bluuebunny/crossref_metadata_2025_split huggingface dataset:
Flocculation of Reference Clays and Arid‐Zone Soil Clays
Authors: Goldberg Sabine , Forster H. S. 
Published: July 2010

AbstractThe effect of electrolyte concentration, exchangeable sodium percentage (ESP), sodium adsorption ratio (SAR), and pH on the flocculation‐dispersion behavior of reference kaolinite, reference montmorillonite, reference illite, and the clay fraction of three arid‐zone soils was investigated. The clay mineralogy of the soils was dominated by either montmorillonite, kaolinite, or illite. The clays were Na‐ or Ca‐saturated and freeze‐dried before use. Critical coagulation concentrations (CCCs) were investigated in the range of pH 5.5 to 9.5, ESP of (here equated with percent Na clay) 0, 5, 10, 20, 40, 60, 80, and 100, SAR of 0, 5, 10, 20, 40, 60, 80, and ∞, and using electrolyte concentrations of 0 to 500 mmolc L−1. The CCC values increased with increasing ESP, increasing SAR, and increasing pH. The pH dependence of kaolinite and illite was greater than that of montmorillonite at all ESPs and SARs. The CCC behavior of the soil clays resembled that of illite, especially in its pH dependence at ESP 100 and SAR ∞. The CCC values of the soil clays, kaolinite, and illite showed a sharp increase at high ESP and SAR, whereas montmorillonite showed a sharp increase in CCC at low ESP and SAR. The CCCs for all soil clays were similar in magnitude, despite their differing clay mineralogies. The CCCs for the reference clays were much lower than those for the soil clays, indicating that extrapolation from reference‐clay results is not possible, and that additional factors such as organic‐matter content and Al‐ and Fe‐oxide content may influence the dispersion of soil clays.
Carbon‐13 Nuclear Magnetic Resonance Spectra of Soil Humic Substances Extracted by Different Mechanisms
Authors: Piccolo A. , Campanella L. , Petronio B. M. 
Published: July 2010

AbstractHumic substances were extracted from an organic soil of Tuscany, Italy, with solutions operating by three different mechanisms: charge repulsion (NaOH under N2), ligand exchange (Na4P2O7 at pH = 7), and H‐bond disruption (dipolar aprotic solvents in mixture with dilute HCl). Solution‐state 13C‐nuclear magnetic resonance (NMR) spectra were obtained for the unpurified and purified (HCl‐HF treatment) extracts, revealing that humic matter obtained through the H‐bond‐disruption mechanism was different from materials extracted using the two other mechanisms. Extracts obtained using dipolar aprotic solvents (DMF, DMSO, acetone) showed better resolved spectra than those using NaOH and Na4P2O7. This was due to a lower content of coextracted silicate materials and lower molecular weights. Spectra of humic substances extracted with acetone and DMF had a higher percentage of aliphatic C than did the spectrum of the extract with DMSO. The latter was, in general, more similar to the spectra of stronger extractants. The H‐bond‐disruption mechanism of dipolar aprotic solvents appeared to have extracted more unsubstituted aromatic rings than NaOH and Na4P2O7, although percent of aromatic C was generally equivalent in the spectra of all extractants. Purification with a HCl‐HF treatment decreased mainly the content of aliphatic, carbohydrate, and amino acid components of all extracts. Poor agreement between values for total acidity of extracts calculated by NMR and those given by chemical methods was also observed in this study.
Decomposition and Interactions among Wheat Residue Components
Authors: Collins H. P. , Rickman R. W. , Elliott L. F. , Bezdicek D. F. , Papendick R. I. 
Published: July 2010

