bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Tillage, Cropping, and Fertilizer Management on Soil Nitrogen Mineralization Potential
Authors: El‐Haris M. K. , Cochran V. L. , Elliott L. F. , Bezdicek D. F.
Published: July 2010

Nitrogen mineralization potentials (No) were determined on soil from a long‐term crop rotation tillage experiment on a Palouse silt loam (fine‐silty, mixed, mesic Pachic Ultic Haploxerolls). Crop rotations included continuous winter wheat (Triticum aestivum L.), alternate winter wheat and (pea Pisum sativum L.), alternate winter wheat and spring wheat, and pea‐alfalfa (Medicago sativa L.)‐green manure, followed by 5 y of alternate spring wheat and winter wheat. Tillage variables were moldboard plowing, chisel plowing, or no‐till. Long‐term N fertilizer rate plots were also studied on a Ritzville silt loam (coarse‐silty, mixed, mesic Calciorthidic Haploxerolls). The tillage plots were cropped annually, whereas the fertilization rate plots were alternately fallowed and cropped to winter wheat with and without spring supplemental irrigation. Moldboard plowing resulted in uniform No values throughout the top 15 cm of soil, but N mineralization potential (No) was greater for chisel plowing and no‐till than for moldboard plowing at the 0‐ to 5‐cm depth and less at the 5‐ to 10‐ and 10‐ to 15‐cm soil depths. The net result was that average No for 0 to 15 cm was unaffected by tillage or crop rotation in the fall sampling. In the spring sampling, average No for either chisel plowing or no‐till was significantly higher than for moldboard plowing. Also, peas‐alfalfa‐green manure followed by alternate spring wheat‐winter wheat had a significantly higher No averge than both continuous winter wheat and winter wheat‐pea but was not different from winter wheat‐spring wheat. The No of the tillage and the crop rotation management treatments were significantly greater with samples obtained in the fall than from those obtained in the spring. Nitrogen mineralization potentials increased linearly with increased N rate on both the dryland and supplemental irrigated treatments. However, supplemental irrigation uniformly increased No compared with the corresponding nonirrigated treatments.
Eolian Influence on Development and Weathering of Some Soils of Point Reyes Peninsula, California
Authors: Crawford T. W. , Whittig L. D. , Begg E. L. , Huntington G. L.
Published: July 2010

Wind‐deposited sands have influenced characteristics of soils on Tomales Point at the northern end of Point Reyes Peninsula in California. The distribution of eolian materials, the interface between eolian and residual granitic parent materials, and mineral weathering were investigated in five pedons along a transect from near the edge of a wave‐cut bluff fronting on the Pacific Ocean to near the crest of a stabilized dune. Based upon distinct textural discontinuities, proportions of rounded and angular sands, organic carbon, and phyllosilicate species in silt and clay fractions, nonconforming zones of eolian materials over granitic residuum were clearly distinguished. The soils along the transect include members of coarseloamy, mixed, isomesic Pachic Haplustolls, coarse‐loamy, mixed, isomesic “Entic” Dystropepts, sandy, mixed, isomesic ustic Dystropepts, and mixed, isomesic Typic Ustipsamment families. A mineral weathering sequence involving the transformation biotite → vermiculite → smectite is evident within the buried granitic residuum along the transect.
Composition and Acidic Functional Group Chemistry of an Aqueous Chestnut Leaf Litter Extract
Authors: Blaser P. , Sposito Garrison , Holtzclaw Kenneth M.
Published: July 2010

The elemental composition, amino acid distribution, infrared spectrum, and carboxyl group content of a chestnut leaf (Castanea sativa L.) litter extract were determined. Proton titration data also were obtained by both continuous and discontinuous titrations. The overall titration endpoint could be identified directly by conductometric titration. Proton formation functions for the extract were computed from the two sets of titration data. In order to explain protonation during titration, the data were fitted to a simple chemical model by nonlinear regression analysis. From this calculation, the acidic properties of the litter extract could be modeled assuming three classes of acidic functional groups, with logarithms of the conditional protonation constants in the ranges: 4.00–4.25, 6.00–6.75, and 8.7–9.0.
Diffusion of Radon through Soils: A Pore Distribution Model
Authors: Nielson K. K. , Rogers V. C. , Gee G. W.
Published: July 2010

A mathematical model was developed for calculating radon diffusion coefficients from water contents and pore size distributions of soil materials. The model accounts for radon diffusion in the air‐filled and the water‐filled pore space, for radon solubility in water, and for Knudsen diffusion in extremely small air‐filled spaces. The model considers soil pores to be composed of all possible serial combinations of the size increments from a measured pore size distribution. Diffusion coefficients for the resulting composite pores are computed and then used to calculate the overall diffusion coefficient of the soil by assuming parallel diffusion through all of the pore combinations. The resulting diffusion coefficients increase with the median pore diameter, and decrease with increasing soil water contents and with increasing widths of the soil pore size distribution. The model diffusion coefficients compare well with measured coefficients and with empirical calculations and are useful in evaluating the required soil cover thickness for uranium mill tailings reclamation.
Effects of Mica Content on Engineering Properties of Sand
Authors: Harris W. G. , Parker J. C. , Zelazny L. W.
Published: July 2010

