bluuebunny/crossref_metadata_2025 huggingface dataset:
Mononuclear and Polynuclear Aluminum Speciation through Differential Kinetic Reactions with Ferron
Authors: Jardine P. M. , Zelazny L. W.
Published: July 2010

The kinetic reaction of ferron (8‐hydroxy‐7‐iodo‐5‐quinoline‐sulfonic acid) with partially neutralized Al solutions of varying basicity and age were investigated with the intent of separating mononuclear and polynuclear Al. Ferron solutions buffered with varying quantities of NaOAc, NH2OH·HCl, and acetic acid suggested that reduction of ferron by NH2OH·HCl may be essential before monotonically increasing absorbance vs. time functions occur for Al reactions with ferron. When ferron is buffered with appropriate quantities of NaOAc and NH2OH·HCl it must be aged for ⋍5 d at room temperature until reduction has slowed. This solution remains stable for ⋍25 d and exhibits consistent kinetic reactions with Al during this time period. A large portion of ferron interactions with partially neutralized Al of varying basicity and age were described by a binary species first‐order rate function, which provided the rates of monomer and small polymer reactions with ferron as well as the mole fraction of monomeric species present (fa). Modelfitted fa are based on the differential kinetic reactions of ferron with Al, thus arbitrary separation times for determining mononuclear and polynuclear Al are avoided. Rate parameters established for mononuclear Al solutions using a single species first‐order equation compared well with those determined for mononuclear Al from partially neutralized solutions using the binary species model. Ferron reactions at longer times were related to the decomposition of large Al polymers, which were welldescribed by pseudo first‐order kinetics.
Determination of Inorganic Mononuclear Aluminum by Selected Chelation Using Crown Ethers
Authors: Evans Andrew , Zelazny Lucian W.
Published: July 2010

This study was conducted to determine whether cation‐selective crown ethers could be utilized to measure inorganic mononuclear Al3+ in solutions containing Al‐complexing ligands. The dibenzo‐18‐crown‐6 ether was found to selectively chelate inorganic mononuclear Al3+ in the presence of common soil cations (Na, K, Ca, Mg, Fe, and Si). Aluminum previously complexed with di‐NaEDTA, oxalic, and citric acid was not chelated by the crown ether. The presence of high concentrations of F‐, SO2‐4, and NO‐3 in the sample solutions did not influence the determination of inorganic mononuclear Al3+. Determination of inorganic mononuclear Al3+ was reproducible to within ±0.17 × 10−6 mol L−1 in the 0.8 to 10 × 10−6 mol Al L−1 concentration range.
Quantitative Evaluation of Pedogenic Changes in Boralfs (Gray Luvisols) of East Central Saskatchewan
Authors: Santos M. C. D. , St. Arnaud R. J. , Anderson D. W.
Published: July 2010

Zirconium oxide/quartz ratios for the soil horizons of three Boralfs (Gray Luvisols) indicated that two of the soils were developed from sufficiently uniform deposits to permit quantitative evaluations of changes resulting from soil formation. A “pedogenic index” based upon total quartz content of horizons allowed the expression, as a percentage, of soil constituents present in relation to original contents in either total horizons or in component soil separates within them. The index, based upon the total quartz content of each horizon, provides values that overcome errors resulting from changes in particle size distribution of quartz such as occurs in Boralfs or other soils where significant physical breakdown of coarse to finer fractions has occurred. The index shows that approximately one‐third of the original sand in the E horizons has been physically weathered to finer sizes, dominantly to coarse silt size, but also down to clay size. Elemental analyses indicate that the Na‐ and K‐bearing minerals are more resistant than the Ca‐ and Mg‐bearing minerals, and that weathering has occurred in all size fractions. As a consequence, Ca and Mg, and to a lesser extent, Na and K, undergo greater net losses from the solum than do Si, Al, and Fe. Redistribution of the latter three elements within the sola is directly associated with the translocation of clay. Physical breakdown and lessivage are the major processes in all three soils, but chemical weathering and leaching losses are also important. Preferential translocation of fine clay (<0.2 µm) and the weathering of coarse clay (2‐0.2 µm) to fine clay size in both E and Bt horizons is substantiated.
Reclamation of an Ultisol Damaged by Mechanical Land Clearing
Authors: Alegre J. C. , Cassel D. K. , Bandy D. E.
Published: July 2010

Mechanical land clearing in 1972 of a Yurimaguas soil (fine‐loamy siliceous, isohyperthermic Typic Paleudult) located in the Amazon Basin of Peru resulted in compacted soil that was abandoned for continuous crop production in 1974. The purposes of this study were to reclaim this abandoned land for continuous cultivation and to evaluate temporal changes in soil physical properties with time after reclamation treatments began. In February 1980, guinea grass [Panicum maximum L.], which covered the compacted soil, was cut by hand, dried, and burned. The following eight reclamation treatments were imposed: (1) control (no till), planted with a planting stick; (2) rototill (12 kW) and stick planted; (3) rototill (48 kW); (4) chisel plow 25‐cm deep, rototill (48 kW); (5) controlled traffic (i.e., assignment of pathways for foot traffic); (6) bedding with hoe and planted with stick; (7) simulated subsoiling to 25 cm with a tile spade; and (8) mulching (mulch applied when seedlings were 10‐ to 25‐cm high). The following soil physical properties were quantitied several times during the study: infiltration rate, cone index (CI), bulk density (ρb), and the soil‐water characteristic. The crop rotation during the 2‐yr‐long period was rice (Oryza sativa L.)‐soybean [Glycine max (L.) Merr.]‐corn (Zea mays L.)‐soybean‐corn‐rice. Compared to the control treatment, all others decreased ρb and CI and increased infiltration rate, macro porosity, and total porosity in the 0‐ to 15‐cm depth. Only chisel plowing and simulated subsoiling alleviated the detrimental effects of the compacted soil below 15 cm. Infiltration rate at the conclusion of the experiment for the control treatment was 9 mm h−1 compared to 148 mm h−1 for the chisel plow treatment. Yield responses were greater for chiseling and simulated subsoiling. For example, the average relative grain yield for each of the three crops was 100% for chiseling; for no‐till, relative yields were 69, 23, and 20% for rice, soybean, and corn, respectively. We conclude that compacted soils similar to the Yurimaguas series can be reclaimed for continuous cropping by using deep tillage practices such as chisel plowing and subsoiling.
Vertical Root Distribution and Strontium Uptake of a Slash Pine Stand on a Florida Spodosol
Authors: Van Rees K. C. J. , Comerford N. B.
Published: July 2010

