bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fractal Scaling of Soil Particle‐Size Distributions: Analysis and Limitations
Authors: Tyler Scott W. , Wheatcraft Stephen W. 
Published: July 2010

AbstractFractal scaling has recently been proposed as a model for soil particle‐size distribution (PSD). In this work, the cumulative number of soil grains greater than a characteristic size, N(R > r), and the cumulative mass distribution, M(r < R), are developed and shown to be proportional to R3‐D and R3‐D, respectively, where r is the grain size, R is a specific measuring scale, and D is the fractal dimension. The cumulative‐number approach to estimate D is shown to be sensitive to the assumed grain density and characteristic size, while the mass distribution is less sensitive to the assumed grain density and characteristic size, and therefore more appropriate for the analysis of field soils. These two models of fractal PSD behavior also constrain the fractal dimension to lie between 0 and 3 for field soils. With constraints on the fractal dimension, soils displaying strict fractal scaling in grain‐size distribution are shown to be a rather small subset of those soils commonly encountered in the field. Earlier work has shown fractal scaling in many soil PSDs with fractal dimensions exceeding 3.0 using the number‐based analysis. The fractal scaling and magnitude of the fractal dimensions found in previous work are shown to be an artifact of the plotting algorithms and assumptions on grain density and size. Although fractal scaling plays an important role in soil water retention and porosity, PSD data alone are not sufficient to fully characterize this scaling.
Evaluation of a Triple Line Source Sprinkler System for Salinity Crop Production Studies
Authors: Aragüés R. , Royo A. , Faci J. 
Published: July 2010

AbstractNumerous line source sprinkler experiments have been described in the literature, but they do not provide an in‐depth analysis of their potential use for salinity crop studies. This work evaluates the advantages and limitations of a triple line source sprinkler system for use in salinity crop tolerance studies. Two outer laterals are used to apply fresh water, while a third lateral centered between them applies saline water. This layout provides duplication of a salinity gradient on each side of the center line while maintaining a uniform application of water. Applied saline water and soil salinity gradients that developed across the laterals on both sides of the center line were correlated (P < 0.001). These gradients were generally linear (P < 0.01) in the 4 yr studied and were not significantly different (P > 0.05) when the laterals were installed parallel to the prevailing wind direction in soils with good infiltration. Soil salinity was uniform at a given distance from the laterals, as indicated by the low coefficients of variation (≤13%) of the electromagnetic sensor readings. Soil salinity increased during the growing season and was higher in the top portion than in the lower portion of the soil profile. This profile distribution was due to limited soil water infiltration. Most of the leaf injury due to foliar absorbed salts was restricted to the lower, older portion of the canopy. This method proves to be useful for salinity crop studies if soils are selected that allow for high leaching fractions, foliar absorption of salts by the crop selected is relatively low, and the system is operated under low wind conditions.
Organic Carbon Distributions in Shallow Soils of Pinyon‐Juniper Woodlands
Authors: McDaniel P. A. , Graham R. C. 
Published: July 2010

AbstractProperties of soils associated with pinyon (Pinus edulis Engelm.)‐juniper (Juniperus spp.) communities of the western USA reflect a mosaic of canopy and interspace environments. This study was initiated to examine the influence of these contrasting environments on organic carbon (OC) distributions and associated soil properties of shallow soils in a pinyon‐juniper woodland of east‐central Utah. The mosaic of interspace and canopy environments results in a complex of soils with two distinct OC distribution patterns. In both interspace and canopy soils, color values and root distributions are related to measured OC. Tree roots are concentrated just above the lithic contact in transitional R/A and Cr/A horizons in all soils. Decay of this root material represents the dominant organic‐matter input to interspace soils, which are essentially devoid of vegetation and lack O horizons. As a result, OC increases with depth and the highest OC contents and darkest soil colors are found in R/A and Cr/A horizons of these soils. Canopy soils also have relatively high OC contents just above lithic contacts but contain maximum OC and darkest soil colors in A1 horizons underlying litter layers. All soils exhibit increases or irregular decreases in OC with depth and have similar distribution patterns for total N and NaHCO3‐extractable P. The OC distribution patterns result in inappropriate classification of some of these shallow upland soils as Fluvents according to the U.S. soil taxonomy.
Moment Method Applied to Solute Transport with Binary and Ternary Exchange
Authors: Leij Feike J. , Dane J. H. 
Published: July 2010