Sand mixtures with variable weight percentage of mica (Wm) in a quartz matrix were evaluated to isolate the effects of mica content on compacted density, compressibility, shear strength, and bearing capacity. Maximum compacted density decreased linearly with increasing Wm, reflecting the inhibitory effect of platy grains on close‐packing of spheroidal grains. The initial tangent axial compression modulus (Eo), a reciprocal index of undrained compressibility, decreased logarithmically with increasing Wm. The relative effect of Wm on Eo was greater at higher confining pressures. Shear strength (φ), bearing capacity (qoh), and California bearing ratio (CBR) also logarithmically decreased with increasing Wm. Curves for Eo, φ, qoh, and CBR showed shoulders marking diminishing effects of mica additions beyond mica weight percentages of 10 to 15%. A hypothesis that the curvilinear nature of parameter‐vs.‐Wm relationships is due to the sensitivity of these parameters to mica‐quartz interaction at particle contacts is supported by observed linearity between the parameters and mica cleavage face area (MFA). The latter is indexed by mica frequency per 100 grains (Fm) measured by petrographic grain count on a specific size fraction. If the range of mica grain thicknesses is small relative to the range of diameters, then Fm for a single size fraction effectively approximates the MFA for the mica over the whole particle size range. Mica effects on certain engineering properties may be indexed more effectively by Fm than by Wm.
Phosphate Sorption by Soils: II. Sorption Measurement Technique
Authors: van Riemsdijk W. H. , van der Linden A. M. A.
Published: July 2010

A computer‐controlled apparatus has been developed for measurement of P sorption by soils. A solution containing P is constantly pumped from a vessel through a soil column and back to the vessel again. Phosphorus concentration in the vessel can be assessed and regulated; constant, increasing and decreasing concentration are optional. The method of pumping solution through a column is convenient for relatively slow reactions and for reactions in which a high soil/solution ratio is required. When a high pumping rate is used, the results are comparable with classical batch experiments. The proposed method, however, has many advantages, e.g., avoiding mechanical disturbance of the soil particles and separating solids from solution. Eight soil samples can be examined at one time. This makes the apparatus suitable for routine as well as research experiments. The analytical part of the apparatus can easily be replaced; other ions of interest (K+, Mg2+, trace elements) can then be studied in the same way.
Nonuniform Leaching from Nonuniform Steady Infiltration
Authors: Philip J. R.
Published: July 2010

The two‐dimensional quasilinear steady flow equation is solved exactly for arbitrary periodic distribution of surface source strength v0 (x) (x, horizontal coordinate), both for flow to infinite depth and to a water table at finite depth. Solutions are given both for the Kirchhoff variable ⊗ and the stream function φ. They are explored in detail for . For each solution emphasis is placed on determining the limits on v0 (x) which ensure that the moisture potential Ψ ⩽ 0, so that the quasilinear formulation is applicable. This essential precaution has sometimes been disregarded. The presence of a water table strongly influences ⊗, but has relatively little effect on φ. This makes possible important mathematical simplifications. Remarkably, simple exact solutions are found for travel times. They reveal singularities in the travel‐time functions overlooked in previous work using a finite difference method. For large times, the family of isochrones behaves like a travelling wave with shape and velocity constant. Streamlines and isochrones are compared for a coarse soil (parameter α = 25 m−1) and a fine one (α = 0.25 m−1). Surface velocity differentials persist much more strongly for the coarse soil, which exhibits much greater horizontal variation of travel times. By one measure, nonuniformity of leaching is 7.8 times greater in the coarse soil than the fine one. A previous study of problems of this class concluded incorrectly that leaching is more uniform for saturated than for unsaturated flow.
Kinetic Analysis of Net Nitrogen Mineralization in Soil
Authors: Juma N. G. , Paul E. A. , Mary B.
Published: July 2010

Studies were conducted to determine the most suitable mathematical equation and the most appropriate method for calculating the values of the parameters of the equation describing the net N mineralization in soil. The cumulative net N mineralized in two treatments of a 15N labeled soil and five unlabeled Saskatchewan soils showed curvilinear trends that could be fitted to either hyperbolic or first order equations. The kinetic parameters of the hyperbolic equation, 15NH0 (potentially mineralizable N) and Tc (time required for 1/2 NH0 to mineralize) determined by nonlinear least squares (NLLS) yielded the best fit to the data for the labeled soil and had the lowest RMS error. Linear regression (1/N vs 1/t) yielded 15NH0 and Tc values which were markedly different than those obtained with the N vs. N/t and t/N vs. t transformations or those obtained with the NLLS method when all the data were considered. The double reciprocal plot gave undue weight to the initial data points. The 15NH0 estimated by NLLS method accounted for 62 and 72% of the total organic 15N remaining in the two treatments of Weirdale loam soil. The NH0 for Saskatchewan soils ranged from 51 to 429 µg N g−1 soil, while the Tc ranged from 7.3 to 45.8 weeks. The 15NF0 values obtained with the first order equation using NLLS method accounted for 39 to 44% of the total organic 15N remaining in soil. The NF0 values for Saskatchewan soils ranged from 35 to 255 µg N g−1 soil while the values of net mineralization rate constant, k, ranged from 0.036 to 0.164 weeks−1. Both equations accurately predicted the amount of net N mineralized over 14 weeks incubation. However, the estimates of potentially mineralizable N and mineralizable N half‐life were dependent upon the model used.
Rubidium as a Controlling Factor in Potassium Release from Micaceous Minerals
Authors: Bashour Isam , Carlson R. M.
Published: July 2010

