bluuebunny/crossref_metadata_2025 huggingface dataset:
Potassium Exchange Behavior in a Weathering Sequence of Volcanic Ash Soils
Authors: Delvaux Bruno , Dufey Joseph E. , Vielvoye Léon , Herbillon Adrien J.
Published: July 2010

Tropical volcanic ash soils are commonly associated within chronosequences and they usually sustain intensive agricultural use. In the Mungo plain, Western Cameroon (Africa), such soils are associated with the following weathering sequence: basaltic ash → allophane → halloysite → kaolinite. This paper was aimed at studying the cation exchange properties of six soils representative of such sequences and looking into their agronomic implications in intensive banana (Musa acuminata Colla) cropping systems. Calcium‐potassium exchange equilibria were performed at pH 4 and 0.01 mol L−1 chloride concentration on A and B horizons of the chosen soils. Their K/Ca exchange selectivity was interpreted through the fitting of the isotherm curves according to a two‐site model and the calculation of the Vanselow and Gapon selectivity coefficients. For some acid soil horizons, K selectivity was measured in different conditions of Al saturation and pH. The least weathered allophanic soils exhibit the lowest measured K selectivity. The halloysitic soils show a strong selective adsorption of K ions, which is associated with the presence of halloysite‐smectite mixed‐layer clays. Potassium selectivity further decreases in the kaolinitic soil. High Al saturation increases K selectivity in acid soil horizons while increasing pH promotes the adsorption of Ca ions. As K retention is low in young allophanic soils, banana plants frequently suffer from K deficiencies in rainy periods. On the contrary, K excess‐induced Mg deficiencies are general on acid kaolinitic soils and are related related to two factors: low Mg reserves, and a high retention of K relative to Mg promoted by high Al saturation.
Mycorrhizal Mediation of Phosphorus Availability: Synthetic Iron Chelate Effects on Phosphorus Solubilization
Authors: Jayachandran K. , Hetrick B. A. D. , Schwab A. P.
Published: July 2010

To determine whether chelation of Fe in slightly acidic soils will release sufficient P from Fe phosphate complexes to stimulate plant growth in P‐limited soils, the effect of EDDHA {ethylenediamine [di(o‐hydroxy‐phenylacetic) acid]}, a strong synthetic Fe‐chelating compound, on plant growth was studied in two P‐deficient native prairie soils and a P‐rich agricultural soil. Under laboratory conditions, EDDHA increased P extractability in the three soils. Subsequently, in a prairie soil/water slurry, repeated application of 10−4 M EDDHA significantly increased big bluestem (Andropogon gerardii Vitman) growth and P uptake as compared with distilled water controls or slurries which received only a single application of 10−3 M EDDHA. In slurries prepared with agricultural soil, growth of big bluestem was not affected by either concentration of the EDDHA. When the effect of EDDHA on growth of mycorrhizal and nonmycorrhizal plants was compared, in the prairie soils without EDDHA, mycorrhizal plants were significantly larger than nonmycorrhizal plants. Mycorrhizal plants in EDDHA‐amended soil had significantly greater growth and P uptake than mycorrhizal plants in unamended soil. However, neither concentration of EDDHA affected growth of nonmycorrhizal plants. In agricultural soil, plant growth was not affected by the mycorrhizal fungus or the EDDHA amendment. It appears that siderophore production by mycorrhizae or other soil microbes can significantly increase P availability in low pH soils and that this is a feasible mechanism by which mycorrhizal plants could assess P sources unavailable to nonmycorrhizal plants.
Diffusion Method To Prepare Soil Extracts For Automated Nitrogen‐15 Analysis
Authors: Brooks P. D. , Stark J. M. , McInteer B. B. , Preston T.
Published: July 2010

A diffusion method that requires less labor than distillation methods was developed for preparing soil KCl extracts for 15NH+4 and 15NO‐3 analyses. The procedure is ideal for preparing samples having low N mass (50–200 µg N) with no cross contamination. The method uses 140 mL disposable specimen containers to hold the sample, and 7‐mm diam, disks of acidified GF/D glass fiber filter paper on stainless steel wire as the acid trap. Devarda's alloy and MgO are used as the reductant and base respectively. Complete diffusion for 40 to 60 mL of sample takes 6 d at room temperature with no shaking. Paired t‐tests comparing analyses of soil extracts of varying 15N enrichment by this method and steam distillation showed no significant difference (p = 0.64). Use of KHSO4 as the trapping acid allows the paper disks to be placed in a Sn capsule and analyzed by direct combustion mass spectrometry. Alternately, H2SO4 can be used and the disks analyzed by an automated NaOBr method. The disks can be easily dried in a desiccator over H2SO4 and mailed for 15N analysis by service laboratories.
Soil, Landscape, and Erosion Relationships in a Northwest Illinois Watershed
Authors: Kreznor William R. , Olson Kenneth R. , Banwart Wayne L. , Johnson Donald L.
Published: July 2010