AbstractDeveloping effective management strategies that protect soil against erosion necessitates an understanding of residue decomposition. Predicting decomposition of crop residues requires knowledge of their chemical and physical composition. Wheat (Triticum aestivum L.) residue decomposition is influenced by the amount of residue, ratio of residue components, and chemical composition of component mixes. This study describes winter wheat residue components and chemical composition, and assesses the effect of mixing residue components on the rate of decomposition. Winter wheat residue levels were measured on 20 field sites having grain yields ranging from 1 to 6 Mg ha−1. Residue was positively correlated with grain yield for the 1984 and 1985 crop years (r2 = 0.99***, 0.94***, respectively [significant at P = 0.001]). Residue‐to‐grain ratios averaged 1.47 for 1984 and 1.17 for 1985. Ratios of stem (ST), leaf sheath (LS), chaff (CH), and leaf blades (L) averaged 37:30:20:13. Total C and N, soluble C, and nonstructural carbohydrate (NSC) concentrations were not correlated with residue or grain yield. Stem and LS components had greater lignin and NSC contents than L and CH components. Rates of C mineralization for components were: L > LS > CH = ST. When components were mixed at the ratio of 32:30:28:10 ST/LS/CH/L, cumulative CO2 evolution was 1.25 times greater than that predicted by summing cumulative CO2 evolved from individual components. Comparison of single‐ and multiple‐term exponential decay models showed that a single‐term model adequately described decomposition of wheat residues.
Organic Amendment Effects on Physical and Chemical Properties of a Sandy Soil
Authors: Tester Cecil F. 
Published: July 2010

AbstractEffects of repeated applications of sewage‐sludge compost on soil properties have not been sufficiently evaluated with field trials. Field studies were established on an Evesboro loamy sand soil (mesic, coated Typic Quartzipsamment, 97% sand) to compare the effects of sewage‐sludge compost, beef manure, and fertilizer amendments on soil properties. The study site had been fallow for 26 yr and should have provided a positive response to the added organic matter. Compost application rates were based on the assumption that material would be applied either only once or annually. Application rates ranged from those that were too low to supply the total N requirement of a crop (e.g., 33 Mg ha−1) to excessively high rates that would produce maximum soil benefits from the added organic matter (e.g., 268 Mg ha−1). Soil properties such as strength (penetrometer resistance), bulk density, water retention, pH, surface area, total N and P contents, and organic matter were evaluated for 5 yr. Addition of sewage‐sludge compost significantly reduced penetration resistance when compared with the control and fertilizer‐amended soils. Compost significantly reduced bulk density, increased soil water content, and modified pH to greater depths. Specific surface area of the soils increased linearly with the addition of compost and C levels indicated that 24 and 37% of the annually added organic matter decomposed during the 1st yr from the sewage‐sludge compost and beef manure, respectively.
Nitrification Potential of Secondary‐Succession Upland Oak Forests: II. Regulation of Ammonium‐Oxidizing Bacteria Populations
Authors: Donaldson Jennifer M. , Henderson Gray S. 
Published: July 2010

AbstractField plots were treated with NH4‐N and Ca(OH)2 to test the hypothesis that NH4 and pH control nitrification in these soils. The most probable number (mpn) of autotrophic NH4‐oxidizing bacteria were estimated in treated and control soils at five dates within a 1‐yr period. Sampling dates coincided with periods of significant phenological development of the vegetation. The effect of the treatments on the population of NH4‐oxidizers was used to assess the treatment effect on soil nitrification potential. The results suggested that soil NH4 is a major factor regulating populations of these microorganisms; however, numbers of NH4‐oxidizers in both treated and untreated soils vary significantly with date of sample collection. The seasonal responses of these microorganisms indicate that vegetation affects NH4‐oxidizer populations, perhaps through the production and release of inhibitory compounds.
Exchange Fertilizer (Phosphate Rock plus Ammonium‐Zeolite) Effects on Sorghum‐Sudangrass
Authors: Barbarick K. A. , Lai T. M. , Eberl D. D. 
Published: July 2010

AbstractFertilizer systems that use an exchange medium in combination with slightly soluble phosphate rock could provide a slow, sustained release of P and avoid the potential problems (e.g., fixation) associated with a large, single application of an element. Consequently, the effectiveness of one NH4‐exchanged zeolite (clinoptilolite) in increasing phosphate‐rock solubility in two soils (Red Feather loamy sand, a Lithic Cryoboralf and Weld loam, an Aridic Paleustoll) was evaluated by measuring increases in dry matter, nutrient content, and nutrient uptake by sorghum‐sudangrass [Sorghum bicolor (L.) Moench‐S. sudanese (Piper) Stapf, ‘NB280S’]. Two phosphate‐rock applicationr ates of 170 and 340 mg P kg−1 soil were used in factorial combination with zeolite/phosphate‐rock ratios of 0, 1.5, 3, 4.5, 6, and 7.5:1. The largest dry‐matter yields through four plant cuttings from the Weld soil generally were found with the 340 mg P kg−1 rate and with increasing zeolite/phosphate‐rock ratio (linear response). Increasing zeolite/phosphate‐rock ratio in this soil generally increased plant P concentrations and uptake. The exchanger fertilizer system increased P availability in the Weld soil by producing lower soil pH (nitrification of NH4 released by the zeolite) than the 0:1 zeolite/phosphate‐rock ratio control and by the adsorption of Ca in the zeolite. The Red Feather soil, which was deficient in K, did not provide definite yield responses because the zeolite sequestered K, thereby reducing plant K concentrations and uptake even though the zeolite increased total P uptake. The NH4‐exchanged zeolite/phosphate rock combination used in the present study seems to be a promising P‐fertilizer system in nonalkaline soils if K or other plant‐essential cations are not limiting.
X‐ray Diffraction Indices for Relative Quantification of Interlayering in Phyllosilicates
Authors: Esser Kjell Bjørgen 
Published: July 2010

