bluuebunny/crossref_metadata_2025 huggingface dataset:
Conditions for Al13 Polymer Formation in Partially Neutralized Aluminum Solutions
Authors: Bertsch Paul M.
Published: July 2010

The influence of synthesis methodology on the formation of the Al13([AlO4Al12(OH)24(H2O)12]7+) polymer was investigated to better establish boundary conditions for its formation. The amount of Al13 polymer formed in solutions ranging in Al concentration from 3.34 × 10−4 to 3.34 × 10−2 mol L−1 was found to be highly dependent on OH/Al ratio (ñ), neutralization rate, mixing conditions, and initial Al concentration. For the 3.34 × 10−3 mol Al L−1 solution synthesized at 1.2 cm3 min−1, the Al13 polymer formed only when ñ exceeded 1.5, whereas this polymer predominated in a solution 3.34 × 10−2 mol L−1 with respect to Al at ñ ≥0.4. There was no evidence for Al13 polymer formation in solutions ≤3.34 × 10−4 mol Al L−1 with ñ = 2.5 synthesized at the 1.2 cm3 min−1 base injection rate; however, the formation of this species could be induced in the 3.34 × 10−4 mol Al L−1 solution by increasing the base injection rate to 100 cm3 min−1. Utilizing an Erlenmeyer flask instead of a beaker for the neutralization reaction resulted in different amounts of Al13 formation, and this was believed to result from differential mixing conditions. The data suggest that the formation of the Al13 polymer in partially neutralized Al solutions is an artifact of synthesis conditions requiring inhomogeneous pH conditions at the point of base injection resulting in the formation of the Al(OH)‐4 ion. It would appear that this polymer is of little general significance to secondary Al mineral formation in acidic weathering environments.
Comparison of Two Methods for Quantifying Extraradical Mycelium of Vesicular‐Arbuscular Mycorrhizal Fungi
Authors: Bethlenfalvay Gabor J. , Ames Robert N.
Published: July 2010

Extraradical mycelium of Glomus mosseae (Nicol. & Gerd) Gerd. and Trappe, a vesicular‐arbuscular mycorrhizal (VAM) fungus, was assessed by two quantitative methods using subsamples of the same soil. Fungal biomass was determined by a chitin assay and the length of fungal hyphae in the soil was obtained by direct microscopic measurements. Total hyphal length, including hyphae <5 µm in diameter, was not correlated (P > 0.05) with total soil chitin; however, the length of hyphae ≥ 5µm in diameter correlated significantly (P < 0.01) with VAM‐fungal biomass. There is a strong relationship between these methods for the determination of the extraradical VAM‐fungal mycelium. The two methods permit the calculation of a “specific mass' (µg/m) for VAM‐fungal hyphae. Considerations for using either method to quantify extraradical VAM‐fungal mycelium are discussed.
Interference of Humic Substances on Chloride Analysis Using the Chloride Ion‐selective Electrode
Authors: Sikora F. J. , Stevenson F. J.
Published: July 2010

Humic substances interfered with the ion‐selective electrode determination of Cl‐ by complexing Ag+ and thereby reducing the activity of the potential determining ion. Binding of Ag+ was proven with a technique that involved equilibrium dialysis and Ag+ determination by atomic absorption spectroscopy. Competition between Ag+ and H+ for binding sites was evident from an increase in millivolt response of the Cl‐ ion‐selective electrode with addition of HNO3 and release of protons upon Ag+ binding in the dialysis experiment. Selectivity coefficients (kCl,HA) for 11 humic and fulvic acids ranged from 0.59 × 10−4 to 1.3 × 10−4 mol g−1 at pH 6.5. Interference is negligible in solutions containing <0.1 g L−1 humic substances, but is serious in samples with low concentrations of Cl‐ (< 10−4.5 M) and high amounts of organic matter (>0.1 g L−1).
Clay Mineralogical and Chemical Properties of Nonallophanic Andepts (Andisols) from Oregon, USA
Authors: Shoji Sadao , Suzuki Yoshinori , Saigusa Masahiko
Published: July 2010

We studied clay mineralogical and chemical properties of Murtip and Quillayute soils from Oregon that are classified as Typic Dystrandepts. The soils are nonallophanic and have clay fractions dominated by chloritized 2:1 minerals. Both showed chemical properties similar to those of most nonallophanic Andisols from Japan and satisfied the criteria for andic soil properties. The strong allic properties of the soils were due to the abundance of chloritized 2:1 mineral and low base saturation.
Weathering Processes of Asbestos‐rich Serpentinitic Sediments
Authors: Schreier H. , Omueti J. A. , Lavkulich L. M.
Published: July 2010

Asbestos‐rich serpentinitic sediments weather rapidly in acid environments and in the process trace metals are released and smectite clays are formed in the soils. A study was carried out in the Sumas River Basin in northwestern Washington State, where a landslide has exposed asbestos‐rich serpentinitic rocks. Between 1975 and 1985 the river draining the landslide has flooded several agricultural fields and on several occasions sediments that are rich in chrysotile asbestos were deposited. The analysis of soil samples from the inundated sites revealed that Ni, Cr, Co, Mn, and Mg were very high in the sediments and leached into the lower more acidic soil horizons. Laboratory extraction experiments were carried out in water and organic acid media. Under neutral and alkaline conditions little chemical breakdown was observed, but in the presence of citric and oxalic acid more than 50% of Ni and Cr is removed by artificial weathering at room temperature. At the same time Mg is removed from the asbestos fiber structure as shown by the energy dispersive x‐ray spectroscopy (EDX) analysis.
A Chronotoposequence of Soils Developed in Loess in Central Louisiana
Authors: Schumacher B. A. , Miller B. J. , Day W. J.
Published: July 2010