Rubidium is ubiquitons in soils and minerals, occurring with K+. Ease of replacement of interlayer K+ for several samples of biotite, muscovite, vermiculite and vermiculite enriched in K+ and Rb+ was compared with Rb+ content to establish Rb+ as a controlling factor in K+ release. Release rates were determined by continuously leaching mineral samples with 0.01 mol/L CaCl2 at 298 K. Replaceability of interlayer K+ decreased as Rb+ content increased to 1% of the exchange sites. Data for K+ and Rb+ treated vermiculite fit the release trends for untreated mica samples. Rubidium is an important factor in the control of K+ replaceability of micaceous minerals.
Alfalfa Growth and Soil Oxygen Diffusion as Influenced by Depth to Water Table
Authors: Bornstein J. , Benoit G. R. , Scott F. R. , Hepler P. R. , Hedstrom W. E.
Published: July 2010

Growth and yield of alfalfa and oxygen diffusion rate (ODR) as influenced by excess water were investigated via three depth to water table (WT) treatments, through two different falling water table sequences. The environment for the study was a simulated profile of a Munson silty clay loam, mesic frigid Aeric Haplaquepts, placed in 12 large cylinders 0.61‐m diam by 1.52 m deep each seeded to Iroquois alfalfa (Medicago sativa L.). Each sequence was run through three consecutive 42‐d growth cycles. The first sequence was one flooding‐recession per growth cycle while the second sequence included three floodings at two‐week intervals during each cycle. Each cycle began immediately after previous crop harvest, with 3‐d saturation followed by lowering the WT to fixed 0.15‐, 0.45‐, and 0.75‐ m depths, respectively. ODR values at a 0.075‐m depth averaged over three growth cycles from the single falling water table treatment showed little change during the saturation to drawdown period for the 0.15‐m WT but highly significant variation for the 0.45‐ and 0.75‐m WT treatments. Growth rates for all treatments followed a pattern of two weeks of rapid growth followed by a declining growth rate to harvest. For the sequence having three flooding‐drawdowns per cycle, crop growth and yield increased significantly as a linear function of WT depth from 0.15 to 0.75 m. The soil water system showed a 3‐ to 4‐d drawdown after each flooding with WT drawdown having a positive effect to a 0.75‐m depth.
Estimating Production of Range Vegetation from Easily Measured Soil Characteristics
Authors: Cannon M. E. , Nielsen G. A.
Published: July 2010

Vegetation production information is essential to rangeland management. Making range production estimates based on harvest data is expensive and time consuming. Few native range sites in Montana or comparable areas have long‐term production data. We therefore classified soil pedons on such sites, and tested thickness of mollic epipedon and other site characteristics as predictors of average range production. Specifically Mollisols under native range with 6‐ to 49‐ yr production records were examined at 14 sites in Montana, Wyoming, North Dakota, and Alberta, Canada. Sites ranged in precipitation, elevation, and latitude from 250 to 560 mm/yr, 595 to 2165 m, and 40 to 50° north. Mean annual standing crop production ranged from 0.4 Mg/ha on a coarse‐loamy, mixed, Aridic Haploboroll to 3 Mg/ha on a fine, montmorillonitic, Agric Cryoboroll. Thickness of mollic epipedon and Munsell color values were recorded for 30 samples per site. Multiple linear regression analysis showed thickness of mollic epipedon predicts long‐term production better than any other single factor tested, R2 = 0.39. Addition of precipitation data improved estimates of production and gave the equation: production (Mg/ha) = −1.34 + 0.023 [thickness of mollic epipedon (cm)] + 0.005 [precipitation (mm)], R2 = 0.72. Separation of sites by vegetation improved correlations between thickness of mollic epipedon and production, possibly because it grouped sites climatically. For Stipa/Bouteloua vegetated sites, production (Mg/ha) = 0.32 + 0.023 [thickness of mollic epipedon (cm)], R2 = 0.66. Depth to carbonates was also related to production.
Effect of Soil Variability on Response to Tillage of an Atlantic Coastal Plain Ultisol
Authors: Anderson S. H. , Cassel D. K.
Published: July 2010

Subsoiling and chisel plowing are deep tillage practices which have increased crop yields on soils containing tillage pans. The relationship between crop response to deep tillage practices as influenced by soil property variability is not well understood. This study was conducted to obtain information about the response of corn (Zea mays L.) to selected tillage practices as influenced by soil variability. The effects of selected tillage practices on soil physical properties and corn production were investigated during 1981 and 1982 in a field with a tillage pan. The surface textural class of the Norfolk series (fine‐loamy, siliceous, thermic Typic Paleudults) in the field ranged from loamy sand to sandy loam. Three distinct soil units were delineated on the landscape based on depth to the B horizon. Four tillage treatments were investigated: disking, bedding, subsoiling plus bedding, and chisel plowing. Soil and plant parameters monitored at various times during the study were in situ mechanical impedance, bulk density, corn height, leaf area, barren stalk population, and grain yield. Significant interactions between tillage and soil unit for grain yield indicate a variable response to tillage due to depth to the B horizon. Mechanical impedance and bulk density in the conventional disk and subsoil treatments were negatively correlated with depth to the B horizon, implying that relatively less root restriction occurs when the B horizon is deeper. Grain yield response to deep tillage (subsoiling and chisel plowing) was significant during 1981 but not in 1982; this behavior was attributed to differences in rainfall distribution between the two years. Barren stalk population was significantly decreased by deep tillage both years.
Gully Rehabilitation—A Three‐Stage Process in a Sodic Soil
Authors: Heede Burchard H. , DeBano Leonard F.
Published: July 2010

