bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nitrogen Mineralization Potentials of Revegetated Lignite Overburden in the Texas Gulf Coast
Authors: Hornby W. J. , Brown K. W. , Thomas J. C. 
Published: July 2010

AbstractFresh mine spoil is virtually devoid of organic matter (OM) and N. The needed N is commonly added as inorganic fertilizer; however, sewage sludge additions could supply both OM and N. This study was conducted to compare the mineralizable N resulting from inorganic fertilizer and sludge applications to overburden. Nitrogen mineralization potentials were determined from laboratory data on a pre‐mined native soil (Elmina fine sandy loam) and 4‐yr old reclaimed mixed overburden that received 180 kg N ha−1 yr−1 as NH4NO3 using the Stanford and Smith model (1972). In addition, the effect of anaerobically digested sewage sludge (sludge) on N‐mineralization potential of overburden was evaluated on samples collected from field plots. Treatments were as follows: 0 kg N ha−1, 212 kg N ha−1 as NH4NO3, 106 kg N ha−1 as NH4NO3 plus 106 kg N ha−1 as sludge, and 212 kg N ha−1 as sludge applied to 13.8 m2 plots of overburden. Soil and spoil samples (0–15 cm deep) were collected from these plots 2 weeks, 26 weeks, and 52 weeks after amendment. Mineralization rates were determined using columns containing 0.2 kg of soil or treated overburden plus 0.1 kg of sand which were incubated for 18 weeks at 35°C. These columns were leached with saturated CaSO4 and a N‐free nutrient solution at 0, 2, 6, 10, 14, and 18 weeks and were extracted to a tension of −0.066 MPa after each leaching. The leachate was analyzed for NH+4 and NO‐3 by colorimetric methods. Application of 56 Mg sludge ha−1 significantly (α = 0.05) increased the total N 26 and 52 weeks after application to levels present in the 4‐yr old mineral fertilized reclaimed spoil. Sludge application also resulted in a sustained release of plant available N for 52 weeks after application. Mineralization potentials 2 weeks after the plots were treated were ranked as unamended overburden = NH4NO3 treated overburden < native spoil = 4‐year old reclaimed overburden < NH4NO3 plus sludge treated overburden < sludge treated overburden.
Aggregation of a Silty Clay Loam Soil by Mycorrhizal Onion Roots
Authors: Thomas R. S. , Dakessian S. , Ames R. N. , Brown M. S. , Bethlenfalvay G. J. 
Published: July 2010

AbstractOnion plants (Allium cepa L.) inoculated in the root zone with a vesicular‐arbuscular mycorrhizal (VAM) fungus, or left uninoculated, were grown in potted soil for 230 d to determine the influence of the VAM fungus (Glomus macrocarpum Tul. and Tul.) on soil structure. The silty clay loam soil was maintained at a moisture content between 25 and 30%. Paired inoculated (+M) and uninoculated (−M) plants were harvested (20 pairs over 150 d) beginning 80 d after planting. Relationships between plant, fungal, and soil parameters and changes with time were evaluated by regression analysis. Root colonization by the VAM fungus in +M plants ranged from 49% to 60% over the sampling period, while no mycorrhizae were detected in the ‐M plants. Total dry mass of VAM plants was five to six times that of the non‐VAM plants. Soil from the +M treatment was significantly better aggregated, more porous, and had greater water permeability than ‐M soil. Root dry mass and VAM hyphal density in the +M soil were both significantly correlated with the relative abundance of water‐stable soil macroaggregates. Correlation of root mass with aggregate abundance was stronger, however, suggesting that soil changes were mainly mediated by direct root effects of a host plant whose growth was stimulated dramatically by its VAM fungal endophyte.
Recovery of Fertilizer Nitrogen by Wheat as Affected by Fallow Method
Authors: Power J. F. , Wilhelm W. W. , Doran J. W. 
Published: July 2010