Surface soils developed in Sicily Island loess (thermoluminescence age 75 000–95 000 yr B.P.) and Peoria loess (thermoluminescence and 14C age 9000–22 000 yr B.P.) were sampled to study a chronosequence in the lower Mississippi River valley. A toposequence composed of an Udalf and an Aqualf was sampled in each of the loesses to evaluate relationships between topography and soil formation. Morphological, physical, chemical, and mineralogical properties were examined to determine the influence of time and topography on soil formation. Soils developed in the older Sicily Island loess had thicker argillic horizons and sola, a greater degree of horizonation, and greater maximum and total sola clay contents than younger Peoria loess‐derived pedons. Chemically, soils developed in the older loess had less exchangeable Ca, more exchangeable Al, lower mean effective cation exchange capacity (ECEC) per unit clay for the whole argillic horizon, lower base saturations, and were more acidic than their younger counterparts. Kaolinite and vermiculite were more abundant in the older Sicily Island loess‐derived soils while smectite and mica percentages were higher in Peoria loess‐derived pedons. Topography influenced soil formation through differences in soil drainage conditions. Soils occupying better‐drained sites had thicker sola and argillic horizons, thinner total surface (A + E) horizons, redder hues, and were more acidic with less exchangeable Ca, lower base saturations, and lower mean ECEC per unit clay for the whole argillic horizon than soils forming under poorly drained conditions. Kaolinite and mica were more abundant in the better‐drained soils while smectite was in greater quantities at the poorly drained sites.
Nitrogen Mineralization in a Desert Soil: Interacting Effects of Soil Moisture and Nitrogen Fertilizer
Authors: Fisher F. M. , Parker L. W. , Anderson J. P. , Whitford W. G.
Published: July 2010

The responses of N mineralization to two patterns of supplemental water, N fertilizer, and a drying‐wetting episode were examined in order to evaluate the effects of variation in timing and intensity of natural precipitation on N availability. Field plots received either 6 mm water/week or 25 mm water/month with or without 10 g N m−2. Samples were collected three times from July 1984 to March 1985 and incubated in the lab for 28 d. The effects of drought were simulated by drying soil at 35°C for 28 d followed by 168‐d leaching incubations. Supplemental water reduced 28‐d mineralization by 22% in soils collected during dry and moderate soil moisture conditions (July 1984, October 1984) but had no effect on soils collected during a moist period (March 1985). Nitrogen fertilizer had no effect on 28‐d mineralization in soils from July but increased 28‐d mineralization by 58% in soils from October and March. Air‐drying increased mineralization rates across all field treatments during the first 14 d of the 168‐d leaching incubations. Mineralization rates were lower in soils from watered plots in both the air‐dry and field‐moist treatments. Air‐drying interacted with both the water and N treatments by increasing watering effects and decreasing fertilizer N effects. The observed drying effects appear to be a net result of several processes that, on the whole, tend to increase N availability. Mineralization rates in both experiments were lower in 6 mm/week soils than in 25 mm/month soils which, in turn, were lower than unwatered controls. We hypothesize that increased moisture availability eventually leads to losses of mineralizable N as initially rapid mineralization converts organic N to inorganic forms that are readily lost from the soil.
Use of Sorptivity to Determine Field Soil Hydraulic Properties
Authors: White I. , Perroux K. M.
Published: July 2010

Convenient and reliable techniques for estimating intact soil hydraulic properties are required for predictions of soil‐water flow in the environment. The dependence of sorptivity, S, on water supply potential, Ψ0, is used here to find the dependence of the intact field soil hydraulic properties soil‐water diffusivity, D(θ), hydraulic conductivity, K(θ), and soil‐water characteristic Ψ(θ) on water content, θ. The approximations used in deconvoluting sorptivity are examined critically using a simple parametric D(θ) that gives analytic solutions applicable to most known soil behavior. We show that the Parlange approximation differs from the exact solution by <5% over a very wide range of D(θ) and over the entire water content range. A rapidly convergent iterative scheme in which this approximation forms the initial estimate is introduced for situations where greater accuracy is required. The technique is tested for a repacked soil, Ustochrept, and the D(θ) derived from S(Ψ0) agrees excellently with conventional measurements. We use the disc permeameter to find S(Ψ0) at 20 sites for an intact field soil, Haplustalf. The D(θ) derived from these measurements is not strongly θ‐dependent. This is attributed to the shape of Ψ(θ), which, in contrast to repacked samples, shows that as θ approaches saturation, Ψ approaches zero gradually. The capillary length found from the K(Ψ) measurements is only 23 mm. Both findings are attributed to the presence of biopores in the field soil. Sorptivity may be used to determine reliably intact soil hydraulic properties whose magnitudes reflect the intricacies of field soil structure.
Computed Tomographic Analyses of Water Distribution in Three Porous Foam Media
Authors: Brown J. M. , Fonteno W. C. , Cassel D. K. , Johnson G. A.
Published: July 2010