The geomorphic, edaphic, and vegetation changes occurring in sodic soils were studied during a gully rehabilitation project in western Colorado. Soil material was collected along transects which traversed individual gullies in the network. A topographic survey was also made of each transect to determine areas of erosion and deposition. Along each transect samples were collected on exposed sodium banks, recent and old gully bank colluvium, sediment deposited in the channel, partially stable gully banks, and stable gully banks. The six sample locations were sampled in 1962, 1965, 1967, and 1981. The samples collected at the six locations were analyzed for pH; soluble calcium, magnesium, and sodium in a saturated extract; total calcium, magnesium, and sodium; water soluble sodium; cation exchange capacity; and soil texture. Exchangeable sodium percentage (ESP) and sodium adsorption ratio (SAR) were calculated. The analysis of the data showed that gully rehabilitation occurred in three stages: nonvegetated sodium banks disintegrated; the colluvial material from these eroded banks was weathered and leached; and, finally when enough sodium had been leached from the eroded material, it was stabilized and vegetated as older colluvial material at the base of high sodium gully banks or as channel alluvium deposited behind gully structures. These changes led to an overall stabilization of the gullies and reduced suspended sediment and peak flows.
Growth and Nutrient Status of Loblolly Pine Seedlings in Relation to Flooding and Phosphorus
Authors: McKee W. H. , Hook D. D. , DeBell D. S. , Askew J. L.
Published: July 2010

Growth and total biomass of 2‐year‐old loblolly pine (Pinus taeda L.) were seriously suppressed by continuous flooding compared to dormant season flooding or drainage to a depth of 61 cm. Dormant season flooding produced larger seedlings than did maintaining the water table at 61 cm. Phosphorus added at 100 mg kg−1 to the surface 15 cm of topsoil increased total biomass with continuous flooding but not with other drainage treatments. Content of N, P, K, Ca, and Mg were closely associated with total seedling biomass. Sodium, Zn, and Fe concentrations were greater in roots than foliage of seedlings. Results indicate that loblolly pine required higher soil P with excessive water and suggest that P is able to at least partly alleviate the need for drainage.
Effect of Cation Exchange on Calculated Hydrodynamic Dispersion Coefficients
Authors: Robin M. J. L. , Elrick D. E.
Published: July 2010

A semiempirical approach based on cation exchange theory is used to express the reaction term of the transport equation for unsaturated transient flow of water into soil. The system described is the horizontal infiltration of a 1M solution of KCl into an initially air‐dry, Ca‐saturated silty clay loam soil. Values of the dispersion coefficient were calculated using an expression for the reaction term which assumes the adsorbed concentration of a cation to be a function of its concentration in solution, as well as of the negative charge concentration of the solution. These dispersion coefficient values were compared to those obtained with a reaction term which assumed the adsorbed concentration to be a function of the concentration in solution only. The results indicate that the dispersion coefficient is affected only slightly by the two choices of the expression for the reaction term. The fact that the dispersion coefficients calculated for the cation using the two models are of the same order of magnitude suggests that the reaction is described adequately by both models. The dispersion coefficient values obtained for Cl‐ and K+ are about one order of magnitude higher than expected. This cannot be explained by the choice of the reaction term and may be due to the presence of immobile water and/or to anion exclusion.
A Simple Method to Evaluate Daily Positive Soil Heat Flux
Authors: Hares M. A. , Ben‐Asher J. , Matthias A. D. , Warrick A. W.
Published: July 2010

Daily positive heat flow into soil is an important component in the energy balance of a soil surface. If surface soil heat flux is assumed to vary diurnally as a sinusoidal function of time, with frequency (ω), the daily positive soil heat flux density can be estimated from 2 ΔTo (λC/ω)0.5 where ΔTo is the amplitude of the diurnal surface temperature wave, λ the thermal conductivity, and C the volumetric heat capacity of the soil. This method of estimation requires the measurement of surface soil temperature at about sunrise and at about mid‐day to determine ΔTo. Also, water content and some soil physical properties need to be known in order to evaluate λ and C. Experimental results obtained with the method were found to be in reasonable good agreement with direct measurements from heat flux plates.
Effect of Raindrop Impact Energy and Water Salinity on Infiltration Rates of Sodic Soils
Authors: Agassi M. , Morin J. , Shainberg I.
Published: July 2010

The effect of water drop impact energy and water salinity on the infiltration rate (IR) of two sodic soils: Calcic Haploxeralf (loess) and Typic Chromoxerert was studied using a rainfall simulation. Rain was applied at two energy levels: high energy rain with kinetic energy of 22.9 J/mm m2 and a low energy rain, with kinetic energy less than 0.01 J/mm m2. In the low energy rain, the initial IR of the soils (44 mm/h) was maintained during a distilled water rain on soils with ESP 2.5, and during saline water rain on soils with ESP values of 6.5 and 17–21.0. In Haploxeralfs with ESP values of 6.5 and 21.0 the final IR (FIR) under low energy rain dropped to 28.8 and 11.5 mm/h respectively. When the same soil and ESP levels were subjected to high energy rain, the FIR during saline water storms dropped to 6–9 mm/h and during distilled water simulated storms the FIR dropped to 0.9–1.4 mm/h. It was concluded, that both the water drop impact energy and the electrolyte concentration in the applied rain have a decisive effect on the IR drop of soils. When the chemical dispersion processes are minimal (low ESP and high water salinity) the mechanical impact of the drops predominate and the crust formation is mainly due to the distintegration of the soil aggregates and their compaction to a thin skin seal. When the soil ESP is high (> 2.5) and the water salinity is low (rain water), chemical dispersion processes have an increasing role in determining the IR of the soils.
Effect of Water Quality and Drying on Soil Crust Properties
Authors: Ben‐Hur M. , Shainberg I. , Keren R. , Gal M.
Published: July 2010