The purpose of this study was to establish the relationship between soil taxonomic description, landscape form and position, and erosion in northwest Illinois. The study area consists of a first‐order drainage basin about 10 ha in size. The hillslopes have mean gradients of 6 to 10% with overland flow the primary contributor to erosion. A detailed geomorphic map of the watershed was constructed on a 1‐m topographic survey base map. Map units were delineated based on slope shape, gradient, and USDA erosion class. Erosion classes were determined for the transect pedons by comparison with two uneroded and uncultivated pedons in area cemeteries with similar slope gradient, slope shape, slope length, and landscape positions. The A horizon thickness and organic C content decreased and clay content increased as a consequence of cultivation and erosion. Transect data for all hillslope geomorphic units showed the erosion classes near the shoulder to be either slightly or moderately eroded. The lower backslopes and upper footslopes, just above the sediment basin, were either severely or very severely eroded, suggesting slope length to be the dominant factor affecting erosion. The geomorphic units with concave across‐slope shapes were found to be less eroded than those with convex across‐slope shapes. All cultivated pedons failed to meet the criteria for Mollisols, which was the taxonomic placement of the uncultivated pedons. Erosion phase, landscape segment, slope shape, slope gradient, and slope length affected the taxonomic placement of the cultivated hill‐slope soils when compared with uncultivated sites.
Use of Color Splitting and a Computer Technique to Separate Soil Moisture Groups
Authors: Al‐Abed S. R. , Lewis D. T. , Samson S. A.
Published: July 2010

A method to quantify the distribution of colors across the surface and interior of soil peds was developed and used on soils that differed in morphological indicators of soil drainage. Soils from two contrasting geomorphic settings were selected for study. In the first of these settings, morphological indicators have not appeared to be useful predictors of actual soil wetness. In the second setting, soil morphology appears to predict wetness reasonably well. Pedons in the second setting provided an independent set of data against which to evaluate judgments made about pedon wetness of the first geomorphic setting. Pedon morphology was determined and duration of saturation was measured for all pedons studied. Saturation measurements were used to place pedons studied in a wet, medium, or dry moisture group. Ped surfaces and interiors were photographed using a 35‐mm camera and color slides were prepared. Color patterns on these slides were analyzed using a digital densitometer. Colors (red, green, and blue) were separated through use of the corresponding filters. Densities of these colors on each slide were determined and ranked within six brightness subranges. Cluster analysis was used to group the color rankings. Groups formed through this procedure coincided with groups (wet, medium, or dry) formed through measurement of duration of saturation. This procedure appeared to be better able to predict actual saturation than did commonly used methods based on horizon color and/or mottle features. It appears to provide a method to remove subjectiveness from soil color measurements and to quantify the measurement of soil color. Its predictive value appears to equal or exceed that of commonly applied techniques.
Earthworm Effects on Corn Residue Breakdown and Infiltration
Authors: Zachmann J. E. , Linden D. R.
Published: July 2010

Earthworm (Lumbricus rubellus Hoffmeister) activity in the field has been implicated in increased rates of residue turnover, surface soil stabilization, and increased infiltration rates due to macroporous flow. A growth‐chamber study was conducted to evaluate some of the field variables associated with L. rubellus activity and tillage systems. Polyethylene buckets packed with sieved soil had either surface‐applied, incorporated, or no corn (Zea mays L.) residue, each with or without worms. Treatments were subjected to diurnal temperature and light sequences, and periodic additions of water were made over 60 d to maintain near‐optimum moisture conditions. Corn was grown in the cultures for an additional 30 d and was harvested before a small amount of concentrated Br solution was sprayed on the soil surface. Cultures were then subjected to simulated rainfall. Corn residue in the surface‐residue treatment with worms degraded 30% faster than in the no‐worm control. Plant growth and N content were not affected by the presence of worms. Burrows and casts formed under surface residue were greater in number and stability than in other worm/residue combinations. The surface‐residue treatment with worms reduced runoff and caused incoming water to bypass the surface soil matrix, moving small quantities of Br to significantly greater depths than in other treatments. Depth of peak Br concentration was greater in no‐residue treatments than in surface‐residue/worm or incorporated‐residue/worm or no‐worm treatments, indicating a substantial difference in the displacement of surface‐applied Br during rainfall. L. rubellus may alter the water balance of field soils while simultaneously hastening decomposition of the residue mat.
Multiple‐Year Response of Winter Wheat to a Single Application of Phosphorus Fertilizer
Authors: Halvorson A. D.
Published: July 2010

Information on multiple‐year responses of irrigated winter wheat (Triticum aestivum L.) to a single application of P fertilizer in the central Great Plains is limited. The effects of one‐time P applications (0, 34, 67 kg ha−1), with 5 N rates applied annually as subplots, on winter wheat grain yield and protein were studied. Winter wheat was grown on the same plots for three consecutive years under limited irrigation on a Weld silt loam (fine, montmorillonitic, mesic Aridic Paleustoll). Single P applications in the fall of 1983 significantly increased grain yields each of three consecutive years. Applying N to P‐fertilized plots resulted in greater yields than when N or P was applied alone. The 67 kg P plus 134 kg N ha−1 treatment produced 5405 kg/ha more grain in three crops than without P and N applied. Grain protein was reduced by P fertilization at low N rates, but increased by N fertilization. Soil‐test P and residual NO3‐N levels were significantly increased by P and N fertilizer additions, respectively. Soil NO3‐N in the 0 to 180‐cm depth for the highest N rate (336 kg N ha−1 in 1984 and 268 kg N ha−1 in 1985–86) was 764 kg N ha−1 without P and 458 kg N ha−1 with 67 kg P ha−1 applied. Downy brome (Bromus tectorum) infestations responded positively to N and P fertilization and tended to increase in severity each year in this monoculture winter wheat system. The results indicate that an adequate level of P and optimum level of N are needed to achieve efficient use of these nutrients by winter wheat and to reduce the amount of potentially leachable NO3‐N in the soil profile.
Interstratified 1:1–2:1 Mineral Formation in a Polygenetic Soil from Southern Ohio
Authors: Jaynes W. F. , Bigham J. M. , Smeck N. E. , Shipitalo M. J.
Published: July 2010