Computer Assisted Tomography (CAT) is commonly used in diagnostic radiology to make nondestructive images and analyses of cross sections of the human body. CAT scanning may also be useful in imaging and measuring spatial distribution and changes in water distribution in porous media. The purpose of this paper is to review some of the details of CAT scanning that are of importance to the application of CAT scanning porous media and to evaluate the use of the CAT scanner to measure the spatial distribution of water in three different porous media. The scanner's response to changes in the spatial distribution of water in three different porous phenolic foam materials after draining for 16 h was investigated. Water content distributions were successfully detected with good resolution on the x‐ray image. Comparisons of CAT vs. gravimetrically determined water content indicated a significant linear relationship between the methods. Results from these experiments indicate that the CAT scanner can nondestructively measure volume wetness in phenolic foam media. The clarity of the CAT images suggests that CAT scanning has great potential for studies where small and rapid changes in water content within small volumes of media are desired.
Kriging with Generalized Covariances
Authors: Morkoc F. , Biggar J. W. , Nielsen D. R. , Myers D. E.
Published: July 2010

Electrical conductivities (EC) of saturated paste extracts of 225 soil samples collected from depths of 30 to 60 cm along five transects were determined. The field was irrigated using a two‐line source sprinkler system that applied two different qualities of irrigation water. The sampling interval along each transect was 1 m. Forty‐five soil samples were collected from each transect, with each transect separated by 10 m. The mean and four directional experimental variograms of the EC were computed. The east‐west (0°) directional variogram showed a structure with a range of 19 m. The raw data showed a skewed distribution with two outliers. One hundred eleven of the total data points were used to check for the presence of a drift and to determine the best generalized covariance function. The best general drift, calculated with mean squares, was found to be of order one. Structural analysis confirmed that the best drift order was one, and the best generalized covariance fit had linear and cubic terms. The best fit covariance function had a mean square error (MSE) of 0.187 and a correlation coefficient of 0.98 from the jackknifing. The cross‐validation of the best covariance fit was performed by removing each data point and estimating from the remaining data (MSE = 0.164). If the difference between the measured and estimated points was greater than twice the standard deviation, that point was considered to be an outlier. The results of cross‐validation, when 111 data points were used, showed no outliers. The scatter diagram of the estimated values and reduced error showed no correlation (r = −0.0035). On the other hand, a high correlation (r = 0.93) was found between the estimated and the true values. The best covariance function with a drift of order one was used to estimate 225 measured values, as well as an additional 1260 values over the entire field with a grid size of 1 × 1.25 m. This technique allowed detailed information to be obtained from a limited number of data points with dependability.
Monovalent Ion Adsorption by an Oxisol
Authors: Charlet Laurent , Sposito Garrison
Published: July 2010

An experimental method was developed to measure simultaneously the net proton surface charge density (σH) and surface excesses of metal (nM) and ligand (nL) on an Oxisol suspended in a ML electrolyte solution. The soil sample was first saturated with a LiClO4 solution whose pH and ionic strength were equal to the maximum values to be used in the adsorption experiments. The ionic strength then was decreased, LiClO4 was exchanged for ML (ML = NaCl or KNO3), and a soil paste was prepared to allow reproducible sampling of small quantities of the whole soil. A discontinuous titration followed in which the soil paste was equilibrated with a series of ML electrolyte solutions of specific pH and ionic strength. Values of nM and nL were measured at 25°C, and it was shown that the point of zero net charge (PZNC) ≈ 4.2, independent of the electrolyte and its ionic strength in the range 4 to 500 mol m−3. Given a negligible permanent surface charge, typical of Oxisols, PZNC = PZNPC (point of zero net proton charge). The net proton surface charge density then could be calculated from titration data renormalized to the PZNC. The net proton surface charge of the Ha‐plustox used in this study vanished at pH 4.2 and showed very little dependence on ionic strength, indicating the dominant role of kaolinitic and organic matter constituents in determining its surface properties. Surface complexation reactions between the soil and a 1:1 electrolyte solution were characterized quantitatively by intrinsic equilibrium constants calculated according to the triple layer model. The average values found were similar to those that have been obtained previously for specimen hydrous oxides suspended in 1:1 electrolyte solutions.
Selenite Adsorption on Alluvial Soils: I. Soil Composition and pH Effects
Authors: Neal Rosemary H. , Sposito Garrison , Holtzclaw K. M. , Traina S. J.
Published: July 2010

The adsorption of selenite by five alluvial soils from the San Joaquin Valley, California, was investigated with respect to the effects of soil composition and pH. Soil samples were prepared in the form of Na‐saturated pastes. Adsorption experiments were carried out in a 50 mol NaCl m−3 background at initial selenite concentrations comparable with those found in natural soil systems. The samples were equilibrated under N2‐stirring in a constant‐temperature apparatus with pH and redox conditions monitored. Selenite adsorption by the soils decreased uniformly with increasing pH in the range 4 to 9 and was independent of soil series above pH 6.
Soil Microsites as a Source of Denitrification Variability
Authors: Parkin Timothy B.
Published: July 2010