The effect of soil crust and drying on the infiltration rate of Calcic Haploxeralfs (Loess) and Typic Rhodoxeralfs (Hamra) was studied using a rainfall simulator. The soils were exposed first to a rainfall of water with low electrolyte concentration [electrical conductivity (EC) ≃ 0.01 dS.m−1] until a steady state infiltration rate was obtained. Thereafter, the crusted soils were dried for different periods of time (24, 48, 72 and 96 h). After drying, the soils were saturated from beneath with tap water, then subjected to a second storm of either water with low electrolyte concentration (EC ≃ 0.01 dS m−1) or saline water (EC œq 5 dS m−1). Drying the crust increased the infiltration rates of the soil in the second storms, and increased its sensitivity to the salinity of the applied water. The results suggest that drying the crust caused its' breakdown, due to both the formation of cracks and the formation of new structure at the soil surface. Drying the crust brings the soil particles, which form the crust, closer together creating a new structure. The new structure at the soil surface makes the soil surface more permeable and more sensitive to the destructive action of the raindrops.
An Electronic Discriminator to Eliminate the Problem of Horizontal Raindrop Drift
Authors: Gantzer C. J. , Alberts E. E. , Bennett W. H.
Published: July 2010

Raindrops falling through still air drift randomly causing difficulty in collecting uniform soil splash samples from single‐drop detachment studies. We developed a simple electronic discriminator to eliminate this problem that can be used easily with any single drop rainfall tower. The main detector of the discriminator consists of two optical light source‐sensors positioned at right angles in a horizontal plane. These sensors detect and select for use only those drops falling within a 6.4 mm square target window. Labor and materials for constructing the discriminator cost about $400. Two experiments were conducted to test the performance of the discriminator. One study analyzed drop masses collected both with and without use of the discriminator, and compared these quantities with drops collected directly from the drop former. No significant difference in mass between drops collected with the device and those collected directly from the drop former was found. A significant (P<0.01) decrease in drop mass was found without use of the device. The discriminator also decreased drop mass variance about six times. The second experiment measured soil splash from uniformly packed cores of Norbourne fine‐sandy loam (Typic Argiudolls) packed at an average bulk density of 1.35 Mg m−3 and equilibrated to −2 kPa soil water potential. Results show an average splash increase of about 46% (4.2 mg) with use of this device versus without it. Soil splash variance was also reduced by 19%, further confirming that use of the discriminator significantly reduces alterations in drop characteristics, thus insuring against biasing of raindrop kinetic energy versus soil splash relationships.
Solute Discharge During Steady Water Drainage from a Sand Tank
Authors: Mansell R. S. , McKenna P. J. , Hall M. E.
Published: July 2010

An alternating direction implicit (ADI) numerical method was used to simulate transient solute movement resulting from a step‐function increase of solute concentration in water applied to a shallow sand tank system with a subsurface drain. Steady water flow in the saturated portion of the tank was simulated using an iterative alternating direction implicit (IADI) numerical method. The saturated‐unsaturated condition in the actual sand tank was approximated by a smaller rectangular flow region of saturation in the model simulation. Isopleths of hydraulic head and solute concentration within the soil demonstrated a decrease in the rate of infiltration from the point vertically above the drain to the point vertically above the midpoint between the drains. Consequently, solute transport was much faster in the surface soil overlying the drain than in the soil near the mid‐point between drains. When cumulative effluent volume was expressed as the number of pore volumes, breakthrough curves for solute concentration in the drainage water revealed early arrival of solute compared to a one‐dimensional system. In spite of the different boundary conditions imposed at the soil surface in the tank and in the model, reasonable agreement was obtained between simulated breakthrough curves and experimental data from the sand tank.
Cation Exchange Equilibria in Soils Expressed as Cation‐Ligand Complex Formation
Authors: Shaviv A. , Mattigod S. V.
Published: July 2010

A model for representing cation exchange reactions as part of the equilibrium reactions in a soil‐water system is proposed. The exchange reaction in this model is considered to be a composite of two half complexation reactions. These complexation reactions are assumed to occur between the exchanging cations and the negatively charged surfaces considered as hypothetical free ligands. The model was added as a subroutine to the GEOCHEM program which calculates ionic equilibrium in soil water systems. Two formation constants, K′Caf for the Ca‐ligand complex and K′Naf for the Na‐ligand complex were estimated by assuming K′2Naf/K′Caf = KVCa‐Na = 1 in the range 1 > ECa > 0.7. A value of log K′Caf = 2.5 was found to provide the best fit to the relationship between ES = (ENa/(CEC‐ENa)) vs. SAR given by the U.S. Salinity Laboratory Report (1954). The fitted value of K′Caf was used for calculating the K‐ligand formation constant; K′Kt and the Mg‐ligand formation constant, K′Mgr, using the appropriate experimental Vanselow selectivity coefficient. The calculated formation constants corresponding to the cations in a given soil water system were used to predict the distribution of the cations in solution and on the solid phase by means of the GEO‐CHEM program. Good agreement was found for the K‐Ca and Ca‐Mg exchange in soils when comparing experimental data to the ones predicted by the proposed model.
Prediction of Phosphate Sorption in Soils from Regular Solid‐solution Theory
Authors: Blanchar R. W. , Stearman G. K.
Published: July 2010