AbstractThe fate of fertilizer N applied to crops is of both environmental and economic concern. To follow fertilizer N recovery in western Nebraska, depleted‐15N NH4NO3 was surface broadcast in April on winter wheat (Triticum aestivum L.) growing on plots fallowed the previous year by plowing, subtillage, and no‐till. Quantities of labeled N taken up by the growing crop, in the upper 100 mm of soil as inorganic N, and in both visible and partially decomposed crop residues, were followed on two sets of plots through the crop‐fallow‐crop sequence (approximately 117 weeks). About 16 to 18% of the labeled N was removed in the grain of the first wheat crop, with an additional 3 to 5% in the second crop. Labeled inorganic soil N decreased to <5% within 1 yr, with little effect of fallow method. No more than 4% was in visible residues at any time for all except no‐till fallow, for which 7 to 13% of the labeled N was found in visible residues from heading of the first crop through the entire fallow period until the second crop was seeded. Likewise, 4 to 9% of the labeled N applied was found in partially decomposed residues of no‐till during this period, compared to no more than 2% for the plow and subtill treatments. Total N in both residue pools combined decreased 50% from October to April of the fallow year for N‐fertilized wheat and 25% for unfertilized wheat. Most of the labeled N in the straw found in the visible residue pool by October was transferred over winter to either the partially decomposed pool or to other undetermined pools (including soil organic matter, microbial biomass, and losses to the atmosphere). Results show that, compared to plow and subtill, no‐till fallow enhanced retention of labeled N in the several crop residue pools and increased N uptake by the two wheat crops.
Runoff and Soil Loss as Influenced by Tillage and Residue Cover
Authors: Stein O. R. , Neibling W. H. , Logan T. J. , Moldenhauer W. C. 
Published: July 2010

AbstractTo gain a better understanding of the interactions between soil detachment, transport capacity, and residue cover, the USDA programmable rainfall simulator was used to erode plots created on established and newly created ridge‐till areas of <1% slope with and without residue cover. A control of conventional moldboard plow‐spring disk was also included. Results showed that for all treatments, ridge sideslope erosion was three to four times greater than total soil loss, suggesting that transport capacity was the limiting factor. For most runs no significant difference in soil loss was measured between ridges of different ages. The presence of residue decreased soil loss to one‐sixth or one‐seventh on older ridges and to one‐half on new ridges. Location of residue was more important than the total amount of residue. Residue placed only on the furrow bottom was as effective in reducing soil loss as residue placed over the entire ridge and furrow, while residue placed only on the ridge side‐slope did not reduce soil loss significantly from treatments without residue.
Relationships of Dense Tillage Pans, Soil Properties, and Subsoiling To Tobacco Root Growth
Authors: Vepraskas M. J. , Miner G. S. , Peedin G. F. 
Published: July 2010

AbstractDeep tillage with subsoilers can fracture tillage pans and increase root development in some soils, but little is known about the precise soil conditions for which subsoiling works best. This study evaluated relationships of soil physical properties, chemical properties, and subsoiling to root distributions in 10 Ultisols. Five sites had dense tillage pans in their E‐B horizons with bulk densities (ρb) ≥1.66 Mg m−3. At each location flue‐cured tobacco (Nicotiana tabacum L.) was grown in subsoiled and nonsubsoiled (moldboard plow/disk) tillage treatments. At approximately 100 d from transplanting, root distributions were described by the trench‐profile method. Soil properties evaluated included bulk density, texture, ped mean weight‐diameter, cone index (CI), Ca and Al saturation ratios, base saturation, and pH. Subsoiling significantly increased the proportion of roots below the E‐B horizon (0.15 m below the Ap), in three of the five sites with E‐B ρb's ≥1.66 Mg m−3, while it had no significant effect on proportion of roots below the E‐B horizon in any of the five sites whose E‐B ρb's were <1.66 Mg−3. A regression analysis showed that ρb of the E‐B horizon, B horizon sand content, and cummulative rainfall accounted for 96% of the observed variation in subsoil root development for the nonsubsoiled treatment across the 10 sites. Soil chemical properties had little effect on variation in subsoil root development across sites.
Effect of Soil Surface Sealing on Splash from a Single Waterdrop
Authors: Bradford J. M. , Remley P. A. , Ferris J. E. , Santini J. B. 
Published: July 2010

AbstractMost soil erosion prediction models do not account for surface sealing and soil crusting effects on soil detachment. The objective of this research was to evaluate surface seal formation and subsequent drying effects on amount of soil detached by single waterdrop impact. Twenty soils ranging in texture from sand to clay were tested. Single drop splash and fall‐cone strength determinations were made on each soil in an uncrusted condition, in a crusted condition immediately following 1 h of simulated rainfall (63 mm/h), and after 2 to 4 weeks of drying. Splash for the uncrusted condition ranged from 8.9 to 61.0 mg/drop and from 0.8 to 13.7 mg/drop for the crusted condition. Subjecting crusted soils to one drying cycle did not significantly alter splash amount. Splash was correlated with soil strength for both uncrusted and crusted conditions for finertextured soils; however, for sands and sandy loams additional research is required for soil strength‐based splash model for crusted conditions.
Water Seepage Through Multilayered Anisotropic Hillside
Authors: Selim H. M. 
Published: July 2010