The spatial variability exhibited by soil denitrification rates is high. As is typical for natural denitrification rate measurements, the individual rates of most samples of a given data set are low; however, a few samples often exhibit extremely high rates. Such data are characterized by highly skewed sample frequency distributions. This study was initiated to investigate the underlying mechanisms responsible for these observations. It was found that “hot‐spots” of high specific denitrification activity were associated with particulate organic C material in the soil. The high specific activities of these hot‐spots (incubated under aerobic conditions with no amendments) were similar to the denitrification activity of the bulk soil measured under conditions of anaerobiosis with added glucose and NO3. This observation served as the basis of a computer model that evaluates the influence of the density and dispersion pattern of these high activity sites on the measured rates of denitrification. Histograms generated from computer simulations are very similar to histograms obtained for real data, supporting the concept that the patchy dispersion of particulate organic material in soil is a major factor influencing the variability of natural denitrification rates.
Distribution and Plant Availability of Soil Boron Fractions
Authors: Jin Jin‐yun , Martens D. C. , Zelazny L. W.
Published: July 2010

The fractionation of soil B and the plant availability of each fraction have not been examined extensively. This laboratory and greenhouse research was conducted to study the distribution and plant availability of B in different soil fractions. Total B in the 14 soils under study ranged from 21.5 to 96.3 mg kg−1. A trace to 0.34% of the total B was in a water‐soluble form; ≤0.23% was 0.02 M CaCl2 extractable (nonspecifically adsorbed B); from 0.05 to 0.30% was mannitol exchangeable (specifically adsorbed B); and from 0.23 to 1.52% was acidified NH2OH·HCl extractable (B occluded in Mn oxyhydroxides). Ammonium oxalate solution (pH 3.25) extracted from 2.8 to 34.4% of the total soil B in the dark (B occluded in noncrystalline Al and Fe oxyhydroxides) and from 17.5 to 73.9% under ultraviolet (UV) light (B occluded in crystalline Al and Fe oxyhydroxides). Residue B, which was considered to be in association with soil silicates, accounted for 2.4 to 79.2% of the total B. Boron concentration in corn (Zea mays L.) tissue correlated positively (α = ≤0.05) with water‐soluble B, CaCl2 extractable B, mannitol exchangeable B, and acidified NH2OH·HCl extractable B. The sum of these four fractions, which were related to B availability, accounted for only 0.4 to 2.0% of the total B in the 14 soils. Boron concentration in corn tissue was unrelated (α = 0.05) to NH4‐oxalate extractable B (either in the dark or under UV light) and to the residue B fraction. These relationships indicate that B in noncrystalline and crystalline Al and Fe oxyhydroxides and in silicates was relatively unavailable for plant uptake.
Genesis and Classification of Clay Soils with Vertic Properties in Saskatchewan
Authors: Dasog G. S. , Acton D. F. , Mermut A. R.
Published: July 2010

Clayey soils formed in glaciolacustrine sediments in semiarid and subhumid regions of Saskatchewan were studied to understand their genesis and to examine their classification according to the amended definition of Vertisols. Although slickensides were common to all soils, semiarid soils displayed weak horizons, whereas subhumid soils had argillic horizons and prominent mollic epipedons. All the soils had high potential to swell and shrink, and were characterized by seasonal moisture deficits sufficient to induce cracking. Soil displacement, as evidenced by slickensides, was attributed to differential wetting in the subsoil. Pedoturbation, as a result of such displacement, has been sufficient to prevent strong horizon formation in semiarid soils but insufficient to counter leaching and illuviation in subhumid soils. Blocky and prismatic structure, when dry, and microfabric considerations support a B horizon designation in these soils, which otherwise exhibit indistinct horizons when moist. It is suggested that Vertisols with frigid and cryic soil temperature regimes should be grouped into a new suborder, Borerts. It is also suggested that soils that have diagnostic horizons other than mollic be excluded from Vertisols even when accompanied by intersecting slickensides.
Reactive Characteristics of Certain Soils from South Nigeria
Authors: Okusami T. A. , Rust R. H. , Juo A. S. R.
Published: July 2010

Statistical relationships were determined between soil pH, effective cation exchange capacity (ECEC), surface area, and some other soil properties for selected soils of southern Nigeria. The soils were mostly hydromorphic with a pH range of 3.6 to 8.1. Exchange acidity was virtually due to exchangeable Al (r = 0.99). Negative ΔpH values indicate a dominant silicate clay mineralogy. The ΔpH (pHKCl‐pHH2O) was correlated with exchangeable Na (r = −0.56), sand content (r = 0.51) and organic C (r = 0.34). Effective cation exchange capacity was low, average of 7.1 cmolc kg−1. No exchangeable Al was found above a soil pH (KCl) of about 4. A derived variable, ΔCEC (difference between CEC measured at pH 8.2 and ECEC), was used as a dependent variable to test pH dependence. The variability observed in ΔCEC values was found to be related to clay content (r = 0.65), exchangeable K (r = −0.11), and organic C (r = 0.34). A regression analysis with BET‐N2 (Brunauer, Emmett, and Teller) specific surface area as the dependent variable showed a strong relationship with clay content (r = 0.96) and ΔpH (r = −0.44) in the best regression equation.
Correspondence of Soil Properties and Classification Units with Sagebrush Communities in Southeastern Oregon: II. Comparisons within a Multi‐taxa Soil‐vegetation Unit
Authors: Lentz R. D. , Simonson G. H.
Published: July 2010