Potassium dihydrogen phosphate (KP) solutions or monocalcium phosphate (MCP) spot placed solids were reacted with eight acidic Missouri soils. After reacting the solid MCP with moist soil for 30 d, a 1‐g soil to 10‐g water suspension was made. Monocalcium phosphate soil suspensions and similar suspensions made with KP solutions were shaken for 16 d. The pH, Eh, electrical conductivity, Al, Ca, Fe, and P contents of the solutions were measured. It was postulated that P sorption sites were not independent of each other, but were altered by P sorbed at adjacent sites and that P sorption could be considered to behave as predicted for a regular solid‐solution. Observed values of P sorbed (PS) and P in solution were fitted to the following equation derived for a regular solid‐solution system: In P = A + B(PS) + C(PS)2. The data for the eight soils fit this equation with regression coefficients (r2) for KP which varied from 0.97 to 0.99 and for MCP from 0.88 to 0.97. The data were fitted to the linear form of the equation; In P = In Pmax + B′(1‐PS/PSmax)2, and no appreciable curvature was observed. The addition of 200 to 800 mg P/kg to soil as KP resulted in higher concentrations of P in solution than when equal amounts of MCP were added. This effect was attributed to MCP dissolving additional reactants capable of precipitating P. When 100 mg P/kg or less was added the concentrations of soluble P from KP and MCP were similar, except in the Barco soil where the addition of MCP resulted in a higher concentration of soluble P than the addition KP.
Single Column Ion Chromatography: II. Analysis of Ammonium, Alkali Metals, and Alkaline Earth Cations in Soils
Authors: Nieto K. Fitzpatrick , Frankenberger W. T.
Published: July 2010

Single column ion chromatography (SCIC) was evaluated as an effective analytical method for the determination of soluble ammonium, alkali metals, and alkaline earth cations in soil extracts. Eluents chosen for determination of the mono‐and divalent cations were 10 mM nitric acid (pH 2.1) and 5 mM ethylenediammonium dinitrate (pH 6.1), respectively. Separation was carried out on a commercially available, low‐capacity, cation exchange column, with conductimetric detection. SCIC can utilize very small sample sizes (≤ 500 µL), and yields linear, reproducible relationships between peak area and concentration of cations. Simultaneous determination of Li+, Na+, NH+4, and K+ or Mg2+, Ca2+, Sr2+ and Ba2+ was performed in < 7 min with precision ranging from 3 to 8%. Determinations can be made against a background of various ions and organic constituents without interferences. Minimum detectable concentrations of the selected cations using a 500 µL loop were: Na2+, Ca2+, and Mg2+ (0.05 mg/L), Li+ and Ba2+ (0.10 mg/L), NH+4‐N (0.5 mg/L), and K+ and Sr2+ (1 mg/L). Results obtained by SCIC agreed closely with those obtained by other methods: NH+4‐N, steam distillation (r = 0.996***); Na+, atomic emission spectrometry (AES) (r = 0.992***); K+, AES (r = 0.999***); Mg2+, atomic absorption spectrometry (AAS) (r = 0.995***); Ca2+, AAS (r = 0.996***). Simplicity of this method makes it feasible to construct a HPLC instrument dedicated for the analysis of cations.
Effect of Rhizobial Extracellular Polysaccharide on Solution Phosphate Levels of Acid Soils
Authors: Cunningham Scott D. , Munns Donald N.
Published: July 2010

Previous work has shown a positive correlation between the ability of a strain to colonize acidic agar and its production of extracellular polysaccharide (EPS) in solution culture. This paper examines the relationship between EPS production and phosphate levels in solution, determining: (i) the interaction of EPS with an oxide (gibbsite) surface, (ii) the effect of EPS on phosphate sorption, and (iii) the effect of EPS on previously sorbed phosphate. Rhizobial EPS was readily adsorbed onto gibbsite. When EPS was present before the addition of phosphate, both the quantity of EPS and its source significantly influenced the amount of phosphate sorbed. Addition of standard amounts of EPS from different strains to a gibbsite suspension with previously sorbed phosphate produced solution phosphate levels which differed significantly. The pH of the EPS added to the gibbsite‐phosphate suspension was also varied; added EPS decreased solution phosphate levels if the EPS was more acidic than the gibbsite suspension, and increased solution phosphate levels if it was more alkaline. Rhizobium in an acid soil may be able to influence the phosphate level of their immediate micro‐environment through the excretion of extracellular polysaccharide at an appropriate pH.
An Evaluation of Aromatic Fraction in Humic Substances
Authors: Ghosal M. , Chian E. S. K.
Published: July 2010