AbstractA mathematical analysis is presented for the steady‐state saturated flow through multilayered hillsides or soil beddings with a sloping surface. Each soil layer was considered anisotropic in nature, i.e., κ ≠ ξ where κ and ξ are the hydraulic conductivity in the vertical and horizontal directions, respectively. The method of solution is an analytical one and is based on the Gram‐Schmidt orthonormalization technique. Potential and stream functions were obtained and flow nets are presented for two‐layered geometries with varying degrees of anisotropy. The range of values chosen were ξ = (1/25)κ to ξ = 16κ and the equivalent hydraulic conductivities for two soil layers K1/K2 were 1:1, 1:10, and 10:1. The selected cases considered illustrate the significance of the degree of anisotropy on the water flow pattern, the relative flow rate as well as the volume of water passing through individual soil layers. Moreover, the greatest influence on the relative flow rate was when the upper layer was anisotropic rather than the lower layer.
Aluminum Speciation: A Comparison of Five Methods
Authors: Hodges Steven C. 
Published: July 2010

AbstractThe objective of this study was to compare five methods with varying chemical approaches to the speciation of Al. The 8‐hydroxyquinoline (HQ) and ferron procedures were used to estimate the inorganic, monomeric forms of Al at reaction times of 15 and 30 s, respectively. Two other procedures, an ion exchange column procedure and a chelating resin procedure, were used primarily to measure organically bound forms of Al. These were compared with a F electrode technique which quantifies Al3+ activity using equilibrium thermodynamic calculations and measured values of F activity and total F. Stability constants are then used to calculate the speciation of inorganic forms of Al, and organically complexed forms are obtained by subtraction from total Al. Sample solutions containing 5 mmol m−3 F, and 7.9, 15.2, 44.5, and 80.4 mmol m−3 Al were synthesized, with and without addition of 1 mol m−3 (as dissolved organic C) purified fulvic acid extracted from the surface horizon of an Edneytown soil (Typic Hapludults). A soil solution extract was also obtained from the soil and analyzed. Excellent agreement (r = 0.999) between predicted and measured Al3+ was obtained for the electrode procedure in solutions without organic matter (OM). The kinetically reactive Al values obtained by the HQ procedure correlated very well with those of the F electrode procedure in predicting [Al3+] and toxic Al (Al3+ + AlOH2+ + Al(OH)+2), (r = 0.91 and 0.90, respectively), but overestimated these Al forms when the Al/organic C ratios were low. The kinetically reactive Al values obtained by the ferron procedure were greater than values obtained by the HQ and electrode procedures since ferron was also able to breakdown Al‐F complexes to a greater extent. The column and chelating resin procedures were able to separate organic and inorganic forms of Al only, thus speciation of inorganic complexes was not feasible. Organically bound Al calculated from the electrode procedure was generally lower but consistent with the values obtained by the chelating resin. The ion exchange column proceduure gave the lowest values of Al‐OM at the lowest Al/OM ratios, indicating that some degradation of Al‐OM complexes may occur during passage through the column. The F electrode procedure, though promising, should not be indiscriminately used over a wide range of pH, Al/F ratios, and DOC contents without more information on the effects of electrode interactions with organic solutes. Furthermore, the procedure is slow and requires the assumption of equilibrium conditions, which may seldom occur for Al in field conditions. It is, however, promising as a tool for the evaluation of other procedures under well controlled experimental conditions.
Dependence of the Gapon Coefficient on Exchangeable Sodium for Mineralogically Different Soils
Authors: Evangelou V. P. , Coale F. J. 
Published: July 2010