A complex soil landscape composed of two dominant soil components supporting a range of heterogeneous sagebrush communities was examined in order to determine if soil properties and classification differed among plant community types. Cluster analysis of 64 vegetation samples identified six recurring plant groupings (RPGs). Properties of RPG soil profiles were statistically compared by defining aggregate horizons (tiers) that were common to all profiles. Recurring plant groupings were characterized by relative canopy cover of Artemisia arbuscula, Artemisia tridentiata ssp. wyomingensis, Festuca idahoensis, Agropyron spicatum; total grasses, and total herbs. Stepwise discriminant analysis selected thickness of mollic epipedon, surface rock fragment cover, and thickness and weighted average dry consistence of the argillic horizon as those that best distinguished between RPG associated soils. Evidence suggests that series separations are justified based on family and class distinctions of higher categories or differences in range of one or more soil properties, including (i) horizon sequence, (ii) mollic epipedon thickness, (iii) structure of BAt subhorizon, (iv) thickness, and (v) weighted average dry consistence of the argillic horizon. Phase level separations of RPG associated soils from identical families are feasible if both physiographic and soil surface criteria are utilized together.
Effect of Aluminum and Iron Oxides on Hydraulic Conductivity of Sandy Loam Soil
Authors: Shainberg I. , Singer M. J. , Janitzky P.
Published: July 2010

Iron and Al oxides and hydroxides have been shown to stabilize pure clay systems from the effect of high exchangeable sodium percentage (ESP). This study examined the effect of Fe and Al additions on the stability of a California Alfisol with serious crusting problems. Changes in saturated hydraulic conductivity were used as a measure of treatment effectiveness. Saturated hydraulic conductivity (HC) of a sandy loam equilibrated with sodium adsorption ratio (SAR) 20 CaCl2‐NaCl solution and leached with distilled water was faster for samples treated with 20 and 40 mmol kg−1 of FeCl3 or AlCl3 compared with untreated and 10 mmol kg−1 treatments. The FeCl3 treatments were more effective than AlCl3 treatments in maintaining HC. Analysis of the column effluent showed that more Al than Fe was removed during leaching. Much of the Fe added to the soils is recovered in oxalate and citrate‐bicarbonate‐dithionite (CBD) extracts, but little Al is recovered because the added Al is removed with the effluent. The stabilizing effect of hydroxy‐Fe polymers against the deleterious effect of exchangeable Na was related to the charge on the polymers and not with the total amount extracted.
Penetrometer Resistance and Bulk Density as Parameters for Predicting Root System Performance in Mine Soils
Authors: Thompson P. J. , Jansen I. J. , Hooks C. L.
Published: July 2010

Material handling methods used in the construction of soils after surface mining often result in a soil with physical and structural characteristics that restrict root development. A method to quickly and easily predict root system performance and compare mine soils on the basis of their suitability for root growth is needed. This study was conducted to determine the effectiveness of penetrometer resistance (as measured by a constant rate cone penetrometer) and bulk density as parameters for predicting root system performance. Both penetrometer resistance and bulk density data fit well into a multiple linear regression model that could be used to predict root length density in the lower portion of the root zone (67–110 cm depth). Results suggest that in the mine soils studied, both bulk density (R2 = 0.81) and penetrometer resistance (R2 = 0.73) are useful predictors of root system performance.
Hydraulic Conductivity of Three Southeastern Soils as Affected by Sodium, Electrolyte Concentration, and pH
Authors: Chiang S. C. , Radcliffe D. E. , Miller W. P. , Newman K. D.
Published: July 2010

In the humid southeastern USA, little attention is given to the effect of electrolyte concentration or low levels of Na on clay dispersion, although dispersion‐related phenomenon such as surface crusting and erosion are common. Our objective was to determine the effect of electrolyte concentration, sodium absorption ratio (SAR), and soil pH on saturated hydraulic conductivity of three soils that differed in parent material. Cores packed with sieved soil at different pHs were leached with 10 pore volumes of solution at varying SAR and electrolyte concentrations. The relative decrease in conductivity during leaching was recorded as a measure of clay dispersion and subsequent clogging of pores. The Cecil soil (Typic Hapludult), which is derived from granitic parent material, was easily dispersed and hydraulic conductivity was sensitive to small changes in electrolyte concentration, SAR, or pH. The Davidson (Rhodic Paleudult) and Iredell (Typic Hapludalf) soils, derived from mafic parent material, were flocculated and insensitive to changes in electrolyte concentration and pH except at very high SAR. The implications are that southeastern soils may differ greatly in structural stability and this may be related to parent material. Dispersive soils need to be identified and managed in an appropriate manner.
Forest Floor and Soil Influence on Response of Douglas‐fir to Urea
Authors: Edmonds R. L. , Hsiang T.
Published: July 2010

Data from the Regional Forest Nutrition Research Project (RFNRP) in Washington and Oregon were analyzed to improve stand‐specific prediction of Douglas‐fir [Pseudotsuga menziesii (Mirb.) Franco] response to urea fertilization. The response variable (relative difference in volume growth between fertilized and control plots 4 yr after fertilization with 448 kg N/ha) was regressed against 28 stand and site variables (e.g., age, elevation, forest floor C/N ratio, soil cation exchange capacity, etc.) using stepwise multiple regression analysis. Data from 120 installations were stratified by thinning level (thinned or unthinned), geographic location (provinces), and site quality (site index and class). Forest floor C/N ratio was the dominant variable related to response. In thinned installations of high site quality (site classes 1 and 2), 60% of variation in response was explained by the forest floor C/N, and 75% of the variation in response was explained with inclusion of surface soil exchangeable K. In thinned, low site quality stands, response was not as well related to forest floor C/N. Analysis of the data by province indicated that S may be limiting in southwest Oregon and P in coastal Washington.
Phosphorus Fertilizer Solution Distribution in the Band as Affected by Application Variables
Authors: Eghball B. , Sander D.H.
Published: July 2010