AbstractWhen modeling transport of exchanging solutes in soils, it is sometimes conveniently assumed that the solutes interact linearly with the solid phase of the soil. In this study, an attempt was made to quantify the influence of nonlinear cation exchange on solute spreading with the moment method. Theoretical expressions for the first four moments were derived based on the equilibrium and physical nonequilibrium models of the advection‐dispersion equation (ADE). Displacement experiments were conducted in which either a NaCl pulse (binary exchange) or a pulse of KBr and NaBr (ternary exchange) was applied to a CaBr2‐saturated medium. Values for the transport parameters were determined with moment analysis and curve fitting. The observed breakthrough curves were somewhat better reproduced with parameters obtained from curve fitting than from the moment method. However, the curve‐fitting program produced some unrealistic parameter estimates for the nonequilibrium model. A disadvantage of the moment method was that the fourth‐order moment sometimes yielded unstable results for the nonequilibrium model. Parameters form the anion displacement were used to estimate the theoretical variance due to hydrodynamic dispersion and nonequilibrium spreading for the cation breakthrough curves. The difference between the variance of the observed cation breakthrough curve and these theoretical variances was used as an approximation of the variance due to nonlinear exchange. Particularly for the ternary exchange, the variance due to nonlinear exchange was often several times greater than predicted according to the transport model. The results enabled us to quantify errors in dispersion coefficient (D) values directly determined from cation‐displacement experiments.
Hydrologic Modeling of Protective Barriers: Comparison of Field Data and Simulation Results
Authors: Fayer M. J. , Rockhold M. L. , Campbell M. D. 
Published: July 2010

AbstractProtective barriers, which consist of layers of silt loam over sand and gravel, have been proposed as covers for waste sites located in semiarid south‐central Washington state. The ability of an uncalibrated model to predict water contents, water storage, and drainage in barriers was tested for durations as long as 1.5 yr. Eight nonvegetated lysimeters containing the barrier layering sequence have been monitored since November 1987. The lysimeters were subjected to one of three precipitation treatments: ambient, 2 × average, and breakthrough (i.e., until drainage occurred). Distributions of measured and simulated water contents with depth were similar; maximum differences ranged from 0.023 cm3/cm3 for the ambient treatment to 0.089 cm3/cm3 near the soil‐sand interface for the breakthrough treatment. Simulated storage followed the trend in the measured values, although differences as much as 5 cm were observed at certain times. Generally, the model overpredicted evaporation in the winter and underpredicted it in the summer. Root‐mean‐square errors were 1.47 and 2.21 cm for the ambient and 2 × ‐average treatments, respectively. Sensitivity tests revealed that the hydraulic‐conductivity function, snow cover, and potential evaporation were important to successful modeling of storage in a protective barrier. When the above parameters and processes were adjusted (though not optimized), the root‐mean‐square error for the 2 × ‐average treatment was reduced 63% to 0.81 cm. For the breakthrough treatment, simulated drainage was obtained only by using field‐measured sorption and saturated‐conductivity data. This result indicates that hysteresis is important to successful modeling of drainage through protective barriers.
Microrelief and Rainfall Effects on Water and Solute Movement in Earthworm Burrows
Authors: Trojan M. D. , Linden D. R. 
Published: July 2010