A polygenetic soil from southern Ohio, formed by loess deposition on a pre‐existing Sangamon paleosol, was examined to determine if the lithologic discontinuity has affected subsequent clay‐mineral weathering or formation. Analyses of the <0.2 µm clays indicated that cation exchange capacities (CECs) and total Mg, K, and Fe contents were lowest near the interface between the loess and underlying paleosol at a depth of approximately 65 cm; in contrast, total Al contents were highest in this zone. An interstratified 1:1–2:1 mineral was identified in materials surrounding the loess‐paleosol contact and was concentrated in the 2.03 g/cm3‐density fraction of the <0.2 µm clay using density‐gradient centrifugation. Alkylammonium exchange of the 2.03 g/cm3‐density fraction demonstrated that the 2:1 component of the interstratified mineral was heterogeneous in charge and included layers characteristic of both smectite and vermiculite. Soil properties and depth distribution of the interstratified mineral suggest a pedogenic origin.
Rapid Digestion Procedure for the Determination of Total Nitrogen and Nitrogen‐15 Content of Soils
Authors: Christianson C. B. , Holt L. S.
Published: July 2010

The effectiveness of a rapid acid‐digestion procedure for total N content and atom % 15N was tested on six soils exhibiting a wide range of physical and chemical characteristics. The procedure uses H2SO4 and H2O2 without addition of a salt or metallic catalyst. Average recovery of total N and atom % 15N from soils digested with the H2SO4/H2O2 digestion procedure compared with a standard Kjeldahl digestion procedure were 98.2% and 100.9%, respectively. The H2SO4/H2O2 digestion takes only 38 min to complete.
Transport of Exchangeable Cations in an Aggregated Clay Soil
Authors: Gaston L. A. , Selim H. M.
Published: July 2010

The objective of this study was to assess the applicability of the classical and mobile‐immobile transport models for describing cation transport in soils. The transport of exchangeable cations for binary and ternary systems in an aggregated clay soil using miscible displacement methods was examined. Packed columns of aggregates of Sharkey soil (Vertic Haplaquept) were saturated with Ca. Pulses of Mg or Mg plus Na were applied to these columns, then eluted with Ca. Chloride was the accompanying anion. These leaching experiments were conducted at constant and variable total solution concentrations. Two pore‐water velocities were used in these experiments. Effluent was collected in fractions and analyzed for concentration of cations. Exchange isotherms were determined for the cation pairs Ca‐Mg, Ca‐Na, and Mg‐Na. Experimental leaching data were compared with predicted breakthrough curves obtained using the classical (or one‐region) and mobile/immobile water (or two‐region) transport models. The two‐region model offered no improvement over predictions obtained using the one‐region model. The locations of all breakthrough peaks were well described by the models; however, peak heights for Mg breakthroughs were consistently over‐estimated. Extension of the model to include the occurrence of CaCl+ and MgCl+ and adsorption of these complexes did not improve model predictions.
Steady‐State Procedure for Determining the Effective Particle‐Size Distribution of Soil Carbonates
Authors: Hartwig R. C. , Loeppert R. H. , Moore T. J.
Published: July 2010

A pH‐stat procedure in conjunction with the equal‐diameter reduction model was used to estimate the effective particle‐size distribution of soil carbonates. Samples were titrated by pH‐stat at pH 3 and 5. The cumulative dissolution data and rate constants for the dissolution of Iceland‐spar calcite were incorporated into simultaneous equations to obtain estimates of the effective particle‐size distributions of soil carbonates. Results obtained by this method from 23 calcareous soils were compared with results obtained by a sieving and sedimentation procedure. The pH‐stat procedure resulted in the estimation of a higher proportion of clay‐size carbonates than was obtained by the sieving and sedimentation procedure. This difference was attributed predominantly to the higher reactivity of soil carbonates compared with Iceland‐spar calcite. The pH‐stat procedure was especially useful for obtaining quantitative estimates of the proportion of highly reactive clay‐size carbonate with <0.2‐µm effective particle diameters.
Kinetics of the Nitrite to Nitric Oxide Reaction in Peat
Authors: McKenney D. J. , Lazar C. , Findlay W. J.
Published: July 2010

Nitrite consumption and net NO production rates were measured across a pH range of about 3 to 8 and a temperature range of 5 to 40 or 10 to 70°C in nonsterile and sterile peat, respectively. The NO was sparged from stirred peat/water (1:10) slurries by N2 or Ar carrier gas and analyzed. Addition of small quantities, 1 to 280 µg NO‐2‐N g−1 dry peat, resulted in immediate No production. Biological production of NO exceeded chemical (nonbiological) production in nonsterile peat at pH >5. At pH >6, rates were less than 5 × 10−9 mol min−1 g−1 dry peat with chemical production rates relatively insignificant. Decreasing pH increased rates significantly, particularly the nonenzymatic process, which apparently dominates NO production at pH <4.5. The chemical process was first order with respect to [NO‐2]. The dependence of [H+] was complex, approximating first‐order behavior at [H+] <4 × 10−4 mol g−1 dry peat and more strongly dependent at higher concentrations. The activation energy for the chemical reaction at pH 5.09 was 52.3 kJ mol−1. The average value for nonsterile peat measured at pH 5.45 and 6.26 was 41.4 kJ mol−1. The stoichiometric coefficient, a, for the overall reaction NO‐2 → a No was 2.14 ± 0.39 in sterile peat and 2.00 ± 0.38 in nonsterile peat. In the latter case, where both enzymatic and nonenzymatic reactions occur, the value may also reflect the nonenzymatic reaction. Other nitrogenous gases, N2O, N2, NOx and CH3ONO were not observed under the flow conditions employed, suggesting that NO is the primary product of NO‐2 reduction.
Nitrogen Management and Nitrification Inhibitor Effects on Nitrogen‐15 Urea: II. Nitrogen Leaching and Balance
Authors: Walters D. T. , Malzer G. L.
Published: July 2010

