bluuebunny/crossref_metadata_2025_split huggingface dataset:
Estimating Generalized Soil‐water Characteristics from Texture
Authors: Saxton K. E. , Rawls W. J. , Romberger J. S. , Papendick R. I. 
Published: July 2010

AbstractSoil‐water potential and hydraulic conductivity relationships with soil‐water content are needed for many plant and soil‐water studies. Measurement of these relationships is costly, difficult, and often impractical. For many purposes, general estimates based on more readily available information such as soil texture are sufficient. Recent studies have developed statistical correlations between soil texture and selected soil potentials using a large data base, and also between selected soil textures and hydraulic conductivity. The objective of this study was to extend these results by providing mathematical equations for continuous estimates over broad ranges of soil texture, water potentials, and hydraulic conductivities. Results from the recent statistical analyses were used to calculate water potentials for a wide range of soil textures, then these were fit by multivariate analyses to provide continuous potential estimates for all inclusive textures. Similarly, equations were developed for unsaturated hydraulic conductivities for all inclusive textures. While the developed equations only represent a statistical estimate and only the textural influence, they provide quite useful estimates for many usual soil‐water cases. The equations provide excellent computational efficiency for model applications and the textures can be used as calibration parameters where field or laboratory soil water characteristic data are available. Predicted values were successfully compared with several independent measurements of soil‐water potential.
The Temperature Dependence of Isothermal Moisture vs. Potential Characteristics of Soils
Authors: Nimmo J. R. , Miller E. E. 
Published: July 2010

AbstractA method has been developed for rapid, transient measurement of hysteretic soil‐moisture characteristics as a function of temperature. While a varying soil‐water pressure was imposed on a thin sample by means of flexible membranes held in firm contact with the soil, water content was measured by gamma‐ray attenuation, and matric potential was measured with tensiometers. The applied pressure was cycled through a program designed to obtain hysteretic θ(ψ) main and scanning curves. Isothermal characteristics were measured for 181‐µm glass beads, Plainfield (Typic Udipsamments) sand, and an undisturbed core of Plano (Typic Argiudolls) silt loam at several temperatures in the 4° to 50°C range. At each temperature the measurements included main drying and wetting curves covering the θ range from 0.30 to 0.05 m3 water/m3 for glass beads, 0.30 to 0.17 for sand, and 0.45 to 0.37 for silt loam. A model has been developed to quantify the temperature dependence as a function of θ. Combined with an isothermal hysteresis model of Mualem, this model requires only three characteristic functions to represent all hysteretic θ(ψ) curves for a given medium at all temperatures. Model calculations for the sand and silt loam data indicate that except near saturation, the temperature effect is greater than can be accounted for by the temperature dependence of the surface tension of pure water. The results rule out several possible explanations but they support the hypothesis that the concentration and effectiveness of dissolved surfactants increases with temperature.
Heat and Moisture Transfer in a Partly Frozen Nonheaving Soil
Authors: Kung Samuel K. J. , Steenhuis Tammo S. 
Published: July 2010

AbstractThe purpose of this research was to develop a computer model to simulate water and heat movement in the soil under freezing conditions. The model was based on the theory of coupled heat and mass transport, which was derived from the theory of irreversible thermodynamics. A finite difference scheme was used to solve the coupled‐fluxes equations in space. The difference scheme used only first‐order derivatives to facilitate the simulation of steep gradients of hydraulic potential at the freezing front. The simulated results were compared against two sets of laboratory experiments in which soil columns were suddenly cooled below freezing at one end. Thermal and hydraulic soil properties used in the simulation model were either obtained from independent measurements on the soil or by well‐established estimating procedures. The simulated results agreed well with the observed values in the first experiment, and in the second experiments the simulated data followed the trend, but a too low ice content was predicted and the freezing front prediction lagged behind. Overall it seems that although the model in its present form is limited to nonheaving conditions, the theory of irreversible thermodynamics is a promising approach to simulate heat and moisture transfer in partly frozen soils.
Temporal Variability of Soil Hydraulic Properties with Wetting and Drying Subsequent to Tillage
Authors: Mapa R. B. , Green R. E. , Santo L. 
Published: July 2010