AbstractMacropores have been implicated in preferential transport of water and solutes in soil, but mechanisms of transport are not fully understood. Our objective was to determine the effect of surface microrelief, microlandscape position, and rainfall intensity on water and solute transport in burrows created by the earthworm Aporrectodea tuberculata. Water, Br‐, and dye movements in burrows were determined in buckets packed with Waukegan silt loam (fine‐silty over sandy or sandy‐skeletal, mixed, mesic Typic Hapludoll) and incubated with earthworms. One centimeter of simulated rainfall was applied at intensities of 2, 4, 7, and 10 cm h−1, and an instantaneous application of water. As rainfall intensity increased, less Br‐ and dye were displaced from the soil surface, but displaced Br‐ and dye were distributed more evenly with depth and deeper in the soil. The same percentage of burrows conducted at low and high intensities, indicating that increased volumes of water were transported in conducting burrows as intensity increased. Burrows located at the lowest elevations in surface microdepressions showed deeper staining than other burrows for the instantaneous treatment and for all treatments combined. A small number of burrows were responsible for deep displacement of water and solute for each treatment. Models designed to predict flow in burrows must consider the quantity of water available to a burrow, which is a function of surface position, and flow within a burrow, which is a function of the internal characteristics of a burrow.
Effect of Sorption on the Biodegradation of Quinoline
Authors: Smith S. C. , Ainsworth C. C. , Traina S. J. , Hicks R. J. 
Published: July 2010

AbstractQuinoline is an N‐containing heterocyclic contaminant associated with creosote wastes and may be biologically degraded under aerobic and anaerobic conditions. Quinoline‐degrading bacteria were utilized to investigate the rate of quinoline desorption from smectite clay at low surface concentrations and its subsequent mineralization. Fluorescence spectroscopy and 14C‐quinoline mineralization techniques were used to compare the observed desorption rates to mineralization rates. Microbial utilization was desorption‐rate limiting. Desorption and microbial utilization may be modeled as pseudo‐first‐order reactions whose first‐order rate constant (kobs) is independent of surface concentration. The difference between quinoline disappearance from solution and from the clay surface as observed by fluorescence spectroscopy was comparable to the difference between microbial utilization of the solution and the surface‐bound species. The utilization of quinoline from solution was about 30 times more rapid than surface‐bound quinoline. The surface‐bound species appeared to be protected from microbial attack and, hence, desorption was required prior to utilization. The desorption process is suggested to be a chemical‐reaction‐controlled process rather than film diffusion controlled, as is typically suggested for an exchange process. The biotransformation of quinoline to 2‐hydroxyquinoline, observed in solution by fluorescence spectroscopy, was about five to eight times faster than the subsequent disappearance of 2‐hydroxyquinoline. When quinoline was sorbed, however, no 2‐hydroxyquinoline was observed in solution or on the surface of the clay. It is suggested that quinoline may be transformed to 2‐hydroxyquinoline at the cell surface and that 2‐hydroxyquinoline is the species that is transported into the cell prior to further degradation.
Ameliorating Chlorosis‐Inducing Soils with Rock Materials of Varying Porosity and Iron Content
Authors: Clemens Gerhard , Singer Arieh 
Published: July 2010

AbstractLime‐induced chlorosis is a severe problem, affecting many crops in arid‐ and semiarid‐zone soils. Applications of Fe chelates are expensive and only effective in the short term. The ameliorating effects of rock materials on three chlorosis‐producing calcareous soils from Israel were determined in pot tests and in the field. Chlorophyll concentrations of peanut plants (Arachis hypogaea L.) grown in pots with additions of up to 15% (v/v) pumice or tuff‐lapilli to the soils were compared with controls and Fe‐ethylenediaminedihydrochloric acid (EDDHA) treatments. Additions of 10% (v/v) tuff‐lapilli were more effective than those of pumice in small‐pot tests of all three soils. Positive effects persisted for a second growth period. In large‐pot tests, only 15% (v/v) additions were effective in two soils. In field tests, the three soils were treated with pumice or tuff‐lapilli (10% v/v) or basalt powder (5.5% w/w). Basalt powder was the most effective in raising chlorophyll concentrations to levels similar to or greater than those obtained from Fe‐EDDHA. Basalt powder was also the most effective in increasing pod and hay yields on two soils. Also, basalt appeared to have long‐term effects. Only where chlorosis was not severe and where poor aeration appeared to be an additional factor were the effects of tuff‐lapilli and pumice equal or even superior to those of basalt powder. On two soils with severe chlorosis, addition of porous, Fe‐poor materials had no effect. Either because the soils were well aerated or because CO2 production was low, CO2 in the soil air was low and not a major factor determining HCO3‐ in water extracts.
Redox Processes and Diagnostic Wetland Soil Indicators in Bottomland Hardwood Forests
Authors: Faulkner S. P. , Patrick W. H. 
Published: July 2010

