bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetic Studies of the Reactions of Benzidine with Humic Acid
Authors: Ononye Aloysius I. , Graveel John G. , Wolt Jeffrey D. 
Published: July 2010

AbstractThe mechanism of the reaction of benzidine (4,4′‐diaminobiphenyl), a toxic biphenyl amine, with humic acid in aqueous solutions has been studied using both commercial and soil‐extracted samples of humic acid. The reaction trend is similar for all the samples and involves a byphasic decay in the concentration of benzidine. The phase I reaction is rapid and complete within 1 h and is approximated by second‐order kinetics, while the phase II reaction (a slow process which attains a steady state in benzidine concentration after about 14 d) follows a single exponential first‐order reaction with respect to benzidine. Sorption of benzidine by humic acid was higher for the commercial samples than for the soil‐extracted sample.
Influence of Oxidation Treatments on Surface Properties and Reactivities of Short‐Range Ordered Precipitation Products of Aluminum
Authors: Violante A. , Huang P. M. 
Published: July 2010

AbstractOrganic C contents, specific surface and P adsorption of pseu‐doboehmites or x‐ray noncrystalline precipitation products of Al formed in the presence of various organic ligands (citric, tartaric, tannic or aspartic acid) and Cl were studied before and after oxidation treatment of NaOCl or H2O2. Contents of residual C after NaOCl or H2O2 treatment ranged from 22 to 60% and from 55 to 90% of the original C, respectively. This evidence coupled with their IR spectra indicates that organic ligands are present on the surfaces and in the structural network of Al precipitation products. Specific surface values of samples formed in the presence of citrate or tannate were increased by NaOCl treatment, whereas those of samples formed in the presence of aspartate or Cl were relatively insensitive to oxidation. Before oxidation, samples formed in the presence of strong chelating ligands (citrate, tartrate, or tannate) adsorbed less P than those formed in the presence of aspartate or Cl. After oxidation, adsorption of P by samples formed in the presence of citrate and especially tannate was substantially increased. This is attributed to partial oxidation of organic ligands binding the precipitates and subsequent disintegration of aggregates. The data thus reveal that the influence of oxidation pretreatment on specific surface and P adsorption ability of Al precipitation products varied with the nature and amount of organic ligands coprecipitated.
Environmental Factors Affecting Microbial Production of Dimethylselenide in a Selenium‐Contaminated Sediment
Authors: Frankenberger W. T. , Karlson U. 
Published: July 2010

AbstractSelenium poisoning from agricultural wastewater has been blamed for wildlife deaths and deformities at Kesterson Reservoir (Merced County, California). One approach in reducing the Se content in seleniferous sediments is based on microbial methylation of Se. This study was conducted to determine the optimum environmental conditions for volatilization of Se. A saline (> 20 dS m−1) seleniferous soil collected from Pond 4, Kesterson Reservoir was assayed for dimethylselenide (DMSe) production by incubating it for up to 120 h at 22 °C under various treatments. The DMSe was monitored by gas chromatography and identified by gas chromatography‐mass spectrometry. The conditions or additions optimum for DMSe production were: pH 8.0; moisture content, field capacity (−33 kPa); temperature, 35 °C; L‐methionine, 100 mg kg−1 soil; galacturonic acid, 3.6 g C kg−1 soil; and protein sources including casein (2.0 g C kg−1 soil) and albumin (0.05 to 2.0 g C kg−1 soil). Albumin applied to soil enhanced gaseous Se production 19.3‐fold over the unamended control. It should be possible to apply these findings in a management practice to detoxify seleniferous sediments.
Long‐Term Tillage and Crop Rotation Effects on Bulk Density and Soil Impedance in Northern Idaho
Authors: Hammel J. E. 
Published: July 2010