Root length distribution of slash pine (Pinus elliottii Engelm. var. elliottii) and associated understory vegetation was investigated for an Ultic Haplaquod in north‐central Florida. One‐third of the length of pine roots (<1 mm in diameter) was present in the argillic horizon below the 1 m depth. Slash pine taproots extended between 200 and 330 cm below the surface, (i.e., 1‐2.3 m into the argillic horizon). Slash pine roots were often found growing in large diameter, dead palmetto roots. Two‐thirds of the soil samples taken from the E horizon had all the pine roots growing in dead palmetto roots. Stable strontium (Sr) was placed in the argillic horizon and in the litter layer. Strontium concentration in the slash pine foliage increased 30 to 50% (depending on the age of the foliage sampled) when the argillic horizon was treated. There was no apparent Sr increase in needle tissue from spiking the litter layer. This effect was most likely due to the competition from associated vegetation.
Sweetgum Seedling Growth and Vesicular‐arbuscular Mycorrhizal Development as Affected by Soil Fumigation
Authors: Snyder C. S. , Davey C. B.
Published: July 2010

The effects of soil fumigation with methyl bromide (390 kg/ha) on sweetgum (Liquidambar styraciflua L.) seedling height, root collar diameter, root morphology, vesicular‐arbuscular mycorrhizal (VAM) infection, soil‐borne spore number, and soil fertility were monitored from seeding in the nursery until lifting. Seedlings in nonfumigated soil had greater heights, root collar diameters, and VAM infection than seedlings grown in fumigated soil. Differences between fumigation treatments were statistically significant for root collar diameter and VAM infection between 92 and 131 d after seeding, and for VAM infection after 320 d (lifting). Soil‐borne spore number increased markedly between 92 and 176 d after seeding but no significant difference between soil fumigation treatments was detected. Soil fertility was not significantly affected by soil fumigation. At lifting, seedlings were graded into large (≥7.6 mm) and small (≤6.9 mm) root collar diameter classes within each soil fumigation treatment and outplanted. Height and diameter growth differences between seedlings lifted from fumigated or nonfumigated soil were not significant after one growing season in the field. However, root collar diameter of seedlings from nonfumigated nursery soil was larger than that of seedlings from fumigated nursery soil after one growing season. Glomus fasciculatum (Thaxt. sensu Gerd.) Gerdemann and Trappe was indigenous to both the nursery and outplanting site.
Agronomic Evaluation of New Ureaforms for Flooded Rice
Authors: Carter M. F. , Vlek P. L. G. , Touchton J. T.
Published: July 2010

Rice (Oryza sativa L.) seldom utilizes more than 20 to 40% of the applied urea. Inefficient N utilization is largely attributed to N loss through ammonia (NH3) volatilization and denitrification. Increased N efficiency can be obtained with a slow‐release fertilizer such as ureaform (UF), which is the condensation product of urea and formaldehyde. A recent development in the production process of UF utilizes paraformaldehyde (PFA) addition to urea, which produces a modified urea fertilizer containing unreacted urea and methylene urea polymers. The purpose of this study was to evaluate N uptake and yield response of flooded rice and to determine NH3 volatilization losses from applications of 15N urea, UF, and methylenediurea. The UF fertilizers evaluated had PFA additions to urea ranging from 0% (urea) to 15% (UF‐15). In a greenhouse study with flooded rice, N uptake was measured and apparent N losses were estimated from an 15N balance. Direct NH3 volatilization losses were measured in a forced‐draft volatilization system. There was an increase in N uptake and a reduction in apparent and measured N losses from the modified urea fertilizers as the proportion of PFA increased. Plant 15N uptake at maturity can be expressed by the quadriatic equation: % recovery in total plant = 18.53 + 1.10%PFA − 0.02%PFA2. Total 15N recovered ranged from 44% as urea to 64% as UF‐15. In the forced‐draft NH3 volatilization study, total NH3 losses were reduced from 55% of the applied N as urea to 34% as MDU, and as the proportion of PFA addition to urea increased, NH3 losses decreased: % of applied N volatilized = 54.74 − 1.25%PFA. Ammoniacal N concentrations in the floodwater peaked on the 1st d after fertilizer application with urea and UF but peaked on the 7th d with MDU.
Barium in Illinois Surface Soils
Authors: Jones Robert L.
Published: July 2010

