bluuebunny/crossref_metadata_2025_split huggingface dataset:
Particle‐size Fractions and their Use in Studies of Soil Organic Matter: II. Cultivation Effects on Organic Matter Composition in Size Fractions
Authors: Tiessen H. , Stewart J. W. B. 
Published: July 2010

AbstractLosses of carbon, nitrogen, and phosphorus from soil particle‐size fractions during cultivation were examined and their implications on the nutrient‐supplying potential of soils is discussed. Particle‐size fractions were obtained by ultrasonic dispersion in water from three north American grassland soils (Cryoborolls) of different textures. Soils that had been cultivated under small grain‐fallow rotations for between 4 and 90 years were compared with similar soils under native prairie. Four years of cultivation of a Blaine Lake silt loam resulted in an extensive depletion of organic matter associated with particles > 50 µm (43% of the initial C lost). This was considered a result of physical disintegration which led to accumulation of these materials in finer particle‐size fractions. With continued cultivation this accumulated material was slowly transformed within the system, accompanied by net losses of 34% C and 29% N from the total soil over 60 years. Reductions in organic P content amounted to 20% and were accompanied by slight increases in inorganic P content.Fine clay (< 0.2 µm) associated organic matter was rapidly depleted during the first 60 years but showed little change thereafter, reaching a new equilibrium level at approximately one‐half its original C content. Losses of fine silt (5 to 2 µm) and coarse clay (2 to 0.2 µm) associated organic materials were substantially less, and the proportion of total soil organic matter in these forms increased with time of cultivation. The relative abundance of these biologically resistant, more humified materials in cultivated soils indicated that the remaining organic matter may have a reduced capability for supplying nutrients by mineralization. The continuing, slow mineralization of these more resistant organic matter fractions of the Blaine Lake soil after 90 years of cultivation suggests that organic matter losses may not level off further in the near future. In addition, losses of organic matter from the B horizon were evident after 60 and 90 years. Organic matter losses during 65 years cultivation of a coarser sandy loam soil showed a similar distribution and magnitude across size fractions, while a heavy clay soil was characterized by a greater stability of the silt and clay associated organic matter, which lost only 10% C during 70 years of cultivation.
In‐Situ Determination of Soil Hydraulic Properties during Drainage
Authors: Dane J. H. , Hruska S. 
Published: July 2010

AbstractIn‐situ soil water retention and hydraulic conductivity relations were determined for two soils from knowledge of initial and boundary conditions and water content profiles during drainage. Empirical relations were assumed for each soil between volumetric water content (θ) and soil water pressure head (h), and between hydraulic conductivity (K) and θ. Assigning values to the parameters in these relations made it possible to solve the general water flow equation for the same initial and boundary conditions as encountered in the drainage experiments. Calculated water content profiles were compared with measured water content profiles at corresponding times. Differences in measured and calculated θ values provided information for changes to be made in the parameters. This procedure was repeated until a satisfactory agreement was found and the determined relations apparently represented the soils in question.
Diffusivity and One‐Dimensional Absorption Experiments
Authors: Clothier B. E. , Scotter D. R. , Green A. E. 
Published: July 2010

AbstractProfiles of normalized volumetric soil water content, Θ, during one‐dimensional absorption are often found to provide a unique profile in terms of the Boltzmann similarity variable, λ. Traditionally, λ(Θ) data have been used to obtain the diffusivity‐water content function D(Θ) by the method of Bruce and Klute. This paper highlights the well‐known inadequacy of this method, and outlines a procedure for deriving D(Θ) by the fitting of a mathematical function to the primary experimental data set, namely λ(Θ). An analytical expression for D(Θ) scaled by sorptivity is provided. A function of the form (1‐Θ)p is shown to fit the λ(Θ) of a fine sand adequately and provide a D(Θ) function that accommodates the soil water diffusivity measured using other methods at near‐saturation.
Kinetics of Oxidation of Arsenite by Various Manganese Dioxides
Authors: Oscarson D. W. , Huang P. M. , Liaw W. K. , Hammer U. T. 
Published: July 2010