Nitrification inhibitors (NI) may reduce N leaching losses, and should have the greatest effect on sandy soils where leaching potential is high. This study used 27 lysimeters to evaluate the effect of a NI, nitrapyrin [2‐chloro‐6(trichloromethyl) pyridine], on soil water percolation (SWP) and N leaching losses from an irrigated sandy loam soil (Typic Hapludoll) planted with corn (Zea mays L.), and monitor the fate of a single application of 15N‐enriched urea over a multiyear period. Urea was applied at 90 and 180 kg N ha−1 yr−1 for a 3‐yr period, with and without NI, and with and without incorporation. Urea + NI reduced SWP between planting and silking in 2 out of 3 yr when growing degree days (GDD) were high. After silking, SWP was reduced when urea + NI was incorporated and leaching load was high. A twofold increase in N rate resulted in an average of 3.4 times more N leached over 3 yr. The NI influenced time of N loss but not total N loss. Leaching losses of fertilizer‐derived N (FDN) were delayed 25 to 50 d when urea + NI were incorporated. The leaching load required to reach the maximum rate of FDN loss was higher with urea + NI. Leaching losses of fertilizer N were three times greater when determined by the difference method than by isotope‐ratio analysis. Differing results with these two calculations are attributed to isotope dilution with indigenous soil N as a result of microbial activity. Nitrification inhibitors may reduce the potential for nonpoint‐source pollution by delaying NO3 leaching, but will be most effective if coupled with proper N rates and conservative irrigation water management.
Identification and Genesis of Fragipans in Ochrepts of North Central Wisconsin
Authors: Habecker M. A. , McSweeney K. , Madison F. W.
Published: July 2010

The morphological and physical properties of a fine‐loamy, mixed, frigid Aquic Fragiochrept at two locations in Taylor County, Wisconsin were examined. At both sites, the fragic zone occurs in bisequal soils beneath eluvial horizons and transgresses a lithologic discontinuity where the loess cap grades into a dense sandy loam till. This study evaluated the utility of several field and laboratory tests for demarcation of the fragipan, and it examined the morphological and physical features of the fragipan in relation to its potential origin. Bulk density was measured using the saran‐coated clod and Uhland ring methods. The upper boundary of the fragipan was distinguished from the overlying horizons by its higher bulk density with the Uhland ring method. Hydraulic conductivity (Ksat) of saturated soil was measured using two methods (falling‐head permeameter and Guelph permeameter). Although Ksat values were low in the fragic zones (10−5.06–10−7.60 m s−1), they were not significantly lower than those measured in underlying nonfragic, dense till horizons. Soil strength tests showed that the site with >10% clay in its fragic horizons had twice the strength of the site with <10% clay. Various macro‐ and micromorphological features indicate that the upper part of the second parent material may be a debris flow sediment, rather than dense basal till and that the fragic zone may have been influenced by permafrost. This influence is seen by the presence of a suite of characteristics associated with permafrost such as vesicular porosity, platy structure, reverse sorting, and silt coatings superimposed on clay coatings or papules.
Nine‐year Response of Thinned Slash Pine to Nitrogen, Phosphorus, and Potassium
Authors: Shoulders Eugene , Tiarks Allan E.
Published: July 2010

Diagnostic procedures are needed for determining response of slash pine (Pinus elliottii Elngelm. var. elliottii) plantations on productive sites to N, P, and K fertilizer late in the rotation. A 25‐yr‐old slash pine plantation (site index = 21 m at 25 yr) in southwest Louisiana was thinned to a residual basal area of 18 m2 ha−1 and fertilized at rates of 0 to 448 kg N ha−1, 0 to 171 kg P ha−1, and 0 and 56 kg K ha−1 at selected levels of N and P. Separate experiments were established to determine response of stands and individual dominant and codominant trees to added nutrients. During 9 yr after application, N fertilizer stimulated diameter but not height or volume growth of stands. The effect of N on diameter growth decreased with increasing tree diameter at breast height (dbh) at age 25. Nitrogen had no significant effect on diameter, height, or volume growth of individual dominant or codominant trees. Phosphorus fertilizer significantly increased diameter, height, and volume growth of stands and individual trees. Regression analyses showed that diameter growth culminated with 110 kg added P ha−1 and volume growth culminated with 132 kg added P ha−1. Height growth increased lineally over the range of 0 to 71 kg added P ha−1. In otherwise comparable treatments, individual trees that were fertilized with 56 kg K ha−1 grew faster in diameter, height, and volume than those receiving none. Currently available diagnostic procedures would have identified the plantation as one that should respond to P and K fertilizer, but not to N.
Iron‐Rich High‐Charge Beidellite in Vertisols and Mollisols of the High Chaouia Region of Morocco
Authors: Badraoui Mohammed , Bloom Paul R.
Published: July 2010