AbstractModeling of water movement in soils requires mathematical representation of hydraulic conductivity and water retention functions. Hydraulic properties of soils are expected to vary over time during a cropping cycle, especially soon after tillage. Field experiments were conducted on two soils, a Typic Torrox and a Vertic Haplustoll, to evaluate the effect of soil deformation from repeated wetting and drying on soil properties such as hydraulic conductivity, sorptivity, and the water content‐suction relationship. Hydraulic conductivity near saturation was the most sensitive measure of temporal changes of hydraulic properties, decreasing 100‐fold with wetting and drying after tillage. Sorptivity measured with negative head, a simple and rapid method, was also sensitive to temporal changes and was judged the most appropriate for variability studies requiring a large number of samples. The impact of temporal changes in hydraulic functions on soil‐water movement was demonstrated by a comparison of water content profiles predicted with a simulation model using input functions obtained before and after irrigation.
Kinetics of Calcite Precipitation in the Presence of Water‐soluble Organic Ligands
Authors: Inskeep William P. , Bloom Paul R. 
Published: July 2010

AbstractThe rate of precipitation of calcite is an important geochemical process which can influence the saturation state of natural waters with respect to pure calcite. The present study was established to determine the influence of water‐soluble soil organic ligands on the rate of calcite precipitation. A reproducible seeded growth method was used to measure the rate constant for calcite precipitation at pH = 8.4 and 25°C, in the presence of varying amounts of total soluble organic carbon (CTS) added as a water‐soil extract (WSE) or Seward fulvic acid (FA). The rate equation which described the rate of calcite precipitation in the present experiments was: R = kfs γ22 ([Ca2+][CO2‐3]‐Ksp γ‐22), where R = rate of calcite precipitation (mol L−1s−1), kf = precipitation rate constant (L2 mol−1m−2s−1), s = surface area of calcite seeds (m2L−1), γ2 = divalent ion activity coefficient, brackets represent concentrations (mol L−1), and Ksp is the solubility of pure calcite at 25°C. Rate constants decreased to zero in the presence of 0.15 mM and 0.028 mM CTS added as the WSE and FA, respectively. The organic C surface coverage on the calcite seeds corresponding to complete inhibition of calcite precipitation was 90 and 30 atoms C nm−2 for the WSE and FA, respectively. The efficacy of inhibition of calcite precipitation in the presence of soluble soil organic matter explains why many natural waters, including soil solutions of Calciaquolls, are oversaturated with respect to pure calcite. Soluble polymeric carbon constituents which adsorb onto potential calcite seeds, render these surfaces inactive as sites for crystal growth.
Competitive Coefficients for the Adsorption of Arsenate, Molybdate, and Phosphate Mixtures by Soils
Authors: Roy W. R. , Hassett J. J. , Griffin R. A. 
Published: July 2010

AbstractThe adsorption behavior of anionic mixtures (binary‐solute combinations of arsenate, molybdate, and phosphate) by three soils (Cecil clay [Typic Hapludults], EPA‐14 [Ultisol], and Catlin silt loam [Typic Argiudolls]) was investigated using the Sheindorf‐Rebhun‐Sheintuch (SRS) equation. The SRS equation is a multicomponent Freundlich‐type adsorption equation. Most of the isotherm data were found to conform to linear SRS expressions, making it possible to derive competitive coefficients on a concentration basis for each binary‐solute system. The adsorption of arsenate and molybdate by all three soils were significantly reduced by the presence of phosphate, which was attributed to competitive interactions. In each solute‐soil system, the adsorption of phosphate was not greatly suppressed by either arsenate or molybdate. The adsorption of arsenate by Cecil clay and EPA‐14 was reduced in the presence of molybdate, whereas arsenate did not compete strongly with molybdate adsorption. In contrast, the adsorption of arsenate by Catlin appeared to be independent of molybdate, while the presence of arsenate lowered molybdate adsorption. In general, the associated competitive coefficient for each solute‐soil system appeared to be consistent with qualitative observations, and was viewed as a single‐valued term indicative of the relative affinity of each soil for a given anion with respect to a competing anion from a binary‐solute mixture.
Soil Nitrogen Availability after Long‐term Continuous No‐tillage and Conventional Tillage Corn Production
Authors: Rice C. W. , Smith M. S. , Blevins R. L. 
Published: July 2010