AbstractThe traditional nonthermodynamic Gapon exchange selectivity coefficient (KG) for Na‐Ca exchange has previously been shown in the literature to be relatively constant for only a restricted range of Na+ equivalent fractions (NNa ≤ 0.40) in the exchanger. This relationship was developed for a heterogeneous group of soils. A linear Langmuir‐type plot of the traditional Gapon equation for Na‐Ca exchange data of mineralogically different soils, clay minerals, and an exchange resin was used to demonstrate the applicability of a constant KG for NNa values >0.40 for some soils. The results demonstrate that, in general, low CEC soils are more likely to demonstrate a constant KG for NNa values >0.40 than are high CEC soils. The data show that a constant KG for NNa values >0.40 was obtained for Georgia kaolin, illite, and several soils of low CEC. However, the plot failed to predict the KG and the CEC for soils, clay minerals, and an exchange resin of high CEC. These high CEC materials exhibited a NNa dependent KG. Using solution ion concentration instead of single‐ion activity affected the magnitude of the KG but did not affect the degree of constancy of the KG for NNa values >0.40. The relationships are of practical importance in the reclamation of sodic soils with an equivalent fraction of Na+ in the exchanger phase (NNa) of >0.40.
Soil Compaction in Double‐cropped Wheat and Soybeans on an Ultisol
Authors: NeSmith D. S. , Radcliffe D. E. , Hargrove W. L. , Clark R. L. , Tollner E. W. 
Published: July 2010

AbstractIn recent years double‐crop winter wheat (Triticum aestivum L.) and soybeans [Glycine max (L.) Merr.] have become quite common in the southeastern USA. To minimize the time between harvest of the winter crop and planting of soybeans, many farmers have adopted reduced or no‐tillage systems. A 2‐yr experiment was conducted on an Ultisol in Georgia to assess the influence of these tillage practices on soil physical properties. Spring tillage treatments were no‐tillage, disking, and moldboard plow plus disking. Fall tillage prior to planting wheat was with a disk. Bulk density and mechanical impedance measurements indicated a compacted layer in the disked and notillage treatments at a depth of 0.15 to 0.25 m. This was attributed, in part, to the fall disking, and it persisted through the winter and into the next growing season.
Long‐term Tillage Practice Effects on Soil Aggregation Modes and Strength
Authors: Hadas A. 
Published: July 2010

AbstractAir dry aggregates of two soils were collected from cultivated fields and a natural reserve, and separated into five diameter groups: 1 to 5, 5 to 10, 10 to 20, 20 to 40, and 40 to 76.4 mm. Tensile strength of aggregates from these size groups was determined by brittle fracturing the aggregates in an unconfined compression unit. Analyses in view of using the brittle fracture theory showed that soil exhibits specific structural states organized hierarchially (e.g., primary, secondary, etc). Each consecutive state has a characteristic internal strength which diminishes and a “cell” structure the size of which increases with respect to the consecutive hierarchial order. This implies that aggregates are made of mixtures of soil materials belonging to the different aggregation states, and the materials of a lower hierarchial order act as cementing or binding material between soil cells of a higher aggregation order (e.g., tertiary aggregation material binds secondary aggregates and the bound mass, consisting of tertiary and secondary aggregates, binds the primary aggregates). Tensile strength of aggregated samples in a cultivated field was greater than that of samples taken from a noncultivated virgin site of the same soil. Internal strength of the basic soil aggregation units was quadrupled under cultivation as compared to that determined for virgin samples. These findings suggest that cultivation and trafficcaused compaction affect the basic smaller structural units of the soil rather than the larger aggregation units.
An Automated Technique for Flow Measurements from Mariotte Reservoirs
Authors: Constantz Jim , Murphy Fred 
Published: July 2010

AbstractThe mariotte reservoir supplies water at a constant hydraulic pressure by self‐regulation of its internal gas pressure. Automated outflow measurements from mariotte reservoirs are generally difficult because of the reservoir's self‐regulation mechanism. This paper describes an automated flow meter specifically designed for use with mariotte reservoirs. The flow meter monitors changes in the mariotte reservoir's gas pressure during outflow to determine changes in the reservoir's water level. The flow measurement is performed by attaching a pressure transducer to the top of a mariotte reservoir and monitoring gas pressure changes during outflow with a programmable data logger. Using a simple linear relation between reservoir gas pressure and water‐level changes with time, the data logger converts the transducer signal into outflow‐flux values. To demonstrate the usefulness of the new technique, two constant‐head experiments are described that have vastly different flux ranges and time durations. The first experiment was a 1‐h infiltration run in which infiltration rates dropped from 0.6 to 0.2 cm/min. The second experiment was a 3‐week evaporation experiment in which the evaporation rate ranged from 1.0 to 3.0 cm/d. Results indicate that the automated flow measurement technique performed well when compared to a manual sight‐tube technique for flux measurements; the difference between the two methods was never more than 9% for the infiltration experiment and 5% for the evaporation experiment. The advantages of the new technique over previously available automated flow measurement techniques include: (i) the ability to rapidly record a large range of fluxes without restricting outflow, and (ii) the ability to accurately average the pulsing flow, which commonly occurs during outflow from the mariotte reservoir.
Copper Activity in Soil Solution: I. Measurement by Ion‐selective Electrode and Donnan Dialysis
Authors: Minnich M. M. , McBride M. B. 
Published: July 2010

