zero N and Ca(NO3)2 treatments and about 1:1 for the urea treatment. Denitrification was responsible for at least 80% of the measured gaseous N loss from the zero N and Ca(NO3)2 treatments. About equal amounts of gaseous N loss from the urea treatment occurred via denitrification and during nitrification of liberated NH+4.
Profile Modification and Irrigation Effects on Yield and Water Use of Wheat
Authors: Eck Harold V.
Published: July 2010

Where water is limited, there are continuous searches for management practices that increase water use efficiency (WUE). Profile modification (PM) of Pullman clay loam (fine, mixed, thermic Torrertic Paleustolls) has been shown to increase yield and WUE of grain sorghum [Sorghum bicolor (L.) Moench] and alfalfa (Medicago sativa L.). We hypothesized that it might increase those of winter wheat (Triticum aestivum L.) and, combined with limited irrigation, might further increase water use efficiency. A 4‐yr study was conducted on a site on which PM treatments (imposed in 1964) included thorough mixing of the soil profile to 0, 0.9, and 1.5 m with a wheel‐type ditching machine. Measurements in 1985 showed that PM still affected infiltration rate, bulk density, and surface elevation of the soil. Irrigation treatments were: (i) fall irrigation only (preplant or preplant + emergence), (ii) fall irrigation plus one spring irrigation, (iii) fall irrigation plus two spring irrigations, and (iv) fall irrigation plus three spring irrigations. Under irrigation Treatment I, compared to yields on unmodified soil, average grain yields were increased 11% by 0.9‐m PM and 20% by 1.5‐m PM. With Treatment II, average increases were 16 and 25%, respectively, but under treatments III and IV, PM did not affect grain yields. Under irrigation Treatment I, compared to WUE on unmodified soil, WUE for grain production was increased 10% on 0.9‐m PM soil and 16% on 1.5‐m PM soil. Under Treatment II, the respective increases were 15 and 21%, but with treatments III and IV, PM had little effect on WUE. Profile modification‐induced increases in wheat grain yield and WUE were small compared to those obtained with grain sorghum and alfalfa in previous studies. Profile modification of Pullman clay loam is not a feasible practice for wheat production because of limited yield response and high energy requirements to accomplish PM.
Effect of Sulfate on Ionic Transport and Balance in a Slightly Acidic Forest Soil
Authors: Khanna P. K. , Weaver G. T. , Beese F.
Published: July 2010

Sulfate (CaSO4) was percolated at low (1.4 mg S L−1) and high (60.8 mg S L−1) concentrations, in a solution of composition equivalent to that of the canopy drip under beech (Fagus sylvatica L.) forests, through undisturbed columns of a slightly acid soil (Terra Fusca Rendzina or Lithic Rendoll). Concentrations of Ca2+, Mg2+, NO‐3, and probably HCO‐3 increased and of K decreased in the percolates. Decomposition of soil organic matter caused a significant production and subsequent leaching loss of 1.0 mmolc m2 of NO‐3 during the experimental period of 156 d. Sulfate was released by the soil during the phase of low SO2‐4 addition but was retained during the phase of high SO2‐4 addition. Production of NO‐3 and probably HCO‐3, retention and release of SO2‐4, and the release of cations involved a significant amount of production/consumption of protons in the soil. Calcium (II) and Mg2+ were leached from the soil but K+ was retained. Breakthrough curves showed peaks, usually wide, for cations when about two pore volumes of solutions had been replaced. Sulfate behaved as a reactive ion in this soil and its transport could be described by a solute transport model using suitable parameters (adsorption isotherms, apparent diffusion coefficients, bulk density, and water content), which were obtained from independent studies.
Field Denitrification Estimation by Nitrogen‐15 and Acetylene Inhibition Techniques
Authors: Mosier A. R. , Guenzi W. D. , Schweizer E. E.
Published: July 2010