The mineralogy of Vertisols and Mollisols, associated in a hydrotoposequence in the western part of the phosphate plateau of Morocco (High Chaouia), was studied using x‐ray diffraction, interlayer swelling with alkylammonium cations, chemical analysis, and infrared spectroscopy. The swelling behavior of Li‐ and K‐saturated clays demonstrated the beidellitic character of the expandable 2:1 layer silicates that dominate the clay mineralogy of these soils. The beidellite has a heterogeneous layer charge, as measured by the swelling with alkylammonium cations, that ranged from 0.50 to 0.66 charges per half unit cell. The swelling of Li‐saturated clays with alkylammonium cations after heating at 300 °C confirmed the tetrahedral location of the charge. Structural formulas calculated for the fine clays showed that the beidellite is similar in all three soils and confirmed that these clays have a high charge density and are Fe rich. Infrared spectroscopy demonstrated that these beidellites contain substantial amounts of Fe3+ in the octahedral sheet. Kaolinite, chlorite, palygorskite, and quartz were also present, especially in the coarse‐clay fractions and in the subsoil. The presence of this Fe‐rich, high‐charge beidellite in the soils helps explain the behavior of soil K and also offers an explanation of K soil test interpretation problems.
Automated Spray System for Application of Solutes to Small Field Plots
Authors: Ghodrati Masoud , Ernst Frederick F. , Jury William A.
Published: July 2010

Uniform application of chemical solutions onto the soil surface is an important step in solute transport field research. An automated spray system is described which facilitates the application of a spatially uniform solution volume to small plots. The system consists of a portable frame which mounts over the plot, a traveling spray boom, and a pressure activated tank. The motorized spray boom allows for a consistent, uniform application of known volumes of solution over the plot area. This sprayer was designed and used for surface application of pesticide, tracer, and dye solutions to plots of 1.5 by 1.5 m. An application uniformity of over 95% was obtained for each chemical within the inner 1‐ by 1‐m area. The range of relative deposition over this inner area was from 95 to 109% of the plot average. The exact design principles could be used to construct similar systems for spraying larger plots.
Measurement of Soil Water Content during Three‐Dimensional Axial‐Symmetric Water Flow
Authors: Kachanoski R. G. , Van Wesenbeeck I. J. , Von Bertoldi P. , Ward A. , Hamlen C.
Published: July 2010

The objective of this work was to develop a method of measuring soil water content during three‐dimensional axial‐symmetric water flow in a laboratory column. A small plexiglass box with a pair of straight and a pair of curved, parallel transmission lines was constructed, packed with soil, saturated with water, and then left to dry out. Soil water content measurements using the time‐domain reflectometry (TDR) method were made using both curved and straight transmission lines. A large laboratory flow box was also constructed with numerous curved TDR probes at different radial distances from one vertical edge of the box. The box was packed with soil and then water was applied from a small surface disc source, (radius = 15 mm) at the corner of the box. Soil water content was measured during the three‐dimensional infiltration experiment. Measured soil water contents were essentially identical (r2 = 0.98) for both the straight and curved lines. The method gave soil water content as a function of time for different radial distances from the point source, or the spatial distribution at different time intervals. The estimated amounts of infiltrated water obtained by numerical integration of soil water content vs. radial distance at 1 and 2 h were within 3% of the measured infiltration amount. The method can be used to test and study the theory of three‐dimensional axial‐symmetric flow of water into soil.
Cation Exchange Isotherms Obtained with Batch and Miscible‐Displacement Techniques
Authors: Bond W. J. , Phillips I. R.
Published: July 2010

In order to predict the transport of reacting solutes through soils, it is necessary to quantify their partitioning between the solution and surface phases. Conventional batch techniques for measuring adsorption isotherms have limitations for many surface reactions, which may be overcome by using miscible‐displacement methods. In this study, an improved miscible‐displacement technique for measuring adsorption isotherms was developed and its results compared with those from a standard batch method for cation exchange in a strongly aggregated, heavy clay soil. The new technique is based on destructive sampling of unsteady, unsaturated flow experiments and an improved method for simultaneously measuring solution‐ and exchangeable‐cation concentrations. Isotherms were obtained by the miscible‐displacement method for total solution concentrations of between 20 and 200 mmolcL−1 from experiments that were terminated after 6 to 24 h. These isotherms were identical with each other and were also not significantly different from those obtained by the batch method for both Na‐Ca and K‐Ca exchange. This confirms that exchange equilibrium was reached in the miscible‐displacement method and that this technique is suitable for measuring exchange isotherms. The results also permit some observations to be made about the rate of approach to equilibrium of ion‐exchange reactions in aggregated soils and the suitability of equilibrium exchange isotherms for application to natural flow regimes.
Critical Coagulation Concentrations of Sodium and Potassium Illite as Affected by pH
Authors: Hesterberg Dean , Page A. L.
Published: July 2010