Phosphorus fertilizer applied with the seed or knifed into the soil as a band application has been shown to be more effective than broadcast P. Several experiments have shown that P fertilizer applied as a band becomes increasingly superior compared with broadcasting P as the P rate increases to the optimum rate. Phosphorus distribution in the band was judged to be a potential contributing factor. Therefore, an experiment was conducted to determine the distribution of P fertilizer solution in the band as affected by P rate and band spacing. A solution applicator was utilized to deliver fertilizer solution as ammonium polyphosphate (10‐15‐0, N‐P‐K) to application knives set about 3 cm above the surface of a catch paper. The fertilizer solution was placed on the paper and the distribution of the fertilizer droplets was measured. Knife spacings of 30, 45, 60, and 75 cm along with four P rates (7.5, 15, 22.5, and 30 kg ha−1), five traveling speeds (1.6, 2.6, 4.5, 7.1, and 9.8 km h−1), and three delivery tube sizes (0.9, 1.1, and 1.5 i.d.) were used. The results indicate that at lower rates the P solution is not distributed as a continuous band but rather as droplets of different sizes. At 7.5 and 15 kg P ha−1, the band consists of droplets at all banding spacings. Continuous bands of solution were formed at 22.5 and 30 kg P ha−1 at spacings >40 and 50 cm. Traveling speed affected the distance between droplets. The greater the speed the smaller the distance between the droplets. The increasing superiority of banding compared with broadcasting as the P rate increases may possibly be explained by the distribution of droplets in the band, where a continuous band may provide greater opportunity for the roots to utilize the fertilizer. When droplets are widely scattered, many droplet‐root contacts are necessary to supply adequate P to the plant, but in a continuous band, only one contact may be sufficient for root uptake of adequate P if the roots continue to proliferate along the continuous P fertilizer band.
Acidification and pH Buffering of Forest Soils
Authors: Magdoff F. R. , Bartlett R. J. , Ross D. S.
Published: July 2010

Horizons (O, A, E, B, and C) of forest soils from Vermont, New York, New Hampshire, and Virginia were equilibrated with various rates of either acid (H2SO4) or base (CaCO3). Most titration curves had a logistic shape with a lower asymptote (between pH 0.3 and 3.1) and an upper asymptote (around pH 7). The lower pH asymptote was highly correlated with equilibration solution Al and with soil pH measured in 1 M NaF. The specific buffer capacity (SBC) of the 26 horizons was related to organic matter (OM). Higher OM levels caused greater SBC. The buffer capacity of the OM was 0.4 mol kg−1 OM−1 pH−1. Using pH, pHNuF, OM, and horizon depth, it is possible to estimate the amount of acid currently in the soil (compared to a reference pH), the quantity of acid needed to lower the pH by a given amount, the amount of pH decrease associated with a given amount of acid input, the lower pH asymptote, and the pH at which solution Al is above a given concentration.
An Improved Procedure for Collection and Preservation of Soil Profiles
Authors: Ottersberg R. J. , Byron T. M.
Published: July 2010

The monolith and lacquer peel methods of soil profile collection proved to be unworkable for an 8‐m high wall that contained both fine loams and loose gravel. A new procedure was developed that has advantages over either of the commonly used procedures. Polyurethane foam is injected as a binder and filler between the soil and the field backing board. The foam dries hard overnight making it possible for two people to remove 2‐m sections of profile on the following day. The field backing board is also the final mounting board, so less time is spent in the laboratory preparing samples than with the traditional monolith procedure. Polyurethane foam makes it possible to collect larger profiles that can be more easily managed than the traditional monolith. It can be used on a wider range of textures than the lacquer peel method, and requires less time in the field because foam requires less drying time than lacquer. The foam method is an efficient way to collect large soil profiles.
Some Personal Reflections on Soil Science and Agriculture, 1936 to 1986
Authors: Aldrich Daniel G.
Published: July 2010

The personal reflections of the author on soil science and agriculture, 1936 to 1986, provide graphic evidence of the changes that have taken place in soil science. By way of illustration, changes in research that have taken place in Div. S‐1, S‐2, S‐3, and S‐4 are highlighted. The forces that drive the changes in soil science relate directly to funds supporting soil and plant research. Such funding is crucial in furthering our understanding of the fundamental chemistry, physics, and biology of soils and our ability to relate and utilize this knowledge in solving soil‐plant‐water problems of agriculture, however and wherever it is practiced today. Over the past half century, U.S. Agriculture has changed dramatically, moving more and more from an independent, production‐oriented sector of the economy toward a technologically advanced, interdependent system that distributes food and fiber worldwide. As these changes in American agriculture continue to take place, the agricultural education and research system is being called upon to broaden the traditional context within which it has functioned in order to address significant societal concerns. These legitimate societal issues include concerns about preserving the viability of our agricultural infrastructure, increasing the agricultural literacy among the general population, maintaining the quality of our environment, and improving the health and nutrition of our citizens. Thus as the case is made for obtaining support for research in soil science and agriculture, it must contain evidence of how fundamental knowledge generated by research expands the foundation of applied or problem‐solving research and development that is vital to society.
Solute Transport in Undisturbed Columns of an Aggregated Tropical Soil: Preferential Flow Effects
Authors: Seyfried M. S. , Rao P. S. C.
Published: July 2010