AbstractThe presence of unique hydrologic, vegetative, and soil characteristics separates wetlands from nonwetlands. The hydrophytic nature of bottomland hardwood forest vegetation emphasizes soil and hydrologic parameters that are often inferred from soil profile characteristics. Our objectives were to determine the relationships among hydroperiod, soil redox processes, and diagnostic wetland soil indicators. Five transects traversing nonwetland, transitional, and wetland habitat were established parallel to the natural moisture gradient in alluvial bottomlands with mature hardwood forest overstory in Louisiana and Mississippi. Soil redox potential and O2 content at 15, 30, 60, and 120 cm were monitored monthly from September 1982 to August 1985 with permanently installed equipment. Water‐table depth in the upper 120 cm of the soil was also measured during this time. Oxygen and redox patterns at 30 cm were analyzed for each site. These patterns were conclusive enough to classify five sites as nonwetland and eight sites as wetland; however, additional data (hydric soils, soil profile descriptions) were needed to delineate the remaining 11 sites. The quantitative data supported the qualitative diagnostic wetland soil indicators, hydrologic regime, and wetland status of 18 of the 24 sites. Bottomland hardwood wetlands in the lower Mississippi River Valley that are seasonally inundated may be oxidized and aerobic throughout the root zone for 60 to 80% of the growing season. Many bottomland hardwood soils would be considered hydric by the current wetland delineation procedure. Hydrology is the determining factor for these sites and proper assessment of the current hydroperiod is critical.
Alfalfa Emergence and Survival Response to Irrigation Water Quality and Soil Series
Authors: Bauder J. W. , Jacobsen J. S. , Lanier W. T. 
Published: July 2010

AbstractIrrigation with saline‐sodic water has increased in the northern Great Plains, due to development of marginal soils and extended drought in the region. A greenhouse study was conducted to determine the effect of irrigation water salinity and sodicity on alfalfa (Medicago sativa L.) seedling emergence and mortality in soils with differing textures. Emerged, live seedlings (designated as percent live seedlings, i.e., percentage of planted seeds that developed into emerged seedlings) were counted at 2‐day intervals for 20 d in a randomized block, 3 × 3 × 3 factorial experiment (irrigation water salinity × Na adsorption ratio × soil series). Total dissolved solids (TDS) concentration of irrigation water was maintained at 0.75, 1.15, and 1.65 g L−1 (−4.2 × 10−2, −6.5 × 10−2, and −9.3 × 10−2 MPa osmotic potential); sodium adsorption ratio (SAR) was maintained at 1.1, 5.1, and 9.6. Two supplemental studies of similar design were conducted to determine water quality and soil effects independently on seedling survival. Irrigation water quality treatments caused the percent live seedling counts to be lower than for distilled water. Little seedling mortality occurred. Irrigation with distilled water had a negative effect on germination and emergence in all three soils, but did not increase seedling mortality after germination. Soil series and preplant TDS‐SAR of the soil had the greatest effect on survival. Irrigation water TDS significantly affected seedling emergence among soil series. Emergence ranged from 65 to 85%, with the highest emergence occurring in the coarse‐textured soil irrigated with the lowest TDS‐SAR water. Mortality ranged from 25 to 45%, with the greatest survival occurring in the fine‐textured soil and intermediate TDS‐SAR combinations. Emergence and mortality were high on well‐drained soils irrigated with high TDS and high SAR water. Results of this study indicate that pre‐emergence alfalfa seedbed irrigation should be (i) limited to well‐drained soils with low indigenous salinity and sodicity, and (ii) confined to periods when salinity and sodicity of irrigation water are lowest.
Soil and Environmental Effects on Urease Inhibition by Ammonium Thiosulfate
Authors: Sullivan D. M. , Havlin J. L. 
Published: July 2010

