bluuebunny/crossref_metadata_2025 huggingface dataset:
Effective Diffusion Coefficients of Soil Aggregates with Surface Skins
Authors: Köhne J. Maximilian , Gerke Horst. H. , Köhne Sigrid
Published: July 2010

Dual‐permeability model simulations and sensitivity studies indicate that preferential solute leaching in structured soil is intensified by a limited solute mass transfer between preferential flow paths and matrix. It is currently unknown how much aggregate skins may affect solute mass transfer. The objective of this study was to evaluate the effect of a skin layer on the effective diffusion coefficient, De, of water saturated soil aggregates. In a diffusion experiment, the concentration decrease of Br− and Cl− in a solution being in contact with soil aggregates was measured. Aggregates with intact and removed surface skins were studied. Two different theoretical approaches were compared: (i) fitting a modified analytical solution of Crank for diffusion out of a solution of limited volume into a plane sheet to obtain De for intact and for skin‐removed aggregates; and (ii) calibrating a numerical solution for diffusion through a two‐layer system to estimate De of the skin layer and the interior part, separately. The De‐values of the skins differed for Br− and Cl− Using the first approach, De was six (Br−) and 15 (Cl−) times smaller for the intact than for the skin‐removed aggregates. The second approach resulted in effective diffusion coefficients of the skin layer being 30 (Br−) and 45 (Cl−) times smaller than those of the interior parts. Aggregate skins may reduce diffusive anion transfer between interaggregate region and soil matrix, an effect which may significantly influence preferential solute transport in structured soil.
Construction and Performance of Large Soil Core Lysimeters
Authors: Derby Nathan E. , Knighton Raymond E. , Montgomery Bruce R.
Published: July 2010

A method was developed to obtain large undisturbed soil cores and instrument those cores to collect vadose zone leachate data under agricultural field conditions. Twenty undisturbed soil core lysimeters were constructed at an irrigated‐field site in southeastern North Dakota. Construction of the undisturbed lysimeters consisted of utilizing a steel cutting bit to collect large (0.61‐m diam. by 1.68‐m deep) soil cores in sections of polyvinyl chloride (PVC) pipe, installing a leachate collection system, installing time domain reflectometry (TDR) soil moisture probes, and then finally placing them below grade so normal farming practices could continue. The described method of core collection is an improvement over other methods in that the cutting bit is reusable, the resulting core is larger and deeper than other methods, no heavy static weights are required, and it is not necessary to expose a free‐standing soil column. Leachate quality and quantity data is reported for 1990 through 1995 and compared favorably with larger, reconstructed profile lysimeters on the same site. Overall, the lysimeters functioned as intended for the first 6 yr of operation; however, two developed leaks and rodents damaged another. Possible sidewall flow was observed and may be avoidable in future designs.
Exponential Distribution Theory and the Interpretation of Splash Detachment and Transport Experiments
Authors: van Dijk A. I. J. M. , Meesters A. G. C. A. , Bruijnzeel L. A.
Published: July 2010

Soil detachment and transport by rainsplash is usually the first step in soil loss and sediment transport. It can be measured using a variety of approaches, including splash cups, trays, and boards. However, the results of splash experiments are affected by their geometry and not readily translated into generally applicable parameters. In this study, we develop a theory that can be used to interpret splash experiments. It is based on the assumption that the spatial distribution of particles splashed from a point source can be described by an exponential decay function, for which there is considerable support in the literature. The theory is evaluated for the cited experimental techniques, partly with the use of a numerical model. It is made clear that conventional measurements of splash and the true rate of detachment by splash are two different entities that can be linked if the average splash length is known. In principle, the theory is not valid for a sloping surface, but analysis of the magnitude of the error involved indicates that in many cases good estimates of detached amounts can still be obtained.
Organic Carbon Leaching from Effluent Irrigated Lysimeters as Affected by Residence Time
Authors: Fine P. , Hass A. , Prost R. , Atzmon N.
Published: July 2010

Under irrigation with secondary effluent, it is often assumed that reduced leaching would delay the transport of effluent organic matter (OM) from within the root zone for long enough for biodegradation to practically eliminate it. This hypothesis was tested in a lysimeter study which compared tap water with low‐quality secondary effluent (total organic C [TOC] = 190 mg C L−1) forEucalyptusirrigation. Lysimeters (200‐L drums) were packed with dune sand or one of two clayey soils (A horizons of a Calcic Haploxeroll and a Typic Palexeralf) and were either not planted or planted. Leaching treatments were leaching fraction 1 (LF 1) (not planted) and LF 0.2, intermittent leaching and prolonged deficit irrigation. These provided residence times of the water in the soil that ranged from 0.8 to over 200 d. While root organic C (OC) made a negligible net contribution to leachate OC, the effluent‐derived OC was rather recalcitrant as was indicated by: (i) the concentrations of TOC in the leachate increased with decreasing LF to over 250 mg C L−1; (ii) the recovery of the applied TOC in the leachate was significant (10–20%) even at RTs over 20 d (LF ≅ 0.06 in the sand‐packed lysimeters). Most all the dissolved and colloidal organic C (DOC) was smaller than 30 kDa. We expect these concentrations of low‐molecular‐weight mobile OC to govern many aspects of the biological and chemical behavior in solutions of effluent‐irrigated soils, especially under reduced‐leaching regimes.
Agronomic and Environmental Soil Phosphorus Testing in Soils Receiving Liquid Swine Manure
Authors: Atia A. M. , Mallarino A. P.
Published: July 2010