The mean total Ba content determined in 174 upland, surface soil samples was 610 mg kg−1 and the contents of the samples formed a normal distribution. An isopleth map of Ba contents was produced from programs calculating contours on a grided surface overlaid on a base map of Illinois. The isopleths are related to loess isopachs in southern Illinois and uniformly decrease from about 700 mg kg−1 near the Mississippi River to near 500 mg kg−1 at the eastern boundary of the state. This change in Ba content may reflect both weathering intensity and aeolian sorting of Ba‐bearing minerals. In northwestern Illinois where loess is also an important parent material, Ba contents are rather invariant in the range 600 to 650 mg kg−1. Where loess is very thin or nonexistent, surface soils of northeastern Illinois contain about 500 mg kg−1, a content thought to reflect the concentration in the tills of this area.
Adsorption of Nonionic Oxyethylated Sulfonamides onto Sand and Kaolin from Aqueous Solution
Authors: Hampson J. W. , Cornell D. G. , Micich T. J.
Published: July 2010

Nonionic surfactants continue to be used as soil conditioners, principally as wetting agents, but optimum surfactant chemical structure has not as yet been completely established. This research using nonionic surfactants, alkyl substituted polyoxyethylated phenylsulfonamides, has determined the effect of varying the ethoxy content and the alkyl side chain on three surfactant characteristics, i.e., adsorption, wetting, and dispersion. It was found that surfactant adsorption on sand and kaolin, two soil components, at a constant pH of 6.0 decreased with higher surfactant ethoxy content. Changing the alkyl side chain from C6 to C8 to C10 increased the apparent surfactant attraction for the adsorbent surface but not the total amount of surfactant adsorbed. The amount of surfactant adsorbed determines the final nature of the adsorbent's surface and its hydrophobic or hydrophilic character. Thus, the wetting and dispersing properties of soil components can be set by the amount of surfactant adsorbed.
The Influence of Anions on Potassium Quantity‐Intensity Relationships
Authors: Evangelou V. P.
Published: July 2010

Quantity‐intensity (Q/I) relationships for potassium (K+) of soils sampled from three Maury silt loam sites (fine‐silty, mixed, mesic, Typic Paleudalfs) representing different crop management practices were investigated in 10−2 molc L‐ each of Cl‐ or SO2‐4 solutions. Soil samples from the three sites were (i) low in exchangeable K+ and organic matter (LK‐LOM), (ii) high in exchangeable K+ with low organic matter (HK‐LOM), and (iii) high in exchangeable K+ with relatively high organic matter (HK‐HOM). A theoretical evaluation of K+ Q/I plots in Cl‐ or SO2‐4 solutions employing the Gapon equation, revealed that the potential buffering capacity for K+ (APBCk), the labile K+ (AExK0) and equilibrium activity ratio for K+ (ARK0) based on single ion activities and ion pairs of CaSO04, KSO‐4 and CaCl+ were independent of the type of solution anion. When considering total dissolved concentration of K+ and Ca2+, the potential buffering capacity for K+ (CPBCK) and equilibrium concentration ratio for K+ (CRK0) differed between Cl‐ and SO2‐4 solutions. The labile K+ (CExK0) remained the same. These results were due to the differences in ion pairing abilities between Cl‐ and SO2‐4 with K+ and Ca2+. The influences of the ion pairs are minimized at decreasing CRK0 values. The experimental data describing Q/I relationships for K+ for the three soil samples were not in full agreement with the theoretical observations. The data showed that the type of anion (Cl‐ or SO2‐4) had an effect on the CRK0 and CExK0, but the values were not significantly different except for the HK‐HOM sample. The experimental data for the soil samples HK‐LOM and HK‐HOM indicated agreement to some extent with the theoretical evaluation. For the same CRK values in the Cl‐ or SO2‐4 anions, a greater change in exchangeable K+ (ΔExK) was observed in the SO2‐4 system than in the Cl‐ system. However, for these two soil samples (HK‐LOM and HK‐HOM) when the Q/I plots were constructed considering single ion activities, differences remained in the Q/I plot components ARK0 and AExK0 between the two anionic systems. For the LK‐LOM soil sample the Q/I plots appeared to be nearly identical for the Cl‐ and SO2‐4 systems in terms of total cation solution concentrations and/or solution single ion activities. This agreed with the theoretical evaluation.
Effect of Liming on the Distribution of Manganese, Copper, Iron, and Zinc Among Soil Fractions
Authors: Shuman L. M.
Published: July 2010

Understanding the effect of soil pH on the distribution of micronutrients among soil forms is a necessary precursor to designing micronutrient extractants that extract the form of the metal available to plants. An experiment was undertaken to determine effects of soil pH changes from different liming sources on the distribution of Mn, Cu, Fe, and Zn among soil fractions and to relate the amounts of micronutrients in the fractions to that extracted by the Mehlich I and DTPA extractants. A sandy soil was amended with rates of 0, 0.99, and 1.98 g kg−1 of three liming materials: calcitic limestone, dolomitic limestone, and an industrial by‐product containing 203 g kg−1 Mg. Following a greenhouse experiment, the soils were extracted with DTPA and Mehlich I and fractionated into exchangeable, organic, Mn oxide, amorphous Fe oxide, crystalline Fe oxide and residual fractions. The extracts and fractions were analyzed for Mn, Cu, Fe, and Zn, and there were very few differences among lime sources. Increasing lime rates decreased exchangeable Zn and increased organic fraction Zn and Mn. This increase in Zn and Mn in the organic fraction as pH is increased shows that pH does not influence metals in some fractions in the same manner as it does plant availability. Iron decreased in the exchangeable and organic fractions as pH increased. Correlations between DTPA‐ or Mehlich I‐micronutrients and those in the fractions were significant (P = 0.05) only for the exchangeable and organic fractions. DTPA‐extractable Fe and Zn values were well‐correlated with plant uptake (0.842** and 0.377*, respectively). The results indicate that a micronutrient soil extractant should remove the exchangeable fraction but none of the oxide fractions and for Mn and Zn, none of the organic fraction.
Managanese Oxide Minerals in Nodules of Two Soils of Texas and Alabama
Authors: Uzochukwu G. A. , Dixon J. B.
Published: July 2010