The effects of saturating cation (Na or K) and pH on the critical coagulation concentrations (CCCs) of illite were measured. Flocculation series tests showed that between pH 6 and 11, the time‐invariant CCCs of Na illite increased from 6 to 58 mol Na m−3; release of interlayer K was controlled by adding 0.1 mol K m−3 to Na‐illite suspensions. The CCCs of K illite increased from 3 to 14 mol K m−3 over the pH range 6 to 10. The lower CCCs of K illite relative to Na illite were consistent with a higher surface affinity for K. Increasing CCC with increasing pH was explained by charge alterations on the edge surfaces due to surface‐specific proton interactions. A comparison of our Na‐illite CCCs to published Na‐kaolinite and Na‐montmorillonite CCCs revealed a greater pH dependence for Na‐illite and Na‐kaolinite CCCs.
Correlation between Soils and Sagebrush‐Dominated Plant Communities of Northeastern Nevada
Authors: Jensen M. E. , Simonson G. H. , Dosskey M.
Published: July 2010

Relationships between sagebrush‐dominated plant communities and soil‐site variables were examined on 372 relatively undisturbed rangeland sites of the Humboldt National Forest in northeastern Nevada, USA. Site and soil‐physical variables that best discriminated between the 15 community types studied included mollic epipedon thickness, elevation, subsoil clay content, total soil depth, subsoil thickness, total water holding capacity, A‐horizon thickness, A‐horizon rock content, rooting depth, and subsoil rock content. Discriminant analysis indicated that 68% of the rangeland sites sampled could be correctly assigned to their appropriate community type based on site and soil‐physical variables. The percentage of sites correctly classified ranged from 25% within the Artemisia tridentata Nutt. ssp. tridentata/Festuca idahoensis Elmer community type to 100% in the Ar. longifolia Nutt./F. idahoensis type. Soil‐chemical variables effective in discriminating between community types included both surface (N, P, divalent/monovalent cation ratio, Ca, pH, base saturation, and organic‐matter content) and subsoil (divalent/monovalent cation ratio, Ca, base saturation, and pH) variables. Based on soil‐chemical criteria, only 32% of the study sites were correctly assigned to their appropriate community type. Results of this study suggest caution when inferring the soil properties of a site from plant community composition.
Ligand Concentration Effects on Aluminum Complexation by a Chestinut Leaf Litter Extract
Authors: Shotyk William , Sposito Garrison
Published: July 2010

The quenching of fluorescence at an emission wavelength dependent on the ligand concentration was used to measure organically complexed Al at pH 4.5 across a range of dissolved organic carbon (DOC) concentrations of chestnut (Castanea sativa L.) leaf‐litter extract. Simultaneous measurements of total inorganic Al were made by a 15‐s reaction with 8‐hydroxyquinoline. These data were combined to calculate quasiparticle model complex stability coefficients (cKT) for Al binding. For the range of DOC from 26 to 150 g m−3, the variation in the value of log cKT was not statistically significant. A conditional stability constant for a 1:1 quasiparticle Al/leaf‐litter complex was calculated after correcting cKT for Al hydrolysis and ligand protonation. Its mean value varied from 108.9 to 108.3 across the range of DOC investigated, but was also not significantly dependent on DOC according to statistical criteria. It was concluded that fluorescence quenching can be used to determine organically bound Al for an environmentally important range of leaf‐litter DOC concentrations.
Ground‐Penetrating Radar Study of Ortstein Continuity in Some Michigan Haplaquods
Authors: Mokma D. L. , Schaetzl R. J. , Doolittle J. A. , Johnson E. P.
Published: July 2010

Continuity of ortstein affects many agricultural and urban land uses. This study was conducted to determine the utility of ground‐penetrating radar (GPR) in studying ortstein continuity. The GPR data were compared with those collected by conventional field techniques. The ortstein is generally strongly cemented and continuous in an area mapped as Saugatuck soils (sandy, mixed, mesic, ortstein, Aeric Haplaquods), and appeared to occupy 75 to 100% of each pedon. Tongues of E horizons and weakly cemented or noncemented materials in the ortstein horizon were easily identified by GPR. Such breaks in the ortstein are difficult to locate with conventional field techniques. These results demonstrate that GPR is useful in determining ortstein continuity.
Stratigraphy and Parent Material Relationships of Red Substratum Soils on the Allegheny Plateau
Authors: Waltman William J. , Cunningham Robert L. , Ciolkosz Edward J.
Published: July 2010

Red (2.5YR 4/6 to 4/8) and brownish yellow (10YR 6/6 to 6/8) subsoils were studied in the Sweden soils (tentative classification: fine‐loamy, mixed, frigid Typic Hapludult) and the Dekalb‐Cook‐port‐Nolo catena (loamy‐skeletal, mixed, frigid Typic Dystrochrept, coarse‐loamy, mixed, frigid Typic Fragiuquult, and coarse‐loamy, mixed, frigid Typic Fragiaquult, respectively) on the unglaciated Allegheny Plateau. The red subsoil horizons are interpreted to be a pre‐Wisconsinan paleosol formed in colluvium and residuum that were derived from acid sandstones of the Huntley Mountain and Pottsville Formations mantling the plateau summits. The paleosol horizons are buried by 1 to 2 m of brown, sandy colluvium of Wisconsinan age, but can be clearly distinguished by an increase of clay content, higher free iron oxide content, extensive weathering and rubification of sandstone rock fragments, and strongly expressed argillic horizons. In the Cookport and Nolo soils, the paleosol occurs beneath a fragipan, with a stoneline marking the surface of the paleosol. The paleosol has been truncated, since A and E horizons are not preserved in the profiles. The paleosol horizons vary in color and iron oxide mineralogy across the catena sequence. The paleosol horizons of the Sweden and Cookport soils morphologically resemble pre‐Wisconsinan till‐derived soils of the Susquehanna Valley. From this study, only one pre‐Wisconsinan paleosol could be identified in the periglacial deposits of the Allegheny Plateau; it has been tentatively correlated with the Sangamon Interglacial. Three separate colluvial deposits were recognized on the plateau summits.
Poorly Ordered Silica and Aluminosilicates as Temporary Cementing Agents in Hard‐Setting Soils
Authors: Chartres C. J. , Kirby J. M. , Raupach M.
Published: July 2010