AbstractThree Mn dioxides—birnessite, cryptomelane, and pyrolusite—were examined for their ability to deplete the concentration of As(III), a highly toxic pollutant, in solution. The depletion [oxidation of As(III) to As(V) and sorption of As(III)] of As(III) by all three Mn dioxides follows first‐order kinetics. The rate constants for the depletion of As(III) by birnessite and cryptomelane at 298 K are 0.267 and 0.189 h−1, respectively. On the other hand, the depletion rate of As(III) by pyrolusite is much slower: the rate constant at 298 K is 0.44 × 10−3 h−1. This difference in the rate of depletion is largely attributed to the crystallinity and specific surfaces of the Mn dioxides. Pyrolusite is highly ordered and has a low specific surface of 0.8 hm2/kg (7.9 m2/g); conversely, birnessite and cryptomelane are poorly crystalline and have relatively high specific surfaces of 27.7 and 34.6 hm2/kg (277 and 346 m2/g), respectively. The energies of activation for the depletion of As(III) by the Mn dioxides range from 26.0 to 32.3 kJ/mol. The reaction appears to be predominantly diffusion‐controlled. The ability of the Mn dioxides to sorb As(III) and As(V) appears to be related to the specific surface and the point‐of‐zero charge of the oxides. The data indicate that, after the systems have reached equilibrium with respect to the sorption of total As, the depletion of As(III) by the oxides is still progressing. This is apparently because of the one‐to‐one relationship between the amount of As(III) depleted and the amount of As(V) appearing in solution.
Regulation of Invertebrate Grazers as a Means to Enhance Biomass and Nitrogen Fixation of Cyanophyceae in Wetland Rice Fields
Authors: Grant Ian F. , Tirol Agnes C. , Aziz Taufiqul , Watanabe Iwao 
Published: July 2010

AbstractThe effect of invertebrate grazing on the growth and N fixation of blue‐green algae (Cyanophyceae) in flooded rice soils was investigated by depressing grazer populations. Grazers were controlled with commercial pesticides and seeds of neem (Azadirachta indica). Algal N fixation and standing biomass were estimated by acetylene‐reduction activity and chlorophyll a measurements. Suppression of ostracod (Ostracoda) grazing by Pertbane or neem seeds tripled blue‐green algal biomass and increased N fixation rates 10‐fold. In the absence of ostracods, free living blue‐green algae multiplied rapidly early in the rice cultivation cycle to be succeeded by chlorophytes. Carbofuran was not an effective control measure. Suppression of molluscan grazing had little effect. The population of tubificids (Tubificidae) was higher in the plots where algal growth was stimulated than in other plots. Total rice grain N was increased up to 37% when grazing was arrested.
Soils on Terraces Along the Cauca River, Colombia: II. The Sand and Clay Fractions
Authors: Alexander E. B. , Holowaychuk N. 
Published: July 2010

AbstractMicroscopic examination and elemental analyses of the sand fractions of the terrace soils show that their compositions are too variable to infer anything very noteworthy about the relative rates of primary mineral weathering. However, the parent materials are sufficiently uniform to reveal a relatively continuous progression of notable changes in clay mineralogy from floodplain through the age sequence of terrace soils. Mica, chlorite, vermiculite, smectite, and kaolinite are present in appreciable quantities in the floodplain soils and mica is present in the sand fractions of all terrace soils, but of these only kaolinite is present in more than minute amounts in the sola of any terrace soils. The quantities of 14A minerals with interlayer Al are greatest in the sola of the youngest terrace soils, but they persist in somewhat reduced quantities throughout all except in the subsoil on the highest terrace. Both amorphous aluminosilicates and gibbsite reach maximum concentrations in the lower terrace soils, thence their quantities decline with increasing age. The Feo/Fed ratio has a similar age trend but peaks sooner, at 0.53 in the higher floodplain soil, and thence decreases steadily with soil age to < 0.01 in the clay fraction of the highest terrace soil. Kaolinite is the major constituent of clay in the sola of all terrace soils. It increases with soil age to approximately 60% of the clay fraction in the highest terrace soil.
Effect of Synthetic Conditioners on Soil Water Retention, Hydraulic Conductivity, Porosity, and Aggregation
Authors: Nimah M. N. , Ryan J. , Chaudhry M. A. 
Published: July 2010

