bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evaluation of Potassium Quantity‐Intensity Relationships by a Computer Model Employing the Gapon Equation
Authors: Evangelou V. P. , Karathanasis A. D. 
Published: July 2010

AbstractThe influence of cation exchange selectivity coefficients on quantity‐intensity (Q/I) relationships of soil systems was evaluated by the Gapon equation. Computer simulations of potassium Q/I plots revealed that the linear potential buffering capacity for K+ (PBCK), when exchangeable K+ constitutes a minor portion of the CEC, depends on the magnitude of the soil CEC and the Gapon exchange selectivity coefficient (KG). This dependency is valid only if the Q/I plot is directly K‐(Ca + Mg) interaction dependent. Upon increasing the CEC and KG, PBCK increases since PBCK = CEC KG. At low KG values the CEC has a lesser influence on increasing the PBCK, and at low CEC values the KG has a smaller influence on the magnitude of the PBCK. The PBCK is also inversely related to soil K‐loading but the influence of K‐loading on the magnitude of PBCK, appears to be important only when exchangeable K+ represents a significant portion of the CEC. The influence of K‐loading on the magnitude of PBCK, however, appears to be considerable only at K‐loading values much higher from those encountered in most agricultural soils. These findings are supported by data available in the literature.
Coastal Plain Soils of Southeastern Nigeria: I. Morphology, Classification, and Genetic Relationships
Authors: Lekwa G. , Whiteside E. P. 
Published: July 2010

AbstractFourteen pedons developed within the Coastal Plain Sands of southeastern Nigeria were investigated. Laboratory studies included particle size distributions on all pedons plus <0.2‐µm clay, pH, organic C, total N, cation exchange capacity, exchangeable bases, and extractable Al on nine of them. X‐ray analyses of selected clay samples and micromorphologic studies of thin sections of some horizons were also made. Exchangeable bases and base saturation percentages were low for these deeply weathered soils and they had low cation exchange capacities. X‐ray diffraction analyses of clay indicated the predominance of kaolinite. In most of the selected soils isotic and undulic plasmic fabrics characterized the micromorphology, indicating relatively advanced weathering stages. Ferri‐argillans were occasionally observed in the deeper horizons in accord with their higher clay and Fe2O3‐d contents (see part II, this issue). Litho‐, topo‐, climo‐ and possible chronosequences of soils were proposed. Biosequences were not clearly evident. Classification according to the U. S. Soil Taxonomy system indicated that most of the pedons were Ultisols (fine‐loamy or coarse‐loamy) with one Dystropept (coarse‐loamy) and one Tropaquod (sandy). Typic Paleustults (fine‐loamy) represented most soils on the higher (older?) physiographic surfaces. Three Typic Paleudults (fine‐loamy), an Arenic Paleudult (coarse‐loamy), a Typic Paleaquult (coarse‐loamy), and a Typic Tropaquult (fine‐loamy) were found on lower land surfaces nearer the coastline. All pedons are in siliceous, isohyperthermic families. Most of the well‐drained soils were found to be Dystric Nitosols according to the FAO/UNESCO World Soil Map legend. Gleyic Acrisols were proposed for the more poorly‐drained associates of Nitosols. A Gleyic Podzol (with a spodic B) and a Dystric Cambisol (with a cambic horizon) were also represented.
Field Aging of Transparent Polyethylene Mulches: II. Influence on the Effectiveness of Soil Heating
Authors: Avissar R. , Naot O. , Mahrer Y. , Katan J. 
Published: July 2010

AbstractPhotometric properties of transparent polyethylene (PE) mulches change significantly during prolonged field utilization. In order to test and explain the effects of these changes on the temperature regime of mulched soil, we developed a one‐dimensional numerical model, which simulates the microclimate of mulched soils. The model consists of three layers: soil, plastic, and the air enclosed between them. Given the thermal and hydraulic properties of the soil, the photometric properties of the plastic, and appropriate climatic conditions, the model computes the diurnal variation in temperature and humidity of the different layers. Field measurements verify the model's ability to predict the temperature regimes of mulched soils. Both numerical and field experiments show that mulching the soil with PE sheets previously used during one solarization season, rather than new ones, results in more effective heating of the soil and, therefore, faster killing of pathogenic soil fungi. This is explained by the relatively higher reflectance of new mulch, due to the condensation of small water droplets on its inner surface. Recycling polyethylene sheets, previously used for agricultural purposes, provides an extremely inexpensive method for soil mulching.
Physical and Chemical Properties of a Haploxeroll after Fifty Years of Residue Management
Authors: Pikul J. L. , Allmaras R. R. 
Published: July 2010