There is uncertainty concerning evaluation of bioavailable P in manured soils. This study assessed P availability in manured Iowa soils by measuring soil P with agronomic and environmental P tests and P uptake by corn (Zea mays L.) and soybean [Glycine max (L.) Merr.]. Soil and plant samples were collected at the V5‐V6 growth stage from trials established at nine locations that received various rates of liquid swine (Sus scrofa) manure, and from farmers' fields that received other animal manures. Soil P was analyzed by the Bray‐P1 (BP), Olsen (OP), and Mehlich‐3 (M3P) agronomic tests, and by the Fe‐oxide impregnated filter paper (FeP), anion‐exchange resin membrane (RP), and water (WP) environmental tests. Soil P at a 15‐cm depth ranged from deficient to 15 times optimum levels for crops. Extracted P was highest for BP, M3P, and RP, intermediate for OP and FeP, and lowest for WP. Relationships between soil P extracted by the tests were linear, trends were similar for manured and unmanured plots, and correlation coefficients were ≥0.70 (correlations were poorest for WP). There was no conclusive evidence for differences between tests in detecting manure‐derived soil P at most sites. However, in some conditions BP, M3P, OP, and RP may extract proportionally more manured‐derived P than FeP and WP. Only the agronomic tests were significantly correlated (0.42 for M3P, 0.44 for BP, and 0.47 for OP) with plant P uptake across sites. Agronomic soil tests would predict plant P availability for crops better than environmental P tests in soils receiving liquid swine manure.
Water Transfer from Soil to Seed
Authors: Wuest Stewart B.
Published: July 2010

Mixed solid‐water‐gas media such as soil can supply water to a dry object as both liquid and vapor. Modelers and agricultural engineers have commonly assumed liquid transport dominates imbibition by seed. This study tests the hypothesis that vapor is the major source of water for imbibition under normal soil moisture conditions. Water uptake was measured under varying degrees of seed‐soil contact. Wheat (Triticum aestivum L.) seeds were suspended in holes in blocks of moist soil (average water potential −0.16 MPa). Hole diameter varied from 13 to 0 mm (no hole), so that the distance between the moist soil and the seed varied from a maximum of 5 mm to intimate seed‐soil contact. The amount of water absorbed by seed in 24 h increased from 15 to 17 mg seed−1 as seed‐soil contact increased from none to maximum contact, indicating that at least 85% of the water absorbed by seed in intimate seed‐soil contact could be attributed to vapor alone. Reevaluation of the role of vapor transport should result in improved multiphase transport models in soil and other media.
A Macroscopic Water Extraction Model for Nonuniform Transient Salinity and Water Stress
Authors: Homaee M. , Feddes R. A. , Dirksen C.
Published: July 2010

Quantitative description of root‐water uptake under combined salinity and water stress is needed to optimize crop yields and water management in arid and semiarid regions. This study was conducted to develop a simple macroscopic root‐water uptake model for nonuniform transient soil water content and salinity conditions in the root zone. This new model and previous models were tested against detailed experimental data obtained with Alfalfa (Medicago sativa L.) grown in the greenhouse in packed sandy loam (Typic Haplaquent) columns. Soil water content, pressure head, and osmotic head distributions in the root zone were varied by means of the amounts, application intervals, and salinities of the irrigation water. Experimental data under separate and combined stresses were used to test the various models using mean values of soil solution osmotic and pressure heads. The simple additive reduction function provided the worst agreement with the experimental data, while for most cases the multiplicative reduction functions could not adequately account for both water and salinity stress conditions. The newly proposed linear reduction function is neither additive nor multiplicative, but was assumed that both the intersect and slope of the reduction function increased with salinity. This model provided excellent agreement with the experimental data, particularly at higher soil solution salinities. The new reduction function could be used with any other nonlinear salinity reduction function.
Adsorption of Humic Substances onto Kaolin Clay Related to Their Structural Features
Authors: Balcke Gerd U. , Kulikova Natalia A. , Hesse Sebastian , Kopinke Frank-Dieter , Perminova Irina V. , Frimmel Fritz H.
Published: July 2010

Eleven well characterized humic substances (HSs) were adsorbed from aqueous solution onto a Na‐kaolin clay. The adsorption affinity (KL), maximum adsorption capacity (b), a coefficient of desorption hysteresis (H), and the concentration of irreversibly adsorbed HS (IHS) were derived from adsorption‐desorption isotherms. These parameters were correlated with structural features of the HS. The adsorption affinity was shown to correlate directly with the aromaticity of the HS and inversely with their polarity, expressed as the O/C atomic ratio. A dependency between polarity and maximum adsorption capacity was not confirmed. The parameters b, H, and IHS expose close correlation with the molecular weight (MW) and the partial negative charge of HS (Z) at the operating pH value. The following quantitative relationship was obtained: b = 715 − 0.06 × MW − 529 × Z (r = 0.92). It allows a selection of HS with respect to the largest content of organic matter in HS‐kaolin clay complexes. Among the HS studied the high molecular weight materials enriched with C‐ and H‐substituted aromatics, such as coal and peat humic acids (HAs), are shown to be the most preferential materials for preparing stable HS‐clay complexes.
Management of Irrigated Agriculture to Increase Organic Carbon Storage in Soils
Authors: Entry James A. , Sojka R. E. , Shewmaker Glen E.
Published: July 2010

