bluuebunny/crossref_metadata_2025_split huggingface dataset:
Drainage of a Tropaqualf Before and After Water Extraction by a Crop
Authors: Klodpeng Thanom , Morris R. A. 
Published: July 2010

AbstractTo improve production of crops planted after lowland rice (Oryza sativa L.) in monosoonal Asia, there is a need to understand more clearly the drainage pattern during the transition from the wet to the dry season. For crops of 75 to 80 d maturity, the top 750 mm of soil contains the bulk of the root system. This study determined the flux of water across the 750‐mm plane and the water table recession patterns during the transition from wet to dry season and again after a crop had removed water from the soil. The study was conducted in three phases on a 9‐m by 9‐m plot of an Aeric Tropaqualfs. In the first phase, the soil was field saturated, covered with plastic sheeting, and drained for 30 d. In the second phase, a cowpea (Vigna unguiculata L. Walp) — sorghum (Sorghum bicolor L. Moench) intercrop was grown for 42 d. In the third phase, 22 mm of water was applied and soil was again covered and drained for 15 d. Volumetric water changes were determined by neutron scattering at 150‐, 300‐, 600‐, 900‐ and 1200‐mm depths. Tensiometers were placed at the same depths. The plot was surrounded by flow barriers to a 750‐mm depth. Drainage through the 750‐mm plane during the first phase amounted to only 11 mm. A perched water table formed in and above the B horizon at 600 mm. The ground water table receded at 30 mm d−1 after it appeared below the perched water table on day 10. During the second phase roots penetrated at about 25 mm d−1 suggesting that the initial high water content was not a major impediment to root development. After a 22‐mm irrigation, the drainage rate during the third phase was 1.2 mm d−1, with drainage apparently coming both from applied water and water remaining in the profile prior to irrigation. The results suggest both opportunities and problems for using soil water remaining after rice harvest during the transition from wet to dry season.
Some Equilibrium Considerations in the Formation of Chlorite in Soils and Sediments
Authors: Kittrick J. A. 
Published: July 2010

AbstractSufficient chlorite stability data are now available so as to permit initial consideration of chlorite equilibria in soils and sediments. Assuming a pH4SiO4 of 3.1 and other conditions approximating the soil solution, stability diagrams indicate that high‐Mg varieties of chlorite and smectite should be stable under an oxidizing condition (pe + pH = 17.7) and should control Mg or Al, or both. Under a mildly reducing condition (pe + pH = 11.5), high Fe2+ chlorites and probably smectites are predicted to dominate equilibria. The lack of rate information may be particularly restrictive considering the extremely low levels of Al anticipated.
Determination of 15N‐Labeled Dinitrogen and Nitrous Oxide with Triple‐Collector Mass Spectrometers
Authors: Mulvaney R. L. 
Published: July 2010

AbstractEquations are derived that permit use of a triple‐collector mass spectrometer for determination of 15N‐labeled dinitrogen (N2) and nitrous oxide (N2O) by procedures recently developed for double‐collector instruments. These equations are based upon the ratios 29N2/28N2 and 30N2/28N2, instead of 29N2/28N2 and 30N2/(28N2 + 29N2).
Evaluation of Simplified Methods for Determining Unsaturated Hydraulic Conductivity of Layered Soils
Authors: Schuh W. M. , Bauder J. W. , Gupta S. C. 
Published: July 2010

AbstractThe simplified field method of L.R. Ahuja et al. (1980) for determining hydraulic conductivity as a function of soil water suction, K(S), and the simplified field method of P.L. Libardi et al. (1980) for determining hydraulic conductivity as a function of soil water content, K(θ), were compared with the instantaneous profile method, to evaluate their suitability for estimating hydraulic conductivity of layered soil. The Ahuja method worked well on coarse and fine‐textured soils and complex soil profiles with stratification. The Libardi method worked well on coarse and fine‐textured, homogeneous materials and homogeneous parent materials underlying stratified soil materials. A calculated matching value (Ko) was used with the Libardi method. Within layered soil materials slopes of the K(θ) curves, calculated with the Libardi method, were adequate; however, calculated Ko values were often inadequate. Fit of calculated values with measured values of hydraulic conductivity could have been improved by using field‐determined Ko values.
Kinetics of Arsenite Sorption in Soils
Authors: Elkhatib E. A. , Bennett O. L. , Wright R. J. 
Published: July 2010