AbstractConservation tillage management for winter wheat (Triticum aestivum L.) production in northern Idaho may increase bulk density (ρb) and soil impedance (SI) of surface layers and limit crop growth, particularly when combined with spring cropping practices which require cultural or tillage operations during moist soil conditions. Bulk density and SI were measured in a long‐term tillage‐crop rotation experiment after 10 yr of continuous management to determine if differences resulting from tillage or cropping practices existed. Soils of the experimental site were two similar series, Palouse (fine‐silty, mixed, mesic Pachic Ultic Haploxeroll) and Naff (finesilty, mixed, mesic Ultic Argixeroll) silt loams. Tillage treatments included conventional (CON, moldboard plow), minimum (MIN, chisel), and no‐tillage (NOT). Crop rotations were a 2‐yr winter wheat‐spring pea (Pisum sativum L.)rotation and a 3 yr winter‐spring barley (Hordeum vulgare L.)‐spring pea rotation. Bulk density was determined on intact cores using gamma attenuation. Soil impedance was measured with a constant‐rate penetrometer. Tillage had a significant (P < 0.05) effect on ρb, but not SI. Crop rotation did not significantly influence either soil property. The main effect of depth and a tillage × depth interaction, however, produced significant (P < 0.01) differences on ρb and SI. Both MIN and NOT had SI values exceeding 1.5 MPa at a depth of 0.05 to 0.15 m, which were 0.5 to 1.0 MPa greater than CON. Higher SI values under reduced tillage while not preventing root growth may, when combined with cool, wet soil conditions during the spring, limit root function and decrease crop growth potential.
Physical Conditions of a Lake Plain Soil as Affected by Deep Tillage and Wheel Traffic
Authors: Johnson B. S. , Erickson A. E. , Voorhees W. B. 
Published: July 2010

AbstractNormal fall and spring tillage practices create poor physical conditions for crop growth on lake plain soils in Michigan. Charity clay [fine, illitic (calcareous), mesic Aeric Haplaquept] (Mahjoory and Whiteside, 1976) is an example of such a soil. It has poor internal drainage due to its naturally dense subsoil and is susceptible to physical degradation because of its unstable surface. Tillage studies were conducted from 1983 to 1985 to evaluate the potential for reducing the physical limitations of Charity clay. Treatments consisted of four combinations of a primary and secondary tillage variable. The primary tillage variable involved the application or omission of deep tillage using a triple‐shanked subsoiler prior to moldboard plowing. The secondary tillage variable involved the presence or absence of tractor wheel traffic prior to planting. Subsoiling improved the physical conditions of Charity clay below the Ap horizon. Soil bulk density (ρb) was reduced by 0.05 Mg m−3, and pore size distribution (PSD) was altered such that the volume of pores with radii larger than 150 µm was doubled. Preplant wheel traffic caused subsoil compaction, increasing ρb by about 0.06 Mg m−3, and altered all indicators of soil compaction in the Ap horizon, especially PSD and saturated hydraulic conductivity. The need to minimize wheel traffic regardless of the primary tillage practices employed was evidenced by the results of this study.
Estimating Root Length Density by the Core‐Break Method
Authors: Bland William L. 
Published: July 2010

AbstractRapid and accurate methods of measuring root length density (RLD, cm root cm−3 soil) are needed for verifying growth predictions and assessing genotypic differences. The core‐break technique, in which the number of roots visible at a broken cross section of a soil core is used to estimate rooting, was evaluated as a means of measuring RLD. Root systems of wheat, Triticum aestivum L., cotton, Gossypium hirsutum L., and sorghum, Sorghum bicolor (L.) Moench, were sampled and core‐break root counts regressed on RLD measured in the same soil core. Linear relationships were obtained between counts and RLD for each crop on each day of sampling. Calibration equations were derived from regressions of all data for a species. Prediction intervals (90%) for an estimate of RLD from the mean of several core‐break counts were about ± 0.3 cm−2 for wheat, ±0.2 cm−2 for cotton, and ±0.8 cm−2 for sorghum. The core‐break method yields only a low‐precision estimate of RLD from the mean of several core counts, even if calibrated for the soil and crop combination of interest.
Modifications of the Minirhizotron Video Camera System for Measuring Spatial and Temporal Root Dynamics
Authors: Ferguson J.C. , Smucker A.J.M. 
Published: July 2010