Elemental analyses were made to determine the total Mn and other selected metal elements in the nodules and whole soils of Benchley (Vertic Argiustolls) (Texas) and Decatur (Rhodic Paleudults) (Alabama). Also, DTPA‐extractable Mn in the whole soils was determined as a measure of Mn available to plants. Managanese oxide minerals in soil nodules were magnetically concentrated, and subsequently identified by x‐ray diffraction (XRD), selective chemical treatments and various thermal methods. Tentative identification of one Mn oxide was done by high‐resolution transmission electron microscopy. The greatest concentration of Mn was in the surface horizon of Decatur and in the subsoil of Benchley. Most of the Mn was in the coarser soil fractions. Zinc, Li, Ba, Cu, Mn, and Fe were more concentrated in the nodules than in the respective whole soil. The correlation between DTPA‐extractable Mn and total Mn was high for Benchley and Decatur whole soils. Two Mn oxide minerals, birnessite and lithiophorite, were identified in the nodules of Benchley. Preferred oriented slide mounts and magnetic concentration of the samples aided in Mn oxide identification by XRD. Lattice fringes attributed to todorokite also were observed in Benchley nodules. Lithiophorite was identified in the nodules of Decatur. Other minerals found in the nodules include smectite, kaolinite, quartz, and goethite in Benchley, and kaolinite, quartz, and hematite in Decatur. Calcium, Zn, Li, Ba, and Cu detected in Benchley and Decatur nodules may be part of the Mn oxide mineral structures.
Spatial Dependence and Interpolation of Soil Properties in West Sumatra, Indonesia: II. Co‐regionalization and Co‐kriging
Authors: Trangmar B. B. , Yost R. S. , Uehara G.
Published: July 2010

Co‐kriging was used to interpolate values of topsoil 0.5 M NaHCO3‐extractable P at 234 locations in West Sumatra, Indonesia, by exploiting its spatial covariance with a more densely sampled property, 25% HCl‐extractable P. NaHCO3‐P and HCl‐P had been sampled at 52 and 107 locations, respectively, in a nongeometric pattern across the 106 650 has region. Isotropic semivariograms of NaHCO3‐P and HCl‐P and their cross semivariogram showed spatial dependence over 6.3, 4.2, and 10.4 km, respectively, at the sampling scale used. The map of co‐kriged values for NaHCO3‐P showed a similar regional pattern but more local detail than that achieved by kriging from NaHCO3‐P samples alone. Co‐kriging reduced estimation variances (relative to kriging) by up to 40% in areas where sampling density of NaHCO3‐P was lowest. Co‐kriging variances exceeded those of kriging by up to 10% in areas where sampling density of NaHCO3‐P was high. In such areas, the covariate HCl‐P had little effect on the interpolated value but still added a component to the estimation variance. Co‐kriging could not be used to interpolate values for extreme locations where there were no NaHCO3‐P samples within the radius of the kriging neighborhood. Despite local improvement in estimation precision the full benefits of co‐kriging interpolation are not universally obtained from nongeometric variate‐covariate sampling patterns.
Distribution of Slope Steepness in the Palouse Region of Washington
Authors: Mulla David J.
Published: July 2010

Slope steepness on eight slope aspects in four 930‐ha study areas of the Palouse region of southeastern Washington were obtained from elevations digitized from the Garfield, La Crosse, Thornton, and Wilcox 7.5‐min topographic quadrangle maps. A statistical analysis showed that slope steepness in these study areas could be described in terms of Gaussian frequency distributions after applying either a log‐normal or square root transformation to the data. In the Garfield and La Crosse study areas, slope steepness was best described using a log‐normal transformation and the Gaussian frequency distribution. The mean slope steepnesses in the Garfield and La Crosse study areas were 8.8 and 9.2%, respectively. In the Thornton and Wilcox study areas, a square root transformation of slope steepness was fit to a Gaussian frequency distribution. Mean slope steepnesses in the Thornton and Wilcox study areas were 12.5 and 12.5%, respectively. To characterize slope steepness distributions for the eight slope aspects studied within each area, from two to five Gaussian models having statistically distinct parameters were required. The quantitative analysis of topography conducted in this paper shows that considerable spatial variability of slope steepness occurs between differing slope aspects of large areas in the Palouse. This information could be used in developing improved runoff and erosion prediction models that account for spatial variability of topography over large areas.
A Model of Competition for Ammonium Among Heterotrophs, Nitrifiers, and Roots
Authors: Riha Susan J. , Campbell Gaylon S. , Wolfe Joe
Published: July 2010