AbstractRecent attention has been focused on the use of synthetic soil conditioners in the modification of soil water relationships especially in arid regions. Soils of extremes in texture—either sands or clays—present problems in this regard. In this laboratory study, Hygromull (a urea formaldehyde) and Agrosil LR and Agrosil S (amorphous sodium hydrosilicates) were evaluated on soils of different textures. Available water content was increased by Hygromull and Agrosil LR. Saturated hydraulic conductivity of the clay soils was improved by Hygromull, while that of the sandy soil was reduced by Agrosil LR. Hygromull increased porosity of all soils but, unlike Agrosil LR, had no effect on aggregation. In contrast, Agrosil S had no effect on any property studied. Notwithstanding the attributes of these conditioners, their acceptance in commercial farming in dry regions will depend on the outcome of field trials and economic considerations.
A Buried Pipe System for Controlling Erosion and Sediment Loss on Irrigated Land
Authors: Carter D. L. , Berg R. D. 
Published: July 2010

AbstractA new system comprised of a buried pipe, with riser inlets from the surface at intervals, along the lower end of furrow‐irrigated fields was designed, installed, and evaluated on 21 fields to determine its effectiveness as an erosion and sediment loss control system for irrigated land. The system utilizes small sediment collection ponds with the riser inlets from the buried pipe serving as overflow outlets for the ponds. This system corrects convex‐shaped field ends caused by erosion and solves an energy related erosion problem common on furrow‐irrigated land. During the first season, these system removed from 80 to 95% of the sediment from runoff water and collected from 4.1 to 40.5 Mg ha−1 from 12 fields on irrigated land where detailed data were collected. All systems performed without problems and all convex end problems except one were corrected the first season. After the convex ends are corrected, the system continues to reduce sediment loss. This new system eliminates the tailwater ditch, puts more land into crop production, reduces weed problems, and prevents the usual problems associated with a wet tail‐water ditch. The buried pipe erosion and sediment loss control system is a major advance in the control of erosion and sediment loss on irrigated land.
Forest Floor, Soil, and Vegetation Responses to Sludge Fertilization in Red and White Pine Plantations
Authors: Brockway Dale G. 
Published: July 2010

AbstractAn undigested, nutrient‐enriched papermill sludge applied to a 40‐year‐old red pine (Pinus resinosa Ait.) plantation at rates of 4, 8, 16, and 32 Mg/ha resulted in nitrogen application rates of 282, 565, 1130, and 2260 kg/ha. An anaerohically digested municipal sludge applied to a 36‐year‐old red pine and white pine (Pinus strobus L.) plantation at rates of 4.8, 9.7, and 19.3 Mg/ha resulted in nitrogen applications of 287, 578, and 1160 kg/ha. Both sludges produced significant forest floor increases in total salt, pH, and concentrations of nitrogen and phosphorous. The municipal sludge applications also resulted in increased levels of trace elements and heavy metals. Accelerated humification developed along the interface between the sludge layer and the accumulated forest litter. Movement of nutrients from the forest floor into the soil was generally limited to nitrate, ammonia, and total phosphorus leaching into the upper soil layers. Very small fluctuations in nutrient levels occurred in the soil below 15 cm. Understory nitrogen and phosphorus levels increased in treated plots on both sites while cadmium increased on plots treated with municipal sludge. Understory hiomass increases of up to 132% over controls were measured on sludge‐treated plots. No metal toxicity symptoms were observed and sludge‐treated understory vegetation remained green later into the growing season well after that on untreated plots had begun to discolor and approach dormancy. Overstory foliar nitrogen concentrations increased on sludge‐treated plots, improving the N:P ratio in the pines. Increases in fasicle dry weight and needle length were noted in sludge‐treated red pine, as were increases in radial growth in white pine. Evidence two growing seasons following sludge fertilization indicated an increased canopy weight, thus an enhanced potential for photosynthesis.
Characterizing Unsaturated Hydraulic Conductivity of Western Kentucky Surface Mine Spoils and Soils
Authors: Ward Andy , Wells L. G. , Phillips R. E. 
Published: July 2010

AbstractA large‐scale laboratory infiltrometer system was used to determine infiltration characteristics of “reconstructed” surface mine spoil and soil horizons. Soil water characteristic curves were determined using the Brooks‐Corey and the Gardner procedures and developed based on desorption tensiometer data. Unsaturated hydraulic conductivity values were determined using the “plane of zero flux” procedure and compared with predictions resulting from models described by Campbell, Burdine, and Mualem for situations involving reconstructed soil and spoil materials. There was generally good agreement between the models and excellent agreement between Campbell's predictions and plane of zero flux results. Both the Gardner equation and the Brooks‐Corey equation gave good estimates of the soil water characteristic curves for the materials. The physical significance of the parameters θr and ψe, when determined by statistical procedures, appears very questionable. In this study, the final steady‐state infiltration rate appeared to be a good estimate of the hydraulic conductivity at apparent saturation.
Relationship of Marsh Elevation, Redox Potential, and Sulfide to Spartina alterniflora Productivity
Authors: DeLaune R.D. , Smith C. J. , Patrick W.H. 
Published: July 2010