AbstractThe sorption of As(III) by 10 surface and subsurface horizons was investigated. An Elovich type equation and a modified Freundlich equation were used to describe the kinetics of the As(III) sorption process. Both equations successfully describe As(III) sorption rates. However, the modified Freundlich equation proved to be superior when both coefficients of determination (R2) and standard errors of estimate (SE) were considered. The SE values from the modified Freundlich equation were consistently lower than those from the Elovich equation. Modified Freundlich equation parameters were regressed against soil chemical and physical properties to indicate possible sorption mechanisms and to identify soil properties that could serve as predictors of arsenite sorption. The regression equations indicated that iron oxides and Eh were the main soil properties controlling arsenite sorption rate.
Pathways of Phosphorus Transformations in Soils of Differing Pedogenesis
Authors: Tiessen H. , Stewart J. W. B. , Cole C. V. 
Published: July 2010

AbstractNine different organic and inorganic soil phosphorus fractions were obtained by a sequential extraction of samples from 168 USDA‐SCS benchmark soils, representing eight soil orders of the Soil Taxonomy. The distribution of P across the different fractions (resin, bicarbonate, hydroxide, sonification‐2nd hydroxide, acid, and acid‐peroxide digest fractions with separate organic and inorganic P determinations) and their relationships to other soil chemical properties were used to evaluate the effects of different soil development on phosphorus composition. Correlation and regression analyses of P distribution and chemical analyses confirmed the partial dependence of organic matter accumulation on available forms of P. Weathering indicators such as base saturation were related to the formation of secondary P forms. The relative proportions of available and stable as well as organic and inorganic P forms were dependent upon soil chemical properties and related to soil taxonomy. Path analysis of relationships between labile and stable P forms showed that in Mollisols much of the labile resin extractable P was derived from inorganic bicarbonate and hydroxide extractable P forms. In more weathered Ultisols, 80% of the variability in labile P was accounted for by organic P forms, suggesting that mineralization of organic P may be a major determinant of P fertility in these soils.
Loess‐Derived Soils, Mississippi Valley Region: I. Soil‐Sedimentation System
Authors: Ruhe Robert V. 
Published: July 2010

AbstractAmong 25 profiles of Typic Hapludalfs at approximately half degrees of latitude from southern Mississippi to southeastern Minnesota, the textural and clay‐mineralogic properties of the soils depend mainly on the sedimentation system at each site. Other physical, chemical, and hydrologic properties that relate to texture and mineralogy are also in part sedimentation‐dependent. Although temperature and precipitation decrease to the north, there is little climatic impact on these properties in these soils.
Weight Loss and Nutrient Dynamics in Decomposing Woody Loblolly Pine Logging Slash
Authors: Barber B. L. , Van Lear D. H. 
Published: July 2010

AbstractSix clearcuts ranging from 0 to 11 yr since cutting in the Piedmont of South Carolina were sampled to estimate the rate of weight loss of logging debris and to study nutrient dynamics in decomposing loblolly pine (Pinus taeda L.) slash. Density changes in wood were characterized using a negative exponential model. Decay coefficient (k) for small‐sized pieces (< 2.5‐cm diam) was 0.051 while decay coefficients for medium‐ (2.5–7.5 cm diam) and large‐ (> 7.5‐cm diam) sized pieces were 0.079 and 0.072, respectively. Overall, woody logging slash exhibited a k value of 0.072. Logging slash in contact with the ground decayed at a 50% higher rate than aerial slash. Concentrations of N and P in woody slash remained relatively constant the first few years after cutting followed by an increase. Concentrations of K, Mg, and Ca decreased in the initial stages of decomposition and then increased in the later stages. A prediction model estimated that N and P quantities in woody slash initially decrease and then increase. After 7 yr, woody slash would contain 107% of the N and 94% of the P contained in the slash initially. Potassium, magnesium, and calcium quantities show a gradual decrease with time. Woody logging slash would lose 77, 56, and 50% of the initial amounts of K, Mg, and Ca, respectively, after 7 yr. Woody logging slash acts as a nutrient sink and may be important in nutrient conservation on cutover areas.
Catalytic Effects of Manganese (IV), Iron(III), Aluminum, and Silicon Oxides on the Formation of Phenolic Polymers
Authors: Shindo H. , Huang P. M. 
Published: July 2010