AbstractGreater inference about the value of long‐term crop residue management requires that soil chemical properties be measured together with soil physical properties. After 54 yr of several different crop residue management treatments in a winter wheat (Triticum aestivum L.)‐fallow system in the Pacific Northwest, soil bulk density (ρb), saturated hydraulic conductivity (Ksat), soil water desorption curves (SWDC), soil organic carbon, and soil pH were all used to quantify the soil physical and chemical state. All wheat straw, chaff, and manure additions were incorporated by spring plowing in an alternating winter wheat‐fallow rotation. The residue treatments were: (i) straw, (ii) straw plus 22 Mg/ha strawy manure, (iii) straw burned in the fall, and (iv) straw plus 90 kg/ha of N as NH4NO3 broadcast before seeding. Straw return in treatments 1, 2, and 4 depended especially on the N added. Soil ρb at 0.02‐m increments was used to locate compacted layers. Respective tillage pan ρb for treatments 1, 2, 3, and 4 were 1.3, 1.2, 1.3, and 1.2 Mg/m3; respective Ksat, using a double tube method, were 0.34, 0.85, 0.29, 0.23 µm/s. Respective Ksat, above the tillage pan, using an air‐entry permeameter were 1.08, 2.24, 1.52, and 2.36 µm/s. Average ρb and Ksat distinguished between treatments with low vs. high return of residue. SWDCs in the plow layer and tillage pan reflected the degree of soil compaction within and among treatments. No treatment differences in Ksat or ρb were found below the tillage pan. The Ksat in the tillage pan, relative to overlying and underlying layers, indicated that the tillage pan governs water flow in this soil. Soil pH of the Ap horizon was 5.6, 6.1, 5.4, and 4.8 for treatments 1, 2, 3, and 4, respectively; respective percent organic carbon was 1.14, 1.53, 1.07, and 1.25. The Ksat in the tillage pan was maintained at a high level only where residue additions were increased and soil pH maintained above 5.6.
Simulated Acid Rain Effects on Jack Pine Seedling Establishment and Nutrition
Authors: MacDonald Neil W. , Hart James B. , Nguyen Phu V. 
Published: July 2010

AbstractA greenhouse study examined the effects of simulated acid rain on jack pine (Pinus banksiana Lamb.) seedling development and the Grayling sand (Typic Udipsamments) growth medium. Five rain pH levels (2.0, 2.5, 3.0, 4.0, 4.7) and two soil horizons (A/E, Bw1) were included as levels of factors. Soil pH decreased only at rain pH 3.0 and below. Exchangeable Ca and Mg were reduced at pH 2.0 in A/E horizon soil only. Germination of jack pine was inhibited at pH 2.0 on both soils. Mortality of germinants was over 95% on both soils at pH 2.0, 42% on A/E soil at pH 2.5, and 2 to 13% in other treatment combinations. Seedling top weight increased and root weight decreased on both soils at pH 2.5. In seedlings grown at pH levels 2.5 to 4.7, tissue concentrations of N, K, Ca, Na, Mn, Zn, and Al increased, but P and Mg were reduced, as rain pH decreased. At pH 2.5, Al toxicity and deficiencies in P and Mg were indicated. Simulated rain approximating pH levels typical of precipitation in northern lower Michigan (> 3.0) did not adversely affect jack pine regeneration or soil properties of the Grayling sand during the 75‐d study.
Determination of the Gibbs Free Energy of Formation of Magnesite by Solubility Methods
Authors: Kittrick J. A. , Peryea F. J. 
Published: July 2010