AbstractData presented suggests that the short height form of Spartina alterniflora observed in inland areas of Louisiana Gulf Coast marshes is caused by toxic concentrations of sulfide, a result of slightly lower elevation and subsequently lower sediment redox potential than the adjacent productive streamside marsh. It is speculated that sulfide may limit growth by preventing nitrogen uptake and root development. Total sulfide concentrations as high as 250 µg g−1 of sediment and free sulfide concentrations in the order of 150 µg g−1 were found in the inland sediment. The inland sediment contained higher NH+4‐N concentrations at depth than the streamside sediment. The higher NH+4‐N concentrations closely paralleled the increasing sulfide concentrations and was inversely related to rooting depth. Maximum NH+4‐N concentrations of 60 and 16 µg N g−1 of dry soil was observed in the inland and streamside sediment, respectively. Redox potential was higher at the surface sediment of the more productive streamside marsh compared to the adjoining inland marsh. The higher redox potential is mainly due to the higher elevation of the streamside area that permitted greater drainage. This in turn allowed the development of more oxidized sediment containing lower sulfide levels. Observed differences in salinity and plant‐dissolved nutrients were not great enough to restrict plant growth.
Runoff Farming for Growing Christmas Trees
Authors: Fink D. H. , Ehrler W. L. 
Published: July 2010

AbstractRunoff farming was used to grow two species of conifers [Quetta pine (Pinus eldarica) and Arizona cypress (Cupressus arizonica)] in a semiarid climate on a sandy soil treated with wax and a clay soil treated with sodium chloride salt. The treated runoff‐contributing areas were varied in length to provide a water supply estimated initially to be two, three, and four times the normal 300‐mm annual precipitation. Twenty‐five trees were planted per species per site per water‐level treatment for a total of 300 trees. Thirty‐seven percent of them (110 trees) were harvested after only three growing seasons. Eighty‐nine percent (67 trees) of the Arizona cypress on the sand‐wax site were marketable, and the remaining 43 trees were from the other three species/site locations. Large differences in tree growth existed among the four species/site locations. The best trees were the cypress grown on the sand‐wax site. Most of the cypress on the clay‐salt site were 1 to 2 years behind those at the sand‐wax site. The Quetta pines grew best on the clay‐salt site where 24% were marketable in 3 years, with most of the remaining projected to be marketable by year four. The pines grew poorly on the sand site suffering > 50% mortality on the two lower water treatments. Only the cypress on the sand‐wax site showed a significant statistical difference in tree growth as related to water level. Runoff farming shows promise of becoming a practical and practicable method for growing Christmas trees and many other crops in arid and semiarid lands where water is scarce.
A Mathematical Model of Soil Erosion and Deposition Processes: I. Theory for a Plane Land Element
Authors: Rose C. W. , Williams J. R. , Sander G. C. , Barry D. A. 
Published: July 2010

AbstractThe paper describes a new mathematical model of soil erosion and deposition on a plane land element. The model makes use of an approximate analytic theory of runoff on a plane assuming kinematic flow. Rates of the following simultaneously occurring erosion/deposition processes are represented mathematically: rainfall detachment, sediment deposition, and soil entrainment by overland flow. The concept of stream power is used in representing the entrainment process. The form of analysis reduces the first‐order partial differential equation expressing conservation of mass of sediment to an ordinary differential equation, which can thus be solved analytically. This solution gives sediment concentration at any time as a function of distance down the plane in terms of four defined soil factors, the slope of the land, two separate cover factors, and the rainfall and runoff rates. The product of water flux and sediment concentration gives sediment flux at any time and position on the plane.
Effect of Crop Residue, Tillage‐Induced Roughness, and Runoff Velocity on Size Distribution of Eroded Soil Aggregates
Authors: Cogo N. P. , Moldenhauer W. C. , Foster G. R. 
Published: July 2010