AbstractThe catalytic effects of three Mn(IV) oxides (birnessite, cryptomelane, and pyrolusite) and short‐range ordered Fe(III), Al, and Si oxides on the darkening of phenolic compound solutions (hydroquinone, resorcinol, and catechol) and the subsequent formation of humic acid (the precipitate formed by acidifying the darkening solution) were investigated. Manganese oxides are very powerful in causing the darkening of phenolic compounds. The rate and degree of the darkening vary with the kinds of Mn oxides, the chemistry of the phenolic compounds, and the pH values of the systems. In the Mn oxide systems, phenolic compounds are converted to humic acid with a relatively high degree of humification (Δlog K: 0.52–0.70; RF: 54–105) through oxidative polymerization. For example, at the initial pH of 6.0, the percent conversion of hydroquinone to humic acid ranged from 36 to 55%. The yields of humic acids formed in the Mn oxide systems are highly correlated with the degree of the darkening measured at 400 nm (r2 = 0.818) and 600 nm (r2 = 0.983). The catalytic effect of Fe oxide on the darkening and the formation of humic acid was relatively limited under the conditions studied. The catalytic effects were not observed in the Al and Si oxide systems. The results obtained in this study indicate that various Mn(IV) oxides common in the environment merit close attention in the abiotic formation of humic substances.
Expansion of Smectites as a Function of Vapor Pressure of Ethylene Glycol
Authors: Hsieh Y. P. , Tsai Ping‐Ping , Hsu Pa Ho 
Published: July 2010

AbstractMagnesium‐saturated, 0.2‐ to 1‐µm fraction of six references smectites and two smectite‐rich soil clays were solvated with ethylene glycol vapor at 65°C under graded relative vapor pressures from 3 to 100%. Each smectite expanded over a range of relative vapor pressure. This observation implied that heterogeneity in layer charge distribution of the smectites was common in the specimens. Relatively, Wards 25 and Wards 27 were least heterogeneous, and Wards 31 and Wards 23 were most heterogeneous among the specimens. The relative expandability of smectites under solvation of ethylene glycol vapor followed the sequence of: SHe‐1>Wards 25 = Wards 27≥SWy‐1> Wards 23>Bowdoin C>LC> Wards 31. The sequence corresponded approximately with that of total layer charge of the specimens. Six of the eight smectites exhibited heterogeneity in a random interstratification manner, two exhibited heterogeneity in a zoned interstratification manner. The moisture‐ethylene glycol interaction enhanced the expansion of smectites when they were partially solvated with ethylene glycol.
Scaling Soil Water Properties and Infiltration Modeling
Authors: Ahuja L. R. , Naney J. W. , Nielsen D. R. 
Published: July 2010

AbstractWe examined variability and interrelation of the scaling factors for Green‐Ampt infiltration parameters of saturated hydraulic conductivity (Ks) and wetting‐front pressure head (hf) in a 9.6‐ha grassland watershed, containing three hydrologically similar silt loam Mollisols. Scaling factors for different depths at a given site appeared to be related. The scaled mean Ks decreased with depth, while the scale mean hf showed no trend. The Ks scaling factors had greater variability between sites than the hf factors, and the relationship between the two sets of factors deviated appreciably from a 1:1 line. However, there was a linear relationship between them, which was utilized in modeling infiltration. The composite infiltration for the watershed calculated by using different, but related, scaling factors for Ks and hf was very close to that obtained by using the same scaling factors, derived from either Ks or hf, for both. However, the distribution and range of the predicted infiltrations were greatly different.
Sodium‐Calcium‐Magnesium Exchange Reactions on a Montmorillonitic Soil: II. Ternary Exchange Reactions
Authors: Fletcher Philip , Holtzclaw Kenneth M. , Jouany Claire , Sposito Garrison , LeVesque C. S. 
Published: July 2010

AbstractThe exchange of magnesium for calcium at 298 K on a montmorillonitic soil separate (principally clay and silt) was investigated in a 50 mol m−3 perchlorate background at pH 5,6, and 7. The charge fraction of sodium in the aqueous solution phase was controlled at 0.70 or 0.85 during the exchange experiments, resulting in average exchangeable sodium percentages ranging from 5 to 25% on the soil. Exchange isotherms for magnesium indicated some preference on the soil for calcium over magnesium. This preference was attributed primarily to the presence of organic matter associated with the soil separate. However, the exchange isotherms showed no effect of pH in the range between 5 and 7, and no effect of exchangeable sodium percentage in the range between 0 and 25%.
Specific Adsorption of Copper on an Hydroxy‐Aluminum‐Montmorillonite Complex
Authors: Harsh J. B. , Doner H. E. 
Published: July 2010