The purpose of this study was to predict the fate of ammonium nitrogen in soils. Ammonium, either from mineralization of native organic material or from applied fertilizer, is taken up by roots, heterotrophs, and nitrifiers. The density of roots in the soil is assumed to remain constant for time periods which are long relative to microorganism response times. It is assumed that heterotroph populations are generally controlled by some substrate other than N. Ammonium levels in soil are shown to be controlled by nitrifiers except for short periods of time following perturbation of the system. Nitrifier populations are controlled by the flow of NH+4 to the substrate pool. Predicted steady state NH+4 concentrations and nitrifier populations agree well with values which are commonly measured in the field. When the system is perturbed, its return to equilibrium is shown to be described by a simple damped oscillation in NH+4 concentration and nitrifier population. The period and time constant of this damped oscillation appear to agree with published values. Careful measurement of steady‐state concentrations and characteristics of the oscillation may allow determination of several important microbe parameters.
Boundary Location from Texture, Soil Moisture, and Infiltration Data
Authors: Hendrickx J. M. H. , Wierenga P. J. , Nash M. S. , Nielsen D. R.
Published: July 2010

The objective was to ascertain how well different soil physical properties or parameters could be used to identify boundary locations along a soil transect. A transect was established with 91 positions, 1 m apart. The infiltration rate was measured along the transect with small (0.3‐m diam) and large (1.0‐m diam) infiltration rings. Thereafter, 91 soil samples were taken at a depth of 0.3 m for texture analysis. Also, 91 neutron access tubes and tensiometers were installed in two parallel lines 0.3 m apart. Soil‐water content was measured 16 times at the 0.3‐m depth before and after flooding the transect. Soil‐water tension was measured 13 times after flooding. The moving split window technique was used as a numerical procedure for boundary location. Boundaries detected—based on soil texture, water content, and water tension data—nearly coincided. Under dry conditions, one set of water content measurements resulted in almost the same boundaries as detected with soil texture data. Under moist conditions, several sets of measurements were needed to detect boundaries. Boundary detection with infiltration data was less satisfactory. Window width had little effect on detection of boundaries. The moving split window technique appears to be a useful tool for establishing boundaries along transects, based on water content and tension data, or in combination with soil texture data.
Evaluation of Green Ash Root Responses as a Soil Wetness Indicator
Authors: Good Billy J. , Faulkner Stephen P. , Patrick William H.
Published: July 2010

Green ash (Fraxinus pennsylvanica Marsh.) seedlings were transplanted to plots along four bottomland hardwood transects in Louisiana which represent a wide range of soil‐moisture and flooding regimes, and include the following soil series: Arkabulta (Aeric Fluvaquents, Rosebloom (Typic Fluvaquents), Norwood (Typic Udifluvents), Moreland (Vertic Hapludolls), Tensas (Vertic Ochraqualfs), Kobel (Vertic Haplaquepts), Goldman (Aquic Hapludalfs) and Fausse (Typic Fluvaquents). Each plot was classified as “wet” or “mesic” based on soil wetness data. Root‐coating constituents (Al, As, Ca, Fe, K, Mn, Ni, P, and Zn) and alcohol dehydrogenase (ADH) activity of the seedlings were assayed after 1.5 yr. A two‐group discriminant analysis function was developed in order to determine how well the seedling root data would predict the predetermined site‐wetness category of each seedling's plot. The deposition of rootcoating constituents and anaerobic respiration were distinct enough between the seedlings of the wet and mesic sites to be useful in the development of a fairly reliable model for site‐wetness classification. The percentages of seedlings correctly grouped into the mesic and wet categories were 88.9 and 92.0, respectively. The variables chosen for inclusion in the discriminant analysis function, in descending order of predictive power, were K, Fe/Mn, Ni, Mg, ADH, and Mn.
Concentration of Iron Oxides from Soil Clays by Density Gradient Centrifugation
Authors: Jaynes W. F. , Bigham J. M.
Published: July 2010

High speed centrifugation with a large‐scale zonal rotor and a linear, tetrabromoethane‐ethanol density gradient (1.0–2.8 Mg m−3) was utilized to fractionate the <0.2µm clay materials from three soils with differing Fe‐oxide mineralogy. Hematite, goethite, and lepidocrocite were concentrated 4‐ to 10‐fold in the high density range (>2.4 Mg m−3) while the low density fractions (<2.2 Mg m−3) were depleted in reductant‐soluble Fe. Density gradient centrifugation also produced useful mineralogical separations of the soil phyllosilicates. In particular, smectite was concentrated in the 1.8 to 2.1 Mg m−3 density range whereas the 2.1 to 2.3 Mg m−3 density range was enriched with kaolinite, vermiculite, and clay mica. Electron microscopy and x‐ray diffraction analyses indicated that Fe‐oxides were present in the materials studied as discrete particles rather than as “coatings” on associated minerals.
Diffusion of Nitrogen‐15 Kjeldahl Digests for Isotope Analysis
Authors: MacKown C. T. , Brooks P. D. , Smith M. S.
Published: July 2010