AbstractSeveral short‐term studies of no‐tillage (NT) vs. conventional tillage (CT) have suggested that N availability is lower in NT. Less is known about the long‐term effects of NT on soil processes and N availability. Recent observations of a NT vs. CT experiment, initiated in 1970 on a Maury silt loam (Typic Paleudalfs), are presented here. During the first 9 yr of this study corn (Zea mays L.) yields with no N fertilizer were consistently greater in CT than NT, but at high N rates yields were approximately equal. Since 1979, there have been no consistent differences between the tillage systems with regard to yield without N or in relative response to N. Inorganic soil N during 1981 and 1982 was usually equal but occasionally greater in NT compared to CT, in contrast to previous observations during the early years of this experiment. Soil N mineralization was estimated in 1982 by a laboratory soil core incubation technique and by observing dilution rates of labeled N added to field microplots. Both of these approaches suggested that N mineralization was at least as great in long‐term NT plots as in long‐term CT plots. We suggest that the lower availability of N frequently observed in NT soils, in some cases can be a transient effect. In this experiment availability of soil N in NT apparently approached that of CT after approximately 10 yr.
Amelioration of an Acid Soil Profile through Deep Liming and Surface Application of Gypsum
Authors: Sumner M. E. , Shahandeh H. , Bouton J. , Hammel J. 
Published: July 2010

AbstractHighly weathered soils in the southeastern USA often have very acid, hard, infertile subsoils not readily penetrated by crop roots. An experiment on a Typic Hapludult involving deep liming, subsoil disturbance and mixing, and surface application of gypsum was conducted to investigate the possibilities of ameliorating such subsoils. Results with alfalfa (Medicago sativa L.) over 4 yr show that liming to 1 m can increase yields by 50% while merely mixing the subsoil without lime incorporation resulted in a substantial yield decline. Surface application of gypsum with sufficient time for it to penetrate the subsoil resulted in 25% yield increases. Deep liming resulted in the complete precipitation of soluble Al and increased the level of soluble Ca allowing roots to freely penetrate the subsoil. Gypsum resulted in a progressive reduction in soluble Al and an increase in soluble Ca creating a similar but lesser effect than liming. Water extraction patterns corroborated the fact that roots were penetrating chemically ameliorated subsoil. Saturation extract studies indicated that gypsum reduced the activity of Al3+ and increased that of Ca2+ substantially. These results suggest that by‐product gypsum from phosphate acid manufacture would be a feasible amendment for acid subsoils.
Silicon Fertilization of Rice on Everglades Histosols
Authors: Snyder G. H. , Jones D. B. , Gascho G. J. 
Published: July 2010

AbstractRice (Oryza sativa L.), one of the world's most widely grown grain crops, is seldom grown on Histosols, in part because of many problems related to plant nutrition. Studies were conducted on Terra Ceia muck (Typic Medisaprists) in the Everglades to determine the effect of calcium silicate slag on ‘Lebonnet’ rice production. Grain yields were increased in excess of 30% in each of 3 yr by preplant application of slag at 10 Mg ha−1 or more. Rice in plots receiving slag had greater height, greater number of panicles per square meter, heavier grains, and less disease. Although the slag contained a number of plant nutrients, Si appeared to be the factor most responsible for the observed results. A positive linear relationship was observed in all years between straw Si and grain yield. First crop straw averaged 1.3, 5.0, and 5.9 dag Si kg−1 in plots receiving 0, 10, and 20 Mg slag ha−1, respectively. A first crop straw Si concentration <3.0 dag Si kg−1 was associated with reduced rice yield. Perhaps Si application should be considered in other regions when difficulties are encountered with rice production on Histosols.
Organic Carbon in Montana Soils as Related to Clay Content and Climate
Authors: Sims Z. R. , Nielsen G. A. 
Published: July 2010