AbstractCopper activity in saturation extracts (2:1 soil/solution) of sludge‐ and Cu‐salt‐treated soil was estimated by ion‐selective electrode (ISE) and by Donnan dialysis. Treatments were a factorial combination of four levels of Cu additions and four levels of total sludge additions. In the Donnan system, the ionic strength of a soil saturation extract was matched with KOAc buffer on opposite sides of a cation perm‐selective membrane. At membrane equilibrium, Cu concentration was determined in the KOAc buffer by voltammetry. Extracts of sludge treatments had sufficient Cu buffering capacity to maintain the same Cu2+ activity before and after dialysis; Cu‐salt treatments exhibited a lower soil solution Cu2+ activity after dialysis indicating the procedure was inadequate for these treatments. The ISE results were more precise, but the technique is only suited for use in aerobic, Cu‐contaminated soils. Values for Cu2+ activity obtained by ISE were approximately an order of magnitude greater than Cu2+ activity values estimated by the Donnan dialysis method. By either procedure, increased total Cu resulted in higher Cu2+ activities and conversely, increased total sludge resulted in decreased Cu2+ activities. Total soluble Cu was highest in the Cu‐salt treatments; sludge rate was associated with increased soluble Cu and a decreased proportion of free Cu2+.
Reduction and Oxidation of Acid Sulfate Soils of Thailand
Authors: Charoenchamratcheep C. , Smith C. J. , Satawathananont S. , Patrick W. H. 
Published: July 2010

AbstractChanges in pH, oxidation potential (Eh), and the solubility of S, Al, Ca, Mg, Fe, Mn, and Si were measured in four acid sulfate soils of Thailand following reduction and subsequent oxidation. Reduced S species accumulated under anaerobic conditions, but oxidized rapidly when the systems were aerated. The SO4 concentration in solution increased as the Eh of the soil suspensions increased and pH decreased to <4. The extreme acidity developed in all soils resulted in the dissolution of Al, Mn, Mg, and Si.
Volcanic Ash‐influenced Vertisols and Associated Mollisols of El Salvador: Physical, Chemical, and Morphological Properties
Authors: Yerima B. P. K. , Wilding L. P. , Calhoun F. G. , Hallmark C. T. 
Published: July 2010

AbstractVertisols and Mollisols have developed from Quaternary pyroclastic deposits in central El Salvador under ustic moisture and isohyperthermic temperature regimes. Pellusterts generally occupy the nearly level constructional landforms (alluvial plains, coastal plains, and concave alluvial toeslopes), are poorly drained and exhibit darkgray to black colors. Chromusterts and Pellusterts with argillic horizons and secondary silica in lower sola occupy more sloping, erosional upland landforms that are better drained. Associated Argiustolls have formed in loamy or clayey andesitic alluvium on nearly level alluvial plains. Vertisols of El Salvador have many properties in common with Usterts of the USA, i.e., high clay contents, slickensides, tilted parallelpipeds, and deep wide cracks that extend to the surface, but they lack gilgai relief, cyclic horizonation, and with a few exceptions, self‐mulching surface horizons. Most have cambic horizons. The amorphous material content of the <2 µm fraction of these soils range from 14 to 28%, pH's range from 5.4 to 7.5, base saturation is >50% (commonly >75%) with Ca and Mg dominant. COLE values are 0.06 to 0.24 and clays are smectitic or kaolinitic. Microfabrics indicate high shrink‐swell. Stress‐oriented plasmic fabrics are largely vo‐masepic, vo‐skel‐masepic and lattisepic for cambic and Bt horizons indicative of microshear failure. Undulic plasmic fabrics dominate in pumice‐rice ash mantles and pyroclastic‐rich parent materials. Illuvial channel ferri‐argillans and organo‐argillans occur in subsoils of the Chromusterts and Argiustolls, respectively. Pedogenesis and plasmolysis increase in the order: andesitic bedrock or alluvium, saprolite (from bedrock), clay‐enriched Bw and Bt horizons, and Bw horizons in upper sola with slickensides and stress‐oriented plasmic fabrics. The best Bt and silica‐enriched (Bq) horizons occur in lower sola below the more physically active upper Bw horizons.