Direct quantification of denitrification N loss from N‐fertilized soils has been a long standing problem in soil N research. Recently 15N or acetylene inhibition methods have been used to make in‐field estimates of N loss from the soil resulting from denitrification. both methods have potential problems that may affect the validity of the data acquired. A field study was conducted to compare the acetylene inhibition approach with a 15N technique for measuring total N evolution (N2O + N2) from a N‐fertilized soil. Miniplots were established in an unplanted clay loam soil and fertilized with 15N‐labeled ammonium sulfate. Total N emissions were followed during three irrigation and subsequent drying events. The total N emissions measured by the acetylene method averaged 12 kg N ha−1 compared to 9 kg N ha−1 measured by the 15N technique from the nonacetylene‐treated plots. This difference between methods was small relative to the spatial variability observed in measuring gaseous N emissions in the field.
A Clay Suspension Stability End Point Titration Method for Measuring Cation Exchange Capacity of Soils
Authors: Pleysier J. , Janssens J. , Cremers A.
Published: July 2010

The silver‐thiourea (AgTU) method for cation exchange capacity (CEC) measurement of soils involves the assessment of Ag in the AgTU soil extracts. Silver can be easily measured by an atomic absorption spectrophotometer or with a radio isotope and scintillation counter. Laboratories for soil analysis in developing countries often do not have access to such instruments. A simple method for measuring Ag in the AgTU soil extracts was, therefore, developed. The method involves a stability end point titration of a stable montmorillonite clay suspension calibrated with AgTU solutions ranging from 5 × 10−4 to 10−2 mol L−1. The AgTU‐CEC measured by this clay titration method was compared with the “effective” CEC by NH4OAc and KCI extractions and with the AgTU‐CEC measured by an atomic absorption spectrophotometer. The correlation coefficients were 0.95 and 0.97, respectively.
Supercritical Gas Extraction of Alkanes and Alkanoic Acids from Soils and Humic Materials
Authors: Schnitzer M. , Hindle C. A. , Meglic M.
Published: July 2010

Three soils and two humic materials were extracted with n‐pentane by supercritical gas extraction. The extracts contained a variety of compounds separated by chemical and gas chromatographic techniques and identified by gas chromatography‐mass spectrometry. The compounds identified in the extracts included n‐alkanes (ranging from n‐C12 to n‐C32), with n‐C26, and n‐C24 alkanes in prominence, and smaller amounts of cyclic alkanes (C19 to C31). The major components, however were n‐fatty acids (n‐C7 to n‐C29), accompanied by lesser amounts of branched fatty acids (C12 to C19), and unsaturated fatty acids (n‐C‐16, n‐C‐18 and n‐C‐18). hydroxy‐fatty acids (C12 to C16), and alkanoic α,ω‐diacids (C15‐C25). The overall even‐to‐odd preference indexes for the n‐alkanes and n‐fatty acids were 1.35 and 4.15, respectively, suggesting microbiological origins for these compounds. Total alkanes extracted from the soils and humic preparations ranged from 4.3 to 8.9 and 32.5 to 201.4 mg/kg, respectively. By contrast, alkanoic acids extracted varied from 94.5 to 208.9 mg/kg for the soils and 740.1 to 1576.6 mg/kg for the humic materials. Supercritical gas extraction appears to be a promising procedure for the relatively mild and efficient extraction of specific organic components from soils and humic materials.
Laboratory Apparatus to Apply and Sample Anhydrous Ammonia in Bands
Authors: Izaurralde R. C. , Kissel D. E. , Swallow C. W.
Published: July 2010

To describe how soil properties affect anhydrous ammonia (NH3) retention, more accurate laboratory methods are needed to apply anhydrous NH3 in a line source (band) and sample the resulting NH3 retention zone. We developed and tested a line‐source NH3 applicator and a method for sampling the resulting NH3 retention zone. The applicator has a system of flow control valves and a flow meter to regulate the rate of NH3 flow to an injection needle. The needle is held stationary while NH3 is injected into a box of soil. The box of soil moves on a platform whose speed can be varied to change the NH3 application rate. The soil sampling method was to sequentially remove concentric cylindrical cores of increasing radii centered around the line of NH3 injection. Ammonia was applied to two soils with different NH3 retention capacities and the resulting NH3 retention zones were sampled. Accurate NH3 deliveries were possible with the system described. The coefficient of variation of the platform speed was <1%. The sampling method gave N recoveries that ranged between 95 to 99%. By using the concentric ring sampling method, ammoniacal‐N concentrations of duplicate retention zones at different distances from the injection line were not significantly different. Thus, the applicator and soil sampling method proved to be both accurate and precise for studying NH3 retention zones in soil.
Argillic Horizon Expression and Classification in the Soils of Two Michigan Hydrosequences
Authors: Cremeens D. L. , Mokma D. L.
Published: July 2010