Solute breakthrough curves (BTC) resulting from miscible displacement of 3H2O in undisturbed soil columns under a range of soil‐water tensions were evaluated in terms of the mobile‐immobile (MIM) water model and the convective‐dispersive (CD) model. The BTC performed under tensions >0.1 kPa were approximately symmetric in shape and accurately described by the CD model, whereas BTC performed under tensions of 0 or 0.1 kPa were quite asymmetric and better described by the MIM model. Application of tension resulted in about a 10‐ to 20‐fold decrease in hydraulic conductivity [K(θ)] with relatively little change in soil‐water content (θ). Highly asymmetric BTC were attributed to bypassing or preferential flow along macropores. Thus, in terms of model selection, bypassing was significant only when soil‐water contents were at or very near saturation. Rhodamine B dye patterns obtained under saturated conditions showed that soil‐water flow (and thus convective transport) was confined to small regions within the columns. However, easily identifiable, discrete channels were not observed in these regions. It appears that flow was conducted via a series of relatively large pores, or continuous pore sequences. Application of tension appears to have disconnected the most rapidly conducting pore sequences, thus reducing the asymmetry in measured BTC and compressing the dye “solute front.” Even so, dye patterns showed that flow was very heterogeneous, as was also evidenced by high dispersion coefficients in the 3H2O experiments. Comparison of the frequency distributions of field‐measured saturated hydraulic conductivity values and measured rainfall intensities indicated that saturated conditions, and hence significant bypassing, are not expected to occur in this soil under field conditions. Observation of water table response to rainfall events supports this conclusion. From these experiments, we conclude that field‐scale models based on the CD model may adequately represent solute movement in soil at this field site.
Movement of Manganese‐54 in Calcareous Soils as Affected by Leaching Solution, Lime Content, Salinization, and Sterilization
Authors: Fahad A. A.
Published: July 2010

Movement of 54 Mn was investigated in calcareous soil columns (untreated, partially depleted lime, salinized, and sterilized) leached with 0.05 mol CaCl2 L−1 followed by 0.03 mol EDTA L−1 (ethyle‐nediaminetetraacetic acid). Manganese was monitored along the soil columns using gamma spectrometry and measured in the effluent during the leaching course (80–120 d). Results indicated that the leaching with CaCl2 for 45 d left 63, 32, and 10% of the applied Mn in the upper 0.5 cm of the silty clay, loam, and loamy sand soils, respectively, with no Mn detected below 5.0 cm. Conversely, leaching with EDTA for 4 d resulted in a nearly uniform distribution of Mn in the 20‐cm soil columns. The various soil treatments caused a reduction in the retention capacity of the three soils for Mn with the maximum reduction occurring in the soils with partially depleted lime. In most cases, leaching with CaCl2 for 45 d produced no Mn in the column effluent except negligible amounts of Mn that were displaced from the sterilized and 50 g lime kg−1 columns. On the other hand, Mn emerged in the effluent immediately after EDTA application and continued until the end of the leaching course. The shape and the position of the breakthrough curves varied depending on the specific soil treatment.
Plant Phenolic Acids in Soils: A Comparison of Extraction Procedures
Authors: Dalton Barry R. , Weed Sterling B. , Blum Udo
Published: July 2010

Plant phenolic acids have been found in plants and soils and some evidence suggests their involvement in biochemical interactions between plants (allelopathy) and organisms living in the soil. This study was conducted to compare the more common extraction procedures used in the recovery of water‐soluble phenolic acids from soil. Various extraction procedures were employed in the recovery of ferulic acid (4‐hydroxy‐3‐methoxycinnamic acid) from steam sterilized soil materials sampled from the A1 and B1 horizons of a Cecil soil (Typic Hapludults, clayey, kaolinitic, thermic) and a Portsmouth soil (Typic Umbraquualts, fine loamy, mixed, thermic). Ferulic acid was added (1000 mg/kg) to soil materials, allowed to equilibrate for 90 d, extracted and quantified by high‐performance liquid chromatography. Eight extracting solutions [H2O, methyl alcohol (CH3OH), 0.5 M sodium acetate (CH3CHOONa), 0.05 and 0.5 M diethylenetriaminepentaacetic acid (DTPA), 0.05 and 0.5 M ethylenediaminetetraacetic acid (EDTA), and 2 M NaOH] and various extraction times were used to recover ferulic acid from soil materials. Amounts of ferulic acid recovered from the A1 horizons were significantly lower than the amounts recovered from the B1 horizons for both Cecil and Portsmouth soil materials. Water and CH3OH recovered the least amounts of ferulic acid, whereas NaOH and 0.5 M DTPA recovered the most. In the B1 horizon materials, a major portion of the ferulic acid anions appeared to be absorbed by polyvalent cations (either exchangeable or nonexchangeable). This paper emphasizes the necessity of choosing the appropriate phenolic acid extractant for the soil phenolic acid fraction of interest.
Macroporous Infiltration and Redistribution as Affected by Earthworms, Tillage, and Residue
Authors: Zachmann J. E. , Linden D. R. , Clapp C. E.
Published: July 2010