AbstractThe adsorption of Na on a prepared hydroxy‐aluminum‐montmorillonite complex (OH‐Al‐SWy‐l) was investigated as a function of pH, time, and Cu concentration ([Cu]). It was found that Na adsorption from 0.01M NaClO4 increased with pH from 0.015 mol kg−1 at pH 4.5 to 0.33 mol (Na+) kg−1 clay at pH 6.6 Adsorption of 0.16 mol (1/2 Cu2+) kg−1 clay did not affect the amount of Na adsorption, showing that specific sites existed for Cu. Adsorption of Cu was found to increase with pH and both adsorption and resistance to extraction with 0.25M Ba(NO3)2 increased with time. At pH 4.6, Cu adsorption approached a maximum near 0.3 mol (1/2 Cu2+) kg−1 clay of which 0.13 mol (1/2 Cu2+) were extracted with Ba(NO3)2. Electron spin resonance (ESR) of the Cu on OH‐Al‐SWy‐l showed that both physi‐ and chemisorbed Cu were present and that solubilization as Cu(NH3)2+4 through exposure to NH3 vapor overnight was possible only if the sample had been previously treated with BaCl2. It was concluded that the OH‐Al‐SWy‐l system provided a much more reactive surface toward Cu adsorption than either montmorillonite or hydrous aluminum oxides. In comparison to smectites Cu was less labile to Ba extraction due, in part, to chemisorption by Al‐OH groups. Relative to values reported for Al(OH)3 polymorphs, Alx(OH)y3x‐y precipitated in the presence of montmorillonite adsorbed more Cu on a mass basis presumably due to a higher surface to mass ratio.
Spatial Variability of Rhizobium japonicum in Two North Carolina Soils
Authors: Wollum A. G. , Cassel D. K. 
Published: July 2010

AbstractThe spatial variability of Rhizobium japonicum populations was evaluated for two soils on the Coastal Plain of North Carolina. The Nahunta soil (fine‐silty, siliceous, thermic Arenic Paleudults) was somewhat poorly drained and had an organic matter content of 20 g kg−1 whereas the Pocalla soil (loamy, siliceous, thermic, Arenic Paleudults) was well drained and had 10 g kg−1 organic matter. One hundred and five soil samples from the Ap horizon were collected from an apparently uniform 18‐m by 18‐m area at each site and were subjected to analysis by the plant infectivity—most‐probable‐number (MPN) technique to determine the number of rhizobia. The log10 MPN (log MPN) of R. japonicum varied from 2.63 to 7.03 g−1 soil; mean log MPN values were 4.10 and 6.07 g−1 soil for Pocalla and Nahunta, respectively. Semivariograms for sample separation distances (h) < 2 m at each site were developed from soil samples collected on transects (fences). Semivariograms for h ≥ 3 m were developed using data collected on a 3‐m grid. Analysis of the semivariograms constructed from the log MPN data indicated a different variance structure at each site. Moreover, the variance structure for log MPN was found to be directional, i.e., it was different in the direction “parallel to the row” compared to the direction “perpendicular to the row.” For the Pocalla soil the semivariance in the “down‐the‐row” direction was greater for values of h < 1.05 m than it was for h ≥ 3 m. This apparent discrepancy is thought to be due to selection of the transect from which the 0.2‐m spaced samples were collected in a region of the field which is not typical of the field as a whole. This result demonstrates the importance of using a sampling regime which is not biased toward one particular area of a field. Root densities, inherent soil properties, seasonality, and management practices are possible contributors to the subtle changes in rhizobia populations that were observed.
Soil Phosphorus Supplying Capacity Evaluated by Plant Removal and Available Phosphorus Extraction
Authors: Aquino B. F. , Hanson R. G. 
Published: July 2010