Increasing the amount of C in soils may be one method to reduce the concentration of CO2 in the atmosphere. We measured organic C stored in southern Idaho soils having long term cropping histories that supported native sagebrush vegetation (NSB), irrigated moldboard plowed crops (IMP), irrigated conservation‐chisel‐tilled crops (ICT), and irrigated pasture systems (IP). The CO2 emitted as a result of fertilizer production, farm operations, and CO2 lost via dissolved carbonate in irrigation water, over a 30‐yr period, was included. Net organic C in ecosystems decreased in the order IP > ICT > NSB > IMP. In this study, if NSB were converted to IMP, 0.15 g C m−2 would be emitted to the atmosphere, but if converted to IP 3.56 g C m−2 could be sequestered. If IMP land were converted to ICT, 0.95 g C m−2 could be sequestered in soil and if converted to IP 3.71 g C m−2 could be sequestered. There are 2.6 × 108 ha of land worldwide presently irrigated. If irrigated agriculture were expanded 10% and the same amount of rainfed land were converted back to native grassland, an increase of 3.4 × 109 Mg C (5.9% of the total C emitted in the next 30 yr) could potentially be sequestered. The total projected release of CO2 is 5.7 × 1010 Mg C worldwide during the next 30 yr. Converting rainfed agriculture back to native vegetation while modestly increasing areas in irrigated agriculture could have a significant impact on CO2 atmospheric concentrations while maintaining or increasing food production.
In‐Season Nitrogen Status Sensing in Irrigated Cotton
Authors: Chua Teresita T. , Bronson Kevin F. , Booker J. D. , Keeling J. Wayne , Mosier Arvin R. , Bordovsky James P. , Lascano Robert J. , Green Cary J. , Segarra Eduardo
Published: July 2010

Nitrogen recommendations for Upland cotton (Gossypium hirsutum L.) in the western USA are based on spring soil NO−3–N tests. In‐season monitoring of plant N status is another approach. Our primary objective was to test spectral reflectance and chlorophyll meter measurements as in‐season N decision aids for irrigated cotton, and to compare these with soil test‐based N management. The secondary objective was to determine the fate of 15N as affected by N management and irrigation modes. Urea ammonium nitrate was applied with low energy precision (LEPA) center‐pivot, surface drip, and subsurface drip irrigation. Microplots received 3 atom% 15N. Soil test N application was based on 0‐ to 60‐cm soil NO−3–N and 1400 kg lint ha−1 expected yield. Thirty‐four kilograms of N per hectare was applied when green vegetative index (GVI) or chlorophyll meter readings relative to well‐fertilized plots were <0.95. Lint yield responded to N at Lubbock in 2000 and 2001, but not at Ropesville. Nitrogen applied with in‐season monitoring in 2000 at both sites was 34 to 101 kg N ha−1 less than soil test N application of 134 kg ha−1, with similar yields. In Lubbock, 2001 lint yields were near the expected yield, and in three of four cases, N applications with in‐season monitoring equaled soil test N applications of 101 kg ha−1 Nitrogen‐15 recovery in plants ranged from 19 to 38%, and was affected by N management in two of three site‐years, but not by irrigation. This study indicates that basing N applications on in‐season monitoring can reduce N applications in low yielding seasons and match the yield potential in high‐yielding seasons.
Management and Soil‐Quality Effects on Fertilizer‐Use Efficiency and Leaching
Authors: Nissen Todd M. , Wander Michelle M.
Published: July 2010

We tested the hypothesis that particulate organic matter (POM) and aggregate dry mean weight diameter (DMWD) are related to fertilizer‐use efficiency (FUE) and leaching susceptibility. Soil cores (15 cm diam. by 50 cm depth) were collected from 12 farm fields representing three cropping systems: conventional (CT) and no‐tillage (NT) management of corn (Zea mays L.)–soybean [Glycine max (L.) Merr.] rotations, and CT applied to more diversified corn–soybean‐based rotations (R‐CT). Three of the four R‐CT farms were organically managed. In a 95‐d greenhouse trial, cores were seeded with corn, amended with 15N‐labeled urea applied at four rates (0, 75, 150, 225 kg N ha−1), and subjected to a stressful moisture regime. Aggregate DMWD, which serves as a rough index of pore‐size distribution, was greater in NT cores. Although total leached N was similar in all cropping systems, increased macropore flow in NT cores led to greater leaching of fertilizer N and less leaching of soil‐derived N, as well as greater moisture stress and decreased plant N uptake. The R‐CT cores had more POM and organic C in the top 30 cm of soil and higher crop biomass and biomass‐N content. However, FUE in R‐CT cores was relatively low since FUE does not account for contributions of indigenous N. For the same reason, FUE remained relatively high in CT systems despite less labile organic matter. Both FUE and SOM conservation declined with increasing N application rates. Increasing labile sources of N, reflected in POM pools, through crop diversification can substitute for incremental increases in fertilizer N and improve long‐term productivity on Illinois Mollisols.
Deep Soil Water Dynamics and Depletion by Secondary Vegetation in the Eastern Amazon
Authors: Sommer Rolf , Fölster Horst , Vielhauer Konrad , Carvalho Eduardo J. Maklouf , Vlek Paul L. G.
Published: July 2010