Two hydrosequences in central Michigan were investigated to evaluate the degree of Bt horizon expression as influenced by the depth and duration of soil saturation. Each hydrosequence was sampled in duplicate and consisted of well or moderately well, somewhat poorly, and poorly drained soils. Total clay ratios, I/E indices (fine clay/total clay of the illuvial zone divided the fine clay/total clay of the eluvial zone), and argillan development were greatest in the well‐drained soils and decreased with decreasing depth to and increasing duration of soil saturation. One of the poorly drained soils lacked Bt horizons while one had Bt horizon expression similar to that of the somewhat poorly drained soils. The water table regimes of all poorly drained soils were similar. The poorly drained soils with Bt horizons contained relatively large amounts of smectite, particularly in the clay films, while those lacking Bt horizons contained virtually no smectite. The Bt horizons developed to a greater degree where moisture fronts penetrated the solum the greater period of the year. Where penetration was retarded by soil saturation, mineralogy contributed to the degree of Bt horizon development.
Clay Minerals, Humus Complexes, and Classification of Four “Andepts” of Maui, Hawaii
Authors: Wada K. , Kakuto Y. , Ikawa H.
Published: July 2010

Clay minerals and humus complexes in the Pane, Kula, Kaipoioi, and Olinda soils, derived from basalt‐andesitic to andesitic volcanic ash on Maui, Hawaii, were studied by a combination of methods. These soils have ustic soil moisture regimes except for the Olinda, which has an udic moisture regime. The clay content of all soil samples was high (35‐73%). Allophane and/or noncrystalline Fe oxides were abundant in the Pane, Kula, and Kaipoioi soils, but they were not identified or were present only in small amounts in the Olinda soil. In the Olinda soil, layer silicates, largely of eolian origin, and hematite were major clay components. Substantial amounts of halloysite and imogolite were found in the surface and subsurface horizons, respectively, of the Pane soil. Maghemite or hematite and magnetite were major silt and fine sand components in all samples and the content of weatherable minerals was <10% except for the Kaipoioi soil. Iron and Al bound with humus increased in the soils in the order of Pane <Kula <Kaipoioi Olinda, showing an inverse relation with formation of allophane and noncrystalline Fe oxides. The organic matter inhibits the formation of allophane and imogolite by lowering of activity of Al through formation of metal‐ligand bonds. Using the U.S. system of soil taxonomy, the sampled Pane soil is classified as an Eutrandept, and the sampled Kula and Kaipoioi soils as Dystrandepts, while the sampled Olinda soil is not classified as an Andept. In the Andisol proposal, the Pane, Kula, and Kaipoioi soils would be classified as Haplustands, while the Olinda would be Hapludand. These taxonomic names require further consideration regarding the definition of the great groups or suborders of Andisols.
Water Sorption Characteristics of Aluminum‐ and Calcium‐saturated Soil Clays
Authors: Karathanasis A. D. , Evangelou V. P.
Published: July 2010