Steam distillation methods are commonly used to prepare Kjeldahl digests for N stable isotope analysis. Steam distillation requires skilled operation of specialized equipment as well as considerable operator time, and is subject to sample cross contamination unless precautionary washing procedures (which further increase sample preparation time) are adopted. A simple, inexpensive, labor saving diffusion method for Kjeldahl digests using disposable polypropylene specimen containers (128 mL) with threaded lids was devised to overcome problems with steam distillation. Diffused ammonia was collected in a disposable test tube (12 by 75 mm) containing an acid trap. Fractionation of N stable isotopes was <1% for diffused diluted simulated Kjeldahl digests, even when <20% of the initial NH3 present was diffused. As diffusion becomes more complete isotope fractionation decreases. Direct comparison of aliquots of the same plant tissue Kjeldahl digest by steam distillation and diffusion over a wide range of 15N enrichments (0.36‐43.3 atom %) indicated that deviation of the two methods was about 1%. The 15N enrichment of diffused samples was consistently slightly less than that of steam distilled samples. The method is recommended for research using 15N enriched or depleted sources, but not for research measuring natural variation in 15N abundance, unless complete diffusion is assured.
Effect of Growth Rate on the Growth of Bacteria in Freshly Moistened Soil
Authors: Hartel Peter G. , Alexander Martin
Published: July 2010

A study was conducted to determine the significance of growth rate on the ability of six bacterial strains to grow in soil immediately following moistening of air‐dry soil and to determine if growth in soil solution could be used as a predictor of bacterial growth in soil. The generation times of the six bacterial strains in soil solution extracted from unincubated Eel silt loam that was air‐dried and moistened immediately before inoculation, and the extent of growth was directly correlated with the rate of growth of the bacteria, except for one species. The six bacteria did not increase in number in Eel silt loam that had been previously incubated for 14 d after moistening. However, addition of glutamate to this soil increased the numbers of the bacteria that grew most rapidly and had essentially no influence on the two slowest growing strains. Similar results were obtained with strains of Pseudomonas and Bradyrhizobium in two other soils or soil solutions obtained from them. The data indicate that growth in soil solution was a good indicator of the ability of bacteria to grow in nonsterile soil when the soil was inoculated immediately following moistening of air‐dry soil and that slow growth, the absence of available C, or both, limit bacterial proliferation.
Simulation of Nitrogen‐15 Immobilization by the Model NCSOIL
Authors: Hadas Aviva , Molina J. A. E. , Feigenbaum Sala , Clapp C. E.
Published: July 2010

The computer model NCSOIL computes the dynamics of C and N transformations in soil. In its original version, the microbial biomass assimilated organic N from the decay of organic pools, and inorganic N was immobilized only when decomposed organics were deficient in N with respect to biomass needs for growth (NCSOIL—direct version). A new version was presented in which it was assumed that microbial biomass immobilized N only from the inorganic pool, while the decay of organic N always resulted in N mineralization (NCSOIL‐MIT version). NCSOIL‐MIT was calibrated and tested for the incorporation of inorganic 15N in the organic soil N against experimental data and compared with the direct version. Net N mineralization was highly sensitive to the microbial efficiency of soil decomposable organic C incorporation. An efficiency of 0.2 gave a good account of net N mineralization for soils unamended with organic substances. NCSOIL‐MIT simulated the incorporation of 15N, added as NH4, into the organic soil pools. The kinetics of 15N immobilization was sensitive to microbial efficiency as well as to other parameters that control soil N turnover. NCSOIL—direct version required the decomposition of polysaccharide‐like material in order to obtain 15N incorporation in the soil organic pools, and the kinetics of 15N immobilization depended on the rate of polysaccharide decomposition.
Wind‐erosion Direction Factors as Influenced by Field Shape and Wind Preponderance
Authors: Skidmore E. L.
Published: July 2010

This investigation expands and improves the procedure for determining median travel distance of wind in traversing a field, information used in solving the wind‐erosion equation. Wind‐erosion roses were simulated by the equation of an ellipse in polar coordinates. The ratio of semimajor axis to semiminor axis was varied to give preponderance values from 1.0 to 4.0. The axis was rotated to simulate field orientation from 0 to 90° relative to prevailing winderosion direction. Length/width ratio for rectangular fields was varied from 1 to 10. The wind‐erosion direction factor, a number that when multiplied by field width gives median travel distance, was calculated for many combinations of variables. When preponderance was 1.0, the wind‐erosion direction factor was 1.03, 1.42, 1.48, and 1.48 for rectangular fields with length/width ratios of 1, 2, 4, and 10, respectively; the factor was not influenced by field orientation. As preponderance increased, the wind‐erosion direction factor approached unity for small angles of deviation and approached the length/width ratio for large angles of deviation. For circular fields surrounded by a nonerodible surface, the wind‐erosion direction factor was 0.91, regardless of wind direction and preponderance.
Storage Effects on Identification of Rhizobia in Soybean Nodules by Elisa
Authors: Matheny T. A. , Kasperbauer M. J. , Hunt P. G.
Published: July 2010

Serological analyses of rhizobia in soybean [Glycine max (L.) Merr.] nodules are time‐consuming and often must be delayed for extended periods. The objective of this study was to assess the impact of drying and long‐term storage on identification of rhizobia in soybean nodules by indirect enzyme‐linked immunosorbent assay (ELISA). Nodules formed on ‘Coker 338’ by Bradyrhizobium japonicum strains USDA 3I1b110, NC1004, and B587 were either air‐dried at 40°C or freeze‐dried, and then stored for 1 month at either ambient temperature, 5, −5 or −60°C. Rhizobia within nodules from all drying and storage combinations were suitable for identification by ELISA. Results of this study indicate that large numbers of nodules can be collected and analyzed for serological identification of rhizobia at a later date, without loss of accuracy.
Water Movement in a Finite Layer: Absorption for Constant Water Content at the Surfaces
Authors: Hornung U. , Parlange J.‐Y. , Hogarth W.L. , Connell L.D. , Peters R.
Published: July 2010