AbstractMany Missouri soils test high in extractable P after long periods of rock phosphate and processed P fertilization. This study was undertaken to determine the P‐supplying capacities of five Missouri soils possessing high levels of extractable P. Initial P levels were evaluated with selected extractants (Bray I, Bray II, Mehlich II, double acid, dilute SrCl2) and through evaluation of the P buffering index. Each soil was cropped under greenhouse conditions for 7 consecutive harvests of grain sorghum (Sorghum bicolor L. cv. Warner 744R). After each harvest, plant P uptake was calculated and extractable P measured as before. For each soil test, regression analyses of plant P uptake were performed. With only one exception, the decline in extractable P in all soils, as measured by all five extractants, was significantly correlated with cumulative P uptake. The highest correlations were obtained with Bray I for Sharkey clay (r = 0.95), Bray I and Bray II for Kennebec silty clay loam (r = 0.97), Bray II for Mexico silt loam and Broseley loamy fine sand (r = 0.95 and r = 0.90, respectively), and Mehlich II for Tiptonville silt loam (r = 0.96). Slopes of the decline in extractable P following intensive cropping show similarities between Bray I and Mehlich II, Bray II and double acid. The quantity of plant available P extracted by Bray II and dilute SrCl2 was found to be inversely related to the P buffer index (PBI). When extrapolating to critical P levels for Bray I (11 mg kg−1) and Bray II (24 mg kg−1) only the Bray II extracted predicted number of harvests in order of soil PBI.
Movement of Calcium and Magnesium in Ultisols from Dolomitic Limestone
Authors: Messick D. L. , Alley M. M. , Zelazny L. W. 
Published: July 2010

AbstractRoot growth and crop yield are limited on many soils by acid subsoil and toxic concentrations of Al and Mn, and deficiencies of Ca and Mg. Calcium and magnesium movement and neutralization of acidity below the zone of limestone incorporation were investigated on seven acid Virginia soils. Dolomitic limestone treatments of 0, 4.5, 9.0, and 13.4 Mg ha−1 on the Coastal Plains and 0, 4.5, 9.0, 13.4, and 18.0 Mg ha−1 on Piedmont and Valley soils were surface‐applied and incorporated (0–20 cm). Four years after limestone application, soil samples were collected at depth increments of 0 to 10, 10 to 20, 20 to 25, 25 to 30, 30 to 40, 40 to 50, and 50 to 60 cm. Samples were analyzed for exchangeable Ca, Mg, and Al, and pH. Calcium and magnesium movement and depth of neutralization decreased with increasing soil clay content. Liming increased cation retention in horizons that received direct lime application apparently due to increased pH‐dependent CEC. Depth of neutralization was lime rate dependent with greater neutralization of acidity at higher limestone rates. Magnesium movement was detected at greater depths than Ca in all soils, but neutralization of acidity did not accompany movement of either Ca or Mg. This demonstrated that the cation moved as a neutral salt or that pH change was not measurable.
Dispersion of Soils by an Ultrasonic Method that Eliminates Probe Contact
Authors: Busacca A. J. , Aniku J. R. , Singer M. J. 
Published: July 2010

AbstractA cup‐type ultrasonic vibrator was evaluated for use in dispersing soils and was calibrated to the standard chemical dispersion plus shaking method. The “cup horn” device isolates the soil suspension from contact with, and potential contamination from, the Ti alloy of the ultrasonic probe‐tip or “horn.” Five soils (2 A horizons and 3 B horizons) representing four soil orders were tested. The soils varied in texture (16–48% clay), clay mineralogy (mixed to kaolinitic), pH (4.9–7.0), and free‐iron (1.9–5.0%). Twenty‐minute cup horn treatment at 200 watts yielded clay contents that were 0 to 9.5% lower than those from the standard method; 25‐minute treatment yielded values 1.5% lower to 21.5% higher than the standard method. Medium and coarse sand fractions in the soils were lower, and very fine sand and silt fractions tended to be higher after cup horn treatment than after the standard treatment. In a second test, approximately 11% (absolute) of sand samples (50–250, 250–2000 µm), and 6% (absolute) of coarse‐silt samples (20–50 µm) shifted to finer fractions after cup horn treatments. Part of this shift was the result of grain abrasion and part was the result of removal of coatings on grains left intact by the standard dispersion treatment. Four of the five soils formed stable dispersions when sonicated in pH 9.5 Na2CO3 solution. The fifth, a very strongly acid soil, flocculated unless titrated to pH 8.5 to 9.5 using 0.1M NaOH after ultrasonic treatment. Coefficients of variation of replicated sand, silt, and clay determinations after cup horn treatment ranged from < 1 to 4%; coefficients of variation of replicated determinations after the standard treatment ranged from 2 to 5%.