AbstractSimple, numerical methods for routine interpretation of x‐ray diffractograms of soil samples are desirable but largely unavailable due to the prevalence of mineral intergrades. A set of indices is proposed that facilitates a comparative estimation of proportions of K‐collapsible vermiculite and smectite, proportions of hydroxy interlayers, and proportions of swelling interlayers. The indices are based on an estimation of the horizontal displacements of the centroids of x‐ray diffraction areas representing a range of d001 spacings after various saturation and heat treatments. A potassium contraction index (KCI), a contraction index at 300 °C (CI300), and a contraction index at 550 °C (CI550) express the degree of interlayer contraction upon K saturation, heating to 300 °C, and heating to 550 °C, respectively, relative to the Mg‐saturated sample. Subtracting the CI300 from the CI550 yields an (Al + Fe)/Mg interlayer index expressing the relative proportions of Al + Fe‐hydroxy interlayers and Mg‐hydroxy interlayers. The indices can be a useful supplemental tool in the study of mineral transformations when computer analysis of x‐ray diffractograms is unavailable.
Collection of Intact Cores from a Rocky Desert and a Glacial Till Soil
Authors: Lewis T.E. , Blasdell B. , Blume L.J. 
Published: July 2010

AbstractA method involving the use of triple‐expanding polyurethane foam was developed for the collection of large intact cores from two problem soil types for use in anion/cation transport studies. Intact cores, 36‐ to 41‐cm diameter, were collected from a Jean series (sandy‐skeletal, mixed, thermic Typic Torriorthent) and a Colonel series (coarse‐loamy, mixed, frigid Aquic Haplorthod). A free‐standing pedestal was isolated. The circumference of the core was reduced, to allow encapsulation with a PVC pipe of appropriate inner diameter. The space between the soil and the PVC pipe was filled with polyurethane foam. After the foam cured overnight, the core was severed at the base by driving a steel plate beneath the PVC pipe. Endcaps were fastened to the PVC pipe and the cores were transported to the laboratory.
Pore Size, Particle Size, Aggregate Size, and Water Retention
Authors: Wu L. , Vomocil J. A. , Childs S. W. 
Published: July 2010

AbstractMeasurements of water retention and pore‐size distribution for a soil are time consuming and affected by changes in aggregate‐size distribution. A method of compared distribution curves was used to relate distributions of pore size (PO), particle size (PA), aggregate size (AG), and pore size from water retention (WR). Seven surface soils varying in texture and aggregation were tested. After normalization to 100% volume, the pore‐, particle‐, and aggregate‐size distribution, as well as water‐retention (converted to pore diameter) curves were each fitted to a linearly transformed logistic function to evaluate their interrelations using R(m/n), a coefficient for the ratio of the diameters of component m to component n. Identical distribution curves have an R(m/n) value of 1. The R(PO/PA) and R(WR/PA) for the seven soils ranged from 0.25 to 2.26 and from 0.18 to 1.34, respectively, indicating that the theoretical packing parameters of 0.225 to 0.414 do not hold for PA distribution. The R(PO/AG) ranged from 0.06 to 0.23 and R(WR/AG) from 0.04 to 0.16. Both ranges of R values smaller than the theoretical packing parameters suggests interactions may occur between large and small aggregates. However, R(PO/AG) and R(WR/AG) values were more consistent and were significantly related to aggregation level and bulk density, suggesting that AG distribution should be used as a parameter to predict PO distribution and water retention. Comparisons between water retention curves and PO distributions from Hg intrusion gave R(PO/WR) ranging from 0.78 to 2.59, showing that equivalent PO for a given soil is not the same when different measuring methods are used.
Reactions of Gypsum or Phosphogypsum in Highly Weathered Acid Subsoils
Authors: Alva A. K. , Sumner M. E. , Miller W. P. 
Published: July 2010