The fraction of aromatic carbon (AC) present in humic substances was reported to be determined by carbon magnetic resonance (CMR). A second method for determining AC is based on the weights of aromatic degradation products obtained by permanganate oxidation of humics. A correct method of computing AC from such data, not available so far, has been developed. AC values thus calculated are found to be much lower than those determined by CMR. The probable cause for such discrepency may be the presence of rings with low aromaticity, like furans, in the structure of humic substances.
Changes in Soil Carbon and Nitrogen Due to Irrigation Development in Nebraska's Sandhill Soils
Authors: Lueking M. A. , Schepers J. S.
Published: July 2010

Carbon and N parameters were compared for nondeveloped and developed soils (predominantly mixed mesic, Typic Ustipsamments, and sandy, mixed mesic Entic Haplustolls). Soil samples were collected from four developed center pivot irrigation sites and from the nondeveloped corners at depth increments of 0‐ to 75‐, 75‐ to 150‐, and 150‐ to 300‐mm. Total C, total Kjeldahl N (TKN), hydrolyzable N, and mineralizable N by autoclave and by a 112‐d incubation study were determined. Changes in TKN were not significant in the 0‐ to 75‐mm depth, but in the second depth increment, TKN increased with development (507 to 569 kg ha−1). Total C also increased at this depth (5650 to 6400 kg ha−1). The C/N ratio increased with development in the surface 75 mm (11.5 to 12.2). Inorganic N increased in the top 300 mm due to development. Mineralizable N by both techniques increased in the 75‐ to 150‐ and 150‐ to 300‐mm depth increments. Steady state values for ln TKN were calculated to be 6.6, 6.4, and 6.8 kg ha−1 for soil depth increments of 0‐ to 75‐, 75‐ to 150‐, and 150‐ to 300‐mm, respectively. The ln total C steady‐state values were 9.1, 8.8, and 9.1 kg ha−1. In some cases, undeveloped soil contained more N and C than these steady‐state values, suggesting that development tended to decrease the soil test values. If the undeveloped soil was lower in N or C than the steady‐state value, development tended to increase the test value. Total C, TKN, hydrolyzable N, mineralizable N (both techniques), and inorganic soil N were all highly correlated. Changes in TKN and total C were not correlated to landscape position or time since development.
Phytotron Experiments to Evaluate the Effect of Growing Plants on Denitrification
Authors: Haider K. , Mosier A. , Heinemeyer O.
Published: July 2010

The amount and availability of plant rhizosphere carbon deposits and their influence on microbial denitrification in soil are not clearly defined. To evaluate this possibly important facet of fertilizer N loss from agricultural soils a study was conducted to simultaneously quantify the carbon fixed by plants and the fate of fertilizer nitrogen applied to the soil during a plant growing season. Corn (Zea mays) or wheat (Triticum aestivum) was grown in a phytotron under a continuous supply of 14CO2 in 15N fertilized soil. The results of the studies show that denitrification was not stimulated in soils planted with corn or wheat compared to unplanted soil. About 60% of the root biomass carbon could be found in the soil as rhizodeposited carbon at the termination of the experiments. Only 5 to 7% of this carbon was, however, extractable with water or 2 M Na2SO4. This suggests that even though a sufficient quantity of carbon was deposited in the soil by the plants that the carbon was not available for denitrification.
Soil‐Landscape Relationships of a Climax Forest in the Allegheny High Plateau, Pennsylvania
Authors: Aguilar Richard , Arnold R. W.
Published: July 2010

The Tionesta Research Natural Area, located in the Allegheny National Forest of northwestern Pennsylvania, is a unique remnant of the old growth American beech (Fagus grandifolia L.)‐Eastern hemlock (Tsuga canadensis L.) forest that once covered over 2400 ha of the Allegheny Plateau. During a detailed soil survey, the soils occurring on the various landscapes in the area were characterized and the relationships between the vegetation and the soils were evaluated. The development of the landscapes in the Tionesta area has been strongly influenced by the contrasting erodibility of alternating layers of sandstone, siltstone, and shale bedrock. The gentle, regional dip of the bedrock in a southwesterly direction has favored the preferential erosion of the south‐facing slopes. The area experienced a periglacial climate during the Late Wisconsin Glaciation. Evidence of this former cold climate is expressed by colluvial (solifluction) deposits and boulder fields on the ground surfaces of the footslope landscapes. Seven distinct soils occur on the various landscapes. These soils are extremely acid to very strongly acid and high in exchangeable aluminum. Low cation exchange capacity and base saturation reflect the abundance of quartz and other primary minerals which are highly resistant to weathering. Podzolization processes are evident and most pronounced in the coarse‐textured, free‐leaching soils under hemlock stands. Drainage appears to be an overriding soil factor influencing the vegetation patterns on the different landscapes with hemlock dominating the stands in wetter areas. Shade‐intolerant species, such as black cherry (Prunus serotina L.), commonly occur on shallow soils on steep slopes where frequent canopy openings associated with blow‐downs have allowed their establishment.
Chemical and Stubble‐Mulch Fallow Influences on Seasonal Soil Water Contents
Authors: Tanaka D. L.
Published: July 2010