AbstractThe current values reported for the Gibbs free energy of formation for magnesite [MgCO3(s)] are bimodally grouped, centered at −1012 kJ mol−1 and in the range −1026 to −1030 kJ mol−1. The solubilities of three natural magnesites in aqueous solution were determined in order to verify the appropriate values. The samples were equilibrated at high solid‐to‐liquid ratios with solutions that were initially undersaturated or supersaturated with respect to magnesite. The chemical activities of pertinent system components at equilibrium were measured analytically or calculated using an ion‐association computer model. The results of 50 solubility determinations yielded a mean Gibbs free energy of formation of −1026.0 ± 2.1 kJ mol−1. Identical values were obtained from undersaturation, using an immiscible displacement technique, and from supersaturated initial conditions. These data suggest that the more negative values reported for the Gibbs free energy of formation are correct; hence, magnesite will be the only thermodynamically‐stable Mg carbonate phase in surface or near‐surface geochemical environments. The attainment of equilibrium in initially undersaturated systems containing either magnesite only or a mixture of magnesite, kaolinite, and montmorillonite was not impeded by the presence of soluble silicon (Si). This observation indirectly discounts the hypothesis that dissolved Si may form magnesium silicate coatings on magnesite surfaces, thus limiting the rate of dissolution and preventing the establishment of chemical equilibrium.
Leaching of Herbicides Through Undisturbed Cores of a Structured Clay Soil
Authors: White R. E. , Dyson J. S. , Gerstl Z. , Yaron B. 
Published: July 2010

AbstractThe leaching of the herbicides bromacil and napropamide through large undisturbed cores of a structured Evesham clay (Aquic Eutrochrept) was studied under continuous and discontinuous watering regimes and at different initial moisture contents. A greater proportion of both herbicides was leached from initially dry cores (θ = 0.24) than from prewet cores (θ = 0.35). This was consistent with differences in the amount of herbicide retained in the soil, most of which was retained in the top 0.05 m. Continuous leaching resulted in greater herbicide breakthrough than did the discontinuous treatment, presumably because some herbicide diffused from the conducting channels into the soil aggregates during the quiescent period, where it was less susceptible to subsequent leaching. At a continuous input rate of 12 mm h−1 to initially dry soil, 85% of the applied napropamide (Kd = 17.7 L kg−1) and almost 100% of bromacil (Kd = 1.73 L kg−1) were leached out of the soil by one pore volume of water. Chloride was used as a tracer for water flow through the soil. Chloride breakthrough curves were analyzed using a transfer function equation, which yielded the median travel time of a solute molecule in the soil. It is suggested that preferential flow of water down cracks and channels between soil aggregates led to short travel times and apparently low volumes of soil water participating in solute transport (θst). The θst values were inversely correlated with the percentages of the applied herbicides that were leached.
A Critical Evaluation on the Use of Kinetics for Determining Thermodynamics of Ion Exchange in Soils
Authors: Ogwada R. A. , Sparks D. L. 
Published: July 2010

AbstractThermodynamics of K‐Ca exchange were compared using equilibrium and kinetic approaches in two Delaware soils. The classical Argersinger theory was employed for the equilibrium approach, while a kinetic approach was studied using miscible displacement, batch, and vigorously mixed batch techniques. These three techniques were used to determine how diffusion affects the comparison between thermodynamic parameters using kinetic and equilibrium approaches. Rate coefficients and energies of activation were profoundly affected by the type of kinetic technique employed and their magnitude was in the order: vigorously mixed batch > batch > miscible displacement. Energies of activation for adsorption (Eaa) in the two soils ranged from 7.42 kJ mol−1 using the miscible displacement technique to 32.96 kJ mol−1 with the vigorously mixed batch, while energies of activation for desorption (Ead) ranged from 11.87 to 42.1 kJ mol−1 for the two methods, respectively. The magnitude of the Eaa and Ead values indicated pronounced diffusion effects in the miscible displacement and batch techniques, which were greatly reduced with the vigorously mixed batch method. Thermodynamic parameters (ΔG°, ΔH°, and ΔS°) calculated using the equilibrium and kinetic approaches compared very well in trend, and gave the same inferences of ion behavior for the two soils studied. However, except for the vigorously mixed batch technique, the magnitude of the thermodynamic parameters for the two approaches compared poorly. For example, the ΔG° values calculated using the equilibrium approach avg 4.67 kJ mol−1 for the two soils, while they avg 4.92 kJ mol−1 with the vigorously mixed batch, 2.12 kJ mol−1 with the batch, and 2.12 kJ mol−1 with the miscible displacement. The degree of comparison between the two approaches was directly related to the extent of diffusion controlled exchange. When the influence of diffusion was significantly reduced, as with the vigorously mixed batch technique, our data would indicate that a kinetic approach can be successfully used to gather thermodynamic information about a soil system.
Soil Physical Properties as Influenced by Cropping and Residue Management
Authors: Skidmore E. L. , Layton J. B. , Armbrust D. V. , Hooker M. L. 
Published: July 2010