Water sorption by Al‐ and Ca‐saturated bentonites and soil clays with montmorillonitic, mixed, illitic, and kaolinitic mineralogy were quantitatively evaluated at water vapor pressure levels (P/P0) of 0.50, 0.90, and 0.98 by thermogravimetry (TG) and differential scanning calorimetry techniques. After a 14‐d equilibration time, Al‐saturated clays adsorbed less water than Ca‐clays at low water vapor pressures but 10 to 12% more at P/P0 = 0.98. Heats of dehydration (ΔH) followed similar trends but the enthalpy required to remove 1 g of H2O from either Al‐ or Ca‐clays was approximately equal for clays with similar mineralogy. Enthalpy per unit weight of H2O decreased with decreasing interlayer space availability reaching minima in kaolinitic clays. Moisture retention differences between Al‐ and Ca‐clays at different P/P0 levels are attributed to structural organization differences of the H2O molecule—exchangeable cation network in the interlayer space as well as differential expansion at high hydration states. Practical implications of these relationships may be higher field moisture capacities, higher moisture retention during drought, and poorer field expression of cracks in acid soils with relatively high degree of Al‐saturation, especially when the soil contains significant montmorillonite quantities. Thirty‐five acid soil samples on which these relationships were tested indicated significant dependence of soil moisture characteristics on the degree of Al saturation of the clay surface.
Transport of Chloride Ion in a Water‐unsaturated Soil Exhibiting Anion Exclusion
Authors: James Ronald V. , Rubin Jacob
Published: July 2010

Miscible displacement techniques were used to create Cl‐ concentration profiles in unsaturated laboratory columns of Delhi sand (Typic Xeropsamments), each having a nearly uniform water content. The three steady flow rates used resulted in three different, average water contents. Chloride concentrations near the top of the column were smaller and penetration of Cl‐ in the column was deeper than expected assuming that Cl‐ is a noninteracting solute. Such observations indicate the presence of anion exclusion. This interpretation is further substantiated by chloride and tritium breakthrough curves obtained from a saturated column of the same soil. The saturated experiments show that tritium occupies the entire measured pore volume of the column, but that Cl‐ is restricted to a smaller pore volume. The formulation of the conventional convection‐dispersion theory for solute transport in soil which includes anion exclusion resulted in model calculations that fitted the unsaturated Cl‐ concentration profiles quite well. The dispersion coefficients obtained for the unsaturated profiles increase with water velocity and are lower than those previously reported for comparable water velocities in the same but saturated soil. The dispersivity of the unsaturated soil is also smaller than that reported for the saturated soil. For the experimental conditions used, the effective Cl‐ exclusion volume was found to be independent of water content and velocity and occupied about ten percent of the unsaturated water content.
Effect of Acidity on Nitrogen Mineralization and Nitrification in Atlantic Coastal Plain Soils
Authors: Weier K. L. , Gilliam J. W.
Published: July 2010

The objective of this study was to determine the effect of acidity on mineralization, nitrification, and N2O evolution during these processes on naturally acid soils from the lower Coastal Plain of North Carolina. Six acid surface soils (pH ≤4.5) from the Tidewater region of North Carolina, with a range of organic matter (OM) contents (28‐850 g kg−1) were limed to give a range of pH values so that the effect of acidity on mineralization of organic N and nitrification of (NH4)2SO4 could be studied under controlled conditions in the laboratory. Cumulative net mineralization over 21 d was significantly (p <0.01) influenced by acidity in four of the six soils. However, no soil exhibited a significant net mineralization increase between the very acid initial pH value and the pH value to which liming is recommended (pH 4.8‐5.2 for Histosols) for crop production. Liming to pH values <7 increased net mineralization in only one soil. Adding a small increment of lime tended to decrease mineralization although this effect was significant in only one soil. Essentially all organic N mineralized was converted to NO‐3 at all pH values. However, the very high acidities tended to inhibit the nitrification of NH+4 added as (NH4)2SO4. There was apparently no influence of organic matter content on any of the processes studied except N2O evolution where the soils with <120 g OM kg−1 evolved the highest amounts of N2O during nitrification. Much of the N2O evolution was apparently due to denitrification because addition of nitrapyrin did not eliminate the evolution. It was concluded that the liming of acid soils in the Tidewater Region of North Carolina would have little influence upon N mineralization rates. The recommended pH values of 4.8 to 5.2 for Histosols appears to be adequate for both mineralization and nitrification.
A Nonweighing Lysimeter Design for Field Studies Using Nitrogen‐15
Authors: Reeder J. D.
Published: July 2010