AbstractData describing 130 A horizons were extracted from the Montana Soil Pedon Database to determine whether there is a relationship between soil clay content and organic C. All sites sampled had either frigid or cryic temperature regimes. The pedons were grouped according to land use, soil classification, temperature regime, and horizon position. Correlations between organic C and clay content were not significant for any group. Apparently clay content has much less influence on organic C accumulation in cool soils of Montana than it does in warmer soils of the southern Great Plains. In Montana, organic C content is better predicted by elevation and mean annual precipitation. The r value for a multilinear regression equation using these variables was 0.88.
Differentiation of Closely Related Xerolls that Support Different Sagebrush Plant Communities in Nevada
Authors: Nettleton W. D. , Brasher B. R. , Spencer E. L. , Langan L. N. , Peterson F. F. 
Published: July 2010

AbstractWe studied 20 pedons and four composite A horizon samples in the Tuscarora Mountain Area in northern Nevada in an effort to differentiate between two morphologically similar Xerolls (Donna and Stampede series) that support strongly contrasting kinds of sagebrush (Artemisia sp.) plant communities. We found no differences between surface horizons by laboratory analyses, but there are significant differences between the soils in clay content of AB, BA, and Bt horizons and in most related properties such as linear extensibility, cation exchange capacity, and 1.5‐MPa water. Thickness of the A horizon has the highest utility as a mapping criterion for the Donna and Stampede soils. Water retention difference between 0.03 and 1.5 MPa and depth of rooting best explain the differences in kind and amount of vegetation found on the two soils.
Measuring Sediment Movement at Low Erosion Rates Using Cesium‐137
Authors: Lance J. C. , McIntyre S. C. , Naney J. W. , Rousseva S. S. 
Published: July 2010

AbstractNew and innovative methods for measuring soil loss and its impact on productivity are needed to accurately assess the value of soil lost by erosion. Cesium‐137 (137Cs), a radionuclide from nuclear weapons tests which is strongly adsorbed to clay, can be used to trace sediment movement. Measurements of 137Cs concentrations in uneroded soils across the southern United States indicated that the 137Cs input was proportional to the average annual precipitation. Distribution of 137Cs within the profile was related to soil properties rather than to rainfall. Cesium‐137 measurements on a small native grass watershed in Oklahoma showed considerable spatial variability in the 137Cs concentrations, but the variability was random and was not correlated with changes in slope. Cesium‐137 concentrations measured on a 10‐m grid in an adjacent small watershed that had been cultivated for 8 yr showed differences with slope positions even though only 17.8 Mg/ha sediment had been removed from the watershed during an 8 yr measurement period. Also, 137Cs concentrations in the cultivated watershed were significantly lower than in the uncultivated watershed. These data show that 137Cs measurements can be used at low erosion rates if enough samples are analyzed. Further research is needed to determine the number of samples needed for different watersheds and to refine the method.
Foliar and Soil Tests for the Prediction of Phosphorus Response in Loblolly Pine
Authors: Wells C. G. , Craig J. R. , Kane M. B. , Allen H. L. 
Published: July 2010

AbstractLoblolly pine (Pinus taeda L.) fertilization studies in the southeast USA were used to relate tree growth response to soil tests and foliar analyses data. In the Lower Coastal Plain, a needle P concentration of 0.80 g kg−1 and less indicated a severe P deficiency, and 5‐yr height growth increased by 50 to 140% after fertilization of young stands with 50 kg P ha−1. Stands with foliar P from 0.80 to 1.0 g kg−1 generally responded 15 to 50% in height growth to fertilization. Height and volume response to P fertilization in the Upper Coastal Plain and Piedmont were not correlated to P concentration of needles. Soil drainage class of the Lower Coastal Plain was useful in separation of soils responsive and unresponsive to P. Loblolly pine growth on 12 of 13 very poorly and poorly drained soils was stimulated 15% or more by P fertilization, whereas this level of response was found on only two of 11 better drained soils. Soils influenced by phosphatic deposits and previous P application should be excluded when using drainage alone as an indicator of P responsiveness. Total soil acidity separated P responsive and unresponsive soils in the Lower Coastal Plain. Where total soil acidity was 5 cmol (+) L−1 and less, height response to P fertilization varied from 15 to 138%. Extractable P as measured was not useful. A maximum volume response of 30% was obtained from P fertilization in the Upper Coastal Plain. When Mehlich 1 extractable P of the 0‐ to 20‐cm depth was <3 mg L−1 the 5‐yr volume response generally was from 14 to 30%. Improved separation of P‐responsive stands appeared possible by using soil acid saturation and pH. As acid saturation increases and pH decreases, the response to P fertilization tends to increase. Phosphorus response in the Piedmont ranged from a negative 19 to positive 21% and no relationship was found for prediction of response within the range of 2 to 6 mg L−1 of Mehlich 1 extractable P.
Soil Response to Trampling Under Intensive Rotation Grazing
Authors: Warren S. D. , Nevill M. B. , Blackburn W. H. , Garza N. E. 
Published: July 2010