Hard‐setting is an important but poorly understood phenomenon in seasonally wetting and drying soils. This study was conducted to determine the role, if any, of chemical cementing agents in a hard‐setting soil. Undisturbed cores from the E horizon of an Aeric Albaqualf were leached in the laboratory with distilled water, 0.15 M ammonium oxalate (pH 3.0 in darkness) and 2 M NaOH/ethylene glycol. The leachates were analyzed for Si, Al, and Fe and the residual materials by infrared spectroscopy. After drying at 40 °C, tensile, shear, and compressive strengths of the cores were determined. All three reagents caused a total loss of tensile strength and decreased shear strength, but had little effect on compressive strength. Amorphous silica is probably the major cementing agent, but the results also indicate that an imogolite‐like aluminosilicate, a feldspathoid mineral, and possibly silica‐Fe complexes may play some part in cementation.
Water‐Droplet Energy and Soil Amendments: Effect on Infiltration and Erosion
Authors: Smith H. J. C. , Levy G. J. , Shainberg I.
Published: July 2010

The impact energy of water droplets from rain or overhead sprinklers can cause a seal to form at the soil surface. This constitutes a severe problem in agricultural lands in the arid and semiarid regions. Spreading a soil conditioner on the surface of the soil and providing a constant supply of electrolytes may prevent seal formation. The effect of droplet impact energy and water quality on infiltration and erosion was studied, using a tank drip‐type rain simulator, in a sandy loam soil (Typic Rhodoxeralf) treated with an anionic polyacrylamide (PAM) and phosphogypsum (PG). Three kinetic energies (KE) of 3‐mm diameter drops were obtained by varying their falling heights. The two qualities of water were distilled water (DW) and tap water (TW), to simulate rain and irrigation water, respectively. Increasing the impact energy reduced the infiltration rate (IR), cumulative infiltration (rain intake), and soil erosion in all treatments. Addition of PAM in the presence of electrolytes (either PG or TW) increased both final IR and cumulative infiltration by 7‐ to 8‐fold compared with the control, and was much more effective than PAM, PG, or TW alone. The PAM + electrolyte treatments decreased soil erosion by more than one order of magnitude compared with the control.
Slope, Aspect, and Phosphogypsum Effects on Runoff and Erosion
Authors: Agassi M. , Morin J. , Shainberg I.
Published: July 2010

The effect of slope, aspect (windward vs. leeward), and phosphogypsum (PG) application on rain amount, runoff, and erosion from a Grumusol soil (Typic Chromoxerert in Israel) was measured in small field plots (1 by 1.5 m) exposed to natural rainstorms. The amount of effective rain on the slopes, as measured with small rain gauges with orifices in a plane parallel to the slope, increased slightly on the windward aspect as slope increased to ∼58% and decreased thereafter. On the leeward aspect, the amount of effective rain dropped steadily to half of the meteorological rain at a slope of 100%. The amount of runoff was not affected by slope on the windward aspect but decreased sharply on the leeward aspect as slope increased. PG releases electrolytes into the percolating and runoff water, prevents dispersion of the particles at the surface, stabilizes the soil structure, and reduced soil erosion. PG applied at 5 Mg ha−1 reduced runoff to about 25% of that in the control and reduced soil loss to 1 to 3% of that in the control. The dramatic effect of PG on erosion increased with slope steepness.
Subsoiling for Sunflower Production in the Southeast Coastal Plains
Authors: Sojka R. E. , Busscher W. J. , Gooden D. T. , Morrison W. H.
Published: July 2010

Crops grown on the Paleudult soils of the South Atlantic Coastal Plain often benefit from disruption of root‐restrictive subsoil layers. In this physiographic area, the response of sunflower (Helianthus annuus L.) to subsoiling was unknown. We hypothesized that in‐row subsoiling would benefit sunflower performance, and that plant performance could be related to profile penetration‐resistance patterns. Sunflower was grown on Norfolk loamy sand in Florence, SC, and on Orangeburg loamy sand (both fine‐loamy, siliceous, thermic Typic Paleudults) in Blackville, SC, in 1985 and in Blackville only in 1987. Plots were either subsoiled using 0.45‐m shanks or not subsoiled. Distribution (and, in most instances, magnitude) of cone indices were significantly different for subsoiled and nonsubsoiled profiles. Accumulation frequency of low cone indices was greater for Florence and Blackville in 1985 but not for Blackville in 1987. For subsoiled treatments, lower cone indices below planted rows persisted to late summer in 1985 at both locations, which favored plant growth. Reduction of soil profile strength produced increased seed yield, oil concentration, oil yield, and seed size in these cases. In 1987, accumulation frequency of soil strength was similar for non‐subsoiled and subsoiled plots shortly after tillage. In this case, plant parameters were not statistically improved with subsoiling. No tillage × N‐rate, hybrid × tillage, or hybrid × N‐rate interactions were observed. If low‐cone‐index isopleths persist throughout the season, then a positive response to subsoiling can be expected.
Corn Response to Seed‐Row Residue Removal
Authors: Kaspar T. C. , Erbach D. C. , Cruse R. M.
Published: July 2010

