bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetic Analysis of Net Nitrogen Mineralization in Soil
Authors: Juma N. G. , Paul E. A. , Mary B. 
Published: July 2010

AbstractStudies 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

AbstractRubidium 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

AbstractGrowth 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

AbstractVegetation 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

AbstractSubsoiling 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

AbstractThe 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

AbstractGrowth 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

AbstractA 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

AbstractDaily 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

AbstractThe 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

AbstractThe 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

AbstractRaindrops 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

AbstractAn 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

AbstractA 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

AbstractPotassium 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

AbstractSingle 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.