AbstractCrop responses to gypsum or phosphogypsum (PG) amendment to acid soils have been highly variable in different soils. Therefore, soil properties influence the mechanisms of amelioration of acid‐soil infertility by gypsum or PG. The effects of gypsum or PG amendments on soil‐solution composition and surface reactions were studied in subsoils (0.6–0.8 m) from cultivated and woodland sites representing three soil series (Bladen: Typic Albaquult; Cecil and Wedowee: Typic Hapludults). Soils were equilibrated in the laboratory with either deionized water or saturated solutions (2.0 g L−1) of either PG or reagent‐grade CaSO4·2H2O (gypsum) at 20, 40, and 60% (v/w) soil moisture contents. Soil solution was displaced by centrifugation. Depletion of Ca and SO4 from gypsum or PG solution during equilibration was due to sorption of the respective ions by the soil. The sorption of Ca and SO4 was considerably greater in the woodland soils than in cultivated soils. The sorption of Ca from PG solution was equivalent to the increase in negative charge in the Cecil and Wedowee soils. In the Bladen soil, the increase in surface charge was lower than the sorption of Ca. The increase in exchangeable cations in the Cecil and Wedowee soils, after equilibration with PG solution, was very similar to sorption of SO4. Equilibration of the soils with PG or gypsum solution decreased the exchangeable Al by 40, 21, and 6 to 7% in the Cecil, Wedowee, and Bladen soils, respectively. The amelioration of acid‐soil infertility by gypsum or PG was due to a combination of SO4‐induced surface charge development, increased cation retention, and a decrease in exchangeable Al. The ameliorative effects of acid‐soil infertility by gypsum or PG amendment were greater in soils dominant in variable‐charge characteristics than in those dominant in permanent‐charge characteristics.
Alkali Basalt Gravel Weathering in Quaternary Allier River Terraces, Limagne, France
Authors: Veldkamp E. , Jongmans A. G. , Feijtel T. C. , Veldkamp A. , van Breeman N. 
Published: July 2010

AbstractWeathering of alkali basalt pebbles was studied in three Quaternary Allier terraces of different ages. The isovolumetric method and Ti‐constant method were applied to quantify compositional changes due to weathering. Bulk density of fresh gravel in the younger terraces (Weichselien and Holocene) was adequately estimated from geochemical data by a multiple linear regression model (R2 = 0.81**, significant at P = 0.01). Since no chemical and micromorphological differences could be demonstrated between fresh gravel and the unweathered cores of partly weathered gravel, the regression model was also applied to calculate the bulk density of the cores of partly weathered pebbles in the oider terraces. The decrease in bulk density of the rind, compared with that of the core, was used as a measure of weathering intensity. The chemical composition of the weathering rind revealed a relative increase in the contents of Ti, Al, Fe, and Mn and a decrease of K, Na, Ca, and Si. Changes were estimated considering Ti essentially immobile. Except for Fe and Mn, all elements tended to decrease in the rind. The relative elemental mobilities were as follows:K > Na > Si > Mg > Ca > P > Al > TiNo relationship was found between weathering intensity and the age of the two oldest terraces or sampling depth. Differences in weathering intensity are predominantly a function of chemical (= mineralogical) composition of the alkali basalt pebbles.
Responses of Biopore Channels from Roots to Compression by Vertical Stresses
Authors: Blackwell P. S. , Green T. W. , Mason W. K. 
Published: July 2010