No‐till corn (Zea mays L.) yields in the central Corn Belt often are limited by slow soil warming caused by surface crop residues. A 3‐yr experiment with a split‐plot design was conducted near Ames, IA, to determine corn response to seed‐row residue removal. Whole‐plot treatments were a factorial combination of two tillage systems (no‐till and moldboard plow) and three residue types (corn, soybean [Glycine max (L.) Merr.], and fiberglass insulation). Residue was removed from bands of various widths (0, 8, 16, 32, and 76 cm) centered on the seed row for five split‐plot treatments. Corn seedlings reached 50% emergence 0.5 d earlier in plots with soybean residue than in those with corn residue. No‐till seedlings reached 50% emergence 0.8 d sooner and 50% tasseling 0.9 d sooner than in the mold‐board‐plow system. Residue removal from the seed row had greater effects on plant growth and yield than either tillage or residue type. Seed‐row residue removal reduced days to 50% emergence and tasseling, increased plant height, decreased grain moisture and barrenness, and increased yield. Removing residue from a 16‐cm wide band resulted in corn yields that were only 3% less than those from bare soil. Plant responses to width of the residue‐free band were described by logarithmic functions. Seed‐row residue removal may allow a compromise between erosion protection and crop yield.
Soil Water Diffusivity Determination by a Modified One‐Step Outflow Method
Authors: Mu'Azu S. , Skopp J. , Swartzendruber D.
Published: July 2010

One‐step outflow procedures represent potentially rapid and convenient procedures to obtain soil‐water‐diffusivity and unsaturated‐hydraulic‐conductivity data. This study presents modifications of the existing procedures that improve and simplify the estimation of the soil water diffusivity and associated water content. The derivation is similar to that of Passioura's. An equation is derived that describes the soil water diffusivity as a function of average soil water content rather than the water content at the top end of the soil core. The results may be used over a range of water contents similar to Passioura's original procedure. The modifications presented here provide a simpler analysis that is more readily applied to one‐step out‐flow experiments.
Comparison of Three Methods for Soil Homogenization
Authors: Schumacher B. A. , Shines K. C. , Burton J. V. , Papp M. L.
Published: July 2010

We used the most common homogenization techniques, namely, grinding and sieving, riffle splitting (open and closed bin), and cone and quartering to homogenize four soils of differing textures. Our objective was to determine the effectiveness, efficiency, and extent of fine particle loss for each technique by examining particle‐size distribution, loss‐on‐ignition organic matter, and pH. Five passes should be used to effectively homogenize a sample, since the least replicate variability almost always occurred after the fifth pass. Riffle splitting was more efficient and had less loss of fines than cone and quartering and is, therefore, the recommended method for soil homogenization. The closed‐bin riffle splitter was apparently better able to contain the loss of fines than the open‐bin riffle splitter. Grinding and sieving (random sampling) was the most efficient process, yet it almost consistently showed greater replicate variability than the other homogenization techniques after the fifth pass, thereby reducing its value for soil homogenization.
Analytical Solution for Two‐Dimensional Heat Conduction beneath a Partial Surface Mulch
Authors: Kluitenberg Gerard J. , Horton Robert
Published: July 2010

Models describing heat conduction in materials subjected to periodically varying surface temperatures are important in agricultural physics and other disciplines of applied physics. To date, most attempts to model soil heat conduction in two dimensions have relied on methods of numerical approximation to solve the heat‐conduction equation. We have developed an exact analytical solution to the heat‐conduction equation in a two‐dimensional region of constant thermal properties. The surface temperature is described by a wave that varies sinusoidally with time and that has mean temperature, amplitude, and phase constant as arbitrary functions of space. In addition to a general solution, a particular solution is presented for a surface temperature pattern corresponding to a partial surface mulch. Calculated temperature and heat‐flux profiles beneath a partial surface mulch indicate that, at certain times of the day, there are large vertical and horizontal spatial variations in temperature and heat flux but, at other times, temperatures are uniform and heat fluxes have similar magnitude and direction. The calculations also show that, near the soil surface, the horizontal component of the heat flux can be quite large.
Simulation of Water Flow from a Percolation Test Hole in Layered Soil
Authors: Jabro J. D. , Fritton D. D.
Published: July 2010

In order to better explain problems in the correlation of percolation test and soil hydraulic conductivity data, a finite‐element program (TWODEPEP) was used to solve Richards' water‐flow equation in cylindrical coordinates. Both saturated and unsaturated aspects of water flow from a percolation test hole were simulated. Inputs for the simulation model were the soil hydraulic conductivity, which was measured using the Guelph permeameter technique, and water‐retention data for each layer of a Monongahela silt loam soil (a fine‐loamy, mixed, mesic Typic Fragiudult). Pressure‐head distribution and rate of water flow were simulated. A thin (approximately 10‐mm) saturated zone near the water source, approximated by the region inside the zero‐pressure line, was nearly constant in size with time, but the wetting front continued to advance. It was also found that the horizontal movement of water in the soil was dominant over the downward vertical movement due to the movement of the water in both the upper and middle layer rather than the lower layer because the soil in these two layers was more permeable than the underlying layer. Simulated flow results agreed with the geometric mean of the field data obtained at six sites. The simulated results in the layered soil were compared with those in a uniform soil to show how soil layers significantly affect water flow from a percolation test hole.