AbstractSoil urease inhibition by ammonium thiosulfate [ATS, (NH4)2S2O3 12‐0‐0‐26S] in fluid fertilizer mixtures with urea‐ammonium nitrate (UAN, 32‐0‐0) has been demonstrated for a limited number of soils. The objectives of this study were to (i) identify soil properties affecting ATS efficacy, (ii) measure ATS effects on gaseous NH3 losses, (iii) evaluate the effects of soil moisture and temperature on ATS efficacy, and (iv) measure the S species present after application of UAN + ATS. Urea hydrolysis inhibition by ATS ranged from 18 to 48% in eight Kansas soils varying in pH, clay, organic C, and carbonate content in an incubation at 20 °C and −0.1 MPa soil matric potential. Ammonia loss was significantly reduced in seven of the eight soils tested (48% in four noncalcareous soils and 22% in three calcareous soils). Urea‐hydrolysis inhibition averaged 29% at 20°C and 37% at 30°C; inhibition averaged 28% at −0.03 MPa and 38% at −0.1 MPa. Tetrathionate (S4O2‐6) was the dominant S anion produced by S2O32‐ oxidation, ranging from 17 to 88% of the applied S. The amount of S4O2‐6 present was not significantly correlated with the degree of ureahydrolysis inhibition. Ammonium thiosulfate inhibited urea hydrolysis in all soils; its efficacy was greatest for soils low in clay and organic C at high temperatures and low soil moisture contents.
Modeling the Transport and Retention of Cadmium in Soils: Multireaction and Multicomponent Approaches
Authors: Selim H. M. , Buchter B. , Hinz C. , Ma L. 
Published: July 2010

AbstractA major challenge in modeling the mobility of solutes in soils is to take into account the time‐ dependent retention of reactive solutes in a transport model that can be evaluated by independent experiments. The kinetics of retention and transport of Cd in two soils were investigated in this study. Time‐dependent batch experiments were carried out to describe the extent of Cd sorption by two soils. Miscible‐displacement experiments were conducted to quantify Cd transport in soil columns that received single and multiple Cd pulses. A multi‐reaction convective‐dispersive transport model inadequately predicted effluent concentrations for both soils when independently measured parameters of retention‐release rate coefficients were obtained from batch data sets. We developed a multicomponent approach that accounts for reversible and irreversible Cd retention during transport in soils. Retention mechanisms considered include instantaneous equilibrium ion exchange and a specific sorption process that was based on a second‐order (Langmuir) kinetic reaction. The multicomponent model adequately predicted the observed breakthrough results. The use of kinetic ion exchange and specific sorption for irreversible retention provided improved overall predictions of the results. Parameter values used for the rates of specific sorption (kt) and that for kinetic ion exchange (α), which provided improved predictions for single‐pulse applications, were similar to those used for multiple‐pulse applications. This finding was consistent for both soils and was considered to add credence to our multicomponent model.
Shrinkage of Bare and Cultivated Soil
Authors: Mitchell Alan R. , van Genuchten M. Th. 
Published: July 2010

AbstractThe surface subsidence of shrink‐swell soils may be used to estimate the soil profile water content and soil behaving. Roots are known to affect cracking patterns by anchoring the soil mass, thus influencing soil shrinkage. Our hypothesis was that plant roots will influence soil shrinkage measured by vertical surface subsidence. We tested this hypothesis by measuring shrinkage in a large weighing lysimeter for bare soil with no root system and for soils under wheat (Triticum turgidum L.) and alfalfa (Medicago sativa L.) crops possessing fibrous and tap root systems, respectively. The volume‐loss shrinkage curves for both bare and cultivated soil were found to conform to the straight‐lines model, with distinct changes in shrinkage zones, in spite of uneven water‐content distributions in the profile. The shrinkage characteristic (i.e., the differential change in bulk volume divided by the change in volume water) was greater for fallow (0.677) than for wheat (0.380) and alfalfa (0.377), with the cultivated conditions being similar. These data suggest that plant roots may have large effects on in situ soil shrinkage rates and the water‐content zones throughout which they occur. This result means that a soil's shrinkage characteristic may change depending on the cropping condition. It also means that shrinkage measurements from soils without rooting systems (e.g., small cores or clods) are not necessarily representative of actual shrinkage properties observed in the field.