An accurate, analytical formulation describes very simply the outflow of water from a soil layer when the potentials (water contents) are maintained constant at both surfaces. The analytical formulation is adapted from a previously developed approach to the present problem. The accuracy of the results is checked by comparison with a precise numerical simulation which is greatly simplified for a Brooks and Corey type diffusivity. It is suggested that a laboratory experiment using this configuration would yield the soil properties relevant for adsorption.
Ionic Diffusion Coefficients as Predicted by Conductometric Techniques
Authors: Jurinak J. J. , Sandhu S. S. , Dudley L. M.
Published: July 2010

Ion diffusion coefficients were determined for Na, Ca, and Cl in three soils under various moisture regimes. The Nernst‐Einstein equation was used in conjunction with bulk soil specific electrical conductivity data to obtain the diffusion coefficient values. The conductivity data were measured in special cells designed to control both solution composition and moisture content. The contribution of both the solution and the surface phases to the total diffusivity of each ion was estimated. The ion diffusion coefficient values were corrected for the nonideality of system. Anion repulsion corrections were also made to account for the surface contribution to Cl diffusion.
Sulfate and Gypsum Determination in Saline Soils
Authors: Skarie R. L. , Arndt J. L. , Richardson J. L.
Published: July 2010

Despite advances in instrumentation for direct determination of SO2‐4, many investigators analyzing saline soils continue to estimate SO2‐4 by difference between the sums of major cations and anions and to measure gypsum by methods that avoid direct SO2‐4 determination. The present study compares SO2‐4 in saturation extracts as estimated by difference with SO2‐4 measured by single‐column ion chromatography for saline Aeric Calciaquolls and Typic Haplaquolls in eastern North Dakota. Results should be applicable throughout the Northern Great Plains. For extracts of sulfatic, saline soils, estimation of SO2‐4 by difference compared favorably with SO2‐4 determined directly. Results were more variable for highly chloridic soil extracts because errors from other methods were large relative to the amount of SO2‐4 present. Gypsum was determined by using a sufficiently dilute extract to completely dissolve the gypsum present in the soil sample. Gypsum content was calculated in two ways, based either on Ca2+ or SO2‐4 measured in the dilute extract. For highly chloridic soils, gypsum contents based on Ca2+ determination were essentially equal to the results based on SO2‐4 data. For sulfatic soils, gypsum contents were lower when Ca2+ values were used due to loss of Ca2+ to the exchange complex during the extraction process.
Soil pH and Extractable Sulfate‐Sulfur Distribution as Influenced by Tree Species and Distance from the Stem
Authors: Wolfe M. H. , Kelly J. M. , Wolt J. D.
Published: July 2010

Stemflow influence on the distribution of soil (NaH2PO4 extractable) SO4‐S and pH was evaluated as a function of tree size class and distance from the stem for red maple (Acer rubrum L.) and scarlet oak (Quercus coccinea Muenchh.) at two locations in Tennessee which have received different historical inputs of S from atmospheric sources. Soil profiles around the base of each study tree were sampled by horizon at 25, 50, 100, and 200 cm from the stem along four transects radiating from the stem at 90° angles. Distance from the stem influenced soil pH of A horizons at 25 cm from the stem of red maple and scarlet oak at both sites. Species had an effect on Bt2 and Bt3 soil SO4‐S concentrations. The Bt2 (0.49 cmol kg−1) and Bt3 (0.67 cmol kg−1) horizons beneath scarlet oaks had greater SO4‐S concentrations than corresponding horizons beneath red maple (0.29 and 0.43 cmol kg−1, respectively). The results of this study indicate that increased sampling intensity combined with tracer studies will be need to clearly determine the effect of stemflow, tree species, and tree size on subtlety‐manifested soil properties such as pH and SO4‐S as well as other elements of interest.
Effect of Phenylphosphorodiamidate on Immobilization and Ammonia Volatilization
Authors: Hendrickson L. L. , Omholt T. E. , O'Connor M‐J.
Published: July 2010

Laboratory incubation experiments were conducted to evaluate the ability of the urease inhibitor phenylphosphorodiamidate (PPD) to reduce NH3 volatilization and immobilization of urea (100 mg N kg−1 of soil). Application of 20 mg PPD kg−1 of soil effectively inhibited urea hydrolysis for approximately 4 d in both soil and oat straw‐amended soil systems. This delayed urea hydrolysis reduced NH3 losses after 7 d from 82 to 19% in the straw‐amended soil, and from 26 to 14% in the soil system. When urea was applied to soil incubated in closed vessels, only 80% of the applied urea could be recovered as inorganic N after 3 d of incubation. This apparent immobilization of N was prevented for 7 d by application of PPD. Immobilization of N in the straw‐amended soil exceeded 40% within 7 d, but the onset of these losses was delayed for at least 3 d by PPD. These results demonstrate that losses of surface‐applied urea via both NH3 volatilization and immobilization can be prevented by application of an effective urease inhibitor.
Diagnosing Nutritional Status of Containerized Tree Seedlings: Comparative Plant Analyses
Authors: Timmer V. R. , Armstrong G.
Published: July 2010