Secondary/fallow vegetation is found extensively in the Eastern Amazon. The role of this deep‐rooting vegetation in the hydrological cycle is unknown. We studied the water dynamics of this vegetation with emphasis on the deeper soil by means of a soil water model. The soil hydraulic properties were optimized in an inverse modeling procedure using the soil water model Hydrus‐1D providing rainfall, actual evapotranspiration (Ea) determined with the Bowen ratio energy balance method (BREB), rooting depth, and distribution, as well as the in situ control measurements of soil water pressure head and soil moisture. In 1997, Ea according to BREB measurements amounted to 1174 mm, in 1998 this was 1475 mm. Modeled drainage at a 10‐m depth in the 2 yr was 951 and 1016 mm, respectively. The model indicated that around 27% of the soil water was taken up below the 0.9‐m depth in the 2‐yr study period. During the severe 1997 dry season, according to the soil water model Ea was reduced drastically, as the soil water storage was depleted. According to micrometeorological measurements, however, Ea was not reduced as extremely. This difference might be due to general uncertainties of the soil water model as well as BREB measurements. On the other hand, formation and subsequent evaporation of early morning dew apparently contributed to Ea, which was not considered in the soil water model. In general, besides slightly lower interception, the water budget of a young secondary vegetation did not differ from that reported for Amazonian primary forest.
Use of Volcanic Mulch to Rehabilitate Saline‐Sodic Soils
Authors: Tejedor M. , Jiménez C. C. , Díaz F.
Published: July 2010

Natural soil salinization and sodication processes that restrict or prevent crop growth are commonplace in arid regions. In saline‐sodic soils of arid parts of the Canarian archipelago, where annual rainfall is <150 mm, a traditional agriculture system has been developed using basaltic tephra mulch. This system has enabled dry crop farming to take place even under the most adverse of natural conditions. The present work compares the salinity‐sodicity in the cultivated layer of soils that were covered with 10 to 15 cm of tephra mulch as recently as 20 yr ago with that of adjacent unmulched soils. These soils have never been irrigated. Results show significant differences in electrical conductivity (EC) and exchangeable Na percentage (ESP). The natural, unmulched soils are extremely saline‐sodic (ECse 43 dSm−1, ESP 44), whereas the mulched soils are neither saline nor sodic (ECse 1.5 dSm−1, ESP 9). The reduction in salinity and sodicity in the mulched soils was related to the change in soil moisture regime caused by the mulch covering, which increases infiltration and reduces evaporation and upward movement of Na+ and other salts. Probably, additional water from dew could also contribute. The greater dilution of soil solution through increased soil water content, increased Na+ leaching and the dissolution of calcium salts may account for the desalinization and desodication. These results were confirmed through monitoring of a soil from the moment it was originally covered with tephra. They also revealed salt leaching process is a short‐term. Tephra mulching can, therefore, be a highly efficient technique for the recovery of saline‐sodic soils under dry farming conditions.
Broadcast and Deep‐Band Placement of Phosphorus and Potassium for Soybean Managed with Ridge Tillage
Authors: Borges Rogerio , Mallarino Antonio P.
Published: July 2010

The efficiency of broadcast and band P and K placement methods for ridge tilled soybean [Glycine Max (L.) Merr.] has not been extensively researched. This study evaluated grain yield, early plant growth, and nutrient uptake (V5–V6 stages), and soil‐test responses to broadcast and deep‐band (15–20 cm below the ridge surface) placements in 14 trials. Fertilizer rates were 0, 14, and 56 kg P ha−1 and 0, 33, and 132 kg K ha−1 A randomized complete‐block design was used. Soil‐test P (STP) was 7 to 61 mg kg−1 (Bray‐P1 test, 15‐cm depth) and soil‐test K (STK) was 100 to 197 mg kg−1 (ammonium acetate test). Phosphorus increased yield (P ≤ 0.1) at four sites. Band P was better at one site (30 kg ha−1) and broadcast P was better (40 kg ha−1) at another site. Both P placements increased dry weight (DW) at two sites. Yield and DW responses to P were observed when STP was <19 mg kg−1 Phosphorus increased plant P uptake at eight sites, and band P was better than broadcast P at three sites. Potassium increased yield at two sites, and only band K increased yield at one of these sites. Potassium increased DW at four sites, and increases were always larger for band K. Band K increased K uptake at 10 sites and broadcast K increased K uptake only at two sites. Soil‐test P in ridges predicted P sufficiency better than mean STP from ridges and valleys at two sites. Although K fertilization seldom increased yield in this study, increased plant K uptake with banding compared with broadcasting suggests that banding may be more efficient for grain production in other conditions.
Field Calibration for Corn of the Mehlich‐3 Soil Phosphorus Test with Colorimetric and Inductively Coupled Plasma Emission Spectroscopy Determination Methods
Authors: Mallarino Antonio P.
Published: July 2010

Use of the Mehlich‐3 soil extractant with an inductively coupled plasma emission spectroscopy (ICP) determination method (M3‐ICP) is displacing the original colorimetry‐based test (M3‐COL). Current interpretations do not distinguish between these two versions, although the M3‐ICP test often measures more P. This study correlated these tests and the Bray‐P1 (BP) test with corn (Zea mays L.) yield response at 59 Iowa locations (78 site‐yr). The mean P measured by the M3‐ICP, M3‐COL, and BP tests was 31, 19, and 17 mg P kg−1, respectively. The M3‐ICP/M3‐COL ratio decreased exponentially with increasing soil P (P ≤ 0.01) but their difference was not correlated with soil P. Relative or absolute differences tended to decrease linearly (P ≤ 0.01) with increasing soil pH or organic C, but the strength of the relationship was poor (R2 = 0.14–0.32). The BP test measured significantly less P in a CaCO3–affected soil (pH 8.1). The R2 of the relationship between M3‐ICP and M3‐COL was 0.84, and was 0.89 between the M3‐COL and BP (0.97 excluding the site with pH 8.1). Critical concentrations defined by Cate‐Nelson and linear‐plateau models for the M3‐ICP, M3‐COL, and BP tests were 20 to 32, 16 to 21, and 13 to 20 mg kg−1, respectively. The M3‐COL and M3‐ICP are equally effective for Iowa soils but interpretations differ. The M3‐ICP test should be considered a different test and its interpretations should be based on field calibrations rather than conversions based on M3‐COL data. A range of 25 to 35 mg kg−1 for the M3‐ICP test would correspond to the optimum class (16–20 mg kg−1) used in Iowa for the M3‐COL and BP tests.
Limitations of the Chemical Potential
Authors: Corey A. T. , Logsdon S. D.
Published: July 2010