This paper describes the design and use of a nonweighing lysimeter in a field study in which 15N cycling was monitored within a revegetated disturbed‐land ecosystem over a period of 5 yr. The design successfully overcame sampling problems associated with a rocky terrain. Recovery of added 15N was satisfactory, with <10% of added 15N unaccounted for two seasons after application. However, the water content of the natural spoil profile could not be exactly duplicated in the lysimeter. Although the lysimeter was designed to minimize sampling problems associated with a specific research site, the design is applicable to other field conditions in which leaching losses need to be monitored.
Influence of Soil Organic Matter Concentrations on Carbon and Nitrogen Activity
Authors: Woods L. E. , Schuman G. E.
Published: July 2010

The relationship of soil organic matter (OM) concentration to microbial biomass concentration and mineralizable OM is central to understanding the establishment and functioning of soil nutrient cycles. These parameters are presumably related to aboveground plant biomass and plant N concentration, but the mechanisms and controls of these interactions are not well understood. To further evaluate these relationships, a field study was established in a series of soil materials whose organic C concentrations ranged from 1 to 21 g kg−1. Surface soil (0‐15 cm) and vegetation samples were collected from plots of each treatment during the 1983 growing season. Microbial biomass was measured by chloroform fumigation and incubation; mineralizable C and N were measured in 20‐d laboratory incubations; plant growth was measured by weighing material clipped from 0.18‐m2 frames; and plant N concentration was measured by Kjeldahl digestion and colorimetric analysis. Microbial biomass increased linearly with soil OM concentration. Mineralizable N and plant production also increased with soil OM, but were greater with 7 than with 15 g kg−1 of organic C. Even though aboveground plant biomass was greater with either 7 or 15 than with 21 g kg−1 organic C, plant N concentrations were highest with 21 g kg−1. Soil OM concentrations were more closely related to microbial biomass than to mineralizable C and N, or to plant biomass and plant N concentrations. Nitrogen mineralization in the laboratory corresponded to plant N concentration in the field. Soil OM concentrations controlled microbial biomass C and N concentrations. However, additional factors also influenced the activity of the microbes and the resultant OM mineralization and plant N concentrations.
Modeling the Plant Uptake of Cadmium and Zinc from Soils Treated with Sewage Sludge
Authors: Mullins G. L. , Sommers L. E. , Barber S. A.
Published: July 2010

To evaluate models for predicting plant uptake of Zn and Cd, a growth chamber study was conducted with soils collected from research plots in Ohio, Indiana, Michigan, and Wisconsin that had been treated 4 yr previously with 100 Mg ha−1 of an anaerobically digested sewage sludge from Chicago, IL. The single application of sludge supplied 19‐kg Cd and 340 kg Zn ha−1. Sludge application increased the concentration of Cd and Zn in the shoots and roots of corn (Zea mays L.) seedlings grown for 16 and 22 d in the four soils. The application of sludge had no effect on the growth and properties of the corn root systems. Soil characteristics and kinetic parameters for Zn and Cd uptake were combined with a nutrient uptake model to predict Cd and Zn uptake by corn seedlings. In the untreated and sludge‐treated soils predicted Cd uptake (Y) was related to observed uptake (X) in nmol pot−1 by: Y = 90.03 + 1.41X (r = 0.81). Overprediction of Cd uptake by 41% may have resulted from an incorrect value of the Michaelis‐Menten constant, Km, and/or neglecting Cd efflux from roots. Calculated Zn uptake in the untreated and sludge‐treated soils was related to observed uptake by: Y = 3.29 + 0.857X (r = 0.91) where units for Y and X are µmol Zn pot−1. A sensitivity analysis was conducted with the model to determine how each soil and plant factor affected predicted Cd and Zn uptake. Plant factors that had the greatest effect on Cd and Zn uptake include the root growth constants, average root radius, and water influx rate. Kinetics of Cd and Zn uptake and half‐distance between roots had little effect on Cd and Zn uptake. Concentration of Cd and Zn in the soil solution (Ci) was the soil parameter showing the greatest effect on predicted metal uptake. In comparison, average buffer power and diffusion coefficients for Zn and Cd had minimal impact on predicted metal uptake.
Iron Redistribution in Three Boralfs (Gray Luvisols) of Saskatchewan
Authors: Santos M. C. D. , St. Arnaud R. J. , Anderson D. W.
Published: July 2010