AbstractAlternate methods of residue management for reduced tillage under irrigation and in double cropping systems are constantly being sought. One method that is becoming increasingly popular is residue burning. Knowing how to best manage crop residues to maintain desirable soil physical properties for decreasing erosion and increasing crop yields in these cropping systems is a problem. This study was conducted to determining the influence of several methods of residue management for winter wheat (Triticum aestivum L.) and grain sorghum [Sorghum bicolor (L.) Moench] on physical properties of Richfield silty clay loam (fine, montmorillonitic, mesic Aridic Argiustolls). Residue management treatments were: residue removed by burning, residue removed by baling and hauling, incorporation of the residue produced during the immediate past cropping season, and incorporation of twice the amount of residue produced by the crop. Most of the soil physical properties measured were not influenced by either grain sorghum or wheat residue management treatments; however, they differed between crops. The soil aggregates from the sorghum plots were smaller, more fragile, less dense, less stable dry, and more stable wet than the aggregates from the wheat plots. The pore size distribution of the soil from the Ap horizon of the sorghum plots was more conducive to water infiltration. The saturated hydraulic conductivity was several times greater in the soil cores obtained from the sorghum plots than those obtained fro the wheat plots.
Optimal Ratios of Saline and Nonsaline Irrigation Waters for Crop Production
Authors: Dinar Ariel , Letey J. , Vaux H. J. 
Published: July 2010

AbstractIncreased demands for freshwater in irrigated agriculture might be offset in some instances by substituting saline waters when they are available. The purpose of this paper is to present a quantitative method for determining the optimal mix of saline and nonsaline waters for crop production. Equal yield curves (isoquants), which quantify the extent of substitutability between waters of different qualities when constant yield is sought, were derived from crop‐water production functions for waters of different qualities computed from a previously published model. Isoquants were derived for several crops for relative yield (RY) values of 1.0, 0.9, and 0.8. The waters considered for mixing were nonsaline waters and waters of electrical conductivity (EC) equal to 4, 6, or 11 dS/m. Extending the supply of water by combining nonsaline and saline water is not always technically or economically feasible, and depends on specific crop and water pricing situations. The technical and economic feasibility of mixing waters of different quality increases as the EC of the saline water decreases, crop tolerance to salinity increases, desired RY decreases, or the relative price of saline to nonsaline water decreases.
Soil Compaction from Harvesting and Site Preparation in the Upper Gulf Coastal Plain
Authors: Gent J. A. , Morris L. A. 
Published: July 2010

AbstractThe impact of intensive forest management practices on the physical properties of a Typic Paleudult was examined to a depth of 0.3 m by collecting 7.6‐cm core samples before harvest, after harvest, and after site preparation. Whole‐tree harvesting of a 22‐yr‐old loblolly pine (Pinus taeda L.) plantation caused significant changes in bulk density to a depth of 0.23 m outside of skid trails, and 0.30 m in primary skid trails. Subsequent chop/burn and shear/windrow site preparation treatments had little added impact on bulk density. Post site preparation differences in aeration porosity and saturated hydraulic conductivity among treatments were nonsignificant.
An Electrical Readout System for Tensiometers
Authors: Lowery B. , Datiri B. C. , Andraski B. J. 
Published: July 2010

AbstractCommercially available pressure transducers (PTs) and tensiometers were combined to continuously monitor in situ soil pore‐water pressure. The transducers were calibrated over a range of 0 to −76.5 kPa and a temperature range from 5 to 40°C. A single calibration equation corrected for zero offset and a small temperature‐induced variation. Field temperature fluctuations between 10 and 30°C had little effect on results from PTs connected to constant pressures of −5 and −11.5 kPa. Wetting fronts were easily mapped with outputs from tensiometers placed at three different depths. From these field data, prior water history and diurnal changes in soil pore‐water pressure were easily obtained. Given variable field conditions, results from the PTs agreed well with closely‐placed Bourdon gauge tensiometers.
Artificial Intelligence, Cognitive Science, and Measurement Theory Applied in Soil Classification
Authors: McCracken Ralph J. , Cate Robert B. 
Published: July 2010