It is often assumed that the negative gradient of chemical potential indicates the direction of transport by diffusion. Diffusion is the transport of a fluid constituent induced by a concentration gradient. The objective of this review paper is to explain the purpose and correct application of the chemical potential. Fick's law is derived here from Newton's second law of motion. Diffusion is a transport mechanism involving the motion of individual molecules, and does not induce a resistance associated with fluid viscosity. Consequently, unlike advection, the mean hydraulic radius of flow channels does not affect resistance to diffusion. A concentration gradient is not reflected in the pressure gradient acting externally on reference volumes of fluid. Both external driving force and a concentration gradient may result in motion of the center of mass of reference volumes of fluid. If a density gradient exists, the vector sum of external forces does not describe the resultant driving force. A concentration gradient induces constituent velocity relative to the fluid boundaries, not relative to the center of mass. Chemical potential includes pressure as a variable, and cannot predict the direction of diffusion because pressure is a driving force for advection, not diffusion. Chemical potential describes equilibrium conditions and is not useful for evaluating mass transport.
Comparison of Three Methods for Field Measurement of Solute Leaching in a Sandy Soil
Authors: Siemens Jan , Kaupenjohann Martin
Published: July 2010

To identify the most suitable technique for measuring solute leaching in a sandy soil, we compared three methods in an irrigation experiment (irrigation rates: 5 and 2.4 mm h−1) using Cl− as a tracer. We tested tensiometer‐controlled suction plates, wick samplers, and ion‐exchange resin boxes installed between fiberglass pads. Ten samplers of each type were installed at a 52‐cm depth (suction plates) or a 60‐cm depth (wick and resin box samplers) into soil monoliths. The recovery of water and Cl− by the suction plates varied little with irrigation rate (107–118%). The wick samplers performed well during 5 mm h−1 irrigation (Cl− recovery: 111%; water recovery: 103%). However, at the irrigation rate of 2.4 mm h−1, the water recovery was significantly lower (70%), probably because the soil suction exceeded the maximum capillary force of the wicks. The wicks did not induce a retardation or additional dispersion of Cl− compared with suction plates. The recovery of Cl− by the resin boxes was only 6%. Tensiometer‐controlled suction plates allowed an overall satisfactory estimation of water and solute fluxes in the sandy soil.
Critical Leaf Potassium Concentrations for Yield and Seed Quality of Conservation‐Till Soybean
Authors: Yin Xinhua , Vyn Tony J.
Published: July 2010

Leaf K concentrations needed for optimum soybean [Glycine max (L.) Merr.] production under conservation tillage systems may be different from those in conventional tillage (moldboard plow) because soil properties (such as soil‐test K distribution) and soybean root distribution within the soil profile under conservation tillage systems differ from those in conventional tillage. Little information is available about adequate leaf K concentrations for soybean on conservation‐tilled soils with significant vertical soil‐test K stratification. This study was conducted at three locations in Ontario, Canada from 1998 through 2000 to estimate the critical leaf K concentrations for conservation‐till soybean on K‐stratified soils with low to very high soil‐test K levels and a 5‐ to 7‐yr history of no‐till management. Three K fertilizer placement methods (band placement, surface broadcast, and zero K), two conservation tillage systems (no‐till and fall tandem disk), and two soybean row widths (19 and 38 cm) were used to create a wide spectrum of production environments. For maximum seed yield, the critical leaf K concentration at the initial flowering stage (R1) of development was 24.3 g kg−1 This concentration is greater than the traditional critical leaf K values for soybean that are being used in Ontario and in many U.S. Corn Belt states. Critical leaf K values for the maximum concentrations of K, oil, and isoflavone in seed were 23.3, 24.1, and 23.5 g kg−1, respectively. The extent of vertical soil‐test K stratification seems to be one of the factors contributing to apparently higher critical leaf K concentrations for conservation‐till soybean.
Microbial Enzyme Activities in a Freshwater Marsh after Cessation of Nutrient Loading
Authors: Prenger J. P. , Reddy K. R.
Published: July 2010