AbstractThe impact of short‐term, high intensity livestock trampling on selected properties of a silty clay soil was determined at the Texas Agriculture Experiment Station located near Sonora, TX. Intensive livestock trampling typical of multi‐pasture rotational grazing systems had a negative impact on soil physical properties. The deleterious effects tended to increase as stocking rate increased. Trampling on dry soil caused disruption of naturally occurring aggregates and compaction of the surface soil layer. Trampling on moist soil deformed existing aggregates and led to the creation of a flat, comparatively impermeable surface layer composed of dense, unstable clods.
Backtitration Technique for Proton Isotherm Modeling of Oxide Surfaces
Authors: Schulthess C. P. , Sparks D. L. 
Published: July 2010

AbstractBatch potentiometric titration analyses were made on a γ‐Al2O3 colloidal suspension and interpreted in terms of the electroneutrality principle. Three titration methods involving a singular reference curve were compared. The first reference used was theoretical, the latter two were representative supernatant curves: an electrolyte solution, and an aliquot of the zero point of titration (ZPT) supernatant. All three methods resulted in similar charge isotherms and a zero point of charge (ZPC) = 8.60. A fourth titration method was developed involving each supernatant of the batch titration sample to act as a unique reference. This latter method is a backtitration technique which accounts for all sources that also consume H+ ions, leaving the difference to be the adsorbed proton concentration only. The NaClO4 electrolyte solution used is postulated to be adsorbed with competitive cation and anion exchange mechanisms with a point of zero salt effect (PZSE) = 7.50.
Nitrogen Mineralization Kinetics with Different Soil Pretreatments and Cropping Histories
Authors: Beauchamp E. G. , Reynolds W. D. , Brasche‐Villeneuve D. , Kirby K. 
Published: July 2010

AbstractA laboratory study was conducted to determine how soil pretreatment (air‐drying, freezing, and field‐moist) and cropping history affects the kinetics of N mineralization. Although most researchers suggest that net N mineralization behaves according to first order kinetics, some have suggested that this process is better described with zero order kinetics. It was hypothesized that the air‐drying pretreatment may be largely responsible for an N mineralization pattern which may be described by first order kinetics. Experimental data showed that net N mineralization followed a first order kinetics pattern regardless of pretreatment. However, the air‐drying pretreatment enhanced N mineralization during the first 7 d of incubation. The traditionally used first order kinetics model (Model I) was extended to take into account an “easily” mineralized N fraction (Ne) mostly released during the first 7 d of incubation. This amended model (Model II) generally provided a much better fit to the experimental data, especially for the air‐drying pretreatment. As a result of the flush of mineralized N during the first 7 d, the total quantity of N released with air‐drying was considerably greater than with the freezing or field‐moist pretreatments. Organic N was released in a linear manner over the 42‐d incubation period and comprised about 10% of the total N released. Since this organic N would probably be mineralized, the total N leached was used to determine mineralizable N values (No) and rate constants (k). Mineralizable N values for bromegrass (Bromus inermis) and alfalfa (Medicago sativum) soils were generally higher than those for corn (Zea mays L.) whereas cropping history had no apparent effect on the k value. There were no significant effects of soil pretreatment on No or k values produced with Model II whereas differences occurred with Model I.