The transformation and translocation of Fe in three Boralfs (Gray Luvisols)3 were studied in relation to the Fe contained within silicate minerals and that existing in oxide forms. Quantitative evaluations of the Fe redistribution using a quartz index technique provided conclusive evidence that losses of Fe from E horizons and gains in Bt horizons are largely accounted for by the translocation of silicate‐Fe as a component of fine clays. The weathering of coarse clay to fine clay was documented; the fine clay fraction remained relatively unaffected. Some dissolution and movement of Fe in solution was also evident, particularly in the two profiles showing evidence of restricted drainage and periodic reduction. Detailed analyses of one of the soils studied indicated an 11% loss of total clay from the solum, involving a 16% loss of total Fe and a 19% loss of silicate‐Fe from the clay fractions. Most of the Fe lost from the clay was recovered in glaebules of sand and silt size, both as reprecipitated oxides and as occluded clay particles. The actual loss of clay from the solum was only about one‐half of the 11% loss indicated from particle size distribution values alone.
Effect of Sodium Polymetaphosphate on Soil Crust Formation and Runoff/Rain Relations
Authors: Ben‐Hur M. , Shainberg I. , Keren R.
Published: July 2010

The effect of sodium polymetaphosphate (NaPMP) on crust formation and on the amount of runoff was studied with two soils, Typic Rhodoxeralfs (sandy loam) and Xeric Torripsamments (loamy sand), using a rainfall simulator. Increasing the rate of NaPMP application in the range ≤ 100 kg ha−1, increased the rate of crust formation and decreased the final infiltration rate (IR). The increased rate of crust formation increased the fraction of runoff of the total rainfall and decreased the threshold rain needed to form runoff. The dispersant, NaPMP, weakened the stability of the aggregates and increased the amount of clay that migrated with the infiltrating water and accumulated in the “washed in” layer. Hence, the effect of NaPMP was more pronounced in a loamy sand, where the low amount of clay limits the formation of a crust, compared with the sandy loam, which contains enough clay to form a crust. In consecutive short storms of 18 mm each with complete drying between storms, the rate of crust formation was slow and the amount of runoff was low in the control treatment, compared with the high efficiency of NaPMP for increasing runoff. The low amounts of NaPMP required to significantly increase runoff gives the potential for commercial use in runoff farming.
Laboratory Modeling of Northern Great Plains Salt Efflorescence Mineralogy
Authors: Keller L. P. , McCarthy G. J. , Richardson J. L.
Published: July 2010

Recent studies of salt efflorescences in North Dakota and from several additional sites in the surrounding region indicated that the mineralogy of the efflorescences is predominantly sulfate salts of Na and Mg: mirabilite, thenardite, epsomite, hexahydrite, konyaite, and bloedite. Experiments consisting of isothermal evaporation of solutions with fixed Na2SO4/MgSO4 ratios were used to construct crystallization isotherms for the Na2SO4‐MgSO4‐H2O system at 28 and 40°C in order to model the salt efflorescence mineralogy. The first precipitates at 28°C were mirabilite, konyaite, and epsomite. At 40°C, thenardite replaced mirabilite as a first precipitate. The results indicated that the mineralogy is best described as a metastable system in which konyaite plays a dominant role. Konyaite is metastable when in contact with its saturated solution, but persists for long periods of time in dry efflorescence. The presence of konyaite in the system also allows mirabilite, thenardite, and epsomite to form supersaturated solutions with respect to the equilibrium phase assemblages. Reference to the liquidus‐solidus‐subsolidus portions of the experimental isotherms enables one to predict >90% of the observed natural assemblages that precipitate from sulfatic saline waters in North Dakota. This information allows us to determine which solid phases are controlling the shallow saline groundwater chemistry.
Water and Chloride Movement Through a Layered Field Soil
Authors: Starr J. L. , Parlange J. ‐Y. , Frink C. R.
Published: July 2010