Accurate assessment of perturbation and recovery from anthropogenic nutrient inputs in wetland ecosystems is important for resource management decisions. Nutrient availability affects detrital decomposition and sediment accumulation rates, contributing to and helping to maintain changes in plant community structure. In this paper we report patterns of microbial enzyme activities as indicators of change in areas of a subtropical wetland 8 yr after cessation of nutrient loading. Select enzyme (acid phosphatase, β‐glucosidase, and dehydrogenase) activities were assayed on detrital material and surface soils collected from different vegetation communities within impacted and reference (unimpacted) areas. Acid phosphatase activity (APA) did not vary as dramatically as total P (TP) in soil, but was distinctly different in detritus of impacted and reference vegetation communities. The APA in soil and detritus was greatest in the reference sites, particularly in the Panicum area. Beta‐glucosidase activity was highest in Typha areas and demonstrated significant temporal variation. Differences in the timing and length of inundation may play a role in observed trends, since the NW Panicum and Cladium reference sites flooded and reached anaerobiosis later in the growing season than did impacted areas. Data from this study indicate ongoing changes in biogeochemical cycling of nutrients in soils and detritus associated with vegetation communities in areas of historic nutrient loading.
Direct and Indirect Effects of Soil Properties on Phosphorus Retention Capacity
Authors: Ige D. V. , Akinremi O. O. , Flaten D. N.
Published: July 2010

Phosphorus retention ability of soil has been predicted from different combinations of soil properties as a result of significant correlations between these variables. However, a significant correlation between P retention capacity and a soil property does not necessarily imply a significant direct effect of the soil property on P retention. The objective of this study was, therefore, to evaluate the direct and indirect influence of soil properties on P retention capacity of neutral to calcareous soils of Manitoba (Canada). One hundred fifteen archived surface soil samples representing major soils of Manitoba were used for the study. The P retention index (PRI) of these soils was determined by the single‐point adsorption method. The relationships between P retention and soil properties were evaluated by correlation analyses while the direct and indirect influences of these soil properties on P retention were evaluated using the path analysis procedures. Significant correlations (p = 0.05) were observed between PRI and pH; CO32−; organic C; sand content; silt content; clay content; exchangeable Ca (CaEx); exchangeable Mg (MgEx); cation exchange capaciaty (CEC); Mehlich‐3 extractable Ca (CaM3); Mehlich‐3 extractable Mg (MgM3); and oxalate extractable Al (AlOx). However, path analysis showed that only CaM3 D = 0.62), MgM3 (D = 0.26), and AlOx (D = 0.21) had significant direct effects (p = 0.05) on PRI. The significant effect of sand (soil texture) was due to the indirect influence of CaM3 Our results show that the PRI for the neutral to calcareous soils of Manitoba is best predicted from CaM3, MgM3, and AlOx Similar analysis conducted to relate the classical Langmuir adsorption maximum with the properties of a subset of soils also showed CaM3, MgM3, and AlM3 as the soil variables that had significant direct effects on soil's P retention.
Soil Manganese Oxides and Trace Metals
Authors: Negra Christine , Ross Donald S. , Lanzirotti Antonio
Published: July 2010

Trace metal accumulation by Mn in synthetic oxides and soil nodules has been attributed to specific adsorption and oxidation at Mn oxide surfaces, yet little is known about trace metal interactions with Mn in bulk soil. We investigated competitive effects of trace metal pretreatment on Cr oxidation in well‐aerated, high‐Mn soils, as well as accumulation of added Pb, Co, and Cu by soil Mn using microfocused synchrotron x‐ray fluorescence (μSXRF). Short‐term equilibrations of divalent Mn, Co, Pb, Cu, and Ni with soil samples weighed to contain equivalent amounts of NH2OH·HCl‐extractable Mn resulted in substantial interference in Cr oxidation, confirming metal interactions with Cr‐oxidizing sites on Mn oxide surfaces. Interference by Cu and Pb was greatest in samples likely to be low in competing sorbents, that is, low‐pH soils and smaller samples of higher Mn soils, respectively. Strongest interference in Cr oxidation resulted from Mn and Co addition, suggesting specific affinity for soil Mn oxide surfaces, and was greatest in high‐pH, high‐Mn‐valence soils previously shown to have the greatest Cr oxidation capacity. Nickel showed the weakest effect. Micro‐SXRF scans revealed substantial spatial correlation of soil Mn with added Co and Pb, but Pb microdistribution was equally correlated with soil Fe. Only modest overlap of soil Mn with added Cu was observed. Our data suggest that specific affinity of Pb, Cu, and Ni for soil Mn oxides was weaker than that of Mn and Co. Higher Mn oxide valence may enhance sorption and subsequent oxidation of these oxidizable metals.
Soil Lime Requirement by Direct Titration with a Single Addition of Calcium Hydroxide
Authors: Liu Min , Kissel D. E. , Cabrera M. L. , Vendrell P. F.
Published: July 2010

Direct titration of acid surface soils is often used to measure soil acidity. However, titration has not been used for routine determination of the lime requirement (LR) in soil testing laboratories, because it is too time‐consuming, requiring multiple additions of base and long equilibration times between additions. Since soil pH as a function of added base can be described well by a linear equation, titration may be adopted by soil testing laboratories using a minimum number of base additions. Our objective was to evaluate the accuracy of a simplified titration procedure, based on an initial pH reading and a second reading following the addition of one dose of Ca(OH)2, followed by extrapolation to the target pH. Seventeen soils were titrated with Ca(OH)2 in both water and 0.01 M CaCl2 with a 30‐min interval between additions. The slopes from the first two data points of the titration in water were frequently in error for estimation of the slopes regressed by all data points to pH 6.5. However, the first two data points in the 0.01 M CaCl2 titration were found to be more reliable for estimating the slopes. Both the initial pH in water and in 0.01 M CaCl2 were used to calculate the LR with the two‐point slope in 0.01 M CaCl2. The LR predicted using the initial pH in 0.01 M CaCl2 gave better estimates of the LR than the initial water pH when compared with the standard 3‐d Ca(OH)2 incubation. A linear regression of LR by the single addition method in 0.01 M CaCl2 (Y) on LR determined with the 3‐d Ca(OH)2 incubation (X) gave the linear equation Y = 0.88 X, r2 = 0.93. It is concluded that the LR predictions with the single addition method in 0.01 M CaCl2 are sufficiently accurate to justify further evaluation under routine laboratory conditions.
Clay Mineralogical Transformations over Time in Hanford Sediments Reacted with Simulated Tank Waste
Authors: Mashal Kholoud , Harsh James B. , Flury Markus
Published: July 2010