AbstractCurrent video cameras used to measure in situ root activities lack essential registration and identification components for repeated accurate measurements. This report describes a rapid, inexpensive and completely portable approach for controlling and identifying camera position when making repeated video recordings from minirhizotrons in large field experiments. These registration handle and microcomputer additions to an agricultural microvideo color camera provide new opportunities for measuring root and nodule development. Preliminary measurements indicated that corn roots appeared and disappeared to depths of 75 cm for different N treatments 86 to 99 d after planting. Additionally, root development, maturation, and death can be observed in situ throughout the root profile. These modifications offer a uniform method for comparing root turnover rates and other specific dynamics of the rhizosphere at 1.2‐cm intervals in contrasting soil and climatic conditions.
Optimal Design of Two‐Chamber, Gas Diffusion Cells
Authors: Glauz R. D. , Rolston D. E. 
Published: July 2010

AbstractTwo‐chamber diffusion cells have been used for measuring the gas diffusivity of packed or undisturbed soil cores. Gas diffusivity is calculated from gas concentrations measured initially and at later times in an inlet chamber. The published analytical solution to diffusion in such diffusion cells for the general case of unequal air chamber size was arranged to solve for the soil‐gas diffusivity explicitly and error analyses conducted in order to provide guidance in designing diffusion cells. An equation to calculate the first root of the resulting equation was derived. The optimum apparatus design was determined from error analysis to minimize experimental error in measuring the soil‐gas diffusivity. The error analysis showed that the inlet and outlet chambers should not necessarily be of equal size, but that the chamber not being sampled should be larger than the sampled chamber. Total measurement error is greatest for very small soil‐air contents and small times between initial and successive measurements of gas concentration. The optimum size of both the exit chamber and the soil core increases with measurement time. Thus, an optimum design of diffusion cells should be selected based upon range of soil‐air contents expected, desired measurement times, and soil core length. Diagrams of total relative error and optimum soil core and chamber lengths with time for several soil‐air contents and total relative error as a function of soil core and sampled chamber lengths provide guidance in designing diffusion cells with minimum experimental error. These estimates of optimum design can be easily changed for additional chamber characteristics or improved precision for measuring gas concentration.
Mechanism of Water Entry into Simulated Macropores
Authors: Phillips R. E. , Zeleznik J. M. , Dunn G. H. , Quisenberry V. L. 
Published: July 2010

AbstractIt is commonly believed that, when the soil is unsaturated, water cannot enter soil macropores that begin below the soil surface. The objective of this research was to show that water under negative pressure can enter simulated macropores, after first establishing a continuous water film on the full length of the macropore walls. The simulated macropores were hollow, cylindrical, straight‐walled glass tubes 4.88, 2.60, and 0.85 mm in diameter. Water flux through the simulated macropores was obtained down to a negative water pressure of −1.02 kPa. This was shown by placing simulated macropores against a porous fritted‐glass plate 60 mm in diameter with pore diameters between 40 and 60 µm after establishing a water film on the walls of the simulated macropores. The flux of water down the simulated macropores varied from 0 to 67 mm3 s−1 depending on the contact of the simulated macropore with the porous plate, which influenced the continuity of water in the porous plate with water films on the walls of the simulated macropores. A water manometer was connected to the bubbler of the burette in order to measure the total negative water pressure operating in the simulated macropores. The total negative water pressure operating in the simulated macropores was equal to the sum of (i) the negative water pressure due to the difference in elevation of water menisci of the water manometer and (ii) the matrix potential in the pores of the fritted‐glass plate.
Using Breakthrough Curves for Parameter Estimation in the Convection‐Dispersion Model of Solute Transport
Authors: Yamaguchi T. , Yokosi S. , Moldrup P. 
Published: July 2010

AbstractWe present two easily applicable models for simultaneous estimation of the convective velocity (u0) and the hydrodynamic dispersion coefficient (D0) from breakthrough curve (BTC) data. The two models can be used for both saturated and unsaturated flow. Both models are derived from an analytical solution to the convection‐dispersion equation (CDE). The first model, labeled the “slope method,” is exact. It uses the slope of the BTC to estimate u0 and D0. The second method is approximate because it is only based on the first term of the analytical solution to the CDE. This model is labeled the “first‐term method” and is not valid for very small values of Brenner number. A simple version of both models is developed. A discussion of numerical stability and choice of increments in the model calculations is given. The simple version of the slope method is found to be too numerically unstable when applied to actual BTC data. The remaining methods are tested against two sets of actual measured BTC data by applying each method several times for different parts of each BTC. The values of coefficient of variation between the results are low for all methods (0.1–1.3% for u0 and 2.7–32% for D0). The agreement between the mean values of the parameters u0 and D0 obtained by using the methods presented in this paper and the parameter values for the same BTC data sets reported by other authors is excellent.
Ion Exchange and Interparticle Forces Between Clay Surfaces
Authors: Pashley R. M. , Quirk J. P. 
Published: July 2010