AbstractRecent advances in artificial intelligence and related fields have relevance to problems encountered in soil classification. Expert systems can be used to strengthen efforts to update and revise soil classification, to maintain large data bases such as Soils‐5, and to involve field personnel in technical evaluation programs. Expert systems may also be applied to other areas of soil science, where judgement and practical experience by experts can be computerized, such as soil management recommendations on irrigation, fertilizer use, and erosion control. Cognitive science research aimed at better understanding of the fundamental aspects of mental representation and categorization may provide stimuli to research on improvements in soil classification. Understanding of the theory of measurement can lead to more efficient, less arbitrary use of quantification techniques in the description and interpretation of soils. The purpose of this paper is to draw to the attention of pedologists and other soil scientists the potential usefulness of recent advances in artificial intelligence, cognitive science, and measurement theory. Following an introduction to these fields, we provide suggestions and specific examples regarding their application to soil classification. Our hope is that this introduction will encourage soil scientists to learn more about these disciplines and consider additional applications to soil science.
Air Encapsulation: II. Profile Water Storage and Shallow Water Table Fluctuations
Authors: Fayer M. J. , Hillel D. 
Published: July 2010

AbstractIn a wet soil, volumetric encapsulated air contents can easily approach 0.06 m3 m−3. The objective of this study was to determine, through simulation, the effect of air encapsulation on profile water storage and shallow water table fluctuations and whether air encapsulation should be considered in modeling field events. Using a two‐dimensional soil moisture code that included a routine designed to model air encapsulation, we simulated profile water storage changes during hypothetical rainfall events and water table responses during actual rainfall events. The simulation results indicated that, following the infiltration of 10 mm of water, profile moisture content differences with and without air encapsulation would be <0.01 m3 m−3 and thus may not be measurable in the field with a neutron probe. Water table levels, however, rose significantly higher in the profile when air was encapsulated. Depending on the initial depth of the water table and the moisture characteristic, the water table rises were two to five times those when air was not encapsulated. For water tables located within 1.3 m of the surface, application of the model to actual rainfall events improved the fit to the measured water table data. In those situations where water table level predictions are important (e.g., wetlands, stream banks), researchers should consider air encapsulation in their analysis of water table fluctuations.
Fluridone Retention and Release in Soils
Authors: Weber J. B. , Shea P. H. , Weed S. B. 
Published: July 2010

AbstractAqueous adsorption/desorption studies showed that fluridone [1‐methyl‐3‐phenyl‐5(3‐trifluoromethyl) phenyl]‐4‐(1H)‐pyridinone) adsorbed to both organic matter and montmorillonite clay surfaces in 18 soils. Adsorption ranged from a high of 0.81 mmol/kg on Earle clay (Vertic Haplaquets) [3.7% organic matter (OM), 59% clay] to a low of 0.02 mmol/kg on an Amarillo loamy sand (Aridic Paleustalfs) (0.5% OM, 8% clay). Fluridone adsorption was highly correlated with montmorillonite clay or organic matter contents of the soils, but the highest correlation coefficients (r = 0.92) resulted when adsorption was correlated with both clay and organic matter contents. Adsorption isotherms for fluridone on three soils (Earle and Tunica [Vertic Haplaquets], and Falaya [Aeric Fluvaquents] were of the S‐type on soils containing low amounts of organic matter and high amounts of montmorillonite clay, and of the L‐type on soils high in organic matter and with low mixed clay mineralogy (Cape Fear [Typic Umbraquults] and Drummer [Typic Haplaquolls]). Isotherms for soils low in organic matter and clay content (Fincastle [Aeric Ochraqualfs] and Norfolk [Typic Paleudults]) were linear (C‐type) or of the L‐type. Fluridone adsorption increased by 38 to 42% when solution pH was decreased from 6.4 to 3.5 and the herbicide was not readily desorbed with water at the low pH level (11–27% released), suggesting that the weakly basic herbicide protonated and was bound by cation exchange forces. Large amounts (58%) were desorbed with water where adsorption occurred at higher pH levels (6.4), suggesting that only physical binding was involved. Incubation of fluridone adsorbed on soil pellets under wet, 50°C conditions reduced fluridone that could be displaced with water by 10 to 20%, as compared with incubations at 25°C, or incubations under dry conditions (25 or 50°C), suggesting that climatic factors may affect adsorption/desorption, mobility in soil, bioactivity, and persistence of the herbicide. X‐ray diffraction studies revealed that the herbicide was adsorbed in the interlayer surfaces of montmorillonite clay and Δd spacing ranged from 0.2 to 0.4 nm.