Buried waste storage tanks at the USDOE Hanford Reservation in Washington State have released solutions containing high concentrations of Na, OH, NO3, and Al into the vadose zone. When such solutions contact vadose zone sediments, mineral transformations will change the sediment matrix. We hypothesized that Si, dissolved from primary and secondary minerals, will combine with Al from the tank waste to form crystalline or poorly crystalline network silicates such as zeolites and feldspathoids. In this study, we characterized the colloidal (<2 μm equivalent diam.) minerals formed when simulated tank solutions reacted with vadose zone Hanford sediments. Variables studied included simulated tank waste (STW) composition, reaction time, and temperature. Hanford sediments were reacted with a series of simulated tank solutions in batch experiments at 25 and 50°C for 1, 10, 25, 40, and 50 d. The mineralogical, structural, and chemical properties of the resulting colloidal fractions and bulk solutions were determined by x‐ray diffraction (XRD), Fourier transform infrared (FTIR), 27Al‐ and 29Si‐magic angle spinning‐nuclear magnetic resonance (MAS‐NMR), scanning electron microscopy (SEM), energy‐dispersive x‐ray analysis (EDAX), colorimetry, atomic absorption spectroscopy, and inductively coupled plasma–atomic emission spectroscopy (ICP–AES). Upon contact with STW, Si was released from the sediments and a portion was incorporated into poorly crystalline solids. The amount of poorly crystalline solids increased initially and reached maximum quantities between 0 and 25 d. Lability of minerals in the presence of NaOH followed the order quartz → kaolinite → illite. New secondary minerals, NO3–cancrinite, NO3–sodalite, and zeolite A, were formed at the expense of the original clay minerals. Zeolite A was labile and disappeared after about 25 d of reaction time. Cancrinite and sodalite, however, appeared to be stable and increased in abundance with time.
Soil Phosphorus and Vegetation Influence on Wetland Phosphorus Release after Simulated Drought
Authors: Bostic E. M. , White J. R.
Published: July 2010

Phosphorus enrichment of marsh soils can act as an internal source of nutrients to the water column, continuing to drive existing wetland eutrophic conditions even after external sources have been terminated. The goal of this study were to determine the effects of soil P concentration and flood intolerant vegetation presence on initial (1–10 d) and extended (10–38 d) P release rates from the soils after reflooding. Intact soil cores were collected from P enriched and unenriched areas of the Blue Cypress Marsh in east‐central Florida. Initial P release was greater in soils with higher soil total P concentrations and containing vegetation. Soil P enrichment resulted in the final water column P concentrations in the enriched cores to be 50% higher than those in the P unenriched cores. A single drawdown and reflood event led to ∼6% of the total soil P released to the water column from the P enriched vegetated treatment compared with a ∼1% of total P released from the P enriched non‐vegetated treatment. Initial P release rates from the enriched, vegetated treatment were five times greater than the enriched, non‐vegetated treatment. Episodic growth of flood intolerant plants under drawdown conditions was shown to be a significant mechanism for nutrient release in ephemerally flooded P enriched wetland systems. Episodic flooding and drying cycles could therefore mobilize P over the long‐term from P enriched to P unenriched areas.
The Relationship Between Cigarette Smoking and Biomarkers of Exposure Across Two Study Centers in Europe
Authors: Lowe Frazer J. , Gregg Evan O. , Bassi Antonella , Puntoni Riccardo
Published: July 2010

The relationship between biomarkers of exposure to cigarette smoke in 24h urine samples collected from groups of 80 smokers (44 males, 36 females) and 40 never smokers (17 males, 23 females) at two centers in Europe was studied. Eight biomarkers (nicotine, cotinine, hydroxycotinine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) and all of the respective glucuronide conjugates) were measured. Subjects from the two centers were pooled and biomarker data analyzed according to the machine smoked tar yield of the brand each subject smoked and the recorded number of cigarettes smoked per day (CPD). A statistically significant relationship between CPD and all of the biomarkers analyzed was found. Smokers of less than 11 CPD had the lowest mean 24h urinary concentrations for all biomarkers measured. However, if the amount of constituent obtained from each cigarette smoked was calculated, then the amount of nicotine obtained per cigarette was highest in this group although the variation was also greatest for this group. The amount of NNK (4-(methylnitrosamino)-1-(3-pyridyl)-1 butanone, the parent molecule of NNAL) obtained per cigarette was not statistically significantly different across all groups. In conclusion, these results confirm the reliability of 24h urinary total nicotine and NNAL concentrations as biomarkers of exposure to specific cigarette smoke constituents across two centers in Europe. These measurements may provide an objective alternative to CPD when grouping smokers for are studies of other endpoints.
Race and 2008 Presidential Politics in Florida: A List Experiment
Authors: Martinez Michael D , Craig Stephen C.
Published: July 2010