AbstractThe forces between muscovite mica surfaces have been measured in water and in NaCl and CaCl2 solutions. Above a critical electrolyte concentration, strong, short‐range repulsive forces arise which are not predicted by DLVO theory. These forces have been identified as hydration forces and have an oscillatory force superimposed with a periodicity corresponding to the diameter of the water molecule. Hydration forces are significant for the swelling of Ca‐clays. Below the critical hydration concentration exchange favors H+. Protons are so strongly adsorbed that as the surfaces are brought to a distance of separation of 2 to 3.5 nm the hydrated cations are replaced by H+ and the surfaces jump into contact due to attractive van der Waals forces. The absence of the hydration forces in the presence of H+ indicates that the water structure is not perturbed by the siloxane layer alone. The strong affinity of the H+ is attributed to the H+ proton being able to approach closely to the surface by forming H3O+ with water H‐bonded to oxygen atoms on the mica basal plane surface. The sites for adsorption are the Al tetrahedra for which the charge is confined to three surface O atoms. Other cations can only approach to within one H2O molecule of the surface because of their primary hydration shell. By comparison, the H+ associated with the surface of montmorillonite hydrate to the full extent and the crystalline swelling (d001 > 4 nm) is similar to Li‐montmorillonite. This difference must be related to the fact that the surface charge for montmorillonite is less discrete being spread over about 10 surface O atoms.
Residual Effects of Chloride Application in a Corn‐Wheat Rotation
Authors: Schumacher W. K. , Fixen P. E. 
Published: July 2010

AbstractSignificant correlations have been noted between soil Cl, Cl uptake, and yield response in spring wheat (Triticum aestivum L.). Little information exists, however, concerning the residual value of Cl, especially in subhumid areas. Therefore, a study was conducted to determine residual effects of Cl application on soil Cl levels and on associated crop yield in a wheat‐corn (Zea mays L.) rotation. Six Cl rates ranging from 0 to 510 kg ha−1 were applied as KCl (muriate of potash) to a soil (Udic Haploboroll) with an initial soil‐Cl content of 19 kg ha−1 in the upper 60 cm. A corn‐spring wheat rotation was practiced between two adjacent sites. Soil Cl levels were measured after the first three seasons at five depth increments to a final depth of 120 cm. Maximum Cl concentrations following the first growing season occurred at approximately 50 cm. By the beginning of the third growing season, most of the Cl had leached below 120 cm. Deep sampling to 3 m after the third growing season indicated maximum Cl accumulation between 1 and 2 m. A positive response of spring wheat to added Cl was observed for the first two growing seasons. Factors contributing to the removal of Cl from the upper 120 cm include above‐average precipitation and large precipitation events. Chloride soil testing is recommended prior to the establishment of a Cl‐responsive crop in regions where responses have been verified.
Soil Development on Stabilized Dunes in Golden Gate Park, San Francisco
Authors: Amundson Ronald G. , Tremback Brian 
Published: July 2010