A study was conducted in the northern Great Plains to determine the effect of chemical and stubble‐mulch fallow of a Williams loam (fine‐loamy mixed, Typic Argiborolls) on soil water contents during 14‐and 21‐month fallow periods. Soil water contents to a depth of 1.70 m were measured by use of the neutron‐scatter technique for two 14‐and three 21‐month fallow periods. The amount of surface residue after harvest ranged from 0.6 to 3.6 Mg/ha during the study. Chemical fallow maintained more surface residue than stubble‐mulch fallow, but no significant differences in soil water contents to 1.70‐m soil depth occurred between the treatments. Gain in soil water occurred after harvest and over the first winter with soil water loss generally occurring during summer for 14‐ and 21‐months of fallow. No gain in soil water contents occurred over the second winter when chemically fallowed for 21‐months. Precipitation frequency and distribution may be just as important as quantity and position of surface residue for chemical fallow to effectively store more soil water than stubble‐mulch fallow.
Phosphorus Application Frequency and Sources for Grain Sorghum
Authors: Janssen K. A. , Whitney D. A. , Kissel D. E.
Published: July 2010

A field study was conducted for 8 yr on an initially low soil test P, Woodson silt loam soil (fine, montmorillonitic, thermic Abruptic Argiaquolls) in east‐central Kansas to determine the effectiveness of ortho‐and polyphosphate fertilizers applied annually at 25 kg ha−1, every 2 yr at 50 kg ha−1, and every 4 yr at 100 kg ha−1 for grain sorghum (Sorghum bicolor L.) production. The first year, yield was higher with the larger, less frequent P applications because of the low P status of the soil. Second‐and third‐year yields were not statistically different. The fourth year, when the time span was longest since the every 4‐yr P application had been applied, yield was lower with the every 4‐yr P application compared to annual P. The every 2‐yr P treatment produced intermediate results. Total grain production for the first 4 yr did not differ significantly with the P application frequency treatments. During the second 4 yr, when soil P levels were higher, the P application frequency treatments produced no significant differences in yearly or total yield. The ortho‐and poly‐phosphate P sources, in general, produced similar response applied annually, or at infrequent intervals. These data suggest that there are Argiaquolls in east‐central Kansas on which infrequent P fertilizer applications can perform similarly to annual P applications.
Classification of Soils with Andic Properties from the Oregon Coast
Authors: Baham John , Simonson G. H.
Published: July 2010

Fourteen pedons from three northern Oregon coastal counties were evaluated for their chemical and physical properties for inclusion in the proposed soil order Andisol (Leamy, 1984). Seven pedons were found to meet the criteria for bulk density, aluminum solubility in ammonium oxalate (Alo), depth, and phosphate retention, and were provisionally classified as Udands. Data for four representative pedons with andic properties are presented. Most of the measured Alp/Alo values for the andic horizons were >0.5 (Table 2), indicating that much of the Al is present in the form of humus‐metal complexes. The relatively low values for oxalate‐extractable Si suggest that these soils contain only small amounts of allophane and/or imogolite. These soils are similar to the nonallophanic, humus rich Udands that have been described in northeastern Japan. The proposed classification is discussed with respect to the guidelines presented in the 6th ICOMAND letter (Leamy, 1984).
Comparison of Liquid Retention Curves with Polar and Nonpolar Liquids
Authors: Lenhard Robert J. , Brooks Royal H.
Published: July 2010

Capillary pressure‐saturation data obtained on unconsolidated porous media containing different clay minerals with different liquids are compared to evaluate the effect of clay‐water interactions on liquid retention characteristics. The clay minerals used were a well‐crystallized kaolinite, an illite, and a Ca‐montmorillonite. The wetting fluids were distilled water and a light hydrocarbon, soltrol, which was assumed not to interact with the clays. The hydraulic variables, capillary pressure and saturation, are transformed to account for differences in contact angle, density, and surface tension of the liquids. The liquid retention functions obtained from the different wetting fluids for the kaolinite samples are statistically similar. For Ca‐montmorillonite and illite, the retention functions are statistically different. The explanation for the difference in retention functions for Ca‐montmorillonite samples is the swelling that occurs with water. The difference in retention functions for illite samples can be accounted for by an immobile water layer.
Effects of Manure Amendment on Soil Chemical Properties and Hydrous Oxides
Authors: Miller W. P. , Martens D. C. , Zelazny L. W.
Published: July 2010

Three Virginia soils with low, moderate, and high amounts of Fe and Mn oxides were amended with swine (Sus scrofa L.) manure at a rate of 100 mt ha−1 in an incubation experiment conducted in the laboratory over 29 days. Changes in pH, redox potential (Eh), and forms of Fe and Mn were monitored in order to assess the effect of high rates of manure loading on the chemical properties of these soils. Manure additions caused immediate reductions of 175 to 325 mv in soil Eh by day 4, although Eh recovered to near untreated soil levels by the end of the study. Minimum Eh levels were related to initial Fe and Mn contents of the soils. Soil pH increased to 7 to 8 in all soils, and organic matter contents, initially 25 g kg−1 higher than control soils, decreased as decomposition proceeded. Soil Mn was rapidly solubilized under the reducing conditions present early in the incubation, as shown by increases in soluble, exchangeable, and adsorbed forms of Mn determined by sequential extraction. Reprecipitation of MnO2 occurred in the high‐Mn soil by day 8, as Eh began to recover. Iron was reduced to more soluble forms only in limited amounts in the soils with the high and medium Fe oxide contents, while significant reduction of amorphous Fe oxide was observed in the soil with low oxide content. These results suggest that toxicities of Fe and especially Mn, along with other trace metals associated with these oxides in soils, may result from high rates of organic waste addition to soils where reducing conditions may persist for some time.