AbstractThe percentages of eroded soil aggregates over 10 size classes ranging from 0.002 to 2.0 mm in diameter as affected by crop residue cover, tillage‐induced roughness, and water flow velocity were investigated under field conditions using simulated rainfall. The soils used were a 4.5% slope Russell silt loam and a 6.5% slope Martinsville loam. With no vegetation present, the smallest eroded aggregates came from a chisel‐plowed surface while the largest came from chisel‐ and moldboard‐plowed surfaces which had been disked. A no‐till treatment gave intermediate values. The D50 size (the aggregate size which 50% of the aggregates exceed) in the absence of soil cover was 0.033, 0.032, 0.020, and 0.011 mm for chisel plow plus disk, moldboard plow plus disk, no‐till and chisel plow, respectively. When soil was covered by residue, the size distribution of the eroded aggregates was not greatly different among the tillage treatments. The D50 size was reduced in this case to about 0.012 mm for all tillage systems. For no‐till, the percentage of the eroded aggregates > 0.05 mm decreased exponentially (r2 = 0.85) with an increase in residue cover. Under chisel plowing residue was not effective in reducing the quantity of larger aggregates in the runoff. An increase in flow rate caused an increase in water flow velocity which, in turn, caused a linear (r2 = 0.94) increase in the percentage of the eroded aggregates > 0.05 mm, for chisel plowing. The results from this study were explained in terms of sediment trapping capacity of the soil surface, as well as runoff transport capacity.
Accuracy of Several Immiscible Displacement Liquids
Authors: Kittrick J. A. 
Published: July 2010

AbstractEquilibrium solutions were displaced from moist samples of gibbsite and calcite of known stability using four different immiscible liquids, carbon tetrachloride, tetrachloroethylene, FC70 (a fluorocarbon), and 1,1,1‐trichloroethane. All four immiscible liquids permitted accurate solution analyses for gibbsite in the pH range near 4. In the pH range near 8.3, 1,1,1‐trichloroethane significantly decreased the pH of solutions displaced from calcite. All solutions in this pH range required protection from CO2 variations. Tetrachloroethylene and FC70 permitted accurate analyses of displaced solutions and are less toxic than CCl4.
Calcium‐Magnesium Exchange on Wyoming Bentonite in the Presence of Adsorbed Sodium
Authors: Sposito Garrison , Jouany Claire , Holtzclaw Kenneth M. , LeVesque C. S. 
Published: July 2010

AbstractThe exchange of magnesium for calcium at 298 K on Wyoming bentonite was investigated in a 50 mol m−3 perchlorate background maintained at pH 7. The charge fraction of Na+ in the aqueous solution phase was controlled at the values of 0.74 or 0.87 during the exchange experiments, resulting in average exchangeable sodium percentages (ESP) of either 16 or 36% on the clay. The Vanselow selectivity coefficient for Ca → Mg exchange was equal to 1.0 and was independent of exchanger composition at both ESP values. This result implied that, under the conditions of the exchange experiments, the clay exhibited equal affinities for Ca2+ and Mg2+ regardless of the quantity of adsorbed sodium present.
Competitive Complexation of Cd(II) and Cu(II) by Water‐Soluble Organic Ligands and Na‐Montmorillonite
Authors: Inskeep William P. , Baham John 
Published: July 2010

AbstractWater soluble extracts obtained from a coniferous forest litter layer (FLLE), dried Chicago sludge (CSE), and a peat soil (PE) were used as a source of organic ligands to study the influence of metal complexation on the adsorption of Cd and Cu by Na‐montmorillonite. Adsorption of 50 to 0.1µM CdT and CuT by Na‐montmorillonite (2 g L−1) was measured in the presence of the FLLE (1.8 mM total carbon) over a pH range of 4 to 8.5 after a 2‐h equilibrium period under humidified N2 gas. Equilibrium activity measurements for Cd2+ and Cu2+ were made with ion selective electrodes for experiments at 50 and 10 µM total metal (MT). After accounting for inorganic complexation, the amount of Cd complexed with organic ligands in the FLLE was much lower than that for Cu. Multiple regression equations where pMads (metal adsorbed) was tested as a function of pH and pMTS (total soluble metal concentration) showed that Cu adsorption decreased with increased pH values in contrast to adsorption in the absence of FLLE. Conversely, the adsorption of Cd was only slightly affected. Adsorption of 10 µM CuT in the presence of CSE and PE showed similar effects on adsorption, revealing the importance of water soluble complexing ligands in controlling Cu speciation.