Twenty porous ceramic samplers at each of four soil depths were arranged in a three‐dimensional pattern to study the movement of water and Cl‐ through a layered sandy loam (sandy, mesic typic Dystrochrepts) over a gravely coarse sand with a perched water table at ∼180 cm. All samplers were used as tensiometers during the initial phase of the experiment in which salt‐free water was ponded at the soil surface. After constant flow conditions were achieved, a pulse of 0.015 M CaCl2 solution was added to the infiltrating water and all samplers were then used to obtain soil water samples for Cl‐ analysis. Variations in soil water pressure were observed to be much smaller than the variations in Cl‐ concentration. Both water and Cl‐ data moved downward in a general one‐dimensional pattern in the finer textured surface layer and in the zone directly above the water table, whereas, the movement between these two depths was three‐dimensional, i.e., by fingering.
Effect of Terrazole on Nitrogen Transformations and Movement in Irrigated Corn
Authors: Mikkelsen R. L. , Jarrell W. M. , Letey J. , Whaley S.
Published: July 2010

A field study was conducted on two sandy loam soils to determine the effect of Terrazole nitrification inhibitor (5‐ethoxy‐3‐[trichloromethyl]‐1,2,4‐thiadiazole) on N movement and transformations. Sweet corn (Zea mays L.) was fertilized with (NH4)2SO4 twice during the growing season for a total application of 250 kg N ha−1. The N applied to one‐half of the fertilized treatments was coated with Terrazole. Three levels of irrigation were established for each field. The treatments on Arlington (Typic Durixeralfs) sandy loam received 55.9, 69.0, and 78.1 cm infiltrated water. The Hanford (Typic Xerorthents) sandy loam treatments received 62.0, 76.7, and 88.2 cm infiltrated water. Soil samples were taken at 20, 40, 60, 80 and 90 d after planting and analyzed for NO‐3 and NH+4. Movement of N was correlated with both the presence of Terrazole and the quantity of water applied. Soil NH+4 was consistently higher in Terrazole treatments, suggesting that nitrification was reduced by the Terrazole. However, there was no significant increase in tissue N concentrations or yield due to Terrazole additions. Denitrification losses in the field were found to be 64% lower due to the presence of Terrazole.
Characterization and Stratigraphy of Soil Parent Materials of West‐central Minnesota
Authors: Crum J. R. , Rust R. H.
Published: July 2010

Within the Alexandria Moraine Complex in west‐central Minnesota there are “islands” of fine textured soils and parent materials embedded within a matrix of coarser textured soils. To study the soils and the stratigraphic relationships of the parent materials, deep borings were made along two transects perpendicular to the Alexandria Moraine. A total of 27 sites were investigated. Particlesize distribution, CaCO3 equivalent, clay‐sized carbonate, and the dominant mineralogy of the >2 mm, 1 to 2 mm very coarse sand (vcos), and <2‐µm fractions were determined. Four glacial materials were identified in this study: New Ulm till, Kandiyohi till, Granite Falls till, and a “mixed” drift of mainly New Ulm and Granite Falls materials. The average clay content of the glacial materials ranges from about 370 g kg−1 in the Kandiyohi to about 130 g kg−1 in the Granite Falls and mixed drifts. The average shale content in the vcos fraction ranges from about 620 g kg−1 in the Kandiyohi till to about 60 g kg−1 in the Granite Falls till. The average CaCO3 equivalent ranges from about 220 g kg−1 in Granite Falls till to about 170 g kg−1 in the mixed drift. Statistically significant differences occur among the glacial materials in the concentration of sand, silt, clay, concentration of shale, carbonate, and crystalline pebbles in the vcos fraction, and the concentration of coarse fragments. A stepwise discriminant analysis was made and the four glacial materials were numerically defined by the first two canonical variables. The stratigraphic relationships of the two areas of Kandiyohi till outcrop studied seem to be quite different. The data from the western part of the county indicate much mixing of New Ulm and Granite Falls tills. Data from the eastern transect indicate the Kandiyohi till is an older till that has been thrust to the surface. It is suggested that the Kandiyohi till is a distinctly different glacial till in that: (i) the soils developed on this till are taxonomically distinct from soils on adjacent tills; (ii) the shale concentrations within the four defined glacial materials in the study region are statistically different; (iii) no other areas of this glacial till have been observed except in the Alexandria Moraine; and (iv) the glacial till outcrops are characteristically narrow linear features.
Parameters for Characterizing Tillage‐induced Soil Surface Roughness
Authors: Linden D. R. , Van Doren D. M.
Published: July 2010