Containerized red pine (Pinus resinosa Ait.) seedlings were fertilized to test the effectiveness of three approaches (critical levels, optimal ratios, and vector analysis) to diagnose seedling nutrient status. Treatments involved a balanced nutrient solution and six imbalanced solutions lacking (−) or enriched (+) with N, P, or K applied to seedlings raised in peat‐filled paperpots. Growth was significantly reduced by ‐N, ‐P, and +N treatments indicating N and P deficiencies and N toxicity, respectively, and probable sufficiency or luxury consumption of P or K for the other treatments. Diagnosis by vector analysis agreed closely with actual growth and nutritional responses to treatments, and was more precise than the other approaches. Vector analysis was independent of predetermined standards or critical values, and improved identification of dilution effects and nutrient interactions which tend to complicate conventional diagnostic techniques.
Two‐site Model for Aluminum Oxide with Mass Balanced Competitive pH + Salt/Salt Dependent Reactions
Authors: Schulthess C. P. , Sparks D. L.
Published: July 2010

A backtitration technique was used to collect proton isotherm data for an Al oxide, and was found to be stoichiometrically related to the cation and anion isotherm behavior. The adsorption of various ions by the Al oxide surface was modeled based on: (i) two surface sites, (ii) pH + salt‐dependent reactions (H+ and Cl‐, 2OH‐, or Na+ and OH‐), (iii) competitive salt‐dependent reactions (Na+ or Cl‐), (iv) CO2(aq) pH‐dependent reactions with the surface‐OH groups, and (v) presence of an unknown M+Cl‐ salt (0.0005 M). The total number of Al sites was 1.7 µmol m−2 or 3.4 µmol m−2 of total available sites. The pH of point of zero salt effect (PZSE) represented the surface condition in which the negative charges (or cation surfaces) equaled the positive charges (or anion surfaces); the cation exchange capacity (CEC) equaled the anion exchange capacity (AEC) at this value. The CEC‐AEC data and proton isotherm data were stoichiometrically correlated. The pH of PZSE values ranged from 7.50 to 7.76 depending on the electrolyte concentration present, with lower values as the concentration increased. The negative shifts in the PZSE values are due to anion impurities initially present on the surface and positive shifts are due to cation impurities.
Selenium Adsorption by Goethite
Authors: Balistrieri Laurie S. , Chao T. T.
Published: July 2010

The adsorption of Se by goethite was studied as a function of time (10 min–24 h), temperature (295.5 and 303.5 K), pH (4–11), particle concentration (3–300 mg/L), total Se concentration (0.02–5 × 10−5 M), oxidation state [Se(IV) and Se(VI)], and competing anion concentration [(anion)/(Se(IV) = 0.25 to 50 000] in order to assess the influence of these factors on Se mobility. The data indicate that (i) the surface sites of goethite are heterogeneous, (ii) the adsorption of selenite [Se(IV)] reaches equilibrium in 2 h and is completely reversible with respect to pH, (iii) the removal of selenite from solution increases with decreasing pH and increasing particle concentration, (iv) the adsorption edge for selenite shifts to lower pH values with increasing total selenite concentrations, (v) selenite adsorbs much more strongly than selenate [Se(VI)], and (vi) the influence of additional anions on selenite adsorption depends on the relative affinity of the anions for the surface and the relative concentrations of the anions. For a given anion concentration ratio, the competition sequence with selenite is phosphate > silicate ≥ citrate > molybdate > bicarbonate/carbonate > oxalate > fluoride > sulfate. Therefore, the conditions that favor the mobility of Se in the environment with respect to adsorption are alkaline pH, high Se concentrations, oxidizing conditions, and high concentrations of additional anions that strongly adsorb.
Pedon Zonation of Hydroxy‐interlayered Minerals in Ultic Haplaquods
Authors: Harris W. G. , Carlisle V. W. , Van Rees K. C. J.
Published: July 2010

The distribution of hydroxy‐interlayered minerals (HIM) was studied in Ultic Haplaquods with respect to horizon and location within the soil matrix. Mineralogy of the clay fraction and of tenacious grain coatings was determined for selected horizons by means of x‐ray diffraction and differential scanning calorimetry. Smectite and kaolinite were the dominant layer silicates in A and E horizons, where sand grains were stripped of coatings and clay occurred as floccules. Hydroxy‐interlayered minerals were the dominant layer silicates in Bh and E′ horizons where grains were coated. Tenacious coatings removed by ultrasound from sands occurring in the Bh and E′ horizons contained more HIM and less quartz than any other portion of the soil matrix. Podzolic stripping of coatings in A and E horizons and transformation of HIM to smectite via interlayer depolymerization could explain the observed HIM depth distribution. Higher HIM concentrations in tenacious coatings in Bh and E′ horizons suggest that the coatings predated podzolization. Hydroxy‐interlayered minerals in Btg1 horizons dispersed in deionized water more readily than did kaolinite, suggesting that differential dispersion in conjunction with a fluctuating water table may be a factor in pedogenic redistribution of clay minerals.
Soil Core Sampling for Hydraulic Conductivity and Bulk Density
Authors: Rogers J. S. , Carter C. E.
Published: July 2010

The Uhland type soil core sampling equipment was used to obtain cores 74 mm in diameter and 76 mm high from the surface 0.25 m of an alluvial soil in Louisiana. Samples were taken in pairs; one sample was taken by hammering the cutting head into the soil, and the other sample was taken by pressing the cutting head into the soil using a hydraulic cylinder. Data for 26 pairs of samples showed that the saturated hydraulic conductivity for the hammered samples averaged 2.36 µm/s, and that for the pressed samples averaged 4.28 µm/s. The difference was statistically different at the 99.5% level. Average oven‐dry weight of soil in the cores was 6 g greater for the hammered than for the pressed cores.