We use the list-experiment methodology to address three questions raised by the presidential candidacy and election of Barack Obama. First, to what degree did white voters hold feelings of racial antipathy toward blacks as a group in 2008? Second, were those feelings manifest in their response to Obama's candidacy and subsequent election as president? Third, to what degree did whites actually take pride in the nomination and election of an African American to the nation's highest office? Our analysis of four statewide surveys in Florida shows that few white voters were upset by Obama's electoral achievements, and many took some pride in his historic candidacy and election. Nevertheless, substantial racism still appears to linger in Florida.
The British General Election of 2010
Authors: Wilson Graham K
Published: July 2010

In a sense, all the parties lost the British General Election of 2010. However, a number of factors including the skilled leadership of David Cameron resulted in the creation of a governing coalition composed of Conservatives and Liberal Democrats that would have seemed highly implausible before and during the election campaign. The coalition, the first to be formed outside a national emergency since Britain became a democracy raises interesting questions about how its Westminster Model system will adapt.
Volume Fraction Determination of Binary Liquid Mixtures by Measurement of the Equalization Wavelength
Authors: Martincek Ivan , Pudis Dusan , Kacik Daniel , Schuster Kay
Published: July 2010

A method for determination of the volume fraction in binary liquid mixtures by measurement of the equalization wavelength of intermodal interference of modes LP01 and LP11 in a liquid core optical fiber is presented in this paper. This method was studied using a liquid core optical fiber with fused silica cladding and a core made up of a binary silicon oil/chloroform liquid mixture with different volume fractions of chloroform. The interference technique used allows us to determine the chloroform volume fraction in the binary mixture with accuracy better than 0.1%. One of the most attractive advantages of presented method is very small volume of investigated mixture needed, as only a few hundred picoliters are necessary for reliable results.
How do the Demographic Changes Influence the Labor Force in the Hospitality Industry?
Authors: Genc Ruhet
Published: July 2010

The new era brings forth economic, social, and demographic transformations and challenges regarding the labor market in the hospitality industry. This research note aims to trace the impact of demographic changes on hospitality labor market and to identify problem areas. The problem
areas identified in the hospitality labor market are labor shortages, skills shortages, high labor turnover, and lack of unionization. Potential solutions for addressing these labor problems are suggested.
Cultural Awareness and the Global Hospitality Business
Authors: Mkono Muchazondida
Published: July 2010

In the contemporary hospitality business, cultural awareness has become an important source of competitive advantage. With the proliferation of multinational hospitality firms, there is cutthroat competition: it is a "survival of the fittest" game. Hospitality firms can outsmart and
outperform each other based on how well they know the cultures of their present and potential markets, as well as the cultural backgrounds of their staff members. A "one size fits all" approach has proved redundant in contemporary international business. This article discusses the role of
cultural awareness in business success and sustainability of the hospitality business. A case study on Hilton's "Wa No Kutsurogi" brand is presented to enable the author to comment on, and draw parallels between, theory and practice from an empirical standpoint. It is argued that consumption
of hospitality products (food and accommodation) is a culture-driven activity, and only those products that interact with customers' "cultures" at an emotional level will appeal to them. The article suggests that culture should be understood in a broad sense: there are several levels and dimensions
to culture. The discussion emphasizes the need to customize hospitality products in accordance with the cultural dynamics of niche markets.
Development of microsatellite markers in Lupinus luteus (Fabaceae) and cross‐species amplification in other lupine species
Authors: Gonzalez Lorena B. Parra , Straub Shannon C. K. , Doyle Jeff J. , Ortega Paula E. Mora , Garrido Haroldo E. Salvo , Butler Iván J. Maureira
Published: July 2010

• Premise of the study: Microsatellite primers were developed in Lupinus luteus L., an emerging temperate protein crop, to investigate genetic diversity, population structure, and to facilitate the generation of better yellow lupine varieties.

• Methods and Results: Thirteen polymorphic primer sets were evaluated in a European and Eastern European accession collection of L. luteus. The primers amplified di‐, tri‐, and tetranucleotide repeats with 2–4 alleles per locus. These revealed a moderate to low level of genetic variation, as indicated by an average observed heterozygosity of 0.0126. Select loci also amplified successfully in the closely related species L. hispanicus Boiss. & Reut. and in the New World species L. mutabilis Sweet.

• Conclusions: These results indicate the utility of primers for the study of genetic diversity across L. luteus populations and related lupine species. The use of these microsatellite markers will facilitate the implementation of several molecular breeding strategies in yellow lupine.
Electrodiagnostic Examination of the Tibial Nerve in Clinically Normal Ferrets
Authors: Bianchi Ezio , Callegari Daniela , Ravera Manuela , Dondi Maurizio
Published: July 2010

Tibial nerves of 10 normal domestic ferrets (Mustela putorius furo) were evaluated by means of electrodiagnostic tests: motor nerve conduction studies (MNCSs), supramaximal repetitive nerve stimulation (SRNS),Fwaves, and cord dorsum potentials (CDPs). Values of conduction velocity, proximal and distal compound muscular action potentials, and amplitudes of MNCS were, respectively, 63.25 7.56 m/sec, 10.79 2.75 mV, and 13.02 3.41 mV. Mean decrements in amplitude and area of compound muscular action potentials of wave 9 with low frequency SRNS were 0.3 3.83% and 0.1 3.51%. The minimum latency of theFwaves and theFratio were, respectively, 8.49 0.65 ms and 1.92 0.17. Onset latency of CDP was 1.99 0.03 ms. These tests may help in diagnosing neuromuscular disorders and in better characterizing the hindlimb paresis reported in many ferrets with systemic illnesses.