Tillage‐induced soil roughness is an important consequence of tillage because water and air transport phenomena are affected. Characterizations of roughness have been statistical in nature and have lacked a physical connection to the configuration features affected by roughness. A new method of analyzing microrelief data is presented that improves the description of the soil surface and should lead to better information about the physical processes affected by tillage. The new procedure results in two surface configuration parameters, limiting slope (LS) and limiting elevation difference (LD), that are based on the slope or inclination of the surface of soil clods and to the average relief (elevation difference), respectively. These two indexes are directly related to the configuration of the surface and also sensitive to differences in roughness. They should help allow roughness to be used simultaneously with other soil properties to predict transport phenomenon.
Effect of Gypsum and Deep‐rooting Perennials on Subsoil Mechanical Impedance
Authors: Radcliffe D. E. , Clark R. L. , Sumner M. E.
Published: July 2010

Subsoil root growth in highly weathered southeastern soils is limited because of poor chemical conditions and high soil strength. Surface‐applied gypsum can leach into the subsoil and amend the chemical properties of these soils. The objective of this study was to determine if gypsum also had a physical effect. Mechanical impedance was measured using a tractor‐mounted penetrometer that gave values of cone index (CI) in gypsum‐treated and nontreated plots of several ongoing experiments. Cone index was lower in the gypsum‐treated plots where alfalfa (Medicago sativa L.) or peach trees [Prunus persica (L.) Batsch] had grown for several years, but there was no reduction in CI in fallow plots treated with gypsum. Samples from the alfalfa plots treated with gypsum had larger stable soil aggregates than samples taken from nontreated plots. We conclude that gypsum amendment increases subsoil root activity, which in turn reduces subsoil mechanical impedance.
Sources of Acidity in Some Forested Udults
Authors: Richter D. D.
Published: July 2010

Three sources of soil acidity (bicarbonate leaching; base‐cation accumulation in aboveground wood, roots, and forest floor; and acid atmospheric deposition) were evaluated in relation to exchangeable acidity of three forested Udults in Tennessee. The Udults have low effective CEC (CECe), from 2.4 to 3.7 cmolc kg−1. In the three soils, H+ from bicarbonate leaching averaged 0.60 kmolc ha−1yr−1 over 2 yr. In five forest stands, 30 to 80 yr in age, H+ from accumulation of excess base (EB) cations [EB = (Ca + Mg + K) − (P + S)] in aboveground wood, roots, and forest floor averaged 1.11 kmolc ha−1yr−1. Atmospheric H+ inputs, estimated from bulk precipitation, averaged 0.67 kmolc ha−1yr−1. Total deposition of atmospheric acidity to these eastern Tennessee forests is on the order of 1 kmolc ha−1yr−1. Variations in H+ inputs were caused by annual differences in the hydrologic cycle and by stand differences due to nutrientcycling and soil‐chemistry effects. In these forest ecosystems, sources of soil acidity from annual bicarbonate leaching and cation accumulation appeared to exceed atmospheric inputs. Exchangeable acidity in the forested Udults was large compared with annual fluxes of acidity. In the upper 60 cm of the three soils, KCl‐exchangeable acidity ranged from 100 to 274 kmolc ha−1, and BaCl2‐TEA (trieth‐anolamine) acidity ranged from 505 to 820 kmolc ha−1. Despite low precipitation pH and low soil CECe, the additional H+ from acid deposition has not caused significant alteration of soil acidity or base solution of these Udults.