The objectives of this study were to determine if burrows produced by two species of earthworms (Aporrectodea tuberculata and Lumbricus rubellus) found in continuous corn (Zea mays L.) in Minnesota altered the infiltration rate and depth distribution of surface applied water. Each species was introduced (212 m−2) to in situ cylinders in plots initially void of worms that had been subjected to tillage with and without residue or no‐till with and without residue for 5 yr. Burrows produced by both species of worms during a 46‐d period increased average infiltration rates of 30 mm of water relative to controls after 46 d. Surface residues more than doubled the number of burrows open to the surface relative to incorporated residues (48 vs. 15 for L. rubellus, 37 vs. 15 for A. tuberculata). Cocoon production, an indicator of potential survivability, was present for both species in the no‐till‐surface residue treatment and for A. tuberculata also in the till‐incorporated residue treatment. Bromide (Br‐) tracer and mass balance for Br‐ in all treatments showed infiltration and Br‐ movement in the upper 5 cm of the profile was fastest in tillage treatments with worms and residues and that Br‐ movement beyond 19 cm was greatest for the no‐till treatments with worms and residues. Pore continuity and survival potential for worms in the no‐till‐residue treatment suggest that this treatment might increase populations of worms in cropland while altering the hydraulic status and erosion susceptibility of soils in the north central USA.
Intermittent Evaporation from Soil Columns as Affected by a Gel‐forming Conditioner
Authors: Al‐Omran A. M. , Mustafa M. A. , Shalaby A. A.
Published: July 2010

The effect of an organic super gel commercially called Jalma (containing 24% humic acids, and 3.8% polysaccharides) at rates of 0.0, 0.4, 0.8, and 1.6% on aggregation index (AI) and relative swelling index (RSI) of loamy sand, sandy loam, and clay loam soils was studied. Furthermore, the influence of these rates and two irrigation intervals, 7 and 14 d, on intermittent evaporation from surface‐treated soil columns were also investigated. Twenty‐two or 44‐mm of water were applied every 7 or 14 d, respectively. The soil columns were placed in a walk‐in controlled growth chamber with potential evaporation of 8.2 mm/d. Addition of 0.4% Jalma significantly increased AI of the three soils by 33 to 38%. Increase of the Jalma rate to 0.8% significantly improved the AI of the fine‐textured sample but not the coarse‐textured samples. Further increase to 1.6% had no significant effect on the AI of the three samples. The lowest rate of Jalma significantly increased RSI of the three samples. The results also indicated a sharp, significant increase in RSI with increase in Jalma rate to 1.6%. In general, Jalma treatment significantly reduced cumulative evaporation and hence increased the amount of water conserved (AWC) after the first wetting/drying cycle. After four evaporation cycles, on 0.4% treated loamy sand, sandy loam, and clay loam soils, the AWC values were, respectively, 4.3, 3.2, and 1.5 times that of the untreated soils. The AWC values for untreated loamy sand, sandy loam, and clay loam soils irrigated every 14 d were, respectively, 2.6, 1.7, and 1.6 times those irrigated weekly.
Effectiveness of Calcium Cyanamide as a Nitrogen Source and Nitrification Inhibitor in a Tropical Soil
Authors: Arora Y. , Nnadi L. A.
Published: July 2010

Field experiments were conducted to test the efficiency of calcium cyanamide (CaCN2) as an N source for wheat (Triticum aestivum L.) and maize (Zea mays L.) over four cropping seasons at the Irrigation Research Station at Kadawa (10°39′N, 08°02′E) Nigeria. Calcium cyanamide applied at recommended N rates, was compared with urea (120 kg N ha−1) and a mixture of urea and CaCN2 [urea (110 kg N) plus CaCN2 (10 kg N ha−1)]. Highest maize grain yields and N uptake were obtained with the mixture of urea and CaCN2 in both years of the study. Wheat yields were unaffected by form of N. Recovery of inorganic N (NO‐3 + NH+4) in the surface soil, 8 weeks after planting wheat in 1984 to 1985, was greatest for the CaCN2 treatment followed by the urea‐CaCN2 mixture, and urea in tha torder. Nitrogen recovery in the 0.6‐m depth was approximately the same for all treatments. A laboratory incubation study using the same soil gave about 80% recovery of inorganic N from added CaCN2 within 8 weeks with most of the N remaining as NH+4 throughout the 8‐week study. Addition of 10 mg kg−1 of N as CaCN2 to the soil inhibited the nitrification of added urea.
Laboratory Permeability Errors from Annular Wall Flow
Authors: Tokunaga Tetsu K.
Published: July 2010

Laboratory saturated hydraulic conductivity measurement errors introduced by permeameter fluid flow within gaps between sample cores and permeameter walls are estimated through a simple model that idealizes gap flow as occurring within a smooth annulus. The inner annulus boundary fluid velocity is matched to the Darcy velocity within the sample core. The ratio of flow within the annulus to that within the core, QRap/Qcore, is shown to have both cubic and linear dependence on the gap width. QRap/Qcore is also shown to be inversely dependent on both the core permeability and the permeameter radius. Although the model is very idealized, the strong possibility of overestimating permeabilities in laboratory cores is demonstrated. Related concerns include flow in fractured porous media, and potential errors in interpreting solute travel times in laboratory columns and field lysimeters.