AbstractThe channels created in soil by roots and soil animals (biopores) play an important role in the subsequent movement of water, air, and new roots through irrigated clay soils in southeastern Australia. The maintenance of these biopores is critical for both crop productivity and erosion control. If these biopores are to remain open, they must be able to withstand the vertical stresses associated with vehicle and animal traffic. This study had three aims: (i) to examine the influence on porosity and permeability of naturally occurring channels, (ii) to determine the magnitude of vertical stresses that artificially created channels could withstand, (iii) to test the effect of channel angle to the direction of the stress. Air‐filled porosity of soil cores at −10 J/kg was decreased in a linear fashion as the applied stress was increased from 50 to 400 kPa. The reduction in air‐filled porosity was relatively independent of the size or the presence of biopores. However, the intrinsic permeability of the soil cores to air was positively correlated with the diameter of the biopores, and the permeability was little affected by applied stresses up to 200 kPa if the initial diameter of the biopores was >3.5 mm. The resistance of the channels to stresses was greatest if the vertical stress was parallel to the axis of the channels. Agricultural practices on these soils should not only encourage formation of biopores, but should also minimize stresses >200 kPa to the subsoil so that these biopores can remain open.
Polymer Effects on Erosion under Laboratory Rainfall Simulator Conditions
Authors: Ben‐Hur M. , Shainberg I. , Letey J. 
Published: July 2010

AbstractSoil erosion by water is a serious problem in several parts of the world. Incorporation of polymers into water applied to soil by a rainfall simulator can improve infiltration rates. This study was conducted to determine the effects of nonionic, anionic, and two charge densities of cationic derivatized guar products on erosion and infiltration rates. The polymers were mixed with distilled water at concentrations from 0 to 20 g m−3 and applied through a rainfall simulator in the laboratory. Untreated distilled water was applied to an Arlington sandy loam soil (Haplic Durixeralf) with the soil surface both unprotected and protected by a fiberglass sheet placed 0.5 cm above the soil surface. All polymer treatments were applied to the unprotected soil surface. Distilled water drop impact greatly reduced infiltration rate and increased erosion, compared with no impact. The anionic and nonionic polymers did not significantly affect erosion or infiltration rate, compared with distilled water. The cationic polymers significantly increased infiltration rate and erosion, compared with distilled water. The higher charge cationic polymer produced significantly higher values than the lower charge polymer at the same concentration. The distilled‐water treatment with impact caused severe aggregate disruption and dispersion, producting a layer of fine material at the surface that decreased infiltration rate. Apparently, the very‐fine particulates became imbedded in the soil matrix, which made them less susceptible to lateral transfer with flowing water. The flocculating action of the cationic polymer created larger particulates, which had very little effect in reducing infiltration rate but were more susceptible to erosion. Under the conditions of the experiment, particulates between 0.05 and 0.25 mm were most susceptible to transport by a thin sheet of flowing water.
Macroporosity and Its Relation to Saturated Hydraulic Conductivity under Different Tillage Practices
Authors: Logsdon S. D. , Allmaras R. R. , Wu L. , Swan J. B. , Randall G. W. 
Published: July 2010

AbstractTillage management influences the distribution of macropores (biopores, cracks, interpedal planes, and packing voids) that may provide pathways for rapid infiltration of water. To aid in predicting ranges of saturated hydraulic conductivity (Ksat), macropore distribution in situ was characterized by exposing selected horizontal planes and tracing macropores on clear polyethylene sheets. A methylene blue solution was used to indicate macropore continuity through the pressure pan. Sixteen undisturbed cores were taken in a grid pattern from each Ap horizon and adjacent subsoil for determination of Ksat. Field marking on plastic sheets was superior to photographic slides as a technique to characterize macropores because film noise (false pores) was eliminated, overall analysis time was reduced, and different features could be separated for analysis. Unfortunately, a bias of pore size between observers was possible. Four sites with four different soil series were examined: Nicollet (fine‐loamy, mixed, mesic Aquic Hapludoll), Rozetta (fine‐silty, mixed, mesic Typic Hapludalf), Waukegan (fine‐silty over sandy or sandy‐skeletal, mixed, mesic Typic Hapludoll), and Normania (fine‐loamy, mixed, mesic Aquic Haplustoll). Below the maximum tillage depth, macropores were present at all locations, but tillage disrupted continuity of pores from the surface. No‐till had macropores throughout the upper 70 cm with continuity observed in the 0‐ to 35‐cm range. Numbers of pores (>0.4‐mm diam.) per m2 ranged from 100 to >3000, representing 0.1 to 2% of the total area. When present, horizontal crack length ranged from 1.7 to 19.3 m m−2. Measured Ksat on undisturbed detached cores ranged from 1.1 to 180 µm s−1 with CVs ranging from 44 to 197%. The Ksat could be estimated within a range (out of eight classes) from descriptions of biopore area, cracks, soil structure, and soil texture.