AbstractThis paper reports the changes in soil properties that have occurred since vegetation was established on unstabilized dunes approximately a century ago in Golden Gate Park, San Francisco, CA. The static and dynamic soil properties under artificially established eucalyptus (Eucalyptus globulus Labill.), Monterey pine (Pinus radiata D. Don), cypress (Cupressus macrocarpa Hartw. ex. Gord.), as well as native live oak (Quercus agrifolia Née), were compared with those of an unstabilized dune. The O and A horizon development occurred under all the vegetated sites with differences in the horizon thickness occurring in response to vegetation type. The organic C in the vegetated sites (40 000 to 80 000 kg C ha−1) was much greater than in the dune (5000 kg C ha−1). The vegetated soils all exhibited severe water repellency in the surface horizons while the dune exhibited none. The oxalate‐extractable Fe in the A horizon of the vegetated soils (1.3–2.3 g kg−1) was greater than that in the dune (≈0.9 g kg−1) suggesting the formation of organically bound Fe and/or poorly crystalline Fe minerals. Dithionite‐citrate‐bicarbonate extracts suggest the formation of more crystalline forms of Fe oxides in the vegetated sites. Soil temperatures were lower and less variable in the vegetated sites (isomesic regime) than the dune site (mesic or thermic regime), apparently slowing biological activity and reducing the soil CO2 contents relative to the dune. Total soil respiration in the vegetated soils (350–400 mg CO2 m−2 h−1) was slightly greater than in the dune (300 mg CO2 m−2 h−1), which lacked any appreciable surface litter undergoing decomposition.
Cotton Root Growth and Soil Water Extraction
Authors: Bland William L. , Dugas William A. 
Published: July 2010

AbstractThe inherent productivity of many fine‐textured soils depends on timely extraction of water stored deep in the profile. Growth of crop roots and their ability to extract water are of central importance to efficient utilization of these soil resources. We observed the rate at which the soil volume was explored and water was extracted by cotton (Gossypium hirsutum L. ‘GP3774’) roots in a fine‐textured soil in a subhumid environment. Measurements of root growth and water extraction were made for 2 yr in a 2.3 m deep weighing lysimeter, 3.0 m2 in area and containing an intact core of a Frio taxadjunct silty clay loam (fine, montmorillonitic, thermic Cumulic Haplustoll). Water extraction was measured with neutron probes at 10 or 11 soil depths in the lysimeter at approximately 5‐d intervals. Root length density [Lv, cm root (cm3 soil)−1 = cm−2] was estimated at 7‐d intervals by counting roots visible against clear observation tubes installed horizontally in the lysimeter every 0.2 m between 0.5 and 2.1 m. Depth of rooting increased up to 35 mm d−1 for part of the season. Maximum Lv at 0.5 m was 1.5 and 0.8 cm−2 in 1984 and 1985, respectively; at 2.1 m comparable values were 0.24 and 0.04 cm−2. When the lysimeter surface area was divided into six 0.5‐m2 regions of soil, the coefficient of variation in Lv among the regions reached 100% both early and late in the season and both at 0.5 and 2.1 m. Crop rows did not affect the spatial distribution of Lv at depths measured. Growth of the root system required about 90 kg ha−1 d−1 for part of the season. Maximal water uptake rate per length of root was approximately 5 mm3 water (mm root)−1 d−1 and occurred at 1.7 to 1.9 m. Redistribution of dry matter invested in roots near the soil surface to deeper in the profile would probably increase total water extraction by the crop.
Submicroscopy of Clay Microaggregates in an Oxisol from Pernambuco, Brazil
Authors: Santos M. C. D. , Ribeiro M. R. , Mermut A. R. 
Published: July 2010

AbstractUltrathin sections were made from dehydrated, unoriented but undisturbed soil microaggregates (pseudosands, about 10–100 µm in size) of an Oxisol occurring in the semiarid region of Pernambuco State, Brazil. Objectives were to determine the nature and arrangements of individual particles that comprise the microaggregates. The dominant clay mineral in the microaggregate is poorly crystalline (irregular, pseudohexagonal in shape), densely packed, randomly oriented kaolinite with an average diameter of 0.2 µm. Poorly crystalline Fe oxyhydroxides, probably ferrihydrite, exist as individual aggregates filling the space between the kaolinite particles. Halloysite and Fe‐Ti‐bearing minerals also occur as accessory minerals. An attempt was made to localize organic matter by ultracytochemical reagents. Cell walls, humified hyphae, and other decomposed organic materials, which were easily identified in large pore spaces, appear to play an important role binding the clay particles in microaggregates. Concentrations of organic matter in the magnetic fraction of clays suggests that part of the humified organic matter may be locked up in organo‐Fe complexes. Ultrathin section analyses suggest that the combination of random orientation of clay particles, organic matter, and aggregates of Fe‐bearing minerals, account for the isotropic nature of the aggregates.